Department of Plant Biology and Program in Ecology, Evolutionary Biology, and Behavior, Michigan State University, East Lansing, Michigan, USA.
United States Geological Survey, Pacific Island Ecosystems Research Center, Hawai'i National Park, Hawaii, Hawaii, USA.
Ecology. 2023 May;104(5):e3994. doi: 10.1002/ecy.3994. Epub 2023 Mar 23.
Although plant-soil feedbacks (interactions between plants and soils, often mediated by soil microbes, abbreviated as PSFs) are widely known to influence patterns of plant diversity at local and landscape scales, these interactions are rarely examined in the context of important environmental factors. Resolving the roles of environmental factors is important because the environmental context may alter PSF patterns by modifying the strength or even direction of PSFs for certain species. One important environmental factor that is increasing in scale and frequency with climate change is fire, though the influence of fire on PSFs remains essentially unexamined. By changing microbial community composition, fire may alter the microbes available to colonize the roots of plants and thus seedling growth post-fire. This has potential to change the strength and/or direction of PSFs, depending on how such changes in microbial community composition occur and the plant species with which the microbes interact. We examined how a recent fire altered PSFs of two leguminous, nitrogen-fixing tree species in Hawai'i. For both species, growing in conspecific soil resulted in higher plant performance (as measured by biomass production) than growing in heterospecific soil. This pattern was mediated by nodule formation, an important process for growth for legume species. Fire weakened PSFs for these species and therefore pairwise PSFs, which were significant in unburned soils, but were nonsignificant in burned soils. Theory suggests that positive PSFs such as those found in unburned sites would reinforce the dominance of species where they are locally dominant. The change in pairwise PSFs with burn status shows PSF-mediated dominance might diminish after fire. Our results demonstrate that fire can modify PSFs by weakening the legume-rhizobia symbiosis, which may alter local competitive dynamics between two canopy dominant tree species. These findings illustrate the importance of considering environmental context when evaluating the role of PSFs for plants.
虽然植物-土壤反馈（植物与土壤之间的相互作用，通常由土壤微生物介导，缩写为 PSFs）被广泛认为会影响植物多样性在局部和景观尺度上的模式，但这些相互作用在重要环境因素的背景下很少被研究。解析环境因素的作用很重要，因为环境背景可能会通过改变某些物种的 PSF 强度甚至方向来改变 PSF 模式。随着气候变化，一个重要的环境因素在规模和频率上都在增加，那就是火灾，但火灾对 PSFs 的影响基本上仍未得到研究。通过改变微生物群落组成，火灾可能会改变可定植植物根系的微生物，从而影响火灾后幼苗的生长。这有可能改变 PSF 的强度和/或方向，具体取决于微生物群落组成的变化方式以及与微生物相互作用的植物物种。我们研究了最近的一场火灾如何改变了夏威夷两种豆科固氮树种的 PSFs。对于这两个物种，在同种土壤中生长的植物表现（以生物量产生来衡量）高于在异种土壤中生长的植物。这种模式是由根瘤形成介导的，这是豆科物种生长的一个重要过程。火灾削弱了这些物种的 PSFs，因此在未燃烧土壤中显著的成对 PSFs 在燃烧土壤中变得不显著。理论表明，像未燃烧地点中发现的那样的正 PSFs 会加强在当地占主导地位的物种的优势。随着燃烧状态的变化，成对 PSFs 的变化表明，在火灾后，PSF 介导的优势可能会减弱。我们的结果表明，火灾可以通过削弱豆科植物-根瘤菌共生关系来改变 PSFs，这可能会改变两种树冠优势树种之间的局部竞争动态。这些发现说明了在评估 PSFs 对植物的作用时，考虑环境背景的重要性。
