1980—2015年风蚀影响下中国北方土壤有机质与养分流失时空特征

中国北方干旱/半干旱区是全球主要的沙尘源区之一,风蚀造成的沙尘排放可导致大量的土壤有机质（SOM）与养分流失,并通过传输与沉降过程对其进行空间再分配,对空气质量、气候变化、植被生长及生物地球化学过程等具有重要影响。本文利用WRF/Chem（Weather Research Forecasting with Chemistry）v3.7.1大气化学传输模型,对1980—2015年间中国北方沙尘排放及其引起的SOM、全氮（TN）与全磷（TP）的时空变化过程进行了精细化模拟,探究了中国北方风蚀引起的SOM、TN与TP养分流失的时空变化特征。结果表明：① 1980—2015年来平均每年约有66.59 Tg的沙尘颗粒排放至大气;② 沙尘排放具有较大的时空差异,沙尘排放源区主要集中在新疆东部、内蒙古西部的巴丹吉林沙漠和腾格里沙漠等地区;③ 每年因沙尘排放引起的SOM、TN和TP流失量分别约为0.07 Tg、0.004 Tg和0.005 Tg;④ 1980—2015年间中国北方沙尘排放及其引起的SOM、TN与TP的流失量具有较强的年际波动,未呈现显著的趋势性变化特征。本研究对于认知风蚀在碳循环与养分循环过程中的作用,以及对深入了解中国北方的土地退化机理具有重要意义。

Spatio-temporal variations of soil organic matter and nutrient losses resulted from wind erosion in northern China from 1980 to 2015

The arid and semi-arid region in northern China is one of the major dust source areas and a major contributor to global dust emissions in the world. The area affected by wind erosion in China accounts for approximately 30% of the national territory, which is a primary contributor to atmospheric dust aerosols in East Asia and frequently transported over long distances to North Pacific Ocean, North America, and even Europe. Dust emissions resulted from wind erosion could generate a large amount of soil organic matter (SOM) and cause nutrient losses. Dust transportation and deposition processes of the wind erosion can redistribute the losses of SOM and nutrient, which can profoundly impact air quality, climate change, plant growth and productivity as well as ecosystem carbon (C) cycling and sequestration in China. However, how dust emissions affect SOM and nutrient losses in this region are poorly understood. In this paper, the WRF/Chem (Weather Research Forecasting model coupled with Chemistry) v3.7.1 atmospheric chemical transport model was adopted to simulate the spatio-temporal variations of dust emissions in northern China from 1980 to 2015. The spatio-temporal variations of losses of SOM, total nitrogen (TN), and total phosphorus (TP) resulted from wind erosion were calculated by the combination of simulated dust emissions and the spatial distribution of SOM, TN, and TP in the research region. Results showed that: (1) the annual dust emission was around 66.59 Tg (< 20 μm) over the past 40 years in northern China; (2) dust emissions showed large spatial and temporal disparities, and the dust source areas are mainly concentrated in regions such as eastern Xinjiang, the Badain Jaran Desert, and the Tengger Desert; (3) spatial patterns of SOM, TN, and TP losses were consistent with those of dust emission rates over the research region; (4) the annual losses of SOM, TN, and TP due to wind erosion are around 0.07 Tg, 0.004 Tg, and 0.005 Tg, respectively; (5) there were no obvious trends but large inter-annual fluctuations in dust emissions and the losses of SOM, TN, and TP resulted from wind erosion during 1980-2015 at the regional scale. Although numerous impacting factors can cause potential uncertainty in the estimation of SOM and nutrient losses by wind erosion, very little is known concerning the linkages between dust processes and the productivity and biogeochemical cycles of terrestrial ecosystems. Losses of SOM and nutrients by wind erosion should be included in projecting plant growth and ecosystem productivity, especially in dust storm-prone areas. It is critical to reduce the uncertainties in simulating regional biogeochemical cycling. This study is of great significance for the impacts of wind erosion on carbon cycle and nutrient cycling, as well as a deep understanding of the mechanism of land degradation in northern China.