氮沉降和凋落物量的改变是全球变化影响森林生态系统的重要途径,然而二者的交互作用对土壤生态过程的影响仍知之甚少。本文研究氮添加(对照和添加10 g N·m~(-2)·a~(-1) )和地表凋落物管理(对照、移除和加倍)对科尔沁沙地樟子松人工林干季( 5月)和湿季( 8月)土壤有效氮、基础呼吸和有效磷等的影响。结果表明:凋落物管理对土壤的影响在对照和氮添加样地中差异较大;在对照样地中,凋落物移除和加倍都显著提高了8月土壤呼吸,对有效磷和氮含量基本上无显著影响;在氮添加样地,凋落物移除与加倍均未影响土壤呼吸和有效磷含量,但显著降低有效氮含量;氮添加和凋落量变化的影响在湿季大于干季;单一的氮添加显著降低了8月的土壤有效磷含量和土壤呼吸,而凋落物量加倍减缓了氮沉降对土壤呼吸的抑制和磷限制性的加剧。
英文摘要:
Nitrogen ( N) deposition and litterfall variation are main pathways by which global change impacts forests,but how they interact to change belowground processes is poorly known. To explore these interactions,we conducted a field manipulative experiment under nitrogen addition( control and N addition as 10 g N·m~(-2)·a~(-1) ) and litter manipulation ( ambient litterfall, litter removal and litter doubling) in a Pinus sylvestris var. mongolica plantation in Keerqin Sandy Land. We measured soil properties such as available N and P concentrations and basal respiration rate in dry and wet seasons ( May and August) 3 years after manipulation. The results showed that impacts of litter manipulation on soil variables differed greatly in the control and N addition plots. In the control plots,both litter removal and doubling greatly elevated soil basal respiration, while generally did not change available P and N concentrations. In N addition plots,both litter removal and doubling did not change basal respiration and available P concentration,but greatly decreased available N concentration. Impacts of N addition and litter manipulation were more obvious in wet season than in dry season. Nitrogen addition alone significantly reduced basal respiration and available P concentration in August,while litter doubling effectively lessened the depression of respiration and enhanced P limitation caused by N addition.