牦牛粪便对川西北高寒草甸土壤养分的影响

川西北高寒草甸是我国四大牧区之一,也是"长江上游生态屏障"建设的重要"生态功能区"之一.近年来牦牛粪便被大量出售,显著地改变了生态系统的养分循环.通过模拟牛粪堆积,研究了牦牛粪便养分释放及其对周围土壤养分(NO3--N、NH4--N、速效K、无机P、有机C、全N和全P)在不同时间和距离条件下的影响.结果表明,在研究区域内,牛粪对草地生态系统具有较强的养分(N、P)贡献能力,据初步统计,其值大致为N素699～932 kg hm-2,P素为110～147 kg hm-2;牛粪养分在夏季具有较快的分解速率,在3 mo左右之后基本分解殆尽;粪便在短期内能显著提高粪下土壤养分的含量,其中,对No3--N含量的提高最为明显,在2 mo左右之后其含量达到初始态的8.4倍,在实验后期,粪便对土壤养分的影响作用逐渐消失;粪便在夏季对周围10 cm内土壤的养分(NO3--N、NH4+N、速效K和无机P)含量能产生显著影响(P<0.05),但影响范围难以达到周围30 cm左右.与通常结论不同的是,在整个实验周期内,牦牛粪便并没有显著提高土壤有机C、全N和全P的含量.图4表1参31

Effect of Yak Dung on High-frigid Meadow Soil Nutrition in Northwestern Sichuan, China

The decomposition of yak dung and its effect on soil nutrition of grassland in northwestern Sichuan, China were investigated. Soil samples were taken around (10 cm and 30 cm radius from center) dung piles on five occasions over a period of 84 days in summer. The samples were analyzed for NO_3~--N, NH_4~(+)-N, available K, inorganic P, total organic C (TOC), total N (TN) and total P (TP). The result showed that yak dung supplied the ecosystem there with substantial nutrients. It was estimated that the N contribution from dung was approximately 699～932 kg hm~(-2) and P. about 110～147 kg hm~(-2). The total quantities of NO_3~--N, NH_4~(+)-N, available K and inorganic P from the initial dung largely decreased to almost none after 84 days. In the initial days (1～9 d), NO_3~--N, NH_4~(+)-N, available K and inorganic P in sioi under the dung piles were found with a significant increase, and after two months the content of NO_3~--N was 8.4 times larger than that in the initial days. The contents of NH_4~(+)-N, available K and inorganic P at place 10 cm from the edge of dung piles increased significantly (P<0.05), but no significant increase was found (P>0.05) at 30 cm. Differing from the common belief, no obvious increases in TOC, TN and TP were observed in the whole experiment process. Fig 4, Tab 1, Ref 31