BRAZILIAN SOIL δ13C ISOSCAPE BASED ON MULTIPLE LINEAR REGRESSION ANALYSIS

Carbon stable isotope ratios (δ13C) have been applied in several environmental contexts, such as feeding habits, origin of migratory species, and vegetation distribution patterns. Brazil presents a vast environmental diversity, which enables the development of studies to identify the soil δ13C distribution patterns. This work aimed to identify the environmental variables that influence the soil δ13C and develop a spatial model of Brazilian soil δ13C, based on multiple linear regression analysis. The model used 717 samples at a depth of 0-20 centimeters and a set of climate, soil, and vegetation variables. The model showed a range of soil δ13C values between -30‰ and -13‰, with the highest estimated values in the southeastern regions and the highest estimated values in northwestern Brazil. The results pointed out regional patterns in the spatial distribution of the soil δ13C and the relationships between the environmental variables incorporated in the model and the soil δ13C. Due to the high environmental diversity of Brazil and the local environmental characteristics, some of these variables presented opposite behavior to that reported in previous studies, which makes necessary the development of studies aimed at the better understanding of these relations. Nevertheless, the soil δ13C isoscape model presented a general panorama of the distribution of Brazilian soil δ13C with a more refined level of detail concerning the existing models for the region.

碳稳定同位素比值（Carbon stable isotope ratios）已被广泛应用于诸多环境研究场景，涵盖食性分析、迁徙物种溯源及植被分布格局研究等领域。巴西拥有广袤多样的环境禀赋，为开展土壤δ¹³C分布格局相关研究创造了有利条件。本研究旨在明确影响土壤δ¹³C的环境驱动变量，并基于多元线性回归分析方法构建巴西土壤δ¹³C空间分布模型。该模型共纳入717份0~20厘米深度的土壤样本，以及一套气候、土壤与植被相关的环境变量集。模型结果显示，土壤δ¹³C值的分布区间为-30‰至-13‰，预估最高值同时出现在巴西东南部与西北部地区。研究结果揭示了土壤δ¹³C空间分布的区域格局，以及模型纳入的环境变量与土壤δ¹³C之间的关联关系。鉴于巴西极高的环境多样性与当地独特的环境特征，部分变量的响应特征与既往研究报道结果存在相悖之处，这表明亟需开展进一步研究以深入阐明此类关联机制。尽管如此，本研究构建的土壤δ¹³C同位素景观模型（isoscape model）仍系统呈现了巴西土壤δ¹³C的分布全貌，相较于该区域现有模型，其细节精度得到了显著提升。