Zhou Huakun

Using Remote Sensing and GIS Technologies to Estimate Grass Yield and Livestock Carrying Capacity of Alpine Grasslands in Golog Prefecture, China

Remote sensing data from the Terra Moderate-Resolution Imaging Spectroradiometer (MODIS) and geospatial data were used to estimate grass yield and livestock carrying capacity in the Tibetan Autonomous Prefecture of Golog, Qinghai, China. The MODIS-derived normalized difference vegetation index (MODIS-NDVI) data were correlated with the aboveground green biomass (AGGB) data from the aboveground harvest method. Regional regression model between the MODIS-NDVI and the common logarithm (LOG10) of the AGGB was significant (r(2) = 0.51, P < 0.001), it was, therefore, used to calculate the maximum carrying capacity in sheep-unit year per hectare. The maximum livestock carrying capacity was then adjusted to the theoretical livestock carrying capacity by the reduction factors (slope, distance to water, and soil erosion). Results indicated that the grassland conditions became worse, with lower aboveground palatable grass yield, plant height, and cover compared with the results obtained in 1981. At the same time, although the actual livestock numbers decreased, they still exceeded the proper theoretical livestock carrying capacity, and overgrazing rates ranged from 27.27% in Darlag County to 293.99% in Baima County. Integrating remote sensing and geographical information system technologies, the spatial and temporal conditions of the alpine grassland, trend, and projected stocking rates could be forecasted for decision making.

Responses of plant community biomass to nitrogen and phosphorus additions in an alpine meadow on the Qinghai-Xizang Plateau

Aims Rising soil temperature under the warming process stimulates microbial activity in soils on the QinghaiXizang Plateau. Moreover, the eastern edge of Qinghai-Xizang Plateau has been experiencing distinct atmospheric nitrogen deposition with an increasing trend. All of these have led to an increase in the available nutrients in soils. This study was aimed to determine the responses of carbon fixation in the alpine meadow to nitrogen and phosphorus additions on the Qinghai-Xizang Plateau. Methods The study was conducted in an alpine meadow ecosystem at the Haibei National Field Research Station of Alpine Grassland Ecosystem, Northwest Institute of Plateau Biology, Chinese Academy of Sciences. Four treatments were set up in 2009, including control, nitrogen addition only (N), phosphorus addition only (P), and combined nitrogen and phosphorus additions (NP). Nutrients were added in June or July each year. The aboveground biomass of functional groups and the aboveand belowground biomass of plant communities were measured by harvesting in 2012. Important findings (1) N and P additions increased the aboveground biomass of grass, and the proportion of grass biomass in the community, but decreased the proportion of forb biomass in the community. Only P addition decreased the aboveground biomass of sedge, and the proportion of sedge biomass in the community. (2) N and P additions increased the aboveground biomass by 24% and 52%, respectively, compared with the control. (3) N addition had no effect on the belowground biomass, whereas P addition slightly increased the belowground biomass. (4) N addition had no effect on the total biomass, whereas P addition significantly increased the total biomass. Therefore, N and P additions could relieve the nutrient limitation and stimulate plant growth. 160 植物生态学报 Chinese Journal of Plant Ecology 2014, 38 (2): 159–166 www.plant-ecology.com Furthermore, the results suggest that the Qinghai-Xizang Plateau could be more limited by P than N on plant growth.

Nitrogen uptake and allocation characteristics of alpine meadow main species under water and nitrogen additions based on 15 N isotope

Aims Resource-use differentiation among species, which can reduce species competition for the same resources, is the main mechanism to maintain species diversity. Changes in soil temperature and moisture conditions, in the context of global change, may affect nitrogen (N) nutrition of plants of alpine meadow ecosystems. Our objective is to compare the characteristics of N uptake and resource allocation of dominant species of alpine meadow with changes in soil N and water. Methods An alpine meadow was treated with N and water addition for three years using the method of 15 N iso- tope injection. We determined the growth responses of dominant species to the N and water additions, as well as the features of N uptake capacity, N allocation and root to shoot ratio. Important findings The species showed significantly different responses to the N and water treatments, with respect to functional traits of species in N absorption capacity, root N content and root to shoot ratio. There was no significant relationship between N absorption capacity and root N content, whereas N absorption capacity was negatively correlated with root to shoot ratio across all plant species. These results indicated there was ecological niche differentiation in N uptake and a trade-off between the N absorption capacity and resource allocation strate- gies among species.

Characteristics of soil respiration in different degraded alpine grassland in the source region of Three-River

摘 要 为了研究高寒草原退化对土壤呼吸的影响, 对三江源区不同退化程度的高寒草原土壤呼吸进行了测定, 分析了土壤 呼吸与生物量、土壤温度以及土壤湿度的相关性, 结果表明: 1)不同退化程度的高寒草原土壤呼吸均表现出一定的月动态, 这 种月动态在不同退化程度间各有不同。2)高寒草原在退化演替序列上生长季平均土壤呼吸速率呈先增加后降低的变化趋势, 其中在中度退化程度下达到最高值((2.46 ± 0.27) μmol·m·s), 显著高于未退化((1.92 ± 0.11) μmol·m·s)和重度退化((1.30 ± 0.16) μmol·m·s)水平(p 0.05), 重度退化程度下呼吸速率显著 低于其他退化水平(p < 0.01)。3)地上生物量和土壤呼吸存在极显著线性正相关关系(p = 0.004), 而地下生物量与土壤呼吸的相 关性不很显著(p = 0.056)。4)除重度退化外, 未退化、轻度退化和中度退化高寒草原土壤呼吸与土壤温度显著正相关; 土壤呼 吸与土壤湿度的二项式拟合方程在轻度退化程度下达到显著水平(p < 0.05), 而在未退化、中度退化和重度退化程度下均达到 极显著水平(p < 0.01)。 关键词 高寒草原, 草地退化, 土壤湿度, 土壤呼吸, 三江源区, 温度