Effects of grazing intensity on soil carbon stocks following deforestation of a Hawaiian dry tropical forest
Effects of grazing intensity on soil carbon stocks following deforestation of a Hawaiian dry tropical forest
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DOI：
10.1111/j.1365-2486.2006.01198.x
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发表时间：
2006-09
影响因子：
11.6
通讯作者：
A. Elmore;G. Asner
中科院分区：
文献类型：
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作者：
A. Elmore;G. Asner
森林转变为牧场对土壤碳（C）储量的影响取决于气候和管理因素的结合，但与放牧强度相关的因素可能是人们了解最少的。为了了解在转化牧场上放牧的长期影响，需要准确测量放牧对各种牧场管理和气候环境下植物近期对土壤碳输入的影响的方法。在这里，我们对夏威夷 100 年前由干燥热带森林转变为牧场的植被结构和土壤有机碳 (SOC) 沿放牧强度和海拔梯度的变化进行了分析。我们使用光合植被、非光合植被 (NPV) 和暴露基质的高光谱遥感来了解放牧对植物凋落物覆盖的影响，从而估算近期植物对土壤的投入（NPV 部分）。森林转变为牧场导致植物生理学从 C3 转变为 C4，因此在土壤核心中使用 δ13C 方法来测量土地转变后牧场植被来源积累的 SOC 的比例。牧场的 SOC 降低了 5-9 kg C m−2，具体取决于放牧强度。来自 C3（森林）来源的 SOC 在整个放牧梯度上保持恒定，表明观察到的 SOC 变化可归因于森林砍伐后 C 输入的变化。相对于森林土壤，牧场的土壤碳储量也有所减少。我们发现，夏威夷森林转变为牧场后，长期放牧会降低土壤有机碳，而且这些变化的幅度比海拔（气候）发生的变化更大。此外，我们还证明了地表凋落物遥感测量与现场 SOC 测量之间的关系，从而可以在有限的现场数据可用的情况下对牧场状况和碳储存进行区域分析。
The effects of forest‐to‐pasture conversion on soil carbon (C) stocks depend on a combination of climatic and management factors, but factors that relate to grazing intensity are perhaps the least understood. To understand the long‐term impact of grazing in converted pastures, methods are needed that accurately measure the impact of grazing on recent plant inputs to soil C in a variety of pasture management and climate settings. Here, we present an analysis from Hawai'i of changes in vegetation structure and soil organic carbon (SOC) along gradients of grazing intensity and elevation in pastures converted from dry tropical forest 100 years ago. We used hyperspectral remote sensing of photosynthetic vegetation, nonphotosynthetic vegetation (NPV) and exposed substrate to understand the effects of grazing on plant litter cover, thus, estimating recent plant inputs to soils (the NPV component). Forest‐to‐pasture conversion caused a shift from C3 to C4 plant physiology, thus the δ13C method was used in soil cores to measure the fraction of SOC accumulated from pasture vegetation sources following land conversion. SOC decreased in pasture by 5–9 kg C m−2, depending upon grazing intensity. SOC derived from C3 (forest) sources was constant across the grazing gradient, indicating that the observed variation in SOC was attributable to changes in C inputs following deforestation. Soil C stocks were also reduced in pastures relative to forest soils. We found that long‐term grazing lowers SOC following Hawaiian forest‐to‐pasture conversion, and that these changes are larger in magnitude that those occurring with elevation (climate). Further we demonstrate a relationship between remotely sensed measurements of surface litter and field SOC measurements, allowing for regional analysis of pasture condition and C storage where limited field data are available.