桉树-牧草复合经营模式下水土流失和土壤肥力的综合评价

本文通过连续5年监测桉树-牧草和桉树纯林地表径流量和土壤侵蚀量,以及种植前后土壤肥力指标,综合分析间种牧草对桉树林地水土流失和土壤肥力的影响,为桉树人工林科学经营提供理论依据。结果表明:桉树纯林地表径流量和土壤侵蚀量分别在27.4~6612 m~3 hm~(-2) a~(-1)和0~14.9 t hm~(-2) a~(-1)之间,表现出随着种植时间呈逐年减少的变化规律,且水土流失主要集中在前2年;桉树-牧草复合经营模式下林地地表径流量和土壤侵蚀量与桉树纯林随种植时间的变化规律一致,但均低于桉树纯林,降低幅度为20.84%~82.85%;与种植前比,桉树-牧草和桉树纯林土壤pH值分别提高了0.03~0.05和0.14~0.18,有机质、全氮、全磷、全钾、碱解氮、有效磷和速效钾均得到提高(土壤交换性钙和镁除外),增幅分别为0.13~3.00倍和0.39~2.11倍;土壤肥力的关联度从大到小的排列顺序为:桉树-牧草桉树纯林种植前;桉树-牧草和桉树纯林0~20 cm土层土壤肥力指标增幅和关联度均大于20~40 cm土层。可见,与桉树纯林比,间种牧草更有利于改善桉树林地土壤肥力,促进桉树林地可持续性经营,是一种较好的桉树林地复合经营模式。

Comprehensive Evaluation of Water and Soil Loss and Soil Fertility under the Eucalyptus-grass Compound Management Model

With an aim to give insights on Eucalyptus plantation management,this studyconducted a five-year monitoring on land surface runoff,soil erosion and soil fertility in a forest with two managements,i.e.,Eucalyptus-grass and Eucalyptus plantations and then comprehensively analyzed and investigatedthe impacts of Eucalyptus-grass plantation on water and soil erosion,as well as soil fertility.The analysis showed that the land surface runoff and soil erosion presented the same decreasing trend with time under the Eucalyptus plantation as under the Eucalyptus-grass plantation and were larger under the former than under the latter plantation.Under the Eucalyptus plantation,they ranged from 27.4 m3 hm-2 a-1 to 6612 m3 hm-2 a-1 and 0 t hm-2 a-1 to 14.9 t hm-2 a-1,respectively,and particularly water and soil erosion happened only in the first two years.Under the Eucalyptus-grass plantation,they decreased by 20.84％-82.85％ Eucalyptus-grass and Eucalyptus plantations increased soil pH by 0.03-0.05 and 0.14-0.18,respectively,and soil organic matter contents,total N,total P,total K,alkalytic N,available P and rapidly available K (except for exchangeable Ca and Mg) by 0.13-3.00 times and 0.39-2.11 times,respectively,when compared with the land beforetree-planting.The correlation degree of soil fertility decreased as follows:Eucalyptus-grass ＞ Eucalyptus ＞ land before tree-planting.The increases in soil nutrient contents and correlation degree between them under the two plantations were larger in 0-20 cm soil layer than in 20-40 cm soil layer.Therefore,the intercropping grass with Eucalyptus improved soil fertility and should be a better compound management for sustainable development of Eucalyptus plantation,compared with simple Eucalyptus plantation.