喀斯特地区不同年限退耕草地的持水性能

Water-holding Capacity of Reclaimed Grassland with Different Ages in Karst Regions

[目的]研究不同年限退耕草地持水性能,为喀斯特地区退耕草地持水性能和水土保持提供科学依据。[方法]选取贵州省安顺市喀斯特地区不同年限退耕草地(5,10,15,20 a)和耕地(对照CK)为研究对象,采用“时空替代法”研究凋落物蓄积量、持水量和拦蓄量以及土壤剖面容重、孔隙度、颗粒组成、含水率及持水量随退耕年限的变化特征。[结果](1)凋落物层蓄积量、最大持水量、最大拦蓄量和有效拦蓄量均表现为:15 a>20 a>10 a>5 a,且凋落物层持水量、吸水速率与浸水时间的关系分别符合对数函数和幂函数。(2)退耕草地砂粒含量和容重随着退耕年限的延长均呈现出先下降再上升的趋势;粉粒、黏粒、总孔隙度、毛管孔隙度、最大持水量和毛管持水量的变化规律与土壤容重相反。(3)凋落物层和土壤层的持水总量表现为:10 a>20 a>15 a>5 a>CK,其中土壤层最大持水量贡献率达到99%以上。[结论]退耕草地不仅增加了凋落物层的生物积累、拦截降雨作用和持水性能,还在改善土壤结构和孔隙状况的同时,提高了土壤持水性能。退耕草地均在退耕10 a以后逐渐趋于稳定。因此,建议在退耕10 a以后种植落叶树种。

[Objective]The water-holding capacity of reclaimed grassland of different ages was studied in order to provide a scientific basis for water retention and soil and water conservation of reclaimed grassland in karst regions.[Methods]Reclaimed grassland of different ages(5,10,15,20 yr)and cultivated land(CK)in a karst area in Anshui City,Guizhou Province was selected as the research objects,and the“space-time substitution method”was used to study litter storage,water-holding capacity,and water storage capacity.The change characteristics of soil profile bulk density,porosity,particle composition,water content,and water-holding capacity were determined for different ages of reclaimed grassland.[Results]①The litter-layer storage capacity,maximum water-holding capacity,maximum storage capacity,and effective storage capacity followed the reclaimed grassland age order of 15 yr>20 yr>10 yr>5 yr.The relationships of litter-layer water-holding capacity and water absorption rate with soaking time were characterized by a logarithmic function and a power function,respectively.②The sand content and bulk density of the reclaimed grassland showed a trend of first decreasing and then increasing as age of reclaimed grassland increased.Changes in silt,clay,total porosity,capillary porosity,maximum water-holding capacity,and capillary water-holding capacity were opposite to the changes in soil bulk density.③The total water-holding capacity of the litter layer and the soil layer followed the order of 10 yr>20 yr>15 yr>5 yr>CK.The maximum water-holding contribution rate of the soil layer was more than 99%.[Conclusion]Reclaimed grassland of different ages not only increased the bioaccumulation,rainfall interception,and water-holding capacity of the litter layer,but also improved soil structure and pore status.The soil water-holding capacity gradually stabilized after 10 years.Therefore,it is recommended that planting deciduous trees after 10 years of farmland conversion to grassland.