Owing to the combined effects of vulnerable physical basis, i.e., arid climate, thick sandy soil, strong wind in winter and spring, and excessive human activities, such as increasing population, irrational and large scale land reclamation, and over grazing, the west of Songliao Plain suffers from the high risk of sandy desertification during the past century. Historically, this region fostered both agricultural and nomadic culture. The west of Songliao Plain, located along the east fringe of farming-pastoral transitional zone in northern China, is highly sensitive to global change. To our knowledge, the analysis of the relationships of RUE with other climatic factors, such as temperature and solar duration, land use/cover change and socio-economic development, is still unavailable. In the past, many attempts were made to address the relationship between RUE and precipitation at both temporal and spatial scales. Understanding how RUE responds to climatic changes is critical to accurately forecast terrestrial C-cycle response and feedback to climate change. More recently, much work has been done to assess the relationship between non-precipitation and land degradation in arid and semi arid area by using time-series of RUE estimated wholly or partly based on satellite remote sensing or ground measurements. RUE is an essential parameter used in ecosystem management. The spatio-temporal patterns of RUE can explicitly present the steady-state of ecosystem water use and thus ecosystem functioning. Consequently, RUE provides an index of degradation that is independent of the effects of rainfall. It has been suggested that RUE can normalize the inter-annual variability in ANPP caused by rainfall variability. The process of vegetation degradation may involve a range of processes including the loss of vegetation cover, the decreasing availability of plant nutrients or the increases in run off due to compaction of top soil. A decrease in RUE reflects a declined capacity of the vegetation to transform water (and nutrients) into biomass. stated that a stable value (≈ four kilogram dry matter/ha/year/mm rainfall) could be found throughout the various arid and semi-arid zones of the world and is independent of the plant species. Rain-use efficiency (RUE) is defined as the ratio of ANPP to precipitation, i.e., the number of kilograms of aerial dry matter phytomass produced over one ha in a year per one millimeter of rain fallen. ANPP has been suggested as an integrative measure of ecosystem functioning and a key variable in assessing the effects of land use changes on ecosystem conditions. Aboveground net primary production (ANPP) indicates an ecosystem’s ability to capture solar energy and convert it to organic carbon or biomass. The demand for latest information on the vegetation cover with regard to climate and ecosystems change has increased recently. Vegetation affects several processes, including water balance, absorption and reemission of solar radiation, latent and sensible heat fluxes, the carbon cycle, etc. Spatially, sunshine duration, temperature and population density were most closely related to RUE in the west of Songliao Plain between 19. Based on the obtained spatial Grey Relation Grade (GRG) values, the pattern of the impact factors clearly showed a spatial heterogeneity. Areas showing increased RUE trends mostly coincided with areas of land cover conversions from grassland to forest, shrub to forest and cropland to forest, which suggested a positive linkage with ecological protection policy and projects at national and local levels. ![]() In total, 4.23% of the total area had experienced a significant increase in RUE, whereas 1.29% of the total area presented a significant decrease. The result demonstrated that vegetation RUE increased slightly with an undulating trend, implying the ecosystem function tended to improve between 19. The grey relational analysis (GRA) method was extended to the spatial scale, and used to select sensitive climate and socio-economic factors that affected RUE variations. Based on regression model by fitting simple linear regression through the pixel-based time series of RUE in the growing season and calculating the slopes, the change trend of RUE was determined. In this study, satellite-based RUE was calculated using time series SPOT VEGETATION (SPOT-VGT) Normalized Difference Vegetation Index (NDVI) images and precipitation data for the study area from 1999 to 2011. ![]() The west of Songliao Plain, located along the east fringe of the agro-pasture transitional zone in northern China, is highly sensitive to global change. ![]() Spatio-temporal patterns of rain-use efficiency (RUE) can explicitly present the steady-state of ecosystem water use and thus ecosystem functioning.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |