不同氮源对三倍体毛白杨落叶分解的影响
Influence of exogenous N resource on triploid Populus tomentosa leaf decomposition
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摘要: 为探索加快毛白杨落叶分解的途径, 采取室内培养的方法研究了添加铵态氮、硝态氮及混合氮对三倍体毛白杨落叶分解速度和主要营养元素释放的影响。结果表明, 添加氮源对三倍体毛白杨落叶分解有一定的促进作用, 不同氮源之间差异显著。140 d后, 施加铵态氮、混合氮和硝态氮的落叶分解率分别为46.0%、30.0%和28.8%, 而对照为27.4%, 处理间差异显著; Olson指数方程拟合结果表明，施加铵态氮、混合氮和硝态氮后落叶分解50%和95%所需时间分别为175 d、316 d、301 d和781 d、1 238 d、1 627 d，比对照分别缩短49.7%、9.2%、13.5%和52.0%、23.9%、14.1%。同时, 添加氮源后对落叶中N、P、K元素的释放影响有所不同, 其中对K元素的释放基本没有产生影响, 随着分解的进行, 不同处理落叶中K元素浓度逐渐降低。但添加氮源对N、P元素的释放产生了显著影响, 与对照相比, 添加氮源缩短了N、P释放的富集时间, 降低了富集的幅度；N、P的富集时间均从对照的21 d缩短到处理的7 d; N的富集幅度从对照为初始浓度的1.94倍降低到处理为初始浓度的1.32~1.56倍, P的富集幅度从对照为初始浓度的2.98倍降低到处理为初始浓度的1.70~2.26倍。因此添加氮源加快了落叶的分解速度，促进了落叶中N、P的释放, 有利于加快养分循环, 提高立地生产力。Abstract: Litter decomposition is important for nutrient cycle in terrestrial ecosystems. Released nutrients by litter decomposition are critical for particularly fast-growing and high-yield pulp forests. Delays in on-site nutrient release could limit forest productivity. It is therefore vital to accelerate the decomposition of leaf litter for the rapid release of needed nutrients in forest plantations. To determine ways of rapid litter decomposition and nutrient release, the effects of exogenous ammonium nitrogen, nitrate nitrogen and mixed nitrogen on triploid P. tomentosa leaf decomposition were determined in a laboratory study. The results showed significant differences in the rates of decomposition of triploid P. tomentosa leaf under the different nitrogen resources. Leaf decomposition significantly accelerated under exogenous ammonium nitrogen. Compared with the control (27.4%), leaf decomposed rates under exogenous ammonium nitrogen, mixed nitrogen and nitrate nitrogen resources were 46.0%, 30.0% and 28.8%, respectively, after 140 d decomposition. The fitting results with Olson exponential equation showed that the times for 50% and 95% leaf decomposition under exogenous ammonium nitrogen, mixed nitrogen and nitrate nitrogen resources were 175 d, 316 d, 301 d and 781 d, 1 238 d, 1 627 d, which were shortened by 49.7%, 9.2%, 13.5% and 52.0%, 23.9%, 14.1%, compared with the control, respectively. There remarkable differences in released main nutrients of litter decomposition under exogenous ammonium nitrogen, mixed nitrogen and nitrate nitrogen resources. K content decreased with increasing degree of decomposition, and was not influenced by exogenous nitrogen resource. However, N and P release was influenced by exogenous nitrogen resource. While the accumulation time of N and P shortened from 21 to 7 days, the degree of N accumulation dropped from 1.94 (under the control) to 1.44 (under exogenous nitrogen) times of initial N concentration. The degree of P accumulation also dropped from 2.98 (under the control) to 1.98 (under exogenous nitrogen) times of initial exogenous P concentration. This suggested that exogenous nitrogen improved on-site productivity via accelerated leaf litter decomposition and N, P release, which in turn shortened the decomposition cycle of triploid P. tomentosa leaf litter.
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