锡林郭勒草原土壤速效氮空间变异分析

土壤速效氮（AN）的含量是反映土壤养分的重要指标之一，对于草原生态系统的稳定和植被群落发展具有重要作用。以锡林郭勒草原为研究区，通过野外采样、室内试验和数据处理，利用地理信息系统（GIS）平台结合地统计学方法对土壤AN的空间变化特征及分异规律进行了分析，结果显示：1） 锡林郭勒草原土壤AN存在显著的空间分异规律。水平方向上，各土层深度AN含量均呈条带状分布并具有从东至西逐渐减少的趋势；垂直方向上，随着土层深度的增加土壤AN含量逐层递减，渐趋稳定。土壤AN总体含量属于中下等水平。各层土壤AN含量存在空间强相关性，其空间变异主要受结构性因素影响，且都具有中等程度变异。2） 不同的草原类型AN含量有着相似的变化趋势。在0~30 cm土层内，垂直变化梯度均表现为草甸草原>典型草原>荒漠草原；在20~50 cm土层内，垂直变化梯度为典型草原>草甸草原>荒漠草原。3） 各层土壤AN含量之间均具有极显著（P<0.01）相关性。土壤AN与速效钾无明显相关性，其与土壤有机质和速效磷有着极显著（P<0.01）正相关关系，与土壤pH则呈极显著（P<0.01）负相关。

Analysis of spatial variability of soil available nitrogen in Xilingol grassland

The content of soil available nitrogen （AN） is an important index of soil nutrient levels， and AN plays an important role in the stability of the grassland ecosystem and in plant community development. This research used field sampling， laboratory analyses and data processing， using a Geographic Information System platform combined with geostatistical methods， to determine AN spatial variation characteristic in Xilingol grassland and factors affecting it. There were 30 sampling sites across six administrative regions， with sampling to 50 cm depth in six soil depth bands： 0-5 cm， 5-10 cm， and thereafter in 10 cm increments. It was found that： 1） The soil AN level displayed significant spatial different law in Xilingol grassland. In the horizontal direction， the content of AN in each depth of soil layer was banded and tends to gradually decrease from east to west. Vertically through the soil horizons， the soil AN content decreased with depth and gradually stabilizes. The soil AN content was at the lower middle level. There was a strong spatial correlation between the AN content of each layer of soil， and its spatial variation was mainly affected by structural factors， and all moderate variability. 2） The soil AN content in different grassland types displayed a similar decreasing trend with soil depth. In the 0-30 cm soil horizon， the AN level ranked： meadow grassland>typical grassland>desert grassland. In the 20-50 cm soil horizon， the AN level ranked： typical grassland>meadow grassland>desert grassland. 3） There was a very significant correlation between AN content in all soil layers （P<0.01）. There was no obvious correlation between soil AN and available potassium， but soil AN had a very significant positive correlation with soil organic matter and available phosphorus （P<0.01）， and a very negative correlation with soil pH （P<0.01）.