Regional differences in soil stable isotopes and vibrational features at depth in three California grasslands

IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Biogeochemistry Pub Date : 2024-11-05 DOI:10.1007/s10533-024-01181-9
L. M. Wahab, S. S. Chacon, S. L. Kim, A. A. Berhe
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Abstract

There are major gaps in our understanding of how Mediterranean ecosystems will respond to anticipated changes in precipitation. In particular, limited data exists on the response of deep soil carbon dynamics to changes in climate. In this study we wanted to examine carbon and nitrogen dynamics between topsoils and subsoils along a precipitation gradient of California grasslands. We focused on organic matter composition across three California grassland sites, from a dry and hot regime (~ 300 mm precipitation; MAT: 14.6 \(\boldsymbol{^\circ{\text{C}} }\)) to a wet, cool regime (~ 2160 mm precipitation/year; MAT: 11.7 \(\boldsymbol{^\circ{\text{C}} }\)). We determined changes in total elemental concentrations of soil carbon and nitrogen, stable isotope composition (δ13C, δ15N), and composition of soil organic matter (SOM) as measured through Diffuse Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS) to 1 m soil depth. We measured carbon persistence in soil organic matter (SOM) based on beta (\({\varvec{\beta}}\)), a parameter based on the slope of carbon isotope composition across depth and proxy for turnover. Further, we examined the relationship between δ15N and C:N values to infer SOM’s degree of microbial processing. As expected, we measured the greatest carbon stock at the surface of our wettest site, but carbon stocks in subsoils converged at Angelo and Sedgwick, the wettest and driest sites, respectively. Soils at depth (> 30 cm) at the wettest site, Angelo, had the lowest C:N and highest δ15N values with the greatest proportion of simple plant-derived organic matter according to DRIFTS. These results suggest differing stabilization mechanisms of organic matter at depth across our study sites. We infer that the greatest stability was conferred by associations with reactive minerals at depth in our wettest site. In contrast, organic matter at our driest site, Sedgwick, was subject to the most microbial processing. Results from this study demonstrate that precipitation patterns have important implications for deep soil carbon storage, composition, and stability.

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加利福尼亚三片草地土壤稳定同位素和振动特征的区域差异
我们对地中海生态系统如何应对预期降水量变化的认识还存在很大差距。特别是,有关深层土壤碳动态对气候变化的响应的数据十分有限。在这项研究中,我们希望沿着加利福尼亚草原的降水梯度,研究表层土壤和底层土壤之间的碳氮动态。我们重点研究了加利福尼亚三个草原地点的有机物组成,从干燥炎热的气候(降水量约为 300 毫米;MAT:14.6)到湿润凉爽的气候(降水量约为 2160 毫米/年;MAT:11.7)。我们测定了土壤碳和氮的总元素浓度、稳定同位素组成(δ13C、δ15N)以及土壤有机质(SOM)组成的变化,这些都是通过漫反射红外傅立叶变换光谱仪(DRIFTS)测量的,测量深度为 1 米。我们根据 beta(\({\varvec{\beta}}\))测量了土壤有机质(SOM)中碳的持久性,该参数基于碳同位素组成在不同深度的斜率,代表了周转率。此外,我们还研究了 δ15N 和 C:N 值之间的关系,以推断 SOM 的微生物加工程度。不出所料,我们在最潮湿地点的地表测得了最大的碳储量,但在安杰洛和塞奇威克(分别是最潮湿和最干旱的地点),底土中的碳储量趋于一致。根据 DRIFTS,最潮湿地点安杰洛的土壤深度(30 厘米)的 C:N 值最低,δ15N 值最高,简单植物源有机物的比例最大。这些结果表明,在我们的研究地点中,有机物在深度上的稳定机制各不相同。我们推断,在最潮湿的研究地点,有机物在深处与活性矿物质的结合具有最大的稳定性。与此相反,最干旱地点塞奇威克的有机物受到的微生物处理最多。这项研究的结果表明,降水模式对深层土壤碳储存、组成和稳定性具有重要影响。
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来源期刊
Biogeochemistry
Biogeochemistry 环境科学-地球科学综合
CiteScore
7.10
自引率
5.00%
发文量
112
审稿时长
3.2 months
期刊介绍: Biogeochemistry publishes original and synthetic papers dealing with biotic controls on the chemistry of the environment, or with the geochemical control of the structure and function of ecosystems. Cycles are considered, either of individual elements or of specific classes of natural or anthropogenic compounds in ecosystems. Particular emphasis is given to coupled interactions of element cycles. The journal spans from the molecular to global scales to elucidate the mechanisms driving patterns in biogeochemical cycles through space and time. Studies on both natural and artificial ecosystems are published when they contribute to a general understanding of biogeochemistry.
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