Overstory Canopy Research Articles

Below-canopy contributions to ecosystem CO2 fluxes in a temperate mixed forest in Switzerland

Forests are structurally complex ecosystems with several canopy layers, each with distinct functional properties contributing differently to the net ecosystem CO2 exchange. A large number of studies have addressed ecosystem-scale net CO2 fluxes in forests, but only few studies have investigated the role of the forest understory. The goal of this study was to quantify the below-canopy contribution to ecosystem CO2 fluxes of a mixed deciduous forest in Switzerland. Below- and above-canopy eddy-covariance (EC) measurements were made continuously over two years, complemented by within canopy wind and CO2 concentration profile measurements.On an annual basis, the below-canopy fluxes indicated a net carbon source dominated by soil respiration, while the above-canopy fluxes were dominated by tree photosynthesis leading to a net carbon sink. Below-canopy fluxes showed a net carbon sink only in spring, with the early emergence of understory plants before overstory canopy leaf-out. Below-canopy respiration partitioned from the EC measurements agreed well with previous chamber-based soil respiration measurements. However, below- and above-canopy fluxes became decoupled under full canopy closure, thus leading to unaccounted below-canopy fluxes when measured only above the canopy. Wind and CO2 concentration profile measurements supported this finding. Decoupling was independent of low turbulence conditions and decoupled periods could be identified using the relationship between the below- and above-canopy standard deviation in vertical wind velocity. A decoupling correction was applied to the above-canopy measurements during decoupled periods and corrected annual net ecosystem production (NEP) agreed well with independent estimates from biomass inventory combined with models. Overall, the below-canopy fluxes contributed 79% to annual ecosystem respiration, but only 9% to annual ecosystem photosynthesis. The decoupling correction reduced annual NEP for the site from about 760 to 330gCm−2yr−1. Our results showed that below-canopy EC measurements are essential in this mixed deciduous forest, and likely in many other forests, to fully understand the carbon dynamics within structurally complex ecosystems.

Forest Structure and Composition Affect Bats in a Tropical Evergreen Broadleaf Forest

The lack of knowledge regarding many aerial insectivorous bats and their relationships with forest characteristics limits conservation decision-making for tropical rainforests and for this important bat group. Therefore, our objective was to understand the effects of forest structure and composition on these bats in the Neotropical evergreen broadleaf forest of Belize, Central America. We conducted bat monitoring and quantified 51 forest characteristics at 24 locations in the Chiquibul Forest Reserve (CFR) from May–July 2014. Simple linear and backward stepwise multiple regression analyses were used to examine relationships between bat richness and activity and forest characteristics. Bat genus richness and total activity were directly related to overstory canopy depth and inversely related to ≤4 structural characteristics. Lasiurus, Myotis, Promops, and Pteronotus spp. were affected by ≤7 forest characteristics; the responses were explained by preferences for less-cluttered, open space for flying and foraging and species-specific food and cover requirements. However, bat richness and activity were often unaffected by forest structure and composition in the CFR, suggesting that at this taxonomic level, bats may not be very sensitive to variation in forest characteristics, may not be very useful indicators of alteration, and may have some tolerance for disturbance and change.

Response of ground-dwelling harvestman assemblages (Arachnida: Opiliones) to European beech forest canopy cover

We studied the effects of the overstory canopy cover on ground-dwelling harvestmen communities in European beech forests in the Western Carpathian Mts. We analyzed the differences in species richness, abundance and composition in two tree canopy cover categories (closed and open canopy). Overall, 1765 individuals belonging to 16 species were caught using pitfall traps. Repeated-measures ANOVA revealed that under both closed and open canopies a similar absolute and rarefied species richness and number of individuals (standardized to 100 pitfall trap days) were caught, and that both species richness and abundance were affected by the season (i.e., time of trap replacement); yet the total number of individuals trapped was more than two times greater under the open canopy than under the closed canopy. Despite the subtle differences in the taxonomic composition of the catches under the open and closed canopies revealed by DCA followed by RDA, the composition of ground-dwelling harvestmen assemblages differed under the two canopy covers. The open canopy was more suitable for heliophilic, xerothermic eurytopic harvestmen species typical for open and ecotonal habitats, such as Egaenus convexus (C.L. Koch) and Oligolophus tridens (C.L. Koch) but still suitable for hemihygrophilic Lophopilio palpinalis (Herbst). The closed canopy stands were preferred by shade-tolerant, hygrophilic eurytopic harvestmen species, such as Trogulus sp. Latreille, Dicranolasma scabrum (Herbst) and Platybunus bucephalus (C.L. Koch). Our results highlight the importance of intra-habitat heterogeneity of a harvestmen community.

Spatial Heterogeneity of the Forest Canopy Scales with the Heterogeneity of an Understory Shrub Based on Fractal Analysis

Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L.) Nutt.) as a focal species. Evergreen and deciduous forest canopy and buffaloberry shrub presence were measured with line-intercept sampling along ten 2-km transects in the Rocky Mountain foothills of west-central Alberta, Canada. Relationships between overstory canopy and understory buffaloberry presence were assessed for scales ranging from 2 m to 502 m. Fractal dimensions of both canopy and buffaloberry were estimated and then related using box-counting methods to evaluate spatial heterogeneity based on patch distribution and abundance. Effects of canopy presence on buffaloberry were scale-dependent, with shrub presence negatively related to evergreen canopy cover and positively related to deciduous cover. The effect of evergreen canopy was significant at a local scale between 2 m and 42 m, while that of deciduous canopy was significant at a meso-scale between 150 m and 358 m. Fractal analysis indicated that buffaloberry heterogeneity positively scaled with evergreen canopy heterogeneity, but was unrelated to that of deciduous canopy. This study demonstrates that evergreen canopy cover is a determinant of buffaloberry heterogeneity, highlighting the importance of spatial scale and canopy composition in understanding canopy-understory relationships.

Assessing the impacts of canopy openness and flight parameters on detecting a sub-canopy tropical invasive plant using a small unmanned aerial system

Small unmanned aerial systems (sUAS) have great potential to facilitate the early detection and management of invasive plants. Here we show how very high-resolution optical imagery, collected from small consumer-grade multirotor UAS platform at altitudes of 30–120m above ground level (agl), can be used to detect individual miconia (Miconia calvescens) plants in a highly invaded tropical rainforest environment on the island of Hawai‘i. The central aim of this research was to determine how overstory vegetation cover, imagery resolution, and camera look-angle impact the aerial detection of known individual miconia plants. For our finest resolution imagery (1.37cm ground sampling distance collected at 30m agl), we obtained a 100% detection rate for sub-canopy plants with above-crown openness values >40% and a 69% detection rate for those with >20% openness. We were unable to detect any plants with <10% above crown openness. Detection rates progressively declined with coarser spatial resolution imagery, ending in a 0% detection rate for the 120m agl flights (ground sampling distance of 5.31cm). The addition of forward-looking oblique imagery improved detection rates for plants below overstory vegetation, though this effect decreased with increasing flight altitude. While dense overstory canopy cover, limited flight times, and visual line of sight regulations present formidable obstacles for detecting miconia and other invasive plant species, we show that sUAS platforms carrying optical sensors can be an effective component of an integrated management plan within challenging subcanopy forest environments.

Understory vegetation dynamics 15 years post-thinning in 50-year-old Douglas-fir and Douglas-fir/western hemlock stands in western Oregon, USA

Recent trends in forest management practices designed to restore or enhance late-successional structure for habitat values typically include provisions for the creation and maintenance of structural and compositional diversity within and among stands. The Pacific Northwest in particular has expanses of young, structurally simple forests that range from high stocking (unthinned and little understory development) to relatively lower stocking having been previously thinned or initially regenerated at low densities. We have remeasured two long-term study sites in Oregon, USA, for 15years to examine structural development and understory persistence at a range of overstory canopy cover, spatial arrangement, and understory treatments (spraying and planting). Understory responses to thinning varied primarily by site and species group, given the range of pre-existing plant communities, and through time. In general, shrub cover increased after thinning, while forb cover increased initially after thinning and then declined. Though spraying effects were still visible 15years after treatment driven by reductions in one dominant understory species, it had little effect on the long-term development of structure at these overstory densities. Indeed, the range of overstory densities and spatial arrangements in this study did not have any large effects because all of the thinning treatments resulted in increased light availability to the understory at least through fifteen years after thinning. Combining more extensive overstory removal and understory treatments likely can be used to stimulate heterogeneous structure and composition development in these forests, including the possible stimulation of persistent early-seral vegetation within older stands.

Quantifying insect-related forest mortality with the remote sensing of snow

Greenhouse gas emissions have altered global climate significantly, increasing the frequency of drought, fire, and insect- and pathogen-related mortality in forests across the western United States. The accuracy of satellite-based estimates of canopy change has been limited by difficulties associated with discriminating overstory canopy from understory vegetation. To overcome this issue, we developed a method to quantify forest canopy cover using winter-season fractional snow covered area (FSCA) data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) snow covered area and grain size (MODSCAG) algorithm. The method utilizes time series of FSCA data to identify images with continuous ground snow coverage and a snow-free overstory, effectively masking out the influence of understory vegetation. Using this method, we determined that MODSCAG-retrieved viewable gap fraction (VGF; i.e. fraction of pixel sub-canopy viewable area) was significantly correlated with an independent product of yearly crown mortality caused by mountain pine beetles derived from Landsat imagery at 25 high-mortality sites in northern Colorado (r−=0.96±0.03,p<0.03). Additionally, we determined the temporal lag between tree mortality and needlefall, showing that needlefall occurred an average of 2.6±1.2years after year of attack. The canopy change detection method described herein is the first to utilize snow cover to mask understory impacts on overstory detection. The method can be applied anywhere in the seasonal snow zone and therefore has wide applicability given that 30% of the global land surface is seasonally snow covered. In this regard, the approach addresses significant limitations of previously published methods of canopy change detection and has broad implications with regard to understanding forest mortality and the representation of disturbance within hydrologic, land surface, and climate models.

Breeding birds in managed forests on public conservation lands in the Mississippi Alluvial Valley

Managers of public conservation lands in the Mississippi Alluvial Valley have implemented forest management strategies to improve bottomland hardwood habitat for target wildlife species. Through implementation of various silvicultural practices, forest managers have sought to attain forest structural conditions (e.g.,canopy cover, basal area, etc.) within values postulated to benefit wildlife. We evaluated data from point count surveys of breeding birds on 180 silviculturally treated stands (1049 counts) that ranged from 1 to 20yearspost-treatment and 134 control stands (676 counts) that had not been harvested for >20years. Birds detected during 10-min counts were recorded within four distance classes and three time intervals. Avian diversity was greater on treated stands than on unharvested stands. Of 42 commonly detected species, six species including Prothonotary Warbler (Prothonotaria citrea) and Acadian Flycatcher (Empidonax virescens) were indicative of control stands. Similarly, six species including Indigo Bunting (Passerina cyanea) and Yellow-breasted Chat (Icteria virens) were indicative of treated stands. Using a removal model to assess probability of detection, we evaluated occupancy of bottomland forests at two spatial scales (stands and points within occupied stands). Wildlife-forestry treatment improved predictive models of species occupancy for 18 species. We found years post treatment (range=1–20), total basal area, and overstory canopy were important species-specific predictors of occupancy, whereas variability in basal area was not. In addition, we used a removal model to estimate species-specific probability of availability for detection, and a distance model to estimate effective detection radius. We used these two estimated parameters to derive species densities and 95% confidence intervals for treated and unharvested stands. Avian densities differed between treated and control stands for 16 species, but only Common Yellowthroat (Geothlypis trichas) and Yellow-breasted Chat had greater densities on treated stands.

Nutritional ecology of elk during summer and autumn in the Pacific Northwest

Nutritional ecology of elk during summer and autumn in the Pacific Northwest

Ecology, distribution, and predictive occurrence modeling of Palmer’s chipmunk (Tamias palmeri): a high-elevation small mammal endemic to the Spring Mountains in southern Nevada, USA

Abstract Although montane sky islands surrounded by desert scrub and shrub steppe comprise a large part of the biological diversity of the Basin and Range Province of southwestern North America, comprehensive ecological and population demographic studies for high-elevation small mammals within these areas are rare. Here, we examine the ecology and population parameters of the Palmer’s chipmunk (Tamias palmeri) in the Spring Mountains of southern Nevada, and present a predictive GIS-based distribution and probability of occurrence model at both home range and geographic spatial scales. Logistic regression analyses and Akaike Information Criterion model selection found variables of forest type, slope, and distance to water sources as predictive of chipmunk occurrence at the geographic scale. At the home range scale, increasing population density, decreasing overstory canopy cover, and decreasing understory canopy cover contributed to increased survival rates.

Riparian overstory–understory interactions and their potential implications for forest-stream linkages

Despite growing recognition that understory vegetation is an essential component of forest ecosystems, research on forest-stream linkages and the management of riparian zones continues to focus on overstory trees. Streamside herbs, grasses and shrubs have the potential to fulfill several functions upon which adjacent stream ecosystems rely, such as providing detritus and prey to aquatic communities. Here we investigated patterns of riparian understory vegetation and the associated invertebrate community along headwater streams in deciduous broadleaf forest managed under traditional silvicultural practices. We studied eleven sites along a large gradient of overstory canopy openness to assess whether and how resource competition with canopy trees limits the growth of riparian understory vegetation and affects the abundance and community composition of understory invertebrates. We found that the height and above ground biomass of understory vegetation increased steadily with decreasing overstory canopy cover, suggesting that the structure of riparian zones is contingent upon antagonistic interactions between overstory and understory plants. We also observed that invertebrate abundance did not track changes in overstory canopy cover and understory plant biomass although some numerically important invertebrate taxa displayed clear preferences to either closed or open-canopy riparian forest. Our findings demonstrate that riparian understory vegetation can achieve fairly high biomass and, therefore, should help maintain inputs of plant litter to aquatic ecosystems in harvested or naturally disturbed riparian forest. Because understory invertebrates may not fully compensate for reduced inputs of canopy invertebrates to streams, retaining trees along streams may still be the most effective management option for headwater streams.

Non-Native Plant Invasion along Elevation and Canopy Closure Gradients in a Middle Rocky Mountain Ecosystem.

Mountain environments are currently among the ecosystems least invaded by non-native species; however, mountains are increasingly under threat of non-native plant invasion. The slow pace of exotic plant invasions in mountain ecosystems is likely due to a combination of low anthropogenic disturbances, low propagule supply, and extreme/steep environmental gradients. The importance of any one of these factors is debated and likely ecosystem dependent. We evaluated the importance of various correlates of plant invasions in the Wallowa Mountain Range of northeastern Oregon and explored whether non-native species distributions differed from native species along an elevation gradient. Vascular plant communities were sampled in summer 2012 along three mountain roads. Transects (n = 20) were evenly stratified by elevation (~70 m intervals) along each road. Vascular plant species abundances and environmental parameters were measured. We used indicator species analysis to identify habitat affinities for non-native species. Plots were ordinated in species space, joint plots and non-parametric multiplicative regression were used to relate species and community variation to environmental variables. Non-native species richness decreased continuously with increasing elevation. In contrast, native species richness displayed a unimodal distribution with maximum richness occurring at mid–elevations. Species composition was strongly related to elevation and canopy openness. Overlays of trait and environmental factors onto non-metric multidimensional ordinations identified the montane-subalpine community transition and over-story canopy closure exceeding 60% as potential barriers to non-native species establishment. Unlike native species, non-native species showed little evidence for high-elevation or closed-canopy specialization. These data suggest that non-native plants currently found in the Wallowa Mountains are dependent on open canopies and disturbance for establishment in low and mid elevations. Current management objectives including restoration to more open canopies in dry Rocky Mountain forests, may increase immigration pressure of non-native plants from lower elevations into the montane and subalpine zones.

Restoration planting options for limber pine (Pinus flexilisJames) in the Southern Rocky Mountains1

Abstract Limber pine Pinus flexilis James populations in the southern Rocky Mountains are threatened by the combined impacts of mountain pine beetles and white pine blister rust. To develop restoration planting methods, six P. flexilis seedling planting trial sites were installed along a geographic gradient from southern Wyoming to southern Colorado. Experimental treatments included: high or low overstory canopy density from existing trees, presence/absence of a nurse object, and presence/absence of hydrogel. Of the P. flexilis seedlings planted, 72% were alive after four growing seasons. There were interactions between nurse object, seedling height at planting, and percent canopy cover that affected the number of healthy seedlings. Denser canopy cover was positively correlated with healthier planted seedlings and hydrogels had no effect. Nurse objects promoted healthier seedlings, particularly when canopy cover was low (0–50% cover), and the specific orientation to the nurse object affected seedling heal...

Spatial arrangement of canopy structure and land‐use history alter the effect that herbivores have on plant growth

The spatial arrangement of past and present human activities could affect the strength of species interactions through changes to environmental conditions. To better understand how land‐use history might mediate the effect of insect herbivory on the growth of four herbaceous plant species at the edges between woodlands and open savannas, we coupled large‐scale manipulations of canopy structure by thinning overstory trees to create savanna habitat in non‐agricultural and post‐agricultural longleaf pine woodlands with local‐scale herbivore exclosures at two distances from habitat edges. Light availability, grasshopper abundance, and herbaceous plant cover all increased in patches that received overstory tree thinning. Land‐use history altered the effect that edges created by the overstory thinning treatments had on grasshopper herbivory for one plant species (Carphephorus bellidifolius). The edge between land‐use histories also altered herbivore effects on three plant species in thinned patches. These edge effects were driven in part by changes in availability of alternative resources for grasshoppers, shady edges, or grasshopper abundance. Canopy manipulation also had important effects on herbivory that were independent of the habitat edge: grasshopper herbivory reduced plant growth of the smallest species (C. bellidifolius) regardless of canopy manipulation, whereas herbivory on two larger species (Solidago nemoralis and So. odora) reduced plant growth mainly in patches with an intact overstory canopy. Collectively, this work suggests that the species‐specific effects of grasshopper herbivory on plant growth were driven by both plant traits (e.g., size or growth rates) and landscape‐mediated changes to grasshopper abundance, light availability, or availability of alternative resources for grasshoppers created by land‐use history and canopy structure. Furthermore, because the heterogeneity in herbivory revealed by our large‐scale experiment is likely linked to plant traits, our results provide a means for understanding the profound, but often idiosyncratic, effects of land‐use legacies and edges on plant populations and communities.

An Analysis of Overstory Tree Canopy Cover in Sites Occupied by Native and Introduced Cottontails in the Northeastern United States with Recommendations for Habitat Management for New England Cottontail.

The New England cottontail (Sylvilagus transitionalis) is a high conservation priority in the Northeastern United States and has been listed as a candidate species under the Endangered Species Act. Loss of early successional habitat is the most common explanation for the decline of the species, which is considered to require habitat with dense low vegetation and limited overstory tree canopy. Federal and state wildlife agencies actively encourage landowners to create this habitat type by clearcutting blocks of forest. However, there are recent indications that the species also occupies sites with moderate overstory tree canopy cover. This is important because many landowners have negative views about clearcutting and are more willing to adopt silvicultural approaches that retain some overstory trees. Furthermore, it is possible that clearcuts with no overstory canopy cover may attract the eastern cottontail (S. floridanus), an introduced species with an expanding range. The objective of our study was to provide guidance for future efforts to create habitat that would be more favorable for New England cottontail than eastern cottontail in areas where the two species are sympatric. We analyzed canopy cover at 336 cottontail locations in five states using maximum entropy modelling and other statistical methods. We found that New England cottontail occupied sites with a mean overstory tree canopy cover of 58% (SE±1.36), and was less likely than eastern cottontail to occupy sites with lower overstory canopy cover and more likely to occupy sites with higher overstory canopy cover. Our findings suggest that silvicultural approaches that retain some overstory canopy cover may be appropriate for creating habitat for New England cottontail. We believe that our results will help inform critical management decisions for the conservation of New England cottontail, and that our methodology can be applied to analyses of habitat use of other critical wildlife species.

The effect of long-term drying associated with experimental drainage and road construction on vegetation composition and productivity in boreal fens

Land-use and climate change are expected to cause drying of vegetation and surface soils in continental boreal peatlands. We examined the effects of multi-decadal drying and drainage on plant community structure and productivity in four fens located in Alberta, Canada. Long-term drying resulted in a two to fourfold increase in total biomass in three of the four fen sites, with a similar large increase in NPP in Treed Fen 1. The treed poor fens consistently had decreased moss cover and productivity with drainage. Across all sites, changes in understory community composition were related to the change in water table position as well as overstory canopy development that occurred post-drainage. Overall, drainage induced a shift toward a drier peatland regime, favoring increased canopy and vascular plant density at the expense of ground-layer mosses or the understory. Within the ground layer communities, drainage favored dry-adapted hummock moss and lichen species over those wet-adapted but dessication-prone species typical of low-lying lawns and hollows. Alteration of fen vegetation due to ecosystem drying will not only influence carbon sequestration but also will increase the vulnerability of peatlands to wildfire, increasing the risk of further ecosystem degradation and possible loss of resilience.

Effects of canopy phenology on deciduous overstory and evergreen understory carbon budgets in a cool‐temperate forest ecosystem under ongoing climate change

AbstractCanopy phenology is a key regulator of carbon cycling in forest ecosystems. To clarify its possible effects on carbon budgets of forest ecosystems under ongoing climate change, we developed a canopy‐phenology model for a forest with deciduous overstory and evergreen understory based on in situ observations, and used it to improve an ecosystem carbon budget model. Under future conditions (2068–2073) based on the IPCC SRES A1B scenario, leaf expansion began 12.5 ± 1.9 days earlier and leaf‐fall ended 11.3 ± 2.7 days later than under current conditions (2002–2007). We also estimated the possible influence of altered light availability on understory vegetation. Even though the photosynthetically active period in the understory (i.e., from the end of spring snowmelt to the beginning of late‐autumn snow cover) expanded by 15.7 ± 15.7 days, the total downward photosynthetic photon flux density above this vegetation during the snow‐free period decreased by 11.8 % because of changing overstory canopy phenology. The net effect of these changes increased ecosystem‐level annual gross primary production (GPP) by 12.5 %, net primary production (NPP) by 12.0 %, and net ecosystem production by 12.1 %, especially in late spring (when the highest solar radiation occurred). The increased GPP and NPP were mostly attributable to changes in overstory vegetation. Our analysis indicates that understanding the temporal variation of canopy phenology dynamics and snow cover is important and that the effects of vegetation phenology on the carbon cycle should be evaluated in future climate change studies.

Photographic assessment of overstory and understory leaf area index in beech forests under different management regimes in Central Italy

Abstract. Forest understory may be strongly affected by silvicultural practices such as thinning, which simultaneously modulates the overstory canopy cover and influences the availability of light. However, the understory layer is rarely considered in management decisions, partly because methods to estimate understory leaf area index are poorly developed. In this study we used two different restricted view angle photographic methods to estimate overstory plant area index LO (zenith cover photography), understory leaf area index LU (nadir cover photography) and their related canopy attributes (foliage clumping, foliage cover, crown cover, crown porosity). These measurements were performed in beech stands under different management regime. Results from photography indicated that not only overstory but also understory canopy attributes were significantly influenced by forest management. In addition, a significant negative correlation was found between LO and LU. We conclude that the photographic methods are effective for monitoring (overstory and understory) canopy status in managed stands, on account of their rapid and not destructive procedures, which allows large scale implementation of the methods.

Application of MODIS snow cover products: wildfire impacts on snow and melt in the Sierra Nevada

Abstract. The current work evaluates the spatial and temporal variability in snow after a large forest fire in northern California using Moderate Resolution Imaging Spectroradiometer (MODIS) snow-covered area and grain size (MODSCAG). MODIS MOD10A1 fractional snow-covered area and MODSCAG fractional snow cover products are utilized to detect spatial and temporal changes in snowpack after the 2007 Moonlight Fire and an unburned basin, Grizzly Ridge, for water years (WY) 2002–2012. Estimates of canopy-adjusted and non-adjusted MODSCAG fractional snow-covered area (fSCA) are smoothed and interpolated to provide a continuous time series of average daily snow extent over the two basins. The removal of overstory canopy by wildfire exposes more snow cover; however, elemental pixel comparisons and statistical analysis show that the MOD10A1 product has a tendency to overestimate snow coverage pre-fire, muting the observed effects of wildfire. The MODSCAG algorithm better distinguishes subpixel snow coverage in forested areas and is highly correlated to soil burn severity after the fire. Annual MODSCAG fSCA estimates show statistically significant increased fSCA in the Moonlight Fire study area after the fire (P &lt; 0.01 for WY 2008–2011) compared to pre-fire averages and the control basin. After the fire, the number of days exceeding a pre-fire high snow-cover threshold increased by 81%. Canopy reduction increases exposed viewable snow area and the amount of solar radiation that reaches the snowpack, leading to earlier basin average melt-out dates compared to the nearby unburned basin. There is also a significant increase in MODSCAG fSCA post-fire regardless of slope or burn severity. Regional snow cover change has significant implications for both short- and long-term water supply for impacted ecosystems, downstream communities, and resource managers.

Natural regeneration of trees in three types of afforested stands in the Taihang Mountains, China.

Natural regeneration is the natural process by which plants replace themselves. It is a cost-effective way to re-establish vegetation, and it helps to preserve genetic identity and diversity. In this study, we investigated the natural regeneration of trees in three types of afforested stands in the Taihang Mountains, China, which were dominated by Robinia pseudoacacia (black locust), Quercus variabilis (Chinese cork oak) and Platycladus orientalis (Chinese arborvitae) respectively. A consistent pattern was found among the three types of stands, being that the density of seedlings was positively correlated with the overstory canopy cover and negatively correlated with the covers of shrub, herb and litter layers. While a positive correlation between the density of seedlings and stand age was found for the conifer stands, negative correlations were found for the two types of broadleaf stands. Correlations between the density of saplings and the stand attributes were not consistent among the three types of stands. The two types of broadleaf stands had higher densities of seedlings and saplings than the conifer stands. While the broadleaf stands had adequate recruits for regeneration, the conifer stands did not have enough recruits. Our findings suggest that the overstory canopy should be prevented from being disturbed, any reduction of the canopy cover will decrease the recruits and affect the regeneration.