毛竹扩张对杉木林土壤及杉木叶片氮磷化学计量特征影响

Effects of Phyllostachys edulis expansion on soil and leaf N, P stoichiometry in Cunninghamia lanceolata forests

为探讨毛竹(Phyllostachys edulis)扩张影响杉木(Cunninghamia lanceolata)生长的内在生态化学计量机制,采用空间代替时间的方法,在井冈山国家级自然保护区选取典型的毛竹-杉木林界面,沿扩张方向依次设置毛竹林、竹杉混交林和杉木林样地,分析样地内土壤、毛竹叶片、杉木新叶、成熟叶和落叶的氮(N)、磷(P)含量、N:P及叶片N、P回收度等指标。结果表明:(1)毛竹扩张提高土壤P含量,由0.32 mg·g^(-1)上升到0.43 mg·g^(-1),增幅达32.6%;(2)毛竹扩张不改变杉木成熟叶的N:P,维持在13.74,但使新叶的P含量上升,从而导致新叶N:P下降21.3%,且使落叶的N:P由21.64下降到18.69,降幅为13.6%;扩张过程中毛竹自身叶片N、P含量及N:P变化无差异;(3)毛竹扩张对杉木叶片N、P回收度不影响。以上说明,在毛竹向杉木林扩张过程中,毛竹自身具有较强的内稳态能力,并通过改变土壤P含量,促使杉木体内P含量及N:P计量失衡,这可能是杉木生长减缓或死亡的重要原因。

To reveal the ecological stoichiometry mechanism of Phyllostachys edulis expansion effects on the growth of Cunninghamia lanceolata individuals,this study analyzed the N,P concentration and N:P ratio of soil,P.edulis leaf and C.lanceolata leaf(young,mature and litter)in P.edulis-C.lanceolata mixed forest and its adjacent C.lanceolata forest and P.edulis forest by the methods of space-time substitution Jinggangshan National Nature Reserve.The results showed that(1)the soil P concentration was increased by 32.6%,from 0.32 mg·g^(-1) in the C.lanceolata forest to 0.43 mg·g^(-1) in P.edulis-C.lanceolata mixed forest.(2)N:P ratio in the mature leaf of C.lanceolata had no variations(13.74)in the three types of forests.However,the P concentration of young leaf was increased,leading to a fall of the N:P ratio by 21.3%.N:P ratio in litters was descended by 13.6%,from 21.64 to 18.69.There was no difference in the leaf N,P concentration and N:P ratio of P.edulis during the expansion process.(3)P.edulis expansion had no significant influences on leaf N and P resorption proficiency of C.lanceolata.These findings indicate that P.edulis has a strong homeostasis ability,and P.edulis expansion can prevent the growth or even cause the death of C.lanceolata by altering the soli P concentration and thus unbalancing the P content and N:P stoichiometry in C.lanceolata.