Ecological Lessons From Long-Term Studies in Experimental Forests chaired by Andy Youngblood and Brian Palik

Longterm Effects of Prescribed Fire on Woody Plant Communities in Red Pine Ecosystems

B. Palik et al. — Thu, 25 Jun 2009 08:00:00 PDT

In the early 1960’s a prescribed burning experiment was initiated on stands of 90-year-old Red Pine in the Cutfoot Experimental Forest. This is one of the oldest, regularly monitored prescribed fire studies in the Lake States. The burns were performed at (1) annual, (2) biennial, and (3) periodic intervals in both summer and dormant seasons. The objectives for the study were to determine the effects of different seasons and periodicities of prescribed burning on the (1) destruction and subsequent regrowth of hazel and other shrub species and (2) the establishment and growth of trees species under red pine. Measurements of the woody plant community have been made periodically through summer of 2005. Results show that annual growing season burns have long-lasting impacts on woody shrub communities, with hazel stem densities substantially lower in this treatment, compared to the others, even 40 years after the last fire. In fact, spring burning increased hazel densities. Moreover, several annual growing season burns appear to be conducive to establishment of an eastern white pine component under the red pine, if a seed source is present after the last fire. The other burn treatments were much less effective at promoting white pine establishment. The study results point out the need for repeated fires during the growing season to control hazel. Moreover, the results demonstrate the long-lasting impact of such fires on woody plant communities in red pine forests.

Long-Term Vegetation Changes in Coweeta Basin, Southern Appalachian Mountains, a USDA Forest Service Experimental Forest

K. Elliott et al. — Thu, 25 Jun 2009 08:20:00 PDT

We used permanent plot inventories of the Coweeta Basin (USDA FS Experimental Forest), Southern Appalachian Mountains of North Carolina (first sampled in 1934 and again in 1969-72 and 1988-93) to describe the distribution of species along an environmental gradient. We also explored the influence of large-scale disturbance on this deciduous forest. Chestnut blight fungus (Endothia parasitica) is an invasive species, which severely damaged populations of Castanea dentata and had widespread and long-term impacts on eastern North American forests. In 1926, local infestations of chestnut blight were reported in the Coweeta Basin; by 1930 most C. dentata trees were dead or dying from the blight. Concurrently, forests were further disturbed by lumbering, which was common across the region from the mid 1800s to the early 1900s. We used nonmetric multidimensional scaling for the analyses of the inventory periods. In 1934, C. dentata was the most abundant tree species. It was present in 98% of the plots and contributed 22% of the total density and 36% of the total basal area. By the 1970s, only sprouting stems of C. dentata remained in the forest due to chestnut blight induced mortality. The canopy dominant, C. dentata, was replaced by more than one species across the environmental gradient. Subsequently, diversity increased significantly over time and was attributed to an increase in evenness of species distribution. Quercus prinus, Acer rubrum, Cornus florida, Tsuga canadensis, and Oxydendrum arboreum increased by 2-5% across the basin following the decline of C. dentata. Tsuga canadensis increased in abundance and distribution, especially near streams across elevations. Liriodendron tulipifera replaced C. dentata in moist coves, which have low terrain shape and high organic matter content. In contrast, Q. prinus and A. rubrum were ubiquitous, much like C. dentata before the chestnut blight, becoming dominant or co-dominant species across all environmental conditions.

Ecosystem Resiliency in the Southeastern Atlantic Coastal Plain - Perspectives From the Santee Experimental Forest

C. Trettin et al. — Thu, 25 Jun 2009 09:00:00 PDT

Documenting the recovery of ecological functions following perturbations is important to addressing issues associated with land use change, climate change and ecosystem restoration. Floodplains on the Santee Experimental Forest were first cultivated for rice in the early1700ís. While the Forest now supports upland and bottomland hardwood forests that are considered typical of the region. However, over that 300-year period of use, the land has been managed under various uses, and it has been impacted by severe tropical storms, most recently in 1989. Research conducted over the last 70 years on the Forest has provided important insights into the recovery of ecosystem functions following, their responses to catastrophic disturbance, and approaches for enhancing site productivity. New technologies may enhance assessment capabilities. For example, recently acquired LIDAR data for the Forest has been used to delineate historical water management structures within the watersheds. Those data have been used to demonstrate that hydrologic functions and pathways were altered during the agricultural use period, with changes to depressional storage, stream flow and runoff routing. The combination of long-term monitoring data and new assessment approaches provides the basis for developing and applying effective ecosystem models. We have utilized ForestDNDC, DRAINMOD, and MikeShe to assess hydrological and biogeochemical functions at multiple scales. Experimental forests provide a needed basis for the development of tools for assessing potential changes in ecological processes.

Using Long-Term Regeneration Data From Multiple Studies to Model Regeneration Outcomes in Southern Appalachian Hardwoods

D. Loftis et al. — Thu, 25 Jun 2009 08:40:00 PDT

The portfolio of research associated with a designated forest research field facility typically consists of both case studies and studies with replicated field designs. This is particularly true on research sites whose establishment predates the widespread use of experimental statistics. Even with the development of statistical methodology, case studies with pre-treatment data collection and post-treatment evaluation of outcomes have continued to be installed for a variety of reasons. Both sources of data, case and replicated studies, can be valuable sources of inference. In this paper, we utilize data from numerous case and replicated studies of natural regeneration treatments applied to southern Appalachian hardwood stands to develop a working hypothesis that is consistent with contemporary concepts of succession and provides the basis for a model to predict species composition following regeneration harvests. The studies used in this effort were located on the Bent Creek Experimental Forest, or on nearby national forests, and have strongly influenced the silvicultural practices employed by managers in the southern Appalachians. The development of a prediction model based on these studies in these relatively complex forests provides an essential tool for managers, further enhancing the value of these long-term data. A modeling framework is suggested, along with one approach to validating and updating the model.

Overstory Dynamics in an Uncut Pine-Hardwood Stand: Lessons From Seventy Years of Passive Management

Don Bragg et al. — Thu, 25 Jun 2009 09:20:00 PDT

Long-term demonstration projects on experimental forests can be adapted from their original goals to provide insights into contemporary research questions. For instance, a 32.4-hectare cutover parcel on the Crossett Experimental Forest, the eventual Reynolds Research Natural Area (RRNA), was reserved in 1936 to act as a control for more intensively managed study areas. Over the last 70+ years, the RRNA has been allow to develop under 'natural' conditions that include no harvesting or other human interventions-with the notable exception of fire control. From 1937 until the most recent measurement in 2007, overall stand basal increased from about 20 to 36 m2/ha. The shade-intolerant loblolly and shortleaf pines in this stand remained relatively constant at two-thirds of total basal area until the mid-1990s, after which they declined noticeably, dropping to just over 50% by 2007. The gradual development of a continuous hardwood, shrub, and liana under- and midstory, coupled with a thick litter layer, has severely suppressed pine regeneration. This long-term project has demonstrated that without intense large-scale disturbance events, perpetuating a significant pine component in mesic old-growth sites of the Upper West Gulf Coastal Plain is highly unlikely. Rather, a strategy that incorporates controlled burns and/or deliberate interventions such as underplanting pine seedlings or the release of well-established pine saplings may provide better opportunities for improving pine representation. This is not the only lesson that the long-term study of the RRNA has provided. The gradual transition from pine to hardwood may not dramatically influence carbon storage in mature, closed canopy stands-our data show an aboveground biomass increase of ~10% during the last two decades, even as pine stocking has declined and overall basal area remains largely unchanged. From a sequestration perspective, the conversion to hardwoods, with their denser wood and larger crowns, has more than offset the loss of pine.

Canada’s National Research Forests – Implications of Long-Term Ecological Research on Management and Policy Decisions

S. Wetzel et al. — Thu, 25 Jun 2009 09:40:00 PDT

The Canadian Forest Service manages two National Research Forests, the Acadia Research Forest (20 km east of Fredricton, New Brunswick) and the Petawawa Research Forest (200 km northwest of Ottawa, Ontario). Both contain a legacy of field research in both natural and plantation forests involving a range of tree species and research which varies in focus from ecosystem processes to forest-level interactions. Results from these studies contribute to forest management and policy decisions by challenging our understanding of forest attributes and dynamics, and their responses to treatment. After a dramatic decline in white and red pine in Canada by the early 1900s, interest in pine management led to the establishment of the first permanent sample plots at Petawawa in 1918. These plots, which considered the effects of thinning pine on future wood volume and pine regeneration, continue to provide invaluable knowledge of the effects of silvicultural treatments on stand dynamics and yields. In addition, they are now being examined in the context of carbon accounting and climate change. Similarly, a study set up in the 1970s to assess understorey white pine release, contributes to present day discussions on forest productivity and sustainability including the effects of biomass removal. Another more recent study evaluating various silvicultural practices on pine growth response, regeneration development and biodiversity contributes to forest policy and silvicultural guidelines for pine management. An examination of ninety years of field research at Petawawa demonstrates the value of long-term research both in addressing present-day concerns as well as issues not contemplated at the time of study establishment, and providing longer-term response data. Many of these studies today are in stands only at mid-rotation age. The Petawawa Research Forest has recently become part of the Canadian Wood Fibre Centre, shifting emphasis to forest productivity, wood quality and fibre attribute research.

Ecological Lessons Learned From the Fort Valley Experimental Forest

M. Moore et al. — Thu, 25 Jun 2009 10:30:00 PDT

The Fort Valley Experimental Forest has contributed many long-term studies and ecological lessons to forest and range research since its inception in 1908. In 1909, T. S. Woolsey (Regional Forester) and G. A. Pearson (Director, Fort Valley) established a network of permanent sample plots in the ponderosa pine, mixed conifer, and spruce forest types throughout Arizona and New Mexico. We revisited many of the ponderosa pine-dominated plots and used ledger data, contemporary data, and dendrochronological techniques to quantify changes in species composition, tree density, and tree size over the past century. We used historical stem-maps to examine variations in tree spatial patterns over time as well. The Coulter Ranch site (24 plots) was part of the nation-wide Methods of Harvest study established in 1913. We examined the short- and long-term consequences of historical harvest method on contemporary pine forest structure and recruitment patterns at this northern Arizona site. In addition to the permanent forest plots, Fort Valley scientists established a series of range plots, known as Hill and Wild Bill, to examine the impacts of livestock grazing and increasing tree densities on herbaceous vegetation. The vegetation on the quadrats was mapped periodically between 1912 and 1941, and we continue to remeasure them today. Since plot establishment, understory abundance and diversity have declined and plant species have responded differentially to grazing and pine ingrowth. Currently, we are reconstructing stand structural dynamics from 1912 to present, and are quantifying litter decomposition rates and nitrification potential to determine how long-term vegetation changes have influenced ecosystem functioning. We are using these long-term forest and range plot data to increase our understanding of vegetation reference conditions, and to quantify the influence of climate and land-use changes on the ponderosa pine ecosystems of the Southwest.

Ecological Lessons From Long-Term Studies: Ponderosa Pine Silviculture at Pringle Falls Experimental Forest

A. Youngblood — Thu, 25 Jun 2009 11:10:00 PDT

Pringle Falls Experimental Forest (Pringle Falls) is the oldest experimental forest administered by the US Forest Service and the site of some of the earliest forest management and silviculture research in the Pacific Northwest. The site, southwest of Bend, Oregon, was selected in 1914, and the Pringle Butte unit was formally established as part of the national network of experimental forests in 1931 as a center for silviculture, forest management, and insect and disease research in ponderosa pine forests east of the Oregon Cascade Range. Early research objectives at Pringle Falls focused primarily on silvicultural methods for harvesting multi-cohort old-growth ponderosa pine stands and converting these lower value stands to higher value young, fast-growing stands. Management direction and research trajectories during this early period of research were driven by a regional interest in protecting forests from insects and fire. The legacy of early research that focused on identifying susceptibility to insect-caused mortality in old-growth pine is proving uniquely valuable today. Management direction and research trajectories have shifted from an emphasis on single-cohort stands back to multi-cohort stands with an emphasis on developing and protecting late-successional and old-growth structure. Examples of ecological lessons will be drawn from long-term studies established and followed by Keen, Brandstrom, Mowat, Barrett, Cochran, Busse, and others that will trace the trajectory of interrelated themes of silviculture, forest ecology, insects, fire and fuels to show how work at Pringle Falls has both followed and influenced societal demands for forest management, and how this trajectory has cycled back to the themes under which the experimental forest was first established.

Innovation in Long Term Silvicultural Research: Uniting the Past and the Future

A. Mitchell et al. — Thu, 25 Jun 2009 10:50:00 PDT

To capitalize on the considerable investments that have been made in long term large scale silviculture research installations in Canada, they must remain platforms for relevant research focused on emerging issues. Using examples drawn from experiences in British Columbia and across Canada we discuss how a catalogue of long term research sites could be used to promote the value of forest research in responding to increasing societal demands for multiple forest values. We will touch on how such a catalog could be used to foster research on wood fibre attributes to optimize the production and use of fibre all along the value chain from standing trees to products and markets.