Jiang Peipei, Meinzer Frederick C, Wang Huimin, Kou Liang, Dai Xiaoqin, Fu Xiaoli
Qianyanzhou Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100190, China.
New Phytol. 2020 Jun;226(6):1656-1666. doi: 10.1111/nph.16502. Epub 2020 May 12.
The degree of plant iso/anisohydry is a popular framework for characterising species-specific drought responses. However, we know little about associations between below-ground and above-ground hydraulic traits as well as the broader ecological implications of this framework. For 24 understory shrub species in seasonally dry subtropical coniferous plantations, we investigated contributions of the degree of isohydry to species' resource economy strategies, abundance, and importance value, and quantified the hydraulic conductance (K ) of above-ground and below-ground organs, magnitude of deep water acquisition (WA ), shallow absorptive root traits (diameter, specific root length, tissue density), and resource-use efficiencies (A , maximum photosynthesis rate; PNUE, photosynthetic nitrogen-use efficiency). The extreme isohydric understory species had lower wood density (a proxy for higher growth rates) because their higher WA and whole-plant K allowed higher A and PNUE, and thus did not necessarily show lower abundance and importance values. Although species' K was coordinated with their water foraging capacity in shallow soil, the more acquisitive deep roots were more crucial than shallow roots in shaping species' extreme isohydric behaviour. Our results provide new insights into the mechanisms through which below-ground hydraulic traits, especially those of deep roots, determine species' degree of isohydry and economic strategies.
植物等水/非等水程度是表征物种特异性干旱响应的常用框架。然而，我们对地下和地上水力性状之间的关联以及该框架更广泛的生态意义了解甚少。对于季节性干燥亚热带针叶人工林中的24种林下灌木物种，我们研究了等水程度对物种资源经济策略、丰度和重要值的贡献，并量化了地上和地下器官的水力导度（K）、深层水分获取量（WA）、浅层吸收根性状（直径、比根长、组织密度）以及资源利用效率（A，最大光合速率；PNUE，光合氮利用效率）。极端等水的林下物种具有较低的木材密度（代表较高的生长速率），因为它们较高的WA和整株K允许更高的A和PNUE，因此不一定表现出较低的丰度和重要值。尽管物种的K与其在浅层土壤中的水分获取能力相协调，但在塑造物种的极端等水行为方面，更具吸收性的深根比浅根更为关键。我们的研究结果为地下水力性状，尤其是深根性状决定物种等水程度和经济策略的机制提供了新的见解。
