Environmental drivers, life strategies and bioindicator capacity of bryophyte communities in high-latitude headwater streams

Abstract

This study reports an investigation of the bryophyte ecology of minimally impacted high-latitude headwater streams, to assess the hypothesis that underlying geology, water physico-chemistry, current velocity and substrate morphology are significant environmental drivers of the species distribution, community composition and abundance of bryophyte vegetation in these naturally highly stressed and disturbed upland ecosystems. Our secondary aim was to determine whether there is evidence that the assemblage and functional attributes of the species present have potential as indicators of water quality and habitat biointegrity in high-latitude headwater streams. The methodology involved repeated intensive surveys, during 2005-2006, at nine sites located on three streams of contrasting underlying geology, within latitudes 56°-58°N, in upland Scotland. Using a stratified random sampling design, quantitative assessments were made of 5 stream vegetation parameters and 52 environmental variables potentially influencing the target sites. TWINSPAN classification, supported by CCA ordination, of the dataset identified four stream bryophyte community types, plus a fifth sample group (characterized by unstable habitat conditions) devoid of bryophytes. The environmental drivers of the vegetation community were primarily associated with streambed stability (flow, substrate composition) and water chemistry (e.g. pH, conductivity, Ca 2? ), which were products of the prevailing underlying geology. The abundance of stream bryophytes was generally a function of predominant growth morphology and life strategy of the species present. Two bryophyte assemblages were identified as characterizing either upland oligotrophic stream habitats of acid-sensitive and base-poor waters (indicators: Scapania undulata, Hygrohypnum ochraceum), or calcareous and mineral-rich streamwaters (indicators: Chiloscyphus polyanthus, Hygrohypnum luridum). The results support the incorporation of bryophytes into river biomonitoring schemes, for use in high-latitude upland streams.

A study of low-temperature and mountain epilithic diatom community in mountain stream at the Han River system, Korea

“…Mountain streams are fragile ecosystems (Kim et al 2012;O'Driscoll et al 2012), sensitive to human influences such as road construction and environmental changes such as those due to climate change (Lang and Murphy 2012). Species richness in these streams is usually limited by extreme environmental conditions (Chapin and Körner 1995) and communities are therefore particularly sensitive to disturbances.…”

Which environmental factors best explain variation of species richness and composition of stream bryophytes? A case study from mountainous streams in Madeira Island

“…They can attain high cover values, especially in streams, and may thus fulfill important ecosystem functions such as the stabilization of the margins of the water courses or the provision of sheltered habitats for microfauna (Richardson and Danehy, 2007;Strayer and Dudgeon, 2010). Bryophyte communities of freshwater habitats can be rich in bryophyte species and some species are even restricted to this habitat (Lang and Murphy, 2012). However, there is considerable variation in species richness and community composition of bryophytes in streams and a number of factors, may be responsible for this variation.…”

“…For example, it has been shown that streams with high nutrient contents due to inputs from agricultural areas have a very impoverished bryophyte flora (Vanderpoorten, 2003;Lujan et al, 2013). Geomorphological and hydrological properties of streams further affect the occurrence of bryophytes (Fritz et al, 2009;Lang and Murphy, 2012;Vieira et al, 2012). For example, velocity of the water or the kind of substrates available (e.g.…”

“…Generally, community ecology of stream bryophytes has been in the focus of a number of studies (Söderström, 2006;Richardson and Danehy, 2007;Lang and Murphy, 2012;Tremp et al, 2012). However, there is considerable bias in these studies with respect to the type of streams studied as emphasized by Lang and Murphy (2012).…”

“…However, there is considerable bias in these studies with respect to the type of streams studied as emphasized by Lang and Murphy (2012).…”