Abstract
Soil disturbance is recognized as an important driver of biodiversity in dry grasslands, and can therefore be implemented as a restoration measure. However, because community re-assembly following disturbance includes stochastic processes, a focus only on species richness or establishment success of particular species will not inform on how plant communities respond ecologically to disturbance. We therefore evaluated vegetation development following disturbance by quantifying species richness, species composition and functional trait composition. Degraded calcareous sandy grassland was subjected to experimental disturbance treatments (ploughing or rotavation), and the vegetation was surveyed during four subsequent years of succession. Treated plots were compared with control plots representing untreated grassland, as well as nearby plots characterized by plant communities representing the restoration target.Species richness and functional diversity both increased in response to soil disturbance, and rotavation, but not ploughing, had a persistent positive effect on the occurrence of specialist species of calcareous sandy grassland. However, no type of soil disturbance caused the plant species composition to develop towards the target vegetation. The disturbance had an immediate and large impact on the vegetation, but the vegetation developed rapidly back towards the control sites. Plant functional composition analysis indicated that the treatments created habitats different both from control sites and target sites. Community-weighted mean Ellenberg indicator values suggested that the observed plant community response was at least partially due to an increase in nitrogen and water availability following disturbance. This study shows that a mild type of disturbance, such as rotavation, may be most successful in promoting specialist species in calcareous sandy grassland, but that further treatments are needed to reduce nutrient availability. We conclude that a functional trait based analysis provides additional information of the vegetation response and the abiotic conditions created, complementing the information from the species composition.
Highlights
Reduction, cessation or suppression of disturbance, such as forest wildfires and dune dynamics, are reasons for a decline in species richness observed today in many of the World’s ecosystems [1, 2]
We evaluated the effect of disturbance, implemented as a restoration option, on both species composition and functional composition in calcareous sandy grassland where the decline in threatened species is believed to be a consequence of reduced soil disturbance
We conclude that disturbance alone could not restore the desired sandy grassland community with a large proportion of specialist species
Summary
Cessation or suppression of disturbance, such as forest wildfires and dune dynamics, are reasons for a decline in species richness observed today in many of the World’s ecosystems [1, 2]. Grazing continuity [5, 6] and low availability of certain macronutrients [7] are important and well-known drivers of grassland plant diversity, but it is increasingly recognized that soil disturbance and the occurrence of bare soil may act as limiting factors to threatened species [8, 9, 10]. Mechanical soil disturbance, such as soil perturbation and topsoil removal, could function as a restoration measure [10, 11, 12, 13]. Grime [23] argued that traits in a system can either converge or diverge depending on the kind of disturbance, which may further impact community diversity
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