Table of Content

10 May 2017, Volume 36 Issue 5

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Impacts of vegetation establishment duration on soil organic carbon accumulation in ChongmingDongtan, China.

ZHANG Qian1, JIANG Jun-yan1,2, LI Xiu-zhen1*, ZHANG Yun-qing1

2017, 36(5):  1173-1179. 

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Estuarine tidal wetlands are highly influenced by land and sea. Some environmental factors change quickly with the vegetation establishment duration and have an important influence on the soil carbon sequestration. Based on field survey and remotely sensed data, we investigated the relationship between soil organic carbon (SOC) content, its accumulation rate and vegetation establishment duration in ChongmingDongtan, the Yangtze Estuary. With the increase of vegetation establishment duration, SOC content increased significantly. SOC content in the vegetation establishment duration of 14 years was about 1.3 times that of 1 year. Soil organic carbon accumulation rate decreased with time and was stabilized at 11 g·m^-2·a^-1 10 years later. SOC content of tidal wetland from Yangtze Estuary was close to those of other coastal wetlands in China, but the accumulation rate was far lower than that on the east coast of the United States, probably due to human disturbance such as overgrazing and harvest. Therefore, there is a great potential for carbon sequestration enhancement by conservation and restoration of coastal wetlands.

Soil organic carbon and its components under different plant communities along a water table gradient in the Poyang Lake wetland.

JIN Qi1, WU Qin1, ZHONG Xin-zi1, HU Jia1, HU Qi-wu1,2*

2017, 36(5):  1180-1187. 

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Soil organic carbon is composed of active, slow and passive fractions. Separating different organic carbon components could help to improve modeling dynamic of soil organic carbon pool and its feedback to global climate change. Poyang Lake is the largest freshwater lake in China. It is a typical subtropical shallow water lake characterized by drastic annual and interannual water level fluctuation. In recent years, climate change and the operation of the Three Gorges Dam have largely altered the hydrological regime of Poyang Lake, resulting in reduction of summer flooding and extension of winter dry season. As a result, the submerged plant communities shrank, whereas the emergent plant communities expanded. In this study, soil samples at 0-15 cm and 15-30 cm depths under seven dominant plant communities were collected along a water table gradient in a typical Poyang Lake wetland. Subsequently, contents of total soil organic carbon (SOC), heavy fraction organic carbon (HFOC), light fraction organic carbon (LFOC), microbial biomass carbon (MBC) and dissolved organic carbon (DOC) were measured. The objectives of this study were to clarify the characteristics of various soil organic carbon components and their affecting factors, and explore the potential impact of community succession on soil organic carbon and its components. Our results showed that the ranges of SOC, HFOC, LFOC, MBC and DOC were 4.92-48.14  mg·g^-1, 4.66-41.42 mg·g^-1, 0.46-6.52 mg·g^-1, 124.22-419.23  mg·kg^-1 and 33.17-153.63 mg·kg^-1, respectively. The organic carbon components varied significantly with plant communities and soil layers. The content of each soil organic carbon component under various plant communities decreased from the top soil to the deeper profile. Soil layers and communities types as well as their interaction all significantly affected the spatial pattern of various organic carbon components. The ratios of HFOC/SOC, LFOC/SOC, MBC/SOC and DOC/SOC were 92.9%, 7.1%, 1.44% and 0.74%, respectively. The distribution patterns of LFOC, MBC and DOC were not spatially consistent, suggesting that these active organic carbon components were not controlled by the same environmental factors. In the short term, the shrink of submerged plant communities and the expansion of emergent plant communities in Poyang Lake wetlands could increase soil organic stock; however, the stability of carbon pool decreased.

Changes of soil physicochemical properties during rocky desertification control in karst mountaincanyon region.

CUI Gao-yang1,4, RONG Li2*, LI Xiang-Dong3, TAN Di1,4

2017, 36(5):  1188-1197. 

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Physical and chemical properties of soils at five stages in the process of karst rocky desertification in 2006-2013 were investigated with chronosequence method in karst plateaucanyon region in Guizhou. This work aims to study the spatial and temporal evolution of soil physicochemical properties, and provide a scientific basis for further control of rocky desertification. The results showed that controlling of karst rocky desertification had generally improved the soil physicochemical properties, such as capillary porosity, total porosity, field moisture capacity, capillary moisture capacity, saturated permeability, pH, total potassium content, available potassium content and total phosphorous content. As time went on, change trends of soil physicochemical properties were stable or fluctuant at early stage and became better subsequently, which appeared as a non-linear pattern. These changes illustrated that there was a lag-effect between the improvements of soil physicochemical properties and plant community structure and microclimate, and they were probably affected by the heavy drought in southwest China in 2009-2010. At the spatial scale, soil physicochemical properties in stage of no rocky desertification had the best performance, and there were no significant differences among the other four stages of rocky desertification. This study demonstrated that the differences of soil physicochemical properties among different stages of rocky desertification became indistinct after long-term control, while “space instead of time” method was inapplicable in the current work. The poor performance of soil properties in stages of potential and slight rock desertification suggested that more attention should be paid to these two stages in the future practice.

Shortterm effect of understory removal on the dynamics of soil respiration, microbial biomass, and root growth in a Fraxinus mandschurica Rupr. plantation.

XIA Xiu-xue, GAO Guo-qiang, WANG Dong-nan, XIAO Li-juan, GU Jia-cun1*

2017, 36(5):  1198-1207. 

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Understory removal was implemented in a Fraxinus mandschurica Rupr. plantation in order to investigate its effect on soil respiration, soil temperature and water content at 5 cm depth, fine root production, and soil microbial biomass carbon (MBC) and nitrogen (MBN) during the growing season in 2015. The results showed that average soil respiration rate increased by 11.87% after understory removal, particularly from the late August to the early September. The soil temperature and water content also increased. The temperature sensitivity of soil respiration (i.e., Q₁₀ value) showed an increment of 15.26% in understory removal treatment. Repeated measures ANOVA indicated that the effects of understory removal on soil variables were not significant, whereas sampling date did. Additionally, there were interaction effects between understory removal and sampling date on the soil respiration rate, temperature and water content. Fine root production of F. mandschurica increased (P>0.05), whereas that of other species (mainly shrubs) was markedly decreased after understory removal. Understory removal decreased MBC by 12.68% and 21.16%, and MBN 16.76% and 25.48% at the depth of 0-10 cm and 10-20 cm respectively, despite all of which were not statistically significant. In both the control and treatment plots, soil respiration rates was only exponentially correlated with soil temperature (P<0.01). Overall, the higher soil temperature and greater fine root production, as well as the alternation of fine root population may contribute to the seasonal increase in soil respiration rate following understory removal. Our findings yield some insights into the interrelationship between understory removal application and soil respiration in temperate forests.

Leaf stoichiometric characteristics of typical desert plants and their relationships to soil environmental factors in the northern margin of the Tarin Basin.

SUN Li1,2, GONG Lu1,2*, ZHU Mei-ling1,2, XIE Li-na1,2, LI Hong-lin1,2, LUO Yan1,2

2017, 36(5):  1208-1214. 

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Studies on the relationship between desert plant leaf stoichiometry and soil environmental factors are of great importance to clarify the mechanism of adaptation and feedback to the soil environment in the process of plant growth. The leaf stoichiometric characteristics of five desert plants (Populus euphratica, Tamarix ramosissma,  Alhagi sparsifolia,  Karelinia caspia and Phragmites australis) were analyzed and their relationships to soil environmental factors were studied by redundancy analysis (RDA). The results showed that the average contents of carbon (C), nitrogen (N) and phosphorus (P) were 451.65, 16.98 and 1.08 mg·g^-1 respectively, each lower than the global average level of plants, and the plant growth was more likely to be limited by both N and P. The leaf stoichiometric characteristics differed significantly among the five species, in which P. euphratica had the lowest C content, A. sparsifolia had the highest N content and N∶P ratio, and Ph. australis and K. caspia had the highest P content. Correlation analysis showed that there was extremely significant positive correlation between N content and P content, while there was no significant correlation between C content and N, P contents. According to RDA results, soil moisture content, salinity and pH value served as a good explanation for the difference of leaf stoichiometric characteristics, among which soil moisture was the major factor affecting leaf stoichiometric characteristics, while the effects of soil total N, total P, total dissolved solids, and organic C contents on leaf stoichiometric characteristics were relatively insignificant.

The responses of leaf water potential of a typical psammophyte Spinifex littoreus to wind erosion, sand burial and sand flow abrasion in coastal area of Pingtan Islan#br# d. 

YANG Xian-ji1,2, DU Jian-hui1,2*, QIN Jing1,2, CHEN Zhi-hua1,2, YANG Lin1,2, LIN Ping1,2

2017, 36(5):  1215-1223. 

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Typhoon, as one of the most common natural disasters in coastal areas, can cause severe threats to the growth of psammophytes by wind erosion, sand burial and sand abrasion. Variations of leaf water potential of the psammophyte Spinifex littoreus under the threats of wind erosion, sand burial and sand abrasion were investigated and corresponding soil water potential, meteorological elements were measured simultaneously after occurrence of typhoon on Pingtan Island, Fujian Province. The results showed that S. littoreus suffered an earlier and more intense water stress after the wind erosion, and its leaf water potential significantly decreased compared with plants without suffering wind erosion (P<0.05), and there was no obvious correlation between leaf water potential and atmospheric water potential (P>0.05). However, the leaf water potential of plants without suffering wind erosion was positively correlated with the atmospheric water potential and relative humidity (P<0.01), while negatively correlated with the temperature (P<0.01). The leaf water potential of S. littoreus that suffered sand burial was higher than that of the ones without sand burial from 10:00 to 16:00, with small amplitude of variations, and lagging response to the meteorological factors. Besides, the leaf water potential of S. littoreus was mainly affected by soil water potential when soil moisture was insufficient, whereas the meteorological factors would become its major influencing factors if soil moisture was sufficient. The leaf water potential of the plants without sand burial was positively correlated with atmospheric water potential and relative humidity (P<0.05), but negatively with the air temperature (P<0.05). With the increasing depth of sand burial, the leaf water potential increase firstly and then decreased, indicating that moderate sand burial would help the plants maintain higher water potential for their adaptation to environmental stresses. Furthermore, the leaf water potential of the abrasive leaves was higher than that of the undamaged ones during most of time, correlating with the atmospheric water potential to an insignificant extent (P>0.05). Nevertheless, the correlations between the leaf water potential of undamaged leaves and atmospheric water potential, relative humidity and temperature were consistent with those of the plants without sand burial.

Influence of pulsed electrical fields on generation of negative air ions by plants and its mechanism.

WU Ren-ye1,2, ZHENG Jin-gui2*, WENG Hai-yong2, ZHANG Wan-chao3, DENG Chuan-yuan3, YE Da-peng4, WANG Qing-shui2, SUN Yuan-fen2

2017, 36(5):  1224-1233. 

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In natural condition, the capacity of plants to generate negative air ions (NAIs) is very weak. However, a pulsed electrical field can result in a substantial improvement of the capacity in NAI generation. To investigate the mechanism underlying NAI generation by plant following the pulsed electrical field stimulation, the present study examined the generation of NAI in Clivia miniata, Echinocactus grusonii, and Chlorophytum comosum among the ten tested plant species (Guzmania lingulata etc) in the  presence of a pulsed electrical field, which possess strong capacity of generating NAI under natural conditions. The results showed that various parameters of pulsed electrical field affected the generation of NAI in the plants. Each plant had its own optimal pulsed electrical field with combination of parameters for the efficient generation of NAI: C. miniata with A₄B₄C₄ (A₄,U = 2.0×10⁴ V; B₄, T=2.0 s; C₄, τ=90 ms), E. grusonii with A₄B₁C₃ (A₄, U=2.0×10⁴ V; B₁, T=0.5 s; C₃, τ = 65 ms) and C. comosum with A₃B₁C₂ (A₃,U=1.5×10⁴ V; B₁, T=0.5 s; C₂, τ=35 ms). With the application of a pulsed electrical field to a plant, the higher voltage in the plant, the greater capacity of NAI generation was (P<0.05). With the enhancement of light intensity, the ability of the plant to generate NAI significantly increased (P<0.05). A plant’s capacity of NAI generation was closely related to the characteristics of leaf stomata. Greater degree of stomatal opening and stomatal density facilitated a stronger ability of the plant to generate NAI (P<0.05). In sum, these results suggested that NAI generation by plants was a complex physiological process that was influenced by several factors, including the presence of pulsed electrical field stimulation, light intensity, and plant characteristics.

Ecophysiological responses of turftype white clover (Trifolium repens) to elevated O₃ concentration.

PING Qin1,2, XU Sheng1，3*, LI Jing4, HE Xing-yuan1, CHEN Wei1, HUANG Yan-qing1

2017, 36(5):  1234-1242. 

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With the development of urbanization and industrialization, the rising concentration of troposphere ozone threatens human health and plant growth, which arouses wide public concern. An experiment was conducted to examine the ecophysiological responses of white clovers (Trifolium repens), which were exposed to different doses of ozone (ambient air, 80 and 160 nmol·mol^-1) in opentop chambers (OTCs). The results showed that (1) O₃ induced typical visible symptoms on white clover’s leaves, and increased the producing rate of O₂^-_·, H₂O₂ content, MDA content in the leaves, improved the activity of antioxidant enzymes, while decreased the content of photosynthetic pigments. (2) Elevated O₃ inhibited white clover’s growth, especially in root. Compared with the control, 80 and 160 nmol·mol^-1 O₃ decreased white clover’s total biomass by 45.80% and 53.12%, and the root dry mass by 61.86% and 67.36%, respectively. (3) 80 nmol·mol^-1 O₃ promoted the synthesis of total phenols and improved the antioxidant level, but it couldn’t ameliorate the decrease of biomass. However, 160 nmol·mol^-1 O₃ decreased the antioxidant capacity of white clover. Meanwhile, it not only resulted in a great loss of total biomass but also caused fatal or serious injuries for white clover. White clovers were sensitive to O₃, so the elevated O₃ may have bad effect on white clover’s growth and turf grass quality.

The impacts of climate change on the potential distribution of Haloxylon ammodendron.

MA Song-mei1*, WEI Bo1, LI Xiao-chen1, LUO Chong2, SUN Fang-fang2

2017, 36(5):  1243-1250. 

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Understanding the impacts of climate change on the distribution of plant species is crucial for the conservation of biodiversity. On the basis of distribution data and environmental variables, we used a maximum entropy model (MAXENT) and GIS tools to estimate the potential distribution range, spatial pattern, and change of Haloxylon ammodendron under reference climate and in 2050 and 2070 (according to the RCP2.6 and RCP6.0 scenarios of IPCC). We obtained the following results: (1) The potential distributions under the reference climate were mainly concentrated in the arid areas of northwest China, especially in Xinjiang: Gurbantunggut Desert, the northern margin and western tip of the Tarim Basin, Alax Left Banner and eastern Alax of Inner Mongolia; Hexi Corridor of Gansu Province; western and northern Ningxia; eastern and southern Qaidam Basin in Qinghai Province. Furthermore, small fragmented patches of suitable area were identified in mngovǐ and Dornogovǐ of Mongolia. (2) Annual precipitation, mean temperature of the wettest quarter, precipitation of the driest quarter and precipitation seasonality (coefficient of variation) mainly limited the distributions of H. ammodendron, and their total cumulative contribution rate was 85.03%. (3) In 2050 and 2070, the range suitable for H. ammodendron would increase significantly, whereas only a few distribution areas in the western tip of the Tarim Basin would fragment and decrease in size. The distribution range and gravity center would shift to northwest and northeast.

Seed germination and growth characteristics of Cyclobalanopsis chungii.

HUANG Yong-rong1,2, ZHUANG Kai3, WU Peng-fei1, MA Xiang-qing1*, LAI Xiao-lan1, TANG Wei-min1

2017, 36(5):  1251-1258. 

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In order to explore the mechanisms regulating the seed germination and initial seedling growth of Cyclobalanopsis chungii, the seed water absorption, bioassay of seed methanol extractives, antioxidant enzyme activity and the content of endogenous hormones during seed germination of C. chungii from different provenances were studied. The results showed that the seedcoat was the main factor blocking the water absorption of seeds. The methanol extractives from cotyledon and radical of C. chungii seeds significantly inhibited the germination percentage of Brassica pekinensis seeds. In contrast, they promoted the shoot and root length of B. pekinensis seeds. Thus, it was proposed that there existed some substances in the seeds of C. chungii affecting the seedling growth. The peroxidase and superoxide dismutase of the seeds collected from Anxi, Minqing and Jianou provenances were all able to keep high activities during their germinating, whereas the malondialdehyde content in seeds varied with different provenances. The MDA content in the seeds from Jianou, Minqing, and Anxi provenances reached the maximum on the 5th, 9th and 13th day after germination. During the seed germination process, the contents of endogenous hormones in the seeds of Jianou provenance reached the maximum earlier, compared to that of Anxi and Minqing provenances. The contents of IAA, GA₃ and CTK in the seeds from Anxi were higher than those from Minqing and Jianou, whereas the pattern of ABA content was opposite.

The effects of nanoTiO₂ on seed germination, seedling growth and physiology of Chinese fir.

LI Yan-juan1,2, ZHUANG Zheng1,2, LIU Qing-qing1,2, SHANG Tian-she1, HUANG Qin-zhong3, ZOU Jia-yong4, LIU Bo1,2*

2017, 36(5):  1259-1264. 

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A study was carried out to investigate the effects of nanoTiO₂ and regulation of nanometer materials on seed germination, seedling growth and physiology of Chinese fir under various concentrations of nanoTiO₂(50, 100, 500, 1000 mg·L^-1). It was revealed that seed germination rate, germination energy, germination index, vigor index were significantly affected by nanoTiO₂. This effect was positively correlated with low concentration but high concentration decreased germination rate and seedling growth. The seed germination rate, germination energy, germination index, vigor index were maximum with nanoTiO₂ at 100 mg·L^-1, with an increase of 66%, 92%, 71% and 299% compared to the control. The fresh weight and root length of Chinese fir seedlings reached the maximum at the 100 mg·L^-1 treatment, which were 35% and 143% higher than those of the control. In the 500 mg·L^-1 treatment, CAT， SOD and POD activities reached the maximum, which were increased by 108%, 488% and 182% respectively, but MDA content decreased by 82% compared with the control. This study indicated that low concentrations of nanoTiO₂ not only promoted seed germination and seedling growth, but also ultimately improved physiological function and might enhance the resistance of Chinese fir to adverse conditions.

Effects of warm water soaking and IAA soaking on germination of Angelica sinensis seeds.

XIAO Sheng-wang1, FANG Xiang-wen2, JIANG Zhi-rong1,3*, CHENG Yao1, MA Yu-ting1

2017, 36(5):  1265-1270. 

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In order to explore dormancybreaking mechanism and increase germination percentage, the effects of different temperatures of water treatments and different concentrations of IAA (indole acetic acid) on the germination process of the seeds of Angelica sinensis were studied. The results showed that soaking seeds with IAA 0.05 g·L^-1 for 3 h and soaking seeds with water 60 ℃ for 2 min had the maximum germination percentages (78% and 80%, respectively), being 1.7  and 2.5 times as high as that of the control. When soaking seeds with water 30, 35, 40, 45, 50, 55, 60, 65, 70 ℃ for 1  and 2 min, there was no significant correlation between germination percentages and temperatures, but a significant correlation was observed for 5, 10 and 15 min. There was no significant correlation between germination percentage and concentration when soaking seeds 1, 3, 6, 12 h with IAA 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 g·L^-1. Soaking seeds with water could improve seed germination percentage, which might relate to permeability of seed coat; however, IAA could improve seed germination percentage, which might be involved in breaking seed dormancy. Consequently, soaking seeds with water 60 ℃ for 2 min and soaking seeds with IAA 0.05 g·L^-1 for 3 h could improve the germination percentages of A. sinensis seeds. Compared with water, IAA pollutes the environment easily. So, soaking seeds with water is an advisable method in actual production.

Effects of clonal integration on the growth of Mikania micrantha in habitats with heterogeneous nutrient availability.

LI Xiao-xia, FAN Zhi-wei, SHEN Yi-de, LI Shao-liang, LIU Yan, HUANG Qiao-qiao*

2017, 36(5):  1271-1276. 

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Heterogeneity in resource availability is common in nature. Clonal plants can adapt to habitats with heterogeneous nutrient availability by clonal integration. We conducted a pot experiment to examine the effects of clonal integration on the performance of a strongly invasive plant in Hainan, Mikania micrantha, growing in habitats with heterogeneous nutrient availability. The results demonstrated that when nutrient availability was heterogeneous, clonal integration increased the biomass of the ramets growing in patches with low nutrient availability, reduced the biomass of the ramets growing in patches with high nutrient availability, and did not significantly change the biomass of the whole clonal fragments. This result was not affected by the direction of resource transportation. Clonal integration did not significantly change the ramets’ photosynthetic rate and specific leaf area, but when the proximal ramets grew under high nutrient conditions, clonal integration changed the root/shoot ratio of the clonal ramets. These results indicate that clonal integration benefits the growth of M. micrantha ramets growing in patches with low nutrient availability. Therefore, clonal integration is an important growth strategy for M. micrantha to adapt to environments with heterogeneous resource availability, and it can allow M. micrantha to expand to low nutrient patches, improving the plant’s invasion and expansion capacity.

Leaf traits of desert plant Lycium ruthenicum Murr. in the lower reaches of Heihe River in response to salinity.

WU Yan, YIN Jian-jun*, LI Shan-jia

2017, 36(5):  1277-1284. 

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The leaf traits, such as total water content (TWC), relative water content (RWC), leaf dry matter content (LDMC), specific leaf area (SLA), specific leaf volume (SLV), leaf thickness (LT), leaf succulence (Suc), leaf density (LD) under different saline conditions, were studied for 8 natural communities of dominant species of desert plant Lycium ruthenicum at the lower reaches of Heihe River in Ejina Area. The differentiation characteristics of intraspecific traits, the relationship among leaf traits, and the relationship of leaf traits and soil salt were also analyzed. The results showed that the variations of leaf traits ranged from 3.99% to 20.33%, in which TWC was the lowest, and SLV was the highest. The leaf traits among communities showed small variation. SLA showed significantly positive relationship with LDMC and LD (P<0.01); SLV was significantly negatively correlated with LDMC (P<0.01), and significantly positively correlated with TWC (P<0.01) and RWC (P<0.05). LDMC was significantly positively correlated with LD (P<0.01). The surface soil salinity (0-20 cm) was positively correlated with LT (P<0.05), SLV (P<0.05), Suc (P<0.05), TWC(P<0.05) and RWC (P<0.01). SLA, SLV, and LDMC were the key leaf traits reflecting adaptability of L. ruthenicum to desert stress. The relationships of leaf traits and surface soil salinity (0-20 cm) reflected the water conservation strategies formed by desert plants to adapt to soil salinity.

Regulatory effects of sulfur dioxide on the physiological process in Arabidopsis plants under drought stress.

WANG Min-rui, YI Hui-lan*

2017, 36(5):  1285-1291. 

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Effects of sulfur dioxide (SO₂) pretreatment on physiological responses of Arabidopsis thaliana to drought stress were investigated. Test plants were comprised of control group, 30 mg·m^-3 SO₂ exposure group, drought stress group and 30 mg·m^-3 SO₂ exposure followed by drought stress group. The results showed that leaf relative water content (LRWC) decreased and leaf wilting increased with increasing drought stress and extension of time for drought stress. SO₂ pretreatment alleviated leaf wilting and maintained higher relative water content under drought conditions. LRWC in SO₂ pretreatment group increased by 4%-10% compared to drought stress group. Moreover, drought stress induced high levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), while SO₂ pretreatment decreased the contents of H₂O₂ and MDA by 10%-19% and 15%-18%, respectively, under drought conditions. Meanwhile, the contents of proline and soluble sugar were significantly increased by 15%-30% and 6%-31% in SO₂ pretreatment group, respectively. In addition, the results of RT-PCR analysis showed that DREB2A, DREB2B, CBF4 and RD29A genes were all upregulated in response to drought stress. These droughtresponsive genes showed higher transcript levels in SO2 pretreatment group than in drought stress group, among which the relative expression level of RD29A increased by 16%. Our results suggested that SO2 pretreatment could improve drought adaptation in Arabidopsis plants by upregulating droughtresponsive genes, alleviating the oxidative stress and promoting the accumulation of osmotic adjustment substances.

Effects of combined application of organic and inorganic nitrogen fertilizers on yield, quality and economic benefit of vegetables.

TANG Gui-rong1.2, ZHOU Xuan3, TIAN Chang1, PENG Hui-hui2, ZHANG Yu-ping1, RONG Xiang-min1*

2017, 36(5):  1292-1299. 

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A field experiment was conducted to study the effects of different combinations of organic and inorganic nitrogen fertilizers on yield, quality and economic benefit of pakchoi and lettuce for three consecutive years from 2011 to 2013. Six treatments were included: no fertilizer (CK), no nitrogen fertilizer (PK), chemical fertilizer (NPK), organic and inorganic fertilizer 1 (20% pig manure N + 80% chemical fertilizer N, NPKM1), organic and inorganic fertilizer 2 (20% biogas manure N + 80% chemical fertilizer N, NPKM2), and organic and inorganic fertilizer 3 (20% pig manure composting N + 80% chemical fertilizer N, NPKM3). The results showed that the combined applications of organic and inorganic nitrogen fertilizer significantly increased vegetable yield. The yields of pakchoi and lettuce were in order of NPKM3 > NPKM1 > NPKM2 > NPK > PK > CK. Compared with the NPK treatment, the yield of NPKM1, NPKM2, NPKM3 treatments increased by 19.84%, 8.31%, 27.38% for pakchoi, and 48.66%, 22.13%, 53.76% for lettuce, respectively. The economic benefit of pakchoi and lettuce ranked in order of NPKM3 > NPKM1 > NPKM2 > NPK > PK > CK. Compared with the NPK treatment, the economic benefit of NPKM1, NPKM2, NPKM3 treatments increased by 21.83%, 9.52%, 23.15% for pakchoi, and 50.46%, 23.10%, 53.50% for lettuce, respectively. Furthermore, the combined applications of organic and inorganic nitrogen fertilizers increased vitamin C and soluble sugar contents, and decreased nitrate and crude fiber contents of pakchoi and lettuce, so as to improve the nutritional quality and taste of vegetables, especially in NPKM3 treatment. In conclusion, the pig manure composting treatment was beneficial to the highyield and highquality of pakchoi and lettuce cultivation, and thus improved economic benefit.

Effects of chitosan on root growth and leaf photosynthesis of maize seedlings under cadmium stress.

QU Dan-yang1, ZHANG Li-guo2, GU Wan-rong1*, CAO Xin-bo1, FAN Hai-chao1, MENG Yao3, CHEN Xi-chang2, WEI Shi1

2017, 36(5):  1300-1309. 

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This study investigated the mechanism of resistance to cadmium (Cd) after chitosan application. Two different varieties of maize, “Zhengdan 958” (Cdtolerant) and “Dongnong 253” (Cdsensitive) were chosen as experimental materials. Effects of 100 mg·L^-1 of chitosan application on plant growth, root feature parameters (root length, root surface, root volume, average diameter, tip number), cell membrane permeability of root, activities of root antioxidant enzymes (SOD, POD), leaf chlorophyll content, photosynthetic parameters (P_n,G_s, T_r, C_i) and the maximal photochemical efficiency (F_v/F_m) of leaf were measured under 80 mg·L^-1 Cd²⁺ stress. The results showed that 80 mg·L^-1 Cd²⁺ inhibited the growth of maize seedlings, destroyed the stability of root cell membrane and antioxidant enzymes system, and had a negative effect on the photosynthesis of leaves. The chitosan application led to a marked increase in root length, root surface and root volume, alleviating the growth inhibition under Cd stress. Chitosan treatment played an important role in stabilizing root plasma membrane structure and function, decreased the malondialdehyde (MDA) content and relative conductivity of root system under Cd stress, inhibited the production of ROS, and increased the activity of SOD and POD. Chitosan treatment increased the contents of chlorophyll a (Chla) and chlorophyll b (Chlb) in leaves, increased the photosynthetic rate and F_v/F_m, which enhanced the photosynthesis of leaves, so as to alleviate the seedling growth inhibition under Cd stress. Dongnong 253 (Cdsensitive) showed a better effect than Zhengdan 958 maize variety. The results provide a theoretical and experimental basis for the application of chitosan to maize Cdresistant production.

Effects of root exudates on the growth and activities of leaf protective enzymes of grafted coffee plants.

SUN Yan1,2, YANG Jian-feng1,2, DONG Yun-ping1,2*, LIN Xing-jun1,2, YAN Lin1,2, HUANG Li-fang1,2, WANG Xiao-yang1,2, CHEN Peng1

2017, 36(5):  1310-1314. 

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Autotoxicity of root exudates is a main reason of coffee continuous cropping obstacle, and grafting is considered as an effective way of alleviating autotoxicity. To clarify the autotoxicityinhibition mechanism of grafting, the allelopathy effect of root exudates of cultivated varieties on grafted plants was measured using a pot experiment. The results showed that the growth of ownrooted coffee was inhibited by root exudates, and the inhibition was strengthened with the increased concentration of root exudates. The growth of grafted coffee was promoted by low concentration of root exudates. The plant height, root length, shoot dry weight and root dry weight of grafted coffee were increased by 22.15%, 6.52%, 44.80% and 20.67% respectively. The root activity and leaf protective enzyme activities were significantly increased. The growth of grafted coffee was not improved by high concentration of root exudates, but still the grafted coffee could grow better compared with the ownrooted coffee; the POD activity, CAT activity and SOD activity were increased by 60.61%, 27.27% and 18.24% respectively. The root activity was significantly increased, and MDA content was significantly decreased. In conclusion, under the treatment of root exudates, some factors such as the leaf protective enzyme activities were increased by grafting, and the growth inhibition was reduced or even the growth was promoted.

Correlation between podophyllotoxin content in Sinopodophyllum hexandrum (Royle) Ying from different populations in Gansu Province and environmental factors.

GUO Qi1,2, ZHANG Jun1,2, WANG Pei-ya1,2, GONG Xiao-fang1,2, PENG Yi-nan1,2, YANG Hui1,2*, DU Wei-bo1,2

2017, 36(5):  1315-1321. 

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To explore the relationships between podophyllotoxin content in Sinopodophyllum hexandrum and environmental factors and to screen the leading affecting factor, the samples of rhizosphere soil and underground parts were collected from six populations of S. hexandrum in Gansu. The podophyllotoxin contents of underground parts and 14 soil factors including moisture, pH, organic matter, total nitrogen, available phosphorus, available potassium, available iron, available copper, available manganese, available magnesium, total iron, total copper, total manganese, and total magnesium were determined. The correlations between podophyllotoxin contents in underground parts and soil factors, elevation and climate factors (annual temperature, annual rainfall, annual sunshine hours, annual maximum temperature, and annual minimum temperature) were analyzed by stepwise regression analysis and path analysis. The results showed that significant differences in podophyllotoxin contents existed among six populations and were relatively consistent within populations, basically with normal distributions. Stepwise regression analysis revealed a significant negative correlation between podophyllotoxin content and annual temperature, annual sunshine hours and total nitrogen in soil, which indicated that the three factors play a predominant role in affecting the podophyllotoxin content in S. hexandrum. Path analysis further revealed that the degree of effect of each factor on the podophyllotoxin content decreased in order of annual temperature, annual sunshine hours, and total nitrogen. These results indicated that appropriate low temperature, shortened sunshine time and decreased nitrogen fertilization could improve the podophyllotoxin content in cultivated S. hexandrum.

Pollination behaviors of main insect pollinators of Schima superba (Theaceae).

YANG Han-bo, ZHANG Rui, SONG Ping, ZHOU Zhi-chun*

2017, 36(5):  1322-1329. 

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Schima superba is a precious broadleaf timber and high efficient biological fireprevention tree in China. S. superba is a kind of xenogamous plant, depending on the pollinators for its seed production. In order to determine the composition of pollinators and the pollination efficiency of the dominant ones, we investigated the behavior, location and number of carried pollen, visiting frequency, and the number of pollen removal and deposit by a single visit to virgin flowers in S. superba seed orchard in Lanxi, Zhejiang Province during 2015-2016. The results showed that three insects Apis cerana, Protaetia brevitarsis, and Popillia mutans were the major pollinators. The peak visiting activities were from 10:00 to 11:00 in A. cerana and P. mutans, and there was no peak of visiting activities in P. brevitarsis. The bodies of three pollinators were able to carry pollens. The carried quantity of pollen grains by P. brevitarsis was significantly higher than that by P. mutans (P<0.001), and the carried quantity of pollen grains of P. mutans was significantly higher than that of A. cerana (P<0.001). The carried quantity of pollen grains on thoracic sternum and abdominal sternum were higher than on other parts. So, the major body parts of pollination were sternum for all three pollinators. The removed and deposited pollen grains and pollination efficiency of A. cerana were all lower than those of P. revitarsis and P. mutans, but were not significantly different. However, A. cerana was dominant in visiting frequency, being as 29 and 8.3 times as P. brevitarsis and P. mutans, respectively. The duration of each visit of A. cerana was lower than that of P. brevitarsis and P. mutans. Therefore, we suggested that A. cerana was the most efficient pollinator for S. superba.

Habitat selection of scent mounts made by Castor fiber birulai in spring and autumn.

ZHEN Rong1,2, CHU Wen-wen2,3, HU Liang2,4, WU Bing1,2, CHEN Gang2, CHU Hong-jun1,2,4*

2017, 36(5):  1330-1338. 

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Understanding habitat selection is fundamental to designing conservation programs and especially critical for ensuring endangered species. We investigated the habitat selection for a rare subspecies of the Eurasian beaver, Castor fiber birulai. Habitat characteristics of preferred scent mounts in Xinjiang Burgen Beaver National Nature Reserve were examined in the fall of 2015 and spring of 2016. The average length, width and height of the scent mounts used in spring were 0.20, 0.18, 0.06 m, and 0.15, 0.08, 0.04 m in autumn, respectively. The width and height was significantly lower in autumn than in spring. Beavers demonstrated a preference for creating scent mounts in areas that were closer to large trees and tall shrubs such as Populus laurifolia and Salix turanica, closer to river edges and banks and further from areas of human disturbance. Our findings provided managers with key insights to guide habitat restoration and protective measures to ensure this rare population of beavers continues to increase.

Seasonal variations of species composition and abundance of zooplankton along the coast of Haizhou Bay.

YU Wen-wen1,2,3, ZHANG Dong-ju1,3, ZOU Xin-qing1,3, LIU Pei-ting2, GAO Ji-xian2, BEN Cheng-kai2, GUO Zhong-ren2, TANG Xiao-hong2, YUAN Jian-mei2, ZHANG Hu2*

2017, 36(5):  1339-1349. 

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Based on the samples collected from the four cruises carried out in winter (March), spring (May), summer (August) and autumn (November) of 2015, the species composition, abundance, biomass, dominant species, biodiversity and distribution of zooplankton along the coast of Haizhou Bay were analyzed. The results showed that totaling 47 species (excluding 17 plankton larvae) were inspected; the ranking of number of species in each season was summer (31 species) > autumn (29 species) > spring (27 species) > winter (17 species). The annual average abundance was 117.31 ind·m^-3, and the ranking of seasonal value of abundance was spring (256.24 ind·m^-3) > autumn (89.81 ind·m^-3) > winter (74.93 ind·m^-3) > summer (48.26 ind·m^-3). The annual average biomass was 249 mg·m^-3, and the ranking of seasonal value of biomass was autumn (369 mg·m^-3) > winter (274 mg·m^-3) > spring (214 mg·m^-3) > summer (140 mg·m^-3). The dominant species in the area were Calanus sinicus, Labidocera euchaeta and Sagitta crassa. The highest diversity index (H), evenness (J) and richness (d) all appeared in summer, and Calanus sinicus made the largest contribution to the zooplankton abundance in the area. Zooplankton had obvious seasonality and transition from south to north. Temperature was primarily responsible for the spatial and temporal distribution of zooplankton on large scale, while the top-down effect accounted for the distribution in small scale.

Ciliate community characteristics and bioassessment of water quality in the Heihe River basin.

NING Ying-zhi*, YAN Zheng-jie, SUN Jing, CHEN Ling-yun

2017, 36(5):  1350-1356. 

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The correlations between ciliate species diversity and community structure and water quality in the Heihe River basin were studied during the period of February 2013 to January 2014. Water samples were collected each season in order to analyze the ciliate community and physicochemical parameters. The results showed that total nitrogen content, chemical and biological oxygen demand, dissolved oxygen content significantly differed from upstream to downstream, while total phosphorus content and pH value had no obvious change. The change of water environment significantly decreased diversity index, richness index, and evenness index of ciliate community in the river, but the saprobic index increased significantly. These results indicated that the composition change of ciliate community can reflect the change of water quality. The redundancy analysis results suggested that the variation of ciliate communities was significantly correlated with the changes of water environmental conditions. Water quality was evaluated as mildly to moderately polluted by biological indicators. These findings suggest that ciliate community structure is a potentially reliable indicator of water quality in the Heihe River basin.

Spatial patterns and macro-scale influencing factors of rural settlements in China.

TAO Ting-ting1, YANG Luo-jun1, MA Hao-zhi1, GUO Qing-hai2, HAN Shan-rui1, LIU Mao-song1, XU Chi1*

2017, 36(5):  1357-1363. 

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Spatial patterning of rural settlements can reflect how land resources are spatially segregated in agrarian societies. In this study, we conducted a systematic sampling at a national scale and used highresolution remotelysensed images to extract information on the rural settlements in eastern mainland China. We used spatial analyses and multivariate regression to quantitatively analyze structural attributes of rural settlements in relation to a set of environmental and socioeconomic factors at a large spatial scale. Results showed that the macroenvironmental factors including climate and topography can well explain the geographic patterns of settlement density, betweensettlement nearest neighbor distance and distribution of Thiessen polygons generated based on settlement points. Settlement density is mainly constrained by topography. In areas with higher waterenergy flux and complex topographic relief, the betweensettlement spatial segregation of land resources tends to present smaller spatial units, while the heterogeneity of such segregation tends to be elevated. In general, spatial structure of rural settlements is co-influenced by land resource supply and topographic constraint, reflecting a macroscale humannature relationship. Our work can help to better understand spatial characteristics of rural settlements at broad scales, and have useful implications to the current practice of ‘New Countryside Constructions’ in China.

Landscape pattern optimization for ecological barrier in the Three Gorges Reservoir Area: A case study in Jiangjin, Chongqing. 

ZENG Li, YANG Qing-yuan*, YANG Ren-hao, CHEN Yi-duo

2017, 36(5):  1364-1373. 

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Ecological barrier in the Three Gorges Reservoir Area is the most important region in national ecological security system. Building regional ecological security pattern by landscape pattern optimization is a hot topic in research worldwide. By adjusting the components of landscape pattern, landscape pattern optimization aims to build pointpolylinepolygon ecological space network and enhance the integrity and connectivity of regional ecosystem. In this study, Jiangjin was chosen as a case study area for landscape pattern optimization. With the support of GIS, the map of landscape pattern was derived from the landuse map of 2014. The ecological sources were chosen by granularity inverse method. Ecological corridors and nodes were built by minimum cumulative resistance. The results showed that (1) 200 m was the best grain to connect the ecological source. There were 10 ecological sources (with a total area of 6.06×10⁴ hm²), 14 new ecological sources (with a total area of 0.01×10⁴ hm²), 22 ecological corridors and 24 ecological nodes; (2) The granularity inverse method could effectively overcome the subjectivity of choosing ecological sources; (3) minimum cumulative resistance could combine the ecological functions and processes and overcome the weakness of mathematical models that are hard to express spatial ecological processes. This study would provide scientific basis to landscape pattern optimization and the enhancement of ecological service value.

Ecosystem service values and spatial differentiation changes during urbanization: A case study of Huanghua City.

RONG Yi1,2, LI Chao3, XU Ce4, YAN Yan1*

2017, 36(5):  1374-1381. 

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Taking Huanghua City as an example, the impacts of spatial and quantitative land use changes on ecosystem service values during urbanization were analyzed. We developed an ecosystem service flow gainandloss matrix and established an assessment model to assess the impacts of urbanization on ecosystem service values. Meanwhile, a human activity intensity index (HAI) was introduced to analyze the spatial differentiation of regional ecosystem service values resulting from the interference of human activities. The results showed that increased urbanization significantly affected the value of ecosystem services. From the flow of ecosystem service value gains and losses, the construction land due to the urbanization resulted in ecosystem service value losses of 76.56 million yuan, which accounted for 44.57% of the total decreased value of ecosystem services during 1990-2011. Spatially, human activity intensity was dominated by low impact strength and high impact strength, and high impact strength mainly distributed in surrounding and eastern coastal areas of Huanghua City. During 1990-2011, the total disturbance continued to increase, with an average increase of 21.43%. The area with great change of activity intensity was also the region with rapid urbanization, with an increase of HAI over 50%.

Carbon emissions and their spatial-temporal patterns in Hunan Province from 2000 to 2014.

PAN Gao1,2, ZHANG He-ping1*, PAN Deng1,2

2017, 36(5):  1382-1389. 

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Based on the data of land use, energy consumption and the growth of economy and population in Hunan Province during 2000-2014, a carbon emission model based on carbon emission coefficient and decoupling analysis were used to analyze carbon emissions and their spatialtemporal patterns and the decoupling relationship between economic development and carbon emissions. The following findings were obtained: (1) The net carbon emission increased rapidly from 2040.91×10⁴ t in 2000 to 10902.56×10⁴ t in 2014, with an average annual increase of 590.78×10⁴ t. (2) The carbon emission per unit area of land and carbon emission per unit area of construction land were 5.15 and 62.55 t·hm^-2, with an average annual growth rate of 13.15% and 8.98%, respectively. (3) The net carbon emissions of all lands, carbon emission of construction land, carbon emission per unit area of land, carbon emission per unit area of construction land and carbon emission of GDP per capita had significant spatial differences among 14 cities in 2014, with a decreasing trend from central and east to west part. (4) There existed a reversed Ushaped curve between carbon emission intensity and GDP per capita, with an inflexion point of the curve at roughly 10000-11000 yuan per capita. (5) The elastic characteristics of carbon emissions, energy consumptions and economic growth mainly showed weak decoupling, strong decoupling, and expanded negative decoupling states in Hunan Province during 2000-2014. In general, the elastic characteristics were weak decoupling.

Spatial and temporal variations in hydrochemical composition of river water in Yellow River Basin, China.

HE Jiang-yi1, ZHANG Dong2,3*, ZHAO Zhi-qi3

2017, 36(5):  1390-1401. 

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We seasonally collected river water samples at four stations along the Yellow River basin, namely Tangnaihai and Qingtongxia stations (upstream), Huayuankou station (middle stream), and Jinan station (downstream) for a period of two years. Major ion concentrations in the river water samples were determined to illustrate possible controlling roles of natural factors and anthropogenic activities. The results showed that: (1) The pH value of river water in different stations in the Yellow River basin ranged from 6.90 to 9.00 with a mean value of 7.94, and TDS values varied from 178 to 685 mg·L^-1, with an average value of 453 mg·L^-1. The average pH values decreased and TDS values increased along the flow path; (2) The water hydrochemical types varied at different stations. The water hydrochemical type was mainly HCO₃Ca at Tangnaihai station, while HCO₃SO₄Ca-Na at both Qingtongxia and Huayuankou stations with SO₄ Ca-Mg and Cl-Na at Huayuankou station in some months, and HCO₃SO₄Na-Ca at Jinan station with Cl-Na in some months; (3) The dissolved ion concentrations varied in different seasons. The values were often low in flood seasons, mainly in July and August, due to the dilution of rainwater, and high in winter (December) and ice melting (March) seasons; (4) The results of this study suggested that variations in water chemical compositions in Yellow River basin are mainly controlled by natural factors. Carbonate weathering dominates at Tangnaihai station with sulfur acid acting. As the river flows into Loess Plateau, the silicate weathering and evaporite dissolution become dominant. Nitrate concentrations increased slightly in May and June at Huayuankou and Jinan stations, possibly related to agricultural irrigation.

Transport processes of sulfonamide antibiotics in soilplant system.

ZHU Feng1, SU Dan1*, AN Jing2*, GONG Xiao-shuang2,3

2017, 36(5):  1402-1407. 

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Chinese cabbage, black soil and brown soil were selected to investigate the transfer characteristics of sulfadiazine (SDZ) and sulfamethazine (SMT) and the influence factors in soilplant system using leaching and pot experiments. The results showed that SDZ had higher transfer ability than SMT in soil. The transfer ability of SDZ and SMT decreased with the increase of soil depth. With prolonged leaching time and increased antibiotic concentration, the transfer ability of SDZ and SMT increased in the same soil layers. The transfer ability of sulfonamides differed with soil type. The transfer ability of SDZ and SMT was higher in brown soil than in black soil. The absorption and transfer of the sulfonamides in plants was impacted by their transfer ability in soil. Chinese cabbage took up more SDZ rather than SMT, and the sulfonamides were mainly detected in the stem and leaf of Chinese cabbage. With the increase of sulfonamide concentration, the residue concentration of sulfonamides in Chinese cabbage was increased. The concentrations of SDZ and SMT in Chinese cabbage were higher in brown than in black soil.

Heavy metal pollution characteristics and human health risk assessment in soils from different functional areas of Baiyin, Gansu, China.

LI You-wen1，4, WANG Jing1, JU Tian-zhen2, WANG Li3, LING Ning1, ZHANG Sheng-nan1, ZHA Xiang-hao1*

2017, 36(5):  1408-1418. 

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In this study, we determined the contents of 8 soil heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in surface soils. These soil samples were collected from five different functional areas of Baiyin City, i.e., living area, industrial district, traffic area, park green space and mountain area. We evaluated the level of heavy metal pollution and human health risk by the single pollution index, composite pollution index  and health risk assessment model. The results showed that soil Cu, Cd, Hg, Pb and Zn levels of all functional areas in Baiyin City exceeded the background values of Gansu.  Composite pollution index showed that the pollution levels of the different functional areas decreased in the order of industrial district > traffic area > park green space > living area > mountain area. In addition, soil Hg, Zn, Pb and Cd pollution in all functional areas except mountain area were more serious than other heavy metals, and Hg pollution was the most serious. Health risk assessment model showed that HI and TCR values of heavy metals to children were higher than those to adults. Besides, HI and TCR of different functional areas followed a pattern of industrial district, living area > traffic area > park green space > mountain area. Among the heavy metals, As, Cr and Pb were the three most important factors contributing to HI in all functional areas, and As and Cr were the two most important factors contributing to TCR in all functional areas.

Mercury concentrations in seafood and health risks of human mercury exposure in Zhou-shan area.

ZHAO Yu-hang1,2, CHEN Min3, TU Rui3, YANG Ai-jiang1,4, LI Ping2*

2017, 36(5):  1419-1425. 

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To assess level of human mercury exposure in Zhoushan area, the total mercury (THg) concentrations in 150 samples of seafood and 136 human hair samples were analyzed. THg concentrations in the seafood ranged 3.73-789 μg·kg^-1 in wet weight with an average of 43.9 μg·kg^-1, which was lower than the national limit of China. There were significant differences of THg concentrations among different species in the seafood. Fish THg concentration was correlated with the body length and weight. The THg concentrations in human hair samples ranged 0.13-8.18 mg·kg^-1 with an average of 1.77 mg·kg^-1. There was 84.6% of population with hair THg concentrations higher than 1 mg·kg^-1 set by USEPA, and 7.4% higher than 2.3 mg·kg^-1 set by the Joint FAO/WHO Expert Committee on Food Additives. Hair THg concentrations showed an increasing trend with the age of studied population and males showed significantly higher hair THg concentrations than females. The results suggested that THg concentrations in the seafood in Zhoushan area were relatively low, but local residents still might have health risk of mercury exposure because of large consumption of seafood.

Recent advances of the research of pollution status and analysis methods for synthetic musk compounds in environment.

TONG Ling*, TIAN Qin, PAN Meng, SONG Shu-ling, YANG Zhi-peng

2017, 36(5):  1426-1435. 

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With abundant production and use of daily chemical products, synthetic musk compounds (SMCs) have entered and distributed widely in the environment. SMCs are strongly lipophilic and hydrophobic, difficult to degrade in the environment, and easy to bioaccumulate. They have potential carcinogenic effects and environmental hormone toxicity, and greatly threaten the health of human beings. More and more attention has been paid to SMCs. In this paper, the pollution source and pollution status of SMCs were reviewed. The pollution levels of SMCs in different environmental media were summarized, and a deep discussion was focused on the concentration and migration of SMCs in aquatic environments. Then, the analysis methods of SMCs in different matrixes were compared. Nowadays, the development of pretreatment technology of SMCs in environmental samples such as air, water, soils, sediments and biological tissues is rapid and more friendly to the environment. For the detection technology, the gas chromatographymass spectrometry (GC-MS) has been used widely, and the high sensitive technology such as ultraperformance liquid chromatographytandem mass spectrometry (UPLC-MS-MS) or gas chromatography×gas chromatography (GC×GC)high resolution mass spectrometry will be applied in real analysis. Studies on pollution status and analysis method of macrocyclic and alicyclic synthetic musks in the environment will be hotspots.

Mechanisms of stable carbon isotope fractionation by phytoplankton and its environmental applications.

HAN Qiong, WANG Bao-li*

2017, 36(5):  1436-1443. 

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Phytoplankton drives aquatic carbon cycle and is a key factor to understand the global carbon biogeochemical cycle. Compared with terrestrial plants, mechanisms of stable carbon isotope fractionation in algal photosynthesis are more complicated. In order to systematically understand the algal carbon isotope fractionation and its environmental application, the current relevant studies were surveyed. Taking cyanobacteria, green algae and diatoms as examples, this paper reviewed their carbon concentrating and carbon isotope fractionation mechanisms. Besides, this paper also summarized the range of algal δ¹³C and its influencing factors, and discussed the application of algal carbon isotope in the scientific fields of paleoceanography, aquatic food web and carbon cycle.

Food sources and trophic level of animals in Guizhou Zhijin cave by means of stable carbon and nitrogen isotopes.

ZHAO Lu, XU Cheng-xiang*, LI Dao-hong, YAN Han-lin

2017, 36(5):  1444-1451. 

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Carbon and nitrogen stable isotope ratios were used to analyze animals’ trophic level and the contribution rates of organic carbon source in light zone of Zhijin cave, Guizhou. The results showed that the δ¹³C of plants ranged from (-43.46±0.06)‰ to (-37.54±0.03)‰, and δ¹⁵N ranged from (0.71±0.01)‰ to (2.38±0.00)‰. The mean of δ¹³C of soil organic matter (SOM) was （-24.99±0.01）‰, which showed that the contribution of the plants to SOM was small. δ¹⁵N of SOM in the light zone was (3.93±0.03)‰, being lower than that of SOM out the cave. The contribution of 6 kinds of organic carbon source to the food sources of cave animals was calculated using IsoSource, and the results showed that the mean rate of contribution of soil organic matter to cave animals (except for the food sources of Tipula sp. and Sypna sp.) was more than 60%, being higher than those from the plants, indicating that soil organic matter was the main food source of cave ecosystem. According to the calculation formula of trophic level, the ecosystem was composed of 3 trophic levels. Soil organic matter was the first trophic level, followed by Diestrammena sp., Pocellio scaber, Camberlinius sp., Bradybaena strictotaenia, Phalangiidae sp., Hahnia sp. Drosophila sp., Uenotrechus sp. and most of spider groups were the third trophic level.

Using stable isotopes to evaluate food web structure in Dalian coastal water.

WANG Luo, DU Shuang-cheng, YANG Ting-yue, CHANG Ya-qing*

2017, 36(5):  1452-1457. 

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Food web structure in Dalian coast was constructed using stable isotopes to evaluate the trophic relationships among biological taxa. The trophic levels of organisms in Dalian coastal area, as a whole, ranged from 1.85 to 4.06, that is, 2.46-2.75 for polychaetes, 2.23-3.37 for echinodermata, 2.82-3.36 for cephalopoda, 2.00-3.27 for gasteropod, 1.85-2.44 for bivalve, 2.50-3.30 for crustacea, and 2.64-4.06 for fish, respectively. The characteristic of trophic level showed that the primary consumers were mainly mollusks such as bivalve, the secondary consumers were composed of invertebrate, and the top predators were cephalopoda, omnivorous and carnivorous fishes, respectively.

Assessment on forest ecosystem health of Lanlingxi watershed based on matter-element model and subcompartment scale.

TIAN Yao-wu1,2*, HUANG Zhi-lin2, XIAO Wen-fa2, ZENG Li-xiong2, XIANG Yong3

2017, 36(5):  1458-1464. 

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This paper aims to offer theory on the spatial contraposition allocation and land-use structural adjustment in Lanlingxi watershed in Three Gorges area. With the data collected from forest inventory survey and obtained from Forest Ecological Station in Three Gorges area (Zigui) of Yangtze River, an indicator system including three level indicators (i.e. vegetation structure, ecological service and ecological environment) and 16 secondary indicators (i.e. forest age structure, canopy density, shrub layer coverage, etc.) were selected to assess forest ecosystem health level based on matterelement model and forest subcompartment scale. The numbers of subcompartments with the integrated assessment grades of “better”, “normal” and “poor” were 83, 115 and 59, accounting for 32.30%, 44.75% and 22.96% of total subcompartments, respectively. An extremely significant positive relationship existed between forest ecosystem health level and soil organic matter density, canopy density (P<0.01), and a significant correlation was found between forest ecosystem health level and bare rock rate, soil porosity. The forest ecosystem health level for the different vegetation types was in order of broadleaf forest, arbor and shrub forest > coniferous forest > economic forest. With extension transformation, the matterelement model can provide more information of every single index, therefore, it is suitable to assess the forest ecosystem health level.