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    10 March 2017, Volume 36 Issue 3
    Diameter class structure, growth dynamic, intraspecific and interspecific competitions of Betula platyphylla on swamp ecotone.
    CHAO Lin1,3, LIU Yan-yan1,3, ZHANG Wei-dong1,2, YANG Qing-peng1,2, WANG Si-long1,2*
    2017, 36(3):  577-583. 
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    In this study, the diameter class, growth dynamic, and intraspecific and interspecific competitions of Betula platyphylla were investigated on swamp ecotone. Furthermore, the relationship between competition intensity and diameter class was analyzed. The results showed that there was an obvious sigmoid functional relationship between basal area at breast height and tree height, and the B. platyphylla trees began to shift from height growth to DBH growth when DBH and tree height were 18.3 cm and 19.4 m, respectively. The regeneration seedlings of the B. platyphylla population were rare, and the diameter class of the B. platyphylla population followed a spindle shape. Lognormal function well represented the relationship between diameter and density. The intraspecific and interspecific competition intensity of B. platyphylla accounted for 48.80% and 51.20% of the total competition intensity, respectively. The  intensity of intraspecific and interspecific competition with B. platyphylla followed the order of B. platyphylla (intraspecific) > Larix olgensis > Alnus hirsuta > Populus davidiana > Quercus mongolica > Padus racemosa > Fraxinus mandschurica > Acer mono > Acer ginnala > Ulmus davidiana. The competition intensity of B. platyphylla declined with increasing DBH. However, the competition intensity exhibited little variation when DBH was larger than 20 cm. The relationship between the competition intensity and DBH of target trees followed the power function (CI=AD-B). This model could effectively predict the intraspecific and interspecific competition intensity of B. platyphylla.
    Effects of simulated nitrogen deposition on the composition and allocation of nonstructural carbohydrates of Phyllostachys edulis.
    LU Ru-bing, DU Ying, BAO Yong-xin, QIU Zi-yan, SONG Chao, SONG Xin-zhang*
    2017, 36(3):  584-591. 
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    The nonstructural carbohydrate (NSC) concentration in plant tissues reflects carbon supply of the whole plant; however, the response of NSC to increasing nitrogen (N) deposition is poorly understood. Phyllostachys edulis is widely distributed in southern China and plays an important role in the construction of ecological environment in subtropical regions and the economic development in mountainous areas. An experiment was conducted in conventionally managed P. edulis plantations with three N addition treatments of 30, 60, 90 kg·hm-2·a-1, and the control (no fertilization) over a 32month period. The results showed that: (1) The soluble sugar was a major component of the NSC in P. edulis. (2) The NSC concentration in three organs of P. edulis was ranked by trunk (4.1%) > leaf (3.6%) > branch (3.3%). (3) The NSC concentration of leaf of 4-year-old P. edulis was significantly lower than that of 2-year-old one (P<0.05), the P. edulis age significantly influenced the NSC concentration in trunk (P<0.05) but not in branch (P>0.05). (4) N deposition significantly influenced the NSC concentrations of branch and trunk (P< 0.05), and the NSC concentrations of trunk under the low N addition treatment (30 kg·hm-2·a-1) was the lowest. (5) The interaction of N deposition and P. edulis age significantly influenced the NSC concentrations of the three organs (P<0.05). The moderate N deposition would promote the growth of P. edulis and contribute to more biomass carbon accumulation.
    Carbon storage and its allocation in soft broadleaved forests with different stand ages in Guangxi.
    CHEN Li1,2,3, SONG Min2,3,4, SONG Tong-qing2,3, WANG Hua1,2*, ZENG Fu-ping2,3, PENG Wan-xia2,3, DU Hu2,3, HAN Chang1,2,3, SU Liang1,2,3
    2017, 36(3):  592-600. 
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    Ecosystem carbon storage and its allocation in soft broadleaved forests were investigated across Guangxi Zhuang Autonomous Region. In total, 42 plots, each with an area of 1000 m2, were selected. The plots covered five stand ages, i.e., young forest, middleaged forest, pre-mature forest, mature forest and overmature forest. The results showed that total ecosystem carbon storage ranked in the order of mature forest (421.98 t·hm-2) > overmature forest (405.23 t·hm-2) > pre-mature forest (218.74 t·hm-2) > middleaged forest (172.94 t·hm-2) > young forest (164.20 t·hm-2). Carbon storage in different ecosystem compartments across different stand ages varied in the order of soil layer > aboveground layer > litter layer, except the mature forest for which carbon storage in the aboveground layer was greater than that in the soil layer. When carbon storage in the soil layer and litter layer was combined, carbon storage in the belowground part was greater than that in the aboveground part. However, the mature forest was an exception for which carbon storage in the aboveground part was greater than that in the belowground part. The carbon storage of the aboveground layer ranged from 32.03 to 222.43 t·hm-2, which accounted for 30.03%-55.28% of the total carbon storage and increased with stand age. The carbon storage of litter layer ranged from 1.51 to 3.58 t·hm-2, which accounted for 0.69%-1.56% of the total carbon storage and showed an “M” type trend. The carbon storage of soil layer ranged from 117.33 to 294.54 t·hm-2, which accounted for 44.06% to 75.69% of the total carbon storage and increased with stand age. The largest carbon pool for the aboveground layer was tree layer (ranging from 27.53 to 220.50 t·hm-2), which accounted for 16.77%-54.41% of the aboveground layer carbon and increased with stand age. The largest carbon pool for the tree layer was in trunk (ranging from 16.99 to 167.91 t·hm-2), which accounted for 61.70%-76.15% of the carbon storage in the tree layer and increased with stand age. The proportions of roots and leaves ranged from 9.07% to 18.60% and from 1.59% to 6.62% of the aboveground carbon pool respectively, and decreased stand age. Carbon storage in the branch ranged from 3.08% to 13.41% of the aboveground carbon pool and showed a trend to decrease with stand age.
    Effects of experimental warming on soil respiration during growing period in cropland in the black soil region of Northeast China.
    FU Wei1, ZHANG Xing-yi1*, ZHAO Jun1, DU Shu-li1, HOU Mei-ting2
    2017, 36(3):  601-608. 
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    Northeast China is more sensitive to climate change than the other areas in China. The temperature sensitivity of soil respiration has dramatic effects on the feedback between carbon cycle of agroecosystem in Northeast China and global warming. Infrared radiators were used to simulate soil warming to investigate the response of soil respiration during the growing period to the experimental warming. The experimental warming significantly increased the mean soil temperature at the depth of 10 cm by 2.76 ℃ during the whole experimental period. Soil respiration rate showed an obvious seasonal variation with a peak at flowering and podbearing stage. The average soil respiration rate was slightly higher in the warmed plots (3.20 μmol·m-2·s-1) than in the control plots (2.96 μmol·m-2·s-1). However, the statistical analysis indicated that the experimental warming had no significant effects on the soil respiration rate. The experimental warming significantly increased the aboveground biomass but had no effects on the root biomass and soil water content. These results indicated that root biomass and soil water content were the main factors regulating the response of soil respiration to warming. We concluded that soil respiration in the twoyear experimental warming could not significantly accelerate soil respiration during the growing period, suggesting that the cropland may be prone to acclimate to experimental warming in the black soil region of Northeast China.
    Effects of thinning intensity on soil active organic carbon in Pinus massoniana plantation.
    ZHAI Kai-yan1,2, MA Ting-yao1,2, JIN Xue-mei1,2, YUAN Zai-xiang1,2, CHEN Bin1,2, GUAN Qing-wei1,2*
    2017, 36(3):  609-615. 
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    We studied the effects of thinning on soil active organic carbon content and their proportion in total organic carbon in a 29-year-old Pinus massoniana plantation after nine years of treatment. Four thinning intensities included: light (25%, LIT), moderate (45%, MIT), high (65%, HIT), and a control (0%, CK). The results showed that compared with the CK, MIT significantly increased soil total organic carbon (TOC) content, while HIT significantly decreased TOC content. The responses of soil particulate organic carbon (POC) and readily oxidized carbon (ROC) to thinning were consistent with the TOC. The light fraction organic carbon (LFOC) content of soil was significantly decreased under the three kinds of thinning intensity in the order of HIT< LIT < MIT < CK. The distribution proportion of POC, LFOC and ROC in the TOC ranged from 30.83% to 64.59%, 10.40% to 26.92% and 3.61% to 4.62%, respectively. Thinning significantly decreased the distribution proportion of LFOC in the TOC. However, thinning had no significant effect on the distribution proportion of ROC in the TOC. MIT significantly decreased the distribution proportion of POC in the TOC. Compared to the CK, MIT was advantageous in the accumulation of TOC with enhanced stability of soil organic carbon.
    Effect of shortterm warming on plant community features of alpine meadow in Northern Tibet.
    JIANG Yan-bin1,2, FAN Miao1, ZHANG Yang-jian2*
    2017, 36(3):  616-622. 
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    Tibetan Plateau is one of the regions that are most sensitive to global change. In the past decades, Northern Tibet experienced significant warming. In this study, opentop chambers (OTCs) were used to simulate warming in alpine meadow in Northern Tibet. A warming gradient was generated by using different heights of OTCs (40, 60, 80 and 100 cm). The responses of plant growth, community composition and structure, and aboveground biomass to warming treatments were investigated. Under the series of treatment, air temperature increment ranged from 1.13 to 2.72 ℃. The temperatures in upper layer soil were also increased, accompanied by the decreased air and soil humidity. Kobresia pygmaea is the primary dominant species in the targeted communities. With increasing temperature, the importance value of K. pygmaea and the cover of sedges decreased. The warming effect on community growth and aboveground biomass accumulation varied with the warming magnitude. Warming promoted plant growth when it was lower than 2.1 ℃. When the warming magnitude was greater than 2.1 ℃, its stimulation effect was weakened, even prohibited plant growth. This study illustrated that the alpine meadow in Northern Tibet was a good indicator for global warming. The varied responses of community structure and biomass to the warming gradient indicated that moderate warming would promote the growth and development of plant communities, but fast temperature increasing would induce warming and drying environment, and less water availability for the ecosystem. Consequently, the productivity of plant community decreased, and the meadow ecosystem deteriorated.
    Soil fungal community characteristics in three types of forest stand in Huyang forest region of Mulei, Xinjiang.
    LIANG Xue, LI Yong-chun*, CHEN Xiang-jun, LI Yong-fu, CHEN Jun-hui, XU Qiu-fang
    2017, 36(3):  623-630. 
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    In present study, we investigated the fungi community characteristics and influencing factors in soil under overmature Populus euphratica (OP), effete P. euphratica (EP) and Tamarix ramosissima (TR) in Xinjiang Mulei Huyang forest region using terminal restriction fragment length polymorphism (T-RFLP), realtime quantitative PCR, and conventional separation and cultivation methods. The results showed that the most obvious difference in soil fungi community structure was observed between OP and TR stands, followed by that between OP and EP stands. The highest Shannon index, Simpson index and evenness index of soil fungi were detected in EP, OP and TR stands, respectively. The abundance of fungi ranged from 6.07×105 to 1.87×106 copies·g-1 dry soil in the three forest soils, and the amount of fungi in OP stands was significantly higher than those in TR and EP stands. Soil pH was positively correlated with Shannon index and evenness index but negatively with Simpson index and fungi abundance. Soil pH significantly influenced fungi community structure, and pH and C/N ratio were the most important environmental factors affecting the distribution of fungi community under EP stands, while total N affected the distribution of fungi community under TR stands. These results showed that there were obvious differences in the community structure, diversity indices and abundance of soil fungi among OP, EP and TR stands, and soil pH was the key factor influencing fungi community characteristics.
    Effects of water and nitrogen addition on soil nematodes and small arthropods in an oldfield grassland of north China.
    SONG Min*
    2017, 36(3):  631-639. 
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    Changes in precipitation and nitrogen deposition have profound impacts on ecological processes and functioning. However, the patterns and mechanisms of soil biota response to such changes are poorly understood. A field manipulative experiment was established to examine the responses of soil animal communities to water and nitrogen addition in an oldfield grassland ecosystem. Neither water addition nor N deposition affected mite or collembolan abundance. Water addition significantly elevated soil nematode abundance by 14.9%. Nitrogen addition had little effect on nematode abundance, but significantly increased the abundance of bacterivores by 45.8%. Our results indicate that soil nematodes were more sensitive than soil mesoinvertebrates to changes in resource availability and microenvironment. In addition, the data indicate that increasing precipitation and N deposition independently affected soil animal community.
    Spatial variability of soil physicochemical properties in the alpine tundra of Changbai Mountain in relation to topographic factors.
    LIU Yu-xia, XU Jia-wei*, JIN Ying-hua, ZHU Rui-shuai, NIU Li-ping, WANG Ai-lin, ZHANG Ying-jie
    2017, 36(3):  640-648. 
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    In order to illustrate the spatial differences of tundra soil physical and chemical properties and provide basic data for retrieving alpine tundra change processes in Changbai Mountain, we collected 132 soil samples. Four topographic factors including elevation, slope, slope aspect, and slope position were selected and 13 soil physicochemical properties were analyzed. We conducted semivariogram analysis, correlation analysis and factor analysis on these properties, and regression analysis and redundancy analysis between soil physicochemical properties and topographic factors. Results showed that: (1) The contents of available nutrients and organic  were high, with an average content of 22.96% for organic matter. The soil was acidic, with an average pH value of 4.86. The particle composition was silt>sand>clay after removing the gravels. Correlation between soil physicochemical properties was high. Three types of factors (inorganic nutrient supply factors, soil particle composition factors, soil organic nutrient supply factor) were derived from 13 soil physicochemical properties. (2) Elevation was the main topographic factor affecting inorganic nutrient supply and organic nutrient supply within the altitude range from 2049 to 2239 m, and it was positively correlated with nutrient content. Slope was the main topographic factor affecting soil organic nutrient supply, and it was negatively correlated with organic nutrient content. Slope position was the main topographic factor of soil particle composition. (3) Elevation, slope, slope aspect and slope position explained 42.8% of variation of soil physicochemical properties, while the first axis explained 28.2% of the variation, the second axis explained 14.6% of the variation. Among the four topographic factors, elevation was the most important factor on the variation of soil physicochemical properties, followed by slope.
    Influence of sand burial and drought on the growth of Paspalum distichum in waterlevelfluctuating zone of the Three Gorges Reservoir.
    LI Qiang*, WANG Shu-min, DING Wu-quan, ZHU Qi-hong
    2017, 36(3):  649-654. 
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    In the waterlevelfluctuating zone (WLFZ) of the Three Gorges Reservoir, vegetation restoration is challenged not only by submersion for long periods, but also by sand deposition, drought, and other factors. To study the influence of sand burial and drought on the germination and growth of Paspalum distichum in the WLFZ of the Three Gorges Reservoir, P. distichum was transplanted and buried in sand of several particle sizes at various depths after antiseasonal flooding. Results showed that germinating seedlings of P. distichum in the WLFZ could not penetrate sand layers deeper than 8 cm with a particle size of less than 2 mm. As particle size decreased, the emergence rate dropped sharply. Under the condition of 4 cm depth, the leaf formation and development were significantly promoted, and leaf number, leaf length and leaf width were significantly accelerated with the increase of particle size. However, combined stress of sand burial and drought significantly inhibited the growth and development of seedlings, and plant height, leaf number, leaf length and leaf width were significantly restrained. The photosynthetic electron transport rate and the heat dissipation ability of the seedlings declined significantly with the decrease of particle size, and their death rate increased significantly. Thus, the ability of P. distichum for growth was significantly reduced with the decrease of particle size and the increase of burial depth under combined stress of sand burial and drought, which would lead to more rapid decline of P. distichum population in the WLFZs of the Three Gorges Reservoir.
    Photosynthesis and transpiration characteristics of Phyllostachys edulis stands with water storage in their stumps.
    ZHANG Lei1, XIE Jin-zhong1*, ZHANG Wei1, JI Lin-ke1, DING Zhong-wen2, CHEN Sheng1
    2017, 36(3):  655-663. 
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    Phyllostachys edulis (Moso bamboo) stands with water storage in their stumps were selected. Three treatments were designed, i.e. 0 stump with water storage (CK), 12 stumps with water storage (T1) and 18 stumps with water storage (T2) in a plot (10 m×20 m), respectively. We measured the photosynthetic pigment content, photosynthesis and transpiration physiological indices of the 2yearold culms and the major environmental factors. We then compared the differences in photosynthetic pigment content, photosynthesis and transpiration rates of Moso bamboo with different numbers of stumps with water storage as well as their relationship with environmental factors. The results showed that: (1) The photosynthetic pigment content was in order of T2 > T1 > CK, and the largest increment of Chla, Chlb, Car and Chla+Chlb contents reached 17.05%, 14.49%, 25.93% and 17.19% respectively. (2) The diurnal variations of net photosynthetic and transpiration rates displayed in a pattern of unimodal curve. Both of them had no “photosynthetic noonbreak” phenomenon and were in order of T2> T1> CK. (3) After increasing stumps with water storage, the reduction of net photosynthetic rate between 12:00 and 14:00 was not caused by nonstomatal factors but by stomatal limitation. (4) Compared with CK treatment, the correlations of the net photosynthetic rate of Moso bamboo with environmental factors in T1 and T2 ranked in different orders. In the three treatments, the correlations of transpiration rate of Moso bamboo with environmental factors were different. Our results indicated that increasing the stumps with water storage in a certain range could increase photosynthetic pigment content, improve the photosynthesis and transpiration ability, increase the accumulation of photosynthetic products and improve the growth of Moso bamboo. Besides, photosynthetic pigment content, photosynthetic and transpiration capacity had a positive correlation with the number of stumps. This study provides a theoretical support for development of watersaving irrigation in Moso bamboo production.
    Effects of nutrient deficiency on the growth of Michelia macclurei seedlings.
    LI Qing-ying, WEN Shan-na, JIANG Qing-bin*, ZHONG Chong-lu*, CHEN Yu, ZHANG Yong, WEI Yong-cheng
    2017, 36(3):  664-669. 
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    A greenhouse experiment was conducted to understand the effects of nutrient deficiency on the growth of Michelia macclurei. Seedlings were subjected to nine nutrient treatments, i.e. complete nutrient mixture (CK), minus nitrogen (N), minus phosphorus (P), minus potassium (K), minus calcium (Ca), minus magnesium (Mg), minus sulfur (S), minus iron (Fe) and minus trace elements (Te). Symptoms were observed and the growth, leaf area, chlorophyll, root activity and biomass were assessed. The results showed that the effect of N deficiency was the most obvious and significantly different from that of the CK. The symptoms included the slower growth and weaker seedlings with small and yellowish leaf blades. Deficiency of other elements did not affect height, diameter, root activity and chlorophyll, but there were significant differences in leaf area, biomass and root/shoot ratio compared to the CK. Therefore, N was the main factor affecting M. macclurei seedling growth. The results of this study provide a theoretical basis for efficient cultivation of M. macclurei.
    Effects of Hg stress on the physio-ecological characteristics of Cinnamomum camphora seedlings under simulated acid rain.
    LIU Xing-yu, WANG Yan-hong*, XU Yi-ran
    2017, 36(3):  670-675. 
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    In this study, Cinnamomum camphora, one of typical trees in Zhejiang Province, was chosen to explore the response patterns of physio-ecological properties of plants under simulated acid deposition (pH 4.0 and 5.6) and Hg stress (0, 0.5 and 10 mg·kg-1) in greenhouse experiment. The results showed that acid deposition and Hg stress significantly increased the ratio of chlorophyll b and chlorophyll a. Under low pH, the higher Hg treatment (10 mg·kg-1) significantly increased the fresh weight of leaf compared with low Hg treatment (0.5 mg·kg-1), while under high pH, Hg treatments had no such effects. Meanwhile, acid deposition and Hg stress had no interactive effects on total dry biomass, but significantly decreased the root/shoot ratio. With the expansion of treatment duration, the height, basal diameter and leaf number increased, but they increased more slowly under higher Hg treatment. Also, for the three traits, the differences between the treatment groups were minor in the early period but significant in the later period. Obviously, the effects of Hg treatment were not only affected by acid deposition but also by treatment duration. Although acid deposition and Hg stress incurred some damages to the growth of the plants, they did not pose negative impacts on the fitness. It is suggested that the C. camphora seedlings could adapt to the alteration of environment and could be treated as a species in ecological restoration.
    The pattern and mechanism of seedling growth and development regulated by Leukamenin E in Arabidopsis thaliana.
    CHENG Wei-ling, DING Lan*, LI Jin-ping, LIU Guo-an, YANG Ning
    2017, 36(3):  676-686. 
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    This paper studied the pattern of the Leukamenin E, an entkaurene diterpenoid regulation on the seed germination, hypocotyl elongation, and root growth and development in Arabidopsis thaliana. In addition, this work also discussed the mechanism of primary root growth, lateral root and root hair development regulated by Leukamenin E possibly through the phytohormone auxin and ethylene pathway in A. thaliana. The results showed that within 10-160 μmol·L-1, Leukamenin E had no obvious effect on seed germination rate; however, higher levels of Leukamenin E (80-160 μmol·L-1) significantly reduced the seed germination speed. The inhibiting effect of Leukamenin E on root growth was more obvious than on hypocotyl elongation. Furthermore, Leukamenin E inhibited the primary root growth through reducing cell mitosis and elongation. Leukamenin E accelerated the lateral root initiation and affected the lateral root numbers, and also reduced the root hair density and shortened the root hair length. Promoting root hair growth was stimulated by exogenous ethephon, an ethylenereleasing agent, and could be reversed by Leukamenin E treatment, which is similar to the effect of the Ag+, an ethylene action inhibitor. These results strongly suggested that the inhibition of Leukamenin E on root hair growth may depend on the ethylene pathway. Leukamenin E markedly increased the IAA level in root, which was detected by using the flow injection chemiluminescence method and the enzymelinked immunosorbent assays, indicating that auxin may play an important role in regulation of root growth by Leukamenin E in A. thaliana.
    Effects of salinity on the photodegradation of chromophoric dissolved organic matter (CDOM) released by seagrass Enhalus acoroides and Thalassia hemprichii leaf litter.
     
    WU Yun-chao1,2, JIANG Zhi-jian1, LIU Song-lin1,2, ZHANG Jing-ping1, LIAN Zhong-lian1,2,3, HUANG Xiao-ping1*
    2017, 36(3):  687-694. 
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    Seagrass leaf litter has been proved to be the main source of chromophoric dissolved organic matter (CDOM) in seagrass beds and CDOM released from seagrass leaf litter is greatly influenced by salinity. According to the salinity range in Xincun Bay, Hainan, China, a salinity gradient (0, 11, 22, 33) was set to study the effects of salinity on CDOM released by leaf litter of two types of seagrass (Enhalus acoroides and Thalassia hemprichii). The results showed that CDOM was rapidly degraded under ultravioletB in four salinity conditions, and significantly higher CDOM and lower DOC photodegradation rates of E. acoroides leaf litter were found under low salinity (0) than under the other three salinity levels. However, no significant difference in organic components of CDOM such as proteinlike and humiclike substances was found during photodegradation for both seagrass species under these four salinity levels. The photodegradation of dissolved organic nitrogen (DON) released by E. acoroides was intensely promoted under 0 salinity. Especially, 26.44% of DON was photodegraded to dissolved inorganic nitrogen (DIN), of which 94.32% was converted to ammonium. However, no obvious effect of extremely low salinity was found on the photodegradation of DON released by T. hemprichii. Therefore, extremely low salinity would influence the photodegradation of CDOM and accelerate the conversion rate from DON to DIN released by E. acoroides, which may change carbon and organic nitrogen cycle in seagrass beds.
    Effect of corn straw leacheate on Daphina magna’s somatic growth and reproduction.
    TANG Ya-li*, YANG Xiao-qin
    2017, 36(3):  695-701. 
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    Terrestrial dissolved organic carbon (t-DOC) is a constitutive part of lake carbon pool and has a profound impact on pelagic food web. Previous field investigation proposed a high contribution of terrestrial organic carbon to zooplankton carbon with an average of 53%. However, terrestrial organic carbon itself cannot support the somatic growth and reproduction of Zooplankton. How can terrestrial organic carbon incorporate to zooplankton biomass? We assume that terrestrial dissolved organic carbon uptake is through an indirect microbial loop. To test this hypothesis, we conducted a lab observation of microbial dynamics during t-DOC (made from corn straw leachate) decay experiment in dark and Daphnia magna feeding experiments with diets including Scenedesmus, decayed and undecayed corn straw, as well as bacteria, flagellate and ciliate isolated during decay experiment. Our results showed that t-DOC can be transferred to bacteria carbon, flagellate carbon and ciliate carbon subsequently. Diets with Scenedesmus and decayed t-DOC supported the highest growth and reproduction rate of D. magna. Diets with flagellate and ciliate showed the medium support to growth and reproduction of D. magna. Diets with undecayed t-DOC and bacteria showed little support to growth and reproduction of D. magna. The results propose a potential path way for t-DOC to be transferred to zooplankton by a microbial loop. Bacteria, flagellates and ciliates finish this bioconversion together. These findings may help us to further understand the linkage between aquatic ecosystem and terrestrial ecosystem and provide a new perspective in lake management.
    Reproductive biology of Exopalaemon carinicauda in Yangtze River Estuary.
    PEI Qian-qian1,2, ZHANG Tao2, YANG Gang2, ZHAO Feng2, SONG Chao2, ZHUANG Ping2*
    2017, 36(3):  702-706. 
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    Reproductive biology of Exopalaemon carinicauda was studied from November 2014 to October 2015 in Yangtze River Estuary. The results showed that the body length of E. carinicauda ranged from 25 to 75 mm with an average of (48±9) mm, and dominant body length was 35-55 mm. Annual variation of monthly sex ratio of E. carinicauda ranged from 0.89 to 1.63 with an average of 1.2±0.22. There was no significant difference between male and female numbers by chisquare test. The main breeding season began in the late March and lasted until late October and the spawning peaks occurred in May and August. The reproductive population was mainly overwintering shrimp in May and June, and mainly smallmedium of nonoverwintering shrimp in July. The absolute fecundity (F) ranged from 660 to 8000 eggs. A positive linear correlation between absolute fecundity and body length (L) was observed as following equation: F=68.86L-2072 (R2=0.498). In addition, the absolute fecundity was also linear with body weight (W), namely, F=318.5W+267.0 (R2=0.504).
    Effect of contents of heavy metal ions in leaves of Phragmites australis irrigated by papermaking wastewater on chlorophyll fluorescence parameters.
    WANG Li-yao, SU Fang-li*, LI Hai-fu
    2017, 36(3):  707-712. 
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    Chlorophyll fluorescence analysis is a commonly used technique to study plant photosynthetic physiology and to detect plant physical condition based on chlorophyll fluorescence parameters, including conversion efficiency (Fv/Fm) and potential activity (Fv/Fo) of photosystem (PS) at PSⅡ reaction center. To study the response of chlorophyll fluorescence parameters of Phragmites australis to irrigation using papermaking wastewater, the concentrations of heavy metal ions (Cr6+, Zn2+ and Cu2+) and chlorophyll fluorescence parameters in leaves of P. australis were observed. The P. australis plants were from Liaohe Estuary wetland, and irrigated with papermaking wastewater with concentration of chemical oxygen demand (CODCr) set to 50, 175 or 300 mg·L-1. The results showed that irrigation using papermaking wastewater significantly affected the concentrations of heavy metal ions (Cr6+, Zn2+ and Cu2+) in leaves (P<0.05). The concentrations of heavy metal ions increased with the increase of CODCr concentration, and the greatest concentrations of Cr6+, Zn2+ and Cu2+ accumulated in leaves were respectively 2.80, 3.66 and 3.86 times as much as those in leaves with nonirrigation of papermaking wastewater. The accumulation of the three heavy metal ions in leaves varied in different growth periods. Cr6+ and Zn2+ mainly were accumulated in mature stage, and Cu2+ mainly accumulated in jointing stage. In addition, the concentration of CODCr in papermaking wastewater also influenced the chlorophyll fluorescence parameters. Fv/Fm and Fv/Fo were improved under irrigation using the papermaking wastewater with concentrations of CODCr 50 and 175 mg·L-1. But when the concentration of CODCr was 300 mg·L-1, Fv/Fm and Fv/Fo were reduced by 8.19% and 24.94% respectively, which illustrates that the function of PSⅡ reaction center was restrained. In conclusion, chlorophyll fluorescence parameters showed different responses to the three heavy metal ions. The values of Fv/Fo and Fv/Fm decreased with the increase of Cr6+ and Zn2+ concentrations, and increased with the increase of Cu2+ concentration. The Fv/Fm was significantly negatively correlated with Cr6+ concentration, while Fv/Fo was significantly positively correlated with Cu2+ concentration.
    Effects of nitrogen reduction on rice yield and nitrogen loss in Taihu area.
    LIU Hong-jiang, GUO Zhi, ZHENG Jian-chu*, CHEN Liu-gen, ZHANG Yue-fang, TONG Hong-yu
    2017, 36(3):  713-718. 
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    In order to determine the suitable nitrogen application rate in high yielding rice field and reduce the agricultural nonpoint source pollution caused by excessive input of agricultural chemical fertilizer in Taihu area, a field experiment was conducted to investigate the effects of nitrogen reduction on rice yield and nitrogen loss by surface runoff in a wheatrice double cropping system. The nitrogen application rate was based on the amount of nitrogen fertilizer applied to rice by local farmers. The rice cultivar of Wuyunjing 29 was grown. Five treatments included no nitrogen fertilizer (N0), local custom fertilization (N1), nitrogen reduction 10% (N2), nitrogen reduction 20% (N3), and nitrogen reduction 30% (N4). These treatments were all carried out with deep application of basic fertilizer by machinery and straw return. Rice yield of N2 treatment was roughly equivalent to that of N1 treatment because of former higher economic index. The total N loss of surface runoff of N2 treatment was reduced by 9.2% compared with that of N1 treatment. From N1 to N4 treatments, the total N loss rate was decreased, but there was no significant difference between N1 and N2 treatments. From the point of view of rice nitrogen partial loss rate, the amount of nitrogen loss in N2 treatment was the least per kilogram of rice. It is proposed that through the deep application of basic fertilizer by machinery and straw return, 10% nitrogen reduction based on local custom fertilization levels in Taihu area can significantly reduce total nitrogen loss via surface runoff and nitrogen partial loss rate of rice and thus keep the nitrogen loss rate at a low level in the paddy field while maintaining the yield of rice.
    Temperature suitability of rice and its variation in Northeast China.
    TAN Fang-ying1*, WANG Jian-lin2, CHENG Lu1
    2017, 36(3):  719-724. 
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    Based on the temperature suitability model, this paper calculated the temperature suitability of rice at different growth stages, and evaluated the mean value and coefficient of variation and the spatiotemporal distribution and change pattern of temperature suitability of rice in Northeast China during 1961-2015. The results showed that the temperature suitability was high with low variability at tillering, booting and heading stages. On the contrary, the suitability was low with high variability during sowing and seeding stages. On the basis of the average temperature suitability of each station during the study period, the main production area of rice in Northeast China was divided into three regions with high, medium, and low suitability, respectively. Spatially, there was a significant northsouth difference in suitability, and the suitability generally decreased with the increase of latitude. Temperature suitability of each developmental stage decreased firstly and then increased, and showed an increased tendency in general from 1961 to 2015. Besides, such increasing trend was most significant from sowing to seeding stage and milky to mature stage, especially after the mid1990s. According to the rate of linear tendency of temperature suitability of each station, the main production area of rice in Northeast China was divided into three regions with high, moderate and low increase in temperature suitability, respectively. Our analysis suggests that the planting environment of rice in Northeast China will be improved, since the lower temperature suitability region would be always companied with a higher tendency of increase in temperature suitability and the regional differences would get smaller.
     
    Evaluation of livestock pollution status in the Three Gorges Reservoir Area of Hubei Province.
    HUANG Mei-ling1,2, XIA Ying1,3*, FAN Xian-peng1,3, HUANG Min2, WU Mao-qian1,3, LIU Dong-bi1,3, ZHANG Fu-lin1,3
    2017, 36(3):  725-733. 
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    In this study, the production of livestock and poultry manure and the discharged amount of COD, nitrogen and phosphorus in the Three Gorges Reservoir Area of Hubei Province during 2001 to 2014 were estimated by the pollutant excretion coefficient of livestock and poultry so as to analyze the environmental pollution status. We also assessed the environmental capability and pollution risk of livestock and poultry husbandry in the study area. The results indicated that the production amount of livestock and poultry manure was mainly from pig. The livestock and poultry manure productions and COD productions were in a growing trend during 2001 to 2014, reaching 3162 and 28 thousand tons in 2014, respectively. Amounts of nitrogen and phosphorus from livestock manure showed a slowly increasing trend during 2001 to 2014. The average values of cropland loading of nitrogen and phosphorus nutrients were 281.2 kg·hm-2·a-1 (TN) and 44.1 kg·hm-2·a-1 (TP) in 2014, which exceeded the EU’s standard limitation (170 kg·hm-2·a-1 for TN, and 35 kg·hm-2·a-1 for TP). The actual total amount of livestock and poultry in the Three Gorges Reservoir Area of Hubei Province was 50% more than the environmental capacity each year during 2001 to 2014. Especially, the number of livestock and poultry in Padang, Yiling, Xingshan and Zigui counties was far more than 50% of the environmental capacity in 2014, suggesting that livestock and poultry breeding in these counties should be strictly controlled.
    Relationship between grassland fauna characters and insectivorous birds at Fuyang Airport.
    LI Yong-min1*, LI Dong-wei1, NIE Chuan-peng1, JIANG Shuang-lin1, ZHAO Zhi-hua2
    2017, 36(3):  734-739. 
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    From May to October 2015, an investigation was made into the grassland fauna communities and avian diversity in three habitats at Fuyang Airport. In total, 12 orders of grassland fauna were found. Orthoptera were dominant, making up 49.5% of the total catches. In addition, common groups included Diptera, Coleoptera, Homoptera, Lepidoptera and Araneae, making up 39.8% of the total number. In terms of total mass, Orthoptera were also the main group, accounting for 80.1% of the total mass of the grassland fauna. Among the three habitats, the mass and diversity were the greatest in grassland, which was the key area for the prevention of the grassland animals. Correlation analysis found a significant relationship (r=0.881, P=0.021) between the number of insectivorous birds and total mass of Orthoptera. Orthoptera is the main prevention object and May is the best time to spray pesticide. The total mass of the grassland fauna and the number of insectivorous birds were the highest in August, which is the key period for prevention and control of bird strike.
    Bird community structure and diversity at Tianjin Binhai International Airport.
    LIU Yi1,2, XU Huan-ran3, YUAN Hong3, HE Bin3, ZHAO Shu-lan1,2, DUO Li-an1,2*
    2017, 36(3):  740-746. 
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    From March 2015 to February 2016, the community structure and diversity of birds at Tianjin Binhai International Airport were investigated by using a fixed radius point count method and line transect method. The results showed that 52 bird species were recorded at Tianjin Binhai International Airport, belonging to 31 families and 12 orders. They included 7 resident species (13.46%), 17 summer migrant species (32.69%), 5 winter migrant species (9.62%) and 23 passing migrant species (44.23%). Among these species, 8 species were widely distributed, 6 species were dominant. Based on the effects of flying height, the weight and quantity of birds, the frequency of occurrences and habitat utilization on flight safety, risk levels of birds were evaluated, and the results indicated that there were 3 serious threat species, Falco tinnunculus, Pica pica, and Passer montanus. We also found that the diversity index was the highest in autumn, and the dominance index was the highest in spring. The diversity index and evenness index were both highest in the wetland reed habitat, the dominance index was the highest in the building area, and the similarity of bird communities was the highest between communities from the airport enclosure and airport building areas. In this study, we compared bird diversity in different seasons and in different habitats, and explored habitat characteristics associated with different bird species in the flight zone, and bird distribution and activity patterns, thereby providing a basis for avoidance of bird strike at the airport.
    Spatiotemporal characteristics and risk analysis of summer corn waterlogging disaster in Jianghuai region.
    ZHANG Gui-xiang1, HUO Zhi-guo1,2*, YANG Jian-ying1, ZHANG Lei3, WU Li1, WANG Tian-ying2, YANG Hong-yi1
    2017, 36(3):  747-756. 
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    To quantitatively evaluate the waterlogging disaster of summer corn and reveal its spatiotemporal characteristics in Jianghuai region, based on the daily precipitation data of 91 stations in the research area from 1961 to 2013, with the growth period data and waterlogging disaster data of summer corn coupled, the different waterlogging disaster grade samples during different growth periods were counted. By using partial correlation analysis, multiple linear regression, normality test and  interval estimation, the waterlogging disaster grade index of summer corn based on the effective rainfall during different growth periods was constructed and validated. The spatiotemporal distribution and risk distribution of summer corn waterlogging disaster were analyzed in the area from 1961 to 2010. The results showed that the rainfall of current waterlogging process, last ten days and the ten days before last ten days had positive correlation with the grade of waterlogging disaster. In the same grade of waterlogging disaster, the jointingtasseling stage’s threshold was the highest, followed by the tasseling mature stage, and the lowest for the emergencejointing stage. The occurrence of waterlogging disaster decreased in 1970s, and then increased gradually after 1980s. The high frequency zone of waterlogging disaster mainly distributed along the Yangtze River, the Huaihe River, lake and coast, and moved gradually northward with the rain belt as the plant growth processed. In the last 50 years, the occurrence of waterlogging disaster generally increased in the emergence to tasseling stage, but mainly decreased in the tasseling to mature stage. The high value area of risk index gradually moved from southwest to northeast with the growth and development of plants.
    Identifying the effects of meteorological variables on spring wheat potential yield in Inner Mongolia based on APSIM model.
    ZHAO Jun-fang1*, PU Fei-yu2, YAN Wei-xiong3, XU Jing-wen2, LI Ning2, PAN Zhi-hua4, ZHANG Yi1, GUO Jian-ping1
    2017, 36(3):  757-765. 
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    Based on the spring wheat field trial data from agrometeorological experiment stations and daily meteorological data in Inner Mongolia, the adaptability of agricultural production system model APSIM in the spring wheat planting areas of Inner Mongolia was analyzed by grey correlation method. The optimum meteorological factors impacting the potential yield of local spring wheat were determined. The response of spring wheat potential yield to climate change was explored. Overall, the potential yield of spring wheat in Inner Mongolia showed a decrease trend from 1961 to 2014, with an average 3560.84 kg·hm-2. Especially, the highest potential yield and the lowest yield were found from 1981 to 1990 (3681.33 kg·hm-2) and from 2001 to 2010 (3432.82 kg·hm-2), respectively. Regional differences in potential yields were significant: in the past 54 years, the distribution of spring wheat potential yield in Inner Mongolia was in belt type gradually increasing from the middle to the east and the west. And the maximum potential yield of spring wheat was found in the western region. The meteorological factors differed in affecting spring wheat potential yield in the different regions of Inner Mongolia. The major meteorological factors affecting the potential yield of spring wheat in the eastern area were the average minimum temperature and the average soil surface temperature during the growth period, followed by the average temperature, the total radiation and the average maximum temperature. The major factors affecting spring wheat potential yield in the western area were the average soil surface temperature, the average temperature and the average maximum temperature, followed by the average minimum temperature, the total potential evapotranspiration and the relative humidity. However, changes in spring wheat potential yield caused by average precipitation and wind speed were not obvious. The spring wheat yield in the middle area was most sensitive to solar radiation and soil temperature, followed by average minimum temperature, average temperature and average maximum temperature; however, it was least sensitive to average wind speed and total precipitation. These results can provide technical support for analyzing the limiting factors of spring wheat growth and yield formation in wheatplanting areas in Inner Mongolia under the future climate change.
    Water chemical characteristics in the wet season in Buha River Basin in Qinghai.
    LI Zong-jie, SONG Ling-ling, TIAN Qing*
    2017, 36(3):  766-773. 
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    This paper reported the hydrochemical characteristics and possible source through the correlation analysis, factor analysis and enrichment factor in the Buha River Basin in wet season in 2014. The results showed that the pH of river water in Buha River Basin ranged between 7.91 and 9.21, with an average of 8.43. The EC ranged from 133 to 871 μS·cm-1, with an average of 383 μS·cm-1. The average ionic concentrations for SO42-, Ca2+, Cl-, Na+, Mg2+, NO3-, K+ and NH4+ were 60.2, 33.1, 31.1, 14.8, 12.8, 8.1, 1.5 and 0.3 μeq·L-1. The ionic abundance of river water in Buha River Basin followed the sequence of Ca2+> Na+> Mg2+> K+> NH4+ for cations, and SO42->Cl->NO3- for anions. The concentrations of Mg2+, Ca2+ and SO42- increased with the increase of altitude, whereas the concentrations of Na+, Cl- and NO3- decreased. The concentrations of K+ and NH4+ showed no change along the altitude. The chemical type for river water was SO42--Ca2+-Cl--Mg2+ type. The water chemistry of Buha River Basin was mainly controlled by evaporates and carbonates weathering products.
    The distribution characteristics of P forms in Miyun Reservoir sediments.
    QIN Li-huan1,2, ZENG Qing-hui1,2, LI Xu-yong2*, CHENG Peng1,2
    2017, 36(3):  774-781. 
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    The forms of phosphorus (P) in sediments is an important factor affecting the exchange between sediment and water interface. A fourstep extraction method was used to analyze various P forms in sediments of Baihe zone in Miyun Reservoir. The results indicated that total P ranged from 505.11 to 829.56 mg·kg-1. The concentrations of various phosphorus forms were ranked in order of HCl-P > BD-P > NaOH-P > NH4Cl-P. HCl-P and BD-P were the main forms of P in the sediments, together accounting for 53%-80% of TP concentration. Spatially, TP concentrations were generally higher from the deep sites and the transitional zone between Baihe zone and Chaohe zone. This pattern may be attributed to the small grain size of the sediments. According to the difference of TP concentration in the interstitial water and overlying water, inflow site (Taoli) and transitional zone (Kubei) were the sources of the internal P loading. Other sites were the sinks of internal P loading. This phenomenon may be determined by the temperature and dissolved oxygen of the overlying water together. The concentrations of various P forms in sediments were decreased from 2002 to 2013, indicating that the comprehensive measures of water environment management in the upstream of Miyun watershed were in effect.
     
    Developing and optimizing ecological networks for the towns along the Three Gorges Reservoir: A case of Kaizhou New Town, Chongqing.
    JIA Zhen-yi1,2, CHEN Chun-di2*, TONG Xiao-xiao2, WU Sheng-jun2, ZHOU Wen-zuo1
    2017, 36(3):  782-791. 
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    Habitat fragmentation and loss have become the major threats to local biodiversity protection and regional ecosystem integrity. Developing urban ecological networks and improving connectivity between habitats could facilitate energy and matter fluxes, species dispersal, genetic exchange and many other ecological processes, and further relieve the ecological environmental crisis in cities. With rapid urbanization in the Three Gorges Reservoir region, natural area fragmentation and habitat loss are inevitable. Taking Kaizhou New Town as an example, our study built the urban ecological networks by leastcost path modeling and GIS technology in order to facilitate the establishment of native tree species. The best threshold for urban ecological networks was obtained by the verification from graph theory functioning index. Finally, the priority of habitat protection and restoration was determined after evaluating the importance grades of patches/connectivities. We set a native tree, Pterocarya stenoptera as a surrogate species and used the habitat suitability assessment values to build the cost surface for leastcost model by Linkage Mapper Toolist. The observed maximum seed dispersal distance (300 m) of P. stenoptera was used as the distance threshold for network analysis. 75 target patches were selected as habitat sources to develop networks. Under the 300 m distance threshold, 98 links were simulated for the network, and were grouped into six grades according to their importance values. We found the links with higher importance values almost all existed along the bank between the Pengxi River and Hanfeng Lake. Among these, the most important link was between Hanfeng Lake Park and Kaizhou Planning Institute; the second important link was located on both sides of the highway bridge over the Pengxi River. The integral index of connectivity of the whole landscape would be reduced by 19.1% if the two links were removed. Additionally, we found that the importance of the link was not significantly correlated with the important values of the two patches that the link connected. Link importance may also relate to the shape and spatial location of patches. Based on these results, we proposed some network improvement strategies. This study combined leastcost path analysis and a graphtheoretical algorithm and provided a scientific, reliable reference for planning and construction of urban ecological networks.
    Spatial pattern and differentiation characteristics of urban heat island intensity in Guangzhou City.
    CHEN Kang-lin, GONG Jian-zhou*, CHEN Xiao-yue
    2017, 36(3):  792-799. 
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    Along with the rapid urbanization, the expansion of population and explosion of urban impervious surface, the phenomenon of urban heat island is becoming more and more prominent and influences social and economic development seriously in negative ways. Based on Landsat 8_OLI image data in 2014, a monowindow algorithm was implemented for the retrieval of land surface temperature in Guangzhou. The retrieval temperature, together with GS+/GIS spatial analysis technology, was used for the analysis of the hierarchical characteristics of thermal intensity and its spatial differential characteristics. The results show that the area size of heat island intensity levels completely followed the normal distribution with a fitting degree of R2=0.971 and the dominant pattern effect of Ⅴ and Ⅵ intensity levels. The centers of heat island intensity level were observed in forms of “single center”, “single center surrounded by multiple subcenters”, and “multiple center”, which followed certain orders of succession. The centers of the rank of cold island intensity were also observed in forms of contiguous cold island center, single cold island center and abnormal cold island center with inconspicuous order of succession. The results of the variable function show that the heat island intensity had high spatial predictability, and obvious regional differences as well as probable hierarchical structure. The results of the study may be helpful for the understanding of the effects of urbanization and regional ecological environment, and the promotion of the sustainable development of the city.
    Estimating potential ecological carrying capacity in Gansu Province.
    PAN Jing-hu*, FENG Ya-ya
    2017, 36(3):  800-808. 
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    Gansu Province is an important ecological barrier in northwest China. The study of spatial pattern of potential vegetation productivity has become basic work toward the ecological environment rehabilitation and reconstruction in arid and semiarid areas of northwest China. Data from some meteorological stations were used to build climate models, and regression trees were applied for estimating potential NDVI based on climate variables and training data of actual NDVI. Then, potential NPP of Gansu Province was simulated by using CASA model and potential NDVI data. On this basis, potential ecological carrying capacity of 14 municipalities in Gansu Province was estimated using the improved ecological footprint approach. Results indicated that potential NDVI and potential NPP decreased from southeast to northwest in Gansu Province. The average potential NDVI and potential NPP of Gansu Province were 0.277 and 272.315 g C·m-2, respectively. The potential ecological carrying capacity per capita (PECC) of the 14 municipalities in Gansu Province presented a distribution pattern of “big at both ends (south and north) but small in the middle”. Gannan Prefecture had the largest PECC, which was 11.616 hm2 per capita, while Jiayuguan City had the least PECC, with only 0.228 hm2 per capita.
    Opportunities and challenges in remote sensing applications to ecosystem ecology.
    ZHANG Yang-jian1,2,4*, FAN Chun-kun3*, HUANG Ke1,4, LIU Yao-jie1,4, ZU Jia-xing1,4, ZHU Jun-tao1
    2017, 36(3):  809-823. 
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    The macroecology is the new developing foci of ecology, which entails ecology to be conducted from the aspect of quantification. The socialeconomic development has been phasing out new requirements on ecological research. Remote sensing, as a technique tool, is being increasingly applied to ecological research. It’s necessary to study the function of remote sensing and the issues of ecology, and to seek the pointcut between them. Those are the developments of remote sensing application, and a useful way to solve the ecological problem. For ecologists without remote sensing background, or vice versa, lack of mutual understanding still remains a hurdle to integration of remote sensing and ecology. In this review, we described how remote sensing can be applied to ecological research. The related history was summarized and the future trend was also predicted. This review was mainly targeted at research on scales above ecosystem level. Specifically, we went over remote sensing application on ecosystem environments, ecosystem biological composition, ecosystem structure, ecosystem material flow and cycling, and ecosystem functions. On the basis of developing remote sensing technology, we pointed out how remote sensing can be combined effectively with ecological research. In the meantime, we summarized the advantages and disadvantages of each remote sensing dataset, which can be used as a guidance for applying remote sensing in ecological research.
    Architecture and technical exploration of big data platform for ecological environment.
    ZHAO Fen1,2, ZHANG Li-yun1,2, ZHAO Miao-miao1,2, SHAO Rui1,2, LIU Li-xiang1, ZHAO Hai-feng1, XU Ming1,3*
    2017, 36(3):  824-832. 
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    The generation of big data technology provides a new way for processing massive data related to ecological environment, as well as monitoring and analyzing global ecological environmental problems. This paper first described the basic concepts of big data, and the concept and feature of ecological environmental big data. Then, considering the system structure of general big data, the architecture of big data platform for ecological environment was designed from four key aspects, including data platform, infrastructure platform, technology platform and application service platform. After the main frame is analyzed, key technologies for building technology platform of ecological environmental big data were elaborated in four parts: data acquisition, data storage and management, data computing pattern and data analysis. Finally, in view of future development and difficulties, we put forward some thinking and proposals.
    Mercury emission from natural sources in China: A critical review.
    TAN Qing-you1, FU Xue-wu2*, HE Tian-rong1
    2017, 36(3):  833-845. 
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    Due to its specific physicochemical nature, mercury (Hg) is a unique heavy metal pollutant that occurs mainly in gaseous elemental form (GEM) in the atmosphere and could be transported globally. Atmospheric Hg could be derived from both anthropogenic and natural sources. The establishment and improvement of global and regional Hg emission inventories play an important role in the studies of global cycling and environmental health perspective of Hg. Due to influence of complicated environmental factors, natural emissions of Hg in China and other regions worldwide are far from well studied compared to anthropogenic Hg emissions. Approximately onetenth of mainland China is located in the circumPacific mercuriferous belts and Hg emission fluxes from various landscapes in China are larger than those of the same type areas of Europe and North America. Over the past two decades, numerous studies regarding Hg emission fluxes from natural sources have been made in China, which contributed significantly to the development of the emission inventory of natural sources in China. In this study, we provide a comprehensive synthesis of the natural Hg emissions in China. This review examines the distribution patterns, influencing factors, and potential mechanisms underlying the Hg emission fluxes from natural sources in China. Additionally, we also highlight the limitations and research needs for natural Hg emissions in future studies.
    Research advance in interactive effects of ozone concentration and soil water deficit on plants.
    WU Rong-un1,2*
    2017, 36(3):  846-853. 
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    Surface ozone concentration has increased, and more parts of land regions are predicted to become drier under the background of global warming. The stress effects of surface ozone and soil water deficit on the natural plants and crops were briefly presented in this review. Subsequently, the interactive effects of surface ozone and soil water deficit on natural plants and crops were commented intensively, highlighting the response characteristics of stomata conductance and antioxidant system. Two opposite conclusions of injury effects of ozone on the plants under the condition of soil water deficit were raveled out for different species of plants and crops. One opinion deemed that drought promoted the formation of abscisic acid, inducing stomatal closure to reduce the injury effects of ozone. The other opinion argued that ozone accelerated ethylene biosynthesis, and then slowed down the stomatal closure of plants and the stomatal sluggishness occurred, revealing no protection of drought. Meanwhile, the advance of assessment methods for the stress effects of ozone under the condition of soil water deficit was reviewed, and the research ideas of assessment methods for interactive effects of ozone and soil water deficit were further confirmed. Finally, the possible research orientations and approaches of interactive effects between surface ozone and soil water deficit on natural plants and crops were proposed.
    A method of stem analysis with polynomial fit by diameter line.
    XIN Hong-lu1,2, WU Bao-guo1,2*
    2017, 36(3):  854-861. 
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    This study introduced a wooden disc measuring method with simple operation and high precision in tree stem analysis. The operational approach can be followed in four steps: (1) Apply digital camera to shoot the dividing ruler placed on the disc; (2) Measure the ring radius by correcting digital images, which is realized by fitting polynomial equation from several fit points; (3) Calculate the coordinate distance between the intersection and the pith through clicking the intersection of lines and the radial of treering successively; (4) Substitute numbers into regression equation to obtain the radius value of ring. Compared to conventional millimeter scale measurement, whose precision reaches only millimeter and sub millimeter, and the professional analysis instrument, whose precision accuracy ranges from 0.0005 cm to 0.0010 cm, this method is more advantageous, with the maximum measure error in radius being 0.007650 cm, the minimum error 0.000040 cm, and the average error 0.002477 cm. With low cost, convenient and simple operation as well as highprecision, this method deserves promotion in analyzing the development of trees.
     
    Application of metapopulation competition mechanism in forest succession simulation of Mount Lushan.
    CHEN Jie, ZHOU Nian-xing*, LI Can, XU Qing-ying
    2017, 36(3):  862-868. 
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    Forest succession simulation can reveal the restoration process and succession patterns of forest vegetation. Vegetation succession simulation in natural reserve is an important theoretical basis for forest conservation. The result of traditional simulation is usually a timeseries data, which is simulated under current ecological environment, hard for validation, and not adequate for the guidance of forest conservation. Therefore, an essential part of simulation is to know how human activities affect forest succession by considering ecological conditions as model variables, and applying the simulation model under different ecological conditions. This study introduced the metapopulation theory into the forest succession simulation by taking Mount Lushan as a case study, and selected 10 dominant species for the simulation. MATLAB was used to simulate different conditions, i.e. current habitats, habitat destruction, and habitat restoration. Combining the area ratio curve of forest succession dynamics and the responses of 10 species to different conditions, this paper summarized the protection measures for different species. The results indicated that the overall succession for all forest populations trended towards evergreen broadleaved forest, and broadleaved trees were dominant in mixed forests. The dominant species in forest community could be divided into three levels: (1) The firstlevel species have strong adaptability to harsh ecological environment, but they are easy to be replaced by species with low dominance when habitats keep stable, and we should prevent artificial introduction of exotic species from excessively occupying the habitats of original dominant species; (2) The secondlevel species are sensitive to habitat change, and serious habitat damage will cause their extinction. However, they can survive under habitat restoration; (3) The thirdlevel species have difficulty to survive even under habitat restoration, and artificial cultivation measures should be taken to protect these species.
    Sensibility and time heterogeneity of Biome-BGC model parameters.
    LIU Qiu-yu1, ZHANG Ting-long1,2*, SUN Rui3,4, WANG Bo-wen1, YE Xin-xin1, LI Yi-zhe1
    2017, 36(3):  869-877. 
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    Ecological process model provides an effective way for studying water, carbon and nitrogen cycles of terrestrial ecosystem. The combination of the model and data assimilation could build a link between observation and simulation, which improves the effectiveness of model and observation methods to reveal the real state of land surface, but the accuracy of simulation and assimilation is directly affected by model parameters. Parameters are constants in traditional opinion; however, some current studies have focused on the timespace heterogeneity of parameters. In this paper, we used Harvard Forest Environmental Monitoring Site (EMS) data to simulate water and carbon flux in Harvard Forest area. Firstly, the sensitivity of parameters was analyzed. Additionally, in order to acquire monthly optimal values of parameters, the values of parameters were changed repeatedly in reasonable range, simulated annealing algorithm was used and objective function was built. Also, the time heterogeneity of sensitive parameter was analyzed through coefficient of variation. The results showed that the ecological model parameters were not constants, and the property of parameters changed with time. In addition, the heterogeneity of parameters was different. In this paper, the sensitive parameters in the Biome-BGC model were divided into corresponding levels based on their time heterogeneity. The results of this study could promote indepth understanding of ecological model parameters and provide an idea for identification and optimization of these parameters, which is helpful to improve the accuracy and effectiveness of model and data assimilation.
    Planting technology of Dendrobium officinale.
    CUI Zhi-yi1, XIAO Yu2, YANG Zeng-jiang1*, XU Da-ping1, ZHANG Ning-nan1, LIU Xiao-jin1, HONG Zhou1
    2017, 36(3):  878-884. 
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    Little information is available on planting technology of Dendrobium officinale, a precious medicinal herb endangered in China. This paper studied the screening of seedling cultivation matrix, the effects of epiphyted tree species and epiphytic position and forest crown density on D. officinale growth and the influence of D. officinale planting on the growth of epiphyted trees. The results showed that: (1) A mixture of pine bark, peanut hull and Acacia mangium bark at volumetric ratio of 1:1:1 was an ideal matrix; (2) Different tree species and epiphytic position had significant effects on the height, stem diameter, and biomass of D. officinale, but they did not show interactive effects. The comprehensive evaluation showed that Santalum album, Acacia mangium and Dalbergia odorifera were superior to Dimocarpus longgana and Averrhoa carambola; (3) The most favorable forest canopy density and light intensity for epiphytic colonization were 30%-50%, and about 62.5% of open space, respectively; (4) The epiphytic colonization of D. officinale significantly increased the diameter of epiphyted trees. Overall, pine bark+peanut hull+Acacia mangium bark as matrix and epiphytic colonization on middleheight trunk of Santalum album or Dalbergia odorifera with 30%-50% of canopy density is an encouraging agroforestry model for planting D. officinale in south China.