Increasing Canopy Cover Research Articles

Early successional riparian vegetation is important for western Yellow‐billed Cuckoo nesting habitat

Western Yellow‐billed Cuckoo (Cuckoo; Coccyzus americanus) populations continue to decline in the western United States despite efforts to increase availability of riparian forest. Cuckoos have unique breeding habitat requirements such as large contiguous tracts of riparian forest (>80 ha), large estimated home ranges (20–90 ha), and dense vertical structure around the nest. However, local habitat‐scale features may be missing in landscapes of predominantly mature riparian forest that may need to be specifically managed for nesting. We used historical nest data (n = 95) from the South Fork Kern River Valley, California, from 1985 to 1996 to identify important nest site features that may be missing in current riparian forests. We found that increased canopy cover and vertical structure at all levels in the canopy greatly increased the probability of Cuckoo nesting. With smaller estimated effect sizes, the probability of Cuckoo nesting increased with increasing willows and forbs and smaller mean tree dbh. Cuckoos selected plots with disproportionately high percent willow cover relative to availability plots regardless of whether sites had low or high percent willow available. Counts of fledged young were positively related to willow percentage. No vegetation variable influenced daily survival rate which was 0.991 (LCI = 0.980, UCI = 0.996). Overall 17‐day nest success was likely high (0.86, LCI = 0.71, UCI = 0.93). In the absence of natural processes that create early successional stage forest, specific management for early successional stage forest is needed to increase the probability of Cuckoo nesting and nest productivity.

Invasive populations of Spiraea tomentosa (Rosaceae) are genetically diverse but decline during succession in forest habitats

Population genetic and ecological data may help to control invasive plants, which are considered to be a major threat to natural habitats. In contrast to expected bottleneck events, genetic diversity of such invasive populations may be high due to extensive propagule pressure or admixture. The ecological impact of invasive species has been broadly evaluated in the field, however, long term-studies on the fate of invasive plants are scarce. We analysed genetic diversity and structure in invasive Spiraea tomentosa populations in eastern Germany and western Poland by using an Amplified Fragment Length Polymorphism approach. Potential hybridisation between co-occurring diploid Sp.tomentosa and tetraploid Sp. douglasii was investigated using Flow Cytometry. The genetic analyses were complemented by data from a thirteen-year vegetation study in an area invaded by both Spiraea species. We found no evidence for spontaneous hybridisation between Spiraea species. In populations of Sp.tomentosa genetic diversity (He=0.26) and genetic structure (ΦPT=0.27) were high and comparable to other outcrossing woody plants. Low levels of clonality, the presence of seedlings and of new patches in sites that had been colonised over the last 13 years imply that populations also increase and spread via sexual reproduction. In all habitat types, species diversity declined following Sp.tomentosa invasion. However, detailed aerial mapping of a forest reserve with ongoing succession revealed that Spiraea spp. populations declined over a ten year period following invasion. Despite its potential dispersal ability and its negative effects on plant communities, invasive Spiraea populations may be controlled by increasing canopy cover in forest habitats.

Landscape and farm-level management for conservation of potential pollinators in Indonesian cocoa agroforests

Cocoa (Theobroma cacao L.), a major commodity globally, depends on insects for pollination. However, the cocoa pollinator identity is largely unknown and there are important knowledge gaps regarding landscape and farm-level management driving pollinators. Here we analyzed flower visitation with two approaches to quantify how landscape and farm-level factors affect potential pollinators (flower visitors) of cocoa in Central Sulawesi, Indonesia. In the first approach (landscape and farm-level) we selected 18 farms and focused on the relative importance of distance to forest (m), potential-pollinator habitats surrounding the farm (i.e. secondary forests and cocoa agroforests [%]), canopy cover (%), leaf-litter amount (kg/m2), and cocoa flower abundance for flower visitors. In the second approach (experimental farm management) we manipulated leaf-litter in 24 farms, because high leaf-litter is suggested to enhance flower visitors. We found that ants and Diptera were the most common flower visitors, and although previous studies suggest ceratopogonids as main cocoa pollinators, none were captured in this study. In the landscape and farm-level approach, potential-pollinator habitats surrounding the farm, and increased canopy cover enhanced ant and Diptera abundance, whereas distance to forest had no effect. In the experimental farm management approach, potential-pollinator habitats surrounding the farm rather than leaf-litter manipulation increased Diptera and ant abundance. In summary conservation of forests and agroforests surrounding the farm, maintaining canopy cover and minimum leaf-litter enhance cocoa flower visitors. Thus, farms with shade trees embedded in a biodiversity-friendly landscape are important for conservation of potential pollinators and pollination services and, thereby, promotion of sustainable cocoa.

Effects of seasonal grazing and annual mowing on floristic composition and plant diversity in the Saral rangeland, Kurdistan, Iran

This study examined the impact of long-term (40 years) seasonal grazing and annual scythe mowing on changes in plant diversity, floristic composition and plant functional groups in the cold semi-arid rangelands of Mangahul-Zardawan located in Saral, Kurdistan. In this investigation, 900 plots (2 m2) were sampled in grazed (450 plots) and mowed sites (450 plots) to measure vegetation and plant characteristics. Data were collected in two consecutive growing seasons from late May to early June in 2017 and 2018. Both years recorded below average rainfall. The results showed that after 40 years, seasonal grazing compared to scythe mowing increased canopy cover and species richness of different functional groups including annuals, perennial grasses, perennial forbs and total vegetation. On the other hand, both the total above-ground plant material and the palatability index were higher for the mowed than the grazed sites, although scythe mowing had caused the Boraginaceae family to disappear. Based on these results, the mean of total plant material (above-ground live + standing dead + litter) was substantially higher in the mowed area, where two-year mean totals were 271 g/m2 compared with 216 g/m2 for the grazed area. In terms of a three-level palatability classification (high, medium and low), only the plants with moderate palatability differed in contribution between the sites, with mowed sites having a significantly greater proportion of this class than the grazed sites. Our results suggested that in the long term, grazing can maintain species richness and the typical floristic composition of rangelands; but when socio-economic issues have priority, mowing has more advantages. In rangelands with the same ecological and geographic conditions, users and managers can choose the most appropriate management approach based on their long- and short-term policies.

Understory plant diversity and composition across a postfire tree density gradient in a Siberian Arctic boreal forest

Cajander larch (Larix cajanderi Mayr.) forests of the Siberian Arctic are experiencing increased wildfire activity in conjunction with climate warming. These shifts could affect postfire variation in the density and arrangement of trees and understory plant communities. To better understand how understory plant composition, abundance, and diversity vary with tree density, we surveyed understory plant communities and stand characteristics (e.g., canopy cover, active layer depth, and soil organic layer depth) within 25 stands representing a density gradient of similarly-aged larch trees that established following a 1940 fire near Cherskiy, Russia. Understory plant diversity and mean total plant abundance decreased with increased canopy cover. Canopy cover was also the most important variable affecting individual species’ abundances. In general, tall shrubs (e.g., Betula nana subsp. exilis) were more abundant in low-density stands with high light availability, and mosses (e.g., Sanionia spp.) were more abundant in high-density stands with low light availability. These results provide evidence that postfire variation in tree recruitment affects understory plant community composition and diversity as stands mature. Therefore, projected increases in wildfire activity in the Siberian Arctic could have cascading impacts on forest structure and composition in both overstory and understory plant communities.

Land‐use history determines stand structure and tree diversity in vanilla agroforests of northeastern Madagascar

AbstractQuestionIn human‐modified tropical landscapes, agroforestry is considered a promising land use to reconcile biodiversity conservation with production goals. The role of agroforests regarding conservation may be strongly influenced by land‐use history; however, few studies have explicitly investigated this. We therefore tested the importance of land‐use history for habitat structure and tree diversity in vanilla agroforests situated in a human‐modified tropical landscape.LocationSmallholder mosaic landscape of northeastern Madagascar.MethodsWe studied tree stand structure, diversity and composition in vanilla agroforests of contrasting land‐use history, old‐growth forests, forest fragments and woody fallows after slash‐and‐burn agriculture, which all contribute to the smallholder mosaic landscape of northeastern Madagascar. The vanilla agroforests were either derived directly from forest or otherwise from woody fallows after slash‐and‐burn agriculture.ResultsLand‐use history strongly influenced tree species diversity and composition in vanilla agroforests and also affected stand structure. Forest‐derived agroforests maintained high levels of tree species diversity and differed in community composition from fallow‐derived agroforests, which had relatively low levels of tree diversity. Additionally, forest‐derived vanilla agroforests harboured a significantly higher percentage of endemic species than fallow‐derived agroforests, and forest‐derived agroforests also shared many species with old‐growth forests and forest fragments. Fallow‐derived vanilla agroforests harboured a lower percentage of endemic species than woody fallows.ConclusionConsidering the land‐use history of agroforests is important to unfold their full potential as elements in a multifunctional human‐modified landscape. Forest‐derived agroforests are an alternative to forest conversion through slash‐and‐burn agriculture and have the potential to sustain high levels of species diversity and important habitat structures. In contrast, fallow‐derived agroforests regain stand structure on degraded historically forested land and thereby have the potential to increase canopy cover and connectivity at the landscape scale.

Woody buffer effects on water temperature: The role of spatial configuration and daily temperature fluctuations

AbstractWater temperature is a key driver for riverine biota and strongly depends on shading by woody riparian vegetation in summer. While the general effects of shading on daily maximum water temperature Tmax are well understood, knowledge gaps on the role of the spatial configuration still exist. In this study, the effect of riparian buffer length, width, and canopy cover (percentage of buffer area covered by woody vegetation) on Tmax was investigated during summer baseflow using data measured in seven small lowland streams in western Germany (wetted width 0.8–3.7 m). The effect of buffer length on Tmax differed between downstream cooling and heating: Tmax approached cooler equilibrium conditions after a distance of 0.4 km (~45 min travel‐time) downstream of a sharp increase in canopy cover. In contrast, Tmax continued to rise downstream of a sharp decrease in canopy cover along the whole 1.6 km stream length investigated. The effect of woody vegetation on Tmax depended on buffer width, with changes in canopy cover in a 10 m wide buffer being a better predictor for changes in Tmax compared to a 30 m buffer. The effect of woody vegetation on Tmax was linearly related to canopy cover but also depended on daily temperature range Trange, which itself was governed by cloudiness, upstream canopy cover, and season. The derived empirical relationship indicated that Tmax was reduced by −4.6°C and increased by +2.7°C downstream of a change from unshaded to fully shaded conditions and vice versa. This maximum effect was predicted for a 10 m wide buffer at sunny days in early summer, in streams with large diel fluctuations (large Trange). Therefore, even narrow woody riparian buffers may substantially reduce the increase in Tmax due to climate change, especially in small shallow headwater streams with low baseflow discharge and large daily temperature fluctuations.

Dynamics of beetle-killed snags following mountain pine beetle outbreaks in lodgepole pine forests

Snags (standing dead trees) are important components of forest ecosystems that, among other benefits, provide critical habitat for many species of wildlife, but also represent important safety concerns to firefighters, forest workers, and the public. We identified factors that influence the fall rates of lodgepole pines, Pinus contorta Dougl. ex Loud., killed by bark beetles during a severe regional-scale outbreak of mountain pine beetle, Dendroctonus ponderosae Hopkins, that occurred in 2004–2012. Data were obtained during annual assessments (2010–2019) of a network of 107 0.081-ha circular plots installed in P. contorta forests in Colorado, Idaho, Montana, Utah and Wyoming, U.S. A total of 3789 P. contorta snags were monitored, and in each case we recorded, among other variables, the year the snag was created and the year the snag fell to the forest floor. Among snag age classes (i.e., number of years since tree death), the highest number of snags (1046) were 12 years since death (YSD), and those 13 and 14 YSD exhibited the lowest fall rates to date (<10%) despite being the oldest in our study. Snags 13 and 14 YSD were among the largest in diameter. Snag fall occurred in every snag age class from 1 to 14 YSD, with the greatest proportion of snag fall events occurring 4–8 YSD. By 2019, 24.7% (937) of snags fell to the forest floor. We modeled snag fall using a Cox’s proportional-hazards model that included six covariates of interest: elevation (m), slope aspect (categorical, cardinal direction), slope (%), canopy cover (%), snag height (m), and snag height:dbh (m, diameter at 1.37 m in height). Slope aspect had the strongest influence on fall rates. Northern aspects, increased canopy cover, and taller snag heights decreased the probability of snag fall. Conversely, southern aspects and increased height:dbh ratios (i.e., taller, skinner snags) increased the probability of snag fall. The predicted half-life (i.e., the amount of time since death required for 50% of the snag population to fall to the forest floor) was ~16 YSD after which the function predicted a linear, ~0.04/year decline in snag survival probability 15–30 YSD. The observed longevity of P. contorta snags confers important ecological benefits for some wildlife, and may offer opportunities for extended periods of salvage. However, checking (cracks) rapidly occurred, and many snags 6 YSD and older had at least one check at 1.37 m and 5.5 m in height, which can negatively impact lumber recovery. The relatively slow snag fall rates observed in our study also lengthen concerns regarding hazard trees, human safety, and protection of critical infrastructure. The implications of these and other results to management of P. contorta forests are discussed.

Changes in plant species richness after cessation of forest disturbance

AbstractQuestionsWhat will happen to species diversity in a forest when exploitation of the canopy foliage terminates? The foliage of the main canopy tree of a mountain evergreen oak forest was harvested at different intensities prior to a forest survey in 1993 and resampled in 2013 after the harvest of canopy foliage ceased (1995). We predict a decrease in herbaceous species richness with increasing canopy cover, and an opposite trend for vines and woody species. We hypothesise that plant species’ alpha and beta diversity will change most in the plots where foliage was most intensively harvested while showing less change in the plots that underwent almost no harvesting.LocationTemperate evergreen laurel–oak forest in the Himalaya, Nepal.MethodsWe resampled all non‐epiphytic vascular plants in 64 plots of 10 m × 10 m in 2013, following the same protocol used in 1993. Plant species were categorised into three life forms; woody (except woody vines), herbaceous, and vines. Uni‐ and multivariate numerical methods were used to assess the significance of the changes in species diversity for different life forms.ResultsVines and woody species increased, whereas herbaceous species decreased, but overall gamma diversity remained unchanged. The overall alpha richness for herbaceous species decreased, while the opposite is true for woody and vine richness. Herbaceous richness decreased and woody richness increased in the areas with low and intermediate disturbance (in 1993), whereas vines remained unchanged. Only vine richness increased in the area that was very disturbed in 1993. Total species richness as well as herbaceous and vine richness decreased with increasing tree canopy cover.ConclusionsPlots that were intensively harvested in 1993 did not recover their richness because vines dominated the forest floor. Management should prevent overexploitation, and only allow low‐intensity canopy disturbance, which may facilitate habitat diversity and thereby enhance species richness.

Tree Removal Likely Improves Thermal Quality of Basking Sites for an Imperiled Timber Rattlesnake Population at the Northern Edge of Its Range

Lack of natural disturbance in many forests in northeastern North America has resulted in increased canopy cover and a reduction of open-habitat patches. Crotalus horridus (Timber Rattlesnake) in this region depends upon open basking and gestation sites, and its populations have declined markedly. We evaluated the utility of mechanical tree removal to restore potential basking habitat for a highly imperiled Timber Rattlesnake population in New Hampshire. We used a before–after, control–impact study to test for the effects of tree removal on environmental temperature and Timber Rattlesnake and other wildlife use of 3 potential basking sites. Mean temperatures were significantly higher and more variable post-treatment, while minimum temperatures were relatively unaffected. The number of temperature readings within the span of selected body temperatures of gravid female Timber Rattlesnakes (25.2–31.7 °C) increased post-treatment. Using time-lapse cameras, we detected rattlesnakes during 5 days at post-treatment sites but on only 1 day at a control site. Detections of potential rattlesnake prey species did not change following treatment, and few potential rattlesnake predators were detected pre- or post-treatment. Our results suggest that tree removal around potential basking sites likely improves thermal habitat quality for Timber Rattlesnakes.

Evaluating the capacity of single photon lidar for terrain characterization under a range of forest conditions

Accurate digital elevation models are key data products used to inform forest management. Light detection and ranging (lidar) technologies have emerged as a useful tool for acquiring detailed terrain information, although the accuracy of this data is known to vary with topographic complexity and the density and characteristics of overlying vegetation. Single Photon Lidar (SPL) provides a high-density point cloud that can be acquired from a much higher altitude than discrete return, small-footprint lidar (hereafter, linear-mode lidar or LML), providing efficiencies and potential cost savings for operational mapping programs. Herein, we assess the absolute and relative accuracies of leaf-on and leaf-off SPL data acquired at different altitudes for characterizing terrain under varying vegetation types and densities and compare to results for LML data. Our assessment was forest-focused and primarily point based, using 299 Real-Time Kinematic survey checkpoints to quantify elevation errors (Δh); however, we also investigated and reported accuracy for linear transects, and conducted a wall-to-wall comparison of the SPL-derived 1-m digital elevation models (DEMs) against an LML-derived DEM. Point cloud characteristics for the leaf-on 2018 SPL data were markedly different, with 88% of returns as first returns, compared to 17% for the LML, and 59% and 46% for the leaf-off SPL data acquired at 3800 m and 2000 m, respectively. Of the datasets considered herein, the SPL data acquired under leaf-on conditions in 2018 had the lowest accuracy and precision for characterizing terrain underneath vegetation cover, with an RMSE of 10.97 cm and a 95th quantile of 24.03 cm; however these values are within commonly accepted error limits for elevation products. The leaf-off SPL data were most accurate overall; however, the differences between the leaf-off SPL data acquired at 3800 m versus 2000 m were often minor (< 1 cm on average), with similar patterns in Δh between the two datasets (r = 0.8). In terms of the relative performance of the lidar datasets examined, results from the analyses of linear transects were similar to those of the checkpoints, but highlighted the variability in elevation accuracy within similar cover types. Wall-to-wall comparisons of the SPL-derived DEMs to the 2012 LML DEM also corroborated the results of the checkpoint assessment, with the 2018 SPL leaf-on DEM having the largest differences (mean difference = 7.44 cm; RMSD = 18.07 cm). Differences between DEMs did not trend consistently with increasing canopy cover or with the percentage of returns that were within ±15 cm of the ground surface. We found that it was not only the density of the vegetation, but also the composition and configuration of both the overstory and understory vegetation that influenced the accuracy with which the lidar characterized the terrain surface. Overall, our results indicated that leaf-on SPL is capable of capturing terrain information under a wide variety of forest and vegetation conditions, albeit at a lower accuracy than what is possible with leaf-on LML or leaf-off SPL, but at a level of accuracy that is within acceptable limits for most forest applications.

Wolf predation risk and moose movement in eastern Finland

Grey wolf Canis lupus is often the main predator of moose Alces alces. Therefore it can be expected that moose are able to recognize the presence of wolves and react to them to avoid predation. We examined the effect of predation risk by wolves on movement patterns by moose in eastern Finland where moose and wolves have co‐existed for centuries. The level of wolf predation risk experienced by 20 radio‐collared adult moose was classified according to the proportion of their fixes in wolf territories. Our results suggest that moose adjust their movement speed according to the degree they are exposed to the presence of wolves. The adjustment occurred in summer but not in winter. In summer the moose more exposed to wolves moved faster than the moose less exposed to wolves. Season and the structure of the surrounding forests also affected moose movement patterns. Both movement speed and the linearity of movement decreased in winter and with increasing canopy cover. We suggest that by increased moving when exposed to higher risk of predation moose try to keep distance to the predator and/or try to keep themselves spatially and temporally unpredictable to their predator. Our results differ from those obtained in Scandinavia where no response of moose movement to predation risk by wolves has been detected. It might be that wolves' continuous presence in eastern Finland compared to Scandinavia provide a reason why moose in our study area reacted to the presence of wolves.

Disentangling the multiple effects of stream drying and riparian canopy cover on the trophic ecology of a highly threatened fish

Abstract Understanding risks to aquatic systems posed by changing drought regimes is particularly important for the conservation of already threatened taxa. However, little is known about how local environmental conditions, especially those in heavily human‐influenced situations, interact with regional shifts such as droughts to alter realised impacts on aquatic communities, including threatened top predators. Here, we investigated the combined effects of stream drying intensity and riparian canopy cover on the trophic interactions of critically endangered kōwaro, or Canterbury mudfish (Neochanna burrowsius) in an agricultural area of New Zealand. Fish populations and their potential prey, both terrestrial and aquatic, as well as environmental variables, including riparian canopy cover and drying measured with stage loggers, were sampled over eight visits to 24 sites spanning orthogonal drying and canopy gradients. Stable isotope ratios, 13C/12C and 15N/14N, were used to investigate trophic links between mudfish and their terrestrial and aquatic prey across these gradients. When non‐native willows (predominantly Salix fragilis) dominated the riparian canopy, increased tree cover led to elevated drying intensity, probably driven by their relatively high water demands compared to other trees. However, in the absence of willows, canopy cover had no effect on drying intensity. Although this was the only direct link between these two environmental factors, they had opposing effects on kōwaro populations, which will be important for management under drought. Increased drying intensity contributed to elevated abundance of microcrustacea and aquatic Diptera larvae, and an increase in the relative abundance of kōwaro juveniles. However, drying‐affected kōwaro populations also had fewer large reproductive adults and elevated δ15N values, probably driven by physiological limitations and an increase in kōwaro cannibalism, respectively. By comparison, increased canopy cover enhanced input of terrestrial invertebrates, a food resource for larger kōwaro, leading to elevated kōwaro δ13C values, no effects on δ15N values, and higher relative abundance of large kōwaro in shaded streams compared to unshaded streams. Thus, the riparian canopy cover was able to offset some of the effects of drying. Overall, we found no interactions between drying intensity and canopy cover affecting kōwaro. However, their opposing effect highlights the important role local conditions such as riparian canopies play on aquatic communities and their potential role as a restoration tool to mitigate the effects of large‐scale shifts such as drought.

The Best Urban Trees for Daytime Cooling Leave Nights Slightly Warmer

Summer air temperatures will continue to rise in metropolitan regions due to climate change and urbanization, intensifying daytime and nighttime air temperatures and result in greater thermal discomfort for city dwellers. Urban heat may be reduced by trees which provide shade, decreasing air and surface temperatures underneath their canopies. We asked whether tree height and canopy density can help to identify species that provide greater microclimate benefits during day and night. We also asked if increased canopy cover of street trees provides similar microclimate benefits. We used continuous measurements of near-surface air temperatures under 36 park trees and from two urban streets to assess these questions. In the park, trees were grouped according to their height (&lt;10 m, 10–20 m, &gt;20 m) and canopy density (low, high), while the effect of canopy cover was tested using streets with high (31%) and low (11%) cover. Daytime near-surface air temperature declined with increasing height and canopy density providing significant cooling benefits. However, this trend was reversed at night when tall trees with dense canopies restricted longwave radiative cooling and trapped warm air beneath their crowns. High canopy cover of street trees reduced daytime air temperatures more, resulting in a lower number of days with hot (&gt;35 °C) and extreme (&gt;40 °C) air temperatures compared to the street that had low canopy cover. These findings suggest that tree species and streetscapes with dense canopy cover improve local thermal conditions during the day but do not seem ideal to allow for nighttime cooling, creating potential discomfort for residents during hot summer nights. Our results indicate that classifying trees using a simple metric can assist in selecting tree species that can alleviate the local negative effect of urban heat during the day, but at the same time, their effect in preventing optimal longwave radiative cooling during the night must be factored into planting strategies.

Infiltration-Friendly Agroforestry Land Uses on Volcanic Slopes in the Rejoso Watershed, East Java, Indonesia

Forest conversion to agriculture can induce the loss of hydrologic functions linked to infiltration. Infiltration-friendly agroforestry land uses minimize this loss. Our assessment of forest-derived land uses in the Rejoso Watershed on the slopes of the Bromo volcano in East Java (Indonesia) focused on two zones, upstream (above 800 m a.s.l.; Andisols) and midstream (400–800 m a.s.l.; Inceptisols) of the Rejoso River, feeding aquifers that support lowland rice areas and drinking water supply to nearby cities. We quantified throughfall, infiltration, and erosion in three replications per land use category, with 6–13% of rainfall with intensities of 51–100 mm day−1. Throughfall varied from 65 to 100%, with a zone-dependent intercept but common 3% increase in canopy retention per 10% increase in canopy cover. In the upstream watershed, a tree canopy cover &gt; 55% was associated with the infiltration rates needed, as soil erosion per unit overland flow was high. Midstream, only a tree canopy cover of &gt; 80% qualified as “infiltration-friendly” land use, due to higher rainfall in this zone, but erosion rates were relatively low for a tree canopy cover in the range of 20–80%. The tree canopy characteristics required for infiltration-friendly land use clearly vary over short distances with soil type and rainfall intensity.

Area is the primary correlate of annual and seasonal patterns of avian species richness in urban green spaces

Urban green spaces (UGS) often support diverse bird assemblages. Current evidence suggests large UGS that are circular in shape and contain abundant tree canopy cover will support more bird species independent of UGS isolation. Here, we use bird occurrence information from the eBird citizen-science database over an 18-year period (2002–2019) to estimate annual and seasonal patterns of avian species richness in well-surveyed New York City green spaces. Area was the strongest correlate of annual (n = 102 UGS) and seasonal species richness (n = 43 UGS), whereas shape and isolation lacked significant relationships. Increasing area by 50% resulted in an 11.5% increase in annual and an 8.2% increase in seasonal species richness. There was no evidence that these relationships contained an upper limit. Tree canopy cover was weakly correlated with annual species richness. The richness of nocturnally migrating species was strongly correlated with area in the spring and autumn, especially for non-passerine species. The species richness of nocturnally migrating passerines was strongly correlated with tree canopy cover in the spring, where a 50% increase in canopy cover resulted in a 23.3% increase in species richness. Our findings emphasize the broad importance of area, the value of tree canopy cover for spring migrants, and the limited relevance of shape and isolation. Efforts to enhance area and tree canopy cover will increase the number of resident and migratory bird species, which will likely increase the number of other area-sensitive forest taxa that occur in urban environments.

Forest regrowth reduces richness and abundance of invasive alien plant species in community managed Shorea robusta forests of central Nepal

BackgroundNatural forests are generally considered to be less prone to biological invasions than other modified ecosystems, particularly when canopy cover is high. Few decades of management of degraded forests by local communities in Nepal has increased canopy cover and altered disturbance regimes. These changes might have reduced the abundance of invasive alien plant species (IAPS) in forests. To understand the status of IAPS in such forests, we studied two community managed Shorea robusta forests (Sundari and Dhusheri) of Nawalpur district in central Nepal. In these two forests, vegetation sampling was done using circular plots 10 m radius at forest edge, gaps, and within canopy. Variation of IAPS richness and cover across these microhabitats were compared, and their variation with tree canopy cover and basal area analyzed.ResultAltogether 14 IAPS were recorded in the study forests; among them Chromolaena odorata, Ageratum houstonianum, and Lantana camara had the highest frequency. Mikania micrantha was at the early stage of colonization in Sundari Community Forest (CF) but absent in Dhuseri CF. Both IAPS cover and richness was higher at forest edge and gap than in canopy plots and both these attributes declined with increasing canopy cover and tree basal area.ConclusionThe results indicate that increase in canopy cover and closure of forest gaps through participatory management of degraded forests can prevent plant invasions and suppress the growth of previously established IAPS in Shorea robusta forests of Nepal. This is the unacknowledged benefit of participatory forest management in Nepal.

Canopy cover and land-use change in Torbay from 2010 to 2018

ABSTRACT Assessing urban forests and land-use by analysing tree canopy cover is a common facet of modern urban forestry. In the UK, however, there are only a very limited number of studies that have assessed canopy cover changes over time. Torbay in Devon was previously assessed for its canopy cover in 2010. Our study carried out a paired-point analysis to assess the canopy cover changes across Torbay that had occurred between 2010 and 2018. From our analysis, canopy cover in Torbay did not significantly change over this time period, whereas there was a significant increase in impervious land-cover and a significant decrease in agricultural land cover. Built land-uses exhibited static or declining canopy cover; woodland and agricultural land saw slightly increased canopy cover. The most substantial land-use transition over this period was from agricultural to residential usage at the peri-urban fringe. Canopy gains in Torbay were driven by the growth of previous tree cover rather than from new tree planting, which gives rise to concern for the future of this district. These findings highlight the need for an overall strategy of tree protection and urban forest planning to maintain or enhance canopy cover when new residential areas are being developed.

Rethinking global carbon storage potential of trees. A comment on Bastin et al. (2019)

Bastin et al. 2019 use two flawed assumptions: 1) that the area suitable for restoration does not contain any carbon currently, and 2) that soil organic carbon (SOC) from increased canopy cover will accumulate quickly enough to mitigate anthropogenic carbon emissions. We re-evaluated the potential carbon storage worldwide using empirical relationships of tree cover and carbon. We use global datasets of tree cover, soil organic carbon, and above ground biomass to estimate the empirical relationships of tree cover and carbon stock storage. A more realistic range of global carbon storage potential is between 71.7 and 75.7 GtC globally, with a large uncertainty associated with SOC. This is less than half of the original 205 GtC estimate. The potential global carbon storage of restored forests is much less than that estimated by Bastin et al. 2019. While we agree on the value of assessing global reforestation potential, we suggest caution in considering it the most effective strategy to mitigate anthropogenic emissions. A preprint version of this article was published on 13 August 2019 at https://doi.org/10.1101/730325

Leaf mass area determines water use efficiency through its influence on carbon gain in rice mutants.

Saving water and enhancing rice productivity are consensually the most important research goals globally. While increasing canopy cover would enhance growth rates by higher photosynthetic carbon gain, an accompanied increase in transpiration would have a negative impact on saving water as well as for sustainability under water-limited conditions. Increased water use efficiency (WUE) by virtue of higher carbon assimilatory capacity can significantly circumvent this trade-off. Here, we report leaf mass area (LMA) has an important canopy architecture trait which when combined with superior carboxylation efficiency (CE) would achieve higher water productivity in rice. A set of 130 ethyl methanesulfonate induced mutants of an upland cultivar Nagina-22 (N22), was screened for leaf morphological traits leading to the identification of mutants differing in LMA. The wild-type, N22, along with a selected low-LMA (380-4-3) and two high-LMA mutants (392-9-1 and 457-1-3), all with comparable total leaf area, were raised under well-watered (100% Field Capacity (FC)) and water-limited (60% FC) conditions. Low Δ13 C and a higher RuBisCO content in high-LMA mutants indicated higher carboxylation efficiency, leading to increased carbon gain. Single parent backcross populations developed by crossing high and the low-LMA mutants with N22, separately, were screened for LMA, Δ13 C and growth traits. Comparison of dry matter accumulation per unit leaf area among the progenies differing in LMA and Δ13 C reiterated the association of LMA with CE. Results illustrated that high-LMA when combined with higher CE (low Δ13 C) lead to increased WUE and growth rates.