Global change had a significant influence to precipitation regimes. To understand the current rainfall pattern and find out how it will change in different regions is important to understand its consequences and take reasonable measures of land management. The Horqin Sandy Land is one of the typical regions in transition zone between cropping area and nomadic area of northern China, and in which the plant communities were very sensitive to climate change, especially rainfall pattern change. The rainfall characteristics includes rainfall amount, rain days, rain event size and inter-events intervals, which determined the basic biotical processes by affecting the soil moisture directly. In this region, the situation of desertification was still arduous, so it was urgent to know the rainfall pattern variations in the context of global climate change. In this study, precipitation date from 1971 to 2013 in Naiman Banner including rainfall amount, rain days, rain-events size and inter-events intervals was analyzed. The result showed that (1) from 1971 to 2000, the annual precipitation, rainfall amount and variability of rainfall events size during growing season (from May to September) all increased in 1970s-1980s then decreased in 1990s, and tended to increase in 2000s. Annual mean rainfall was 291.9 mm, accounting for 85.32% of annual precipitation (338.8 mm). (2) During the growing season, the rainfall in July was maximum (104.2 mm), May (32.7 mm) and September (32.8 mm) were minimum, and the variation coefficient of rainfall per month were all above 0.49. The rainfall pattern was characterized by small events (<10 mm), which accounting for 64.41% of the total events and only 16.95% of the total rainfall, while the large events (≥30 mm) accounted 12.47% of total events and 48.17% of the total rainfall which determined the annual precipitation. The intra-annual variation of events size tended to increase. (3) The mean interval between 2 effective events (≥5 mm) was 9.4 d, and the short intervals (1-10d) was dominated. The mean annual rain-days (43.1 d) tended to decrease by 2.8 d/10a, while the intra-annual variation of intervals tended to increase. Consequently, under the scenarios of climate change, the increasing variability of rainfall pattern may affect the carbon cycle in the grassland and exacerbate the degree of drought in this region which may influence the stability of local grassland ecosystem, and threat the development of animal husbandry.
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