Understanding land use effects on carbon sequestration in various soil fractions is vital to mitigating climate change and restoring soil functions. The objective of this study was to explore the effects of land use on soil organic carbon (SOC) fractions in different soil types. For this purpose, we studied the effects of long-term (>20 years) land use including dryland pasture (DP), irrigated pasture (IP) and irrigated cropland (IC) on SOC in water-stable aggregates, particle-size fractions, and their coupling relations at the surface soils (0–7.5 cm) in the Canterbury Plains, New Zealand. For each land use, three typical soil types with contrasting drainage levels (i.e. well drained Lismore soil, LIS; imperfectly drained Templeton soil, TEM; and poorly drained Waterton/Temuka soil, WAT) were selected. Macroaggregate-occluded mineral-associated organic carbon (M-MAOC) contributed to the majority of the total SOC difference and drove the response of SOC to land use change. On average, M-MAOC followed an order of IP > DP > IC. The effects of land use change from DP to IP and IC on M-MAOC varied, and these variations were dependent on soil type. The relative gain in M-MAOC with change in land use from DP to IP was the greatest in the well drained LIS soil, while both the relative and absolute loss in M-MAOC following the land use change to IC was the greatest in the poorly drained WAT soil. The interactive effects of managements (e.g. irrigation and cultivation) and soil type (e.g. soil water condition) on aggregate size distribution and macroaggregate-associated C concentration were important in explaining the responses of M-MAOC to land use change. This study advances the mechanistic understanding of total SOC dynamics in response to land use (changes) in different soil types. It also highlights the potential of M-MAOC to serve as a diagnostic fraction to reflect changes in total SOC, which may have application to global warming mitigation.

中文翻译：

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土壤大团聚体吸留矿物伴生有机碳驱动土壤有机碳对土地利用变化的响应


了解土地利用对不同土壤部分固碳的影响对于缓解气候变化和恢复土壤功能至关重要。本研究的目的是探讨土地利用对不同土壤类型土壤有机碳（SOC）的影响。为此，我们研究了长期（>20年）土地利用（包括旱地牧场（DP）、灌溉牧场（IP）和灌溉农田（IC））对水稳定团聚体、颗粒尺寸分数、以及它们在新西兰坎特伯雷平原表层土壤（0-7.5 cm）的耦合关系。对于每种土地利用，选择三种具有对比排水水平的典型土壤类型（即排水良好的利斯莫尔土壤，LIS；排水不完善的坦普尔顿土壤，TEM；和排水不良的沃特顿/特穆卡土壤，WAT）。大团聚体吸留矿物相关有机碳 (M-MAOC) 造成了总 SOC 差异的大部分，并驱动了 SOC 对土地利用变化的响应。平均而言，M-MAOC 遵循 IP > DP > IC 的顺序。土地利用从 DP 到 IP 和 IC 的变化对 M-MAOC 的影响各不相同，并且这些变化取决于土壤类型。在排水良好的 LIS 土壤中，随着土地利用从 DP 变为 IP，M-MAOC 的相对增益最大，而在土地利用变化为 IC 后，M-MAOC 的相对和绝对损失在排水不良的 LIS 土壤中最大。排水的 WAT 土壤。管理（如灌溉和耕作）和土壤类型（如土壤水分条件）对团聚体尺寸分布和大团聚体相关碳浓度的交互影响对于解释 M-MAOC 对土地利用变化的响应非常重要。 这项研究推进了对不同土壤类型土地利用（变化）响应的总 SOC 动态的机制理解。它还强调了 M-MAOC 作为诊断分数来反映总 SOC 变化的潜力，这可能适用于缓​​解全球变暖。