Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, Butantã, São Paulo, SP, 09715-030, Brazil.
Department of Physical Geography, University of Passau, Innstraße 40, 94032, Passau, Germany.
Int J Biometeorol. 2019 Dec;63(12):1683-1692. doi: 10.1007/s00484-019-01786-y. Epub 2019 Aug 27.
Widely distributed tree species usually face different growth conditions across gradients of climate variables. Hymenaea courbaril inhabits most of Neotropical lowlands, where its growth is limited by low precipitation under seasonal precipitation regimes. However, it is still unclear what are the drivers of growth variability at its distribution limits, where populations are most vulnerable to climate change. We evaluated the role of precipitation and temperature variability on the growth rate of two populations of H. courbaril at the southern limits of its occurrence. Sampling sites comprise two semi-deciduous forest fragments with weathered and chemically poor soils, similar temperature conditions, only differing in size and in precipitation regime. To achieve that goal, we built two tree-ring chronologies using standard dendrochronological methods, one with 21 trees (37 radii) and the other one with 13 trees (24 radii). First, we evaluated if site conditions would affect average growth patterns, and then, we tested the climate-growth relationships and the teleconnections with the Equatorial Pacific sea surface temperature (SST). The results show that trees display similar average growth rates throughout life without evidence of influence from differing fragment sizes. Nonetheless, precipitation positively influences annual growth in the drier site, while it has a negative effect on growth in the wetter site. In contrast to previous studies, temperature has a stronger influence than precipitation on the growth of these trees. Monthly, seasonal, and annual mean temperatures showed a negative influence on trees growth. The variability of the regional temperature and, consequently, of the growth rate of the trees is partially dependent on the SST of the Equatorial Pacific. In conclusion, this study shows that temperature is a key limiting growth factor for this species at its southern distribution limits and periods with warmer temperature will likely reduce annual growth rate.
分布广泛的树种通常在气候变量梯度上面临不同的生长条件。雨树（Hymenaea courbaril）栖息于新热带地区的大部分低地，其生长受到季节性降水模式下低降水的限制。然而，在分布范围的限制下，哪些是生长变化的驱动因素，以及这些种群在气候变化面前最脆弱，这些问题仍不清楚。我们评估了降水和温度变化对其分布范围南端的两个雨树种群生长速度的影响。采样地点包括两个半落叶林片段，这些片段具有风化和贫化的土壤，温度条件相似，只是在大小和降水模式上有所不同。为了实现这一目标，我们使用标准的树木年代学方法构建了两个树木年轮序列，一个序列包含 21 棵树（37 个半径），另一个序列包含 13 棵树（24 个半径）。首先，我们评估了站点条件是否会影响平均生长模式，然后测试了气候-生长关系以及与赤道太平洋海表温度（SST）的遥相关关系。结果表明，树木在整个生命过程中显示出相似的平均生长速度，没有迹象表明片段大小的差异会影响生长。然而，降水在较干燥的地点对年生长有积极的影响，而在较湿润的地点则对生长有负面影响。与之前的研究相反，温度对这些树木的生长影响比降水更大。月平均、季平均和年平均温度对树木生长有负面影响。区域温度的变化，以及树木生长速度的变化，部分取决于赤道太平洋的 SST。总之，本研究表明，温度是该物种在其南部分布限制下的关键生长限制因素，而更温暖的温度期可能会降低年生长率。
