模拟氮沉降对油松林单一及混合叶凋落物分解的影响

通过长期原位模拟氮沉降试验,研究暖温带油松林单一和混合叶凋落物分解对外源氮添加的响应过程与机制。氮处理水平分别为对照(0 kg/(hm2a),N0),低氮(50 kg/(hm2a),N1),中氮(100 kg/(hm2a),N2)和高氮(150 kg/(hm2a),N3)。利用凋落袋法对天然林油松针叶、辽东栎阔叶、油松--辽东栎混合叶以及人工林油松针叶进行原位分解试验。研究结果表明,自然状态下天然林油松针叶、辽东栎阔叶、油松--辽东栎混合叶、人工林油松针叶分解95%所需时间分别为7.58、4.89、6.92、8.03 年。氮沉降显著促进了人工林油松针叶的分解,抑制天然林辽东栎阔叶的分解;分解前期,N沉降促进天然林油松针叶、油松--辽东栎混合叶分解,并在分解后期对油松针叶分解产生抑制作用,而对油松--辽东栎混合叶分解无显著影响。在氮沉降持续增加的背景下,研究结果可为油松林生态系统物质循环和能量流动提供基础数据。 

Effects of simulated nitrogen deposition on decomposition of single and mixed leaf litters in the plantation and natural forests of Pinus tabulaeformis.

Through a long-term in situ simulated nitrogen ( N) deposition experiment, we explored the response and mechanism of single and mixed leaf litters decomposition to exogenous nitrogen addition in warm-temperate Chinese pine ( Pinus tabulaeformis) forests. The levels of simulated N deposition were set as control (0 kg/(hm2·a), N0), low N (50 kg/(hm2·a), N1), medium N (100 kg/(hm2·a), N2), and high N ( 150 kg/( hm2·a ) , N3 ) . Litterbag method was used for decomposition of single P. tabulaeformis litter, single Quercus liaotungensis litter, mixed P. tabulaeformis-Q. liaotungensis litter in the natural forest and single P. tabulaeformis litter in the plantation. The results showed that the time of 95% mass loss was 7. 58 years for single P. tabulaeformis litter, 4. 89 years for single Q. liaotungensis litter and 6. 92 years for mixed P. tabulaeformis-Q. liaotungensis litter in the natural forest. And the time of 95% mass loss was 8. 03 years for single P. tabulaeformis litter in the plantation. N deposition significantly accelerated the decomposition of single P. tabulaeformis litter in the plantation while inhibited that of single Q. liaotungensis litter in the natural forest. At the start, N deposition increased the rates of mass loss of single P. tabulaeformis litter and mixed P. tabulaeformis-Q. liaotungensis litter in the natural forest; however, it inhibited the decomposition of single P. tabulaeformis litter and had no significant effect on the decomposition of mixed P. tabulaeformis-Q. liaotungensis litter at the later stage of decomposition. Our results provide basic data for material cycling and energy flow of Chinese pine forest ecosystems under the context of increased N deposition.