Assessing the relative role of climate change and human activities in desertification of North China from 1981 to 2010

Desertification is a severe environmental problem induced by both climate change and human activities.This study assessed the relative contribution of climate change,human activities,and different climatic and anthropogenic factors in desertification reversion and expansion of North China from 1981 to 2010.The results showed that the desertification of North China had changed significantly over the past 30 years;desertification reversion and expansion covered an area of 750,464 km^2, and the spatial distribution of these regions exhibited considerable heterogeneity.For desertification reversion, climate change and human activity accounted for 22.6% and 26%,respectively of total reverted land.Wind speed reduction and the improvement ofhydrothermal conditions were the most important climatic factors for desertification reversion in the arid region of Northwest China (ARNC) and the Three-River Headwaters region (TRHR),and the reduction in grassland use intensity was the most important anthropogenic factor related to desertification reversion in Inner Mongolia and regions along the Great Wall (IMGW). For desertification expansion,the relative role of climate change was more obvious,which was mainly attributed to the continuous reduction in precipitation in eastern IMGW, and the increase in grassland use intensity was the main factor underlying regional human-induced desertification expansion.

Soil bacterial communities interact with silicon fraction transformation and promote rice yield after long-term straw return

Returning crop straw into the soil is an important practice to balance biogenic and bioavailable silicon(Si)pool in paddy,which is crucial for the healthy growth of rice.However,owing to little knowledge about soil microbial communities responsible for straw degradation,how straw return affects Si bioavailability,its uptake,and rice yield remains elusive.Herein,we investigate the change of soil Si fractions and microbial community in a 39-year-old paddy field amended by a long-term straw return.Results show that rice straw return significantly increased soil bioavailable Si and rice yield from 29.9%to 61.6%and from 14.5%to 23.6%,respectively,when compared to NPK fertilization alone.Straw return significantly altered soil microbial community abundance.Acidobacteria was positively and significantly related to amorphous Si,while Rokubacteria at phylum level,Deltaproteobacteria,and Holophagae at class level was negatively and significantly related to organic matter adsorbed and Fe/Mn-oxide-combined Si in soils.Redundancy analysis of their correlations further demonstrated that Si status significantly explained 12%of soil bacterial community variation.These findings suggest that soil bacteria community and diversity interact with Si mobility by altering its transformation,thus resulting in the balance of various nutrient sources to drive biological Si cycle in agroecosystem.

Assessing the effect of desertification controlling projects and policies in northern Shaanxi Province, China by integrating remote sensing and farmer investigation data

To combat desertification, the Chinese govern- ment has launched a series of Desertification Controlling Projects and Policies over the past several decades. However, the effect of these projects and policies remains controversial due to a lack of suitable methods and data to assess them. In this paper, the authors selected the farming- pastoral region of the northern Shaanxi Province in China as a sample region and attempted to assess the effect of Desertification Controlling Projects and Policies launched after 2000 by combining remote sensing and farmer investigation data. The results showed that the combina- tion of these two complementary assessments can provide comprehensive information to support decision-making. According to the remote sensing and Net Primary Production data, the research region experienced an obvious desertification reversion between 2000 and 2010, and approximately 70% of this reversion can be explained by Desertification Controlling Projects and Policies. Farmer investigation data also indicated that these projects and policies were the dominating factor contributing to desertification reversion, and approxi- mately 70% of investigated farmers agreed with this conclusion. However, low supervision and subsidy levels were issues that limited the policy effect. Therefore, it is necessary for the government to enhance supervision, raise subsidy levels, and develop environmental protection regulations to encourage more farmers to participate in desertification control.