Plant community responses to experimental climate manipulation in a Welsh ombrotrophic peatland and their palaeoenvironmental context

Abstract

We test whether vegetation community composition from a 10‐year climate manipulation experiment on a Welsh peat bog resembles vegetation communities during periods of climate change inferred from a peat core. Experimentally warmed and combined warmed and droughted treatments drove significant increases in ericaceous shrubs but Sphagnum was unaffected. Similarly, Calluna vulgaris seeds increase during inferred warmer periods in the palaeoecological record. Experimental short‐term episodic drought (four 4‐week drought treatments) did not affect vegetation. Plant community composition has undergone several abrupt changes throughout the past c. 1500 years, often in response to human disturbance. Only slight changes occurred during the Medieval Climate Anomaly (c. 950–1250 Common Era [CE]) in vegetation and hydrology, while abrupt changes occurred during the Little Ice Age (c. 1300–1850 CE) when water tables were highest, suggesting that these shifts were driven by changes in water table, modulated by climate. A period of water table drawdown c. 1800, synchronous with historical records of increased drainage, corresponds with the development of the present‐day vegetation community. Modern analogues for fossil material, characterized by abundant Rhynchospora alba and Sphagnum pulchrum, are more common after this event. Vegetation changes due to climate inferred from the palaeo record differ from those observed in the experiments, possibly relating to differences in the importance of drivers of vegetation change over varying timescales. Whereas temperature is frequently identified as the dominant driver of plant community change in experiments, sustained changes in water table appear to be more important in the long‐term record. We find evidence that recent climate change and other anthropogenic stressors (e.g. drainage, heavy metal and nitrogen pollution) may promote the development of novel plant communities without analogues in the fossil record. These communities may be poorer at sequestering carbon and may respond differently to future climate change.

Mites (Oribatida and Mesostigmata) and Vegetation as Complementary Bioindicators in Peatlands

“…However, only persistent changes in the depth of the water table resulted in obvious changes in vegetation, while no observable effects of drainage were observed with transient lowering of the water table (Talbot et al, 2010) or during short-term experimental drought (Andrews et al, 2021). The effects of long-term (10 yrs) drought were different on different plant groups: ericaceous shrubs such as Calluna vulgaris (L.) Hull were affected by it, while Sphagnum was unaffected (Andrews et al, 2021). On the other hand some studies show that a short-term water table change may still impact the vegetation and carbon dynamics of peatland (Morris et al, 2013;Planas-Clarke et al, 2020).…”

“…Often, as part of the active protection of peatlands, it is recommended that trees are removed (Czerepko et al, 2018). However, only persistent changes in the depth of the water table resulted in obvious changes in vegetation, while no observable effects of drainage were observed with transient lowering of the water table (Talbot et al, 2010) or during short-term experimental drought (Andrews et al, 2021). The effects of long-term (10 yrs) drought were different on different plant groups: ericaceous shrubs such as Calluna vulgaris (L.) Hull were affected by it, while Sphagnum was unaffected (Andrews et al, 2021).…”