Key message

Minimum wood density is a proxy of soil moisture during the early growing season. Maximum wood density responds to late growing-season drought.

Abstract

Seasonally dry areas are ideal settings to refine our understanding of tree growth proxies of water availability. Despite recent methodological advances in quantitative wood anatomy and wood density, our knowledge of wood density responses to climate at intra-annual scales in seasonal drought-prone regions is still limited. The objective of this study is to elucidate how minimum (MnD) and maximum (MxD) wood density respond to hydroclimate variability of two coexisting conifers growing in a moisture-stressed environment. We prepared wood samples to obtain MnD and MxD values in Pinus lumholtzii and Pinus durangensis trees co-occurring in a drought-prone site located in northern Mexico. MnD and MxD were correlated with temperature, water balance and a drought index considering the period 1970‒2013. The P. lumholtzii MnD negatively responded to growing-season water availability as indicated by the negative correlations with water balance, and considering short to mid-term droughts lasting from 2 to 8 months. Both species showed a decrease in MxD during the last 15 years associated to a rise in temperature and drier conditions. Winter-spring water balance was positively associated with MxD, but July water balance showed a negative correlation. Intra-annual density data can represent robust proxies of hydroclimate variability in similar seasonally dry areas. Specifically, MnD should be further investigated as a surrogate of water availability effects on earlywood during the early growing season.

中文翻译：

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最小和最大木材密度作为季节性干旱地区同时存在的两种墨西哥松树中可用水的代理

关键信息

最低木材密度是生长初期土壤水分的代表。最大的木材密度可应对生长季节后期的干旱。

抽象

季节性干旱地区是理想的环境，可以加深我们对树木可用水生长代理的理解。尽管最近在定量的木材解剖结构和木材密度方面在方法学方面取得了进步，但我们对季节性干旱多发地区木材密度在年内尺度上对气候的响应的认识仍然有限。这项研究的目的是阐明木材的最小（MnD）和最大（MxD）密度如何响应在潮湿环境中生长的两种同时存在的针叶树的水温变化。我们准备了木样获得MND和MXD值松lumholtzii和松durangensis墨西哥北部干旱多发的土地上同时存在树木。考虑到1970-2013年，MnD和MxD与温度，水平衡和干旱指数相关。该P. lumholtziiMnD对生长季节的水可利用性负响应，这与水平衡呈负相关，并考虑了持续2到8个月的中短期干旱。在过去的15年中，这两个物种的MxD均下降，这与温度和干燥条件的升高有关。冬春季水平衡与MxD正相关，但7月水平衡显示负相关。年内密度数据可以代表相似的季节性干旱地区水气候变化的有力代理。具体来说，应进一步研究MnD，以替代水分在早期生长季节对早材的影响。