Laughlin Daniel C, Delzon Sylvain, Clearwater Michael J, Bellingham Peter J, McGlone Matthew S, Richardson Sarah J
Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.
INRA, BIOGECO, University of Bordeaux, 33615, Pessac, France.
New Phytol. 2020 May;226(3):727-740. doi: 10.1111/nph.16448. Epub 2020 Feb 29.
Hydraulic failure explains much of the increased rates of drought-induced tree mortality around the world, underlining the importance of understanding how species distributions are shaped by their vulnerability to embolism. Here we determined which physiological traits explain species climatic limits among temperate rainforest trees in a region where chronic water limitation is uncommon. We quantified the variation in stem embolism vulnerability and leaf turgor loss point among 55 temperate rainforest tree species in New Zealand and tested which traits were most strongly related to species climatic limits. Leaf turgor loss point and stem P50 (tension at which hydraulic conductance is at 50% of maximum) were uncorrelated. Stem P50 and hydraulic safety margin were the most strongly related physiological traits to climatic limits among angiosperms, but not among conifers. Morphological traits such as wood density and leaf dry matter content did not explain species climatic limits. Stem embolism resistance and leaf turgor loss point appear to have evolved independently. Embolism resistance is the most useful predictor of the climatic limits of angiosperm trees. High embolism resistance in the curiously overbuilt New Zealand conifers suggests that their xylem properties may be more closely related to growing slowly under nutrient limitation and to resistance to microbial decomposition.
水力衰竭解释了全球干旱导致树木死亡率上升的大部分原因，凸显了了解物种分布如何受其栓塞脆弱性影响的重要性。在此，我们确定了在一个长期水分限制并不常见的地区，哪些生理特征解释了温带雨林树木的物种气候极限。我们量化了新西兰55种温带雨林树种茎干栓塞脆弱性和叶片膨压丧失点的变化，并测试了哪些特征与物种气候极限关系最为密切。叶片膨压丧失点和茎干P50（导水率为最大值50%时的张力）不相关。在被子植物中，茎干P50和水力安全边际是与气候极限关系最为密切的生理特征，但在针叶树中并非如此。木材密度和叶片干物质含量等形态特征并不能解释物种气候极限。茎干抗栓塞能力和叶片膨压丧失点似乎是独立进化的。抗栓塞能力是被子植物树木气候极限最有用的预测指标。新西兰针叶树过度发达，具有较高的抗栓塞能力，这表明它们的木质部特性可能与在养分限制下生长缓慢以及对微生物分解的抗性更为密切相关。
