Solidago canadensis. To conduct this research, three kinds of nitrogen levels(N0, N5 and N12)were set up to simulate different degrees of nitrogen deposition and five different competition levels(intraspecies and interspecies)through controlled simulation experiments to obtain S. canadensis litter. Then the allelopathy of the extract of the S. canadensis litter leaf on Lactuca sativa seeds was studied. The results were as followes:(1)Solidago canadensis litter of different invasion levels under N0, N5 and N12 nitrogen addition treatment significantly inhibited the germination and growth of Lactuca sativa. In addition, the allelopathic effect of the extract at the initial stage of invasion(S1A3)under the addition of N5 was the most significant, and its germination speed index, germination vitality index, root length, plant height, and leaf length were respectively reduced by 61%, 79%, 84%, 68% and 13% compared with the control. At this time, the total phenol and total flavonoid content in litter were 0.48 mg·g^-1and 1.50 mg·g^-1, respectively.(2)Under the same nitrogen addition, the degree of invasion had a significant effect on the allelopathic effect of Solidago canadensis. With the increase of the proportion of Artemisia argyi, the allelopathic effect of the extract significantly increased and the content of litter allelochemicals in the early invasion(S1A3)was significantly higher than that in the late invasion(S3A1).(3)When the invasion degree is the same, the allelopathic effect of N5 nitrogen addition treatment is significantly higher than that of N0 or N12 nitrogen addition treatment.(4)Nitrogen addition has an interaction with the degree of invasion and their combined effect significantly affects the allelopathic effect of Lactuca sativa seeds. It can be inferred that nitrogen deposition may enhance the allelopathic inhibition effect of Solidago canadensis litters on native plants and further promote the successful invasion of invasive plants. This study provides a theoretical reference for further research on the allelopathy and ecological control of S. canadensis.]]> 2020/12/14 9:34:20 *]]> HU Wenjie, LIANG Qiuju, HE Yuhan, SUN Jianfan^* 7true -2·d^<sup>-1 and 102.82 μg·m^-2·d^<sup>-1, accounting for a large percentage of total deposition flux. The correlation analysis showed that there was a positive correlation between As and Cr, Zn and Cu, Cd and Pb indicating that they were from similar or same sources. However,there was no significant correlation between other metals. Applying the geoaccumulation index method, the following conclusions were reached: All seven heavy metals were seriously polluted, of which Cd was at the extremely high pollution level. According to the characteristics and sources of heavy metal pollution around Caohai Lake, heavy metal pollutions were considered mainly caused by many factors, including industrial structure and production and life style, and even the leftover of primitive zinc smelting industry in the vicinity.]]> 2020/12/14 9:34:20 1,3, LIN Shaoxia^3*, XIE Shuang², LI Lin¹, CHEN Liang¹, HE Jinlin³, HUANG Hetian²]]> ZHANG Zhuanling^1,3, LIN Shaoxia^3*, XIE Shuang², LI Lin¹, CHEN Liang¹, HE Jinlin³, HUANG Hetian² 6true Cunninghamia lanceolata)plantation. C, N, and P concentrations and stoichiometric characteristics of litterfall(leaf, branch and fruit)and soil(0-20 cm, 20-40 cm, 40-60 cm)were analyzed. Four simulated nitrogen deposition treatment levels were N0(0 kg N·hm^-2·a^-1), N1(60 kg N·hm^-2·a^-1), N2(120 kg N·hm^-2·a^-1)and N3(240 kg N·hm^-2·a^-1), respectively. Each treatment comprised three replicate plots of 20 m × 20 m which were sprayed with urea on the forest floor at the beginning of each month. The results were as follows:(1)C, N and P contents and stoichiometric ratios of litterfall were higher than that of soil. The stoichiometric ratios of litterfall showed the same order as soil of C/P>C/N>N/P; The C, N contents of litterfall decreased in the order of leaf > fruit > branch, while P decreased in the order of leaf > branch > fruit.(2)N deposition promoted N content in litterfall leaf(+4.24%), branch(+15.97%), and fruit(+6.47%), respectively; N deposition increased N/P while decreased C content, C/N and C/P in litterfall branch; Medium-high level of N deposition(N2 and N3)increased soil N content, and low level of N deposition(N1)increased soil C/P and N/P.(3)Significant positive correlation existed between litterfall N and soil N, while negative correlation between soil C/P and litterfall C/P, N/P, and between soil P and litterfall N/P. It is indicated that litterfall N was one of the important soil N sources, and soil N content mainly influencing the ratio of litterfall N/P after long-term N deposition.]]> 2020/12/14 9:34:20 1, SHEN Fangfang¹, LIU Wenfei¹, MENG Qingyin², TONG Hao³, CHEN Guanpeng¹, XU Jin¹, FAN Houbao^1*]]> LIAO Ke¹, SHEN Fangfang¹, LIU Wenfei¹, MENG Qingyin², TONG Hao³, CHEN Guanpeng¹, XU Jin¹, FAN Houbao^1* 5true -2·a^-1 and a mean value of 219.76 g C·m^-2·a^-1 from 2000 to 2015. Spatially, vegetation NPP in the middle part of the Xiliaohe Basin was lower than the edge sides. The changing slope of vegetation NPP ranged from -16.53 to 16.65 and 95.74% of the regions showed an increasing trend.(2)The total NPP among different vegetation types ranked as grassland > cultivated vegetation > broad-leaved forest > shrub > meadow > coniferous forest. The vegetation types of carbon sequestration in the Xiliaohe Basin were mainly grassland, cultivated plants and broad-leaved forest, and coniferous forest had strong carbon sequestration capacity.(3)Vegetation NPP was higher in the area coved by brown soil, cinnamon soil and moisture soil, and lower in the chestnut soil and aeolian soil.(4)Compared with temperature, precipitation was the main prominent contribution to the changing trend of NPP in the past 16 years. The warm-wet climate and the implementation of ecological construction projects promoted the growth of vegetation in the Xiliaohe Basin. These results provide a scientific basis and data support for the later basin ecological environment governance.]]> 2020/12/14 9:34:20 *, HU Ke]]> ZHU Liya, SUN Shuang^*, HU Ke 4true Artemisia frigida, Potentilla tanacetifolia, Aneurotepidimu chinensis, and Melissitus ruthenica in the steppe were collected in August 2014. Contents of carbon, nitrogen and phosphorus, and ratios of C:N and N:P in different plants in field experiment under nitrogen fertilization and mowing treatments were investigated. The effects of nitrogen fertilization and mowing on carbon, nitrogen and phosphorus, and ratios of C:N and N:P were analyzed with ANOVAs. The differences of stoichiometry characteristics under different treatments were analyzed with Post-Hoc tests. The results were as follows: Neither nitrogen fertilization nor mowing altered carbon content in the steppe. Nitrogen fertilization significantly elevated the plant nitrogen content(P<0.05), thus decreased the C:N ratio(P<0.05)and increased the N:P ratio(P<0.05). Mowing increased the nitrogen content of Melissitus ruthenica by 0.18%(P<0.05), decreased the nitrogen content of Aneurotepidimu chinensis by 0.13%(P<0.05), but did not affect the nitrogen content of Aartemisia frigida or Potentilla tanacetifolia. Mowing significantly elevated the phosphorus contents of Artemisia frigida and Potentilla tanacetifolia(P<0.05), but did not affect the phosphorus content of Melissitus ruthenica or Aneruotepidimu chinensis. The study has approved that nitrogen fertilization and mowing can affect the plant stoichiometry characteristics in the steppe, but the affect varied with species. The results provide data support for the study on plant functional traits in the grassland.]]> 2020/12/14 9:34:20 *]]> CHEN Anqun, XUAN Juan, WANG Dong, LIU Yinzhan^* 3true Litsea species under the current and future climate conditions of China(2061-2080), and to analyze and classify their suitable habitats. The results were as follows: Litsea cubeba was widely distributed in the south to the Yangtze River in China, and under the future climate with two(RCP2.6, RCP8.5)carbon dioxide concentrations, during 2061—2080 the suitable area for its distribution was reduced by 4.9%and 0.5%, respectively; L. coreana was mainly distributed in central and northern subtropical regions of China, and under the climate scenarios with two carbon dioxide concentrations, in 2061—2080 the total suitable area would be increased by 5.6% and 4.5%, respectively; L. greenmaniana was mainly distributed in the south subtropical regions of China; L. mollis was widely distributed in the subtropical region. Under the future climate RCP2.6 scenarios, the suitable area of the two species would be shrinked by 1.0% and 3.3%, respectively, and under the climate RCP8.5, the suitable area of the two species would be shrinked by 5.6% and 8.3%, respectively. These results reveal that due to different ecological requirements, Litsea species will have different distributional responses to the future climate. The introduction and cultivation of Litsea species should consider the influences of climate change.]]> 2020/12/14 15:38:09 1, CAO Kunfang^1,2*]]> ZHENG Weiyan¹, CAO Kunfang^1,2* 2true Hippophae neurocarpa, a woody plant endemic to the Qinghai-Tibet Plateau, were used as materials to determine the degree of oxidative damage, activity of antioxidant system enzyme, content of total flavonoid in leaves and its antioxidant activity under UV-B radiation intensity of 62 μW·cm^-2 under UV-B radiation treatment for 0-6 d, to explore the physiological and ecological response mechanism of H. neurocarpa to UV-B radiation. The results were as follows: With the increasement of UV-B radiation time, the contents of hydrogen peroxide(H₂O₂)and membrane lipid peroxidation product(MDA)increase significantly; The activity of catalase(CAT)in antioxidant system enzyme increased significantly; The activities of peroxidase(POD)and ascorbate peroxidase(APX)decreased first and then increased, and the activities were significantly lower than that the control check, while the activity of superoxide dismutase(SOD)has no significant changes; The content of total flavonoid increased significantly with the accumulation of radiation time, the total flavonoid as non-enzymatic antioxidants had a significant positive correlation with clearance rate of 1, 1-Diphenyl-2-Picrylhydrazyl(DPPH)and its content changes. The above results indicate that the H. neurocarpa resist the oxidative damage caused by radiation mainly depends on the improvement of the CAT activity and the increase of the content of total flavonoid. The results of the experiment provide a theoretical reference for understanding the countermeasures of woody plants like H. neurocarpa grown on the Qinghai-Tibet Plateau for adapting to UV-B radiation.]]> 2020/12/14 9:34:20 *]]> ZHOU Xuan, JIA Zhipeng, WANG Juan, DU Meina, SU Xue^* 1true