Intraspecific variation influences performance of moss transplants along microclimate gradients

Translocating deadwood in ecological compensation benefits saproxylic beetles, but effects are dependent on substrate density

Ecological compensation is increasingly used to offset habitat and biodiversity loss resulting from changes in land use, large infrastructure projects (e.g., roads and railroads) or industrial expansions (e.g., mines, harbours), but the effectiveness of specific compensation strategies remain largely untested. When old-growth forest ecosystems are impacted by such projects, designated compensation areas may also require additional restoration or habitat enrichment. For organisms that rely on habitats that require decades to develop, such as advanced decayed wood, restoration will require novel approaches. We tested whether translocation of deadwood of various decay stages and large dimensions enhance saproxylic beetle communities within compensation areas in a large boreal forest landscape in Sweden. Experimental plots (50 m in diameter) within the compensation zone were enriched with 0, 16, or 48 deadwood substrates. We collected beetles using flight intercept traps prior to translocation and again 1 and 4 years after translocation and compared species richness, abundance and assemblage composition across treatment and over time. We showed that translocation of relatively high densities of deadwood (48 substrates per plot) increased species richness of saproxylic beetles. Increased beetle richness could have occurred from direct transport of beetles in experimental substrates and/or through attraction of beetles to the translocated substrates. Our results indicate that translocation of deadwood can serve as an important tool in ecological compensation and restoration if sufficient amounts of deadwood are translocated. While promising, the long-term success of restoring saproxylic biodiversity through translocation of deadwood depends on whether translocated substrates continue to provide suitable habitat for beetles over time and whether benefits for biodiversity can be enhanced through targeted translocation of specific combinations of deadwood.

Phenotypic plasticity of Eurohypnum leptothallum in degraded karst ecosystems: Adaptative mechanisms and ecological functions driven by warming temperatures

Phenotypic plasticity is a critical mechanism for plants to adapt to rapid climate change and other global change drivers. Eurohypnum leptothallum is widely distributed in fragile subtropical karst ecosystems, exhibiting strong drought tolerance, water retention, and soil stabilization capabilities, playing a vital ecological role in nutrient cycling and ecological restoration. Our study investigated the specific manifestations of phenotypic plasticity in epilithic E. leptothallum within degraded karst ecosystems. Results showed that E. leptothallum exhibited high phenotypic plasticity in the heterogeneous environments of degraded karst ecosystems. In the temperature range of 21.5 °C-59.5 °C, E. leptothallum developed a set of adaptive mechanisms in response to warming temperatures through the trade-offs and combinations in most morphological traits (increasing in shoot height, stem cortical ratio and leaf middle cell lumen area, decreasing in stem diameter and stem central strand ratio, making leaf shape, cell shape and lumen shape tend to ellipse) and physiological traits (increasing in C, Ca, C:N, C:P, N:P, Fv/Fm and Y(NO), decreasing in qP). Furthermore, these phenotypic variations may confer certain ecological benefits to the degraded karst ecosystems and are expected to contribute to the maintenance and sustainable development of structural stability and species diversity in degraded karst ecosystems and even global ecosystems in the early stages of global warming. The findings provide a new perspective for exploring the response of bryophytes to environmental changes, a theoretical basis for predicting the adaptive strategies of E. leptothallum and its potential ecological functions to degraded karst ecosystems under global warming.

Enhanced bryophyte communities, but challenges for lichens following translocation of deadwood in ecological compensation

Habitat restoration and ecological compensation are gaining attention as methods to offset habitat loss from landscape exploitation, but few studies assess their impact on species and communities, particularly in boreal forests. We evaluated a novel ecological compensation method; the translocation of deadwood and associated species from an impact area to a compensation area. Our study focused on assessing species richness and assemblage composition of epiphytic bryophytes and lichens on translocated (637 substrates) and naturally occurring Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) logs in a compensation area in northern Sweden. We also assessed the effects of translocated deadwood density and dead wood type on these assemblages. We recorded 52 bryophyte species and 38 lichen species. For lichens, only species confined to deadwood were included. Translocated logs significantly altered bryophyte and lichen assemblages in the translocation plots. Bryophyte richness increased over time as colonization was higher than species loss, while lichen richness remained stable with colonization of new species and disappearance of translocated species occurring at similar rates. Bryophyte colonisations mainly involved generalist forest species. Higher deadwood density in translocation plots increased bryophyte species richness but had no effect on lichens, whereas diverse deadwood types promoted conservation success for both groups. Logs of intermediate decay and snags (deadwood originating from standing dead trees) supported distinct communities, though lichen species on snags declined four years post-translocation. Our results highlight the need to include diverse substrates in conservation translocations to maximize the number of translocated species. Although translocating entire communities presents challenges, it offers a promising tool for species conservation and ecological restoration.

Spatiotemporal variation in population dynamics of a narrow endemic, Ranunculus austro-oreganus

PREMISE

Understanding how population dynamics vary in space and time is critical for understanding the basic life history and conservation needs of a species, especially for narrow endemic species whose populations are often in similar environments and therefore at increased risk of extinction under climate change. Here, we investigated the spatial and temporal variation in population dynamics of Ranunculus austro-oreganus, a perennial buttercup endemic to fragmented prairie habitat in one county in southern Oregon.

METHODS

We performed demographic surveys of three populations of R. austro-oreganus over 4 years (2015-2018). We used size-structured population models and life table response experiments to investigate vital rates driving spatiotemporal variation in population growth.

RESULTS

Overall, R. austro-oreganus had positive or stable stochastic population growth rates, though individual vital rates and overall population growth varied substantially among sites and years. All populations had their greatest growth in the same year, suggesting potential synchrony associated with climate conditions. Differences in survival contributed most to spatial variation in population growth, while differences in reproduction contributed most to temporal variation in population growth.

CONCLUSIONS

Populations of this extremely narrow endemic appear stable, with positive growth during our study window. These results suggest that populations of R. austro-oreganus are able to persist if their habitat is not eliminated by land-use change. Nonetheless, its narrow distribution and synchronous population dynamics suggest the need for continued monitoring, particularly with ongoing habitat loss and climate change.

Canopy cover and soil moisture influence forest understory plant responses to experimental summer drought

Extreme droughts are globally increasing in frequency and severity. Most research on drought in forests focuses on the response of trees, while less is known about the impacts of drought on forest understory species and how these effects are moderated by the local environment. We assessed the impacts of a 45-day experimental summer drought on the performance of six boreal forest understory plants, using a transplant experiment with rainout shelters replicated across 25 sites. We recorded growth, vitality and reproduction immediately, 2 months, and 1 year after the simulated drought, and examined how differences in ambient soil moisture and canopy cover among sites influenced the effects of drought on the performance of each species. Drought negatively affected the growth and/or vitality of all species, but the effects were stronger and more persistent in the bryophytes than in the vascular plants. The two species associated with older forests, the moss Hylocomiastrum umbratum and the orchid Goodyera repens, suffered larger effects than the more generalist species included in the experiment. The drought reduced reproductive output in the moss Hylocomium splendens in the next growing season, but increased reproduction in the graminoid Luzula pilosa. Higher ambient soil moisture reduced some negative effects of drought on vascular plants. Both denser canopy cover and higher soil moisture alleviated drought effects on bryophytes, likely through alleviating cellular damage. Our experiment shows that boreal understory species can be adversely affected by drought and that effects might be stronger for bryophytes and species associated with older forests. Our results indicate that the effects of drought can vary over small spatial scales and that forest landscapes can be actively managed to alleviate drought effects on boreal forest biodiversity. For example, by managing the tree canopy and protecting hydrological networks.

Tree species matter for forest microclimate regulation during the drought year 2018: disentangling environmental drivers and biotic drivers

Tree canopies are considered to effectively buffer climate extremes and to mitigate climate change effects. Droughts, which are predicted to become more frequent in the course of climate change, might alter the microclimatic cooling potential of trees. However, our understanding of how microclimate at the tree canopy level is modulated by environmental and tree characteristics and their interactions is still limited. Here, we investigated canopy temperature regulation for five mature co-occurring tree species for two contrasting hydrological situations during the severe drought in 2018. Even though we observed a significant drought-induced decline in canopy cover and transpiration across tree species, we found evidence that differences in the water use strategies of trees affected cooling mechanisms differently. Although a large share of the variations in the cooling potential of trees was explained by direct and indirect effects of meteorological factors, we identified a gradual shift in importance from latent heat flux to components defining the magnitude of sensible heat flux on the energy budget of tree as the drought gained severity. The decrease in latent heat fluxes, approximated by sap flow rates, furthermore resulted in a reduced cooling potential and an equalization of tree species canopy temperatures.

Comparison of Exposure Techniques and Vitality Assessment of Mosses in Active Biomonitoring for Their Suitability in Assessing Heavy Metal Pollution in Atmospheric Aerosol

The most widespread and used technique is the moss-bag method in active biomonitoring of air pollution using mosses. In the literature, we can find various studies on the standardization of this method, including attempts to standardize treatments and preparation procedures for their universal application. Few works comprehensively focus on other methods or compare other techniques used in active biomonitoring with mosses, especially including measurements of their vital parameters. Our experiment aimed to assess air pollution by selected heavy metals (Cu, Zn, Cd, Pb, Mn, Fe, and Hg) using three moss species (Pleurozium schreberi, Sphagnum fallax, and Dicranum polysetum) during a 12-week exposure in an urban area. Mosses were exposed simultaneously using four techniques: moss bag in three variants (exposed to air for total deposition of heavy metals, exposed to air for only dry deposition, and sheltered from the wind) and transplants in boxes. Increases in heavy metal concentrations in mosses were determined using the relative accumulation factor (RAF). The actual quantum yield of photosystem II photochemical was also analyzed as the main vitality parameter. The results indicate that all moss species during the changing environmental conditions survived and retained their vitality, although it decreased by >50% during the exposure. The best biomonitor was the moss P. schreberi, whose RAF increments were the highest throughout the study period for the majority of elements. The moss-bag technique had a statistically significant effect (almost 40%) on the concentration value of a given metal for a certain species, and thus it is the most recommended technique that can be applied in air quality monitoring in urban areas. Environ Toxicol Chem 2022;41:1429-1438. © 2022 SETAC.

Can high-resolution topography and forest canopy structure substitute microclimate measurements? Bryophytes say no

Increasingly available high-resolution digital elevation models (DEMs) facilitate the use of fine-scale topographic variables as proxies for microclimatic effects not captured by the coarse-grained macroclimate datasets. Species distributions and community assembly rules are, however directly shaped by microclimate and not by topography. DEM-derived topography, sometimes combined with vegetation structure, is thus widely used as a proxy for microclimatic effects in ecological research and conservation applications. However, the suitability of such a strategy has not been evaluated against in situ measured microclimate and species composition. Because bryophytes are highly sensitive to microclimate, they are ideal model organisms for such evaluation. To provide this much needed evaluation, we simultaneously recorded bryophyte species composition, microclimate, and forest vegetation structure at 218 sampling sites distributed across topographically complex sandstone landscape. Using a LiDAR-based DEM with a 1 m resolution, we calculated eleven topographic variables serving as a topographic proxy for microclimate. To characterize vegetation structure, we used hemispherical photographs and LiDAR canopy height models. Finally, we calculated eleven microclimatic variables from a continuous two-year time- series of air and soil temperature and soil moisture. To evaluate topography and vegetation structure as substitutes for the ecological effect of measured microclimate, we partitioned the variation in bryophyte species composition and richness explained by microclimate, topography, and vegetation structure. In situ measured microclimate was clearly the most important driver of bryophyte assemblages in temperate coniferous forests. The most bryophyte-relevant variables were growing degree days, maximum air temperature, and mean soil moisture. Our results thus showed that topographic variables, even when derived from high-resolution LiDAR data and combined with in situ sampled vegetation structure, cannot fully substitute effects of in situ measured microclimate on forest bryophytes.

Effects of stand structure and ungulates on understory vegetation in managed and unmanaged forests

Conventional conservation policies in Europe notably rely on the passive restoration of natural forest dynamics by setting aside forest areas to preserve forest biodiversity. However, since forest reserves cover only a small proportion of the territory, conservation policies also require complementary conservation efforts in managed forests in order to achieve the biodiversity targets set up in the Convention on Biological Diversity. Conservation measures also raise the question of large herbivore management in and around set-asides, particularly regarding their impact on understory vegetation. Although many studies have separately analyzed the effects of forest management, management abandonment, and ungulate pressure on forest biodiversity, their joint effects have rarely been studied in a correlative framework. We studied 212 plots located in 15 strict forest reserves paired with adjacent managed forests in European France. We applied structural equation models to test the effects of management abandonment, stand structure, and ungulate pressure on the abundance, species richness, and diversity of herbaceous vascular plants and terricolous bryophytes. We showed that stand structure indices and plot-level browsing pressure had direct and opposite effects on herbaceous vascular plant species diversity; these effects were linked with the light tolerance of the different species groups. Increasing canopy cover had an overall negative effect on herbaceous vascular plant abundance and species diversity. The effect was two to three times greater in magnitude than the positive effects of browsing pressure on herbaceous plants diversity. On the other hand, a high stand density index had a positive effect on the species richness and diversity of bryophytes, while browsing had no effect. Forest management abandonment had few direct effects on understory plant communities, and mainly indirectly affected herbaceous vascular plant and bryophyte abundance and species richness and diversity through changes in vertical stand structure. Our results show that conservation biologists should rely on foresters and hunters to lead the preservation of understory vegetation communities in managed forests since, respectively, they manipulate stand structure and regulate ungulate pressure. Their management actions should be adapted to the taxa at stake, since bryophytes and vascular plants respond differently to stand and ungulate factors.

The macroecology of plant populations from local to global scales

Population ecologists develop theoretical and pragmatic knowledge of how and why populations change or remain stable, how life histories evolve and devise management strategies for populations of concern. However, forecasting the effects of global change or recommending management strategies is often urgent, requiring ecologists to work without detailed local evidence while using data and models from outside the focal location or species. Here we explore how the comparative ecology of populations, population macroecology, can be used to develop generalisations within and between species across different scales, using available demographic, environmental, life history, occurrence and trait data. We outline the strengths and weaknesses of using broad climatic variables and suitability inferred from probability of occupancy models to represent environmental variation in comparative analyses. We evaluate the contributions of traits, environment and their interaction as drivers of life history strategy. We propose that insights from life history theory, together with the adaptive capacity of populations and individuals, can inform on 'persist in place' vs 'shift in space' responses to changing conditions. As demographic data accumulate at landscape and regional scales for single species, and throughout plant phylogenies, we will have new opportunities for testing macroecological generalities within and across species.

The largest moss carpet transplant in Antarctica and its bryosphere cryptic biodiversity

As part of the reconstruction of the Brazilian Antarctic Station on King George Island, three areas of moss carpet were transplanted to minimize the impact of the new facilities on the local biodiversity. A total of 650 m² of moss carpet was transplanted to neighboring but previously uncolonized locations and has subsequently survived for the last 3 years. Antarctic moss carpets typically comprise low moss species diversity and are often monospecific. We investigated the cryptic biodiversity that was transplanted along with the carpets using a metabarcoding approach through high throughput sequencing. We targeted 16S rRNA for Bacteria and Archaea, ITS for Fungi and Viridiplantae and Cox1 for Metazoa. We detected DNA representing 263 taxa from five Kingdoms (Chromista, Fungi, Metazoa, Protista and Viridiplantae), two Domains (Archaea and Bacteria) and 33 Phyla associated with the carpet. This diversity included one Archaea, 189 Bacteria, 24 Chromista, 19 Fungi, eight Metazoa, seven Protista and 16 Viridiplantae. Bacteria was the most abundant, rich and diverse group, with Chromista second in diversity and richness. Metazoa was less diverse but second highest in dominance. This is the first study to attempt transplanting a significant area of moss carpet to minimize anthropogenic environmental damage in Antarctica and to use metabarcoding as a proxy to assess diversity associated with Antarctic moss carpets, further highlighting the importance of such habitats for other organisms and their importance for conservation.

Effects of heavy metal-mediated intraspecific variation in leaf litter on the feeding preferences of stream detritivores

Plant litter inputs from terrestrial ecosystems are indispensable resources for stream ecosystems. Heavy metal pollution in the environment may indirectly affect the food webs of streams by changing the traits of leaf litter. In the present study, willow leaf litter was collected in polluted and non-polluted sites (natural willow), and leaf litter was produced in the lab by exposing willow saplings to different concentrations of heavy metals in water (cultivated willow). The collected willow leaf litter was used for feeding preference experiments with stream detritivores (shrimps and snails). Metal pollution significantly decreased the lignin concentration and toughness of litter and increased Zn and Cd concentrations. Both detritivores preferred to consume metal-enriched litter, with their consumption rates of this litter being significantly higher than those of non-enriched litter. The toughness of the willow litter was the key factor determining the feeding preferences of shrimps and snails. The detritivores that consumed metal-enriched leaf litter contained more Zn and Cd in their bodies than those that consumed non-enriched litter. The Zn and Cd concentrations in shrimp faeces were higher for shrimps that consumed metal-enriched litter than for those that consumed non-enriched litter. The heavy metal concentrations and chemical oxygen demand (COD) of the water following litter consumption were significantly higher for the metal-enriched litter than for the non-enriched litter, resulting in decreased water quality in the former context. The specific resource allocation patterns that result from heavy metal pollution in the environment will have ecological consequences.

Intraspecific variation influences performance of moss transplants along microclimate gradients

Identifying the environmental drivers of population dynamics is crucial to predict changes in species abundances and distributions under climate change. Populations of the same species might differ in their responses as a result of intraspecific variation. Yet the importance of such differences remains largely unexplored. We examined the responses of latitudinally distant populations of the forest moss Hylocomiastrum umbratum along microclimate gradients in Sweden. We transplanted moss mats from southern and northern populations to 30 sites with contrasting microclimates (i.e., replicated field common gardens) within a forest landscape, and recorded growth and survival of individual shoots over 3 yr. To evaluate the importance of intraspecific variation in responses to environmental factors, we assessed effects of the interactions between population origin and microclimate drivers on growth and survival. Effects on overall performance of transplanted populations were estimated using the product of survival and growth. We found differences between southern and northern populations in the response to summer temperature and snowmelt date in one of three yearly transitions. In this year, southern populations performed better in warm, southern‐like conditions than in cold, northern‐like conditions; and the reverse pattern was true for northern populations. Survival of all populations decreased with evaporation, consistent with the high hydric demands and poikilohydric nature of mosses. Our results are consistent with population adaptation to local climate, and suggest that intraspecific variation among populations can have important effects on the response of species to microclimate drivers. These findings highlight the need to account for differential responses in predictions of species abundance and distribution under climate change.