Plant-Soil Feedbacks and Facilitation Influence the Demography of Herbaceous Alpine Species in Response to Woody Plant Range Expansion

Abstract

Plant species migrations, or range shifts, in response to changing climate are one of many interacting factors influencing plant population and community dynamics in an era of global change. Range shifts may cause novel assemblages of competing species because species may respond to changing climate at different rates. Range-expanding species may directly influence resident species through resource competition or indirectly by modifying the local environment both aboveground and belowground. Further, range-expanding plant species can create novel plant-soil feedbacks (PSFs) by altering soil microbial community structure and function and the interactions of resident plant species with microbial symbionts. These changes can have important implications for resident plant population dynamics and their ability to coexist with novel competitors. Here we test the impacts of competitive interactions and plant-soil feedbacks (PSFs) of a range-expanding sagebrush species (Artemisia rothrockii) on the demography and population growth rates of two resident alpine plant species (Koeleria macrantha and Eriogonum ovalifolium). We use an experimental, multi-year field approach combined with integral projection modeling to determine how PSFs and competition influence species coexistence in both the historic and range expansion zone of A. rothrockii. We find that sagebrush has an overall net negative effect on herbaceous plant demography, primarily due to negative PSFs for plants growing in sagebrush-conditioned soil. However, these negative soil effects are partially buffered via facilitation effects for herbs growing under or nearby sagebrush canopies. In general, population growth rates were more sensitive to survival than other demographic rates, furthermore this sensitivity to survival was higher for herbaceous species in sagebrush soils. Identifying the major drivers of plant population dynamics and species interactions remains an important and unresolved question in ecology. PSFs are a central mechanism influencing plant species interactions, yet the majority of PSF research has made little direct connection between plant population dynamics and PSFs in situ. We believe that utilizing a field-based approach, focusing on multiple components of plant demography, is an important next step in understanding the role of PSFs and species interactions in a changing world.

Regeneration Αnalysis of the Juniperus excelsa Mixed Stands in Prespa National Park of Greece as a Base for the Assessment of the Appropriate Silvicultural Treatment for the Conservation of the Species

“…No significant difference was found between the number of plants established and growing under facilitation and those established and growing in full light (p>0.05), suggesting that facilitation is not the major mechanism in the regeneration of Greek juniper in mixed stands with small gaps (MSSG). To a large extent, facilitation may affect the success of plant establishment (Badano et al 2016, O'Brien et al 2019, Collins et al 2019, Lucero et al 2019, Petrou and Milios 2020, Duarte et al 2021. When discussing the importance of nursing plants in the establishment of Greek juniper plants, Milios et al (2007) note that in the middle portion of Nestos Valley in Greece, almost all of the regeneration plants of the species were discovered under the facilitation of nurse plants.…”

Legacy effects post removal of a range-expanding shrub influence soil fungal communities and create negative plant-soil feedbacks for conspecific seedlings

“…While soil legacies of non-native 'invasive' plant species are well documented (Elgersma et al 2011;Suding et al 2013;Lankau et al 2014), we know much less about the soil legacies of native range expanding species and how they may feedback to influence plant performance. This is particularly true for biotic soil legacies, including changes in soil microbial community structure and function, as the impacts and feedbacks of native range expansions on soil microbial communities is still an active area of study (Collins et al 2019(Collins et al , 2020Manrubia et al 2019;Ramirez et al 2019;Koorem et al 2020).…”