Is spring burning a viable management tool for species‐rich grasslands?

Abstract

Running title: Burning and grassland management 60 word "summary of what is exciting about the MS": Within the context of evidence-based conservation, we provide clear evidence that spring burning is not a viable long-term alternative to grazing or mowing. We do this by using odds ratios for finding indicator species, rather than using more traditional methods of vegetation analyses, and by meta-analyses of the outcomes from 11 field trials. 1 Abstract Question:The management of species-rich semi-natural grasslands, a fragmented and threatened vegetation type in Europe, involves costs. Mowing is expensive and grazing can be difficult to achieve and maintain for logistical reasons. Is annual spring burning, potentially cheaper than mowing and grazing, a viable management tool for species-rich grasslands?Location: Long-term field trials in 11 grasslands in southern Sweden. Methods:We calculated the odds for a species being an indicator of good management, an indicator of poor management, and an indicator of nitrogen influence in spring-burnt plots, grazed plots, and annually mowed plots. Odds ratios contrasting spring-burnt plots with grazed plots and spring-burnt plots with mowed plots were subjected to meta-analyses in which we compared the odds ratios after 1, 8, and 14 spring burns. For a single trial, we also analysed data after 1, 8, 14, 28, and 39 spring burns. Results:Compared with mowed and grazed plots, the odds of the four different indicators of good management decreased in spring-burnt plots, while the odds for the two indicators of poor management increased. There was no trend in the two indicators of excess nitrogen. Therefore, the conservation value of vegetation in spring-burnt plots becomes impoverished over time relative to traditional management. Conclusions:Spring burning is not an appropriate long-term management method if the aim is to maintain the conservation value of the vegetation in traditionally managed semi-natural grasslands.

Flower abundance and vegetation height as predictors for nectar-feeding insect occurrence in Swedish semi-natural grasslands

“…Although best management practice for conservation of species-rich grassland is built on an increasing foundation of research, it is almost exclusively based on vascular plants (Wahlman and Milberg, 2002;Wallis de Vries et al, 2002;Marriott et al, 2004;Milberg et al, 2014;Tälle et al, 2015Tälle et al, , 2016. However, there is an increasing awareness that management needs to consider also other components of biodiversity in species-rich grassland, most notably nectar-feeding insects, like bumblebees, butterflies and day-flying moths (Littlewood et al, 2012;van Klink et al, 2015).…”

The conservation benefit of mowing vs grazing for management of species‐rich grasslands: a multi‐site, multi‐year field experiment

“…However, as few studies have used odds ratios to convert vegetation data, more studies are needed to put the current effect sizes into perspective. Milberg et al () studied the effect of spring burning on grassland vegetation compared with grazing and mowing, and recorded d = 0.28; while Tälle et al () compared different methods for mowing, and failed to detect an effect (d = 0.1).…”

“…Despite an overlap in species composition, the effect sizes varied between indicator systems. Milberg et al () recommended the use of management‐specific indicator systems, as compared to e.g. species lists of typical grassland species.…”

“…This enabled the comparison of data from different sites and years and gathered using different methods. When using evidence‐based conservation to deal with the management of plant communities it is important to find biologically relevant indicators that can be used in meta‐analyses (Milberg , Milberg et al , Tälle et al ). Furthermore, there is often an overlap between the species lists of different indicator systems.…”

“…Furthermore, there is often an overlap between the species lists of different indicator systems. Despite this, the choice of indicator system might influence the results (Milberg et al ). Therefore we included two different indicator systems.…”