桉树取代马尾松对土壤养分和酶活性的影响

桉树取代马尾松造林是我国南方典型土地利用变化类型之一,为了探讨该土地利用变化对土壤质量的影响,采用成对设计方法,研究了我国广西桉树取代马尾松造林对土壤养分、微生物生物量和酶活性的影响。结果表明:桉树取代马尾松造林后,土壤全碳、易分解碳库、中等易分解碳库、难分解碳库、全氮和碱解氮含量显著降低,但速效磷显著增加,这可能是由于桉树林施肥和磷素在土壤中移动性弱导致;土壤微生物生物量碳、氮、酚氧化酶、过氧化物酶、蛋白酶、脲酶和酸性磷酸酶活性显著降低。树种变化、桉树林轮伐期短、林下植被差、炼山、翻耕等可能是土壤养分、微生物和酶活性降低的驱动因子;施肥有助于缓解土壤养分降低。在林地转变和经营时,适当保持林下植被和凋落物、减少土壤扰动和合理施肥将有助于改善土壤质量,实现桉树林的可持续经营。

Impacts of replacement of pinus with eucalyptus on soil nutrients and enzyme activities

Converting Pinus to Eucalyptus plantations is a typical land use change in Southern China. In order to find the effects of converting Pinus to Eucalyptus plantations on soil ecosystem conditions, soil nutrients, microbial biomass and enzyme activities were studied in 9 pairs of Eucalyptus urophylla × grandis and Pinus massoniana plantations in Guangxi, China. The results showed that, after converting Pinus to Eucalyptus plantations, soil carbon, nitrogen and their availability significantly decreased, but available phosphorus significantly increased; soil microbial biomass significantly decreased; soil cellobiosidase, phenol oxidase, peroxidase, protease, urease and acid phosphatase activities significantly decreased. The tree species change, short rotation, poor understory coverage and litter layer, fire and tillage might be the factors of decreased soil nutrients, microbial biomass and enzyme activities during converting Pinus to Eucalyptus plantations. Fertilization might alleviate soil nutrients decrease. Keeping proper understory coverage and litter layer, reducing soil disturbance and fertilization should be considered to improve soil ecosystem condition during converting Pinus to Eucalyptus plantations and the plantation management.