人为干扰对鼎湖山马尾松林土壤细根和有机质的影响

通过处理 (根据当地习惯收割凋落物和林下层 )和保护 (无任何人为干扰 )样地的比较试验 ,1990～ 1995年期间研究了人为干扰对鼎湖山生物圈保护区马尾松 (Pinus massoniana)林土壤细根和有机质的影响。在此 5 a的研究期间 ,由于人为干扰活动而直接从处理样地取走的林下层和凋落物总量为 2 1.7t/ hm2。在保护样地 ,林下层生物量从 2 .2 t/ hm2增加至 11.10 t/ hm2 ,地表凋落物 (包括枯死的林下层 )量则从 3.0 t/ hm2 增加至 13.3t/ hm2 。收割林下层和凋落物这种人为干扰活动对林地土壤细根生物量的影响不明显 ,但却显著降低土壤轻腐殖质 (Soil lightorganic matter)量。在细根分解过程中 ,其分解速率在处理样地(试验结束时细根残存量占起始量的 4 0 .8% )显著高于在保护样地 (试验结束时细根残存量占起始量的 4 4 .3% ) ;与 Ca、Mg和K元素不同 ,N和 P两种元素的释放速率在处理样地显著高于保护样地 ,表明这种人为干扰活动不仅直接取走所收割的林下层和凋落物中的养分 ,而且还可能增加林地有效养分的流失潜力

Effects of human impacts on fine roots and soil organic matter of a pine forest in subtropical China

Effects of human impacts on fine roots and soil organic matter of a pine forest in subtropical China were studied by comparing treatment (harvesting understory and litter according to practice of local people) and control (no harvest) plots in a pine forest from 1990 to 1995. During this studied period, the total amount of material harvested by this practice in treatment plots was 21.7 t/hm~2. In control plots, the standing stocks of understory increased from 2.2 to 11.1 t/hm~2 at a significantly linear pattern, while the standing stocks of litter (including dead understory) increased from 3.0 to 13.3 t/hm~2. Harvesting practice had no significant effect on the standing fine root biomass, but significantly reduced soil light organic matter in pine forest. Mass loss in decomposing fine roots was linear in both control and treatment plots. Fine roots decomposed significantly faster in treatment (40.8 percent of initial mass remaining at the end of the 448 day experiment) than in control plots (44.3%). Nutrient losses from decomposing fine roots were significantly faster in treatment plots than in control plots for N and P, but there were no significant difference for other elements. These trends indicated that there could be a higher potential for nutrient loss by harvesting understory and litter (more nutrients available for understory uptake and litter mobilizing N during early stage of decomposition) and by leaching in treatment plots.