Old Forests Research Articles

Forage availability and moose winter browsing in forest landscapes

In a large-scale survey, comprising 38 landscapes throughout Sweden, we measured winter forage availability and use by moose within different forest- and land types, and also at three different spatial scales: plot, tract and area.Measured as percent cover of browse species within moose browsing range, young forests contained significantly more browse (16.5 ± 1.20%: mean ± SE) compared with older forests (6.7 ± 0.57%) or non-forest land (5.9 ± 0.67%). Total cover of browse species increased with increasing mean tree height in forests, and peaked at around 22% when the trees were 3–5 m. The relative consumption was highest in young forests (9.2 ± 0.98%) compared with non-forest land (7.8 ± 1.40%) or older forests (5.8 ± 0.78%). The selection order did not vary much among forest- or land types, with aspen, willows, rowan and oak being the most selected species.A multiple regression, including four independent variables (moose index, cover of Scots pine, cover of other species and temperature sum) explained 45% (young forests), 18% (older forests) and 36% (non-forest land) of the variation in relative consumption. In young forests, moose index and cover of Scots pine accounted for 40 and 44%, respectively, of the explained variation. Model selection, using AICc, further emphasized the importance of moose index and cover of Scots pine, as these variables were included in the most parsimonious models for all forest- and land types.At the tract level, we recorded a proportional relationship between total cover of browse species and absolute consumption, suggesting an ideal free distribution. Taking into account the availability of forage, the degree of browsing and the proportion of each land type in the landscape, we calculated that 44.3% of the total forage consumption occurred in young forests, 42.3% in older forests and 13.4% in non-forest land.Our main conclusions are that moose conform to an ideal free distribution based on availability of forage within the landscape, and that all forest- and land types, not just young forests, are important as sources of browse for moose. Thus, it may be possible to release the browsing pressure on damage-sensitive young forests by increasing the food supply in other forest- and land types. Furthermore, managers needs to consider both the size of the moose population and the amounts of browse in the landscape when deciding on prudent management actions.

Fungal community shifts underpin declining mycelial production and turnover across a Pinus sylvestris chronosequence

Abstract Fungi play critical roles in ecosystem processes such as decomposition and nutrient cycling, but have also been highlighted as significant contributors to organic matter build‐up in boreal forest soils. Ectomycorrhizal (ECM) mycelial biomass and necromass dynamics have recently been highlighted as essential for regulating build‐up of soil organic matter. Understanding the extent to which shifts in mycelial community or growth trait composition cause changes in mycelial production and turnover over ecological gradients would aid a mechanistic understanding of these important processes at an ecosystem scale. Here, we test the hypotheses that shifting species and mycelial trait (exploration type) composition within the mycelial community underpin changes in biomass turnover with increasing forest age. We quantified mycelial turnover and assessed fungal community composition in a chronosequence of eight, 12‐ to 158‐year‐old, managed Pinus sylvestris forests. Turnover was estimated by determining mycelial biomass (ergosterol) in a sequence of ingrowth mesh bags and applying mathematical models. Fungal communities in the bags were identified using Pacific Biosciences sequencing of fungal ITS2 amplicons. To evaluate the accuracy of this method to represent all ECM fungi, community composition in bags was followed over time and compared with communities in soil. Mycelial communities changed with stand age, but we found no evidence that there were concurrent shifts in mycelial exploration types. Forest age and turnover were significantly correlated with ECM mycelial community composition and collectively explained 39.4% of total variation. The similarity between fungal communities in mesh bags and in soil was strongly forest age dependent, with communities in mesh bags diverging from soil communities in stands older than 60 years. However, in all stands, when bag incubation time exceeded 75 days, communities became more similar to soil communities. Synthesis. Our results support the idea that shifts in fungal community composition underpin the forest age‐related decrease in mycelial turnover; however, since ingrowth mesh bags exclude some mycorrhizal species in older forests, it remains a possibility that turnover estimates were not reflecting the entire community. While we found no evidence that mycelial exploration types of fungi changed systematically with forest age, we suggest that other traits that relate to biomass turnover and necromass degradation require further study, as they may explain the extent to which ectomycorrhizal fungi regulate and contribute to soil organic matter accumulation.

Landscape host abundance and configuration regulate periodic outbreak behavior in spruce budworm Choristoneura fumiferana

Landscape‐level forest management has long been hypothesized to affect forest insect outbreak dynamics, but empirical evidence remains elusive. We hypothesized that the combination of increased hardwood relative to host tree species, prevalence of younger forests, and fragmentation of those forests due to forest harvesting legacies would reduce outbreak intensity, increase outbreak frequency, and decrease spatial synchrony in spruce budworm Choristoneura fumiferana outbreaks. We investigated these hypotheses using tree ring samples collected across 51 sites pooled into 16 subareas distributed across a large ecoregion spanning the international border between Ontario (Canada), and Minnesota (USA). This ecoregion contains contrasting land management zones with clear differences in forest landscape structure (i.e. forest composition and spatial configuration) while minimizing the confounding influence of climate. Cluster analyses of the 76‐yr time‐series generally grouped by subareas found within the same land management zone. Spatial nonparametric covariance analysis indicated that the highest and lowest degree of spatial synchrony of spruce budworm outbreaks were found within unmanaged wilderness and lands managed at fine spatial scales in Minnesota, respectively. Using multivariate analysis, we also found that forest composition, configuration, and climate together accounted for a total of 40% of the variance in outbreak chronologies, with a high level of shared variance between composition and configuration (13%) and between composition and climate (9%). At the scale of our study, climate on its own did not explain any of the spatial variation in outbreaks. Outbreaks were of higher frequency, lower intensity, and less spatially synchronized in more fragmented, younger forests with a lower proportion of host species, with opposing outbreak characteristics observed in regions characterised by older forests with more concentrated host species. Our study is the first quantitative evaluation of the long‐standing ‘silvicultural hypothesis’ of spruce budworm management specifically conducted at a spatio‐temporal scale for which it was intended.

Modified forest rotation lengths: Long-term effects on landscape-scale habitat availability for specialized species

We evaluated the long-term implications from modifying rotation lengths in production forests for four forest-reliant species with different habitat requirements. By combining simulations of forest development with habitat models, and accounting both for stand and landscape scale influences, we projected habitat availability over 150 years in a large Swedish landscape, using rotation lengths which are longer (+22% and +50%) and shorter (−22%) compared to current practices. In terms of mean habitat availability through time, species requiring older forest were affected positively by extended rotations, and negatively by shortened rotations. For example, the mean habitat area for the treecreeper Certhia familiaris (a bird preferring forest with larger trees) increased by 31% when rotations were increased by 22%, at a 5% cost to net present value (NPV) and a 7% decrease in harvested volume. Extending rotation lengths by 50% provided more habitat for this species compared to a 22% extension, but at a much higher marginal cost. In contrast, the beetle Hadreule elongatula, which is dependent on sun-exposed dead wood, benefited from shortened rather than prolonged rotations. Due to an uneven distribution of stand-ages within the landscape, the relative amounts of habitat provided by different rotation length scenarios for a given species were not always consistent through time during the simulation period. If implemented as a conservation measure, prolonging rotations will require long-term strategic planning to avoid future bottlenecks in habitat availability, and will need to be accompanied by complementary measures accounting for the diversity of habitats necessary for the conservation of forest biodiversity.

Bears napping nearby: daybed selection by brown bears (Ursus arctos) in a human-dominated landscape

Daybeds are essential for the survival of brown bears (Ursus arctos L., 1758) and may represent a population-limiting resource in human-dominated landscapes. In this study, we demonstrate which land-cover types and bear characteristics affect daybed selection in north-central Slovakia. We used the positional and activity data of 21 bears acquired by GPS–GSM telemetry to identify 3864 daybeds. By use of K-select analysis and linear mixed-effects modelling, we explored how bears chose these places for their daytime resting. The most important drivers for daybed selection were the presence of dense regenerating forests and forest–shrubbery belts in farmland. Bears avoided resting in older forests without suitable undergrowth. Females selected daybeds differently depending on the presence of dependent cubs. During spring – early summer, females with cubs of the year avoided other bears by selecting more rugged terrain. These females also selected daybeds significantly closer to human settlements than adult males, possibly to avoid the risk of infanticide. In late summer – autumn, all bears selected daybeds closer to human settlements than in spring, probably because they were attracted by maize (Zea mays) fields and fruit trees. Many daybeds were located outside protected areas in farmland closer to people, which could increase bear–human conflicts.

The negative influences of the new brazilian forest code on the conservation of riparian forests

AbstractMore than one million hectares of riparian forests were degraded or altered in Mato Grosso State (Brazil) up to 2009. The aim of the research is to set a comparative scenario to show differences in the quantification of environmental liabilities in riparian forest areas resulting from the change in native vegetation protection rules due to the transition between Laws 4771/65 and 12651/2012. Data collection took place in a marginal stretch of Vermelho River in Rondonópolis County, Mato Grosso State. The following data set was taken into consideration: aerial images derived from unmanned aerial vehicle, Rapid Eye satellite images and orbital images hosted at Google Earth. The spatial resolution of those images was compared. The aerial photos composed a mosaic that was photo-interpreted to generate land use and occupation classes. The riparian forest areas of a rural property were used as parameter, and their environmental situation was compared in 05 meter and 100 meter strips. Thus, by taking into consideration the current rules, 23,501 m2of area ceased to be an environmental liability within the riparian forest and became a consolidated rural area. According to the previous Forest Code, in a different scenario, that is, in a set of rural properties, the public authority would receive USD 68,600.00 in fines. The new Brazilian Forestry Code of 2012, which replaces the previous one made in 1965, exempts those responsible for rural property from regenerating previously deforested native vegetation - an obligation established by older Forest Code. We have shown that the new Forest Code has diminished the legal responsibility of the rural owners in relation to the maintenance of forest fragments in their properties.

Estimation of change in forest height growth

Abstract Forest height increment rate is related to the forest growth conditions. Data bases of previous forest inventories contain information about forest heightage relationship on large number of forest stands while repeated measurements of permanent sample plots provide an excellent reference for comparison. Repeated airborne laser scanning of forest stands is an additional source for the estimation of change in forest structure. In this study, height growth of middle-aged and older forest stands for about 10 year period was compared to an algebraic difference model on permanent sample plots (66) and for a sample of forest stands with repeated airborne laser scanning data (61). The model was based on a large dataset of forest inventory records from the period of 1984–1993. Statistically significant increased forest height growth was found in permanent sample plots based on tree height measurements (9 cm yr−1) as well in stands with repeated laser scanning data (4.5 cm yr−1) in South-East Estonia compared to the algebraic difference model. The difference between the two data sets was explained by their mean age and site class, but the increased forest height growth compared to the old forest inventory data indicates improved growth conditions of forests in the test area. The results hint also that empirical data-based forest growth models need to be updated to avoid biased growth estimates.

Local variability in the timing and intensity of tropical dry forest deciduousness is explained by differences in forest stand age

Tropical Dry Forest deciduousness is a behavioral response to climate conditions that determines ecosystem-level carbon uptake, energy flux, and habitat conditions. It is regulated by factors related to stand age, and landscape scale variability in deciduous phenology may affect ecosystem functioning in forests throughout the tropics. This study determines whether observed phenological differences are explainable by forest age in the southern Yucatán Peninsula in Mexico, where forest clearing for shifting cultivation has created a mosaic of forest stands of varying age. Matched-pair statistical tests compare neighboring forest pixels of different age class (12–22 years versus 22+ years) and detect significant differences in Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI)-derived metrics related to the timing and intensity of deciduousness during three dry seasons (2008–2011). In all seasons, young forests exhibit significantly more intense deciduousness, measured as total seasonal change of EVI normalized by annual maximum EVI (p < 0.001), and larger normalized EVI change during successive dry season months relative to start-of-dry-season EVI (p < 0.001), than neighboring older forests subject to similar environmental conditions.

Differentiating Structural and Compositional Attributes across Successional Stages in Chilean Temperate Rainforests

The landscape in the lowlands of south-central Chile is dominated by agricultural lands and forestry plantations of exotic species. Natural forests are restricted to successional forests, while old-growth forests are nearly absent. The lack of old-growth forests may deprive society from some ecosystem services. Both successional and old forests differ in their ecological functions and in the ecosystem services they can provide. To promote old-growth characteristics in successional forests, it becomes necessary to know which compositional and structural attributes differentiate forests along succession. We aim at identifying the differential attributes among successional and old-growth forests in the lowlands in the northern portion of the Valdivian Rainforests. We analyzed 19 variables in seven different forests and found statistically significant differences in 13 of them. A subset of these variables illustrated major patterns that differentiate successional stages, of which a few could be more easily controlled through management. The latter include lowering tree densities (from &gt;3000 to &lt;1500 trees per hectare), increasing volume of large trees, especially of shade-tolerant species, and structural heterogeneity (a Gini coefficient &gt;0.7 represents older forests). While successional forest show a rapid recovery, forest managers would need to focus in controlling these attributes to increase their old-growth characteristics.

Research Article: Soil respiration in upper Great Lakes old-growth forest ecosystems

Forests, through photosynthetic fixation of carbon dioxide, serve as natural carbon (C) sinks, thereby offsetting a substantial fraction of anthropogenic greenhouse gas emissions. However, forests of the upper Great Lakes region are on average getting older, prompting uncertainty in the region's future capacity to sequester C. Several studies demonstrate higher-than-expected rates of C sequestration in biomass and soils, or net ecosystem production (NEP), of older forests, with declining C losses from soils a proposed mechanism sustaining NEP as forests age. Forest plots spanning nearly 200 years of ecosystem development and including three different old-growth forest types were used to examine changes with age in growing season soil respiration (Rs) - the C emitted from soils by roots and soil microbes. How heterotrophic soil respiration (Rh) - the C emitted from soils by microbes only - varies among old-growth forest types and with soil environment was also examined. Mean growing season Rs and soil temperature were significantly lower in old-growth forests, with the former declining as forests aged. Laboratory incubations and scaled estimates of Rh suggest significantly higher rates in more tree species diverse mixed canopy old-growth forests than in less diverse conifer and deciduous old-growth forest stands. Soil moisture was an important driver of Rh in all old-growth forest types, particularly in the top, carbon-rich organic horizon. Based on the results of this study, it can be concluded that declining C emissions from the soils of old-growth forests may contribute to unexpectedly high rates of forest C sequestration as forests age.

Tree species and time since afforestation drive soil C and N mineralization on former cropland

Conversion from agriculture to forestry is considered a measure for mitigation of atmospheric CO2 but the impacts on soil C and N processes remain still unclear. We investigated heterotrophic respiration (RH), specific carbon mineralization (CMIN) and nitrogen mineralization (NMIN) in Norway spruce (Picea abies (Karst.) L.) and oak (Quercus robur L.) chronosequences on former cropland by laboratory incubation. The RH was estimated as the release of C per gram soil and CMIN as the release of C per gram of soil organic matter (SOM). Seven Norway spruce stands (16–44years), eight oak stands (4–43years), a cropland, a 35years old permanent pasture and a 200-year-old oak-dominated forest were sampled (0–5cm and 5–15cm soil layers) in early spring. The SOM content gradually increased with stand age in 0–5cm but remained the same in the 5–15cm soil layer. The RH in the 0–5cm layer gradually increased with time since afforestation in both tree species while there was no change in CMIN. In 5–15cm, neither RH nor CMIN changed significantly after afforestation, but oak stands had significantly higher RH than Norway spruce. The NMIN and nitrification in 0–5cm significantly increased with stand age and only nitrification was higher in oak. In 5–15cm, only NMIN in oak increased with stand age, but both NMIN and nitrification were significantly higher in oak than spruce. Cropland RH, CMIN and NMIN rates were comparable to those found within the first decades of afforestation, whereas the 200-year-old forest and the pasture generally had RH and NMIN rates similar to the older chronosequence stands.We conclude that potential RH and soil N mineralization increased with time since afforestation and were tree species specific. Soil organic C stock gains observed in this area during the first 45years after afforestation were not driven by decreased SOM decomposability, leaving increased litter C inputs as a more likely explanation. The lower CMIN in the 200-year-old forest suggests that future studies should include older forests to assess if the stability of C and the retention of N may increase in a longer term perspective.

Spring and Winter Home Ranges of the Haida Gwaii Northern Saw-Whet Owl (Aegolius acadicus brooksi)

Abstract Using radiotelemetry we determined for a managed landscape, seasonal home-range sizes and habitat compositions of the threatened Haida Gwaii subspecies of the Northern Saw-whet Owl (Aegolius acadicus brooksi). We trapped 17 owls, and successfully monitored seven: four adult males from May−June 2011 (spring) and three owls (adult male, juvenile male, juvenile female) from January−February 2012 (winter). The adult males in spring moved up to 2.9 km in a 24-hr survey period and had nonoverlapping 95% fixed kernel home ranges (276−375 ha) that were composed of four defined habitat classes (open, early seral forest, mid-seral forest, older forest). Comparisons between internal core-use areas (50% and 30% fixed kernels) and the larger surrounding 95% fixed kernel home ranges suggested these males used foraging and roosting habitat proportional to its availability within the home ranges. The three tagged winter owls had larger 95% fixed kernel home ranges (690−1310 ha) than those in spring, and moved up...

Variation In Early-Successional Habitat Use Among Independent Juvenile Forest Breeding Birds

ABSTRACT Adults and juveniles of some forest breeding birds shift habitat use during the post breeding season from late to early successional forest. Juveniles of smaller passerine species are difficult to radio-track, and there is limited information on their habitat preferences, especially once they become older and independent. We determined if independent hatch-year birds captured in early-successional habitat remained there for extended periods, or if these habitats were only occupied infrequently during foraging activities. We determined habitat use for Ovenbirds (Seiurus aurocapilla), Worm-eating Warblers (Helmitheros vermivorum) and Red-eyed Vireos (Vireo olivaceus) during the independent post-fledging period in the Missouri Ozarks. We placed radio transmitters on 29 hatch-year birds captured in clearcuts and attempted to relocate them for 24 days in the summer of 2012. All three species had a greater relative probability of use of clearcut forest stands with small trees than older forests. Ovenbi...

Patterns of plant functional variation and specialization along secondary succession and topography in a tropical dry forest

Long-term human disturbance of tropical forests may favor generalist plant species leading to biotic homogenization. We aimed to a) assess if generalist species dominate across different successional ages and topographical positions in a tropical dry forest with a long history of human disturbance, b) to characterize functional traits associated with generalist and specialist species, and c) to assess if a predominance of generalists leads to a homogeneous functional structure across the landscape. We used a multinomial model of relative abundances to classify 118 woody species according to their successional/topographic habitat. Three species were classified as secondary-forest specialists, five as mature-forest specialists, 35 as generalists, and 75 as too rare to classify. According to topography, six species were hill specialists, eight flat-site specialists, 35 generalists, and 70 too rare. Generalists dominated across the landscape. Analysis of 14 functional traits from 65 dominant species indicated that generalists varied from acquisitive strategies of light and water early in succession to conservative strategies in older forests and on hills. Long-term human disturbance may have favored generalist species, but this did not result in functional homogenization. Further analyses considering other functional traits, and temporal and fine-scale microenvironmental variation are needed to better understand community assembly.

Landscape Structure and Mature Forest Biodiversity in Wet Eucalypt Forests: A Spatial Analysis of Timber Production Areas in South-Eastern Australia

Fire and timber harvesting can diminish the extent of older forests in the near term. The amount and configuration of mature and regenerating forest in the landscape (landscape structure) influences habitat suitability for mature-forest-associated species. We applied spatial analysis to describe the landscape structure of three wet eucalypt forest landscapes in south–eastern Australia and used the results from empirical biodiversity studies to frame interpretation of possible impacts on habitat suitability. We determined the extent of structurally mature forest, its reservation status, and the extent to which it may be edge affected. We also assessed how landscape structure potentially impacts the re-establishment of mature-forest-associated species into previously harvested areas through the proximity to (mature forest influence)—and extent of (landscape context)—mature forest in the surrounding landscape. Our analyses were designed to inform forest management initiatives that draw on these landscape-scale concepts. Central Highlands Victoria had less structurally mature eucalypt forest (4%) compared to North West Tasmania (14%) and Southern Forests Tasmania (21%). Detrimental effects of edge influence on structurally mature forest appeared relatively minor. Low levels of mature forest influence combined with low-medium surrounding mature forest cover (landscape context) indicate potential limitations on recolonisation of coupes by mature-forest-associated species. Our results vindicate the recent shift toward variable retention silviculture and landscape context planning. Our approach to landscape analysis provides a useful framework for other managed forest landscapes.

Effects of forest height and vertical complexity on abundance and biodiversity of bats in Amazonia

Anthropogenic activities have accelerated habitat change, loss, and fragmentation, threatening biodiversity over large portions of the tropics. The resulting anthropogenically created landscape mosaics often include forests of different successional stages or that have experienced different levels of anthropogenic use, which affect the physical structure of the forest (e.g., forest height, vertical complexity of vegetation). These physical characteristics of forests may affect the abundance and biodiversity of forest inhabitants, and obscure effects of landscape changes (e.g., percent forest cover) on animal species. Because bats are ecologically diverse and include seed dispersers, pollinators, and top predators, they contribute to the structure and function of forests, and directly affect forest integrity and regeneration. Thus, understanding how variation in the vegetative structure of forests affects the abundance and biodiversity of bats may provide important information to effectively manage and conserve forest fragments. We surveyed bats at 24 sites in the southern Brazilian Amazon, and quantified vegetation structure (density, height, and basal area of trees, density of understory, and canopy openness). Using generalized linear mixed-effects models, we tested simple relationships of each structural characteristic with community- (taxonomic and phylogenetic dimensions of biodiversity), guild-, and population-level attributes of bats. Models for total abundance, taxonomic biodiversity (species diversity and dominance), and phylogenetic diversity were significant, increasing with tree height and basal area, and decreasing with canopy openness. At the population level, abundances of frugivores (Carollia perspicillata, Rhinophylla pumilio, Artibeus planirostris, A. obscurus, A. lituratus, Uroderma bilobatum) and nectarivores (Lonchopylla thomasi, Glossophaga soricina) were related significantly to vegetation structure. Abundances of some understory frugivores exhibited negative relationships with tree height, choosing younger forests, whereas abundances of canopy frugivores were highest in closed canopy forests. Of the nectarivores, L. thomasi was more abundant in older forests (negative relationship with density of trees), whereas G. soricina was more abundant in areas with low canopies and low basal area (i.e., earlier successional forest). Consequently, effective management of forest fragments should include consideration of local forest age and vegetation structure, as well as forest connectivity and patch size. In general, protecting areas with large trees and closed canopies enhances the persistence of pollinators and seed dispersers.

Mapping spatial distribution of forest age in China

AbstractForest stand age is a meaningful metric, which reflects the past disturbance legacy, provides guidelines for forest management practices, and is an important factor in qualifying forest carbon cycles and carbon sequestration potential. Reliable large‐scale forest stand age information with high spatial resolutions, however, is difficult to obtain. In this study, we developed a top‐down method to downscale the provincial statistics of national forest inventory data into 1 km stand age map using climate data and light detection and ranging‐derived forest height. We find that the distribution of forest stand age in China is highly heterogeneous across the country, with a mean value of ~42.6 years old. The relatively young stand age for Chinese forests is mostly due to the large proportion of newly planted forests (0–40 years old), which are more prevailing in south China. Older forests (stand age &gt; 60 years old) are more frequently found in east Qinghai‐Tibetan Plateau and the central mountain areas of west and northeast China, where human activities are less intensive. Among the 15 forest types, forests dominated by species of Taxodiaceae, with the exception of Cunninghamia lanceolata stands, have the oldest mean stand age (136 years), whereas Pinus massoniana forests are the youngest (18 years). We further identified uncertainties associated with our forest age map, which are high in west and northeast China. Our work documents the distribution of forest stand age in China at a high resolution which is useful for carbon cycle modeling and the sustainable use of China's forest resources.

Using an agent-based model to examine forest management outcomes in a fire-prone landscape in Oregon, USA

Fire-prone landscapes present many challenges for both managers and policy makers in developing adaptive behaviors and institutions. We used a coupled human and natural systems framework and an agent-based landscape model to examine how alternative management scenarios affect fire and ecosystem services metrics in a fire-prone multiownership landscape in the eastern Cascades of Oregon. Our model incorporated existing models of vegetation succession and fire spread and information from original empirical studies of landowner decision making. Our findings indicate that alternative management strategies can have variable effects on landscape outcomes over 50 years for fire, socioeconomic, and ecosystem services metrics. For example, scenarios with federal restoration treatments had slightly less high-severity fire than a scenario without treatment; exposure of homes in the wildland-urban interface to fire was also slightly less with restoration treatments compared to no management. Treatments appeared to be more effective at reducing high-severity fire in years with more fire than in years with less fire. Under the current management scenario, timber production could be maintained for at least 50 years on federal lands. Under an accelerated restoration scenario, timber production fell because of a shortage of areas meeting current stand structure treatment targets. Trade-offs between restoration outcomes (e.g., open forests with large fire-resistant trees) and habitat for species that require dense older forests were evident. For example, the proportional area of nesting habitat for northern spotted owl (Strix occidentalis) was somewhat less after 50 years under the restoration scenarios than under no management. However, the amount of resilient older forest structure and habitat for white-headed woodpecker (Leuconotopicus albolarvatus) was higher after 50 years under active management. More carbon was stored on this landscape without management than with management, despite the occurrence of high-severity wildfire. Our results and further applications of the model could be used in collaborative settings to facilitate discussion and development of policies and practices for fire-prone landscapes.

Forest Age Influences In-stream Ecosystem Processes in Northeastern US

A disturbance or natural event in forested streams that alter available light can have potential consequences for nutrient dynamics and primary producers in streams. In this study, we address how functional processes (primary production and nutrient uptake) in stream ecosystems respond to changes in forest canopy structure. We focus on differences in incoming irradiance, nutrient uptake (NO3, NH4, and PO4) and open-channel metabolism seasonally in 13 forested streams that drain forests with different canopy structures (10 to >300 years old) in the northeastern United States. Light irradiance was related to forest age in a U-shaped pattern, with light being the greatest in both young open forests ( 245 years old), whereas the darkest conditions were found in the secondary growth middle-aged forests (80–158 years old). Streams that had adjacent open or old-growth riparian forest had similar conditions with greater standing stock biofilm biomass (chl a), and elevated ER in October compared to streams with middle-aged riparian forests. Compared to all sites, streams with old-growth riparian forest had the greatest in-stream primary production rates (GPP) and elevated background nutrient concentrations, and to a lesser degree, increased nutrient retention and uptake (V f). Streams draining older forests tended to be more productive and retentive than middle-aged forests, likely due to increased light availability and the age and structure of surrounding forest canopies. Middle-aged forests had the least variation in response variables compared to streams in young and old-growth riparian forests, likely a result of uniform canopy conditions. As the structure of widespread middle-aged forests in NE US is altered by loss of specific tree species, climate change, and/or human activity, it will impact in-stream production and nutrient dynamics and may ultimately alter nutrient loading in downstream catchments.

Spatial micro-distribution of methanotrophic activity along a 120-year afforestation chronosequence

Methanotrophic bacteria drive upland soil methane (CH4) uptake. Land-use change often affects their activity, but the mechanisms involved are not well understood. We studied soil-atmosphere CH4 fluxes along a 120-year Norway spruce afforestation chronosequence on subalpine pasture, testing whether effects were related to shifts in the spatial niche of methanotrophs. Previous field data had shown that soil 14CH4 uptake increased with forest age, and that this effect was driven by decreased water filled pore space due to higher rainfall interception in the more developed canopies of older forest stands. The spatial distribution of methanotrophic activity was determined by 14CH4-labelling followed by soil section preparation, aggregate size fractionation, aggregate erosion, and micro-autoradiographic imaging. Uptake rates of CH4 measured in laboratory incubations of soil cores as well as their water contents largely followed the in situ measurements previously made in the field. 14CH4 assimilation was heterogeneously distributed, and occurred further down the soil profile in older forest that had a more developed organic layer that did not contribute to CH4 uptake. Assimilation was largest in 2—8 mm aggregates, and higher at the exterior than in the interior of aggregates. Our data indicates that differences in soil aggregation and related methanotrophic activities did not contribute substantially to higher CH4 uptake in older forest, mostly because aggregation did not change much with age. On a per mass basis, however, large aggregates contributed less to CH4 uptake due to their unfavorable surface to volume ratio. More generally, we argue that the (sub-)aggregate heterogeneity of soil microbial activity and diversity is underexplored, although it critically determines ecological interactions that drive ecosystem-level processes.