云南干热河谷印楝和大叶相思人工纯林与混交林养分循环特征

为了更好地指导干热河谷不同恢复模式下人工林经营过程中的养分管理以及造林模式的筛选，以元谋干热河谷10年生印楝和大叶相思为研究对象，对其纯林及混交林内N、P、K、Ca、Mg主要养分元素的积累、分配和循环进行研究.结果表明： 印楝纯林、大叶相思纯林及印楝+大叶相思混交林5种营养元素的总积累量分别为333.05、725.61和533.85 kg·hm^-2，印楝纯林各器官养分积累量为枝＞干＞根＞叶＞皮，大叶相思纯林与混交林均为枝＞干＞叶＞根＞皮.印楝纯林内5种养分元素的积累量为Ca＞K＞N＞Mg＞P，大叶相思纯林与混交林一致，均为Ca＞N＞K＞Mg＞P.林分养分年存留量为62.72～162.19 kg·hm^-2·a^-1，总归还量为48.82～88.86 kg·hm^-2·a^-1，年吸收量为111.54～251.05 kg·hm^-2·a^-1，均以大叶相思纯林最高，其次是混交林，印楝纯林最低.林分对营养元素的利用系数为0.34～0.39，循环系数为0.35～0.44，周转期为6.54～8.17 a.印楝纯林内N和P的归还量小，循环速率低；大叶相思纯林内N和P的循环速率较大，有利于林地养分的维持；混交林内养分吸收量和归还量为印楝纯林的186.2%和167.2%，N、P和K的循环速率大于印楝纯林，Ca的周转期短于大叶相思纯林的50%.印楝和大叶相思混交种植有利于林地土壤肥力的恢复和生产力的维持.

Nutrient accumulation and cycling in pure and mixed plantations of Azadirachta indica and Acacia auriculiformis in a dry hot valley,Yunnan Province,southwest China.

To ease the implementation of effective nutrient management for plantations with different vegetation restoration patterns and to assist in the selection of appropriate species and forestation patterns, nutrient (N, P, K, Ca and Mg) accumulation and cycling were investigated and compared in three plantations (10-year-old Azadirachta indica, Acacia auriculiformis and mixed A. indica-A. auriculiformis plantations) in Yuanmou Valley, a dry-hot valley of Yunnan Province, Southwestern China. The result showed that total nutrient accumulations were 333.05, 725.61 and 533.85 kg·hm^-2 in pure plantations of A. indica and A. auriculiformis, and in A. indica-A. auriculiformis mixed plantation, respectively. The nutrient accumulation of various organs was ranked as branches > stems > roots > leaves > bark in the A. indica plantation and branches > stems > leaves > roots > bark both in the A. auriculiformis plantation and in the mixed plantation. Changes in accumulation of various nutrients in the mixed plantation were similar to that in the A. auriculiformis plantation (Ca > N > K > Mg > P), which were different from the A. indica plantation (Ca > K > N > Mg > P). Annual net nutrient accumulation, return and absorption in these plantations ranged from 62.72 to 162.19 kg·hm^-2·a^-1, 48.82 to 88.86 kg·hm^-2·a^-1 and 111.54 to 251.05 kg·hm^-2·a^-1, respectively, which were all the highest in the A. auriculiformis plantation, followed by the mixed plantation, and were the lowest in the A. indica plantation. The nutrient utilization coefficient, the cycling coefficient and the recycling period were estimated to be from 0.34 to 0.39, 0.35 to 0.44, and 6.54 to 8.17 a, respectively. The lower nutrient return and circulation rate of N or P in the A. indica plantation showed that this plantation had a poor ability to maintain soil fertility, while the highest nutrient circulation rate of N or P was observed in the A. auriculiformis plantation that displayed the advantage in maintaining soil nutrients and stand productivity. The nutrient return and nutrient absorption in the mixed plantation were 167.2% and 186.2%, of those in the A. indica plantation, and the circulation rate of N, P and K were higher than those in the A. indica plantation, while the recycling period of Ca in mixed plantation was 50% shorter than that in A. auriculiformis plantation. Soil fertility and nutrient supply were improved in the A. indica and A. auriculiformis mixed plantation.