植被恢复十年喀斯特坡地细根对土壤碳氮存留与可利用性的影响

Fine root effects on the retention and availability of soil carbon and nitrogen after ten years of vegetation restoration in a karst slope ecosystem

土壤碳氮存留与可利用性对恢复生态系统的稳定性和可持续性产生重要影响,研究其细根控制过程对深入理解植被恢复的作用及其针对性应用具有重要意义。依托中国科学院环江喀斯特生态系统观测研究站10年植被恢复平台,通过分析8种植被恢复模式植物(细根生物量、δ^(13)C、δ^(15)N)、土壤(有机碳、总氮、δ^(13)C、δ^(15)N、团聚体、砂粒、交换性钙、可溶性有机碳和氮、铵态氮、无机氮、微生物生物量碳和氮)理化性质的变化和关系,阐明细根对土壤碳氮存留与可利用性的影响。研究结果表明:细根对土壤碳氮存留的影响可能主要基于对土壤团聚体结构的改善,加强了对土壤原有机碳、氮的保护和存留,而细根有机质输入的影响是较弱的;细根可能通过影响微生物调控土壤可利用性碳和氮;因高的细根生物量和固氮植物,封育林和刈割草地模式具有较高的土壤碳氮存留效应。综上所述,喀斯特植被恢复过程中细根对土壤碳氮存留与可利用性产生积极的影响。因此,石漠化生态工程治理可以考虑根系发达与固氮植物共同引种。

The retention and availability of soil carbon(C) and nitrogen(N) significantly affect the stability and sustainability of the restored ecosystem. Research about how fine root regulates soil C and N processes is significant importance for thoroughly understanding the role of vegetation restoration and its specific application. An experiment was carried out at the vegetation restoration plot which has lasted for ten years in Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences. We analyzed the changes and relationships in plant(fine root biomass, δ^(13)C, δ^(15)N) and soil(soil organic C, total N, δ^(13)C, δ^(15)N, soil aggregates, sand content, exchangeable Ca2+, dissolved organic C and N, NH+4, inorganic N, microbial C and N) physiochemical properties among eight vegetation restoration models, in order to clarify the effects of fine root on soil C and N retention and availability. The results showed a significant relationship between fine root and soil organic C and total N, indicating that fine root played an important role in regulating soil C and N retention. The significant relationships between fine root and soil aggregates, sand content, exchangeable Ca2+ and soil water content, combined with the proportion of C input derived from new vegetation, the changes and relationships of plant and soil δ^(13)C and δ^(15)N further indicated that the effects of fine root on soil C and N retention may mainly depend on improving soil aggregate structure, which enhanced the conservation and retention of the original soil C and N;while the effect of fine root organic matter inputs was weak. The results showed a significant relationship between fine root and dissolved organic C and N, NH+4 and inorganic N, indicating that fine root affected soil C and N availability. The significant relationships between fine root and soil microbial C and N further indicated that fine root may regulate soil C and N availability by affecting microbes. Our results showed that the higher soil C and N concentrations in spontaneous regeneration and aboveground vegetation removal models compared with other six models. The better sequestrated soil C and N in spontaneous regeneration and aboveground vegetation removal models may be due to higher fine root biomass and nitrogen fixing plants. Together, fine root played the positive effect on the retention and availability of soil C and N during vegetation restoration in a karst slope ecosystem. Thus, well-developed roots and nitrogen fixing plants can be jointly planted during rocky desertification ecological restoration.