不同林龄云南松凋落叶分解及养分归还特征

Leaf Litter Decomposition and Nutrient Return Characteristics of Pinus yunnanensis at Different Forest Ages

为探讨不同林龄云南松的凋落叶产量及分解养分归还特征,以云南玉溪磨盘国家森林公园不同林龄(15 a、30 a和45a)云南松为对象,采用样地法及网袋法,经过1 a的定位观测,对云南松凋落叶产量、分解及养分(N、P、K、Ca和Mg)归还特征进行了研究。结果表明:(1)磨盘山地区不同林龄云南松凋落叶产量在11月至翌年1月最大,为1.92～3.30 t·hm^(-2),占全年凋落叶量48.98%～56.44%,而2—4月凋落叶产量最少,仅占全年的8.81%～10.50%;不同林龄年凋落叶产量表现为30 a(5.92 t·hm^(-2))>45 a(5.05 t·hm^(-2))>15 a(3.29 t·hm^(-2));(2)不同林龄云南松凋落叶在分解1 a内总失质量率表现为30 a(40.82%)>15 a(40.41%)>45 a(38.06%);随林龄的增加,凋落叶分解半衰期分别为1.11 a(15 a)、1.29 a(30 a)和1.39a(45 a),分解周期分别为4.82 a、5.23 a和5.60 a,分解系数分别为0.40 a^(-1)、0.41 a^(-1)和0.38 a^(-1);(3)凋落叶分解过程中N归还量在各时期均为30 a>45 a>15 a,并随时间推移呈现出不断增加的趋势,而其他养分元素归还量在分解过程中均呈现出不同的波动情况,N、Ca和Mg归还量均在11月至翌年1月期间达到最大值,P、K则在8—10月期间归还量达到最大;(4)经过1 a的分解,不同林龄所测定的5个养分元素归还总量为45 a(250.75 kg·hm^(-2))>30 a(239.64 kg·hm^(-2))>15 a(164.17kg·hm^(-2))。

After one year of positioning observation,the characteristics of leaf litter decomposition and nutrient return of Pinus yunnanensis at different forest ages(15 a,30 a and 45 a)in Yuxi Mopan Forest Park of Yunnan were measured and analyzed by using sample plot and litter bag methods.The results showed that,(1)The leaf litter amount of P.yunnanensis was the highest in November to January of next year,which was 1.92-3.30 t·hm-2,accounting for 48.98%-56.44%of the whole year,however,the amount of leaf litter in February and April was the least,only accounting for 8.81%-10.50%of the whole year.The total amount of leaf litter at different forest ages was 30 a(5.92 t·hm-2)>45 a(5.05 t·hm-2)>15 a(3.29 t·hm-2).(2)The total mass loss rate of leaf litter decomposition of P.yunnanensis at different forest ages was 30 a(40.82%)>15 a(40.41%)>45 a(38.06%).The half-life of leaf litter decomposition was 1.11 a(15 a),1.29 a(30 a)and 1.39 a(45 a),the decomposition period(needed to decompose 95%)was 4.82 a(15 a),5.23 a(30 a)and 5.60 a(45 a),and the annual decomposition coefficients was 0.40 a-1,0.41 a-1 and 0.38 a-1,respectively.(3)The amount of N return was 30 a>45 a>15 a in each period of leaf litter decomposition,and it showed an increasing trend with the passage of time.However,the return of other nutrient elements showed different fluctuations during decomposition.The return amount of N,Ca and Mg reached their maximum values during the period from November to January of the next year,while the return amount of P and K reached the maximum during the period from August to October.And(4)after one year decomposition,the total amount of nutrient return determined was 45 a(250.75 kg·hm-2)>30 a(239.64 kg·hm-2)>15 a(164.17 kg·hm-2)at different forest ages.