Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China.
The Joint Center for Global Change Studies, Beijing 100875, China.
Sci Rep. 2017 Jan 9;7:40383. doi: 10.1038/srep40383.
Bamboo (Phyllostachys pubescens) expansion into adjacent forests is a widespread phenomenon in subtropical regions, and it has greatly changed the dominance hierarchy from trees to bamboos. This process may be accompanied by changes in productivity, nutrients accumulation and biogeochemical cycles. We compared the net primary production (NPP) and major pools and fluxes of nitrogen (N) in bamboo-dominant forest (BDF) and neighboring secondary evergreen broadleaved forest (EBF) in South China using the space-for-time substitution method. We found that the mean NPP of the BDF was 30.0 t ha yr, which was 51.5% greater than that of the EBF (19.8 t ha yr). The plant N pool for the BDF was 37.5% larger than that of the EBF, whereas the soil inorganic N pool significantly decreased by 31.2% with conversion of the EBF to BDF. Additionally, the ratio of N return to N uptake was 0.69 in the BDF and 0.88 in the EBF because of the lower litter N return of the BDF compared with that of the EBF. These results indicated that the expansion of P. pubescens significantly increased the NPP and plant N accumulation but reduced the soil N available pool and slowed the N cycling rate, which could lead to soil degradation.
毛竹（Phyllostachys pubescens）向相邻森林扩张是亚热带地区广泛存在的现象，它极大地改变了从树木到竹子的优势层次结构。这一过程可能伴随着生产力、养分积累和生物地球化学循环的变化。我们采用时空替代法比较了中国南方毛竹占主导地位的森林（BDF）和相邻的次生常绿阔叶林（EBF）的净初级生产力（NPP）和氮（N）的主要库和通量。我们发现，BDF 的平均 NPP 为 30.0 t ha yr，比 EBF（19.8 t ha yr）高 51.5%。BDF 的植物 N 库比 EBF 大 37.5%，而 EBF 转化为 BDF 后，土壤无机 N 库显著减少了 31.2%。此外，由于 BDF 的凋落物 N 归还率低于 EBF，BDF 的 N 归还与 N 吸收的比值为 0.69，而 EBF 的比值为 0.88。这些结果表明，毛竹的扩张显著增加了 NPP 和植物 N 积累，但减少了土壤有效 N 库，减缓了 N 循环速率，这可能导致土壤退化。
