Pine Cover Research Articles

Using the Forest Maturity Index to model understory regeneration of post-agricultural forest in the NE Carpathians

The regeneration dynamics of understory vegetation in recent forests, arising from extensive agricultural land abandonment, is closely related to soil properties and proximity to ancient forests. However, the role of topography in shaping this regeneration process, especially in mountainous regions, remains unclear.This study addresses this gap by investigating the regeneration rate of understory vegetation in mountainous recent forests within the NE Carpathians, a region profoundly shaped by large-scale population displacements in the 1940s, leading to widespread agricultural land abandonment and the subsequent development of new forests.We quantified the understory regeneration rate of recent forests through extensive phytosociological relevé surveys conducted in one vegetation season. Data were collected from 194 randomly selected plots of recent forests and 100 plots of ancient forests, each exhibiting diverse topographic characteristics. By calculating the Forest Maturity Index based on ancient forest species and employing a parametrized multiple regression model, we identified key factors influencing the understory regeneration process. We further used the obtained regression formula to model the forest regeneration rate across the entire study area (40,975 ha).Proximity to ancient forests positively influenced understory regeneration. Elevation and slope also emerged as significant determinants, with the understory regeneration rate decreasing with elevation and increasing with slope steepness. Furthermore, a higher cover of pine in the tree stand had a suppressive effect. The above-mentioned dependencies resulted in substantial variations in the modeled understory regeneration of post-agricultural forests.The utilization of the Forest Maturity Index offers invaluable insights into identifying and subsequently safeguarding well-regenerated forests. Given the prevalence of forest secondary succession in various regions, this index emerges as a key indicator for future assessments and management strategies.

Density-dependent dynamics help explain the simultaneous expansion and decline of woodlands in the western US

Woodlands across the globe have expanded in recent centuries in response to shifts in climate, land use, and disturbance patterns, but are expected to be particularly vulnerable to decline as a result of environmental change. Gaps in our understanding of the drivers of woodland spatial dynamics, however, limit our ability to forecast range shifts. While the effect of extrinsic factors, such as fire and climate, on woodlands are well-documented, we lack knowledge on the role of intrinsic factors such as density-dependence in driving tree abundances and distributions across space and time. We used two remotely-sensed datasets of tree cover and climate predictors in Bayesian state-space models to test the effects of climate and density on the spatiotemporal changes in pinyon pine (Pinus monophylla) cover in the Great Basin, USA. We compared models with only climate predictors to models including both climate and tree cover (i.e. density-dependence). Models including density-dependence better explained observed dynamics than climate alone. Pinyon pine cover increased at the fastest rate in areas with intermediate precipitation and low maximum temperatures. Spatial effects of climate interacted with temporal variation in climate. In cool, wet areas, growth was higher in warm, dry periods. In warm, dry areas, it was favorable to have cool periods. However, positive direct effects of climate at mid to high elevation were partially offset by density-dependence. Because extant density was positively correlated with average precipitation and negatively correlated with temperature, pinyon pine cover often declined in climatically favorable areas. Our results indicate that direct effects of warming and drying climate will likely lead to increases in cover at high elevations and declines at low elevations in the long-term. However, the added effects of density-dependence may create counter-intuitive patterns with increases in low density, low elevation areas in the near term and declines in seemingly favorable high density cooler-wetter locations. As a result, management intended to increase woodland resilience through silvicultural treatments like density reductions may have the greatest impact at intermediate elevations where increasing climate stress coincides with high tree densities.

Trajectories of plant communities in Massachusetts, USA cranberry farms discontinued from agriculture

Retirement of cultivated croplands creates potential for ecosystem and wetland restoration, but vegetation and soil legacies of cropping influence the development of post-agriculture vegetation. In low-lying coastal watersheds of southeastern Massachusetts, cranberries (Vaccinium macrocarpon Aiton) are cultivated in commercial farm units that are diked, leveled and sanded beds created from historic wetlands. Current low cranberry prices and expanding cranberry production elsewhere now increase the likelihood of cranberry farmland retirement. We quantified the trajectories of plant species richness and cover, and plant characteristics (life form, native or non-native, wetland or non-wetland) in a chronosequence of cranberry farm beds that ranged from cultivated units to those retired from cropping and revegetated for 90 years with no post-cropping management. Species richness increased from active beds to 10–20 year-old beds and subsequently decreased. Post-retirement species richness was overwhelmingly dominated by native species. Shrub and tree richness and cover increased steadily over time. The richness of wetland, upland and facultative species all increased quickly after retirement and then declined in the oldest retired beds. The basal area and canopy cover of red maple (Acer rubrum) and pitch pine (Pinus rigida) increased over time. Vegetation followed a relatively consistent successional trajectory and the plant community after five to nine decades was predominantly forest and dominated by non-wetland plants. Encouragement of long-term persistence of greater diversity and cover of wetland plant species on retired cranberry farms will likely require active hydrological and soil modifications that decrease sand depth and raise water tables.

Impacts of longleaf pine (Pinus palustris Mill.) on long-term hydrology at the watershed scale

Threats from climate change and growing populations require innovative solutions for restoring streamflow in many regions. In the arid western U.S., attempts to increase streamflow (Q) through forest management have had mixed results, but these approaches may be more successful in the eastern U.S. where greater precipitation (P) and lower evapotranspiration (ET) offer greater potential to increase Q by reducing ET. Longleaf pine (Pinus palustris Mill.) (LLP) woodlands, once the dominant land cover in the southeastern United States, often have lower ET than other forest types but it is unclear how longleaf pine cover impacts watershed-scale hydrology. To address this question, we analyzed 21 gaged rural watersheds. We estimated annual water balance ET (ETwb) as the difference between precipitation (P) and streamflow (Q) between 1989 and 2021 and quantified low flow rates (7Q10) among watersheds with high and low LLP cover. To control for climate variability among watersheds, we compared variation in hydrology metrics with biotic and abiotic variables using the Budyko equation (ETBudyko) to understand the differences between the two ET estimates (∆ET). Watersheds with 15–72 % LLP cover had 17 % greater mean annual Q, 7 % lower annual ETwb, and 92 % greater 7Q10 low flow rates than watersheds with <3 % LLP. LLP cover decreased ET and increased Q by 2.4 mm or 0.15 % Q/P per 1 % of watershed area, but only when LLP was managed as open woodlands. Our results demonstrate that ecological forest restoration in these systems, which entails mechanical thinning and re-introduction of low-intensity prescribed fire to maintain open woodlands, and enhance understory diversity, can contribute to decreases in ET and increases in Q in eastern forests.

Динамика живого напочвенного покрова на начальных этапах формирования лесных культур средней подзоны тайги

The growth of artificial origin stands in the clear-cut areas of the taiga zone is closely related to the development of herbaceous vegetation. The aim of the study was to study the dynamics of the species composition and structure of the ground cover of forest plantations at the early stages of formation in the conditions of the middle taiga subzone, as well as to identify the most competitive species in terms of phytocenotic activity. In the course of field studies, the taxonomic composition and ecological and coenotic structure of the living ground cover of experimental pine and spruce crops of the 1st and 2nd age classes were determined, depending on the tillage with plows PLP-135 and PLD-1.2. Species abundance ranges from 32 to 39 species in crops aged 15 years, and from 16 to 36 species in crops aged 23 years. The typological structure of the plant community naturally changes over time. The similarity coefficients for the composition of families in 15-year-old crops vary from 0,48 to 0,89 depending on tillage. Plant communities of forest crops with soil cultivation with the PLP-135 plow and reconstruction of deciduous young growth are the closest to each other in terms of family composition (R = 0,89). Plant communities of the ground cover of forest crops with tillage with the PLD-1.2 plow differ in family composition (0,48…0,58). As a result of phytocenotic analysis, we came to the conclusion that the structure of the ground cover of forest plantations naturally changes over time: the group of highly active species of the ground cover is quite numerous in 15-year-old crops and includes 15 species (33 % of the species composition of the flora). In 23-year-old forest plantations, only four species from the group of highly active plants were identified.

Recovering of soil organic matter and associated C and N pools on regenerated forest ecosystems at different tree species influence on post-fire and reclaimed mine sites

Understanding the processes in soils after disturbances could be helpful in better designing restoration practices. The labile fraction of soil organic carbon (LSOC) plays a vital role in recovering soil properties and quality. This study compared labile C and N fractions, including microbial biomass C (MBC), cold-water-soluble C (WSC), water-soluble N (WSN), hot-water-extractable C (HWC), hot-water-extractable N (HWN), particulate organic carbon (POC), and particulate organic nitrogen (PON) in post-mining, post-fire, and undisturbed soils under different tree cover (Scots pine, common birch, and black alder). Nearly 30 years after the disturbance, post-mining soils were characterized by lower soil organic carbon (SOC) and total nitrogen (TN) as well as their labile fractions compared to those of post-fire and undisturbed soils. Disturbed soils had less stable SOC than undisturbed soils. Compared to the post-fire site, the higher proportion of WSC in SOC in post-mining soils suggests higher SOC turnover and leaching potential during primary succession compared to secondary succession. The post-fire soils had a similar SOC stock to undisturbed soils but differed in the C and N labile fractions stock. Post-fire soils were characterized by higher POC stocks due to charcoal admixture and lower WSN, HWC, and HWN fractions than undisturbed soils. The studied tree species differently affected the recovery of SOM properties after disturbances. Post-mining soils under alder had higher SOC, TN, and labile fractions (except MBC) than soils under birch and pine cover. However, this was not true for the post-fire site, where only WSN was higher under the alder. The soils under birch stands had the highest MBC stocks across all sites. The soils under pine had less stable SOM than those under birch and alder, which may accelerate podzolization processes. Results indicate a longer time for the recovery of C and N pools during primary succession than in secondary succession on sandy soils. Alder, as phytomelioration species that increases the C and N pools in post-fire sites, has limited usefulness.

The Pine-Oak Forest of the Rio Conchos Basin, Mexico: Key to Rain Production and Soil Erosion Control

Under the current climate crisis, the ecological integrity of forest ecosystems is key to increasing resilience and the sustainability of water and soil resources. Most forests around the world have experienced deforestation and degradation in the past few decades; however, the rate at which these occur varies depending on many factors, including the type of trees, management, and climate. We conducted a review of the deforestation, degradation, and soil erosion of the pine-oak forest within the Rio Conchos basin in northern Mexico. Preference was given to recent studies (last 10 years) conducted within this basin. Out of 27 recent publications on oak forests in Mexico, 19 focused on this forest and half of them were in Spanish. The results show that pine trees are more affected than oak trees, also that the deforestation rate has increased with time and is greater at higher elevations, making this area vulnerable to loss of topsoil during extreme hydrological events. Studies report an annual change in cover rate between 1985 and 2016 of −1.2% for pine, oak and mix vegetation. More recently, between 2000 and 2018, the change in pine cover was calculated as −2.8% concurrent with a +3.4% increase in cover of oak and other secondary vegetation. Proposed conservation strategies vary from runoff control to increased collaboration between landowners, government agencies, and stakeholders.

Low Kirtland’s Warbler fledgling survival in Wisconsin plantations relative to Michigan plantations

Abstract The Kirtland’s Warbler (Setophaga kirtlandii) is a formerly endangered habitat specialist that breeds mainly in young jack pine (Pinus banksiana) forests in northern Lower Michigan, USA. The species is conservation-reliant and depends on habitat management. Management actions have primarily focused on creating jack pine plantations, but the species also breeds in red pine (Pinus resinosa) plantations in central Wisconsin, USA. However, the plantations were not intended as breeding habitat and have suboptimal pine densities. While nesting success is similar between low-density red pine plantations and optimal jack pine habitat, it is not clear if low-density red pine plantations support high fledging survival. If high-quality nesting and post-fledging habitat are not synonymous, fledgling survival and breeding population recruitment may be low. We characterized survival, habitat use, and movement patterns of dependent Kirtland’s Warbler fledglings in Wisconsin red pine plantations and compared fledgling survival between Wisconsin and Michigan. Mayfield cumulative survival estimates at 30 days post-fledging were 0.20 for Wisconsin fledglings and 0.43–0.78 for Michigan fledglings. Logistic exposure cumulative survival estimates for Wisconsin fledglings were 0.23–0.34 at 30 days post-fledging. Fledglings in Wisconsin used areas where vegetation cover and density of red and jack pine were high relative to available areas but not at greater proportions than what was available. Our findings demonstrate that red pine plantations with low pine densities were not equally suitable as nesting and post-fledging habitat, as fledgling survival rates were low. We hypothesize that reduced habitat structure, and not particular pine species, likely contributed to reduced fledgling survival in Wisconsin. Thus, we recommend including red pine as a component in managed Kirtland’s Warbler habitat only if tree densities approach optimal levels.

Northern Yellow Bat Dasypterus intermedius Activity and Habitat Selection on an Atlantic Barrier Island

Knowledge and understanding of bat activity and habitat associations are important for effective conservation and management, especially in landscapes undergoing land use changes. Dasypterus intermedius (northern yellow bat), a broadly distributed species in the Coastal Plain of the southeastern United States, is a species of conservation concern due to habitat loss. We examined the influence of landscape factors on D. intermedius activity on Little Saint Simons Island (LSSI), Georgia, USA, an Atlantic barrier island characterized by a limited human disturbance history. From April to October 2013, we recorded a total of 6,921 D. intermedius passes and 138 feeding buzzes among six land cover types across three biologically relevant seasons. We used GLMMs to model total and foraging activity using landscape variables and season as covariates. We found no significant differences in total activity among cover types, but observed a clear pattern of greater activity in cover types with low vegetation clutter. We observed significantly greater total activity later in the year after juveniles became volant and were able to forage on their own. Based on feeding buzzes, our results demonstrated greater foraging activity in maritime grasslands than in the oak and pine cover types. Distance to water, edge, and roosting habitat had little influence on total or foraging activity. Our results provide baseline information regarding D. intermedius habitat use from a relatively undisturbed coastal environment that can aid management decisions when considering bats in landscapes experiencing changes from development.

Cenopopulation of Epipactis helleborine (Orchidaceae) in forest ecosystems that have been anthropogenically transformed to various degrees

Because of developed symbiotic connections of the root system of trees, mycorrhiza-forming fungi and the orchid family Orchidaceae in forest ecosystems of the northeast Polissia Region – cultivated Pinus sylvestris, which are now 100–120 years old, recovery of cenopopulations of Epipactis helleborine has been observed in locations of mixed and broad-leaved forests. In natural plant cover of mature pines of the region, indigenous vegetation is gradually recovering – there occur young Quercus robur, Tilia cordata, Acer platanoides of various ages, crown density of understory formed by Coryllus avellana has reached 0.6, above-ground organic leaf foliage that is able to sustain moisture and increase fertility of soil accumulates, creating sufficient conditions of shading for seedlings and juvenile individuals of forest orchids. Special studies revealed a relationship between density of E. helleborine specimens and crown density of the tree stand, shrub strata, structure of soil cover, expressed in cenoses under various degrees of recreational pressure. Density of individuals of forest orchids in the studied populations ranges 10.0 to 0.1 ind./10 m2. Dynamics were seen in groupings of Betuleto-Pineta corylosa, Querceta (roboris) corylosa, Querceto-Pineta corylosa, Acereto (platanoidis) –Tilieto (cordatae) – Quercetum (roboris) aegopodiosum in the territory of the nature-reserve fund and structurally similar anthropogenically pressurized cenoses. We determined that all examined cenopopulations in old indigenous zonal cenoses in the territory of the nature reserve fund are normal, they may be considered relatively stable, ontogenetic spectra are incomplete, mostly with right-sided age spectrum – maximum numbers of virgin and generative individuals of various stages. Low density of individuals and incomplete spectra of cenopopulations in light oak forests are natural, and now the largest share of generative and virgin individuals is concentrated in this area. Impact of recreation, unavoidable due to proximity to a road, is a negative factor directly decreasing their density. Ontogenetic spectra of all cenopopulations are incomplete – no seedlings were found in the natural conditions due to underground type of germination. Much more interesting data may be obtained by monitoring studies of age and morphometric dynamic changes during several years.

Population and reproductive structure of an endangered juniper from coastal pine forests

Plant species adapted to coastal systems are suffering severe declines. This is the case of the critically endangered Juniperus navicularis, which colonizes fossil dunes in the southwestern Iberian Peninsula and grows in the understory of pine plantations. This endemic juniper presents low reproduction rates and a decreasing number of populations has been reported in its western distribution edge. However, age structure and the demographic situation of its easternmost populations, that have been recently discovered, remain unknown. We used dendrochronological procedures to estimate the age structure of the easternmost isolated population of J. navicularis, considering three subpopulations under contrasting management regimes and selecting plots under pine cover and in open areas. We also assessed sex ratio, age at maturity and reproductive effort. We observed the predominance of 20–40 years-old stems in all study plots and a remarkable lack of young stems in open areas. Stem density was higher under pine canopies. There, junipers were, on average, younger than pine trees, meaning that junipers had grown in already forested areas. Only one sex per plot was found in all study plots but one, in which no reproductive stems were recorded, suggesting the existence of clonal growth. Reproductive effort increased with age in females, but was independent in males. We hypothesize that clonal growth might occur as a survival strategy to endure the harsher conditions of distribution edges. These results will help to develop more effective management strategies to preserve this endangered species, contributing to our understanding of dynamics of coastal ecosystems and setting the basis for future genetic studies.

Moderate pine cover maximizes 10-year survival and growth in late-successional species of contrasting functional strategies

Monospecific pine forests are widespread due to extensive afforestation efforts and natural colonization of abandoned croplands in the Mediterranean Basin. It was originally thought that pines would facilitate the natural colonization of native late-successional resprouter species (e.g., hardwoods), but these species can be compromised if competition with pines outweighs their facilitative effect on these hardwood species. Managing the density or canopy cover of these widespread pine forests can potentially provide some “optimum” balance between facilitation and competition to maximize success in the introduction of late successional species while maintaining a tree stratum. We tested the response (survival and growth across 10 years) of six resprouter species covering a wide range of plant functional strategies, from drought-tolerant sclerophyllous shrubs and trees to malacophyllous drought-sensitive trees, across an experimental gradient of Aleppo pine canopy cover. Seedling performance varied according to the functional strategy, pine cover and time. High pine cover generally enhanced seedling survival, whereas moderate pine cover generally enhanced seedling growth, although this response was modulated by the functional strategy of the seedling species. Interactions between pines and seedlings were only detectable 2–3 years after plantation, increasing in intensity with time. The latter highlights the need of medium to long-term studies to evaluate plant-plant interactions in these water-limited environments with slow successional trajectories. Our results could be attributed to the shade tolerance of most of the introduced trees, combined with their low tolerance to the combination of high sunlight radiation and drought. We found an optimal pine cover of ca. 50% (equivalent to 300–400 trees/ha) in which both survival and growth of late successional species can be maximized, which help to select best locations for more efficient reforestation programs and set a threshold value to decide whether or not to perform tree thinning to enhance ecosystem diversity and, subsequently, resilience.

Examining the Integration of Landsat Operational Land Imager with Sentinel-1 and Vegetation Indices in Mapping Southern Yellow Pines (Loblolly, Shortleaf, and Virginia Pines)

The mapping of southern yellow pines (loblolly, shortleaf, and Virginia pines) is important to supporting forest inventory and the management of forest resources. The overall aim of this study was to examine the integration of Landsat Operational Land Imager (OLI ) optical data with Sentinel-1 microwave C-band satellite data and vegetation indices in mapping the canopy cover of southern yellow pines. Specifically, this study assessed the overall mapping accuracies of the canopy cover classification of southern yellow pines derived using four data-integration scenarios: Landsat OLI alone; Landsat OLI and Sentinel-1; Landsat OLI with vegetation indices derived from satellite data—normalized difference vegetation index, soil-adjusted vegetation index, modified soil-adjusted vegetation index, transformed soil-adjusted vegetation index, and infrared percentage vegetation index; and 4) Landsat OLI with Sentinel-1 and vegetation indices. The results showed that the integration of Landsat OLI reflectance bands with Sentinel-1 backscattering coefficients and vegetation indices yielded the best overall classification accuracy, about 77%, and standalone Landsat OLI the weakest accuracy, approximately 67%. The findings in this study demonstrate that the addition of backscattering coefficients from Sentinel-1 and vegetation indices positively contributed to the mapping of southern yellow pines.

Bottom-up cascading effects of quarry revegetation deplete bird-mediated seed dispersal services

Quarrying activities cause profound modifications on ecosystems, such as removal of vegetation cover, biodiversity loss and depletion of ecosystem services. Ecological restoration stands as a solution to revert such effects. Concomitantly, awareness is currently being given on ecosystem services and ecological processes to evaluate restoration efficiency.The objective of the study was to assess restoration success in a quarry subjected to restoration practices for the last 40 years involving the plantation of native Mediterranean vegetation and the non-native Aleppo pine Pinus halepensis. The study was carried out by assessing the effectiveness of seed dispersal service provided by birds in the restored quarry by comparing this service to neighbouring natural (shrubland) and other semi-natural areas (oak-pine mixed open and Aleppo pine forest) present at the landscape. For this purpose, we explored bird composition structure and seed dispersal networks using point counts and faecal samples of mist-netted birds. We also collected vegetation structure data and explored its effect on bird community composition.Our results showed that bird abundance in the restored quarry was significantly lower, and its bird community was compositionally different than natural shrubland and semi-natural areas. For instance, seed-dispersing birds, woody and shrub/ground foragers and partially migrators were the most affected groups at the restored area. Bird community composition and their traits were likely driven by vegetation characteristics, with higher native vegetation cover and fruit richness promoting higher bird abundance and Aleppo pine cover negatively influencing seed-dispersing birds. Concurrently, seed dispersal network in the restored quarry was less complex than in other areas.Seed dispersal services in the restored quarry were below the reported values for neighbouring natural and semi-natural areas and are likely driven by the low abundance of seed-dispersing birds. We consider that the causes affecting this group's low abundance can be related to revegetation measures favouring Aleppo pine, combined with a shallow soil depth and poor soil quality, which may have constrained native vegetation development.We conclude that seed dispersal services at the quarry are depleted, which may suggest a low restoration success concerning ecosystem functioning. Our results strengthen that quarry revegetation with non-native species must be avoided, since it alters bird community composition, and consequently, affects seed dispersal service provided by birds.

Mapping and Monitoring the Canopy Cover and Greenness of Southern Yellow Pines (Loblolly, Shortleaf, and Virginia Pines) in Central-Eastern Tennessee Using Multi-Temporal Landsat Satellite Data

Southern yellow pines such as loblolly, Virginia and shortleaf pines constitute forest products and contribute significantly to the economy of the United States (U.S.). However, little is understood about the temporal change in canopy cover and greenness of southern yellow pines, especially in Tennessee where they are used for timber and pulpwood. This study aims to map and monitor the canopy cover and greenness of southern yellow pines i.e., loblolly (Pinus taeda), shortleaf (Pinus echinata), and Virginia (Pinus Virginiana) pines in the years 1988, 1999 and 2016 in central-eastern Tennessee. Landsat time-series satellite data acquired in December 1988, November 1999 and February 2016 were used to map and monitor the canopy cover and greenness of loblolly, shortleaf and Virginia pines. The classification and mapping of the canopy cover of southern yellow pines were performed using a machine-learning random forest classification algorithm. Normalized Difference Vegetation Index (NDVI) was used to monitor the temporal variation in canopy greenness. In total, the canopy cover of southern yellow pines decreased by about 35% between December 1988 and February 2016. This information could be used by foresters and forest managers to support forest inventory and management.

Habitat Associations of Golden Eagle Prey Inferred from Prey Remains at Nesting Sites in Utah, USA

Golden Eagles (Aquila chrysaetos) can prey on a wide variety of species, but population persistence is often thought to depend on the abundance of a few key prey species. We investigated Golden Eagle prey remains at 254 nesting sites in north-central Utah, USA, from 1970–2014. We hypothesized that variation in observed prey at the nesting site could be predicted by ecoregion or localized (6.4-km radius) environmental factors. We identified 147 prey species representing a minimum of 26,734 individuals, with the majority of species occurring at low frequencies. Golden Eagle prey remains were dominated by black-tailed jackrabbits (Lepus californicus), with cottontails (Sylvilagus spp.), rock squirrels (Otospermophilus variegatus), and yellow-bellied marmots (Marmota flaviventris) also found frequently, and occasionally in large numbers per nesting site. We found natural groupings of prey species by multivariate analyses. Nonmetric multidimensional scaling (NMDS) identified three prey assemblages typical of sagebrush (Artemisia spp.)steppe, wetland, and mountain ecosystems. Canonical correspondence analysis (CCA) and permutational multiple analysis of variance (PERMANOVA) suggested that prey assemblages were associated with environmental variables, including: (1) forest cover and elevation vs. sagebrush and pinyon pine (Pinus spp.) cover; and (2) alfalfa (Medicago sativa), crop, and wetland cover vs. elevation and forest, sagebrush, and pinyon pine cover. Observed prey were better predicted by measured environmental factors than biogeographic boundaries. The abundance of the four most frequently recorded prey species was influenced primarily by habitat, and to a lesser degree by overall diversity of prey remains, precipitation, and time trend variables, as suggested by Poisson regression models. Our analyses indicate that Golden Eagle prey varied within and between ecoregion boundaries, and that prey were more strongly predicted by localized environmental factors than by climate or time.

Influence of light, water stress and shrub cover on sapling survival and height growth: the case of A. unedo, F. ornus and S. domestica under Mediterranean climate

Resprouter species are of great interest for Mediterranean forest resilience as they can survive fire or drought by activating dormant vegetative buds to produce regrowth. Understanding which factors control the early growth and survival of these species is needed to develop strategies to enhance stand resilience. In this study, three broadleaved resprouter species, two trees—Fraxinus ornus and Sorbus domestica—and a shrub—Arbutus unedo—were planted under a gradient of pine cover. Sapling survival and height growth were monitored for 6 years, 2 years after their plantation, as well as light and shrub cover. We developed a two-strata forest water balance model, which produces a water stress index. We aimed to determine the effect of light, water stress and shrub cover on sapling survival and height growth using a modelling approach. We found that high levels of transmittance had a negative impact on both survival and height growth of F. ornus and S. domestica, while it had a positive effect on A. unedo growth. Water stress was found to negatively affect survival and height growth of all species. Lastly, shrub cover had an overall positive effect on the survival and growth of saplings, indicating a facilitating effect of the shrubs. Our results suggest that shade-tolerant tree species like F. ornus and S. domestica are more suited to moderate and light cover, while photoinhibition-tolerant shrub species like A. unedo are more adapted to open conditions. To maximize sapling survival and growth, we recommend preserving the shrubby understorey when present.

Landowner Concern about Wildfires and Implementation of Fuel Reduction Treatments

AbstractFuel reduction treatments implemented by nonindustrial private forest (NIPF) landowners affect wildfire hazard potential on both their tracts and surrounding lands. However, it is not clear how concerned they are about wildfire damages and what actions they are willing to take to lower wildfire hazard. This study determined the landowner concern level about wildfire damages and identified factors affecting their concern and fuel treatment implementation using seemingly unrelated and binary probit models, respectively. Approximately, 68% of landowners were concerned about property damage due to wildfires, and 45% implemented some fuel reduction treatments. The most common and least costly fuel treatment was prescribed burning ($18/acre) followed by chemical ($59/acre) and mechanical ($127/acre) treatments. Raising awareness about potential monetary losses due to wildfires, assisting landowners in preparing written forest management plans, and prioritizing areas with predominant pine cover will encourage landowner participation in hazardous fuel reduction programs and facilitate more effective wildfire mitigation.

Habitat Associations of Golden Eagle Prey Inferred from Prey Remains at Nesting Sites in Utah, USA

Golden Eagles (Aquila chrysaetos) can prey on a wide variety of species, but population persistence is often thought to depend on the abundance of a few key prey species. We investigated Golden Eagle prey remains at 254 nesting sites in north-central Utah, USA, from 1970–2014. We hypothesized that variation in observed prey at the nesting site could be predicted by ecoregion or localized (6.4-km radius) environmental factors. We identified 147 prey species representing a minimum of 26,734 individuals, with the majority of species occurring at low frequencies. Golden Eagle prey remains were dominated by black-tailed jackrabbits (Lepus californicus), with cottontails (Sylvilagus spp.), rock squirrels (Otospermophilus variegatus), and yellow-bellied marmots (Marmota flaviventris) also found frequently, and occasionally in large numbers per nesting site. We found natural groupings of prey species by multivariate analyses. Nonmetric multidimensional scaling (NMDS) identified three prey assemblages typical of sagebrush (Artemisia spp.)steppe, wetland, and mountain ecosystems. Canonical correspondence analysis (CCA) and permutational multiple analysis of variance (PERMANOVA) suggested that prey assemblages were associated with environmental variables, including: (1) forest cover and elevation vs. sagebrush and pinyon pine (Pinus spp.) cover; and (2) alfalfa (Medicago sativa), crop, and wetland cover vs. elevation and forest, sagebrush, and pinyon pine cover. Observed prey were better predicted by measured environmental factors than biogeographic boundaries. The abundance of the four most frequently recorded prey species was influenced primarily by habitat, and to a lesser degree by overall diversity of prey remains, precipitation, and time trend variables, as suggested by Poisson regression models. Our analyses indicate that Golden Eagle prey varied within and between ecoregion boundaries, and that prey were more strongly predicted by localized environmental factors than by climate or time.

Microclimate in Mediterranean pine forests: What is the influence of the shrub layer?

Forest cover creates a specific microclimate by buffering most environmental variables. If the influence of the overstory on microclimatic variables has been well studied, the role of the understory has received less attention. In this study we investigated how the shrub layer modifies solar radiation, air temperature (T), relative air humidity (RH), vapor pressure deficit (VPD) and soil moisture under different thinning treatments in an Aleppo pine forest (Pinus halepensis Mill.). Microclimatic variables were measured along a vegetation cover gradient made up of three pine densities (dense, medium, low) and open conditions, with or without the presence of shrubs. The results were analyzed with a focus on the summer period which represents a major bottleneck for plant development in the Mediterranean area.Average T and VPD values increased with decreasing vegetation cover (+1.38 °C and +0.21 kPa for the whole year) while RH decreased (-2.34%). Along the same gradient, daily amplitude of T, RH, VPD increased while the buffering capacity decreased. These patterns were more pronounced during the summer period compared to the whole year and were primarily driven by overstory transmittance. However, the shrub layer played a significant role in the low pine cover treatment where it was developed and in open conditions. Soil water content in the forest area was higher under low pine cover without shrubs than it was in the other treatments, though differences were less marked during summer drought episodes. In open conditions, soil moisture was always significantly lower beneath the shrub canopy than outside it. Despite a reduction in soil moisture, shrubs may represent safe sites for woody seedling development in sparse pine forests and in treeless areas by buffering the microclimate during the summer period.