South-facing Slopes Research Articles

Novel brominated flame retardants (NBFRs) in soil and moss in Mt. Shergyla, southeast Tibetan Plateau: Occurrence, distribution and influencing factors

Research on the environmental fate and behavior of novel brominated flame retardants (NBFRs) remains limited, especially in the remote alpine regions. In this study, the concentrations and distributions of NBFRs were investigated in soils and mosses collected from two slopes of Shergyla in the southeast of the Tibetan Plateau (TP), to unravel the environmental behaviors of NBFRs in this background area. The total NBFR concentrations (∑7NBFRs) ranged from 34.2 to 879 pg/g dw in soil and from 72.8 to 2505 pg/g dw in moss. ∑7NBFRs in soil samples collected in 2019 were significantly higher than those in 2012 (p < 0.05). Decabromodiphenyl ethane (DBDPE) was the predominant NBFR, accounting for 90% of ∑7NBFRs on average. The ratio of the concentrations in moss and soil showed significantly positive correlations with LogKOA except for DBDPE (p < 0.05), indicating that the role of mosses as accumulators compared to soils are more pronounced for more volatile NBFRs. In addition, the concentrations of NBFRs generally decreased with increasing altitude on the south-facing slope, whereas on the north-facing slope some NBFRs exhibited different trends, suggesting concurrent local and long-range transport sources. Normalization based on total organic carbon/lipid concentrations strengthened the correlation with altitude, implying that the altitude gradient of the mountain slope and forest cover could jointly affect the distribution of NBFRs in the TP. Furthermore, principal components analysis (PCA) with multiple linear regression analysis (MLRA) showed that the average contribution of the mountain cold trapping effect (MCTE) accounted for the major (77%) contribution and forest filter effect (FFE) has only a modest contribution to the deposition of NBFRs in soil.

Slope aspect and altitude effect on selected soil organic matter characteristics in Beskid Mountains forest soils

Abstract In the era of dynamic climate change, it is important to have knowledge on the interactions between climatic factors and processes occurring in the soil environment. The present study aimed to determine how slope aspect and altitude above sea level influence carbon and nitrogen accumulation and dehydrogenases activity of forest soils. The study was conducted in the Beskid Żywiecki in the south-facing part of Poland. Soils of the same texture, with similar vegetation species composition, in different altitude variants (600, 800, 1000 and 1200 m above sea level) and different north-facing and south-facing slope aspect were selected for the study. For each height and slope aspect variant, samples were collected from the surface horizons of soils for further analyses. The basic chemical properties and dehydrogenases activity of the soil samples were determined. Carbon and nitrogen stocks in the surface horizons of the soils were calculated. The analyses confirmed the influence of location conditions on the carbon and nitrogen stocks in mountain forest soils. The stock of carbon and nitrogen increased with the height up to 1000 m a.s.l. In the soils at the highest altitude, the reserve of carbon and nitrogen decreased regardless of the slope aspect variant. There were no statistically significant differences in carbon and nitrogen stocks between slope aspect variant. The highest dehydrogenases activity was associated with the organic horizons of the soils at the lowest altitude in height gradient. In our study, higher dehydrogenases activity was observed in the north-facing slope soils, and this finding can be explained by more stable thermal conditions.

Shifts and plasticity of plant leaf mass per area and leaf size among slope aspects in a subalpine meadow.

The composition of vegetation on a slope frequently changes substantially owing to the different micro‐environments of various slope aspects. To understand how the slope aspect affects the vegetation changes, we examined the variations in leaf mass per area (LMA) and leaf size (LS) within and among populations for 66 species from 14 plots with a variety of slope aspects in a subalpine meadow. LMA is a leaf economic trait that is tightly correlated with plant physiological traits, while the LS shows a tight correlation with leaf temperature, indicating the strategy of plants to self‐adjust in different thermal and hydraulic conditions. In this study, we compared the two leaf traits between slope aspects and between functional types and explored their correlation with soil variables and heat load. Our results showed that high‐LMA, small‐leaved species were favored in south‐facing slopes, while the reverse was true in north‐facing areas. In detail, small dense‐leaved graminoids dominated the south slopes, while large thin‐leaved forbs dominated the north slopes. Soil moisture and the availability of soil P were the two most important soil factors that related to both LMA and LS, and heat load also contributed substantially. Moreover, we disentangled the relative importance of intraspecific trait variation and species turnover in the trait variation among plots and found that the intraspecific variation contributed 98% and 56% to LMA and LS variation among communities, respectively, implying a large contribution of intraspecific trait plasticity. These results indicate that LMA and LS are two essential leaf traits that affect the adaptation or acclimation of plants underlying the vegetation composition changes in different slope aspects in the subalpine meadow.

Effect of slope aspect on vegetation characteristics in mountain rangelands of Tajikistan: considerations for future ecological management and restoration

Tajikistan’s rangelands are mostly mountainous and consist of summer and winter pastures. Vegetation structure and composition in these diverse landscapes are generally influenced by environmental factors. The objective of this study was to assess the effects of aspect on vegetation characteristics of two mountainous pastures (summer and winter) over two seasons (autumn and spring) in Tajikistan. A three-way ANOVA was conducted using GLM procedures to test the main effects and interactions of these factors on vegetation attributes. The biomass production (kg DM ha−1) was significantly greater on the north-facing aspects for both summer and winter pastures in spring (483.4, 326.1) and autumn (57.2, 143.9), compared with south-facing aspects (57.2, 143.9 in spring and 18.5, 48.2 in autumn, respectively). Plant cover and plant density were also greater on north than south-facing slopes for summer and winter pastures in spring and autumn. Aspect significantly affected species diversity, botanic composition, and plant life forms of both pastures mainly for grasses and geophytes. There were greater vegetation responses on north than south-facing slopes, implying that aspect is important when designing mountain rangeland restoration. Given this complexity, land managers should thoroughly assess the conditions of the target site before defining restoration objectives and interventions.

The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study

In the northern hemisphere within snow-dominated mountainous watersheds north-facing slopes are commonly more deeply weathered than south-facing slopes. This has been attributed to a more persistent snowpack on the north facing aspects. A persistent snowpack releases its water into the subsurface in a single large pulse, which propagates the water deeper into the subsurface than the series of small pulses characteristic of the intermittent snowpack on south-facing slopes. Johnston Draw is an east-draining catchment in the Reynolds Creek Critical Zone Observatory, Idaho that spans a 300 m elevation gradient. The north-facing slope hosts a persistent snowpack that increases in volume up drainage, while the south-facing slope has intermittent snowpack throughout the drainage. We hypothesize that the largest difference in weathering depth between the two aspects will occur where the difference in snow accumulation between the aspects is also greatest. To test this hypothesis, we conducted four seismic refraction tomography surveys within Johnston Draw from inlet to outlet and perpendicular to drainage direction. From these measurements, we calculate the weathering zone thickness from the P-wave velocity profiles. We conclude that the maximum difference in weathering between aspects occurs ¾ of the way up the drainage from the outlet, where the difference in snow accumulation is highest. Above and below this point, the subsurface is more equally weathered and the snow accumulations are more similar. We also observed that the thickness of the weathering zone increased with decreasing elevation and interpret this to be related to the observed increase soil moisture at lower elevations. Our observations support the hypothesis that deeper snow accumulation leads to deeper weathering when all other variables are held equal. One caveat is the possibility that the denser vegetation contributes to deeper weathering on north-facing slopes via soil retention or higher rates of biological weathering.

Microclimatic Gradient as a Source of Variations in Cultivable soil Microfungal Communities at the Negev Desert, Israel

We studied the effect of microclimatic gradient on the spatial (8 habitats) and seasonal (autumn, winter, and summer) variations of culturable soil microfungal communities at the north-facing slope (NFS) and the south-facing slope (SFS) of Nahal Boker, the Central Negev Desert, Israel. Using the soil dilution plate method, a total of 122 species from 56 genera was isolated. The communities' composition was subjected to pronounced interslope variations in each season. While xerotolerant melanin-containing species (mainly with the protective multicellular spore morphology) predominated in the soil of NFS, peaking up in the summer, thermotolerant and thermophilic Aspergillus spp. were especially abundant at the SFS. Aspergilli also dominated the thermotolerant communities isolated at 37 °C from both slopes. The more severe microclimatic regime at the SFS resulted in the least pronounced spatial and seasonal intraslope variability of the community composition as compared to the more benign and heterogeneous NFS. The quantitative parameter—the density of microfungal isolates, exhibited significant and positive relationship with organic matter and moisture content. In seasonal dynamics, the severe summer conditions significantly reduced the differences in isolate density at the NFS, which were markedly expressed in the autumn and winter between habitats receiving additional water by runoff and the adjacent habitats that did not benefit from runoff water.

Modeling spatially distributed snow instability at a regional scale using Alpine3D

AbstractAssessing the avalanche danger level requires snow stratigraphy and instability data. As such data are usually sparse, we investigated whether distributed snow cover modeling can be used to provide information on spatial instability patterns relevant for regional avalanche forecasting. Using Alpine3D, we performed spatially distributed simulations to evaluate snow instability for the winter season 2016–17 in the region of Davos, Switzerland. Meteorological data from automatic weather stations were interpolated to 100 m horizontal resolution and precipitation was scaled with snow depth measurements from airborne laser scanning. Modeled snow instability metrics assessed for two different weak layers suggested that the weak layer closer to the snow surface was more variable. Initially, it was less stable than the weak layer closer to the ground, yet it stabilized faster as the winter progressed. In spring, the simulated snowpack on south-facing slopes stabilized faster than on north-facing slopes, in line with the regional avalanche forecast. In the winter months January to March 2017, simulated instability metrics did not suggest that the snowpack on south-facing slopes was more stable, as reported in the regional avalanche forecast. Although a validation with field data is lacking, these model results still show the potential and challenges of distributed modeling for supporting operational avalanche forecasting.

Shading and Masking of PV Collectors on Horizontal and Sloped Planes Facing South and North—A Comparative Study

With the increase in PV system installations, the available free land and rooftops for these systems may become scarcer, and therefore sloped fields facing the north may be utilized for that purpose. In deployments of PV collectors in multiple rows, either on horizontal or sloped planes, the second and subsequent rows are subject to two effects: shading and masking. Both effects reduce the electric energy generated by the PV systems. Multiple rows of collectors are deployed on horizontal planes and on sloped planes facing south, and literature on the topic has been published. No literature deals analytically with deployments of PV fields on north-facing slopes in the northern hemisphere, to the best of our knowledge. The present study develops explicit analytical expressions for the shadow height and length cast on a collector row by a row in front in multiple-row PV systems installed on slopes facing north. In addition, analytical expressions are developed for row spacing and sky view factors, altogether leading consequently to the determination of shading and masking losses. Having the developed expressions, a comparison was made between PV deployments on north-facing sloped planes to PV deployments on horizontal and south-facing slopes regarding shading and masking losses. The main finding is that the percentage of masking losses (diffuse radiation) may exceed the percentage of shading losses (beam radiation) in PV fields. At the local site 32∘ N, collector inclination angle β=25∘ and sloped-plane ε=10∘, for example, the percentage of masking losses for a horizontal plane is 6.90%; for a sloped plane facing south, the losses are 5.39%, and for a sloped plane facing north, the losses are 6.86%. In comparison to the masking losses, the percentage of shading losses for the horizontal plane is 0.83%; for the sloped plane facing south, the losses are 0.42%, and for the sloped plane facing north, the losses are 1.37%.

Managing climate change microrefugia for vascular plants in forested karst landscapes

Microrefugia are small areas that support favourable climate and allow species to persist during regional and global climate changes. Dolines in karst landscapes may provide such areas for many climate change-vulnerable species. Here we provide a better understanding on how plant species indicate changes in their environment (temperature, soil moisture and light availability) after a few years of partial canopy removal from dolines and their close surroundings (logged areas: >1 ha). We place our results in the context of the most widely used forest management practices within the study area (Mecsek Mts, Hungary), in addition to presenting a general framework for the maintenance of doline microrefugia in forested karst landscapes. Three types of habitats were investigated: dolines before logging, dolines after logging, and the forested plateau. Three large dolines and three sites on the plateau were selected for vegetation sampling. All dolines were sampled before logging and 5–10 years after partial canopy removal. Logging resulted in a 50–80% reduction of canopy cover in the dolines and their close surroundings. We established a transect across each doline from north to south passing through doline bottoms, and across each plateau site. We estimated the percentage cover of vascular plant species (tree saplings – up to 1 m in height, shrubs and herbs) along the transects using 1 m × 1 m vegetation plots, determined the diagnostic species of the doline and plateau habitats, and used multivariate methods and linear mixed-effects models during analyses. Plant species indicated clear gradients of the main microclimatic factors within the dolines and that significant changes took place after logging. Canopy removal caused substantial changes in the main microclimatic factors of most doline microhabitats (e.g., south-facing slopes). The vegetation of the dolines before logging indicated moister conditions than that of the plateau and cooler and shadier conditions than that of the dolines after logging. These and our previous results suggest that logging may directly and indirectly influence dolines to be microrefugia under global warming. By applying our framework to refugia conservation and management for the karst landscape in the Mecsek Mts, we can conclude that the protection of old forests and natural forest dynamics in as many large dolines as possible and the implementation of close-to-nature forestry practices may be essential to maintain regional biodiversity in the long run.

Occupancy patterns of prey species in a biological corridor and inferences for tiger population connectivity between national parks in Bhutan

AbstractSite occupancy models, accounting for imperfect detection and the influence of anthropogenic and ecological covariates, can indicate the status of species populations. They may thus be useful for exploring the suitability of landscapes such as biological corridors, to ensure population dispersal and connectivity. Using occupancy probability models of its principal prey species, we make inferences on landscape connectivity for the movement of the tiger Panthera tigris between protected areas in Bhutan. We used camera-trap data to assess the probability of site occupancy (Ψ) of the sambar Rusa unicolor, wild boar Sus scrofa and barking deer Muntiacus muntjak in biological corridor no. 8, which connects two national parks in central Bhutan. At least one prey species was recorded at 17 out of 26 trapping locations. The probability of site occupancy was highest for the barking deer (Ψ = 0.52 ± SE 0.09) followed by sambar (Ψ = 0.49 ± SE 0.03) and wild boar (Ψ = 0.45 ± SE 0.07). All three species had higher occupancy probability at lower altitudes. Sambar occupancy was greater farther from settlements and on steeper and/or south-facing slopes. Barking deer also had higher occupancy on south-facing slopes, and wild boar occurred mainly close to rivers. Our findings suggest that this biological corridor could facilitate dispersal of tigers. Protecting prey species, and minimizing anthropogenic disturbance and habitat fragmentation, are vital for tiger dispersal and thus functional connectivity amongst populations in this area.

A latitudinal cline in a courtship song character of Drosophila melanogaster

The courtship song of male Drosophila melanogaster is generated by wing vibration and contains an interpulse interval (IPI) which is species-specific and usually falls in the mean range of 30–40 ms. The IPI is extremely temperature-sensitive, so we wondered whether flies collected along the eastern coast of Australia between latitudes 16.9°S and 42.9°S might have adapted to the different thermal conditions and show differences in mean IPI. We observe a significant correlation between IPI and latitude in addition to the well-known association between latitude and body size (Bergmannn’s Rule). However, somewhat surprisingly we could not detect a significant association between body size and IPI. We also examined flies collected from the North and South-facing slopes of ‘Evolution Canyon’ in Israel and observed differences in IPI that support the view that thermal adaptation can shape this important song character. We also examined the songs of flies from Kenya and observed no correlation between altitude of collection and IPI. In all three experiments, body size did not correlate with IPI. A global analysis of all three sets of populations on three continents revealed a strong association between IPI and latitude. We speculate that IPI is shaped by thermal and sexual selection whereas body size is also shaped by natural selection.

Linking behavioral states to landscape features for improved conservation management.

A central theme for conservation is understanding how animals differentially use, and are affected by change in, the landscapes they inhabit. However, it has been challenging to develop conservation schemes for habitat‐specific behaviors.Here we use behavioral change point analysis to identify behavioral states of golden eagles (Aquila chrysaetos) in the Sonoran and Mojave Deserts of the southwestern United States, and we identify, for each behavioral state, conservation‐relevant habitat associations.We modeled behavior using 186,859 GPS points from 48 eagles and identified 2,851 distinct segments comprising four behavioral states. Altitude above ground level (AGL) best differentiated behavioral states, with two clusters of short‐distance movement behaviors characterized by low AGL (state 1 AGL = 14 m (median); state 2 AGL = 11 m) and two associated with longer‐distance movement behaviors and characterized by higher AGL (state 3 AGL = 108 m; state 4 AGL = 450 m).Behaviors such as perching and low‐altitude hunting were associated with short‐distance movements in updraft‐poor environments, at higher elevations, and over steeper and more north‐facing terrain. In contrast, medium‐distance movements such as hunting and transiting were over gentle and south‐facing slopes. Long‐distance transiting occurred over the desert habitats that generate the best updraft.This information can guide management of this species, and our approach provides a template for behavior‐specific habitat associations for other species of management concern.

Plastic bimodal growth in a Mediterranean mixed-forest of Quercus ilex and Pinus halepensis

Mediterranean tree species have evolved to face seasonal water shortages, but may fail to cope with future increases in drought frequency and intensity. We investigated stem radial increment dynamics in two typical Mediterranean tree species, Aleppo pine (Pinus halepensis), a drought-avoiding species, and holm oak (Quercus ilex), a drought-tolerant species, in a mixed forest and on contrasting slope aspects (south- and north-facing). Intra- and inter-annual growth patterns were modelled using the VS-Lite2 model for each tree species and slope-aspect. Both species showed a bimodal growth pattern, with peaks coinciding with favourable conditions in spring and autumn. A bimodal growth pattern is always observed in P. halepensis, while in Q. ilex is facultative, which suggests different strategies adopted by these species to cope with summer drought. More specifically, trees on south-facing slope showed a more evident bimodal pattern and more intra-annual density fluctuations. In recent decades, the intensity of both growth peaks has diminished and drifted away due to the increased summer drought. The VS-Lite2 model reveals a niche partitioning between both species. Differences in growing season’s length and timings of growth peaks in both species are relevant for their coexistence and should be considered for estimating mixed-forest responses under climate change scenarios.

Topography modulates near-ground microclimate in the Mediterranean Fagus sylvatica treeline

Understanding processes controlling forest dynamics has become particularly important in the context of ongoing climate change, which is altering the ecological fitness and resilience of species worldwide. However, whether forest communities would be threatened by projected macroclimate change or unaffected due to the controlling effect of local site conditions is still a matter for debate. After all, forest canopy buffer climate extremes and promote microclimatic conditions, which matters for functional plant response, and act as refugia for understory species in a changing climate. Yet precisely how microclimatic conditions change in response to climate warming will depend on the extent to which vegetation structure and local topography shape air and soil temperature. In this study, we posited that forest microclimatic buffering is sensitive to local topographic conditions and canopy cover, and using meteorological stations equipped with data-loggers we measured this effect during 1 year across a climate gradient (considering aspect as a surrogate of local topography) in a Mediterranean beech treeline growing in contrasting aspects in southern Italy. During the growing season, the below-canopy near-ground temperatures were, on average, 2.4 and 1.0 °C cooler than open-field temperatures for south and north-west aspects, respectively. Overall, the temperature offset became more negative (that is, lower under-canopy temperatures at the treeline) as the open-field temperature increased, and more positive (that is, higher under-canopy temperatures at the treeline) as the open-field temperature decreased. The buffering effect was particularly evident for the treeline on the south-facing slope, where cooling of near-ground temperature was as high as 8.6 °C for the maximum temperature (in August the offset peaked at 10 °C) and as high as 2.5 °C for the average temperature. In addition, compared to the south-facing slope, the northern site exhibited less decoupling from free-air environment conditions and low variability in microclimate trends that closely track the free-air biophysical environment. Although such a decoupling effect cannot wholly isolate forest climatic conditions from macroclimate regional variability in the south-facing treeline, it has the potential to partly offset the regional macroclimatic warming experienced in the forest understory due to anthropogenic climate change.

Effects of human-altered landscapes on a reintroduced ungulate: Patterns of habitat selection at the rangeland-wildland interface

Successful species reintroductions require land managers to balance the goal of viable wildlife populations with potential risks to human enterprise. Such risks are particularly acute at the wildland-agriculture interface, where native and domestic species are likely to come into contact. In a national park in northern California, we combined insights from three lines of evidence – long-term visual surveys, short-term GPS telemetry, and satellite remote sensing-based animal detections – to characterize spatial overlap between reintroduced tule elk (Cervus canadensis nannodes) and domestic cattle and to estimate the importance of multiple environmental features as predictors of habitat selection by elk. Our results indicate that, at large spatial scales (i.e., home-range level), cattle were the primary driver of habitat selection, with the occurrence of elk being negatively associated with cattle across all seasons. In addition, elk consistently selected for grasslands on gentle, south-facing slopes that occurred at high elevation and close to ponds. NDVI was a seasonally important, positive predictor of habitat selection, with a marked reversal when this resource was concentrated inside of fenced cow pastures during the dry summer months. By contrast, a novel analysis of satellite-derived animal locations yielded no evidence of avoidance of cattle by elk (within pasture areas commonly used by elk), indicating that this population has acclimated to the presence of cattle through spatial partitioning of resources. Thus, this once-imperiled native ungulate exhibits patterns of habitat selection that reduce the potential for grazing conflicts with cattle, even in cases where access to forage is limited.

Local Landscape Position Impacts Demographic Rates in a Widespread North American Steppe Bunchgrass

Photo 1. Widely spaced bluebunch wheatgrass (Pseudoroegneria spicata) surrounded by smaller annual grasses on a south-facing slope at Wallula Gap Biological Station, WA, USA. Photo credit: Timothy Parker. Photo 2. Densely distributed bluebunch wheatgrass (Pseudoroegneria spicata) and other perennial bunchgrasses on a north-facing slope at Wallula Gap Biological Station, Washington, USA. Photo credit: Timothy Parker. Photo 3. A comparison between a north-facing slope (left) and a hotter, drier south-facing slope (right) at Wallula Gap Biological Station, Washington, USA. Note the widely spaced green clumps of bluebunch wheatgrass (Pseudoroegneria spicata) on the south-facing slope in the foreground and the much denser concentration of green perennial grasses, many of which are bluebunch wheatgrass, on the north-facing slopes. Photo credit: Timothy Parker. These photographs illustrate the article “Local landscape position impacts demographic rates in a widespread North American steppe bunchgrass” by Shriver et al. published in Ecosphere. https://doi.org/10.1002/ecs2.3351

How the interplay between management and interannual climatic variability influences the NDVI variation in a sub-Mediterranean pastoral system: Insight into sustainable grassland use under climate change

The modification of precipitation regimes and the increase in summer aridity under the predicted climate change scenarios are hypothesized to have repercussions on the semi-extensive pastoral systems of Mediterranean grasslands, leading to change in forage quantity/quality, increased interannual variability in phytomass production, reduction of the carrying capacity of rangelands, and worsening of animal welfare. The research aims were to find what climatic features affect changes in the annual peak of Aboveground Net Primary Production (ANPP), and how topographic variables and management conditions influence these variations in a pastoral system of central Apennines (Italy).We monitored Normalized Difference Vegetation Index (NDVI) variations at the peak of phytomass production using Landsat satellite images, used as a proxy for ANPP changes in the most productive phase of the growing season, when herds are carried to pastures and hay-meadows are mown, on a dataset of 10,000 randomly sampled pixels (30 × 30 m), in the years 2003, 2007, 2009, 2010, and 2013−2015. We investigated the relation between NDVI and climatic variables, topographic parameters, vegetation physiognomy, and management type, using generalized linear mixed-effects modeling, variation partitioning, and correlation analysis.We observed an increase in average yearly temperatures and high variability in the rainfall seasonal distribution pattern, particularly of spring precipitation. Climatic fluctuations influenced the overall amount of forage production more than management and topographic conditions. The spring variation of climatic variables (precipitation in March, drought stress in April and May), the drought and cold stress intensities in the previous year and the cold stress in the preceding winter were the main drivers of NDVI change. The landform factors interacted with climate variability in determining the amplitude of NDVI changes, which were the widest in semi-flat mountain tops and flat valley bottoms and the smallest in south-facing slopes. The effect of the climatic variables on NDVI was different depending on the management condition, suggesting that grassland management partially filters the climatic drivers of changes in forage production. Based on our results, the most productive grassland communities and the areas used for grazing by domestic herbivores could be the most impacted by the predicted climate changes for the Mediterranean basin, potentially reducing the economic sustainability of semi-extensive farming in the Apennine mountains.

Signatures of an abiotic decomposition pathway in temperate forest leaf litter

Photodegradation helps explain why leaf litter mass loss rates are comparable between mesic environments and drylands, despite water availability limiting decomposer activity in drylands. With photodegradation, light energy directly mineralizes photoreactive organic molecules such as lignin, which contrasts with biotically-driven decomposition where lignin persists in decomposing leaf litter relative to other compounds. Photodegradation of leaf litter has largely been studied in dryland systems, but whether it occurs in mesic, deciduous forest systems is uncertain. As such, we examined potential photodegradation in maple and oak litter in the Southern Appalachian Mountains (USA) during the non-growing season, when newly fallen leaves are exposed to maximum solar radiation without deciduous canopies. The proportion of oxidized lignin in the leaf litter relative to other carbon compounds decreased with maximum solar radiation during the non-growing season. With a closed canopy, however, the proportion of total lignin relative to other compounds in the leaves increased. This pattern was particularly strong for the syringyl- S6 and guaiacyl-G6 lignin monomers. The relative proportion of S6 and G6 in the litters was reduced by 10–65% in the first 5 months. The largest reductions in lignin occurred on south-facing mountain slopes where solar radiation was highest (relative to north-facing slopes) in the Northern Hemisphere. Overall, however, the changes in lignin did not alter cumulative litter mass lost. Our results suggest that photodegradation promotes the transformation and relative loss of lignin in the early stages of litter decomposition in mesic deciduous forests.

Effects of forest disturbance on seasonal soil temperature changes in the Tatra Mountains in southern Poland

Abstract The purpose of the study was to examine the effects of forest disturbance on seasonal changes in soil temperature in the Tatra Mountains (Poland). In the years 2015–2020 soil temperatures were measured at a depth of 20 cm on north- and south-facing mountain slopes in a catchment where forest was disturbed by hurricane-force winds in 2013 and in a control neighboring woodland catchment. The effect of forest disturbance was manifested first and foremost in an increase in the soil temperature during the summer months – average by 1.8 to 2.4 °C on a south-facing mountain slope – and by about 1 °C on a north-facing slope. The buffer effect of forest on soil temperature can be observed via lower coefficients of correlation between soil temperature and air temperature in a woodland catchment versus a disturbed catchment in the summer. In the winter, the effect of forest disturbance on soil temperature was less pronounced than in the summer. Small differences in soil temperature in the winter between the woodland catchment and the disturbed catchment were associated with the presence of snow cover and its capacity to yield thermal insulation. Good insulation of the soil from the atmosphere generated by snow cover yielded a very weak relationship between soil temperature and air temperature in the winter. In springtime the soil temperature increased the fastest on a south-facing slope in the disturbed catchment while in the autumn season, soil temperatures declined most rapidly on a slope facing north in the disturbed catchment.

Thermal adaptations of adults and eggs in the Arctic seed bug Nysius groenlandicus (Insecta: Hemiptera) from South Greenland

Temperatures in Arctic and sub-Arctic regions are highly variable, with long, and cold winters, and short summers. Studies on thermal biology of ectotherms from these latitudes have mostly focused on how organisms cope with cold temperatures. However, temperatures in microhabitats such as south-facing slopes can occasionally reach high and potentially stressful temperatures. Such microclimatic conditions are challenging for organisms, since they need to time their development to coincide with the short summer, while coping with thermal extremes during summer and winter. In the present study, we investigate upper and lower thermal limits of adults and eggs in Nysius groenlandicus, a univoltine seed bug widely distributed in Greenland and alpine areas of Scandinavia and with preference for dry and sunny habitats. Secondly, we investigate the survival strategy of the overwintering egg stage during cold exposure. We found a clear association between the microhabitat temperatures experienced by each specific life stage and their heat and cold tolerance. Thus, adults and eggs, which are both exposed to high summer temperatures, showed a high heat tolerance. Adults which do not overwinter had very poor cold tolerance, whereas eggs produced in autumn were very cold hardy (with some survival at − 21 °C). Cold tolerance of the eggs of N. groenlandicus was based on freeze avoidance through extensive supercooling and by conserving water. These results suggest life stage-specific adaptation to heat and cold stress in Arctic and sub-Arctic insects, and highlight new research avenues addressing adaptation to higher and more variable temperatures in Arctic and sub-Arctic regions.