Abstract
AbstractGlobal change experiments such as experimental warming and nutrient addition strongly affect the structure and functioning of high latitude and altitude ecosystems. However, it is often unknown to what extend such effects are permanent or whether changes persist after environmental conditions return to pre‐treatment levels. In this study, we assess the legacy effects of temperature manipulation and nutrient addition experiments on alpine soil micro‐arthropod (i.e., Collembola and Oribatida) communities nine years after the treatments were discontinued. Treatment effects on the vegetation were still detectable six years after cessation, although grazing increased the recovery rate. Because micro‐arthropods are often closely associated with vegetation, we expected to find that treatment effects on Collembola and Oribatida abundance and species composition persisted to date, reflecting plant community dynamics. Also, we expected large‐bodied, drought‐resistant Collembola species that live on top of the soil to show less strong legacy effects. We did not find legacy effects of environmental treatments on Collembola and Mesostigmata in terms of abundance. However, we found persistent changes in community composition of Collembola and Oribatida, suggesting treatment effects persist to date. The generalistFolsomia quadrioculatawas the most responsive Collembola species to initial treatments, most likely due to its variable life‐history strategy. Although its abundance recovered,F. quadrioculataremained dominant in Collembola communities after cessation of the treatments. Grazing affected community composition of both Collembola and Oribatida, but we did not find grazing to reduce legacy effects on micro‐arthropod as it did for vegetation. We therefore conclude that the environmental treatments had only temporary effects on micro‐arthropods in terms of overall abundance, but that effects on individual species and therefore species composition may be long‐lasting and less predictable.
Highlights
Over the last decades, ecosystems at high latitude and altitude have experienced a significant temperature increase (Isaksen et al 2016, Rizzi et al 2017) and this is expected to continue in the future (Stocker 2014)
Statistical analyses We examined the effects of environmental treatment, sampling year, and herbivory on Collembola and Acari abundance and species richness with linear mixed-effect models using the lmerTest-package (Kuznetsova et al 2015), lme4package (Bates et al 2014), and output via the sjPlot-package (Lu€decke 2016) in R version 3.4.2 (R Core Team 2017)
This shows that Collembola abundances in the treated plots were reduced to pretreatment levels, and that these treatments did not have legacy effects on Collembola abundance nine years after the treatments were discontinued
Summary
Ecosystems at high latitude and altitude have experienced a significant temperature increase (Isaksen et al 2016, Rizzi et al 2017) and this is expected to continue in the future (Stocker 2014). The responses to such environmental manipulations can be rapid (within a few growing seasons, e.g., Klanderud and Totland 2005), it is often unknown to what extend treatment effects on ecological communities persist after they are discontinued. While environmental conditions such as temperature and soil nutrient status often return rapidly to pre-treatment levels after cessation of experimental treatments (Boxman et al 1998, Limpens and Heijmans 2008, O’Sullivan et al 2011), the effects on community composition may be long-lasting (Strengbom et al 2001). Such persistent legacy of environmental treatments may indicate that the ecosystem has experienced a regime shift (Scheffer et al 2001, Van Nes and Scheffer 2007), and that restoring pre-treatment conditions are not sufficient to allow the ecosystem to recover
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