杉木、观光木混交林群落细根N、P养分现存量动态变化

通过对杉木、观光木混交林和杉木纯林细根的养分现存量动态进行研究 ,结果表明 ,混交林细根N、P养分现存量分别是纯林的 1.3和 1.2倍 ;年归还量分别是纯林的 1.2 3倍和 1.14倍 ,且分别占混交林凋落物N、P养分年归还量的 38.3%和 6 7.4 % ;年分解量分别是纯林的 1.2 6和 1.2 3倍 ,而年累积量分别是纯林的 1.2 3和 1.14倍 ,可见混交林细根具有比纯林更高的养分累积和周转能力。混交林和纯林群落中林下植被细根在群落细根N、P养分循环中占有重要地位 ,而杉木和观光木 <0 .5mm径级细根则是其细根养分循环功能的主体。混交林和纯林杉木活细根N养分现存量动态变化呈单峰型 ,P则呈双峰型 ;死细根N、P养分现存量动态变化均呈倒“S”型。混交林中观光木细根的N、P养分现存量动态变化与杉木的较相似 ,但其活细根P养分现存量动态变化呈单峰型。混交林与纯林中林下植被活细根N、P养分现存量动态变化均呈双峰型 ,而死细根的动态变化则呈单谷型

Dynamics of Standing Crop of N and P for Fine Roots of Mixed Forest of Cunninghamia lanceolata and Tsoongiodendron odorum

Dynamics of standing crop of N and P for fine roots of pure and mixed Tsoongiodendron odorum forests of Cunninghamia lanceolata were studied. The standing crop of N and P for fine roots of mixed forest were 1.3 and 1.2 times, and annual return were 1.23 and 1.14 times as much as those of pure forest, respectively, which were 38.3% and 67.4% of those returned through litterfall. Annual decomposition was 1.26 and 1.23 times, and annual accumulation was 1.23 and 1.14 times, respectively, as much as those of pure forest. It showed that fine roots of mixed forest had a higher accumulation capacity and a more rapid turnover rate of nutrients. Fine roots of undergrowth played an important role in nutrient cycling of fine roots of forest community. Roots <0.5 mm in diameter was the major body in nutrient cycling of fine roots. Seasonal dynamics of standing crop of nutrient in living fine roots of C. lanceolata showed a single apex curve for N and double apices one for P, and those for N and P in dead fine roots both showed an "S" curve. The dynamics for fine roots of T. odorum were similar to those of C. lanceolata , except for that of P in living roots which showed a single apex curve. The dynamics of standing crop of N and P for living fine roots of undergrowth in both stands showed a double apices curve, and those for dead roots showed a single vale one.