Plant Ecology and Ecosystems Research, Albrecht-Von-Haller Institute for Plant Sciences, University of Göttingen, Göttingen, Germany.
Department of Botany, Ecology and Plant Physiology, University of La Laguna, La Laguna, Spain.
Oecologia. 2023 Apr;201(4):1089-1107. doi: 10.1007/s00442-023-05353-6. Epub 2023 Mar 22.
Tropical forests are threatened by anthropogenic activities such as conversion into agricultural land, logging and fires. Land-use change and disturbance affect ecosystems not only aboveground, but also belowground including the ecosystems' carbon and nitrogen cycle. We studied the impact of different types of land-use change (intensive and traditional agroforestry, logging) and disturbance by fire on fine root biomass, dynamics, morphology, and related C and N fluxes to the soil via fine root litter across different ecosystems at different elevational zones at Mt. Kilimanjaro (Tanzania). We found a decrease in fine root biomass (80-90%), production (50%), and C and N fluxes to the soil via fine root litter (60-80%) at all elevation zones. The traditional agroforestry 'Chagga homegardens' (lower montane zone) showed enhanced fine root turnover rates, higher values of acquisitive root morphological traits, but similar stand fine root production, C and N fluxes compared to the natural forest. The decrease of C and N fluxes with forest disturbance was particularly strong at the upper montane zone (60 and 80% decrease, respectively), where several patches of Podocarpus forest had been disturbed by fire in the previous years. We conclude that changes on species composition, stand structure and land management practices resulting from land-use change and disturbance have a strong impact on the fine root system, modifying fine root biomass, production and the C and N supply to the soil from fine root litter, which strongly affects the ecosystems' C and N cycle in those East African tropical forest ecosystems.
热带森林受到人为活动的威胁，如转为农业用地、砍伐和火灾。土地利用变化和干扰不仅会影响地上生态系统，还会影响包括生态系统碳氮循环在内的地下生态系统。我们研究了不同类型的土地利用变化（集约型和传统农林复合经营、砍伐）以及火灾干扰对乞力马扎罗山（坦桑尼亚）不同海拔地区不同生态系统的细根生物量、动态、形态以及通过细根凋落物向土壤输送的相关碳氮通量的影响。我们发现，在所有海拔地区，细根生物量（80-90%）、细根生产力（50%）和通过细根凋落物向土壤输送的碳氮通量（60-80%）都有所下降。传统的农林复合经营“查加家园”（低山地带）表现出较高的细根周转率、较高的获取性根形态特征值，但与天然林相比，其立木细根生产力和碳氮通量相似。在高山带（分别减少 60%和 80%），森林干扰导致的碳氮通量减少尤其强烈，前几年几处柏科森林已被火灾干扰。我们的结论是，土地利用变化和干扰导致的物种组成、林分结构和土地管理实践的变化对细根系统有强烈影响，改变了细根生物量、生产力以及通过细根凋落物向土壤提供的碳氮供应，这强烈影响了这些东非热带森林生态系统的碳氮循环。
