Recolonization potential of bryophyte diaspore banks in harvested boreal mixed-wood forest

Abstract

Bryophyte diaspore banks are a potential source of reproductive propagules that may be able to colonize newly available habitat after forest harvesting. However, their role and the factors influencing the successful establishment of species remain poorly understood. To investigate these aspects of diaspore banks, we obtained mineral soil samples from mixed and coniferous stands of boreal mixed-wood forest in northern Alberta, Canada, which had recently experienced a range of harvesting intensities. Samples were germinated in growth cabinets under two light regimes. The composition of germinated bryophyte species was compared among forest types, harvesting intensities, and light levels, and also related to edaphic conditions and geographic location of the sample site. Germinated species composition was not related to forest type or harvesting intensity, but was associated with measured edaphic variables and geographic space, indicating that similarity in species composition reflected similarity in edaphic conditions and spatial proximity. This was partly because of spatial dependence of edaphic variables. Light intensity had a significant influence on the development of species assemblages and individual species responses. Richness and cover of acrocarpous mosses (fugitive, colonist, and shuttle life-history strategies) were significantly reduced under low light conditions, but pleurocarpous mosses (perennial strategy) were not affected. Shannon diversity and the frequency of reproduction were significantly greater with high light. Pleurocarpous mosses that are characteristic of intact forests germinated frequently, suggesting that diaspore banks may influence their recovery after disturbance. Diaspore banks are a repository of species at sites affected by forest harvesting; however, diaspore germination and establishment will be constrained by the local environment, including edaphic conditions and light intensity.

Environmental drivers of the bryophyte propagule bank and its comparison with forest-floor assemblage in Central European temperate mixed forests

“…These two assemblages were different; only two species (Atrichum undulatum and Dicranella heteromalla) had considerable abundance in both groups. Liverworts did not establish a diaspore bank in the studied temperate forests, which is confirmed by earlier results from boreal (Jonsson, 1993;RossDavis & Frego, 2004) and tropical regions (MacielSilva et al, 2012;but see Bisang et al, 2003;Caners et al, 2009). Some dominant species of the forestfloor vegetation that produce huge numbers of spores (e.g.…”

“…were associated with stands with relatively less acidic litter and soil conditions. Other studies focusing on the propagule bank also confirm that Pohlia nutans prefers relatively acidic soil conditions both in boreal (Rydgren et al, 2004;Caners et al, 2009) and mixed forests (RossDavis & Frego, 2004).…”

“…In addition to the aforementioned importance in bryophyte diversity, the role of the bryophyte propagule bank is diverse: ensuring the survival of bryophytes under unfavourable conditions and after disturbance, facilitating regeneration and colonization, and regulating population size (Van Tooren et al, 1990;Jonsson, 1993;Lloret, 1994;During, 1995During, , 1997Hock et al, 2008;Caners et al, 2009;Vanderpoorten & Goffinet, 2009). While for phanerogams many types of dormancy and dormancy-breaking mechanisms have been described, in the case of bryophyte propagules, knowledge is sparse (Sundberg & Rydin, 2000;During, 2001;Hock et al, 2004).…”

“…In contrast to forest-floor bryophytes, the relationship between forest site conditions and the bryophyte diaspore bank has hardly been studied (Caners et al, 2009). Comparative studies between forest-floor bryophytes and diaspore banks in forests are also sparse Jonsson, 1993;Rydgren & Hestmark, 1997;Hebrard, 2001;Rydgren et al, 2004;Szű cs, 2013;Iglesias et al, 2015).…”

Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments

“…37-39). For example, taxa from earlier successional stages can be stored and germinate when conditions are favorable, despite their absence in the extant communities (40). In our culture assays we not only exclude weedy species but also species not identified in the original LIA sample, which could be because of diaspores of unknown age (extant or LIA).…”