南亚热带桉树混交林土壤酶活性及其化学计量比特征OA

In response to declining productivity in Eucalyptus monoculture plantations,the 18-year-old pure E.urophylla plantations and Eucalyptus-native mixed plantations with native tree species proportions of 20%,30%,40%,and 50%in Heshan,Guangdong were investigated.By measuring the biomass and carbon(C),nitrogen(N),and phosphorus(P)contents of litter,as well as the pH,C,N,P contents,soluble C and N contents,and microbial C and N contents in the 0-10 and 10-20 cm soil layers,and the activities of β-D-glucosidase(BG),N-acetylgluco-saminidase(NAG),and acid phosphatase(AP),the relationship between soil enzyme activities and their stoichiometric ratios and the physical and chemical properties of litter and soil was explored.The results showed that with the increase of the proportion of native tree species,the activities of BG and NAG in the 10-20 cm soil layer first decreased and then increased,while the activities of AP in both the 0-10 and 10-20 cm soil layers first decreased and then increased.The C:P and N:P ratios of enzymes first increased and then decreased.The mixed plantations to some extent alleviated the carbon and nitrogen limitations of soil microorganisms,improved soil fertility,and promoted microbial activity.Correlation and redundancy analysis indicated that the soil enzyme activities and their stoichiometric ratios in the 0-10 cm soil layer were mainly related to the properties of litter,while in the 10-20 cm soil layer,they were mainly related to the physical and chemical properties of soil.This study clarified the pathways of mixed plantations in improving soil nutrient status,regulating soil enzyme activities,and their differential regulation in different soil layers,which has application value for guiding the transformation of low-efficiency Eucalyptus plantations and the management of mixed plantations.