Grasslands ancient and modern: Soil nutrients, habitat age and their relation to Ellenberg N

Abstract

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 parameterize 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. |

Green hay transfer for grassland restoration: species capture and establishment

“…As indicated by our own results and those of other studies, even though green hay application is a very useful method for restoring a large number of species from target communities, nonetheless a sizeable proportion of species from green hay donor sites usually fails to establish at green hay recipient sites. Our results clearly indicate that this deficit is not just due to microsite limitation at the recipient site (as, for example, demonstrated by Pywell et al 2003; Wagner et al 2019; Löfgren et al 2020), but also due to limitations inherent to green hay method. Species that are less abundant at a green hay donor site are less likely to be captured as seeds, and in grassland types with a wide spread in species phenology, using just a single cut may further limit the range of species captured by the method (Scotton & Ševčíková 2017).…”

Habitat conservation state and plant diversity respond to different drivers in semi‐natural grasslands

“…Our results point to soil development as one of the key drivers and indicators of decreasing HCS. This is consistent with recent findings on both long‐grazed and nutrient‐impoverished grasslands (Löfgren et al, 2020), and high nature value semi‐natural grasslands (Milberg et al, 2020). Variability in soil conditions was also found to be extremely relevant in determining the variation in specific functional traits, especially for canopy height in semi‐natural grasslands on calcareous substrates (Price et al, 2017).…”

Pasture age impacts soil fungal composition while bacteria respond to soil chemistry

“…Pasture age had limited effects upon plant and soil properties within our dataset, likely due to the range in environmental conditions covered by our survey. Previous studies have found declines in soil available phosphorus with increasing pasture age (Asner et al, 2004;Löfgren et al, 2020). While the trend was non-significant we did find lower Olsen P in older fields, likely due to the length of time since fertilisation.…”

“…In particular there were greater differences in microbial taxa in pastures that had been established for over 50 years compared to younger pastures, demonstrating the importance of long-term farm management in determining microbial community structure. Pasture age influences plant rooting, community structure, soil structure and chemical properties (Faville et al, 2020;Löfgren et al, 2020;Tozer et al, 2016). In longer established pastures plant/soil interactions are better established, and we also found plant and soil chemistry interactions to be important for both bacterial and fungal community composition.…”

“…These interactions may reflect the difficulty in separating out the inter-correlated responses of soil properties and plant communities to environmental and management factors. For example, Löfgren et al (2020) found that changes in plant communities over a >200 year pasture age gradient were often associated with changes in soil chemistry, particularly phosphorus and to a lesser extent nitrogen. It has also been found that plant community properties are more representative of historical, rather than current, soil conditions, particularly in metrics such as the Ellenberg scores (Wamelink et al, 2002).…”