Global environmental change effects on plant community composition trajectories depend upon management legacies

Abstract

The contemporary state of functional traits and species richness in plant communities depends on legacy effects of past disturbances. Whether temporal responses of community properties to current environmental changes are altered by such legacies is, however, unknown. We expect global environmental changes to interact with land-use legacies given different community trajectories initiated by prior management, and subsequent responses to altered resources and conditions. We tested this expectation for species richness and functional traits using 1814 survey-resurvey plot pairs of understorey communities from 40 European temperate forest datasets, syntheses of management transitions since the year 1800, and a trait database. We also examined how plant community indicators of resources and conditions changed in response to management legacies and environmental change. Community trajectories were clearly influenced by interactions between management legacies from over 200 years ago and environmental change. Importantly, higher rates of nitrogen deposition led to increased species richness and plant height in forests managed less intensively in 1800 (i.e., high forests), and to decreases in forests with a more intensive historical management in 1800 (i.e., coppiced forests). There was evidence that these declines in community variables in formerly coppiced forests were ameliorated by increased rates of temperature change between surveys. Responses were generally apparent regardless of sites' contemporary management classifications, although sometimes the management transition itself, rather than historic or contemporary management types, better explained understorey responses. Main effects of environmental change were rare, although higher rates of precipitation change increased plant height, accompanied by increases in fertility indicator values. Analysis of indicator values suggested the importance of directly characterising resources and conditions to better understand legacy and environmental change effects. Accounting for legacies of past disturbance can reconcile contradictory literature results and appears crucial to anticipating future responses to global environmental change.

Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers

“…Such mechanisms reflect the interplay between historical land use and climate change (Perring et al, 2018), enabling us to confirm the far-reaching effects of management legacies on vegetation in savanna ecosystems. Such mechanisms reflect the interplay between historical land use and climate change (Perring et al, 2018), enabling us to confirm the far-reaching effects of management legacies on vegetation in savanna ecosystems.…”

Decadal effects of thinning on understory light environments and plant community structure in a subtropical forest

“…The lack of differences in light availability among the three treatments indicates that the differences in the relative coverage of plants of different functional groups cannot be explained by the current differences in light availability. Legacy effects of past management practices on plant communities are widely recognized (Perring et al 2017), and some may be even irreversible (Dupouey et al 2002). Ferns generally favor shaded habitats (Watkins and Cardel us 2012) so that the large increases in light availability immediately following the thinning (Chiang et al 2012) likely negatively affected their growth leading to their low coverage in the thinned plots.…”

Local species assemblages are influenced more by past than current dissimilarities in photosynthetic activity

“…For the recent past (e.g. These effects can arise through site-specific environmental factors, for instance altered conditions because of agricultural practices (Perring et al 2016(Perring et al , 2018 or different sequences and successional recovery from changes in past vegetation cover (Johnson and Miyanishi 2008, Walker et al 2010, Watson et al 2014. the capacity of past events to influence present and future ecological assemblages (Harrison et al 2011, O'Connor et al 2014, Ogle et al 2015, have been proposed as mechanisms that shape species assemblages.…”

“…However, this has -to our knowledge -not been assessed comparatively across multiple taxonomic groups. Depending on the type and magnitude of a past changes in vegetation cover (as a proxy for land-surface changes) plant assemblages can either be dominated by small, fast sprouting or taller, nutrient-demanding species (Jakovac et al 2016, Perring et al 2018. Depending on the type and magnitude of a past changes in vegetation cover (as a proxy for land-surface changes) plant assemblages can either be dominated by small, fast sprouting or taller, nutrient-demanding species (Jakovac et al 2016, Perring et al 2018.…”