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在桂西北喀斯特地区以原生林地为对照,选取了玉米-红薯轮作地、放牧+火烧草地和自然恢复地3种不同人为干扰的生态系统,研究土壤剖面养分、微生物活性对干扰强度的响应。结果表明,土壤有机碳和全氮随土壤深度的增加而降低,全磷变化较小,说明磷素主要来源于土壤母质,且淋溶作用较小;原生林地0-30 cm土壤有机碳、全氮、全磷、微生物量碳、氮、磷、碱解氮显著高于自然恢复地、放牧+火烧草地和玉米-红薯轮作地(p<0.05),说明原生生态系统可维持较高的土壤肥力和微生物活性;3种人为干扰的生态系统,自然恢复地和放牧+火烧草地0-5 cm土壤有机碳含量显著高于玉米-红薯轮作地,说明自然恢复有利于提高表层土壤肥力和有机碳积累;玉米-红薯轮作地表层0-15 cm土壤全磷和有效磷含量显著高于自然恢复地和放牧+火烧草地,主要受施肥影响;60-100 cm,原生林地、自然恢复地和放牧+火烧草地土壤全氮显著高于玉米-红薯轮作地,说明农耕旱地土壤下层氮受雨水影响较大,淋失严重。自然恢复地和放牧+火烧草地表层(0-15 cm)土壤碱解氮、微生物量碳、氮、磷显著高于玉米-红薯轮作地,说明减少人为干扰和实行自然恢复可显著提高土壤氮的有效性和微生物活性。因此,提高农田管理水平、施行保护性耕作,推行自然恢复、减少人为干扰是提高喀斯特退化生态系统土壤生产力和增加土壤有机碳积累的有效措施。
In the karst area of northwestern Guilin, China, three different man-made disturbed ecosystems including corn-sweet potato rotation, grazing + grassland burning and natural restoration were selected to study the response of soil nutrient and microbe activity to disturbance intensity. The results showed that soil organic carbon and total nitrogen decreased with the increase of soil depth and little change of total phosphorus, indicating that phosphorus was mainly derived from soil parent material and had less leaching action. In 0-30 cm soil organic carbon in primary forest, Nitrogen, total phosphorus, microbial biomass carbon, nitrogen, phosphorus and alkaline hydrolysis nitrogen were significantly higher than those of natural restoration, grazing + fire grassland and corn-sweet potato rotation (p <0.05), indicating that the native ecosystem could maintain high soil fertility And microbial activity. The organic carbon content of 0-5 cm soil in three man-made disturbed ecosystems, natural restoration land and grazing + fire grassland was significantly higher than that of corn-sweet potato rotation, indicating that natural restoration is beneficial to increase the surface soil fertility and organic carbon accumulation ; The contents of total phosphorus and available phosphorus in 0-15 cm soil layer of corn-sweet potato rotation were significantly higher than those of natural restoration and grazing + fire-burning grassland, which were mainly affected by fertilization; 60-100 cm, native woodland, natural recovery and grazing + The total nitrogen in grassland soil was significantly higher than that of corn-sweet potato rotation, which indicated that the nitrogen in the lower layer of agricultural soil was more affected by rainwater and the leaching loss was serious. The contents of soil available nitrogen, microbial biomass carbon, nitrogen and phosphorus in the natural restoration and grazing + fire grassland surface (0-15 cm) were significantly higher than those in the field of corn and sweet potato rotation, indicating that reducing man-made disturbance and implementing natural restoration could significantly increase soil nitrogen Effectiveness and microbial activity. Therefore, raising farmland management level, implementing conservation tillage, promoting natural restoration and reducing human disturbance are effective measures to increase soil productivity and increase soil organic carbon accumulation in degraded karst ecosystems.