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| 1 | Effects of Grazing Exclusion on Plant Productivity and Soil Carbon, Nitrogen Storage in Alpine Meadows in Northern Tibet, China显示文摘Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon(SOC) and soil total nitrogen(STN) storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass(AGB), belowground biomass(BGB), SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation(MAP). Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer(10 cm) after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversity conservation. | XIONG Dingpeng SHI Peili SUN Yinliang WU Jianshuang ZHANG Xianzhou | 2014 | Chinese Geographical Science2014，24，4： | 21 |
| 2 | Integrating structure and function:mapping the hierarchical spatial heterogeneity of urban landscapes显示文摘Background:Cities are social-ecological systems characterized by remarkably high spatial and temporal heterogeneity,which are closely related to myriad urban problems.However,the tools to map and quantify this heterogeneity are lacking.We here developed a new three-level classification scheme,by considering ecosystem types(level 1),urban function zones(level 2),and land cover elements(level 3),to map and quantify the hierarchical spatial heterogeneity of urban landscapes.Methods:We applied the scheme using an object-based approach for classification using very high spatial resolution imagery and a vector layer of building location and characteristics.We used a top-down classification procedure by conducting the classification in the order of ecosystem types,function zones,and land cover elements.The classification of the lower level was based on the results of the higher level.We used an objectbased methodology to carry out the three-level classification.Results:We found that the urban ecosystem type accounted for 45.3%of the land within the Shenzhen city administrative boundary.Within the urban ecosystem type,residential and industrial zones were the main zones,accounting for 38.4%and 33.8%,respectively.Tree canopy was the dominant element in Shenzhen city,accounting for 55.6%over all ecosystem types,which includes agricultural and forest.However,in the urban ecosystem type,the proportion of tree canopy was only 22.6%because most trees were distributed in the forest ecosystem type.The proportion of trees was 23.2% in industrial zones,2.2%higher than that in residential zones.That information“hidden”in the usual statistical summaries scaled to the entire administrative unit of Shenzhen has great potential for improving urban management.Conclusions:This paper has taken the theoretical understanding of urban spatial heterogeneity and used it to generate a classification scheme that exploits remotely sensed imagery,infrastructural data available at a municipal level,and object-based spatial analysis.For effective planning and management,the hierarchical levels of landscape classification(level 1),the analysis of use and cover by urban zones(level 2),and the fundamental elements of land cover(level 3),each exposes different respects relevant to city plans and management. | Yuguo Qian Weiqi Zhou Steward T.A.Pickett Wenjuan Yu Dingpeng Xiong Weimin Wang Chuanbao Jing | 2020 | Ecological Processes2020，9，1： | 1 |
| 3 | Research on Acidic Stability of Immobilized Heavy Metals in Sediment from Polluted River显示文摘The heavy metals can accumulate in sediment after discharged into surface water bodies. Before the sediment can be further landfilled or recycled,a large amount of heavy metal in it needs to be treated,known as solidification/stabilization. The properties of treated sediment may change with environment such as acid rain and landfill time,which may lead to the release of heavy metals from treated sediment into environment,posing great risks to environment and human health. In this study,the quantitative relationship has been tested between the dissolution of heavy metals from treated sediment and the p H of the leaching solution,by changing the p H of the treated sediment-leaching solution continuously. The results showed that when the p H of the treated sediment-leaching solution was higher than 5. 5,the heavy metals released from the treated sediment into solution were relatively low;when the p H of the treated sediment-leaching solution dropped to about 5. 5,a large amount of Cu,Zn,Ni and other heavy metals were released. The solidification of Cu,Zn,Cr and Cd in the treated sediment is relatively stable,while that of Ni and Pb still need to be improved. The buffer capacity of the treated sediment to acid is 0. 999 meq/g,which means it has relatively high capacity to buffer the pH change caused by external acid. | Deqin ZHAI Dingpeng XIONG Yuxi YANG Shuo TAN | 2020 | Meteorological and Environmental Research2020，11，2： | 0 |
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