放牧对青藏高原高寒草地土壤有机碳含量的影响

Effects of grazing on soil organic carbon contents in alpine meadow on Tibetan Plateau

摘要:

【目的】受气候变化和人类活动影响，青藏高原生态安全屏障仍然面临退化草地面积大、固碳能力降低等生态风险。揭示放牧对青藏高原高寒草地土壤有机碳含量影响及调控因素，对于提升高寒草地生态屏障功能具有重要作用。【方法】采用 Meta 分析，明晰不同放牧强度对青藏高原土壤有机碳含量、理化性质影响的平均效应值，结合混合效应模型，揭示放牧对土壤有机碳影响效应的主要调控因素。【结果】放牧干扰极显著降低高寒草地土壤有机碳含量，降幅约 13. 93%，平均效应值-0. 15±0. 04 （P＜0. 001）。轻度、中度和重度放牧草地土壤有机碳降幅分别为 12. 19%、13. 06% 和 15. 63%，轻度放牧处理未达到显著性检验水平。放牧干扰显著降低高寒草地土壤速效钾、全磷、全氮和全钾含量，降幅分别为 14. 55%、10. 74%、9. 14%（P＜0. 01）和 3. 17%（P＜0. 05）。放牧显著增加速效氮含量和土壤容重，增幅分别为 11. 90% 和 12. 66%。放牧草地土壤有机碳效应值，主要受土壤速效钾、全氮含量、土壤容重和海拔影响，均达到显著性检验水平，效应值变异的解释强度为 69. 73%。【结论】轻度放牧提高土壤速效钾含量，有利于降低放牧引起的青藏高原高寒草地碳排放量。

Abstract:

【Objective】 The ecological security barrier of the Qinghai Tibet Plateau still faces ecological risks such as large degraded grassland area and reduced carbon sequestration capacity，because of climate change and hu- man activities. Revealing the influence and regulation factors of grazing on soil organic carbon content of alpine grass- land in Qinghai-Tibet Plateau plays an important role in improving the ecological barrier function of alpine grassland 【Method】 Meta - analysis was used to clarify the average effect values of different grazing intensities on soil organic carbon content and physicochemical properties on the Qinghai - Tibet Plateau. Combined with the mixed effects model，the main regulatory factors of grazing effects on soil organic carbon were revealed.【Result】 This study re- vealed that grazing disturbance significantly reduced the content of soil organic carbon in alpine grassland approxi- mately 13. 93%. Meanwhile，the average effect size was -0. 15±0. 04（P＜0. 001）. The decrease of soil organic car- bon in light，moderate and heavy grazing grasslands was 12. 19%，13. 06% and 15. 63% respectively. But the effect of light grazing treatment was insignificant. Grazing disturbance significantly reduced the contents of soil available po- tassium，total phosphorus，total nitrogen，and total potassium in alpine grasslands by 14. 55%，10. 74%，9. 14%（P＜ 0. 01） and 3. 17%（P＜0. 05），respectively. . Grazing activity significantly increased the content of available nitrogen and bulk density by 11. 90% and 12. 66% respectively. The effect size of soil organic carbon was mainly driven by soil available potassium，total nitrogen，bulk density，and altitude in grazing grassland （P＜0. 05）. The total explana- tory intensity of effect value variation reached 69. 73%.【Conclusion】 Light grazing and increasing the content of soil available potassium are beneficial to alleviate the effect of grazing on soil carbon content of alpine meadows in the Qin- ghai Tibet Plateau.