Table of Content

10 September 2016, Volume 35 Issue 9

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Surface litter stoichiometry for five forest types in alpine region, Qinghai, China.

ZUO Wei1,2, HE Kang-ning1,2*, TIAN Yun1,2, WANG Wei-lu1,2

2016, 35(9):  2271-2278. 

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Litter is a link of material cycle and energy flow in forest ecosystems. It plays a very important role in soil improvement, seedling generation, and soil and water conservation, and it is also essential for shaping C, N and P cycling in forest ecosystems. In this study, five different types of litter from Larix principisrupprechtii forest, Picea crassifolia forest, L. principisrupprechtii and P. crassifolia mixed forest, P. crassifolia and Betula platyphylla mixed forest, and B. platyphylla forest under same site conditions in Qinghai alpine region were selected to study the nutrient contents and stoichiometry of litter. The results showed that with the deepening of litter decomposition layer, the organic carbon content, available phosphorus content, carbon/nitrogen ratio, and carbon/phosphorus ratio in litter of the five stands showed a decreasing trend. P. crassifolia forest litter had higher contents of ammonium nitrogen, nitrate nitrogen, and available phosphorus than the other four stands. The nitrogen contents of broadleaved forest and coniferousbroad forest floor litter were significantly higher than that of coniferous forest and coniferous mixed forest floor litter, and the nitrogen content of broadleaved forest floor litter was 1.23 times as high as that of coniferous forest floor litter. On the contrary, the phosphorus content of coniferous forest litter was 1.26 times as high as that of broadleaved forest litter. In comparison of the stoichiometry of five kinds of floor litter, it could be drawn that litter decomposition of broadleaved forest and coniferousbroad forest was mainly limited by phosphorus, while litter decomposition of coniferous forest and coniferous mixed forest was co-limited by nitrogen and phosphorus.

Effects of N and P addition on soil available nitrogen and pH in a subtropical forest.

SU Yu-qin1,2, LIU He-ming1,2, ZHENG Ze-mei1,2*, LIN Li1,2, LI Bin-bin1,2, WANG Xi-hua1,2

2016, 35(9):  2279-2285. 

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In order to understand the effects of N and P addition on soil available nitrogen and pH in a subtropical evergreen broadleaved forest dominated by Schima superba, we investigated contents of soil NH₄⁺-N, NO₃^--N and pH. Four N and P addition treatments were included as follows: CK (no addition of N and P), N (50 kg N·hm^-2·a^-1), P (15 kg P·hm^-2·a^-1) and NP (100 kg N·hm^-2·a^-1+15 kg P·hm^-2·a^-1). The results showed that: 1) The soil NH₄⁺-N and NO₃^--N concentrations were significantly increased after N addition, and the range of stimulation increased with prolonged nitrogen fertilization time. The soil NO₃^--N concentration was significantly decreased by P addition, and there was no significant impact on soil NH₄⁺-N concentration under P addition. NP addition significantly increased the soil NO₃^--N concentration, and N addition alone had more obvious effects on the soil NO₃^--N concentration than NP addition. The response of soil NH₄⁺-N concentration to NP addition turned from insignificant to significant over time. 2) The soil pH decreased obviously with prolonged N addition and NP addition time, while remained stable under P addition. 3) Relative to the increase of nitrate nitrogen concentration, the same increase of soil ammonium nitrogen concentration resulted in a greater decline in pH value.

Effect of size inequality on aboveground biomass and species diversity of plant communities.

KANG Xin1, WANG Xiao-mei1, HOU Chang-ying2, ZHENG A-bao2, ZHANG Cun-kuan3, XU Chi1, LIU Mao-song1*

2016, 35(9):  2286-2292. 

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Size inequality is ubiquitous in plant populations. Studying its influence on community productivity and species diversity is of significance for natural secondary forest management. We selected 7 plots of typical subtropical secondary forest communities in the Lishui Forest Farm, Jiangsu Province. We studied the relationship between the coefficients of variation (CV) of tree height and diameter at breast height (DBH), aboveground biomass and species diversity index (Shannon index). The results showed that, (1) the CV of tree height was less than that of DBH, but its impact on the community biomass and species diversity was generally greater than that of DBH inequality. (2) In the broadleaved mixed forest (with a low canopy cover) dominated by Pinus massoniana, community biomass was positively correlated with individual size inequality, while a negative correlation was found in the deciduous broadleaved forest and in the broadleaved mixed forest dominated by Cunninghamia lanceolata (with a higher canopy cover). (3) Species diversity was positively correlated with size inequality, but the relationship was weak in the community with low canopy cover. In summary, individual size inequality was beneficial for increasing species diversity, and had a positive effect on aboveground biomass of low cover communities.

Comparison of carbon pools of alpine wetland and meadow ecosystems on the Qinghai-Tibet Plateau.

FENG Jin, YUAN Wei-ying, GAO Jun-qin*, AN Jing, ZHANG Xiao-ya

2016, 35(9):  2293-2298. 

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Carbon pools of alpine wetland and meadow ecosystems in the Qinghai-Tibet Plateau play a vital role in carbon cycling of Chinese terrestrial ecosystems. This study selected three types of habitats including inside tussock, outside tussock in wetlands and alpine meadow in the QinghaiTibet Plateau, and analyzed their carbon pool difference of vegetation, 0-30 cm soil layer and ecosystem. Results showed that vegetation carbon pools in wetland inside tussock (1.54±0.11 kg·m^-2) and outside tussock (1.57±0.20 kg·m^-2) were significantly higher than that in meadow (0.83±0.05 kg·m^-2). Soil organic carbon (SOC) pool in wetland outside tussock was 21.99±1.18 kg·m^-2, significantly higher than that in meadow and inside tussock. There was no significant difference in SOC between wetland outside tussock and meadow. The total ecosystem carbon pool in wetland outside tussock was the highest (23.53±1.18 kg·m^-2), but there was no significant difference between that in wetland inside tussock (19.53±1.43 kg·m^-2) and that in meadow (18.70±0.81 kg·m^-2). Therefore, it is necessary to distinguish carbon pools in wetland inside tussock and outside tussock to accurately estimate carbon stocks in alpine wetland in future.

Influence of altitude on main seed reserves of common species in alpine meadow on the northeastern Tsinghai-Tibet Plateau.

YANG Hui-xian1, BU Hai-yan1*, GE Wen-jing1, WANG Xue-jing1, XU Dang-hui1, XIA Yu-bin1, MA Bing1, WANG Shun-xia2

2016, 35(9):  2299-2312. 

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The components and contents of main seed reserves are very important to seed germination and subsequent seedling establishment. The different seed germination and seedling growth strategies might be shaped by the difference in contents of seed reserves due to their different functional effects. In this study, the main reserve contents in seeds of 227 species on the northeastern TsinghaiTibet Plateau was analyzed, which could provide a theoretical basis for adaptability of alpine plants. The contents of crude fats were determined by Soxhlet extraction with petroleum (60-90 ℃) as solvent for 8 hours; the contents of soluble sugar and starch were determined by anthrone colorimetric method; protein contents were obtained by Coomassie Brilliant Blue G-250. The results showed that regardless of intraspecific and interspecific variation, the contents of crude fats and soluble sugar were higher and the protein content was lower at high altitude, and the starch content had no obvious change with increasing altitude. Due to the decreased temperature with increasing altitude, relatively higher percentages of fats and soluble sugars in seeds at higher altitude might provide enough energy for seed germination and initial growth of seedlings. Therefore, this pattern might be an adaptive selection to alpine environment.

Population structure and spatial pattern of Alchornea davidii in different disturbed Karst habitats in Chongqing.

ZENG Jia-qing, ZHU Jia-xing, WANG Wei, TAO Jian-ping*

2016, 35(9):  2313-2320. 

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Alchornea davidii is an adaptive species, playing important roles in water and soil conservation in Karst areas. To analyze the differences of population structures, dynamics and spatial patterns of A. davidii, and further to provide guidance for its better use in vegetation restoration, a comparative study was carried out under four different disturbed (mild, moderate, strong and severe) Karst environments in Chongqing. The results showed that: (1) the population age structure presented an upward pyramid type and the population size kept growing under moderate, strong and severe disturbances. (2) Population survival curve followed a stable Deevey Ⅱ curve under mild and moderate disturbances, but a Deevey Ⅲ curve with a strong population increase under strong and severe disturbances. (3) Populations under mild and moderate disturbances had higher survival rate and life expectancy, and their survival rate and cumulative mortality rate had smaller fluctuation than those under strong and severe disturbances. The populations under severe disturbance suffered a severe environmental screening from the first age class to the second age class. (4) The values of dynamic quantitative index V_pi and V′_pi increased with disturbance intensity, indicating that the populations had higher growing ability in highly disturbed environment. (5) All populations under different disturbances showed an obvious clumped distribution at five different plot sizes, and the patchiness index of populations in highly disturbed environments was lower than that in lowly disturbed environments, which suggested that the former populations were more expanding. Therefore, A. davidii is suitable for early stage vegetation restoration in Karst areas.

Effects of environmental factors on the composition and richness of understory species in low-function forests in Beijing low mountain areas.

XUE Ou, WEI Tian-xing*, ZHU Jin-zhao

2016, 35(9):  2321-2328. 

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This study examined the relationship between environmental factors and composition and richness of the understory species in three typical low-function forests (Pinus tabuliformis, Robinia pseudoacacia and Platycladus orientalis) in Beijing low mountain areas, to explore the response of species to the environmental factors in shrub and herb layers and confirm the primary factors determining the species richness. A total of 34 plots were established for investigation. Canonical correspondence analysis (CCA) was used to elucidate the relationship between species composition and environmental factors (altitude, slope aspect, slope position, slope, and canopy density), partial CCA to calculate the respective importance of environmental factors in species composition, and grey correlation degree analysis to fit the response of species richness to each environmental factor. Our results indicated that the net effects of altitude and slope on species composition in shrub layer were significant (P<0.05), and that of canopy density in herb layer was significant (P<0.05). Slope had the greatest effect on species richness in shrub layer with the grey correlation value 0.734, and altitude showed the highest correlation degree with a value of 0.700 in herb layer. Species composition and richness in each layer responded distinctly to the same environmental factor. Altitude and slope were the main factors affecting species composition in shrub layer among the five factors, and canopy density was the main factor in herb layer. Slope and altitude were the main factors affecting species richness in shrub and herb layers, respectively.

Species composition and community structure of open forest land in Aerxiang of Zhangwu County in northwestern Liaoning Province based on large sample plot method.

BAI Xue-jiao1,2, ZHONG Bo-wen1, WEI Ya-wei1,2, QIN Sheng-jin1,2, ZHOU Yong-bin1,2, YIN You1,2*

2016, 35(9):  2329-2335. 

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Zhangwu County is located in the southern margin of Horqin sandy land in northwestern Liaoning Province. The restoration and reconstruction of vegetation communities in this area is the research focus. In this paper, a 100 m×100 m monitoring plot was established in July 2014 in the open forest land in Aerxiang, Zhangwu County, Liaoning Province by using the large plot forest monitoring method. All woody and lianas individuals with diameter at breast height above 1 cm were investigated. The results showed that the number of species in this open forest land was less than that of the montane region of eastern Liaoning, totaling 10 species, belonging to 9 families 9 genera. The number of independent individuals was 393, and the number of individuals was 592 in the monitoring plot. Crataegus pinnatifida var. majo r and Populus × canadensis were dominant species according to importance value (0.316 and 0.295, respectively). Ulmus pumila and Pinus sylvestris var. mongolica occupied a certain proportion in this open forest land (with abundance of 47 and 26, respectively), and their regeneration was good. From the spatial distribution of species, the main tree species in forest except for P. sylvestris var. mongolica did not exhibit obvious aggregated distribution pattern; some small trees and shrubs or vines exhibited relatively aggregated distribution pattern, but did not exhibit a clear correlation with terrain.

Biomass of mulberry under planting modes of different gender combinations.

ZHU Juan1, LIU Gang2, XIAO Juan1, ZHU Shi-hui1, ZENG Zhen1, XU Xiao1, DONG Ting-fa1*

2016, 35(9):  2336-2340. 

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Seedlings of Morus alba were grown in different sex cultivation modes (female-female, F-F; male-male, M-M; female-male, F-M) to evaluate their biomass and allocation. The results showed that the total biomass of M. alba in modes F-F and F-M were higher than in M-M, with increments of 31.6% and 39.2%, respectively. The leaf biomass of M-M was lower than that of F-F (-41.7%), while the root biomass of F-M was higher than that of F-F (+34.5%). Root biomass fraction and root to shoot ratio of F-M were the highest among the three cultivation modes. Our results indicated that the biomass of M. alba was related to the sexrelated cultivation mode, with the highest in F-M and the lowest in M-M among the three treatments.

 

Photosynthetic performance of five tree species seedlings in subtropical China.

TANG Jing-chao1, LIU Ping2, SHI Zuo-min1,3*, LUO Da1, LIU Shi-rong1

2016, 35(9):  2341-2347. 

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Leaf photosynthetic characteristics of five tree species, i.e. Dalbergia odorifera, Acrocarpus fraxinifolius, Erythrophleum fordii, Castanopsis hystrix and Betula alnoides seedlings were studied in this paper. The results showed that D. odorifera, B. alnoides and A. fraxinifolius had higher light saturation point (LSP) and light compensation point (LCP) than C. hystrix and E. fordii, so that the former group could make better use of highintensity illumination, while the later group could tolerate shading. High utilization capacity of CO₂ (i.e. lower carbon dioxide compensation point (CCP) and higher carboxylation efficiency (CE)) enabled D. odorifera with high photosynthetic capacity. Balanced supply capacity of CO₂ (i.e. stomatal conductance (g_s) and intercellular CO₂ concentration (C_i)) and utilization capacity of CO₂ enabled A. fraxinifolius with high photosynthetic capacity too. Although B. alnoides had high capacity of supplying CO₂ to photosynthetic apparatus, low capacity of using CO₂ limited its photosynthetic capacity. E. fordii and C. hystrix had low supply and utilization capacity of CO₂, resulting in their lower photosynthetic capacity than the other tree species.

Effects of snow cover on seed germination of ten desert plant species.

BIE Bi-wu1,2, ZHOU Xiao-bing1, ZHANG Yuan-ming1*

2016, 35(9):  2348-2354. 

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In this study, ten desert species including three lifeforms from Gurbantunggut Desert were selected to study the effects of different snow covers on seed germination. Three kinds of snow cover treatments were settled, i.e. snow doubling, natural snow and snow removal. Based on the results from indoor experiments, the seed germination types could be divided into four types, including high germination percentage with rapid germination rate, high germination percentage with slow germination rate, low germination percentage with rapid germination rate, and low germination percentage with slow germination rate. The treatments of double snow cover had positive or neutral effects on seed germination, while snow removal showed negative or neutral effects. After indoor regermination of those seeds which did not germinate in field sites, we found that snow cover had positive, neutral or negative effects on total germination percentages. Our results indicated that the germination of seeds from desert ecosystems had diverse germination types, which were related to the plant growth environment. The snow cover affected plant presence by changing the field or total germination percentages. Different species in the desert ecosystems evolved into different response strategies under changing environments (i.e. snow cover), most of which were not lifeform depended. The diversity of seed germination responses resulted from longterm evolution, being beneficial for the plant community to keep its structure and function stability.

Effects of  nitrogen forms and  ratios on photosynthetic characters and enzyme activities in nitrogen metabolism of Phyllostachys violascens. 

YE Li-sha, CHEN Shuang-lin*

2016, 35(9):  2355-2360. 

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In order to provide scientific guidance for nitrogen fertilization in Phyllostachys violascens stands, a pot experiment was  carried out with five ratios of NO₃^--N∶NH₄⁺-N at 1∶0, 2∶1, 1∶1, 1∶2 and 0∶1. Measured indicators included chlorophyll a (Chla), chlorophyll b (Chlb) and carotenoids (Car) contents, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (T_r), and activities of nitrate reductase (NR) and glutamine synthetase (GS) in leaves of Phyllostachys violascens. Results showed that, with increasing NH₄⁺-N proportion in nitrogen supply, the  photosynthetic pigment contents, G_s, C_i and T_r  rose at first and then fell. These variables under the treatment of ammonium/nitrate ratio at 1∶2 were significantly higher than those under the other treatments, while C_i variation was opposite. With increasing the proportion of NH₄⁺-N, the activities of NR and GS showed a trend of increase at first and then decrease, being not significantly different among the mixed nutrition treatment, but higher in the mixed nutrition treatments than in the single nitrogen treatments. Overall, it might be concluded that P. violascens  is a kind of plant that slightly prefers ammonium, and that mixture of ammonium and nitrate can facilitate leaf photosynthesis and nitrogen assimilation.

Properties of soil aggregates in purple soils during re-vegetation on sloping land in relation to soil characteristics.

YANG Ning1,2, ZOU Dong-sheng2*, FU Mei-yun1, YANG Man-yuan1, LIN Zhong-gui1

2016, 35(9):  2361-2368. 

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Five types of plots, grass (GS), frutex and grass (FG), frutex (FX), arbor and frutex (AF), and arbor (AR) communities, were selected to study the properties of soil aggregates in different revegetation stages and their main influencing factors of purple soils on sloping land in Hengyang, Hunan Province, China by using spatial series instead of time series. The five communities in purple soils on sloping land were similar in site conditions, and denoted as five different successive stages. The relationships between the properties of soil aggregates and the main influencing factors were determined by canonical correlation analysis (CCA) and principal component analysis (PCA). The results showed that the contents of large aggregates increased significantly in the process of revegetation (P<0.05); the aggregates >5 mm diameter were dominant in 0-2 m soil layer, accounting for 50%-80%, followed by the aggregates 5-2 mm diameter with a proportion of 10%-15%. With the deepening of soil layers, the sum of aggregates decreased significantly in GS, FG and AF (P<0.05), increased after a decrease and then decreased in FX (P<0.05), and increased at first and then decreased in AR (P<0.05). In different re-vegetation stages and different soil layers, mean weight diameter (MWD) of aggregates showed different variation patterns: in 0-40 cm soil layer, highest in FW (P<0.05); in 40-80 cm soil layer, decreased after an increase and then increased with re-vegetation (P<0.05); in 80-130 cm and 130-200 cm soil layers, increased significantly with revegetation (P<0.05). With the deepening of soil layers, MWD decreased significantly in GS, FG and FX (P<0.05), and increased at first and then decreased in AF and AR (P<0.05). CCA showed that soil organic matter (SOM) and total nitrogen (TN) had great influence on aggregates >5 mm and 1-0.5 mm, while Al₂O₃, Fe₂O₃ and <0.01 mm physical clay had great influence on aggregates 2-1 mm and 0.5-0.25 mm. PCA showed that SOM, TN, Al₂O₃ and Fe₂O₃ were the main factors influencing soil aggregates, followed by <0.002 mm clay and <0.01 mm physical clay. Our study indicated that re-vegetation could change soil structure, leading to re-distribution of soil aggregates and formation of macro-aggregates, and therefore improving the stability of soil aggregates.

Impacts of leaf litter decomposition of invasive plant Ambrosia trifida on soil nematode community structure.

LU Xiu-rong1, LIU Ting1, WANG Rui1, WANG Hui1*, DUAN Yu-xi2

2016, 35(9):  2369-2378. 

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To reveal the impacts of exotic plant invasions on soil ecosystem, we studied the effects of leaf litter decomposition of the invasive plant Ambrosia trifida on soil nematode community structure and diversity. Leaf litters of the invader and the co-occurring native Artemisia selengensis collected in Shenyang were added on soils in micro-ecotrons, and decomposed for different periods. Then we collected the soils and analyzed nematodes. The results showed that the invader had a higher litter decomposition rate than the native species, which may be associated with the higher nitrogen concentration for the invader. With increasing treatment time the differences in the densities of bacterivores, fungivores, and total nematodes increased between treatments. After 45 days of leaf litter decomposition, the densities of total nematodes and fungivores were significantly higher in invasive plant litter treatment than in native plant litter treatment. After 90 days of treatments, the densities of bacterivores and fungivores were significantly higher in invasive litter treatment than in native plant litter treatment. There was an increasing trend in enrichment index but a declined trend in structure index with increasing treatment time. After 90 days of treatments, the structure index was significantly higher in the invasive plant litter treatment than in the native plant litter treatment, while the difference in soil nematode diversity index was not significant between treatments. Our results suggest that leaf litter decomposition of the invasive species facilitates soil nematode proliferation and alters its community structure, but has no effect on α diversity.

 

Effects of land use change on soil organic carbon fractions in mangrove wetland of Zhangjiangkou. 

CHEN Zhi-jie1,2, HAN Shi-jie1, ZHANG Jun-hui1*

2016, 35(9):  2379-2385. 

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The effect of land use change on soil organic carbon (SOC) is a major research context of global carbon cycling. SOC content and its fractions were determined from soils collected from three land use types including mangrove wetland (WS), dry land (converted from wetland, DS) and paddy soil (PS) in Zhangjiangkou, Fujian, China. Results showed that SOC content in WS soil was significantly higher than that in DS (by 29.50%) and PS (19.56%). Conversion of WS to DS increased the contents of dissolved organic carbon (DOC), microbial biomass carbon (MBC) and mineralassociated organic carbon (MOC) significantly by 40.39%, 248.43% and 144.00% respectively, while decreased the contents of heavy fraction organic carbon (HFOC), light fraction organic carbon (LFOC) and coarse particulate organic carbon (CPOC) contents by 20.91%, 46.44%, 36.58%, respectively. The content of all SOC fractions in PS were higher than in DS, but lower than in WS, except MBC, FPOC and MOC. Pearson correlation showed that SOC content significantly correlated to HFOC, LFOC, CPOC and MOC contents. These findings suggest that the conversion of mangrove wetland to dry land might trigger the loss of SOC, while soil C content could be increased by reasonable management.

Effects of poplar-maize intercropping on soil moisture and soil nutrient contents in northern Liaoning of China.

WANG Ke-lin1, HUANG Yue1, SUN Xue-kai1, ZENG De-hui1*

2016, 35(9):  2386-2392. 

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A great amount of tree-based intercropping systems has been established in Northeast China. Understanding the distribution patterns of soil moisture and soil nutrients of treebased intercropping systems can be beneficial to the ecological sustainability and productivity improvement of tree-based intercropping systems. An investigation was conducted in poplar-maize intercropping and maize monoculture systems in Fujia Mechanical Forest Farm in Liaoning Province to examine the effects of treebased intercropping on the distribution of soil moisture and soil nutrients after maize harvesting. Results showed that intercropping  led to a significantly lower soil moisture in the 0-100 cm soil layer, higher soil inorganic nitrogen content in the 10-100 cm soil layer and higher soil organic nitrogen content in the 0-50 cm soil layer, and also increased the difference of soil organic carbon, total phosphorus contents between the 0-30 cm soil layer and the 30-100 cm soil layer. Furthermore,  intercropping  altered the correlations of soil moisture and soil nutrients. Soil organic nitrogen, organic carbon and total phosphorus contents significantly correlated with soil moisture and soil inorganic nitrogen content in the maize monoculture system, while weakly correlated with these variables in the poplar-maize intercropping system. These results provide scientific guidance for soil water and nutrient management of tree-based intercropping systems, and lay a foundation of further study of soil nutrient cycling in agroforestry systems in northern Liaoning Province.

Comparison of the energy balance characteristics of cropland on catchment and field scales in low hilly region of red soil.

LI Yang1,2, JING Yuan-shu1,2,3*, LI Gen1,2, JING Zhi-hao1,2

2016, 35(9):  2393-2403. 

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Analysis of energy balance characteristics of cropland and its affecting factors has great significance to improve agricultural production and hydrothermal resource utilization in the region of red soil. Based on the data measured by large aperture scintillometer, Bowen ratio instrument and automatic meteorological station in a hilly region of red soil, we analyzed the characteristics of energy balance and the correlation between water and heat flux and meteorological elements in the hilly region of red soil. The results showed that the diurnal variation of the components of energy balance all showed a monotone trend on the two scales due to the weather conditions. The latent heat flux had the greatest values, while sensible heat flux and soil heat flux values were lower. The monthly variation of components of energy balance presented a same trend on the two scales. The sensible heat flux was lower on the catchment scale than on the field scale, but the latent heat flux was vice versa. The net radiation, air temperature, relative humidity, atmospheric pressure, and average wind speed were the main factors affecting water and heat fluxes on the two scales, while vapor pressure and precipitation had inconsistent effects on water and heat fluxes on the two scales.

Effects of elevated atmospheric CO₂ and temperature on diurnal courses of photosynthesis in leaves of Japonica rice.

ZHOU Ning1,2, SHEN Shi-bo1, JING Li-quan1, WANG Yun-xia3, ZHU Jian-guo4, YANG Lian-xin1*, WANG Yu-long1*

2016, 35(9):  2404-2416. 

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A widely cultivated inbred Japonica rice (Oryza sativa L.) Wuyunjing 23 was grown at two levels of CO₂ (ambient and elevated CO₂ concentration) and two temperature regimes (ambient and elevated temperature) by using a free air CO₂ enrichment (FACE) technology. The diurnal courses (i.e., at 09:00, 11:00, 13:00, 15:00 and 17:00) of leaf photosynthesis at different growth stages of rice were measured, namely 61, 75, 92, 109 and 118 days after transplanting (DAT). Net photosynthetic rate (P_n) and leaf water use efficiency (WUE) of rice on 61 DAT increased nearly 40% by elevated CO₂ concentration (200 μmol·mol^-1 more than ambient CO₂). The increment significantly decreased with the advance of the growth stages, and even disappeared at the late grainfilling stage. A consistent trend of decrease was detected on stomatal conductance (G_s) and transpiration rate (T_r) at different time points on 75, 92 and 109 DAT under elevated CO₂ concentration, and the greatest reduction reached 14% and 5% for G_s and T_r, respectively. Elevated CO₂ concentration had no significant effect on the ratio of intercellular to air CO₂ concentration (C_i/C_a) and stomatal limitation value (L_s) during the early rice growth season, but significantly increased C_i/C_a at the last three growth stages in the range of 4%-8%, resulting in decreases in L_s in the range of 10%-27%. Average temperature increase of 1 ℃ had a positive effect on P_n, G_s, T_r and WUE at the early rice growth stages, but negative effects were found at the late grain filling stages. No clear CO₂ by temperature interaction was detected for most of the measured photosynthetic traits except P_n on 61 DAT. The above results suggested that the elevated atmospheric CO₂ level had a greater effect than the elevated temperature on photosynthetic parameters of Wuyunjing 23. The elevated CO₂ induced photosynthetic down-regulation on rice was observed at two temperature regimes.

Effects of reduced nitrogen and phosphorus applications and iron plaque formation on root growth of rice seedlings under mercury stress.

HUANG Tian-yuan1, DENG Hong1,2,3*

2016, 35(9):  2417-2421. 

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Through the measurement of root morphology and biomass distribution, this paper studied the response of rice (Oryza sativa L. cv. Lvhan No. 1) root growth to nitrogen deficiency, phosphorus deficiency and iron plaque formation under mercury stress. The results showed that nitrogen deficiency, phosphorus deficiency and iron plaque formation all promoted the growth of root. The three treatments (nitrogen deficiency, phosphorus deficiency and iron plaque formation) lengthened the root by 35.8%, 75.3% and 102.2%, respectively. In addition, the root surface area promoted by 46.6%, 47.8% and 60.8%, respectively, and the rootshoot ratio raised to 29.9%, 27.3% and 28.23%, respectively, compared to 22.1% in the control group. When mercury was added into the culture solution (0.5 mg Hg(II)·L^-1), however, the growth promoting effect faded away. Mercury stress alone could inhibit the root growth, but the effect was not statistically significant. However, induced iron plaque could promote the root growth with nutrition deficiency under mercury stress, showing that the root length increased by 64.6% under nitrogen deficiency and the length, surface area and tips improved by 74.9%, 56.5% and 94.7% under phosphorus deficiency, respectively. Overall, mercury has negative effects on root system establishment of rice seedlings, weakening rice root’s response to nutrition deficiency. On the other hand, iron plaque formation can improve the growth of root system, and protect the roots from mercury stress to a certain extent.

Effects of transgenic Cry1Ab/Ac rice on the species diversity of zooplankton community in paddy fields.

MO Shu-yin1, LIU Yu-fang1*, SUN Li-chuan1, LI Fei1, GE Feng2

2016, 35(9):  2422-2428. 

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To understand the safety of transgenic Bt rice on zooplankton community in paddy fields, a safety evaluation experiment was conducted in 3 consecutive years in Xiangtan, Hunan Province, by using the transgenic Cry1Ab/Ac rice ‘Huahui No. 1’ (HH1 for short) as Bt rice material and the nontransgenic parent rice ‘Minghui63’ (MH63 for short) as control. The zooplankton community in paddy fields was used as bioindicator. The results showed that the similarity coefficients of all species composition and the dominant species of zooplankton community in HH1 and MH63 paddy fields were higher than 0.70 and 0.89, respectively. By comprehensive and temporal dynamic analyses, the parameters of zooplankton community in HH1 paddy fields in 2012, 2013 and 2014 displayed almost equal values and similar trends compared with those in MH63 paddy fields. These results suggested that transgenic Cry1Ab/Ac rice had no obvious adverse effect on zooplankton community in paddy fields.

Effects of food deprivation on fast-start swimming and predator-prey interaction between a predator and prey fish species.

QIN Ying-lian, PENG HAN Liu-yi, FU Shi-jian*

2016, 35(9):  2429-2434. 

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Fast-start is one of the important swimming modes, which is closely related to predation and escape behaviors in fish species. The aims of the present study were to compare the effects of food deprivation on fast-start swimming performance between a predator Channa argus and a prey Pseudorasbora parva and the consequent outcome of predatorprey interaction. To achieve our goals, variables related to faststart swimming were measured in C. argus after 0, 7, 14, 28, 63 (semilethal starvation time) days of starvation and P. parva after 0, 7, 14 (semilethal starvation time) days of starvation under water temperature of (25±1) ℃. The predationprey interaction course was also documented after 0, 7 and 14 days of starvation. The results showed that C. argus showed  significantly higher maximum linear velocity (V_max), moving distance during first 120 ms (S_120ms) and maximum linear acceleration (A_max) than P. parva (P<0.05), whereas their reaction latency (R) showed no significant difference. All measured variables of fast-start swimming in both fish species were quite conservative as only the semilethal group (14 or 63 days) showed significantly lower V_max, shorter S_120ms and slower R (P<0.05), with the predator showing relatively profound change in R and the prey showing relatively profound change in V_max. Fourteen days of starvation resulted in more hunting activities of the predator and shorter duration while hunting successfully. The present study suggested that the faststart swimming of the prey was more sensitive to starvation than that of the predator and the two species showed different response strategies possibly due to differences in availability of food resources and foraging modes. In general, starvation with the same degree would be more beneficial to the predator according to the outcome of predatorprey interaction.

Spatial-temporal distribution of Antarctic krill fishing ground and their relationship with sea surface temperature in waters around the South Shetland Islands.

RUAN Chao1,2, ZHANG Heng1*, CUI Xue-sen1, WU Yu-mei1, YANG Sheng-long1

2016, 35(9):  2435-2441. 

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According to the data on the catch of the Antarctic krill in the Southern Ocean of 48.1 fishing area and sea surface temperature (SST) obtained by remote sensing method, this study analyzed the spatialtemporal distribution of catch per unit of fishing effort (CPUE) of the Antarctic krill and the relationship between CPUE with SST from 2010 to 2014. The results showed that the Antarctic krill fishery mainly distributed in the northeast of the South Shetland Islands (61°S-64°S, 58°W-60°W). Generally, there were obvious seasonal changes in CPUE of this fishery. The second higher value of CPUE appeared in December (about 16.0 t·h^-1). Until February of the next year, the CPUE gradually decreased, and then an increasing trend was observed from February to April. The CPUE reached the highest value in April (about 16.5 t·h^-1), and then began to decrease after April. From December to February of the following year, the fishery center moved towards the Southeast and there was a huge change in the fishery center. From February to May, it roughly moved to the West and arrived at its southern end. A slight change of fishery center happened from March to May, mainly at 63°S-63.5°S, 58.5°W-59.5°W. Moreover, in June, October and December, the fishery center gradually developed northward and reached the northernmost or easternmost part in December. On the whole, the suitable SST values of 48.1 fishery in Antarctic krill fishing areas ranged from -0.1 to 1.2 ℃. It was suggested that summer and autumn (from December to May in the next year) were the main fishing seasons due to the suitable SST.

Physiological response of Lantana camara L. under lead stress and subcellular distribution of lead.

LUO Xian1, FANG Ji-yu2, ZHANG Chun-mei2, JIA Yong-xia2*, ZHANG Shi-rong3, XU Xiao-xun3, LI Ting2

2016, 35(9):  2442-2448. 

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In this study, a pot experiment was conducted to investigate the growth, antioxidant enzyme activities and lead (Pb) uptake, translocation and Pb subcellular distribution of Lantana comara L. under Pb treatment with different concentrations. The results showed that the dry weight of L. camara reached the maximum when the Pb concentration was at 100 mg·kg^-1, and significantly higher than the control, whereas the dry weight decreased significantly when soil Pb was higher than 600 mg·kg^-1, and the growth of L. camara was inhibited significantly. When the Pb concentration in soil was lower than 600 mg·kg^-1, the activity of antioxidant enzymes in L. camara was higher, which could alleviate the Pb induced oxidative stress. However, these activities displayed decreases when the soil Pb was higher than 600 mg·kg^-1, MDA contents and electrolyte leakage in L. camara were enhanced significantly, and induced membrane lipid peroxidation damage. With the increasing of Pb concentration in soil, the contents of Pb in different organs of L. camara increased gradually, and Pb content in root was higher than that in shoot when the Pb concentration in soil was lower than 1200 mg·kg^-1, and vise versa. It was suggested that L. camara root had a strong Pb retention capacity, which can reduce the toxicity of Pb to the organs of shoot. The proportion of Pb in soluble fraction in roots and leaves were highest, followed by cell wall. Therefore, L. camara is a Pbtolerant plant; its tolerance mechanism includes antioxidant system response, root retention, isolation in soluble fraction and cell wall immobilization.

Winter bedsite selection by hazel grouse (Bonasa bonasia) in Liangshui National Nature Reserve, Heilongjiang Province.

XU Ling-xia1, XU Lin2, WANG Guang-xin2, ZONG Cheng1*

2016, 35(9):  2449-2454. 

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Habitat use and selection is one of the mechanisms for wildlife adaptation to natural environment, and winter bed-site selection is an important strategy of increasing antipredation ability, energy storage, and withstanding harsh weather. To determine winter habitat selection strategy of hazel grouse (Bonasa bonasia), we investigated a total of 34 bed-site locations and randomly selected relative control plots, then identified and measured 20 potential factors influencing bedsite habitat selection in Liangshui National Nature Reserve from November 2015 to January 2016. Methods of factor distribution frequency, principal component analysis, and Bailey’s discriminant analysis were used. The results showed that hazel grouses preferred strongly to mixed coniferous and broadleaved forests with low tree density, high shrub density, and flat sunny slope (slope gradient <10°). The primary factors influencing hazel grouse’s bed-site selection were distance to road, tree density and shrub density. Hazel grouses preferred bed-sites less than 10 m far from the road, randomly selected sites 10 to 50 m far from the road, and avoided sites more than 50 m far from the road. Hazel grouses tended to bed-sites with 300-400 trees·hm^-2 and more than 2500 shrubs·hm^-2; randomly selected those with more than 400 trees·hm^-2 or less than 2500 shrubs·hm^-2. This study provided significant information for winter survival and habitat management of hazel grouses.

Reintroduction of an endangered species, Changium smyrnioides, into urban green spaces based on temporal niche.

ZHU Kang-di1, YANG Guo-fu1, FAN Mei-ying1,2, LU Yi-jun3, QU Ze-long1, REN Yuan1, GE Ying1, CHANG Jie1*

2016, 35(9):  2455-2462. 

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Urban green spaces have received more and more attention for rare and endangered species conservation. However, the conservation potential in urban green spaces has been less studied. Based on the habitat survey of Changium smyrnioides in cities Hangzhou and Ningbo and the eco-physiological experiment, we determined the temporal niche of this species. Then we investigated the urban green spaces to search the habitats that are similar to that in the field and analyzed the potential and the way for reintroducing C. smyrnioides into urban green spaces. Results show that C. smyrnioides mainly occurs under the deciduous trees in eastern subtropical forest. When the deciduous trees are with no leaves from November to next April, the understory light and temperature conditions are suitable for the growth of C. smyrnioides. In Hangzhou and Ningbo, C. smyrnioides begins to germinate during December and January, and enter a period of high photosynthesis and rapid growth with optimal temperature and light in March; it blooms and the photosynthesis becomes weak in May; it enters dormancy after seed maturation in June. In urban green spaces of Hangzhou and Ningbo, the deciduous tree species account for 62% and 60% of the total number of tree species, respectively. The spaces under these deciduous trees have the potential for C. smyrnioides cultivation. Moreover, the understory habitats of the important deciduous species that similar to the wild species are most suitable for C. smyrnioides reintroduction. At present, there are 18.97 and 18.42 km² of potential habitats for C. smyrnioides in urban green spaces of Hangzhou and Ningbo respectively, and if the potential habitats are taken full use of, 1.01×10⁸ and 0.98×10⁸ individuals of C. smyrnioides can be cultivated, respectively.

 

Measurement and spatial-temporal differences of niche of urban agglomerations on northern slope of Tianshan Mountains.

HU Meng-meng, ZHANG Jun-min*, LIANG Er-min, PENG Li-yuan

2016, 35(9):  2463-2470. 

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Using niche theory and spatial autocorrelation method, an evaluation system for niche of urban agglomerations on the northern slope of Tianshan Mountains was designed; characteristics and changes of niche in socio-economic dimension and urban development dimension from 2003 to 2013 were measured, and then niche spatial structure of urban agglomerations was analyzed. The results showed that the gradient of niche status and trend in the socio-economic dimension was larger than that in the urban development dimension, the former was affected by industrialization, and the latter was constrained by resource endowment. The general niche of the urban agglomerations on the northern slope of Tianshan Mountains was in a relatively stable unipolar group structure. The niche of the UrumqiChangji metropolitan area with Urumqi as the core was far higher than that of ShiheziShawanManasi and KuitunKelamayiWusu secondary groups, in which UrumqiChangji was as a unipolar group, and the latter two as multipolar groups. In recent years, niche distribution patterns and change trends were basically consistent; hotspots were more and expanded in 2013 compared with those in 2003. The core area showed the trend of agglomeration and enhancement, but the level of development was uneven, with the eastern part being better than the central and western parts. Especially, the role of polarization function and agglomeration in UrumqiChangji metropolitan area was even more obvious, where the process of urbanization was much higher than in other regions, and secondary groups also relied on their own advantages in resources to develop. Urban agglomeration had roughly formed a scale, and the urban economy became the core motivation to promote economic development.

Spatial variation and determinants of near-surface N₂O concentration in Shanghai during spring.

WEI Ning1,3, SHE Qian-nan1,3, PENG Xia2,3, ZHU Xi-yang1,3, PAN Chen2,3, XU Qian1, LIU Min1,3*, XIANG Wei-ning1,3

2016, 35(9):  2471-2477. 

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The sources and sinks of atmospheric N₂O have already been well analyzed both on global and regional scales. However, the spatiotemporal distribution characteristics and mechanism of N₂O concentration in urban areas is relatively unclear. In this study, we investigated the spatial pattern and determinants of nearsurface urban N₂O concentration during spring in Shanghai, the commercial and financial center of China. A total number of 173 sampling points covering the whole urban area were collected and analyzed with gas chromatograph (GC). The results indicated that the average N₂O concentration for the region was 311.0±2.0 nmol·mol^-1, with the highest and lowest values in central city (312.0±1.4 nmol·mol^-1) and Qingpu district (309.9±1.7 nmol·mol^-1) of Shanghai, respectively. There was no significant correlation between the concentration of N2O and urbanization. N2O concentration in transportation area and commercial area differed from green land area. N₂O emission from urban rivers, biogenic sources in rural cropland soils and fossil fuel combustion were the main sources of near-surface N₂O in Shanghai.

Correlation of the landscape ecological risk on multi-scales in Shenzhen City.

ZHANG Tian, LIU Yan-xu, PENG Jian, WANG Yang-lin*

2016, 35(9):  2478-2486. 

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Assessment of urban landscape ecological risk could be the quantitative basis of the urban landscape management and the comprehensive risk prevention. In view of the ambiguous relationships of urban landscape ecological risks on various scales, we calculated the correlation of six representative landscape ecological risks on the scales of pixels, watersheds, and subdistricts in Shenzhen City by using the Revised Universal Soil Loss Equation (RUSLE) and the habitat quality evaluation model. The results showed that the higher average value and variation coefficient of the landscape ecological risks in Shenzhen City were found in the western, northern and southeast parts. The soil erosion risk presented a significant negative correlation (P<0.05) with the other risks, while a significant positive correlation (P<0.05) was found among the four risks of urban heat island, habitat damage, surface hardening and crowd gathering. Moreover, the correlation between the landscape diversity and risk increased with the enlargement of the statistical scale. Urban landscape ecological risk was positively correlated to landscape connectivity, which is quite different from the previous studies and reflects the particularity of urban landscape pattern. Therefore, changes in the relationship among urban landscape ecological risks at various scales confirm the needs of multi-scale comprehensive risk prevention of city management.

Change of wetland landscape at Poyang Lake and its response to water level fluctuation.

YOU Hai-lin1,2, XU Li-gang2，3*, LIU Gui-lin2, WU Yong-ming1, LIU Li-zhen1, JIANG Jia-hu2

2016, 35(9):  2487-2493. 

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Based on the 16 high-resolution autumn remote sensing images during 1973-2013, the classification characteristics of wetland landscape and spatial distribution pattern of vegetation and their succession trends in Poyang Lake were studied through  interpretation technology. Combined with water level fluctuations corresponding to the day of each remote sensing image obtained, the change of wetland landscape types at Poyang Lake wetland and its dynamic response to water regime were explored by multivariate statistical method. The results showed that: 1) there were 9 types of extracted wetland landscapes, viz, deepwater, moderatedepth water, shallow water, Carex, reed, swamp, sparsegrassland, mudflat and bareland. The total area of the 9 types of extracted wetland landscapes did not change significantly, which was always maintained at about 3000 km² during 1973-2013; 2) the areas of swamp and sparse-grassland both revealed an increasing trend with a higher increase for swamp, and the area of Carex declined while that of reed increased; 3) there was a significant negative correlation between the water level and the mudflat area. The water level fluctuation had no significant correlation with the areas of the bare-land and wetland vegetation. The results are helpful to explore the eco-hydrology process and its trend at Poyang Lake wetland, and provide a scientific reference for the maintenance of stable ecosystem functions of the seasonal freshwater lake wetland.

Variation of vegetation coverage and its response to climate change in Gannan Plateau from 2000 to 2014.

WANG Wei-jun1, ZHAO Xue-yan1*, WAN Wen-yu1, LI Hua1， XUE Bing2

2016, 35(9):  2494-2504. 

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MODIS NDVI data from 2000 to 2014 were adopted to extract the time series of the vegetation coverage in Gannan Plateau, and its spatial and temporal variation were analyzed. The response of vegetation coverage to climatic variations at annual and monthly time scales was analyzed by using phenological phase, temperature and precipitation time series at Gannan meteorological stations from 2000 to 2014. The results showed that the annual mean temperature increased with an annual rate of 0.04 ℃ and the annual mean precipitation increased with an annual rate of 4.7 mm in the Gannan Plateau from 2000 to 2014. Spatially, precipitation decreased from the southwest to the northeast and the annual mean temperature decreased from the southeast to the northwest. During the past 15 years, the vegetation coverage increased from the southeast to northwest in Gannan Plateau. The mean vegetation coverage was 77.5%, and exhibited apparent spatial heterogeneity, being the highest (77.8%) in forest and the lowest (60.3%) in alpine and subalpine grassland. There was a slight increase of vegetation coverage over the study period with an annual rate of 0.32%. The increase in sloping grassland area was as high as 1.04% per year and the plain grassland area increase was 0.47% per year, while the increases in coverage of alpine and subalpine meadow and forest were lower (0.19% and 0.10% per year, respectively). On the contrary, the marsh wetlands, alpine and subalpine grassland had a slight decrease of vegetation coverage over the study period (-0.03% and -0.06% per year, respectively). At the annual time-scale, there were no significant positive correlations between vegetation coverage and annual temperature or precipitation. However, the vegetation coverage was mainly affected by temperature in alpine and sub-alpine grassland, alpine and sub-alpine meadow, sloping grassland, plain grassland and marsh wetlands, while the vegetation coverage in forest was mainly affected by precipitation. At the monthly timescale, the time-lag response of vegetation coverage to precipitation occurred mainly in early and late growing season, while the time-lag response to temperature occurred mainly in key growth stage, and such response to precipitation was better than that to temperature.

Effects of damming on plant diversity in the inundated and riparian zones of the Three Gorges Reservoir Area, China.

ZHANG Ai-ying1,2, XIONG Gao-ming1, FAN Da-yong1, XIE Zong-qiang1*

2016, 35(9):  2505-2518. 

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The Three Gorges Reservoir adopts a hydrological regime of 175 m water level in winter and 145 m water level in summer, and has formed a reservoir inundated zone with an area of 348 km² since 2007. This change leads to the disappearance of original plant species and plant communities, and the formation of permanent waters and the appearance of novel plant communities that gradually adapt to the environment of riparian zone. We analyzed the plant species diversity in the inundated zone and riparian zone of the Three Gorges Reservoir Area (TGRA) before and after the operation of the reservoir. Results showed that: (1) There were 769 vascular plant species, belonging to 400 genera of 121 families in the inundated area before damming. Perennial herbs, annual herbs and shrubs were co-dominated in this area. After damming, the vascular plant species dropped dramatically to about 300, with shrub losing its dominant role. The percentage of annuals increased from 26.42% to 45.46%, while perennials decreased from 44.43% to 32.47%. Woody plants (trees and shrubs) decreased from 23.71% to 15.15%. (2) In the first three years after the formation of the riparian zone (2008-2010), species decreased persistently. Some species (such as Cynodon dactylon and Xanthium sibiricum) showed advantages in competition after several times of intense submergence. (3) Species diversity increased with elevation in the riparian zone after damming. Species richness index showed an exponential rise, with 8 at 158 m, 10 at 164 m and 13 at 170 m. Shannon index showed an S rise, with two inflection points at 150 m and 171 m. After 8 years of formation of the reservoir riparian zone, the structure and function of plant communities is still changing and far from steady state, and further studies are needed to reveal temporal and spatial trends of plant communities and underlying mechanisms.

Progress in the simulation of drought stress effect on crop production.

MI Na1, ZHANG Yu-shu1*, CAI Fu1, GAO Li-li2, JI Rui-peng1, YU Wen-ying1, GUO Ning2

2016, 35(9):  2519-2526. 

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Among the two types of models that can be used for simulating the main physiological processes that affect crop yield under water deficit stress, a distinction can be made between water management models that do not explicitly simulate crop growth but that have been developed for irrigation planning, and crop growth simulation models that simulate main processes of crop growth (leaf area growth, biomass production and partition). Crop growth models usually estimate the effects of drought stress on carbon assimilation by use of the ratio of actual transpiration to potential transpiration. In recent years, the proposed coupled models that couple the processes of carbon assimilation, transpiration, energy balance, and stomatal behavior improve mechanisms in simulation of the effects of drought stress on crop production. This study synthesizes the mechanisms involved in the different models (FAO water production function, AquaCrop, CERESMaize, WOFOST, EPICphase and coupled models) and presents the main processes of these typi-cal models on how to simulate the drought stress effect on crop growth and development. Based on above discussion, further research in the crop production models is proposed, such as improving the simulation of the effects of drought stress on crop penology, considering the response of anthesissilking interval to water deficit, considering the mechanisms of subsequent effects of drought stress after water recover, developing more physically and physiologically based models. Additionally, effective multidisciplinary collaboration between model programmers, field experimentalists, and plant physiologists will be necessary to model enhancements. Field experiment is an important data source for model developments and enhancements.

Termite caste and postembryonic development.

XU Li-jun1, JI Bao-zhong1*, LIU Shu-wen2, DING Fang1, WANG Ya-zhao1

2016, 35(9):  2527-2536. 

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The division of termite caste involves ontogeny, anatomical structure, external morphology, behavior, group function and other factors. These factors and the contradict perspectives of different authors cause the diverse definitions of caste. In this review, we introduced the types of termite moult, summarized the definition of termite caste and the pathways of termite postembryonic development. Moreover, problems relating with termite caste and the postembryonic development were also discussed.

 

Plateau pika ecology: A review.

PAN Xuan, MIGMAR Wang-dwei*

2016, 35(9):  2537-2543. 

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Plateau pika (Ochotona curzoniae) is a small and dominant lagomorph, endemic to the Qinghai-Tibetan Plateau. This species is of ecological significance for maintaining the biodiversity of grassland ecosystem and improving soil quality in the Qinghai-Tibetan Plateau. Currently, considerable studies have been published on plateau pika ecology. This paper addresses habitat selection, population ecology, reproduction ecology, and behavioral ecology of plateau pika. It also discusses plateau pika’s adaptation to the plateau and correlation with grassland ecosystem. Finally, we put forward the direction of future research on the adaptability of plateau pika on the plateau and its ecological significance.

Photosynthetic characteristics of different plant species based on a mechanistic model of light-response of photosynthesis.

YE Zi-piao1*, HU Wen-hai2, YAN Xiao-hong2,3, DUAN Shi-hua2

2016, 35(9):  2544-2552. 

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To investigate the photosynthetic characteristics of Humulus scandens, Paulownia fortunei and Solanum nigrum, the lightresponse curves of photosynthetic electrons and photosynthesis were measured simultaneously by LI-6400-40B chlorophyll fluorometer. Then the differences in the photosynthetic characteristics of these plants and their courses were studied based on a mechanistic model of lightresponse of photosynthetic electron flow and photosynthesis. The results showed that H. scandens had the lowest chlorophyll content, while its eigenabsorption crosssection was the maximum. The chlorophyll content of P. fortunei was 1.2 times as much as that of S. nigrum, while the electron transport rates of both plants were almost same. The main reasons that determine the differences of photosynthetic characteristics of different plant species are: (1) the eigenabsorption crosssection of lightharvesting pigments of S. nigrum was greater than that of P. fortunei; (2) the minimum average lifetime of photosynthetic pigment molecules in the excited state for S. nigrum was shorter than that of P. fortunei; and (3) the use efficiency of photosynthetic electron of S. nigrum was higher than that of P. fortunei. Moreover, the photosynthetic characteristics of the plants were probably affected by the lightresponse of the effective light absorption cross-section of photosynthetic pigments and the lightresponse of the photosynthetic pigments in the lowest excited state.

Intraspecific and interspecific competition analysis of Cunninghamia lanceolata ecological forest based on weighted Voronoi diagram.

CAO Xiao-yu, LI Ji-ping*, CHEN Lei, HU Yuan-jie

2016, 35(9):  2553-2561. 

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A total of 18 fixed plots were chosen to investigate tree point information within Cunninghamia lanceolata ecological forests in Fushou Forest Farm, Pingjiang County, Hunan Pro-vince. The weighted Voronoi diagram was generated based on the effect weight of DBH, tree height and average crown diameter on forest competition zone determined by using grey relational degree to determine tree competition unit. Accordingly, we put forward W_V_Hegyi competition index that can reflect forest competition more scientifically and that was used to analyze intraspecific and interspecific competition within and between C. lanceolata (dominant species) and other associated tree species. The results showed that the effect weights of DBH, tree height and average crown diameter on forest competition zone were 0.38, 0.29, and 0.33, and the number of competitive trees towards one single object tree ranged from 2 to 14 with 13 possible values in the tree competition unit determined by the weighted Voronoi diagram. According to the simulation effect of curve model based on competition index and DBH of target trees, W_V_Hegyi competition index was better than Hegyi competition index and V_Hegyi competition index. The competitive pressure of dominant species (C. lanceolata) mainly came from intraspecific competition. The average intraspecific competition indexes of C. lanceolata in 3 age groups (young forest, middleaged forest and nearmature forest) were 1.36, 0.99, and 0.63, and the average interspecific competition indexes of the 3 age groups were 0.87, 0.82, and 0.46, respectively. The average intraspecific competition indexes were 1.56, 1.37 and 1.21 times of interspecific competition indexes, respectively. The competition pressure of other associated species mainly came from interspecific competition. Since the proportion of these species was very small, they had little effect on the competition situation within whole C. lanceolata ecological forest stands.

 

Comparison of the prediction models of the potential geographical distribution of Forsythia suspense.

YANG Yang1, WEI Hai-yan1*, WANG Dan1, SHANG Zhong-hui1, MAO Ya-juan1, YANG He-yu2, GU Wei2

2016, 35(9):  2562-2568. 

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Forsythia suspense (Thunb.) Vahl. is a kind of bulk medicinal material. It is also a common species for ornamental use and for water and soil conservation. Based on 119 current geographical distribution records of F. suspense and 12 related factors, including climate, soil and topography, the potential geographic distribution of F. suspense was assessed by generalized linear models (GLM), random forest (RF), generalized boosting model or usually called boosted regression trees (GBM/BRT), and artificial neural network (ANN) in the BioMod2 package. The results showed that the four models had good performance, among which the RF model had the best efficiency, with high values of evaluation indexes, including AUC (0.95), TSS (0.81), and KAPPA (0.68). For the growth of F. Suspense, the sensitivity of temperature was higher than that of precipitation. The potential geographic distribution of F. suspense situated in the mountains and along rivers in Shaanxi, Shanxi, Hubei, Henan, Liaoning. The suitable habitats of F. suspense are characterized by an altitude of 250-2200 m, annual mean temperature of 12.1-17.3 ℃ and annual precipitation of 400-1000 mm. This study provides guidance for F. suspense’s planting.