放牧对滇西北高原沼泽湿地土壤N2O排放的影响机制研究

Nitrous oxide (N2O) is an important greenhouse gas. The effects of N2O on the global climate and environment is long-term and potential. Wetlands is a potential source or sink of N2O because of its special environment. Recently, most of studies focused on the effects of different distributions on the N2O production in wetlands. However, there were not a study about the effect of grazing on the N2O production in wetlands. The marsh on the plateau in Northwest of Yunnan is located on the agriculture and husbandry interlace zone. This will be a typical area for the study about effect of grazing on N2O production in wetlands. In this study, typical marsh in Northwest of Yunnan was selected as study area. The methods of collecting the samples in field and incubating the soil core in lab were used. The aim of this study is to investigate the effects of gazing (the disturbance of animals moving and animal excreta) on the N2O production from typical marsh soils in Northwest of Yunnan. The results will be contribute to estimate the N2O production from typical marsh soils in Northwest of Yunnan and assess the role of marsh in Northwest of Yunnan in global climate change. Moreover, the results will provide not only a theoretical basis for the study of grazing effects on the wetlands, but also a theoretical foundation for the study of grazing management and wetland conservation.

N2O作为一种重要的温室气体，其对全球气候及环境的影响是长期和潜在的。湿地由于其独特的环境条件，使其成为潜在的N2O排放源或汇。近年来，干扰对湿地N2O排放的影响受到广泛关注，但关于放牧对湿地N2O排放的影响研究尚未见报道。滇西北高原沼泽湿地地处农牧交错带，是研究放牧对湿地N2O排放影响研究的典型区域，本研究以滇西北高原典型沼泽湿地为研究区，采用野外采样和室内培养分析相结合的方法，对比研究放牧过程中不同动物活动（牦牛践踏和藏香猪翻拱）干扰和动物排泄物（粪便和尿）输入对沼泽湿地土壤理化性质、微生物活性及功能基因、硝化和反硝化作用、N2O排放通量的影响，阐明放牧过程中动物活动和排泄对滇西北高原沼泽湿地土壤N2O排放的影响机制，为放牧干扰对湿地影响研究提供理论基础；有助于准确估算滇西北高原沼泽湿地N2O排放量，正确评估滇西北高原沼泽湿地在全球气候变化中的作用；为畜牧业管理和湿地保护提供理论依据。

纳帕海是滇西北高原沼泽湿地集中分布区，同时也是受放牧干扰最为典型和严重的区域。本研究选取纳帕海沼泽湿地为研究区，采用野外监测采样和室内培养相结合的方法，对比研究不同放牧干扰（践踏干扰和翻拱扰动）和牦牛排泄物（粪便和尿液）输入对沼泽土壤理化性质、酶活性、微生物及功能基因、潜在硝化势（PNR）、反硝化速率（DR）、N2O排放通量的影响。研究表明：①不同放牧干扰均显著提高PNR和DR（P<0.05），翻拱比践踏的影响更显著。土壤pH、总氮（TN）和硝酸盐（NO3--N）含量的变化是影响氨氧化微生物群落结构的主要因素，NO3--N和亚硝酸盐还原酶（NIR）在调节反硝化速率中起着重要作用。践踏主要通过土壤容重影响微生物群落结构，而翻拱活动主要通过改变NO3--N影响微生物群落结构。放牧干扰通过改变土壤理化性质直接影响PNR，同时通过影响AOA及AOB的多样性间接影响PNR，直接影响大于间接影响。放牧干扰通过改变土壤理化性质直接影响DR，同时通过影响nirS及nirK和酶活性间接影响DR，间接影响大于直接影响。.②粪便输入显著降低土壤PNR，尿液输入显著提高土壤PNR（P<0.05），排泄物输入均显著提高了土壤DR和N2O 排放 (P < 0.05)，尿液输入比粪便输入更显著促进土壤N2O排放。排泄物输入显著提高土壤脲酶和过氧化氢酶活性（P<0.05），从而显著影响AOB群落结构（P<0.05）。排泄物输入显著提高NO2--N、TOC和AP含量（P<0.05），从而显著影响nirK和nirS的群落结构（P<0.05）。AOB和nirK比AOA和nirS群落对排泄物输入更敏感。排泄物输入显著增加土壤TP含量（P<0.05），不仅直接影响PNR，还通过改变AOB群落结构而影响PNR。排泄物输入显著增加土壤含水量、AP和NO2--N（P<0.05），不仅直接影响DR，还通过影响反硝化微生物和酶活性影响DR。