Peter J. Smallidge

Pathogens, Patterns, and Processes in Forest EcosystemsPathogens influence and are influenced by forest development and landscape characteristics

lthough pathogens are regarded as agents responsible for the specific dynamics of natural forest communities (Dickman 1992, Dinoor and Eshed 1984, Haack and Byler 1993, van der Kamp 1991), they have received little attention at the landscape level, especially compared to catastrophic abiotic disturbances, such as fire and blowdowns (Foster and Boose 1992, Heinselman 1973). With so much emphasis today on ecosystem management and the maintenance of natural disturbance regimes, the role of pathogens deserves careful scrutiny. Pathogens (biotic agents that incite disease) differ from many abiotic disturbances by selectively eliminating the less vigorous or genetically unfit individuals of a population, yet the biotic and abiotic agents are similar in that both function to recycle essential elements and to alter forest development and landscape patterns. Pathogen interaction with abiotic disturbance to control the direction and rate of forest succession also has received minimal attention, although such

Vegetation management for the maintenance and conservation of butterfly habitats in temperate human-dominated landscapes

Abstract Many temperate butterfly species occur in habitats where human activities have altered the natural or long-term disturbance regime, and current activities modify the structure and availability of butterfly habitats over several spatial and temporal scales. Indeed, human activities modify key ecological processes sufficiently that the maintenance of some butterfly populations depends on human intervention to provide suitable habitat. Combined changes in historic and current disturbance regimes and human land-use practices necessitate active vegetation and habitat management to conserve and expand many butterfly populations. Efforts to protect temperate butterfly habitats often have resulted in successional changes that reduce habitat suitability. Butterfly habitats commonly deteriorate through a reduced intensity and frequency of long-term disturbance or management patterns that result in smaller and fragmented patches of early successional habitat. Fragmentation of otherwise continuous habitats can result in the forced dependence of a metapopulation structure. Because some butterfly larvae require one or a few host plants or adults are selective for nectar or oviposition sites, habitat management plans that include selection of an appropriate site for subsequent vegetation management activities may enhance conservation efforts. Vegetation management activities within an area can be coordinated to provide a mosaic landscape with habitats suitable for numerous species. Recommended vegetation management strategies vary with plant community type, historic disturbance regime, desired vegetation structure and composition, spatial pattern of habitat patches, land ownership patterns, and economic constraints. Because butterflies respond directly and indirectly to vegetation management and to the mosaic nature of habitat patches within the landscape, management plans must accommodate the constraints of the regional landscape and the spatial and temporal dynamics of the prescribed disturbance or management regime. We review efforts to manage temperate plant communities for butterfly habitat, and discuss general strategies for developing a vegetation management program for butterfly habitats in human-dominated landscapes. A case study of Karner blue butterfly habitat conservation efforts is provided.

Community characteristics and vegetation management of Karner blue butterfly (Lycaeides melissa samuelis) habitats on rights-of-way in east-central New York, USA

Lupinus perennis L. (blue lupine) and associated nectar species represent critical habitat for the endangered, federally listed Lycaeides melissa samuelis Nabokov (Karner blue butterfly), and exist on transmission line rights-of-way in New York, USA. While rights-of-way provide habitat and may represent a potential corridor for butterfly dispersal among sites, few data are available to quantify habitat characteristics. We investigated rights-of-way in east-central New York to: characterize L. perennis populations and associated plant communities; quantify the relationship between L. perennis and both environmental characteristics and management schemes; and assess the relationship between butterfly population size and habitat characteristics. Lupinus perennis individuals were robust in communities with Comptonia peregrina, species in the Poaceae, and Daucus carota. Lupinus perennis and L. m. samuelis abundance were correlated positively with high relative light intensity and large patch areas, and inversely correlated with the number of years since the last management activity. There was no clear relationship between vegetation patterns and the different types of recent rights-of-way vegetation management schemes. To enhance L. perennis and L, m. samuelis populations, vegetation management on rights-of-way should reduce trees and shrubs, and increase light intensity to a level of photosynthetically active radiation that exceeds 65% of the maximum possible light intensity. Other manageable conditions associated with a larger index of L. m. samuelis population size include larger habitat areas and more frequent vegetation management that reduces the cover and density of woody species. The relationship between both L. perennis clump size and L. m. samuelis population size with the distance to the warm edge of the right-of-way suggests a potential influence of microclimate and merits further attention. Vegetation management based on infrequent mechanical removal of woody stems (e.g. handcutting, mowing, brush-hogging) was associated with increased woody plant density. A more frequent mechanical treatment or a seasonally timed application of an appropriate herbicide would be more effective at controlling the woody vegetation that competes with L. perennis.

Forest community composition and juvenile red spruce (Picea rubens) age-structure and growth patterns in an Adirondack watershed

L. (red maple), is replaced. Fagus grandifolia Ehrh. (American beech) was codominant in the overstory with A. rubrum, and was dominant in the understory. Picea rubens saplings were more frequently found on mounds than other microtopographical positions, but not on mounds that were of recent origin. Picea rubens saplings had an unimodal age-structure characteristic of an even-aged population, which suggests a pattern of episodic regeneration coincident with local windthrow disturbance. Picea rubens that occurred on mounds, rocks, and intact areas tended to be larger and older than those found in pits. The establishment and survival of juvenile P. rubens were limited by the availability of microsites coincident with good seed years, and the suitability of microsites for growth once stems were established. Terminal and lateral growth increments of P. rubens saplings were similar among microtopographical positions and between reference and limed subcatchments before and in the two years after liming. In 1992, the terminal increment of P. rubens was not different from the 1991 terminal increment on treated subcatchments, but in reference subcatchments the terminal increment was less than in 1991. The potential role of P. rubens in future forests is discussed.

Limited invasion and reproduction of loblolly pines in a large South Carolina old field

The invasion and subsequent reproduction of loblolly pines (Pinus taeda) in a large (142 ha) old field in Aiken County, South Carolina, USA has occurred more slowly than expected based on successional studies performed in the 1930s and 1940s. Although the field was abandoned in 1951, only 57 pines invaded a centrally-located 26.7-ha study plot. Pines are normally expected to completely occupy an abandoned field within 25 years. Most of the trees in the center of the field were established between 1955 and 1965 and have shown limited reproduction and dispersal of offspring. The median number of offspring per parent tree is 13, and 90% of the offspring are located within 20 m of the parent. The limited pine invasion may be due to the large size of the abandoned field

Watershed liming and pit and mound topography effects on seed banks in the Adirondacks, New York, USA

Abstract Seed bank species composition, density, and frequency were evaluated as seedling emergence relative to differences in substrate chemistry associated with watershed liming and pit and mound topography (microsites) on the Woods Lake watershed, western Adirondack Mountains, NY. Liming was expected to affect calcicole and calcifuge species richness and density, while species that form persistent versus transient seed banks were expected to vary with microsite. Two of five subcatchments were limed in October, 1989 with 6.89 t ha−1 of pelletized CaCO3. Forest floor samples were collected in May 1991 and 1992 from pit, mound, and undisturbed microsites in limed and reference (untreated) subcatchments. Water soluble calcium concentrations in forest floor samples collected in May 1992 from limed subcatchments were almost ten times greater than forest floor samples from reference subcatchments, but there were no differences in soluble calcium concentration among microsites within a subcatchment. Species richness and abundance varied among microsites, but the magnitude depended on year and lime treatment. Relative frequencies of Betula alleghaniensis (yellow birch) and Oxalis acetosella (wood sorrel) exceeded 80% in both years, with a slightly greater frequency from limed than reference subcatchments. Differences in relative frequency for several species between subcatchments were not consistent between years. The relative frequency of all species by microsite was generally greater from limed than reference subcatchments. Total density and the density of individual species by microsite varied between treatments within subcatchments and between years, although some patterns exist. Seed bank patterns vary appreciably between years and among microsites. Differences in seedling emergence from pit versus mound microsites varied between years and depended on whether the microsites were in limed or reference subcatchments. These data suggest that there are no detrimental short-term effects of watershed liming on seed banks of upland deciduous forests. Microsites may affect plant community composition most through germination and survical of propagules.

Structure and composition of forest stands affected and unaffected by ash yellows

The incidence and effect of the mycoplasmal disease ash yellows in forest stands were evaluated in 50 plots located in six northeastern states. Three forest types identified by a vegetation analysis were dominated by Fraxinus americana, Acer saccharum, or F. pennsylvanica. The density of dead F. americana was greatest on sites dominated by this species, and the height of dead F. americana relative to live trees, or vertical distribution, differed among the forest types. Total tree mortality was generally greater in yellows-affected plots than in unaffected plots because of greater F. americana mortality (.)

UNDERSTORY VEGETATION-ENVIRONMENT RELATIONSHIPS IN CLEARCUT AND MATURE SECONDARY FORESTS OF WESTERN MARYLAND

Abstract Understory vegetation of 17 clearcuts 1 to 26 years old and three mature secondary forests in Garrett County, Maryland was sampled during the summer to investigate species composition and abundance during forest regeneration. Canonical correspondence analysis (CCA) was used to determine which measured environmental variables (EVs) were significantly related to species distributions among the sites and to characterize species abundances along these environmental gradients. Stand age and site moisture were the most important EVs related to species distributions. Biplots of EV vectors and species scores indicated early successional and shade-associated species (e.g. Rubus spp. and Arisaema triphyllum, respectively) that were most abundant in recent clearcuts (<10 yr old) and shade-associated species that were most abundant in older clearcuts and mature stands. Early successional species declined or disappeared as regenerating tree canopies started to close. Species distributions were significantly related to site moisture despite the broad range of light availability associated with differences in stand age and overstory basal area among the study sites.

EFFECTS OF WATERSHED LIMING ON PICEA RUBENS SEEDLING BIOMASS AND NUTRIENT ELEMENT CONCENTRATION

Effects of watershed liming on the biomass and tissue chemistry of plantedPicea rubens Sarg. (red spruce) seedlings were investigated for two growing seasons after two subcatchments in a forested Adirondack, New York (U.S.A.) watershed were limed aerially with 6.89 t ha−1 of calcitic limestone (CaCO3).Picea rubens has been the focus of numerous atmospheric deposition research studies, but less well investigated for responses to amelioration.Picea rubens seedlings were planted in limed and reference subcatchments and harvested the first and second growing season after liming to measure total, foliar, and stem (i.e., branch) biomass, and concentrations of Ca, Mg, K, Al, Na, and P in the annual growth increment of foliage and branches. In the second year after liming, both foliage and stem biomass of seedlings from reference plots were at least 50% greater than seedling biomass from limed plots. Seedlings in limed areas had significantly greater foliar concentrations of Mg and P in the first year after liming, but not in the second year. Foliar Ca was not significantly different in limed than reference seedlings. Foliar Al concentrations were greater in reference than limed seedlings, but still below documented toxicity levels. Stem concentrations of Mg, K, and P in seedlings from limed areas decreased significantly between the first and second growing season after liming, while reference seedling stem concentrations either increased or declined only slightly. Correlations among foliar nutrients and foliar biomass from limed plots were negative and suggest an inverse dilution effect. Foliar Al concentrations were negatively correlated with Ca, Mg, K, and P in seedlings from reference plots, but positively correlated in limed plots. The adverse response ofP. rubens seedlings to time may reflect changes in nutrient availability associated with changes in soil pH.

Using a Natural Disaster to Understand the Educational and Technical Assistance Needs of Small-scale Forest Landowners

Natural disasters occur in all forests, and may provide an opportunity for forestry extension educators and natural resource professionals to reach landowners with education and technical assistance. The 1998 ice storm that hit northern New York State, USA in January 1998, was used to assess the educational and technical assistance needs of forest owners. The degree of commonality among private forest landowners and maple syrup producers in their preferred delivery methods and messengers for educational materials was explored as a result of this natural disaster. Most respondents surveyed indicated that newsletters or special mailings were the best way to reach them. However, some evidence was found that small-scale forest landowners find personal contacts more useful than written materials when considering adopting a new practice. Evidence exists that some people likely sought information for the first time as a result of the storm and many think about the possibility of future ice storms when making management decisions. Responding effectively to a teachable moment created by a natural disaster requires the ability to disperse quickly relevant educational materials through a knowledgeable and trusted human network and into the hands of affected individuals before they begin making resource management decisions.