Department of Biology, University of Florida, Gainesville, Florida, 32611, USA.
Biología de la Conservación, Cenicafé, Km4 vía antigua, Chinchiná-Manizales, Colombia.
Ecology. 2019 Dec;100(12):e02850. doi: 10.1002/ecy.2850. Epub 2019 Aug 20.
There is now strong evidence suggesting that interactions between plants and their species-specific antagonistic microbes can maintain native plant community diversity. In contrast, the decay in diversity in plant communities invaded by nonnative plant species might be caused by weakening negative feedback strengths, perhaps because of the increased relative importance of plant mutualists such as arbuscular mycorrhizal fungi (AMF). Although the vast majority of studies examining plant-soil feedbacks have been conducted in a single habitat type, there are fewer studies that have tested how the strength and direction of these feedbacks change across habitats with differing dominating plants. In a fragmented montane agricultural system in Colombia, we experimentally teased apart the relative importance of AMF and non-AMF microbes (a microbial filtrate) to the strength and direction of feedbacks in both native and nonnative plant species. We hypothesized that native tree species of forest fragments would exhibit stronger negative feedbacks with a microbial filtrate that likely contained pathogens than with AMF alone, whereas nonnative plant species, especially a highly invasive dominant grass, would exhibit overall weaker negative feedbacks or even positive feedbacks regardless of the microbial type. We reciprocally inoculated each of 10 plant species separately with either the AMF community or the microbial filtrate originating from their own conspecifics, or with the AMF or microbial filtrate originating from each of the other nine heterospecific plant species. Overall, we found that the strength of negative feedback mediated by the filtrate was much stronger than feedbacks mediated by AMF. Surprisingly, we found that the two nonnative species, Urochloa brizantha and Coffea arabica, experienced stronger negative feedbacks with microbial filtrate than did the native forest tree species, suggesting that species-specific antagonistic microbes accumulate when a single host species dominates, as is the case in agricultural habitats. However, negative feedback between forest trees and agricultural species suggests that soil community dynamics may contribute to the re-establishment of native species into abandoned agricultural lands. Furthermore, our finding of no negative feedbacks among trees in forest fragments may be due to a loss in diversity of those microbes that drive diversity-maintaining processes in intact tropical forests.
现在有强有力的证据表明，植物与其特定的拮抗菌相互作用可以维持本地植物群落的多样性。相比之下，非本地植物物种入侵导致的植物群落多样性的衰减可能是由于负反馈强度的减弱，这也许是因为植物互惠共生体（如丛枝菌根真菌 (AMF)）的相对重要性增加。尽管绝大多数研究植物-土壤反馈的研究都在单一的栖息地类型中进行，但很少有研究测试这些反馈在具有不同优势植物的栖息地之间如何变化。在哥伦比亚的一个山地农业系统中，我们进行了实验，分别分离了 AMF 和非 AMF 微生物（微生物滤液）对本地和非本地植物物种的反馈的相对重要性。我们假设，森林碎片中的本地树种与可能含有病原体的微生物滤液相比，与 AMF 单独作用时会表现出更强的负反馈，而非本地植物物种，尤其是一种高度入侵的优势草种，无论微生物类型如何，都会表现出整体较弱的负反馈，甚至正反馈。我们分别将 10 种植物中的每一种与 AMF 群落或来自同种植物的微生物滤液或来自其他 9 种异源植物的 AMF 或微生物滤液进行互惠接种。总的来说，我们发现滤液介导的负反馈的强度远强于 AMF 介导的负反馈。令人惊讶的是，我们发现两种非本地物种，Urochloa brizantha 和 Coffea arabica，与微生物滤液的负反馈比本地森林树种更强，这表明当一种单一的宿主物种占主导地位时，会积累特定的拮抗菌，这是农业生境中的情况。然而，森林树木与农业物种之间的负反馈表明，土壤群落动态可能有助于将本地物种重新引入废弃的农业土地。此外，我们发现森林碎片中的树木之间没有负反馈，这可能是由于驱动完整热带森林多样性维持过程的那些微生物的多样性丧失。
