华南典型尾叶桉纯林经营对土壤理化性质、微生物和线虫群落的影响

桉树是我国华南地区的重要速生营林树种，具备极高的经济价值，然而我国桉树人工林的发展还存在巨大争议，桉树营林的生态环境效应还有待进一步考究。针对我国华南地区典型尾叶桉(Eucalyptus urophylla)纯林经营的潜在生态问题，选取广东鹤山森林生态系统国家野外研究站的10树种混交林(10 species mixed forest plantation, 10S)、30树种混交林(30 species mixed forest plantation, 30S)和桉树纯林(Eucalyptus monoculture, E)三种林型，另外设置桉树砍伐(Eucalyptus cutting, EC)和桉树砍伐清除林下灌草(Eucalyptus cutting and understory removal, ECUr)这两种常见经营措施的处理，通过比较不同林型和管理措施下土壤理化性质和生物指标的差异，解析了桉树营林对土壤理化特性、土壤微生物以及线虫群落的影响。本结果表明：三种林型间的土壤理化特性没有显著差异，但桉树纯林的土壤真菌生物量、真菌细菌比、食细菌线虫多度显著高于10和30树种混交林...

Effects of Eucalyptus plantations and management on soil physico-chemical properties, microbial and nematode communities in South China

Eucalyptus is one of the world''s most widely planted tropical and sub-tropical fast-growing hardwoods, which has extremely high economic value. Plantations of eucalyptus have been extensively established in South China during the past decades. However, there is an ongoing debate concerning the environmental effects and the development of eucalyptus plantations in South China. The ecological/environmental effects of eucalyptus plantations need to be further studied. This study contraposed the potentially ecological problems of typical eucalyptus in South China, selected three types of plantations including 10 species mixed plantation (10S), 30 species mixed plantation (30S), and eucalyptus monoculture (E), and established two treatments of eucalyptus cutting (EC) and eucalyptus cutting with understory removal (ECUr) in the eucalyptus monocultures. The influences of eucalyptus management on soil physical and chemical characteristics, soil microorganisms and nematode communities were analyzed by comparing the differences in soil physical and chemical properties and biological indicators under different forest types and management measures. The results showed that there was no significant difference in soil physico-chemical properties among the three plantation types. However, the soil fungal biomass, the ratio of fungal biomass to bacterial biomass, and the bacterivorous nematode abundance of the eucalyptus monoculture were significantly higher than those of the 10 and 30 species mixed plantations. Besides, the nematode diversity and fungivorous nematode abundance of the eucalyptus monoculture were apparently higher than those of 10 species mixed plantation. Under different eucalyptus forest management measures, the eucalyptus cutting treatment did not significantly affect the soil physico-chemical and biological properties. But the eucalyptus cutting with understory removal treatment remarkably reduced the soil water content, the ratio of fungal biomass to bacterial biomass, the abundances of total nematodes, bacterivorous nematodes, fungivorous nematodes and omnivorous-carnivorous nematodes. The results indicated that the eucalyptus monoculture had generally better soil physico-chemical and biological characteristics than the mixed plantations of native species at the same age. In other words, the soil quality of the eucalyptus plantation was not lower than the mixed plantations. Our results also indicated that eucalyptus cutting decreased the soil quality, particularly when the understory was removed. Overall, the eucalyptus plantations could be beneficial to the environment when used as a measure of ecosystem restoration. As an economic tree species, however, unreasonable management practices of eucalyptus plantations may induce severe soil degradation, such as soil erosion, nutrient depletion, biodiversity loss, and production decline. Therefore, the trade-off between ecological and economic benefits of the eucalyptus plantations may need to focus on forest management measures in the future.