Early Successional Stands Research Articles

Forest age drives saproxylic beetle biodiversity in the southeastern United States

Old forests are valuable for biodiversity conservation because they provide uninterrupted forest cover over time and late-successional habitat, promoting low-mobility and late-successional species. However, forest age may be less important in highly forested landscapes because dispersal limitation is reduced. We investigated how species richness and community composition of saproxylic beetles (Coleoptera) are influenced by forest age and the surrounding landscape in the southeastern United States (Georgia). Forests in this region are highly fragmented and dominated by early-successional stands. We sampled beetles in 20 old forests (mature in 1938) and 20 young forests (originating after 1938), located along a landscape forest cover (LFC) gradient. Old and young forests were structurally similar but tree communities differed along a Quercus (old) to Pinus (young) gradient. Regional diversity of saproxylic beetles was higher in old forests, and high species turnover between forest age groups suggests they both help to maintain regional biodiversity. Two models of local richness had near equal merit: one showed higher richness in old forests regardless of LFC, while the other showed higher richness in old forests at high LFC. Contrary to expectations, neither model supports old forests losing importance in highly forested landscapes. Higher richness in old forests is likely due to temporal stability and late-successional habitat, promoting low-mobility and specialist species. Because the land area of young forests exceeds that of old forests, old forests are disproportionately important for saproxylic biodiversity in the region.

Plant–soil feedbacks in a diverse grassland: Soil remembers, but not too much

Abstract Plant–soil feedbacks (PSFs) are one of the major drivers of species coexistence in highly dynamic and low‐diversity communities, such as early successional stands or agricultural systems. However, in stable and species‐rich communities, PSFs are much more complex because of numerous species interactions. In this study, we aimed to reveal if PSFs of a dominant species can be detected within a diverse plant community and to what extent they can be influenced by the effects of co‐occurring species. We investigated PSFs between a dominant grass, Festuca rubra, and three other species from a species‐rich mountain grassland, taking advantage of the 18‐year field removal experiment. We tested whether such a long‐term presence/absence of Festuca can shape the feedback of the grassland community and whether these effects prevail in the lower soil layer, where Festuca roots are relatively more abundant, compared to the upper soil layer. We evaluated how experimentally induced soil legacies of Festuca in a pot experiment are modified by subsequently grown plants, both at the level of plant responses and changes in abiotic and biotic soil properties. At the level of the entire community, the soil legacies of the dominant Festuca were not detectable. However, the responses of the plants differed between the soil samples from the upper and lower soil layer. The pot experiment showed that the soil legacies of subsequently growing plants interact, influencing soil properties as well as plant responses to these altered soils. Generally, we found a stronger signal of the most recent conditioning, although the effect of the first conditioning plant was still detectable in many of the measured variables. Plant biomass in the feedback phase was mainly linked to the levels of plant‐available soil nitrogen, although it was also affected by the composition of microbial communities. Synthesis. We showed that plant‐induced soil legacies can be altered by legacies of co‐occurring species, complicating plant–soil feedbacks in diverse communities. Despite the detectable legacy effects on final plant biomass, in the short term, plant growth responds more strongly to the levels of available nutrients. We also highlight the vertical distribution of plant–soil feedbacks.

Early-succession secondary forests following agropastoral abandonment are key winter habitats for the conservation of a priority bird in the European Alps

In contrast to old-growth forests, early-successional stands remain understudied despite potentially harbouring species of conservation interest. With this work, focused on hazel grouse Tetrastes bonasia, a cryptic and indicator species known to select for close-to-natural forests, we evaluated winter densities, home range, microhabitat selection and diet, combining DNA-based mark-recapture and metabarcoding from faecal samples. In total, 216 droppings, collected over 2 years along forest transects in the Italian Alps, were successfully genotyped and 43 individuals were identified. Density estimates were similar to values reported by other studies in the Alps with an average of 4.5 and 2.4 individuals/km2 in the first and second study year, respectively, and mean home ranges estimated at 0.95 km2. According to habitat selection models and eDNA-based diet analysis, hazel grouse selected early-succession secondary-growth forests formed after the abandonment of traditional agropastoral activities. These forests, mostly composed of hazel Corylus avellana, Norway spruce Picea abies and Sorbus spp., provided winter food resources and shelter. The diet analysis also highlighted forest arthropods as a non-negligible source of food. Birds avoided areas subject to intensive browsing by ungulates; small forest roads seasonally closed to traffic had positive influence on hazel grouse (i.e. higher abundance of droppings), while roads open to traffic had no effect. Importantly, despite the high coverage of mature forest habitats of Community Interest (53% of our study area), droppings were more abundant in non-listed early-succession secondary forests with similar plant composition. Our results suggest that forest succession after agropastoral abandonment may be beneficial for some forest birds of conservation interest, while acknowledging its negative effects on the previous grassland biodiversity.Graphical abstract

Temporal patterns of vegetation recovery after wildfire in two obligate seeder ash forests

In recent years, novel, high-severity wildfire regimes have driven major changes in the structure and function of forests globally. Indeed, many forests are vulnerable to recruitment failures and collapse in the event of decreased intervals between fires, including forests dominated by the Australian obligate seeders, Alpine Ash (Eucalyptus delegatensis) and Mountain Ash (Eucalyptus regnans). Disturbance responses in these forests are often described collectively, with limited understanding of their potential differences. Despite this, management recommendations and ecological implications are often applied broadly across both forest types. Here, using an empirical dataset collected over an eleven-year period (2009–2020), we compare plant communities in south-eastern Australian Alpine Ash and Mountain Ash forests in mature stands (last burned in 1926/1939), and young stands (burned by high-severity wildfire in 2009). To do this, we used measures of forest structure (basal area of dominant plant life-forms) collected over eight years, and the abundance (projective foliage cover) of vascular plant species. We provide evidence of similar, positive-linear trends in the recovery of forest structure in both Alpine Ash and Mountain Ash forests in the first eight years post-wildfire in 2009. Mature Alpine Ash and Mountain Ash forests were compositionally different but had a similar structure and abundance of plant life-forms. Moreover, controlling for the influence of forest type, young stands were compositionally different from mature stands, and were associated with an increase in the abundance of Acacia, herb, ground-fern and graminoid species, and a decline in tree-fern and tree species. Further investigation in young stands revealed marked differences in plant community composition between forest types, with young Mountain Ash forests characterized by a lower abundance of shrub, Acacia and graminoid species, relative to Alpine Ash forests of the same age. Overall, our findings indicate that Alpine Ash and Mountain Ash forest plant communities may have similar structural and functional responses to predicted increases in wildfire. This suggests that when the broad structure and function of forest vegetation is a consideration, ecological implications and management recommendations may be broadly applicable to both Alpine Ash and Mountain Ash forests. However, further consideration is required in early successional stands where differences in species composition between forest types may have implications for management (e.g. increases in flammability). In a period of uncertainty in the future of ash-type forests, our study provides a timely insight into the comparative successional trajectories of their respective plant communities and provides a baseline for future studies.

Removal of cattle accelerates tropical dry forest succession in Northwestern Mexico

AbstractDomestic livestock influence patterns of secondary succession across forest ecosystems. However, the effects of cattle on the regeneration of tropical dry forests (TDF) in Mexico are poorly understood, largely because it is difficult to locate forests that are not grazed by cattle or other livestock. We describe changes in forest composition and structure along a successional chronosequence of TDF stands with and without cattle (chronic grazing or exclusion from grazing for ~ 8 year). Forest stands were grouped into five successional stages, ranging from recently abandoned to mature forest, for a total of 2.7 ha of the sampled area. The absence of cattle increased woody plant (tree and shrub) density and species richness, particularly in mid‐successional and mature forest stands. Species diversity and evenness were generally greater in sites where cattle were removed and cattle grazing in early successional stands reduced establishment and/or recruitment of new individuals and species. Removal of cattle from forest stands undergoing succession appears to facilitate a progressive and non‐linear change of forest structure and compositional attributes associated with rapid recovery, while cattle browsing acts as a chronic disturbance factor that compromises the resilience and structural and functional integrity of the TDF in northwestern Mexico. These results are important for the conservation, management, and restoration of Neotropical dry forests.

Formerly managed forest reserves complement integrative management for biodiversity conservation in temperate European forests

In Central Europe, the predominant conservation strategy in forests is integrative management, seeking to balance economic interests with conservation goals. This is complemented by unmanaged strict forest reserves, most often small and with a history of forest management. Whether and how such reserves contribute to conservation when the surrounding forest is under progressive integrative management remains unclear.We compared forest structure and biodiversity of several taxa between formerly managed forest reserves and stands under progressive integrative management in beech and beech-oak forests. Alpha diversity was higher in reserves for birds and bats and higher in managed stands for plants and beetles, with no significant differences for fungi. Community composition differed between reserves and managed stands for plants, wood-decomposing fungi, beetles and birds. Reserves had 17 indicator species, including three red-listed species, and managed stands had 34, including one red-listed species. Diversity metrics differed between reserves and managed stands for both beech and beech-oak forests.Our results indicate that progressive integrative management and reserves, even when located in formerly managed stands, are complementary approaches benefitting different taxa and hosting partly different communities. Higher numbers of plants and beetles in managed stands were associated with higher light availability, as reserves in our study were undisturbed mature stands characterized by low light availability and low deadwood volumes. To benefit light and deadwood demanding species, new reserves should include early or late successional stands. If this is not feasible, restoration measures prior to designation or where possible under current protection status should be discussed.

Key perspectives on early successional forests subject to stand-replacing disturbances

In forests subject to stand-replacing disturbances, early successional stands can provide important habitats for a range of species not typically present in long-undisturbed areas. Compared to old-growth forests, the habitat values of – and key ecological processes in – early successional forests have been less studied, perhaps due to a perception that early successional forests revert to a homogenous “clean slate” following stand-replacing disturbances. In this paper, we draw on 36 years of long-term research in the Mountain Ash (Eucalyptus regnans) and Alpine Ash (Eucalyptus delegatensis) forests of south-eastern Australia, together with examples from elsewhere around the world, to show that not all kinds of early successional forests are created equal. We argue that the ecological values of early successional forests can be profoundly affected by six inter-related factors: (1) The evolutionary context and environmental domain of a given ecosystem. (2) Successional stage and condition of a forest stand prior to disturbance. (3) Disturbance intensity, severity and type (e.g. wildfire versus clearcutting). (4) Post-disturbance conditions including climate and weather. (5) Post-disturbance management (e.g. salvage logging) which can have significant impacts on biological legacies. And, (6) The relative spatial extent and spatial arrangement of early and late successional forest across a landscape. These factors can influence ecological values directly, or through effects on the types, amount and spatial patterns of biological legacies present in early successional forest. We present a conceptual model highlighting the inter-relationships between these factors and illustrate its use through a detailed case study.Strategies to improve the management of early successional forests include: (1) Identifying the species associated with post-disturbance environments and the reasons why they occur in such environments. (2) Understanding the types, numbers, and spatial patterns of biological legacies that remain after natural disturbance. (3) Identifying critical areas that should be excluded from logging or other human disturbance. (4) Limiting the extent of post-disturbance activities like salvage logging that undermine the ecological values of, and ecosystem processes in, early successional forests. And, (5) Balancing the relative amounts of early successional versus late successional forest in a given landscape or region to ensure that a variety of forest types are present at any given time, and that critical biological legacies are retained. Paradoxically, ensuring that landscapes support extensive areas of late successional forest is critical so that future early successional forests are not devoid of the biological legacies necessary for ecosystem function and recovery.

Nitrogen–phosphorous interactions in young northern hardwoods indicate P limitation: foliar concentrations and resorption in a factorial N by P addition experiment

Resorption, the processof withdrawing foliar nutrients prior to leaf abscission, is one of the most important nutrient conservation mechanisms in trees. Along with foliar nutrient concentrations, foliar resorptioncan be used to infer nutrient limitation. We collected green and senesced leaves of five species in early successional stands in the White Mountains of New Hampshire. In unmanipulated controls, foliar N:P ratios ranged from 20 to 31 and litter N:P ratios ranged from 19 to 36. These values suggest P limitation, although this forest type has been assumed to be N-limited. Additionally, N:P resorption ratios in control plots were < 1, reflecting proportionately more conservation of P through resorption than N. Four years into a full-factorial N × P fertilization experiment, N and P additions had increased N and P concentrations in leaves; more importantly, P addition reduced N concentration, possibly indicating alleviation of growth limitation by P. Resorption of P was less proficient (indicated by the concentration of an element in leaf litter) with P addition, as expected. Resorption proficiency and efficiency (the proportion of leaf nutrients resorbed) of N increased with P addition, suggesting increased demand for N with alleviation of P limitation. Resorption of P was more proficient and efficient with N addition, consistent with exacerbated P limitation. Temperate forests on glaciated soils are generally thought to be N-limited, but long-term N × P manipulations in this biome are lacking. Our results suggest that decades of anthropogenic N deposition may have tipped the balance to P limitation in these forests.

Spatial patterns and competition in trees in early successional reclaimed and natural boreal forests

Spatial distribution of plants in early successional stands provides an indication of future plant community structure and population dynamics. Determining the factors driving plant interactions and their demographic relationships at stand initiation is critical to gain a better understanding of plants’ responses to competition and limited resource conditions. Reclaimed ecosystems are ideal for studying such community mechanisms because they are completely reconstructed ecosystems with known community filters such as soil type, propagule composition, and the presence of both planted and naturally establishing trees. The current study explored the spatial patterns and competition-facilitation mechanisms in deciduous and evergreen trees in two oil sands reclaimed sites with different reclamation age (2-year old and 5-year old) and cover soils (wetland peat origin – PMM; and forest floor origin – FFMM) in Alberta, Canada, and compared this with a naturally-disturbed site at 5 years since fire. Spatial point pattern analysis was performed using pair correlation function g(r), mark correlation function kmm(r), and bivariate g-function. Intraspecific competition in deciduous seedlings was stronger in the 5-year old reclaimed site than in the 2-year old site. Spatial patterns in deciduous seedlings on PMM were aggregated at 1–3 m scale similar to the natural site, whereas seedlings on FFMM sites had aggregated patterns at greater than 5 m scale. Planted conifers had regular pattern at 1–2 m scale in the 2-year old sites which reflects the plantation spacing, but showed a random pattern in the 5-year old sites indicating the effect of random mortality. Bivariate spatial analysis indicated a significant repulsion between deciduous and coniferous seedling at 1 m in the 2-year old PMM site and a significant attraction in the 5-year old FFMM site suggesting that the mechanism of competition-facilitation between trees is different in different cover soils. Density dependent thinning was only observed in the 2-year old PMM and natural sites; however, a gradual increase in nearest neighbour distances with increasing seedling size in all the reclaimed sites suggests that density dependent thinning has started.

Landscape variation in tree regeneration and snag fall drive fuel loads in 24-year old post-fire lodgepole pine forests.

Escalating wildfire in subalpine forests with stand-replacing fire regimes is increasing the extent of early-seral forests throughout the western USA. Post-fire succession generates the fuel for future fires, but little is known about fuel loads and their variability in young post-fire stands. We sampled fuel profiles in 24-year-old post-fire lodgepole pine (Pinus contorta var. latifolia) stands (n=82) that regenerated from the 1988 Yellowstone Fires to answer three questions. (1) How do canopy and surface fuel loads vary within and among young lodgepole pine stands? (2) How do canopy and surface fuels vary with pre- and post-fire lodgepole pine stand structure and environmental conditions? (3) How have surface fuels changed between eight and 24years post-fire? Fuel complexes varied tremendously across the landscape despite having regenerated from the same fires. Available canopy fuel loads and canopy bulk density averaged 8.5Mg/ha (range 0.0-46.6) and 0.24kg/m3 (range: 0.0-2.3), respectively, meeting or exceeding levels in mature lodgepole pine forests. Total surface-fuel loads averaged 123Mg/ha (range: 43-207), and 88% was in the 1,000-h fuel class. Litter, 1-h, and 10-h surface fuel loads were lower than reported for mature lodgepole pine forests, and 1,000-h fuel loads were similar or greater. Among-plot variation was greater in canopy fuels than surface fuels, and within-plot variation was greater than among-plot variation for nearly all fuels. Post-fire lodgepole pine density was the strongest positive predictor of canopy and fine surface fuel loads. Pre-fire successional stage was the best predictor of 100-h and 1,000-h fuel loads in the post-fire stands and strongly influenced the size and proportion of sound logs (greater when late successional stands had burned) and rotten logs (greater when early successional stands had burned). Our data suggest that 76% of the young post-fire lodgepole pine forests have 1,000-h fuel loads that exceed levels associated with high-severity surface fire potential, and 63% exceed levels associated with active crown fire potential. Fire rotations in Yellowstone National Park are predicted to shorten to a few decades and this prediction cannot be ruled out by a lack of fuels to carry repeated fires.

Fires of the Last Millennium Led to Landscapes Dominated by Early Successional Species in Québec’s Clay Belt Boreal Forest, Canada

This study presents the long-term (over the last 8000 years) natural variability of a portion of the Picea mariana-moss bioclimatic domain belonging to Québec’s Clay Belt. The landscapes are dominated by mesic-subhydric clay and early successional forests composed of Populus tremuloides, Pinus banksiana and Picea mariana. The natural variability (fires and vegetation) of one of these landscapes was reconstructed by means of pollen and macroscopic charcoal analysis of sedimentary archives from two peatlands in order to assess when and how such landscapes were formed. Following an initial afforestation period dominated by Picea (8000–6800 cal. Years BP), small and low-severity fires favored the development and maintenance of landscapes dominated by Picea and Abies balsamea during a long period (6800–1000 BP). Over the last 1000 years, fires have become more severe and covered a larger area. These fires initiated a recurrence dynamic of early successional stands maintained until today. A decline of Abies balsamea has occurred over the last centuries, while the pollen representation of Pinus banksiana has recently reached its highest abundance. We hypothesize that the fire regime of the last millennium could characterize Québec’s Clay Belt belonging to the western Picea mariana-moss and Abies balsamea-Betula papyrifera domains.

Functional Diversity of Small and Large Trees along Secondary Succession in a Tropical Dry Forest

Functional Diversity is considered an important driver of community assembly in environmental and successional gradients. To understand tree assembly processes in a semideciduous tropical forest, we analyzed the variation of Functional Richness (FRic), Functional Divergence (FDiv), and Functional Evenness (FEve) of small vs. large trees in relation to fallow age after slash-and-burn agriculture and topographical position (flat sites vs. hills). FRic of small trees was lower than null model predicted values across the successional gradient, and decreased unexpectedly in older successional ages. FRic of large trees was higher than null model predictions early in succession and lower in late-successional stands on hills. Dominant species were more similar (low FDiv) in early and intermediate successional stands for small trees, and on hills for large trees, suggesting that species that are best adapted to harsh conditions share similar traits. We also found evidence of competitive exclusion among similar species (high FEve) for small trees in early successional stands. Overall, our results indicate that community assembly of small trees is strongly affected by the changing biotic and abiotic conditions along the successional and topographical gradient. For large trees, hills may represent the most stressful conditions in this landscape.

Refugial role of urbanized areas and colonization potential for declining Crested Lark (Galerida cristata) populations in the Czech Republic, Central Europe

Urban environment is only rarely considered an exclusive refuge for rapidly declining bird species. Crested Lark (Galerida cristata) is a species in Central Europe whose synanthropization began in the second half of the twentieth century due to dramatic changes in agriculture and landscape structure. We analyze how changes in these distribution patterns mirror landscape structures and demonstrate colonization potential from adjacent refuges. We used the Czech Breeding Bird Atlas data from two periods, 1985–1989 and 2001–2003, to model distribution change patterns for Crested Larks in two parts of the country, Bohemia and Moravia. Mapping quadrats comprised the sampling units, and binomial species presence or absence was used to model the change patterns using generalized linear models while considering landscape structure, demographic data and dominant habitat attributes as predictors. Despite similar attributes of landscape structures in Bohemia and Moravia, Crested Larks clearly differed in their extinction patterns. Within isolated Bohemia, the remnant subpopulations were restricted to early successional stands around commercial areas in urban zones. In Moravia, only altitude appeared related to the species’ disappearance. Moravia is connected at the south to the Pannonian Plain with stable or increasing Crested Lark populations, which we consider responsible for the significantly higher number of newly occupied quadrats in Moravia. Our results indicate the more isolated Bohemian population is more prone to extinction than is the Moravian population with its greater colonization potential. The study notes a rare example of urban zones serving as refuges for a bird species demanding early successional stands.

Shifts in functional traits among tree communities across succession in eastern deciduous forests

Throughout the eastern deciduous forest (EDF) region, disturbances, including fire, wind storms, and landslides, interweave with complex topography and vegetation history to produce a mosaic of forest types and ages. Forest composition and dynamics following disturbance can depend on the interaction of plant traits related to resource capture, regeneration, and growth with changes in the post-disturbance environment. Appropriate traits should vary predictably with the stand age of a forest community as this acts as a proxy for time since last disturbance. We used Forest Inventory and Analysis data to investigate the hypothesis that community level means of seed mass and wood density increase, and leaf nitrogen decreases, with age of eastern deciduous forests, reflecting a shift from light-seeded, fast-growing early successional vegetation to heavier-seeded, slower-growing vegetation. As hypothesized, seed mass and wood density were positively correlated with stand age; however, the relationship differed among ecoregions of the EDF. Northern forests in the Warm Continental Division showed lower seed mass and wood density values in young stands, with a stronger increase in these values as succession advanced relative to more southerly ecoregions. This could reflect slower succession, preponderance of light-seeded and low wood density early post-disturbance deciduous trees such as Populus tremuloides and Betula papyrifera, or presence of conifers in early successional stands. Leaf nitrogen showed no consistent relationship with stand age, suggesting no consistent relationship of photosynthetic rate or soil nitrogen content with tree composition over succession throughout the EDF. Instead, leaf nitrogen differed among the ecoregion divisions and showed a unimodal distribution with latitude, peaking near the middle latitudes of the Hot Continental and Prairie Divisions. Collectively, the results indicate functional trait shifts over succession throughout the EDF, in agreement with a shift from ruderal to more competitive or stress-tolerant strategies, but also point to differences in the strength and shape of that shift among ecoregions. Early post-disturbance forest harbors a unique combination of functional traits. Further, disturbance that creates a mosaic of forest stand ages is important for maximizing not just species diversity, but functional diversity as well.

American Woodcocks' (Scolopax minor) Use Of Pine Plantation Habitat During Spring In Central Arkansas

Abstract We evaluated sites on an industrial forest in central Arkansas that American Woodcocks (Scolopax minor) used for courtship during their spring migration. Our main objective was to determine the vegetation characteristics used by male woodcocks on their courtship sites within early successional pine stands. We quantified use within three stages of early successional pine stand; pine seedling (1 year old), young-pine sapling (2–3 years old), and old-pine sapling (4–5 years old). We used crespuscular surveys as an index to the number of woodcock using each stand. We completed surveys in January–March 2010 and 2011 on eight stands of each stage (n = 24) during 7–10 day sampling periods across spring migration. We quantified the vegetation structure of each stand including the percent of bare ground, standing herbaceous, flattened herbaceous, shrub, coarse woody debris, and canopy cover and horizontal density. We found that woodcocks used stands with greater shrub, standing herbaceous, and flattened...

Wildlife-mitigated precommercial thinning maintains the abundance of fruit shrubs in a boreal forest

In boreal forests, fruits are an abundant resource in late summer and benefit many wildlife species. Fruits are mainly found in early successional stands, which are often subject to precommercial thinning designed to increase diameter growth of residual trees and manage stand species composition. Concerns about the consequences of precommercial thinning on wildlife have led to various methods of precommercial thinning with mitigation for wildlife. In summers 2007 and 2008, we examined the impact of wildlife-mitigated thinning on fruit shrub abundance and distribution at the Forêt Montmorency, Quebec. The abundance of fruit shrubs of all species except Amelanchier was similar in thinned and control stands but was highly variable among individual stands. Amelanchier shrubs appeared to benefit from thinning, especially 10 to 20 years after clearcutting. Fruit shrubs were highly clustered within early successional stands, but less so after thinning. We conclude that wildlife-mitigated precommercial thinning does not reduce access to fruits for birds and other frugivores and may even facilitate it in eastern Canadian boreal forests.

Boreal forest sensitivity to increased temperatures at multiple successional stages

Rising temperatures may force boreal forests in central Siberia to transition to alternative ecological states, affecting species composition and carbon storage dynamics. A full understanding of how forests of different ages respond to warming remains elusive, despite being fundamental for proper forest management in the region. To document the sensitivity of Siberian forests of different successional stages to rising temperatures. We use the FAREAST forest gap model to investigate the variation in biophysical response of boreal forests of different stand ages as temperatures rise and question whether there is varying sensitivity at different successional states. Our model predicts that mid-successional forests are more resistant to warming temperatures in low-level warming scenarios and resist biophysical changes more so than forests over 200 years old. This response diminished in more intense warming scenarios. Specifically, forest biomass increased with temperature; however, dieback of Siberian larch and replacement by Siberian Silver birch and by Siberian pine in early-successional stands yielded a net decrease in carbon storage. Mid-succession and old growth forests did not transition to pine forests, however, and may serve as a location for refugia of northern boreal species.

Influence of management intensity on the productivity of early successional Acadian stands in eastern Maine

Early successional stands composed of naturally regenerated hardwood and conifer species are abundant in the forests of northeastern North America. Substantial improvements in the composition and growth of these stands may be possible with early management intervention. Unfortunately, stand responses to early management inputs are poorly understood since many of these stands are rarely manipulated. We examined the response of early successional stands to combinations of two management intensities (with and without enrichment planting and different levels of vegetation control) and three compositional objectives (hardwood, mixedwood and conifer). The treatments were designed to represent management options available in the region, including hardwood thinning, conifer release and a combination of treatments to promote hardwood –conifer mixedwood stands. Seven years after treatment, yields of the two hardwood thinning treatments ranged from 43.4 to 56.6 Mg ha 21 , which were similar to the 52.9 Mg ha 21 yield of the untreated control but with 17 and 46% lower densities, respectively. In the conifer release treatments, the removal of hardwoods promoted conifer dominance and resulted in yields between 19.9 and 30.4 Mg ha 21 7 years after treatment. The conifer release treatments will likely be dominated by conifers in the future with varying hardwood densities due to hardwoods establishing in gaps without conifers. After 7 years, yields of the mixedwood treatments were between 19 and 47% greater than the conifer release treatments due to the retention of thinned hardwood stems and represent stands that dominate much of the forestland in the region. Results from this study demonstrated that early successional stands can be effectively managed during early stand development to improve growth and the longer term composition.

Avian use of early-successional boreal forests in the postbreeding period

ABSTRACT. The postbreeding period is critical for many forest birds and especially for juveniles, which must learn to forage on their own before the fall migration. During this period, many birds of the boreal forest are found in early-successional stands (ESS), where fruit abundance is typically high. Boreal forest birds may use ESS to exploit fruit or for reasons other than access to fruit, namely to forage along forest edges or simply to transit through clearcuts between patches of mature forest. We tested whether frugivory, edge use, and transit through small (<65 ha) clearcuts between mature-forest patches accounted for bird abundance in ESS in a boreal forest of Quebec during the summers 2007 and 2008. Fifteen of the 33 species captured in ESS were postbreeding frugivores. Removal of all fruits from Sambucus racemosa, a dominant fruiting plant, within 10 m of mist-netting sites reduced the number of frugivores captured by 45% but did not affect nonfrugivores. Numbers of birds captured were independe...

Carbon Accumulation Patterns During Post-Fire Succession in Cajander Larch (Larix cajanderi) Forests of Siberia

Increased fire activity within boreal forests could affect global terrestrial carbon (C) stocks by decreasing stand age or altering tree recruitment, leading to patterns of forest regrowth that differ from those of pre-fire stands. To improve our understanding of post-fire C accumulation patterns within boreal forests, we evaluated above- and belowground C pools within 17 Cajander larch (Larix cajanderi) stands of northeastern Siberia that varied in both years since fire and stand density. Early-successional stands ( 70-year old), aboveground larch biomass, ANPPtree, and soil organic layer C pools increased with stand age. These stands were low density and multi-aged, containing both mature trees and new recruits. The rapid accumulation of aboveground larch biomass in high-density, mid-successional stands allowed them to obtain C stocks similar to those in much older low-density stands (~8,000 g C m−2). If fire frequency increases without altering stand density, landscape-level C storage could decline, but if larch density also increases, large aboveground C pools within high-density stands could compensate for a shorter successional cycle.