North-facing Slopes Research Articles

Solar Radiation Drives Potential Demographic Collapse in a Perennial Bunchgrass via Dramatically Reduced Seedling Establishment

Many perennial plants in semiarid rangelands have experienced population declines, and understanding the ecological and demographic processes behind these declines is important to slowing or reversing them. Although anthropogenic disturbances drive many declines, other sorts of environmental variability, such as the differences in solar radiation with aspect, may impact population success locally. We experimentally assessed the role of solar radiation in driving an apparent decline in a common perennial bunchgrass, bluebunch wheatgrass (Pseudoroegneria spicata), on south-facing slopes at a site in the Columbia Basin of North America. Across three separate experiments on south-facing slopes, we observed dramatically (5−36 ×) higher seedling success in plots shaded to approximate the solar radiation of north-facing slopes relative to adjacent open (unshaded) plots. When we applied the rates of seedling success from these experiments to demographic models from this site, we found that seedling success in unshaded plots was often too low to allow a stable population on south-facing slopes, but that seedling success in shaded plots was often high enough to allow a stable or increasing population on north-facing slopes. We originally hypothesized that the primary mechanism driving this effect was water stress caused by greater evaporation from hotter open plots. However, despite soils in open plots being consistently hotter than soils in shaded plots, we did not observe a clear pattern of greater soil moisture in shaded plots. Therefore, it appears that higher solar radiation or higher temperatures on south-facing slopes may be sufficient to dramatically reduce seedling survival, and that the higher density of bluebunch wheatgrass on north-facing slopes relative to south-facings slopes may be driven primarily by this low survival of seedlings. As climate warms, the reduced seedling survival that threatens our bluebunch wheatgrass population may be expected to threaten many other species of perennials in similar rangelands.

Modeling the effect of slope aspect on temporal variation of soil water content and matric potential using different approaches by HYDRUS-1D

Slope aspect affects microclimate and soil moisture conditions, and thus has an important effect on the hydrological cycle. Given the lack of precise field data on this effect, two soil temperature, moisture and matric potential monitoring sites on north- and south-facing slopes have been established since 2017 in sandy loam soil under beech forest in a small valley near Ebergötzen, central Germany. HYDRUS-1D software was used with different approaches (including Rosetta, RETC, and RETC–measured θs approaches) for deriving soil hydraulic parameters of the van Genuchten model, to simulate temporal variability of soil water content and matric potential in the two slope aspects. Due to different microclimatic conditions, the south-facing slope was warmer and drier than the north-facing slope (two-years average temperatures 9.71 and 9.36 °C, and two-years average soil water contents 0.17 and 0.26 cm3 cm-3, respectively). The model was satisfactorily calibrated and validated on the two slopes. The calibration for the wet period was better on the south-facing slope (R2 = 0.772) than on the north-facing slope (R2 = 0.690). The simulation performance by HYDRUS-1D was better in the wet period than in the dry period. In the dry period, the model was better calibrated for the north-facing slope (R2 = 0.880) than for the south-facing slope (R2 = 0.691). The better calibration results for the wet period of south-facing slope can be explained by the location of the majority of measured soil water retention data which were in the near-saturation zone on the north-facing slope, and discontinuity of second-order derivative of the van Genuchten equation at saturation point when shape parameter (n) is smaller than 2. According to the model ability and different datasets used for the model validation, the north-facing plot was validated better than the south-facing plot for both wet and dry periods. Given that Rosetta was developed based on a soil hydraulic dataset from temperate climates, and the shortcomings of the hydraulic model, our results indicated that the Rosetta–derived approach was a reliable source for soil hydraulic parameters in both slope aspects for the wet period. However, the RETC–derived parameters were more accurate than Rosetta for the dry period on the north-facing slope.

Changes in species diversity along the ephemeral streams in eastern Mediterranean Mountainous Ecosystem, a case study for Ahir Mountain (Kahramanmaraş-Türkiye).

Ephemeral streams are important habitats that support biodiversity, especially in mountainous ecosystems in arid and semi-arid regions, and are among those that will be most affected by global climate change. This study aimed to examine the trends in plant species diversity of ephemeral stream beds and their relationship with environmental variables (aspect, elevation, soil) in the eastern Mediterranean region.For this purpose, 40 sample plots were applied in the valley cross sections of the ephemeral stream beds (valley bottom, side and ridge) on two main slopes (north and south) in 2019. The abundance values of plant species were determined and the number of individuals in each sample plot was counted. In addition, soil samples were taken at a depth of 0-30 cm and analyzed. With the data obtained, the importance value index of all species was calculated, and the diversity and species richness of the sample plots were determined.A total of 130 plant taxa were identified in the study area. The most dominant species were Astragalus kurdicus (IVI value: 25.97), Helichrysum plicatum (21.94), Taeniatherum caput-medusae subsp. crinitum (15.51), Hordeum bulbosum (15.33), Bromus erectus (15.32), and Minuartia juniperina (14.14). Both plant richness and endemism rate showed a significant relationship with increasing elevation. Plant diversity values of south-facing slopes were higher (2.23) than those of north-facing slopes (2.21). In addition, we found that phosphorus is an important factor in the distribution of plant species along the ephemeral stream beds, and as the amount of phosphorus increases, species richness and diversity also increase.

Application of landslide susceptibility towards urbanization suitability zonation in mountainous settings

Amplified susceptibility to landslides poses challenges to sustainable and equitable urban development. Thus, in this study, we introduce an artificial intelligence and geographic information system-based approach, urbanization suitability zonation (USZ), for spatial assessment of land suitability for urbanization, which accounts multiple factors, including a focus on landslide susceptibility. Further, the proposed USZ is tailored to assess health of current urbanization patterns, depicting the driving factors behind it by establishing a best-case urbanization suitability (BUS) and weighted urbanization suitability (WUS). The BUS portrays a hypothetically ideal land suitability scenario as a function of equally weighted factors, while the WUS portrays land suitability changes when factors are weighted hierarchically. An examination of current development against the BUS provides idealness of current urbanization patterns. The WUS aids in assessing the significance of factors in influencing the current urbanization pattern, and checks its resemblance with the BUS. The mountainous Indian township of Mussoorie is selected as the study area to exercise the USZ by considering seven factors with different weights, and subsequently generated a BUS map and 7 WUS maps (WUS–I to VII), which all display urbanization suitability distribution in five different classes. The BUS map shows that ∼98 % of current development falls in higher-suitability areas, indicating its preferability. Among the different WUS maps, the WUS-II aligns best with the BUS and current built-up, with slope gradient and transportation connectivity as key factors, and according to it, high-suitability areas are generally the central and south-facing slopes, while north-facing slopes are unsuitable, in general.

Changes in aggregate-associated carbon and microbial respiration affected by aggregate size, soil depth, and altitude in a forest soil

This study investigates the variations of aggregate-associated organic carbon (OC) and microbial respiration (MR) with respect to aggregate size, soil depth, and land altitude in a forest soil. The research was conducted in Arasbaran forest, East Azerbaijan province, Iran. Four sites were selected at different altitudes: 0–600 m, 600–1200 m, 1200–1800 m, and 1800–2400 m above sea level (a.s.l.), along the north-facing slope of the forest region. Soil samples were collected at five depths: 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, and 80–100 cm, with three replications for each depth. The soil samples were then fractioned into four aggregate size classes: <0.053 mm, 0.053–0.25 mm, 0.25–2 mm, and >2 mm. Both soil samples and aggregate fractions were analyzed for OC content and MR. The results revealed that OC content and MR in both soil samples and aggregate fractions increased with altitude and decreased with soil depth. Moreover, aggregate-associated OC increased with aggregate size. Specifically, as soil aggregate sizes increased from <0.053 mm to >2 mm at different altitudes, the mean occluded OC content of aggregates increased by approximately four times. Similarly, the mean aggregate-associated MR intensified eight times with the increase in aggregate size. A significant positive correlation was also observed between OC and MR rates of all aggregates. Furthermore, aggregates larger than 2 mm exhibited the highest contribution to the total soil OC storage (47.47–57.22%) and CO2 production rate (20–21%). These findings underscore the critical role of large macro-aggregates (>2 mm) in soil carbon storage and microbial activity, particularly in surface soils at higher altitudes.

North-facing roadside slopes: Anthropogenic climate microrefugia for orchids

Facing global climate change is a great challenge for organisms. Numerous species respond to a changing climate by shifting their geographical ranges, adapting to the local climate or finding microrefugia to persist under unfavorable macroclimatic conditions. Orchids are frequently found in roadside verges, and it was demonstrated that roadsides could serve as refugia for them in a changing landscape. We investigated whether roadside slopes, facing different compass directions could serve as microrefugia for orchids, using our database spanning across 18 European countries. Our results showed that the probability of orchid occurrence in north-facing roadside slopes are greater than on south-facing slopes. Further, we found a significant difference in the probability of orchid occurrence in different exposures under unfavorable macroclimatic conditions. In south-facing slopes, the probability of orchid occurrence decreased with increasing annual mean temperature and increasing precipitation seasonality. This suggests that harsh microclimatic environments intensify the negative effects of the macroclimate in south-facing slopes. Moreover, roadside slopes with cooler microclimatic conditions might facilitate the persistence of orchids under a warming and increasingly stochastic climate.

Morphometric characteristics and paleogeographic implication of glacial cirques in Eastern Black Sea Mountains (Türkiye)

The Eastern Black Sea Mountains, located in the northeastern region of Anatolia and running parallel to the Black Sea coast, underwent glaciation during the Quaternary. The mountain range contains 811 cirque sites. Although the majority of the cirques are simple, 309 are complex, according to their developmental features. In Anatolia, intensive cirque development is observed only on north-facing slopes in several mountains, while in the Black Sea Mountains, 66.5 % of the cirques are located on north-facing slopes and 14.5 % on south-facing slopes. Differences in cirque morphometry between the north- and south-facing slopes were primarily influenced by aspect, which had a significant influence on Quaternary glaciation. While the northwest-facing cirques are the largest, the east- and southeast-facing cirques are the smallest. This situation is related to that air masses that bring rain to the mountains generally come from the northwest. The mean cirque floor elevation is 2815 m, while 90 % of the cirques have floor elevations between 2479 and 3130 m. In light of these measurements, the former Equilibrium Line Altitude (ELA), initially positioned above 2480 m, underwent a complete stabilization at elevations exceeding 2800 m within the Black Sea Mountains. However, these averages are not sufficient to represent the former ELA across the mountain. According to the cirque floor elevations, the cirques in the N-sector have a mean elevation of 2760 m, while the cirques in the S-sector have a mean elevation of 3004 m, and there is a 244 m difference between the two sectors. In the NW basin, the cirques start at 2434 m and reach a permanent former ELA level at 2743 m. In the SE basin, on the other hand, the cirques start at 2635 m and become permanent at 2920 m. Aspect had a significant effect on the distribution of other morphological elements associated with the cirques. The N-sector cirques harbor 73.5 % of the cirque lakes and 81.8 % of the rock glaciers. The average depth of the cirques in the northern sector stands at 388 m, whereas it diminishes to 341 m in the southern sector. Negative correlations emerge between former ELA levels and both latitude and distance from the watershed, while positive correlations align with distance from the coast. Based on these correlations and the associated distribution maps, a clear trend emerges: the former ELA diminishes as one travels north, approaches the coast, and encounters decreasing topographic elevations.

Geological Significance of the Perrot Spring in Mont Avic Natural Park (NW Alps)

Alpine areas shaped in a normally fissured bedrock do not typically contain important groundwater aquifers. In contrast, a wide Quaternary cover in mountainous areas, especially of landslide deposits, can make large aquifers promising for water withdrawals. A geological study of the central sector of the Chalamy Valley, a right tributary of the main Dora Baltea River (Aosta Valley) in which the Perrot Spring is located, was carried out, with the aim of providing a preliminary assessment of hydrogeological significance. The main interest of this investigation is, in addition to the high discharge of the Perrot Spring, its location within Mont Avic Natural Park, which is a very busy area with walkers, cyclists, visitors, and scholars. The geological survey shows a thick body of sandy silty glaciolacustrine sediments, consequent to the barrage of the Chalamy Valley from the glacier hosted in the main Aosta Valley. These sediments, outcropping in the north-facing slope of the Chalamy Valley, are involved in significant gullies and covered by a thick landslide accumulation located in the northern slope of the Bec de Nona, formed by very heterometric sediments. A wide detachment scarp is shaped in serpentinite characterized by evident fracture systems. The preliminary hydrogeological significance for the Perrot Spring, located at the boundary between glaciolacustrine and landslide sediments, was proposed. In detail, the thick landslide cover, characterized by high permeability, represents an important aquifer with a relatively fast groundwater flow to the spring. The underlying glaciolacustrine sediments of the low band of the slope, typically with very low permeability, favor the concentration of groundwater near the boundary with landslide sediments and the spring supply.

Dependence of some physiological indicators of generative and vegetative organs of Sambucus nigra on habitat conditions

We carried out studies on water deficiency of Sambucus nigra L. (black elderberry) plant leaves extract and fruit juice, relative turgidity, sucrose content in fruits, chlorophyll content in the leaves, as well as gas exchange rates in the leaves, in particular, the changes in the concentrations of oxygen released during photosynthesis by leaves and carbon dioxide released during leaf respiration depending on habitat conditions (altitude of the habitat, position of slopes, average annual precipitation). Taking into account the difference in climatic conditions and the generality of some indicators, Vanadzor (1326–1600 m above sea level) and Stepanavan (1400–1830 m above sea level) regions of Lori Province, "Dilijan" National Park, Lake Parz, and the forest areas adjacent to the city of Dilijan (1240–1612 m above sea level) in Tavush Province in Armenia were chosen as the research sites. The test samples were taken from eight different test sites in Lori and Tavush provinces. Tavush Province is more humid than Lori Province. The highest rate of water deficiency in the leaves of the studied plants was recorded in S. nigra f. laciniata (L.) Zabel., and the lowest in S. nigra in Vanadzor forest. It can be assumed that the index of water deficiency in the leaves may depend on the position of the slopes of the test sites and the value of the filtration coefficient of the soil types. On the north-facing slope at the height of 1341 m above sea level and on the south-facing slope at the height of 1830 m above sea level, the values of water deficiency of the leaves are almost the same. Such data allows us to assume that the degree of water deficiency in the leaves is also affected by the filtration coefficient of habitat soil types. In two points that have north-facing positions, the water deficiency of leaves at the height of 1341 m above sea level is 2.14 times more than at the height of 1328 m above sea level. At 1328 m above sea level the filtration coefficient is small and the plant absorbs a lot of water. Based on the data we received we obtained rankings of plants according to the different criteria of the experimental plants: water deficiency in leaves tissues, relative turgidity, the sum of chlorophylls in the leaves, the sucrose content in the fruits, percentage of oxygen released as a result of photosynthesis, percentage of carbon dioxide released as a result of respiration. We found a certain dependence between the indicators of the water regime and the height above sea level of the researched habitats. We also found out that the water regime is influenced by certain microclimatic conditions such as the position of the slopes, whether they are north or south facing, as well as the average annual precipitation. Knowing the physiological processes taking place in the vegetative and generative organs of the S. nigra plant is important from the point of view of evaluating the intensity of growth and development of the generative organs. We consider that the results of the study will be applicable in the process of plant selection based on the indicators of the physiological processes taking place in the plant organism.

Monitoring montane-subalpine forest ecotone in the Pyrenees through sequential forest inventories and Landsat imagery

Key messageAbies alba Mill.–Pinus uncinata Ramond. ecotone dynamics are examined along both altitudinal and protection level gradients by combining field inventories and Landsat data. An upward expansion of A. alba to the subalpine belt is observed in the last decades as a result of stand maturation after logging cessation.ContextHigh-mountain forests constitute sensitive locations to monitor the impacts of global change on tree-species composition and ecotone dynamics. In this study, we focus on the Spanish Pyrenees where silver fir (Abies alba Mill.) coexists with mountain pine (Pinus uncinata Ramond.) forming montane-subalpine ecotones.AimsThe main goal of this study is to assess the spatiotemporal dynamics of the silver fir–mountain pine ecotone and its underlying driving factors.MethodsWe reconstructed the spatial distribution and dynamics of the species by combining remote sensing imagery and field plot data from 1989 to 2015, employing support vector machine techniques for image classification. Using variance analysis and mixed effects models, we then analyzed the evolution of basal area and replacement index, a measure of relative change in species composition, over time and altitude range. Additionally, we explored their relationship with site factors and protection level (National Park vs. protection buffer zone).ResultsSilver fir has expanded its distribution in both the National Park and the protection buffer zone, whereas mountain pine has remained stable. Both species exhibit increased basal area associated with stand maturation and a higher level of protection. The replacement index indicates a rise in silver fir in the understory on North-facing slopes, attributed to stand densification. These findings are particularly noticeable in the area with the highest level of protection.ConclusionThe cessation of traditional land uses has led to ongoing stand densification, promoting succession and favoring the increased abundance of silver fir at its uppermost locations, where this species outcompetes mountain pine.

Spatial differences of ice volume across High Mountain Asia

Advanced knowledge of glacier ice volume is vital for water resource assessment. Previous studies have focused on the estimation of ice volume, but the quantitative understanding of the spatial variability of ice volume across High Mountain regions is currently lacking. Here, we used global-scale ice thickness, debris cover and equilibrium line data to analyse ice-volume differences at various scales across High Mountain Asia (HMA). The results showed that 6.3% of the HMA glaciers are covered by debris, with debris area and volume accounting for 9% and 13.8% of the total glacier area and volume, respectively. An average debris-cover volume ratio of 13% was observed. The spatial distribution of ice volume across the HMA varies considerably from region to region. The ice volume is predominately distributed on north-facing slopes and accounts for approximately 38% of the total. It is very common in Altay and Sayan, East Tian Shan, West Kunlun, East Kunlun and Qilian Shan. Meanwhile, ice volumes in the Himalayas and Hengduan Shan are mainly distributed on the southeast aspect. Relative weight functions showed that glacier area, maximum length and average thickness are closely related to ice volume, with average relative weights of 63.7%, 22.5% and 9.8%, respectively. This study is important for the evolution of glacier volume and water resource assessment.

Interacting ecological filters influence success and functional composition in restored plant communities over time.

A trait-based community assembly framework has great potential to direct ecological restoration, but uncertainty over how traits and environmental factors interact to influence community composition over time limits the widespread application of this approach. In this study, we examined how the composition of seed mixes and environment (north- vs. south-facing slope aspect) influence functional composition and native plant cover over time in restored grassland and shrubland communities. Variation in native cover over 4 years was primarily driven by species mix, slope aspect, and a species mix by year interaction rather than an interaction between species mix and slope aspect as predicted. Although native cover was higher on wetter, north-facing slopes for most of the study, south-facing slopes achieved a similar cover (65%-70%) by year 4. While community-weighted mean (CWM) values generally became more resource conservative over time, we found shifts in particular traits across community types and habitats. For example, CWM for specific leaf area increased over time in grassland mixes. Belowground, CWM for root mass fraction increased while CWM for specific root length decreased across all seed mixes. Multivariate functional dispersion remained high in shrub-containing mixes throughout the study, which could enhance invasion resistance and recovery following disturbance. Functional diversity and species richness were initially higher in drier, south-facing slopes compared to north-facing slopes, but these metrics were similar across north- and south-facing slopes by the end of the 4-year study. Our finding that different combinations of traits were favored in south- and north-facing slopes and over time demonstrates that trait-based approaches can be used to identify good restoration candidate species and, ultimately, enhance native plant cover across community types and microhabitat. Changing the composition of planting mixes based on traits could be a useful strategy for restoration practitioners to match species to specific environmental conditions and may be more informative than using seed mixes based on growth form, as species within functional groups can vary tremendously in leaf and root traits.

Asymmetric glaciation, divide migration, and postglacial fluvial response times in the Qilian Shan

Abstract Glacial-interglacial cycles have repeatedly perturbed climate and topography in many midlatitude mountain ranges during the Quaternary. Glacial erosion can move drainage divides and induce fluvial adjustments downstream, yet the time scale over which these adjustments occur remains unclear. We examined landscape evolution in the northwest-southeast–trending Qilian Shan, where the contrast in solar insolation between north- and south-facing slopes has generated larger glaciers on the northern range crest. Our analyses suggest that this asymmetric glaciation has caused southward migration of the main drainage divide, prompting river channels below the extents of ice on north-facing slopes to become oversteepened for their drainage area and channels on south-facing slopes to become analogously understeepened. These changes in steepness should accelerate or slow down postglacial fluvial incision, even in the regions where topography has not been directly modified by glacial erosion. Numerical modeling suggests these discrepancies persist for millions of years, much longer than the duration of recent glacial-interglacial cycles, implying a widespread and enduring influence of intermittent glaciations on landscape evolution in glaciated mountain ranges during the Quaternary.

Empirical relationship for the estimate of pyroclastic soil thickness using slope steepness

The assessment of soil thickness plays a primary role in different areas of the geosciences, including landslide hazards and soil erosion assessment. Nevertheless, the thickness of the cover deposits is difficult to measure over large areas while the prediction with numerical models is still challenging. In this study, some topographic attributes, namely slope angle and profile curvature, are investigated as proxies for the estimate of soil thickness of pyroclastic cover through empirical relationships. The study area is the North-facing slope of the Lattari Mts. (Campania, Southern Apennines), which were historically affected by several flow-like landslides and flash floods. The dataset was collected with both direct and indirect measurements from field surveys and investigations in two test sites of the study area.The topographic parameters were derived from DEMs at three different cell sizes, respectively at 1 × 1 m, 5 × 5 m, and 10 × 10 m. The slope angle at 5 × 5 m resulted in the most fitting parameter with the soil thickness, whereas the curvature showed a low correlation at all the investigated scales. The relationship for the Pyroclastic Thickness Estimation (PTE) is defined by an exponential law, which was validated by an internal and external dataset and checked against other predictive models used in the literature for similar study areas.

Diversity, Distribution and Vegetation Assessment of Woody Plant Species in the Cold Desert Environment, North-Western Himalaya, India

The species richness, distribution and community structure in cold desert regions across the world are poorly understood because of their inaccessibility and remoteness. Similarly, the structure and composition of forest resources, including other management units (i.e., agroforestry and forestry systems), have hardly been studied in the cold desert of the Lahaul valley. However, such information is a prerequisite to understanding the trends and changes in the vegetation distribution under global climate change scenarios, especially considering the sensitivity of plant species in high-altitude areas of the Himalayan region. High anthropogenic activity has exerted tremendous pressure on available forest resources, including other management units in the cold desert of the Lahaul valley. Standard ecological methods were used to obtain an ecological (i.e., status, structure, composition and vegetation patterns) understanding of the region for biodiversity conservation and environmental sustainability. The present study was aimed at understanding the trend, structure and composition of plant species in the cold desert region of the western Himalaya. A total of 64 species (27 trees and 37 shrubs) of vascular plants were recorded in the present study. Tree diversity demonstrated greater variation along the gradients and slope aspects. Salix fragilis trees, with a 102 tree ha−1 density and a few trees of Populus nigra, were found to be sparsely distributed under the agroforestry system on the south-facing slopes in Khoksar. In Jahlma, Salix fragilis grew in an agroforestry system with a density of 365 tree ha−1. However, in Hinsa, Juniperus polycarpos was a dominant tree species in the agroforestry system, with a density of 378 tree ha−1. On the north-facing slopes in Kuthar, a higher number of trees and bushes were present due to natural regeneration maintained by farmers along the edges of terraced agricultural fields. The south-facing slopes showed a relatively lower species richness and diversity as compared to north-facing slopes at similar locations due to relatively less favourable growth conditions under sun-exposed, extremely xeric soil conditions. The highest level of species turnover was found between the altitudes of 2400 m and 3000 m. Betula utilis showed the highest adaptability at higher altitudes (&gt;3500 m). The vegetation analysis results and information generated in the present study are useful for gaining an ecological understanding of the cold desert ecosystem in the Lahaul valley. Sustainable forest resource management, including other management units (e.g., agroforestry and forestry systems), is crucial for improving the vegetation pattern, structure and function of the cold desert ecosystem, thereby contributing to climate change mitigation, adaptation, biodiversity and ecosystem service conservation.

Spatiotemporal Variability of Alpine Meadow Aboveground Biomass and Sustainable Grazing in Light of Climate Warming

Understanding spatiotemporal variability of aboveground biomass (AGB) in alpine grassland ecosystems is required to better formulate sustainable grazing strategies, especially in climate-sensitive areas such as the Qinghai-Tibet Plateau. Drawing from recent modeling results, we analyzed spatial variability in grassland AGB over seasonal and annual timescales. Theoretical livestock carrying capacity (LCC) was predicted in relation to projected warming and simulated pika disturbance. We found that elevation and slope were key determinants of the distribution of AGB and its change. Although grasses and shrubs occupied an equivalent area, the latter generated approximately double the amount of total biomass, but the former generated slightly more available biomass. Although pika habitat extended over 45.3% of the study area, the impacts of pika only reduced the total available AGB (AGBV) by < 0.07%. The actual LCC (2.16 SU · ha−1 [sheep unit per hectare]) of the study area was lower than the theoretical LCC (2.77−2.96 SU · ha−1). Under climate warming scenarios of 1.0°C, 1.5°C, and 2.0°C, the actual LCC can be increased by 0.82-1.25, 0.99-1.53, and 0.77−1.23 SU · ha−1, respectively. Although systematic climate warming increased AGB, impacts were especially marked at lower elevations and on north-facing slopes because of higher soil water availability. Results highlight that rather than implementing LCC in a static manner in light of climate warming, deeper understanding of biomass availability and the combined effects of climate change and topographic heterogeneity is required to support better management of grasslands.

Snag persistence rates and patterns following mountain pine beetle epidemic in the Elkhorn Mountains, Montana, USA

Bark beetle (Dendroctonus spp.) epidemics generate snags, providing nesting and foraging opportunities for woodpeckers and other disturbance-associated wildlife. Forest managers need to know how long snags persist to include wildlife habitat conservation in their objectives, but published studies of snag persistence following disturbance under-represent beetle-killed forest. We analyzed snag persistence rates in relation to environmental covariates following a mountain pine beetle (Dendroctonus ponderosae) epidemic in the Elkhorn Mountains (Montana, U.S.A.) over a 6-year study period (2010–2015). We evaluated hypothesized relationships with topography, local tree density, and snag characteristics. Consistent with our hypotheses, we found snags with greater diameter at breast height (DBH), younger snags, and broken-top snags persisted relatively long. Also consistent with our hypotheses, snags located in areas of relatively rugged topography and greater tree densities persisted longer. Moreover, we estimated a diameter-height ratio ≥ 4.8 cm × m−1 as a useful threshold for distinguishing broken-top snags likely to persist longer than other snags. Greater snag persistence on north-facing slopes and on topographic high points were inconsistent with our hypotheses, suggesting these conditions may be less useful for understanding snag dynamics. Our study contributes to general knowledge capable of helping managers identify snags most likely to persist and thereby provide extended habitat value for nesting woodpeckers.

Asynchronous glacial dynamics of Last Glacial Maximum mountain glaciers in the Ikh Bogd Massif, Gobi Altai mountain range, southwestern Mongolia: aspect control on glacier mass balance

Abstract. Mountain glacier mass balance is affected by factors other than climate, such as topography, slope, and aspect. In midlatitude high-mountain regions, the north–south aspect contrast can cause significant changes in insolation and melt, resulting in local asynchrony in glacial dynamics. This study documents the asynchronous response of two paleoglaciers in southwestern Mongolia to the local topoclimatic factors using 10Be exposure age dating and 2D ice surface modeling. 10Be surface exposure age dating revealed that the Ikh Artsan south-facing valley glacier culminated (MIA1) at 20.1 ± 0.7 ka, coinciding with the global Last Glacial Maximum (gLGM). In contrast, the north-facing Jargalant paleoglacier (MJ1) culminated at 17.2 ± 1.5 ka, around Heinrich Stadial 1 and during the post-gLGM Northern Hemisphere warming. Our temperature-index melt model predicts that ablation will be substantially lower on the north-facing slope, as it is exposed to less solar radiation and cooler temperatures than the south-facing slope. The 2D ice surface modeling also revealed that the south-facing Ikh Artsan Glacier abruptly retreated from its maximum extent at 20 ka, but the Jargalant Glacier on the shaded slope consistently advanced and thickened due to reduced melt until 17 ka. The timing of the modeled glacier culmination is consistent within ± 1σ of the 10Be exposure age results. Extremely old ages ranging from 636.2 to 35.9 ka were measured for the inner moraines in the Jargalant cirque (MJ2–MJ4), suggesting a problem with inheritance from boulders eroded from the summit plateau.

Camera Trap Methods and Drone Thermal Surveillance Provide Reliable, Comparable Density Estimates of Large, Free-Ranging Ungulates.

Camera traps and drone surveys both leverage advancing technologies to study dynamic wildlife populations with little disturbance. Both techniques entail strengths and weaknesses, and common camera trap methods can be confounded by unrealistic assumptions and prerequisite conditions. We compared three methods to estimate the population density of white-tailed deer (Odocoileus virgnianus) in a section of Pilot Mountain State Park, NC, USA: (1) camera trapping using mark-resight ratios or (2) N-mixture modeling and (3) aerial thermal videography from a drone platform. All three methods yielded similar density estimates, suggesting that they converged on an accurate estimate. We also included environmental covariates in the N-mixture modeling to explore spatial habitat use, and we fit models for each season to understand temporal changes in population density. Deer occurred in greater densities on warmer, south-facing slopes in the autumn and winter and on cooler north-facing slopes and in areas with flatter terrain in the summer. Seasonal density estimates over two years suggested an annual cycle of higher densities in autumn and winter than in summer, indicating that the region may function as a refuge during the hunting season.

Mapping groundcover of clover species in hill pastures in Wairarapa

Tokaroa Farm (608 ha) with sheep and beef in the Wairarapa has predominantly sunny, north-facing slopes. Average annual rainfall is 810 mm with three months summer-dry. High quality pasture is needed in late winter/early spring for lactating stock and in spring to finish stock early. The survey mapped the distribution of resident subterranean (sub) and white clovers across four land classes based on slope and aspect. ArcGIS identified 60 GPS points that were visually assessed in December 2019 and November 2021. At the majority of points in both years, both white and sub clover were present. In 2019, white clover groundcover was 18.1% and higher (P&lt;0.05) than sub clover at 12.6%. Management class had no effect. In 2021 there was no species effect (both ~11%) but there was a trend (P=0.062) for less white clovergroundcover in the ‘shady’ class (6.7%) than the ‘flat’ class at 17.5%. Pasture management was focused on promoting early season sub clover, but the unexpectedly high groundcover of white clover provided feed during wetter than average summers. Understanding the continuum from summer-dry annual sub clover areas to summer-wet perennial white clover dominance across New Zealand pastures provides tools for the selection and management of appropriate legumes.