Table of Content

10 August 2018, Volume 37 Issue 8

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Fine root biomass of artificial forests in loess hilly region and its influencing factors.

DAI Yin-yue, SUN Ping-sheng, KANG Di, DENG Jian, REN Cheng-jie, YANG Gai-he, HAN Xin-hui, FU Guang-jun

2018, 37(8):  2229-2236. 

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To reveal the difference of fine root biomass among different artificial forests and the driving factors in hilly loess region, we collected fine root samples from plantations with different tree species and stand ages. Fine root biomass and its vertical distribution, community diversity, soil physicochemical properties as well as their relationships were investigated in eight artificial forests, including 40-, 30- and 15-year-old Caragana korshinskii; 45- and 15-year-old Robinia pseudoacacia; 15-year-old Platycladus orientalis; 40-year-old mixed shrubs (Caragana korshinskiiand Prunus armeniaca) and 15-year-old mixed Robinia pseudoacaciaand Platycladus orientalis forest. The results showed that fine root biomass in the 0-30 cm soil layer in artificial forests with same age followed the order of 15-year-old Platycladus orientalis > 15-year-old Robinia pseudoacacia> 15-year-old Caragana korshinskii.The fine root biomass of Caragana korshinskii and Robinia pseudoacacia forests increased significantly with the increases of stand age (P<0.05). The fine root biomass of 40-year-old Caragana korshinskii and 45-year-old Robinia pseudoacacia increased by 57.8% and 41.0% compared with that of 15-year-old Caragana korshinskiiand 15-year-old Robinia pseudoacacia, respectively. There was no significant difference of the fine root biomass between the mixed forests and pure forests of similar stand age. The fine root biomass significantly decreased with the increases of soil depth. The results of RELATE (a nonparametric form of Mantel test) and “Best” model selection procedure showed that the relationships between fine root biomass and soil physicochemical properties were significant (r=0.303,P<0.01), with soil TN and SOC contents showing the greater impacts on fine root biomass. There was no significant relationship between fine root biomass and community diversity in different artificial forests. Our results suggested that fine root biomass of artificial forests can increase with the increases of stand age and thus soil carbon and nitrogen contents.

Effects of photovoltaic panels on the characteristics and diversity of Leymus chinensiscommunity.

ZHAI Bo, GAO Yong, DANG Xiao-hong, CHEN Xi, CHENG Bo, LIU Xiang-jie, ZHANG Chao

2018, 37(8):  2237-2243. 

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Large-scale construction of photovoltaic plants would affect environment and consequently plant community in steppe. In this study, we analyzed the effects of photovoltaic plants on species diversity and the growth status of Leymus chinensis in a steppe of Tumd Left Banner, through vegetation investigation and sampling at different locations under the photovoltaic panels. The results showed that: (1) A total of 14 plant species belonging to seven families and 13 genera were found under photovoltaic panels. L. chinensis was widely distributed at various locations under and around photovoltaic panels. (2) Patrick richness index, Shannon diversity index, Pielou evenness index and Simpson dominance index under the photovoltaic panels were significantly higher than those in the front and rear of the panels. (3) The height, coverage, density and basal stem diameter of L. chinensis under the panels were significantly higher than those in the front and rear of the panels. There was no significant difference in the corresponding indices from south to north in the control. (4) Biomass of L. chinensis under the panels was significantly higher than that in the front and rear of the panels. Moreover, there was no significant difference in the biomass of L. chinensis from south to north in the control group. Our results provide a scientific basis for ecological restoration of the photovoltaic plants in steppe areas.

 

Geographical distribution of vegetation biomass of subalpine meadow in Shanxi Province. 

MA Li, XU Man-hou, ZHOU Hua-kun, JIA Yan-yan, WANG Xiao-xian, Xi Wen-tao

2018, 37(8):  2244-2253. 

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In this study, we selected typical subalpine meadow distributed in Shanxi Province to explore the geographical distribution of vegetation biomass of subalpine meadow at the community level. After biomass was harvested, the variation of total biomass (TB), aboveground biomass (AGB), below-ground biomass (BGB) and root:shoot ratio (R/S) were analyzed at different geographical gradients (longitude, latitude, and altitude). The results showed that TB, AGB, and BGB substantially varied across the region. The variation was the largest for the AGB with a range of 32.50-756.00 g·m^-2, followed by the BGB with a range of 140.50-1586.50 g·m^-2. The variation in TB was the smallest with a range of 248.25-2342.50 g·m^-2. The TB decreased significantly with altitude (P<0.05), whereas increased slowly with longitude (P>0.05), and slightly decreased with latitude (P>0.05). The largest TB was found at 1700-1800 m, 113.4-113.85°E, 35-35.5°N (with an average of 896 g·m^-2). The AGB decreased significantly with increasing latitude and altitude (P<0.001), and gradually increased with longitude (P<0.05). The largest AGB was found at 1700-1800 m, 112.05-112.5°E, 35-35.5°N (with an average of 366.06 g·m^-2). The BGB showed a trend of “decreaseincreasedecrease” as the latitude increased, but increased slightly overall (P>0.05), slightly increased with longitude (P>0.05), and increased significantly with the increases of altitude (P<0.05). The maximum BGB was found at 3000-3100 m, 113.4-113.85°E, 35-35.5°N (with an average 745.63 g·m^-2). The R/S increased significantly with increasing latitude and altitude (P<0.05), slightly increased with longitude (P>0.05), and showed a significant exponential function with latitude and altitude (P<0.05), characterized by isometric growth (average power exponent of 1.025). Results from redundancy analysis showed that latitude and altitude had greater impacts on the biomass of subalpine meadow, while longitude had less impact. The AGB was negatively correlated with longitude, latitude, and altitude. Subalpine meadow allocated more biomass to belowground parts.

Effects of plant diversity on soil microbial community in a subtropical forest.

SU Xiao-lin, LI Ying-Bin, YANG Bo, LI Qi

2018, 37(8):  2254-2261. 

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Changes of plant diversity and composition can directly or indirectly influence soil ecological processes. Tree species traits and diversity are important driving factors for soil microbial community. Based on Biodiversity-Ecosystem Functioning Experiment China (BEF-China) in Xingangshan of Jiangxi Province, we investigated the microbial community composition in four diversity treatments (mono species, 2 species, 4 species, and 8 species) by phospholipid fatty acid (PLFA) method. Our results showed that the soil microbial community structure differed significantly among different plant diversity treatments. The microbial total PLFA increased with the increases of plant diversity from mono species to 4 species, and then decreased at the 8 species treatment. Soil properties explained 28.4% of the variation in microbial community structure, while litter properties explained 12.3% of the total variation. However, the subgroup PLFAs of microbial community showed no significant variation due to the higher heterogeneity in the forest ecosystem and the response lag of belowground ecological processes. Therefore, the effects of plant diversity gradient on the belowground subsystem are needed to be monitored in the long term, in order to accurately evaluate the relations between the aboveground biodiversity and ecosystem function.

Effects of grassland management patterns on soil stoichiometry on the QinghaiTibetan Plateau.

LI Meng-tian, QIN Yan-yan, CAO Jian-jun, XU Xue-yun, YANG Shu-rong, ZHANG Xiao-fang, GONG Yi-fan

2018, 37(8):  2262-2268. 

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After the implementation of grassland contracting system, two grassland management patterns were formed in the QinghaiTibetan Plateau, namely singlehousehold management pattern (SMP) and multihousehold management pattern (MMP). The soil stoichiometry under two grassland management patterns were compared in Nagqu, China. The results showed that in the 0-30 cm soil layer, there were no differences in the ratios of SOC∶ STN, SOC∶STP and STN∶STP between SMP and MMP. In the vertical direction, regardless of management pattern, the SOC∶STP and STN∶STP at the 0-15 cm soil layer were significantly higher than those at the 15-30 cm soil layer. At the 15-30 cm soil layer, the SOC∶STP and STN∶STP were significantly higher under the MMP than under the SMP. In addition to a significant linear correlation between SOC and STN, there were nonlinear coupling relationships between SOC and STP, STN and STP, as well as SOC, STN, STP and their stoichiometric ratios. Phosphorus was a main limiting factor of soil in the study area. Our results suggested that although soil nutrients were significantly different between MMP and SMP, there was no difference in soil nutrient stoichiometry. Therefore, soil stoichiometry may not be effective in evaluating soil quality in this area.

Effects of Cl^- and SO₄^2- inputs on soil organic carbon mineralization in Phragmites australis wetland of the Liaohe estuary.

LIU Kai, YANG Ji-song, YUAN Xiao-min, SHEN Zhuang, ZHENG Dong-mei, ZHENG Jia-yu

2018, 37(8):  2269-2276. 

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Soil samples (0-10, 10-20, 20-30, 30-40 cm layers) of Phragmites australis wetland in the Liaohe estuary were collected, and the closed incubation-gas chromatography was used to examine the effects of chloride (Cl^-) and sulfate (SO₄^2-) concentrations on soil organic carbon mineralization. The results showed that both the mineralization rate and the cumulative mineralization of soil organic carbon in the surface soil (0-10 cm) were significantly higher than those of the subsoil layers (10-40 cm). During the 20day incubation, mineralization rate showed a decreasing trend with time. In the Cl^- treatment groups, the low concentration of Cl^- (75 mmol·L^-1) promoted mineralization, while the high concentration (450 mmol·L^-1) significantly inhibited the mineralization. In the SO₄^2- treatment, there was no significant effect of ionic concentrations on the mineralization rate for all the soil layers. Our results indicate that Cl^- has a stronger effect than SO₄^2- on organic carbon mineralization for P. australis wetland soil in the Liaohe estuary. The increases of salinity in future may accelerate the loss of soil organic carbon in the wetland of Liaohe estuary.

Individual size dependence of the relationship of twig and leaf traits of Lavandula angustifolia.

ZHANG Jing, ZHAO Cheng-zhang, LEI Lei, LI Xue-ping, REN Yue

2018, 37(8):  2277-2284. 

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The variation of branch and leaf traits across plant individuals with different sizes is a canopy building strategy for the adaptation of plants to heterogeneous environment. To examine how twig and leaf traits of Lavandula angustifolia depended on individual size, we conducted an experiment in a three-year-old L. angustifolia plantation in Goldwater Lake Wetland Park, Jinchang, China in late July 2017. Leaf area, leaf thickness, leaf number, twig number, twig length, crosssectional area of twig and bifurcation angle of  L. angustifolia individuals in a 200 m×50 m plot were measured. The plants were classified into three grades based on their volume (size I: d(the cube root of plant volume) ≤60 cm, size II: 60 cm <d≤90 cm, and size III:d>90 cm). Correlation analysis was performed to examine the relationships between twig and leaf traits and individual size. With the increase of plant size, single leaf area, twig number, twig length and twig crosssectional area increased, while leaf number, leaf thickness and bifurcation angle decreased. The leaf area, twig length and number as well as crosssectional area of L. angustifolia were positively correlated with individual size (P<0.05), whereas the leaf number, leaf thickness and bifurcation angle were negatively correlated with individual size (P<0.05). In order to improve the efficiency of resource use, individuals with large size tended to have a large and thin leaves and allocate more biomass to twigs, while small individuals tended to have a small and thick leaves and short, thin twigs. These results reflected the phenotypic plasticity of leaves and twigs for different individual sizes of L. angustifolia.

Contribution of arbuscular mycorrhizal fungi to water absorption by Cyclobalanopsis glauca.

ZHANG Zhong-feng, ZHANG Jin-chi, XU Guang-ping, ZHOU Long-wu, LI Yan-qiong

2018, 37(8):  2285-2292. 

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To examine the contribution of mycorrhizal networks to plant water uptake in karst areas, Cyclobalanopsis glauca seedlings, the main afforestation species in karst areas, were inoculated with mixed Funneliformis mosseae and Rhizophagus intraradices. A root compartmentalization system was used to control the connection between C. glauca seedlings, with adjacent plantsbeing connected only through mycorrhizal networks. Stable hydrogen isotope abundance was used to trace water transport between the mycorrhizal networks and C. glauca seedlings. Our results showed that the density of mycelium decreased with increasing distance from plant roots; the mycelium around C. glauca roots could be found even at a distance of 10-15 cm. There was a significantly positive correlation between hydrogen isotope abundance and mycelial density in the rhizosphere soil. During drought stage, C. glauca seedlings absorbed water via hydraulic lift, with water being transported between adjacent seedlings through the mycorrhizal networks. The contribution of mycorrhizal networks to water transport was estimated using a mixed linear model. The results showed that 1.7%-2.2% of water in the receptor chamber of seedlings was absorbed from the soil of donor chamber by the mycorrhizal networks. The results indicated that water transport by mycorrhizal networks is important for plants with shallow roots in the karst area during the dry season.

Effects of extra-deepplanting on shoot growth and root development of Ulmus pumilaL. seedlings in sandy soils.

LIU Chun-peng, LI Xiang-jun, AN Ping, XU Zhen-hua, LIU Ze-yong, MA Chang-ming

2018, 37(8):  2293-2299. 

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Two-year-old seedlings of Ulmus pumilaL. were planted in sandy soils in the downstream region of Yongding River, to study their shoot growth and root development after extra-deep-planting. Long root and commonroot seedlings were planted at 1 m depth of soil (designated as LD and CD, respectively), and commonroot seedlings were conventionally planted at 0.3 m depth of soil as control (CC). In the second year after planting, soil water contents were mea-sured from surface to 1 m depth at 0.2 m intervals. Shoot and root growth parameters were mea sured  at the end of the experiment. Results showed that: (1) Soil water contents in deep layer (below 60 cm) were relatively stable and generally higher than the shallow layer (0-40 cm) throughout the growing season. (2) Shoot growth was significantly different among the treatments, with LD being the best and followed by CD and CC. (3) Root development was generally better in LD treatment than the other two treatments. (4) The distribution of roots were different among treatments, whereas whole root and fine roots at different soil layers exhibited similar distribution in each treatment. Roots were intensively developed in 0-0.2 m for the LD, in 0-0.2 and below 0.8 m for the CD, and in 0-0.4 m for the CC. No roots were found below 0.8 m in CC treatment. The growth of LD seedlings was better than CD and CC ones. Root distribution pattern of LD corresponded with the water distribution in different soil layers, which may be contributed to the water absorption of seedlings. Therefore, we recommend long-root seedlings with extra deepplanting for afforestation in arid sandy lands. Considering the low cost of transportation and appropriate root distribution, commonroot seedlings can also be recommended for afforestation.

Effects of straw incorporation modes on root distribution and water use efficiency of spring maize in Northeast China.

HANG Wen-ke, SU Si-hui, SUI Peng-xiang, TIAN Ping, MEI Nan, WANG Feng, WANG Mei-jia, ZHANG Jiao, QI Hua

2018, 37(8):  2300-2308. 

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To investigate the practicability of straw strip incorporation mode in Northeast  China, six straw incorporation modes were arranged in Tieling County, Liaoning Province. Compared to wholelayer rotary tillage (T1S0) and wholelayer plowing tillage (T2S0), the four strawincorporation modes of interrow rotary tillage (T1S1), intervalrow rotary tillage (T1S2), interrow plowing tillage (T2S1) and intervalrow plowing tillage (T2S2) had significant effects on soil water content, root distribution, maize yield and water use efficiency. The plow pan profiles were broken under T2S1 and T2S2, which decreased soil bulk density and improved soil water storage capacity. Total root biomass was increased under T2S1 and T2S2, with enhanced proportions of deep roots in soil profiles. Compared to T1S0, the depths of root length density concentrated area were increased by 46.54% and 49.87% for T2S1 and T2S2, respectively. Compared to T2S0, the depths of root length density concentrated area were increased by 37.50% and 40.70%, respectively. Leaf area index was significantly increased under T2S1 and T2S2, which could delay leaf senescence and improve dry matter accumulation. There was no significant difference in dry matter weight and leaf area index among T2S1, T2S2 and T2S0, but the mean value of T2S1 and T2S2 increased by 25.02% and 21.93% respectively compared with T1S0.  T2S1 and T2S2 resulted in the highest leaf protective enzyme activity and the lowest MDA content. In dry-year, yields of T2S1 and T2S2 were increased by 3.80% and 4.05% respectively compared to T1S0. In wet-year, yields had no significant differences among these treatments. For both years, T2S1 had the highest water use efficiency and followed by T2S2. They had 16.28% and 12.77% higher water use efficiency respectively compared to T1S0. Therefore, mode T2S2 is worth for more popularizing.

Interactive influence of salinity and organic pollutants in soil and irrigation water on the growth of rice seedlings.

SHAO Yu-fei, MA Jian, CHEN Xin, JIN Wen-kai, YU Hai-bo, YUAN Lei

2018, 37(8):  2309-2316. 

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Rice seedlings in some paddy fields of Wulao Village, Wanghua District, Fushun City in the spring of 2017 wilted after irrigation with water from Yangbai River. In situ investigation of soil and irrigation water regarding salinity, polycyclic aromatic hydrocarbons (PAHs) and heavy metals was conducted, followed by experiment with factorial treatments of soil and irrigation water, to reveal the impacts of salinity and organic pollutants from soil and water on the growth of rice seedlings. The results showed that salinity of water and paddy soil exceeded the level of agricultural standard. The concentrations of heavy metal Hg and PAHs in some fields were higher than the standard level of agricultural land, which partially accounted for the rice wilting. Results from the crosssimulation experiment showed that the wilting rate of rice seedlings in contaminated field soil irrigated with water from Yangbai River, artificial saline water or tap water was 89.7%, 79.3% and 0.67%, respectively. In contrast, the wilting rate of seedlings in uncontaminated field soil irrigated with Yangbai River water, artificial saline water and tap water was lower, with wilting rate of 42.3%, 34.7% and 0% respectively. Organic contaminants discriminated the Yangbai River water and artificial saline water under the same salinity, and PAHs and salinity were the main indicators discriminating the contaminated and normal soil in study area. Our results indicated that salinity of paddy field soil was relatively high after longterm irrigation with lesssalty water from Yangbai River, but quickly increased to the unfavorable range of 0.25%-0.58% after a sudden rise in salinity of irrigation water (0.35%), leading to the wilting of rice seedlings. Organic contaminants (PAHs) accumulated in the topsoil further aggravated the wilting of rice seedlings under excess salinity in water and paddy soil.

Regional differentiation of water footprint during summer maize production in Henan Province.

MAO Jun, SHAO Rui-xin, GUO Jia-meng, WANG Yong-chao, YANG Qing-hua

2018, 37(8):  2317-2323. 

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Water footprint during crop production, an aggregative indicator quantifying the utilization of water resource during the whole crop development, clearly reflects the type, quantity, and efficiency of water consumption. This tool provides a new method for assessing agricultural water resources management. Based on the calculation of maize productivity, we evaluated the spatialtemporal variations in six different regions of Henan during 1990-2015. The water footprint of maize production in Henan stayed at a low level after decreasing with fluctuation. The water footprint varied greatly among different regions. The western region of Henan Province had the highest water footprint, while the eastern, mid-southern and northern parts of Henan had lower water footprint than the average value at province level. The major portion (80%) of water footprint during maize production was contributed by green water. Temporally and spatially, the proportion of green water was negatively correlated with the precipitation during maize growth period. Based on the analysis of water footprint of the maizeproducing region, it is a good choice to use the stressresistant varieties to increase water use efficiency, and decrease area of maize planting in the western and southern parts of Henan where water footprint was high. However, the maize planting area should be maintained or expanded in the eastern, central southern and northern parts of Henan where the water footprint was lower.

Effects of clonal integration on tolerance to burial in Mikania micrantha under different soil nutrient conditions.

HUANG Qiao-qiao, SHEN Yi-de, FAN Zhi-wei, WANG Ya, LIU Yan, LI Xiao-xia

2018, 37(8):  2324-2330. 

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Clonal plants can adapt to stressful environments through clonal integration, the effects of which on stress tolerance may be environmentdependent. With a greenhouse pot experiment, we examined the effects of clonal integration on the tolerance to partial burial (only distal ramets were buried) of clonal fragments (with two nodes) of the noxious invasive species, Mikania micrantha, in Hainan under different soil nutrient conditions (low or high level). The results showed that when the distal ramets were buried at 3 cm depth, they all emerged with a high rate, regardless of the existence of clonal integration. When the distal ramets were buried at 6 cm depth, clonal integration significantly increased emergence rate (from below 17% to 67%). These results were independent on soil nutrient conditions. For the clonal fragments with emergence of both their proximal and distal ramets, burial depth and clonal integration did not significantly affect their total biomass, although the biomass of proximal or distal ramets might be changed. Even for clonal fragments with distal ramets buried at 6 cm depth, clonal integration could maintain their biomass at a level similar to that with distal ramets unburied. These results were also not dependent on soil nutrient conditions. Therefore, clonal integration is one of the ecological strategies of M. micrantha to adapt to partial burial, which could increase the survival of the buried ramets of M. micrantha and plant fitness when subjected to partial burial. The effect of clonal integration on emergence rate and biomass production of M. micrantha did not significantly differ under different soil nutrient conditions, which may be due to that the amount of resources transported between clonal ramets had no variation, or that the burial depth (6 cm) was not enough to lead to differences in plant growth.

Effects of nitrogen nutrition on the growth and active components of Isatis indigotica Fort. seedlings.

GUAN Jia-li, WANG Gang, Chen Xi, ZHANG Meng-rui, MIAO Yu-jing, TANG Xiao-qing

2018, 37(8):  2331-2338. 

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To study the effects of nitrogen (N) nutrition on the growth and active components of Isatis indigoticaFort., five N levels (0, 2.5, 5, 10, 15 mmol·L^-1, designated as N0, N1, N2, N3, N4 respectively) were applied in a pot experiment in greenhouse. The growth characteristics, photosynthesis parameters, N assimilation contents, N metabolism enzyme activities, the contents of indigo, indirubin, and total flavonoid in leaves and epigoitrin content in roots were measured. The results showed that plant height, main root diameter, and dry biomass of I. indigotica seedlings significantly decreased and rootshoot ratio increased under N0-N3 treatments. With the decreases of N level, the chlorophyll content, carotenoid content, net photosynthetic rate, transpiration rate and stomatal conductance of leaves gradually decreased, while the intercellular carbon dioxide concentration increased. The contents of soluble protein, free amino acid, and nitric N in leaves were decreased, and nitrate reductase activity and glutamine synthase activity were inhibited under low N nutrition. The contents of indirubin and total flavonoid in leaves under N0-N2 treatments were at higher levels. In contrast, contents of indigo in leaves were decreased significantly under low N nutrition and epigoitrin contents in roots were the lowest at N0 treatment. In conclusion, the growth and partial physiological characteristics of I. indigotica seedlings were significantly influenced by low N levels. The contents of indigo in leaves and epigoitrin contents in roots were declined under low N levels, while the accumulations of indigo and total flavonoid were promoted. Considering the biomass and active component contents, the yield and active components will show good performance under the N application levels of 10-15 mmol·L^-1.

Time-concentration effects of GA₃ on germination of Astragalus membranaceus under severe drought and salt stresses.

WANG Nan, GAO Jing, HUANG Wen-jing, LI Bo, TANG Zhi-shu, SONG Zhong-xing, LIU A-Ping

2018, 37(8):  2339-2344. 

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To explore the influences of soaking time and applied concentration of GA₃ on seed germination of Astragalus membranaceus under severe drought and salt stresses, five concentrations (0, 50, 100, 200 and 400 mg·L^-1) of GA₃ were used to soak seed separately in five duration periods (6, 12, 24, 36 and 48 h), and then treated seeds were transferred to -0.6 MPa PEG and -0.9 MPa NaCl solutions to conduct experiment, with total germination percentage and mean germination time being measured. With the extension of soaking time and increased GA₃ concentration, total germination percentage of A. membranaceuswere enhanced under both stresses, and the differences were significant among treatments (P<0.05). Under NaCl stress, the highest total germination percentage was 83.33%, which occurred in treatment of soaking seeds for 36 h with 100 mg·L^-1 GA₃. Under PEG stress, the highest total germination percentage was 80.00% which occurred in treatment of soaking seeds for 48 h with 100 mg·L^-1 GA₃. Total germination percentages were suppressed in high concentrations (more than 200 mg·L^-1) of GA₃ over 24 h. Changing seed coat’s permeability and enhancing embryo viability may be the key factors under GA₃ soaking treatments, which effectively promoted seed germination. Results simulated by Design Expert software indicated that 100 mg·L^-1 GA₃ with soaking seeds for 36 h would be an optimum treatment for germination under integrated severe osmotic stress.

Effects of calcium on stress-resistance physiology and photosynthesis of Polygonatum cyrtonema Hua under high temperature and strong light stress.

LIANG Yong-fu, WANG Kang-cai, SUI Li, XUE Qi, YI Jia-ning

2018, 37(8):  2345-2353. 

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To understand whether exogenous calcium could alleviate damages in Polygonatum cyrtonema Hua caused by high temperature and strong light stresses, the effects of different Ca²⁺ concentrations on the photosynthesis and physiological indices of stressresistance of P. cyrtonema were assayed under high temperature and strong light environment. P. cyrtonema was cultivated in pots and irrigated with modified Hoagland’s solution with five Ca²⁺ concentrations (5, 10, 15, 20, 25 mmol·L^-1). Stress treatments were started by exposing plants to high temperature and strong light, with photosynthesis and physiological parameters being measured ten days later. The biomass of roots and stems and the contents of active compounds were measured after P. cyrtonema were tumbled. There were two controls, with plants being irrigated with Hoagland’s solution and cultivated at 25 ℃/shade, as well as under high temperature and strong light. The results showed that proper Ca²⁺ concentration alleviated damages of high temperature stress by enhancing the activities of SOD and CAT, inhibiting hydrogen peroxide (H₂O₂) and superoxide anion radical (O₂^-_·) accumulation, and reducing malonaldehyde content and relative conductance. Furthermore, the addition of Ca²⁺ increased chlorophyll contents, stomatal conductance, proline and soluble protein contents, maximal photochemical efficiency of photosystem II (F_v/F_m), effective quantum yield of photosystem II (Yield), relative electron transport rate (ETR) and photochemical quenching index (q_P) and decreased NPQ. The stressresistance of P. cyrtonema was declinedwith increasing Ca²⁺ concentration. In this study, Ca²⁺ concentration at 10 mmol·L^-1 alleviated stress damages in P. cyrtonema caused by high temperature and strong light and increased the yield and content of active compounds.

Physiological manifestations of maize seedling roots regulated by exogenous trehalose under low temperature stress.

LIU Xuan, TIAN Li-xin, TONG Hao-yang, ZUO Shi-yu, LI Jing

2018, 37(8):  2354-2361. 

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To investigate the physiological properties of maize seedlings in enhancing the chilling resistance under exogenous trehalose, a pot experiment was carried out with ‘Xianyu 335’. The effects of 12 mmol·L^-1 exogenous trehalose on root biomass, antioxidant enzyme activities and osmotic adjustment substances of maize seedlings at different chilling temperatures (0, 2, 4, 6 and 8 d) were examined. The results showed that chilling stress significantly inhibited root growth and dry matter accumulation of maize seedlings, increased antioxidant enzyme activity, and destroyed the level of osmotic regulation. In response to trehalose application, root surface area, root length and fresh dry weight of maize seedling significantly increased, activities of SOD, POD and CAT in roots first increased and then decreased, MDA content and relative conductivity in roots significantly reduced. The contents of proline, soluble protein and soluble sugar in the roots were also increased first and then decreased. Compared with the CK+L treatment at the 6th day of chilling treatment, the root surface area, root length and dry weight under the treatment of T+L increased by 18.25%, 4.73%, 2.48% and 21.43%, respectively. The activities of SOD, POD and CAT significantly increased by 17.26%, 23.79% and 30.78%, respectively. The MDA content and relative conductivity significantly decreased by 45.13% and 63.25%, respectively. The contents of proline, soluble protein and soluble sugar in T+L treatment were the highest at the 6th day after chilling stress, being 2.93, 0.51 and 2.58 times higher than that under CK+L treatment, respectively. It is concluded that trehalose can regulate the physiological level of roots of maize seedlings under chilling stress, improve the ability of stress resistance of maize seedlings, and accelerate root growth. Trehalose has a synergistic effect on the physiological regulation of crop growth under low temperature stress. At chilling environment, trehalose can significantly enhance the expression of enzymes in the antioxidant system and the accumulation of osmotic substances.

Genetic variation of Phragmites australis and its relationship with salinity in the coastal wetland of Yellow River Delta.

ZHANG Li-wen, WANG An-dong, ZHAO Ya-jie, CHEN Lin, SONG Jian-bin, YANG Chang-zhi, HAN Guang-xuan

2018, 37(8):  2362-2368. 

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Investigating plant genetic diversity can provide basic knowledge for vegetation conservation and ecological restoration. Leaves of 280 individuals from seven Phragmites australis populations in the Yellow River Delta were sampled. We analyzed the genetic structure and diversity of seven P. australis populations at 12 loci using microsatellite markers, and analyzed the relationship between genetic diversity and salinity. Results showed that the genetic diversity in these P. australis populations was low. The Nei’s genetic diversity index (H) ranged from 0.077 to 0.107 and the Shannon information index (I) ranged from 0.133 to 0.185. However, the genetic diversity of two populations from high marsh was relatively high (H=0.101-0.107, I=0.176-0.185). The genetic divergence of these populations was low (G_ST=0.062), with most of them coming from intrapopulation. Moreover, there was no significant relationship between genetic distance and geographic distance (r=0.026, P=0.354). However, the relationship of genetic diversity and salinity was positively significant (R_{adj 2}=0.597, P=0.026). These results suggested that P. australis populations from tidal marsh in the Yellow River Delta should be protected and that seedlings or propagules from populations of other regions could be used to enrich genetic diversity of P. australis in the degraded wetland during restoration.

The bioinformatics analysis of P450nor from algae.

WANG Qun, XIAO Xuan, SHAO Yi-lun, SUN Hao, XU Hui

2018, 37(8):  2369-2375. 

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Nitrous oxide (N₂O) is an important greenhouse gas, which could be produced by bacteria, fungi, algae and higher plants. Bacteria produce N₂O through nitrification and denitrification. P450nor is the key enzyme involved in the production of N₂O in fungi. However, the mechanism of N₂O production in algae and higher plants has rarely been reported. In this study, algae, whose evolution status is between fungi and higher plants, was taken as a research object. From the uploaded data in GenBank, we obtained three different P450nor protein sequences from three algae species (Chlamydomonas reinhardtii, Gonium pectorale and Chlorella variabilis), which were systematically close to P450nor protein from fungi. Then, their functions and evolutionary relationships were examined. Those proteins are considered as soluble, non-secretory and hydrophilic ones in mitochondria. All of them included Pfam P450 conserved domain and three conserved motifs, suggesting that algae P450nor is highly conservative. Evolutionary analysis showed that the P450nor of algae and fungi has a high homology, implying that P450nor of algae and fungi have similar biological functions. Due to the special phylogenetic status of algae, our results would provide  molecular evidence for N₂O biosynthesis of algae and a clue to the imbalance of global N₂O budget.

The species diversity of butterfly community in Saihanwula Nature Reserve of Inner Mongolia.

GE Xin-yu, HONG Xue-meng, MA Fang-zhou, LIU Bo, LI Jun-lan

2018, 37(8):  2376-2383. 

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To understand diversity of butterfly community and the effects of human disturbance in different habitats of Saihanwula Nature Reserve, butterfly community composition was surveyed from 2016 to 2017 in five different habitats, i.e. mountain grassland, river wetland, mountain forest, typical steppe, and wetland meadow. A total of 1826 butterfly individuals were collected, of which 71 species belonging to five families 55 genera were identified. Pieridae had the most number of individuals. Nymphalidae had the most number of species and families. The composition of butterflies differed among different habitats. The highest species number was in mountain forest, with 58 species from 47 families, while the least was in the typical steppe, with 10 species from nine families. The analysis of butterfly community characteristics showed that the Nymphalidae had the highest Shannon diversity index (2.93) and Margalef richness index (5.44). Hesperiidae had the highest Pielou evenness index (0.86) and Papilionidae had the highest Berger-Parker dominance index (0.77). There was a significant difference in the diversity of butterflies among habitats, with the diversity index being the highest in mountain forest and the lowest in the typical steppe. Moreover, the diversity index of butterfly community had obvious temporal pattern, being the highest in July and the lowest in September. The Jaccard community similarity (0.43) was the highest between mountain grassland and wetland meadow. There was a clear relationship between diversity of butterfly community and vegetation type. Human disturbance had negative effects on butterfly community diversity.

Distribution and spatial autocorrelation pattern of arthropods in agricultural landscape.

BIAN Zhen-xing, GUO Xiao-yu, YU Miao

2018, 37(8):  2384-2393. 

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Understanding the distribution and spatial autocorrelation pattern of arthropods in cropped and non-cropped habitats is a basis for optimizing agricultural landscape layout and composition. In this study, arthropods were sampled from three sites with 1 km×1 km grids with a proportion of non-cropped habitats from 10% to 20% in Liaozhong County in the lower Liaohe Plain. The distribution of arthropods was analyzed and spatial autocorrelation of arthropods onregional and local scales was analyzed based on GeoDa. The results showed differences in the average number and population size of arthropods among different habitats, with the most individual number of arthropods in ditches. The individual number decreased from woodland, grassland, pond, hedge, farmland, rural road to orchard. The population size of arthropods decreased from farmland, woodland, hedge, rural road, ditch, grassland, pond to orchard. The spatial distribution of arthropods had significant spatial autocorrelation and aggregation status. There were “hot spots” with high-high aggregation of arthropods in ditch, grassland, woodland and hedge, whereas there were “cold spots” with low-low aggregation of arthropods in continuous farmland. There were no obvious high-high aggregation areas in rural road and orchard. Therefore, agricultural landscapes combined with ditches, grasslands, woodlands and hedges had positive effects on arthropods quantity.

The phototaxis behavior of Schizothorax prenanti in low light intensity.

XU Jia-wei, CHEN Jing, LIN Chen-yu, LIU Yan, BAI Yan-qin, ZHANG Ning, YING Ru-cheng, SHI Xiao-tao

2018, 37(8):  2394-2402. 

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The color preference and phototactic behavior of wild subadult Schizothorax prenanti were investigated, aiming at finding out their preference for light color and light intensity. Fish behaviors were observed under five different lighting conditions (red, yellow, blue, green and dark) and three flow rates (0, 0.15 and 0.30 m·s^-1). In the light color selection experiment, the color preference in static water was observed under the different lighting conditions with the luminance intensity of 10 lx. The color preferable order of S. prenanti for the five kinds of light colors was green, blue, black, red and yellow. The distribution ratio and selection index in the green and blue light regions were greater than that in the red and yellow light regions (P<0.05). In the phototaxis experiment, the phototactic behaviors were observed under different flow rates (0, 0.15 and 0.30 m·s^-1) at the luminance intensity of 20 lx. The results indicated that S. prenanti showed a positive phototactic behavior to the blue and green light under the hydrostatic and hydrodynamic conditions. In contrast, fish showed a negative phototactic behavior to the red and yellow light. S. prenanti preferred low luminance intensities and the phototactic behavior did not increase with increasing water flow rate. The phototactic threshold was 1.40-2.65 lx. Our results indicated that green light with a luminance intensity of 20 lx is appropriate for attracting S. prenanti in the engineering projects.

Contribution of basal carbon sources to aquatic animals in typical sections of the Pearl River.

ZENG Yan-yi, YANG Wan-ling, LI Hai-yan, PENG Song-yao, LAI Zi-ni

2018, 37(8):  2403-2410. 

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The destruction of riverine habitats and the decline in the integrity of aquatic functions is a problem in the Pearl River due to over-exploitation and over-utilization of water resources. To protect river habitats and maintain the integrity of river ecosystems in the Pearl River, we need to know how different carbon sources contribute to the aquatic food web. The potential basal carbon sources and dominant consumers were sampled in three typical sections of the Pearl River in March and August 2015, with the δ¹³C and δ¹⁵N of potential carbon sources and dominant consumers being then determined. The IsoSource estimation results showed that, in the wide-open water upstream habitats, C₃ plants contributed more than 50% (within the 50% confidence level) to the dominant consumers. The downstream habitats were covered by large areas of submersed plants, which contributed almost, or more than 50% (within the 50% confidence level) to local consumers. In the downstream habitats, submersed plants became the dominant source to most consumers, while C₃ plants were the secondary carbon source. In the bifurcation section, phytoplankton contributed nearly or more than 40% (within the 50% confidence level) to the local consumers and became the dominant source supporting many consumers, while both submersed plants and C₃ plants were secondary sources. Therefore, the primary contribution sources to local consumers varied in different river sections with different habitats, which may be related to the proportion of different carbon sources and their availability to consumers. Our results suggest that the conservation of multiple habitats is essential for maintaining the functional integrity of aquatic ecosystems of the Pearl River.

Vertical distribution of Daphnia ephippia and its correlation with total nitrogen and total phosphorus in the sediments of Meiliang Bay in Lake Taihu.

HE Ping, ZHANG Kun, DENG Dao-gui, LIU Qi, GUO Hong-hui, ZHANG Ting-ting, SUN Yu-chen

2018, 37(8):  2411-2417. 

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The vertical distribution of ephippia (or resting eggs) of Daphnia species and its correlation with the concentrations of total nitrogen and total phosphorus in the sediments (25-1 cm) of Meiliang Bay in Lake Taihu were studied. The results showed that the ephippia of threeDaphnia species (D. galeata, D. pulex and D. similoides sinensis) in the sediments of Meiliang Bay were identified, with D. galeata being the dominant species. The ranges of average ephippial density and the density of ephippia containing resting eggs of Daphnia species were 0.03-2.01 and 0-0.33 ind·g^-1 dw, respectively. The average densities of ephippia containing resting eggs of three Daphnia species at the T₁ and T₂ sampling points were higher than that at the T₃ sampling point. In the sediment layers of 16-1 cm, the concentration of total nitrogen (TN) at the T₁ sampling point and that of total phosphorus (TP) at the T₂ sampling point showed obvious increasing trends, while their changes at the T₃ sampling point were limited. There was a significant relationship between ephippial densities of D. pulex and TP content at the T₁ sampling point (P<0.05), while the ephippial densities of D. similoides sinensis at the T₃ sampling point and the density of ephippia containing resting eggs of D. galeata at the T₂ sampling point were significantly correlated with both TN and TP contents (P<0.05). The vertical distribution of the ephippial (or resting eggs) density ofDaphnia species in the sediments could recur the historical succession of Daphnia species in lakes, which was related to the levels of total nitrogen and total phosphorus.

Characteristics of plankton community structure and eutrophication status in Dongting Lake in the season with normal water level.

WANG Meng-qi, WANG Jin-cheng, WANG Qi, YANG Chao-yun, ZOU Zhen-hua, QIAN Bao

2018, 37(8):  2418-2429. 

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To evaluate plankton community structure and eutrophication status in Dongting Lake, water quality and the current situation of plankton community structure were investigated inAugust 2017. There were 24 sampling points, which distributed in “Sankou”, “Sishui” and other inflow river cross sections, lake regions and outlet sections. The results showed that phytoplankton in Dongting Lake had a total of 75 species belonging to 53 genera from six phyla. The average algae density was 458.3 × 10⁴ cells·L^-1, and average biomass was 0.92 mg·L^-1 (ranging from0.06-3.64 mg·L^-1). Cyanophyta and Bacillariophytadominated in Dongting Lake, which made the lake a Cyanophyta Bacillariophyta lake.Aulacoseira granulata and Cyclotella comensis were the dominant species in “Sankou” while Aulacoseira granulata and Microcystis aeruginosa dominated in “Sishui”. Aulacoseira granulata, Microcystis aeruginosa, Merismopedia tenuissimaand Phormidium tenue were dominant species in lake regions. In terms of zooplankton, 20 genera from four phyla were identified, with total density from 5.0 to 3.4×10³ ind·L^-1. Dominant zooplankton varied with “Sankou” (Difflugia), “Sishui” (Difflugia and Tintinnidium) and lake regions (Difflugia and Polyarthra). To evaluate the eutrophication level, we used three assessment methods, including comprehensive nutritive index, Shannon index and Margalef index. All indices indicated that the lake was under eutrophication. Compared with other freshwater lakes such as Taihu and Chaohu, Dongting Lake was positioned at the lower trophic level and had relatively lower algal density. However, the trend of historical eutrophication implied that the water quality status in Dongting Lake was not optimistic. As a result, more attention should be paid to water body of Dongting Lake and endeavor on ecological remediation is critically needed.

Distribution characteristics of jack mackerel (Trachurus japonicus) habitat in the offshore waters of northern South China Sea.

YAN Ran, FAN Jiang-tao, XU Shan-nan, XU You-wei, SUN Ming-shuai, CHEN Zuo-zhi

2018, 37(8):  2430-2435. 

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We analyzed the temporal and spatial distribution of jack mackerel (Trachurus japonicus) in the offshore northern South China Sea, based on the eight-cruise data of the offshore fishery resource survey in the northern South China Sea from 2014 to 2017 and remote sensing image data, including sea surface temperature, sea salt surface mass concentration, and chlorophyll concentration. We established habitat suitability index (HSI) model for each season with utilization of maximum model, minimum model, arithmetic mean model and geometric mean model separately. The catch per unit effort (CPUE) was used as suitability index (SI). The accuracy of each model was tested. The results showed that each SI model fitted accurately and had a normal distribution. Geometric mean model was better for habitat modeling, with an average accuracy of 92%. The area of high biomass mainly distributed in area with HSI more than 0.6, and the other area of high HSI would be potential fishing grounds. Results from principal component analysis showed that sea surface temperature was the most significant factor affecting the distribution of offshore jack mackerel. Our results indicated that HSI models can be used to analyze abundance and spatial distribution of offshore jack mackerel resources in the northern South China Sea.

Effects of the pattern of agricultural shelterbelt network on evapotranspiration of oases in arid region: A case study from Sangong River basin in Xinjiang.

SUN Hao, LIU Li-juan, LI Xiao-yu, ZHANG Zhen-yu

2018, 37(8):  2436-2444. 

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As the most sensitive component of water expenditure of farmland in arid region, evapotranspiration is a key component of water and energy balance in oasis ecosystems. Shelterbelt is an important ecological barrier to oasis farmland in arid region, with undeniable impacts on evapotranspiration of oasis farmland. In this study, the impacts of distribution patterns of farmland shelterbelts on oasis evapotranspiration were studied in the typical watershed of the north slope of the Tianshan Mountains in Xinjiang. The results showed that the shelterbelts can not only effectively reduce the evapotranspiration of oasis farmland, but also maintain the relatively stable evapotranspiration at a relatively low level at a certain extent. For the pattern function of the shelterbelts, there was a significant and negative correlation between the ratio of belt to patch and the evapotranspiration of shelterbelts (P<0.01), the ring degree and farmland evapotranspiration were negatively correlated (P<0.05), while the connectivity had no significant effects on evapotranspiration (P>0.05), indicating that the distribution density of shelterbelts and the degree of formation of shelterbelt network structure had significant effects on farmland evapotranspiration, whereas the connectivity of the shelterbelt network with basic grid shape had no effect on evapotranspiration. Our results suggest that studying the impact of shelterbelt pattern on evapotranspiration at the landscape level would be helpful for the planning and management of farmland shelterbelts.

Spatial variability of soil salinity and “salt island” effect around oasis reservoir in arid area.

CHAI Chen-hao, WANG Yu-gang, ZHOU Hong-fei, ZHU Wei, LIU Li-juan

2018, 37(8):  2445-2452. 

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Oasis reservoir, a node of hydraulic system in the inland river watershed, plays an important role in transporting water in the process of regional agriculture development. We examined the effect of reservoir on soil salt accumulation with the Binghu Reservoir and Liuchengzi Reservoir in the Sangong River watershed as cases. The spatial variability of soil salinity around reservoir under two landscape types was studied by classical statistics, geostatistics and GIS. The results showed that: (1) Salt contents of soil profiles were higher in the natural landscape type around Liuchengzi Reservoir (0-20 cm: 20.77 g·kg^-1; 20-40 cm: 14.96 g·kg^-1; 40-60 cm: 16.9 g·kg^-1) than that of Binghu Reservoir (0-20 cm: 7.81 g·kg^-1; 20-40 cm: 5.66 g·kg^-1; 40-60 cm: 5.24 g·kg^-1) dominated by the irrigation landscape. Soil salt content showed a great variability (CV>100%) in each soil layer around the Binghu Reservoir and was moderately variable (10%<CV<100%) around the Liuchengzi Reservoir. (2) Soil salt content had a moderate spatial autocorrelation (0.25<C₀/(C₀+C)<0.75) around both reservoirs. Spatial dependence of soil salt content was mainly due to random factors resulted from the strong anthropogenic activities around Binghu Reservoir. The influence of structural factors gradually increased with soil depth. In contrast, the spatial variability of soil salinity was mainly induced by structural factors around Liuchengzi Reservoir. (3) There was “salt island” phenomenon around the agricultural reservoirs. Non-saline soil was a major type around the Binghu Reservoir, with the area of which increased with soil depth. However, saline soil was a dominant type around the Liuchengzi Reservoir, whose area increased with soil depth.

The variation of ecological sensitivity in Guangdong Hong KongMacao Greater Bay Area in recent 20 years.

GAN Lin, CHEN Ying-biao, WU Zhi-feng, QIAN Qing-lan, ZHENG Zi-hao

2018, 37(8):  2453-2462. 

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Ecological sensitivity assessment, an important method to study the potential problems of regional ecology, plays an important role in regional ecological planning and management. In this study, we selected seven sensitive factors from the aspects of natural ecology, city expansion and ecological services, and established level index system of sensitive factors. We assessed ecological sensitivity of single factors and comprehensive factors using the analytic hierarchy process (AHP) under GIS platform. The results showed that: (1) From 1997 to 2007, the proportion of zones with nonsensitivity or low sensitivity increased by 3.91%, the proportion of moderate sensitive zone decreased by 0.57%, and the proportion of extreme sensitivity zone and high sensitivity zone decreased by 3.31%, indicating an overall reduction in ecological sensitivity. (2) From 2007 to 2017, the proportion of zones with nonsensitivity or low sensitivity increased by 2.38%, the proportion of moderate sensitivity area decreased by 3.71%, and the proportion of extreme sensitivity zone and high sensitivity zone increased by 1.32%, indicating an overall declining trend of ecological sensitivity. (3) High sensitivity areas were mainly distributed in woodlands and nature reserves in Zhaoqing, Huizhou, and Jiangmen. Ecosystems in these areas were vulnerable to disturbance, so protection should be strengthened. Low sensitivity areas were mainly distributed in Guangzhou, Shenzhen, Foshan and other central cities where ecosystems had good stability. These ecosystems can be reasonably exploited and utilized when their safety is guaranteed. Our results provide scientific basis for green sustainable development and environmental management in the Guangdong Hong KongMacao Greater Bay Area.

Land surface temperature fluctuation characteristics and key influencing factors in estuarine wetland.

ZHENG Hui-zhen, CHEN Yan-hong, PAN Wen-bin, ZHENG Peng, CAI Yuan-bin

2018, 37(8):  2463-2470. 

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We analyzed land surface temperature (LST) fluctuation characteristics in urbanization based on retrieval of LST, profile analysis and model construction in the wetland distribution area of Minjiang River. The results showed that: (1) Dramatic changes in land use/land cover had occurred from 1993 to 2016 in this area. The area of water, forest, grassland, cropland, and wetland decreased, while the built-up land increased. Especially, the area of wetland decreased from 37.00 km² to 29.15 km². (2) The LST varied with different land use types. For instance, builtup land and bare land had positive contribution on LST rise, while waters, forest, grassland, and wetland had opposite effects. The LST increased during wetland deterioration, which had a negative impact on cooling effect. (3) The urban expansion transformed wetland to builtup land, which played a key role in the fluctuation of LST. (4) There was a negative correlationbetween LST and normalized difference vegetation index (NDVI) and normalized difference moisture index (NDMI), and a positive correlation between LST and normalized difference impervious surface index (NDISI). (5) The NDMI and NDISI played a greater role in LST than did NDVI. The results would be helpful in estuarine wetland conservation in the future.

The influence of the construction of Xi’an Metro Line 2 on land use change.

WEI Zhong-yu, SU Hui-min, HUANG Rong-jing

2018, 37(8):  2474-2482. 

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Taking the areas of 800 m surrounding Xi’an Metro Line 2 as research object, the Google Earth’s high-resolution images in 2005, 2011, and 2017 were used to obtain land use data. The impacts of rail transit construction on land use were analyzed, and a prediction of land use transformation was made based on the CA-Markov model. Results showed that: (1) The construction of urban rail transit accelerated the transformation of land use types. Low-density and low-income lands, such as agricultural land and forest land, were converted to high-density and high-income lands, such as residential land. (2) Changes of station types mainly occurred in the beginning of operation phase of the rail transit and the station types were transformed to characteristic ones gradually. (3) The results predicted by the CA-Markov model revealed that the proportion of traffic facilities and the secondclass residential lands around the metro stations would increase in the future, while the proportion of the third class residential and industrial lands would decrease. In conclusion, land use types around the metro stations were relatively scattered around rail transit system and some metro stations were not well integrated with their surrounding buildings. Therefore, land use types around rail transit need further optimization to obtain optimal land use pattern and maximum land revenue.

Analysis on the spatio-temporal changes of PM₁₀ concentration over Ningxia using satellite remote sensing.

MAO Hui-qin, CHEN Hui, LI Qing, ZHANG Yu-huan, WANG Zhong-ting

2018, 37(8):  2483-2489. 

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To clarify the changes of atmospheric environment in Ningxia since 2013, PM₁₀ concentration over Ningxia from 2013 to 2016 was retrieved using a geographically weighted regression procedure based on satellite remote sensing, meteorological data and ground-based PM₁₀observation data. Results showed an obvious spatial variation of PM₁₀ concentration in Ningxia, with much higher in the middle semiarid regions and along Yellow River areas and much lower in the southern and northwest mountain regions. The yearly averaged PM₁₀ concentration from 2013 to 2016 over whole Ningxia ranged from 76 to 127 μg·m^-3, with a mean value of 100 μg·m^-3. There were seasonal differences of PM₁₀ concentration, with high values in winter (129 μg·m^-3) and spring (116 μg·m^-3) and low values in autumn (92 μg·m^-3) and summer (68 μg·m^-3). The interannual variation of PM₁₀ concentrations over Ningxia showed a decrease trend from 2013 to 2016, with a decrease rate of 15.8 μg·m^-3 per year. However, the differences of PM₁₀ concentration among different regions of Ningxia had decreased as indicated by the decreases of spatial standard deviation from 14.8 μg·m^-3 in 2013 to 6.5 μg·m^-3 in 2016, with a decrease rate of 2.8 μg·m^-3 per year.

Effects ofTypha angustifolia decomposition system on the remediation of cadmium polluted freshwater.

DU Jing-jing, ZHOU Yin-fei, ZHANG Yu-yan, GUO Rui-lin, LI Ke

2018, 37(8):  2490-2496. 

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We investigated the remediation effects of Typha angustifolia litter and its microbial decomposers on Cd²⁺ induced pollution. The impacts of Cd²⁺ with different concentrations (0.1, 1.0, 10 μg L^-1) on the growth and reproduction of Daphnia carinata were examined firstly and then 0.1 μg L^-1 of Cd²⁺ was used as the test concentration. The growth and reproduction of D. carinata were monitored after the addition of naturally incubated litter and Cd²⁺ incubated litter for 15 and 21 days. The results showed that the survival rate of D. carinata significantly decreased in the presence of Cd²⁺. The highest concentration of Cd²⁺ (10 μg L^-1) showed the strongest toxic effect, with the survival rate of D. carinata being only 40%. The growth and reproduction rates of D. carinatawere significantly improved under both naturally and Cd²⁺ incubated litter. For the reproduction parameters of D. carinata, the time for the first brood was shortened by 1-2 days, the number of offspring was increased by 22%-81%, and the reproduction rate was increased 3.07-4.7 times. Such a result indicated that T. angustifolia litter with microbial decomposers could quickly restore the food chain under Cd²⁺ pollution. Dactylaria and Massarina were the dominant species among the decomposers of T. angustifolia litter, which could perform the remediation effect on cadmium pollution in the aquatic ecosystems.

Temporal and spatial variation of soil heavy metal contents in different vegetation types in Three Gorges Reservoir area.

GUO Yan, CHENG Rui-mei, YANG Shao, SHEN Ya-fei, XIAO Wen-fa, LEI Lei, WANG Xiao-rong

2018, 37(8):  2497-2504. 

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In this study, transfer characteristics and the spatial and temporal variation of metal ions were investigated by measuring concentration of heavy metals in soil from waterlevel-fluctuating zone (flooded elevation: 145-175 m; control elevation: 175-185 m) at Zigui, Three Gorges Reservoir area in 2009 and 2015. Using the geo-accumulation index, we evaluated the pollution degree of heavy metals at different elevations in two waterflooded years. The results showed that the contents of heavy metals accumulated in soil at different altitudes both in 2009 and 2015 were in order of Fe>Mn>Cu (Zn). With the increased duration of flooding years, more heavy metals accumulated in secondary shrub land than in abandoned farmland. The accumulation of soil heavy metals was more obvious in low altitude area, and the flooded elevation facilitated the accumulation of Cu and Fe, while the control elevation facilitated the accumulation of Zn and Mn. The migration of heavy metals did occur in soil of various vegetations: with the increase of water level fluctuation period, the contents of Cu and Zn at water elevation in secondary shrub land was increased, up to 41.1%, 23.1%, 50% and 9.3%, and 28.6%, 50%, 38.6% and 56.8%, respectively. The contents of Cu and Zn in abandoned farmland decreased, with decreasing ranges of 28.3%-48.5% and 15.5%-29.9%, respectively. Through pollution assessment (I_geo), it was found that, after seven times of water level fluctuation, the soil in secondary shrub land was mainly affected by comprehensive pollution (including Cu, Zn, Fe and Mn) while the abandoned farmland was mainly affected by compound pollution (including Fe and Mn).

Research advances in atmospheric sulfur cycle models.

BAI Yang, GUO Qing-jun, GUO Zhao-bing, WEI Rong-fei, SHEN Xiao-yu, WANG Jin-jin, REN jie, FENG Lian-jun

2018, 37(8):  2505-2514. 

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We summarized the basic contents and the applicable conditions of typical atmospheric sulfur cycle models, especially the classical atmospheric sulfur cycle model and the independent sulfur cycle model which is based on OsloCTM2 model. We introduced atmospheric sulfur cycle models which are coupled with some general circulation models such as ECHAM, LMDZ, CSIRO, MASINGAR, RCA2, NICAM and MIROC. Although there are many kinds of atmospheric sulfur cycle models, there are still some problems such as lack of relevant data support, comprehensive consideration of chemistry, radiation and dynamics, and interdisciplinary integrated research in the study of sulfur cycle models. To solve these problems, we proposed to optimize the quality of atmospheric sulfur emission and observation data, establish a shared database system, formulate relevant database usage regulations, strengthen the cooperation and resource sharing among subjects, and establish comprehensive highresolution atmospheric sulfur cycle models.

The current situation and trend of tourism eco-compensation.

LI Shu-juan, GAO Ning

2018, 37(8):  2515-2523. 

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In recent years, environmental problems caused by tourism activities have attracted more and more attention, and thus research on eco-compensation in tourism has been increased. As a systematic institutional arrangement, the main purpose of tourism eco-compensation is to protect the tourism ecosystems and to reconcile the contradiction between tourism development and ecological protection so as to promote the sustainable development of tourism. Therefore, the research on tourism eco-compensation has received attention. Here, we reviewed the related contents of eco-tourism compensation, including concept clarification, subjecobject definition, standard accounting and compensation approach, and expound the status of research in tourism eco-compensation. Meanwhile, we found out the problems of tourism eco-compensation in China by comparative analysis of domestic and foreign research status, to provide reference for perfecting China’s tourism eco-compensation theory and practice. Moreover, we proposed future directions that should be strenthened in tourism eco-compensation research, such as performance appraisal, spatial and temporal distribution, level division, and policy of tourism eco-compensation.

The simulation in wind-driven seed dispersal of Ulmus pumila in sparse woodland steppe.

LIU Ming-yu, TANG Yi

2018, 37(8):  2524-2531. 

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Seed dispersal plays an important role in the natural regeneration of elm (Ulmus pumilaL.) in sparse woodlands. To explore the effects of wind on seed dispersal of elm, an individual based model was build to simulate wind-driven seed dispersal. The results showed that in all wind directions, seed number increased along with the increase of distance and reached the peak at the 3-4 steps (cells), and then seed number decreased. Furthermore, the seed dispersal distance and accumulation in seed number were almost the same in all wind directions. Our results suggest that individual based model is a useful tool to explore seed dispersal process and its influencing factors. Our results are helpful for understanding the regeneration of elm in sparse woodland steppe and thus providing basis for vegetation restoration in the Horqin Sandy Land.

Method and application of climate quality evaluation for juicy peach.

YANG Dong, JIN Zhi-fen, DING Ye-yi, HUANG He-lou, WANG Zhi-hai

2018, 37(8):  2532-2540. 

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The quality evaluation system based on meteorological elements (climate quality) is more convenient and acceptable than that based on physiological and biochemical indices. However, the simulation accuracy of climate quality model needs to be improved. Based on the observational datasets of peach quality and meteorology in Fenghua (2006-2016) and Cixi (2015-2016) in Zhejiang Province, the climate quality of juicy peach was evaluated. The Monte Carlo method and threat score (TS) analysis method were employed to improve the accuracy of the integrated quality evaluation. The spatial and temporal variations of peach quality in Zhejiang were analyzed using the climate quality model. The Monte Carlo method well reduced the uncertainty of integrated quality by 21% (16%-26%). The prediction accuracy of ensemble model constructed by TS score analysis method was significantly higher than that of a single model. The correlation coefficient between the integrated qualities established by the climatic quality ensemble model and biochemical factors based model was as high as 0.97, with the absolute error and root mean square error being 0.01 and 0.02, respectively. From 1971 to 2000, the climate trend rate of peach quality in Zhejiang Province was -0.02·10 a^-1. In the early 21st century, the climate trend rate reached -0.05·10 a^-1, and the annual fluctuation increased. The climate quality of peaches in Zhejiang Province was 0.55 (0.49-0.63), decreasing from coastal regions to inland. The climatic quality evaluation model based on Monte Carlo method and TS score analysis can well simulate the integrated quality of juicy peach in Zhejiang Province, providing an effective method for the refined assessment of peach quality at regional scale.

Effect of preservation methods on culturable microorganisms from Tibetan Plateau lake waters.

GUO Chun-yan, YUE Lin-yan, ZHAO Kang, XING Peng, KONG Wei-dong

2018, 37(8):  2541-2548. 

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A high diversity of psychrophilic and psychrotolerant bacteria have been identified in Tibetan Plateau lakes. Isolating pure strains of these bacteria can provide us essential knowledge on the mechanism of coldadaptation. However, it has always been a technical obstruct on how to transport these precious samples from the field to laboratories without reducing bacterial viability. Here, the influence of water sample preservation methods on the bacterial viability was investigated. We first isolated pure bacterial strains from water samples cryopreserved at -80  ℃ and fridgestored at 4  ℃, and classified these bacteria based on their 16S rRNA gene sequences. Seven unique 16S operational taxonomic units (OTUs) were recovered from the water samples stored at -80  ℃, which were identified asBacillus sp. D-U164(2010), Bacillus simplex, Exiguobacterium sp. Mkj28, Bacillus muralis, Acinetobactersp. L-HG-2BW, Exiguobacterium sp. AC-CS-C2, and Bacillus thuringiensis, respectively. In contrast, 14 OTUs were recovered from the water samples stored at 4  ℃, and were classified as Proteobacterium M71 D72, Chryseobacterium sp. 12 4K, Bacillus sp.HJ14, Bacillus pumilus, Stenotrophomonas sp. LL75,Bacillus muralis, Bacillus cereus, Brevundimonas bullata, Stenotrophomonas sp. Cza24, Microbacteriumsp. VKM Ac2016, Stenotrophomonassp. Ala15, Bacillussp. T4(2013), respectively. Our results indicated that higher diversity of culturable bacteria was recovered from fridgestored water samples than that of cryopreserved. Bacillussp. can be isolated from water samples cryopreserved at -80  ℃ and fridgestored at 4  ℃.