| Rainfall erosivity shows the potential ability of the soil loss caused by rainfall, and is one of the most important reasons for soil erosion. At first, this paper analyzed rainfall and erosive rainfall distribution characters using daily rainfall data during 1960 to 2000 from 16 weather stations in Heilongjiang province; and then we calculated rainfall erosivity using daily rainfall erosivity model, we analyzed the spatial and temporal distribution of rainfall erosivity, and the relationship between these distribution and rainfall amount in Heilongjiang province. The major results as follows:1. The distribution of rainfall and erosive precipitation in Heilongjiang provinceThe annual average rainfall is 517.57mm, the annual average rainfall is 333.58mm in summer (6-8 months), accounting for 64.45% of the annual average rainfall; the annual average rainfall time is 109 day, and in summer average rainfall time is 43 day, accounting for 39.45%. In the 16 weather stations, average annual erosive rainfall frequency is between 9 to 15 days, the maximum is 1.7 times than the minimum; average annual total rainfall amount with daily rainfall above erosive threshold is between 192 mm to 387 mm, the maximum is 2 times above the minimum. Linear trends of rainfall in 16 stations are all positive in Heilongjiang province, annual rainfall amount increased 2.94mm per 10 years, linear trends of erosive rainfall are all positive, and erosive rainfall amount increased 3.52mm per 10 years. The result shows:the range of erosive rainfall amount is greater than that of rainfall amount. The trend of rainfall time for erosive rainfall is increase in overall, with rate of 0.15d/10a.2. The spatial distribution of rainfall erosivity in Heilongjiang provinceAverage annual total rainfall erosivity (R factor) is between 794 to 2144 MJ·mm/(hm2-h-a), the maximum is almost 3 times than the minimum. The spatial distribution of rainfall erosivity is increasing from northwestern to south central, eastern is lower than central region, the spatial distribution of rainfall erosivity is similar to the spatial distribution of rainfall amount. Rainfall erosivity is mainly concentrated from June to September, and reach its highest value at later July or begin of August. The total rainfall erosivity between June to September is about 88% to 95% of annual total value, rainfall erosivity of western is slightly higher than that of eastern.3. The temporal distribution of rainfall erosivity in Heilongjiang provinceTrend of annual rainfall erosivity from 1960 to 2000 is increasing. Rainfall erosivity increase with rate of 1.47 MJ-mm/(hm2-h). There are eleven weather stations that with positive trend, the rate of the change for rainfall erosivity is largest in Mudanjiang, with rate of 15.6 MJ·mm/(hm2·h); while there are five weather stations that with negative trend, the rate of change of rainfall erosivity decrease fastest in Qiqihar, which is-16.8 MJ·mm/(hm2·h).4. The relationship between rainfall erosivity and others climatic factors The change trend of annual rainfall erosivity is consistent with that of annual precipitation, and the temporal change is similar. Annual rainfall erosivity and annual precipitation is positively correlated, they are positive correlation with correlation coefficient of 0.94. Rainfall erosivity and temperature, minimum temperature is also positive correlation, but rainfall erosivity and maximum temperature is negatively correlated, but correlation coefficient is not significant.
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