NOAA/WDS Paleoclimatology - Lopez - San Miguel de Velasco - SCBR - ITRDB BOL019

Given the scarcity of instrumental climatic data in the South American tropics, it is valuable to explore the dendrochronological potential of the numerous tree species growing in the region. In this paper, we assessed for the first time the dendrochronological characteristics of Schinopsis brasiliensis, an arboreal species from the dry-tropical Cerrado and Chaco forests in Bolivia and adjacent countries. Similar to most woody species in the Cerrado and Chaco regions, growth rings of S. brasiliensis are delimited by the presence of thin but continuous lines of marginal parenchyma. Based on 22 samples from 15 trees, we present the first ring-width chronology for this species covering the period 1812–2011 (200 years). Additionally, a 106-year floating chronology from S. brasiliensis was developed using cores from four columns from the church of San Miguel, Santa Cruz, built in the period 1720–1740. Standard dendrochronological statistics indicate an important common signal in the radial growth of S. brasiliensis. The comparison of variations in regional climate and ring widths shows that tree growth is directly related to spring-summer rainfall and inversely related to temperature. Following the winter dry season, rainfall in late spring and early summer increases soil water supply, which activates tree growth. In contrast, above-average temperatures during the same period increase evapotranspiration, intensify the water deficit and reduce radial growth. The dependence of S. brasiliensis growth on water supply is evidence of its dendrochronological potential for reconstructing past precipitation variations in the extensive tropical Cerrado and Chaco forest formations in South America. Using wood from historical buildings opens the possibility of extending the chronologies of S. brasiliensis over the past 400–500 years.

鉴于南美热带地区器测气候数据的匮乏，探究该区域分布的众多树种的树轮年代学潜力具有重要学术价值。本研究首次评估了玻利维亚及周边国家干热带塞拉多（Cerrado）和查科（Chaco）森林中的乔木物种巴西肖乳香（Schinopsis brasiliensis）的树轮年代学特征。与塞拉多和查科地区多数木本物种一致，巴西肖乳香的生长轮以薄而连续的边缘薄壁组织带为界。基于15株树木的22个样本，本研究构建了该物种首个树轮宽度年表，时间跨度为1812年至2011年，共计200年。此外，本研究利用圣克鲁斯市圣米格尔教堂（建于1720-1740年）4根木柱的芯样，构建了巴西肖乳香的106年浮动年表。标准树轮年代学统计结果显示，巴西肖乳香的径向生长存在显著的公共信号。区域气候与树轮宽度的变化对比分析表明，该树种的生长与春夏降雨量呈正相关，与气温呈负相关。在冬季旱季过后，晚春至初夏的降雨会提升土壤水分供给，从而激活树木生长。反之，同期气温高于平均值会加剧蒸散发作用，加重水分亏缺，进而抑制径向生长。巴西肖乳香的生长对水分供给的依赖性，证明其具备树轮年代学潜力，可用于重建南美广袤的热带塞拉多与查科森林群落的历史降水变化。利用历史建筑中的木材，可将巴西肖乳香的树轮年表延伸至过去400至500年。