滇西北纳帕海湿地景观格局变化及其对土壤碳库的影响

采用3S技术和In-situ原状土就地取样技术,对滇西北纳帕海湿地26a来的景观格局变化及其驱动下的湿地土壤碳库变化研究表明:纳帕海景观格局变化显著,与1974年相比,景观破碎化程度增强、斑块形状趋于复杂、呈离散分布,湿地景观类型总面积比例呈略有增加(1994年)至大幅减小(2000年)的变化,非湿地景观类型总面积比例则呈略有减小(1994年)至大幅增加(2000年)的变化并取代湿地景观成为基质景观.响应景观类型面积变化,土壤碳储量由1974年的33.46×104 t增至1994年的36.91×l04 t,2000年降至32.92×104 t;随景观类型的转化,1974-1994年土壤碳库积累量为6.08×104 t,择放量为2.63×104 t,1994-2000年积累量为2.01×l04 t,但碳释放量为5.99× 104 t,是前20a的2.28倍.纳帕海湿地景观格局和土壤碳库的变化是自然和人为因素共同作用的结果,在地质、水文和气候等自然因素提供的变化背景上,排水、垦殖、过度放牧、无序旅游、汇水区植被破坏等强烈的人为活动干扰加剧了变化.

Landscape pattern change and its influence on soil carbon pool in Napahai wetland of Northwestern Yunnan

The wetland landscape dynamics and its environmental effects have been considered as a research hotspot. But researches about soil carbon pool changes driven by landscape pattern changes were rarely seen. To address this issue, a study was carried out in the Napahai wetland, a sensitive region of global changes in northwestern Yunnan, adopting the In-situ intact soil sampling methodology and supported by the "3S" tools.Results showed that the landscape altered significantly within 26 years. Compared with 1974a, the fragmentation of Napahai landscapes was increasing, the landscape shapes became more complicated, dispersed, and dominated by large patches, the matrix of the Napahai landscapes has been converted from wetland types to the ever-increasing human land use types. At the land level,the patch number and landscape shape index increased 42% and 12.19% by 1994, as well as 40% and 1.02% by 2000. The aggregation index decreased 0.56% (by 1994) and 0.52% (by 2000). Landscape diversity and landscape dominance firstly increased 0.844% and 0.847% by 1994 and then decreased 3.130% and 3.134% by 2000. At the class level, the changes of wetland types trended to complexity, the area percentage of water body, marsh and swampy meadow increased form 70.29% (1974) to 72.20% (1994) then decreased to 48.79% (2000), however, that of meadow and farmland decreased a bit in 1994 then largely increased in 2000a. The landscape pattern changes of the wetland had impacts on the wetland's soil carbon storage fluctuation. Responding to the landscape area changes, soil carbon storage increased from 33.46×10⁴t (1974) to 36.91×10⁴t (1994) and then decreased to 32.92×10⁴t (2000). With the landscape type transformations, the soil carbon sequestration and emission form 1974 to 1994 reached respectively 6.08×10⁴t and 2.63×10⁴t. The soil carbon sequestration form 1994 to 2000 reached 2.01×10⁴t, nonetheless, the emission increased sharply, which is up to 2.28 times of that of 1974-1994.The landscape pattern changes, the soil carbon storage and its "source/sink" shifts have been imposed by both natural factors and human impacts. Under the context of geology, hydrology and climate changes, human disturbances such as wetland drainage, reclamation, overgrazing, and vegetation destruction of catchments have further intensified the changes of wetland.