Interference dynamics in mixed red alder/Douglas-fir forests

This study characterized the nature and dynamics of interference in mixed red alder (Alnus rubra Bong.)/Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands in the Pacific Northwest, USA. Long-term spatial and tree measurements from the Cascade Head (CH) and H.J. Andrews (HJA) Experimental Forests in western Oregon and Delezene Creek (DC), Washington were utilized to investigate neighborhood and population-level measures of interference. Existing neighborhood and population-level measures of interference were modified to evaluate the intensity and importance of intra- and inter-specific interference. The relationship between relative growth rate and population-level and neighborhood interference were examined over 9 years at the CH and HJA study sites and 38 years at the DC study site. In general, the effects of intra-specific interacted with the effects of inter-specific interference to influence the relative growth rates of red alder and Douglas-fir at all of the sites. Performance of the interference measures as predictors of relative growth rates varied between species and with stand structure. In general, population-level indices were the best predictors of relative growth rates for the species with heights greater than the other interacting species over a given interval of time. In contrast, neighborhood indices were the best predictors of relative growth rates for the species with subordinate or equivalent tree heights to the dominant species over a given interval of time. These results were consistent for both species, all three study sites, and all measurement periods when interference occurred and suggest that the importance of neighborhood interference varies with the competitive status of a species. A conceptual model synthesizes the importance of neighborhood and population-level interference as a function of relative dominance of a species. In addition, the literature suggests that this model may also be appropriate for individuals within a population

Threats to North American Forests from Southern Pine Beetle with Warming Winters

In coming decades, warmer winters are likely to lift range constraints on many cold-limited forest insects. Recent unprecedented expansion of the southern pine beetle (SPB, Dendroctonus frontalis) into New Jersey, New York, Connecticut, and Massachusetts in concert with warming annual temperature minima highlights the risk that this insect pest poses to the pine forests of the northern United States and Canada under continued climate change. Here we present the first projections of northward expansion in SPB-suitable climates using a statistical bioclimatic range modeling approach and current-generation general circulation model (GCM) output under the RCP 4.5 and 8.5 emissions scenarios. Our results show that by the middle of the 21st century, the climate is likely to be suitable for SPB expansion into vast areas of previously unaffected forests throughout the northeastern United States and into southeastern Canada. This scenario would pose a significant economic and ecological risk to the affected regions, including disruption oflocal ecosystem services, dramatic shifts in forest structure, and threats to native biodiversity

Patterns and drivers of recent disturbances across the temperate forest biome

Increasing evidence indicates that forest disturbances are changing in response to global change, yet local variability in disturbance remains high. We quantified this considerable variability and analyzed whether recent disturbance episodes around the globe were consistently driven by climate, and if human influence modulates patterns of forest disturbance. We combined remote sensing data on recent (2001-2014) disturbances with in-depth local information for 50 protected landscapes and their surroundings across the temperate biome. Disturbance patterns are highly variable, and shaped by variation in disturbance agents and traits of prevailing tree species. However, high disturbance activity is consistently linked to warmer and drier than average conditions across the globe. Disturbances in protected areas are smaller and more complex in shape compared to their surroundings affected by human land use. This signal disappears in areas with high recent natural disturbance activity, underlining the potential of climate-mediated disturbance to transform forest landscapes.A.S. and R.S. acknowledge support from the Austrian Science Fund (FWF) through START grant Y895-B25. C.S. acknowledges funding from the German Academic Exchange Service (DAAD) with funds from the German Federal Ministry of Education and Research (BMBF) and the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007–2013) under REA grant agreement Nr. 605728 (P.R.I.M.E.—Postdoctoral Researchers International Mobility Experience). T. D. acknowledges funding from the Fonds institutionnel de recherche de l’Universitédu Quebec en Abitibi-Te ́ miscamingue, the Natural Sciences and Engineering Research ́ Council of Canada (NSERC), Tembec, and EACOM Timber Corporation. Á.G.G. was supported by FONDECYT 11150835. S.J.H. and T.T.V. acknowledge NSF Award 1262687. A.H. was partially supported by NSF (award #1738104). D.K. acknowledges support from the US NSF. D.L. was supported by an Australian Research Council Laureate Fellowship. A.S.M. was supported by the Environment Research and Technology Development Fund (S-14) of the Japanese Ministry of the Environment and by the Grants-in-Aid for Scientific Research of the Japan Society for the Promotion of Science (15KK0022). G.L.W.P. acknowledges support from a Royal Society of New Zealand Marsden Fund grant. S.L.S. acknowledges funds from the US Joint Fire Sciences Program (project number 14-1-06-22) and UC ANR competitive grants. M.S. and T.H. acknowledges support from the institutional project MSMT CZ.02.1.01/0.0/0.0/16_019/ 0000803. M.G.T. acknowledges funding from the University of Wisconsin-Madison Vilas Trust and the US Joint Fire Science Program (project numbers 09-1-06-3, 12-3-01-3, and 16-3-01-4). The study used data from the TRY initiative on plant traits (http://www.trydb.org). The TRY initiative and database is hosted, developed and maintained by J. Kattge and G. Boenisch (Max Planck Institute for Biogeochemistry, Jena, Germany). TRY is currently supported by Future Earth/bioDISCOVERY and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzi

Introduction: Ecology and Silviculture of Temperate Mixedwood Forests

This is intended to serve as the introduction to the Special Issue on the Ecology and Silviculture of Temperate Mixedwood ForestsThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Building on the last “new” thing: exploring the compatibility of ecological and adaptation silviculture

Sustaining the structure, function, and services provided by forest ecosystems in the face of changing climate and disturbance regimes represents a grand challenge for forest managers and policy makers. To address this challenge, a range of adaptation approaches have been proposed centered on conferring ecosystem resilience and adaptive capacity; however, considerable uncertainty exists regarding how to translate these broad and often theoretical adaptation frameworks to on-the-ground practice. Complicating this issue has been movement away, in some cases, from other recent advances in forest management, namely ecological silviculture strategies that often focus on restoration. In this paper, we highlight the areas of compatibility and conflict between these two frameworks by reviewing the four principles of ecological silviculture (continuity, complexity and diversity, timing, and context) from the perspective of global change adaptation. We conclude that given many commonalities between the outcomes of ecological silviculture and conditions conferring adaptive capacity, the four principles remain a relevant starting point for guiding operationalization of often theoretical adaptation strategies.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Long-Term Evolution of Composition and Structure after Repeated Group Selection Over Eight Decades

: In northeastern North America, group selection is frequently used in northern hardwood forests to maintain uneven-aged stand structure and promote regeneration of tree species spanning a range of shade tolerances. For this study, long-term application of group selection at the Bartlett Experimental Forest, New Hampshire, USA provided a unique opportunity to address cohort and stand level progression after 80-years of treatment. Cohort-level evolution reflected successional and developmental dynamics associated with even-aged forest systems, whereas aggregate, stand-level conditions were consistent with expectations for uneven-aged systems. As cohorts aged, diameter distributions progressed towards descending monotonic forms and species composition transitioned from shade-intolerant species to shade-tolerant species. Standing deadwood and downed woody material in cohorts followed trajectories of aging even-aged stands through time. Although American beech (Fagus grandifolia Ehrh.) was a primary species across cohorts and at the stand level, stand level regeneration included a mixture of ecologically and commercially valuable species. These long-term results offer important insights into emergent cohort and stand-level conditions and processes that may affect continued recruitment of desirable compositional and structural conditions in stands managed using group selection over numerous cutting cycles.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Increasing the utility of tree regeneration inventories: Linking seedling abundance to sapling recruitment

Tree regeneration surveys provide insight into potential forest change and trajectories of stand development, which can guide management in an era of global change. However, most tree regeneration surveys tend to be coarse and/or rapid assessments which can introduce considerable uncertainty into translating estimates of seedling abundance into models of sapling recruitment and subsequent overstory tree abundance and composition. Observations of seedling abundance changes across size classes may be essential to accurately predicting recruitment from seedling sized trees to advanced size classes, which is fundamental to informing our understanding of future forest composition and dynamics. Using the USDA Forest Service’s Forest Inventory and Analysis (FIA) program’s Regeneration Indicator (RI) dataset, in which seedlings are monitored by six height classes, we developed Boosted Regression Tree models to predict presence of sapling recruitment for five common, north temperate and boreal tree species as a function of seedling abundance by height class and site/stand factors. Models using the six RI seedling height classes were compared to models using the single seedling size class as commonly surveyed by programs such as FIA. Use of seedling height classes improved models for all species. Seedlings > 1.5 m tall were the most influential predictors of recruitment for each species while seedlings in classes < 1.5 m tall were either removed entirely from models or had low relative influence (<8%). Seedlings < 0.3 m tall had both positive and negative relationships with sapling recruitment depending on species, suggesting that abundances of small seedlings should be interpreted cautiously. This approach demonstrates the importance of collecting relatively coarse seedling height data during regeneration surveys with potential application to other regions and scenarios to expand the utility of tree regeneration surveys to predict future forest dynamics

Appendix A. Regression equations for predicting exposed crown area from tree diameter at breast height.

Regression equations for predicting exposed crown area from tree diameter at breast height