Coastal heathland vegetation is surprisingly resistant to experimental drought across successional stages and latitude

Abstract

In the last decade, several major dwarf‐shrub dieback events have occurred in northern European coastal heathlands. These dieback events occur after extended periods with sub‐zero temperatures under snow‐free conditions and clear skies, suggesting that coastal heathlands have low resistance to winter drought. As climate projections forecast increased drought frequency, intensity, and duration, coastal heathlands are likely to experience more such diebacks in the future. There are, however, few empirical studies of drought impacts and responses on plant communities in humid oceanic ecosystems. We established a drought experiment with two distinct levels of intensified drought to identify responses and thresholds of drought resistance in coastal heathland vegetation. We repeated the experiment in two regions, separated by five degrees latitude, to represent different bioclimatic conditions within the coastal heathlands' wide latitudinal range in Europe. As coastal heathlands are semi‐natural habitats managed by prescribed fire, and we repeated the experiment across three post‐fire successional phases within each region. Plant community structure, annual primary production, and primary and secondary growth of the dominant dwarf‐shrub Calluna vulgaris varied between climate regions. To our surprise, these wide‐ranging vegetation‐ and plant‐level response variables were largely unaffected by the drought treatments. Consequently, our results suggest that northern, coastal heathland vegetation is relatively resistant to substantial intensification in drought. This experiment represents the world's wettest (2200 mm year−1) and northernmost (65°8'N) drought experiment to date, thus filling important knowledge gaps on ecological drought responses in high‐precipitation and high‐latitude ecosystems across multiple phases of plant community succession.

A Fire Revealing Coastal Norway’s Wildland–Urban Interface Challenges and Possible Low-Cost Sustainable Solutions

“…The suggested measures build on the local, historical, and institutional context including sustainability in all dimensions; environmental, societal, economic, and governance when reintroducing a fire-resilient, well-managed, semi-natural heathlands socio-ecological system (SES) that has stood the test of time. This SES may bounce back from, or reinvent itself, after shock, e.g., fire and drought [ 78 ], and support healthy and safe communities [ 79 ]. This system provided positive social and environmental (economic) externalities [ 80 ].…”

Vitality of heather (Calluna vulgaris) along gradients of climate, structure and diversity in dry lowland heathland habitats of Northern Germany

“…However, the analysis provided in this thesis found no evidence that the total life span of (Haugum et al 2021).…”

“…This is a finding which is not new and is reported several times before (e.g. recently Haugum et al 2021, Webb et al 2010), but it highlights again the need for the provision of suitable early-stage habitat conditions, achievable with high-intense (soil) disturbance (e.g. de Graaf et al 2009;.…”

“…Consequently, Calluna has a wide tolerance towards water shortage and a high resistance to drought (e.g. Albert et al 2012;Bannister 1964a, b;Gordon et al 1999, Haugum et al 2021Kongstad et al 2012). However, this drought resistance seems to be limited to moderate drought conditions under oceanic or sub-oceanic climate conditions, and Calluna rather suffers under longer droughts like occasionally occurring in subcontinental regions (Marrs & Diemont 2013;Gimingham 1972;own observations in 2013 and2018, Chapter 4).…”

“…Practical approaches to compensate the climate-change related enhanced susceptibility of post-disturbance Calluna recruitment may be 1) Heathlands with higher heterogeneity provide a higher resilience towards ecological stressors and climate change (Haugum et al 2021). Hence, maximising the spatial heterogeneity of disturbed and undisturbed sites on a small scale for minimizing the effects of drought-induced failing Calluna establishment and subsequent grass dominances.…”