刚果桉人工林营养元素生物循环研究

Biological Cycling of Nutrients in Eucalyptus ABL12W5 Plantation Ecosystem

对刚果12号桉无性系W5人工林营养元素积累、分布和生物循环进行了研究。结果表明,刚果桉W5不同组分的营养元素含量存在差异。树叶的主要营养元素N、P、K、Ca、Mg含量均较高,树皮的Ca、K含量较高,树干主要营养元素的含量均较低;刚果桉W5人工林主要营养元素年净积累量随林龄增长而增加,2年生的主要营养元素净积累量的增幅最大;刚果桉W5人工林的N、K或Ca的年吸收量与总存留量较高,Mg次之,P最小。植后第5年,Ca的吸收与存留增加明显;刚果桉W5人工林归还林地的主要营养元素比例很低,2～5年生林木以凋落物形式归还的营养元素在12%～15%,其中N、Mg的归还率在20%以上,Ca的在8%～14%,P的在6 5%～9%,K的不足5%。与热带半落叶季雨林比较,刚果桉W5人工林的养分循环率要小得多,说明这一人工林土壤养分趋向于减少。

The accumulation, distribution and biological cycling of nutrients in eucalyptus ABL12W5 plantation ecosystem were studied in Leizhou peninsula, China. Results showed that: the nutrients concentrations were different in various components of eucalyptus ABL12W5, higher content of N, P, K, Ca and Mg being in the leaf, higher one of Ca, K in the bark, and the lowest one of N, P, K, Ca and Mg in the bole; the annual net accumulation of nutrients raised with stand age, and the highest raised degree in the annual net accumulation of nutrients was found in 2 ages stand of eucalyptus ABL12W5; there were also different in the annual absorption and total accumulation of nutrients, N, K or Ca being the highest, following by Mg, P being the lowest; there was obvious raise in absorption and accumulation of Ca in 5 ages of stand of eucalyptus ABL12W5; the returned rates of nutrients of eucalyptus ABL12W5 were very lower, being above 20% for N and Mg, 8% to 14% for Ca, 6.5% to 9% for P, and lower than 5% for K. The eucalyptus plantation ecosystem was in the decline of soil nutrients.