Attributes Of Old-growth Forests Research Articles

Quantifying old-growth forest of United States Forest Service public lands

Old-growth forests are globally valued for their ecological attributes, cultural significance, and in many cases their rarity. Yet, defining and quantifying these forests has been a difficult task. This study developed an approach to consistently estimate extent of old-growth forest on United States Department of Agriculture (USDA) Forest Service National Forest System (NFS) lands, using NFS regional old-growth definitions applied to the US national forest inventory (conducted by the USDA Forest Service Forest Inventory and Analysis [FIA] program). This method was developed in response to a presidential order (EO#14072, April 22, 2022) and federal laws (e.g., Infrastructure Investment and Jobs Act, 2021; Inflation Reduction Act, 2022). We worked with NFS experts to obtain regionally approved criteria for establishing old growth status based on NFS definitions, assessments, and related documents. NFS regional old growth definitions focus on structural characteristics of forests with criteria for old growth status commonly including minimum abundance of large live trees (in eight of nine regions), tree or stand age (in eight of nine regions), and dead large tree density (in three of nine regions). Determining the regional criteria to use was straightforward for some NFS regions where old-growth forest definitions were specific, and in some cases, had already been applied to FIA data to quantify old-growth forest area. In other NFS regions, such as where definitions have never been applied in an operational manner, or where there were merely assessments of remnant old-growth forest conditions, determining exact criteria was more difficult. We estimate that there are approximately 10 million ha of old growth across NFS forests, as defined by NFS criteria, with the preponderance in the western US states. This study produces the first old-growth forest assessment at the national scale based on NFS definitions and FIA’s statistically-rigorous national forest inventory of the US. These methods can be repeated with future inventories or modified when definitions change to produce updated estimates of old-growth forest attributes, and such work is already underway.

Old-growth attributes in a maturing secondary Indiana state forest: an opportunity for balanced management1

Primary old-growth forests are rare in the state of Indiana and are found only in small, isolated patches of nature preserves. Recent research underscores the values of large tracts of secondary old-growth (referred to in this paper as “older” forests), including carbon sequestration, forest resiliency, mitigation of climate change impacts, and conservation of biological diversity. Due to historical management, many portions of Indiana state forests are maturing, and yet the “older” successional stage is underrepresented. One of these maturing forests, the site of our study, is in south-central Indiana within the Back Country Area (BCA) of the Morgan-Monroe/Yellowwood State Forest (two state forests, herein called a complex, including parcels in three counties with the largest block of forests spanning Brown and Monroe counties). Our study of the forest structure of the BCA addresses the following questions: (a) Is this mature forest developing ecological attributes of old-growth forests, thus making it a good candidate for an older forest reserve? (b) Does this forest support the plant community characteristic of natural areas of Indiana? We analyzed forest stand metrics, coarse woody debris and snags, age of the largest live trees, and the floristic quality of the herbaceous layer. We then compared these data with published accounts from Indiana nature preserves. Metrics such as tree basal area, number of large-diameter trees, and number of snags are within the range of those measured in existing old-growth forests of Indiana. Analysis of tree cores and log cross-sections shows that 78% of the sample trees were over 100 yr old, with 24% over 130 yr, which is also comparable to old-growth forest nature preserves in the state. The metrics of the Floristic Quality Assessment of the broader plant community of the BCA are comparable to or higher than the metrics from published assessments of Indiana nature preserves. Collectively, the attributes measured indicate that the BCA supports a maturing secondary forest with old-growth characteristics. In the absence of further timber harvest, the BCA as a reserve could reach older forest status within 50 yr. Our study demonstrates that the BCA forest is a prime candidate for an older forest reserve. This study of the BCA could also serve as a model for future assessments of potential older forest reserves in other state forests. Reserves of older forests free from harvest are not incompatible with other management goals and can be a valuable part of a broader-scale management plan. These forest reserves should be promoted across the state to increase the representation within Indiana's state forest system of late-successional secondary forest exhibiting ecological attributes of old-growth forests, thereby enhancing the role of state forests in biodiversity protection and climate mitigation.

Woodland salamander population structure and body condition under irregular shelterwood systems

Ecosystem-based management aims to preserve old-growth forest attributes using techniques mimicking natural disturbances. One such technique is irregular shelterwood logging, but its impacts on forest floor organisms are poorly known. Our objective was to quantify the effects of three different treatments of irregular shelterwood on population structure and the body condition of the eastern red-backed salamander (Plethodon cinereus) 5–6 years following harvesting. A total of 64 sites in western Québec were sampled using artificial refugia and quadrat searches. Large salamanders (>32 mm) were more abundant in the gap treatment than in strip, uniform, or control treatments. Small salamanders (≤32 mm) followed the same pattern, although the differences were marginal. For a given treatment, small salamanders were as abundant as large salamanders. Salamander body condition differed between the 2 years of sampling but did not differ among treatments, regardless of salamander size. We conclude that environmental conditions in irregular shelterwood treatments 5–6 years following harvesting support populations of small vertebrates on the forest floor.

Driving factors of conifer regeneration dynamics in eastern Canadian boreal old-growth forests.

Old-growth forests play a major role in conserving biodiversity, protecting water resources, and sequestrating carbon, as well as serving as indispensable resources for indigenous societies. Novel silvicultural practices must be developed to emulate the natural dynamics and structural attributes of old-growth forests and preserve the ecosystem services provided by these boreal ecosystems. The success of these forest management strategies depends on developing an accurate understanding of natural regeneration dynamics. Our goal was therefore to identify the main patterns and drivers involved in the regeneration dynamics of old-growth forests with a focus on boreal stands dominated by black spruce (Picea mariana (L.) Mill.) and balsam fir (Abies balsamea (L.) Mill.) in eastern Canada. We sampled 71 stands in a 2 200 km2 study area located within Quebec's boreal region. For each stand, we noted tree regeneration (seedlings and saplings), structural attributes (diameter distribution, deadwood volume, etc.), and abiotic (slope and soil) factors. The presence of seed-trees located nearby and slopes having moderate to high angles most influenced balsam fir regeneration. In contrast, the indirect indices of recent secondary disturbances (e.g., insect outbreaks or windthrows) and topographic constraints (slope and drainage) most influenced black spruce regeneration. We propose that black spruce regeneration dynamics can be separated into distinct phases: (i) layering within the understory, (ii) seedling growth when gaps open in the canopy, (iii) gradual canopy closure, and (iv) production of new layers once the canopy is closed. These dynamics are not observed in paludified stands or stands where balsam fir is more competitive than black spruce. Overall, this research helps explain the complexity of old-growth forest dynamics, where many ecological factors interact at multiple temporal and spatial scales. This study also improves our understanding of ecological processes within primary old-growth forests and identifies the key factors to consider when ensuring the sustainable management of old-growth boreal stands.

Effect of Old-Growth Forest Attributes on Lichen Species Abundances: A Study Performed Within Ceahlău National Park (Romania)

Abstract — This study is based on finding a representative pattern of interactions between old-growth forest attributes and lichen species abundances. The field activities were performed within Ceahlau National Park, Neamţ County, North-Eastern Romania. In total 38 sampling units of 10 by 10 m were randomly selected, within these all phorophytes with circumferences that exceed 70 cm were selected. On each phorophyte, a frame of 20 by 20 cm was randomly fixed and all lichen specimens included were sampled. Relationships between macrovariables, microvariables and response variables were tested using the Kendall rank order correlation coefficient. To explain the influence of macrovariables and microvariables on response variables, polynomial regression was used.The results indicated that lichen species abundances are significantly influenced by macrovariables such as herb coverage, altitude, slope, multilayered canopies and host phorophyte diversity.With regard to the microvariables, the aspect, rhytidome cr...

Decline in bryophyte diversity in predominant types of central European managed forests

The extent to which the diversity of forest-inhabiting bryophytes is related to forest management practices has been the subject of a recent study. However, the question of how these practices affect the spatial distribution pattern of bryophyte diversity throughout managed European forests remains unanswered. We surveyed bryophyte diversity in six large forest complexes in the Czech Republic. Our sites encompass a range of managed forest stands (including various temporal phases such as clearings and young forests) across a gradient of environmental conditions. In general, the bryophyte species richness in managed forests was less than in unmanaged forests. Only unmanaged forest stands that provided suitable substrates such as large dead woody debris and large diameter beeches (Fagus sylvatica) were able to support rare bryophyte species. Mature managed forests with simplified tree structure, dominated by either deciduous or coniferous species shared similar bryophyte species richness (α-diversity) and pool (γ-diversity). It appears that forest management, which leads to the loss of old-growth forest attributes, may result in low-diversity bryophyte communities regardless of tree species composition. Nevertheless, bryophyte species turnover (β-diversity) was spatially uniform in mature managed forests dominated by conifers, but quite variable in those dominated by deciduous tree species. Managed forests with diverse tree structure and composition approximated the species pool size of unmanaged forests, in spite of their small contribution to the total area of managed forests. Hence, forest management as commonly applied in the managed forests of the Czech Republic does not appear to be conducive to the persistence of diverse bryophyte assemblages. We suggest that some essential changes in forest management practices are necessary to maintain the conditions favorable to the preservation of bryophyte diversity in central European forests.

Does a set-aside conservation strategy help the restoration of old-growth forest attributes and recolonization by saproxylic beetles?

The decline of many saproxylic species results from the decrease in old-growth structures in European harvested forests. Among conservation tools, protected reserves withdrawn from regular harvesting and extended rotations have been employed to restore old-growth attributes in structurally simplified managed forests, even if the effects of such management actions on forest habitats and biodiversity remain largely unknown. In this study, we compared structural stand features and saproxylic beetle assemblages in two stand classes – recently harvested stands and long-established reserves, where less or more than 30 years had elapsed since last harvest. Habitat and saproxylic beetle data were collected according to standardized protocols in 153 plots in seven lowland deciduous forests. Tangible contrasts in stand features were found between long-established reserves and recently harvested plots. Indeed, most higher-value densities and volumes were found in unharvested areas. The difference was weaker for microhabitat-bearing tree density than for deadwood; some deadwood features, such as volume of large downed and standing deadwood showed a very pronounced difference, thus indicating a marked deleterious effect of forest harvesting on these elements. Deadwood diversity, on the other hand, was only slightly affected and the level of stand openness did not change. The response of saproxylic beetles to delayed harvesting was weaker than the structural changes in deadwood features. Indeed even if only some guilds weakly increased in non-harvested plots, harvesting classes significantly affected the abundance of a quarter of the species tested. Our results tend to question measures such as rotating and temporarily ageing patches. We argue in favor of permanent strict fixed-location reserves. Future work should examine how stands recover old-growth forest attributes and how the associated saproxylic fauna colonizes in the long term.

Modeling tree spatial distributions after partial harvesting in uneven-aged boreal forests using inhomogeneous point processes

Old-growth forests are characterized by their compositional and structural complexity, which contributes to local biodiversity. To maintain these old-growth attributes in boreal forests, traditional even-aged management systems based on clear-cutting are gradually shifting to ecosystem-based management, which includes partial harvesting in uneven-aged stands. We investigated the spatial structure of trees within 31 plots that had been established in Canadian boreal forest after selection cutting. We used an approach based on heterogeneous point processes to investigate the relationship between tree density and distance to the nearest logging trail. Tree density was positively and log-linearly related with distance to logging trails, with large trees being particularly scarce near the trails. Using a statistical approach based on mixed models with random plot effects that accounted for distance to the nearest trail, we assessed how the spatial pattern of trees affected the diameter increment of trees. Seven-year diameter increments of trees with diameters <14cm were negatively related to the distance to logging trails. Accordingly competitive interactions among trees left after partial harvesting, which aim at preserving old-growth forest attributes, were different from those of natural boreal forests. Based on these results, a stochastic model was applied using heterogeneous Gibbs point processes to realistically describe and simulate the location of residual trees after selection cutting in boreal stands that were represented by forest inventories without spatial information on tree location.

Land ownership drives stand structure and carbon storage of deciduous temperate forests

In European cultural landscapes, forest area is subdivided into a mosaic of stands of different ownership types and sizes. Differences in ownership and different goals of the owners have a potentially decisive influence on the provision of forest ecosystem services and the implementation of instruments for the conservation of biodiversity. This study hypothesizes that forest ownership is an indirect determinant of forest management approaches and is thereby relevant for biodiversity conservation and carbon sequestration. We compared structure and species composition of forest stands in clusters of different ownership types, namely state-owned, municipal and small-scale private forests, in southwestern Germany. Although close-to-nature management has been practiced in public forests for some time, our study demonstrates that tree species diversity does not vary significantly between ownership types but is correlated with biogeographical factors. However, small-scale private forests comprise significantly higher levels of structural diversity, more dead wood and greater carbon storage capacity than both categories of public forests. This is contrary to other studies, where publicly owned lands were found to host higher biodiversity, and differs from the global trend, where continued fragmentation of private lands threatens forest sustainability. The importance of small-scale private forests, e.g. for the conservation of old-growth and dead wood dependent species, seems due to less intensive and more diverse forest management. The role of such forests for biodiversity conservation and carbon regulation may be jeopardized through forest conversion and wood mobilization initiatives accompanying rising natural resource prices. To safeguard forest biodiversity and ecosystem services, ownership-specific incentive schemes should be coordinated and refined. In public forests, close-to-nature management approaches should be complemented with binding goals aimed at promoting old-growth forest attributes and allowing site-specific variation in management practices. To conserve diversity in small-scale private forests, financial incentives and remuneration schemes for the provisioning of forest biodiversity and ecosystem services should be developed. Moreover, consulting and the provision of information on sustainable forest and conservation management should be intensified.

Partial cutting in old-growth boreal stands: An integrated experiment

The uncut boreal forest of eastern Québec is largely composed of stands with an irregular structure. Traditionally, even-aged silvicultural systems have been used for these forests but a strong interest has developed in alternative approaches. In 2004, an integrated experiment was established to provide a general assessment of harvesting uneven-aged boreal forest stands with a wide variety of treatments. Here, we summarize the key results of this experiment, which involved four silvicultural treatments differing in the level of tree retention: a clearcut with advance growth protection, a severe partial cut protecting small vigorous merchantable stems (75%–90% basal area removed), and two patterns of selection cutting (35% basal area removed). We evaluated treatment effects on vegetation attributes and animal species assemblages. We also assessed whether or not selection cutting approaches could become broadly used on an operational basis by examining simple forms of application and assessing their economic profitability. We found that many attributes of old-growth forests can be maintained with selection cutting, even with simple approaches that do not invest in marking trees to cut. Unlike more severe cuts, silvicultural treatments with more than 55% tree retention largely maintain the animal assemblages associated with old forests. Financial analysis showed that selection cutting is profitable over the long time frame, but clearcutting remains more profitable. This greater profitability is related to the first entry, whereas future entries will be more profitable with selection cutting.

Contrasting responses of epiphytic and dead wood-dwelling lichen diversity to forest management abandonment in silver fir mature woodlands

In the Alps, many forests are under abandonment because of direct protection or the unprofitability of timber production. The objective of this study was to analyse the effect of silviculture abandonment on the species richness and composition of epiphytic and dead wood-dwelling lichens in silver fir woodlands. An abandoned and a currently non-intensively managed forest watershed of the eastern Italian Alps that were matched for topography, stand structure, plant community and history of use were selected and randomly sampled for the lichen diversity of their silver fir mature stands. Generalised linear mixed models were used for the analyses of the species richness, whereas the species composition patterns were explored by redundancy analysis. The diversity of both of the lichen guilds were explained by the microhabitat conditions related to the contrasting management regimes, but they had opposite responses to the abandonment of the silvicultural activities. The epiphytic lichen communities were richer in species in the managed than in the abandoned silver fir woodlands. However, the effect of a 50year management cessation on the epiphytic lichens may change in the long term when natural disturbances create gaps and increase the attributes of old-growth forests. The dead wood-dwelling lichen species richness was higher in the abandoned forest because an increased availability of types of dead wood is usually rare in managed forests. The dead wood-dwelling lichen communities of the managed forests were a subset of a more diverse community that was developing in the abandoned forest. Our results indicated that, in non-intensively managed silver fir mature stands, lichen diversity may benefit from the retention of logs and snags, which provide habitat features typical of old-growth forests.

Assessment and management of old-growth forests in south eastern Australia

Old-growth forests in south eastern Australia are important for biodiversity conservation, recreation, carbon storage, social values and, to a declining extent, for timber production. Developing a comprehensive definition of old-growth forest that can apply across all Australian vegetation types has been challenging. Old growth can be viewed from ecological and social perspectives. For policy and management purposes old growth has been defined as a growth stage in forest development, incorporating ecological maturity and lack of evidence of past disturbance. Classification and assessment of old growth has largely been restricted to those areas covered by regional forest agreements (RFAs) between different states and the Federal Government. Old growth can be impacted by wildfire, timber harvesting, insect pests, diseases and other disturbances. Climate change will also present challenges for the future management of old-growth forests. There is increasing scientific understanding of the relationships between species, forest growth stage and old-growth forest attributes. To meet biodiversity conservation objectives, the management focus is shifting from assessing and protecting old-growth forests, to providing for forests across the landscape with old-growth attributes. This approach may be at odds with other conceptions of old growth based on notions of undisturbed systems free of human influence.

LIDAR remote sensing for secondary Tropical Dry Forest identification

This study evaluates the use of waveform LIDAR data for the characterization of secondary forests stages in a Tropical Dry Forest (TDF) area of Guanacaste, Costa Rica. A secondary forest succession is defined here as regrowth of woody vegetation following a complete or heavy forest clearance for pasture, agriculture, or other human activity. We first compare the known spatial distribution of three main TDF successional stages (Early, Intermediate and Late successional stages) as constrained by published field observations of tree height with that obtained from a three-class classification of the LIDAR data. In doing so we explicitly assess the possibility of using LIDAR data to map the distribution of the three main TDFs stages. We demonstrates that changes in the forest vertical structure (such as height) associated with principal successional stages (Early, Intermediate and Late) of TDF secondary growth can be effectively identified from LIDAR data. The successional sequence observed is related to changes in the vertical distribution of woody components that occur when forest patches evolve from an Early Stage which is dominated by sparse trees and grass, to initial stages of intermediate secondary succession characterized by small canopies and a high density of understory regeneration, and then to more complex and developed stages of intermediate and late stage secondary succession which share some attributes of Old growth forests. We then focus on the Intermediate successional Stage since it is of highest interest to policy makers dealing with programs implementing payments for environmental services. We show that an analysis of the LIDAR data can identify successional three subclasses within the Intermediate Stage providing further insights in the development of secondary forest growth. A validation of the three new forest classes is provided using field observations showing a mean tree height and standard deviation of 6.16±0.87, 7.82±0.31 and 8.62±1.22. m.

Old-growth forests: report from the plots established by Aldo Pavari

The canonical attributes of old-growth forests, their importance for management approaches fostering the development of structurally complex conditions are reported. The relict presence of primary forests led to withdraw from the regular silvicultural management patches of forests and assign them to a non-intervention regime. They have been referred to as “unmanaged forest reserves”. In this context, at mid 1900, A. Pavari established a network of 24 permanent plots at the purpose of “saving from anthropogenic disturbance and studying the natural evolutive pattern of different forest types to establish wellgrounded rules of management”. Most of plots set up by Pavari have nowadays lost their effectiveness because of various occurrences. Five plots are described here as for their numerical, structural and compositional dynamics. The recorded parameters draw systems that, even if far from equilibrium, show the occurrence of positive evolutive patterns. Differences to natural forests are, basically, the heritage of the previous multiple uses of forest soil and stand as well. On this basis, the component species have modified their presence in term of richness, evenness and dominance, depending on their auto-ecology,resistance or resilience. The long-term monitoring of primary forests and secondary systems left to the natural evolution finds out manifold, sound reasons today. The practice of ordinary management has been reduced greatly and the foreseeable trend is to increase further over the next period. According to its progress, many forests are experiencing a prolongation of the prearranged rotations and a post-cultivation phase is becoming the rule; stands are therefore getting older. Findings by old-growth forests and unmanaged forest areas monitoring will provide references for managing this diffuse condition.

The irregular shelterwood system: Review, classification, and potential application to forests affected by partial disturbances.

Structurally different from even-aged and balanced uneven-aged stands, irregular stands are an integral part of forested landscapes in northeastern North America. The maintenance or restoration of irregular stand structure may be desirable, especially in areas under ecosystem-based management. This can be achieved at the stand level through the implementation of irregular shelterwood systems. The objectives of this synthesis are to assemble the existing knowledge about the system, clarify the terminology in use, and discuss its place in silviculture in northeastern North America. Irregular shelterwood is compared with other regeneration methods and we propose a classification based on three variants. This silvicultural system is compatible with ecosystem-based management in forest types driven by partial stand mortality and gap dynamics and provides opportunities for maintaining old-growth forest attributes. However, it presents important challenges, especially with regards to planning, growth and yield prediction, and operational application.

Silviculture for old-growth attributes

Silviculture to maintain old-growth forest attributes appears to be an oxymoron since the late developmental phases of forest dynamics, described by the term old-growth, represent forests that have not experienced human intervention or timber removal for a long time. In the past, silvicultural systems applied to old-growth aimed to convert it into simplified, more productive regrowth forests substantially different in structure and composition. Now it is recognised that the maintenance of biodiversity associated with structural and functional complexity of late forest development successional stages cannot rely solely on old-growth forests in reserves. Therefore, in managed forests, silvicultural systems able to develop or maintain old-growth forest attributes are being sought. The degree to which old-growth attributes are maintained or developed is called “old-growthness”. In this paper, we discuss silvicultural approaches that promote or maintain structural attributes of old-growth forests at the forest stand level in (a) current old-growth forests managed for timber production to retain structural elements, (b) current old-growth forests requiring regular, minor disturbances to maintain their structure, and (c) regrowth and secondary forests to restore old-growth structural attributes. While the functions of different elements of forest structure, such as coarse woody debris, large veteran trees, etc., have been described in principle, our knowledge about the quantity and distribution, in time and space, of these elements required to meet certain management objectives is rather limited for most ecosystems. The risks and operational constraints associated with managing for structural attributes create further complexity, which cannot be addressed adequately through the use of traditional silvicultural approaches. Silvicultural systems used in the retention and restoration of old-growthness can, and need, to employ a variety of approaches for managing spatial and temporal structural complexity. We present examples of silvicultural options that have been applied in creative experiments and forestry practice over the last two decades. However, these largely comprise only short-term responses, which are often accompanied by increased risks and disturbance. Much research and monitoring is required still to develop and optimise new silvicultural systems for old-growthness for a wide variety of forest ecosystem types.

Old-growth Policy

Most federal legislation and policies (e.g., the Wilderness Act, Endangered Species Act, National Forest Management Act) fail to speak directly to the need for old-growth protection, recruitment, and restoration on federal lands. Various policy and attitudinal barriers must be changed to move beyond the current situation. For example, in order to achieve the goal of healthy old growth in frequent-fire forests, the public must be educated regarding the evolutionary nature of these ecosystems and persuaded that collaborative action rather than preservation and litigation is the best course for the future of these forests. Land managers and policy makers must be encouraged to look beyond the single-species management paradigm toward managing natural processes, such as fire, so that ecosystems fall within the natural range of variability. They must also see that, given their recent evidence of catastrophic fires, management must take place outside the wildland—urban interface in order to protect old-growth forest attributes and human infrastructure. This means that, in some wilderness areas, management may be required. Land managers, researchers, and policy makers will also have to agree on a definition of old growth in frequent-fire landscapes; simply adopting a definition from the mesic Pacific Northwest will not work. Moreover, the culture within the federal agencies needs revamping to allow for more innovation, especially in terms of tree thinning and wildland fire use. Funding for comprehensive restoration treatments needs to be increased, and monitoring of the Healthy Forest Initiative and Healthy Forest Restoration Act must be undertaken.

Maintaining attributes of old-growth forests in coastal B.C. through variable retention

Variable retention is a new approach to harvesting and silvicultural systems that was developed by ecologists in the Pacific Northwest region of North America to address a wide array of forest management goals. Variable retention recognizes that natural disturbances, such as fire, wind or disease, nearly always leave some standing structure from the original forest. This structural complexity plays an important role in forest ecosystem function and biological diversity. A new "retention silvicultural system" was defined that leaves trees distributed throughout harvested areas. This system facilitates retention of structural features of old-growth forests, such as live and dead trees of varying sizes, multiple canopy layers, and coarse woody debris. Weyerhaeuser's British Columbia Coastal Group will use the variable retention approach for all harvesting by 2003. More than 75% of the company's coastal harvesting in British Columbia used variable retention in 2001. Company guidelines describe the amount, type, and spatial distribution of retention for groups and individual trees. An adaptive management program is monitoring the amount and type of structural attributes retained in relation to the original forest. Key words: old-growth forests, variable retention, silvicultural systems, biodiversity, landscape zoning

Effects of area on old-growth forest attributes: implications for the equilibrium landscape concept

To investigate applicability of the equilibrium landscape concept to various attributes of vegetation, the effects of sampling area (or grain size) on structural and compositional stand parameters were determined in an old-growth hemlock-hardwood forest. Three l-ha plots, each gridded into 100 0.01-ha subplots, were established on the Roaring Fork watershed in Great Smoky Mountains National Park, Tennessee, USA. Estimates for 10 different stand descriptors were calculated for a variety of grain sizes (subplot aggregation levels) ranging from 0.01 to 1 ha. The stand descriptors included measures of physical structure (basal area and biomass) as well as measures of species composition (relative basal area). All stand descriptors exhibited high deviation from the corresponding 3-ha mean at grain sizes approximating observed canopy gap area ( 0.5 ha. The relationship between sample variance and grain size was inverse and approximately log-log linear for all descriptors. Biomass, basal area, and large canopy tree density had relatively steep slopes. These variables of physical structure presumably were related to canopy gap size and distribution. The remaining measures of density and relative basal area had gentler slopes, indicating a milder decrease in variation with increasing grain size. Coefficients of variation for each parameter also showed this response to grain size, with compositional parameters having relatively high variation at scales > 0.5 ha. In general, the nature of physical structure patches (e.g. total basal area and biomass) differed from that of composition patches (e.g. relative basal area of individual species). This contrast should be considered in equilibrium landscape concepts and vegetation sampling design.