Forest optimisation models including timber production and carbon sequestration values of forest ecosystems: a case study

The integration of carbon sequestration value of forest ecosystems into forest management planning models has become increasingly important in sustainable forest management. This study analyses the economic effects of different minimum cutting ages on timber and carbon sequestration values for a Scots pine forest clumped mainly in older age classes in northeast Turkey. The analysis is performed by formulating three optimisation models. The objective of each model is to maximise net present value (NPV) of harvested timber, net present value of carbon sequestration and the total net present value of timber production and carbon sequestration, respectively. Results showed that increasing the minimum cutting ages by 10 years increased the NPV of timber by 10.5%. However, the current minimum cutting ages were optimal for maximizing the NPV of carbon and the sum of the NPV of timber and carbon benefits. In addition, the model outputs were found to be quite sensitive to unit carbon prices.     

Life History as a Predictor of Salamander Recovery Rate from Timber Harvest in Southern Appalachian Forests,U.S.A

Forest management often represents a balance between social, economic, and ecological objectives. In the eastern United States, numerous studies have established that terrestrial salamander populations initially decline in abundance following timber harvest, yet the large‐scale and long‐term consequences are relatively unknown. We used count data from terrestrial survey points to examine the relation between salamander abundance and historic timber harvest while accounting for imperfect detection of individuals. Overall, stream‐ and terrestrial‐breeding salamanders appeared to differ by magnitude of population decline, rate of population recovery, and extent of recolonization from surrounding forest. Specifically, estimated abundance of both species groups was positively associated with stand age and recovery rates were predicted to increase over time for red‐legged salamanders (Plethodon shermani) and decrease in stream‐breeding species. Abundance of stream‐breeding salamanders was predicted to reach a peak by 100 years after timber harvest, and the population growth rate of red‐legged salamanders was predicted to undergo a significant increase 100 years after harvest. Estimated abundance of stream‐breeding salamanders in young forest stands was also negatively associated with the distance to adjacent forest, a result that suggests immigration has a role in the recovery of these species. Our results indicate that salamander abundance in young forest stands may be only modestly lower than in more mature forest but that full recovery from timber harvest may take a substantial amount of time and that species life history may affect patterns of recovery. Historia de Vida como un Vaticinador de la Tasa de Recuperación de una Salamandra a la Colecta de Madera en los Bosques del Sur de los Apalaches, E.U.A     

Effects of Postfire Salvage Logging on Deadwood‐Associated Beetles

Abstract: In Canada and the United States pressure to recoup financial costs of wildfire by harvesting burned timber is increasing, despite insufficient understanding of the ecological consequences of postfire salvage logging. We compared the species richness and composition of deadwood‐associated beetle assemblages among undisturbed, recently burned, logged, and salvage‐logged, boreal, mixed‐wood stands. Species richness was lowest in salvage‐logged stands, largely due to a negative effect of harvesting on the occurrence of wood‐ and bark‐boring species. In comparison with undisturbed stands, the combination of wildfire and logging in salvage‐logged stands had a greater effect on species composition than either disturbance alone. Strong differences in species composition among stand treatments were linked to differences in quantity and quality (e.g., decay stage) of coarse woody debris. We found that the effects of wildfire and logging on deadwood‐associated beetles were synergistic, such that the effects of postfire salvage logging could not be predicted reliably on the basis of data on either disturbance alone. Thus, increases in salvage logging of burned forests may have serious negative consequences for deadwood‐associated beetles and their ecological functions in early postfire successional forests.     

Effects of Timber Harvesting on Southern Appalachian Salamanders

We compared the species richness and abundance of salamanders on six recent clearcuts (< 10 years old) with that of salamanders on 34 mature forest stands (>50 years old) in southern Appalachian forests in western North Carolina, U.S.A. Catches of salamanders from plots in mature forest stands were about five times higher than those on recent clearcuts. Almost all species and major taxonomic groups of salamanders were adversely affected by timber removal. Mean number of species collected per plot was about twice as great in mature forest stands as in clearcuts. Analyses of stand age versus salamander catch for 47 plots indicate that 50–70 years are required for populations to return to predisturbance levels following cutting. We conservatively estimate that clearcutting in U.S. national forests in western North Carolina results in a loss of nearly 14 millton salamanders annually. It also is chronically reducing regional populations by more than a quarter of a billion salamanders (9%) below that which could be sustained if mature forests were not cut.     

Carbon stocks across a chronosequence of thinned and unmanaged red pine (Pinus resinosa) stands

Forests function as a major global C sink, and forest management strategies that maximize C stocks offer one possible means of mitigating the impacts of increasing anthropogenic CO2 emissions. We studied the effects of thinning, a common management technique in many forest types, on age-related trends in C stocks using a chronosequence of thinned and unmanaged red pine (Pinus resinosa) stands ranging from 9 to 306 years old. Live tree C stocks increased with age to a maximum near the middle of the chronosequence in unmanaged stands, and increased across the entire chronosequence in thinned stands. C in live understory vegetation and C in the mineral soil each declined rapidly with age in young stands but changed relatively little in middle-aged to older stands regardless of management. Forest floor C stocks increased with age in unmanaged stands, but forest floor C decreased with age after the onset of thinning around age 40 in thinned stands. Deadwood C was highly variable, but decreased with age in thinned stands. Total ecosystem C increased with stand age until approaching an asymptote around age 150. The increase in total ecosystem C was paralleled by an age-related increase in total aboveground C, but relatively little change in total belowground C. Thinning had surprisingly little impact on total ecosystem C stocks, but it did modestly alter age-related trends in total ecosystem C allocation between aboveground and belowground pools. In addition to characterizing the subtle differences in C dynamics between thinned and unmanaged stands, these results suggest that C accrual in red pine stands continues well beyond the 60-100 year management rotations typical for this system. Management plans that incorporate longer rotations and thinning in some stands could play an important role in maximizing C stocks in red pine forests while meeting other objectives including timber extraction, biodiversity conservation, restoration, and fuel reduction goals.     

Variability over space and time in the genetic structure of the winged kelp Alaria marginata

The genetic structure of Alaria marginata Postels & Ruprecht was investigated spatially and seasonally using amplified-fragment length polymorphisms (AFLP). Using one primer, 206 scoreable bands were produced. Individual plants that were separated by as little as a few decimeters to >100 km could be distinguished, and followed an isolation-by-distance model. Genetic similarity (average April data) ranged from 76% for patches (a few decimeters in diameter), to 71% for individual kelp stands (15 m across) and 67% for a group of stands separated by 185 km. Greater genetic similarity of patches occurred at a wave-sheltered site than at a wave-exposed site. The lower wave action may limit meiospore dispersal, resulting in patches of related sporophytes. Genetic similarities between A. marginata stands indicated a pattern of gene flow that is consistent with local currents. In one stand, genetic similarities were markedly different between seasons. This seasonal pattern may be the result of different age groups dominating the sampled stands over time. The genetic structure of A. marginata comprises local scale (patch and within-stand) heterogeneity and larger scale (between-stands) homogeneity. Received: 30 September 1998 / Accepted: 26 October 1999     

Ethnobotany of Woody Species in Second-Growth, Old-Growth, and Selectively Logged Forests of Northeastern Costa Rica

Abstract: We assessed quantitatively the woody species used for timber, medicine, and other products in 10 tropical wet-forest stands with different land-use histories in the Atlantic lowlands of northeastern Costa Rica. Species were classified into 20 use categories based on regional ethnobotanical studies. Three size classes of woody vegetation were sampled in nested, contiguous plots along transects: trees (≥5 cm diameter at breast height [dbh]), saplings (>1 m high, <5 cm dbh), and seedlings (>20 cm high, <1 m high). Our study included five second-growth stands, three old-growth stands, and two selectively logged stands. Of the 459 woody species surveyed, 70% of the species and 86% of the total number of individuals had at least one use. Overall, species richness was highest for medicinal species (167 species). Absolute and relative abundance of medicinal and timber trees was significantly higher in second-growth stands than in old-growth and selectively logged stands. For 8 of the 15 use categories examined statistically, stem density showed no significant differences across forest types for any stem size class. Young, tropical, second-growth forests and selectively logged forests have high utilitarian as well as conservation value and will likely become important sources of forest products. The success of secondary forest regeneration, however, depends critically upon conservation of genetically diverse source populations in forest fragments and protected old-growth stands.     

Creation and preservation of vegetation patterns by grazing

Structural patterns of tall stands (“tussock”) and short stands (“lawn”) are observed in grazed vegetation throughout the world. Such structural vegetation diversity influences plant and animal diversity. A possible mechanism for the creation and preservation of such patterns is a positive feedback between grazing and plant palatability. Although some theoretical studies have addressed this point in a non-spatial setting, the spatial consequences of this feedback mechanism on the stability and spatial characteristics of vegetation structure patterns have not been studied.We addressed this issue by analyzing a spatially explicit individual-based plant-grazer simulation model, based on published empirical relations and the assumption of optimal foraging.In the model, the selection by the grazer of short stands (that have a higher energy content and are more palatable) is affected by traveling costs and the spatial organization of swards. Nevertheless, the most selected biomass in this type of short stands was the optimal biomass predicted by cropping and digestion constraints. As a result of the optimal foraging strategy, the grazers displayed Lévy-flight traveling behavior during the simulations with characteristic exponent μ ≈ 2.Patterns of short and tall stands created by grazing were preserved for at least a decade. Even in seasonal habitat, the spatial organization of the patterns remained relatively constant, despite fluctuations in the area of short stands. Heterogeneity of initial vegetation increased heterogeneity of the grazing-induced pattern, but did not affect its stability.The area of short stands that was preserved by grazing scaled with the herbivore mass to the power 0.4 and with the carrying capacity of the vegetation to the power −0.75.Patterns of tall and short stands can be created and perpetuated by optimally grazing ruminants, irrespective of possible underlying soil patterns. The simulations generate predictions for the stability and spatial characteristics of such structural vegetation patterns.     

Vegetation development in coastal foredunes in relation to methods of establishing marram grass ( Ammophila arenaria )

In coastal foredunes marram grass (Ammophila arenaria) is used to stabilize windblown sand. The development of traditionally plantedAmmophila into a more natural foredune vegetation may take 5–10 yr. For economic reasons, traditional planting may be replaced by alternative techniques such as planting seeds or disk-harrowing rhizome fragments. In this paper, we compare the initial vegetation development of traditionally planted stands with stands established from seeds and from rhizomes. The experiments were conducted on an artificial foredune originating from dredged sea sand. The total experimental area covered more than 100 ha and the vegetation development was studied for 6 yr. The data were analysed bya priori grouping of plant species according to their ecology, as well as by Principal Components Analysis (PCA) and Redundancy Analysis (RA) of the percentage ground cover per plant species. Comparing ecological groups of plants showed that all planting methods delivered equal numbers of plant species that are indicative for coastal dunes. PCA and RA showed that methods based on the use of rhizome material resulted in a higher percentage cover of clonal perennials (Calammophila baltica, Festuca rubra ssp.arenaria, Carex arenaria andCirsium arvense) than the traditionally planted stands and the stands obtained from seeds. The latter two were characterized by the dominance of annuals, bi-annuals and (mostly nonrhizomatous) perennials. Initially, the rates of succession were highest in the stands obtained from rhizomes. However, after 3–6 yr there were no differences between the various stands. During the first four years, the percentage cover by rhizomatous foredune plants developed faster than that of annuals, bi-annuals and perennials. After 6 yr, the latter contributed almost as much to the percentage cover as the clonal species.     

A regional forest ecosystem carbon budget model: impacts of forest age structure and landuse history

This study investigated the impacts of landuse history and forest age structure on regional carbon fluxes for the forests in the Pacific Northwest of the United States based on a two-stage modeling strategy. In the first stage, an individual-based forest ecosystem carbon flux model (IntCarb) at stand scale is developed. IntCarb combines components from the ZELIG and CENTURY models to simulate forest development and heterotrophic respiration, respectively. Stand scale carbon fluxes simulated by IntCarb strongly depend on stand age. A forest stand can be a carbon sink for up to 200 years old with a peak at 30–40 years old. Old-growth stands are carbon neutral to the atmosphere in the long term. For any particular year, an old-growth stand can be either a carbon sink or source. The interannual variation of Net Ecosystem Productivity (NEP) for an old-growth stand is primarily determined by heterotrophic respiration. Due to the high spatial variability of stand ages, forest age structure needs to be taken into account to improve estimation of carbon budgets of forest ecosystems over large areas. In the stand stage, a regional carbon budget model (RegCarb) is developed to estimate regional carbon fluxes over large areas based on forest age structure, adjusting for the nonrespiratory carbon losses (timber harvesting). Our initial estimate with RegCarb for the Pacific Northwest of the United States indicates that this region was a tremendous carbon source to the atmosphere from 1890 to 1990 due to extensive logging of old-growth forest. Projection for the role of forests in this region in global carbon cycle in the future strongly depend on the amount of timber to be harvested, i.e. how the age structure of forests in this region is to be altered.     

Forest age influences oak insect herbivore community structure, richness, and density.

Plant succession is one of many factors that may affect the composition and structure of herbivorous insect communities. However, few studies have examined the effect of forest age on the diversity and abundance of insect communities. If forest age influences insect diversity, then the schedule of timber harvest rotation may have consequent effects on biodiversity. The insect herbivore community on Quercus alba (white oak) in the Missouri Ozarks was sampled in a chronoseries, from recently harvested (2 yr) to old-growth (approximately 313 yr) forests. A total of nine sites and 39 stands within those sites were sampled in May and August 2003. Unique communities of plants and insects were found in the oldest forests (122-313 yr). Density and species richness of herbivores were positively correlated with increasing forest age in August but not in May. August insect density was negatively correlated with heat load index; in addition, insect density and richness increased over the chronoseries, but not on the sunniest slopes. Forest structural diversity (number of size classes) was positively correlated with forest age, but woody plant species richness was not. In sum, richness, density, and community structure of white oak insect herbivores are influenced by variation in forest age, forest structure, relative abundance of plant species, and abiotic conditions. These results suggest that time between harvests of large, long-lived, tree species such as white oak should be longer than current practice in order to maintain insect community diversity.     

Simulated Responses of a Forest-Interior Bird Population to Forest Management Options in Central Hardwood Forests of the United States

I used estimates of carrying capacity, survival, fecundity, and edge effects to simulate the responses of a forest-interior bird population to selection cutting clearcutting, and no timber harvest. I also modeled population sensitivity to changes in fecundity, survival, K , and edge relationships. Because model parameters are based on scant data, results should he regarded as hypotheses to be further investigated or measures of the relative impact or sensitivity (given model assumptions). Simulated population size was greater with no timber harvest than with clearcutting and greater with clearcutting than with group selection when edge effects were included in the model. Without edge effects, population levels were only slightly lower under group selection than under no timber harvest, and greater than clearcutting. Edge effects had only a small impact on population levels under clearcutting. Clearcut size did not have much effect on population levels, but longer and shorter rotation ages resulted in higher and lower population levels, respectively. The model was very sensitive to declines in mean fecundity and survival, suggesting that factors affecting mean demographic rates could be more important than local edge effects. Some methods of timber harvest may be compatible with the conservation of forest-interior birds, but better demographic data and information on habitat suitability of selectively cut forests and young even-aged stands is needed to adequately evaluate management options.     

Vegetation development in coastal foredunes in relation to methods of establishing marram grass (Ammophila arenaria)

In coastal foredunes marram grass (Ammophila arenaria) is used to stabilize windblown sand. The development of traditionally plantedAmmophila into a more natural foredune vegetation may take 5 – 10 yr. For economic reasons, traditional planting may be replaced by alternative techniques such as planting seeds or disk-harrowing rhizome fragments. In this paper, we compare the initial vegetation development of traditionally planted stands with stands established from seeds and from rhizomes. The experiments were conducted on an artificial foredune originating from dredged sea sand. The total experimental area covered more than 100 ha and the vegetation development was studied for 6 yr. The data were analysed bya priori grouping of plant species according to their ecology, as well as by Principal Components Analysis (PCA) and Redundancy Analysis (RA) of the percentage ground cover per plant species. Comparing ecological groups of plants showed that all planting methods delivered equal numbers of plant species that are indicative for coastal dunes. PCA and RA showed that methods based on the use of rhizome material resulted in a higher percentage cover of clonal perennials (Calammophila baltica, Festuca rubra ssp.arenaria, Carex arenaria andCirsium arvense) than the traditionally planted stands and the stands obtained from seeds. The latter two were characterized by the dominance of annuals, bi-annuals and (mostly nonrhizomatous) perennials. Initially, the rates of succession were highest in the stands obtained from rhizomes. However, after 3 – 6 yr there were no differences between the various stands. During the first four years, the percentage cover by rhizomatous foredune plants developed faster than that of annuals, bi-annuals and perennials. After 6 yr, the latter contributed almost as much to the percentage cover as the clonal species. Nomenclature: van der Meijden et al. (1990) for plant species. The plant species were classified into ecological groups according to van der Meijden et al. (1991) and Mennema et al. (1980).     

Integrating selected ecological effects of mixed European beech–Norway spruce stands in bioeconomic modelling

The simplicity of many bioeconomic models has been criticised several times, due to their lack of realism resulting from a deterministic nature and a single-species focus. In this context it was interesting to test the financial sensitivity of bioeconomic modelling against fairly well documented ecological effects in mixed forests. For this purpose our study linked existing results of ecological research with bioeconomic modelling. The presented methodological approach could not only show the importance of considering ecological effects in bioeconomic models; it in fact enabled prioritising ecological research from a financial point of view.In a first step, the possible influence of the tree species mixture on forest stand resistance, productivity and timber quality was derived from existing studies. In a second step, the available Monte Carlo simulations for Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.), simulated under site conditions and risks typical of southern Germany, were extended by the mentioned ecological effects and then evaluated from a financial perspective.The results showed a clear influence of all tested ecological effects on the financial indicators, financial risk and return. While testing each ecological effect separately, an increased resistance against wind, snow and insect attacks had the greatest influence on financial risk and return. It over-proportionally enhanced the financial return while simultaneously the financial risk was reduced. In contrast, a degraded timber quality could eliminate the positive effect of risk compensation in mixed forests almost completely. The least influence on the financial indicators finally showed a changed volume growth in mixed forests.A combination of the separately tested ecological effects (increased resistance, changed volume growth and decreased timber quality), between both tree species, underlined the dominating importance of the stand resistance. The integration of ecological effects, induced by interdependent tree species, in our bioeconomic model resulted in significantly lower financial risk than ignoring these effects. Moreover, the financial return of mixed stand variants with a proportion of Norway spruce greater than 60% even exceeded that of the most profitable pure stand.In conclusion this paper clearly confirmed that ignoring ecological effects in bioeconomic models could lead to seriously biased financial results. While a changed volume growth proved rather to be of minor importance for European beech/Norway spruce stands, tree resistance and timber quality may change the financial results significantly.     

Traditional Ecological Knowledge and Practice for Edible Wild Plants: Biodiversity Use by the Rarámuri,in the Sirerra Tarahumara,Mexico

The Rarámuri who live in the Sierra Tarahumara of Chihuahua State, Mexico have developed local knowledge and harvesting strategies for edible wild plants that have the effect of conserving the biodiversity of their forest ecosystem. This paper presents the results of ethnobotanical research undertaken in the community of Basìhuare in the Sierra Tarahumara, to provide details on some practical aspects of the Raráamuri worldview regarding interconnections between people and their environment. This traditional philosophy forms the basis for the use of edible wild plants and the harvesting strategies practiced in Basìhuare, such as selective harvesting, environmental modification and domestication. These activities provide the opportunity for harvesters to monitor the landscape and the plant resources that occur on the land, as well as present a setting for the communication and exchange of traditional ecological knowledge. However, Rarámuri harvesting practices are under stress because of increased external pressures from commercial timber extraction and other development. We discuss the state of traditional ecological knowledge and its transmission in the context of development activities in the region. The key to sustainability in the Sierra Tarahumara may be the maintenance of traditional management practices for edible wild plants, and other nontimber forest products, that lead to the conservation of biodiversity by creating patchiness and renewing the plant cover on the land.     

Wildfire, Fuel Reduction, and Herpetofaunas across Diverse Landscape Mosaics in Northwestern Forests

Abstract:  The herpetofauna (amphibians and reptiles) of northwestern forests (U.S.A.) is diverse, and many species are locally abundant. Most forest amphibians west of the Cascade Mountain crest are associated with cool, cascading streams or coarse woody material on the forest floor, which are characteristics of mature forests. Extensive loss and fragmentation of habitat resulted from logging across approximately 50% of old-growth forests in northern California and approximately 80% of stands in Oregon and Washington. There is a complex landscape mosaic and overlap of northern and southern biotic elements in the Klamath-Siskiyou Region along the Oregon and California border, creating a biodiversity hotspot. The region experiences many low-severity fires annually, punctuated by periodic major fires, including the Biscuit fire, the largest in North America in 2002. In the fire's northern portion, severe fire occurred on >50% of stands of young, managed trees but on only about 25–33% of old-growth stands. This suggests that the legacy of timber harvest may produce fire-prone stands. Calls for prescribed fire and thinning to reduce fuel loads will remove large amounts of coarse woody material from forests, which reduces cover for amphibians and alters nutrient inputs to streams. Our preliminary evidence suggests no negative effects of wildfire on terrestrial amphibians, but stream amphibians decrease following wildfire. Most reptiles are adapted to open terrain, so fire usually improves their habitat. Today, the challenge is to maintain biodiversity in western forests in the face of intense political pressures designed to "prevent" catastrophic fires. We need a dedicated research effort to understanding how fire affects biota and to proactively investigate outcomes of fuel-reduction management on wildlife in western forests.     

Evaluation of sampling methods for the estimation of structural indices in forest stands

The paper is about the accurate (i.e. unbiased and precise) and efficient estimation of structural indices in forest stands. We present SIAFOR, a computer programme for the calculation of four nearest-neighbour indices, which describe the spatial arrangement of tree positions, the distribution pattern of species, and the size differentiation between trees. The study uses SIAFOR as a sampling simulator in eight completely stem-mapped forest stands of varying area and structural complexity. We statistically evaluate two sample types (distance and plot sampling), comparing sampling error, bias and minimum sample size for index estimation. We introduce the concepts of measurement expansion factor (MEF) and design expansion factor (DEF) for the technical evaluation of sample type efficiency (optimal sample type). Results indicate that sampling error can reach high levels and that minimum sample sizes for index estimation often amply exceed the limit of 20% of tree density or 20 trees per species per hectare, that we set as the highest feasible sample size in normal situations. We found clear feasibility limits (in terms of minimal tree densities and reachable accuracy levels) for the estimation of all investigated indices. Generally, equal or higher sample sizes are needed for plot sampling than for distance sampling to reach equal accuracy levels. Nevertheless, plot sampling resulted more efficient for the estimation of tree size differentiation at low to medium accuracy levels. For all other investigated indices distance sampling resulted more efficient than plot sampling. Minimum sample size increases with accuracy and is negatively correlated with tree density. At a given accuracy level minimum sample size is highest for the estimation of relative mingling and lowest for tree size differentiation; furthermore it is generally lower in large stands than in small ones. Because of the consistency of our conclusions in all of the investigated stands, we think they apply in most stands of similar area (between 1 and 10 ha) and species diversity (not more than four species).     

Hunting Increases Dispersal Limitation in the Tree Carapa procera, a Nontimber Forest Product

Abstract:  The sustainability of seed extraction from natural populations has been questioned recently. Increased recruitment failure under intense seed harvesting suggests that seed extraction intensifies source limitation. Nevertheless, areas where more seeds are collected tend to also have more intense hunting of seed-dispersing animals. We studied whether such hunting, by limiting disperser activity, could cause quantitative dispersal limitation, especially for large crops and for crops in years of high seed abundance. In each of four Carapa procera (Meliaceae) populations in French Guiana and Surinam, two with hunting and two without, we compared seed fate for individual trees varying in crop size in years of high and low population-level seed abundance. Carapa seeds are a nontimber forest product and depend on dispersal by scatter-hoarding rodents for survival and seedling establishment. Hunting negatively affected the proportion of seeds dispersed and caused greater numbers of seeds to germinate or be infested by moths below parent trees, where they would likely die. Hunting of seed-dispersing animals disproportionally affected large seed crops, but we found no additional effect of population-level seed abundance on dispersal rates. Consistently lower rates of seed dispersal, especially for large seed crops, may translate to lower levels of seedling recruitment under hunting. Our results therefore suggest that the subsistence hunting that usually accompanies seed collection is at the cost of seed dispersal and may contribute to recruitment failure of these nontimber forest products. Seed extraction from natural populations may affect seedling recruitment less if accompanied by measures adequately incorporating and protecting seed dispersers.     

Use of Historical Logging Patterns to Identify Disproportionately Logged Ecosystems within Temperate Rainforests of Southeastern Alaska

The forests of southeastern Alaska remain largely intact and contain a substantial proportion of Earth's remaining old‐growth temperate rainforest. Nonetheless, industrial‐scale logging has occurred since the 1950s within a relatively narrow range of forest types that has never been quantified at a regional scale. We analyzed historical patterns of logging from 1954 through 2004 and compared the relative rates of change among forest types, landform associations, and biogeographic provinces. We found a consistent pattern of disproportionate logging at multiple scales, including large‐tree stands and landscapes with contiguous productive old‐growth forests. The highest rates of change were among landform associations and biogeographic provinces that originally contained the largest concentrations of productive old growth (i.e., timber volume >46.6 m³/ha). Although only 11.9% of productive old‐growth forests have been logged region wide, large‐tree stands have been reduced by at least 28.1%, karst forests by 37%, and landscapes with the highest volume of contiguous old growth by 66.5%. Within some island biogeographic provinces, loss of rare forest types may place local viability of species dependent on old growth at risk of extirpation. Examination of historical patterns of change among ecological forest types can facilitate planning for conservation of biodiversity and sustainable use of forest resources. El Uso de Patrones Históricos de Tala para Identificar Ecosistemas Talados Desproporcionadamente en Bosques Lluviosos Templados del Sureste de Alaska Albert & Schoen 11‐839     

Current versus future reproduction: an experimental test of parental investment decisions using nest desertion by mallards (<Emphasis Type="Italic">Anas platyrhynchos</Emphasis>)

Past investment in offspring may be important in determining a parent's ability to reproduce in the future and, hence, should affect the relative value of current offspring. However, there have been surprisingly few clear tests of whether animals actually adjust parental care in response to diminished opportunities for future reproduction. We modified the experimental protocol of Sargent and Gross [Behav Ecol Sociobiol (1985) 17:43–45] to examine offspring desertion by mallards ( Anas platyrhynchos), and decoupled the influence of past investment from expected current benefits by controlling for the effect of offspring age on clutch value. Using 9 years of nest mortality data, we accounted for the increasing prospects of egg survival with clutch age by calculating clutch sizes throughout incubation with equivalent expected benefits. Applying this approach, we experimentally reduced 203 clutches at two different incubation stages such that they had equivalent expected benefits but differed in the amount of past investment. Nest desertion rates did not differ between early- and late-incubated clutches that had equivalent expected benefits. Rather, the probability of desertion increased with the severity of the clutch reduction treatment. These results suggest that female mallards adjust parental care according to the expected benefits of current offspring, rather than to diminished prospects for future reproduction due to past investment. We further examined whether females assessed expected benefits on the basis of clutch size alone or clutch size adjusted for the age of the clutch. Using Akaike's Information Criterion, the most parsimonious model to explain the probability of deserting an experimentally reduced clutch included both the proportion of the clutch remaining and clutch age. Thus, female mallards appear to fine-tune their level of parental care not only according to the relative number of offspring in the clutch, but also to the increased prospects for offspring survival as they age.