高原山地石漠化过程中土壤团聚体稳定性及其化学计量特征

Soil aggregate stability and its stoichiometric characteristics in process of rocky desertification in plateau mountains

石漠化演替过程中不同石漠化等级土壤团聚体稳定性及其碳、氮、磷化学计量特征是评价石漠化地区土壤恢复效应的有效途径。该文以五个不同石漠化等级的样地为研究对象,利用湿筛法分析0~20 cm土层土壤不同粒级团聚体分布状况、稳定性水平和化学计量特征。结果表明:(1)相较而言,无石漠化样地中>2 mm和0.25~2 mm两级水稳性团聚体含量最高,其平均直径(MWD、GMD)最大,而可蚀性K值最低。(2)不同石漠化环境中团聚体有机碳、全氮和全磷的变化范围是20.78~56.28 g·kg-1、1.17~2.14 g·kg-1和0.41~0.97 g·kg-1,无石漠化样地各级团聚体有机碳、全氮含量较高,全磷含量在五种环境中变化规律不明显;团聚体C/N、C/P和N/P的变化范围分别是11.50~28.60、25.19~121.75和1.65~4.69,无石漠化样地团聚体C/N、C/P和N/P均明显高于潜在、轻度、中度和强度,较小粒径C/N较高,而C/P和N/P较高为>2 mm和0.25~2 mm两粒径。(3)团聚体中有机碳分别与其C/N、C/P呈极显著正相关,而全磷含量则与C/P、N/P两者呈极显著负相关(P<0.01),团聚体C/N、C/P和N/P变异水平表现为C/P>C/N>N/P。该地从无石漠化到强度石漠化演替过程中土壤团聚体稳定性和各粒径团聚体中有机碳和全氮含量均呈现先下降后上升的趋势,无石漠化土壤结构较好,团聚体中氮元素成为影响该退化生态系统中土壤质量的主要限制性元素。

Soil aggregate stability and its stoichiometric characteristics are the effective ways to evaluate the effect of soil restoration in rocky desertification areas.Five plots with different rocky desertification grades were set up.Indicators including the content,stoichiometry,and stability of different aggregate fractions were analyzed by wetting.The results were as follows:(1)In comparsion,the contents of water stable aggregates>2 mm and 0.25-2 mm were the highest in the nil rocky desertification plots,and their average diameters(MWD and GMD)were the largest,but the K value of erodibility was the lowest.(2)The soil organic carbon,total nitrogen,and total phosphorus contents in the five sample plots were 20.78-56.28 g·kg-1,1.17-2.14 g·kg-1 and 0.41-0.97 g·kg-1,respectively.The composition of organic carbon and total nitrogen in aggregates of the nil rocky desertification sample plot were the highest,and the variation of total phosphorus content were not obvious in the five environments.The ranges of C/N,C/P and N/P of five environmental aggregates were 11.50-28.60,25.19-121.75 and 1.65-4.69,respectively.The C/N,C/P and N/P of the aggregate in the nil rocky desertification sample plot were significantly highest.Averaged C/N values in the small-size aggregates were higher than in aggregates of other sizes,while the maximum values C/P and N/P were>2mm and 0.25-2 mm.(3)There was a significant positive correlation between organic carbon and C/N,C/P,and a significant negative correlation between total phosphorus and C/P,N/P(P<0.01).The overall trend of the variation level of soil aggregate stoichiometry was C/P>C/N>N/P.The stability and the contents of organic carbon and total nitrogen in aggregates with different particle sizes decreased firstly and increased from nil rocky desertification to severe rocky desertification in the study area.The soil structure of nil rocky desertification is good;what is more,nitrogen in the aggregate is the major factor affecting the soil quality in the degraded ecosystem.