Concentration of Metals in Plant Litter Produced in Regions of Caatinga in Southwest Bahia, Brazil

Plant litter has several functions in a forest ecosystem. Studies about plant litter are of great importance to better understand and conserve ecological environments. The objective of this study was to investigate the concentration of metals (Fe, Co, Ca, Cu, Ni, Mg, Mn and Zn) in Caatinga plant litter in the southwest region of Bahia. Plant litter was collected in summer (January/2017) and winter (August/2017). Concentrations were determined by flame atomic absorption spectrometry (FAAS). The results were submitted to multivariate analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA). The average amount of plant litter found in January and August was 1190 and 1329 kg ha-1, respectively. The twigs fraction provided the largest amount of biomass to the plant litter since this deposition occurred in greater quantity in August, a period of drought. Metal concentrations (g kg-1) in the analyzed samples ranged from 1.39-257 (Fe), < limit of quantification (LOQ)-0.269 (Co), 0.0036-0.61 (Cu), 1.39-8.76 (Ca), 0.0022-0.56 (Ni), 0.137-1.52 (Mg), 0.033-1.91 (Mn) and 0.0022-0.8 (Zn). The multivariate analysis showed that the composition of plant litter is altered seasonally.

植物凋落物（plant litter）在森林生态系统中具有多种生态功能。针对植物凋落物的研究，对于深入认知与保护生态环境具有重要价值。本研究旨在测定巴伊亚州西南部卡廷加（Caatinga）植被凋落物中金属元素（Fe、Co、Ca、Cu、Ni、Mg、Mn及Zn）的含量。研究分别于2017年夏季（1月）与冬季（8月）采集植物凋落物样本，金属元素含量通过火焰原子吸收光谱法（flame atomic absorption spectrometry, FAAS）测定。所得结果采用多元统计分析、主成分分析（principal component analysis, PCA）及层次聚类分析（hierarchical cluster analysis, HCA）进行处理与分析。2017年1月与8月采集的植物凋落物平均储量分别为1190 kg·ha⁻¹与1329 kg·ha⁻¹。枝条组分是植物凋落物生物量的主要贡献来源，且该组分在旱季的8月沉降量更高。待测样品中各金属元素的含量（单位：g·kg⁻¹）范围如下：Fe为1.39~257，Co为低于定量限（limit of quantification, LOQ）~0.269，Cu为0.0036~0.61，Ca为1.39~8.76，Ni为0.0022~0.56，Mg为0.137~1.52，Mn为0.033~1.91，Zn为0.0022~0.8。多元统计分析结果表明，植物凋落物的组分组成存在季节性差异。