Data from: The contribution of successional grasslands to the conservation of semi-natural grasslands species – A landscape perspective

These data have been used in the following works: Schmid, B. C., Poschlod,
P., & Prentice, H. C. (2017). The contribution of successional
grasslands to the conservation of semi-natural grasslands species – A
landscape perspective. Biological Conservation, 206, 112-119.
doi:10.1016/j.biocon.2016.12.002 Oskar Löfgren, Karin
Hall, Barbara C. Schmid, Honor C. Prentice. (in
revision: Journal of Vegetation Science). Grasslands
ancient and modern: soil nutrients, habitat age and their relation to
Ellenberg N   Abstract (Schmid et al. 2017) Many species that are
typical of calcareous, semi-natural grasslands (“typical grassland
species”) are declining in Europe as a result of habitat-loss and
-fragmentation. Whereas populations of these species are expected to be
largest in old semi-natural grasslands, these species may also occur in
successional grasslands on previously arable fields. We used a
space-for-time approach to analyse changes in the frequencies of typical
grassland species, and changes in soil properties, over a 280-year
arable-to-grassland succession within a Swedish landscape. Our study
revealed that a number of typical grassland species had higher frequencies
in mid-successional (50–279 years) than in old (≥280 years) grasslands.
Mid-successional grasslands also contained many of the typical grassland
species that were present in old grasslands, but at lower frequencies, and
had soil conditions similar to those of old grasslands. Early-successional
(5–14 and 15–49 years) grasslands contained few typical grassland species.
In highly fragmented landscapes, mid-successional grasslands provide
additional habitat for many typical grassland species, and can function as
temporary refugia (“substitute habitat”) for these species until old
grasslands are “restored”. The overall population sizes of some typical
grassland species and red-listed species are likely to be substantially
increased by the presence of mid-successional grasslands within the
landscape. Our study suggests that, rather than focussing solely on old
grassland fragments, conservation strategies for typical grassland species
should adopt a dynamic, landscape-based perspective that recognizes the
role of successional grasslands. Ensuring a continuous development of
mid-successional grasslands is expected to be beneficial for populations of
many typical grassland species.   Abstract (Löfgren et al. in
revision: Journal of Vegetation Science)  Questions. To what
extent does the long-term process of grassland succession reflect changes
in nutrient availability or other effects of grassland history? Plant
communities in ancient, semi-natural pastures include many species
associated with nutrient-poor soils. However, semi-natural pasture
communities can also develop on previously arable sites – as nutrient
levels decline over time. In Europe, Ellenberg N-values represent species’
overall nutrient preferences, and are often used as a proxy for
soil-nutrient availability. But how well do N-values actually reflect
species’ relationships with measured nutrient concentrations during
grassland succession? Location. A successional series of grazed,
previously arable to ancient, grasslands on the Baltic island of Öland,
Sweden. Methods. We collected data on community composition and soil
nutrient (phosphorus, ammonium, nitrate) concentrations. We used Bayesian
joint community modelling to parametrize species’ relationships with
nutrients and grassland age, and quantified the relative contributions of
the variables. Species responses were then compared with Ellenberg
N-values. Results. Phosphorus was the best explanatory variable for most
species. However, species occurrences were not simply explained by
gradients in particular nutrients, but by combinations of different
nutrients and grassland age. There was overall agreement between N-values
and species’ nutrient responses – although the occurrences of species with
identical N-values may be explained by different nutrients. Species with
high and low N-values represent more reliable nutrient-indicators than
intermediate-N species, but their occurrences also reflect other factors
that, as with nutrients, depend on the grassland age. Conclusions. Our
results confirm that Ellenberg N provides a robust indication of the
overall nutrient preferences of individual grassland species. However, in
grassland sites developing on previously arable land – where nutrient
availability is strongly associated with habitat age – N-values may
represent an integrated response not only to nutrients but also to other
historical processes that drive grassland community assembly.