Table of Content

10 May 2018, Volume 37 Issue 5

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Age-related N, P, and K stoichiometry in different organs of Picea schrenkiana.

SUN Xue-jiao, CHANG Shun-li, SONG Cheng-cheng, ZHANG Yu-tao

2018, 37(5):  1291-1298. 

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Ecological stoichiometry is effective in studying the relationships between species and their environment. There are knowledge gaps in understanding the allocation of nitrogen (N), phosphorus (P), and potassium (K) in different organs, and how this allocation changes with age. Samples of roots, stems, and leaves of Picea schrenkiana at different growth stages were collected from the northern slope of Tianshan Mountains. N, P, and K concentrations were mea sured to analyze the stoichiometry at different growth stages, with the aim to examine allocation strategy and allometric relationship. The results showed that: (1) The allocations for N, P, and K among different organs were in the order of leaf > stem > root. With increasing age, the N, P, and K concentrations in leaves first increased and then decreased; N and K concentrations in stems increased gradually; N concentration in roots decreased, whereas P and K concentrations showed a gradual increase. (2) The stoichiometric ratios in different organs were 20.25-27.61 for N∶P,0.28-0.41 for N∶K, and 0.01-0.02 for P∶K. With increasing age, N∶P, N∶K, and P∶K in leaves and stems first increased and then decreased; N∶P and N∶K in roots decreased, and P∶K ratio showed no obvious pattern. Organ type, forest age and their interaction had significant effects on N, P, and K stoichiometry. (3) The proportions of N, P, and K contents allocated in different organs were following the order of stem > root > leaf. The N, P, and K concentrations in leaves, and N and K concentrations in stems and roots showed significant allometric relationships (leaves: N-P^0.956,P=0.001; N-K^-0.254, P<0.001; P-K^-1.568,P<0.001; stems: N-K^-0.326, P=0.011; roots: N-K^-0.529,P=0.007). Our results suggested that the N, P, and K stoichiometry of the organs changed at different growth stages as affected by environmental factors and the nutrient absorption and allocation.

Responses of leaf chemical trait and economics spectrum in desert plants to varied soilwater and salinity.

ZHANG Xue-ni, LI Yan, YANG Xiao-dong, HE Xue-min, LV Guang-hui

2018, 37(5):  1299-1306. 

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Exploring the responses of leaf chemical traits and their economics spectrum to environmental changes would help understand plant adaptive strategy from a functional perspective. In this study, responses of plant chemical traits and their correlations at species and communitylevels to different soil water and salinity conditions in the Ebinur Lake Wetland National NatureReserve, northwest of Xinjiang Uygur Autonomous Region were analyzed. The results showed that: (1) With the decreases of soil water and salinity, leaf C content at community level (p_i) significantly decreased (P<0.05), Ca content marginally significantly decreased (P<0.1), leaf S, K, Na and Mg contents significantly increased (P<0.05), and leaf N and P contents showed no significant changes (P>0.05). (2) Alpha trait value (α_i), representing interspecific differences of plants within community, was higher than co-occurred species in the plots with high soil water and salinity, while it was lower than co-occurred species in the plots with low soil water and salinity. The increases of the range ofα_i indicated an intensifying trait divergence with changes of soil water and salinity. (3) Beta trait values (β_i) represented the ecological niche in community trait gradient. β_iof plant N, S, K, Na, Mg in the plots with low soil water and salinity was higher than that in the plots with high soil water and salinity, while C and Ca contents showed the opposite pattern. Suchβ_i differences indicated the significant effects of soil water and salinity on ecological niche of species chemical trait. The range ofβ_i trait became smaller with the decreases of soil water and salinity, indicating the decrease of ecological niche breadth. (4) Trade offs between  light-capture chemistry such as C, N and P and osmotic-metabolic regulation chemistry such as S, K, Ca, Na and Mg were intensified as soil water and salinity decreased. Our results provide theoretical basis for understanding the resource use strategy and adaptation mechanism of desert plants under stress environments.

Niche and interspecific association of dominant plant species in saline-alkaline soils ofdesert steppe zone.

ZHANG Dong-mei, ZHAO Wen-zhi, LUO Wei-cheng

2018, 37(5):  1307-1315. 

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Saline-alkaline soil is one of the common habitat types in desert steppe zone. Studying species niche and interspecific association is important for scientific management of salinealkaline ecosystems and vegetation recovery. Here, we analyzed interspecific association and niche among 26 dominant species along the gradient of soil moisture and salinity near the Huamachi saline lake in desert steppe zone in Dingbian County, Shaanxi Province. We discussed the relationship between niche overlaps and interspecific association. Methods used in this study included niche breadth, niche overlap, variance ratio method, χ² test and Ochiai index based on a 2×2 contingency table. The results showed that: (1) Across the soil moisture and salinity gradient, Kalidium gracile, Kalidium cuspidatum and Suaeda glaucahad the higher niche breadths than other species. Thus, those species were the constructive species in saline-alkaline soil of desert steppe zone. (2) The species with lower niche breadth had larger niche overlap, and competed the limited resources. The species with higher niche breadth had relatively larger niche overlap. Some species, such asSalicornia europaea and Suaeda salsa, had relatively higher niche breadth, but had lower niche overlap with a few species, indicating weak competitionbetween them. (3) Macro association was significantly positively correlated among 26 dominant species, whereas species pairs with Ochiai index greater than 0.6 only accounted for 17.85% of total species pairs. This result indicated that the plant community was in a relatively stablesuccession status, and that interspecific association degree was not close. (4) Ochiai index was significantly positively correlated with niche overlap along the soil moisture and salinity gradients, with a stronger correlation existed between Ochiai index and niche overlap along the salinity gradient. However, it was difficult to  reveal completely the inherent mechanism of interspecific association through the regression relationship between niche overlap and Ochiaiindex.

Evaluation of the stand spatial structure of Pinus tabuliformisecological forest in West Beijing.

ZHANG Lian-jin, LAI Guang-hui, FENG Huan-ying, DU Man-yi, GAO Xu, GUO Jia, ZHAO Ming-wei, YU Hai, MA Qing-hua

2018, 37(5):  1316-1325. 

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The main aim of this study is to provide a theoretical basis for the optimization and adjustment of the spatial structure of mixed and pure Pinus tabuliformis ecological forest in Beijing Jiulong Mountain by analyzing the spatial structure of P. tabuliformis ecological forest and evaluating its management urgency. Based on empirical data, the spatial structure characteristics of P. tabuliformis ecological forests were analyzed using seven spatial structure parameters including mingling, dominance, uniform angle index, crowding, stand layer index, open degree, and competition index. Ten indices were selected to construct the evaluation index system of management urgency from four aspects of density, pattern, competition and mingling, and their standards were determined. Meanwhile, the management urgency of P. tabuliformisecological forest was evaluated. Results showed that: (1) Trees in both mixed forest and pure forest were close to random distribution. Compared with the mixed forest, the spatial structure of pure forest was relatively simple, tree species composition was simple, dominated by non-mixture and low-mixture and with a trend of single aggregation. (2) Tree size differentiation was insignificant, and P. tabuliformis and Larix principis rupprechtii were dominant species. (3) Trees were in a state of dense, and trees of the very dense had a higher proportion. (4) Most trees were in the middle and upper forest layers, with no obvious forest layer structure. (5) Both stands were under moderate competition. Compared with the pure forest, the open degree of the mixed forest was lower and its growth space was not enough. (6) Management urgency of the pure and mixed forest was 0.6 and 0.5, respectively. The grades of management urgency for those two stands were particularly urgent and very urgent, which illustrated that most of the characteristics of P. tabuliformis ecological forest did not meet the standards. It is necessary to adopt reasonable management strategies to optimize the spatial structure of theP. tabuliformis ecological forests, with the aim to improve forest status and achieve sustainable development.

Environmental factors affecting plant species diversity of understory herbaceous communities in a chronosequence of Pinus tabuliformis forest in Liaoheyuan Nature Reserve.

SHI Jia-yu, HAN Hai-rong, CHENG Xiao-qin, DONG Ling-ling, TIAN Hui-xia, CAI Meng-ke

2018, 37(5):  1326-1333. 

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As an indispensable component of forest ecosystems, species of herbaceous layer play a crucial role in regulating the community stability and ecological function of forests. We examined the relationships between the composition of understory community and the environmental factors in Pinus tabuliformis forests with different stand ages in Liaoheyuan Natural Reserve,aiming to reveal the main factors driving understory species composition. The results showed that stand age was an important factor driving the spatial variation of soil chemical properties in the forests. However, there was no linear relationship between forest age and the species diversity and richness index within the herb layer. The results from CCA ordination and Monte Carlo test showed that stand age, stand density, mean diameter at breast height, canopy density, and slope were main factors determining the composition of the herb layer, indicating that forest canopy structure determined the distribution pattern of herb layer plant communities in this region.

The relationship between light interception and photosynthetic physiological characters in vertical level within the canopy ofSalix matsudana in Zhangye Wetland.

YAO Wen-xiu, ZHAO Cheng-zhang, CHEN Jing, WANG Jian-liang, LI Qun, ZHANG Wei-tao

2018, 37(5):  1334-1340. 

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The correlation between canopy light interception (LI) and leaf photosynthetic physiological characteristics reflects the response and adaptation of plant functional traits to the changes of light conditions, which is the result of integrative effects of canopy structure and environmental conditions. A total of 10 plots were randomly selected from the floodplain wetlands on the edge of the Heihe River in Zhangye City, Gansu Province, China. According to the principle of equal division, the canopy of Salix matsudana in those plots was divided into the upper, middle, and lower levels. The relationship between LI, transpiration rate (T_r), and net photosynthetic rate (P_n) of each canopy level was examined. The results showed that, with the decreases of canopy level of S. matsudana, leaf area index (LAI), mean leaf angle (MLA), leaf thickness, photosynthetically active radiation (PAR),LI, T_r, andP_n showed a decreasing trend, while leaf area was gradually increasing. Leaf moisture content first increased and then decreased. The type of leaf aggregation changed from aggregation to dispersion. In the upper and lower canopy, the relationships between LI and T_r and P_n showed significant positive correlations (P<0.05). In the middle layer, they showed significant positive correlations (P<0.01). Inside the canopy, theupper leaves used conservative survival strategy that reduced LI,T_r and P_n, while the middle and lower leaves showed the exploitative strategy that increased LI,T_r and P_n, reflecting the optimal allocation of resources between wetland plant’s traits according to functional requirements in heterogeneous habitats.

Allocation of nitrogen, phosphorus and soluble sugar in twigs and leaves of tropical cloud forests in Hainan Island.

LI Chao, SHAO Xiao-li, WANG Xu, JIANG Huan, CHENG Yi-kang, XIAO Chu-chu, LONG Wen-xing

2018, 37(5):  1341-1348. 

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Studies on allocation of nitrogen (N), phosphorus (P) and soluble sugar in plants of tropical cloud forest play an important role in understanding the growth and adaptation of plants to the environment. We measured the contents of N, P and soluble sugar in the twigs and leaves from the 282 species of tropical cloud forests in three sites (i.e., Bawangling Mountain (BWL), Jianfengling Mountain (JFL) and Limushan Mountain (LMS)) of Hainan Island, aiming to clarify the correlations of N, P, and soluble sugar in different vegetative organs. The results showed that the contents of N, P and soluble sugar in leaves were significantly higher than those in twigs. In twigs and leaves, the contents of soluble sugar were (15.06±9.4) and (32.14±19.57) g·kg^-1, the contents of N were (3.48±1.02) and (9.51±5.26) g·kg^-1, and the contents of P were(0.23±0.15) and (0.56±0.44) g·kg^-1, respectively. The contents of N and P in the leaves and stems were the highest in LMS and the lowest in BWL. The content of soluble sugar in the twigs of BWL was significantly higher than that in LMS and JFL, whereas the content of soluble sugar in leaves was significantly lower than that of LMS and JFL. In twigs and leaves, there were significantly positive correlations between N and P contents, while soluble sugar contents were not significantly related to P contents. Moreover, N and P contents in twigs were significantly positive correlated with that in leaves, while there was no significant correlation in soluble sugar content between twigs and leaves. In addition, we found that P was a main limiting factor for plant growth and population development in the tropical cloud forests of Hainan Island.

Effects of grazing and enclosure on foliar and soil stoichiometry of grassland on the QinghaiTibetan Plateau.

XU Xue-yun, CAO Jian-jun, YANG Lin, YANG Shu-rong, GONG Yi-fan, LI Meng-tian

2018, 37(5):  1349-1355. 

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Ecological stoichiometry reflects the interactions of energy balance and multiple chemical elements in ecosystems. This study focused on the C, N, and P concentrations and the stoichiometry characteristics of leaves of dominant plant species and soil between grazed and enclosed grassland in Nagqu, Tibet, to explore the effects of different grassland utilization strategies on soil and plants and the interrelations between them. The results showed that soil pH of grazed grassland (7.30) was significantly higher than that of enclosed grassland (7.13). Foliar P concentration in grazed grassland was significantly higher than that in enclosed grassland (1.25 vs 1.05 g·kg^-1) but C∶P ratio in grazed grassland was significantly lower than that in enclosed grassland (335.21 vs 434.60). Foliar C concentration was significantly negatively correlated with N and P concentrations. Foliar N concentration had significantly positive correlation with P concentration. Leaf N concentration had no significant correlation with soil total N concentration, and leaf P concentration was significantly negatively correlated with soil total P concentration, suggesting that plants were probably limited by P availability in the grassland. Our results provide a scientific basis for the sustainable management of grassland in the Qinghai Tibetan Plateau.

Soil organic carbon fractions and physicochemical properties affected by irrigation with Yellow River water.

DONG Lin-lin, ZHANG Hai-dong, YU Dong-sheng, YANG Fei-xia, SHI Xue-zheng

2018, 37(5):  1356-1363. 

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Irrigation is an important strategy to ensure agricultural production, with consequences on soil physicochemical properties. We examined the effects of irrigation on soil organic carbon fractions and other soil properties in the Ningxia Irrigation Zone, which was irrigated by the sedimentladen Yellow River water. Compared to control treatment (non-irrigated and non-cultivation soil), irrigation significantly increased total soil organic carbon, heavy and light fraction organic carbon by 272%, 222% and 318%, respectively. Heavy fraction organic carbon was a major part of the total organic carbon, accounting for >65% of total organic carbon. The higher content of heavy fraction organic carbon, the more stable the soil organic carbon pool was. After cultivation and irrigation with Yellow River water, soil total N and P significantly increased from 0.27 and 0.85 g·kg^-1 to 0.77 and 1.68 g·kg^-1 (P<0.05), respectively. Soil aeration and water retention were enhanced, the salinization degree and soil pH were reduced, and soil fertility was promoted by irrigation with sedimentladen Yellow River water. Overall, irrigation with Yellow River water is an effective strategy to improve soil properties and land productivity in this region.

Effects of thinning on phosphorus fractions of rhizosphere soil in Pinus massoniana plantations.

YE Yu-qian, ZHAO Jia-hao, LIU Chang, GUAN Qing-wei

2018, 37(5):  1364-1370. 

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We investigated the responses of phosphorus (P) fractions of rhizosphere soil to thinning in a 30-year-old Pinus massoniana plantation after 10 years of thinning. There were four thinning intensities: control (CK, 0%), low intensity thinning (LIT, 25%), moderate intensity thinning (MIT, 45%), and high intensity thinning (HIT, 65%). The results showed that MIT significantly reduced the total P and organic P concentrations, whereas HIT significantlydecreased the concentrations of inorganic P in the rhizosphere soil. LIT and MIT increased soil acid phosphatase activity, available P, microbial biomass P, and easily available P (H₂O-Pi, NaHCO₃-Pi and NaHCO₃-Po) in rhizosphere soil, but decreased NaOH-Po. Thinning had no effect on the non-available P. Except for non-available P, all the P fractions in rhizosphere soil were higher than those in bulk soil, indicating a positive rhizosphere effect. Soil P content was closely correlated with soil moisture, pH, organic matter content and acid phosphatase activity. These results suggest that LIT and MIT improved soil P availability, which could be used asefficient management practices inP. massoniana plantations.

Dormancy mechanism of the seeds of a rare and endangered plant, Garcinia paucinervis.

ZHANG Jun-jie, WEI Xiao, CHAI Sheng-feng, WU Shao-hua, ZOU Rong, QIN Xin-mei, FU Rong

2018, 37(5):  1371-1381. 

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The process of seed germination ofGarcinia paucinervis, a rare and endangered plant, is extremely long. Clarifying its dormancy mechanism would provide a theoretical basis for germplasm conservation and sustainable utilization of this species. In this study, we examined the seed coat structure and water absorption characters, the germination of seeds removed part of seed coats and endosperm, the activities of crude extract of endosperm and embryos, seed germination after storage or stratification and under different temperature treatments as well as contents ofendogenous phytohormone during germination. The results showed that the seed coat ofG. paucinervis was mainly composed of parenchymatous layer without palisade layer. The cuticle of abaxial surface was thin. The seed coat had little inhibition to water absorption. With the extent of the elimination of seed coats and endosperm at the side of micropyle, seed germination gradually extended and its germination percentage was even reduced. The treatment of cutting off at the side of hilum had limited effects on seed germination. Endogenous inhibitors for seed germination would exist in endocarp, seed coats, endosperms, and embryos. The embryo rate of fresh seeds reached 86.12%, and showed no significant change after cold stratification. Cold stratificationdelayed seed germination but had no significant effect on germination percentage. Stratification at 4 ℃ was a better method for seed storage of G. paucinervis. Seed germination was sensitive to the changes of temperature. Seed dormancy was broken at 32 ℃, and then the germination was significantly accelerated. During the seed germination, ABA (abscisic acid) content decreased, whereas the ratios of GA (gibberellin) to IAA (indole-3-acetic acid) and GA to ABA significantly increased. The ratios of endogenous accelerants to inhibitors were gradually partial to acceleration. Our results indicated thatG. paucinervis seeds belong to physiological dormancy caused by existence of endogenous inhibitors and lack of germination accelerants. The dormancy characteristics of G. paucinervis seeds would facilitate the responses of seedlings to the seasonal changes of habitats, favor population survive under stress environment, and avoid seedling competition. The barrier of seed germination stage caused by vegetation destruction was one of the reasons for theendangerment ofG. paucinervis.

Responses of survival and growth of Caragana korshinskii seedlings to water addition and sand burial.

LUO Yong-hong, YAN Xing-Fu, SUN Yi, ZHANG Jin-feng

2018, 37(5):  1382-1390. 

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To understand the adaptive strategies of growth and survival ofCaragana korshinskii seedlings to sand burial and water availability in desert, an experiment was conducted in a desert shrubland in Lingwu Baijitan National Nature Reserve of Ningxia. The results showed that water addition facilitated the survival and growth of C. korshinskii seedlings. The final retention rate (FRR), shoot height (SH), leaf area per plant (LAPP) and total dry mass (TDM) of seedlings all significantly increased under water addition (P<0.05). Moreover, lateral root number (LRN), leaflet blade number (LBN), relative growth rate (RGR) and net assimilation rate (NAR) all increased to some extent. The survival and growth of C. korshinskii seedlings were inhibited by sand burial. The FRRs of seedlings with water addition were significantly higher than that without water addition by the end of the experiment (P<0.05). Basal stem diameter, LBN, LAPP, TDM, RGR of sand buried seedlings significantly decreased (P<0.05), but it was not the case for SH. The taproot length, LRN and NAR of seedlings declined in various degrees. The specific leaf area (SLA), specific root length (SRL) and specific shoot length (SSL) of sand buried seedlings were significantly higher than those without sand burial (P<0.05), while root shoot ratio (RSR) of the former was substantially lower than the latter (P<0.05). The SRL of sand buried seedlings significantly declined under water addition (P<0.05). No significant difference in RSR, SLA and SSL of seedlings, however, were detected between treatments of water addition and no water addition regardless of sand burial.

The effects of nitrogen application rate on photosynthetic characteristics of potato under intercropping.

ZHU Qi-lin, XIANG Rui, TANG Li, LONG Guang-qiang

2018, 37(5):  1391-1397. 

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Synergistic effects of shading and nitrogen (N) supply are the basis for establishing an efficient intercropping system of maize and potato. In this study, field experiments with monoculture and intercropping under four different N application levels (N0, 0 kg·hm^-2; N1, 62.5 kg·hm^-2; N2, 125 kg·hm^-2; N3, 187.5 kg·hm^-2) were conducted to assess the effects of N supply on the photosynthetic characteristics and yield of potato. The results showed that yield advantage of intercropping decreased with the increase of N application levels. Compared with that of monoculture, the potato yield of intercropping system was decreased by 2.66%-43.71%. There was a significant difference in P_n between the potato close to the maize side (I-M) and that close to itself side (I-P), with the value of P_n being greater in I-P than in I-M. In comparison to that under monoculture, the P_n of potato under intercropping system was decreased by 8.41%-31.09%, light compensation point decreased by 62.23%  and dark respiration rate decreased by 60.90% at the same N level. Excessive N application and intercropping with maize reduced photosynthetic rate, stomatal conductance and transpiration rate of potato, with the magnitude of decreases being enlarged with the increase of N application levels. Proper control of N application level, as N1 in this study, would be beneficial to maintaining high photosynthetic rate and alleviating the yield reduction of potato after intercropping with maize.

Effects of CO₂ enrichment on photosynthetic characteristics of greenhouse tomato during fruiting stage.

ZHANG Zhen-hua, SUN Sheng, LIU Yang, LI Jing, YUAN Hong-xia, ZHENG Jin-ying, XING Guo-ming

2018, 37(5):  1398-1402. 

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There is an acute shortage of CO₂ for winter and spring production of tomato in solar greenhouse. Here, we explored the effects of CO₂ enrichment on the photosynthetic pigment content, net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r),intercellular CO₂ concentration (C_i) and water use efficiency (WUE) of tomato cultivar ‘Xinghai 12’, to identify the suitable CO₂ concentration for tomato growth during fruiting stage and finally to provide theoretical basis for tomato production in solar greenhouse of north China. Four treatments with different CO₂ concentrations were applied in this study: (400±25) μmol·mol^-1 as control (without CO₂ enrichment, C₀), (600±25) μmol·mol^-1 (C₁), (800±25) μmol·mol^-1 (C₂), and (1000±25) μmol·mol^-1 (C₃). The results showed that CO₂ enrichment notably increased the photosynthetic pigment contents of tomato during fruiting stage. P_n, C_i and WUE were significantly improved, while G_s and T_r were significantly decreased. In addition, the C₃ treatment showed the strongest effects. It was therefore concluded that CO₂ enrichment of (1000±25) μmol·mol^-1 could effectively improve the photosynthetic system of leaves and increase the photosynthesis of greenhouse tomato plants during fruiting stage, and thus would facilitate the growth and development of tomato.

Differences in element concentrations between two lichensXanthoria mandschurica andCandelaria fibrosa from Taihang Mountains, Shanxi, China.

JIA Sheng-ju, ZHANG Chao, LUO Zhi-ding, ZHANG Shuo, MA Hui-chun, WANG Chuan-hua, LIU Hua-jie

2018, 37(5):  1403-1409. 

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Lichens have been widely used in biomonitoring of atmospheric element deposition. However, assessment of environmental input of elements could be interfered by the differences in element concentrations among lichens. Two foliose lichen species, epilithic Xanthoria mandschurica (XM) and epiphytic Candelaria fibrosa (CAF), were collected from three sites around the Changzhi Basin, Shanxi Province, China. The concentrations of 51 kinds of elements in lichens were measured by inductively coupled plasma mass spectrometry (ICP-MS). The purpose was to compare element concentrations between the two lichens and to address the possible ecological reasons. The results showed that the concentrations of 40 elements differed greatly between XM and CAF, among which 36 elements (Al, Ba, Be, Bi, Ca, Ce, Cs, Dy, Er, Eu, Fe, Gd, Ge, Ho, La, Li, Lu, Mn, Na, Nb, Nd, Ni, Pb, Pr, Sc, Si, Sm, Sr, Tb, Th, Ti, Tm, U, V, Y and Yb) showed higher concentrations in XM than those in CAF, possibly due to the higher dry deposition on XM, higher susceptibility of XM to geochemistry of local rocks, but higher canopy interception on CAF. The concentrations of four elements (K, P, S and Zn) were significantly higher in CAF, probably due to the canopy leaching that carried more nutrients to the epiphytic lichens. Little differences between lichens were found in the concentrations of other 11 elements (As, B, Cd, Co, Cu, Hg, Mg, Rb, Sb, Se, and Tl). Our results indicated that the variations of lichen species, geochemistry of substrate, and vegetation should be considered when we monitor atmospheric deposition using lichens.

Allelopathic effects of linolenic acid secreted by macroalgae onProrocentrum donghaiense.

DING Ning, WANG Ren-jun, Gao Pei-ke, CHEN Jia-lin, HAN Mei-ao-xue, WANG Jian-guo, LIU Xiu-xia, ZHENG Ning-ning

2018, 37(5):  1410-1416. 

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Prorocentrum donghaiense is one of the dominant species in harmful algal blooms. To understand the physiological and biochemical responses of P. donghaiense under stress of linolenic acid secreted by macroalgae, the growth, photosynthetic efficiency and the activities of antioxidant enzymes of algal cells were investigated. The results showed that low concentration(<200 μg·L^-1) of linolenic acid promoted the growth ofP. donghaiense. With the increase of linolenic acid concentration from 200 to 1000 μg·L^-1, the growth ofP. donghaiense was inhibited, with the inhibitory rate being up to 90% within 48 h at the concentration of 1000 μg·L^-1. At 200-1000 μg·L^-1 linolenic acid, the contents of photosynthetic pigment and the quantumefficiency (F_v/F_m) of P. donghaiense decreased. When the concentration of linolenic acid was 1000 μg·L^-1, the F_v/F_m ofP. donghaiense was 33.87% of that in the control. The activities of CAT, SOD and GPx, and the contents of GSH, GSSG, AsA and DHA in P. donghaiense cells first increased and then decreased with increasing concentrations of linolenic acid. The content of MDA increased sharply with the increase of linolenic acid concentration, indicating that the level of membrane lipid peroxidation intensified. Our results suggested that the growth of P. donghaiense was promoted at low concentration of linolenic acid but was inhibited at high concentration mainly due to the reduction of photosynthetic efficiency and the damage of membrane lipid peroxidation, which provides a scientific basis for the prevention and control of red tide caused by P. donghaiense.

Diversity and interspecific associations of ground Coleoptera in a broad-leaved Korean pine mixed forest.

NI Juan-ping, CHENG Sai-sai, GAO Mei-xiang, ZHANG Chao, LI Jing-ke

2018, 37(5):  1417-1425. 

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Biotic interaction is considered as an important driver for community assembly. However, it is still unclear for the interspecific associations of soil animal communities at different spatial scales. To reveal species composition, diversity and interspecific associations of ground Coleoptera adults at small scale, and to verify whether negative interspecific associations are common in congeneric/coordinal species pairs, an experiment was conducted in a 9 hm² permanent plot in a broad-leaved Korean pine mixed forest in Xiaoxing’an Mountains, Heilongjiang Province, China. Traps were used to capture ground Coleoptera beetles in August and October 2015. The results showed that: (1) A total of 1394 Coleoptera adults were collected in the two months, belonging to nine families and 58 species, in which Carabidae and Staphylinidae beetles were dominant in abundance. The abundance and species richness of Coleoptera in October were significantly lower than those in August. Moreover, the community diversity was significantly different between the two months. (2) The associations among individuals in Carabidae, Silphidae and Staphylinidae communities were significantly positive. The overlaps of spatial niche between two species from different families were narrow and the species associations between them were almost random. For beetles from the same family, most species pairs were random associations and few species pairs were significantly positive/negative associations. Our results demonstrated that the species composition and diversity were significantly different for ground Coleoptera adults in summer and autumn at small scale. Random associations were detected for almost all species pairs, whereas negative associations were not common for congeneric/coordinal species pairs.

Swimming behavior and metabolism responses of juvenile grass carp under the exposure of water-borne lead (Pb²⁺).

XU Meng, YUAN Xi, JING Jin-jie, HUANG Ying-ping, TU Zhi-ying, XU Tao

2018, 37(5):  1426-1431. 

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To investigate the effects of water-borne lead (Pb) on the swimming capability and metabolism of jevenile grass carp (Ctenopharyngodon idella), critical swimming speed (U_crit) and oxygen consumption rate (MO₂) were measured in water with four concentrations of Pb²⁺ (0, 0.75, 2.24, 3.73 mg·L^-1) at 20 ℃. The results showed that after exposure to 3.73 mg·L^-1 Pb²⁺, U_crit significantly decreased (P<0.05), being 91.22% of that of the control group. The swimming speed was linearly correlated withMO₂. With the increase of Pb²⁺ concentration, the difference of the maximum and minimum oxygen consumption rate increased first and then decreased. It was decreased by 17.68% after exposure to 3.73 mg·L^-1 Pb²⁺ compared to the control group. Exposure to low concentration of Pb²⁺ decreased the oxygen consumption efficiency, which might be the main reason for the decrease of the swimming capability of grass carp. Ourresults could be used to assess and control water Pb²⁺ risk in river and thus provide reference for environmental management.

Vulnerability to angling of two Cyprinidae species.

YANG Ya, FU Shi-jian, PENG Jiang-lan, ZENG Ling-qing

2018, 37(5):  1432-1437. 

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Fishes are constantly subjected to strong angling pressure in nature. There are substantial inter and intra specific differences in the vulnerability to angling in fishes. To investigate the differences of vulnerability to angling between two species of Cyprinidae and whether such difference might be related to their external morphology, we used juveniles of two widely cultured species in China, Carassius auratus gibelio and Cyprinus carpio, as the experimental model. We conducted a series of angling experiments including three treatments \[gibel carp Carassius auratus gibelio, common carp Cyprinus carpio and mixed group (Carassius auratus gibelio plus Cyprinus carpio)\] in the laboratory at (25±0.5) ℃. There were three replicates for each treatment with each replicate including 40 individuals. After 20 fish individuals had been angled for each replicate, the angling activity was ceased for this replicate. During the angling process, we recorded the total angling time for each replicate and angling rank number of the individual which was successfully angled, and then calculated average time spending on angling for each individual. The body length of C. carpio in the mixed treatment was larger than those in other two treatments. The condition factor of the common carp group was higher than those of other two treatments. The condition factor of both the angled common carp and gibel carp in the mixed group was larger than that of the un-angling common carp. We found no difference in total angling time among the three treatments. However, there was a significant difference in the average time spending on-angling among the three treatments, with the time spending on angling of the common carp being longer than that of the gibel carp in the mixed treatment. The proportion of angled gibel carp was higher than that of the angled common carp in the mixed group, and the average angling rank number of the gibel carp was smaller than that of the common carp. Our results suggested that the juvenile gibel carp had a higher vulnerability to angling than the juvenile common carp, which may be related to the differences in ecological habits and morphological traits.

Genetic diversity of Xenophysogobio boulengeriin the upper Yangtze River based on mtDNA control region sequences.

DONG Wei-wei, WANG Deng-qiang, TIAN Hui-wu, YU Li-xiong, SHEN Shao-yi, DUAN Xin-bin, CHEN Da-qing

2018, 37(5):  1438-1443. 

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Xenophysogobio boulengeri is an endemic fish in the upper reaches of the Yangtze River, which mainly distribute in the main river from Chongqing to Shuifu and Minjiang River, a tributary of the Yangtze River. The natural resource of this species declined in recent years. In this study, mtDNA control region sequences were used to analyze the population genetic structure of X. boulengeri. A total of 38 polymorphic sites were detected from data set of 839 bp, which defined 41 haplotypes from 178 individuals. The average haplotype diversity (H_d) and nucleotide diversity (P_i) were 0.817 and 0.002, respectively. Analysis of molecular variance (AMOVA) indicated that most of the genetic variation (96.05%) existed within populations. However, pairwise AMOVA showed that F_ST values among Jiangjin population and other populations, and among Shuifu population and other populations were greater than 7%, indicating moderate genetic divergence between these populations. The mismatch distribution and neutral test revealed that X. boulengeri population had experienced an expansion event in about 0.0173 Ma. The haplotype network structure and NJ phylogenetic tree demonstrated single genetic population. Our results suggest that X. boulengeri should be wholly conserved in situ.

Food chemical discrimination of the Turpan wonder gecko, Teratoscincus roborowskii.

HE Wen-feng, DUAN Zhen-yuan, SHI Lei

2018, 37(5):  1444-1449. 

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The cotton swab method was used to investigate the chemical identification mechanism of the Turpan wonder gecko (Teratoscincus roborowskii) with different types of food. We examined the lingual responses of the Turpan wonder gecko to different food stimuli. Tongue-flick rate (TFR) and tongue-flick attack score (TFAS) were used as indices. The Turpan wonder gecko showed different TFR and TFAS in response to different food stimuli and to different ripeness levels of caper fruit. The gecko showed the highest TFR value in response to ethanol stimulation. When presented with ripe caper fruit, the TFR was significantly higher than that with decayed and unripe fruits. The gecko showed significantly higher TFAS in response to ripe caper fruit and cologne than to distilled water. The TFAS for ripe caper fruit and alcohol was significantly higher than that for decayed caper fruit and distilled water. Our results support the hypothesis that vomeronasal organ of Turpan wonder gecko may play an important role in locating caper fruit and discriminating its ripeness. It verifies that some sit and wait predators have the ability of chemical discriminating and can identify the surrounding environment and prey information by tongue flick.

Spatiotemporal dynamics of heat index for spring maize at different developmental stages in Northeast China.

WANG Pei-juan, HUO Zhi-guo, CHEN Peng-shi

2018, 37(5):  1450-1458. 

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The spatiotemporal dynamics of heat index of spring maize at different developmental stages of the whole growing season were examined using datasets including daily average air temperature during the past 55 years (1961-2015) at 82 meteorological stations and thephenophases of spring maize from 1981 to 2013 at 50 agrometeorological stations. The results showed that the heat index of spring maize at different developmental stages exhibited significantly increasing trends. The rapidest increase of heat index occurred at the trefoil elongation stage, reaching up to 0.20 a^-1. The slowest increase was at the flowering milky ripening stage, with a value of 0.09 a^-1. The increasing trends of heat index in more than 50% meteorological stations passed the 0.1 significant test at all developmental stages except for the emergencetrefoil stage, and the percentages at both the trefoilelongation stage and the whole growth period reached up to 95%. The heat index of spring maize over the past 55 years displayed spatial distribution patterns, with higher values in the southwestern regions and lower values in the middle and northern regions for both whole growth period and different developmental stages. Moreover, the change rate of heat index for spring maize was faster in the northern regions than that in the southern regions. In terms of spatiotemporal dynamics, the area with smaller heat index during the whole growth period was gradually shrinking, whereas the area with larger heat index was gradually expanding over time.

The succession of potential vegetation in China and its sensitivity under climate change. 

DU Huai-yu, ZHAO Jun, SHI Yin-fang, CHE Yan-jun

2018, 37(5):  1459-1566. 

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The study of potential vegetation can reveal the impacts of climate on vegetation. It is the starting point for studying vegetation environmental classification and relationships, and the key point for studying global change and terrestrial ecosystems. It has guiding significance for the restoration and reconstruction of regional vegetation. Using the comprehensive sequential classification system (CSCS), we carried out a GIS simulation study on the spatial distribution of potential vegetation in China in the past 30 years (1986-2015) and the future three periods (2030s, 2050s and 2080s) under the RCP4.5 scenarios issued by IPCC5, and analyzed its sensibility to climate change. The results showed that: (1) Differences existed in the number of potential vegetation classes and the proportion of each class in different periods. The tropical-extrarid tropical desert (VIIA) was commonly absent in all periods. (2) With respect to the distribution area of potential vegetation, the area of cold-dry potential vegetation decreased whereas that of warmhumid potential vegetation increased, with extension, reduction and fluctuation being the three typical variation patterns. Moreover, the gravity centers of potential vegetation categories moved in different directions and at different distance. (3) The sensitivity of potential vegetation toclimate change differed, with different sensitivity regions showing an interphase distribution. The distribution areas of regions with the highest, higher, and lower  sensitivity accounted for 2.28%, 14.39% and 43.82% of the total national area, respectively.

Reconstruction of precipitation history in Taibai Mountain of Qinling Mountains based on tree-ring width and meteorological data in recent 160 years.

SU Kai, BAI Hong-ying, ZHANG Yang, HUANG Xiao-yue, QIN Jin

2018, 37(5):  1467-1475. 

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As the demarcation line between northern and southern China, Qinling Mountains is a hotspot of global climate change investigations. To reveal the precipitation dynamics in Taibai Mountain, the peak of Qinling Mountains in 1852-2012, we used the tree-ring width index of Larix chinensis in Taibai Mountain and the meteorological data in Baoji City and Mei County nearby, to reconstruct the series of total precipitation from previous November to current June in this area during the past 160 years based on the multiple regression method. The results showed that the reconstruction captured 39.6% (R²_adj =0.370, F=15.11,P<0.001) of the observed precipitation variance during the past 160 years. This result was validated by the documented climate disaster events as well as other tree-ring based precipitation reconstructions from the surrounding area. The reconstructed precipitation data were characterized by obvious wet/dry variation and periodic fluctuation. During the past 160 years, the wet periods were in 1875-1885, 1908-1923 and 1983-2002; the main drought periods were in 1857-1867, 1886-1907, 1923-1935 and 1954-1965. Four main cycles of precipitation existed in the study site with periods of 47-54, 17-22, 13 and 3-7 years. Moreover, we found a trend of strengthened major cycles but weakened minor cycles. The climate change in Taibai Mountain was also affected by larger-scale hydroclimate.

GeoDAbased spatial correlation analysis of landscape fragmentation in Bailongjiang Watershed of Gansu. 

ZHANG Jin-xi, GONG Jie, MA Xue-cheng, LIU Dong-qing

2018, 37(5):  1476-1483. 

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Landscape fragmentation is one of the research hotspots in landscape ecology. The spatial distribution of landscape fragmentation can provide scientific basis for landscape pattern optimization. In this study, we analyzed the spatial correlation of landscape fragmentation of Bailongjiang Watershed in Gansu in 2014 using landscape pattern index, grid analysis, and spatial autocorrelation methods based on GeoDA and ArcGIS. The results showed that the Moran’s Ivalues of the landscape pattern indices, i.e. edge density (ED), contagion index (CONTAG), and Shannon’s diversity index (SHDI) under different grid sizes ranged from 0.478-0.501, 0.276-0.374, 0.406-0.436, respectively, indicating a stronger spatial positive correlation and a landscape fragmentation with the agglomeration. Taking 10 km×10 km as the characteristic scale to examine the spatial agglomeration effect of landscape fragmentation, we found that the areas with higher landscape fragmentation degrees were mainly distributed in the middle of Wudu District, and that the areas with lower landscape fragmentation degrees were located in southern Wenxian. Moreover, the Moran’s I value of human activity intensity with ED was 0.170, and the Moran’s I value of human activity intensity with SHDI was 0.180, with positive spatial correlation. However, the Moran’s I value of human activity intensity with CONTAG was -0.095, with negative spatial correlation, highlighting the role of human activity intensity in driving the spatialdistribution characteristics of landscape fragmentation. Our results suggest that GeoDA can be applied to landscape ecological spatial analysis.

Analysis of spatial heterogeneity of groundwater depth in the Fukang oasis of Xinjiang based on the geostatistics.

LIU Hai-li, QI Shan-zhong, LIU Li-juan, LI Xiao-yu

2018, 37(5):  1484-1489. 

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Based on the observed data of groundwater depth of Fukang, Xinjiang, from 1993 to 2015, the semivariogram analysis and Kringing Spatial Interpolation Analysis based on the geostatistics were carried out to examine groundwater depth, using SPSS, GS+ and ArcGIS. The results showed that the groundwater depth of oasis in Fukang had a strong spatial correlation. The changes of groundwater level were mainly caused by structural factors, but were less influenced by random factors. The depth of groundwater gradually deepened from northwest to southeast. The groundwater depth presented a temporal decline in 1993-2015, with an obvious reduction occurring in areas with groundwater level less than 8 m, which mainly concentrated in the oasis being influenced by human activities. Therefore, the human activities have strong impacts on the depth of groundwater in this area.

Functional identification and spatiotemporal pattern analysis of production living ecological space in watershed scale: A case study of Bailongjiang Watershed in Gansu.

LIU Dong-qing, MA Xue-cheng, GONG Jie, LI Hong-ying

2018, 37(5):  1490-1497. 

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From a perspective of production-living-ecological (PLE) space, a functional space evaluation system of “production suitability, living suitability, and ecological importance” was constructed to understand the spatial pattern and evolution characteristics of the PLE function of Bailongjiang Watershed in southern Gansu from 1990 to 2014. The results showed that: (1) The strong production functional spaces (SPFS) were mainly distributed in Tanchang-Zhouqu-Wudu section along both bank areas of Bailongjiang, both bank areas of Baishuijiang, and the central and eastern parts of Wenxian, which were characterized with high population density. They were roughly bounded by the Tanchang-Zhouqu-Wudu section of Bailongjiang, with the eastern parts being the semi-productive functional space (S-PFS) and the western being the weak production functional space (WPFS). The areas of the SPFS and S-PFS were shrunk by 2434.54 and 294.07 km² respectively, while WPFS was expanded by 2728.62 km². The pattern was relatively fragmented during 1990-2002, with no obvious patch gathering areas. The strengthened areas were concentrated in the northwestern part of Diebu during 2002-2014, while the weakened areas were located in the middle and lower reaches of the watershed. (2) The spatial pattern of the living functional space was similar to that of the functional space for production. The area of the strong living functional space was increased by 119.32 km². With some fluctuations, the half living functional space was reduced by 508.23 km² and the weak living functional space was increased by 388.90 km². The changes of such pattern were mainly concentrated in the Tanchang-Zhouqu-Wudu section of both bank areas of Bailongjiang and the most area of Wenxian, being strengthened in 1990-2002, but weak in 2002-2014. (3) The ecological functional space was the strongest in the northwestern and southeastern parts, followed by middle part, and the weakest in west part of the watershed. The area of the strong ecological function space was increased by 3118.13 km² after a sharp drop. The area of the semi-ecological function space was decreased by 508.23 km². The area of the weak ecological function space was decreased by 1566.08 km² in fluctuation. During 1990-2002, the strengthened areas were mainly located in the northwest corner of the watershed, and the weakened zones were concentrated in the junctional zones between Zhouqu and Diebu and between Zhouqu and Wudu, southern Wudu, and southwestern Wenxian. During 2002-2014, the function was degenerated in the northwest corner of the watershed, and improved in the junctional area of Diebu and Zhouqu, and the southeastern Wudu. (4) The changes of land use pattern and ecosystem services caused by deforestation and the project of returning farmland to forest and grassland were the major causes for the changes of spatial pattern of PLE space. Our results provided reference for the identification of PLE functional space in similar mountainous watersheds.

The changes of landscape ecological pattern as affected by the expansion of urban construction land use in oasis: A case of Liangzhou District of Wuwei City, Gansu.

WEI Shi-mei, PAN Jing-hu, WEI Wei

2018, 37(5):  1498-1508. 

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The landscape ecological pattern of urban land-use expansion in Liangzhou District of Wuwei City, Gansu from 1985 to 2015 was analyzed by circle analysis, landscape index andurban expansion intensity index, with land-use status data in 1985, 1995, 2005 and 2015 in ArcGIS 10.2 and Fragstats 4.2. The whole study area was divided into four directions, i.e., northeast (NE), southeast (SE), southwest (SW) and northwest (NW). Each direction was divided into 23 concentric circles of 3 km incrementing radius to analyze the spatiotemporal evolution characteristics of urban spatial expansion and the land use and landscape pattern changes during this process. The results showed that the urban construction land of Liangzhou District was mainly distributed within 3 km of economic center. The area of urban construction land continuously increased from 1985 to 2015. The east and southeast were the main directions of urban expansion. The shape of landscape patch for urban construction land was simple. With the disturbance of human activities, the number of patches was increasing and the fragmentation was intensified. The aggregation of patches was higher when they were closer to the urban economic center.

Roof greening in urban area of Beijing during 2005-2015: Development trends, distribution patterns and policy promotion.

LIU Bo-jie, WANG Shi-hao, LU Fei, WANG Xue-yan, Marina Bergen Jensen, ZHENG Shan-wen, LIU Li, SHAN Ming-yun, ZHAO Ke-xian

2018, 37(5):  1509-1517. 

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Based on the data of roof greening in urban areas of Beijing and relevant policy documents released from 2005 to 2015, the situation of roof greening in urban Beijing was clarified. The distributions of roof greening in each urban district of Beijing as well as building types were examined. Moreover, the proportion of roof greening in urban greening coverage and its annual dynamics were investigated. The promotion effect of documented policy on the development of roof greening was analyzed. The results showed that from 2005 to 2015 the total installation area of green roof in Beijing urban areas was 1.23×10⁶ m², with an annual average of 1.12×10⁵ m². Up to 2015, the sequence of accumulated area of newly constructed roof greening for all urban districts was Chaoyang > Dongcheng > Haidian > Xicheng > Fengtai > Shijingshan. Regarding the distribution of roof greening on different building types, public buildings for governmental agencies, colleges and schools, institutes, and hospitals were the main components, accounting for62.0%-80.4% of the annual total expansion area from 2011 to 2015. During this period, theproportion of roof greening in urban greening coverage increased over time, which was larger in capital functional core zone than in capital functional extension zone. However, up to 2015, roof greening took up only 0.30% of greening coverage in Beijing urban areas, indicating great potential in the future expansion of urban roof greening in Beijing. Strengthening incentive measures and promulgation of compulsory measures were suggested to promote the development of roof greening in urban Beijing.

Heat island effect and its relationship with land use in Chengdu City.

CUI Lin-lin, LI Guo-sheng, JI Dong-jian

2018, 37(5):  1518-1526. 

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Urban heat island effect, a typical feature of urban climate, plays an important role in urban planning and people’s production and life. Based on the Landsat 8 TIRS data, we adopted the split window algorithm to estimate the surface temperature of the central urban area of Chengdu City at four different time points, and then analyzed the spatial and temporal dynamics of heat island effect and its influence factors. The algorithm achieved an accuracy of 1.6 K without synchronous meteorological observation data to adjust the atmospheric transmissivity. There was an obvious heat island effect in the central area of Chengdu, with the area of such lands accounting for about 30% of the total area. The spatial variation of surface temperature in spring and summer was obviously larger than that in winter. The heat island effect out of the third-ring was more obvious than that of the area within it. There was a high temperature area between Wuhou District and Shuangliu District. The negative correlation between normalized difference vegetation index(NDVI) and land surface temperature (LST) was the most obvious in summer, suggesting that urban heat island effect could be alleviated by planting green plants. The correlation between LST and modified normalized difference water index (MNDWI) in summer was lower than that in spring and winter, indicating that water may have limited effect in alleviating urban heat island effect in summer. The positive correlation between normalized difference build-up index (NDBI) and LST at four time points showed that human activities may be an important cause of urban heat island effect, and thus NDBI is an effective index for urban heat island effect.

Evolution of coastal wetlands under the influence of sea reclamation in Bohai Rim during 1985-2015.

WEI Fan, HAN Guang-xuan, ZHANG Jin-ping, LI Yun-zhao, ZHAO Jian-min

2018, 37(5):  1527-1537. 

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Coastal wetlands are unique ecosystems formed by amphibious mutual effects. Human activities severely affect wetland evolution. Since the 1950s, China has experienced a massive sea reclamation, which resulted in extremely rapid degradation and loss of coastal wetlands. Studies on the evolution of coastal wetlands and its correlation with human activities are of great significance for managing and protecting wetland resources. The spatialtemporal evolution characteristics of coastal wetlands under the influence of sea reclamation were examined based on the TMremote sensing images in four years (1985, 1995, 2005, and 2015). The transfer matrix of land use and approach of landscape pattern analysis were used in this study. These data were analyzed by 3S technology and the software of eCognition 9.0, and FRAGSTATS 4.2. The results showed that the hotspots of changes in coastal wetlands were Yellow River Delta, Laizhou Bay, Bohai Bay and Liaohe River Delta. The natural wetland area decreased by 45.37%, whereas the artificial wetlands expanded by 57.23% in the past 30 years. Aquatic farm and salt field increased most significantly, which were mainly changed from moor and intertidal zone. Natural wetlands were converted into artificial ones, and artificial wetlands were converted into non-wetlands. Natural wetlands became more artificial. The landscape pattern tended to be fragmented and equilibrated. Meanwhile, the landscape heterogeneity decreased due to the strong human disturbance. Sea reclamation occupied a large area of natural wetlands such as moor and intertidal zone, with an increment of 1606.79 km² in the past 30 years. The main land use types were aquatic farm and construction land. The national policy and economic factors drastically affected the evolution of coastal wetlands. Human activities, including farmland reclamation, urban construction, and tidal flats exploitation were the main driving forces for the evolution of the Bohai Rim coastal wetlands.

Pollution characteristics and sources of cadmium in soils of the karst area in South China.

LUO Hui, LIU Xiu-ming, WANG Shi-jie, LIU Fang, LI Ying

2018, 37(5):  1538-1544. 

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Heavy metal pollution in soils has become an extensive concern of the ecological environment problems in China. Understanding of distribution and source of Cd pollution in soil in karst areas could provide a basis for the assessment and management of soil environmental quality. Here, we collected the soil Cd related research literature, which covers 206 cities (counties) from eight provinces of southern China. We used the single factor pollution index method to evaluate Cd pollution levels and used the Pearson’s correlation analysis to reveal the linkage between the Cd concentrations and the area of exposed carbonate rock, and discussed the source of pollution. The results showed that: (1) The soil in karst areas of southern China had high Cd concentration, with a geometric mean value of 0.36 mg·kg^-1, which was higher than the national average, the world average and the regional average of non-karst areas. (2) The pollution degree in different provinces was in order of Guangxi > Hunan > Sichuan > Guangdong > Guizhou > Chongqing > Yunnan > Hubei. (3) Anthropogenic activities including mining, urbanization, and agricultural activities were not the main reasons for high soil Cd concentrations in karst areas of southern China. The high background value of Cd in carbonate rocks and the relative enrichment of Cd in weathered carbonate rocks were the main natural factors for high Cd concentrations in karst areas of southern China.

Pollution characteristics of mercury in particulate matters around a coal-fired power plant in Guizhou Province in spring.

QIU Hao, LI Jin-juan, GUO Xing-qiang, XU Yi-yuan, CAI Bao-de

2018, 37(5):  1545-1549. 

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To analyze the pollution characteristics of mercury in particulate matters with different sizes, TSP, PM₁₀, and PM_2.5 samples were collected around a coal-fired power plant in Guizhou Province in spring of 2017. Concentrations of mercury in these samples were measured by a cold atomic fluorescence mercury analyzer. The results showed that the volume concentrations of TSP, PM₁₀, and PM_2.5 were 83.7-162, 65.2-130 and 43.6-87.1 μg·m^-3, which exceeded the limit level by 0, 5.63%, and 25.7%, respectively. he volume concentrations of mercury (Cv_(Hg)) in TSP, PM₁₀, and PM_2.5 were 68.5-102, 58.9-84.9, and 51.4-80.9 pg·m^-3 and the mass concentrations of mercury (Cm_(Hg)) were 571-810, 627-913, and 693-1083 ng·g^-1, respectively. Spatially, the concentrations of mercury in the samples collected at upwind direction were much lower than that at the downwind direction. Mercury concentration in the samples at dominant wind direction was generally higher than that at the non-dominant wind direction. Therefore, the local wind direction and sampling site influenced mercury concentration. The ratios of mercury in PM_2.5 to that in PM₁₀ were 67.5%-95.2% and the ratio between PM₁₀ to TSP were 83.1%-98.8%, which were higher than those of particle mass concentrations, indicating that mercury was mainly enriched in fine particles.

The concentrations, distribution, and interrelation of mercury and selenium in human body in Wanshan mercury mining area.

TU Rui, CHEN Min, DING Li, CHANG Chuan-yu, WANG Hui-qun, LI Ping

2018, 37(5):  1550-1555. 

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Selenium (Se) was released into the surrounding environment as an associated element of mercury (Hg). When examining the Hg pollution in Wanshan Hg mining area, Guizhou Province, we should consider the presence of Se. To assess the Hg and Se levels, distribution, and their interactions in the residents in Wanshan mercury mining area, a total of 30 people were randomly selected in this study. The blood, urine, and hair samples were collected for determination of the concentrations of total mercury (THg), methylmercury (MeHg) and Se. The results showed that THg in 31% of blood samples and 93% of hair samples from the studied population exceeded the limits of 5.8 μg·L^-1 and 1 mg·kg^-1 recommended by United States Environmental Protection Agency (USEPA), respectively. Urine Hg in 24% of the studied population exceeded the limit of 5 μg·L^-1 recommended by the United Nations Industrial Development Organization (UNIDO). The results indicated that the studied population was exposed to both MeHg and inorganic Hg. Hair Se contents in 90% of the study population were at the medium and high levels. Sufficient Se in the human body may inhibit the accumulation of Hg and thusreduce the health risks of Hg exposure in local residents.

Biogeochemical cycle of mercury in rice paddy ecosystem: A critical review. 

MENG Qi-yi, QIAN Xiao-li, CHEN miao, ZHAO lei, FENG Xin-bin, MENG Bo

2018, 37(5):  1556-1573. 

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Mercury (Hg), a highly toxic heavy metal pollutant, has been recognized as a pollutant with priority control by China, the United Nations Environment Program (UNEP), World Health Organization (WHO), European Union (EU) and the United States Environmental Protection Agency (USEPA). The toxicity of Hg depends on its chemical speciation, in which methylmercury (MeHg) is the most toxic compound. Inorganic mercury (IHg) can be transformed into MeHg in certain condition, and then accumulated and biomagnified in the food chain, posing a potential threat to human health. Paddy soil is an important site for MeHgproduction. Rice field is an important source of MeHg in terrestrial ecosystems. Numerous studies have reported the MeHg contaminated rice worldwide. Recent studies have confirmed that rice consumption is the major pathway of MeHg exposure in Hg mining area and in certain Hg contaminated areas. Biogeochemical processes of Hg in paddy field ecosystem have been well understood in the past decades. This review systematically summarized the biogeochemical processes of Hg in paddy field ecosystems, including: (1) status of Hg pollution in paddy field ecosystem; (2) Hg methylation in rice paddy and its primary controlling factors; (3) the mechanism of Hg accumulation in rice plant; (4) health risks of human exposure to MeHg through rice intake; (5) management strategies to reduce MeHg in rice. With those results gathered, we summarized the shortcomings of the previous studies and prospected the future researches as well.

Research progress of element and isotope identification technology for the origin and quality of tea.

TONG Cheng-ying, HE Shou-yang, DING Hu

2018, 37(5):  1574-1583. 

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Tea is one of the landmark agricultural products in China, which has profound cultural background and regional resource advantages. The origin tracing and quality identification of tea are of great significance. Here, we systematically reviewed the research progress of geochemical methods such as multi-elements, rare earth elements and stable isotopes in the origin tracing and quality identification of tea, and analyzed the advantages and disadvantages of these methods. The future research should clarify the migration and transformation of elements and isotopes in “soil-tea fresh leaf-made tea”, and identify the roles of various factors such as processing methods, human activities and pollutants in “planting-growing-processing” in affecting the originality information and quality of tea. At the same time, such progresses should be combined with the traditional identification technology and large data method. It is necessary to comprehensively compare various statistical models to establish and improve the elementisotope fingerprints of the main tea producing areas and famous tea products. All these efforts have far-reaching influences on improving tea plantation and ecological environment, selecting superior tea varieties, protecting the advantages of famous tea products, setting up correct product awareness, and establishing a good trade order.

Research progress on limb autotomy and regeneration of crabs.

ZHANG Cong, HUANG Gen-yong, XU Min-jie, PANG Yang-yang, CHENG Yong-xu, YANG Xiao-zhen

2018, 37(5):  1584-1588. 

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Limb autotomy and regeneration of crab, a self-protection mechanism, is an effective behavioral strategy for facing with extreme conditions such as predators, competitors, and harsh environments. The most common autotomy type is single-limb autotomy. After being autotomized, the crab usually recovers through the regeneration and molting cycle. There is a high rate of limb autotomy of medium-sized crabs (4-6 g) in the growing stage, which has no variation between genders. The single-limb autotomy usually occurs in one side. The probability of autotomy posterior limb is obviously higher than that of the front one. Moreover, the limb autotomy showed interspecific and intraspecific differences, and are dependent on habitat conditions. Limb autotomy affects the growth, survival and feeding habits of crabs. In this review, we summarized the main animal species and parts with the phenomenon of autotomy and regeneration. With the crab as an example, we illustrated the patterns and reasons of limb autotomy, and the influences of limb autotomy on regrowth and regeneration. This review also proposed some prospects for furtherexploration of the patterns and mechanisms of autotomy and regeneration.

Hyperspectral pretreatment methods on leaf SPAD value prediction in winter wheat.

WU Gai-hong, FENG Mei-chen, YANG Wu-de, WANG Chao, SUN Hui, JIA Xue-qin, ZHANG Song, QIAO Xing-xing

2018, 37(5):  1589-1594. 

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To select the appropriate pre-treatment method and thus to improve the predictiveaccuracy of leaf SPAD value, the leaf spectra were processed with normalized correction (NC), multiple scatter correction (MSC), baseline correction (BC) and their combinations. Successive projection algorithm (SPA) and stepwise multiple linear regression (SMLR) were used for establishing the predictive model and determining the optimal spectral pre-treatments. The results showed that increased N application rate could improve the SPAD values. The second top leaf and the first top leaf had the highest value of near-infrared spectral reflectance at early growth stage and after the flowering stage, respectively. The pre-treatment of NC method had the highest-predictive model performance with R²=0.770 andRMSE=1.483, whereas  the MSC pre-treatment resulted in poorer model performance. The validated model with the pre-treatment of BC+NC combination had the best prediction (R²=0.755, RMSE=1.540). Pre-treatment obviously increased the prediction; however, improper pre-treatment would reduce the prediction ability. Our results indicated the single pre-treatments or the combinations did not always improve the model performance.

Isolation and screening of a plant pathogen-antagonistic bacterium and antagonisticsubstance.

CHEN Zhi-jie, XIE Jiang-hui, CHEN Yu-feng, ZHOU Deng-bo, GAO Zhu-fen, QI Chun-lin

2018, 37(5):  1595-1604. 

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In this study, the antagonistic bacteria against plant diseases were isolated and screened from soybean paste. The antagonistic substances were extracted from fermentation broth. After that, we examined the inhibition mechanism and basic properties of antagonistic substances. Bacteria were isolated by dilution-plate method. Antagonistic bacteria were screened through plate-confrontation method. The strains were identified by morphological observation, physiological and biochemical experiments, and phylogenetic tree based on the strain’s 16S rDNAsequences. The antagonistic substance of fermentation broth was extracted by ammonium sulfate fractional precipitation. The protein content of the crude extracts was measured by Bradford method. The inhibition effects of antagonistic substances were observed by scanning electron microscope. The antimicrobial spectrum of antagonistic substances and stability of antimicrobial activity of antagonistic substances were determined through agar bore diffusion method. Within the 18 bacterial strains  isolated from soybean paste, the best antagonistic bacterium strain was screened and named as 4-z-3, which was identified as Bacillus siamensis. Its inhibitory rate to pathogen was 62.78%, and the inhibitory rate of fermentation broth of 4-z-3 to pathogen was 53%. The crude extracts of 4-z-3 had the highest inhibition rate at 60.8% when the saturation of ammonium sulfate was 20%-30%. At the optimum saturation of ammonium sulfate, the protein content of the crude extracts was 3.45%. The antagonistic substances had good antagonistic effect against various pathogens. The hyphae of the pathogenic fungi treated with crude extracts of 4-z-3 were destroyed, which caused great absence of cell shape and integrity. In terms of stability, crude extract was insensitive to heat, with the inhibition activity significantly decreased only at 90 and 100 ℃. The crude extract was insensitive to acids and alkalis, with 81.6% inhibition activities of crude extracts being remained at pH 4. The crude extract was insensitive to protease, and theinhibition activity of crude extracts only decreased by 19.6% when the inhibition rate was the lowest. The crude extract was not sensitive to ultraviolet light, with 92.5% inhibition activities of crude extracts being remained after irradiated by ultraviolet light for 12 h. Our results demonstrated that strain 4-z-3 would be a promising agricultural biocontrol bacterium. Antagonistic substances of 4-z-3 can effectively control various plant diseases. Moreover, the antibacterial activity of antagonistic substances is stable.