Contrasting patterns of radial growth rate between Larix principis-rupprechtii and Pinus sylvestris var. mongolica along an elevational gradient are mediated by differences in xylem hydraulics
Contrasting patterns of radial growth rate between Larix principis-rupprechtii and Pinus sylvestris var. mongolica along an elevational gradient are mediated by differences in xylem hydraulics
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DOI：
10.1016/j.foreco.2021.119524
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发表时间：
2021-10
影响因子：
3.7
通讯作者：
Mingyong Li;Q. Leng;Guang‐You Hao
中科院分区：
文献类型：
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作者：
Mingyong Li;Q. Leng;Guang‐You Hao
物种特有的环境适应性导致不同物种在自然界中具有不同的适宜分布范围。研究不同树种生长性能相对优势随海拔梯度的变化及其机制，对于选择山区森林经营的海拔最佳树种至关重要。据广泛报道，木质部水力学在水资源有限的环境下对树木生长和生存发挥着关键作用，但它是否以及如何调节具有对比水可用性的不同海拔的树木生长性能仍不清楚。在这里，我们结合了树木年轮分析和木质部水力测量，研究了鲁普雷希特王子落叶松（Larix principis-rupprechtiiMayr）和蒙古松（Pinus sylvestrisvar.mongolicaLitvinov）的树木径向生长模式及其与水相关生理学的联系，沿海拔 1336 米至 1825 米之间的 500 米海拔梯度。在中国北方的半干旱地区，这两种树种都被广泛用于造林。结果表明，在较高海拔地区，鲁普雷希特落叶松的径向生长率（以累积断面积增量和树龄的线性回归线斜率反映）高于蒙古松，这与中高海拔地区前一种树种相对于后者木质部水力效率的优势相吻合，即边材面积比水力传导率和叶面积与边材面积比较高。然而，在比较低海拔地区两种针叶树的径向生长速率时，出现了相反的模式，这可能是由于鲁普雷希特王子落叶松干旱引起的木质部栓塞导致导水率损失明显更大。鲁普雷希特王子落叶松生长季节的树轮宽度指数与与水相关的气候变量之间的强相关性证实了这一点，但低海拔蒙古松则不然。我们的研究为这两个物种在不同海拔地区的生长表现差异提供了机制解释，并暗示鲁普雷希特王子落叶松在气候变化的影响下存在生长衰退的潜在风险，鲁普雷希特落叶松是目前该地区最广泛使用的造林树种，特别是在低海拔地区的干旱环境下。
Species-specific environmental adaptability results in different species having different suitable distribution ranges in nature. Investigating the change of relative advantages in growth performances among tree species along elevational gradients and the underlying mechanism are essential for selecting elevation-specific optimal species in forest management in mountainous regions. Xylem hydraulics has been widely reported to play a key role in tree growth and survival under water-limited environments, but whether and how it regulates tree growth performances at different elevations with contrasting water availability remain unclear. Here we combined tree-ring analyses and measurements of xylem hydraulics to investigate the patterns of tree radial growth and their linkages with water-related physiology for Prince Rupprecht's larch (Larix principis-rupprechtiiMayr) and Mongolian pine (Pinus sylvestrisvar.mongolicaLitvinov) along a 500-m elevational gradient between 1336 and 1825 m a.s.l. in a semi-arid area of northern China where both species were widely used for afforestation. Our results showed that the radial growth rate, reflected by the slope of linear regression line for cumulative basal area increments and tree age, was higher in Prince Rupprecht's larch than in Mongolian pine at higher elevations, which coincided with the advantages in xylem hydraulic efficiency, i.e. higher sapwood area-specific hydraulic conductivity and leaf area to sapwood area ratio for the former species relative to the latter one at the middle and high elevation sites. However, the reversed pattern appeared in comparing radial growth rate for the two conifers at the low elevation sites that might be due to obviously greater loss of hydraulic conductivity caused by drought-induced xylem embolism for Prince Rupprecht's larch. This is corroborated by strong correlations between the tree-ring width indices and water-related climate variables during the growing season in Prince Rupprecht's larch but not in Mongolian pine at low elevations. Our study provides a mechanismic explanation for contrasting growth performances between the two species across elevations and implies a potential risk of growth decline under the influence of climate change in Prince Rupprecht's larch, the currently most widely used species for afforestation in this region, particularly under the drought-prone environment in the low-elevation sites.