喀斯特峰丛洼地退耕还林还草的土壤生态效应

Soil ecological effects of converting cropland to forest and grassland in depressions between karst hills

摘要:

石漠化生态重建的关键是恢复植被，本质是提高土地生产力。本文以典型喀斯特峰丛洼地的坡耕地为对照，对退耕种植任豆、香椿、板栗、柑橘、任豆+桂牧1号、桂牧1号和撂荒7种主要模式固定标准地的21个土壤指标进行调查分析，探讨了退耕还林还草的土壤综合生态效应，筛选了优化模式。结果表明，与同纬度地区的红壤相比，喀斯特峰丛洼地的土壤质量除全钾和速效磷含量稍低外均较高；退耕还林还草显著或极显著提高了大部分土壤主要养分、水分和矿质养分含量，降低了SiO₂含量，除任豆模式外均恢复到了石漠化以下水平，同时提高了土壤微生物种群数量、B_C、B_C/SOM和B_C/TN，但B_N和B_N/TN略有降低；聚类分析直观地将坡耕地和7种模式分为土壤显著改良型、改良型、缓慢改良型和改良迟滞型4种类型，其中香椿和板栗的土壤生态效应最好。

Abstract:

The key to ecological restoration of rocky desertification is to recover vegetation, of which the nature is to improve soil productivity. With a tract of farmland on the slope of depression in between typical karst hills as control, integrated ecological effect of the practice of “Grain for Green” was analyzed by determining 21 soil indexes of seven models of “Grain for Green”, i.e. converting farmland to land of Zenia insignis, Toona sinensis, Castanea mollissima, Citrus reticulata, Zenia insignis + Guimu No. 1 Forage, Guimu No. 1 Forage, or desertion for comparison with those of the control. On such a basis, an optimal model was screened out. Results show that in comparison with red soil in regions at the latitude, the soil in karst depression was higher in soil nutrient except for total potassium and available phosphorus. The practice of “Grain for Green” significantly increased most of the soil main nutrients, soil water content, and mineral nutrients, but reduced the content of SiO₂, indicating that all the seven models, except for cultivation of Zenia insignis, had their nutrient status restored up to the pre-rocky desertification level. Besides, the practice also increased microbial population, B_C, B_C/SOM, and B_C/TN, but decreased slightly B_N and B_N/TN. Clustering analysis intuitively divided the slope field and 7 conversion models into 4 types, i.e. remarkable improvement, improvement, slow improvement, and sluggish improvement, and the models of cultivation of Toona sinensis and Castanea mollissima are best in soil ecological effects.