三倍体毛白杨不同有机残体分解及氮磷释放特征

Mass Losses and Nitrogen and Phosphorous Dynamics during the Decomposition of Different Organic Residues of Triploid Populus tomentosa

采用网袋法研究三倍体毛白杨落叶、小枝（直径小于0.5 cm）、细根（直径小于2mm）和皮的分解速率以及N,P动态。结果表明：4种有机残体在357天中分解速率存在显著性差异,到试验结束时（2008年11月）细根的分解率最大（42.5%）,其次是落叶（30.5%）和皮（26.0%）,小枝的分解率最低（20.9%）;Olson指数方程对4种有机残体的分解拟合效果较好,相关系数R2为0.96～0.98,由此计算得到4种有机残体的年分解率分别为42.88%,31.74%,26.25%和20.54%;不同有机残体分解初期存在N,P元素富集现象,但富集程度与富集持续的时间存在差异,细根、叶、皮、小枝中N的富集度分别为11.6%,127.2%,122.6%和126.7%,P的富集度分别为105.9%,172.9%,123.0%和163.9%,因此N,P的富集度均以叶最高,以细根最低;从富集持续的时间来看,细根、叶、皮、小枝中的N富集持续时间分别为205,239,297和265天,以皮持续的时间最长,P富集持续的时间分别是205,205,265和239天,以小枝持续的时间最长;从不同有机残体释放的N,P量来看,细根释放量最多,其次是叶,皮和小枝释放量较少。三倍体毛白杨纸浆林中不同有机残体在养分归还上存在不同特点,尤其是皮和小枝分解率低,养分富集持续时间长,今后应采取针对性措施加快其分解,以不断提高林地生产力。

In order to understand the decomposition rate and nutrient dynamic of different organic residues of triploid Populus tomentoza,and to find out feasible ways for maintaining and improving long- term soil productivity,litterbag method was used to investigate the decomposition rate and macro nutrients（ N,P） release of leaf litter,fine branch litter（ ≤5 mm）,fine root litter（ ≤2 mm） and bark litter for 357 days. By the end of experiment,decomposition rates of fine root litter,leaf litter,bark litter and fine branch litter were 42. 5%,30. 5%,26. 0%,and 20. 9%,respectively and were significantly different（ P 0. 001） among different organic residues. The decomposition process of the 4 residues fitted well to Olson equation,with values of correlation efficient square ranging from 0. 96 and 0. 98. According to Olson equation,annual decomposition rates of different residues were significantly different,from 42. 88% for fine root litter, 31. 74% for leaf litter,26. 25% for bark litter,to 20. 54% for fine branch litter. Enrichment of N,P in remains was observed in the 4 residues,but the duration and amplitude of enrichment were different for different residues. Enrichment amplitude of N was 11. 6%,127. 2%,122. 6%,126. 7% and of P was 105. 9%,172. 9%,123. 0%,163. 9%, respectively for fine root litter,leaf litter,bark litter and fine branch litter. The duration of N enrichment was 205d, 239d,297d,265d,respectively for fine root litter,leaf litter,bark litter and fine branch litter. The duration of N enrichment for bark litter was the longest. The duration of P enrichment was 205d,205d,265d and 239d,respectively for fine root litter,leaf litter,bark litter and fine branch litter. The duration of P enrichment for fine branch litter was the longest. The maximum of N,P release was from fine root litter,secondly from leaf litter,the minimum from bark litter and fine branch litter. These results indicated that different residues had different characters in nutrient release and needed toemploy proper measures to promote decomposition and nutrient release,especially for bark litter and fine branch litter due to their lower decomposition rate and longer nutrient enrichment.