大气CO2浓度升高和氮添加对镉污染下两种树木叶片元素含量及回收率的影响

Effects of Elevated Atmospheric CO2 Concentration and Nitrogen Addition on Element Concentration and Resorption in Leaves of Two Tree Species Under Cadmium Pollution

摘要:

选择造林树种大叶相思(Acacia auriculiformis)和樟树(Cinnamomum camphora)为对象，采用开顶生长箱(open-top chamber, OTC)构建实验林，探讨镉(Cd)胁迫及其与大气CO₂浓度升高、氮(N)添加的复合作用对2种树木叶片N、P养分利用策略和Cd积累特征的影响。试验设5个处理：对照(CK)、加Cd [10 kg Cd/(hm²·a)] (Cd)、加Cd与加CO₂ (700 μmol/mol) (CdC)、加Cd与加N [100 kg N/(hm²·a)] (CdN)、加Cd加CO₂加N (CdCN)。处理约2.5 a后，测定两树种的成熟叶和衰老叶中N、磷(P)和Cd含量。结果表明，不同处理对两树种叶片P含量及P回收率均无显著影响，但显著影响叶片N含量及N回收率；CdN处理下两树种叶片N含量升高；Cd和CdN处理下樟树叶N回收率显著降低。Cd、CdC、CdN和CdCN处理下两树种叶片Cd积累浓度及樟树成熟叶中的Cd/N和Cd/P升高。大叶相思叶片N、P回收率显著高于樟树，Cd积累浓度显著低于樟树。速生豆科固氮树种大叶相思比普通非固氮树种樟树具有更好的N、P养分利用策略和抵御叶片积累Cd的能力，表明大叶相思可以作为Cd污染林地土壤生态修复的适宜树种。

Abstract:

In order to investigate the effects of cadmium (Cd) pollution and its combinations with elevated atmospheric CO₂ concentration and nitrogen (N) addition on N and phosphorus (P) utilization strategies and Cd accumulation in leaves, two afforestation tree species (Acacia auriculiformis and Cinnamomum camphora) were selected, and the open-top chambers (OTCs) was used to construct the simulated experimental forests of the two tree species. The five treatments were control (CK), adding Cd [10 kg Cd/(hm²·a)] (Cd), adding Cd and CO₂ (700 μmol/mol) (CdC), adding Cd and N [100 kg N/(hm²·a)] (CdN), adding Cd, CO₂ and N (CdCN). After treatment for about 2.5 years, the mature and senescent leaves of two tree species were collected to measure the concentrations of N, P and Cd. The results showed that the foliar P concentration and P resorption efficiency had no significant changes under different treatments, but the N concentration and N resorption efficiency in leaves were significantly affected. The N concentration in leaves of two species increased under CdN treatment, and the N resorption efficiency in C. camphora leaves decreased significantly under Cd and CdN treatments. Under the treatments of Cd, CdC, CdN and CdCN, the Cd accumulation in leaves of two species, as well as the Cd/N and Cd/P ratios in mature leaves of C. camphora increased. The N and P resorption efficiencies were significantly higher, while the Cd accumulation was significantly lower in A. auriculiformis than those in C. camphora. It was demonstrated that the fast-growing leguminous N-fixing tree species (A. auriculiformis) had better N and P utilization strategies and stronger resistance to Cd accumulation than the common non-N-fixing tree species (C. camphora), suggesting that A. auriculiformis could be suitable for ecological restoration in Cd polluted forest sites.