Metapopulation dynamics and future persistence of epiphytic cyanolichens in a European boreal forest ecosystem

Abstract

1.One approach to biodiversity conservation is to set aside small woodland key habitats (WKHs) in intensively managed landscapes. The aim is to support species, such as epiphytes, which often depend on old trees and are negatively affected by intensive forestry. However, it is not known whether the number of host trees within these areas can sustain species in the long term.2.We studied metapopulation dynamics and assessed the future persistence of epiphytes assuming host tree numbers similar to those observed in large north European WKHs. The study species were seven cyanolichens confined to Populus tremula in the boreal study area. Colonizations and extinctions were recorded in 2008 on trees that had been surveyed 13 years earlier. We applied generalized (non)linear models to test the importance of environmental conditions, facilitation and spatial connectivity on the metapopulation dynamics. We also simulated the effects of tree numbers and tree fall rates on future species persistence.3.Metapopulation dynamics were explained by tree quality, size or tree fall. In one species, colonizations increased with increasing connectivity, and in a second species it increased if other lichens sharing the photobiont with the focal species were present, suggesting facilitation. Both stochastic extinctions from standing trees and deterministic extinctions caused by tree fall should be accounted for in projecting epiphyte metapopulation dynamics.4.One to three infrequent, sexually dispersed study species face a significant extinction risk within 50 years, especially in areas with low tree numbers.5.Synthesis and applications. During the coming decades, infrequent, sexually dispersed, epiphytic lichens are likely to be lost from small woodland habitat set asides in intensively managed landscapes. Local extinction will be a consequence of low colonization rates and tree fall. Low colonization rates can be prevented by retaining large trees on which lichen species colonization rates are the highest and by assuring a high density of occupied trees. The negative effect of tree fall should be compensated for by assuring continuous availability of old trees. This can be achieved by decreasing the populations of large browsers, or by retaining trees with high conservation value during management operations.

Richness of Lichen Species, Especially of Threatened Ones, Is Promoted by Management Methods Furthering Stand Continuity

“…These include, a larger bark surface which increases the probability of colonization [40], pronounced bark textures including crevices [22], [40] and rot holes [41], which provide a range of microhabitats, and the fact that many lichen species associated with old-growth conditions can only establish on older trees [42]. The retention of numerous mature to over-mature trees in forests appears important for maintaining a high species richness of epiphytic lichens [43]–[45] and to conserve rare and threatened lichen species in managed forests [21], [29], [46], [47]. These trees can act as population centers for the dispersal of lichen propagules and provide refuges for those species which depend on old trees [3], [48]–[50].…”

Local Competition and Metapopulation Processes Drive Long-Term Seagrass-Epiphyte Population Dynamics

“…Despite these limitations, simple metapopulation models continue to be remarkably useful tools for understanding spatial dynamics in a wide variety of circumstances [9]–[12] One such area where the metapopulation scale approach has dominated our understanding is the study of epiphytes [13]–[15]. Epiphytes form an important component of many ecological communities, providing a substantial amount of additional biomass, carbon sequestration and niche diversity [16], [17].…”

Metapopulation Dynamics of the Mistletoe and Its Host in Savanna Areas with Different Fire Occurrence

“…Thus, agreeing with Overton [9], we opted to approach our studied mistletoe populations using the metapopulation framework. A similar approach was used in several studies with species of epiphytic bryophytes in boreal forests modeled the metapopulation dynamics in habitat patches [18], [22], [23], [28], [29], [30], [31].…”