Forest Ecological Processes chaired by Bill Adair

Seven-Year Results of Testing Paper Mill Residual Sludge as a Soil Ameliorant of Iron Mine Tailings

M. Bridgen — Tue, 23 Jun 2009 08:20:00 PDT

Paper mill residual solids, extracted from a settling pond in Newton Falls, NY, were tested for their efficacy as a site ameliorant. The test site was a twenty-five-year-old sand tailings, created by a former iron mining operation. Sludge was applied in trenches, as either 20% or 40% solids. Black locust, hybrid poplar, and willow seedlings were planted over the site to establish near forest-like vegetation. Seven years after establishment, overall survival is about 80%. The entrenched sludge provided increased soil moisture retention, deeper root development, increased nutrient availability and retention, and larger leaf sizes. Sludge applications resulted in greater above-ground height growth and greater root development for all species. Hybrid poplar cuttings exhibited the greatest rate of shoot development, while black locust seedlings exhibited the greatest rate of root development. The sludge application has produced a faster growing, more valuable ecosystem. This new artificial ecosystem has a greater variety of woody and herbaceous plants, higher fungi, and insects. It has a taller and more diverse vertical structure, contributing to increased wildlife habitat for at least some bird and mammal species.

Wood Anatomy of Arbutus unedo Reflects Site-Specific Responses to Increased Drought Frequency

C. Copenheaver et al. — Tue, 23 Jun 2009 08:40:00 PDT

Recently, the Mediterranean region has experienced unprecedented drought. Climate models predict an increase in drought frequency and duration. Therefore, quantifying the response of Mediterranean plants to drought is important. We contrasted wood anatomy and dendroecological features of a Mediterranean shrub, Arbutus unedo, at a xeric and a mesic site on the Italian island of Elba. Radial microsections of Arbutus unedo were stained, described, and crossdated. Annual ring widths of radial microsections were measured and compared with regional temperature and precipitation. False rings are common and distinguishable from true annual ring boundaries only by viewing radial microsections under high magnification. False ring formation was more common at the xeric site and was caused by below average rainfall in late summer (xeric site) and below average rainfall and high temperatures in spring and summer (mesic site). Given the predictions for increased drought, plants currently growing at mesic sites will likely adopt the growth patterns of plants currently growing at xeric sites. Thus, late summer precipitation will limit growth rates for woody plants. Arbutus unedo demonstrated its dendroecological value and future work on climate initiated shifts in Mediterranean vegetation should take advantage of the potential found in annual ring records of shrubs.

Effects of Regeneration Practices on the Growth in Loblolly Pine Plantations From the Perspective of Hierarchy Theory

Thomas Dean et al. — Tue, 23 Jun 2009 09:00:00 PDT

The long-term effects of high-production harvesting and subsequent site-preparation practices are typically evaluated from a limiting resource perspective. Machines used in the harvesting compact the soil reducing aeration and uptake of water and nutrients. Moving the entire tree from the site removes organic matter and parts of the forest floor. Models translate these effects into direct consequences on tree growth and ultimately productivity. Trees response often conflicts with model predictions in many cases. Hierarchy theory does not require organisms to behave deterministically to account for behavior, but it does require a different approach. Our proposed talk will present an application of hierarchy to account for tree responses to soil and environmental changes due to high-production harvesting in some southern commercial plantations. We will present some hypotheses concerning the responses of height and diameter growth based on hierarchy theory and present data to evaluate applicability of this theory to tree growth in response to harvesting and perhaps other types of perturbations.

Influence of Coarse Woody Material (CWM) on Soil Microarthropods in Black Spruce-Feather Moss Forests of Western Quebec

Enrique Doblas-Miranda et al. — Tue, 23 Jun 2009 09:20:00 PDT

Increasing demands for biofuels have opened the possibility for an overall decrease in the amount of residual coarse woody material (CWM) in forests. While CWM is known to be an important resource for saproxylic species that reside within downed logs, the relative importance of CWM for organisms residing beneath, in the soil is poorly understood. In this context, CWM likely modifies conditions as well as nutrient levels for soil communities that lie beneath. The relative importance of CWM for underlying soil communities may be accentuated in the black-spruce clay-belt region of Western Québec where soil nutrients are extremely limited by paludification and extensive Sphagnum growth. To better understand the importance of CWM for soil microarthropods in this region, we sampled the soil microarthropods directly under CWM and 50 cm. apart, in 20 sites representing different states of development of a black spruce-feather moss forest type. While previous studies in other forest types showed little effect of woody material, our preliminary results suggest that Oribatid mites are influenced by CWM. However, contrary to our expectations, they have lower abundances and diversity in soil directly under logs than in open areas. We hypothesize that as nutrients in the forest floor are rendered inaccessible due to the thick Sphagnum layer of this forest, detritivore mites depend on recent leaf litter as nutrient resource. Conversely, logs in this case are likely to work as a cover to litter fall.

Initial Response of Saplings and Stump Sprouts to Experimental Canopy Gap Formation in a Northern Hardwood Forest

J. Dyer et al. — Tue, 23 Jun 2009 09:40:00 PDT

The response of forest regeneration to canopy gap formation plays a key role in forest stand dynamics and future species composition of mesic forests. Results from controlled, replicated experiments, however, are limited. We measured light environment and extension growth for saplings and stump sprouts in and around experimentally harvested canopy gaps two years after formation to evaluate the initial response of shade tolerant sugar maple (Acer saccharum) versus mid-tolerant bitternut hickory (Carya cordiformis) and white ash (Fraxinus americana). Gap areas (projected) ranged from 9 to 443 m≤ and were chosen to represent the typical range found in old-growth forests of the Great Lakes region. No saplings (>0.5 cm dbh) were browsed by deer, but because of heavy browsing on stump sprouts, analysis of extension growth on sprouts was restricted to a subset of plots fenced to exclude deer. Surprisingly, sugar maple saplings attained higher extension growth rates across all light conditions than the two mid-tolerant species (18.2 vs. 13.0 cm, respectively; p = 0.004). Sugar maple sapling extension growth varied significantly as a function of pre-treatment growth rate and gap area (p < 0.001). Extension growth of mid-tolerant saplings was not significantly correlated with any measured variable. However, stump sprouts grew two to five times faster than saplings (p < 0.001), and unlike the trend among saplings, mid-tolerants grew faster than sugar maple (100.1 vs. 67.8 cm, respectively). Our results indicate that sugar maple saplings respond to canopy gap formation more quickly than midtolerant associates and that stump sprouts outgrew saplings considerably. In addition, the importance of stump sprouting to gap regeneration increased significantly in larger gaps because of harvest damage to saplings. However, saplings have an advantage of greater initial height, so future competitive status may depend on changes in relative growth rates over the next few decades.

Facing Changes in Atmospheric Transparency: Mediterranean and Sub-Arid Trees Growth Responses for the Last 150 Years

L. Humbert et al. — Tue, 23 Jun 2009 10:30:00 PDT

Short term variations in atmospheric transparency, such as volcanic eruptions, are known to affect forest productivity. But few ecological studies are available for long term impacts of regional changes in atmospheric transparency (also called global dimming). It has been shown that ecosystem carbon fluxes are affected by current changes in the atmospheric composition. However, the impact of these changes on the productivity of trees are unknown. By selecting data with strict criteria we present results for tree ring width sites across the globe representing Mediterranean and sub-arid ecosystem. These data were within a 50 km and 150 km range of aerosol optical depth (AOD) stations. We investigated the interactions of the AOD and changes in the solar constant which were estimated from solar cycles on tree growth from tree ring chronologies. Results show interactions between AOD and solar irradiance on growth. A decrease in atmospheric air quality increased the negative impact of solar irradiance on growth during most of last century. The slope of this relationship changed slowly until in turned positive in the 60's-70's. We argue that decreases in atmospheric transparency result in less radiation for photosynthesis, but lead to higher fraction of diffuse irradiance. Overall, plant photosynthesis in complex, multilayerized canopies, such as those of trees, will benefit from this increased diffuse irradiance. We propose that this amelioration of growth observed is due to a decreased in sun leaf overheating and more generally in water stress during summer drought whereas shade leaf will benefit from more diffuse light. These findings have important implications for modeling of forest response to anthropogenic changes of the atmosphere and questioned some management policies in ecosystems with very dry seasons. Showing that trees responses are highly complex.

Effects of Landform and Other Environmental Variables on Forest Site Quality in the Appalachian Mountains

W. McNab et al. — Tue, 23 Jun 2009 10:50:00 PDT

Subregions are ecosystems of mesoscale size occurring between macroscale ecoregions of national extent and landscape units of subregional area within the U.S. Forest Service hierarchical classification framework of ecological units. The objective of this multi-disciplinary project was to develop a consistent national map of subregions from regional map products that had been developed independently by regional teams working with academic and conservation groups knowledgeable of ecosystems at local and state scales. Regional maps were joined and ecosystems were reviewed for consistency by a small national team consisting of representatives from each regional group. The national map received additional independent review for revision and refinement of ecosystems. The rationale and methodology for delineation of ecosystems shown on the map 'Ecological Subregions: Sections and Subsections of the Conterminous United States' is described in this report. Components of climate, geology, landform, soils and vegetation were integrated to form 190 sections and 1,234 subsection map units. This map represents the first approximation of ecological units at the subregions scale in the western U.S. and is a refinement of a 1995 map of Eastern subregions. Following its publication in 2007, the subregions map provides a basis for ecological mapping on Forest Service lands at the next lower finer scale: landtype associations. Case studies demonstrate use of the subregion map for ecosystem analysis in the Great Lakes Area and Appalachian Mountains in the southern United States. The 2007 map of subregions, supporting documents on methodology and databases of selected environmental data are available on CD. *Note: This abstract supplements and updates a preliminary report on the same topic that was presented, but not published, at the 2007 NAFEW, in Vancouver.

Physiological Understanding of Loblolly Pine Growth: Fertilization, Clonal and Interactive Responses

J. Seiler et al. — Tue, 23 Jun 2009 11:10:00 PDT

Plantation loblolly pine is one of the most intensively managed pine forest ecosystems in the world. Throughout this managed system millions of acres are fertilized annually. Much is known about the positive growth and yield responses due to fertilization yet the physiological processes responsible for this growth enhancement remain unclear. For example it has been well established that loblolly pine leaf areas increase greatly when fertilized and the phrase ‘leaves grow trees’ has become well established in loblolly pine management discussions. However, increased leaf area is not a physiological response. Forest industry is beginning to produce, screen and deploy clonal material for plantations. A physiological understanding of the growth response to fertilization is needed for rapid, early, clonal screening and would also allow a basis for genetic marker screening. For a number of years we have been investigating the physiological responses that occur immediately following nitrogen fertilization. Specifically, we have investigated changes in leaf level gas exchange and root respiration in response to fertilization. Through a series of studies spanning nearly ten years we have found some consistent changes in physiology that occur after fertilization that we believe lead to growth enhancement. However, recent studies with clones of loblolly pine suggest that no one physiological model may explain the growth response even in closely related clones. This presentation will synthesize numerous studies and present testable hypothesis for future work.