Understory Vegetation Cover Research Articles

Leaf traits-mediated effects of tree diversity on insect herbivory on Populus laurifolia in a riparian forest ecosystem

Tree diversity and landscape features have long been considered as the main drivers of insect herbivory in forest ecosystems. However, relatively little is known about how local and landscape factors, directly and indirectly, acting at different spatial scales affect insect damage under natural, non-outbreak conditions. Here, 30 mixed and pure forest stands were selected in natural forests along the Irtysh river in Xinjiang, Northwest China. To assess the effects of landscape-scale forest isolation, tree diversity, stand position, tree size, understory vegetation cover, and leaf traits on leaf herbivory on Populus laurifolia, we measured three leaf traits (i.e., leaf area, specific leaf area, and leaf dry matter content) and defoliation intensity of insect herbivores in host poplars in 30 sampling plots within mixed and pure forest stands. We also explored the indirect effects of tree diversity on insect herbivory via changes in leaf traits. We found that both forest isolation and tree height had positive effects on insect herbivory, but vegetation cover negatively affected it. Insect herbivory was lower in mixed than in pure forest stands, however, this difference was only significant in stands at the near distance from the river. All leaf traits differed significantly between mixed and pure stands, and varied with tree height. In addition, insect herbivory was positively correlated with leaf area and specific leaf area. However, the influence of tree diversity and tree size on insect herbivory mainly act indirectly through changes in leaf area and specific leaf area. Our results indicate that insect herbivory can be driven by a complex system of ecological factors at multiple scales, and offer an insight into the key role of leaf traits in driving tree diversity-herbivory interactions in a natural forest ecosystem. Thus, these findings are crucial to improve risk assessment and potential prevention strategies of insect damage in riparian forests in real-world situations.

Competitive ability of natural Douglas fir regeneration in central European close-to-nature forests

Douglas fir (Pseudotsuga menziesii) has regenerated naturally in European forests since the middle of the 20th century. Some cases of an invasive character of the species have been reported under specific site conditions, but systematic data on the extent of natural regeneration and spread of Douglas fir across different forest communities are largely lacking. Due to its potential tolerance to increasing summer droughts, Douglas fir has been suggested as a sustainable future tree species for Central European forests. In this study, we investigated natural regeneration of Douglas fir in comparison to native tree species in 39 forest stands in Switzerland belonging to different forest communities. We analyzed the regeneration success of Douglas fir, Norway spruce (Picea abies), silver fir (Abies alba), and European beech (Fagus sylvatica) with respect to ecological site conditions. The proportion of Douglas fir seedlings (<130 cm height) was <5% in the majority of stands; but in four stands, Douglas fir was the most abundant species among seedlings. In most other stands, Norway spruce (occurring in 37 stands/dominant in 10 stands), silver fir (38/2 stands) and beech seedlings (35/10 stands) were more abundant than Douglas fir seedlings. Saplings (≥130 cm height but <12 cm diameter at breast height) of Douglas fir were observed in five stands with proportions between 10% and 23% and in eight stands with proportions of <10%, in particular in stands with a high proportion of Douglas fir seed trees. Beech saplings occurred in 28 stands and were most abundant in eleven stands. Saplings of silver fir (24/3 stands) and Norway spruce (19/6 stands) were less frequent. The abundance of Douglas fir seedlings correlated positively with the proximity to seed trees and light transmission of the canopy, but negatively with understory vegetation cover and litter abundance. Ungulate browsing did not significantly affect the regeneration of any tree species in the study stands. On the Central Plateau, Douglas fir was mainly planted in productive beech forest communities where it is strongly limited due to its low competitiveness compared to beech and other fast-growing deciduous tree species. On dry and less productive sites, where the canopy is not closed, Douglas fir is able to establish successfully. On such sites, a close monitoring of Douglas fir regeneration and the potential implementation of control measures is recommended.

Comment mettre la génomique forestière et la génomique de la conservation au service des communautés autochtones?

Les projets d’aménagement durable et de conservation (ADC) des ressources naturelles en collaboration avec les peuples autochtones ayant recours à une approche en génomique sont en émergence. Les informations et applications issues de la génomique peuvent leur être utiles particulièrement dans un contexte de changements climatiques. Toutefois, le défi de transposer ces applications dans la pratique et de les mettre au service des communautés demeure. Nous présentons ici une revue de littérature exploratoire qui aborde (1) les utilités démontrées de la génomique dans les projets d’ADC impliquant les peuples autochtones, (2) certains enjeux qui peuvent limiter l’adoption des applications de la génomique et (3) le travail collaboratif entre chercheurs et communautés autochtones dans les études analysées. Les utilités démontrées identifiées ont été essentiellement de nature socioécologique. La nature complémentaire des savoirs autochtones et des savoirs scientifiques en génomique a été reconnue comme une opportunité qui devrait être développée davantage pour relever les défis actuels, tels que les changements climatiques. En ce qui concerne l’adoption de cette technologie en ADC dans la pratique, en plus de faire face à des enjeux similaires à d’autres utilisateurs finaux, l’intégration des besoins, des valeurs traditionnelles et des connaissances des communautés autochtones dans les projets de génomique représente également un défi dans un contexte de décolonisation de la recherche en génomique. Finalement, la collaboration communauté-chercheur a été identifiée comme un élément clé pour favoriser la réussite de la transposition de la génomique en ADC.

Twenty-six years of aspen regeneration under varying light conditions in a boreal mixedwood forest

Density, height, and diameter at breast height of trembling aspen (Populus tremuloides Michx.) sucker regeneration were assessed over a 26-year period in openings created by harvesting in a 40-year-old aspen stand in northeastern Ontario (Canada). The opening types were 9- and 18-m diameter circles, 9- and 18- _ 150-m east-west strips, and a 100- _ 150-m clearcut, representing a range of light conditions. Density, height, and diameter at breast height of aspen regeneration were significantly affected by opening type, location relative to opening, and time since harvest. By year 26, aspen densities in circular openings declined to 0, despite high initial recruitment, and trembling aspen heights were significantly lower in the 9-m strips than in the 18-m strips or the clearcut. Year 26 aspen density, volume, and basal area increased with increasing initial light intensity, with the highest rate of increase between 80 and 100% light levels. Understory vegetation cover was largely unaffected by opening size; however, substantial understory aspen regeneration occurred in the smaller openings. Results support the traditional view that aspen is best managed under the clearcut silvicultural system, and &gt;80% full light is recommended for adequate long-term aspen regeneration.

Spatial and temporal variation of epigaeic beetle assemblages (Coleoptera, Carabidae, Staphylinidae) in aspen-dominated mixedwood forests across north-central Alberta.

Epigaeic beetle assemblages were surveyed using continuous pitfall trapping during the summers of 1992 and 1993 in six widely geographically distributed locations in Alberta’s aspen-mixedwood forests prior to initial forest harvest. Species composition and turnover (β-diversity) were evaluated on several spatial scales ranging from Natural Regions (distance between samples 120–420 km) to pitfall traps (40–60 m). A total of 19,885 ground beetles (Carabidae) representing 40 species and 12,669 rove beetles (non-AleocharinaeStaphylinidae) representing 78 species was collected. Beetle catch, species richness, and diversity differed significantly among the six locations, as did the identity of dominant species. Beetle species composition differed significantly between the Boreal Forest and Foothills Natural Regions for both taxa. Staphylinidae β-diversity differed significantly between Natural Regions, whereas Carabidae β-diversity differed among locations. Climate variables such as number of frost-free days, dry periods, and mean summer temperatures were identified as significant factors influencing beetle assemblages at coarse spatial scales, whereas over- and understory vegetation cover, litter depth, shade, slope, and stand age influenced beetle assemblages at finer spatial scales. Significant interannual variation in assemblage structure was noted for both taxa. Because composition of epigaeic beetle assemblages differed across spatial scales, forest management strategies based only on generalized understanding of a single location will be ineffective as conservation measures. In addition, site history and geographic variation significantly affect species distributions of these two beetle families across the landscape. Thus, we underscore Terry Erwin’s suggestion that biodiversity assessments focused on species assemblages at different spatial scales provide a sound approach for understanding biodiversity change and enhancing conservation of arthropod biodiversity.

Coffee pulp accelerates early tropical forest succession on old fields

Abstract Applying nutrient‐rich agricultural by‐products, such as fruit peels and pulp, to degraded land has been proposed as a strategy to overcome a number of barriers to tropical forest recovery. While such linkages between agroindustry and restoration represent win–win scenarios, practical applications remain largely unexplored. In this case study, we tested coffee pulp as an amendment to catalyze forest succession on post‐agricultural land in southern Costa Rica. A 0.5‐m‐deep layer of coffee pulp was deposited across a 35 × 40‐m area and an adjacent similar‐sized control plot (no coffee pulp addition) was delineated. Over 2 years, we measured changes in soil nutrients, ground cover, understory vegetation, tree establishment and canopy cover across both coffee pulp and control treatments. Our results show that soil carbon, nitrogen, and phosphorous were substantially elevated in the coffee pulp compared to control treatment after 2 years. Coffee pulp addition significantly altered the ground cover characteristics, eliminating pasture grasses, facilitating establishment of herbaceous plants and increasing the percent area covered by leaf litter. Early‐successional trees and shrubs established quickly in the coffee pulp treatment, reaching 30‐fold greater mean basal area and 20‐fold greater woody stem density (&gt;1‐cm‐dbh) compared to the control treatment. Structural metrics showed fourfold greater mean canopy height in the coffee pulp compared to control treatment. Canopy height &gt;5 m was ∼40% in the coffee pulp but was negligible (&lt;3%) in the control treatment. Our study highlights the significant potential for using agricultural waste, such as coffee pulp, to jump start forest succession on degraded tropical lands and encourages further research to optimize linkages between agroindustry and restoration.

Assessing the contribution of understory sun-induced chlorophyll fluorescence through 3-D radiative transfer modelling and field data

A major international effort has been made to monitor sun-induced chlorophyll fluorescence (SIF) from space as a proxy for the photosynthetic activity of terrestrial vegetation. However, the effect of spatial heterogeneity on the SIF retrievals from canopy radiance derived from images with medium and low spatial resolution remains uncharacterised. In images from forest and agricultural landscapes, the background comprises a mixture of soil and understory and can generate confounding effects that limit the interpretation of the SIF at the canopy level. This paper aims to improve the understanding of SIF from coarse spatial resolutions in heterogeneous canopies by considering the separated contribution of tree crowns, understory and background components, using a modified version of the FluorFLIGHT radiative transfer model (RTM). The new model is compared with others through the RAMI model intercomparison framework and is validated with airborne data. The airborne campaign includes high-resolution data collected over a tree-grass ecosystem with the HyPlant imaging spectrometer within the FLuorescence EXplorer (FLEX) preparatory missions. Field data measurements were collected from plots with a varying fraction of tree and understory vegetation cover. The relationship between airborne SIF calculated from pure tree crowns and aggregated pixels shows the effect of the understory at different resolutions. For a pixel size smaller than the mean crown size, the impact of the background was low (R2 > 0.99; NRMSE < 0.01). By contrast, for a pixel size larger than the crown size, the goodness of fit decreased (R2 < 0.6; NRMSE > 0.2). This study demonstrates that using a 3D RTM model improves the calculation of SIF significantly (R2 = 0.83, RMSE = 0.03 mW m−2 sr−1 nm−1) when the specific contribution of the soil and understory layers are accounted for, in comparison with the SIF calculated from mixed pixels that considers only one layer as background (R2 = 0.4, RMSE = 0.28 mW m−2 sr−1 nm−1). These results demonstrate the need to account for the contribution of SIF emitted by the understory in the quantification of SIF within tree crowns and within the canopy from aggregated pixels in heterogeneous forest canopies.

Relationship among water penetration, soil structure and understory vegetation according to the land conditions around the greenway in Kohoku New Town

In the slope forest of suburban area, which is affected by the land development, rainwater is getting to be more difficult to be penetrated because of the long-term compaction of surface soil. In the slopes along the greenway in Kohoku New Town, we selected survey plots according to the land conditions and the existence of understory vegetation cover, comparing original slopes of tablelands, slopes of constructed fill and cut mud slopes. We investigated rainwater penetration capacity, soil softness, soil particle size composition, and cover and biomass of understory vegetation, and analyzed their relationships. As a result, soil softness and the hierarchical diversity of understory vegetation had positive correlation with water penetration capacity, and these relationships were found in the cut mud slopes, same as in the original slopes, although no such relation was confirmed in the filled slopes. In the filled slopes, the effect of the underground structure to water penetration is stronger than that of surface soil, but in the cut mud slopes, hierarchical vegetation and softened surface soil are distributed with higher water penetration capacity. It was suggested that it is important to utilize such cut mud slopes to recover rainwater penetration capacity, with conserving the developing vegetation, in the restructuring of the greenway.

Understory vegetation dynamics of Chinese fir plantations and natural secondary forests in subtropical China

Understory vegetation is a vital component of forest ecosystems and contributes to terrestrial plant diversity, nutrient cycling and energy flows. Plantations and natural secondary forests are two dominant types that emerge following stand-replacing disturbances in managed landscapes. However, to date, the long-term dynamics of the cover, diversity, and composition of understory vegetation in plantations and secondary forests remain poorly understood. We sampled understory vegetation of Chinese fir plantations and natural secondary forests with their ages spanning 4 to 40 years and used primary forests as a reference in subtropical China. The cover and species diversity of the shrub layer were significantly higher in the natural secondary forests than in Chinese fir plantations in two younger age classes, but they converged in older stands. In the herb layer, Chinese fir plantations possessed a higher total and vascular species diversity across all age classes, but their covers did not differ significantly between the two forest types, except for a higher cover of vascular plants in the 8–12-year-old Chinese fir plantations. The bryophyte cover did not differ with forest type nor stand age, while bryophyte species diversity was significantly higher in Chinese fir plantations. The cover and species diversity of understory vegetation in the primary forests were similar to those in the 35–40-year-old natural secondary forests. Across all forest types and age classes, the cover and diversity were positively correlated within each plant group, and the shrub cover and diversity were negatively correlated with vascular diversity in the herb layer, but neither the cover nor the diversity of bryophytes was correlated with those of the shrub layer or herb layer. Species composition differed significantly with forest type and stand age. Natural secondary forests had more similar understory species composition to primary forests than Chinese fir plantations did. Our results suggest that forest management may increase the diversity of the herb layer, but at the expense of the abundance and diversity of the shrub layer. The shrub layer may not regenerate, or its regeneration will be slow due to exhausted seed and propagulum banks after multiple management rotations. Moreover, the high cover of the shade-intolerant and nutrient-demanding herbaceous plants in Chinese fir plantations may have adverse effects on ecosystem service functions.

Carabid Beetle Assemblages (Coleoptera: Carabidae) in a Seminatural Grassland and the Adjacent Old Beech Forest in Northeast Japan.

The decline and disappearance of seminatural grasslands in Japan have caused a reduction in plant and animal species inhabiting such grasslands. We aimed to understand the assemblage structure, species diversity, and distribution of carabid beetles in traditionally managed seminatural grasslands, by comparing with the adjacent old beech forest. We investigated the carabid beetle assemblages in a seminatural grassland maintained by prescribed burning and annual mowing, and the adjacent old beech forest in Yamagata Prefecture, northeast Japan. We recorded several forest species along with open habitat species and habitat generalists in the grassland, suggesting that forest species may utilize the adjacent grasslands as temporary habitats. Cluster analysis showed that the assemblage structure of carabid beetles in the grassland differed from that in the beech forest. There were no clear differences in the carabid assemblages between the burned grassland sites and the grassland sites mowed in July after burning. This suggests that the annual mowing had little influence on the response of grassland carabid species in parts of the grassland. We recorded Harpalus roninus (Coleoptera: Carabidae), a rare carabid species in Japan, indicating that this beetle can be a characteristic of the studied grassland. Redundancy analysis showed that the eight abundant grassland species were associated with canopy openness, grass height, and understory vegetation cover, whereas the five most common species recorded from the beech forest were associated with litter depth and soil moisture.

Native and non-native understory vegetation responses to restoration treatments in a dry conifer forest over 23 years

Restoration of fire-prone forests is a common practice intended to increase resilience to wildfire, drought, and bark beetles. However, the long-term effects of restoration treatments on understory species, particularly non-native species, are poorly understood. We investigated long-term (23 years) effects of restoration treatments on native and non-native understory vegetation at the Lick Creek Demonstration-Research Forest, a ponderosa pine/Douglas-fir forest in western Montana, USA. Restoration treatments included shelterwood-with-reserves harvesting implemented alone or in combination with prescribed burning under either wet or dry conditions, plus a no-action control. Changes in understory vegetation cover and species richness (measured pre-treatment, 2, 3, 4, 5, 15, and 23 years post-treatment) were analyzed by growth form (forb, graminoid, and shrub) and origin (native vs. non-native) to test how understory dynamics respond to disturbance intensity. We also accounted for basal area of trees to consider how differential overstory conditions affected final treatment responses. Native vegetation cover responses followed predictable successional patterns: after initial declines by grasses and shrubs immediately after disturbance (43% and 40% reduction, respectively), all groups increased, peaked about five years after disturbance (74% greater than pre-treatment on average) and then generally declined to levels similar to pre-treatment. The magnitude of these changes was related to the disturbance intensity (i.e., cut-and-dry-burn > cut-and-wet-burn > cut-and-no-burn > control). For all native groups, variation in tree basal area at year 23 explained remaining differences among treatments. Non-native grasses and forbs followed similar overall trajectories, but cover of these groups increased immediately after treatment and rose more steeply to their peak five years post-treatment (12 times greater than pre-treatment on average), with differences persisting through year 23. While non-native cover responses in year 23 were negatively correlated with tree basal area, as seen for native taxa, overstory conditions alone did not fully account for differences between burned and unburned treatments. This suggests that effects of burning unrelated to tree regeneration favored non-natives. Nonetheless, in the last sampling year treatment-induced increases in non-native cover were modest, suggesting that after 23 years understory responses in this forest type were fairly resilient to restoration treatments. However, because forest structure and composition were reverting to pre-treatment conditions by year 23, retreatment may be necessary at intervals of <23-years in our system, which could exacerbate non-native responses. Results of our long-term experiment provide insight into how different forest restoration treatments and their timing may affect understory susceptibility to non-native plant invasion.

Does Conservation Practice and Site Age Influence Vegetation Structure and Avian Abundance in Restored Fields?

ABSTRACTFarmland set‐aside programs provide important habitat for many wildlife species, yet little information exists regarding how vegetation structure and species respond to conservation practice and site age. This information could provide managers with a guide for how to implement, enhance, and maintain wildlife benefits of conservation programs. We describe how vegetation structure and avian species respond to conservation practice and time since restoration at 172 sites enrolled in the Conservation Reserve Enhancement Program (CREP) in Illinois, USA. We surveyed 172 sites enrolled in 4 different conservation practices (CP) within CREP during the breeding seasons of 2012–2015 using avian point counts and vegetation surveys. Vegetation structure and composition varied among CPs, with hardwood tree plantings (CP3A) having the greatest amount of understory vegetation and tree cover. Conversely, permanent wildlife habitat (CP4D) had the greatest grass cover and least tree cover. Many bird species were found in similar numbers across CP types; however, only dickcissel (Spiza americana) density was greater in sites enrolled as permanent wildlife habitat. Bell's vireo (Vireo bellii) and yellow‐billed cuckoo (Coccyzus americanus) were more numerous in hardwood tree plantings. Dickcissel density decreased and field sparrow (Spizella pusilla) density increased as fields aged, but the relationships were not consistent among CP types. Differences among CPs largely resulted from differences in dominance in woody vegetation due to initial habitat management and differential succession rates. Interestingly, many of our focal species had wider successional tolerances than previously suggested. Overall, our results demonstrate that conservation benefits change over time depending on the starting CP, that there can be considerable similarity in vegetation structure and bird communities among what appear to be very different conservation practices. This information can be used to target conservation benefits toward conservation priority species. © 2020 The Wildlife Society.

Understory Species Identity Rather than Species Richness Influences Fine Root Decomposition in a Temperate Plantation

Different silvicultural treatments that are applied at plantation establishment may drive different vegetation succession pathways. These divergent vegetation types subsequently feed back to influence soil carbon and nitrogen cycles. One potential mechanism of feedback is through litter decomposition, and in particular fine root decomposition (FRD; &lt;2 mm roots). In the present study we investigated how blade scarification, fertilization, and vegetation control influenced over- and understory vegetation 27 years after plantation, and whether these different vegetation communities affected FRD. In a design using factorial combinations of the three treatments at the Petawawa Research Forest (Laurentian Hills, ON, Canada), we conducted an in situ FRD experiment, with fine roots from the entire vegetation community (both over- and understory) of each plot. The different silvicultural treatments affected overstory basal area, understory species richness and FRD. No correlation was noted between understory species richness and FRD. Instead, we found that understory vegetation (especially fern and herb) cover best explained FRD. We conclude that silvicultural treatments affect FRD through subsequent vegetation succession and that this effect is more likely due to species-specific effects inducing a favorable soil environment than to a higher species richness per se.

Changes in understory vegetation including invasive weeds following mountain pine beetle outbreaks

Bark beetle outbreaks alter forests in many ways including stand structure, fuels and fire behavior, wildlife habitat, and aesthetic value. Less understood are the effects outbreaks have on understory vegetation, despite the importance for overstory succession, nutrient cycling, water quality, soil erosion, and wildlife. Beetle outbreaks also change forests in ways that could promote invasion by nonnative weeds, but this is rarely studied. We assessed changes in cover of understory vegetation and presence/abundance of weeds in lodgepole pine forests in Colorado, Idaho, Montana, Utah and Wyoming, USA following recent mountain pine beetle outbreaks. Incipient beetle populations began in 2004, peaked around 2008, and returned to endemic levels by 2012. Understory vegetation was sampled in 2010, 2012, 2014 and 2018. Total understory cover and cover of shrubs and graminoids remained unchanged, while cover of forbs generally increased. Forb cover was negatively correlated with shrub and canopy cover. Approximately 20% of plots contained weeds and weed abundance increased over time. Presence of weeds was negatively correlated with graminoid cover and positively correlated with tree mortality and snag fall. By 2018, weed abundance was only positively correlated with snag fall. Localized soil disturbance created when snags uproot and fall appears to act as sites of weed invasion and proliferation. Lastly, we provide a global review of the effects of bark beetle outbreaks on understory vegetation which reveals a prevailing short-term increase following outbreaks, but the magnitude of response and cover type affected varies with beetle species/forest type and time since outbreak.

Landscape configuration and habitat complexity shape arthropod assemblage in urban parks

The urbanization process systematically leads to the loss of biodiversity. Only certain arthropods are resilient to the urbanization process and can thrive in the novel conditions of urbanized landscapes. However, the degree to which arthropod communities survive in urban habitats depends on landscape and local effects and biological interactions (e.g., trophic interactions). In the present study, we examined the relative importance of various factors at landscape (isolation, edge density and area of surrounding greenery) and local (size of park, canopy cover, understory vegetation cover, defoliation depth, weight of dried leaves, soil temperature, soil moisture, and soil pH) spatial scales on the diversity of ants, beetles and spiders in urban parks. Our results indicated that park edge density was negatively correlated with diversity metrics in ants, beetles, and spiders in urban parks relative to the degree of proximity with the peri-urban forest. In other words, parks that located adjacent to the peri-urban forest may not necessarily have high biodiversity. The results suggested that man-made structures have been effective dispersal barriers that limit the spillover effects of ants and spiders but not the spillover of comparatively strong fliers, such as beetles. However, the area of surrounding greenery may have facilitated the colonization of forest-dependent taxa in distant parks. Large parks with reduced edge density supported a higher arthropod diversity because of the minimal edge effect and increased habitat heterogeneity. Vegetation structure consistently explained the variability of ants, beetles, and spiders, indicating that understory plant litter is crucial for providing shelters and hibernation, oviposition, and foraging sites for the major taxa in urban parks. Therefore, efforts should focus on the local management of ground features to maximize the conservation of biological control in urban landscapes.

Invasive red oak (Quercus rubra L.) modifies soil physicochemical properties and forest understory vegetation

This study assessed the effects of invasive Quercus rubra on soil physicochemical properties and understory vegetation in native plant communities. Chemical properties of senesced tree leaves were also analysed. The study was performed at paired invaded-native plots in managed forests in southern Poland. Freshly fallen senesced leaves were characterized in terms of C, Ca, K, Mg, N, P, total phenolics and condensed tannins concentrations. Soil physicochemical parameters, namely bulk soil density, moisture, water holding capacity (WHC), pH, organic C, total Ca, K, Mg, N, P, exchangeable Ca, K, Mg, N-NH4, N-NO3, P-PO4, and total phenolics were analysed in organic and mineral soil horizons, and condensed tannins were analysed in organic soil horizon. The diversity, cover and composition of understory vegetation were assessed. Although, senesced leaves of Q. rubra and native trees, Quercus robur, Fagus sylvatica, Carpinus betulus and Acer pseudoplatanus among others, differed only in total K, N and C/N ratio, we observed considerable differences in soil physicochemical parameters between the plot types. Soil beneath Q. rubra was characterised by significantly lower WHC, organic C, total Mg, N, P, exchangeable Ca, Mg, N-NH4, N-NO3, total phenolics and higher moisture in organic and mineral soil horizons as well as lower content of P-PO4 and condensed tannins in organic soil horizon relative to native plant communities. Q. rubra negatively influenced species richness and cover of understory vegetation. The changes in soil physicochemical parameters and understory vegetation under Q. rubra may be associated with low quality (low N, high C/N) litter that decomposes slowly and generates a physical barrier, limiting seed germination and seedling growth. The changes in soil properties and vegetation under invasive Q. rubra indicate that this species may alter the structure and function of forest ecosystems and should be avoided in forest management practices.

A multi-sensor, multi-scale approach to mapping tree mortality in woodland ecosystems

Woodland ecosystems, dominant on nearly 4% of all terrestrial land globally, are faced with a variety of threats, including increasingly prolonged and severe droughts, invasive insect outbreaks, and the rapid spread of pathogens. While many remote sensing methods have been developed for the detection and quantification of mortality in forested environments, woodland ecosystems present unique challenges to accurately mapping tree die-off due to relatively lower canopy covers, smaller and irregularly-shaped tree crowns, and greater influence of understory vegetation and soil cover on reflectance. To address these challenges, we developed a multi-sensor, multi-scale approach combining the analytical strengths of centimeter-resolution unmanned aerial system imagery for interpreting individual tree-level mortality, airborne lidar for crown mapping and quantifying percent canopy mortality, and Landsat imagery for upscaling mortality estimates to a regional scale. This approach utilizes a new algorithm for delineating the shapes of small, irregular woodland tree crowns using lidar. To demonstrate the application of this method, we map the extent and severity of a recent tree mortality event in piñon-juniper (PJ) woodlands of southeastern Utah. Our results suggest that 39% of PJ in this region has experienced some level of mortality, with patches exceeding 50% mortality. An analysis of potential mortality drivers revealed that canopy cover, terrain, and recent winter precipitation conditions are most directly linked with mortality, although the explanatory power of the mortality driver model was low. Our approach demonstrates a methodology that could be used for tree mortality mapping and scaling in a variety woodland ecosystems, and can provide a strong basis for further ecophysiological, ecological, and carbon cycle studies involving woodland tree mortality.

Effects of experimental prescribed fire and tree thinning on oak savanna understory plant communities and ecosystem structure

In the Midwestern United States, oak savannas have been reduced in area by at least 99% since European settlement, mirroring global trends for savannas, grasslands, and shrublands. Most remaining patches are highly degraded following decades of fire suppression and other anthropogenic impacts, and subsequent tree and shrub encroachment. Yet, reintroducing fire alone may not be sufficient to restore these ecosystems on desired timelines and mechanical thinning may be an important step in the restoration process, to increase understory light and promote the ground layer community. However, it is unclear how plant community dynamics develop under burn-only compared to thin-and-burn restoration scenarios. We investigated the impacts of prescribed fire and mechanical tree thinning on ecosystem structure and plant community dynamics over eight years in an oak savanna restoration experiment in southern Michigan. Established in 2010, this experiment utilized 15 0.4–1.2-hectare treatment units receiving either repeated prescribed fire alone, a combination of repeated prescribed fire and mechanical thinning, or no management. We used this design to test how differences in management affect understory and overstory structure, specifically understory vegetative cover and light availability associated with canopy openness, and plant community dynamics, specifically ground layer plant species richness and composition. We found that, over eight years of restoration, the response of ecosystem structure and the plant community was greatest in units where mechanical thinning was combined with prescribed fire. Thinned and burned units had greater canopy openness, vegetative cover, and plant species richness. Plant species composition also diverged between managed and unmanaged units. Canopy openness increased rapidly, within two years of restoration, while vegetative cover increased more gradually, over five years, and increases in richness were less pronounced overall. Composition diverged initially between managed and unmanaged units and continued to shift throughout the study period. Some effects of management peaked after four years, but were transient by the end of the study. Additional management will be necessary to capitalize on the initial response to restoration toward an oak savanna ecosystem. We predict that additional thinning will further increase light availability and development of graminoid fuels and in combination with prescribed fires will continue to promote open canopy structure and a ground layer dominated by savanna-associated species.

Оценка компонентов нижних ярусов растительного покрова в антропогенно нарушенных березняках Красноярской лесостепи

The vegetation cover characteristics of anthropogenically disturbed birch stands of Krasnoyarsk forest-steppe are studied. The research purpose is to study the current state of under story vegetation cover of the birch stands, which have been exposed to recreational and anthropogenic impacts for a long time, as well as to assess the degree and nature of its changeover the 12-year period since the last research. The studies were carried out on the sample plots laid out in mixed herbs birch stands. Cenosises are characterized by V–VI age classes,II–IV quality classes, and 0.6–0.9 density of stocking. The birch stands are located in the main transfer of Krasnoyarsk industrial emissions. Phytocenoses were under significant anthropogenic and recreational impact for a long time. At each facility, 30 sites (1 m2 each) were laid, where species composition, horizontal and vertical structure, projective cover and occurrence of undergrowth and forest live cover species were assessed. The comparative analysis of floristic lists was performed using the Sorensen-Czekanowski coefficient (Ksc). The degree of species diversity was estimated by using the Shannon index; the degree of recreational transformation – synanthropization index. Cuttings were taken from 10 sites (20 × 25 cm each) for recording the phytomass stock of forest live cover on each sample area. Plants were cut off at the litter level, sorted by species, dried and weighed. Rating scales of digression were used to study the recreation influence. The degree of anthropogenic impact was determined by the content of toxic ingredients in plants of living ground cover. It is found that the toxic elements concentration in plants does not reach excessive values at which homeostasis disturbance happens. It was concluded that the changes in vegetation cover observed in 2017 in relation to the state of 2005 are more due to recreational than anthropogenic impact; which changed due to the introduction of a new technology at the JSC “RUSAL Krasnoyarsk Aluminum Plant”, which made it possible to reduce toxic industrialemissions. According to the study results, the species composition of the undergrowth and forest live cover was determined, the features of its change over a 12-year period were revealed. It is noted that species diversity has decreased and the proportion of synanthropic species has increased across all plots. Total forest live cover phytomass and individual species phytomass are determined at each plot. The regularities of change in different species contribution to the total stock of phytomass, depending on recreational impact changes, were identified. The ground cover recreational digression stages are determined by analyzing the changes in species diversity, the quantitative ratio of ecological-cenotic groups, the structure and the absolute value of phytomass. For citation: Goncharova I.A., Skripal’shchikova L.N., Barchenkov A.P., Shushpanov A.S. Understory Vegetation Cover Components Assessment in Anthropogenically DisturbedBirch Stands of Krasnoyarsk Forest-Steppe. Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 1, pp. 75–87. DOI: 10.37482/0536-1036-2020-1-75-87 Funding: The study was carried out within the framework of the basic research projects of the Sukachev Institute of Forest SB RAS “Biodiversity of Indigenous Coniferous and Derivative Forest Ecosystems” (No. 0356-2016-0301) and “Dynamics of Siberian Forests in a Changing Climate. Monitoring of the Living State, Productivity and Ranges of the MainForest-Forming Species of Woody Plants” (No. 0356-2018-0739).

Quantifying Understory and Overstory Vegetation Cover Using UAV-Based RGB Imagery in Forest Plantation

Vegetation cover estimation for overstory and understory layers provides valuable information for modeling forest carbon and water cycles and refining forest ecosystem function assessment. Although previous studies demonstrated the capability of light detection and ranging (LiDAR) in the three-dimensional (3D) characterization of forest overstory and understory communities, the high cost inhibits its application in frequent and successive survey tasks. Low-cost commercial red–green–blue (RGB) cameras mounted on unmanned aerial vehicles (UAVs), as LiDAR alternatives, provide operational systems for simultaneously quantifying overstory crown cover (OCC) and understory vegetation cover (UVC). We developed an effective method named back-projection of 3D point cloud onto superpixel-segmented image (BAPS) to extract overstory and forest floor pixels using 3D structure-from-motion (SfM) point clouds and two-dimensional (2D) superpixel segmentation. The OCC was estimated from the extracted overstory crown pixels. A reported method, called half-Gaussian fitting (HAGFVC), was used to segement green vegetation and non-vegetation pixels from the extracted forest floor pixels and derive UVC. The UAV-based RGB imagery and field validation data were collected from eight forest plots in Saihanba National Forest Park (SNFP) plantation in northern China. The consistency of the OCC estimates between BAPS and canopy height model (CHM)-based methods (coefficient of determination: 0.7171) demonstrated the capability of the BAPS method in the estimation of OCC. The segmentation of understory vegetation was verified by the supervised classification (SC) method. The validation results showed that the OCC and UVC estimates were in good agreement with reference values, where the root-mean-square error (RMSE) of OCC (unitless) and UVC (unitless) reached 0.0704 and 0.1144, respectively. The low-cost UAV-based observation system and the newly developed method are expected to improve the understanding of ecosystem functioning and facilitate ecological process modeling.