石漠化山地植被恢复过程土壤团聚体氮分布及与氮素矿化关系研究

为阐明岩溶石漠化区植被恢复对土壤氮素积累与供应的影响,分析了土壤各级团聚体不同形态氮库分配特征以及团聚体氮库与土壤氮素矿化之间的关系.结果表明:1各样地土壤团聚体全氮、轻组氮、碱解氮、矿质氮含量基本上随团聚体粒径减小而升高,峰值出现在0.25 mm粒径.除矿质氮外,各种氮形态在不同样地之间,总体上表现为弃耕地草地灌丛地灌乔林地乔木林地、人工金银花地人工林地.2各粒径团聚体有机氮库容量受团聚体粒径质量分数控制,其中5~10mm、2~5 mm粒径团聚体有机氮库容量较大,土壤氮主要贮存于大团聚体中,大团聚体对土壤碳、氮的贮存有重要意义.3团聚体全氮贮量中,0.25~1 mm、5~10 mm、2~5 mm粒径对土壤净氮矿化量贡献大,其它粒径贡献较小.随植被恢复进程,土壤中5 mm粒径团聚体质量分数逐渐提高,大团聚体氮贮量相应提高,在增强土壤供氮能力的同时,加强了对有机氮的贮存与保护.

Nitrogen Fraction Distributions and Impacts on Soil Nitrogen Mineralization in Different Vegetation Restorations of Karst Rocky Desertification

In order to illuminate the impact on soil nitrogen accumulation and supply in karst rocky desertification area, the distribution characteristics of soil nitrogen pool for each class of soil aggregates and the relationship between aggregates nitrogen pool and soil nitrogen mineralization were analyzed in this study. The results showed that the content of total nitrogen, light fraction nitrogen, available nitrogen and mineral nitrogen in soil aggregates had an increasing tendency along with the descending of aggregate-size, and the highest content was occurred in <0.25 mm. The content of nitrogen fractions for all aggregate-classes followed in the order of abandoned land< grass land< brush land< brush-arbor land< arbor land in different sample plots. Artificial forest lands had more effects on the improvement of the soil nitrogen than honeysuckle land. In this study it also showed the nitrogen stockpiling quantity of each aggregate-size class was differed in all aggregate-size classes, in which the content of nitrogen fraction in 5-10 mm and 2-5 mm classes of soil aggregate-size were the highest. And it meant that soil nutrient mainly was stored in large size aggregates. Large size aggregates were significant to the storage of soil nutrient. For each class of soil aggregate-size, the contribution of the nitrogen stockpiling quantity of 0.25-1 mm class to soil net nitrogen mineralization quantity was the biggest, and following>5mm and 2-5 mm classes, and the others were the smallest. With the positive vegetation succession, the weight percentage of>5 mm aggregate-size classes was improved and the nitrogen storage of macro-aggregates also was increased. Accordingly, the capacity of soil supply mineral nitrogen and storage organic nitrogen were intensified.