DOI: 10.5061/dryad.34tmpg4r4
title: Higher plant colonisation and lower resident diversity in grasslands more recently abandoned from agriculture

description: 1. Rates of species colonisation and extirpation are increasing in plant
 communities worldwide. Colonisation could potentially help compensate for,
 or compound, resident diversity loss that results from global
 environmental change. 2. We use a multifactorial seed addition grassland
 experiment to examine relationships between plant colonisation, resident
 species diversity and key community assembly factors over three years. By
 manipulating colonist seed rate, imposing disturbance and examining
 abundance and diversity impacts of 14 formerly absent sown colonists in
 communities that varied in successional stage and time since agricultural
 abandonment, we were able to disentangle effects of global change factors
 (species introduction, novel disturbance and land use change) that are
 usually confounded. 3. Evidence suggested that cover abundance of sown
 colonists was most strongly influenced by successional stage of recipient
 communities, though number of growing seasons was also important for the
 group of seven colonists with resource conservative “slow” life history
 traits. Colonist type, seed rate and disturbance had weaker relationships
 with colonist cover. 4. Factors affecting sown colonist cover were highly
 conditional. A negative relationship between plot-level disturbance and
 colonist cover in early successional communities meant that, despite a
 positive relationship in late succession, colonisation was negatively
 related to disturbance overall, defying theoretical expectations. 5.
 Non-sown resident diversity was negatively related to colonist cover and
 positively related to successional stage. Resource acquisitive colonists
 with “fast” life history traits appeared to limit cover of “slow
 colonists” when the two groups were sown together, likely reflecting niche
 pre-emption. 6. Communities at earlier stages of succession had lower
 resident diversity and experienced higher levels of colonisation than
 communities at later stages of succession. Elevated colonisation and lower
 resident diversity both appeared to be symptoms of human-induced land use
 change. However, results suggested that resource competition from plant
 colonists may also limit resident diversity in grasslands abandoned from
 agriculture more recently. Synthesis: Our findings point to the importance
 of resource availability and competition on plant colonisation and
 colonist impacts on residents. Although colonisation is potentially a
 source of biodiversity in the short-term, our results suggest that plant
 colonists that reach high abundance may be a further threat to resident
 plant diversity in secondary grasslands recovering from a recent history
 of agriculture.
description: Data provided is the results of a grassland seed addition x
 global change experiment. The data consists of vegetation surveys
 conducted over three growing seasons between July 2013 and August 2015,
 alongside measurements of resource availability. The data provided is
 focused on the summed abundance of seeded colonists. Data was compiled and
 prepared into its current form using R version 4.2.2