Table of Content

10 July 2020, Volume 39 Issue 7

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Responses of phylogenetic structure of plant to different habitats in Jiayuguan Caohu Wetland.

ZHAO Lian-chun, DUAN Kai-xiang, ZHAO Cheng-zhang, WANG Ji-wei, WEN Jun

2020, 39(7):  2123-2130. 

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The relationship between plant phylogenetic structure and habitats is an important topic in ecology, which can reveal the mechanisms underlying plant adaptation to environment and community assemblage. To clarify the adaptation of plants to different habitats across wetland, sand dune and gobi at the local scale in arid area, we examined plant phylogenetic structure and its change in different habitats across marsh, salt marsh, sand dune, and gobi in Jiayuguan Caohu National Wetland Park. The results showed that soil moisture, salt content, bulk density, and pH significantly differed across habitats. Consequently, plant phylogenetic structure changed adaptively. The pedigree diversity index of plants in sand dune was the highest, followed by salt marsh, and the lowest for gobi and marsh. Plant species in different habitats had different phylogenetic structure, with the phylogenetic structure in marsh, sand dune and gobi habitats being under aggregation mode and no obvious phylogenetic structure in salt marsh. At the local scale, environmental filtering was the main factor affecting species distribution in marsh, sand dune, and gobi, while both competition exclusion and habitat filtering affected species distribution in salt marsh.

Regeneration composition of woody plant species under forest gap in Maolan Karst evergreen deciduous broad-leaved mixed forest.

LUO Si-qiong, ZHANG Guang-qi, GUO Qi-qiang, LIU Sha-qian, QI Yu-jiao

2020, 39(7):  2131-2139. 

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We investigated the regeneration composition of woody plant species in the gaps with different characteristics (gap size, gap age, and causes of gap formation) in Maolan Karst forest by calculating the importance values, density, and richness of woody species, and analyzing the relationships between their regeneration and different gap characteristics. Our results showed that gap size significantly affected the density and richness of woody species. Both the density and richness of shadetolerant species (0.32 individual·m^-2 and 3.26 species·m^-2, respectively) and intermediate shade-tolerant species (0.40 individual·m^-2 and 2.54 species·m^-2, respectively) in large gaps (>200 m²) were significantly higher than those in small gaps (≤200 m²), suggesting that large gaps (>200 m²) could provide suitable light conditions and growth environment for shade-tolerant species and intermediate shade-tolerant species. Dominant species in young gaps were shade-tolerant species, with an importance value of 0.377. Dominant species of middle-aged gaps were intermediate shade-tolerant species, with an importance value of 0.400. Dominant species of old gaps were shade-intolerant tree species, with an importance value of 0.325. Those results suggested that shade-intolerant species gradually became dominant with the increasing gap age. The cause of forest gap formation had a significant effect on the density of woody species. The density of intermediate shadetolerant species (0.43 individual·m^-2) and shadeintolerant species (0.43 individual·m^-2) in the gaps caused by the lianas twining was significantly higher than that that in the gaps caused by the artificial cutting, disease, or insect pests, suggesting that the gaps caused by lianas twining could provide suitable conditions for shadeintolerant species and intermediate shadetolerant species.

Sexual differences in growth and physiological properties of southern-type poplar clones in response to continuous drought and re-watering.

DUAN Qi-ying, TIAN Ye, E Xiao-wei, QIN Guang-zhen, ZHANG Jia-yu

2020, 39(7):  2140-2150. 

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Drought is an important environmental factor restraining the distribution and growth of southern-type poplar clones. Sex-specific poplar clones may have different tolerance and corresponding physiological responses to drought stress. In this study, we compared the sex-specific response to continuous drought stress and rewatering in a pot experiment using one-year-old cuttings of male (Populus deltoides ‘Nanlin 3804’) and female (P. × euramericana ‘Nanlin895’) southerntype poplar clones. The results showed that continuous drought significantly restrained the growth of both female and male poplar clones. Under continuous drought stress, membrane lipids of leaf cells and tissues sustained peroxidation, which led to the destruction of membrane system. Furthermore, leaf MDA content, antioxidant enzyme (SOD and POD) activity, and free proline content increased significantly under continuous drought before plant death. Under severe drought, the leaves of both clones lost water quickly, with a “concentrated” phenomenon of chlorophyll. Compared to female clone, the above-ground biomass of male clone was lower, while root biomass increased under continuous drought, thereby enhancing its water absorption capacity and reducing transpiration and water loss. Meanwhile, male clone increased the antioxidant enzyme activities in leaves earlier and more greatly, and kept for much longer period, than female clone. Such differences alleviated the peroxidation of membrane lipid, maintained normal physiological functions of cells and tissues, and delayed plant death. After re-watering, the male clone recovered to normal physiological state more quickly, which ensured its higher growth than female clone. In general, male clone of southern-type poplar showed relatively stronger drought tolerance than female clone, thus it could be used for afforestation in mountainous areas.

Quantitative fluctuation and mathematical description of vegetation distribution on the floodplains of Lingshan River in Zhejiang Province.

ZHU Xing-xue, XIA Ji-hong, WANG Ying-jun, DOU Chuan-bin, LI Chao-da, YANG Meng-zhuo, YANG Lu-bo, CHENG Yue-zhou

2020, 39(7):  2151-2158. 

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Riparian vegetation is the key factor driving ecosystem function of riparian zone. We analyzed the spatial distribution and quantitative fluctuation characteristics of vegetation in the floodplains of Lingshan River in Longyou County, Zhejiang Province from 2015 to 2019, using TWINSPAN and CCA methods. We constructed a measurement formula of vegetation fluctuation. There were 189 plant species in 158 genera, 53 families and seven plant community types on the floodplains of Lingshan River from 2015 to 2019. The relative water surface elevation was the dominant factor driving vegetation fluctuation. With the increase of relative water surface elevation, plant communities changed from the hygrophyte communities to the mesophyte communities, while the composition changed from herb-dominant to shrub-grass and tree-shrub-grass. The fluctuation of dominant plant populations on the floodplains could be divided into three types: rising fluctuation, declining fluctuation, and compound fluctuation. Vegetation fluctuation had obvious directionality, with annual fluctuation ratio of vegetation on the floodplains ranged from -0.250 to 0.219. Vegetation fluctuation was positive in 2015, 2018, and 2019, and negative in 2016 and 2017. Our results provide a reference for river ecological restoration.

Nutrient allocation in different organs of typical aquatic plants along littoral zone and the ecological significance.

ZHANG Jie, HU Yue-min, FU Dong-wang, ZHU Jin-ge, DENG Jian-cai

2020, 39(7):  2159-2166. 

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We analyzed nutrient concentrations in different organs of Phragmites australis, Typha orientalis and Acorus calamus in various growth stages, dominant emergent plant species along littoral zone of Xukou Bay, Lake Taihu. Then, the removal of nitrogen and phosphorus was estimated based on nutrient concentration, biomass, as well as plant distribution. The results showed that total nitrogen concentrations in the sediments of littoral zone were 1373.0-2919.8 and 2240.6-3923.4 mg·kg^-1 in the flowering and fading stages, respectively, while total phosphorus concentrations were 437.1-687.3 and 556.0-790.7 mg·kg^-1, respectively. Total nitrogen and total phosphorus concentrations were significantly differed across organs of three emergent plants in both flowering and fading stages (P<0.05), with a trend of leaves > roots > stems. Total nitrogen and total phosphorus concentrations in the leaves and stems of three emergent plants in the flowering stage were higher than those in the fading stage, but an opposite trend of total nitrogen and total phosphorus concentrations in the roots. Total carbon concentrations in different organs were in the order of root ≈ stem > leaf, which did not significantly vary with growth stages. The highest total nitrogen concentration in leaves and stems was observed in P. australis and T. orientalis, respectively. Total nitrogen concentration in roots was similar among those three species. The highest total phosphorus and total carbon concentrations in different organs were observed in T. orientalis and P. australis, respectively. Harvesting the three dominant emergent plants in fading stage could remove 21.8 tons (18.47 g·m^-2) of total nitrogen and 1.6 tons (1.36 g·m^-2) of total phosphorus, and thus reduce the secondary pollution caused by in situ decomposition of aquatic plants.

Responses of foliar element contents and stoichiometry of dominant plant species to the cessation of N and P fertilization.

HAN Xiao-xiao, LIN Li-tao, YU Zhan-yuan, GANG Qun, HUANG Yue, LIN Gui-gang, ZENG De-hui

2020, 39(7):  2167-2174. 

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Uncovering plant C, N, and P stoichiometric characteristics contributes to betterunderstanding of plant adaptation strategies. To clarify the responses of the contents and stoichiometry of main elements in dominant plant species to the cessation of N and P fertilization, a longterm field experiment was carried out to measure C, N, P contents in mature leaves of three main dominant species in a Horqin sandy grassland, including Chenopodium glaucum (collected in 2010), Phragmites australis (collected in 2010 and 2019), and Cannabis sativa (collected in 2019). The results showed that after the cessation of fertilization, foliar C content of the three dominant species did not differ significantly among the treatments. Two years after the cessation of N application (2010), foliar N content in Chenopodium glaucum significantly differed among the treatments (P=0.001). In the 2nd year after the cessation of P application, foliar P contents ofChenopodium glaucum and Phragmites australis were significantly differed among the treatments (P=0.000; P=0.029). Eleven years after the cessation of N and P fertilization, foliar N contents of Chenopodium glaucum, Phragmites australis did not differ significantly among the treatments. Foliar P content of Phragmites australisremained different in the P added plots while no difference in foliar P content of Cannabis sativawas observed. Foliar N∶P ratio was 5.33-12.63 and 19.78-24.63 for Chenopodium glaucum and Phragmites australis after two years of N and P cessation, respectively, and was 4.96-5.67 and 15.86-20.38 for Phragmites australisand Cannabis sativa after 11 years of fertilization cessation, respectively. The combined N and P fertilization promoted plant N and P absorption, with reversible and shortterm legacy effects of N and P addition on the foliar N and P contents of dominant species. Our results provide scientific basis for fertilization management in the restoration of Horqin grassland ecosystems.

Variations in C, N and P stoichiometry of Pinus sylvestris var. mongolica seedlings under continuous

WANG Kai, SHEN Chao, SONG Li-ning, Lü Lin-you, ZHANG Da-peng

2020, 39(7):  2175-2184. 

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We examined the stoichiometric responses of Pinus sylvestris var. mongolica seedlings to drought stress by growing two-year-old P. sylvestris var.mongolica seedlings in pots and setting continuous natural drought treatment. We measured C, N and P contents in different organs (current-year needle, one-year-old needle, stem, coarse root and fine root) of the seedlings under the conditions of 60%, 40%, 30% and 20% of field waterholding capacity. Under drought stress, the variation coefficients of N and P content, C∶P and N∶P were the highest in coarse root, and the variation coefficient of C content was the highest in fine root. Meanwhile, the variation coefficients of C and P content and C∶P were the lowest in one-year-old needle, the minimum variation coefficients of N content and C∶N were found in currentyear needle, and the minimum variation coefficient of N∶P was found in stem. With decreasing soil field capacity, C content in current-year needle showed a hump change, whereas it elevated and then reduced in one-year-old needle, stem and coarse root, and it decreased and then increased in fine root. Nitrogen content decreased and then increased in current-year needle, but it declined in one-year-old needle, stem and coarse root, whereas it showed a hump pattern in fine root. Phosphorus content was promoted in current-year needle, but it declined and then increased in one-year-old needle, stem, coarse root and fine root. In addition, C∶N increased in one-year-old needle, stem, coarse root and fine root, but C∶P declined in currentyear needle, while N∶P decreased in all organs. There were close correlations among different organs for the same element but not for different elements. Therefore, with increasing drought stress, N limitation was gradually aggravated to the growth of P. sylvestris var.mongolica seedlings, and N use efficiency improved. Meanwhile, the contents of various elements were more stable in needle and stem than that in coarse root and fine root.

Effects of riparian vegetation buffers on the removal efficiency of suspended solids and nitrogen in Liaohe River protected area.

ZHANG Hong-ling, LI Tian-jiao, ZHAO Zhi-Fang, MA Guo-feng, CHEN Su, SUN Li-na

2020, 39(7):  2185-2192. 

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Migration of nitrogen through runoff from cropland to river results in low utilization of fertilizer as well as water pollution and eutrophication. Proper riparian vegetation buffering between riverbank and cropland could protect the aquatic ecosystems. Four types of vegetation buffer strips (Artemisia strip, Lolium perenne strip, Salix integra +L. prenne strip, and Amorpha fruticosa +L. perenne strip) were constructed in Liaohe River protected area close to cropland. We measured the removal efficiency of runoff volume, suspended solids (SS), NO₃^--N, NH₄⁺-N and TN in runoff and ground water. The results showed that, with increasing riparian vegetation strip width, the removal rate of runoff volume, SS, and nitrogen increased. A 5mwidth L. perenne strip reduced SS by 69.1%, while a 5mwidth A. fruticosa+L. perenne strip removed 57.6% of NO₃^--N in runoff. Vegetation strips with 13mwidth averagely reduced SS, NH₄⁺-N, NO₃^--N and TN by 95.6%, 91.3%, 75.9%, and 82.9%, respectively. The removal rate of N in runoff was significantly lower than that in ground water. The removal rate of NO₃^--N and TN in ground water within 5mwidth vegetation strip recorded negative value, indicating that vegetation buffer strengthens infiltration of nonpoint source N and thus increases the risk of NO₃^--N loss in subsurface flow. Among the four types of vegetation buffers, A. fruticosa+L. perenne strip had the highest removal efficiency of N in runoff and ground water.

Analysis on the potential suitable areas of four species of the subgen. Amygdalus in arid Northwest China under future climate change.

DUAN Yi-zhong, WANG Jia-hao, WANG Chi, WANG Hai-tao, Du Zhong-yu

2020, 39(7):  2194-2204. 

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To clarify the impacts of climate change on the geographic distribution of four species of subgen. Amygdalus in China, we collected 193 geographic coordinates and 19 bioclimatic variables of four species of subgen. Amygdalus. The potential suitable areas of A. communis, A. nana, A. mongolica,andA. tanguticaunder the climatic conditions of the past times (the last interglacial period and the last glacial maximum period), current and future periods (2050s) were predicted using MaxEnt models. The results showed that, under current climate, the suitable areas ofA. communis are mainly distributed in Yumin, Gongliu, Shache, Yingjisha, Hetian counties, and Urumqi of Xinjiang. The area with low suitability for A. communis in Urumqi has decreased compared to the past. Compared with the current climae, the total area with low suitability under the future climate conditions would increase by 0.17%, mainly due to increased area in Jiuquan of Gansu Province. Under current climate conditions, the suitable areas of A. nana are mainly distributed in Buerjin, Emin, Yumin counties of Xinjiang. Compared to the past, the total distribution area of A. nana decreased first and then increased in Buerjin and Emin counties. Under the future climate conditions, the total distribution area of A. nanawould decrease by 0.85%. Under current climatic conditions, the suitable area of A. mongolica is mainly distributed in East Gobi, Hohhot, Alax Gobi, and Ordos of Inner Mongolia. Compared to the past, the total distribution area of A. mongolica decreased first and then increased. Under the future climate conditions, the distribution area of A. mongolica would decrease by 3.39%. Under current climate, the suitable area of A. tangutica is mainly located in Maerkang and Maoxian counties of Sichuan; which has increased compared to the past. Under the future climate conditions, the total area of A. tanguticawould increase by 0.25% mainly due to the increased lowly suitable area. Mean annual precipitation is the main environmental factor affecting the distribution of A. communis, while precipitation seasonality (coefficient of variation) is the main environmental factor affecting that of A. nana. Temperature seasonality (standard deviation×100) is the main environmental factor affecting the distribution of A. mongolica and A. tangutica.

Allelopathic effects of extracts from Jerusalem artichoke tuber on seed germination and growth of Lactuca sativa L.

ZHAO Meng-liang, WANG Zi-ying, ZHAO Wen-ju, REN Yan-jing

2020, 39(7):  2205-2213. 

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Taking extracts from fresh Jerusalem artichoke tubers, the powder of drying Jerusalem artichoke tubers and inulin as allelochemicals, we measured germination rate, bud length, root length, superoxide dismutase (SOD), malondialdehyde (MDA), and soluble protein to analyze the allelopathic effects of different Jerusalem artichoke tuber extracts on seed germination and growth of lettuce (Lactuca sativa L.). Results showed that at the concentration of inulin solution of 40 mg·mL^-1 (T4), germination rate was the highest, being 20.1% higher than that of control. In the next place, germination rate was 9.6% higher than that of control when the extract solution concentration of dry sample was 5 mg·mL^-1 (T1). At the solution concentration of 40 mg·mL^-1 (T4), dry sample treatment promoted the growth of lettuce seedling’s buds, with a growth rate of 9.2% higher than that of control. When the solution concentration of dry sample was 5 mg·mL^-1 (T1), lettuce had the longest roots, being 28.3% higher than that of control. When the concentration of fresh extract of Jerusalem artichoke tuber was 20 mg·ml^-1 (T3), SOD activity of lettuce reached the highest, while MDA content was lower than that of control, indicating that the extract from fresh Jerusalem artichoke tuber could effectively improve the resistance of lettuce. When the concentration of inulin solution was 5 mg·ml^-1 (T1) and 10 mg·mL^-1 (T2), the contents of MDA and protein were significantly lower than that of control. The comprehensive allelopathic effect index was used to analyze the effects of Jerusalem artichoke tuber extract on seed germination of lettuce. The extract solution of both fresh and dry Jerusalem artichoke tubers had positive effects on the germination of lettuce, while that of inulin had strong negative effect. In the actual production, different concentrations of extract solution should be applied according to different growth requirements to achieve the best effect. Our results indicated that the powder of Jerusalem artichoke tuber as allelochemicals could play a more effective role in promoting seed germination and seedling growth of lettuce.

Effects of spraying different exogenous substances on physiological indices and cadmium and arsenic accumulation in rape under combined pollution of cadmium and #br# arsenic.

ZHANG Sheng-nan, HUANG Yi-wen, CHEN Shi-bao, WANG Meng, HUANG Yi-zong, HAN Nian

2020, 39(7):  2214-2222. 

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To alleviate the stress from heavy metals and reduce their toxic effects on crops, the effects of jasmonic acid (JA), melatonin (MT), spermidine (SPD), and 2,4-epibrassinolide (EBL) on physiological indices, uptake and accumulation of Cd and As in rape under combined Cd and As stress were examined. The results showed that spraying JA and MT at a concentration of 200 μmol·L^-1 significantly increased and spraying 20 μmol·L^-1 EBL significantly reduced the chlorophyll SPAD value of rape leaves. Spraying 500 μmol·L^-1 SPD and 20 μmol·L^-1 EBL significantly reduced the MDA content in rape leaves by 41.0% and 52.3%, respectively, whereas 20 μmol·L^-1EBL treatment significantly increased the SOD activity of rape leaves by 88.2%. Spraying 200 μmol·L^-1 MT significantly decreased Cd concentration in the shoots of rape by27.8% compared with CK treatment, while spraying 200 μmol·L^-1 JA and 20 μmol·L^-1 EBL significantly increased As concentration in the shoots of rape by 159.8% and 136.8%, respectively. Our results suggested that JA, MT, SPD and EBL can alleviate the stress of combined Cd and As pollution on rape, providing remediation materials for controlling heavy metal pollution in croplands.

Effects of fertilization and water level on ecological stoichiometry of soil and rice straw.

GAO Qing-lei, LI Zi-chuan, YIN Li-chu, SUN Shao-bo, SONG Zhao-liang

2020, 39(7):  2223-2232. 

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The effects of long-term fertilization and field water level variation on the contents and stoichiometric ratios of total carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) in rice straw and soil were examined based on a 36-year fertilization experiment in combination with a two water level controlling field experiment. The results showed that, compared with chemical fertilizer application, the contents of C, N, and S increased by 35%, 15%, and 56% in soil treated with normal-level organic fertilizer, increased by 67%, 42% and 43% in the soil treated with high-level organic fertilizer, respectively. Soil P contents under treatments of high-level organic fertilizer and normal-level organic fertilizer were decreased by 38% and 21%, respectively. The highest soil C and N contents were found under the treatment with highlevel organic fertilizer. In contrast, plants with long-term chemical fertilizer application had the highest levels of C, N and P. Changes in element contents of soil and plant were more dependent on subsequent fertilization scheme. In general, soil element content was more sensitive to fertilization than that in plants. The results of different water level treatments showed that soil C, N, S and P contents at high water level were significantly higher than those at low water level, except that higher P content in soil was observed at low water level treated with high-level organic fertilizer. In addition, there was an interactive effect between fertilization and water level on soil and plant ecological stoichiometry.

Carbon footprint of rice production under organic and conventional fertilization modes.

ZHU Feng-ting, LI Ao, YU Xiao-man, MENG Bo, BAI Jin-heng, WANG Hou-xin, LIU Ming-da, MA Dian-rong

2020, 39(7):  2233-2241. 

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To clarify the effects of organic manure on carbon footprint of rice production, a field experiment was conducted with four treatments: pig manure (ZM), cow dung (NM), chicken manure (JM), and chemical fertilizer (CF) as a control. Life cycle assessment was used to evaluate carbon emissions from paddy systems, carbon sequestration, carbon footprint of rice production, and carbon footprint per unit yield. The results showed that greenhouse gases emission during rice planting was the main source of carbon emission in paddy fields. Carbon emission of rice fields was stimulated by the application of organic manure. Compared with CF, carbon emissions under ZM, NM, and JM treatments were increased by 34%, 30%, and 65% respectively. CO₂emission during the process of rice planting made the most contribution to carbon emission in rice fields across all treatments. The positive environmental effect was higher under the treatments with organic manure than under that with chemical fertilizer application, with the increases of carbon sequestrations under ZM, NM, and JM treatments being 2.3, 2.8, and 1.9 times higher than that of CF treatment, respectively, which could offset 76%, 92%, and 55% of carbon emissions. The effects of organic manure application on carbon footprint of rice production varied with the types of organic manure, and all of them decreased carbon footprint per unit yield compared to CF treatment, with a decrease of 55%, 83% and 22% under ZM, NM and JM treatments, respectively. With a full consideration of poultry manure treatment, fertilizer production and management, as well as carbon emissions during rice planting and rice yield, we conclude that organic fertilization is beneficial to reducing carbon footprint per unit yield of rice, with best performance of cow dung treatment.

Effects of different mulching practices on soil water consumption and potato tuber yield in dryland farming.

MA Jian-tao, CHENG Hong-bo, CHEN Yu-zhang, LI Ya-wei, LAN Xue-mei, LI Rui, CHAI Yu-wei, CHANG Lei, CHAI Shou-xi

2020, 39(7):  2242-2250. 

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We examined the effects of different mulching practices on soil moisture, water consumption characteristics, tuber yield, and water use efficiency of potato field, by setting up two kinds of whole maize straw strip mulching (ST) and plastic film mulching (PT) in a semiarid area of central Gansu, with bare flat land (CK) as control. The results showed that both mulching practices significantly increased soil water storage in 0-200 cm profile during sowing to harvest stages (P<0.05). Soil water storage peaked during the harvest stage under the ST treatment (12.3%) and during starch accumulation stage under PT treatment (9.1%), respectively. Water consumption of potato under both mulching practices during the whole growing stage was lower than that of CK, with the largest decrease (by 23.4%) under the ST practice. The ST pattern significantly reduced soil water consumption in the early (from sowing to tuber initiation) and later growth stage (from starch accumulation to harvest), while significantly increased soil water consumption in the middle growth stage (from tuber initiation to starch accumulation) andincreased deep soil water storage. By contrast, PT practice mainly reduced soil water consumption in the early and middle growth stage and significantly increased soil water consumption in the later growth stage. ST and PT practices significantly increased tuber yield by 32.4% and 32.9%, and water use efficiency by 73.8% and 48.8%, respectively. In conclusion, the whole maize straw strip mulching can significantly improve soil moisture in 0-200 cm soil layer in the middle and late growth stage of potato, increase soil water consumption in the critical growth stage of potato, and thus significantly improve potato yield and water use efficiency.

Climatic suitability of winter wheat and summer maize in the North China Plain.

ZHAO Yan-xi, XIAO Deng-pan, BAI Hui-zi, TANG Jian-zhao

2020, 39(7):  2251-2262. 

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Studies on the degree of crop climate suitability are beneficial to coping with the impacts of climate change on crop production, rationally developing and utilizing agricultural climate resources, and ensuring security of food production. In this study, we established crop climate suitability degree model. Based on multisite meteorological and phenological observation data of the North China Plain, we calculated the climate suitability degrees of typical crops (winter wheat and summer maize) during 1981 to 2017, and analyzed their spatialtemporal variation. The sunshine, temperature, precipitation and synthetic climate suitability degrees of winter wheat in the North China Plain during the growing season were 0.69, 0.63, 0.50 and 0.58, respectively. The lack of precipitation during growing season was the limiting factor of winter wheat growth in the North China Plain, while the sunshine, temperature, precipitation and synthetic climate suitability degrees of summer maize during growing season were all higher than 0.60. The change trends of temperature, precipitation and synthetic climate suitability degrees of winter wheat in the whole growing season were not obvious, but the sunshine suitability degree decreased with a rate of 0.020 （10 a^-1). During the whole growing season of summer maize, only the sunshine suitability degree decreased significantly, and the temperature, precipitation and synthetic climate suitability degrees did not change. Spatially, the sunshine suitability degree of winter wheat during the whole growing season increased from southwest to northeast, and the temperature suitability was generally low in the north and high in the south, while the precipitation and synthetic climate suitability degrees gradually increased from north to south. During the whole growing season of summer maize, the sunshine suitability degree increased from southwest to northeast, while the temperature suitability degree decreased from east to west, the precipitation suitability increased from northwest to southeast, and the synthetic climate suitability showed a “stepped” spatial distribution increasing from west to east.

Effects of moso bamboo invasion on soil active organic carbon and nitrogen in a evergreen broad-leaved forest in subtropical China.

CHI Xin-chen, SONG Chao, ZHU Xiang-tao, WANG Nan, WANG Xiao-yu, BAI Shang-bin

2020, 39(7):  2263-2272. 

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Moso bamboo has expanded its range by invading the broad-leaved forests of southern China. Its invasion can alter soil carbon and nutrient cycling in invaded habitat because plant traits of moso bamboo differ from native species. Here, we examined the effects of moso bamboo invasion on soil active organic carbon and nitrogen along a transect of evergreen broad-leaved forest, mixed bamboo and broad-leaved forest, and pure moso bamboo forest. The concentrations of watersoluble organic carbon and nitrogen in soils and microbial biomass carbon and nitrogen were measured to examine the effects of moso bamboo invasion on soil active organic carbon and nitrogen in evergreen broad-leaved forest and the seasonality of such effects. The mean annual concentrations of watersoluble organic carbon and nitrogen and microbial biomass carbon and nitrogen were significantly different among forest types. The overall performance was in the order of broad-leaved forest > mixed forest > moso bamboo forest (P<0.05), which was generally consistent across seasons. Water soluble organic carbon and nitrogen contents and microbial biomass carbon and nitrogen of the three habitats experienced paralleled seasonal changes. Soil water soluble organic carbon content and microbial carbon were the highest in autumn and the lowest in summer. There was a significant positive relationship between the contents of soil active organic carbon and nitrogen (P<0.01). Moso bamboo invasion into evergreen broad-leaved forests reduced soil active organic carbon and nitrogen contents, which decreased the contents of original soil nutrients and changed the structure of the original soil organic carbon and nitrogen pools. Our results provide insight into the management of abandoned moso bamboo stands and basic data for future study of the effects of moso bamboo invasion on soil properties.

Responses of soil labile organic carbon and carbon pool management index to alpine wetland degradation.

QIAN Hong-yu, ZHOU Hong-xin, LUO Yuan-jun, PU Yu-lin, ZHANG Shi-rong, LI Ting, JIA Yong-xia

2020, 39(7):  2273-2282. 

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Clarifying the effects of alpine wetland degradation on soil labile organic carbon and carbon pool management index (CPMI) is of great significance for ecological restoration of degraded alpine wetlands. We collected soil samples from relatively pristine (RPM), lightly degraded (LDM), moderately degraded (MDM), heavily degraded (HDM), and severely degraded marsh (SDM) to examine the responses of the contents of soil total organic carbon (TOC), labile organic carbon fractions, and carbon pool management index (CPMI) to wetland degradation in the Zoige Wetland Nature Reserve. The results showed that soil TOC content at 0-100 cm ranked in the order of RPM>LDM>MDM>HDM>SDM. Compared with RPM, the content of water soluble organic carbon (WSOC), dissolved organic carbon (DOC), and permanganate oxidized carbon (PXOC) in soils of all degraded alpine wetlands decreased, and the contents of WSOC, DOC and PXOC in MDM, HDM and SDM significantly decreased by 25.79%-76.76%, 35.90%-92.81%, and 32.07%-80.06% respectively. The ratio of soil labile organic carbon (WSOC/TOC, DOC/TOC, and PXOC/TOC) gradually increased with the aggravation of wetland degradation, while soil CMPI gradually decreased. Therefore, alpine wetland degradation may decrease soil carbon sink capacity and soil quality by increasing the activity of soil organic carbon.

Relationship between soil microbial community structure and micro-ecological environmental factors in Xiaolinghe estuarine wetland of Liaodong Bay.

ZHANG Guang-shuai, YAN Ji-shun, ZHAO Quan-min, YU Yong-hai, YU Xiu-bo, ZHANG Quan-jun, CAI Yue-yin, GONG Wei

2020, 39(7):  2283-2291. 

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To reveal the response of soil microbial community to changes of micro-ecological environment, five monitoring transects were set up in Xiaolinghe estuarine wetland of Liaodong Bay, with four monitoring plots in each transect. The transect G was close to the polder embankment of the culture pond, while the other four transects (Transects A, B, C, D) were situated in proper sequence towards the water area with an interval of 100 m. Phospholipid fatty acids (PLFA) analysis was applied to determine soil microbial community structure. Results showed that the polder embankment significantly affected soil microbial community structure and microecological environmental factors. Abundance of soil microbes of the tidal flat outside the polder embankment increased first and then decreased along the direction from the shore towards the water area. Total bacteria, Gram-positive bacteria, Gram-negative bacteria and fungi of transect C were significantly 33.33%, 22.00%, 50.07% and 35.65% higher than that in transect D (close to water area). PLFA signatures were significantly correlated with soil K⁺, Ca²⁺, total N, Mg²⁺ and NO₃^--N concentrations. Results of variation partitioning analysis showed that soil base ion contents together explained 72.9% of the variation of microbial community structure. Abundance of fungi, actinomyces and Gram-positive bacteria significantly decreased by means of a negative power function with increasing Mg²⁺/Ca²⁺. In summary, polder embankment and base ion content had significant effects on soil microbial community structure.

Mechanism underlying the interaction between dissolved humic acid and polycyclic aromatic hydrocarbons.

DING Hai-tao, ZHAO Qing, SONG Wei, ZHANG Xue-jiao, ZHANG Si-yu, LI Hai-bo

2020, 39(7):  2292-2301. 

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Dissolved humic acids (DHAs) are widely found in nature, which affect the environmental fate of polycyclic aromatic hydrocarbons. Focusing on pyrene, one of the common polycyclic aromatic hydrocarbon pollutants, we used a multi-bag equilibrium system to compare the partition coefficients of different DHAs with pyrene to explore the relationship between the composition of humic acid (HA) and its ability to bind pyrene and the underlying mechanisms. The results showed that HA is mainly composed of aromatic carbon, aliphatic carbon, and oxygen-containing and nitrogen-containing functional groups. The ability of HA to bind pyrene (K_DOC is 120.36-172.40 μg·g^-1 C) increased with the increases of HA aromatic (SUVA254 is 2.51-4.18) and hydrophobic component content (A260 is 1.21-2.04), and decreased with the increases of its aliphatic (H/C is 1.02-1.34) and polar functional group \[(N+O)/C is 0.48-0.69\]. Our results suggest that DHA is a micelle-like structure with aromatic carbon as a hydrophobic core, and the aliphatic chain and the polar functional group distributed on the aliphatic chain being hydrophilic. Our results provide theoretical support for assessing ecological risk of polycyclic aromatic hydrocarbons.

Selection of cleansing agents for petroleum-contaminated soil and assessment of their efficiency.

NIU Ming-fen, YIN Zhi-hui, WANG Qi, LI Gang, GUO Shu-hai, LI Bai-lin

2020, 39(7):  2302-2308. 

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High-efficiency washing agents, including surfactant and assistant cleansing agents, were screened for soil contaminated by high-concentration petroleum. We assessed the elution efficiency and optimized elution parameters according to the effects of absorbing total petroleum and different group components. The results showed that surfactants SYO(0.25%), SDBS(0.25%), TX-100(0.25%), and AEO(0.75%) were better in desorbing petroleum. The optimized cleansing condition was shaking strength of 500 r·min^-1 at 65 ℃ for 60 min. Under such condition, the desorption efficiency of TX-100 was the highest, reaching 78.87%. The effect of Na₂SiO₃ was the best among three screened assistant cleansing agents, with the elution rate being increased by 21.52% when mixed with SDBS. The mixture of Na₂SiO₃ and SDBS desorbed 85% of saturated hydrocarbon and aromatic hydrocarbon. More than 80% of resin and asphaltene were desorbed. Our results provide reference for cleansing soil contaminated with heavy oils.

Remediation effect of chemical leaching on Cr(VI) contaminated fine soil and its economiccost.

WANG Dong-hui, LI Guang-hui, QIN Shi-qiang, JIANG Yue, TAO Wei-guang, GONG Shi-hui, WANG Jing

2020, 39(7):  2309-2315. 

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Chemical leaching is characterized by high efficiency, thorough rehabilitation, and reduction of contaminated soil. However, the cost of soil leaching is relatively high and the fine soil after chemical leaching needs to be solidified and stabilized, which limits the large-scale application of this technology. Cr(VI) contaminated fine soils were collected from Chongqing to explore the remediation effect and economic feasibility of chemical leaching. The results showed that, with increasing concentrations of oxalic acid, citric acid, acetic acid, and hydrochloric acid, the removal rate of Cr(VI) in soil increased gradually, with oxalic acid and citric acid having the best performance. The chemical leaching effect and stability were the best when the liquid-solid ratio was 5∶1-10∶1, which decreased when the liquidsolid ratio was greater than 10∶1 or lower than 5∶1. As processing time increased, the removal rate of Cr(VI) increased and the leaching concentration of Cr(VI) in soil decreased. Using oxalic acid and citric acid as mixed eluent, under the condition of liquidsolid ratio of 5∶1 and leaching for 45 min, the removal rate of Cr(VI) in soil was 62.73%, the leaching concentration of Cr(VI) was 0.64 mg·L^-1, being lower than 1.5 mg·L^-1 of the standard of Cr(VI) landfill. The cost of Cr(VI) contaminated fine soil leaching eluent was estimated as 300 CNY·t^-1 soil, with economic feasibility for engineering application.

Vegetation NDVI characteristics and response to extreme climate in Sichuan and Chongqing from 2000 to 2017.

FENG Lei, YANG Dong, HUANG Yue-yue

2020, 39(7):  2316-2326. 

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Based on the MOD13Q1 vegetation index products and extreme temperature and extreme precipitation indices from 2000 to 2017, we examined the temporal and spatial variations of NDVI in Sichuan and Chongqing during the growing season, and analyzed the relationshipbetween NDVI and extreme indices with correlation analysis method and Lasso regression model. The results showed that the average NDVI value of Sichuan and Chongqing was 0.6134, with a change rate of 0.033 （10 a-¹）. The NDVI values and their change rates in the eastern region were higher than those in the western region. The NDVI value and change rates in Chengdu City and Chongqing City were significantly lower compared with the surrounding areas. The responses of eastwest borders and east of Sichuan and Chongqing and its northerly area to the extreme climate indices were more obvious. Except for the number of cold days and the maximum daily precipitation, other indices were positively correlated with NDVI. Among which, the area with positive correlation between average temperature and NDVI was the largest, accounting for 81.79% of the total, while the area with negative correlation between the number of cold days and NDVI was the largest, accounting for 76.57%. The predicted values calculated by the Lasso regression model were well fitted with the NDVI values extracted by remote sensing (R=0.81), and the model verified the correlation results and also made up the deficiencies of correlation analysis considering only a single extreme index. The NDVI in Sichuan and Chongqing region was more significantly affected by temperature than by precipitation, which were mainly positively correlated. Heavy rainfall was not conducive to the growth of vegetation in the short term.

Multiple spatial-scale analysis on the distribution patterns of forest burned areas: A case study of Jiangxi Province.

YAN Sai-jia, WU Zhi-wei, FU Jing-jing, GU Xian-li, ZHANG Yu-jing, DU Lin-han

2020, 39(7):  2327-2336. 

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It is difficult to reveal spatial distribution patterns of forest fire at a single spatial scale. Here, we explored the spatial variability, correlation, and scale effects of forest burned area in Jiangxi Province between 2003 and 2015 at three spatial scales (city, county, and township levels) using the approaches of variation coefficient, spatial autocorrelation statistics, and scale variance analysis. There were significant differences in the changes of forest burned area among different years, with an overall pattern of increasing first and then decreasing over time. The burned area was the largest in 2008, and the spatial variability was the smallest, showing obvious aggregation characteristics. The distribution pattern of forest burned area differed across spatial scales. With the decreases of spatial scale, the degree of spatial autocorrelation of forest burned area increased, with an increased contribution rate to the whole spatial distribution pattern of forest burned areas. The hotspots of burned area were mainly distributed in the central and southern Jiangxi, which were closely related to local natural and human activities. Understanding distribution patterns of forest burned areas at different spatial scales provide a scientific basis for rational resources allocation of regional forest fire prevention.

The spatial-temporal characteristics of coordinated development between urbanization and resources and environmental carrying capacity in Northwest China: A case study of Lanzhou-Xining urban agglomeration.

ZHANG Wei-ping, SHI Pei-ji, ZHAO Wu-sheng, FENG Tao, FU Chun-yu

2020, 39(7):  2337-2347. 

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The coordination between urbanization and environment is one of key issues for regional socio-economic development. We constructed an evaluation index system of urbanization and resources and environmental carrying capacity, and measured the spatiotemporal characteristics of urbanization, resources and environmental carrying capacity and coordination degree of Lanzhou-Xining urban agglomeration from 2005 to 2017 using the entropy method and coordination degree model. The results showed that the comprehensive index of urbanization shows a continuous upward trend, with the contribution of social urbanization being gradually increased and a “polarization” development model in space. There were significant differences in social urbanization between the two core cities (Lanzhou and Xining) and the surrounding counties. The comprehensive index of resources and environmental carrying capacity showed a fluctuating upward trend, of which the level of resources and environmental performance needs to be improved. Spatially, it was high in the east region and low in the west region, consistent with the topographic distribution. From the perspective of coordination types, the degree of coordination between urbanization and resources and environmental carrying capacity was between 0.4 and 0.5, which is on the verge of imbalance, with obvious spatial agglomeration characteristics. The coordinated areas were concentrated in the two provincial capitals (Lanzhou and Xining) and some surrounding counties, while the less coordinated areas were concentrated in the southern and western counties. Our results provide reference for the coordinated development of urbanization and resources and environmental carrying capacity in the Lanzhou-Xining urban agglomeration.

Diel vertical distribution patterns of Raphidiopsis raciborskii in Dashahe Reservoir.

XUE Xian-guang, FANG Guang-hong, ZOU Chu-jun, ZHU De-ping, XIAO Li-juan, PENG Liang

2020, 39(7):  2348-2355. 

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To understand the diel vertical distribution patterns of Raphidiopsis raciborskii in Dashahe Reservoir,we carried outa survey on September 20-21 (wet season) and December 31 (dry season) of 2018. The distribution patterns of R. raciborskii population were examined with Morisita’s index and mean retention depth, and the differences of which were tested with a oneway ANOVA. A multiple regression model was used to analyze the effects of environmental variables on diel vertical distribution. The results showed that R. raciborskii clumped in water column in wet season, mainly distributed in the depth from 0.5 to 2 m, with a mean retention at 1.5 m. They were randomly distributed in dry season. R. raciborskii did not show vertical migration in both wet and dry seasons. Thermal stratification was the key factor driving diel vertical distribution of R. raciborskii in the reservoir.

Microbial community in phycosphere of red-tide alga Karenia mikimotoi and in situ algicidal effect.

DING Ning, ZHENG Ning-ning, WANG Ren-jun, SUN Li, LI Chen, GAO Pei-ke

2020, 39(7):  2356-2363. 

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We analyzed microbial community composition in phycosphere of red-tide alga Karenia mikimotoi by 16S rRNA high-throughput sequencing, and investigated the inhibitory effect of the phycosphere microorganisms on the growth of K. mikimotoi with in situ nutritive stimulation. The results showed that Proteobacteria was the dominant bacterial population in phycosphere of K. mikimotoi, with an abundance of 48.1% for α-Proteobacteria and 8.6% for γ-Proteobacteria. Sphingobacteria and Cyanobacteria accounted for 22.4% and 10.8%, respectively. Axenic culture of K. mikimotoi was obtained via treatment of the combined antibiotics. Nutrient addition did not affect the growth of K. mikimotoi. When 2216E culture medium, glycerol and sodium citrate in 5% volume ratio were added to cultivation system of K. mikimotoi, their growth was inhibited, with an inhibition rate of 99.6%, 96.0% and 91.5%, respectively. The response of phycosphere microbial community to 2216E stimulation showed that the abundance of αProteobacteria increased to 58.7% (within which Rhodobacteraceae increased from 8.7% to 22.3% and Thalassobaculum increased from 2.7% to 13.3%), and that of γ-Proteobacteria increased to 13.3% (within which Pseudomonas increased from 2.4% to 4.9%). There were diverse microbial populations in phycosphere ofK. mikimotoi, whereas appropriate amount of nutrient addition would provide the in situ alga-inhibiting effect of phycosphere bacteria.

Community composition and activity rhythm of dominant flower-visiting insects from different flowering plants in tea gardens.

ZHANG Xiao-ming, YANG Zhi-bin, ZHAO Zi-hua, CHEN Bin, DU Guang-zu, CHEN Guo-hua

2020, 39(7):  2364-2373. 

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In this study, we investigated species and residence time of flower-visiting insects on six different flowering plant species in a tea garden by catching with a net and observation. We analyzed the dominant species of visiting insects and their activities on different flowering plant species. The results showed that there were 31 species of flowervisiting insects belonging to 25 families and seven orders, 12 species belonging to 10 families and five orders on Begonia grandis and Begonia semperflorens, respectively. Both Monolepta hieroglyphica and Apolygus lucorum were the dominant species on these two plant species. There were 21 species of flower-visiting insects belonging to 16 families and six orders on Salvia japonica, with the dominant species being Cletus trigonus. There were 34 species of flower-visiting insects belonging to 26 families and seven orders on Euryops pectinatus, with the dominant species being Bacch maculata, Xenocatantops brachycerus, and Dolichopus meridionalis. There were 39 species of flower-visiting insects belonging to 32 families and eight orders on Impatiens balsamina, with dominant species being Crematogaster rogenhoferi. There were 21 species of flower-visiting insects belonging to 18 families and 7 orders on Digitalis purpurea, and the dominant species were Bombus breviceps and D. meridionalis.A. lucorum and D. meridionalis had the longest residence time on D. purpurea, with residence time of 55.33 and 25.12 s·min^-1, respectively. C. trigonus had the longest residence time of 57.50s·min^-1 on E. pectinatus.C. rogenhoferi had the longest residence time of 13.47 s·min^-1 onI. balsamina.B. maculatehad the longest residence time of 58.33 s·min^-1 on B. semperflorens. X. brachycerus had the longest residence time of 58.26 s·min^-1 on B. grandis. The two dominant predators, B. maculata and D. meridionalis, had the highest proportion (22.41% and 13.32%, respectively) and frequency (3.60 times and 2.13 times, respectively) of visiting flowers on E. pectinatus. E. pectinatus attracted most species of natural enemy, with longer stay of the dominant natural enemy species than on other plant species. Therefore, we should increase the abundance of flowering plants that can attract more diversity of natural enemies to promote the role of natural pest control in tea gardens.

Responses and the influencing factors of different earthworm groups to  electroshocking sampling in poplar-birch forests in Changbai Mountains.

SHEN Zhi-feng, YU Bin-bin, LI Su-li, LIU Shu, ZHU Dan-dan, FU Sheng-lei, ZHANG Wei-xin

2020, 39(7):  2374-2382. 

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Electroshocking is an environment-friendly approach for earthworm sampling. However, the application of this approach is limited by the varied efficiency of electroshocking across stand conditions and earthworm community composition. In early November of 2017, we investigated earthworm community composition in the poplarbirch forests at three different developmental stages in Changbai Mountains using electroshocking and hand-sorting extraction. We examined the effects of potential factors, such as forest developmental stage, ecological group, population size, life stage of earthworms, soil temperature, and soil moisture on electroshocking efficiency. The electroshocking efficiency of earthworm varied across different stages of forest development. The electroshocking efficiency of earthworms was the highest in the 40-year-old poplar-birch forest, being 68.5% and 57.4% for earthworm number and biomass, respectively.Eisenia nordenskioldi, an epigeic species, was most active and had an electroshocking efficiency of 100%. In contrast, Drawida changbaishanensis, an endo-anecic species, was dormant during the experiment, with electroshocking efficiency down to 0. The electroshocking efficiency of the slow endogeic species Eisenia andrei ranged from 22.2% to 58.3%. There was no significant correlation between Eisenia andrei population size and electroshocking efficiency for both the number (r=0.139, P=0.381) and the biomass (r=0.025,P=0.877). The electroshocking efficiency of adults of Eisenia andrei was significantly higher than that of juveniles (P=0.014). Soil temperature had a significant effect on the electroshocking efficiency, with the value being 0 when soil temperature <6 ℃, 34.6%±13.1% when soil temperature 6-10 ℃, and 46.0%±8.7% when soil temperature>10 ℃. Soil moisture did not affect electroshocking efficiency of earthworms. Overall, the electroshocking efficiency was closely related to the activity of earthworms. Earthworm ecological group, life stage, and soil temperature affected earthworm activity, and consequently changed the electroshocking efficiency of earthworms. Due to different sensitivity of earthworms to electroshocking, long-term experimental study on the ecological functions of different earthworm groups can be performed through different manipulations of earthworm community structure using the electroshocking approach.

Effects of Caragana korshinskii litter on soil arthropod community in a desertified region.

ZHANG An-ning, LIU Ren-tao, LIU Jia-nan, ZHAO Juan, CHANG Hai-tao, CHEN Wei

2020, 39(7):  2383-2391. 

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Using the litterbag method, we investigated community structure of soil arthropods during litter decomposition in microhabitats with different sizes (very small, small, medium, and large) of Caragana korshinskii shrubs in Yanchi County of Ningxia, northern China. The results showed that litter remaining mass, P content, K content, and soil electrical conductivity significantly increased with increasing shrub size (P<0.05), whereas litter cellulose content, lignin content, and soil pH were not different among shrubs with different sizes. In total, 18 families of arthropods belonging to 10 orders were captured. Tydeidae, Tenerifidae, Oribatida, and Hypogastruridae were the dominant groups, occupying 67.4% of the total individuals. There were four common groups, occupying 27.3% of the total abundance. The remaining 10 groups were relatively rare, only accounting for 4.9% of the total abundance. Soil arthropod community composition in shrub litter was significantly different among the four types of shrub microhabitats, highlighting the sensitivity and adaptability of soil arthropods to the changes of litter microhabitats. Simpson dominance index of arthropods significantly increased with the increasing size of C. korshinskii shrubs (P<0.05), whereas total abundance, group number, Shannon diversity index, evenness index, and richness index of soil arthropods did not significantly differ among the shrubs with different sizes. Total abundance, group number and diversity index were closely correlated with soil electrical conductivity, litter remaining mass, lignin content, cellulose content, and P and K contents (P<0.05). It was concluded that variations of litter remaining mass and quality (lignin content) with the increasing size of C. korshinskii shrubs could result in a large change in soil arthropod community composition. The increasing size of shrubs promoted the aggregation of soil arthropods, with significant increases of Simpson dominance index but minor effects on group number and other diversity indices in the desertified region.

Habitat selection of overwintering common crane (Grus grus) based on individuals tracking by satellite technology.

DUAN Ya-tian, LIU Qiang, LEI Yu, LI Jun-dong, LIU Wen, LI Zhen-ji, WANG Ru-bin

2020, 39(7):  2392-2399. 

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Understanding species habitat selection is of great significance for the protection of endangered animals and their habitats. In the winter of 2014, we investigated the daytime habitat selection of seven overwintering common cranes (Grus grus) by satellite tracking technology and a random forest model at Weining Caohai Nature Reserve in Guizhou Province. The results showed that the common crane had obvious selectivity to habitats (distances from nocturnal roosting site, woodland, grassland, marsh, open water and cropland), human disturbance (distances to residential areas, main roads, village roads), and elevation (P<0.05), but not to slope (P>0.05). The results of the random forest regression modeling showed that the distances from main road, nocturnal roosting site, residential areas and grassland had the greatest impacts on their habitat selection. Common cranes preferred areas near water source (858.86±29.39 m) and nocturnal roosting site (1914.70±59.14 m), and away from residential areas (312.87±10.28 m) during the daytime. In terms of the distance from the main road and the village road, the number of activity points of common cranes was significantly smaller than that of random points, indicating that common cranes may be forced to adapt to disturbances by road traffic when using cropland as their main feeding sites. The rapid urban/town expansion and road construction were the main factors threatening the survival of common cranes in Caohai and surrounding areas.

Monitoring of wintering waterbirds in the Nanji Wetland National Nature Reserve of Poyang Lake.

ZHI Yi-jin, YI Jian-feng, LIU Wei, GONG Hao-lin, SHAO Ming-qin, DAI Nian-hua, LI Quan-jiang, YANG Fu-cheng

2020, 39(7):  2400-2407. 

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Waterbird diversity was monitored annually using direct count method in 13 sampling sites of Nanji Wetland National Nature Reserve of Poyang Lake during the period of December 20 to January 10 from 2013 to 2018. A total of 129633 individuals of waterbirds belonging to 7 orders, 12 families and 45 species were recorded, with 11604 to 33053 individuals each year. Within all the recorded species, Siberian crane (Grus leucogeranus), Hooded crane (Grus monacha), and Oriental white stork (Ciconia boyciana) are listed in the first category of China’s〖JP〗 nationally protected bird species, while five other species are listed in the second category. A total of nine dominant species were recorded in this reserve, with Anatidae and Scolopacidae being the most abundant. More dominant species were recorded from 2013 to 2014 and 2017 to 2018. In contrast, only two dominant species were recorded from 2015 to 2016. Our results showed many waterbird groups were similar in abundance variation, indicating that appropriate water level can provide suitable wetland complex for various waterbird groups. The peak abundance of Podicipedidae occurred in correspondence with the low abundance of most waterbird groups, indicating that water level had significance in maintaining waterbird diversity. The similarity index of waterbird species among different sampling sites ranged from 0.51 to 0.91. Species richness and abundance increased during monitoring period due to the increased population size and encountering rate of Green winged teal (Anas crecca), Common pochard (Aythya ferina), and Pied avocet (Recurvirostra avosetta) during 2016 and 2018. The diversity index and evenness index reduced from 2015 to 2016 because Swan goose (Anser cygnoid) or Pied avocet were absolutely dominated in the community. This reserve is rich in waterbird diversity. Oriental white stork and White spoonbill (Platalea leucorodia) had large and stable population size. Cranes could almost be detected each year. This reserve played an important role in the maintenance of bird diversity and endangered waterbird conservation especially for Oriental white stork. The duration of this monitoring work was long, which preliminarily documents the patterns of population dynamics of dominant and nationally protected waterbirds and thus provides important scientific basis for waterbird conservation and habitat management in this reserve.

Investigation of beach debris at spawning ground of Green Sea Turtles (Chelonia mydas) at Qilianyu Islands, Northeastern Xisha Islands.

ZHANG Ting, LIN Liu, JIAN Li, WANG Zhao, KONG Li, WANG Jichao, SHI Haitao

2020, 39(7):  2408-2415. 

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Beach debris at spawning grounds is a major threat to the nesting and hatching of sea turtle. The Qilianyu Islands, a subgroup of islands in the northeastern part of the Xisha Islands, is the largest spawning ground for green sea turtles (Chelonia mydas) in China. Although this site is far from the mainland and relatively isolated with a small human population, pollution could not be ignored. We surveyed beach debris in and around the spawning ground of C. mydas on six islands of Qilianyu. We found that the beach debris consisted of plastic, metals and glass, with plastic being the dominant type, accounting for 82.07% in number and 45.98% in mass. The average number density of beach debris was 0.38 pieces·m^-2, and the average mass density was 7.66 g·m^-2. Compared with other spawning grounds, the average density of beach debris here was lower, but with higher proportion of plastic debris. After categorizing the type of debris, we found that most debris was from household goods (74.33%), followed by that from shipping/fishing activities (9.11%). Based on the words on the plastic debris, we inferred that the geographic source was primarily from abroad (82.02%), mainly from Southeast Asian countries, such as Vietnam and Malaysia, accounting for 96.3% of foreign debris. To better protect this important spawning ground, we recommend strengthening beach debris reduction and cleanup at Qilianyu, with much stronger regional cooperation.

Research progress on the application of ridge rice field in ecological cultivation.

GUO Hui-juan, FU Zhi-qiang, LI Chao, HE Bao-liang, YAN Ling-ling, XU Ying, LONG Pan

2020, 39(7):  2416-2425. 

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Ridge tillage is one of the important farming methods in rice paddy, with long history and obvious benefits. It has experienced thousands of years of development, and formed three types of paddy ridge tillage, i.e., filmmulched semidry ridge mode, infiltrated ridge mode, and laddershaped ridge mode. In this review, we summarized the development history, types and characteristics of paddy ridge tillage, and its ecological, economic and social benefits combined with ecological planting and raising. The ecological cultivation of ridge rice field optimizes water and soil conservation and reduces environmental pollution. It can increase the ratio of output and cost, with a net income growth of 1060-52010 Yuan per hectare compared to plain cro pping. Therefore, rice paddy ridge tillage with ecological cultivation is a good way to transform lowyield fields, absorb labors, and develop rural tourism.

Review on the study of blue sheep (Pseudois nayaur).

JIANG Zhi-liang, MIGMAR Wang-dwei

2020, 39(7):  2426-2435. 

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Information on habitat quality, animal behavior, population dynamics, and predator-prey interaction is crucial for wildlife management. Blue sheep (Pseudois nayaur) is a second-class national protected animal in China, mainly distributed on the Qinghai-Tibetan Plateau and surrounding regions. It is the prey of rare carnivores, including snow leopard (Panthera uncia), wolf (Canis lupus) and brown bear (Ursus arctos). In the 20th century, as an important game species, blue sheep suffered mass killing and trafficking, which affected their population size and distribution as well as the food resources of the predators. Currently, conflicts often occur between the protection of blue sheep and human interests, due to lack of available information on the management of blue sheep. The distribution of blue sheep is spread over the entire Qinghai-Tibetan Plateau. While studies have concentrated on their population distribution, behavior and taxonomy in Ningxia, Gansu, Qinghai and Xinjiang, no research has been conducted on the central Tibetan Plateau. There is consequently a lack of assessment on habitat quality for blue sheep, and on the effects of human activities, and its significance as food resource of the snow leopard. Moreover, few studies focus on the transmission of epidemic disease from livestock to blue sheep, though studies have been done on veterinary, fecal microbiota and nutriology of blue sheep. Many studies have examined the evolution and adaptation of blue sheep, but macro-ecology studies are lacking, resulting in knowledge gaps in population dynamics and controversy about classification and fuzzy geographic distribution. The use of new techniques to handle macro-ecology problems have been heavily debated, including molecular recognition, computer recognition, drones and camera traps. We suggest intensify the protection of the dwarf blue sheep and the blue sheep in Helan Mountains. For better monitoring of population dynamics and wildlife management, protective measures could be the implementation of animal and environmental monitoring systems in reserves with new techniques, increasing frequency of wildlife detection out the reserves, the establishment of new protected reserves and monitoring stations, and enlarging the areas of current reserves.

CLDAS-based refined agricultural climatic division of spring wheat  in Inner Mongolia.

WU Rong-sheng, WU Rui-fen, JIN Lin-xue, WANG Hui-zhen, YUE Kun, SONG Hai-qing, LIN Hong-jin, ZHENG Feng-jie

2020, 39(7):  2436-2445. 

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With hourly and high-resolution (0.0625°×0.0625°) temperature and precipitation data of CMA Land Data Assimilation System (CLDAS-V2.0), as well as groundbased observation data from 119 meteorological stations during 1981 to 2015, we determined the agricultural climatic division index of spring wheat planting distribution in Inner Mongolia by considering the agricultural climatic and productivity characters, according to climate suitability and key meteorological factors. The comprehensive division index of spring wheat was ranked. Raster calculating and multiple regression approaches were used to construct the refined agricultural climatic division maps of spring wheat planting distribution in Inner Mongolia. Our results showed that the CLDAS-based classification was generally consistent with that based on the data of the meteorological stations, with the former having more details regarding the spatial pattern. Furthermore, the comprehensive division index based on the data from meteorological stations was highly correlated with average yield at county level from 1987 to 2016 (R=0.70, P<0.01), indicating its suitability to predict the distribution of climate suitability of spring wheat in Inner Mongolia under climate warming. Seasonal drought and dry hot wind during filling stage largely constrained spring wheat production in Inner Mongolia. Good irrigation facilities in Hetao and West Liaohe Plain, as well as high precipitation along the Greater Khingan Range, made them ideal places for wheat production. Adequate water-heat conditions and low risk of dry hot wind in eastern Mt. Yinshan, the northern and southern foots of Greater Khingan Range were suitable for wheat production. The dry farming areas of the northern and southern foots of Mt. Yinshan, the foothills of Mt. Yanshan and West Liaohe Plain were sub-suitable for spring wheat planting, due to the potential drought damage in critical growth period. Strong water deficit and high risk of dry hot wind made western Inner Mongolia unsuitable for spring wheat planting. Our classifications provide basis for spring wheat production in Inner Mongolia.

Application of Landsat data in analyzing the influence mechanism of dissolved organic carbon in Taihu Lake.

HAN Zeng-lei, XIAO Min, WANG Zhong-liang

2020, 39(7):  2446-2455. 

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Dissolved organic carbon is an important component of carbon cycle in basin waters. Based on the meteorological data, remote sensing inversion parameters, and Landsat-8 OLI_TIRS satellite digital image in May 2015, we analyzed the correlations between the inversion data of the Landsat water quality model and the parameters of the dissolved organic matter (DOM) in Taihu Lake and clarified the DOM sources and its characteristics. The results showed that water quality parameters (including chlorophyll-a concentration, blue-green algae density, water transparency and turbidity calculated using inversion algorithm based on red, near-infrared and blue bands from the Landsat image) and the normalized suspended matter index were all consistent with the abundance distribution of DOC in Taihu Lake, with DOM as the main autochthonous. Based on the Landsat image, we conducted land-use supervision classification in Taihu sub-basins. The results showed that land use/cover of the basin were important factors affecting characteristics including protein-like substance content and aromaticity. Our results confirmed that remote sensing inversion is an important tool for obtaining data of organic matter in waters. This technique provides feasible way for tracing the sources and characterizing the properties of DOM, as well as showing the influencing degree on DOM with high reliability. It would be an important technology for understanding environmental carbon cycle, and sets a reference for calculation of carbon pool, assessment of water ecological risk, and monitoring of environmental change in the basin.

Estimation models of soil water-salt based on hyperspectral and Landsat-8 OLI image.

JIA Ping-ping, SUN Yuan, SHANG Tian-hao, ZHANG Jun-hua

2020, 39(7):  2456-2466. 

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Monitoring and evaluation of soil salinity and water content quickly and timely is important for agricultural production and land restoration in saline areas. Based on data of measured soil water and salt content, and hyperspectral reflectance and contemporaneous Landsat-8 OLI image in Pingluo, northern Yinchuan of Ningxia, we used resampling technology to match the measured hyperspectral data with OLI image bands, screened out sensitive bands and 11 salinity indices by 11 linear and nonlinear multiple function models. We established the regression models between soil salt content (SSC) and water content (SMC) with multiple linear regression (MLR), partial least squares regression (PLSR), and support vector machine regression (SVM). The results showed that the reflectance of resampling measured hyperspectral bands had a significant correlation with that of the OLI image bands under different soil salinity and water content. The R² of SSC inversion models was 0.626, 0.510 and 0.829 for MLR, PLSR and SVM, respectively, and was 0.455, 0.204 and 0.731 in SMC inversion models. Results from the accuracy evaluation of the models through the validation set showed that the SVM model had better performance in predicting SSC and SMC than MLR and PLSR. Our results provide reference for the prediction of soil salinity and water content in different periods in the study region and similar regions.