Table of Content

10 November 2019, Volume 38 Issue 11

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Effects of artificial sand-fixing plantations on ammonia-oxidizing bacterial community in Horqin Sand Land.

ZHANG Ying, YU Li, LIANG Cai-ping, FENG Shu-wei, CAO Cheng-you

2019, 38(11):  3235-3244. 

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We investigated ammonia-oxidizing bacteria (AOB) community under different types of sand-fixing plantation, including Artemisia halodendron, Hedysarum fruticosum, Salix gordejevii, Pinus sylvestris var.mongolica, Populus simonii, and Caragana microphylla. The composition, abundance, community structure and potential nitrification were measured using the clone library analysis of amoA gene, fluorescent quantitative PCR, terminal restriction fragment length polymorphism technique and the shakenslurry procedure, respectively. The results showed that Nitrosospira cluster 3a was the most dominant group in AOB community, followed by cluster 6. The average abundance of Nitrosospira cluster 3a and cluster 6 varied significantly among different sand-fixing plantations. The highest abundances of Nitrosospira cluster 3a as well as AOB were detected in C. microphyllaplantation. The concentrations of total nitrogen, soil organic matter, and available potassium were the main factors shaping AOB community structure. There was significant difference of potential nitrification rate among sand-fixing plantations, with C. microphyllahaving the highest potential nitrification rate. Potential nitrification rate had a significantly positive correlation with AOB abundance and soil total nitrogen concentration. Our results suggested that artificial sandfixing plantation type had no effects on AOB community composition and structure, but affected the relative abundances of dominant groups, AOB abundance, and the potential nitrification rate. The AOB abundance and the relative abundance of Nitrosospira cluster 3a could be used as indicators of the recovery of AOB. The restoration of AOB community was the best in the C. microphyllaplantation among all plantation types tested.

Leaf nutrient characteristics and water use strategy of Tamarix ramosissima in artificial shelterbelt and natural community in south margin of the Taklamakan Desert, China.

MENG De-kun, MIN Xiao-jun, ZANG Yong-xin, MA Jian-ying

2019, 38(11):  3245-3253. 

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The establishment and maintenance of artificial ecological barriers in arid areas require drip irrigation to replenish water to plants on artificial shelterbelt. However, continuous drip irrigation leads to the accumulation of salt in the surface soil, which would threaten the growth and ecological function of artificial shelterbelts. To examine the effects of drip irrigation on leaf nutrient characteristics and water use strategies of desert plants in arid regions, we measured leaf nutrient content, water use efficiency, stable hydrogen isotope (δD) and stable oxygen isotope (δ¹⁸O) values of stem water and assessed potential water sources (soil water and groundwater) of Tamarix ramosissima growing in the shelterbelt and natural communities on the southern margin of the Taklimakan Desert. The results showed that the utilization rate for middle-layer soil water (40-100 cm) in T. ramosissima of the shelterbelt community was higher than that in the natural community, while groundwater was the main water source, indicating that root system of drip irrigated T. ramosissima could reach the groundwater layer. Foliar N and P concentrations of T. ramosissima in the shelterbelt community were significantly higher than those in the natural community, indicating that water supply affected the absorption and transfer of key nutrients. The long-term water use efficiency of T. ramosissima in the shelterbelt community was significantly higher than that in the natural community, which may be related to salt stress caused by irrigation or higher foliar N and P concentrations. The drip irrigation associated salt stress had not caused toxicity to T. ramosissima. After the successful establishment of shelterbelt plants, irrigation can be reduced or stopped, which would facilitate to water conservation and the maintenance of shelterbelt stability.

Water balance and influencing factors in typical plantation ecosystems in northern China under drought conditions.

ZHAO Jia-chen, JIA Jian-bo, JIA Guo-dong, CHEN Li-xin

2019, 38(11):  3254-3263. 

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To explore water balance and influencing factors in typical plantation ecosystems under drought conditions in northern China, we analyzed water balance components and influencing factors in Pinus tabuliformis and Platycladus orientalisplantations in Beijing mountain region in a dry year (2014). The results showed that the rainfall in 2014 was only 47% of longterm mean value (1958-2011). Transpiration accounted for the highest proportion of total water loss in both forests. The stand transpiration of P. tabuliformis and P. orientalis plantations was 247.16 and 259.89 mm, respectively. The other water loss pathways ranked following the order: soil evaporation (P. tabuliformis, 87.26 mm; P. orientalis, 60.02 mm) > canopy interception (P. tabuliformis, 56.63 mm; P. orientalis, 50.23 mm) > litter evaporation (P. tabuliformis, 9.99 mm; P. orientalis, 8.30 mm). Soil water was at a state of the annual deficit but was replenished during the second half of the growing season. The annual water deficit of the P. tabuliformisand P. orientalis stands was 81.24 and 67.45 mm, respectively. Stand water loss was significantly affected by environmental factors. Meanwhile, transpiration was significantly correlated with the stand diameter at breast height. Canopy interception was affected by canopy closure and wind speed. In conclusion, with precipitation as the single water source, water balance in both P. tabuliformis and P. orientalis stands cannot be met during a dry year. Therefore, these stands will face substantial survival challenge associated with precipitation reduction under climate change.

Effects of Pinus sylvestris var.mongolicasand fixation plantations with different ages on soil pH in Zhanggutai, Liaoning Province.

LEI Ze-yong, BAI Jin-ning, ZHOU Feng-yan, YU Dong-wei, LI Yao

2019, 38(11):  3264-3272. 

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Establishment of Pinus sylvestris var.mongolica plantations is an important strategy to control desertification. Afforestation generally changes soil pH. However, changes in soil pH caused by the establishment of P. sylvestris var. mongolica sandfixing forests are not well documented. In this study, we measured soil pH (0-100 cm soil layer) in P. sylvestris var. mongolica forests at different developmental stages (young, middleaged, mature, and overmature) in Zhanggutai of Liaoning Province. The results showed that the range of pH values shifted from two levels (0-10 or 0-20, 20-100 cm) to three levels (0-10 or 0-20, 20-40, 40-100 cm). With the increases of stand age, soil pH decreased significantly in 0-20 cm layer, and kept unchanged in 20-40 cm layer. Soil pH in 40-100 cm layer of young and mature forests were significantly higher than that of over-mature forests, while there was no significant difference between over-mature forests and grasslands. Soil pH was significantly positively related to total K content and negatively related to available P content in 0-10 cm soil layer. There was a significant negative correlation between soil pH and available K and soil organic C contents, a positive correlation with soil water content in 10-20 cm layer, and positive correlations with available N, total N and total P contents in 20-40, 40-60, 60-80 cm soil layers. In young forests, soil pH was positively correlated with C/P ratio, available N, bulk density in 20-40 and 60-80 cm layers, respectively, and negatively correlated with N/P ratio in 80-100 cm layer. In middleaged forests, soil pH was negatively correlated with C/P ratio in 10-20 cm layer, and positively correlated with FS (the sum percentage of clay (<0.002 mm) and silt (0.002-0.05 mm)) and total N content in 20-40 cm and 40-60 cm layers, respectively. In mature forests, soil pH of 0-10 cm layer was significantly positively correlated with soil bulk density and available P, and positively related to soil moisture, available K and FS. Soil pH was positively correlated with total N in 20-40 cm layer and negatively correlated with C/N ratio in 60-100 cm layer. In over-mature forests, soil pH was positively correlated with available N in 0-10 cm layer, while negatively correlated with total K. There was a positive correlation between soil pH and total N in 10-20 cm layer.

Spatial distribution pattern and association of Populus euphratica community in different habitats along the Tarim River.

ZENG Yong, ZHAO Cheng-yi, LI Chuan-jin, ZHENG Jin-qiang, Lü Guang-hui, LI Yan

2019, 38(11):  3273-3282. 

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Based on the survey data from the quadrats of riverside, transitional, and desert margin zones around the Tarim River, spatial distribution patterns and associations of P. euphraticacommunity were analyzed in three habitats using paired correlation function g(r). The results showed that population structural characteristics of P. euphratica varied among different habitats. In the riverside, the age structure showed an inverted J-curve, indicating an increasing population. In the transitional zone, the age structure showed a normal curve, indicating a stable population. In the desert margin, the age structure showed an inverted L-curve, indicating a decline population. The species from the P. euphraticacommunity showed different spatial distribution patterns in different habitats. Karelinia caspica, Phragmites australis, Calamagrostis pseudophragmites, and Tamarix ramosissimawere aggregated, but Apocynum venetum was distributed roughly at random in the riverside. In the transitional zone, Apocynum venetum and Alhagi sparsifoliawere aggregated, but Lycium ruthenicum and P. euphratica were aggregated at smaller spatial scales and randomly distributed at larger spatial scales. Halogeton arachnoideuswas aggregated in desert margin. Species from the P. euphraticacommunity showed different spatial associations in different habitats. The four pairs of P. euphratica vs.C. pseudophragmites, P. euphratica vs.Poacynum hendersonii, C. pseudophragmitesvs. P. australis, and P. australis vs. T. ramosissima were positively associated in the riverside. In the transitional zone, the seven pairs of Halimodendron halodendron vs. L. ruthenicum, L. ruthenicum vs. K. caspica, L. ruthenicum vs.H. halodendron, H. halodendron vs.A. sparsifolia, K. caspica vs. A. sparsifolia, A. sparsifolia vs.K. caspica, and Inula salsoloides vs.K. caspica were positively associated, butA. venetum vs. T. ramosissima was negatively associated.Salsola ruthenicavs. H. arachnoideus was negatively associated in the desert margin zone.

Effects of water stress on non-structural carbohydrates distribution in poplar seedlings.

WANG Kai, LIN Ting-ting, Lü Lin-you, LIU Jian-hua, HUANG Shu-man

2019, 38(11):  3283-3290. 

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To understand the effects of water stress on non-structural carbohydrate (NSC) distribution in leaves, stems and roots of poplar seedlings, one-year-old poplar seedlings were grown under suitable water level, mild, moderate and serious drought treatments for 15, 30, 45 and 60 days in pots. The results showed that compared with the suitable water treatment, soluble sugar and NSC contents firstly increased and then decreased in leaves and stems with increasing treatment time under water stress treatments. Soluble sugar and NSC contents declined in roots under mild and moderate stress treatments, whereas they firstly elevated and then reduced under serious stress treatment. Starch content in leaves firstly increased and then declined under mild stress treatment, whereas it firstly decreased and then increased under moderate and serious stress treatments. Water stress significantly decreased starch and NSC contents in stems and roots after 45 days of water treatment. On the 60th day of water treatment, the decline rate of NSC content in different organs followed the order: roots>stems>leaves. Meanwhile, the decline rate of starch content was greater than that of NSC content. Soluble sugar content declined in leaves, but being stable in stems and roots. These results indicated that water stress decreased NSC reserves of poplar seedlings, which may lead to death due to environmental stresses.

Effects of pruning on soil microbial community in the Caragana microphyllaencroached grassland.

HAO Guang, WANG Xiao-ping, DING Xin-feng, DONG Ke, YANG Nan, GAO Shao-bo, WANG Jin-long, CHEN Lei, HE Xing-dong, ZHAO Nian-xi, GAO Yu-bao

2019, 38(11):  3291-3297. 

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To examine the response of soil microbial community to pruning of encroaching shrub species and explore the relationships between soil microbial community composition/structure and soil physicochemical properties and plant community, we set up treatment of pruning Caragana microphylla plots and control plots without pruning in the C. microphyllaencroached grassland of Inner Mongolia. Three months later, soil physicochemical properties were measured, composition and structure of plant communities were investigated, and soil microbial community composition and structure at the depths of 0-5 cm and 15-20 cm were analyzed by phospholipid fatty acids (PLFA) method. Compared with control, pruning treatment decreased the total aboveground biomass, with a significant decrease of Artemisia intramongolica biomass, while significantly increased species richness and Shannon index. Soil pH was significantly lower at 0-5 cm layer, and soil total carbon content, total nitrogen content, and C/N were significantly higher at 15-20 cm soil layer. The PLFAs contents of total microbes, Gram-positive bacteria (G⁺), Gram-negative bacteria (G^-), bacteria (B), fungi (F) and actinomyces (Act) were significantly higher, and G⁺/G^- was lower at 0-5 cm layer. Results of redundancy analysis (RDA) showed that soil pH was positively correlated with the PLFAs content of G⁺, and negatively correlated with that of G^-, F and Act. Soil total nitrogen content was positively correlated with PLFA contents of G⁺, G^-, B, F and Act, while Shannon index was negatively correlated with that of G⁺ and positively correlated with that of G^-, F and Act. Total aboveground biomass was negatively correlated with the PLFAs contents of G^-, F and Act. These results indicated that soil microbial community composition and structure would respond rapidly to the changes of plant community and soil physicochemical properties caused by pruning, which could be used as an indicator for soil health and provide guidance for the restoration of shrubencroached grassland.

Effects of urbanization on community structure and plant diversity in evergreen broadleaved forests of the Pearl River Delta.

LI Chu-jun, CHEN Xiao-mei, WEN Xiao-hao, LIN Min-dan, XU Zhan-ying

2019, 38(11):  3298-3305. 

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Rapid urbanization greatly influence succession of the remaining forests in cities. The effects of urbanization on plant community structure and species diversity in the remaining forests of southern China remain unclear. This study was conducted to examine the effects of urbanization on the community structure and diversity of the evergreen broadleaved forests in the Pearl River Delta by investigating species composition in arbor, shrub and herbaceous layers and calculating diversity indices of species abundance (Margalef index), diversity (Shannon index) and evenness (Pielou index) in six forests (including three urban forests and three suburban forests). There were 46 species and 42 genera belonging to 31 families in the urban forests, while 96 species and 75 genera belonging to 44 families in the suburban forests. The urban forests contained dominant species, which are mostly drought  and nutrient poor-tolerant. In contrast, there was no obvious dominant species in the suburb forests, with most species in these forests being hygrophilous and shade-tolerant. Three kinds of diversity indices, including Margalef index, Shannonindex, and Pielou index, were significantly lower in the urban forests than that in the suburban forests. Differences in plant diversity and community composition were mainly in the tree layer. Our results suggest that urbanization reduces plant species diversity and promotes species homogenization in the evergreen broadleaved forests.

Seasonal dynamics of soil microbial community structure in urban forest. 

TAN Xue-lian, KAN Lei, ZHANG Lu, ZHENG Jia-yi

2019, 38(11):  3306-3312. 

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Soil microbes play an important role in forest ecosystem and are the driving factor of material cycling. Few studies have been conducted on the seasonal changes and the influencing factors of soil microbial communities in urban forests. Using high-throughput sequencing methods, we investigated the seasonal changes of soil microbial community in the urban forest of Dongguan and analyzed their influencing factors. The results showed that the structure and diversity of soil microbial community significantly differed among seasons. The total abundance of soil microbes was significantly lower in wet season than in dry season. In contrast, both Chao1 index and Shannon index showed the opposite seasonal patterns compared with that of microbial abundance, with higher diversity and structure in the bacterial and fungal community in wet season. In adaptation to the seasonal change, bacteria mainly adjusted their total abundance, while fungi changed their total abundance and species composition. Soil available boron was the major factor influencing bacterial community structure, while soil pH was the major factor influencing fungal community structure. Exchangeable calcium and exchangeable magnesium in soil were the important factors influencing both bacterial and fungal communities.

Effects of forest restoration on distribution and growth of rattan in lowland rainforest, Hainan Island.

XU Rui-jing, HU Xuan, QI Liang-hua, LIU Guang-lu, PENG Chao, SHU Qi

2019, 38(11):  3313-3319. 

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Rattan is an important non-woody forest resource and plays a critical role in global biodiversity conservation and economic development. To understand the effects of forest restoration process and stand structure of tropical rainforest on the distribution and growth of rattan, we conducted a research on secondary rain forests in three different restoration stages in Ganshiling, Hainan Island using the methods of quadrat investigation and sequencing analysis. The results showed that: (1) The abundance of rattan was the highest in the early-middle stage of restoration (74±43), followed by the middle stage (32±37), and the lowest in the early stage (0±0). The frequency distribution of rattan manifested overall as early-middle stage>middle stage>early stage. The ground diameter growth of Calamus rhabdocladus(13.62±8.39 mm), Plectocomia microstachys (8.01±3.05 mm), C. walkerii (6.54±7.52 mm) and Daemonorops jenkinsiana (3.62±2.52 mm) in the middle stage was greater than that in the early-middle stage (7.52±3.75, 6.72±3.33, 4.73±5.20, 3.51±2.4 mm). The ground diameter growth of C. tetradactylus (1.32±0.53 mm) was smaller than that in the middle stage (7.87±6.45 mm). The height growth of C. rhabdocladus (131.35±62.72 cm) and D. jenkinsiana (23.93±15.23 cm) in the middle stage was greater than that in the early-middle stage (90.02±92.13, 23.72±17.93 cm), but the height growth of C. tetradactylus (8.31±0.85 cm), C. walkerii (32.43±30.91 cm) andP. microstachys (31.62±8.74 cm) was lower than those in the early-middle stage (54.30±50.77, 48.46±78.11, 34.35±7.10 cm). (2) Most of the rattan species were distributed in the forests at the earlymiddle stage and middle stage of the restoration. The shrub communities were not conducive to the distribution of rattan. D. jenkinsiana, C. rhabdocladus, C. walkerii and C. tetradactylus tended to be distributed in the communities at the early-middle stage of the restoration, while P. microstachys was mostly distributed in the communities at the middle stage of the restoration. (3) The average tree height was positively correlated with the abundance of rattan. Stem density was positively correlated with the abundance of rattan. The maximum and average diameters at breast height were positively correlated with the abundance of P. microstachys. It was suggested that the protection of tropical rain forests should be strengthened in respect of the conservation of rattan resources and that stand structure should be adjusted according to different rattan species or suitable stand structure should be selected for near-natural cultivation.

Effects of light intensities on seedling emergency and early growth of Pinus massoniana.

GUO Si, LIU Qing-qing, WANG Da-yang, WANG Chang-hui, LIU Bo, WANG Zheng-ning

2019, 38(11):  3320-3326. 

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Pinus massoniana, a pioneer species, plays an important role in restoration of degraded ecosystem and controlling soil erosion in south China. Most P. massoniana plantations are sparse and dwarfish, with low quality and poor natural regeneration. To test whether light is a limiting factor for seedling emergence and growth of P. massoniana, the effects of five light intensities (5%, 15%, 40%, 60%, 100% of full sun light) on seedling emergence, survival, growth, and morphological plasticity were investigated. The results showed that seedling emergency, germination index, and vitality index were significantly affected by light intensity (P<0.05). Seedling emergency, germination index, and vitality index reached the maximum at 40% light intensity. With increasing light intensity, stem length decreased, while root collar diameter and root length increased. The highest total biomass, root biomass, stem biomass, leaf biomass, and robustness of seedlings were observed under 100% light intensity. With increasing light intensity,the ratio of root to shoot and root biomass allocation increased, while the stem and leaf biomass allocation declined. The results suggested that seedling emergence was inhibited under high and low light intensity while low light intensity inhibited seedling growth. Our results provided experimental evidence that light is a key ecological factor affecting seedling emergence and growth of P. massoniana.

Effects of drought stress on germination and seedling growth of heteromorphic achenes of Bidens alba.

YAN Xiao-hong, ZENG Jian-jun, ZHOU Bing, WANG Ning, YUE Dong-mei

2019, 38(11):  3327-3334. 

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Bidens alba, an invasive annual species from the genus Bidens in Asteraceae, has heteromorphic achenes. However, the ecological significance of heteromorphic achenes is still unknown. The differences of morphology, germination and seedling growth of the heteromorphic achenes under drought stress were compared by laboratory observation and bioassay. The differences of germination strategies and the adaptation of the heteromorphic achenes of B. alba to drought were examined. The results showed that: (1) There were significant differences in morphology and germination strategies between central achenes and peripheral achenes of B. alba. Total length, body length, and thousandgrain weight of central achenes were higher than those of peripheral achenes, but the width was reverse, central achenes germinated slowly, and peripheral achenes germinated fast and evenly. (2) Compared with the control, at 5%-25% of PEG-6000, germination rate, germination potential, germination index and vigor index of central achenes were enhanced at lower concentrations but inhibited at higher concentrations, and the solutions mostly showed increasing inhibition on the four indices of peripheral achenes withincreasing concentrations (P<0.05). (3) Compared with the control, seedling root length of central achenes was significantly promoted by PEG-6000 solutions at 5% concentration but inhibited at 20%-25% concentrations (P<0.05). Seedling height and fresh mass of central achenes was significantly inhibited at 10%-25% and 15%-25% concentrations respectively (P<0.05). The seedling root length of peripheral achenes was significantly inhibited at 15%-25% concentrations, and their seedling height and fresh mass was significantly inhibited at 5%-25% concentrations (P<0.05). Our results suggest that there were significant differences in the morphology and germination strategies between central achenes and peripheral achenes of B. alba. The centralachenes had stronger adaptation to drought. Those characteristics were helpful for the colonization of central achenes in new habitats and for population continuation of peripheral achenes in original habitats.

Effects of salt stress on growth and ion homeostasis of highbush blueberry seedlings.

WU Feng-zhang, WANG He-xin

2019, 38(11):  3335-3341. 

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Two-year-old cutting seedlings of highbush blueberry (Vaccinium corymbosum L. “DII”) grown in pots were treated with sodium chloride (NaCl) concentrations of 0, 100, 200, and 300 mmol·L^-1 for 40 days. We analyzed dry matter accumulation, leaf damage, and the variation in the content of sodium, potassium, calcium, magnesium, and chloride ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, and Cl^–). We also investigated the accumulation, transportation, and distribution of these ions within roots, stems, and leaves to better understand the physiological mechanism of salinity adaptation of “DII”, to aid highbush blueberry breeding of salt-tolerant varieties and achieve more efficient cultivation. The results showed that the reduction in dry weight of “DII” was non-significant under low salt concentration (100 mmol·L^-1), but became significant under medium and high salt concentrations (200-300 mmol·L^-1). The salt stress index (SI) of “DII” increased with increasing salt concentration. Na⁺and Cl^- accumulated heavily in the leaves. The absorption of K⁺ in the stems and leaves, Mg²⁺ in the stems, and Ca²⁺ in the roots remained stable under low salt treatment, while there was a significant decrease in the absorption of K⁺, Ca²⁺, and Mg²⁺ in the roots and K⁺ in the stems and leaves under higher salt concentrations. Under treatments with high salt concentrations, there was a significant decrease in whole transport capacity of K⁺, Ca²⁺, and Mg²⁺ from roots to leaves, which destroyed the ion balance in leaves, resulting in ion toxicity and growth inhibition.

Effects of darkness and temperature on the formation, survival and germination of temporary cysts of Scrippsiella trochoidea.

ZHANG Jian-neng, WANG Zhao-hui, GUO Xin

2019, 38(11):  3342-3348. 

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Scrippsiella trochoidea is a worldwide algal bloom dinoflagellate. Temporary cysts are the immobile cells, which formed by vegetative cells to withstand transient adverse environmental conditions. The temporary cyst of S. trochoidea plays an important role in the life cycle and occurrence of algal blooms. Effects of darkness on the formation, survival and germination of temporary cystsofS. trochoidea were examined under three temperatures (8, 20 and 25 ℃) in this study. Results showed that formation of temporary cysts started at the first day after darkness treatment, with the highest cyst formation rate occurring at day 3 to day 5. In addition, the peak of cyst formation delayed at higher temperatures. The final accumulative cyst formation rates were 15.9%, 20.1%, and 9.9% at 8, 20, and 25 ℃, respectively. Temporary cysts could not survive for a long time, whose death occurred just after one day of formation. All cysts died after 8-16 days of storage at darkness. The survival time was longer at low temperature, with the half-lethal time being 5.9, 2.9 and 2.7 days at 8, 20 and 25 ℃, respectively. There was no mandatory resting period for temporary cysts, with germination occurring within 24 hours after incubation. The maximum accumulative germination rates of 43.3%-65.6% were obtained at 3-6 days. The germination rate was higher for cysts formed at low temperature. Our results indicated that S. trochoidea was easy to form temporary cysts, which germinated rapidly under suitable conditions. This study highlighted the importance of temporary cysts in the population dynamics and bloom occurrence and collapse of S. trochoidea.

The variation of accumulated temperature in Songnen Plain and its impact on crop yield.

Lü Jin-ying, YAN Chao, JIA Tian-yu, WANG Fang-yuan, SUN Hong-chao, DONG Shou-kun, GONG Zhen-ping

2019, 38(11):  3349-3356. 

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Based on daily temperature data (1951-2017) from meteorological stations of Changchun, Harbin, Baicheng, Qiqihar, Hailun and Nenjiang in Songnen Plain, we calculated the accumulated temperature above 10 ℃ in each region and constructed the annual activity accumulated temperature sequence of each meteorological station. We analyzed the variation characteristics of active accumulated temperature in different regions of Songnen Plain and constructed predicting model of the active accumulated temperature in the next decade using the autoregressive integrated moving average model (ARIMA model). Meanwhile, using the production data of soybean, maize and rice in Heihe, Suihu, Harbin, Siping and Shenyang provided by the website of the National Bureau of Statistics of China, we established regression relationship between activity accumulated temperature and crop yield. The results showed that the active accumulated temperature in the six meteorological stations had significant variation over the past 67 years, and the periods of 1981-2010 were the main years for the increase in accumulated temperature. Since 1993, the active accumulated temperature increased obviously, and the average activity accumulated temperature in 2001-2017 increased by 243.6-420.3 ℃·d compared with 1951-2000. Moreover, the active accumulated temperature increase in the northern Songnen Plain was greater than that in southern part. The ARIMA model predicted that the active accumulated temperature variation of Songnen Plain in 2018-2027 will rise, with the enhancement across the six meteorological stations would be between 25.7 and 96.9 ℃·d. The predicted values of the active accumulated temperature are within the confidence interval. The activity accumulated temperature and crop yield showed a quadratic curve. When the active accumulated temperature was below 3300 ℃·d, maize yield increased with the increase of accumulated temperature. When the active accumulated temperature was below 3800 ℃·d, the yield of soybean and rice increased with the increases of accumulated temperature.

Comparison of resource utilization efficiency and economic benefit of different paddyupland rotation systems in Jianghuai region.

MENG Yu-hui, JIN Wen-jun, DONG Zhao-rong, WEN Yong-kang, LIANG Fei, DING Feng-lei, WU Xiao-wen, SONG He

2019, 38(11):  3357-3365. 

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Jianghuai region is the main doublecropping area in China, where the paddyupland rotation is a typical cultivation pattern. We conducted an experiment with three cropping systems: wheatrice (WR), rapeseedrice (RR) and fallowrice (FR) in the Anhui Lujiang National Modern Agriculture Demonstration Zone. The annual crop yield, accumulated temperature utilization rate, economic benefit and utilization efficiency for nitrogen (N), phosphorus (P) and potassium (K) under different systems were compared from 2016 to 2018. The results showed that mean annual yield of WR was 4018 and 5767 kg·hm^-2 higher than that of RR and FR, respectively. There was no significant difference in summer crops (rice) among the three systems. The difference in annual yield  mainly resulted from the difference of winter crop yield. The average yield of wheat was three times more than that of rapeseed. In terms of economic benefits, net income of WR was the highest. The average net income of WR was 6246 and 5182 yuan·hm-2 higher than that of RR and FR, with 59.69% and 44.95% of enhancement, respectively. Due to climate variability and disease, the interannual fluctuation of income of the RR was substantial. Compared with WR and FR, the utilization rate of accumulated temperature of the RR was increased by 9.98% and 39.33%, respectively. The nutrient utilization rate of WR was the lowest, as the two-year average nutrient balance index of N, P and K of WR was significantly higher than the other two systems. The FR had the highest N utilization rate, and the RR had the highest P and K utilization rate. In summary, the economic benefit of RR was significantly lower than WR. The RR had higher utilization rate of accumulated temperature and lower environmental risk. To promote the development of RR, it is necessary to improve the level of mechanized production of RR. Furthermore, the waste of light and heat in winter fallow pattern is serious and thus it is urgent to screen out the adaptable and ecofriendly crops for winter fallows.

Responses of phenology, quality and yield of juicy peach to climate change in Zhejiang Province.

YANG Dong, ZHU Jia-min, DING Ye-yi, JIN Zhi-fen

2019, 38(11):  3366-3375. 

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Based on biological and meteorological data of medium and late ripening juicy peaches in Fenghua, Zhejiang from 2003 to 2017, simulation models of phenology, quality and yield of juicy peaches were built using GA-BP neural network. The phenology, quality and yield series of juicy peaches in Zhejiang Province were established based on observation data from 67 basic meteorological stations from 1971 to 2017, then the responses of phenology, quality and yield of juicy peaches to climate change was analyzed. The absolute error of ensemble model for phenological simulation was less than 1.5 days, and the relative error of quality and yield simulation was 5% and 5%-7%, respectively. During the past 47 years, the initial flowering, mature and leaf fall periods of medium and lateripening peaches were advanced, the vegetative growth period of medium-ripening peaches was significantly shortened, and the period of reproductive growth of late-ripening peaches was significantly prolonged. Since the 1980s, the interannual phenological fluctuation of medium and late-ripening peaches increased. Reproductive growth duration of medium-ripening varieties increased in the northern part of the province and decreased in the south, while the vegetative growth duration declined. Reproductive growth duration of lateripening varieties increased. The areas with significant increase were mainly concentrated in Ningbo JinhuaQuzhou, while the vegetative growth duration had relatively small fluctuation across the province. The quality of medium-ripening peaches showed a downward trend, with a climatic tendency rate of -0.01·10 a^-1. The quality of late-ripening peaches showed a very significantly upward trend, with a climatic tendency rate of 0.032·10 a^-1. The climatic quality of medium-ripening peaches decreased significantly in Ningbo ShaoxingJinhuaQuzhou, with a climatic tendency rate less than -0.015·10 a^-1. The magnitude of the enhancement of the quality of late-ripening peaches in the northcentral part was greater than that in the south, with the climatic tendency rate in Ningbo and Jiaxing was greater than 0.04·10 a^-1. The climatic tendency rates of medium and late-ripening peach yield were 0.17  and -0.093 t·hm^-2·10 a^-1, respectively. In the eastern coastal areas and the border areas of Hangzhou, Shaoxing and Jinhua, the yield per unit area increased significantly, with a climatic tendency rate being greater than 0.18 t·hm^-2·10 a^-1. In the northeastern part of Zhejiang, the yield of lateripening peaches decreased significantly, with the climatic tendency rate in central Jiaxing and northern Ningbo being less than -0.2 t·hm^-2·10 a^-1, and the areas with increasing yield per unit area were mainly concentrated in the southern part of Zhejiang and the northwestern part of Ningbo.

Larval instar-dependent effects on predation behavior of stinkbug Arma chinensis attackingSpodoptera litura larvae.

YANG Zhi-Hao, MENG Ling, LI Bao-Ping

2019, 38(11):  3376-3381. 

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Predation behavior is widely utilized to evaluate the potential of a predator in biological pest control. The common approaches using mathematic modeling or direct observation in microcosms without plants often lead to either over or under-estimation of the potential. This study aimed at estimating behavioral parameters of predation on different instar larvae of Spodoptera litura by the predatory stinkbug Arma chinensis across nymphal instars in laboratory experiments using potted plants. Different instars of S. litura larvae (L1, L2, L3 and L4) were individually subjected to predation by variable instars of individual A. chinensisnymphs (2nd, 3rd, 4th and 5th instar) on potted soybean (Glycine max). Predation behavior during two hours was recorded and analyzed to detect the trend across predator’s instars in response to variable instar caterpillars. Preyhandling time decreased in a quadratic pattern across stinkbug nymphal stages when encountering L1, L2 or L4 prey, and in a cubic pattern when encountering the L3 prey. Prey consumption increased linearly with the increase of stinkbug nymphal instar for the L2, L3 or L4 prey, and showed an “archshaped” curve for the L1 prey. Predation success increased linearly with the increase of stinkbug instar for the L2 prey, and had no correlation with it for the L1, L3 or L4 prey. The number of stylet stinging did not change with stinkbug instar. Our findings suggest that the evaluation of predation of S. litura by A. chinensis should take into account of the age of both prey and predator.

The reentry behavior and its relationship with hydraulic conditions during upstream migration of Schizothorax o’connori.

WU Zhen, YANG Zhong-yong, SHI Xiao-tao, JIANG Yong-qiang, CHEN Li, JIN Zhi-jun

2019, 38(11):  3382-3393. 

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Analyzing the swimming behavior of fish during upstream migration and its response to the hydraulic conditions of fishway is the key to optimizing fishway design and improving the upstream efficiency and success rate of fish. Taking Schizothorax o’connori as the research object, we analyzed the influence of each hydraulic factor on the reentry behavior and renewed upstream migration by combining the flow field, turbulent kinetic energy field and strain rate field with the upstream migration or reentry trajectories of fish together. We further explored the underlying causes of reentry behavior by combining the energy consumption rate of fish during upstream migration. The results showed that fish had general reentry behavior during upstream migration, and most of its reentry behavior was to search for a suitable path of upstream migration. The velocity of fishway was the dominant factor triggering the reentry behavior. The reentry behavior of fish was concentrated in the high velocity regions. After reentry, the fish tended to select low velocity regions to renew upstream migration. The turbulent kinetic energy had a significant contribution to the direction of reentry movement. Fish tended to return from lower turbulent kinetic energy regions, and selected higher turbulent kinetic energy regions to renew upstream migration. The strain rate had a relatively minor effect on the reentry behavior. Results of correlation analysis between the hydraulic factors and the energy consumption rate at the track points of upstream migration indicated that the high energy consumption and physiological stress were the internal causes that triggered the reentry behavior.

Effects of different substrates on the sprint performance of Phrynocephalus helioscopus (Agamidae).

ZHENG Peng, LIANG Tao, WANG Xin-hui, GUO Cheng-tao, MIAO Jia-shuai, SHI Lei

2019, 38(11):  3394-3399. 

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Substrate type is an important factor affecting the locomotor performance of lizards, but empirical evidence is scarce. We compared the sprint speeds and morphological indices of Phrynocephalus helioscopus on substrates with different properties, including gravel, clay, and sand. We found no significant differences in sprint speed or sprint sensitivity among different substrate types. However, the sprint performance of P. helioscopus was correlated with morphological indices, which were affected by substrate properties. On substrates with larger substance gap lengths, widths, and areas, such as large gravel, we detected a significant negative correlation between the toe length (digit Ⅰ of the hand and digit III of the feet) of P. helioscopus and its maximum sprint speed (P<0.05). On substrates with a smaller proportion of supporting area such as midsized gravel, there was a significant negative correlation between the hind limb length of P. helioscopus and its maximum sprint speed (P<0.05). We found significant positive correlation between the length of digit IV of the hand of P. helioscopus and its maximum sprint speed on substrates with smaller substance gap lengths, widths, and areas or those with larger proportions of supporting area such as small gravel (P<0.05). In conclusion, the similar levels of performance on different types of substrate suggest that P. helioscopus follows the “jack of all trades and master of none” locomotor strategy.

Distribution, source and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in PM_2.5 in Beijing Olympic Park in heating and nonheating seasons.

SONG Guang-wei, HU Jian, CUI Meng, LIU Hai-hong, CHEN Xin, DONG Xin-yuan, ZHAO Chang-qiu

2019, 38(11):  3400-3407. 

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We collected 67 particulate matter (PM_2.5) samples in the Beijing Olympic Park from December 2017 to June 2018 to examine the concentration, distribution characteristics and sources of polycyclic aromatic hydrocarbons (PAHs) in PM_2.5, and assess the health risks during the heating season and non-heating season. The PAHs were detected by the GC-MS. The average values of the total concentrations of 16 PAHs associated in PM_2.5 in the heating season and non-heating season were 213.6 and 52.5 ng·m^-3, respectively. The molecular diagnostic ratios and principal component analysis were applied to apportion the sources of PAHs. The results showed that the sources of PAHs were mainly derived from the combustion of petroleum and coal during heating period, and from vehicular emissions during non-heating period. The health risk evaluation of PAHs was conducted by the model of incremental lifetime cancer risk (ILCR). There were potential carcinogenesis risks when exposed to PAHs associated in PM_2.5.

Pollution status and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soil of a large chemical engineering site.

ZHANG Yu, SONG Guang-wei, LIU Hai-hong, TIAN Yao, WANG Jing, DAI Zi-jun

2019, 38(11):  3408-3415. 

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A total of 95 soil samples from 18 profiles and five soil layers were collected from a large chemical engineering site in northeast China, with 16 priority polycyclic aromatic hydrocarbons (PAHs) being detected by GC/MS. The concentration, spatial distribution of PAHs in surface soils (0-3 m) and the vertical distribution across soil profile (0-16 m) were analyzed. The potential risks were assessed by the model of incremental lifetime cancer risk (ILCR). The results showed that ∑PAHs in the surface soils ranged from 0.13 to 553.5 mg·kg^-1, with an average of 67.0 mg·kg^-1. The ∑PAHs concentration was relatively high around the chemical company and the thermal power plant. 4ring PAHs were dominant in the depths of 0-3 m and 4-7 m, while lowring (2-ring and 3-ring) PAHs were dominant in the depths of 8-11 m. The ∑PAHs concentrations decreased with increasing soil depth in the undisturbed soil profiles, while relatively high concentrations of PAHs were found at a depth of more than 16 m in the disturbed soil profiles. According to the Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land in China, the concentration of BaP exceeded the value of soil environmental quality pollution risk control standards for class I construction land by 60.6 times. The results of health risk assessment showed that the ILCRs value was 9.6×10^-11-7.2×10^-5, being potential carcinogenic risk.

Effects of different ameliorations on the physical properties of saline-sodic soil on the Songnen Plain.

YANG Hong-tao, AN Feng-hua, ZHANG Lu, ZHAO Dan-dan, ZHU Wen-dong, YANG Fan, WANG Zhi-chun

2019, 38(11):  3416-3424. 

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Soil salinity-sodicity is a major factor leading to tremendous yield losses in many arid and semi-arid regions around the world. It is well recognized that saline-sodic soil is the most difficult to ameliorate and utilize. Extreme physical properties of salinesodic soils, in most cases, result in soil conditions unsuitable for crop growth. Amelioration of salinesodic soils can be accomplished using various methods. The dynamics of water and salt movement have been well documented in literatures. However, changes of soil physical properties of saline-sodic soils afterameliorating for several years have rarely been evaluated. A field experiment was conducted to evaluate the effects of five years amelioration by growing rice in conjunction with different physical/chemical materials, including desulfurization gypsum (GR), sand soil (SS), organic matter (OM), and an amendment (TJ, developed by Da’an sodic land experiment station), on the Songnen Plain, Northeast China. The results showed that physical properties of salinesodic soil were significantly improved by the selected amelioration methods (P<0.05). Soil clay particles were reduced significantly, while sand particles were significantly increased. Additionally, soil bulk density was significantly reduced and water infiltration rate was significantly increased. TJ showed the best effects in improving soil physical properties, then followed by OM. Furthermore, SS showed the lowest amelioration effects on soil physical properties. These findings would provide basic data support to saline-sodic soil management.

Effects of opencast coal mining on soil properties and plant communities of grassland.

HAN Yu, WANG Qi, ZHAO Wei, SHI Na-na, XIAO Neng-wen, ZHANG Zhou-ai, QUAN Zhan-jun

2019, 38(11):  3425-3433. 

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Soil properties, species composition, and plant community structure were examined in three different opencast mines of Shengli Coal Mining area. Redundancy analysis and cluster analysis were used to examine the relationship between soil properties and plant communities. The soil fertility of the research area was evaluated using gray correlation analysis. The results showed that: (1) The impact of opencast coal mining on soil water content was complicated. Soil water content of the west second mine and the east second mine decreased by 1.9% and 14.0% respectively, but the west third mine increased by 63.6%. Soil nutrients in the opencast area were lost compared with the control area, and the total potassium and available nitrogen contents were significantly reduced by 6.3% and 47.2%, respectively. (2) Species richness in the opencast mining area was declined by 26.3%-57.9% and the importance value of the dominant species decreased. The richness index and diversity index of plant community were significantly declined, and the grassland turned into aridification and degradation. (3) There was high correlation between soil properties and species diversity indices. The concentrations of total potassium and available potassium were the key factors determining plant community structure. (4) Soil fertility far from the opencast mining sites was better than that near the sites. Therefore, the influence of opencast coal mining on soil fertility was within a certain range around the mining sites.

Effects of temperature and pyrite slurry concentration on the pollutant release during pyrite bio-oxidation process.

DONG Yan, BI Wen-long, ZHOU Li-xiang, QIN Jun-mei, ZHANG Jian, LIU Fen-wu

2019, 38(11):  3434-3440. 

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Acid mine drainage (AMD) production during mining industry has the characteristics of extensive pollution, long duration, and serious harm. Biooxidation of pyrite is the main cause of AMD. Exploring the details of pyrite bio-oxidation is of great significance to understand the pattern of AMD production under natural conditions. In this study, shaking flask experiments were carried out to investigate the effects of temperature (10-30 ℃) and pyrite slurry concentration (0.67%-2%) on pyrite biooxidation process. The results showed that bio-oxidation of 1 g pyrite for 18 days released 0.6 mmol, 64.53 mg, and 151.0 mg of H⁺, total Fe and SO₄^2-, respectively at 30 ℃ with pyrite slurry concentration of 2%. Compared with the pyrite slurry concentration of 2%, the amount of released H⁺ and total Fe in pyrite bio-oxidation systems decreased by 13.3% and 18.2% respectively when the pyrite slurry concentration was reduced to 0.67%. Compared with temperature 30 ℃, when temperature was decreased to 10 ℃, the amount of released H⁺ and total Fe in pyrite bio-oxidation systems decreased by 80.0% and 82.6%, respectively. The SO₄^2- concentration showed a distinct increasing trend in pyrite bio-oxidation system under high pyrite slurry concentration (1%-2%) and high temperature (20-30 ℃), whereas the SO₄^2- concentration did not change under low pyrite slurry concentration (0.67%) and low temperature (10 ℃). Biooxidized pyrite surface showed erosion pits with different densities according to the bio-oxidation degree under different treatments. In addition, secondary iron minerals covered the bio-oxidized pyrite obviously when the pyrite biooxidation was at 30 ℃. Our results provide supports for further understanding the formation mechanism of AMD.

Organic acid secretion and aluminum absorption kinetics by Lactarius deliciosus and Pisolithus tinctoriusunder aluminum stress.

JIANG Ya-nan, GU Xi-rong, ZHOU Qian, JIA Hao

2019, 38(11):  3441-3449. 

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To understand the roles of organic acids and mycelium adsorption in Al-resistance, two species of ectomycorrhizal fungi (ECMF), namely Lactarius deliciosus strain 2 (Ld 2) and Pisolithus tinctorius strain 715 (Pt715) with the ability of Al-resistance ranked as Ld 2 >Pt 715, were cultured in acidic medium with or without Al³⁺. Organic acids and Al³⁺ concentrations in medium were examined after 21 d. Results showed that organic acids in culture medium were different between the species of ECMF. It was ranked as formic acid > oxalic acid in Ld 2 culture medium, whilst as tartaric acid > formic acid > oxalic acid > succinic acid inPt 715 culture medium, whether the two ECMF were cultured with or without Al addition. Moreover, Al³⁺ addition significantly increased both formic acid and oxalic acid secreted by Ld 2, whilst both tartaric acid and formic acid secreted by Pt715. Al³⁺ absorption by the two ECMF was active, which followed the kinetic model of ion absorption. The CEC,C_min, I_max, and adsorptive Al³⁺ in Ld 2 mycelium were higher than in Pt 715 mycelium. In contrast, both the K_m and absorptive Al³⁺ were lower inLd 2 mycelium than in Pt 715 mycelium. Therefore, both organic acids secretion and Al³⁺ adsorption by mycelium were important in Al resistance of ECMF. They may act in different ways. On the one hand, organic acids secretion could contribute to the activation and utilization of nutrients. On the other hand, Al³⁺ adsorption by mycelium could prevent Al³⁺ from entering the symplast.

Canonical correlation analysis on the comprehensive environmental quality of Guangxi.

HUANG Liang-mei, CHEN Bei, LU Xiao-yan, RUAN Shan-shan, LIN Hui, LI Jia-li, LAN Bo-tao

2019, 38(11):  3450-3459. 

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We analyzed the canonical correlation between environmental quality monitoring indicators of Guangxi and statistical indicators of yearbook such as nature, economy, population, energy, pollutant emissions at three time scales of 5 years (from 2011 to 2015), 10 years (from 2006 to 2015) and 15 years (from 2001 to 2015) by canonical correlation analysis (CCA). Results showed that: (1) The canonical correlation between factor’s environmental quality and nature, economy, population and energy of Guangxi had an upward trend with the increases of time scales. The correlation was statistically significant at the time scales of 10 and 15 years. However, establishing the canonical correlation at the time scale of 5 years needed a close increase in the time of quarterly samples. (2) The major loading of atmospheric environmental quality was charged by the comprehensive pollution index of air quality, sulfur dioxide, fine particulate matter (PM_2.5), and nitrogen dioxide. The major loading of water quality was charged by the comprehensive pollution index of water quality, COD_Mn, ammonia, DO, and Cd. The major loading of ecological environment was charged by ecological index, vegetation coverage index, and water network density index. The major loading of key pollutant sources monitoring indices was charged by the number of enterprises that discharge waste water, waste gas and municipal wastewater treatment plants, and standard discharge rate of sewage treatment. (3) Air quality indices including integrated pollution index of air quality, SO₂, PM_2.5, NO₂ as well as frequency of acid rain had positive correlation with water quality indices including integrated pollution index of water quality, COD_Mn, Cd, DO, ammonia, petroleum, and total phosphorus, while the pH of acid rain had negative correlation with these indices of air and water quality. The number of pollutant sources enterprises had positive correlation with the concentrations of main atmospheric and water quality indices. (4) Nature, economy, population, energy, and pollutant emissions were the driving forces for the changes of comprehensive environmental quality of Guangxi. The adjustment of environmental quality monitoring evaluation indicators had profound impacts on the dynamics of environmental quality. Our results provide reference to regional economic development, land use optimization, energy utilization, environmental protection, and environmental quality evaluation.

Filtering algorithms of HJ-1 A/B NDVI time series data and phenology of typical tree species in Xiamen.

LI Hui, PENG Ren-chao, LI Wan-kai, ZHU Xiao-ling, HUANG Yu-tong, NIE Qin

2019, 38(11):  3460-3471. 

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NDVI (Normalized Difference Vegetation Index) time series analysis can reveal the phenological changes of vegetation cover. With the characteristics of high spatial resolution and high temporal resolution, HJ-1 A/B satellite can provide abundant time series optical data for the application and analysis of phenological characteristics of tree species at the medium and small scales. In this study, we used Savizky-Glolay (S-G) filtering method and Harmonic Analysis of NDVI Time-Series (Hants) to reconstruct 58 HJ-1 NDVI time series data curves of eight typical tree species in Xiamen City. Mean value, mean absolute error and correlation coefficient were selected to quantitatively evaluate the filtered results. Phenological characteristics of the eight tree species were analyzed using NDVI ratio. We further examined the effects of meteorological factors including temperature and precipitation on NDVI time series fluctuation of the eight tree species. The results showed that both S-G and Hants filtering methods can restore the NDVI fluctuation shape of the vegetation characteristic of obvious phenological changes, with Hants filter being the best choice due to its ideal smoothness effect. The filtered NDVI curves showed that NDVI values of all the tree species except Eucalyptus urophylla were at a high level. The intra-annual fluctuation of NDVI time series was not intense, with obvious double peaks. Moreover, the NDVI values peaked firstly in May and June, and then declined in July and August. The second peak occurred in October, which was lower than the first peak. The growth period of all the species lasted for 7-8 months. Except that E. urophylla entered growth period at the end of February, the other tree species entered growth period at the end of April, ended in November, and reached the growth peak in July. In addition, tree growth was sensitive to the abrupt drop of precipitation in July. The lag period of such responses differed among tree species, with differences in the speed of growth reduction, but most of the species had low values of NDVI ratio in August. Our results provide reference for the selection of filtering methods for HJ-1 A/B NDVI time series data, characterizing the phenology of typical tree species, and fine classification of tree species in subtropical regions.

Comprehensive assessment of ecological risks based on urban expansion: The case of Hohhot.

MA Chen-yang, ZHEN Jiang-hong, FENG Yan-wei, FENG Yi, TAO Yun, HAN Shuai

2019, 38(11):  3472-3479. 

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The expansion of construction land during urbanization is bound to occupy the cultivated land, grassland, and other ecological lands, and to destroy ecosystem structure and function. Clarifying the change of ecological risk in urban expansion is of great significance for urban land planning and risk control. Here, we established an ecological risk evaluation system of “Hazards Exposure InfluenceResponse” based on the urban land expansion in Hohhot. The ecological risk of Hohhot in 1990, 2001, 2010, and 2016 was assessed and ranked. The results showed that the scope of urban land in Hohhot was expanding continuously, with increasing expansion rate and intensity. There were significant differences in the expansion intensity and change tendency of construction land among the four precincts of Hohhot. Temporally, the comprehensive ecolo-gical risk of Hohhot and its four precincts showed an upward trend. The ecological risk increased from low level to moderate level. There was a strong correlation between risk value and urbanization intensity index. Spatially, the comprehensive ecological risk level was gradually reduced from urban center to the edge. The spatial variation of risk value was affected by urbanization intensity. The highest risk proportion in Hohhot was from lower level to moderate level. There was a significant difference in the proportion of risk levels among the four precincts. The comprehensive ecological risk values of the four precincts were represented by Yuquan > Huimin > Saihan > Xincheng, which is consistent with the urbanization intensity index.

Integrated gap analysis of Korean pine (Pinus koraiensis) forest ecosystem conservation based on multiple protected area types.

FU Li-qiang, CHENG Kun, ZONG Cheng, MA Jian-zhang

2019, 38(11):  3480-3486. 

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The management system of protected areas in China is facing great changes. The protected area system with national parks as the main body will be gradually established to solve the problems in the spatial layout of protected areas. Previous studies on gap analysis mostly overlaid on the nature reserve distribution maps. In this study, we conducted a comprehensive gap analysis for Korean pine forest ecosystems based on various forms of protected areas, which will be helpful for the unified planning and management of protected areas and for enhancing the conservation effectiveness. The results showed that the distributions of nature reserves, forest parks, wetland parks, geological parks and scenic areas were all concentrated in the county-level administrative areas with the distribution of Korean pine forests. Meanwhile, other types of protectedareas played important roles in maintaining balance and complement for the nature reserves. According to the comprehensive gap analysis of all protected areas, conservation gaps existed in 52.83% of areas of Korean pine forest ecosystems, and suitable forms of protected areas need to be increased to the existing sites in future. We proposed some specific suggestions for the reformation, overall planning, and construction of protected area system to solve gap problems in the comprehensive conservation of Korean pine forest ecosystems.

Characterization of the wind regime along Tianjin-Qinhuangdao High-speed Railway.

SUN Mei-ling, ZHANG Sai, MA Jing-jin

2019, 38(11):  3487-3495. 

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Severe wind disaster is one of the most important factors affecting the operation of high-speed trains. Herein, two methods are used to conduct risk assessment alongside the Tianjin-Qinhuangdao High-speed Railway with the aim to identify high-risk areas. One is based on the historical observation data from the meteorological stations along the railway during 2009-2018, while the other one is the high-resolution WRF (Weather Research and Forecasting) simulation of processes regarding the typical severe wind weather during the same period. The results showed that there is an obvious seasonal variation of the wind risk along the railway. In addition to the wind intensity that reaches the highest in spring, the wind frequency ranks the first in spring as well, followed by winter and obviously higher than that in summer and autumn. The analysis based on observation data of meteorological stations revealed several high-risk areas: the railway section located in Tianjin Binhai running from southwest to northeast and that located in eastern Tangshan running from west to east. These railway sections are identified also by the WRF simulation of severe wind weather processes, suggesting that the result of WRF simulation is well in line with that from observation data of meteorological stations. The main wind direction along the Tianjin-Qinhuangdao High-speed Railway is northwest in spring and winter and southeast in summer when the wind is at a right angle to the railway section located in Tianjin Binhai. Due to the influence of crosswind on the train, the operational risk of this railway section will be increased under these severe wind conditions.

Thermal environment characteristic and cooling effect of greenery in Beijing First Green Belt area.

SUN Zhe

2019, 38(11):  3496-3505. 

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We investigated the thermal environment characteristics of Beijing First Green Belt (BFGB) area, which is defined as the sub-districts intersected with the belt, and identified the cooling effect of greenery. Land surface temperature (LST) was retrieved and greenery land cover was interpreted by Landsat 8 image data in 2015, and thermal environment characteristics and cooling effect of greenery were analyzed by GIS spatial analysis, moving window landscape pattern indices, and statistical analysis methods. Heat island intensity in the study area showed a pattern of “south high and north low” and “east high and west low”. BFGB inner zone had higher proportion of strong heat island area than the outer zone, suggesting that governance in the belt was not sufficient to effectively regulate the thermal environment. At sub-district level, 55.74% of sub-districts had net contribution to strong heat island. Greenery ratio was negatively correlated with the proportion of heat island area and positively correlated with the proportion of cool island area, suggesting that high greenery ratio in sub-districts could effectively mitigate heat island. At grid sampling point level, sampling points with net contribution to strong heat island accounted for 51.69%. Buffer zone with a 500 m radius was generated by every sampling point. The regression model showed that the impact radius of greenery on mitigating heat island effect was between 150-200 m, and that 1% enhancement of greenery within 50-100 m and 100-150 m circles can result in 0.023 and 0.013 ℃ decrease of LST. From the greenery spatial pattern, the larger the patch area, the simpler the shape, the more aggregated the spatial distribution, the stronger the cooling effect is; while the higher the patch density, the more complex the shape, the more dispersed the spatial distribution, the weaker the cooling effect is.

A review of research on soil carbon storage and its influencing factors in the Tibetan Plateau.

WANG Li, ZENG Hui, ZHANG Yang-jian, ZHAO Guang, CHEN Ning, Li Jun-xiang

2019, 38(11):  3506-3515. 

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The Tibetan Plateau is highly sensitive to global climate change, and is the controller for regional climate in the Pan-Third Pole region. On the Tibetan Plateau, soil carbon accounts for a high proportion of the ecosystem carbon and is extremely important for ecosystem carbon cycling. However, there are still plenty of uncertainties for current soil carbon storage estimation on the Tibetan Plateau, with different estimation methods also having great discrepancies. Here, we reviewed research progress on soil carbon storage on the Tibetan Plateau during the past 30 years, and compared the results of different studies. We also analyzed the spatial and temporal variation of soil carbon storage based on two kinds of influencing factors (inherent, such as geographical factor, soil property, vegetation type; and variable, such as climate change, human activities). In terms of estimation models and methods, the process models such as CENTURY and TEM, which consider multiple processes affecting soil carbon storage, had higher accuracy compared with the EVI and NDVI models, and interpolation estimation. Averaged across different studies, soil organic carbon storage in the top 20 cm of the alpine grasslands is about 10 Pg C (1 Pg=10¹⁵ g), and that in the top 200 cm of the alpine permafrost is approximately 16.5 Pg C. Soil inorganic carbon storage in the top 100 cm of the alpine grassland is about 14 Pg C. The soil carbon storage on the Tibetan Plateau decreases gradually from southeast to northwest. The effects of variable factors on soil carbon storage varied greatly. The estimation accuracy of soil carbon storage is affected by sampling location, data source type, estimation method, and soil depth. Future studies of soil carbon storage on the Tibetan Plateau should pay attention to establishing a common standard for soil carbon storage estimation. Under the common standard, the comparability among different studies is boosted. Meanwhile, expanding sampling area and sample size, increasing sampling depth and maintaining the temporal coherence among each sampling period can efficiently abate uncertainty in soil carbon storage estimation on the Tibetan Plateau. With these improvements, our understanding on Tibetan Plateau ecosystem responses to climate change would be advanced and our prediction on its future status be more accurate.

Metagenomics reveal responses of soil microbial community in grassland to global changes.

DU Xiong-feng, YU Hao, WANG Shang, DENG Ye

2019, 38(11):  3516-3526. 

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Grasslands play significant ecological roles in the biosphere. Soil microorganisms are a key factor in maintaining the function and stability of grasslands. Over the past decade, metagenomic technologies have provided new tools for analyzing microbial communities in various ecosystems. Here, we summarized the applications of metagenomics in grasslands. The latest progresses in the responses of soil microbial community to global change, especially climate change, atmospheric composition change, land use change, and exotic species invasion, are included. These studies are of great importance for fully improving our understanding of the ecological functions of soil microbial community in grasslands, and their significance in maintaining the balance of biosphere. Finally, we provide some prospective on the application of metagenomic tools in studying soil microbial communities in grasslands.

A review on the improvement of salt-affected soil nutrients by Elaeagnus angustifoliaL.

WU Hai-wen, YANG Xiu-yan, WANG Ji-ping, LIU Zheng-xiang, ZHU Jian-feng, ZHANG Hua-xin

2019, 38(11):  3527-3534. 

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Planting multi purpose and salt-tolerant tree species is one of the most effective ways for ecological restoration of salt-affected soil, with great ecological and economic benefits.Elaeagnus angustifolia L. is a representative tree species as a pioneer species for ecological restoration of salt-affected soil in China. E. angustifolia can significantly improve nutrient concentrations in salt-affected soil, with the mechanism underlying nutrient transport being still unclear. Based on the analysis of geographical distribution and climatic adaptability, we summarized the degree and ways of improving nutrient status in salt-affected soil by E. angustifolia from the aspects of soil nutrient increase, biological N-fixation, leaf litter and fine root decomposition. We quantitatively elaborated the key processes of nutrient transport and the effect of soil salinity, giving a straightforward understanding of the positive effects of E. angustifolia on salt-affected soil.E. angustifolia was distributed in most salt-affected areas of China, with great geographical and climatic adaptability. E. angustifolia had high salt tolerance, and could significantly increase nutrient content, especially N content, in moderate and severe saline-alkali soils. The prominent fertilization effect of E. angustifolia attributed to its efficient biological N-fixation and rapid litter and fine root decomposition, which release a large amount of N into soil in a short time, thus rapidly improving soil fertility. The processes of biological N-fixation and nutrient release were affected by soil salinity. Further studies of nutrient transport mechanism of E. angustifolia in salt-affected soil should focus on the long-term positioning monitoring with nitrogen cycle as the kernel, and the combination of qualitative and quantitative research for salt types and E. angustifolia provenances. Precise understanding of the mechanism, pathway and function of E. angustifolia on improving salt-affected soil nutrients is helpful to establish the mechanism model of soil improvement by tree species represented by E. angustifolia from the perspective of nutrient management, which provides scientific support for precise ecological restoration and vegetation construction for salt-affected soils.

Research advances in key factors affecting seedling regeneration above treeline.

WEI Shan-shan, WANG Yang, YU Fei

2019, 38(11):  3535-3541. 

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Treeline is a special ecotone between the upper forest limit and tree species line. It is an ideal ecological indicator for climate change as it is sensitive to climate change. The position of half of global treelines is upward, with the rest maintaining relatively stable under the background of global warming. The treeline is strongly affected by seed production, dispersal and seedling establishment. Most studies have analyzed the mechanism of treeline structure from the aspects of temperature, precipitation, illumination, and disturbance, and found that low temperature limits treeline dynamics. However, single factor is hard to explain the global treeline variation. Most studies focused on the effects of abiotic factors on the distribution of treeline and little attention has been paid to the effects of seed dispersers on seedling establishment in treeline ecotones, especially on the treeline dynamics. Future studies should focus on the distribution of seedlings and saplings in treeline under global warming, such as the effects of seed caching behavior of animals in treeline community on the seedling regeneration of treeline, so as to provide scientific basis for exploring the biotic responses to climate warming from the perspective of interactions between seed dispersers and treeline dynamics.

RNA-Seq application in study of arbuscular mycorrhizal fungi.

DENG Jie, LI Fang, ZHANG Wei-zhen, DUAN Ting-yu

2019, 38(11):  3542-3550. 

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Arbuscular mycorrhizal (AM) fungi are important microbial components in agroecosystems. These fungi establish symbiotic associations with nearly 80% of vascular plants. The symbiotic relationship accompanied by plant evolution is a key factor affecting plant growth and diversity. In recent years, RNA-Seq has been widely used to study the molecular mechanism of stress defense, metabolism, protein synthesis and other biological processes in AM fungi and plant symbionts. We summarized the research progress of functional genes involved in plant stress defense, protein synthesis, protein folding/degradation, energy metabolism, signal transduction, and transcription during symbiosis, including those differentially expressed genes related to symbiosis such as phosphate transporter, lectin precursor, glutathione S-transferases, Mtha1 plasma membrane ATPase, and ribosomal protein, and reveals their functional characteristics. These findings provide theoretical basis for further research on the mechanism of AM fungi-plant symbiosis.

A comparison study of the evapotranspiration measured by lysimeter and eddy covariance.

WANG Wei-na, ZHANG Xiang, ZHANG Li-feng, LIU Xiao-qin, ZHAO Liang, LI Qi, GU Song

2019, 38(11):  3551-3559. 

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To accurately examine the water budget of degraded meadow ecosystems in the Three-River Source Region, eddy covariance system (EC) and lysimeter were used to continuously measure the evapotranspiration (ET) of a degraded meadow. Our results showed that ET mea-sured by two methods had the same trend of annual variation. The annual cumulative ET measured by EC was 481 mm (accounting for 86% of annual precipitation), which was lower than that measured by lysimeter (558 mm). The annual energy balance ratio (EBR) of turbulent fluxes measured by eddy covariance against the independently available energy was about 0.78. TheEBR in the growing season was higher than that in the non-growth season. When the friction-velocity (u^*) was less than 0.25 m·s^-1, the EBR increased with the increasing u^*. There was no significant change in EBR when u^*>0.25 m·s^-1. The changes in soil heat flux relatively lagging behind the net radiation might be one of the causes of energy imbalance. The value of ET measured by EC was getting close to that by lysimeter with the increases of net radiation, temperature and wind speed. Soil water content had no obvious effect on ET measured by both methods. The results suggested that there was a good relationship of the ET obtained with both methods, but ET may be underestimated by EC in this meadow ecosystem.

Assessment of phage diversity in Drosophila melanogaster intestine by RAPD-PCR.

DU Bei-bei, SUN Hao, YANG Wei-chao, DONG Yu-ling, XU Hui

2019, 38(11):  3560-3566. 

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As one of the main drivers of microbial community structure and function, virus is of great significance in studying the ecologically evolutionary processes of microbial community in animal’s intestine. In this study, the ecological characteristics of intestinal phage were explored using Drosophila melanogaster as a model with random PCR amplification of polymorphic DNA (RAPD-PCR) virus fingerprints technique. The results showed that the diversity of phage in wild-type D. melanogaster was higher than that of InR mutant D. melanogaster model. InR mutant D.melanogaster intestinal phage may undergo a short-term disturbance after hatching into adults, with the intestinal phage diversity of day 15 being significantly lower than that on day 3. In contrast, no significant changes were found in healthy wild-type fruit flies. The abundances of phages and bacteria were measured using an epifluorescence microscope. The wild-type D.melanogaster free phages and bacteria on day 3 and day 15 were all at a stable state. On the third day, the abundance of the InR mutant D.melanogaster intestinal bacteria was significantly reduced, and the virusbacteria abundance ratio (VBR) was significantly higher than other groups. On the 15th day, the diversity of InR mutant D.melanogaster phage was reduced, and VBR was also significantly lower than other groups. Therefore, the results of this study indicated that there was a significant difference between the InR mutant D.melanogaster phage and the wild-type phage. Moreover, the random polymorphic DNA polymerase chain reaction (RAPD-PCR) virus fingerprint technology is applicable for the rapid assessment of enterovirus diversity.