Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
Department of Biology, MSC03 202, University of New Mexico, Albuquerque, NM, 87131-0001, USA.
Plant Cell Environ. 2017 Sep;40(9):1861-1873. doi: 10.1111/pce.12991. Epub 2017 Jun 20.
Disentangling the relative impacts of precipitation reduction and vapour pressure deficit (VPD) on plant water dynamics and determining whether acclimation may influence these patterns in the future is an important challenge. Here, we report sap flux density (F ), stomatal conductance (G ), hydraulic conductivity (K ) and xylem anatomy in piñon pine (Pinus edulis) and juniper (Juniperus monosperma) trees subjected to five years of precipitation reduction, atmospheric warming (elevated VPD) and their combined effects. No acclimation occurred under precipitation reduction: lower G and F were found for both species compared to ambient conditions. Warming reduced the sensibility of stomata to VPD for both species but resulted in the maintenance of G and F to ambient levels only for piñon. For juniper, reduced soil moisture under warming negated benefits of stomatal adjustments and resulted in reduced F , G and K . Although reduced stomatal sensitivity to VPD also occurred under combined stresses, reductions in G , F and K took place to similar levels as under single stresses for both species. Our results show that stomatal conductance adjustments to high VPD could minimize but not entirely prevent additive effects of warming and drying on water use and carbon acquisition of trees in semi-arid regions.
解析降水减少和蒸气压亏缺（VPD）对植物水分动态的相对影响，并确定适应是否可能影响未来这些模式，这是一个重要的挑战。在这里，我们报告了在经历了五年降水减少、大气增温和它们的综合影响后，花粉松（Pinus edulis）和刺柏（Juniperus monosperma）树木的比液流密度（F）、气孔导度（G）、水力传导度（K）和木质部解剖结构。在降水减少的情况下没有发生适应：与环境条件相比，两种物种的 G 和 F 都较低。增温降低了两种物种对 VPD 的气孔敏感性，但仅对花粉松保持了 G 和 F 达到环境水平。对于刺柏，增温下土壤水分减少否定了气孔调节的好处，导致 F、G 和 K 减少。尽管在综合胁迫下也发生了降低的 VPD 对气孔的敏感性，但 G、F 和 K 的降低水平与单一胁迫下的两种物种相似。我们的结果表明，高 VPD 下的气孔导度调整可以最小化，但不能完全防止半干旱地区树木的增温和干燥对水分利用和碳获取的附加影响。
