Shrub Cover Research Articles

Impacts of Participatory Forest Management on Land Use/Land Cover of Adaba-Dodola Forest in South Eastern Ethiopia and its Implication to REDD+ Implementation.

Despite various interventions to protect forests, many developing countries, including Ethiopia, continue to face substantial forest conservation challenges, particularly where local communities heavily rely on forests for their livelihoods. Recognizing the urgency of this issue, the government of Ethiopia introduced Participatory Forest Management (PFM) and devolved forest management responsibilities to enhance forest conservation. Therefore, this assessment examines the impacts of PFM on forest cover based on an analysis of the Land Use/Land Cover Change (LULCC) over the last 23 years in Adaba-Dodola, and its implications for REDD+ implementation. The study involved determining the LULCC of the Adaba-Dodola forest after the introduction of PFM from 2000 to 2023. Landsat images of 2000, 2012, and 2023 were analyzed to detect LULCC. The study result showed that the Adaba-Dodola forest cover increased by 1.83% since the PFM was introduced. The decreased agricultural land by 0.87% was the main factor attributed to the increase in shrub cover, while shrubland attributed to the rise in forest cover. Net areas of about 148 ha/year of shrublands were converted into forest land owing to significant forest regeneration, while shrublands had a net gain of 110.5 ha/year from agriculture and grasslands between 2000 and 2023. The increase in forest cover is attributed to the effectiveness of PFM in halting deforestation and promoting forest conservation. Thus, the PFM approach is a tool for preserving forest ecosystems and mitigating the adverse effects of deforestation and forest degradation, therefore would be used as an umbrella for implementing REDD+.

Shrub cover declined as Indigenous populations expanded across southeast Australia.

Wildfires in forests globally have become more frequent and intense because of changes in climate and human management. Shrub layer fuels allow fire to spread vertically to forest canopy, creating high-intensity fires. Our research provides a deep-time perspective on shrub fuel loads in fire-prone southeastern Australia. Comparing 2833 records for vegetation cover, past climate, biomass burning, and human population size across different phases of human occupation, we demonstrated that Indigenous population expansion and cultural fire use resulted in a 50% reduction in shrub cover, from approximately 30% from the early to mid-Holocene (12 to 6 thousand years ago) to 15% during the late to mid-Holocene (6 to 1 thousand years ago). Since the start of British colonization to the present, shrub cover has increased to the highest ever recorded (mean of 35% land cover), increasing the risk of high-intensity fires.

EVALUATION OF PLANTS BASED ON ECOLOGICAL TOLERANCE CRITERIA: A CASE STUDY OF URBAN OPEN GREEN SPACES IN RIZE, TURKIYE

In addition to aggressive urbanization, climate change and ecological challenges also have serious negative effects on urban green areas. Moreover, the selection of inappropriate plants in urban green space landscape projects increases the severity of these negatives. Therefore, inappropriate plant selection is considered a significant threat to the sustainability of urban green spaces. This situation highlights the importance of selecting plants with high ecological tolerance in urban park landscape projects. In this study, all tree, shrub, and ground cover plants identified in 11 urban parks and open green areas in Rize province were evaluated in terms of ecological tolerance criteria (air pollution, drought, wind, temperature, cold, and salinity). A total of 223 plant taxa were examined (77 native, 3 semi-native, 143 exotic), and it was determined that 149 taxa (49 native, 100 exotic) were sensitive to at least one of these criteria, while the remaining 74 taxa (27 native, 47 exotic) had sufficient tolerance to all ecological variables examined. Prunus serrulata Lindl. ‘Kanzan’ was identified as the taxon with the weakest ecological tolerance, and the resilience statuses of the other taxa were presented in the assessment table created. As a result, it was found that there are taxa used in Rize urban open green areas that pose risks against ecological factors, and recommendations were made for future landscape planting projects.

Variation in species-specific responses to habitat fragmentation and land cover structure in urban small mammal communities

Abstract Urbanization is a key driver of habitat loss and fragmentation worldwide, yet many urban ecosystems contain vegetated habitat patches that support diverse wildlife communities. Managing urban systems to support robust wildlife communities requires us to understand the mechanisms that drive the response of species to the urban environment. Small mammals are key components of terrestrial ecosystems (e.g., seed predators, prey) and likely also carry out these roles in urban ecosystems; however, the effects of urbanization on small mammal communities are understudied. To identify how species-specific responses to urban environments shape community composition, we quantified both overall community and species-specific changes in small mammal abundance across an urbanization gradient in a Midwestern US metropolitan area. We combined small mammal trapping and land cover data to generate a hierarchical community abundance model. Species diversity increased with increasing proportional cover of human-modified land cover (i.e., impervious surfaces and turfgrass). This finding is driven by high species diversity on sites bordering streams in mowed parks and low diversity on sites with high tree canopy closure. Additionally, modeling results indicated that species responded differently to landscape attributes, leading to variation in small mammal community composition across the urbanization gradient: prairie-associated species tended to be more abundant in tall vegetation bordering mowed parks while habitat generalists tended to be more abundant on sites with greater canopy closure and shrub cover. Our results suggest that studies that focus on community-level responses (e.g., species richness) to urbanization may miss important species-specific responses. It may be particularly important to assess both species-specific and community-level responses in cities at ecotones (e.g., between forest and grassland) where species with different habitat requirements may replace one another in different types of green spaces, thereby changing community composition without affecting species diversity or richness. Our findings also indicate that vegetated urban patches, especially patches with tall vegetation cover and low canopy cover, are important habitat for prairie-associated small mammal communities, providing conservation options in heavily altered landscapes.

Dryland state transitions alter trophic interactions in a predator-prey system.

Environmental change is expected to alter trophic interactions and food web dynamics with consequences for ecosystem structure, function and stability. However, the mechanisms by which environmental change influences top-down and bottom-up processes are poorly documented. Here, we examined how environmental change caused by shrub encroachment affects trophic interactions in a dryland. The predator-prey system included an apex canid predator (coyote; Canis latrans), an intermediate canid predator (kit fox; Vulpes macrotis), and two herbivorous lagomorph prey (black-tailed jackrabbit, Lepus californicus; and desert cottontail, Sylvilagus audubonii) in the Chihuahuan Desert of New Mexico, USA. We evaluated alternative hypotheses for how shrub encroachment could affect habitat use and trophic interactions, including (i) modifying bottom-up processes by reducing herbaceous forage, (ii) modifying top-down processes by changing canid space use or the landscape of fear experienced by lagomorph prey and (iii) altering intraguild interactions between the dominant coyote and the intermediate kit fox. We used 7 years of camera trap data collected across grassland-to-shrubland gradients under variable precipitation to test our a priori hypotheses within a structural equation modelling framework. Lagomorph prey responded strongly to bottom-up pulses during years of high summer precipitation, but only at sites with moderate to high shrub cover. This outcome is inconsistent with the hypothesis that bottom-up effects should be strongest in grasslands because of greater herbaceous food resources. Instead, this interaction likely reflects changes in the landscape of fear because perceived predation risk in lagomorphs is reduced in shrub-dominated habitats. Shrub encroachment did not directly affect predation pressure on lagomorphs by changing canid site use intensity. However, site use intensity of both canid species was positively associated with jackrabbits, indicating additional bottom-up effects. Finally, we detected interactions between predators in which coyotes restricted space use of kit foxes, but these intraguild interactions also depended on shrub encroachment. Our findings demonstrate how environmental change can affect trophic interactions beyond traditional top-down and bottom-up processes by altering perceived predation risk in prey. These results have implications for understanding spatial patterns of herbivory and the feedbacks that reinforce shrubland states in drylands worldwide.

Climate Predicts NDVI Better Than Plant Functional Group Attributes Along a Latitudinal Gradient in Nunavik

ABSTRACTAimThis study aims to describe the latitudinal pattern in plant functional groups' (PFGs') biomass and cover in Nunavik to test whether PFG attributes are better Normalized Difference Vegetation Index (NDVI) predictors than climate.LocationThe study spans a 700‐km latitudinal gradient from the lichen woodland to prostrate shrub tundra vegetation zones across Nunavik, Canada.TaxonOur analysis focuses on the following PFGs: erect and prostrate shrubs, herbaceous plants, bryophytes, and lichens.MethodsBiomass and cover data of the different PFGs were sampled in 40 sites distributed across the latitudinal gradient. NDVI data were obtained through remote sensing, while climatic, permafrost depth, and surficial deposits were derived from various databases. The PFG models were built to explore relationships between average NDVI (2016–2020) at the sampling site and ecological attributes such as PFG biomass or cover but also other variables such as surficial deposits and permafrost depth. A second series of models, the climatic models, were built using only climatic variables such as seasonal temperature and precipitation.ResultsThe most parsimonious PFG model was built with the biomass data of erect shrubs, herbaceous plants, bryophytes, and lichens and included surficial deposits and permafrost depth (R2 = 0.74). This biomass model performed better than the most parsimonious cover model (cover of erect shrubs and herbaceous, surficial deposits, permafrost depth; R2 = 0.63). However, the most parsimonious climatic model (fall temperature, annual, and winter precipitations) exhibited superior predictive power compared to the ecological ones (R2 = 0.87).ConclusionsPFG models built with PFGs aboveground biomass or cover are good predictors of NDVI of the plant formations sampled along the latitudinal gradient in Nunavik. Despite the intrinsic association between NDVI and vegetation attributes, our study emphasizes the importance of the regional climate in the control of primary productivity in Arctic and subarctic ecosystems. This study provides new insights into the interpretation of NDVI data and enhances our understanding of Arctic vegetation responses under rapid climate change. Furthermore, it underscores the balance between climatic drivers and ecological dynamics in shaping fragile Arctic ecosystems.

The microclimatic effects of the native shrub Ephedra californica (Mormon tea) in California drylands.

The impacts of climate change can be profound in many ecosystems worldwide, including drylands such as arid and semi-arid scrublands and grasslands. Foundation plants such as shrubs can provide microclimatic refuges for a variety of taxa. These shrubs can directly influence micro6 environmental measures, and indirectly increase the local environmental heterogeneity as a result. We examined the hypothesis that, in comparison to an open gap, foundation shrubs improve the microclimate beneath their canopy and that microclimate is in turn a significant predictor of annual vegetation. The following predictions were made: 1) mean air temperature (NSAT), ground temperature (SGT), and vapour pressure deficit (VPD) will be significantly lower under the shrubs than in the open microsites; 2) shrub canopy size predicts microclimate; 3) site-level aridity estimates and percent shrub cover influence annual plant abundance and richness; and 4) the site13 level mean of NSAT and VPD predict annual plant abundance and richness. Our study took place in Southwestern California, U.S.A. We used a handheld device with a probe to measure microclimatic variables such as near-surface air temperature (NSAT), near-surface relative humidity (NSRH), and surface ground temperature (SGT) at the shrub species Ephedra californica and in the open gap, across six sites in California, United States. Air temperature and RH were then used to calculate VPD. The mean number of vascular plant species across each site was also recorded. Only SGT was significantly reduced under shrub canopies. Canopy volume was not a significant predictor of all three microclimatic variables, demonstrating that even small, low-stature shrubs can have facilitative effects. Furthermore, total shrub cover and aridity at sites significantly predicted mean plant richness and abundance. There were significantly more plants associated with shrubs and there were significantly more species associated with the open. Mean air temperature and VPD at the site-level significantly predicted vegetation abundance and richness, though microsite-level differences were only significant for richness. Foundation shrubs are a focal point of resiliency in dryland ecosystems. Understanding their impact on microclimate can inform us of better management, conservation, and restoration frameworks.

Urban green space, human heat perception and sleep quality: A repeated cross-sectional study

Urban heat poses significant challenges to public health, as exposure to high temperatures is associated to heat stress, resulting in heat strain, sleep deprivation, and cardiovascular morbidity and mortality. As the frequency of heat waves is increasing due to global warming, urban green spaces are often proposed as a nature-based solution to mitigate urban heat stress. This study investigated the impact of urban green space on perceived heat stress and sleep quality, using questionnaires and detailed land cover data. We surveyed 584 respondents during four heat and four control events in the summers of 2021 and 2022, assessing perceived heat stress, sleep quality, and mental health. Using structural equation models, this study analysed the influence of both tree cover and grass and shrub cover on perceived heat stress and sleep quality, while controlling for risk and vulnerability factors. The outcomes revealed that during heat events, enhanced tree cover was associated with reduced heat stress (B = -0.484, 95% CI [-0.693, -0.275], p = 0.001), while increased grass and shrub cover was associated with both reduced heat stress (B = -0.361 [-0.529, -0.193], p = 0.000) and improved sleep quality (B = -0. 241 [-0.399, -0.083], p = 0.003). Conversely, during control events, stress indicators were more strongly associated with individual vulnerability factors rather than surrounding green space. These results emphasize the importance of combining trees with lower vegetation in urban planning to mitigate heat-related stress and enhance sleep quality, thereby improving overall well-being during heat events.

Predicting Fractional Shrub Cover in Heterogeneous Mediterranean Landscapes Using Machine Learning and Sentinel-2 Imagery

Wildfires pose a growing threat to Mediterranean ecosystems. This study employs advanced classification techniques for shrub fractional cover mapping from satellite imagery in a fire-prone landscape in Quinta da França (QF), Portugal. The study area is characterized by fine-grained heterogeneous land cover and a Mediterranean climate. In this type of landscape, shrub encroachment after land abandonment and wildfires constitutes a threat to ecosystem resilience—in particular, by increasing the susceptibility to more frequent and large fires. High-resolution mapping of shrub cover is, therefore, an important contribution to landscape management for fire prevention. Here, a 20 cm resolution land cover map was used to label 10 m Sentinel-2 pixels according to their shrub cover percentage (three categories: 0%, >0%–50%, and >50%) for training and testing. Three distinct algorithms, namely Support Vector Machine (SVM), Artificial Neural Networks (ANNs), and Random Forest (RF), were tested for this purpose. RF excelled, achieving the highest precision (82%–88%), recall (77%–92%), and F1 score (83%–88%) across all categories (test and validation sets) compared to SVM and ANN, demonstrating its superior ability to accurately predict shrub fractional cover. Analysis of confusion matrices revealed RF’s superior ability to accurately predict shrub fractional cover (higher true positives) with fewer misclassifications (lower false positives and false negatives). McNemar’s test indicated statistically significant differences (p value < 0.05) between all models, consolidating RF’s dominance. The development of shrub fractional cover maps and derived map products is anticipated to leverage key information to support landscape management, such as for the assessment of fire hazard and the more effective planning of preventive actions.

Long‐term and landscape impacts of buffel grass on arid plant communities: Ecosystem shifts and acceleration by fire

AbstractPlant invasions drive biodiversity loss, transform ecosystems, and promote positive‐feedback cycles between invasion and fire. However, the long‐term impacts of invasive grasses across landscapes with diverse plant communities and interactions with fire are poorly known. Our objectives were to examine whether buffel grass (Cenchrus ciliaris), a globally significant plant invader, altered the abundance of understory and overstory plants, homogenized plant composition, and shifted ecosystems from woodlands to grassland and to explore interrelationships between invasion and fire. We combined two methodological approaches to assess invasion spread and impacts of buffel grass in the Aṉangu Pitjantjatjara Yankunytjatjara (APY) Lands of arid central Australia: a before‐after‐control‐impact (BACI) experiment over 25 years at 15 sites and a paired‐plot (randomized‐block) experiment at 18 sites. Both experiments spanned two geographic regions and multiple vegetation communities situated on flat plains and rocky hills. We used generalized linear mixed models to analyze predictions about plant abundance and permutational multivariate ANOVA (PERMANOVA) and permutational multivariate analysis of dispersion (PERMDISP) to examine changes in community composition. Fire and invasion interactions were explored using fire history or the relative fire tolerance of plant species as covariates, predictors, or responses. Fire interacted with the invasion process in multiple ways. Invaded sites had burnt more frequently and recently than native sites in one region, and where propagules were present in 1995, buffel grass abundance increased most when fires ensued. Abundance of understory plant functional groups (native grasses, ferns, and vines) decreased with invasion, and understory shrubs decreased due to frequent fires in invaded sites. Overstory composition shifted from fire‐sensitive species toward fire‐tolerant species, but this was not directly attributable to invasion. Partial evidence for ecosystem regime shifts included homogenization of understory communities in invaded rocky hills, and an increase in woody shrub cover at native but not invaded sites over 25 years, resulting in a 5% cover difference by 2019. Impacts were detected across heterogeneous ecological communities at a scale not previously tested amongst high background community variability. Although invasion is not dependent on fire, the acceleration of invasion spread and impacts with fire is a critical consideration for future research and management of grass invaders.

Drivers of Pinus halepensis Plant Community Structure across a Post-Fire Chronosequence

The Pinus halepensis (Aleppo pine) forests prevailing in the western part of the Mediterranean Basin are amongst the most severely affected by fire due to their inherent flammability. Our understanding of the environmental factors driving post-fire community dynamics is currently limited by the lack of time-series data at temporal scales. In this present study, we analyzed a chronosequence of Greek Aleppo pine forests spanning a post-fire period of 65 years. Our goal is to explore the role of post-fire age, altitude, exposure, slope level, parent-rock material, rock cover, and cover of evergreen sclerophyllous shrubs (maquis) on plant assemblage diversity (species richness and Menhinick’s diversity index) and composition. Post-fire age had a significant effect on taxonomic distinctness and community turnover but not on species richness. Taxonomic distinctness increased with post-fire age due to a higher prevalence of the families Fabaceae, Asteraceae, and Poaceae during the early post-fire period. Maquis cover was significantly associated with Menhinick’s diversity index, taxonomic distinctness, and community turnover. Exposure and slope influenced only Menhinick’s diversity index. The turnover in species composition was primarily driven by the geographical proximity of the forests and secondarily by post-fire age and the maquis cover. This highlights the importance of the initial floristic composition in the process of autosuccession after a fire in Mediterranean-climate ecosystems.

Microhabitat coverage influences avian species composition more than habitat heterogeneity in Hong Kong urban parks

The relationship between habitat heterogeneity and diversity can underpin design of urban spaces for biodiversity conservation. The area-heterogeneity trade-off hypothesis predicts that higher habitat heterogeneity should result in an increase in species richness but only up to a point, beyond which habitat micro-fragmentation leads to decreases in species diversity. However, the strength of area-heterogeneity trade-offs at small spatial scales is not well studied. We studied the relationship between avian diversity and habitat heterogeneity in 16 small urban parks across Hong Kong during the winter dry season across 2016 and 2017 (ten repeated surveys in total for each park). Habitat heterogeneity was assessed by measuring the evenness of microhabitat coverage of seven habitats as well as vertical canopy cover. In total, 12,973 individuals of 73 bird species were recorded in the study. Habitat heterogeneity had a small but negligible effect on total bird species richness or abundance. However, water coverage was positively related to total, intermediately rare and habitat specialist bird species richness, and shrub coverage was positively related to total and common bird species richness. These results demonstrate that environmental heterogeneity had little effect on avian species richness in urban green spaces at small spatial scales. We also found that microhabitat coverage can affect avian diversity and abundance, and these effects are specific to certain groups of bird species. When managing urban green spaces for biodiversity conservation in densely urbanized cities, a decrease in management disturbance (e.g. tree topping or pesticide application) will likely benefit avian species. Together with the fact that some locally uncommon species were observed throughout the study, capacity exists for environmental enhancement of these small urban parks to contribute to local avian conservation.

Spatial dynamics and drivers of recent changes in grass and shrub cover in submontane grassland plant communities

AbstractShrub encroachment into grassland ecosystems has been increasingly observed and documented worldwide in recent years. A grass–shrub transition can affect the diversity, abundance and functional integrity of grassland plant communities and understanding the drivers behind these processes is therefore crucial. While potential environmental drivers are often investigated, the role of spatial patterns of neighbouring shrub density in local shrub encroachment has been less well studied. The aim of this study is to investigate the relative role of neighbouring shrub density and topography as potential key drivers of shrub encroachment in a typical montane grassland ecosystem in New Zealand. We used the SPOT (Satellite Pour l’Observation) 6/7 multispectral imagery captured on one day in 2013 and in 2017 to calculate recent changes in shrub/grass cover during this period. Using the Normalised Difference Vegetation Index (NDVI), we classified the study area into grassland and shrubland and quantified the extent and change in these two land-cover types over the study period. We then investigated the relationships between changes in land cover and neighbourhood shrub density, elevation and aspect. Between 2013 and 2017, there was an overall shrubland increase of + 0.35% of the study area per year, and grassland decrease of −0.43% per year. Locations at which any change in vegetation type occurred were more likely to be at mid-elevation (c. 600–1,000 m a.s.l.) and on west-facing slopes. Highest shrub expansion rates were observed on areas that were on warmer, north-facing slopes and at elevations below 900 m a.s.l.; this is consistent with areas below the pre-human, natural treeline which is estimated to be at very similar elevations. We found a marked threshold in the degree to which neighbourhood shrub density correlated with local shrub encroachment: local shrub encroachment only occurred when shrub cover in the neighbourhood exceeded 40% and peaked at c. 60% indicating the potential for a sudden grass–shrub regime shift once shrub cover reaches a certain level. Our study provides new evidence from the Southern Hemisphere of a measurable and interacting effect of topography and neighbourhood shrub density on recent shrub encroachment rates in montane grasslands even over short time periods.

Stream Restoration Effects on Habitat and Abundance of Native Cutthroat Trout

ABSTRACTRestoration practitioners spend more than $1 billion each year restoring US rivers and streams but commit comparatively few resources to evaluating project effectiveness. Meanwhile, monitoring and disseminating the outcomes of restoration projects remains our best opportunity to learn from past successes and failures and to, ultimately, improve the cost effectiveness of restoration. We monitored the physical and biological outcomes of a stream restoration project in the Rocky Mountains, the goals of which were to improve habitat for and productivity of native Colorado River Cutthroat Trout (CRCT) and the scope of which included three contiguous reaches under different restoration treatments. Moreover, we evaluated the efficacy of the restoration project relative to its stated goals and objectives. To test for restoration effects on physical and biological indicators we coupled a before‐after, control‐impact (BACI) study design with (generalized) linear mixed models. Over the course of 7 years, we detected restoration‐related increases in floodplain connectivity, streambank stability, and riparian shrub cover, as well as decreases in summer stream temperature. Despite measured improvements in native trout habitat, we detected no evidence of a restoration effect on density or biomass of age‐1 and older CRCT. Although our study was somewhat limited in scope, our findings contribute toward a relatively small body of work on monitoring and effectiveness of river restoration.

Continuous Monitoring of Vegetation and Soil Recovery After Eucalyptus grandis Removal in Dense Trees and Shrubs Areas

ABSTRACTInvasion by invasive alien plants is a global challenge and South Africa has invested billions of Rands to manage invaders through the Working for Water programme. However, regular monitoring after alien plant clearing is hardly done, yet it forms the basis for assessing clearing programme effectiveness, particularly ecosystem recovery trajectories. I monitored both vegetation and soil recovery 6 years after Eucalyptus grandis clearing by Working for Water at Zvakanaka Farm in Limpopo Province of South Africa. Vegetation diversity and soil physical properties were surveyed in 2019 and re‐surveyed in 2022 on fell‐and‐removal and fell‐and‐stackburn cleared treatments and compared to the nearby uninvaded treatment. Results show a significant increase in species richness in 2022 compared to 2019 in the fell‐and‐removal treatment. Cover of both native trees and shrubs as well as forbs was significantly higher in 2022 compared to 2019 in the fell‐and‐removal treatment compared to the fell‐and‐stackburn treatment. Most secondary invaders such as Acacia mearnsii, E. cloeziana, Lantana camara and Rubus rigidus that frequently occurred in 2019 showed decreased occurrence in 2022 on both cleared treatments. Between the two sampling years, soil compaction improved on the fell‐and‐removal treatment only, whereas hydraulic conductivity increased significantly in 2022 compared to 2019 in both the fell‐and‐removal and fell‐and‐stackburn treatments. Soils that were strongly and severely repellent in 2019 in the fell‐and‐stackburn treatment were becoming slightly repellent in 2022. These results show varied vegetation and soil improvements between 2019 and 2022 in both the fell‐and‐removal and fell‐and‐stackburn cleared treatments an indication that recovery is moving towards a positive vegetation and soil recovery trajectory in the direction of the uninvaded treatment. Recommendations for successful passive restoration such as secondary invasion follow‐up clearing are discussed.

Predicting plants in the wild: Mapping arctic and boreal plants with UAS-based visible and near infrared reflectance spectra

Biophysical changes in the Arctic and boreal zones drive shifts in vegetation, such as increasing shrub cover from warming soil or loss of living mat species due to fire. Understanding current and future responses to these factors requires mapping vegetation at a fine taxonomic resolution and landscape scale. Plants vary in size and spectral signatures, which hampers mapping of meaningful functional groups at coarse spatial resolution. Fine spatial grain of remotely sensed data (<10 cm pixels) is often necessary to resolve patches of many Arctic and boreal plant groups, such as bryophytes and lichens, which are significant components of terrestrial vegetation cover. Separation of co-occurring small vegetation patches in images also requires high spectral resolution. Our goal here was to test the capabilities of UAS-based imaging spectroscopy for mapping plant functional types (PFT) using high spatial and spectral resolution data over Arctic and boreal vegetation at four sites in central Alaska. We then tested several Machine and Deep learning models of PFT cover using the reflectance spectra. The best models were very simple, balancing both bias (overfitting caused by imbalance sample sizes) and variance (fit to the independent validation data), explaining > 50 % of the independent ground cover estimation and > 84 % accuracy in estimating validation pixels. We explored the impact of spectral resolution on PFT mapping by including vegetation indices and a gradient of narrow (5 nm) to wide (50 nm) band features in our classification models across. Vegetation indices were the most important predictors for classifying PFTs, while including band features improved models, with narrow and wide bandwidths having similar importance but models with wide bandwidths performing slightly better. We conclude that Arctic and boreal PFT reflectance can be pooled across sites for mapping with relatively few labeled pixels. Underfit, simple algorithms outperformed deep learning, at least with these small sample sizes, in classifying PFTs by balancing bias and variance. Future work should aim to increase the number of labeled pixels and the detail of labels to further improve mapping taxonomic precision.

Thinning relationships of woody encroachers in a US southwestern shrubland

Woody plant encroachment degrades the economic and environmental potential of drylands by altering processes such as nutrient fluxes, ecohydrology, and ecosystem services. Though past research has investigated the encroachment process, relatively little is known about post-encroachment shrub community ecology. To better quantify dynamics within post-woody encroachment shrub communities, we combined USGS lidar height data and multispectral imagery to estimate shrub density, shrub height, shrub cover, and shrub volume across the Jornada Basin Long Term Ecological Research (JRN-LTER) site in southern New Mexico, USA. Structural estimates were analyzed in search of telltale signs of community competition, specifically, the presence of thinning relationships. Results demonstrated density-dependent thinning relationships in shrub communities of creosote and mesquite, indicating a large role for competition in arid shrub communities even at relatively low shrub densities and cover (∼35% cover). In addition, shrub volume estimates better modeled the expected thinning dynamics of shrub communities than shrub canopy cover measurements. Overall, our results indicate the utility of lidar data in extending two-dimensional descriptions of woody vegetation structure (i.e., woody canopy cover) into the critical third dimension (i.e., woody plant volume), as well as the relative importance of competition and demographic bottlenecks to vegetation structure in drylands.

The relative importance of local versus regional habitat structure variation on the abundance of two generalist mutualists along a forest disturbance gradient

Mutualistic interactions are key to biodiversity generation and maintenance, being pollination and seed dispersal interactions essential for plant reproduction. However, anthropogenic habitat disturbance can alter these interactions. We studied the regional and local effects of habitat disturbance on two generalist mutualist animals of southern Chile temperate rainforests: the hummingbird Sephanoides sephaniodes and the marsupial Dromiciops gliroides, which perform key roles as pollinator and seed disperser, respectively. We sampled 12 sites corresponding to four disturbance conditions (mature native forest, secondary forest, native forest under selective logging, and exotic forest plantations) in which we estimated the number of S. sephaniodes and D. gliroides records (as a proxy of relative abundance) using camera traps. We measured seven habitat structure variables at each site, known to influence their occurrence. Specifically, we examined S. sephaniodes and D. gliroides abundance variation at (i) a regional scale (among disturbance conditions) and (ii) at a local scale (among sampling sites). Dromiciops gliroides abundance decreased as disturbance increased, but S. sephaniodes abundance was highly variable. At the local scale, S. sephaniodes and D. gliroides abundances were largely variable among sites, influenced by habitat structural features, such as bamboo and shrub cover and woody debris. Our results show that although habitat disturbance may influence mutualist abundances, they can tolerate disturbance if minimum structure and resource requirements are met, but respond idiosyncratically to local conditions. Examining local-scale variability may provide valuable information on ecological processes, which often goes unnoticed when local sites are considered as replicates in landscape-level studies.

Wildland Firefighter Estimated Ground Evacuation Time Modeling to Support Risk-Informed Decision-Making

Wildland firefighters often work in remote settings with multiple hazards that can cause life-threatening injuries. Prompt access to medical care is key to reducing injury consequences. For the last decade, a spatial model of wildland firefighter estimated ground evacuation time (GET) has been used when developing operational response strategies in the contiguous United States (CONUS). This paper describes our updated and improved GET model and the resulting decision support spatial data representing the estimated time to evacuate to a hospital from anywhere within the CONUS using ground transportation only. The new GET model leverages updated input datasets and has improved off-road travel time estimation methods that incorporate the latest science on how terrain slope influences pedestrian travel rates. It also accounts for a novel set of landscape variables not previously considered, including minor roads and trails, streams, woody debris, cliffs, and an improved handling of shrub cover. When compared to a set of recent safety incidents, the reported evacuation times were correlated with the model predictions. The spatial patterns of GET from the new model are similar to the old product; however, we found that, on average, the new version of GET yields slightly faster evacuation times, but with regional variation in this trend.

Competition between resprouting chaparral and the recruits of a serotinous conifer following stand-replacing fire

In western North America, fire regimes are shifting towards more frequent, larger, and more severe wildfire. There is concern that this will shift the vegetation type in many areas, especially on the lower, drier slopes. In northern California, mature serotinous conifers and resprouting shrub species easily regenerate in severe patches of any size. There is no consensus, however, regarding the effects of shrub competition on conifer recruitment; conifer response to shade varies with shade tolerance and abiotic factors. Many conifers and almost all chaparral shrubs are shade intolerant, and we expect shading to be the main driver of the inter-species competition between these taxa on dry low-elevation, slopes We chose to examine early post-fire regeneration of knobcone pine (Pinus attenuata), a shade intolerant serotinous conifer, because (a) as a serotinous species we could be assured of a high initial density of recruits, and (b) it is mainly found on lower-elevation slopes in a matrix of chaparral. We examined the competitive interactions of the pine and shrubs within the 2018 Carr and Delta fires at the third and fourth post-fire years, as well as at the 2008 Motion Fire at the 14th post-fire year, focusing on two measurements of shrub shading: inter-shrub porosity (% shrub cover) and intra-shrub porosity (species-specific ground-level light availability). Our response variables included recruitment success (recruits per ovulate cone) and growth (height). We only chose stands where knobcone pine was a minor pre-fire component to ensure a high density of vigorously resprouting shrubs. We found (1) there were significantly fewer pine recruits under shrubs, with the bulk of the shrub-induced mortality of knobcone pine occurring before the third growing season; (2) knobcone pine averaged about six established recruits per burned parent tree by the third year following fire; and (3), extrapolating from height reconstruction of post-fire knobcone pine regeneration from the 2008 Motion Fire, the remaining tree recruits are expected to persist and dominate the stand within a decade of the fire. We conclude that competition with shrubs on low elevation sites in northern California does have a negative effect on knobcone pine density but is insufficient to seriously impede a dramatic post-fire increase in conifer density when conifer regeneration arrives promptly following fire.