Progress 10/01/19 to 09/30/20
Outputs
Target Audience:Professional foresters, students, and academics in forestry Changes/Problems:Due to a cancelled sabbatical in 2020 which had envisioned working with colleagues in Europe on Project 7, this project will be delayed or will have to be entirely cancelled. Project 8 is contingent on funding by the PA Bureau of Forestry who hasindicated a reluctance to fund the project. What opportunities for training and professional development has the project provided?Participated in the annual NASP training program (National Advanced Silviculture Program) at the University of TN How have the results been disseminated to communities of interest?Meetings and discussions with stakeholders such as foresters with the Pennsylvania Game Commission What do you plan to do during the next reporting period to accomplish the goals?Data have been collected to continue work on Projects 1, 2, and 3. Projects 3-6 have been completed. I am in consultation with the PGC for funding of project 9.
Impacts
What was accomplished under these goals?
Goal 1: Project 1, i.e., the analysis spatially explicit tree ages in an old-growth Carpathian European beech forest, has been completed. Multi-aged micro-neighborhoods found in this old-growth forest challenge the forest cycle model of stand development in primeval European beech forests. Whereas close-to-nature silviculture in European beech forests often consists of even-aged management approaches such as shelterwoods, repeated small-scale disturbances lead to neighborhoods where differentially aged trees occur in close spatial proximity, pointing to uneven-aged forest management as the silvicultural equivalent that may be able to create and maintain primeval-like age and size structures. This project is in the process of being expanded to investigate the spatially explicit age and size distributions at larger scales in several forest types. Data have been acquired from collaborators in Italy and statistical analyses will commence in late 2020 and throughout 2021. Project 2, i.e., the analysis of individual-tree and stand-level growth in Douglas-fir dominated old-growth forests, was started. Structural variability in natural Douglas-fir forests hinders restoration targets for the full old-growth developmental sequence. To guide stage-specific restoration, we developed a simple index of the vertical diversification (VD) stage. VD-associated sub-stand structures were objectively identified by quantifying live-tree size structures across a developmental sequence of ten pristine stands in the Oregon Cascades. Floating neighborhoods were used to delineate natural tree neighborhoods based on triangulated irregular networks in five concentric rings of ever-greater spatial extent (averaging 60-2060 m2). Diameter distributions summarized the most frequently encountered tree size structures among neighborhoods with increasing deviation from the neutral multivariate core. Of 18 observed diameter distribution types (DDTs), the core DDT characterized all-sized tree neighborhoods reflective of vertical diversification, which was most abundant in early old-growth (VD) stands and least abundant at the extremes of the sequence. Vertical diversification declined in older stands, whose more distinct DDTs had peaks in larger trees and multiple size classes, likely reflecting horizontal diversification (HD). This new approach illustrates that structural restoration of VD stands could be facilitated by the single-tree selection method, while that of HD stands may be promoted with both single-tree and group-selection as well as targeted release. This study will be followed up by a quantification of the horizontal diversification stage in 2021. Project 3, i.e., testing the hypothesis that structural complexity develops synchronously with biomass in temperate hardwood forests has been completed. Small-scale disturbance regimes that maintain the complex structures of old-growth European beech (Fagus sylvatica L.) forests have long confounded the development phases assigned by classification protocols based on inconsistent and poorly substantiated archetypal structures. Such protocols further preclude objectively testing the long-held assumption that biomass accumulation and structural complexity are developmentally asynchronous. We developed and demonstrated an alternative protocol for capturing stadial condition based solely on a deadwood share cut-off (30%) and proportional live-tree volume in seven progressive tree size classes. The proportions of a 10-ha primeval European beech forest in the Ukraine assigned in 156.25 m2 grid cells to each of the resulting sequential Biomass Preponderance phases were in keeping with previously reported estimates: 1.8% in the Open/Seedling phase, 7.6% Understory, 4.8% Lower Midstory, 4.7% Upper Midstory, 9.1% Lower Overstory, 22.6% Overstory, 26.3% Upper Overstory, and 11.2% in the Emergent phase; the final 12% was assigned to the deadwood-rich Degradation Stage. Volume, basal area, and mean tree size increased distinctly with each subsequent upgrade phase of the Initiation, Aggradation, and Culminations stages and declined in the downgrade Degradation stage in accordance with the forest life cycle. With local adaptation, the proposed Biomass Preponderance phase classification protocol could be applied to any site or forest type. Further, in contrast to expectations narrowly based on the distribution of volume among canopy layers, a synchronous pattern was observed for size-based structural complexity metrics (including the standard deviation of tree diameters, the Gini coefficient for basal area, the diameter differentiation index T, and the structural complexity index SCI), providing a natural model for the simultaneous optimization of volume and complexity in managed forests. Project 4, the testing of structural complexity captured by spatially explicit structure indices as a function of spatial scale was examined in two stem-mapped stands in central Pennsylvania. In this project, rather than employing one large plot, optimal sampling of both inventory metrics and spatially-explicit structural indices can be achieved in Eastern Hardwoods with a combined sampling scheme in which a subset of small, fixed area subplots are also stem-mapped. Managing forest stand structures for multiple objectives requires accurate and precise estimates of desired structural features that may be best estimated at different scales. In this project, we document minimum necessary plot sizes for structural metrics and spatially-explicit indices to characterize stand structure in a typical mature North American Eastern hardwoods forest. Metrics and indices (Index of Aggregation, Diameter Differentiation Index, Dissimilarity Coefficient, Structural Complexity Index) were calculated within 40 randomly placed plots of 0.05 to 1.75 ha in extent in two 2.0 ha stem-mapped stands. Estimation adequacy was determinedby 1) precision (varied < 10% among plots) and 2) accuracy (within 10% of the 2.0 ha value at 5th and 95th percentiles). Minimum plot sizes to meet both precision and accuracy standards were 0.25-0.75 ha for the spatially-explicit indices and 1-2 ha for stand structures. A minimum of five0.10 ha subplots would be needed for indices, and 9-20 for most metrics, but an untenable 288 for the density of large diameter trees. Because a single sampling plot would require an inefficiently large extent, a better approach may be a combined sampling scheme in which a subset of small, fixed area subplots are additionally stem-mapped. Potential impact of this research is to more efficiently inform forest managers whose objectives are not primarily focused on timber production, but who aim toward wildlife habitat outcomes. Goal 2: Project 9, i.e., the development of early stand interventions to silviculturally control the development of mixed-oak stands to achieve desired objectives commenced with several field visits and discussions with personnel of the Pennsylvania Game Commission (PGC). The PI is in consultation with the PGC to develop a proposal to apply and test early stand entries to enhance the diversity of ground flora and improve habitat quality.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Zenner, E.K., J.E. Peck, and M.L. Hobi. 2020. Development phase convergence across scale in a primeval European beech (Fagus sylvatica L.) forest. Forest Ecology and Management 460:117889, 9 pp.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Mafi-Gholami, D., E.K. Zenner, A. Jaafari, and D. Tien Bui. 2020. Spatially explicit predictions of changes in the extent of mangroves of Iran at the end of the 21st century. Estuarine, Coastal, and Shelf Science 106644, 10 pp.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Thees, O., M. Erni, R. Lemm, G. Stadelmann, and E.K. Zenner. 2020. Future potentials of sustainable wood fuel from forests in Switzerland. Biomass and Bioenergy, 105647, 141.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Zenner, E.K., J.E. Peck, and V. Trotsiuk. 2020. Multi-aged micro-neighborhoods challenge the forest cycle model in primeval European beech. iForest 13: 209214.
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Progress 10/01/18 to 09/30/19
Outputs
Target Audience:Forestry professionals, academics, consultants, private forest landwoners. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Training both for undergraduate and graduate students. Presentations to practitioners and decision-makers. How have the results been disseminated to communities of interest?Results have been distributed through participation in conferences, as well as through publications. What do you plan to do during the next reporting period to accomplish the goals?Dr. Zenner will be on sabbatical in the spring of 2020 to learn about dendroecological reconstruction of tree ages and growth in support of some of the suggested projects. Funding will be sought from the Bureau of Forestry for Project 8, although this has not been successful up to now.
Impacts
What was accomplished under these goals?
Goal 1: Project 1, i.e., the analysis of four stem-mapped plots with known ages of individual trees ages in an old-growth Carpathian European beech forest, has been completed. Neighboring trees exhibit tremendous age variability, pointing to the spatial coexistence of differently aged shade-tolerant individuals rather than patches of even-aged trees. In this forest, small-scale disturbances that release an abundant layer of advance regeneration would be a sensible approach to perpetuate their functions and dynamics. Project 2, the analysis of individual-tree and stand-level growth in western coniferous forests will commence in the fall of 2020. We developed the floating neighborhood approach to identify natural sub-stand structures associated with the vertical differentiation stage. Delineating natural tree neighborhoods based on triangulated irregular networks in five concentric rings of ever-greater spatial extent, we summarized multivariate size structures in a development sequence of ten natural Douglas-fir dominated stands to identify the most frequently encountered neighborhood diameter distribution types (DDTs) that increasingly deviated from the common core. Roughly 200 years after stand-replacing disturbance, ongoing layering and gap dynamics lead to ever greater heterogeneity in the vertical diversification stage. All-sized tree neighborhoods were observed in all stands and were most abundant in early old-growth and least abundant at the extremes of the developmental sequence. Vertical diversification declined toward the end of the sequence, exhibiting more distinct DDTs with peak abundances in larger trees and multiple size classes, possibly reflecting increasing horizontal diversification. High sub-stand heterogeneity indicates that old-growth restoration guidelines would benefit not only from setting a wide range of stand-level structural goals but should also allow a wide range of naturally occurring sub-stand structures. Project 3, i.e., the quantification of the effects of scale on development phase assignment and the pathways of subplot convergence with increasing scale, has been completed. We applied an objective development phase classification protocol to subplots of a 10-ha stem-mapped primeval European beech forest ranging from 156.25m^2 to 10000 m^2 in extent. The proportions of eight development phases assigned to each subplot were tallied at each scale and the pathways by which phases merged across scale were summarized. As spatial scale increased, the simpler "immature" phases converged into the more complex "mature" phases across multiple pathways and were no longer assigned by the 1250-2500 scale. The multi-sized phase dominated with increasing scale until ultimately all subplots converged on this phase. We confirmed the scale dependency of development phase assignment and showed that the simpler development phases are assigned predominantly at the smaller scales that correspond to the prevailing disturbance regime while complex phases are assigned predominantly at larger scales. Because the assignment of development phases at fine spatial resolutions is necessary for investigating the full mosaic cycle, across-scale approaches help identify the spatial scale of predominant disturbances and the rate at which phase transitions occur across scales in primeval forests. We also investigated the patch mosaic-development stage model. The model posits the unity of patches and development stages in primeval temperate forests and links patchiness to the synchronized, coarse-scale canopy senescence, and breakup processes that initiate the demographic transition to new regeneration patches that then asynchronously progress through sequential development stages. Inconsistent transitions among development stages set expected coarse-scale canopy senescence against observed, predominantly fine-scale canopy-gap dynamics. Applying a multi-scale approach to quantify the extent to which the initial, Optimum, and Decay stages are characterized by the interspersion of neighborhoods of variously sized trees (i.e., patch types) in nine Oriental beech stands, we found that differences among stages in patch type richness and composition occurred primarily at the finest scales and diminished rapidly with increasing scale. Most patch types were ubiquitous and the few patch types unique to a particular stage occurred at very low abundances. Patch types composed of advance regeneration were most prevalent in the Initial stage but were absorbed into the matrix structure at scales > 500 m^2. In all three stages, the most heterogeneous patch type encompassed > 90% of all trees at scales > 100 m^2. To portray fine-scale dynamics resulting in similar patch type compositions across development stages, we introduced the new patch mosaic-gap reabsorption model that avoids the unity of patch and "demographic" stage to focus instead on "structural" stages. Project 4, the testing of the delayed oak canopy dominance hypothesis in two stem-mapped stands in central Pennsylvania will commence in 2021 after measuring 15-year changes in composition and spatial structure. Projects 5/9, whose aims are to characterize developmental changes between ages 0 and 20 following stand-replacement disturbances in mixed-oak stands and the development of early stand prescriptions led to a revision of oak seedling regeneration models based on measurements of regeneration success in 23 stands at the stem exclusion stage of development (mean 17.4 years since harvest). The best-fitting model based on advance regeneration used plot aggregate heights of oak stems >15 cm in height. Best models based on post-harvest regeneration (ages 1, 4, and 7 since harvest) used height of the dominant oak seedling in a plot in conjunction with heights of the tallest black birch, red maple, and other species, respectively. Oak seedling height was most explanatory variable, by a large margin, but the others were also statistically significant in every model. Black birch had the strongest negative influence on oak seedling success, but red maple was a much more frequent competitor. AUC values increased as regeneration developed, from pre-harvest to age 7, but were nearly as great at age 4 as at age 7 (0.87 vs. 0.89). This suggests that age 4 would be an optimal time for silvicultural interventions intended to increase the success of oak regeneration. Goal 2: The perpetual provision of desired ecosystems is strongly contingent the ability to regenerate forests. Project 1 identified silvicultural approaches based on small-scale disturbances that ensure successful natural regeneration. Further, projects 2, 3, 5 and 9 enable the identification and derivation of intermediate stand interventions (i.e., at different times and using a variety of treatments during the period between regeneration efforts) to produce structurally complex stands and species mixtures that have been linked to enhanced resilience to stressors such as climate change. Project 6, the economic and ecological sustainability of using small-diameter trees to ensure the supply of forest woody biomass was completed. Amounts of forest woody biomass for energy production at different costs were identified at different levels of subsidies for the entire country of Switzerland and the major regions in the country. We identified regions where investments into woody bioenergy are warranted. These results guide companies do direct their investments into promising regions where expansion of bioenergy would not compromise the sustainability of forests and thereby successfully support the energy transition toward renewables. Finally, the project identifies areas where the formulation of forest policies regarding subsidies for the sustainable provision of bioenergy and the application of silvicultural treatments can be expected to enhance long-term resource utilization and economic development of the forestry sector.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Zenner, E.K., J.E. Peck, and K. Sagheb-Talebi. 2019. Patchiness in old-growth oriental beech forests across development stages at multiple neighborhood scales. European Journal of Forest Research, 138:739752.
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Peck, J.E. and E.K. Zenner. 2019. Common ground among beech forest development stages: matrix vs. stage-typical live tree structure. Journal of Vegetation Science, 30(5):893904.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Erni, M., Burg, V., Lemm, R., Stadelmann, G., Schweier, J., Zenner, E., & Thees, O. (2019). How can forest wood contribute to the energy transition in Switzerland?: A regional analysis. Presented at the SCCER BIOSWEET Annual Conference. Lucerne.
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Progress 02/01/18 to 09/30/18
Outputs
Target Audience:The target audience consists predominantly of forestry professionals. This includes not only scientists who research forests, but also managers that are concerned with forest ecosystem management. Specifically, target audiences that are intended to apply research results are foresters who work in public land management agencies such as the Bureau of Forestry and the USDA Forest Service, as well as NGOs interested in creating and maintaining structural complexity in managed forests. Furthermore, consultants tasked to write management plans that go beyond the single objective of timber production would be a prime target audience. Finally, efforts include formal classroom instruction to undergraduate and graduate students (FOR 410: Forest ecosystem management; FOR 421: Silviculture) and presentations to foresters, ecologists, and natural resources professionals. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Dr. Zenner uses the latest research results in his annual training at the University of Tennessee where he teaches a 2-day workshop that includes 35 silviculturists who work for the USDA Forest Service. The goal of this workshop is to teach the latest research on stand dynamics to improve silvicultural prescriptions. How have the results been disseminated to communities of interest?The results have been primarily disseminated through peer-reviewed publications, as well as presentations at international conferences, workshops, and to forest management organizations. For example, results of projects 5 and 9 will be presented to Pennsylvania Department of Conservation and Natural Resources, Bureau of Forestry staff in a meeting in December 2018. What do you plan to do during the next reporting period to accomplish the goals?Projects 1, 3, and 6: Submit manuscripts for publication. Project 2: Start data analysis and write-up for publication. Projects 5 and 9: Complete analyses described above, write up research for publication, and begin looking at developmental models for red maple and black birch.
Impacts
What was accomplished under these goals?
Goal 1:Data analysis of the stem-mapped and aged tree plots in the old-growth European beech forest of Uholka-Shyrokyj Luh in the Carpathian Mountains of the Ukraine (Project 1) has been completed. Our results show that tree-to-tree variability in ages of neighboring trees spanned several decades to several hundreds of years, challenging the concept of development stages that assumes that structural complexity in forests is a function of the spatial coexistence of heterogeneous patches with internal homogeneity of tree ages and sizes. Our results indicate that structural complexity is a function of tree-to-tree age and size heterogeneity rather than of patch-to-patch age and size heterogeneity. This has major implications for silviculture in that the single-tree selection method (i.e., uneven-aged silviculture) rather than even-aged regeneration approaches more closely emulate natural regeneration dynamics in beech forests. The analysis of individual-tree and stand-level growth in western coniferous forests (Project 2) will commence in the fall of 2020. Data from nine stem-mapped mixed Douglas-fir stands that span a period of 20 years are in hand and we are in the process of checking/preparing the data for analysis. Data on the stem-mapped 10 ha monitoring plot in the old-growth European beech forest of Uholka-Shyrokyj Luh in the Carpathian Mountains of the Ukraine have been obtained from the WSL Swiss Federal Research Institute (Project 3) and we have assigned development phases to the entire monitoring area across spatial scales (from 0.0156 to the entire 10 ha area). We are analyzing the data to test whether development stages converge with increasing scale to the Plenter phase. A further analysis of changes in development phases over a 15-year period will be started in 2019 under the leadership of my WSL colleagues. The testing of the delayed oak canopy dominance hypothesis in two stem-mapped stands in central Pennsylvania (Project 4) will commence in 2021 after we had a chance to measure 15-year changes in composition and spatial structure of the stands. We made significant progress this year in characterizing developmental changes between ages 0 and 20 following stand-replacement disturbances in mixed-oak stands (Project 5). The influence of pre-disturbance conditions on the success of oak regeneration have been successfully modeled with a high degree of determinism, and opportunities are being examined for silvicultural interventions to redirect developmental trajectories beginning at age 4. Goal 2:The economic and ecological sustainability of using small-diameter trees to ensure the supply of forest woody biomass was investigated in collaboration with colleagues from the WSL Swiss Federal Research Institute (Project 6). Data have been analyzed and a manuscript is in the final phase if preparation. The paper quantifies the amounts of forest woody biomass for energy production at different costs of wood and different levels of subsidies for the entire country of Switzerland as well as the major regions in the country. Briefly, there is a reduction between 85-98% between the theoretically available wood potential (i.e., all harvested wood would be used for bioenergy production) and the actually available wood potential that deducts amounts from areas withdrawn from production to serve ecological purposes and amounts that cannot be produced at the current market value for bioenergy wood. Results have major implications for companies who would like to invest into the woody bioenergy sector. Our manuscript identifies the regions where such investments are warranted.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Steiner, K.C., B.S. Stein, and J.C. Finley. 2018. A test of the delayed oak dominance hypothesis at mid-rotation in developing upland stands. Forest Ecology and Management 408: 1-8.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Zenner, E.K. and J.E. Peck. 2018. Floating neighborhoods reveal contribution of individual trees to high sub-stand scale heterogeneity. Forest Ecology and Management, 412:2940.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Zenner, E.K., J.E. Peck, and K. Sagheb-Talebi. 2018. One shape fits all, but only in the aggregate: Diversity in sub-stand scale diameter distributions. Journal of Vegetation Science, 29: 501510.
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