宁夏东部荒漠草原灌丛引入对土壤水分动态及亏缺的影响

全球气候变化背景下,荒漠草原人工灌丛引入加速其灌丛化进程,对草原土壤水分产生重要影响。为了解宁夏东部荒漠草原灌丛引入过程中土壤水分动态及亏缺现状,选取了封育草地、放牧草地、不同年限(3a、12a、22a)和间距(40 m、6 m、2 m)灌丛柠条(Caragana korshinskii)地进行土壤水分测定,并利用土壤水分相对亏缺指数(compared soil water deficit index,CSWDI)、样地土壤水分相对亏缺指数(plot compared soil water deficit index,PCSWDI)对土壤水分亏缺进行定量分析。结果表明:灌丛引入过程中不同年限、间距灌丛地0—200 cm土层土壤含水量均显著低于封育草地与放牧地(P0.05);各样地季节动态均表现为春季返潮、夏季消耗、秋季蓄积的季节规律,但不同年限、间距灌丛地表现为春季返潮微弱,土壤含水量仅为7.80%—10.90%,显著低于封育草地和放牧地(11.90%—16.09%);灌丛引入过程中各灌丛地0—100 cm有效储水量(-16.98—18.69 mm)均低于封育草地(34.67 mm),虽在种植22a灌丛地和2 m间距灌丛地略有升高,仍不足20.00 mm。土壤水分相对亏缺量(除封育草地外)为6.69—97.16mm;灌丛引入过程中各样地不同土层CSWDI值呈波动变化,除封育草地各土层无显著的亏缺外,其他样地均存在亏缺,亏缺值为0.03—12.10,PCSWDI值均随着灌丛引入年限和密度的增加呈增大趋势。荒漠草原灌丛引入过程产生土壤水分过度利用,使得土壤水分亏缺,并加剧其深层土壤水分的消耗。

Soil moisture dynamics and deficit of desert grassland with anthropogenic introduced shrub encroachment in the eastern Ningxia, China

In addition to global climate change, the anthropogenic shrub (Caragana korshinskii) introduction in the eastern desert grassland accelerated the shrublands encroachment process in Ningxia, which influence the soil moisture storage and distribution. In this study, we aimed at understanding the soil moisture dynamic and deficit during the process of shrub introduction. We selected different sites in grassland including enclosed grassland, grazed grassland, shrublands with different planting years (3a, 12a, 22a), and shrublands with different planting intervals (40m, 6m, 2m) and analyzed the dynamics of soil moisture, compared soil water deficit index (CSWDI) and plot compared soil water deficit index (PCSWDI). We found that the soil water content of 0-200 cm soil layer of the shrublands with different planting years and intervals were 7.80%-10.90%, significantly lower than that of the enclosed grassland and grazing lands ranging from 11.90% to 16.09%, especially in spring soil moisture recovery period. The effective water storage of 0-100 cm soil layer of the shrublands were less than that of 20.00 mm (-16.98-18.69 mm), which was lower than that of the enclosed grassland (34.67 mm). Except the enclosed grassland were no relative deficit, the other lands were all relative deficit, ranging 6.69 mm to 97.16 mm. The CSWDI of different soil layers in different lands were 0.03-12.10, similar to relative deficit amount. The changes of PCSWDI in different lands showed an increasing trend of the soil water deficit with the increase of shrub introduction years and density. This study showed that the process of shrub introduction in desert steppe intensified the soil moisture deficit resulting in excessive consumption and utilization of the deeper soil moisture.