鼎湖山南亚热带森林细根生产力与周转

PRODUCTION AND TURNOVER RATE OF FINE ROOTS IN TWO LOWER SUBTROPICAL FOREST SITES AT DINGHUSHAN

报道了鼎湖山季风常绿阔叶林和针阔叶混交林群落０～４０ｃｍ土层中细根（≤２ｍｍ和２～５ｍｍ）的现存量、死亡量、生产力和周转率，并比较了用“连续钻取土芯法”和“埋无根土柱法”来估算表层土（０～２０ｃｍ）细根生产力的差异。结果表明：在０～４０ｃｍ土层中，季风常绿阔叶林≤２ｍｍ和２～５ｍｍ细根现存量分别为６．５９ｔｈｍ－２和４．８１ｔｈｍ－２，死根比率各为２９．９％和２２．９％；针阔叶混交林≤２ｍｍ和２～５ｍｍ细根现存量分别为５．３５ｔｈｍ－２和４．２４ｔｈｍ－２，死根比率各为３４．４％和２４．０％。细根现存量的季节性变化不显著。季风常绿阔叶林细根年分解量、年死亡量和年净生产力分别为０．９０，１．５９，２．６５ｔｈｍ－２ａ－１（≤２ｍｍ）和０．４１，０．６３，１．２５ｔｈｍ－２ａ－１（２～５ｍｍ），针阔叶混交林的相应数值各为０．８０，１．４１，２．４２ｔｈｍ－２ａ－１（≤２ｍｍ）和０．３７，０．６２，１．２１ｔｈｍ－２ａ－１（２～５ｍｍ）。季风常绿阔叶林细根年周转率为０．５７（≤２ｍｍ）和０．３４次ａ－１（２～５ｍｍ），针阔叶混交林分别为０．６９（≤２ｍｍ）和０．３８次ａ－１（２～５ｍｍ）。

Fine roots were sampled in a monsoon evergreen broad leaved forest(MEBF),and a nearby mixed coniferous( Pinus massoniana ) and broad leaved forest (MCBF), located in Dinghushan Biosphere Reserve. The standing pools of live and dead fine roots in the 0￣40cm soil depth were sampled seasonally for one year, annual dry mass loss of the decomposing fine roots was measured and mortality and production were calculated. The comparison of soil coring and in growth method for estimating the fine root production in the surface soil (0￣20cm) was also made. The mean standing pools of roots ≤2mm and 2￣5mm in the 0￣40cm soil were 6 59(29 9%) and 4 81(22 9%) t·hm -2 for the MEBF, while 5 35(34 4%) and 4 24(24 0%) t·hm -2 for the MCBF with the portion of dead roots given in parentheses. The standing pool did not fluctuate dramatically with various sampling occasions. In the MEBF, annual mass loss, mortality, net production for fine roots were 0 90,1 59,2 65t·hm -2 ·a -1 (≤2mm),and 0 41,0 63 and 1 25t·hm -2 ·a -1 (2～5mm),respectively. While the corresponding values in the MCBF were 0 80,1 41,2 42 t·hm -2 ·a -1 (≤2mm),and 0 37,0 62,1 21t·hm -2 ·a -1 (2～5mm),respectively. The annual turnover rates were 0 57(≤2mm) and 0 34 times·a -1 (2～5mm) for the MEBF, and 0 69(≤2mm) and 0 38 times·a -1 (2～5mm) for the MCBF, respectively.