School of Biological Sciences, University of Utah, 257 South 1400 East, Salt Lake City, UT 84111, USA.
Department of Geography, University of California Santa Barbara, 1832 Ellison Hall, UC Santa Barbara, Santa Barbara, CA 93106, USA.
Tree Physiol. 2021 Aug 11;41(8):1323-1335. doi: 10.1093/treephys/tpab005.
Species interactions mediate tree responses to water limitation because competition and/or facilitation alter plant physiology and growth. However, because it is difficult to isolate the effects of plant-plant interactions and water limitation from other environmental factors, the mechanisms underlying tree physiology and growth in coexisting plants under drought are poorly understood. We investigated how species interactions and water limitation impact the physiology and growth of trembling aspen (Populus tremuloides), narrowleaf cottonwood (Populus angustifolia) and ponderosa pine (Pinus ponderosa) seedlings in a controlled environment growth chamber, using aspen as a focal species. Seedlings were grown in pots alone or with a con- or hetero-specific seedling, and were subjected to a water limitation treatment. Growth, water status and physiological traits were measured before, during and after the treatment. Under well-watered conditions, the presence of another seedling affected growth or biomass allocation in all species, but did not impact the physiological traits we measured. Under water limitation, the presence of a competing seedling had a marginal impact on seedling growth and physiological traits in all species. Throughout the study, the magnitude and direction of seedling responses were complex and often species-specific. Our study serves as an important step toward testing how species' interactions modify physiological responses and growth in well-watered and water-limited periods.
种间相互作用介导了树木对水分限制的响应，因为竞争和/或促进会改变植物的生理和生长。然而，由于难以将植物-植物相互作用和水分限制的影响与其他环境因素分开，因此对于在干旱条件下共存植物中树木生理和生长的机制知之甚少。我们使用白杨作为焦点物种，在控制环境生长室中研究了种间相互作用和水分限制如何影响颤杨（Populus tremuloides）、窄叶棉白杨（Populus angustifolia）和黄松（Pinus ponderosa）幼苗的生理和生长。幼苗在单独的盆中或与同种或异种幼苗一起生长，并进行水分限制处理。在处理之前、期间和之后测量生长、水分状况和生理特性。在水分充足的条件下，另一个幼苗的存在会影响所有物种的生长或生物量分配，但不会影响我们测量的生理特性。在水分限制下，竞争幼苗的存在对所有物种的幼苗生长和生理特性只有轻微影响。在整个研究过程中，幼苗响应的幅度和方向复杂且常常是物种特异性的。我们的研究是朝着测试物种相互作用如何在水分充足和水分限制期间改变生理响应和生长的方向迈出的重要一步。
