Bryophyte abundance, composition and importance to woody plant recruitment in natural and restoration forests

Abstract

Restoration of tropical forests can lead to enhanced ecosystem services and increases in native biodiversity. Bryophytes may be an integral part of the forest restoration process and can serve a critical role in forest functioning. However, the recovery of bryophytes and their ability to facilitate woody plant establishment during restoration remains poorly studied, especially in the tropics. We investigate how bryophyte abundance and community composition, as well as woody plant seedling associations with bryophyte mats and other ground cover types change from under the canopy of intact forest to under trees in restoration corridor plantings in Hawaii. Restoration corridors consisted of corridors of koa (Acacia koa) trees that were planted roughly 30 years ago. Some corridors were planted around remnant ʻōhiʻa trees (Metrosideros polymorpha) that can be several hundred years old. We sampled under ʻōhiʻa in intact forest and both koa and ʻōhiʻa trees in restoration corridors. In restoration corridors, bryophyte abundance was low relative to intact forest and species diversity was a subset of that found in intact forest despite restoration corridors being several decades old. Seedlings strongly associated with bryophytes across all habitats suggesting that bryophytes may significantly enhance forest seedling establishment when present in restoration corridors. Other ground cover types like woody litter and nurse logs also had a positive association with forest seedlings but were rare in restoration corridors. Grass remained a dominant ground cover type in restoration corridors under koa and remnant ʻōhiʻa trees and only a single seedling was ever found growing in this grass. Enhancing bryophyte growth and recovery within restoration plantings through the reduction of grass cover could facilitate native plant establishment.

Forest canopy-cover composition and landscape influence on bryophyte communities in Nothofagus forests of southern Patagonia

“…Therefore, hypothesis (i) was partially accepted. Our results are in agreement with previous findings of studies conducted on other continents (e.g., North America, Europe and Asia), where bryophyte cover, richness and diversity varies among forest types or stand conditions (e.g., post harvesting or natural disturbances) due to specific biotic and abiotic drivers [1,6,8,55,56].…”

“…In contrast, the deciduous forests the more essential substrate was litter. This result is important to consider when implementing conservation strategies, because the heterogeneity of old-growth forests contributes to the substrate diversity where bryophytes can occur [ 12 , 56 ]. In future studies (e.g., on conservation management), the contribution of substrate diversity in old-growth forests must be explored and linked to bryophyte occurrence and frequency, which are important to consider in the development of new conservation strategies.…”

Spatial patterns of tree recruitment in a montane Hawaiian wet forest after cattle removal and pig population control

“…First, grass cover is usually higher under Acacia koa compared to Metrosideros polymorpha due to higher soil inorganic N and light availability under Acacia koa, as well as higher woody litter under Metrosideros polymorpha (Denslow, Uowolo, & Hughes, 2006;McDaniel & Ostertag, 2010;Yelenik, 2017). Second, remnant Metrosideros polymorpha trees offer more favourable micro-sites (e.g., bryophytes, logs, or woody litter), allowing recruits to have less competition with grass than under planted Acacia koa trees (Yelenik, 2017;Rehm, Thomas, Yelenik, Bouck, & D'Antonio, 2019). Finally, although birds have recolonized the Acacia koa plantation in upper Hakalau Forest, they remain less abundant than in the Metrosideros polymorpha-dominated open forest zone of Hakalau Forest, especially frugivores (Camp, Pratt, Gorresen, Jeffrey, & Woodworth, 2010;Paxton et al, 2018).…”

Plant–plant interactions change during succession on nurse logs in a northern temperate rainforest

“…As the community develops, the amelioration of disturbance and stress by the physical presence of plants (e.g., stabilizing slopes, herbivory protection, microclimate, providing substrate, nutrients, and water) results in competitive interactions becoming more important over time as plants can put more of their energy toward growth and reproduction (Brooker & Callaghan, 1998; Egler, 1954; Ricklefs, 1977; Walker & Chapin, 1987; but see Maestre et al., 2005). While vascular plants have largely been the focus of plant–plant interaction research, bryophytes can have facilitative or competitive interactions with vascular plants depending on multiple abiotic and biotic factors (Doxford et al., 2013; Gornall et al., 2011; Gough, 2006; Rehm et al., 2019; Sedia & Ehrenfeld, 2003; Soudzilovskaia et al., 2011; Staunch et al., 2012). In locations where bryophytes dominate the ground cover, such as in the arctic and boreal forest, bryophytes can structure the composition of vascular plant communities as they are often more tolerant of the stressful conditions than the vascular plants that grow among them (Gavini et al., 2019; Gornall et al., 2011; Gough, 2006).…”