Table of Content

10 June 2017, Volume 36 Issue 6

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Carbon storage and allocation in hardwood broad-leaved forests with different stand ages in Guangxi.

WANG Hua1,2, SU Liang1,2,3*, SONG Tong-qing2,3, ZENG Fu-ping2,3, PENG Wan-xia2,3, DU Hu2,3, CHEN Li1,2,3, ZHANG Fang2,3

2017, 36(6):  1465-1472. 

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Based on the data of biomass at five different stand ages, i.e., young forest, middleaged forest, pre-mature forest, mature forest and overmature forest, the carbon storage and distribution patterns of hardwood broadleaved forests at different ages in Guangxi were studied. The results showed that the total carbon storage of the hardwood broadleaved forest ecosystems presented in the order of overmature forest (514.44 t·hm^-2), mature forest (439.92 t·hm^-2), young forest (325.29 t·hm^-2), middleaged forest (315.27 t·hm^-2), and premature forest (214.64 t·hm^-2). The carbon storage distribution of different stand ages was in the order of soil layer > vegetation layer > litterfall layer, and belowground part > aboveground part. The carbon storage of the vegetation layer ranged from 79.12 to 179.17 t·hm^-2, which accounted for 23.09%-43.84% of the total carbon storage and increased with stand age. The carbon storage of litterfall ranged from 0.91 to 2.32 t·hm^-2, which accounted for 0.21%-0.76% of the total carbon storage and showed a “W” type variation with the increasing age. The carbon storage of soil layer ranged from 120.55 to 335.27 t·hm^-2, which decreased firstly and then increased with the increasing age and accounted for 56.16%-76.91% of the total carbon storage. The maximum carbon storage of vegetation layer was tree layer (ranging from 72.35 to 173.07 t·hm^-2), which accounted for 28.92%-76.58% of the tree layer carbon storage and increased with stand age. The maximum carbon storage of the tree layer was trunk (ranging from 44.99 to 110.87 t·hm^-2), which accounted for 17.98%-47.77% of the carbon storage of tree layer and increased with stand age. The proportion of root, branch and leaf accounted for 4.46%-11.82%, 4.52%-11.90%, and 1.95%-5.09% respectively, and increased with stand age.

Rainfall redistribution of Eucalypt plantation in Nanning, Guangxi, China.

REN Shi-qi1,2,3, XIANG Dong-yun2,3, XIAO Wen-fa1*, CHEN Jian-bo2,3,LIANG Yan-fang4, YANG Zhong-ning4, TANG Qing-lan2,3, WU Qi2,3

2017, 36(6):  1473-1480. 

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To understand the characteristics of rainfall redistribution of eucalypt plantations for improving management plan of eucalypt plantations so as to enhance capacity of water and soil conservation of forest stands, this paper did a research on monitoring outside and inside rainfall, throughfall and stemflow from July 2015 to May 2016 based on Guangxi Nanning Eucalypt Plantation Ecosystem Observation and Research Station to analyze characteristics of rainfall redistribution of a Eucalyptus urophylla × E. grandis plantation. The results showed that the total of rainfall was 1536 mm, the total of throughfall was 1042 mm, which accounted for 68% of rainfall, the total of stemflow was 9.2 mm, which only accounted for 0.6% of rainfall, and the total of interception was 490 mm, which accounted for 32% of rainfall. A logarithmic function relationship was established between monthly throughfall and rainfall, and an obvious throughfall was observed when rainfall was more than 25 mm. Throughfall and throughfall rate increased with increasing rainfall intensity; when rainfall intensity was more than rainstorm, the whole outside rain nearly penetrated canopy, forming inside rain. Under the conditions of light rain, moderate rain, heavy rain and rainstorm, accumulative throughfall showed an increasing quadratic polynomial function relationship with accumulative rainfall. Meanwhile, the throughfall beginning time of light rain and moderate rain lagged behind rainfall about 20 min and 10 min, respectively; however, the time of throughfall and rainfall showed a simultaneous change tendency under the heavy rain and rainstorm. In spite of too little stemflow which was ignored in the process of rainfall redistribution estimation, its role should not be neglected. Monthly rain showed a positive power function relationship with monthly interception, but a negative exponential function relationship with interception rate.

Correlation between different lifeform species and habitat in secondary Picea forest.

YANG Xiu-qing, SHI Chan, WANG Xu-gang, MA Hui-jing, YAN Hai-bing*

2017, 36(6):  1481-1487. 

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Based on the survey data of a 4hm² fixed monitoring plot in Pangquangou Nature Reserve on Guandi Mountain, we analyzed correlation between different lifeform species distribution and two habitat factors-terrain and soil in a secondary Picea forest using variance decomposition (RDA) and fitted relationships between the dominant species of trees, small trees and shrubs and principal components of habitat factors by generalized additive model (GAM). The results showed that: (1) Terrain and soil together explained the distribution of trees (53.34%), small trees (55.65%) and shrubs (45.83%), including an independent explanation by terrain (8.36%, 5.06% and 5.48%, respectively), an independent explanation by soil (31.12%, 44.22% and 32.04%, respectively), and a joint part explanation (13.86%, 6.37% and 8.31%, respectively); (2) The principal component analysis of 13 habitat indexes showed that the first four principal components represented 38.76%, 25.73%, 19.41% and 8.93%, respectively, with a cumulative contribution rate of 92.83%; (3) For different species and lifeform species, the degree of correlation between their distribution and the four principal components was different by GAM fitting. The deviations explained by the model were 0.76%-29.00% for tree layer, 0-20.30% for small tree layer and 0.10%-23.50% for shrub layer. Each species and life form were better associated with PC1, and altitude, aspect, available K, N and Mg played an important role in species distribution. The result indicated that the effects of habitat factors such as terrain and soil on the different lifeform species distribution were different, which promoted the coexistence and biodiversity maintaining of species in the secondary Picea forest on Guandi Mountain.

The population structure and dynamics of Quercus variadilis in Nanjing Spirit Valley.

YUAN Zai-xiang1,2, JIN Xue-mei1,2, MA Ting-yao1,2, CHEN Bin1,2, GUAN Qing-wei1,2*, WANG Ling1,2

2017, 36(6):  1488-1494. 

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To evaluate the population dynamics of Quercus variabilis in Nanjing Spirit Valley, this study established a static life table, depicted survival curves and function curves, and made predictions with a timesequence model, based on a field investigation of Q. variabilis population in a deciduous broadleaved forest plot. The results showed that (1) the population was in the stage of expending with dynamic indices (V_pi and V′_pi>0). The survival curve displayed an intermediate pattern between Deevey-I and Deevey-II types. Together with the results from age-class analysis and the patterns of secondary succession, it was suggested that the Q. variabilis population was in a transition between expending stage and stable stage. However, the timesequence model indicated that the period of the transition would be long. Additionally, the fluctuation of population structure showed that, driven by strong environmental filtering, the population resistance, life expectancy and population stability increased while death density decreased with time. (2) Through 70 years of secondary succession in this deciduous broadleaved forest, the population of Q. variabilis showed a fluctuation dynamic, which generally trended to be stable but with a decreasing trend in seedling and sapling frequency. Thus, in terms of forest management, promoting the growth of Q. variabilis seedlings and saplings and ensuring their survival rate can maintain the growth and stability of the Q. variabilis population for the sustainable development of the deciduous broadleaved forest in Nanjing Spirit Valley.

Physiological responses of Cinnamomum camphora seedlings to drought stress and planting density.

WANG Zhuo-min, ZHENG Xin-ying, XUE Li*

2017, 36(6):  1495-1502. 

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In order to understand the mechanism of physiological response of plants to drought stress, one-year-old Cinnamomum camphora seedlings with different planting densities (10, 20, 40, 80 seedlings·m^-2) were grown in drought stress environments by manual simulation, and their physiological indices were determined at 4, 8, 12, 16, 20 d after drought stress. The results showed that the water content of seedlings under drought stress decreased with the extension of drought duration and the decrease amplitude increased with increasing planting density in each drought stage. The chlorophyll content of seedlings except for the density of 10 trees·m^-2 increased and then followed by a decrease with increasing drought duration, and the variation amplitude increased with increasing density. Soluble sugar, soluble protein contents and SOD activity of seedlings under different planting densities increased with increasing drought duration, whereas their proline and MDA contents tended to increase, and the variation amplitude of these indices increased with increasing density. Generally, the drought resistance of C. camphora decreased with increasing density of seedlings.

Effects of nutrient stress on seedling growth and foliar nutrient status of Dalbergia odorifera.

ZHAO Xia, XU Da-ping*, YANG Zeng-jiang, LIU Xiao-jin, ZHANG Ning-nan

2017, 36(6):  1503-1508. 

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Major nutritional elements nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S) were tested with sand culture method for their deficiency or overdose effects on seedling growth and foliar major element composition of Dalbergia odorifera. Specific leaf symptoms were observed in all nutritional stress treatments after 20 days, especially those of N, P and Mg. The nutritional stress had significant effects on seedling growth, with percentages of decrease being 64.5%, 61.6% and 56.0% in seedling height, 95.1%, 92.8% and 76.3% in leaf area, and 92.1%, 93.0% and 80.6% in biomass caused by P deficiency, P overdose, and N deficiency, respectively. Vector analyses indicated that deficiency of major nutritional elements could lead to synergism or antagonism between foliar major nutrient elements, such as pronounced synergism between Ca and N but antagonism of Ca (reduction) with P and K (overdose).

The influence of snowstorm on Platycladus orientalis plantations in southern Shandong.

WANG Xuan1, CAO Bang-hua2*, MAO Pei-li1, WANG Shu-mei1, CAO Zhen-yu1, JIANG Qian-kun1

2017, 36(6):  1509-1514. 

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In order to provide a theoretical basis for snowstorm prevention of forest plantations in Shandong Province, the degree of snow harm of Platycladus orientalis plantations in Baodugu Forest Farm in Zaozhuang City was investigated using typical sampling method and the influence of slope, elevation and stand structure character on the degree of snow harm was explored. The results showed that the damage degree of P. orientalis plantations was significantly influenced by the slope and elevation. P. orientalis plantations exhibited more seriously damage on the sunny slope than on the shady slope. Similarly, the damage degree at the high elevation was more serious than at the low elevation. The trees with the diameter at breast height (DBH) from 6 to 18 cm were more vulnerable to the damage on the sunny slope, whereas no significant effects were observed on the shady slope. Correlation analyses showed that damage degree was significantly negatively correlated with tree height (except altitude 296 m of the shade slope), whereas its correlations to other stand structure characters varied with slope direction and altitude. Therefore, the combination of site condition and stand structure was the main factor affecting the snow disaster of the P. orientalis plantations in this area.

Dynamic characteristics of forest soil phosphorus in the early succession after fire in Great Xing’an Mountains.

KONG Jian-jian*, ZHANG Heng-yu, JING Shuang

2017, 36(6):  1515-1523. 

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Fire is an important driver in boreal forest ecosystems, and deeply affects biogeochemical processes. The early succession after fire (<15 years) is a critical period influencing recovery of postfire vegetation structure and functions that are impacted by changes of soil nutrients after fire. In this study, we investigated the dynamic characteristics of forest soil phosphorus (P) in an unburned control and burned sites dating 1-year-post-fire, 5-year-post-fire and 11-year-post-fire, respectively  at Huzhong Natural Reserve in the Great Xing’an Mountains of Northeastern China. Our results showed that wildfire immediately caused great increases of soil total P (TP) and available P supply rates, with increasing 55% and 270% respectively, compared to control plots. Such increases had significant positive relationships with fire severity. In the 5-year and 11-year post-fire plots, soil TP concentrations were still higher than those in the control plots. However, we did not find the significant relationship between soil TP and fire severity. In the 11-year-post-fire plots, soil available P supply rates recovered to pre-fire levels. Soil TP and available P supply rates were significantly positively correlated to soil water content. This study indicated that soil P increased immediately after fire and then gradually decreased with time extension of last fire. Fire severity can exert important effects on soil P in the short term, but soil property may become a critical factor influencing soil P with succession.  

Responses of root morphology to sand microhabitats for typical psammophyte Corispermum candelabrum.

HAN Xu1,2, LI Xue-hua1,3*, LIU Si-yang1,2, JIA Mei-yu4, MIAO Chun-ping1

2017, 36(6):  1524-1530. 

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Corispermum candelabrum, a typical psammophyte, is widely distributed around semiactive sand dunes of Horqin sandy land. Studies on roots in response to sand microhabitats would help us to deeply understand plant’s mechanisms of adaptation to environmental disturbance or stress in sand dunes. In this study, the excavation method was applied to harvest roots in different soil layers and analyze root morphological variation in different microhabitats along sand dunes (transitional zone, bottom of windward slope, middle of windward slope, the top of sand dune, leeward slope). The results showed that most roots occurred in the layer of 0-10 cm and root diameter was usually less than 1 mm. Along transitional zone to the top of sand dune, aboveground biomass, belowground biomass, root length density, root surface area density and tissue density decreased, while increased at leeward slope. Other indexes such as specific root length and specific root surface area displayed an opposite trend. Roots showed a significant correlation with soil moisture in different microhabitats. We concluded that plants growing in transitional zone with adequate water and nutrients usually take advantages in larger root systems. On the other hand, when growing in the top of sand dune with strong wind erosion and sand burial and water deficit, they usually showed strong efficiency of resource absorption. That means this species has developed reasonable roots allocation for sandy microhabitats.

Population structure and dynamics of Metasequoia glyptostroboides parent trees.

LIN Yong1, AI Xun-ru1*, YAO Lan1,2, GUO Qiu-ju1, ZHANG Min-xia3, CHEN Jun1

2017, 36(6):  1531-1538. 

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The population structure and dynamics characters reflect the survival status of plant species and their interactions with environment. Metasequoia glyptostroboides, a famous living fossil, is one of the greatest botanical discoveries of the 20th century. Even extensively planted around world, we still know little about the current population status of M. glyptostroboides parent trees in the natural ecosystem. In this study, the population structure and dynamics were analyzed based on the investigation data on the natural population of M. glyptostroboides parent trees. The results showed that: (1) The natural regeneration of M. glyptostroboides was extremely weak and the individuals <40 cm DBH (diameter at breast height) only accounted for 4.5% of the total population. The spindleshaped DBH structure indicated a depression tendency for M. glyptostroboides population. (2) The survival rate of the population was low for young individuals and the survival ability of middle aged individuals were strong. After reaching Ⅷ class age, the number of survival individuals decreased greatly. The survival curve of the population approached to DeeveyⅢ  type. (3) The population showed a slight decrease at the early stage, fluctuation at the middle stage and depression at the late stage. The young stage was the fragile period during the population life history. After the Ⅷ class age, the population entered the period of physiological recession. (4) The time sequence analysis predicted that the number of young and middleaged individuals would gradually decrease and old individuals would increase for the upcoming eight years. It’s very hard to maintain the longterm stability of M. glyptostroboides population. Our results indicated that the extreme lack of young individuals was the main reason for the depression tendency of M. glyptostroboides population. In order to restore population, it’s urgent to provide proper artificial aid recovery and reinforce protection of existing parent trees as well as their habitats.

Meta-analysis of the effects of nitrogen addition on photosynthesis of forests.

WANG Fang1,2, ZHANG Jun-hui1*, GU Yue1,2, ZHAO Ting1,2, HAN Shi-jie1

2017, 36(6):  1539-1547. 

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Studies on the effect of nitrogen addition on the eco-physiological traits and growth of forests are of great importance, providing basic information for assessing the mechanism of forest dynamics. Here, we conducted a metaanalysis upon 32 studies to reveal the response of tree photosynthesis to N addition. We found that tree photosynthetic rate increased as a whole (10.24%), and the influence of N addition on temperate trees (11.45%) was higher than that on tropical trees (10.32%); broadleaved tree species was more sensitive to N addition than conifers. The responses ratio of tree photosynthetic rate varied with N addition level and experimental duration. When the nitrogen addition level was less than 25 kg·hm^-2·a^-1, tree photosynthetic rate increased (6.28%) insignificantly. The tree photosynthetic rate increased with the nitrogen addition level, with increments of 13.50% and 13.09% at 25-50 and 50-100 kg·hm^-2·a^-1, respectively. However, the tree photosynthetic rate increased insignificantly when the nitrogen level was more than 100 kg·hm^-2·a^-1. Generally, the photosynthetic rate was improved significantly in the experiment less than 5 years, but inhibited in the experiment longer than 5 years. The inhibition effect became insignificant in the experiment longer than 10 years. Excess nitrogen addition would lead to nutritional imbalance in plants (increased foliar N and decreased foliar P, K, Ca and Mg), which may contribute to the changes of photosynthetic pigments and enzyme activities.

Effects of freezing-thawing on soil carbon and nitrogen mineralization in temperate forest ecosystems.

ZHAO Yuan1,2, ZHOU Wang-ming1*, WANG Shou-le1,2, ZHOU Li1, YU Da-pao1, DAI Li-min1

2017, 36(6):  1548-1554. 

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In midhigh northern latitude and high altitude regions, a phenomenon of soil freezingthawing cycles generally occurs in the late autumn and early spring. With the global warming, effects of such freezingthawing cycles on the processes of soil carbon (C) and nitrogen (N) cycling are attracting more attention. In the present study, we collected soil samples from different types of forest in Changbai Mountain, including Pinus koraiensis, Betula platyphylla and Larix olgensis. We carried out a laboratory incubation experiment to investigate how freezingthawing cycles (-10 to 10 ℃) affect soil C and N mineralization at low soil water content (40%) and high water content (supersaturation). The results show that freezingthawing cycles significantly restricted C mineralization rate under different water conditions (except for the P. koraiensis soil at low soil water content). Such restriction was more pronounced with increase in the frequency of freezingthawing cycles. Freezingthawing cycles interacted with soil water content to affect soil N mineralization; they increased N mineralization rate at the low water content, whereas such influence was different at the high soil water content. These results indicate that freezingthawing cycles in the late autumn and early spring significantly drove soil C and N mineralization in Changbai Mountain, the extent of which depended on freezingthawing frequency and soil water content.

Effects of crop types on soil microbial functional diversity in sloping agricultural land of Zhangjiachong in Zigui County.

XU Lin1, ZHANG Xue-jiao1, TIAN Zhong-sai1, CHENG Dan-dan1,2*

2017, 36(6):  1555-1563. 

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To assess the effect of crops on the utilization of carbon sources by soil microorganisms, we chose one piece of sloping agricultural land in Zhangjiachong, part of the Three Gorges Reservoir area in Zigui County, Hubei Province as the study site. An experiment was designed considering three types of crops, including tea, orange and peanuts, with or without hedges. In total, 18 soil samples were collected from 6 plots with 3 replicates in each plot. Soil physicochemical properties were determined, and soil microbial functional diversity was measured by Biolog ECO plates. Effects of crops and hedges on soil microbes, soil physicochemical properties and the relationships between them were explored by multivariate statistical analysis. The results indicated that hedge had no  significant effects on soil physicochemical properties, but crops did. Soil samples from the peanut plots showed lowest availability of nitrogen, phosphorus and potassium (P<0.001). Soil microbial activity was higher in the orange plot (without hedge) than that in the other plots (P<0.05). The functional diversity indices were in order of: orange plots > peanut plots > tea plots (P<0.05). Amino acids and polymers were the dominant carbon sources of soil microbial metabolism from all sample plots (P<0.05). The utilization of aromatic and amine carbon significantly differed among different crop lands (P<0.01), while hedge greatly affected the utilization of carbohydrates and carboxylic acids. The soil physicochemical variables had minor influence on the carbon source utilization by soil microbes in the orange plots. The utilization of carbon sources in the tea plots was highly affected by the soil factors such as soil pH, available nitrogen and available phosphorus, and that of soil microorganisms in the peanut plots was correlated with total nitrogen and available potassium. The results indicated that in  nutrientpoor soil, soil physicochemical properties, soil microbial activities and carbon source utilization were different among different crop plots, and soil microbial metabolism of carbon sources was correlated with soil physicochemical properties.

Herbaceous plant diversity and its response to canopy structure of tree plantation based on 1 hm² plot at Chongming Island, Shanghai.

LIU Xiao-tong1,2, DAI Xing-an1, HU Ting1,2, CHEN Xiao-bo2, ZHANG Qing-fei2*

2017, 36(6):  1564-1569. 

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In order to study the relationship between herbaceous plant diversity and canopy structure in urban forest, this paper investigated the structure of herbaceous plants in a 1 hm^2 plot of Chongming Island in Shanghai. The results showed that: (1) There were 40 species of herbs in the plot which belonged to 20 families and 39 genera, and the species of Asteraceae family were dominant. (2) The understory herbaceous structures, the dominant herbaceous species and their species diversity indexes in different communities were significantly different. The diversity index of herbaceous plants in Cinnamomum camphora community was the largest, while that of Bischofia polycarpa community was the lowest. All indexes changed with the same trend, i.e., evergreen broadleaved forest (dominated by Cinnamomum camphora) > deciduous coniferous and broadleaved mixed forest (dominated by Metasequoia glyptostroboides-Bischofia polycarpa) > deciduous broad-leaved forest (dominated by Firmiana platanifolia) > deciduous broad-leaved forest (dominated by Bischofia polycarpa). (3) In the same community, the herb diversity indexes also showed a trend of an initial increase and then a drop with different gradients of density and canopy closure.

Light use efficiency of plants and the environmental impact factors in different alpine ecosystems.

ZHOU Zi-juan*, SU Pei-xi, SHI Rui, XIE Ting-ting

2017, 36(6):  1570-1577. 

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Light use efficiency is an important indicator of plant photosynthesis, and also is crucial for improving ecosystem productivity. In this study, we selected Zoige Plateau, an ecologically sensitive alpine area, to evaluate the light use efficiency of the dominant plant species in two typical ecosystems, namely alpine meadows and wetlands, and to analyze the impacts of environmental factors on light use efficiency in each ecosystem. The net photosynthetic rate and light use efficiency of Elymus nutans dominated in alpine meadows were higher than those of Carex muliensis dominated in alpine wetlands, but the difference was not significant. Regarding Potentilla anserina, a common species in both ecosystems, the net photosynthetic rate and light use efficiency were higher in alpine wetlands than in alpine meadows. Regression analyses revealed that there were highly significant correlations between the light use efficiency of the two dominant plant species (E. nutans and  C. muliensis) and microclimatic and edaphic factors. In contrast, the light use efficiency of the common plant species P. anserina was mainly affected by microclimatic factors only. This study indicated that the light use efficiency varied with alpine plant species. For the dominant species, the light use efficiency was mainly influenced by microclimatic factors, especially air temperature, which was the most important factor affecting the light use efficiency of alpine plants.

Effects of continuous drought stress during key growth phases on photosynthetic characteristics of spring maize in Northeast China.

CAI Fu1, MI Na1, JI Rui-peng1, MING Hui-qing2, XIE Yan-bing1, YU Wen-ying1, ZHANG Yu-shu1*， GAO Li-li3

2017, 36(6):  1578-1589. 

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Based on water stress treatments in different key growth stages from jointing to mature periods of maize with the method of continuous nowater complementing for a long time, photosynthetic characteristics of spring maize Danyu 39 during the processes of drought of different levels and rehydration were dynamically measured. The response characteristics of the variables associated with photosynthesis including net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s) and intercellular CO₂ concentration (C_i) as well as the photosynthetic parameters such as apparent quantum yield (AQY), maximum net photosynthetic rate (P_nmax), light compensation point (LCP) and light saturation point (LSP) to drought were investigated. The results showed that P_n, T_r, G_s and C_i decreased with the intensified continuous drought stress. In response to the drought, the variables mentioned above were more obvious in tasseling stage than in jointing stage, and T_r was faster than P_n, and C_i was more apparent under low than high light intensity. In addition, the responses of the variables to rewatering after the drought differed markedly and their restoration abilities declined with prolonged drought duration and were weaker in tinseling stages than in jointing stage. Specifically, the P_n of the plant suffering short drought exceeded that of the normal plant under condition of suitable soil moisture after rewatering. Meanwhile, the response of T_r to re-watering fell behind that of P_n and its restoration ability to rewatering after  drought was weaker than that of P_n. The response of C_i to rewatering after drought was more sensitive under high light intensity. Moreover, as the drought was worsened, AQY first increased then decreased; P_nmax diminished constantly with an increasing response speed and its recovery capability to rewatering decreased; LCP and LSP increased and decreased respectively. Furthermore, AQY, LSP, P_nmax and the range of available light intensity used by photosynthesis increased significantly with soil water content (SWC), while a significant negative correlation was found between LCP and SWC.

The relationships between leaf anatomical structure, anthocyanins and photosynthetic characteristics in Perilla frutescens.

SUI Li, WANG Kang-cai*, LIANG Yong-fu, XUE Qi

2017, 36(6):  1590-1596. 

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In this study, we investigated the leaf anatomical structure, pigment content, and photosynthetic characteristics of Perilla frutescens from 9 sites. The results showed that all the leaves of P. frutescens from the 9 sites were bifacial leaf, containing a palisade tissue with onelayer tightly arranged long columnar cells and a spongy tissue with 2 or 3 layers cell. Furthermore, there were more stomata (mostly oval) and glandular hairs in the lower epidermis of the leaves. The diameter and density of stomata of P. frutescens significantly differed among different sites. The P. frutescens from Yantai had the largest stomata diameter, and that from Wuxi had the greatest stomata density. Nevertheless, the stomatal diameter and density of the P. frutescens from Nanjing were the minimum. The contents of chlorophyll and anthocyanin of P. frutescens from the different sites showed significant differences. The more purple leaf color was, the higher anthocyanin content and the lower chlorophyll content were. However, the leaf of the P. frutescens from Baoding, Handan and Xingtai had higher contents of chlorophyll and anthocyanins. There was a negative correlation between the anthocyanin content and net photosynthetic rate in P. frutescens leaves. For example, the P. frutescens from Yantai had a lower anthocyanin content but higher net photosynthetic rate, while the P. frutescens from Nanjing had a higher anthocyanin content but lower net photosynthetic rate. The leaf anatomical structure and pigment content of P. frutescens were significantly different among different sites, and they had a certain correlation with net photosynthetic rate. This study laid a foundation for further study on germplasm resources and breeding of P. frutescens.

Proteomics analysis of sweet sorghum in response to soda saline-alkali stress.

DAI Ling-yan1, DU Ji-dao2, ZHANG Yu-xian2, ZHU Hong-de2, YIN Kui-de1*

2017, 36(6):  1597-1605. 

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In order to understand the molecular mechanism of sweet sorghum related to its adaptation to soda saline-alkali stress at the protein level, the variety M-81E, which has better tolerance to soda salinealkali stress, was selected as the material. Various proteins were identified by twodimensional electrophoresis and mass spectrometry together with the bioinformatics analysis. Dynamic changes of antioxidant enzyme activities in M81E were detected under soda salinealkali stress. Among the identified 44 proteins, 30 and 14 showed up and downregulated expressions, respectively, which were mainly related to the biological processes of material and energy metabolism, signal transduction and transcription regulation. Gene ontology analysis showed that the differential proteins were mainly involved in redox biological processes. KEGG enrichment analysis showed that the differential proteins were significantly involved in metabolic pathways such as carbon metabolism, carbon fixation in photosynthetic organisms, glycolysis and biosynthesis of secondary metabolites. The network of proteinprotein interaction showed that proteins interacted with each other and directly or indirectly involved in the metabolic pathway. Compared with the control, SOD and CAT activities were significantly decreased (P<0.05) after soda salinealkali treatment for 4 hours and GSHPx activity was not significantly changed, while POD activity increased significantly (P<0.01) in the sweet sorghum seedlings. Correspondingly, the contents of MDA and H₂O₂ in the treated group were lower than those in the control (P<0.01). POD could be the key enzyme to scavenge ROS in sweet sorghum at the early stage of soda salinealkali stress. The activities of various antioxidant enzymes decreased differently after 16 h treatment, and were still higher than the control after 24 h treatment but the contents of MDA and H₂O₂ increased sharply.

Structure dynamics of arthropod community on Seriphidium terraealbae and Calligonum leucocladum in Gurbanggut desert and its ecotone.

SU Jie, LI Ting, HAN Guo-dong, JIANG Rui-xu, ZHANG Jian-ping*

2017, 36(6):  1606-1613. 

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The diversity and dynamics of arthropods on Seriphidium terraealbae and Calligonum leucocladum in southern marginal zone of Gurbanggut Desert was explored in order to protect S. terraealbae and C. leucocladum and provide reference for rationally using arthropods in ecotone. The fixedpoint sampling method was used once a week in this research. The habitats were divided into desert and ecotone. A total of 677 specimens were collected, which belonged to 2 classes, 10 orders and 22 families. The species richness index and biodiversity index were significantly greater in ecotone than in desert. The dominance index was opposite. The individual number of natural enemy insects was significantly higher in ecotone than in desert. The main herbivore groups were Fulgoroidea, Cicadellidae, Acridoidea, Miridae, Curculionidae, and Aphididae; the main natural enemy insects groups were Chalcidoidea, Braconidae, Ichneumonidae, Chrysopidae, and Araneida. The individual number of herbivore reached two peaks in middle of May and early July; the number of natural enemy insects reached two peaks behind the herbivore in late May and middle of July. The natural enemy insects were rich for S. terraealbae and C. leucocladum in ecotone, and most of them could fly and transfer to farmland and desert ecosystems as supplement, being important in the ecological significance. Accordingly, S. terraealbae and C. leucocladum should be protected from overgrazing in ecotone.

Effects of grazing on soil ciliate community in swamp meadow.

NING Ying-zhi1*, YANG Yuan-gang1, SU Chang1, CHEN Ling-yun1， DU Guo-zhen2

2017, 36(6):  1614-1621. 

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Soil ciliate communities were investigated in a swamp meadow in Maqu, Gannan at three levels of grazing intensity (grazing prohibition, seasonal grazing and fullyear grazing). A total of 105 species were identified, belonging to 8 classes, 17 orders, 30 families and 39 genera. The soil ciliate species diversity index was the highest under seasonal grazing, followed by grazing prohibition and the lowest under fullyear grazing. The C/P index (the ratio of species number of Colopodid ciliates to species number of Polyhymenophora ciliates) was in order of seasonal grazing < grazing prohibition < full-year grazing. The ciliate communities had higher similarity between the sites of grazing prohibition and seasonal grazing and there were larger differences of ciliate communities between the sites of fullyear grazing and grazing prohibition. Furthermore, soil moisture and organic matter content were significantly positively correlated with species number, density and diversity index (P<0.01); total phosphorus content was significantly positively correlated with density (P<0.01), species number and diversity index (P<0.05). The redundancy analysis of ciliate community composition parameters (species number, species diversity index, density) and soil environmental factors (soil temperature, moisture, pH, organic matter, total nitrogen, total phosphorus, available phosphorus and inorganic nitrogen) showed that organic matter content had the greatest impact on the community composition of soil ciliates, followed by soil moisture, and total nitrogen content.

Effects of salinity on the growth and survival of Barnea dilatata juveniles.

XIE Xi1, WANG Qing-zhi1*, ZHAO Xi-chun2, TENG Wei-ming1, JIN Cheng-hai1, LIN Shan-shan1, ZHANG Ming1, ZHOU Zun-chun1

2017, 36(6):  1622-1627. 

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Hatcheryreared Barnea dilatata juveniles were maintained under different salinity levels of 15, 20, 25, 30, 35 and 40 psu at 20±1 °C to study the effects of salinity on the survival and growth. The results showed that the survival rate was over 90.0% under salinity of 20, 25, and 30 psu after 28 days, which was significantly higher than that observed under salinity of 15, 35, and 40 psu. The bivalves exhibited the highest increase of wet weight under the salinity of 20 and 35 psu, with the specific growth rate (SGR) at 2.963%·d^-1 and 3.028%·d^-1, respectively. The shell length and height showed similar changes in SGR between 25 and 35 psu. The highest ratio of organic and inorganic materials (OIR) was detected in the edible part of juveniles cultured under the salinity of 30 psu (OIR 4.396). The bivalves grown under 25 psu salinity had the second highest OIR at 3.375. Collectively, data from this study provide valuable information for the selection of suitable sites for B. dilatata aquaculture and for maintaining optimal rearing conditions at the B. dilatata hatcheries.

Variation of egg spot traits of Pomacea canaliculata, an invasive species across latitudes.

ZHANG Can-yu1,2, XU Meng1, FANG Miao1,2, LUO Du1, GU Dang-en1, MU Xi-dong1, WEI Hui1, HU Yin-chang1*

2017, 36(6):  1628-1636. 

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We collected the egg spots of golden apple snails (Pomacea cancliculata) across 11 latitudes (18°N to 28°N) during June to October 2015, which covered the major colonized areas from north to south boundaries in China. We measured the length, width, height, weight, volume of egg spots, and the diameter and number of eggs across latitudes, and analyzed the differences of these traits among latitudes and their relationship with latitude using step regression method. The results indicated that across all latitudes, the egg spot length, width, height, weight and volume were 20-60 mm, 10-26 mm, 6.5-18 mm, 0.6-5.1 g and 1.0-7.0 cm³, with mean values of 35.94 mm, 15.12 mm, 10.53 mm, 1.9 g and 3.0 cm³, respectively. The egg number of each egg spot was 81-621, with an average number of 279. Egg diameter ranged from 1.35 mm to 3.00 mm and the mean diameter was 2.16 mm. There were no significant differences in egg spot length, width, and height among latitudes, while significant differences were observed in egg spot weight and the egg number of each egg spot among latitudes. There were greater egg spot weight and egg diameter at the high latitudes than at the low latitudes. The step regression indicated that, to predict egg number of apple snails at different latitudes, different egg spot traits were needed. For example, the number of eggs could be predicted by egg spot width and volume at 19° N, while only egg spot volume could be used for 20° and 21°N, and egg spot weight could be used for 25°, 26° and 27°N. Generally, the egg spot length (x₁), width (x₂) and volume (x₃) were needed in better predicting egg number (y) across different latitudes by using the following formula: y=3.897x₁+9.042x₂+46.152x₃-135.044. This study provided insights into the spatial variation of reproduction characters, reproduction adaptation and biological control of P. canaliculata colonized in China.

 

Water quality of ecological breeding pond for Chinese giant salamander (Andrias davidianus) in Zhangjiajie City.

SONG Ying-jie1,2, LUO Qing-hua1,2*, HU Xiao2,3, WANG Han1,2, WEI Meng-ya2

2017, 36(6):  1637-1642. 

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In order to provide a basis for optimizing the structure of ecological breeding ponds for Chinese giant salamander (Andrias davidianus), the change processes of water quality in the ponds were analyzed and the main factors affecting the changes were discussed. Twelve ecological breeding fields in Zhangjiajie City were investigated. The main water quality indexes were mea-sured at the inlet, center and outlet of each pond. The results showed that the water quality indicators met the growth requirement for Chinese giant salamanders and the first standard of breeding water discharge standard from pond except for turbidity. From the inlet to the center, to the outlet of the ecological pond, the water turbidity and dissolved oxygen (DO) showed a decreasing trend while total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (COD) and total hardness (GH) showed an increasing trend. The good selfpurification of water in the ecological breeding ponds made the turbidity fell by 31.7%. Due to the reasonable engineering structure and certain water velocity, TN, TP, COD and GH were kept within the requirements for Chinese giant salamanders. Ecological breeding pools are simple in structure and economic; however, the efficiency of settling pond needs to be further improved to insure water turbidity demand of Chinese giant salamanders.

Reducing cadmium pollution in present-season leafy vegetable by calcium formate application through irrigation.

CAI Ke-hang1,2, HUANG Bin1*, CHEN Xin1, SHI Yi1

2017, 36(6):  1643-1649. 

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Soil pH controlbased approaches are often adopted for remediation of Cdlightly and moderately contaminated agricultural soils, but their overall effects are generally not good in pHcircumneutral soils. In this study, enhancing the conversion from exchangeable Cd to carbonatebounded Cd in rhizosphere soil with little soil pH change by calcium formate solution irrigation during vegetable growth period was proposed for reducing Cd uptake by vegetable from pHcircumneutral soil. The laboratory experiment showed that lowconcentration calcium formate (1.3-3.9 g·L^-1) promoted the dissolution of exchangeable Cd. Meanwhile, soil alkalinity increased with little pH change after formate biodegradation within 24 hours, favoring further conversion of the dissolved Cd into less bioavailable carbonatebounded Cd. The results from the subsequent pot experiment with brown soil (total Cd 1.03 mg·kg^-1, pH 7.3) planted with cole showed that addition of calcium formate at 76, 152 or 228 mg·kg^-1 soil through irrigation twice in the middle and late growing period decreased Cd level in the edible part of cole by 31.6%, 32.7% and 39.4%, respectively, while soil pH changed little compared with the control. Such differences among different treatments disappeared in the subsequent cropping season. The reduction of Cd uptake by presentseason leafy vegetable by calcium formate application is attributed to its enhanced conversion of exchangeable Cd into carbonatebounded Cd in soil. Nevertheless, its effectiveness needs to be further assessed with consideration of impacting factors such as the composition and content of soil exchangeable cations, soil ironmanganese oxides and organic matter.

Effects of soil additives on the uptake and translocation of lead and cadmium by Pteris vittata L.

YANG Shu-shen1,2, YANG Jun2*, YANG Jun-xing2, WAN Xiao-ming2, LEI Mei2, CHEN Tong-bin2, LIU Shu-qing1

2017, 36(6):  1650-1657. 

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Aiming to investigate the effects of NH₄H₂PO₄, citric acid and EDTA on the accumulation and translocation of lead (Pb) and cadmium (Cd) by Pteris vittata L., a pot experiment was conducted using two types of Pb and Cd co-contaminated soils (fluvoaquic soil and meadow cinnamon soil) collected from northern China. Results indicated that EDTA significantly increased the aboveground Pb concentrations of P. vittata by 33.9 folds in fluvoaquic soil and by 5.97 folds in meadow cinnamon soil, respectively. Due to the inhibition of EDTA on the biomass of P. vittata, the extent of increase in Pb amount accumulated in the aboveground part was less, being 9.22 folds in fluvoaquic soil and 1.18 folds in meadow cinnamon soil, respectively. Similarly, EDTA increased the aboveground Cd concentrations of P. vittata by 9.16 folds in fluvoaquic soil and 2.40 folds in meadow cinnamon soil respectively, but did not increase the amount of Cd accumulated in the aboveground parts of P. vittata. Neither NH₄H₂PO₄ nor citric acid treatment increased the concentration of Pb and Cd in P. vittata. This study can provide a basis for the remediation of Pb-Cd cocontaminated soil.

Biological characteristics of four Sb(Ⅲ)tolerant bacteria and their growth-promoting effects on the rape in soils contaminated by antimony.

NIE Xiao-hong1, YIN Hao1, GUO Dong-chu1, GUO Hui1, ZHOU Jin-xing2, PENG Xia-wei1*

2017, 36(6):  1658-1666. 

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Some Sb(Ⅲ)tolerant plant growth-promoting bacteria were isolated from the heavy metals contaminated soil around the Xikuangshan antimony mine, Hunan Province, by the CDM medium. Based on morphological observation, physiologicalbiochemical test and 16S rRNA gene sequence analysis, these bacteria were identified. Their biological characteristics including Sb(Ⅲ) tolerance, absorption and oxidation, growthpromoting properties, adaptabilities to pH and salinity, and their growthpromoting effects on rape seedlings were investigated by a pot experiment. The results showed that four Sb(Ⅲ)tolerant and growthpromotion bacteria were isolated (XKS-1, XKS-2, NXH-2, NXH-3) belonging to the genera of Pseudomonas, Ensifer, Raoultella and Stenotrophomonas. Their minimum inhibitory concentrations (MIC) of Sb(Ⅲ) were higher than 25 mmol·L^-1, and they could adsorb and oxidize Sb(Ⅲ). These four strains could produce indoleacetic acid (IAA) and siderophore. The effects of pH and salinity on the growth of four bacteria were different. Compared with the noninoculated control, height and root length, chlorophyll a and chlorophyll b contents of rape seedlings treated with four bacteria were increased by 4%-26%, 13%-32%, 23%-35% and 5%-32% respectively at low and intermediate Sb concentrations. These four bacteria had no significant effect at high Sb concentration. Results from this study highlight that these four Sb(Ⅲ)tolerant bacteria had strong adaptability to the environment, which could be used for bioremediation of soil polluted by antimony.

Effects of nest construction cost and nest materials on reproduction of Parus major.

LI Yin, ZHANG Lei, ZHANG Cong-ying, SHU Xue-tong, LI Dong-lai, YIN Jiang-xia, WAN Dong-mei*

2017, 36(6):  1667-1671. 

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Nest construction effort may affect the reproduction of parent birds and their subsequent capacity to care for offspring. The difference of nest material components may also affect bird reproduction. This study examined the influence of nest construction cost and nest material components on breeding performance of Parus major by analyzing 35 nests. The results showed that total nest mass was negatively correlated with the number of fledglings, fledging success rate and breeding success rate. The mass of feather and its proportional contribution to the total nest mass were positively correlated with clutch size, the number of hatchlings, and fledglings, but negatively correlated with firstegg date. Clutch size and the number of hatchlings were positively related to the mass of plant stem and its proportional contribution to the nest mass. The results suggest that there would be fewer fledglings with less fledging success and breeding success from the nest that costs more energy from parents during construction. In contrast, the nest with more insulation and supporting materials will ensure better breeding performance.

Calls Characteristics and temporal rhythm of calling behavior of Rhacophorus rhodopus in the breeding season.

SUN Zhi-xin1, WANG Tong-liang1, ZHU Bi-cheng2, WANG Ji-chao1*

2017, 36(6):  1672-1677. 

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Acoustic communication is one of the most important means of communication in anurans. The call behavior of many male frogs has a circadian rhythm that is affected by temperature and relative humidity. In this study, the calls of 61 males of Rhacophorus rhodopus were collected from May to June 2016. We investigated the call structure and circadian variations of calling patterns and their relationship with air temperature and relative humidity over 22 days. The results showed that R. rhodopus had two basic call types: monosyllabic and multisyllabic calls (note number 2-20, with an average of 6.27±2.94). There were no fundamental frequency differences between monosyllabic calls (212.51±21.63 Hz) and multisyllabic calls (225.39±26.80 Hz). The note duration, dominant frequency, and internote interval of monosyllabic calls (16.93±1.68 ms, 2289.87±120.14 Hz, 610.99±178.48 ms, respectively) were greater than those of multisyllabic calls (14.83±1.27 ms, 2213.32±106.95 Hz, 60.66±8.56 ms, respectively). Male R. rhodopus called from 19:00 to 03:00 every night, with a peak at about 22:00. The results showed that R. rhodopus communicated more efficiently by changing the dominant frequency, note number and internote interval. The calling behavior of R. rhodopus was affected by air temperature and relative humidity to a certain extent.

Identification and tissue distribution of odorant binding proteins of female antennae Anoplophora nobilis Ganglbauer (Coleoptera: Cerambycidae).

LI Guang-wei*, CHEN Xiu-lin, SHANG Tian-cui

2017, 36(6):  1678-1689. 

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To explore the OBP genes of antennae Anoplophora nobilis Ganglbauer, the transcriptome of female antennae was generated using Illumina HiSeq2500, the OBPs were identified by GO annotation and traditional DNA sequencing, and the tissue distribution of OBPs was performed by semiquantitative PCR. The results showed that 16 OBPs were identified from female antennae A. nobilis, including 11 Minus-C OBPs, three Classical OBPs and two Plus-C OBPs. Each OBP with a signal peptide at Nterminal consisted of 16-25 amino acids. OBPs in each subfamily have their own typical conservative Cys residues. The AnobOBPs are highly divergent and the sequence similarities range from 8.00% to 48.44%. Phylogenetic analysis showed that although OBPs of the same or different species are highly divergent, the great majority of OBPs in each subfamily is still clustered into independent clade, suggesting that they have a common ancestor. The expression levels of 16 female antennae AnobOBPs were significantly different, with the RPKM values ranging from 12.0 to 9065.5. AnobOBP1, AnobOBP2, AnobOBP3 and AnobOBP7 exclusively expressed in antennae, and the other AnobOBPs expressed in antennae and other tissues, including head, thorax, abdomen, leg and wings, indicating that the OBPs in insects may also participate in other functions in addition to chemosensation. This study established a foundation for determining the chemoreception molecular mechanism of A. nobilis, which would provide a new perspective for controlling the borer pests by using semiochemicals.

Evaluating the landscape pattern of the farmland windbreaks in the Manas River Basin oasis.

YANG Shu-ya, YANG Hui-jin, LIU Li-juan, LI Xiao-yu*

2017, 36(6):  1690-1698. 

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In the farmland landscape, the windbreak network, as an important corridor system, plays a crucial role in conserving landscape connectivity and biodiversity. In this study, high reso-lution remote sensing images were employed to calculate the relative errors of the landscape metrics of farmland windbreaks in the existing situation and the ideal situation, and evaluate the landscape pattern of the farmland windbreaks in the Manas River Basin oasis. The result shows that, for the farmland windbreaks in Manas County, Shawan County, and the Regimental Farm, the relative errors of their landscape metrics were 0.7240, 0.7374 and 0.7579 for the ratio of belt to patch, 0.5307, 0.5629 and 0.6863 for the connectivity, and 0.6577, 0.6380 and 0.4945 for the ring degree, respectively. The relative error of each landscape metric was greater than 0.15, which indicates the farmland windbreaks in the Manas River Basin oasis cannot meet the good quality standard. The prominent problems include the limited windbreak area, uneven windbreak distribution, small number of closed grids, and poor standforming conditions. In order to achieve the sustainability of the farmlands, the missing windbreaks need to be supplemented and the density of windbreaks should also be increased.

Vegetation phenology changes along an urban-rural gradient in Northeast China based on remote sensing.

QIU Jia-qi1,2, FANG Lei1, YANG Jian1*

2017, 36(6):  1699-1707. 

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Changes of vegetation phenology along the urban-rural gradients can reflect how urbanization regulates local water and heat conditions. Remote sensing can provide vegetation phenology at large scales (e.g. regional or global), making it a great alternative to traditional observation method. Taking three provincial capital cities (Shenyang, Changchun, Harbin) in Northeast China as examples, this study examined two critical phenology parameters (start of growing season, and end of growing season) in the buffer zones within 20 km from these urban areas, which were calculated from time series MODIS NDVI images using SavitzkyGolay filtering and segmented Gaussian method. Changes of multi-year mean parameters along the urbanrural gradients in relation to land surface temperature and forest coverage were analyzed. The results show that areas closer to urban sites tend to have earlier start of growing season, later end of growing season, and greater variability. Along the urban-rural gradients, 1 ℃ increase of land surface temperature in spring and last winter leads to an advance in start of growing season by 6-31 days, while 1 ℃ increase of land surface temperature in summer and autumn leads to a delay in end of growing season by 0.9-7.6 days. In some buffer zones, increase of forest coverage also contributes similar advances in start of growing season and delays in end of growing season.

Response of alpine meadow vegetationsoil system to climate change: A review.

MA Li1, XU Man-hou1*, ZHAI Da-tong2, JIA Yan-yan1

2017, 36(6):  1708-1717. 

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Alpine meadows occur in low temperature environments and are highly sensitive to climate warming. The response of alpine meadows to climate warming will help predict the possible impact of future climate change on alpine ecosystems. To deepen understanding of the mechanisms of alpine ecosystem responses to climate change, from the individual plant level, the community level, and in relation to the physical, chemical and biological properties of soil, we reviewed the effects of warming on vegetationsoil system of alpine meadow. We identified uncertainties in recent studies on the influences of climate warming on alpine meadow ecosystems and set out guidelines for future research on these issues. Rising temperature can promote the growth and development of alpine meadow plants. Plant photosynthetic and respiration rates, biomass and species diversity increase under moderate warming. However, different plant species have different physiological structures and ecological niches, which interact with the amplitude and duration of increasing temperature. This can result in variations of plant photosynthesis and respiration intensity, biomass allocation and phenological phases. Excessive temperature rises tend to simplify alpine meadow ecosystems and ultimately cause a reduction in species diversity, which influence community succession. Rising air temperature increases soil temperature, reduces soil moisture and has a mixed effect on soil organic carbon. Under shortterm warming, soil carbon and enzyme activity increase, raising the soil respiration rate. Over time, the soil respiration rate shows an adaptation to temperature rise. The response models to temperature vary according to their different components and the life processes of species in alpine meadow ecosystems. This leads to large uncertainties in the effects of climate warming on various components of plant and soil ecosystems in alpine meadows. We suggest to find a quantified threshold for the positive and negative effects on alpine meadow vegetation and soil system components under different amplitudes and durations of warming, and to address the response mechanisms from viewpoint of ecologicalmolecular biology.

Measurement and application of zinc stable isotope in environmental science.

KONG Jing1,2, GUO Qing-jun1,3*, WEI Rong-fei1,2, ZHU Guang-xu4, HU Jian4

2017, 36(6):  1718-1726. 

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Zinc is widely used in metallurgy, agriculture and energy, which make lots of zinc enter into the environment. The emergence of multicollector inductively coupled plasma mass spectrometry has gradually allowed for the application of zinc isotope in tracing the sources of pollution. Referring to the previous studies of zinc isotopes, this paper discusses the progress in aspects of the purification and enrichment method, the instrument mass fractionation correction method, composition of zinc isotope in natural substances and isotopic fractionation mechanism. The applications of zinc isotope as a probe in contaminated soil, sediment, water, and atmosphere are also discussed. Zinc is necessary to life. The isotopic fractionation of zinc isotope can occur during the process of biological absorption, mineral adsorption, evaporation, condensation, and so on. More information about the variation of zinc isotope composition in different reservoirs is needed and the related mechanism of isotopic fractionation should be further studied, which can contribute to the widespread use of zinc isotope in the field of environmental science.

Distribution characteristics of δ¹⁸O in soil water in China based on GCMs.

PAN Su-min, ZHANG Ming-jun*, WANG Sheng-jie, MA Rong, YANG Sen, CHEN Rong

2017, 36(6):  1727-1738. 

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The largescale spatial distribution of stable isotopic composition in soil water is jointly controlled by the precipitation isotope and its natural environment, and is vital information in simulation of isotopes in different types of water in land surface process. Considering the deficiency of existing insitu monitoring in soil water isotope on a large scale, GCM (General Circulation Models) is an effective tool to understand the spatial distribution of soil water isotope. Based on the simulations of several GCMs including LMDZ (free), LMDZ (nudged) and MIROC (free), the spatial and temporal characteristics of δ¹⁸O in soil water in China’s land surface were analyzed, and the relationships between soil water δ¹⁸O and other parameters (surface air temperature and δ¹⁸O in precipitation) were also presented. The results showed that: (1) The oxygen isotopes in soil water were enriched in southeastern China and relatively depleted in northeastern, northwestern China and Tibetan Plateau. The lowest values were found in Tibetan Plateau. The isoscape of soil water δ¹⁸O coincided with that of precipitation δ¹⁸O on a national scale. During 1979-2007, the annual, summer and winter means of δ¹⁸O in soil water presented an arising trend. (2) The soil water δ¹⁸O correlated with surface temperature, and a positive correlation was generally detected at high and mid latitudes; the strong positive correlations were seen at the inland areas far away from oceans. (3) The correlations of isotopes in soil water and precipitation simulated in the three data sources were all positive across China, which suggests the precipitation is usually the ultimate origin of soil water. The correlation coefficients were relatively large in northwestern China, and gradually declined from south to north in northeastern China. The correlation coefficient presented a circular distribution in Tibetan Plateau with weak correlations in the center.

Escaped aquacultural species promoted the alien species invasion in the Yangtze River: A case study of sturgeons.

GAO Yu, LIU Jian-yi, ZHANG Ting-ting, FENG Guang-peng, ZHANG Tao, YANG Gang, ZHUANG Ping*

2017, 36(6):  1739-1745. 

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Aquaculture escapes include several pathways. Direct escapes provide us a “natural” experimental experiment for fish invasion ecology. Indirect escapes are released by local people. An additional escape of agriculture is from the abandonment of ornamental fishery. Taking alien sturgeon escape in Qingjiang River basin in 2016 as an example, we discussed the potential impacts of these escapes on alien species invasion in the Yangtze River, including their hybridization and competition with native species Acipenser sinensis (a protected species at national level), and spread of disease. We conclude that public education on the ecological impacts of indirect releases of aquaculture species needs to be strategically emphasized in the region. Meanwhile, sound monitoring programs and controlled releases are also needed to reduce their impacts. This review also pointed out the directions of monitoring and tracking direction after aquaculture escapes and the prospects of the future development direction of impact assessments of aquaculture escapes on the alien species invasion in the Yangtze River.

Measuring stem disk rings using GIS tools.

MENG Sheng-wang, ZHOU Guang, YU Jian, ZHOU Hua, LIU Qi-jing*

2017, 36(6):  1746-1751. 

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Treering width measurement is not only an important basis for studying tree growth process and forest production, but also a crucial skill in forest measurement. The objective of this study was to propose three methods which take advantage of image processing software for measuring ring widths of stem disk. Based on highresolution image scanned or took by camera, coordinate information was extracted with the help of geographic information system (GIS). The ring widths were then computed as the distance between two points. This approach could not only improve the measuring accuracy, but also make the measurement more costeffective. In addition, it is especially practical when specialized instruments are not available.

Simulation of water and carbon fluxes in a broad-leaved Korean pine forest in Changbai Mountains based on Biome-BGC model and Ensemble Kalman Filter method.

ZHENG Lei1,2, SONG Shi-kai1,2, YUAN Xiu-liang1,2, DONG Jia-qi1,2, LI Long-hui1*

2017, 36(6):  1752-1760. 

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Data assimilation provides an effective way to integrate the model simulation and remote sensing observation, through the integration of remote sensing data in the run of the model, adjusting the model trajectory to reduce model error and improve simulation accuracy. This paper uses the ensemble Kalman filter (EnKF) assimilated MODIS LAI into the BiomeBGC model in growing season to simulate the water and carbon fluxes in a broadleaved Korean pine forest in Changbai Mountains. At the same time, the simulated snow sublimation and the parameters of the calculation method of soil temperature are improved, which can effectively reduce the error of the ecological respiration in winter. The result shows that as compared with the original model simulated without data assimilation, the improved Biome-BGC model with the assimilation of the MODIS LAI makes the correlation coefficient between the simulated values and the observed values of the gross ecosystem primary productivity (GPP) increased by 0.06, and reduced the centered rootmeansquare error (RMSE) by 0.48 g C·m^-2·d^-1, ecosystem respiration (RE) correlation coefficient increased by 0.02, centered rootmeansquare error decreased by 0.20 g C·m^-2·d^-1; the correlation coefficient of net ecosystem exchange of carbon (NEE) increased by 0.35, centered rootmeansquare error decreased by 0.50 g C·m^-2·d^-1. Meanwhile, data assimilation has no significant effect on the simulation precision of evapotranspiration (ET), but the improved model improves the correlation coefficient of ET. The data assimilation based on EnKF algorithm improves the accuracy of the carbon flux simulation in the broadleaved Korean pine forest in Changbai Mountains, and has an important significance on more accurate estimation of carbon flux at regional scale.

A method to determine the critical soil moisture of growth indicators of summer maize in  seedling stage.

MA Xue-yan1,2, ZHOU Guang-sheng1,3*

2017, 36(6):  1761-1768. 

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Deficit in soil moisture is the main cause of drought to crops. Accurate determination of crops’ responding thresholds to soil water is of great importance for identification and monitoring of the occurrence and development of crop drought. Based on the data of a progressive drought simulation experiment with six initial soil water levels on summer maize, oneway MANOVA was performed to identify maize growth indicators that respond earlier to soil water variations, and a way to identify their responding thresholds to soil water by using the statistic tolerance limits for normal populations was proposed. The results showed that the stem and leaf water content, transpiration rate, net photosynthetic rate, stomatal conductance, and leaf area of summer maize responded earlier to soil water in the seedling stage, and their corresponding critical soil moistures in terms of relative soil moisture at 0-30 cm depth were 72%, 65%, 62%, 60%, 58%, and 46%, respectively, indicating that the stem water content, leaf water content, transpiration rate, net photosynthetic rate, stomatal conductance, and leaf area would be affected successively as the soil water decreased and drought occurred. These results could provide reference to the monitoring and quantitative assessment of the development of drought to summer maize during the seedling stage, and also a way to determine responding thresholds of ecosystems.