Higher Tree Canopy Cover Research Articles

Multi‐scale species density model for conserving an endangered songbird

AbstractHabitat modeling across a landscape that has gradients of habitat conditions requires potential predictor data that can be quantified at biologically relevant scales. We used remotely sensed data to develop a multi‐scale density model in 2018 for the golden‐cheeked warbler (Setophaga chrysoparia; warbler), a species that breeds in Ashe juniper (Juniperus ashei)‐oak (Quercus spp.) woodlands in central Texas, USA. We first classified Ashe juniper and broadleaf tree cover at a 1‐m resolution and used this to map potential habitat across the warbler's >67,000‐km2 breeding range. We then designed a survey for estimating warbler density based on hierarchical distance sampling. We used stratified random sampling to survey for male warblers at 1,804 points across the continuum of tree canopy cover and composition and detected 810 warblers during our surveys. We developed a suite of potential predictor variables for modeling warbler density that reflected vegetation, topography, climate, and anthropogenic land use conditions across the breeding range and developed these at 3 scales representing the territory, site, and landscape. We modeled warbler density and used the best fit model to produce a spatially explicit estimate. Predicted warbler density was influenced by tree canopy cover and canopy height at the territory scale (100‐m radius); tree canopy cover, percent of the canopy comprised of juniper, and an interaction between canopy cover and compound topographic index at the site scale (1‐km radius); and annual temperature range at the landscape scale (5‐km radius). We estimated a population size of 217,444 male warblers (95% CI = 153,917–311,965) and >3,000 males in each recovery unit. After controlling for the duration of point count surveys, our estimate of population size was similar to that reported from the only previous breeding range survey conducted in 2008–2009. Our model results indicated that management activities to increase warbler density should promote woodlands with high tree canopy cover, approximately 60–80% Ashe juniper composition, and tree heights >3 m. In contrast to a patch‐based approach, our treatment of habitat variables as continuous helped to credibly map the warbler distribution across areas with broad transitions from woodlands to shrublands. By measuring these predictor variables at biologically relevant scales, we allowed the warbler survey data to define habitat relationships instead of using anthropogenically defined habitat patches. Outcomes from our study show the benefits of developing spatial products tailored to individual species of interest for conservation and management decisions.

Influence of trees on landscape temperature in semi-arid agro-ecosystems of East Africa

In the Dodoma region of Tanzania, overexploitation of natural resources has led to a severe land degradation and, consequently, to the need to restore local ecosystems. Within the possible strategies, the farmer managed natural regeneration agroforestry is strongly being promoted in the area. To validate the utilisation of this practise, this research aims (i) to assess the benefits of trees on microclimate studying the relationship between land surface temperature (LST) and tree canopy cover (TCC) in farmlands and (ii) to propose an operative tree density threshold to be set as objective by restoration activities in the area. Data collected with an unmanned aerial vehicle were integrated with Landsat 8 and Sentinel 2 satellite imagery. LST was retrieved through the practical single channel algorithm and TCC was calculated with a supervised classification. Pixel-based analyses at a resolution of 30 m and 10 m were performed, and the resulting data statistically analysed through the coefficient of determination, the Kruskal–Wallis test, and the Dunn test. Results showed that the TCC of the surveyed areas was 5.1%, and a significant decrease in LST of 1.32 °C (p < 0.01) was found in the areas with the highest TCC, during the late dry season. From these preliminary analyses, a threshold of 10% TCC is suggested for farmlands in this agroecological zone to bring beneficial microclimate changes in terms of temperature. Considering the average plant phenotype characteristic of the area, it corresponds to a tree density of 50 trees ha −1 . • LST decrease of 1.32 °C found in areas with high TCC in the late dry season. • 10% TCC threshold, or 50 trees ha −1 should be reached using restoration. • Integration of Landsat 8 with Sentinel 2 data gave improved analysis.

Associations of objective and perceived greenness measures with cardiovascular risk factors in Philadelphia, PA: A spatial analysis

There is mounting scientific evidence that greenness is associated with improved cardiovascular health. However, few studies have distinguished between vegetation type, measured perceived green space access, or investigated heterogeneity of associations across categories of neighborhood sociodemographic and racial/ethnic composition. We conducted an ecologic spatial analysis of associations of three objective measures of greenness (percent vegetation cover, percent tree canopy cover, and greenness density), and one measure of perceived access to green spaces with census tract level percentages of the adult population who were obese, ever had a high blood pressure diagnosis, and ever had a diabetes diagnosis, in the city of Philadelphia, PA, year 2013. We explored effect modification by census-tract level percent living in poverty and percent non-Hispanic Black categories. We used data from the Southeastern Pennsylvania Household Health Survey (SEPAHH) linked with high-resolution landcover, remotely sensed, and American Community Survey data and estimated associations using spatial lag models. We observed modest protective associations between percent of the adult population reporting perceived access to green spaces and percent with the cardiovascular risk factors, particularly in moderate and high poverty census tracts. Percent tree canopy cover was also protective against the cardiovascular risk factors, particularly in census tracts with low percentages of the population living in poverty and with low percent non-Hispanic Black populations. These results suggest that perceived access to green spaces and objectively measured high tree canopy cover, may protect against cardiovascular disease, but associations may vary across neighborhood sociodemographic categories.

Associations of the residential built environment with adolescent sleep outcomes.

Over 75% of US high school students obtain insufficient sleep, placing them at risk for adverse health outcomes. Identification of modifiable determinants of adolescent sleep is needed to inform prevention strategies, yet little is known about the influence of the built environment on adolescent sleep. In this prospective study, actigraphy was used to assess sleep outcomes among 110 adolescents for 14 days each in eighth and ninth grades: duration (hours/night), onset and offset, and sleeping ≥8 hours. Home addresses were linked to built environment exposures: sound levels, tree canopy cover, street density, intersection density, population density, and housing density. Mixed-effects regression estimated associations of built environment measures with sleep outcomes, adjusting for sex, race, parent education, household income, household size, grade, weeknight status, and neighborhood poverty. A 1-standard deviation (SD) increase in neighborhood sound was associated with 16 minutes later sleep onset (β = 0.28; 95% confidence interval (CI): 0.06, 0.49) and 25% lower odds of sleeping for ≥8 hours (odds ratio (OR) = 0.75, 95% CI: 0.59, 0.96). A 1-SD increase in neighborhood tree canopy was associated with 18 minutes earlier sleep onset (β = -0.31, 95% CI: -0.49, -0.13) and 10 minutes earlier sleep offset (β= -0.17, 95% CI: -0.28, -0.05). No associations were observed for density-based exposures. Higher neighborhood sound level was associated with lower odds of sufficient sleep, while higher tree canopy cover was associated with more favorable sleep timing. Neighborhood sound levels and tree canopy cover are potential targets for policies and interventions to support healthier sleep among adolescents.

Seasonal habitat utilisation and morphological characteristics of Chamaeleo dilepis on Telperion Nature Reserve, Mpumalanga, South Africa

ABSTRACT Limited information on the habitat utilisation and seasonal activity of flap-necked chameleons (Chamaeleo dilepis) is available. We investigated habitat utilisation, seasonal distribution, and sexual dimorphism of C. dilepis on Telperion Nature Reserve (a privately protected natural area) in South Africa. Seven broad plant habitat units were surveyed for one year, which included a wet and a dry season. Plant species richness and species diversity, woody plant densities and canopy cover were recorded and analysed in each of the habitat units. Location, sex, age class and morphological measurements were recorded for located chameleons. Gravid adult females were found to be significantly heavier and larger than adult males, but no differences were found in size or mass for subadults. The occurrence of hatchlings was significantly influenced by rainfall, whereas minimum temperature had a significant influence on the occurrence of adults and subadults. Hatchlings occurred from mid-December to March in habitats associated with high shrub and grass canopy cover and low plant species diversity. Subadults were located from mid-March to the end of May in woody habitats and adults were located from the end of October until the end of May. Subadult and adult chameleons preferred dense woodland with high tree canopy cover and rockiness with high plant species diversity. The results of this study suggest that C. dilepis on Telperion have seasonal habits influenced by rainfall, minimum temperature and habitat structure.

Improving burn severity retrieval by integrating tree canopy cover into radiative transfer model simulation

Burn severity mapping greatly informs fire management and can be used to predict post-fire vegetation recovery. Satellite remote sensing is a cost-effective method for estimating burn severity, providing a comprehensive spatially explicit view of whole landscapes. However, the proportion of tree canopy cover (TCC) affects the reflectance signal, obscuring background char and ash. Consequently, traditional optical satellite remote sensing methods that do not account for variation in TCC misclassify burn severity, especially in areas with extremely low or high TCC. In this study, TCC data served to parameterize and constrain the inversion of the Forest Reflectance and Transmittance (FRT) radiative transfer model (RTM) to alleviate spectral confusion when retrieving burn severity. The methodology was evaluated using field measurements of burn severity for a series of wildfires in the fire-prone tropical savannas of northern Australia and the western United States. Burn severity classes were used for Australia while the Composite Burn Index (CBI) for US. Reflectance data from Sentinel-2A Multi-Spectral Instrument (MSI) and Landsat-5 Thematic Mapper (TM) corresponding to post-fire field survey dates were used to retrieve burn severity using FRT RTM (with and without using TCC information in its parameterization and inversion) and two standard empirical burn indices, dNBR and RdNBR, for comparison. Using FRT RTM without TCC constraint produced an overestimation for low burn severity in regions with low TCC and an underestimation for moderate and high burn severity in regions with high TCC. Burn severity estimation accuracy significantly improved by integrating TCC in the parameterization and inversion of FRT RTM. The overall accuracy in northern Australia increased from 65% to 81%, and the kappa coefficient increased from 0.35 to 0.55. In the western United States, R2 between estimated and observed CBI, increased from 0.33 to 0.54, root mean square error (RMSE) reduced from 0.53 to 0.43, and in all instances, the method performed better than dNBR and RdNBR. The method used in this study achieved more accurate burn severity mapping, thus assisting land managers to better understand post-fire vegetation resilience and forest management.

Developing an Automated City of Whittlesea Urban Tree Canopy Inventory Using Airborne LiDAR and Aerial Imagery

The City of Whittlesea is in Melbourne’s north and is one of the largest municipalities in metropolitan Melbourne. The council GIS team using current aerial photos from 2017 and LiDAR (“LiDAR” stands for Light Detection and Ranging) point clouds 2009 products to identify trends in urban tree canopy cover in the established suburbs of the municipality between 2009 and 2017. The tree canopy coverage was calculated for residential properties, road reservations, public land and park sites within urban parts of Bundoora, Epping, Lalor, Mill Park, Thomastown, and South Morang. From the total project area of approximately 3499 hectares a test site was selected based on an extension of one of the LIDAR data tiles (e325n5828). This project investigates only 6 meters and higher tree canopy cover within the project area. The objectives of the project were to establish a methodology to calculate the urban tree canopy coverage from LiDAR 2009 data, that can be replicated in future calculations. The calculated urban tree canopy coverage from LiDAR 2009 data is 9%, compared to 8% coverage in 2017, based on aerial photography. This estimate was compared to similar Local Governance Areas that range from 12% to 40%. A key to planning and managing urban tree canopy is first to understand the quantity, quality, tree density and distribution of the resource across the landscape. Tree inventories and urban tree canopy analyses comprise an assortment of tools, technologies, and procedures that help us understand the structure and function of our urban tree canopy. The data and information gleaned from urban tree canopy assessments enable resource professionals and policymakers to make informed decisions about ordinances, housing diversity strategy, and budgeting, future tree planting programs and reduce urban heat islands.

A landscape genetic analysis of swamp rabbits (Sylvilagus aquaticus) suggests forest canopy cover enhances gene flow in an agricultural matrix

Habitat loss and fragmentation pose a continued and immediate threat to wildlife and create a persistent need for ecological information at the landscape scale to guide conservation efforts. Landscape features influence population connectivity for many species and genetic analyses can be employed to determine which of these features are most important. Because population connectivity through dispersal is important to the persistence of swamp rabbits (Sylvilagus aquaticus (Bachman, 1837)) at the northern edge of their range, we used a landscape genetic approach to relate gene flow to landscape features that may impact dispersal success. We tested resistance values for attributes of land cover, watercourse corridors, canopy cover, and roads and used causal modeling and redundancy analysis to relate these representations of landscapes to genetic distance for swamp rabbits in southern Illinois, USA. Models that included canopy cover had the strongest correlations with genetic distance and were supported by our methods whereas other models were not. We concluded that high tree canopy cover enhances gene flow and landscape connectivity for swamp rabbits in southern Illinois. Our study provides important empirical evidence that landscape variables may impact the habitat connectivity of swamp rabbits. Preserving dispersal routes for swamp rabbits should focus on improving canopy cover, in both bottomland and upland, to connect suitable habitat.

Landscape-level habitat use and movement patterns of black bears in northeastern Arizona

Abstract Little is known about black bear (Ursus americanus) populations in northeastern Arizona, an area characterized by rugged canyon topography and varied habitat composition. We placed global positioning system collars on four bears in this area to characterize second-order, landscape-level habitat use and examine habitat use and movement patterns of bears across this landscape. Data from four global positioning system collars revealed that bears use areas with higher tree canopy cover and terrain ruggedness, indicating that forest and escape cover are important factors driving black bear habitat use at the landscape level. Movement patterns revealed long, linear mean daily movements that follow the structure of the canyon topography. These long, linear movements also allow bears to take advantage of the mosaic of habitats and food resources available in this unique landscape.

Is Planting Equitable? An Examination of the Spatial Distribution of Nonprofit Urban Tree-Planting Programs by Canopy Cover, Income, Race, and Ethnicity

This article examines the spatial distribution of tree-planting projects undertaken by four urban greening nonprofit organizations in the Midwest and Eastern United States. We use a unique data set of tree-planting locations, land use data, and socioeconomic information to predict whether a census block group ( n = 3,771) was the location of a tree-planting project between 2009 and 2011. Regression results show tree-planting projects were significantly less likely to have occurred in block groups with higher tree canopy cover, higher median income, or greater percentages of African American or Hispanic residents, controlling for physical and socioeconomic conditions. In addition, when canopy cover or income was low, plantings were even less likely to have occurred in neighborhoods with high percentages of racial or ethnic minorities. Findings suggest nonprofit plantings might reduce existing income-based inequity in canopy cover, but risk creating or exacerbating race-based inequity and risk leaving low canopy minority neighborhoods with relatively few program benefits.

Spatial and temporal domains of scale of grazing cattle

Spatio-temporal patterns of cattle grazing were studied in four annual grassland pastures in California, differing mainly in tree canopy cover. Cows were equipped with global positioning collars that recorded position, temperature and head movements at 5-min intervals during 6 days in each of four seasons repeated during 2 years. The time animals took to traverse areas of varying diameter revealed patches of 6–9-m diameter in the pastures with low, and 18–21-m diameter in the pastures with high tree canopy cover. In agreement with the current model, crookedness of cow paths had two distinct domains. Within distances of 0–40 m, paths were relatively straight and similar, but from 40 to 200 m, they became increasingly tortuous. Correlation of sequential turning angles identified patches of movement with diameters between 40 and 100 m, which correspond to the ‘patch’ level of grazing within grazing sites. Seasonal changes in meal patterns were consistent with changes in temperature and forage quality and interacted with the distribution of shade. Thus, spatial distribution of grazing and temporal distribution of meals were inextricably linked. Low forage quality and high temperatures in summer resulted in highly concentrated grazing around trees. Conversely, winter and early spring forages of very high quality and low availability motivated more widely distributed grazing, with low proportion of areas being re-grazed. Resting sites acted as beginning and end of grazing bouts. We conclude that shade distribution can modulate meal start and duration.

Habitat requirements, short-term population dynamics and coexistence of native and invasive Impatiens species: a field study

The genus Impatiens (Balsaminaceae) includes three widespread species in the Czech Republic, central Europe: the native I. noli-tangere, and two invasive species, I. parviflora and I. glandulifera, differing in the dynamics of invasion. They all occur in similar habitats and share basic life-history characteristics, which make them a suitable model for studying species traits associated with invasiveness. In this study we investigated differences in habitat requirements of these Impatiens species, their coexistence and short-term population dynamics in the field. We established 84 1 × 1 m permanent plots in five localities where all three species co-occurred. In each plot vascular plant species were determined, their cover estimated and all individuals of Impatiens species counted. Site characteristics including tree canopy cover, soil moisture, nitrogen and carbon content, and slope were measured directly. Nutrients, light, humidity and soil reaction were estimated using Ellenberg indicator values. The presence of I. noli-tangere was strongly correlated with high soil moisture, that of I. parviflora with high tree canopy cover and low soil moisture. Impatiens glandulifera exhibited a unimodal response to tree canopy cover, avoiding both very shaded and fully open sites. The current-year abundances of all species were negatively related to those of congeneric species. These results suggest that the coexistence of Impatiens species in the same habitat is due to microsite differentiation. Further spread of I. glandulifera to new habitats, and reduction of the native I. noli-tangere niche, can be expected in areas where the latter species co-occurs with competitively strong invasive congeners.

Long-term urbanization effects on tree canopy cover along an urban–rural gradient

Urban forestry can benefit from improved knowledge of urbanization’s effects on tree canopy cover (TCC), a prominent urban forest indicator. This study examined changes in TCC over a long time frame, with respect to land cover (LC) changes, and across municipal boundaries. Specifically, I used air photos at 14 dates from 1937 to 2009 to develop an exceptionally long record of TCC change in Minnesota’s Twin Cities Metropolitan Area. During the study period overall TCC nearly doubled from 17% to 33% while the proportion urban land cover rose by 47%, highlighting the opportunity for substantial TCC gains following urbanization in previously agricultural landscapes, even in regions that were forested prior to European settlement. Results demonstrate that more intensely developed sites generally had lower TCC, and older urban sites had higher TCC. Modern TCC was not adequately characterized by linear distance along the urban–rural gradient, but instead peaked near the center of the gradient where mature residential neighborhoods are prevalent. Compared to other land cover changes, urbanization events caused the highest rate of immediate TCC loss (9.6% of events), yet urban areas had the second highest TCC (>35%) in 2009, indicating that urban land gained TCC relatively efficiently following development. The results of this study provide new historical context for urban forest management across an urban–rural gradient, and emphasize the need to consider ecological legacies and temporal lags following land cover changes when considering TCC goals in urban settings.

The influence of local, landscape and spatial factors on the distribution of the Lusitanian and the Mediterranean pine voles in a Mediterranean landscape

This study evaluated the relative contributions of local and landscape factors, and of spatial structure on the regional distribution of both the Lusitanian ( Microtus lusitanicus Gerbe, 1879) and Mediterranean pine voles ( Microtus duodecimcostatus de Selys-Longchamps, 1839) over an area of 1613 km 2 within a Mediterranean landscape in central Portugal. Three sets of explanatory variables (20 local, 23 landscape, and 6 spatial) were analysed independently by means of a generalized linear model, followed by a variance partitioning procedure. Variance in the distribution patterns of M. lusitanicus and M. duodecimcostatus largely was explained by fine-scale environmental factors but spatial effects also were important, especially for the distribution of M. duodecimcostatus. The close proximity of verges and the high abundance of humidity and coarse sand in the soil were the most influencing local-scale factors for the presence of M. lusitanicus; meanwhile on a larger scale, the high abundance of linear habitats was the main landscape feature determining its occurrence. Regarding the presence of M. duodecimcostatus, the close proximity of verges, high tree canopy cover and herbaceous vegetation biomass were the most influential local explanatory variables for its occurrence, while the absence of shrubs in the surrounding habitat was the main factor regulating species presence at a landscape scale. Similarities identified between the two species primarily were related to descriptors of cover, food and burrows, while differences were related to opposing spatial trends and coarse-scale descriptors.

Responses of herbs and shrubs to reduced root competition under canopies and in gaps: a trenching experiment in old-growth Douglas-fir forests

We tested the effect of root trenching on vegetation in closed-canopy and gap locations in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. Based on theory, we expected belowground competition to be intense in a region with low summer rainfall, and trench responses were expected to be greater in the high light environment of the gaps. We installed 1 m deep trenches around study plots and lined the trenches to prevent reinvasion by tree roots. Soil moisture was measured monthly during the growing season for the first 3 years after trench installation. Vegetation in these trenched plots was compared with control plots 10 years after installation of the plots. Trenched plots with no vegetation manipulation averaged 92% total understory cover, while untrenched plots averaged 47% cover. Contrary to our expectation, both vegetation and soil moisture responses to trenching were greater in areas of high tree canopy cover than in gaps. Trenched plots under closed canopies were moister than control plots throughout the growing season, while the trenching effect became apparent in the overall wetter gaps only at the end of the growing season. We conclude that understory plants at these sites were limited at least as much by belowground competition as by aboveground competition.

Silvopastoral systems in Northwestern Patagonia II: water balance and water potential in a stand of Pinus ponderosa and native grassland

The climate of the ecotone between forest and steppe in North-Western Patagonia, is of Mediterranean type, with rainy winters and dry summers. As a consequence, most of the region presents water deficits during part of the spring and all the summer. Water interactions between Pinus ponderosa Doug. (Laws) and Stipa speciosa (Trin. et Rupr.), a native grass species, were studied. The experimental site includes ten silvopastoral plots (five with 350 pruned pines/ha and five with 500 pruned pines/ha), one plot with 500 unpruned pines/ha, one plot with 1000 pines/ha and an open pasture. Pre-dawn water potential of pines and grasses, and soil water moisture under and between tree crowns, and in the open pasture, were measured during October to April. Also, local water balance of these situations was studied over the same period. Evapotranspiration was higher in silvopastoral systems than in the open pasture (average difference of 95 mm). Greatest soil water consumption was observed in silvopastoral systems, mainly at the deepest layers(80–140 cm). Rain interception by pines was important only at the end of the dry season. Pre-dawn water potential of trees was stable during the study period. Better water status was found in grasses growing under high tree canopy cover compared to those in the open treatments, before and after the driest month (January). Silvopastoral systems use water resources that otherwise are lost from the system. Therefore the higher productivity of these systems may partly reflect this more exhaustive use of resources.