Martin G. Raphael

Bio: Martin G. Raphael is an academic researcher from United States Forest Service. The author has contributed to research in topics: Population & Northern spotted owl. The author has an hindex of 29, co-authored 93 publications receiving 3084 citations.

Modeling the Dynamics of Snags.

Abstract: Many wildlife species required standing dead trees (i.e., snags) as part of their habitat. Therefore, the ability to predict future density, distribution, and condition of snags can assist resource managers in making land-use decisions. Here we present methods for modeling the dynamics of snags using data from a 10-yr study on the rates of decay, falling, and recruitment of snags on burned and unburned plots in the Sierra Nevada, California. Snags (all species) in advanced stages of decay usually fell within 5 yr, and snags created by fire decayed rapidly and fell quicker (within 10 yr) than those on unburned plots. Pine (Pinus spp.) snags decayed more rapidly than fir (Abies spp.). Although there was an overall net increase in snag density on unburned plots, most of this increase was in the smaller (>13-38 cm diameter at breast height [dbh]) size classes; there was a net decrease in the larger (>38 cm dbh) snags preferred by many birds for nesting and feeding. Overall, snags remained standing the longest that were larger in diameter, shorter in height, less decayed, fir rather than pine, and lacking tops. A Leslie matrix model of snag dynamics predicted changes in snag decay and density only when adjusted for the specific environmental factors(s) causing initial tree mortality. Many snags are created by episodic events, such as fire, disease, drought, and insects. Models of snag dynamics must include the species and condition of trees becoming snags, as well as the factor(s) causing the tree to die. Forest managers must consider this episodic creation of snags when developing snag-management guidelines, and when planning tree-salvage programs based on short-term inventories.

Bird Habitat Relationships in Natural and Managed Forests in the West Cascades of Oregon

Abstract: Ecologists have advocated retaining various densities of canopy trees in harvest units in Pacific Northwest forests. In contrast to clear-cutting, this practice may better emulate the patterns of disturbance and structural complexity typical of natural forests in the region. Several ecological attributes, including vertebrate habitat diversity, are thought to be associated with stands of complex structure. The goal of this study was to determine bird abundance in canopy retention sites relative to other common stand types in the Pacific Northwest and to develop habitat functions for extrapolating bird abundance across current and future landscapes. We used data from five previous studies in the west central Cascades of Oregon to compare bird abundance and to develop habitat functions for forest birds across a wide range of natural and managed stand structures and ages. The 67 stands included clearcuts, retention sites, young closed-canopy plantations, mature stands, and old-growth stands. ANOVA revealed that 18 of the 23 species included in the analysis differed significantly in abundance among the stand types, with some species being primarily associated with each of the stand types. The habitat variables used to build habitat functions included tree density by size class, mean tree diameter, and variation in tree diameter. Linear, polynomial, and various nonlinear regression models were evaluated for each bird species. Significant habitat functions were generated for 17 of the 23 bird species. The analyses identified four habitat-use guilds among the 17 bird species: open-canopy; open-canopy with dispersed large trees; structurally complex closed-canopy; and structurally simple closed-canopy guilds. This study is the first in the Pacific Northwest to compare bird abundances across natural stands, traditionally managed plantations, and stands managed under ecological forestry approaches. The results suggested that canopy tree retention benefits many, but not all, of the bird species we studied, Moreover, the nonlinear responses of bird abundance revealed thresholds in tree density at which bird abundance changed dramatically. Knowledge of these thresholds allow managers to design stands for specific biodiversity objectives. The habitat functions presented here can be used to predict bird abundance based on habitat measurements derived from field data, remotely sensed data, or output from computer models of forest dynamics.

Alternative Silvicultural Regimes in the Pacific Northwest: Simulations of Ecological and Economic Effects

Abstract: New silvicultural strategies to sustain both ecological and human communities are being developed and implemented on federal forest lands in the Pacific Northwest (PNW) United States. Two important stand-level components of the new silviculture regimes are rotation age and retention level of live trees in harvest units. Ecologists have suggested that canopy tree retention and longer rotations will create patterns of stand structure in managed forest that are similar to those in natural forests, and promote long-term ecological productivity and biodiversity. Forest economists, however, are concerned that canopy tree retention and long rotations may reduce wood production, although the high value of large logs produced by these new silvicultural regimes may compensate for reduced growth rates. We used the forest model ZELIG to perform a factorial simulation experiment on long-term responses of ecological and economic variables to nine retention levels and four rotation lengths. ZELIG output on forest structure and composition was input to a forest economics model that calculated net value of wood products in 1989 dollars. The simulated stand data were also linked with regression equations to predict the densities of 17 bird species as a function of tree size class distribution. Five replicates of each treatment were run for the 240-yr simulation period. Results indicated that stand structure under each of the canopy tree retention levels was more similar to the pre-treatment natural forest than following clear-cutting. Variation in tree size under intermediate levels of retention, however, did not reach the level of the natural forest during the simulation period. Tree species composition was strongly related to retention level and rotation age. Shade-intolerant Douglas- fir (Pseudotsuga menziesii) lost dominance to shade-tolerant species under intermediate retention levels and longer rotations. Wood production decreased significantly with increasing retention level and rotation age, with a notable threshold between retention levels of 0 and 5 trees per hectare. Net wood products value did not decrease as rapidly with retention level, and did not differ much among rotation ages, because of the high value of large logs. Bird species responded individualistically to retention level and rotation age. Some had peak densities under short-rotation clear-cutting, but most were associated with structurally complex, closed-canopy forest. Consequently, bird species richness increased significantly with retention level and rotation age. Within the assumptions and limitations of our models, this application provided knowledge on trends and thresholds that can help land managers to choose silvicultural regimes that best balance their management objectives. We concluded that retention level and rotation age strongly influence ecological and economic responses in PNW forests; efforts are needed to reduce uncertainty about these effects.

Winter Resting Site Ecology of Marten in the Central Rocky Mountains

Abstract: We investigated the resting site ecology of American marten (Martes americana) in the central Rocky Mountains during 2 winters, 1985-86 and 1986-87. We found 8 marten used 57 resting sites on 141 occasions. Marten rested primarily in subnivean sites associated with coarse woody debris, including logs and stumps. Use of spruce (Picea spp.)-fir (Abies lasiocarpa) stands by adults was greater than expected and use of lodgepole pine (Pinus contorta) stands was less than expected on the basis of spatial availability. Juveniles used stand types in proportion to spatial availability. Fidelity to individual resting sites and to subnivean sites associated with coarse woody debris was highest among adults. Type of resting site used depended on air temperature at the time of resting; above-snow sites were used during the warmest weather, and subnivean sites associated with coarse woody debris were used during the coldest weather. Marten rested for longer periods where coarse woody debris formed all or part of the resting site than they did at other sites. Log densities were higher and mean log diameters greater in spruce-fir stands than in lodgepole pine stands. Resting sites associated with coarse woody debris occurred primarily in spruce-fir stands, whereas other resting sites occurred in other stand types. Resting sites were closer to streams and lakes than expected. The importance of resting where coarse woody debris is available to provide thermal cover may explain the apparent dependence of marten on old-growth forest in the central Rocky Mountains in winter. J. WILDL. MANAGE. 53(1):191-196 Resting sites used by American marten have been described for a wide range of geographic locations and include a variety of natural and man-made microhabitats (Campbell 1979, Steventon and Major 1982, Martin and Barrett 1983, Buskirk 1984). Locations of resting sites range from the forest canopy to beneath the soil surface. Winter resting sites are often associated with coarse woody debris (CWD), including logs, stumps, and snags (Steventon and Major 1982, Martin and Barrett 1983, Spencer 1987). In summer, marten generally rest in sites above the ground, often in the canopy layer (Masters 1980, Burnett 1981, Martin and Barrett 1983). Temporal differences in resting site preferences could be explained by thermoregulatory needs of marten, or by other factors such as vulnerability to predation. Marten live where above-snow air temperatures (Ta) in winter are lower than their lower critical temperature (T,c = the temp at which an animal must increase its metabolic rate above resting levels to offset thermal losses [16 C]) (Buskirk et al. 1988) by ?50 C. Thus they would appear to pay high energetic costs to rest at or near To in winter. Marten are associated with late successional stands of conifer-dominated forest over a wide geographic area (Francis and Stephenson 1972, Koehler and Hornocker 1977, Simon 1980, Bateman 1986) and have a close and seemingly obligatory association with old-growth stands in the Rocky Mountains in winter (Campbell 1979). However, a clear understanding of why marten are associated with old-growth is lacking. Patte ns of use of resting sites may provide a better understanding of the apparently obligatory nature of this association. We report on characteristics of resting sites used by marten in the Medicine Bow Mountains, Wyoming during 2 winter field seasons. We identify environmental and behavioral correlates of resting site use and draw inferences about the importance of resting site types for thermoregulation. We also discuss the importance of CWD as a resting site component in understanding the old-growth dependency of marten during winter. L. R. Forrest provided invaluable assistance during the winter field studies. We appreciate the cooperation of R. H. Abell, for allowing use of a portion of his trapline for field work. This research was supported by the Committee for Research and Exploration, National Geographic Society, the U.S. Forest Service (USFS), Rocky Mountain Forest and Range Experiment Station, and the Office of Research, University of Wyoming. We thank the Wyoming Game and

FRAGSTATS: spatial pattern analysis program for quantifying landscape structure

Abstract: McGarigal, Kevin; Marks, Barbara J. 1995. FRAGSTATS: spatial pattern analysis program for quantifying landscape structure. Gen. Tech. Rep. PNW-GTR-351. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 122 p. This report describes a program, FRAGSTATS, developed to quantify landscape structure. FRAGSTATS offers a comprehensive choice of landscape metrics and was designed to be as versatile as possible. The program is almost completely automated and thus requires little technical training. Two separate versions of FRAGSTATS exist: one for vector images and one for raster images. The vector version is an Arc/Info AML that accepts Arc/Info polygon coverages. The raster version is a C program that accepts ASCII image files, 8or 16-bit binary image files, Arc/Info SVF files, Erdas image files, and IDRISI image files. Both versions of FRAGSTATS generate the same array of metrics, including a variety of area metrics, patch density, size and variability metrics, edge metrics, shape metrics, core area metrics, diversity metrics, and contagion and interspersion metrics. The raster version also computes several nearest neighbor metrics. In this report, each metric calculated by FRAGSTATS is described in terms of its ecological application and limitations. Example landscapes are included, and a discussion is provided of each metric as it relates to the sample landscapes. Several important concepts and definitions critical to the assessment of landscape structure are discussed. The appendices include a complete list of algorithms, the units and ranges of each metric, examples of the FRAGSTATS output files, and a users guide describing how to install and run FRAGSTATS.

Ecological-niche factor analysis: how to compute habitat-suitability maps without absence data?

Abstract: We propose a multivariate approach to the study of geographic species dis- tribution which does not require absence data. Building on Hutchinson's concept of the ecological niche, this factor analysis compares, in the multidimensional space of ecological variables, the distribution of the localities where the focal species was observed to a reference set describing the whole study area. The first factor extracted maximizes the marginality of the focal species, defined as the ecological distance between the species optimum and the mean habitat within the reference area. The other factors maximize the specialization of this focal species, defined as the ratio of the ecological variance in mean habitat to that observed for the focal species. Eigenvectors and eigenvalues are readily interpreted and can be used to build habitat-suitability maps. This approach is recommended in situations where absence data are not available (many data banks), unreliable (most cryptic or rare species), or meaningless (invaders). We provide an illustration and validation of the method for the alpine ibex, a species reintroduced in Switzerland which presumably has not yet recolonized its entire range.

Bayesian artificial intelligence

Abstract: Bayesian Reasoning. Introduction to Bayesian Networks. Inference in Bayesian Networks. Bayesian Network Applications. Bayesian Planning and Decision-Making. Bayesian Network Applications II. Learning Bayesian Networks I. Learning Bayesian Networks II. Causality vs. Probability. Knowledge Engineering with Bayesian Networks I. Knowledge Engineering with Bayesian Networks II. Application Software.

On the usage and measurement of landscape connectivity

Abstract: This paper examines the usage and measurement of “landscape connectivity” in 33 recent studies. Connectivity is defined as the degree to which a landscape facilitates or impedes movement of organisms among resource patches. However, connectivity is actually used in a variety of ways in the literature. This has led to confusion and lack of clarity related to (1) function vs structure, (2) patch isolation vs landscape connectivity and, (3) corridors vs connectivity. We suggest the term connectivity should be reserved for its original purpose. We highlight nine studies; these include modeling studies that actually measured connectivity in accordance with the definition, and empirical studies that measured key components of connectivity. We found that measurements of connectivity provide results that can be interpreted as recommending habitat fragmentation to enhance landscape connectivity. We discuss reasons for this misleading conclusion, and suggest a new way of quantifying connectivity, which avoids this problem. We also recommend a method for reducing sampling intensity in landscape-scale empirical studies of connectivity.