Combating desertification in China: Monitoring, control, management and revegetation

The net primary production (NPP) of Chinese terrestrial vegetation in 1997 was estimated based on the CASA model. The geographic distribution of NPP was explored using GIS and remote sensing imagery (NOAA/AVHRR),together with spatial data on vegetation, climate, soil type and solar radiation. The model estimates China's terrestrial NPP in 1997 as 195 PgC, or about 40% of the worlds terrestrial total. NPP decreased from southeast China toward the northwest. Southern Hainan Island, Southwestern Yunnan and Southeastern Tibet showed large NPP values, with the value exceding 900 gC·m -2·a -1, whereas the Takelamagan desert located in western China had very small values-less than 10 gC·m -2·a -1.

Application of casa model to the estimation of chinese terrestrial net primary productivity

Impacts of anthropogenic land use/cover changes on soil wind erosion in China.

Drying of terrestrial areas is a critical issue in our era of climate change. However, there is limited knowledge on the current spatial status of drylands, which can be assessed using updated and more rigorous data than information used in the initial dryland estimations. Here we investigate the current extent of drylands globally, continentally and nationally by analysing one of the most recent aridity database (1950–2000 period) and compare statistically, for the first time, with the initial dryland estimations (1951–1980). Using diachronic analysis between the databases, we found that drylands are currently almost 4% larger worldwide than expected and cover 45.4% of the Earth's land surface. This net increase of global dryland areas is due to the expansion of arid (+3.4%) and semi-arid (+0.9%) areas, whilst hyper-arid zones decreased (−0.8%) and dry sub-humid areas remained stable. Except for Europe and South America, all continents have experienced a net expansion of arid environments in the recent climate database. Our findings show that Asia is home to the world's largest increases in dryland areas, where China alone accounts for almost one third of the new lands exposed to aridity worldwide. The Earth's drier conditions can generally be attributed to climate changes occurring after 1980. Our results highlight large-scale drying processes and therefore the exacerbation of land degradative conditions at low and middle latitudes. Also, our findings signal the danger of triggering certain positive feedbacks in global warming, considering the newly-identified drylands migration towards higher latitudes in North America and Asia, which can modify the albedo and destabilize the large carbon pools in permafrost, peatlands or boreal forests.

Recent changes in global drylands: Evidences from two major aridity databases

What drives the vegetation dynamics in the Hengduan Mountain region, southwest China: Climate change or human activity?

Accurately identifying the contributions of climate change and human activities to desertification will support effective strategies for combating desertification. In this study, we employed the changes in net primary productivity (NPP) in areas of aeolian desertification on the Qinghai-Tibet Plateau from 2000 to 2014 to determine the dynamics of desertification. Changes in the potential NPP (PNPP) and the difference between PNPP and actual NPP (ANPP) revealed the relative contributions of climate change and human activities to desertification. We found overall mitigation of desertification during the study period. However, desertification varied both spatially and temporally. Areas with mitigation accounted for 80.1% of the total desertified land; other areas experienced exacerbation. In 67.3% of the area of mitigation, the improvement was attributed to climate change, and especially to increased precipitation. Climate change also accounted for the exacerbation of desertification in 38.0% of the total area in which desertification worsened, largely due to reduced precipitation. Therefore, climate change was the dominant factor for mitigation of desertification, and human activities were the dominant factor for exacerbation of desertification. The dominant factors for mitigation and exacerbation varied spatially. In the central and northeastern Qinghai-Tibet Plateau, climate change was the primary factor for mitigation of desertification and human activities dominated the exacerbation of desertification. In the southern and western Qinghai-Tibet Plateau, the reverse was the case. The ecological protection projects that have been implemented since 2000 in most of the Qinghai-Tibet Plateau have not yet become a dominant factor in controlling desertification processes.

Quantitative assessment of the relative roles of climate change and human activities in desertification processes on the Qinghai-Tibet Plateau based on net primary productivity

Monitoring of aeolian desertification on the Qinghai-Tibet Plateau from the 1970s to 2015 using Landsat images.

A wind erosion event is the basic minimum unit of an aeolian process. To understand the characteristics of such events, we analyzed wind speed data from 1980 to 2015 from 151 meteorological stations in the area of northern China subject to wind erosion. We classified wind erosion events into 15 levels based on the maximum wind speed during each event, and analyzed wind speed distribution of these different levels of events. The wind speed in each event level showed a significant linear distribution, providing the basis for improving the calculation of wind erosion: Qj = Tj ∙ ∑i=1i=j[R(ui) ∙ F(ui)] (details in the article). This would help to improve the calculation accuracy based on wind level compared to values based on average wind speed. We found that low-level wind erosion events were frequent but shorter, whereas high-level events were less frequent, but lasted longer and contributed more to wind erosion. >87% of the total wind erosion events lasted no >10 h. Only 9% of the individual wind erosion events lasted 11 to 20 h. Fewer than 4% of individual events lasted >20 h. Thus, it is important to consider the roles of both weak wind erosion events (

Statistical characteristics of wind erosion events in the erosion area of Northern China

Field observations of wind profiles and sand fluxes above the windward slope of a sand dune before and after the establishment of semi-buried straw checkerboard barriers

Yaping Shen

Papers

Quantitative assessment of the relative roles of climate change and human activities in desertification processes on the Qinghai-Tibet Plateau based on net primary productivity

Monitoring of aeolian desertification on the Qinghai-Tibet Plateau from the 1970s to 2015 using Landsat images.

Statistical characteristics of wind erosion events in the erosion area of Northern China

Field observations of wind profiles and sand fluxes above the windward slope of a sand dune before and after the establishment of semi-buried straw checkerboard barriers

Sediment grain–size characteristics and relevant correlations to the aeolian environment in China's eastern desert region