中亚热带典型人工林常见乔灌木根际效应——以江西泰和千烟洲为例

Rhizosphere effects of overstory tree and understory shrub species in central subtropical plantations——A case study at Qianyanzhou, Taihe, Jiangxi, China

为了深入探讨人工林内不同植物根际效应的差异,为人工林生态系统林下植被管理提供理论依据,该研究以江西泰和千烟洲站区杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)和湿地松(Pinus elliottii)3种人工林(1985年前后营造)为研究对象,测定林内乔木及其林下常见灌木檵木(Loropetalum chinense)、杨桐(Adinandra millettii)和格药柃(Eurya muricata)的根际和全土土壤碳、氮、磷含量及pH值,比较不同林分类型下优势乔灌树种的根际效应。结果发现:(1)乔木根际土壤大部分化学性质指标显著高于或低于全土(p<0.05),而林下灌木根际土壤与全土土壤化学性质的差异与物种有关,如檵木根际土壤大部分化学性质显著不同于全土,而格药柃根际土壤大部分指标与全土无显著差异。(2)除硝态氮(NO_3~–-N)外,林下灌木不同物种之间的根际效应有别,具体表现为檵木pH值、铵态氮(NH_4^+-N)、可溶性有机碳(DOC)、全氮(TN)、全碳(TC)、碳氮比(C/N)、有效磷(AP)和全磷(TP)的根际效应显著高于格药柃,TN、TC、C/N和AP的根际效应也显著高于杨桐,但杨桐与格药柃间的根际效应无显著差异。(3)杉木的根际效应显著强于林下3种灌木;马尾松和湿地松的根际效应与檵木无显著差异,而马尾松的根际效应显著高于杨桐和格药柃,湿地松的根际效应显著高于格药柃。该研究表明相对于林下灌木(尤其是格药柃),乔木具有较强的根际效应,暗示了乔木具有更高的养分捕获能力。但林下灌木与乔木根际效应的差异与灌木种类和林分类型有关。因此,人工林林下植被管理除了考虑适量保留林下灌木外,可依据人工林类型,充分考虑灌木种类选择,进而最大地发挥人工林生态系统的生产和生态功能。

Aims The objective was to explore the differences in rhizosphere effect among different plants in plantation and provide important theoretical basis for understory vegetation management in plantation ecosystem. Methods We collected bulk and rhizosphere soils of overstory trees and understory shrubs（Loropetalum chinense, Adinandra millettii and Eurya muricata） in Cunninghamia lanceolata, Pinus massoniana and Pinus elliottii plantations which were planted in about 1985, at Qianyanzhou Ecological Research Station, Taihe, Jiangxi, to investigate soil pH value, soil nitrogen, carbon and phosphorus content and to access their rhizosphere effects. Important findings（1） Most of the chemical properties of rhizosphere soil and bulk soil were significantly different for overstory tree species（p〈 0.05）, while the differences between bulk soil and rhizosphere soil of understory shrubs were related to understory shrub species. For example, most of the properties were significantly different between bulk and rhizosphere soils for L. chinense, but not for E. muricata.（2） Rhizosphere effects among shrub species were significantly different except for those of nitrate nitrogen（NO3^–N）. Specifically, the rhizosphere effects of pH, ammonium nitrogen（NH4^＋-N）, dissolved organic carbon（DOC）, total nitrogen（TN）, total carbon（TC）, carbon-nitrogen ratio（C/N）, available phosphorus（AP） and total phosphorus（TP） of L. chinense were significantly higher than those of E. muricata. And the rhizosphere effects of TN, TC, C/N and AP of L. chinense were significantly higher than those of A. millettii. No significant differences were found between the rhizosphere effects of A. millettii and those of E. muricata.（3） The rhizosphere effects of C. lanceolata were significantly higher than those of the three understory shrubs. But no significant difference was found between P. massoniana or P. elliottii and L. chinense. While the rhizosphere effects of P. massoniana were significantly higher than those of A. millettii and E. Muricata, and the rhizosphere effects of P. elliottii were significantly higher than those of E. muricata. The results showed that the rhizosphere effects of overstory tree species were higher than those of understory shrubs（especially for E. muricata）, indicating overstory tree species have stronger ability to obtain nutrients. But the differences in rhizoshpere effects between overstory trees and understory shrubs varied between shrub species and forest types. Therefore, this study suggested that understory shrub species should be considered according to forest stand type in plantation management in order to provide higher productive and ecological value.