Table of Content

10 August 2017, Volume 36 Issue 8

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Effect of nitrogen deposition and soil nematode on soil organic carbon mineralization in a Larix gmelinii plantation.

LIU Jing1,2, SUN Tao1, CHENG Yun-yun1,2, WANG Qing-kui1,3*

2017, 36(8):  2085-2093. 

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Atmospheric nitrogen deposition contains both inorganic and organic nitrogen. How-ever, most of the previous studies focused on the effect of inorganic nitrogen deposition on soil organic carbon (SOC) mineralization; little information on how organic nitrogen deposition affects SOC mineralization is available. In this experiment, surface soils (0-10 cm) were collected in a longterm experiment of simulating nitrogen deposition that included the control (CK), inorganic nitrogen (IN), organic nitrogen (ON), and inorganic + organic nitrogen (IN∶ON=7∶3; MN) treatments in a larch (Larix gmelinii) plantation. These soil samples were divided into two groups with or without nematocide to investigate the role of soil nematode on SOC mineralization under the background of nitrogen deposition. All soils were incubated at 25 ℃ for 62 days, and the rate of SOC mineralization was measured. The results showed that the SOC mineralization was significantly suppressed by nitrogen deposition, and it was reduced by 15.7%, 23.9%, and 34.3% in IN, ON and MN treatments compared to CK treatment, respectively. This suggested that the suppression of mixed nitrogen deposition on SOC mineralization was higher than that of inorganic or organic nitrogen deposition alone. Thus, the suppression of atmospheric nitrogen deposition on SOC mineralization might be underestimated by using a single type of inorganic or organic nitrogen deposition. The rate of SOC mineralization increased when nematocide was added to soils. The effect value of nematocide increased by 0.08%, 42.40% and 29.0% in IN, ON and MN treatments compared with the CK treatment, respectively. The result indicated that the effect of soil nematode on SOC mineralization depended on the form of nitrogen deposition. Furthermore, cumulative amount of SOC mineralization was significantly positively related to C∶N ratio, available phosphorus concentration and the ratio of fungi to bacteria, but was significantly negatively correlated with NO₃^--N concentration and the ratio of grampositive bacteria to gramnegative bacteria. So, nitrogen deposition was helpful to decrease CO₂ emission from soil in temperate forest ecosystems under the background of global change.

Soil nutrient characteristics of different restoration patterns in Huajiang gorge of Guizhou karst plateau.

BAO Qian1, YANG Rui1*, NIE Chao-jun2, LI Wan-hong1, LIU Yun-zhi1

2017, 36(8):  2094-2102. 

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Huajiang gorge is a typical comprehensive control area of karst plateau rocky desertification in Guizhou Province. To understand soil nutrient status and the correlation of physical and chemical factors of different restoration patterns, soil samples from 0-10, 10-20 and 20-30 cm under six restoration patterns were collected, with abandoned land as control. The results showed that soil organic carbon, total N, total P and total K contents of the six different restoration patterns were increased by 72%, 37%, 60% and 72% compared to the abandoned land, respectively. Soil available N, available P and available K contents were increased by 61%, 10% and 106%, respectively. Soil organic carbon and nutrient contents in different soil layers were significantly different; soil organic carbon, total N, total P, total K, available N, available P and available K contents in the 0-10 cm layers were 1.52, 1.14, 1.20, 1.06, 1.41, 1.27, and 1.29 times of those in the 20-30 cm layer respectively, showing a surface accumulation effect. Correlation analysis showed that soil organic matter and bulk density were the key factors in the soil physicalchemical factors of the gorge area, and vegetation factors and soil factors were the two important factors that need to be taken into account in screening restoration patterns and planting in rocky desertification control areas.

Effects of vegetation type of water conservation forests on soil NH₄⁺-N and NO₃^--N lea-ching in Dahuofang watershed.

HU Ya-lin1, LIU Jie2, FAN Zhi-ping3*, TU Zhi-hua3, LU Cong3, LIU Jian-zhi3

2017, 36(8):  2103-2110. 

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Vegetation types play an important role in controlling soil nitrogen (N) leaching that is a key indicator of soil N loss and water eutrophication in a watershed. In this study, we measured soil NH₄⁺-N and NO₃^--N leaching using ionexchange resin bags method in Acer mono-Quercus mongolica, Larix gmelinii and Populus davidiana water conservation forests in the Dahuofang watershed. Our results showed that soil NH₄⁺-N and NO₃^--N concentrations were significantly different under different vegetations during the precipitation abundant season from July to September. Soil NH₄⁺-N accounted for 73.40%-93.30% of soil total inorganic N. In July, soil NO₃^--N concentration was the highest in A. mono-Q. mongolica and P. davidiana forests, while soil NO₃^--N content in L. gmelinii plantation was the highest in August. NO₃^--N is the main form of soil N under leaching loss, and soil N loss was higher in L. gmelinii plantation compared to A. mono-Q. mongolica and P. davidiana forests. Soil microbial biomass carbon (MBC) and nitrogen (MBN) decreased gradually with increasing soil depth, and soil MBC and MBN was significantly higher in A. mono-Q. mongolica and P. davidiana forests than that in L. gmelinii plantation. There was a negative relationship between soil N loss and MBN, suggesting a reduced soil N leaching loss by soil microbial retention. Our results implied that more attention should be paid to the protection of natural secondary forests and the promotion of the artificial water conservation plantations into natural secondary forests in the Dahuofang watershed in order to reduce soil N loss.

Effects of salinity on DOC concentration and CO₂ production of wetland soil in Liaohe estuarine.

YUAN Xiao-min1, YANG Ji-song1*, LIU Kai1, ZHENG Dong-mei1, SONG Chang-zhan2

2017, 36(8):  2111-2117. 

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To identify the effect of salinity on dissolved organic carbon (DOC) concentration and the rate of carbon dioxide (CO₂) production of soil, we collected soils from reed wetland in Liaohe estuary at different depths (0-10, 10-20, 20-30 and 30-40 cm). After washed to different salinity levels (CK, 2.5, 5, 10 mS·cm^-1) with synthesized saline solution, soil samples were incubated for 56 days at 28 ℃. The results showed that salt treatment had no significant effect on the DOC concentration in the topsoil layer (0-10 cm) during the 56d incubation period, but significantly affected the DOC concentrations in the subsoil layers (10-20, 20-30 and 30-40 cm), and elevated salinity decreased the DOC concentration. However, salt treatment had no significant effect on the rate of CO₂ production in any soil layers. The DOC concentration and CO₂ production rate were significantly different among different soil layers, and the mean values were significantly higher in the topsoil layer than in the subsoil layers. The results provide a basis for understanding the response of carbon cycles to salt changes in estuary wetlands.

Effects of straw mulching and scarification on soil labile organic carbon pool in a Phyllostachys edulis plantation.

ZHAO Rui-yu1, LI Zheng-cai1*, WANG Bin1, GE Xiao-gai1, DAI Yun-xi2, ZHAO Zhi-xia1, ZHANG Yu-jie1

2017, 36(8):  2118-2126. 

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In order to understand the effects of tillage regimes after mulching with rice straws on soil total organic carbon (TOC) and labile organic carbon (LOC) contents in bamboo (Phyllostachys edulis) stands, we investigated the organic carbon contents in 0-50 cm soil layer of bamboo stands in Huangyan District of Taizhou, Zhejiang Province. The treatments were set as bamboo stands mulched continuously for two years with (MST) and without soil scarification (MWST), and natural growth bamboo (CK). The results showed that compared with the CK treatment, soil TOC and light fraction organic matter (LFOM) increased by 8.7%-43.8% and 22.2%-90.8%, 13.2%-111.0% and 36.7%-238.5%, when treated with MST and MWST respectively. The easilyoxidized carbon (EOC) content in the depth of 0-50 cm MST soils was enhanced by 21.9%-97.5% compared to CK condition, whereas the EOC content was enhanced obviously in the depth of 0-20 cm MWST soils, but decreased in the depth of 20-50 cm soils. In addition to the significant differences in 10-20 cm soil layer, the change of watersoluble organic carbon (WSOC) was not obvious in other soil layers under the three treatments. The ratio of soil WSOC to TOC in CK condition was higher than in the other two treatments. The ratio of EOC to TOC in depth of 0-20 cm soil layer displayed in order of  MWST > MST > CK, and this ratio in the 20-50 cm soil layer decreased in the order of CK > MST > MWST. The correlation between each LOC and TOC reached a significant level (P<0.01) under all treatments. Under the three treatments, soil TOC, WSOC, EOC, and LFOM exhibited significant (P<0.05) or extremely significant (P<0.01) correlations with soil nutrients (total nitrogen, hydrolyzable nitrogen, available phosphorus, available potassium, exchangeable calcium, exchangeable magnesium).

Spatialtemporal dynamics of vegetation pattern in a typical riparian buffer zone of the middle and lower reaches of Yellow River.

ZHAO Qing-he1, LIU Qian2, MA Li-jiao3, DING Sheng-yan1*, LU Xun-ling1, ZHANG Yi-fan1, CAO Zi-hao1

2017, 36(8):  2127-2137. 

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Vegetation structure of the riparian buffer zone is of great importance for maintaining various ecological services. Therefore, selecting a typical riparian buffer zone in the transition region from the hills to the plain area of the middle and lower reaches of the Yellow River as the research object, we analyzed the spatialtemporal dynamics of vegetation landscape pattern and the associated drivers, via landscape pattern analysis, buffer analysis, and regression analysis, based on the high resolution remote sensing images in 2003, 2009, and 2015 observed from the Google Earth satellite. The results showed that croplands were the landscape matrix of the typical riparian buffer zone of the middle and lower reaches of Yellow River, and riparian vegetation (forest and grassland) exhibited an increasing trend during 2003-2015. Influenced by the wandering of the Yellow River and agricultural reclamation and abandonment, the mutual transformation between water area and flood pain was frequent, and the transformation frequency from cropland to other landscape types was high. The main transformation directions of forest land were grassland, residential area, and cropland, and the main transformation directions of grassland were cropland and forest land. The spatial distribution of changes in vegetation was different in different periods. Landscape pattern analysis indicated that the landscape connectivity of vegetation in the study area was high, the degree of landscape fragmentation increased gradually, and patch shape tended to be more complicated. However, different vegetation types showed different trends, therein, geometrical shape of forest and grassland patches became more complicated and regular respectively, and spatial connectivity of forest land was higher than that of grassland. Grassland and forest patches showed obvious gradient features along the residential areas, riparian ditches, ponds, and road buffers. Meanwhile, regression analysis indicated that changes in grassland and forest patches were driven less by riparian and road buffers, but significantly by the expansion of residential areas. The response of changes in grassland and forest patches to ditches and ponds were different, therein, changes in grassland patches were significantly driven by ditches, while changes in forest patches were significantly driven by ponds.

Understory plant species diversity of rubber plantations in Yunnan Province.

HUANG Xian-han1,2,3, LAN Guo-yu1,2*, YANG Chuan1,2,3, XIAO Bi-wen3, WU Zhi-xiang1,2, TAO Zhong-liang1,2

2017, 36(8):  2138-2148. 

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Based on the plant species survey data of 49 plots (10 m×10 m) in the rubber plantations in Yunnan Province, species composition and diversity, coefficient of similarity and environmental factors of understory plants were analyzed by using the species richness (S), Shannon index (H), Simpson index (D), Srensen index (C_s) and RDA ordination in this paper. The results showed that there were 387 vascular plant species, belonging to 102 families and 274 genera in the rubber plantations. The most common species were Eupatorium odoratum, Cyrtococcum patens, Paspalum conjugatum and Urena lobata. The S, H and D values of rubber plantations were the highest in Xishuangbanna, and the lowest in Honghe. The H and D values of the 8-10 years old rubber plantation were the lowest. The S, H and D values at altitude 500 to 700 m were the highest. The S, H and D values on slope greater than 25° were obviously higher than those on slope between 2° to 15°. A certain similarity of species composition existed among Honghe, Xishuangbanna, Puer, Lincang and Dehong, of which the C_s between Lincang and Puer was 0.47, being the highest. Temperature, precipitation, altitude and other four influencing factors together explained only 20.23% of total variation of dominantspecies distribution.

Difference in response of radial growth of Picea schrenkiana to climate warming in the eastern and western Tianshan Mountains.

ZHANG Yan-jing1,2, YU Rui-de1,2*, ZHENG Hong-wei1,2, GAN Miao1,2, YANG Mei-lin1, SHI Bing-bing1,2

2017, 36(8):  2149-2159. 

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The relationship between tree growth and meteorological factors of Picea schrenkiana in upper and lower forest of eastern and western Tianshan Mountains was studied by climatological method, to reveal the radial growth of P. schrenkiana in response to climatic factors in different regions and the sensitivity of P. schrenkiana under the influence of climate warming. Through a large number of data collection and analysis, the results showed several interesting points. First, the statistical characteristics of chronology were more significant and radial growth of trees was more sensitive to climatic factors in Zhaosu than in Hami. Second, the growth of trees in the two regions was affected by temperature and precipitation. From western to eastern Tianshan Mountains, the significantly positive correlation was reversed to be significantly negative between tree radial growth and temperature in the lower forest boundary, while the relationship between tree growth and precipitation in the upper forest boundary changed from significantly negative to significantly positive. Third, at the lower elevations of Zhaosu and Hami, climate had a stronger influence on the growth of P. schrenkiana during 1984-2015 with increasing temperature than during 1957-1983 with decreasing temperature, whereas the growth of trees displayed reversed patterns in response to climate between the two periods at higher elevations of Hami. Furthermore, as the temperature increased, the promoting effect of temperature on the radial growth of trees increased significantly in the lower forest boundary of Hami in April, while the inhibitory effect of temperature on the radial growth of trees increased significantly in the lower forest boundary of Zhaosu and Hami in June. However, the promoting effect of temperature in June on P. schrenkiana growth decreased significantly in the upper forest boundary in Hami. The promoting effects of precipitation increased significantly for the radial growth of P. schrenkiana in lower forest boundary in Zhaosu and in upper forest boundary in Hami in May and June, respectively. The inhibitory effect of temperature in April and precipitation in October on P. schrenkiana growth decreased significantly in the lower forest boundary in Hami. As the temperature increased, the relationship between tree growth and the local climate factors changed insignificantly, because the precipitation in the upper forest boundary in Zhaosu can meet the growth of trees.

Extreme precipitation characteristics in eastern Liaoning mountainous region from 1960 to 2015.

LI Xiu-fen1,3, WANG Ping-hua2, LIU Jiang1*, JIN Lei1， ZHAO Tong-bin4, SUN Ying-jie1, PENG Feng1, PAN Yu-hong1

2017, 36(8):  2160-2168. 

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In this paper, the daily precipitation data from 11 representative metrological stations in eastern Liaoning mountainous region during 1960-2015 were used to extract the maximum daily precipitation as the index. The spatialtemporal distribution characteristics of extreme precipitation in eastern Liaoning mountainous region during the past 56 years were analyzed, and the precipitation extremes in different reappearance periods were calculated by using EOF, SYM8 wavelet analysis, and optimal probability distribution model fitting methods. The results showed that (1) There were three extreme precipitation patterns in the studied region: the consistent pattern in all of the subregions, the pattern with consistency in the north and south but opposite in the middle, and the opposite pattern in the middle and both sides of mountains. The interannual oscillations of time coefficients for the three patterns were larger. (2) The extreme precipitation decreased slowly in the studied region before 1983, and then approached a stable value, showing obvious cycles of about 11 years and 20 years. The extreme precipitation difference between the southnorth area and the middle area decreased first and then increased, with oscillation cycles of about 11 years and 17 years. The difference between the middle and both sides of mountains approached a stable value before 1984, and then decreased slowly, with a most significant change cycle of 10 years. (3) From 11 representative meteorological stations, the fitting results with PearsonⅢ distribution was the best for 6 stations, lognormal distribution for 3 stations, and Gumbel distribution and Weibull distribution for the other 2 stations. (4) For various given reappearance periods, the theoretical extreme precipitation values of eastern Liaoning mountainous region had relatively large regional differences and they were generally higher in south than in north.

Effects of plastic film mulching and planting density on soil temperature and maize yield in rain-fed area of Northeast China.

CHEN Zhi-jun, ZHANG Lin-lin, JIANG Hao, SUN Shi-jun*

2017, 36(8):  2169-2176. 

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Maize yield and soil temperature will be changed in different color film mulchings and plant densities. In recent years, maize yield is increasing mainly due to using of plastic mulching and high tolerant maize hybrids. However, the understanding of effects of plastic mulching and plant density on soil temperature and maize yield still need improvement. This study aimed to evaluate the effects of plastic film mulching and plant density on maize yield and soil temperature. The field experiment was conducted in main plots under three types of mulching (nonmulching, black plastic film mulching and transparent plastic film mulching), which were divided into three subplots with different plant densities (60000, 75000 and 90000 plants·hm^-2) at Shenyang Agricultural University, Shen-yang, Northeast China, during maize growing season of 2016. The daily variation of 0-25 cm depth average temperature of different treatments all showed a normal distribution trend. Average temperature of 0-25 cm soil depth was higher under transparent film treatments than under black film and nonmulching treatments, and increased with the decrease of plant density. Combination of black film mulching and the density of 9000 plants·hm^-2 reached a maximum yield of 14264.6 kg·hm^-2. The soil temperature in heading stage had negative influence on maize yield. These results can help smallholders to choose reasonable agricultural techniques to improve maize yield in rainfed area of Northeast China.

Characteristics of accumulation, distribution and translocation of dry matter in maize hybrids differing in maturity duration.

QIAN Chun-rong1,2, WANG Rong-huan1, ZHAO Jiu-ran1*, YU Yang2, XU Tian-jun1, HAO Yu-bo2, JIANG Yu-bo2, GONG Xiu-jie2, LI Liang2, GE Xuan-liang2

2017, 36(8):  2177-2183. 

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Nine maize hybrids differing in maturity duration were planted in Harbin in 2014 and 2015 to study their characteristics of accumulation, distribution and translocation of dry matter, and to provide theoretical guidance for selecting suitable maize varieties adapting to wholly mechanized maize production. The results showed that kernel number and yield of midlate maturity hybrids were higher than those of midearly and superearly maturity ones, but the yield difference between midlate and midearly hybrids was not significant. Dry matter accumulated before or after silking increased with hybrid’s longer growth stage. Difference in dry matter accumulated after silking between midlate and midearly hybrids was not significant. The grain accounted for the main proportion of dry matter after maturity, and the order from high to low proportion of other organs was stem, leaf, cob, bract, and leaf sheath. The harvest index of midearly hybrids was four percents higher than that of superearly and midlate ones. Matter translocation from vegetative organs were different, and dry matter translocation from leaf was found in the three types of hybrids, but dry matter translocation from leaf sheath was not observed in the superearly maturity hybrids and was found once a while in the midearly and midlate maturity ones. The percentage of dry matter accumulated after silking was from 56% to 69%, and the contribution rate of dry matter accumulated after silking to yield was from 89% to 98%. Therefore, the grain yield depended on assimilation products after silking but not on dry matter translocation from vegetative tissues in Harbin. The amount of dry matter accumulated before and after silking was significantly positively correlated with effective accumulated temperature above 10 ℃ from seedling to silking, and significantly negatively correlated with effective accumulated temperature above 10 ℃ from silking to mature.

Effects of N addition on carbohydrate contents in different diameter fine roots of Pinus tabuliformis seedlings.

GU Li-cha1, WANG Guo-liang1,2*

2017, 36(8):  2184-2190. 

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Increasing nitrogen (N) deposition significantly affects global forest ecosystems. It is not clear how N deposition affects carbohydrate contents of different diameter fine roots, which limits the understanding on the mechanism of plant physiology and growth affected by N deposition. We set up a N addition experiment with 2-year-old Pinus tabuliformis seedlings to examine the effects of different N addition levels on nonstructural carbohydrate (NSC) and structural carbohydrate (SC) contents in different diameter fine roots. Four N treatments were designed, including N0, N3, N6 and N9 (0, 3, 6 and 9 g N·m^-2·a^-1, respectively). The results showed that: (1) the carbohydrate contents (512.97 mg·g^-1) in fine roots with 0-0.5 mm diameter were significantly lower than those (638.83 mg·g^-1) in fine roots with 1-2 mm diameter. The NSC, soluble sugar and starch contents in the fine roots with 0-0.5 mm diameter were significantly lower than those in fine roots with 0.5-1 and 1-2 mm diameter; (2) The SC and the cellulose contents had an increasing trend with the increase of fine root diameter, while lignin content showed a decreasing trend. Different responses of carbohydrate components in different diameter fine roots to N addition were observed in this study. N addition had no significant influence on the NSC, soluble sugar and starch contents in the 0-0.5 and 0.5-1 mm fine roots, except that N9 treatment significantly reduced the NSC and soluble sugar contents in 1-2 mm fine roots (by 16.20% and 29.90%, respectively) and N3 treatment significantly increased the soluble sugar content in the 0-0.5 mm fine roots (69.65%); (3) Nitrogen addition had no significant influence on the SC and lignin contents. N3 treatment significantly increased the cellulose content in 0-0.5 and 0.5-1 mm fine roots (35.3% and 57.0%, respectively), while N9 treatment significantly reduced the cellulose content in 1-2 mm fine roots (30.39%); (4) N3 treatment significantly increased NSC/SC ratio in the fine roots with 0-0.5 mm diameter, but had no significant effect on those with 0.5-1 and 1-2 mm fine roots. Our results indicated that N addition may influence fine root physiological function and growth via affecting NSC, soluble sugar contents and NSC/SC ratio in the fine roots with 0-0.5 and 0.5-1 mm diameters.

 

Effects of exogenous IAA application on endogenous hormone contents and tillering in sorghum.

ZHOU Yu-fei1,2, YAN Tong1, ZHANG Jiao1, WANG Yi-tao3, WANG Na1, WU Qi1, SUN Fei1, XU Wen-juan1, HUANG Rui-dong1*

2017, 36(8):  2191-2197. 

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Two sorghum varieties (Liaoza 10 and Liaoza 19) were used as the plant materials and exogenous auxin (IAA) was sprayed on the plant leaves at the threeleaf stage with three concentrations of exogenous IAA (0, 100, 200 mg·L^-1, respectively). Effects of exogenous IAA application on endogenous hormone contents and tillering in sorghum were determined. Results showed that exogenous IAA application significantly affected the endogenous hormone contents of sorghum. Exogenous IAA application substantially increased endogenous IAA and gibberellic acid 3 (GA₃) contents but decreased zeatin riboside (ZR) and abscisic acid (ABA) contents in sorghum 3 days after spraying IAA. Endogenous IAA, GA₃ and ABA contents obviously declined but ZR content increased 6 days after the treatment of IAA. The exogenous IAA enhanced the probability of tillering at the first and fourth tillering nodes and decreased the probability of tillering at the second tillering node in sorghum. The exogenous IAA application inhibited the occurrence of multitillers by increasing the probability of a single tiller per plant. Meanwhile, the exogenous IAA reduced the tillering incidence and ineffective tillering rate. Exogenous IAA application increased the sorghum yield by promoting the main agronomic characteristics including panicle length, 1000grain weight, and grain weight per panicle.

 

Water and photosynthetic physiology of Lappula semiglabra seedlings under different dew input amounts.

GONG Xue-wei1,2, Lü Guang-hui1,3*, Martin Welp4, Seigmund Missall4, HALIK Umut1,2,5, MOU Zong-Jiang6

2017, 36(8):  2198-2205. 

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As an important supplementary water source, dew plays an irreplaceable role in the desert ecosystem. Changes in input amount of dew can exert an important impact on the ecological processes of ephemerals. The effect of dew input on water and photosynthetic physiology of Lappula semiglabra seedlings were investigated under three simulated dew levels, reduced amount (W₀), natural amount (W₁) and doubled amount (W₂), in Ebinur Lake Wetland National Nature Reserve in Xinjiang, China. The results showed that doubled dew treatment significantly improved plant water status of seedlings, whereas reduced dew treatment decreased leaf water potential and water content of seedlings to some degrees. Under reduced dew treatment, the transpiration rate and net photosynthetic rate of seedlings (P<0.05) decreased significantly, moreover, the net photosynthetic rate changed from doublepeak curve to singlepeak curve. Doubled dew treatment delayed the reduction process of stomata conductance of seedlings, while reduced dew treatment decreased stomata conductance of seedlings. Difference in dew input amount had no significant effect on intercellular CO₂ concentration. The instantaneous water use efficiency of the leaves of L. semiglabra seedlings did not exhibit marked difference (P>0.05) under different dew input amounts (P>0.05), which indicated a stable water use strategy of desert ephemerals.

Simulation on photosynthetic lightresponse of Quercus variabilis and Robinia pseudoacacia in the southern foot of the Taihang Mountain.

REN Bo1, LI Jun2, TONG Xiao-juan1*, MU Yan-mei2, ZHANG Jin-song3, MENG Ping3

2017, 36(8):  2206-2216. 

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Photosynthesis is one of the important physiological processes of plants, and it can reflect the response of plants to environmental change. Photosynthetic lightresponse model is a main way to evaluate the mechanism of the response of photosynthesis to light and obtain photosynthetic parameters. In this paper, leaf photosynthetic lightresponse curves of Quercus variabilis and Robinia pseudoacacia were measured using a LI-6400XT photosynthetic measurement system in the growing season of 2016 in the southern foot of the Taihang Mountain. The rectangular hyperbola (RH), nonrectangular hyperbola (NRH) and the rectangular hyperbola correction (YZP) models were used to simulate photosynthetic lightresponse curves of the shaded and sunlit leaves. Moreover, the lightresponse parameters fitted by the RH, NRH and YZP models were examined. Compared with the NRH and YZP models, the maximum net photosynthetic rate (P_max), initial light use efficiency (α) and dark respiration rate (R_d) fitted by the RH model were higher. The light saturation point (I_s) could not be derived from the RH model. Photoinhibition could not be simulated by the NRH model, and the value of P_max fitted by the NRH model was significantly larger than that obtained by the YZP model. However, α fitted by the NRH model was close to the measured one. Photoinhibition could be simulated by the YZP model. Compared with the shaded leaves, the P_max values of the sunlit leaves for Q. variabilis and R. pseudoacacia were 24.41% and 18.28% higher, and the α values of their shadedleaves were 22.08% and 15.41% larger, respectively. R_d of the shaded leaves of each species was higher than that of its sunlit leaves, and the R_d value of R. pseudoacacia shaded leaves was 7.13% higher than sunlit leaves. Both P_max , I_s and R_d were correlated with relative humidity and stomatal conductance of Q. variabilis, and α was primarily affected by relative humidity. Both P_max and I_s of R. pseudoacacia had significant positive relationships with relative humidity and G_s.

The influences of wind speed on pollenmediated gene flow from transgenic cotton.

YAN Shuo1,2, ZHU Jia-lin1,3, ZHU Wei-long1,4, QIN Meng2, LIU Hui2, ZHAO Shou-qi2, WANG Lu2, ZHANG Jing1, ZHANG Qing-wen1, LIU Xiao-xia1*

2017, 36(8):  2217-2223. 

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The genetically modified (GM) crops have been globally commercially cultivated for 20 years, and public concerns are persistent overheating about ecological risk of gene flow. This study investigated the pollenmediated gene flow (PGF) frequency of Cry1Ac from transgenic cotton SGK321 (Cry1-Ac/CpTI) to nontransgenic cottons Shiyuan 321 and Zhongmian 35 under three wind conditions (0.54, 0.92 and 1.27 m·s^-1) in greenhouses by PCR and Bt protein assays. Our results revealed that PGF varied depending on the wind speed when Shiyuan 321 was the pollen receptor, and was the highest under low speed wind and the lowest under high speed wind. With Zhongmian 35 as pollen receptor, PGF was very low, and not dependent on the wind speed. PGF depended on the variety of pollen receptors, and total PGF to pollen receptor of Shiyuan 321 (GM parental line) (10.63%) was higher than that of Zhongmian 35 (2.50%). PGF declined exponentially with increasing distance between GM cotton and nonGM receptors. Our research provided some reference for ecological safety assessment of windmediated gene flow.

Bird community diversity and similarity in Zhangye National Wetland Park of Gansu Province in winter and spring.

FENG Wei1,2, ZHAO Cheng-zhang1,2*, YUE Ran1,2, ZHANG Xiang3, JIN Jian-xin3

2017, 36(8):  2224-2231. 

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The spatiotemporal pattern of bird community diversity and similarity is the theoretical basis of understanding the environmental adaptation mechanism of birds. In the conservation area of Zhangye National Wetland Park, the heterogeneity of bird community structure and diversity in winter and spring was studied with transect method. The results showed that there were significant differences in bird abundance and bird richness among months (P<0.05). The bird abundance increased first and then decreased, while the richness decreased first and then increased, with the highest values appearing in March and November, respectively. There were significant differences in the abundance and richness of the resident, migratory and passing birds among months (P<0.05). The peak values of abundance and richness of the 3 types of bird species didn’t occur simultaneously. With the monthly replacement, Shannon diversity index of birds increased firstly and then decreased, while Pielou evenness index showed an opposite trend. The variation trends of Simpson dominance index and Pielou evenness index were basically similar. There were differences in the community similarity of birds in different months, the highest (0.923) value was between January and February while the lowest one was between November and April (0.348). The different peaks of bird abundance and richness distribution on time scales and the difference of similarity coefficient among the communities in the wetland park were closely related to the migrating rhythm of bird population, food resource, and wetland habitat, which reflected the adaptability of birds to environmental screening.

 

#br# Nestsite selection of mallard (Anas platyrhynchos) in Daqing Longfeng Wetland.

FAN Pei-li1, SONG Cheng-qi1, LI Cheng-xu1, WANG Meng1, ZHENG Shuo1, ZHANG Yu-tan1, QI Yan-ping1*, CHEN Xue-long1, WANG Hong-hai2, WANG Ya-fei3, WANG Hai-xia2

2017, 36(8):  2232-2236. 

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Main environment factors for nest-site selection of mallard (Anas platyrhynchos) were surveyed with direct observation and sampling method in Longfeng Wetland from May to July 2016. The environmental factors were investigated for 38 mallard’s nests and 38 adjacent none-nest sites as contrast samples. The results showed that the nest-site selection of the mallard was specific and nonrandom. The main environment factors in nest-site selection of mallard were the density, height and coverage of vegetation, the proportion of bare land and the proportion of hay, successively. These factors suggested that mallard preferred the environment with higher concealment, higher herb coverage and being far away from the road. Accordingly, the concealment became the most important factor for nestsite selection of A. platyrhynchos.

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CHENG Jian-wei1, LIU Xin-min3, HAO Bai-hui1, ZHANG Xin-yu1, ZHANG Yu-ping1, MA Wen-hong1.2*

2017, 36(8):  2237-2245. 

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Variation pattern and adaptive significance of different subtypes of leukocytes in the king ratsnakes (Elaphe carinata) from birth to 30 days of postembryonal period.

SUN Jia-luo, GAO Hui-qing, LIAN Li-yan, ZHANG Zhi-qiang*

2017, 36(8):  2246-2251. 

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To explore the establishment of the immune system during postembryonic development, and provide basic biological data for further healthy culture and disease diagnosis, the changes of body mass (BM), body length (BL), the ratio of BM to BL, and the percentages of different subtypes of leukocytes from hatched group (on day 0 after hatching), sloughing group (on day 7-10 after hatching), 10-day group fed with chicken egg fluid (on day 20 after hatching), and 20day group fed with chicken egg fluid (on day 30 after hatching) were measured in the king ratsnakes (Elaphe carinata). The snakes were cultured under (26±2) ℃ indoor temperatures and 70%-80% relative humidity. Five individuals per group were sampled. BM was increased by 20.37% from day 0 to day 30, but no significant group differences were found (P>0.05). BL was longer in both sloughing and 10-day groups than that in the hatched group (P<0.05). There was no significant difference in the ratio of BM to BL among the four groups (P>0.05). No group differences were observed for the percentages of neutrophils, basophils and lymphocytes (all P>0.05). The percentage of monocytes was higher in the hatched group, and lower in the 10-day group, but did not show significant group differences (P>0.05). However, the percentage of eosinophils was significantly higher in the 10-day group than in the hatched group (P<0.05). During the 30-day postembryonic development, BM and BL displayed continuously increased tendencies, and different subtypes of leukocytes occurred before they were hatched. The percentages of monocytes and eosinophils showed reverse tendencies, the former was reduced and the latter was increased from day 0 to day 30. These results may be related to initial food stimulation after feeding and more wounded probability caused by biting each other due to their living habits, suggesting that it is necessary to feed the king ratsnakes with fluid food during early postembryonic stages, and put juvenile snakes of similar body size into the same culture room.

Morphological differences among four populations of Chinese grass shrimp (Palaemonetes sinensis).

ZHAO Ying-ying1, ZHU Xiao-chen1, XU Wei-bin1, JIANG Ye1, LI Zhi1, HAN Zhi-bin1, WANG Shi-yue1, DONG Jing1, WEI Hua1, BAI Wen-lin1, LI Xiao-dong1,2*

2017, 36(8):  2252-2256. 

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Morphological differences in 18 morphological parameters among four populations (Anshan, Dalian, Shenyang and Panjin population) of Chinese grass shrimp (Palaemonetes sinensis) were studied using three multivariation analysis methods, including cluster analysis, principal component analysis and discriminant analysis. Cluster analysis revealed that the populations of Panjin and Anshan were clustered together due to the smallest difference in their morphology, while had a gradually increased difference with Dalian and Shenyang populations. The Mantel matrix tests showed that there was no significant relationship between geographic and  Euclidean distances (r=0.576, P=0.901). Seven principal components with an accumulative variance percentage of 84.74% were extracted by principal component analysis, and indicated the morphological differences mainly resulting from carapace characters. Four discriminant functions were obtained, with the discrimination accuracy being 66.00%-97.00%, and the integrated discrimination accuracy being 77.83%. The results provided a scientific basis for the protection and use of germplasm resources and for artificial selection breeding of Chinese grass shrimps.

Foraging behavior toward different food baits and observation of sensilla on the head surface of Melanotus cribricollis larva (Coleoptera: Elateridae).

MENG Hai-lin, YE Bi-huan, SHU Jin-ping*, ZHANG Wei, Zhang Ya-bo, WANG Hao-jie

2017, 36(8):  2257-2265. 

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Melanotus cribricollis (Coleoptera: Elateridae) is a dominant soildwelling insect that is known to damage and destroy bamboo shoots in southern China. It is very difficult to monitor and control this kind of wireworm. To aim at understanding the mechanism of food foraging of wireworm below ground, we tested the orientation behavior towards different food baits and observed the type, amount and distribution of sensilla on the antennae, maxillary palp and labial palp of Melanotus cribricollis larva’s head surface by using scanning electron microscopy. The results showed that wireworms were attracted by germinating seeds of corn and wheat, and bamboo shoots, and the attraction of wireworms towards bamboo shoots was significantly stronger than that towards germinating seeds of corn and wheat, and raw oatmeal. Four types of sensilla were recorded in antennae including sensilla chaetica, sensilla basiconica, hook sensilla and dickshape sensilla. Three types of sensilla, including sensilla basiconica, sensilla coeloconica and sensilla ampullaceal, were found in maxillary palp; seven types of sensilla were observed on labial palp surface, including sensilla basiconica, sensilla coeloconica, sensilla ampullaceal, sensilla trichodea, sensilla processus mastoideus, sensilla groove and sensilla dumbbell. Our results confirmed that volatile organic compounds (VOCs) played an important role in food foraging of wireworm, and provided basic information for understanding the function of sensilla of larval head in food foraging.

 

Relationship between the feeding preference of yellow-spined bamboo locust,  Ceracris kiangsu and bamboo leaf quality.

ZHANG Shou-ke1, ZHANG Wei1, SHU Jin-ping1*, MENG Shuai-shuai2, WANG Hao-jie1

2017, 36(8):  2266-2273. 

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Ceracris kiangsu is one of major defoliators in the bamboo distribution area in southern China. To aim at understanding the relationship between occurrence of the pest and host plants, we tested the feeding preference towards 9 bamboo species belonging to 7 genera, and determined the contents of palatable chemicals (soluble sugar, soluble protein, tannins and silicon) and nutrient elements (N, P, K, Na, Ca and Mg) in the 9 bamboo species. Also, the effects of leaf chemicals on feeding preference for C. kiangsu were analyzed. The results showed that C. kiangsu had significant feeding preference on different bamboo species (P<0.001), and the nine bamboos could be classified into two groups, ‘preferred host’ and ‘acceptable host’. The preferred host group only included Phyllostachys edulis. Nine variables including moisture content, total nitrogen content, phosphorus content, sodium content, calcium content, magnesium content, silicon content, soluble sugar content and total tannins content improved a stepwise discriminant model to predict feeding preference of C. kiangsu, and total nitrogen content, phosphorus content, sodium content and total tannins content might be the most important factors. Our findings proved that plant palatability and nutrient level were closely related to the feeding preference of the phytophagous insect, and the contents of nutrient elements as N, P, and Na in bamboo lea-ves were an important reason for host selection of C. kiangsu. Our results provided scientific reference for further studies on the health management of bamboo forests and the host selection of C. kiangsu.

Antioxidant system responses and bioaccumulation of Zn in wetland plants under Zn stress.

YANG Jun-xing1,2, HU Jian2, LEI Mei2, YANG Jun2, Guo Jun-mei2, CAO Shao-kuan3, YE Zhi-hong1*, CAO Liu4

2017, 36(8):  2274-2281. 

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Constructed wetlands are considered as an effective and lowcost technology to clean up toxic metals such as zinc (Zn) from contaminated wastewater. The effect of Zn treatment on biomass, Zn tolerance, soluble protein and antioxidant enzymes of leaves in 18 candidate wetland emergent plants grown in soils without (control, CK) and spiked with 600 and 1200 mg Zn·kg^-1 were studied in a pot trial. The results showed that there were significant differences in Zn tolerance indices and accumulation among the 18 plant species. The biomass, Zn tolerance indices and leaf protein contents of the 18 plant species decreased with the increasing soil Zn concentrations. Activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in leaves of most of the 18 plant species increased with the increasing soil Zn concentrations. Zinc accumulation by the 18 plant species was strongly dependent on the plant species and soil Zn concentration. However, Zn translocation from root to shoot was generally low in the 18 plant species. Enhancement of SOD, POD and CAT activities revealed that the antioxidant system of wetland plants played an important role in alleviating Zn toxicity in the 18 plant species. The data obtained should help to select proper wetland plant species for use in remediating Zncontaminated wastewater and soils.

Effects of pre-exposure to selenium on the accumulation and toxicity of copper in Lumbriculus variegatus.

MU Lei1, WU Xing1, CHEN Hong-xing1, Paul L. Klerks2, XIE Ling-tian1*, LUO Yong-ju3*

2017, 36(8):  2282-2288. 

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The present study assessed the effects of preexposure to Se on the accumulation and toxicity of copper (Cu) in Lumbriculus variegatus. Furthermore, the effects of exposure routes and the Se species were also evaluated. L. variegatus were preexposed to environmentally relevant concentration of Se in sediment (dietary at 20 μg·g^-1 dry wt) or in solution (dissolved at 15 μg·L^-1) for 2 weeks. The Se species included selenite (Se(Ⅳ)), selenate (Se(Ⅵ)) and selenoLmethionine (Se-L-Met). The Se preexposed L. variegatus were subsequently exposed to 15 μg·L^-1 of Cu for 7 days. The accumulation of Cu and the levels of thiobarbituric acid reactive substances (TBARS) were determined. The results showed that mortality did not occur in all the treatments except for the Se-L-Met sediment treatment during the 2 week exposures. Preexposure to all the three forms of Se from both the dietary and dissolved routes significantly decreased the accumulation of Cu in the worms except for preexposure to dissolved Se(Ⅵ). The Se preexposed worms had significantly lower levels of TBARS than the control worms. The protective potential of pre-exposure to Se against Cu toxicity was in the order as Se(Ⅵ) > Se(Ⅳ) ≈ Se-L-Met in the dissolved exposure, while in the dietary exposure, the protective potential of the three species was comparable. The results suggested that preexposure to Se at environmentally realistic concentrations can offer protection against Cu toxicity in L. variegatus. Future research on the interaction of Se and Cu is warranted to better understand the mechanisms underlying this protection in the worm in particular and possibly in other aquatic organisms in general.

The responses of two algal species, Microcystis aeruginosa and Scendesmus quadricauda to ammonium.

DAI Liang-liang1,2, GUO Liang-liang1,2, LI Lu1,2, ZHOU Wei-cheng3, LI Gen-bao1*

2017, 36(8):  2289-2295. 

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In order to explore the role of ammonium nitrogen (NH₄⁺-N) in the succession of algae communities, we studied the influence of ammonium nitrogen on growth, physiological characteristics and cellular morphology of Microcystis aeruginosa and Scendesmus quadricauda under monoculture and coculture in the laboratory. The monoculture experiments showed that the 5.0-20 mg·L^-1 of ammonium nitrogen benefited the growth of M. aeruginosa and S. quadricauda. However, M. aeruginosa was more sensitive to ammonium nitrogen than S. quadricauda. When the ammonium concentration reached 50 mg·L^-1, the photosynthetic activity of M. aeruginosa declined from 0.35 to 0.07 on the second day, while that of S. quadricauda declined from 0.63 to 0.47 on the fourth day. With the increase of cultivation period and ammonium concentration, the damage of the plastid of S. quadricauda was aggravated. The twocelled S. quadricauda was more likely to be generated at ammonium concentration equal to or greater than 10 mg·L^-1, whereas the fourcelled S. quadricauda was more likely to be generated at ammonium concentration less than 10 mg·L^-1. The coculture experiment showed that the 0.5-2.0 mg·L^-1 of ammonium was beneficial to the growth of S. quadricauda while 5.0-20 mg·L^-1 was beneficial to the growth of M. aeruginosa. These results showed that M. aeruginosa was fit to grow at the high concentration of ammonium nitrogen (5.0-20 mg·L^-1), therefore, it may be a good strategy to keep ammonium at low levels (≤2.0 mg·L^-1) for control of algal bloom of M. aeruginosa.

Distribution and pollution assessment of heavy metals in paddy soil in Danzhai AuHg mining area, Guizhou, China.

YU Zi-heng1,2, HUANG Guo-pei2, ZHANG Hua2, LI Qiu-hua1, ZHONG Shun-qing2, ZHANG Yu-tao3, SHANG Li-hai2*

2017, 36(8):  2296-2301. 

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The spatial distribution of five heavy metals (As, Cd, Cr, Hg, Pb) in  paddy soils from four different zones in Danzhai AuHg mining of Guizhou Province were analyzed, and the pollution status was assessed by  single factor index and Nemerow comprehensive index. The contents of As, Cd, Cr, Hg and Pb were 7.66-73.5, 0.233-0.777, 58.3-125, 1.13-77.1 and 23.7-111 mg·kg^-1 (n=28), with averages of (31.2±17.2), (0.426±0.136), (95.3±15.6), (20.4±22.7) and (49.9±23.9) mg·kg^-1 (n=28), respectively. Heavy metal contents in soils varied with different zones, with higher As, Hg and Pb contents in village area, higher Pb content in national road area, and higher As and Hg contents in tailing area. The Nemerow comprehensive index showed that 92.86% of soil samples were polluted heavily with Hg pollution and slightly with As pollution. The As and Hg contents in brown rice exceeded the China’s national standard. The release of As and Hg in the process of AuHg mining and smelting with water migration is the main way to paddy soil pollution

Impacts of farming landscape patterns on soil heavy metal pollution in towns of Southern Jiangsu Province.

SUI Chuan-jia1, PAN Jian-jun2*, YU Hong2, WEI Shan-bao1

2017, 36(8):  2302-2311. 

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Landscape pattern is easily affected by human activities. In order to accurately grasp the influences of landscape pattern on heavy metal pollution of soil and implement more targeted prevention and control measures, GIS and geostatistical analysis method were adopted. Based on a villagelevel small scale, the contents of 8 kinds of heavy metals in surface soil of cultivated land were measured in a town in South Jiangsu. The study objectives were to reveal the pollution characteristics of the 8 kinds of heavy metals and their spatial distribution pattern, to discover the influences of landscape pattern in buffer area, and to analyze the relationships between overall landscape pattern and heavy metal pollution in administrative villages. The results showed that the content of Cd exceeded national soil quality secondary standard of China. The heavy metal pollution levels were all less than 1; 99.36% of the cultivated land were not polluted and 0.64% of the cultivated land were on the alert against heavy metal pollution. In the buffer area, there was a significant correlation between contents of As, Ni, Pb, Hg, Cd and Zn and some landscape pattern indexes (P<0.05), while there was no significant correlation between contents of Cr and Cu and landscape pattern. There was a significant positive correlation between landscape connectivity/aggregation degree and comprehensive pollution index of heavy metals (P<0.05). Therefore, our results well explained the comprehensive pollution degree of heavy metals in cultivated lands in each administrative village.

Technologies of improving water use efficiency of high quality forage grasses: A review.

ZHAO Dan-dan1,2,3, MA Hong-yuan1,3*, YANG Kun4, YANG Hong-tao1,2,3, YANG Fan1,3, WANG Zhi-chun1,3

2017, 36(8):  2312-2320. 

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The deficiency of water resources is a core inhibiting factor for grass growth in arid and semiarid grasslands worldwide. Thus, development of technologies aimed to improve the wateruse efficiency and grass productivity is the key to sustainable development of the grass industry. In this paper, we briefly reviewed the strategies for improving wateruse efficiency of grasses from methods of irrigation, soil surface mulching, tillage modes, microorganism regulations and the application of materials inhibiting plant respiration. Furthermore, based on the main problems existing in current studies related to improvement of water use efficiency, we provided research perspectives for the future, which included the four following aspects: developing new varieties of highquality grasses with high drought tolerance, paying more attention to insitu field experiments and the mechanisms in wateruse efficiency, employing advanced technologies in basic researches, and developing comprehensive technology and management systems for improving wateruse efficiency of grasses.

Phenology of grassland plants: A mini review.

BAO Xiao-ying1, CUI Shu-juan1,2, WANG Qi1,2, LI Bo-wen1,2, MENG Fan-dong1,2, Tsechoe Dorji2,3, CUI Xiao-yong1*, WANG Shi-ping2,3*

2017, 36(8):  2321-2326. 

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Plant phenology is a periodic event with environmental change, being much sensitive to environmental change. Most of the studies have observed that warming advanced onsets of greenup and flowering, but delayed completely leaf coloring. However, fruitingset kept relative stable under temperature change compared with other phenological sequences. There were hierarchical responses of phenological sequences in duration to temperature change (i.e. warming and cooling). In particular, more attention should be paid to observation of community phenology under future climate change because the response of individual plant phenology to climate change could not predict the response of the community phenology due to different responses from different plants. Although grazing is a major land use for natural grasslands, how grazing affects the effects of climate change on plant and community phenology is still unclear. Meanwhile, few studies have been performed on the synchrony of aboveground and root phenology, nonlinear change of phenological sequences and its mechanisms due to experimental method and technology limitations under future climate change.

Advances in research on the separation of soil carbon emissions.

PANG Rui1,2, LIU Min1,2, LI Mei-ling1, XU Xing-liang1*

2017, 36(8):  2327-2335. 

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As the major component of global carbon cycle, soil respiration is a key to understand belowground carbon emissions and soil organic carbon stability. However, soil respiration is composed of different components, and many key terms related to soil respiration are still onesided understood and improperly used, which hinders further research on soil carbon cycling. Thus, this paper summarized the advances in belowground carbon emissions according to the sources of carbon use, production locations and pathways for the components of soil respiration. Correspondingly, we clarified the terms related to soil respiration. Furthermore, we interpreted the contributions of different components of soil respiration to atmospheric CO₂ and their responses to global warming. Finally, combined with hot topics in current soil carbon cycle research, we emphasized the necessity and ecological significance to distinguish the components of soil respiration in terrestrial ecosystems. We prospected that exploring the mechanisms responsible for rhizosphere priming effect will be a key for the future research on ecosystem underground carbon cycling. Knowledge of rhizosphere priming effect will greatly improve our understanding dynamics of soil organic carbon and its stability.

Progress in crop phosphorus utilization under abiotic stresses.

TIAN Zhi-jie1,2, LI Jing-peng1, YANG Fu1*

2017, 36(8):  2336-2342. 

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Phosphorus (P) is important to crop development and stress resistance. Abiotic stresses can seriously affect P absorption, utilization and translocation in crops, and then plant metabolism and grain yield. Considering excessive P application and stress resistant breeding of crops, we summarized the P characteristics and physiological mechanisms in crops under three kinds of abiotic stresses: drought, salinity and low temperature. The P efficiencies of crops were also discussed. Abiotic stresses not only damage the root development and function directly, but also seriously reduce the mobilization and availability of inorganic phosphate in soil, leading to physiological P deficiency of crops. Phosphorus application can effectively relieve the damage from the abiotic stresses, promote water and nutrient uptake, and then partly enhance the tolerance of crops to the stresses. Moreover, there are significant differences between crop species or genotypes in responding to P applications and abiotic stresses. It would be better to combine the stress tolerance with high P efficiency in improving P utilization under abiotic stress conditions. Further research on crop P responses under abiotic stress should pay attention to P availability in rhizosphere in soil, optimal P application and screening of crop gene resources of high stress resistance and P efficiency.

Daily torpid mammals: Species distribution, physiological and ecological characteristics.

TANG Hua-dan, LI Si-yi, CHEN Lu, ZHANG Xiao-fei, CHEN Hong-yu, YANG Ming*

2017, 36(8):  2343-2350. 

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Daily torpor in mammals is characterized by temporal reductions in body temperature and metabolic rate during a day, and is an important survival strategy for mammals to cope with the adverse environmental conditions such as cold climate and food shortage. In this review, we analyze the taxonomic classification, geographical distributions, living environment, body size and diets, body temperature and metabolic rate in nearly a hundred species of daily torpid mammals reported in the literatures. Daily torpid mammals are subordinate to marsupials (Marsupialia) and placentalia (Placentalia); these species are mostly distributed in temperate regions (latitude range from 20° S to 30° S and longitude from 30° N to 40° N), where the environmental conditions varied seasonally and diurnally. Daily torpid animals are relatively smaller, and they need nutritionrich foods. Almost every herbivorous animal cannot significantly reduce their body temperature. For daily torpid mammals, the average body temperature is 19.75 °C and the metabolic rate during torpor is 34% of basal metabolic rate. Revelation of the mechanism of low metabolism and hypothermia in daily torpor will provide important theoretical and practical significance for human health and biomedical research.

Coupling effects of iron and sulfur on the migration and transformation of methylmercury in soilrice system: A review.

ZHONG Shun-qing1,2, QIU Guang-le2, FENG Xin-bin2*

2017, 36(8):  2351-2357. 

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Methylmercury (MeHg) has a strong neurotoxicity, and the health risk caused by its accumulation in rice grain has gained a lot of attention. The origin of MeHg in rice (Oryza sativa L.) comes mainly from paddy soil. The spatial variation of iron and sulfur contents in soil is large, and the interaction of iron and sulfur  changes with the course of wet and dry alternation in rice planting and O₂ secretion from rice roots. Changes of the content and transformation of MeHg in soil influence the MeHg availability to rice plants. This review comprehensively summarized the research achievements of iron and sulfur and their interaction effects on mercury methylation and MeHg migration and transformation in soilrice system, and put forward the potential aspects of future studies. This review will benefit further research on the regulation of MeHg formation and uptake, and on the reduction of health risks of MeHg.

Hydrogen and oxygen stable isotope tracing of eco-hydrological processes in water bodies mixing the mainstream and a tributary of the Three Gorges Reservoir.

YE Zhen-ya1, WANG Yu-chun1,2*, HU Ming-ming2, WANG Guo-jun1, LIANG Shun-tian2, WANG Qi-wen2, GAO Ji-jun2, LIU De-fu1

2017, 36(8):  2358-2366. 

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There exists heterogeneity in water dynamics in different areas of the Three Gorges Reservoir tributaries after impoundment. In order to illustrate the processes of ecological hydrology in tributaries, a tributary (Zhuyi Bay) was chosen to analyze the spatiotemporal characteristics of hydrogen and oxygen isotopic compositions using isotope tracing technique. The water mass characteristics of endmember mixing process of the mainstreamtributary and sourcetributary was also revealed. The results showed that: (1) In backwater area of Zhuyi Bay, the δD values ranged from -84.1‰ to -54.4‰, and δ¹⁸O from -11.71‰ to -8.13‰. These values were respectively similar to those of adjacent water body in mainstream, while obviously less than those in source water of the tributary (δD: -49.6‰ to -46.1‰; δ¹⁸O: -7.61‰ to -7.19‰). (2) The rate of water recharge of the mainstream of Yangtze River to the backwater area of Zhuyi Bay was approximately 95% using binary linear mixed model. This value indicated that bay water was mainly affected by the backward flowing from the mainstream to the tributary. (3) The backward flowing from the mainstream of Yangtze River to Zhuyi Bay occurred in the middle layer of Zhuyi Bay estuary during preflood hydrofluctuation period and dry period, whereas in the uppermiddle layers during flood period and storage period. Hydrogen and oxygen isotope tracing technique has relatively good applicability in analyzing the mode of backward flowing. (4) Yangtze River locates in monsoon climate areas, and the main factors affecting hydrogen and oxygen isotope compositions of Zhuyi Bay in rainy season could be ordered in significance as: backward flowing > rain > isotope fractionation. However, this order changed as backward flowing > isotope fractionation > rain in dry season.

Water sources for Tamarix chinensis Lour. in different habitats on Chenier Island.

ZHU Jin-fang1,2,3, LIU Jing-tao2*, SUN Jing-kuan2, ZHAO Yan-yun2, LU Zhao-hua2,3, LI Jun-sheng1

2017, 36(8):  2364-2374. 

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Tamarix chinensis is one of dominant species and widely distributed in the Chenier Island of the Yellow River Delta. To detect the water use patterns of T. chinensis, we conducted a comparative study at two habitats, seaside and dune crest. Soil moisture, soil salinity and oxygen isotope compositions in the xylem water of T. chinensis were measured during two plant growth seasons. The IsoSource model was used to calculate the feasible contributions of potential water sources to T. chinensis xylem water. In July 2013 with high precipitation, 90.9% of the xylem water in T. chinensis at the seaside was from the 20-40 cm soil layer, while 51.2% of the xylem water at the dune crest was from the 60-100 cm soil layer. In July 2014 with low precipitation, 58.4% of the xylem water at the seaside was from the 20-60 cm soil layer and 67.0% of the water at the dune crest from shallow groundwater. In addition, T. chinensis at the dune crest took up deeper water source than at the seaside because of the difference of soil and groundwater salinity. Thus, the water sources of T. chinensis varied with habitats and precipitation. These results suggested that T. chinensis could adapt to variable habitats and precipitation by altering the water use patterns, which benefits its competition capability for water resources and the maintenance of ecosystem stability of the Chenier Island under stresses.

A comparative study on the classification methods of grassland plant communities: A case of Hulunbuir grassland.

YANG Zhu-zhu1,2, Lü Xiao-tao1,2, SONG Yan-tao3, JIA Zi-jin3, WU Yun-na3, WANG Zheng-wen1,2*

2017, 36(8):  2375-2384. 

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Many methods are used in vegetation classification; however, their applications in a single vegetation type are seldom empirically compared. Here, three commonlyused methods, including dominancetype classification, TWINSPAN and UPGMA, were used to classify the communities from 40 sampling sites in Hulunbuir grassland. The dominancetype classification divided these communities into 16 groups, while TWINSPAN and UPGMA divided into 10 and 11 groups, respectively. The coherence coefficient was 0.94 between dominancetype and UPGMA, 0.91 between TWINSPAN and UPGMA, and 0.87 between dominancetype and TWINSPAN. The highest coefficient indicated that the results of dominancetype classification and UPGMA were highly consistent. By calculating the variance of species richness, total aboveground biomass and average similarity coefficient of three methods, the cumulative variance of each method was obtained: 1131 for dominancetype classification, 976.8 for TWINSPAN, and 952.8 for UPGMA. The largest variance suggested that the results of dominancetype method had the highest variation within groups, and thus the results from dominancetype classification might need to be adjusted. The difference of within groups for UPGMA was the smallest. Results from the present study indicated that UPGMA should be more suitable for the classification of plant communities in Hulunbuir grassland, compared with the dominancetype classification that was widely used in the previous community classification literature. Our results had great implications for the future research focusing on the vegetation classification of grasslands in China.