Tracking succession by means of 3D scans of plant communities in a glacier forefield to infer assembly processes

Abstract

In primary successions, assembling plant communities are key for ecosystem functioning and stability. Often, plant successions are described on a taxonomic, functional and/or phylogenetic level, where species' identities, traits or evolutionary histories are considered. In this study, we exploited community features characterizing whole plant assemblages to capture emerging properties only available at the community level. Next to features aggregating over multiple plant species, we used a customized multispectral 3D plant scanner extracting digital community features as proxies for the frequency distribution of traits, productivity, prevalence of plant competition, and plant strategies and functions. Using these community features, we provide a comprehensive description of plant successions along glacier forefield. Additionally, we used a community feature‐based framework assessing the covariance of community feature dissimilarities and environmental dissimilarity to explore the mechanisms underlying plant community assemblies. Our data indicate a shift from fast‐growing and acquisitive, to slow‐growing and conservative plant strategies; increased productivity; higher competition between plant species; and an increasing contribution to the biogeomorphic stability along the successional gradient. Our results further indicate that stochastic processes dominate in early succession, whereas communities are mainly shaped by deterministic processes including environmental filtering and species interactions at late succession. We conclude that assessments of plant community features, facilitated by the use of field‐ready 3D scanners, provide complementary information to trait‐based approaches on the species level with implications for ecological processes.

Coexistence despite competition: Vegetation structural complexity shapes bryophyte diversity over succession

“…An additional benefit of 3D-laser scanning techniques is provision of phenotypic properties of whole plant communities (i.e. community features sensu He, Hanusch, Saueressig, et al, (2023)) rather than integrating speciesspecific traits to community-wide indices. Using community features focuses the analysis on broader effects within ecological communities by acknowledging effects, that cumulate as the sum and mixture of impacts arising from several plant individuals and species.…”

“…Using community features focuses the analysis on broader effects within ecological communities by acknowledging effects, that cumulate as the sum and mixture of impacts arising from several plant individuals and species. Adopting such a "community feature perspective" could thus provide ecologists with fresh insights into competition effects and other ecological processes that go beyond individual or species-level analyses (He, Hanusch, Saueressig, et al, 2023;Zieschank and Junker, 2023).…”

“…In the vegetation period 2021 (from 16 July to 23 July), we conducted an on-site plot scanning in the field with a multispectral 3D scanner 'PlantEye' (Phenospex, F500, Heerlen, the Netherlands, (He, Hanusch, Saueressig, et al, 2023;Zieschank and Junker, 2023). The plant eye is equipped with an active sensor that projects a near-infrared (940 nm) laser line vertically onto the plant canopy (Kjaer and Ottosen, 2015;Maphosa et al, 2017).…”

“…In this study we used digital community measurements of biomass (BM), leaf area index (LAI) and growth height-corrected light penetration depth (LPD) as proxies for vegetation structure. Settings of Software used to calculate community features followed (He, Hanusch, Saueressig, et al, 2023). LPD is a measure for the depth to which light can penetrate through the vegetation layer.…”

“…To assess the interactions between vascular plants and bryophytes, field measurements of plant biomass or vegetation structure are required that often use destructive methods that can significantly alter the trajectory of successional seres (Catchpole and Wheeler, 1992). The adoption of 3D multispectral plant scanning technology offers a non-invasive approach to capturing morphological and physiological traits of entire plant communities, potentially serving as a suitable alternative to traditional destructive methods (He, Hanusch, Saueressig, et al, 2023;Zieschank and Junker, 2023). Through digital whole-community phenotyping, parameters can be measured that provide insights into community features, such as biomass estimates and morphological characteristics indicative of vegetation structure that are typically not accessible through observational field studies.…”