作 者 ：何斌,秦武明,余浩光,刘运华,覃林,覃永华
期 刊 ：生态学报 2007年 27卷 12期 页码：5158~5167
Keywords:Acacia mangium plantation, age class, nutrient elements, biological cycling,
摘 要 ：对马占相思人工林6种营养元素(N、P、K、Ca、Mg、S)的含量、积累、分布和生物循环特点以及随林分年龄的变化趋势进行了研究。结果表明:(1)林木不同组分营养元素含量的大小次序为树叶＞干皮＞活枝＞枯枝或树根＞干材;各组分和凋落物中营养元素含量以N最高,其次是Ca或K,然后是S和Mg,P最低;林地土壤中,以K的含量最高,其次是Ca、Mg、N和P,S最低;随林龄的增加,0～40cm土壤N、P和S含量呈增加趋势;(2)4年、7年生和11年生林分营养元素总积累量分别为1022.08、1997.08和2633.45 kg•hm-2,其中乔木层营养元素贮存量依次占73.64%、82.39% 和83.65%，林下植被层依次占13.74%、8.74%和620%,地表现存凋落物层依次占12.62%、8.87%和10.16%;乔木层以N积累量最大,占总贮存量的53.90%～60.07%,P最小,仅占0.90%～1.23%;(3)马占相思林中不同组分营养元素积累量的分配随林龄的增长发生变化,由4年生以树叶和树枝占主导,逐渐转移到7年生和11年生以干材和树皮为主导;(4)林分营养元素年积累量依次为7年生(235.06 kg•hm-2•a-1)＞11年生(200.26 kg•hm-2•a-1)＞4年生(188.16kg•hm-2•a-1);林木各组分营养元素年积累量总的变化趋势为:树干＞树叶＞树枝＞根系＞树皮,同一组分各营养元素年积累量与各组分营养元素积累量变化顺序一致，即为N＞Ca＞K＞S＞M＞P;(5)林分营养元素年吸收量分别为382.35、432.04 kg•hm-2•a-1和403.15 kg•hm-2•a-1,年归还量分别为194.19、196.98 kg•hm-2•a-1和202.89 kg•hm-2•a-1,营养元素的循环系数分别为0.51、0.46和0.50,利用系数为0.51、0.26和0.18,周转期为3.88、8.35和10.86。可见,马占相思人工林早期营养元素利用率低,归还速率较快,林分生长到近熟期(11a)时营养元素的周转期较长,但其归还速率仍然较快,有利于林地地力的恢复、维持和提高。
Abstract:Due to adaptation to the infertile habitat,Acacia mangium is widely planted as pioneer species in tropical and south subtropical regions in China.The content,accumulation,distribution and biological cycling of six nutrient elements (N,P,K,Ca,Mg and S) as well as their changes with growth of stands in A．mangium plantation of three different age classes(4-year-old,7-year-old and 11-year-old)were studied．The results show that concentrations of these six nutrient elements in different components of A．mangium plantation were in the order of leaves > bark > alive branch > dead branch or root > stem.In plant,concentration of N was the highest among the six elements,followed by K and Ca,while Mg and P were the lowest in various components of A．mangium plantation.In the soil, concentration of K was the highest,then Ca,Mg,N,P,and S concentration was the lowest among six elements. Concentrations of N,P and S in the 0-40cm of soil depth increased with increasing stand age.The total nutrient accumulations at three different age classes plantation were 1022.08 kg•hm-2,1997.08 kg•hm-2 and 2633.45 kg•hm-2,respectively.Of the total storage of nutrients,73.64%-8365% was distributed in arbor layer,6.20%-13.74% at forest floor layer,8.87%-12.62% at standing litter layer.Among six elements，N accumulation in arbor layer was largest,covering 53.90%-60.07％ of total nutrient storage.P accumulation in arbor layer was the lowest,only 0.90%-1.23% of total nutrient storage.The accumulations of nutrients in A．mangium varied with different stands growth stages.Most nutrient elements accumulated in leaves and branches at 4-year-old stage,while they gradually moved gradually in stem and bark at 7-year-old and 11-year-old.Nutrient annual net accumulations in three age classes plantation were 188.16 kg•hm-2•a-1,235.06 kg•hm-2•a-1 and 200.26 kg•hm-2•a-1, respectively.Comparison of nutrient annual net accumulation in different components was in the order of stem > leaves > branches > roots > bark.Changes in annual net accumulation of various nutrients in the same component was similar to that in various components,N>Ca>K>S>Mg>P.The annual absorption of six nutrient elements in three age classes plantations were 382.35 kg•hm-2•a-1,432.04 kg•hm-2•a 1 and 403.15 kg•hm-2•a-1,respectively.The annual returns equaled to 194.19 kg•hm-2•a-1,196.98 kg•hm-2•a 1 and 202.89 kg•hm-2•a-1,respectively.The nutrient utilization coefficients were 0.51,0.26 and 0.18,respectively.The cycling coefficients were 0.51,0.46 and 0.50,respectively.The recycling periods were 3.88,8.35 and 10.86,respectively.As observed，the nutrient utilization efficiency in early stage in A．mangium plantation was lower but return rate was higher.When stands approached near-mature stage(11-year-old),the recycling period of nutrients increased with the augmentation of return rate,resulting in the recovery,maintenance and enhancement of forestland fertilization.
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