Table of Content

10 August 2019, Volume 38 Issue 8

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The temporal variation of needle’s non-structural carbohydrate and photosynthetic feature with phenological periods in seven spruce species.

WANG Shu-yuan, WANG Ming-hao, NIU Ying-zhi, HE Fei, ZHAO Chang-ming

2019, 38(8):  2283-2290. 

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As one of the main tree species in northeast and western China, spruce is of great significance in forest carbon sequestration, water conservation and ecological safety barrier. The dynamics of non-structural carbon (NSC) provides an important reference for studying forest carbon storage and carbon supply. We recorded the phenology of 10-year-old saplings of seven spruce species in a common garden, and measured the NSC concentration and net photosynthetic rate of current and one-year-old needles. The results showed that the sequencing of germinating stage was Picea asperata < P. wilsonii< P. meyeri < P. likiangensisvar. linzhiensis<P. crassifolia<P. likiangensis var. rubescens<P. koraiensis, the sequencing of extension period was P. meyeri < P. crassifolia < P. asperata < P. wilsonii < P. koraiensis < P. likiangensis var. ubescens< P. likiangensisvar. linzhiensis, but the bud-break period had no variation among species. The phenological differences were manifested by phenotypic acclimation to environmental changes, for instance, effective cumulative temperature (R=0.996^*), soil moisture content (R=-0.807^*), and adaptation to the original habitat. The seasonal dynamics of NSC concentration was similaramong species. The variation of starch concentration of current and one-year-old needles was unimodal and that of soluble sugars increased first and then tended to be stable. Moreover, the NSC concentration of current-year needles was lower than one-year-old needles, with the starch concentration ranging from 20 to 50 mg·g^-1 and 70 to 150 mg·g^-1, and the soluble sugars ranging from 80 to 150 mg·g^-1 and 200 to 350 mg·g^-1, respectively. Furthermore, the net photosynthetic rate always increased after the starch concentration decreased in both types of needles, suggesting the coordination between the net photosynthetic rate and the concentrations of starch and soluble sugar. Our results provide reference for comprehensive understanding NSC seasonal dynamics of different Picea species.

Evaluation of water conservation capacity of Pinus massoniana plantation with different densities in Hubei water source area of Danjiangkou Reservoir area.

DING Xia, CHENG Chang-jin, QI Liang-hua, ZHANG Jian, LEI Gang, LIU Xue-quan

2019, 38(8):  2291-2301. 

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To clarify water conservation capacity of forests in water source area of the Middle Route of South to North Water Transfer Project in flood season, we estimated water conservation capacity of Pinus massoniana plantations with different stand densities in Longkou Forest Farm of Danjiangkou Reservoir area. Three densities (i.e., high, medium and low) of P. massoniana plantations were chosen, and the waterholding capacity of the canopy, litter and soil layers for each density was examined from June to September 2018, using field observations and laboratory analysis. The canopy interception of three densities of P. massonianaplantation ranged from 56.13 to 77.68 mm, which increased with the increasing stand density, while the penetrating rainfall showed an opposite trend. Litter biomass increased with the increasing stand density with a range of12.76-19.56 t·hm^-2. Litter biomass was greater in the non-decomposition layer than that in the semidecomposed layer. The total litter thickness under high density was the largest, followed by medium and low density. The maximum and effective water holding capacity of litter varied from 21.32 to 28.24 mm and from 16.82 to 22.51 mm, respectively. Both parameters showed the following trend: medium density>high density>low density. The water holding capacity and water absorption rate of litter had a logarithmic and power function with soaking time, respectively. Soil bulk density inP. massoniana plantation with low density was the largest, followed by high and medium density, with a range of 1.45-1.54 g·cm^-3 at the depth of 0-30 cm. The rank of total soil porosity for the three stand densities was opposite to that of soil bulk density, with a mean ranging from 42.18% to 45.71%. The effective water holding capacity of soil varied from 2.94 to 4.81 mm, and ranked in the order of medium density>low density>high density.The overall water conservation capacity of P. massoniana plantation was 204-237.55 mm, with an order: medium density>high density>low density. In summary, the medium density ofP. massoniana plantation exhibited the highest water conservation capacity. Reasonable density of P. massoniana stand should be maintained in forest management in the future.

Effects of water level and nitrogen concentration on growth and biomass allocation of Scirpus nipponicus seedlings.

GU Yong-bo, PAN Yan-wen, CHEN Fang-yuan, LOU Yan-jing, TANG Zhan-hui

2019, 38(8):  2302-2309. 

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To understand the effects of different water levels and nitrogen concentrations on growth and biomass allocation of Scirpus nipponicus seedlings in Momoge National Nature Reserve, we conducted a controlled experiment with three levels of water depth (5, 35, 65 cm) and three levels of nitrogen  (4, 8, 12 mmol·L^-1). The results showed that water levels had significant effects on the growth, biomass accumulation and allocation of S. nipponicusseedlings (P<0.05). With water level increasing, individual height of plant increased, tiller number, tuber number and root biomass decreased, the biomass of rhizome, tuber, belowground, aboveground parts and total biomass all increased first and then decreased, biomass allocation to aboveground increased, but that to belowground (include root and tuber) decreased. Nitrogen concentration had significant effects on the plant height, tuber number, aboveground and belowground biomass allocation (P<0.05), but had no effect on tiller number and biomass accumulation (P>0.05). In summary, the optimum water level for the growth of S. nipponicus seedlings was 35 cm. Low water level had a positive effect on the absorption and utilization of nitrogen by plants. Both high water level and high nitrogen concentration had a negative effect on the growth of S. nipponicus.

Effects of plant species identity and diversity on nitrous oxide emission and functional gene abundance in constructed wetlands.

SUN Hong-ying, XIN Quan-wei, LIN Xing-sheng, LUO Hai-ling, LIN Hui, MA Zhi-hui, LAN Si-ren

2019, 38(8):  2310-2317. 

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To investigate the effects of plant species identity and diversity on nitrous oxide emission and functional gene abundance under moderate effluent C/N ratio, we constructed a vertical flow constructed wetlands in the laboratory. Three plant species, Phragmites australis, Lythrum salicaria ,and Pontederia cordata,which are commonly used in constructed wetlands and with good landscape effects, were selected to establish the monocultures of each species and one threespecies mixture. Results showed that nitrous oxide emissions from the mixtures (24597.0 μg N₂O·m^-2·d^-1) were higher than the mean values of the three monocultures (11744.8 μg N₂O·m^-2·d^-1) (P<0.001). Similarly, the absolute abundances of amoA (6.33×10⁷ copies·g^-1 soil) and nirS (1.92×10⁶ copies·g^-1 soil) from the mixtures were also higher than the mean values of the monocultures (5.70×10⁷ and 1.58×10⁶ copies·g^-1 soil). In addition, the effluent NO₃^--N concentrations in the mixtures were lower than that in the three monocultures (P<0.01), but there was no significant difference in the NH₄⁺-N concentration, microbial biomass and plant biomass between the mixtures and the mean values of monocultures (P>0.05). There were significant differences in the nitrous oxide emission, absolute abundance of amoA, absolute abundance of nirS, effluent NH₄⁺-N concentration, microbial biomass and plant biomass among the three monocultures,but with no significant difference in the effluent NO₃^--N concentration among the three monocultures.The effects of plant richness on nitrous oxide emission, amoA absolute abundance and nirS absolute abundance were greater than those of species identity, whereas the effects of plant species identity on effluent NO₃^--N concentration were greater than that of plant richness.

The characteristics of urban forest structure within the Sixth Ring Road of Beijing.

MA jie, JIA Bao-quan, ZHANG Wen, LIU Xiu-ping, LI Xiao-ting, LIU jia

2019, 38(8):  2318-2325. 

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The structure of urban forest determines the appearance and total green biomass of urban forest and consequently its eco-efficiency. A stratified sampling survey was conducted on the urban forest within the range from 1 km outside the Sixth Ring Road to the center of Beijing to analyze species diversity and arbor specifications and their spatial variation, and find out current problems and variation pattern in gradient, with the aim to provide reference for the diversity conservation and scientific management of Beijing’s urban forests. Through a survey of 847 plots of various types of urban forests, we recorded woody plants of 50 families, 106 genera and 159 species, 75% of which are indigenous species. The urban forest communities are dominated by a few species. Populus tomentosaCarr. and Sophora japonica L. are the tree species used most in quantity (9.7%) and most frequently (28.45%). For arbors, the average DBH is 19.79 cm and the average crown breadth is 5.4 m. The overall specification is small with limited difference. The urban forests in Beijing showed an obvious change in gradient from the inside to the outside towards the direction of urban development. Species richness outside 4th Road is higher than that inside, with the highest richness of 112 species within 4th-5th Roads. The diversity and homogeneity gradually decreased. The arbor specification becomes smaller. Species composition, diversity, and arbor specification in “six urban districts” are better than those of other administrative areas.

Gravity transfer characteristics and common relationships of mangroves in China and mangrove communities in typical area. 

HE Yu-hua, ZHANG Dong-shui, QIU Bing-wen, LI Yan-ting, HAN Yong-shun, LIU Xian-zhao

2019, 38(8):  2326-2336. 

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With the development of society and economy, the gravity center and spatial structure of mangrove communities would change. The center of gravity model could be used to construct transfer distance and direction, and explore spatial transfer characteristics and distribution pattern of mangrove communities.  Multisource and multitemporal remote sensing data in past 25 years were used to extract information of mangrove forests in China and information of Avicennia marina, Kandelia obovata, Aegiceras corniculatum, Phragmites karka and Cyperus malaccensis in a typical reserve of Zhangjiang Estuary by GIS and remote sensing technology. With the center of gravity model, gravity transfer characteristics and common relations of mangroves in China and mangrove communities in the typical reserve of Zhangjiang Estuary were analyzed from whole to part perspective. The results showed that: (1) There was a clear deviation of mangrove center of gravity in the northeast direction. This deviation was mainly reflected in longitude, with an imbalance between the east and the west. Mangrove center of gravity was mainly located at the entrance to the sea, and pointed to the area where river network was dense and economic was prosperous. (2) Center of gravity of mangrove communities was dominated by the direction of southeast, pointing to high aggregation area of the mangrove communities. Mangrove communities gradually spread to northern and eastern areas. The center of gravity showed a trend toward the north. (3) The common characteristics of provincial-level mangrove forests and those in the typical area were of consistency, retraction and hierarchy. The main features were as follows: both directions of gravity transfer of mangrove forests and mangrove communities were basically consistent with the trend of coastal intertidal zone; the directions of track of the two pointed to the harbor or estuary bay covered well by waves; the center of gravity of provincial-level mangrove forests and those in the typical area had different degrees of retraction after 2005 and 2011, respectively. To a certain extent, the center of gravity transfer of mangrove communities in the typical area belonged to the enlarged situation of provincial-level mangrove gravity center transfer, with the former reflecting the local internal structure characteristics and the latter reflecting the overall characteristics. Our results would help management agencies to propose protective measures and plans for the balanced, stable and sustainable growth of mangrove.

Effects of different forest management practices on fine root decomposition and nutrient release in Pinus massonianaforests.

WANG Xiao-rong, NIU Hong-yu, ZENG Li-xiong, LEI Lei, PAN Lei, HU Wen-Jie, XIAO Wen-fa

2019, 38(8):  2337-2345. 

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As a vital carbon sink in forest ecosystems, fine roots (≤2 mm in diameter) with short life span and high metabolic activity are sensitive to environmental changes. It is important to understand the mechanisms of fine root decomposition and nutrient release in response to forest management practices. To examine the effects of forest management on fine root decomposition, we employed three selective cutting managements, including shrub cutting (SC), nonPinus massoniana cutting (NPMC) and dominant P. massoniana cutting (DPMC), and a control with no cutting (NC) in P. massonianaplantation in the Three Gorges Reservoir area in 2013. After three years of forest management, litterbags filled with P. massoniana fine roots were buried in soil under different treatments. Mass losses and nutrient concentrations of fine roots were measured every three months. After one year decomposition, forest managements had significant effects on soil temperature and humidity, soil nutrients and soil microbial biomass carbon and nitrogen, but had no significant effect on the fine root decomposition rate. There were no significant correlations between fine root decomposition rate and environmental factors. During decomposition, C residual rates gradually decreased, showing a pattern of DPMC>SC>NC>NPMC. Nitrogen was immobilized first and then released, while P followed a mode of release immobilizationrelease. The release rate of P was significantly reduced by selective cutting management. In all, the changes of environmental factors caused by forest management practices are not the dominant factors driving fine root decomposition of P. massoniana.The quality of fine root initialmatrix is the decisive factor. Selective cutting management can increase C release but decrease N and P release rate.

Changes of functional traits of six common garden plant species across an urban-rural gradient of Chongqing.

ZHAO Yuan-yuan, CHEN Hong-xing, CHEN Hong, WANG Hai-yang

2019, 38(8):  2346-2353. 

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Plant functional trait is of great significance to examine the adaptation strategies of plant species. In this study, we measured functional traits including both vegetative and reproductive organs and biomass allocation of six common plant species in Chongqing, including Distylium chinense, Acer palmatum, Loropetalum chinense, Broussonetia papyrifera, Ginkgo biloba, and Magnolia denudate under different habitats, aiming to examine their adaptation strategies in urban environment. The results showed that the functional traits except specific leaf area and biomass allocation were significantly different (P<0.05), with their values decreased along theruralsuburban urban gradient. Except forAcer palmatum, all species allocated the most biomass to reproductive organs and least to stems. Based on the results of principal component analysis of functional traits, the six species could be divided into three categories. The vegetative and reproductive organs of urbanadapted group were basically unaffected by the urban environment. The vegetative organs of the semi urban adapted group were little affected while the reproductive organs obviously affected. Both vegetative and reproductive organs of the urbanunadapted group were severely affected. The overall evaluation on functional traits showed that the performance of plants living in forest parks near country was the best, followed by those in suburban parks, and those in urban parks the worst.

 

Effects of soil water and salinity on relationships between desert plant functional diversity and species diversity.

ZHANG Xue-ni, LI Yan, HE Xue-min, Lü Guang-hui

2019, 38(8):  2354-2360. 

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Understanding the responses of the relationships between plant functional diversity and species diversity to the variation of soil water and salinity is beneficial to revealing the mechanisms underlying species coexistence in stressful environment. In this study, we analyzed plant functional diversity, species diversity, and the variation of their relationship under high and low soil water and salinity environment in a desert near Ebinur Lake. We found that: (1) Functional divergence in high soil water and salinity environment was significantly lower than that in low soil water and salinity environment, whereas the pattern of species diversity index (Fish-α) was opposite. (2) Results from both simple and multiple regression analysis showed that species diversity significantly improved functional diversity (RaoQ) and functional richness in conditions with high soil water and salinity, while in low soil water and salinity environment, species diversity improved functional diversity and functional evenness, but suppressed functional divergence. (3) Species diversity had higher predictive power for functional diversity in low soil water and salinity environment. (4) Functional richness, divergence and evenness were more sensitive to the changes of soil water and salinity. Overall, this study provides valuable clues for plant community assembly, recovery and management in desert.

Effects of light quality on seed germination and seedling growth of Chinese fir.

2019, 38(8):  2361-2368. 

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Light is one of the key factors affecting natural regeneration of forest (seed germination and seedling growth traits). However, the effects of light quality on early regeneration of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) remain unclear. We investigated the effects of light quality on seed germination and seedling growth of Chinese fir with five treatments of different light qualities in laboratory: 8 h white light (W), 8 h red light (R), 6 h red light 2 h far red light (R-FR), 4 h red light 2 h far red light2 h red light (R-FR-R), and dark (D, as control). The results showed that light quality significantly affected seed germination of Chinese fir. D and R-FR-R treatments promoted, while R treatment inhabited seed germination of Chinese fir. Root length, cotyledon length, total biomass and leaf biomass ratio were promoted, and stem growth was inhibited under R and R-FR-R treatments. The stem growth was promoted under far red light treatment. Our results demonstrated that seeds of Chinese fir were insensitive to light. The germination percentage reached the maximum under treatment D. Chinese fir seed could adapt to heterogeneous light conditions.

Effects of high temperature during burning on Sphagnumspore germinability: A simulated experimental study.

GUO Hong-bo, XU Xue-ying, BU Zhao-jun, FENG Lu, Lü Xi-yao, WANG Jian-Yi, CHEN Yong-da, Shuayib Yusup, LU Fan

2019, 38(8):  2369-2376. 

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It is not clear how fire, an important factor maintaining ecosystem stability, affects spore banks of Sphagnum, the dominant plants in peatlands. In this study, mature spores of three Sphagnum species and peat soil collected from peatlands in the Changbai Mountains were used as experimental materials. We simulated a process of fire in laboratory and measured soil temperature at different depths. Four temperature levels (20, 40, 60 and 100 ℃) and five time levels (0.5, 1, 2, 4 and 10 min) were set to simulate a heat shock experiment to treat Sphagnumspores. The effects of temperature and time of heat shock on spore germination percentage were assessed with germination test. During the process of fire, temperature decreased with soil depth. Surface peat reached an extreme high temperature of 300 ℃, while it was only 70 ℃ at the layer 1 cm below the surface, reflecting the good thermal buffering property of peat soil. Compared to the treatment at 20 ℃, 40 ℃ heat shock increased  20% of spore germination percentage of S. fuscum and 50% of S. magellanicum,while 60 ℃ heat shock could double the spore germination percentage of S. capillifolium. In contrast, 100 ℃ treatment strongly decreased spore germinability. Our results indicate that the efficient thermal insulation of peat soil may keep Sphagnum spores away from lethal high temperature and that moderate heat shock may facilitate spore germination of Sphagnum.These may be of great significance for the establishment of Sphagnumspores in peat and population persistence in response to fire disturbance.

Seed dispersal by black snub-nosed monkey (Rhinopithecus bieti) at Mt. Lasha, Yunnan, China.

LI Ning, GAO Shuai, CHEN Si-yu, REN Yuan-hao, LI Yan-peng, HUANG Zhi-pang, XIAO Wen, CUI Liang-wei

2019, 38(8):  2377-2381. 

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Primate is an important seed dispersal vector in forest, which plays an important role in forest regeneration. While many foreign scientists focused on the seed dispersal behaviors of primate, the studies on primate seed dispersal behaviors were still at the primary stage in China. In this study, we observed the fruit foraging behaviors of black andwhite snub-nosed monkeys (Rhinopithecus bieti) at Mt. Lasha and counted the intact seeds from the feces collected from the night-roosting sites and noon-sleeping sites. R. bieti consumed fruits from 14 plant species, belonging to nine families. Six out of the 14 species were from Rosaceae, with a percentage of 42.86%. Fruit traits influenced fruit choice of R. bieti, who preferred fleshy fruits (85.71%, n=12) and red fruits (57.14%, n=8). The distribution pattern of feces between night-roosting sites and noon-sleeping sites was different, with 75% of feces being found in the sleeping sites and 25% in noon-nap sites. Most of Rosaceae seeds were found under the nightroosting sites of R. bieti in conifer forest, indicating that R. bieti could affect the regeneration of broadleaved tree species in conifer forest. Our results highlight the important role of R. bieti in seed dispersal in forest ecosystem.

Relationship between plant functional group distribution and soil properties under the disturbance of plateau pika (Ochotona curzoniae).

YE Guo-hui, CHU Bin, ZHOU Rui, ZHANG Fei-yu, HUA Xian-ze, HUA Rui, WANG Ting, DONG Ke-chi, HUA Li-min

2019, 38(8):  2382-2388. 

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The aim of this study was to understand the distribution of plant functional groups and its relationship with soil properties under the disturbance of plateau pika (Ochotona curzoniae). We investigated plant community structure and soil properties in three plots where pika were active in an alpine meadow in Maqu County, eastern Tibet Plateau. We used the number of pika’s holes as an indicator of disturbance intensity and analyzed the relationship between plant functional group and soil properties. The results showed that the height and cover of plant community decreased with the increases of pika disturbance intensity. There was a similar response in diversity index of plant functional groups, particularly for Cyperaceae and forb. Along the gradient of pika disturbance intensities, total soil P and organic C concentrations increased, while soil pH and soil compaction significantly decreased (P<0.05). Results from the RDA and partial RDA analyses revealed that the distribution of plant functional groups was significantly correlated with the concentrations of total soil phosphorus and total potassium under pika disturbance (P<0.05).

Effects of soil temperature on the growth of Carex duriuscula in Mu Us bottomland.

QIAO Xiao-ying, MA Shao-yang, HOU Hui-fang

2019, 38(8):  2389-2396. 

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Soil hydrothermal conditions affect plant growth, species distribution, and community stability. Here, a temperaturecontrolling experiment was performed using Carex duriuscula, a dominant species in the Mu Us bottomland. There were four soil temperature conditions, including control, warming Ⅰ, warming Ⅱ, and cooling. Plant height, spike number, and the contents of chlorophyll, malondialdehyde and soluble sugar of C. duriusculawere measured periodically. The results showed that: (1) Plant height was positively correlated with soil temperature before August, but negatively correlated with soil temperature after August.  (2) The contents of malondialdehyde and soluble sugar of C. duriuscula were positively correlated with soil temperature from the end of August to the beginning of September and negatively correlated with soil temperature from midSeptember to October. Warming or cooling treatment inhibited chlorophyll synthesis. Malondialdehyde and soluble sugar could be used as indicators of the effects of soil temperature on plant growth. (3) Regression models with soil temperature as an independent variable and plant growth parameters or physiological parameters as dependent variables were constructed. The exponential model of plant spike number and soil temperature could be used to predict the effects of soil temperature on the growth of C. duriuscula due to the high fitting degree of the model.

Effects of shading on growth and photosynthetic characteristics of four edible fern species in Northeast China.

WANG Yan-lin, GAO Shan-shan, HE Xing-yuan, LI Yan, LI Pei-yang, ZHANG Yue, ZHAO Da-wei, ZHONG Qing-lin, CHEN Wei

2019, 38(8):  2397-2404. 

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The growth and photosynthetic characteristics of four edible fern species including Matteuccia struthiopteris (L.) Todaro, Athyrium multidentatum(Doll.) Ching, Osmunda cinnamomea (L.) var.asiatica Fernald, and Pteridium aquilinum(L.) Kuhn var.latiusculum (Desy.) Underw. ex Heller were examined under three shading conditions (35%, 13% and 8% of full sunlight). The results showed that plant height  of the four species decreased, while specific leaf area (SLA) and leaf water content (LWC) increased with the enhanced shading degree. The net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of the four species decreased and the intercellular CO₂ concentration (C_i) increased with the enhanced shading degree. The maximal photochemistry efficiency of PSⅡ (F_v/F_m) of the four species under the three shading treatments varied between 0.7 and 0.8. The nonphotochemical quenching coefficient (NPQ) decreased with enhanced shading degree. The chlorophyll (Chl) content, especially chlorophyll b content (Chl b) of the four species increased with the enhanced shading degree except for P. aquilinum var. latiusculum, which decreased at 8% of full sunlight. P. aquilinum var. latiusculum had higher SLA, P_n, Φ_PSⅡ, but lower NPQ and Chl a/b compared with other species. In summary, the four fern species were suitable to grow under 35% of full sunlight. Although they had certain tolerance to lower light conditions, their growth was restrained to some extent, and P. aquilinum var. latiusculum had the maximum shade tolerance capacityamong the four species. Our results provide scientific basis for the cultivation, management, and utilization of the four fern species.

Effects of high temperature and high humidity stress and restoration on the fast fluorescence induction dynamics of tomato leaves.

ZHAO He-li, YANG Zai-qiang, WANG Ming-tian, WEI Ting-ting, WANG Lin, SUN Qin, ZHANG Xu-ran

2019, 38(8):  2405-2413. 

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To clarify the combined effects of high temperature and high humidity stresses on the growth of tomato, a threefactor orthogonal test of temperature, relative humidity and duration was carried out using “Jinguan 5” as material from June to September 2018 in the Agricultural Meteorological Laboratory in Nanjing University of Information Science and Technology. There were four levels of temperature: 32 ℃/22 ℃, 35 ℃/25 ℃, 38 ℃/28 ℃, 41 ℃/31 ℃ (day/night temperature), three levels of air relative humidity: 50%±5%, 70% ±5%, 90%±5%, and four durations (3, 6, 9, 12 d), with 28 °C/18 °C and 50%-55% humidity as control (CK). We measured photosynthesis parameters and rapid chlorophyll fluorescence induction kinetic parameters of tomato leaves. The results showed that when maximum temperature was within the range of 32-41 ℃, light saturation point (LSP), apparent quantum efficiency (AQE), maximum net photosynthetic rate (P_max), maximum photochemical efficiency (F_v/F_m), photosynthetic performance index (PI_abs), comprehensive performance index (PI_total), quantum yield for electron transfer (φ_Eo), quantum yield for reducing electron acceptor at the PSI receptor side (φ_Ro), light energy for electron transfer (ET_o/CS_m), and number of active reaction centers (RC/CS_m) decreased as temperature increased. The rapid chlorophyll fluorescence induction curve changed. J, I, and P phase decreased, with a negative value of ΔK. At high temperatures, LSP, AQE,P_max,F_v/F_m, PI_abs, PI_total, φ_Eo, φ_Ro,ET_o/CS_m,RC/CS_m and other indicators at the treatment with a humidity of 70% were significantly higher than that of 50% and 90%. There were no significant differences among indicators of different processing days and recovery days. Our results suggest that high temperature stress would destroy the structure and function of photosynthetic system of tomato seedlings. When the maximum temperature exceeds 35 ℃, increasing the air relative humidity to 70% can stabilize the photosynthetic reaction center and alleviate the damage of high temperature stress on the photosynthetic system.

Sex ratio and sexual difference of functional traits in the endangered plant Cercidiphyllum japonicum.

MA Wen-bao, LIAO Cheng-yun, JI Hui-juan, CHEN Xue, DONG Ting-fa

2019, 38(8):  2414-2419. 

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Population with a biased sex ratio and sexual difference in functional traits may have negative effects on population dynamic in dioecious species. However, few studies have examined the sexual difference in the endangered dioecious species. In this study, we investigated the sex ratio and the sexual differences in morphology and photosynthetic nutrient and water use efficiency in the leaves of adult Cercidiphyllum japonicum Sieb. et Zucc. in Xiaozhaizigou National Nature Reserve in western Sichuan Province. Our results showed that the sex ratio was biased towards females (F/M=1.97; χ²=4.46, P=0.035). The diameter at breast height, crown width, maximum photosynthetic rate, apparent quantum yield, maximum carboxylation efficiency, specific leaf area, leaf nitrogen content, and use efficiencies of water, nitrogen and phosphorus of females were 44.50%, 27.94%, 20.11%, 50%, 21.14%, 14.32%, 14.86%, 158.7%, 19.74% and 28.03% higher than those of males, respectively, while stomatal conductance, intercellular CO₂ concentration, transpiration rate, and light compensation point of females were 20.83%, 24.61%, 56.11% and 44.44% lower than those of males, respectively. These results indicated the existence of sex ratio bias and sexual dimorphism in ecophysiological traits, which may cause its endangerment. The sexrelated difference should be considered in the future study of endangered mechanisms in dioecious species.

Pollination ecology of the invasive plant species pokeweed.

WU Ran-ran, LIU Lin-de, ZHANG Li, HOU Yu-ping, WANG Li-juan

2019, 38(8):  2420-2425. 

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Pollination ecological characteristics of pokeweed (Phytolacca americana) were systematically studied by measuring flowering phenology, flower quantitative characters, pollen vitality and histochemistry, stigma receptivity, pollen germination on stigmata, outcrossing index, pollenovule ratio, pollinators, and mating system. The aim of this study is to understand the mechanism underlying successful invasion of pokeweed. The results showed that the flowering span of pokeweed was 45-70 d. The life span of single flowers was 2-3 d, including goblet flowering, petal flattening, petal sagging and petal rewinding stage. The corolla was no larger than 1 cm in diameter in petal sagging stage. The distance between the anther and the stigma was 1-2.5 mm, promoting selfpollination. There was a significant difference in pollen viability between petal flattening stage and petal sagging stage (P<0.05), and no significant difference between goblet flowering stage and petal flattening stage (P>0.05). The pollen viability during petal flattening stage was higher than 85%. In the petal flattening stage, the stigma receptivity was the highest and the synthetic stigmata cracked into 9 to 10, which increased the surface area of stigma for receiving more pollen. Results from the scanning electron microscope revealed that pollen had been germinated on the stigma of this stage. Therefore, the timing of anther loose pollen coincided with the timing of synthetic stigma cracking, which might be beneficial to selfpollination. Each flower contained 1667-3222 pollen grains and 9-10 ovules. The pollen ovule ratio (P/O) was 340.88±34.99 and hybridization index (OCI) was 3. The P/O ratio suggests that pokeweed is facultative autogamous. Pokeweed has fatcontaining pollen. At least four different species of insect taxa, such as bees, wasps, scorpion flies, and thinwax bees, were the “principal pollinators”. In conclusion, pokeweed is selfcompatible with high pollen viability and strong stigma receptivity. The cooccurrence of high pollen viability and strong stigma receptivity is conducive to improve fruit setting. Those reproductive mechanism and pollination characteristics are the main factors for the successful invasion of pokeweed.

Effects of rural mixed wastewater irrigation on soil nutrient content, enzyme activity, and microbial diversity.

LIU Hui, FAN Dong-fang, HUANG Yin-di, WU Yong-gang, HU Lin-na

2019, 38(8):  2426-2432. 

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The effects of rural mixed wastewater irrigation treatment (WG) on soil pH, nutrient content, enzyme activity, and microbial diversity were examined in a soil column simulation experiment. Compared with clean water irrigation treatment (CK), WG treatment increased the contents of soil total potassium, total phosphorus, available potassium, and alkalihydrolyzable nitrogen (4.54%-46.84%), while decreased soil pH, the concentrations of organic matter, total nitrogen and available phosphorus (2.02%-32.61%). The activities of soil catalase and acid phosphatase were lower than CK (P<0.01), while the activities of soil urease and invertase were higher than those in CK (P<0.05). The diversity indices (Shannon, Ace, Chao and Coverage) of bacteria and fungi increased in soil, but the Simpson index decreased and the relative abundances of each dominant species of bacteria and fungi at the genus level were changed. The results of evaluation based on Nemerow comprehensive index showed that mixed wastewater irrigation can improve soil fertility. Our results provide the theoretical basis and technical guidance for the field experiment of rural mixed wastewater irrigation model in demonstration area.

Optimization of cultivated land quality evaluation for land consolidation.

ZHAO Rui, WU Ke-ning, CHEN Tian-qian

2019, 38(8):  2433-2441. 

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It is urgently needed to explore methodology and indicator system of cultivated land quality and thus to meet the needs of land quality change assessment in the context of land consolidation. Based on current achievements in the evaluation of cultivated land quality, the evaluation methods and indicator systems were improved from five aspects, including geomorphologic characteristics, soil properties, farming conditions, health status, and biological characteristics. A case study was carried out for the land improvement project of Wenxian County, Henan Province, using an integrated algorithm. In this study, the indicators involving geomorphologic characteristics, soil properties and farming conditions of cultivated land were weighted and summed, and the coefficients of health status and biological characteristics were obtained using the “1+X” model. The changes of cultivated land quality indicators before and after land consolidation were evaluated, with the cultivated land quality being divided into five levels. Results showed that the proposed cultivated land quality evaluation system can more accurately examine the effects of land consolidation on cultivated land quality before and after the implementation of the land improvement project. The new cultivated land quality evaluation system is superior to the Cultivated Land Quality Classification Regulations of China. Our results provide a reference for the evaluation of cultivated land quality for land consolidation.

Zoning of cultivated land quality improvement potential based on limiting factor analysis.

SHAO Ya-jing, YUAN Xue-feng

2019, 38(8):  2442-2449. 

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The aim of this study was to identify the types of dominant limiting factors of cultivated land quality in Baoji City. According to the spatial distribution of the improving potential of limiting factors, we divided the potential zoning of cultivated land quality improvement, and discussed the improvement measures of cultivated land quality in different potential zones. The results showed that the main type of limiting factors of cultivated land quality was the type of single factor, including soil layer, organic matter, and irrigation, which accounted for 66.11% of total area. The improving potential of cultivated land quality in Baoji City was at a medium level. The distribution trend was high in the north and low in the south, with certain spatial clustering characteristics. A total of 334 administrative villages in Baoji City have a high potential for improving the quality of cultivated land, which shows “HH” distribution type (Grade I District). Thus, we can increase the intensity of land consolidation projects in this region to improve the overall level of cultivated land quality. Strategies to improve the quality of cultivated land in the central part of Baoji City should focus on increasing the effective soil layer thickness, increasing the content of soil organic matter, and improving the irrigation conditions of agricultural land. In addition, the improvement of soil erosion should be strengthened in the northern region, and effective measures to reduce the impacts of rock outcrop and topographic slope on the quality of cultivated land should be taken in the southern region.

Effects of nitrogen application rate and soil sterilization on root knot nematode infecting tomato roots.

Lü Hao-feng, WANG Ya-fang, LI Guo-yuan, WANG Jing-guo, LIN Shan

2019, 38(8):  2450-2455. 

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The safety and sustainability of greenhouse vegetable production are seriously threatened by the frequent occurrence of root knot nematode disease. To explore the effects of nitrogen (N) fertilizer application rate and soil sterilization on root knot nematode infecting tomato roots, a pot experiment was carried out with a twofactorial (N application rate and soil sterilization) randomized block design. The N application rates were 100 and 300 mg·kg^-1. Soil sterilization included gamma ray sterilization and nosterilization. The results showed that the root knot numbers per unit root length and unit root dry weight in low N application rate were reduced by 42.5% and 30.4%, respectively, as compared to high N application rate under the non-sterilization condition, while the dry weight of shoot and root increased by 43.9% and 31.4%, respectively, and agronomy use efficiency of N increased by 4.3 times. Gamma ray sterilization effectively eliminated the infection of root knot nematodes to tomato roots and the aboveground dry weight increased by 31.8%. Appropriate reduction of N application rate can significantly reduce root knot nematode infecting to tomato roots, promote tomato growth, and improve N agronomy use efficiency.

 

The bacterioplankton variation of Litopenaeus vannamei culture before and after the disease emergence.

DU Shi-cong, HUANG Lei, YANG Kun-jie, YAO Zhi-yuan, CHEN He-ping, ZHANG De-min

2019, 38(8):  2456-2465. 

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The health status of shrimp (Litopenaeus vannamei) is highly correlated with the bacterioplankton communities in aquaculture water. Here, the dynamics of bacterioplankton diversity, composition and the association within key taxa were investigated by 16S rRNA highthroughput sequencing. The results showed that before the disease outbreak, the Shannon index of bacterioplankton in diseasedtrend ponds was significantly lower than that of the healthy ponds with a constant reduction. Accompanied by disease outbreaks, the bacterioplankton of diseased ponds was distinct from that of the healthy ponds, with community characterized by lower temporal stability. Before the disease onset, the average relative abundance of Chloroflexi, Saccharibacteria, and δproteobacteria in the diseased ponds were significantly higher than that in healthy ponds, while the change of Bacteroidetes was opposite. In addition, some diseaseindicated OTUs in the diseased ponds were affiliated with Vibriaceae and Flavobacteriaceae. OTU1 which belonged to Rhodobacteraceae was healthy indicator in healthy ponds before the disease outbreak. Results from the network analysis showed that most of the OTUs interacting with OTU1 belonged to the Flavobacteriaceae, which might play an important role in the bacterioplankton communities. Overall, the incidence of shrimp might be highly associated with a variety of bacterioplankton communities, and the opportunistic pathogens could rapidly multiply, leading to the incidence of shrimp when the “ecological niche opportunity” occurred. Preservation and restoration of bacterial community equilibrium would be an effective strategy for shrimp disease prevention.

The relationship between the fishing ground of mackerel (Scomber australasicus) in Arabian Sea and the environment based on GAM model.

YANG Sheng-long, FAN Xiu-mei, WU Yu-mei, ZHOU Wei-feng, WANG Fei, WU Zu-li, ZHANG Bian-bian, FAN Wei

2019, 38(8):  2466-2470. 

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The relationship between mackerel (Scomber australasicus) catch per unit effort (CPUE) and sea surface environmental factors of the Arabian Sea were evaluated by using general additive model (GAM) based on the satellitebased oceanographic data of sea surface temperature, sea surface chlorophyll-a concentration, sea surface current  and sea surface height  as well as purse seine catch data of Chinese fishing boats from 2016 to 2017. The results showed that the percentage of deviance explained by GAM was 30.1%. The fishing grounds were affected by the Indian Ocean monsoon. The CPUE of mackerel was higher in winter monsoon and lower in summer monsoon. The CPUE of mackerel mainly located in 65°E and 13-15°N. The optimum sea surface temperature was 26-28 ℃. The appropriate chlorophyll concentration range and sea surface height were 0.2-0.5 mg·m^-3  and 0.2-0.4 m, respectively. The relative importance of the several variables affecting the CPUE of mackerel was in the order of sea surface height, longitude and latitude, sea surface temperature, and chlorophyll concentration.

Age determination and growth characteristics of finless porpoise Neophocaena asiaeorientalis sunameri in Liaoning coastal waters.

TIAN Jia-shen, LU Zhi-chuang, WANG Zhen, DU Jing, HAN Jia-bo

2019, 38(8):  2471-2476. 

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We measured the morphological parameters and growth characteristics of 39 dead finless porpoises (Neophocaena asiaeorientalis sunameri) collected along Liaoning coastal waters from 2007 to 2018, and identified the age of 27 finless porpoises collected from 2014 to 2018 by observing teeth growth layer. The results showed that ages of the dead animals ranged from 0 to 4 years, with 21 male and 18 female. There was no significant difference in length and weight between male and female with the same ages (P>0.05). Both weight (Y=137e^-2.475exp(-0.205t)) and length (Y=232(1-0.680e^-0.161t) were significantly correlated with age (P<0.01). Moreover, the growth rates of weight and length showed decreasing trends with the increases of age. The discovery times of dead finless porpoises varied among different areas of Liaoning coastal waters. They were always discovered in the northern Yellow Sea during March to June, and mainly distributed on the coast of Xinghai Bay to Laohutan Beach, while in Liaodong Bay of Bohai Sea they were usually discovered during the period from October to November, mainly distributed in the northern waters of Changxing Island. The death of finless porpoise in Liaodong Bay occurred mostly in fishery period, which may be closely related to fishing. The distribution period of finless porpoise death was alternated with that of spotted seals in Liaodong Bay. Whether it was related to the adaptation capacities of both species to the sea water temperature, their food competition and seasonal migration needs further study.

Gender differences in thermal tolerance of zebrafish in response to temperature acclimation.

XIA Ji-gang, HUANG Yan, FU Shi-jian, PENG Jiang-lan

2019, 38(8):  2477-2481. 

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To clarify gender differences in thermal tolerance of fish in response to temperature acclimation, the thermal tolerance parameters, such as critical thermal maxima (CT_max), lethal thermal maxima (LT_max), critical thermal minima (CT_min) and lethal thermal minima (LT_min), were measured in male and female zebrafish (Danio rerio) after two weeks of acclimation at preferential temperature (28 ℃), low temperature (20 ℃), and high temperature (34 ℃). Our results showed that acclimation temperature (AT) and its interactions with gender had significant effects on the thermal tolerance of zebrafish (P<0.05). No significant difference was found in thermal tolerance between females and males at 28 ℃ acclimation (P>0.05). Females were more resistant to high temperature than males at 20 ℃ acclimation, whereas they were less resistant to low temperature than males at 34 ℃ acclimation. Those results indicated that the thermal tolerance of males and females was highly consistent at suitable reproductive temperature, but was significantly different at non-suitable reproductive temperatures.

Effects of complexed ironbearing material on physiological and biochemical characteristics and arsenic accumulation in Oryza sativa L. under arsenic stress.

CHENG Yan, CHEN Lu, MI Yan-hua, YANG Xiao-hong, DU Li-juan, DUAN Hong-ping, LI Mao-xuan

2019, 38(8):  2482-2489. 

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Heavy metal in soil is closely related to the quality of agricultural products. In this study, a pot experiment with rice (Oryza sativa L.) under arsenic stress was conducted to examine the effects of different application times and concentrations of complexed iron-bearing material on SPAD value, activities of antioxidant enzymes (SOD, POD, CAT), arsenic uptake and accumulation in rice. The results showed that the activities of SOD, POD and CAT were inhibited in rice under arsenic stress. The addition of complexed iron-bearing material reduced MDA concentration, alleviated the inhibition of arsenic on photosynthesis and activities of SOD, POD and CAT in rice, and decreased the arsenic uptake and accumulation. With respect to adding times, adding complexed ironbearing material before booting stage had better effect than adding before transplanting on controlling arsenic uptake in rice. There was a significant negative correlation between the concentration of arsenic in shoot and the application level of complexed iron-bearing material. Adding complexed iron-bearing material at the level of 0.2 g·kg^-1 before booting stage had the best effect on alleviating arsenic stress, with a 59.22% reduction of arsenic concentration in shoot.

Variations in spring phenology of different vegetation types in the Mongolian Plateau and its responses to climate change during 2001-2017.

JIANG Kang, BAO Gang, WULANTUYA, ZHANG Wen, JIANG Li, LIU Chao

2019, 38(8):  2490-2499. 

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With MODIS NDVI data from 2001 to 2017 smoothed by the S-G and HANTS methods, we applied three phenological extraction models (the cumulative NDVI based Logistic curvature (CUM), rate of change of curvature (RCC), dynamic threshold method) to identify the start of growing season (SOS) in the Mongolian Plateau. The response characteristics of the SOS to climate change were analyzed on the vegetation type scale. The results showed that although the S-G method was slightly better than the HANTS method, both of them had relatively less influence on extracting the SOS. Among the three phenological extraction methods, CUM method had better extraction accuracy. The average SOS of the Mongolian Plateau was approximately 124 d. Spatially, the earlier SOS was observed in the southwestern part of the plateau and the Hentiy Mountain areas, whereas the later SOS occurred in Hangay Mountains and western part of the Greater Khingan Mountain. Temporally, the SOS generally showed a weak advancing trend (-0.04 d·a^-1). Spatially, the delayed SOS was observed in the Hangay Mountains, and the advanced SOS occurred in the Greater Khingan Mountain, Hentiy Mountain, the Great Lakes basin, and central and western Inner Mongolia. At the vegetation type scale, expect for the forest vegetation (-0.67 d·a^-1), there were no apparent trends of SOS in other vegetation types. The temperature prior to the SOS, especially in March, negatively correlated with the SOS in the Mongolian Plateau, and the precipitation in the autumn and winter of the previous year had a positive correlation with the SOS.

Ground concentration distribution and source of PM_2.5 in Guanzhong Region.

HAN Lei, LI Yun-qi, ZHAO Yong-hua, WANG Da, GUO Si-qi

2019, 38(8):  2500-2507. 

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Atmospheric quality is closely related to human living environment. Atmospheric pollutants, especially fine particulate matter, directly and indirectly endanger human health. Therefore, many cities put the monitoring of fine particulate concentration at an important position. We analyzed the correlation between MODIS highresolution aerosol products (aerosol optical depth, AOD) and PM_2.5 concentration monitoring data in Guanzhong area in spring 2017 and constructed a direct fitting model. A multiple regression model containing meteorological elements was established by combining meteorological observation data. Those two models were compared. The results showed that the multivariate regression model with meteorological factors had better fitting degree for the spatial distribution of PM_2.5 in Guanzhong area (r²=0.768,P<0.01). In the spring of 2017, the spatial distribution of PM_2.5 (AOD) in Guanzhong area showed a trend of being high in the east region and low in the west region. The highest value appeared in Xi’an, Weinan and Xianyang, being 1.019, 0.911, and 0.124, respectively. Results from the principal component analysis of a typical polluted weather and simulation of its potential transmission path based on HYSPLIT backward trajectory model showed that atmospheric quality in Guanzhong area in spring 2017 was affected by multipollutants, multipollutant sources and multichannel combined pollution, and the air mass mainly came from southwestern Mongolia. Our results provide reference for the prevention and control of air pollution and ecological environment protection in Guanzhong area.

Spatial and temporal heterogeneity of landscape naturalness in Jinshui Lake National Wetland Park of Gansu Province. 

GOU Fang-zhen, ZHAO Cheng-zhang, LI Zi-qin, REN Jie, MA Jun-yi, CHEN Yan-Long

2019, 38(8):  2508-2514. 

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Landscape naturalness reflects the spatial and temporal distribution of landscape elements, which is of great significance to improve ecosystem integrity and stability. Using GIS and AHP (Analytic Hierarchy Process), we analyzed the changes of landscape naturalness in Jinchuan Jinshui Lake National Wetland Park of Gansu Province by interpreting the remote sensing images in 2003, 2009, and 2015. The results showed that landscape diversity index, evenness index and patch richness increased over time, while landscape dominance and landscape separation decreased. Most ecological function indices increased, including habitat provision, function maintenance of plant community, weighted average patch fractal dimension of area, and vegetation coverage increased. The ecological disturbance indices such as artificial disturbance index and average area of artificial landscape showed decreasing trends. The landscape naturalness index of wetland parks increased from 0.4761 in 2003 to 0.7485 in 2015. The implementation of wetland park conservation and restoration project changed land cover structure, enhanced the stability, ecological elasticity and service value of ecosystem, and greatly improved the landscape naturalness of Jinshui Lake National Wetland Park.

Spatiotemporal variation in vegetation coverage and its driving forces in Ningxia during 2000-2016.

HUANG Yue-yue, YANG Dong, FENG Lei

2019, 38(8):  2516-2523. 

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Based on MODIS NDVI remote sensing and contemporaneous weather data, we used trend analysis, coefficient of variation and Hurst index to investigate the dynamics of vegetation coverage in Ningxia from 2000 to 2016. The vegetation coverage showed an overall increasing trend over time, with a large difference between north and south. NDVI increased significantly from 2000 to 2005, relatively slowly increased from 2006 to 2011, and slightly decreased from 2012 to 2016. Precipitation and humidity index showed the greatest response to vegetation growth. In the growing season, NDVI showed an overall rising trend, with 79.88% of the study region showing significant increase in NDVI. Seasonal NDVI increased at a rate of 0.026·10 a^-1,0.07·10 a^-1 and 0.049·10 a^-1 in spring, summer and autumn respectively, during 2000-2016. Although the vegetation coverage in 62.13% of the vegetationcovered area continued to increase, some regions exhibited decreasing vegetation coverage. The continued improved area in vegetation coverage in southern forest area was larger than that in northern irrigation area around the Yellow River.

Spatiotemporal distribution of salt spray deposition in the coastal areas of South China: A case study of the Gulei Peninsula, Fujian.

HOU Meng-Ying, LI Qian-Qian, YUAN Tian-Tian, WANG Wen-Qing, FAN Zhi-Yang, HONG Ci-Zai

2019, 38(8):  2524-2530. 

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Salt spray is one of the main factors affecting plant growth in coastal areas. This study aimed to investigate the spatial and temporal distribution of salt spray deposition and its driving factors, and provide scientific basis for the selection and configuration of coastal greening plants. The experiment was conducted along the coast of the Gulei Peninsula, Fujian. The experimental sites were divided into zones with and without shelterbelts. Cylinders were used to measure salt spray deposition at a variety of distances from the shoreline. Cylinders were installed at different heights in shelterbeltfree areas to measure the salt spray deposition variation. Our results showed that salt spray deposition decreased as the distance from the shoreline increases. During the winter, salt spray deposition decreased rapidly with distance closer than 500 m from the shoreline. The rate of decrease finished at longer distances. The shelterbelt significantly reduced salt spray deposition, with a 15.4% decrease in winter. At the sites without shelterbelt, there was no significant difference in deposition among locations at different heights. Results from the principal component and redundancy analyses showed that distance from the shoreline, wind speed, and frequency of a northwest wind were key factors driving salt spray deposition. We concluded that shelterbelt construction was an effective measure to protect plants from ocean salt water vapor.

Effects of nitrogen deposition on elemental availability in bulk soils and soil aggregates of grasslands.

CAO Yan-zhuo, WANG Ru-zhen, ZHANG Yu-ge, LI Hui, Lü Xiao-tao, JIANG Yong

2019, 38(8):  2531-2539. 

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Understanding the nitrogeninduced changes of nutrient availability in bulk soils and soil aggregates is essential for studying soil nutrient supply as well as ecosystem structure and functioning under global change. Here, we reviewed research advances in elemental distribution of both bulk soils and soil aggregates as well as the mechanisms underlying their responses to nitrogen deposition in grassland ecosystems. A large number of studies have focused on soil carbon, nitrogen, phosphorus and sulfur availability, with the results depending on the form and duration of nitrogen addition as well as ecosystem types. Nitrogen deposition affects elemental bioavailability by altering the turnover of carbon, nitrogen, phosphorus and sulfur, as well as their distribution within soil aggregates. Relatively few studies have investigated the effects of nitrogen addition on exchangeable base cations and available micronutrients in bulk soils of grasslands. Soil acidification induced by N deposition causes imbalance in the leaching of calcium and magnesium among soil aggregates, with higher leaching losses in macroaggregates. Soil acidification is the main cause for higher availability of iron, manganese, and copper within soil aggregates.Nutrient concentrations in soil microaggregates are less sensitive to environmental changes. Currently, there are limited studies on the responses of soil aggregation and elemental availability within soil aggregates to nitrogen deposition. Further studies should focus on the coupled responses of elemental availability and enzymatic activities within soil aggregates, and analyze the feedback of soil physical structure and chemical composition to plant communities.

Research advances in the effects of serotonin and dopamine on the agonistic behavior of decapod crustaceans.

PANG Yang-yang, ZHANG Cong, SONG Ya-meng, SONG Xiao-zhe, CHENG Yong-xu, YANG Xiao-zhen

2019, 38(8):  2540-2544. 

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Serotonin (5-HT) and dopamine (DA) as neurotransmitters are important for many physiological functions by combining with different types of receptors. Both of them are widely distributed in different tissues of many animals, which play important role in agonistic behavior. There are five major 5-HT receptors (including 5-HT1A, 5-HT1B, 5HT2A, 5HT2B and 5-HT7) and four receptors of dopamine (DA1A, DA1B, DA2 and DA4) in crustaceans. The distributions of 5-HT, DA and their receptors are species and tissuespecific. In addition, 5-HT and DA participate in the regulation of agonistic behavior of decapods crustaceans by different regulation mechanisms. 5-HT can regulate the release of cyclic adenosine monophosphate (cAMP) or hyperglycemic hormone (CHH), which can promote or inhibit the agonistic behavior in crustaceans. In contrast, dopamine could affect the agonistic behavior by mediating the release of cAMP and COMT.

Ecological restoration of Shichuan River in Fuping.

WEI Jing, WANG Huan-yuan, SUN Zeng-hui, ZHANG Lu

2019, 38(8):  2545-2552. 

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Since China proposed the construction of the “mountains-rivers-forests-farmlands-lakes-grasslands” community of shared life, the third batch of ecological protection and restoration project has been launched. However, some engineering designs lack integrity, resulting in “true destruction” and “pseudoecology” phenomena. Taking the Shichuan River comprehensive improvement project as an example, this study focused on the environmental problems, including the excavation of river sand and gravel in the Shichuan River, industrial pollution, and the pollution of gas, water and soil caused by the burning of garbage by the nearby villagers. The ecological and living environment continued to deteriorate, and the fish and shrimp gone extinction, polluted water and garbage were widely distributed. The techniques of reconstructing ecological river channels, restoring ecology, reshaping landscape, land leveling, PE composite geomembrane, and soil remediation were applied to construct a community of shared life. We also analyzed the ecological, economic and social benefits. The implementation of the project provided clean soil and stable soil structure for the Shichuan River, effectively improved the environment, enhanced the quality of life, achieved production development and good ecology, and continuously met the needs of social development and construction of beautiful villages. It provided theoretical basis and practical support for constructing the watershed-level community of shared life.

Health assessment of mangrove swamp in Zhangjiang Estuary based on GIS and RS.

ZHONG Lian-xiu, LU Chun-yan, WANG Zong-ming, LIU Ming-yue, CHEN Yuan-li, LIN Xiao-qing, SU Ying, JIA Ming-ming

2019, 38(8):  2553-2563. 

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Based on land cover data of 2005, 2011, 2015 and 2017 from Google Earth, we established the health assessment index system of mangrove swamp ecosystem in Zhangjiang Estuary. Combining with pressure stateresponse (PSR) model and ecosystem health index, temporal and spatial differentiation of ecosystem health and driving factors of health level for mangrove swamp were analyzed. The results showed that: (1) From 2005 to 2017, the health status of mangrove swamp gradually deteriorated from sub-health to general health. The health status of pressure and response decreased dramatically, while the state health status improved slightly. (2) From 2005 to 2017, there were significant differences in health status among sub-regions. In the first stage (i.e. from 2005 to 2011), the health index from large to small was in order of the west region, the middle region, the east region, the north region and the south region. In the second stage (i.e. from 2015 to 2017), the health index from large to small was in order of the east region, the middle region, the west region, the north region, and the south region. (3) The increases of sea level, Spartina alterniflora invasion, aquaculture expansion, and seawall construction were the major driving factors for the deterioration of mangrove swamp ecosystem health. Meanwhile, nature reserve establishment and conservation measure implementation played positive roles in maintaining mangrove swamp ecosystem health.

Effects of sampling time on soil respiration of alpine wetlands under dryingrewetting cycles.

DING Yan, ZHANG Xiao-ya, JIANG Li-hua, LI Qian-wei, YUE Yi, GAO Jun-qin

2019, 38(8):  2564-2569. 

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Soil respiration is an important component of global carbon cycle. The rate of soil respiration varies with time. Accurate measurement of soil respiration rate is necessary to evaluate soil carbon emission. To evaluate soil respiration accurately, we conducted an incubation experiment with soil collected from a Zoigê alpine wetland. Soils were randomly separated into several parts after homogenization, and then were subjected to two or four drying-rewetting cycles. During each drying-rewetting cycle, CO₂ was collected for eight or four times. CO₂ emissions between each sampling time and the whole drying-rewetting cycle were compared. The results showed that the optimum sampling times were on the 4th day of the highfrequent drying-rewetting cycle (8 days per cycle). Under the lowfrequent cycle (16 days per cycle), the optimum sampling time was different between the high and low intensities, which was on the 6th day and the 4th day, respectively. An alternative approach was to collect the samples on the 4th day of the first cycle, and then sampled every 8 days. These findings suggest that the optimum sampling time of soil respiration depends on soil dryingrewetting cycle. Sampling during the middle period of drying-rewetting cycle accurately represents soil respiration during each cycle. Optimizing the sampling time could contribute to accurate evaluation and prediction of soil CO₂ emission in alpine wetland ecosystem under climate change.

Assessing the suitable distribution area of Pinus koraiensis based on an optimized MaxEnt model.

JIA Xiang, WANG Chao, JIN Hui, ZHAO Ying, LIU Li-jie, CHEN Qing-hong, LI Bing-yan, XIAO Ying, YIN Hang

2019, 38(8):  2570-2576. 

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Understanding the suitable habitat distribution of Korean pine (Pinus koraiensis) is significant for genetic resource conservation of Korean pine and vegetation restoration of broadleaved Korea pine mixed forest. In this study, we optimized the parameters (such as feature combination and regularization multiplier) of MaxEnt model. Using 168 geographical distribution records of Korean pine and 22 environmental factors, we simulated the habitat suitability of Korean pine and identified the major environmental factors controlling its distribution. The results showed that the complexity and degree of overfitting of the model were relatively low. The model was more accurate when the feature combination was linear, quadratic, hinge and product equation, and regularization multiplier was 3. Korean pine was mainly distributed in the eastern mountain area of Northeast China. The highly suitable area, low suitable area, and unsuitable area accounted for 19.24%, 28.54% and 52.22% of the total area, respectively. Annual precipitation, precipitation seasonality, elevation, and annual mean temperature played important roles in regulating the distribution of Korean pine, with the suitable threshold of each factor being 630-1090 mm, 86%-97%, 210-1140 m and 0.3-4.3 ℃, respectively.