No long-term effect of land-use activities on soil carbon dynamics in tropical montane grasslands
No long-term effect of land-use activities on soil carbon dynamics in tropical montane grasslands
复制标题
DOI：
10.5194/bg-2017-113
复制
发表时间：
2017-04
期刊：
影响因子：
--
通讯作者：
V. Oliver;I. Oliveras;J. Kala;R. Lever;Y. Teh
中科院分区：
文献类型：
--
作者：
V. Oliver;I. Oliveras;J. Kala;R. Lever;Y. Teh
山地热带土壤是一个巨大的碳(C)储存库，既是二氧化碳的源，也是二氧化碳的汇。CO2排放增加在很大程度上源于人为干扰后土壤有机质(SOM)的分解和损失。因此，为了了解、评估和预测热带土地管理的影响，有必要对土壤有机质的稳定和分解进行定量的了解。特别是，不稳定的土壤有机质是土壤有机质如何应对土地利用和管理做法变化的早期和敏感指标，这可能对长期碳储存和大气二氧化碳浓度上升产生重大影响。这项研究的目的是调查放牧和火灾历史对秘鲁山地草原土壤碳动态的影响，这是一个研究不足的生态系统，覆盖了秘鲁约四分之一的陆地面积。采用密度分级和粒度分级相结合的方法对土壤中不稳定和稳定的有机质库进行了量化，并对土壤CO2通量和分解进行了测量。放牧和焚烧一起显著增加了土壤CO2通量和分解速率，并作为驱动因素降低了温度。尽管土地利用对土壤总碳库没有显著影响，但火牧结合降低了土壤游离碳库中碳的比例，尤其是在较低深度(10-20 cm和20-30 cm)。与放牧土壤相比，对照土壤中的游离Lf占土壤总质量的20%，土壤C含量的30%，其回收率最小(10%)，C含量显著降低(14%)。火烧土壤中的碳在封闭的土壤中所占的比例(12%)明显高于非火烧土壤(7%)，而在重氟土壤(~70%)中，不同处理之间的差异不显著。火烧与放牧的协同作用引起了土壤碳动态的变化。CO2通量增加，主导的温度驱动因素被其他一些过程所掩盖，如植物C和N分配的变化促进了自养呼吸。此外，当这两种人为活动发生在同一地点时，游离Lf受到负面影响。最有可能的结果是减少了碎屑被并入土壤。这项研究的一个积极发现是，土壤总碳储量没有受到显著影响，遮挡的LF和重F中的长期C储量也没有受到负面影响。这可能是因为低强度的火力、耐火的牧草和放牧压力低于门槛而导致严重退化。
Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO 2 . Enhanced CO 2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long term carbon storage and rising atmospheric CO 2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands; an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A combination of density and particle-size fractionation was used to quantify the labile and stable organic matter pools, along with soil CO 2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO 2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free LF, especially at the lower depths (10–20 and 20–30 cm). The free LF in the control soils made 20 % of the bulk soil mass and 30 % of the soil C content compared to the burnt-grazed soils, which had the smallest recovery of free LF (10 %) and significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the non-burnt soils (7 %) and there was no significant difference among the treatments in the heavy F (~ 70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO 2 fluxes were increased and the dominant temperature driver was obscured by some other process, such as changes in plant C and N allocation promoting autotrophic respiration. In addition, the free LF was negatively affected when these two anthropogenic activities took place on the same site. Most likely a result of reduced detritus being incorporated into the soil. A positive finding from this study is that the total soil C stocks were not significantly affected and the long term C storage in the occluded LF and heavy F were not negatively impacted. Possibly this is because of low intensity fire, fire-resilient grasses and the grazing pressure is below the threshold to cause severe degradation.