Bryophyte cover and richness decline after 18 years of experimental warming in alpine Sweden

Impact of changing climate on bryophyte contributions to terrestrial water, carbon, and nitrogen cycles

Bryophytes, including the lineages of mosses, liverworts, and hornworts, are the second-largest photoautotroph group on Earth. Recent work across terrestrial ecosystems has highlighted how bryophytes retain and control water, fix substantial amounts of carbon (C), and contribute to nitrogen (N) cycles in forests (boreal, temperate, and tropical), tundra, peatlands, grasslands, and deserts. Understanding how changing climate affects bryophyte contributions to global cycles in different ecosystems is of primary importance. However, because of their small physical size, bryophytes have been largely ignored in research on water, C, and N cycles at global scales. Here, we review the literature on how bryophytes influence global biogeochemical cycles, and we highlight that while some aspects of global change represent critical tipping points for survival, bryophytes may also buffer many ecosystems from change due to their capacity for water, C, and N uptake and storage. However, as the thresholds of resistance of bryophytes to temperature and precipitation regime changes are mostly unknown, it is challenging to predict how long this buffering capacity will remain functional. Furthermore, as ecosystems shift their global distribution in response to changing climate, the size of different bryophyte-influenced biomes will change, resulting in shifts in the magnitude of bryophyte impacts on global ecosystem functions.

Climate Change May Pose Additional Threats to the Endangered Endemic Species Encalypta buxbaumioidea in China

Rare and endangered plant species (REPs) are important in biodiversity conservation, and some REPs with narrow habitats are facing serious challenges from climate change. Encalypta buxbaumioidea T. Cao, C, Gao & X, L. Bai is an endangered bryophyte species that is endemic to China. To explore the consequences of climate change on the geographic distribution of this endangered species, we used maximum entropy to predict the potential distribution of this species in China under current and three future scenarios (RCP 2.6, RCP 4.5, and RCP 8.5) of two time periods (2050 and 2070) in China and assessed its conservation gaps. Twelve species occurrence sites and nine environmental variables were used in the modeling process. The results show that E. buxbaumioidea distribution is affected mainly by the annual mean temperature, isothermality, precipitation of the coldest quarter, and NDVI. According to species response curves, this species preferred habitats with annual mean temperature from −3 to 6 °C, precipitation of the coldest quarter from 14 to 77 mm, isothermality of more than 70%, and NDVI in the second quarter from 0.15 to 0.68. Currently, the most suitable habitat for this species is mainly distributed in the Qinghai–Tibet plateau, which is about 1.97 × 105 km2. The range would sharply reduce to 0.13–0.56% under future climate change. Nature reserves overlap with only 7.32% of the current distribution and would cover a much less portion of the area occupied by the species in the future scenarios, which means the current protected areas network is insufficient. Our results show that endangered bryophyte species are susceptible to environmental stress, especially climate change; therefore, the habitats of bryophytes should be taken into account when it comes to setting up protected areas.

Cryptogam plant community stability: Warming weakens influences of species richness but enhances effects of evenness

Community stability is a fundamental factor sustaining ecosystem functioning and is affected by species richness and species evenness. The Arctic is warming more rapidly than other biomes, and cryptogam plant species (specifically lichens and bryophytes in this study) are major contributors to tundra biodiversity and productivity. However, to our knowledge, the impacts of warming on cryptogam community stability and the underlying mechanisms have not been investigated. We conducted a 13-year summer warming experiment in mesic birch hummock tundra vegetation near Daring Lake in the continental interior of low Arctic Canada and recorded patterns of cryptogam species abundance in several different growing seasons. Warming decreased the stability of total community abundance, had no effects on species richness, but increased species evenness and species synchrony. Structural equation model analyses indicated that higher species richness was the principal factor associated with the stronger community abundance stability in the control plots and that this effect was driven primarily by a negative correlation with species synchrony. By contrast, higher species evenness was the principal factor associated with the weakened community abundance stability in the warming plots, and this effect was driven primarily by a positive correlation with species synchrony. Our study suggests that climate warming could reduce cryptogam plant community stability in low Arctic tundra and, therefore, decrease important ecosystem services, including carbon storage and food availability to caribou in northern regions.

Homogenization of bryophyte species after alpine grassland restoration

The causes of decreasing plant species richness include abandonment of traditional management and the spread of invasive species, even in alpine habitats. Studies on the restoration and management of alpine habitats are predominantly focused on vascular plants, although an important part of alpine vegetation and its diversity is formed by bryophytes. We used bryophytes to indicate changes that occur after the clearcutting of nonindigenous dwarf pine (Pinus mugo Turra) and attempted to reveal the community to which the development of bryophyte species structure was directed. We compared species richness and composition between surveys to test for changes in spatial heterogeneity bryophyte communities. We also tried to reveal the main ecological drivers of the restoration process. The study was performed in the (sub)alpine area of the Eastern High Sudetes Mts. (the Czech Republic). We estimated bryophyte species cover and compared the composition of the bryophyte community in autochthonous grassland areas, areas under the dwarf pine canopy, and clearcut areas to reveal the pattern of shifts 9 years after the treatment. We also measured soil characteristics to reveal the environmental habitat conditions. Evidence of taxonomic homogenization of habitat after dwarf pine removal was found. Light conditions and attributes of litter were the driving factors of successional changes in the bryophyte communities, which led to taxonomic homogenization. This finding explains the slow restoration process due to dwarf pine legacy on the clearcut area. The succession trends were also shaped by unobserved factors, such as climate change and environmental eutrophication. We highly recommended active management and long-term monitoring.

Impact of ambient temperature, precipitation and seven years of experimental warming and nutrient addition on fruit production in an alpine heath and meadow community

Alpine and polar regions are predicted to be among the most vulnerable to changes in temperature, precipitation, and nutrient availability. We carried out a seven-year factorial experiment with warming and nutrient addition in two alpine vegetation communities. We analyzed the relationship between fruit production and monthly mean, maximum, and min temperatures during the fall of the pre-fruiting year, the fruiting summer, and the whole fruit production period, and measured the effects of precipitation and growing and thawing degree days (GDD & TDD) on fruit production. Nutrient addition (heath: 27.88 ± 3.19 fold change at the end of the experiment; meadow: 18.02 ± 4.07) and combined nutrient addition and warming (heath: 20.63 ± 29.34 fold change at the end of the experiment; meadow: 18.21 ± 16.28) increased total fruit production and fruit production of graminoids. Fruit production of evergreen and deciduous shrubs fluctuated among the treatments and years in both the heath and meadow. Pre-maximum temperatures had a negative effect on fruit production in both communities, while current year maximum temperatures had a positive impact on fruit production in the meadow. Pre-minimum, pre-mean, current mean, total minimum, and total mean temperatures were all positively correlated with fruit production in the meadow. The current year and total precipitation had a negative effect on the fruit production of deciduous shrubs in the heath. GDD had a positive effect on fruit production in both communities, while TDD only impacted fruit production in the meadow. Increased nutrient availability increased fruit production over time in the high alpine plant communities, while experimental warming had either no effect or a negative effect. Deciduous shrubs were the most sensitive to climate parameters in both communities, and the meadow was more sensitive than the heath. The difference in importance of TDD for fruit production may be due to differences in snow cover in the two communities.

Bryosphere Loss Impairs Litter Decomposition Consistently Across Moss Species, Litter Types, and Micro-Arthropod Abundance

The bryosphere (that is, ground mosses and their associated biota) is a key driver of nutrient and carbon dynamics in many terrestrial ecosystems, in part because it regulates litter decomposition. However, we have a poor understanding of how litter decomposition responds to changes in the bryosphere, including changes in bryosphere cover, moss species, and bryosphere-associated biota. Specifically, the contribution of micro-arthropods to litter decomposition in the bryosphere is unclear. Here, we used a 16-month litterbag field experiment in two boreal forests to investigate bryosphere effects on litter decomposition rates among two moss species (Pleurozium schreberi and Hylocomium splendens), and two litter types (higher-quality Betula pendula litter and lower-quality P. schreberi litter). Additionally, we counted all micro-arthropods in the litterbags and identified them to functional groups. We found that bryosphere removal reduced litter decomposition rates by 28% and micro-arthropod abundance by 29% and led to a colder micro-climate. Litter decomposition rates and micro-arthropod abundance were uncorrelated overall, but were positively correlated in B. pendula litterbags. Bryosphere effects on litter decomposition rates were consistent across moss species, litter types, and micro-arthropod abundances and community compositions. These findings suggest that micro-arthropods play a minor role in litter decomposition in the boreal forest floor, suggesting that other factors (for example, micro-climate, nutrient availability) likely drive the positive effect of the bryosphere on decomposition rates. Our results point to a substantial and consistent impairment of litter decomposition in response to loss of moss cover, which could have important implications for nutrient and carbon cycling in moss-dominated ecosystems.