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Media type:
E-Book
Title:
Cryptogamic Diversity Response to Climate Trends
:
Temperature Extremes, Rather than Dry Spell Length, Drive Bryophyte and Lichen Spatio-Temporal Diversity Changes
Description:
Despite the widespread assumption that bryophytes and lichens are litmus for climate change, direct tests linking the response of their temporal diversity trends to large-scale climate trends are still lacking. In this study, based on 20-year time series data from 132 forest sites across Poland, we present the first attempt to relate temporal diversity trends of bryophytes and lichens occurring on different forest substrates to temporal trends in major climatic variables, including climate extremes, and to highlight the differences between the two groups. After controlling for the effect of management intensity, we tested how temporal trends in α and β diversity of bryophytes and lichens responded to the variation in mean annual temperature (MAT), 95th percentile of maximum temperature (T95), and number of consecutive days with precipitations below 1mm (CDD1). Analyses were successively performed including stand age, used as proxy for structure, as an additional variable. Our results showed that both bryophyte and lichen diversity strongly responds to T95 and MAT, while CDD1 only affects bryophyte diversity depending on the forest stand age. Specifically we found that: 1) of the three tested climatic variables, T95 is the one most consistently driving cryptogamic diversity, especially for lichens; 2) bryophyte species richness changes are related to T95, MAT and CDD1 only in young stands, while bryophyte temporal β diversity is related to MAT in young stands and to T95 and CDD1 in mature stands; 3) increasing T95 trends have an invariably negative impact on both bryophyte and lichen diversity, while increasing MAT trends consistently promote it. Our study clearly indicates that cryptogam diversity is mainly threatened by temperature extremes and it also highlights that local environmental conditions may partially modulate the impact of regional climate trends on bryophyte diversity, whereas lichens diversity is entirely constrained by macro-scale climate trends