氮沉降和干旱对阔叶红松林凋落物分解的影响

氮沉降和降水减少耦合作用对我国北温带森林凋落物分解的影响还知之甚少,通过常规的凋落物分解袋法进行了对照(CK)、施氮(N, 50 kg/(hm·a))、降雨减少(RP,-30%)和降雨减少加施氮(RP+N)4个处理对长白山阔叶红松林主要树种叶凋落物分解和碳、氮元素动态影响的研究。结果表明:凋落物分解95%需要6.025～15.167年,椴树的分解速率最快,其次是蒙古栎,红松最慢,三者混合后分解率介于期间。分解系数结果显示:施氮能在一定程度上促进紫椴叶凋落物的分解, 施氮对红松凋落物和混合凋落物分解则表现出抑制作用, 降雨减少对分解表现为明显的抑制作用,干旱情况下施氮后4种凋落物的分解系数介乎氮沉降和降雨减少两者之间,说明氮沉降和降雨减少存在交互作用。总体看来,氮沉降对凋落物分解和氮元素含量有一定的影响,并且与分解阶段和凋落物种类有关,降水减少对凋落物分解和碳氮元素比值具有显著的抑制作用。 

Effects of nitrogen deposition and drought on litter decomposition in a temperate forest

To study the responses of nitrogen ( N ) deposition and drought on litter decomposition, we conducted an in situ experiment in a broadleaf﹣Korean pine mixed forest in Changbai Mountains by using litterbag technique. Four treatments were installed, i. e. , null level of N ( CK) , N addition ( N, 50 kg N/( ha·a ) ) , precipitation reduction ( RP, - 30%) and precipitation reduction combined with N addition ( RP+N) . The results showed that it would take 6. 025 to 15. 167 years to decompose 95% of mass of litter used. Among the tree species, Tilia amurensis ( TA) had the highest decomposition rate, followed by Quercus mongolica ( MQ) , and Pinus koraiensis ( PK) showed the lowest decomposition rate. After 92 d and 154 d, although the litter decomposition rate with N addition was higher than those with CK, no significant difference was found; whereas the decomposition rate of litter in RP and RP +N treatments was significantly lower than that of CK (P<0. 05). But after 365 d and 457 d, the differences between RP, RP+N and CK were also significant. Compared with CK, N and drought treatments had a 42. 64% -51. 01% decrease of litter C/N ratio. As a whole, N deposition had no significant effects on litter decomposition and C and N concentration, but RP and RP +N significantly inhibited the litter decomposition, and C and N release.