Ecophysiological and foliar nitrogen concentration responses of understorey Acacia spp. and Eucalyptus sp. to prescribed burning

Ma, Ling; Rao, Xingquan; Lu, Ping; Bai, Shahla Hosseini; Xu, Zhihong; Chen, Xiaoyang; Blumfield, Timothy; Xie, Jun

Ecophysiological and foliar nitrogen concentration responses of understorey Acacia spp. and Eucalyptus sp. to prescribed burning

2015

Eucalyptus spp. is a dominant tree genus in Australia and most Eucalyptus spp. are canopy dominant species. In Australian natural forests, Eucalyptus spp. commonly are associated with understorey legumes which play a crucial role for ecological restoration owing to their nitrogen (N) fixing ability for replenishing the soil N lost after frequent prescribed burning. This study aimed to explore to what extent physiological responses of these species differ 7 and 12 years after last fire. Two most common understorey Acacia spp., Acacia leiocalyx and A. disparrima, as well as one non-leguminous Eucalyptus resinifera, were studied due to their dominance in the forest. Both A. leiocalyx and A. disparrima showed higher carbon (C) assimilation capacity, maximum photosynthetic capacity, and moderate foliar C/N ratio compared with E. resinifera. A. leiocalyx showed various advantages compared to A. disparrima such as higher photosynthetic capacity, adaptation to wider light range and higher foliar total N (TNₘₐₛₛ₎. A. leiocalyx also relied on N₂-fixing ability for longer time compared to A. disparrima. The results suggested that the two Acacia spp. were more beneficial to C and N cycles for the post burning ecosystem than the non-N₂-fixing species E. resinifera. A. leiocalyx had greater contribution to complementing soil N cycle long after burning compared to A. disparrima.

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