退化草原土壤有机质对氮素添加梯度的响应

选取内蒙古锡林郭勒典型草原区两种不同退化程度草原群落(轻度和重度退化草原群落),设置氮素添加梯度实验(分别添加NH₄NO₃ 0, 30, 50, 80 g·m^-2),分析退化草原土壤有机质含量对氮素添加的响应,意图找出氮肥作用于不同退化程度草原时的最适值。结果表明,不同退化程度的草原对于氮素添加的响应不同:对于轻度退化草原,氮素添加对土壤有机质的影响主要集中在0~20 cm土层,30 g·m^-2处理时土壤有机质显著高于其他3个氮素水平,氮素的添加显著提高土壤有机质含量,说明氮素是轻度退化草原主要的限制因子;对于重度退化草原,当施氮量为30 g·m^-2时,0～10 cm层土壤有机质含量相对较高,但没有达到统计学上的显著差异。土壤有机质在氮素添加梯度下各层变化不显著,说明氮素不是重度退化草原的主要限制因子。

Response of The Soil Organic Matter Content to Nitrogen Addition Rate in Degraded Grasslands

In this study we selected two communities in different degree of degraded grasslands (lightly degraded grassland and heavily degraded grassland ) in Xilin Gol, Inner Mongolia. Then we set up nitrogen addition rate test (respectively adding NH₄NO₃ 0g/m², 30g/m², 50g/m², 80g/m²) to analyze the response of the soil organic matter content on the nitrogen adding gradient,and find the optimal values of nitrogen fertilizer applied at different degree of degraded grassland. The results showed that the response of the different degree of degraded grassland to nitrogen addition is different. For lightly degraded grassland, the response of nitrogen addition on soil organic matter is mainly concentrated in the 0-20cm layer, and nitrogen addition at a rate of 30g/m², soil organic matter was significantly higher than the other three nitrogen levels, nitrogen addition significantly increased soil organic matter content, which meant that nitrogen is the major limiting factor in lightly degraded grassland. For heavily degraded grassland, when nitrogen rate was 30g/m², 0-10cm layer of soil organic matter content is relatively high, but did not reach a statistically significant difference. Adding nitrogen gradient did not change soil organic matter content significantly, which meant that nitrogen is not the main limiting factor in heavily degraded grassland.