不同年龄阶段秃杉人工林微量元素分布及其生物循环特征

Microelements Distribution and Biological Cycling of Taiwania flousiana Plantations at Different Age Stages

为了研究不同年龄阶段秃杉人工林微量元素的生物循环特征,以广西南丹县秃杉人工林为研究对象,通过样地调查观测和室内样品分析,对不同年龄阶段(9、17、25和37年生)秃杉人工林的5种微量元素(Fe、Mn、Zn、Cu和B)分布及其生物循环特征进行了研究。结果表明:(1)5种微量元素在乔木层中平均质量分数为w(Mn)>w(Fe)>w(Zn)>w(B)>w(Cu);各微量元素在秃杉不同器官的质量分数存在差异且随林龄变化而变化。(2)9、17、25和37年生的秃杉人工林微量元素总贮存量分别为15.828、29.675、35.428和48.379 kg·hm^(-2),其中乔木层微量元素贮存量随林龄的增加而减少,分别占总贮存量的91.32%、88.00%、84.53%和83.59%;灌草层微量元素贮存量分别占总贮存量的2.41%、2.76%、3.94%、3.62%;凋落物层微量元素贮存量分别占总贮存量的6.27%、9.24%、11.52%、12.79%;各微量元素中Mn或Fe的贮存量最高,其次是Zn和B,Cu的贮存量最低。(3)乔木层中微量元素贮存量的分配随林龄的增加发生变化,树干(干材和干皮)和树根的比例随林龄增加而增大,树冠(树叶和树枝)所占比例则表现为相反的变化趋势。(4)林分微量元素年积累量分别为1.606、1.536、1.218和1.041 kg·hm^(-2)·a^(-1),随林龄的增加而减少。不同微量元素中Mn的年净积累量最高,其次是Fe、B和Zn,Cu的年净积累量最低。(5)微量元素年吸收量分别为2.800、3.344、4.527和4.630 kg·hm^(-2)·a^(-1),年归还量分别为1.164、2.651、3.309和3.589 kg·hm^(-2)·a^(-1),微量元素的利用系数分别为0.194、0.128、0.149和0.117 a,循环系数分别为0.416、0.793、0.731和0.775;周转期分别为12.417、9.851、9.203和11.014 a。因此,秃杉人工林生长9年生时微量元素的积累较快,但归还速率慢,周转期较长,会较多消耗林地微量元素的有效养分;9年生后微量元素积累速率逐渐减慢,归还速率加快,有利于促进生态系统微量元素生物循环,维持和提高林地生产力。

In order to explore the biological cycle characteristics of microelements in Taiwania flousiana plantation at different stage ages,the distribution and biological cycling of five microelements(Fe,Mn,Zn,Cu and B)in different stage ages(9,17,25 and 37 a)of the T.flousiana plantation at Nandan County of Guangxi were studied through sample plots survey and sampling analysis.The results showed that:(1)The content of Mn was the highest among the five microelements,followed by Fe,Zn,B,and Cu in arbor layer of T.flousiana plantation.The microelement contents in different organs also varied with stand age of T.flousiana.(2)The total micronutrients storage at 9,17,25 and 37 a T.flousiana plantation were 15.824,29.665,35.413,and 48.359 kg·hm^(-2),of which the tree layer,shrub and herb layer,and the ground litter layer accounted for 82.01%-88.93%,5.18%-6.57%,and 5.89%-11.55%of the total,respectively.(3)The storage of microelements in tree layer varied with different stand ages;of which the proportion of trunk(stem and bark)and root of the total increased with stand age,while the proportion of crown(leaves and branches)showed the opposite trend.(4)Annual net accumulative amounts of microelements in four stage ages of T.flousiana plantations were 1.606,1.536,1.218,and 1.041 kg·hm^(-2)·a^(-1),respectively,which decreased with the increase of stand age.The annual net accumulations of different microelements was highest in Mn,followed by Fe,Zn,B,and Cu.(5)The annual absorption of microelements in four ages stages plantations were 2.800,3.344,4.527,and 4.630 kg·hm^(-2)·a^(-1),respectively.The annual returns were 1.164,2.651,3.309,and 3.589 kg·hm^(-2)·a^(-1) respectively.The annual returns were 2.800,3.344,4.527,and 4.630 kg·hm^(-2)·a^(-1),respectively.The microelements utilization coefficients were 0.194,0.128,0.149,and 0.117,respectively.The cycling coefficient were 0.416,0.793,0.731,and 0.755.The recycling periods were 12.417,9.851,9.203,and 11.014 a,respectively.Therefore,9-a T.flousiana plantation had a faster microelements accumulation rate,a lower return rate,and a longer turnover period,which would consume more microelements from soil;After 9 a,the accumulation rate of microelements gradually slowed down and the return rate accelerated,which was conducive to promoting the biological cycle of micronutrient in ecosystem and maintaining and improving the productivity of forest land.