Process-Based Modeling to Assess the Effects of Recent Climatic Variation on Site Productivity and Forest Function across Western North America

A process-based forest growth model, 3-PG (Physiological Principles Predicting Growth), parameterized with values of soil properties constrained by satellite-derived estimates of maximum leaf area index (LAI[subscript max]), was run for Douglas-fir (Pseudotsuga menziesii) to contrast the extent to which site growth potential might vary across western North America between a cool, wet period (1950–1975) and a more recent, generally warmer and drier one (2000–2009). LAI[subscript max] represents a surrogate for overall site growth potential, as demonstrated from a strong correlation between the two variables, with the latter based on the culmination of mean annual increment estimates made at 3356 ground-based U.S. Forest Service survey plots across the states of Oregon and Washington. Results indicate that since 2000, predicted LAI[subscript max] has decreased more than 20% in portions of the Southwest USA and for much of the forested area in western Alberta. Similar percentage increases in LAI[subscript max] were predicted for parts of British Columbia, Idaho and Montana. The modeling analysis included an assessment of changes in seasonal constraints on gross primary production (GPP). A general reduction in limitations caused by spring frost occurred across the entire study area. This has led to a longer growing season, along with notable increases in summer evaporative demand and soil drought for much of the study area away from the maritime influence of the Pacific Ocean.Keywords: Douglas-fir, FIA survey plots, Climate change, Leaf area index, 3-PG model, Productivit

Impact of partial harvesting on the net ecosystem production of a mixed conifer forest following mountain pine beetle attack

The recent mountain pine beetle (MPB) outbreak has had a major impact on the carbon (C) cycling of lodgepole pine forests in British Columbia. Mitigation efforts to control the insect outbreak have led to increased harvesting rates in the province. This study determines whether partial harvesting as an alternative forest management response to clearcutting can increase the net ecosystem production (NEP) of a mixed conifer forest (MPB-09) in Interior BC. Using the eddy-covariance (EC) technique, the C dynamics of the 70-year old stand were studied over the two years after partial harvest following MPB attack and also compared to an adjacent clearcut (MPB-09C) over the growing season. The annual NEP at MPB-09 increased from -107 g C m⁻² in 2010 to -57g C m⁻² in 2011. The increase of NEP was because the associated increase in annual gross ecosystem photosynthesis (GEP) from 812 g C m⁻² in 2010 to 954 g C m⁻² in 2011 exceeded the increase in annual respiration (Re) from 920 g C m⁻² to 1011 g C m⁻² in the two years of study. During the growing season of 2010, NEP at MPB-09C was -132 g C m⁻² indicating high C losses in the clearcut. MPB-09 was a C sink during the growing season of both years, increasing from 9 g C m⁻² in 2010 to 47 g C m⁻² in 2011. The increase of NEP in the partially harvested forest suggests stand recovery following harvest, which corresponds to a 25% increase in the maximum assimilation rate in the second year. This study shows that retaining the healthy residual forest can greatly enhance the C sequestration of MPB-attacked stands and has important implications for forest management.Land and Food Systems, Faculty ofGraduat

Mapping the distribution of conifer tree species in response to environmental changes across western North America using a physiologically based approach

Over the past decade, changes in climate have been sufficient to affect both the composition and function of forest ecosystems. The extent that projected climate change will continue to impact tree species vulnerabilities remains unclear and has been mainly assessed based on simple relationships between the distribution of mature trees and climate variables. The objective of this thesis was to assess the effects of regional climate and soil variations on the current and future distribution of 20 major conifer tree species across western North America and determine the impacts of changing environmental variables on tree species vulnerabilities. The spatial variation in properties of soil water availability and soil fertility was combined in the process-based model 3-PG to provide detailed projections of species shifts in response to changes in environmental conditions. The relative importance of limitations imposed on photosynthesis by suboptimal temperatures, frost, solar radiation, soil water and vapor pressure deficits was ranked in a decision tree analysis based on tree species occurrences across the region. The baseline distributions of the tree species were predicted with an average accuracy of 84% (κ = 0.79), based on their recorded presence and absence on 43,404 field survey plots. Inclusion of soil properties was crucial to improving the overall accuracy of the species distribution models and 75% of the species directly responded to changes in the soil water input. At the ecoregion level, this thesis identified the highest vulnerability of the 20 tree species analyzed to occur within the North American Deserts, particularly in the Thompson-Okanagan Plateau of British Columbia (BC). Comparison of areas suitable for tree species range expansion with a large empirical dataset on tree seedling occurrences in BC agreed on average 79%, serving as indicators of early species responses to climate shifts in the province. Outcomes of this thesis demonstrate species-specific responses to current and future climatic variations and can contribute to informing forest management for climate change adaptation.Forestry, Faculty ofGraduat

Effects of climate on the growth of Swiss uneven-aged forests: Combining >100 years of observations with the 3-PG model

Stand-level process-based models have rarely been applied to uneven-aged forests that contain many size classes and negative exponential shaped size distributions. However, the relative simplicity of such models, in terms of parameterisation, use and interpretation, could make them valuable tools for studying and managing such forests. In particular, the effects of climate change on the stand-level growth of forests with negative exponential shaped size distributions has received very little attention compared with even-aged forests. The first objective of this study was to validate 3-PG, a stand-level process-based model, for five types of uneven-aged forests in Switzerland; (1) Fagus sylvatica dominated, (2) Picea abies dominated, (3) mixtures of Picea abies and Abies alba, (4) mixtures of Picea abies, Abies alba and Fagus sylvatica, and (5) mixtures of Larix decidua, Pinus cembra and P. abies. The second objective was to use 3-PG to examine how climate change has influenced the growth of these forests since the 1930s. 3-PG predictions of biomass, biomass partitioning in above- and belowground components, and light absorption were validated using inventory data from 23 plots, which had been monitored for an average of 81 years (15 to 112 years). For all species and size classes (2–3 per species), 3-PG produced accurate predictions of root biomass, stem biomass and outputs derived from it such as mean diameter, basal area and height, which were all highly correlated with the observed values (R2 > 0.86). The slope of predicted versus observed values was often not significantly different to 1 (averaged 1.13) and the bias averaged −1.2%. 3-PG simulations to examine the effects of climate change without the confounding effects of stand structure and management, showed that the growth of the five forests types has, on average, increased by 17% since the 1930s. The growth was mainly influenced by temperature, while in the case of A. alba, growth was largely influenced by vapour pressure deficit. The accelerated growth rates imply that thinning intensities also need to increase to prevent high stand densities from inhibiting regeneration in these uneven-aged forests. This study shows that 3-PG can be used to predict the growth dynamics of uneven-aged mixed-species forests, and to our knowledge, this is the first time a stand-level process-based forest growth model has been used and validated for such forests.ISSN:0378-1127ISSN:1872-704

Process-Based Modeling to Assess the Effects of Recent Climatic Variation on Site Productivity and Forest Function across Western North America

A process-based forest growth model, 3-PG (Physiological Principles Predicting Growth), parameterized with values of soil properties constrained by satellite-derived estimates of maximum leaf area index (LAIᵐᵃˣ), was run for Douglas-fir (Pseudotsuga menziesii) to contrast the extent to which site growth potential might vary across western North America between a cool, wet period (1950–1975) and a more recent, generally warmer and drier one (2000–2009). LAIᵐᵃˣ represents a surrogate for overall site growth potential, as demonstrated from a strong correlation between the two variables, with the latter based on the culmination of mean annual increment estimates made at 3356 ground-based U.S. Forest Service survey plots across the states of Oregon and Washington. Results indicate that since 2000, predicted LAIᵐᵃˣ has decreased more than 20% in portions of the Southwest USA and for much of the forested area in western Alberta. Similar percentage increases in LAIᵐᵃˣ were predicted for parts of British Columbia, Idaho and Montana. The modeling analysis included an assessment of changes in seasonal constraints on gross primary production (GPP). A general reduction in limitations caused by spring frost occurred across the entire study area. This has led to a longer growing season, along with notable increases in summer evaporative demand and soil drought for much of the study area away from the maritime influence of the Pacific Ocean.Forestry, Faculty ofNon UBCForest Resources Management, Department ofReviewedFacult

Calibration of the process-based model 3-PG for major central European tree species

Process-based forest models are important tools for predicting forest growth and their vulnerability to factors such as climate change or responses to management. One of the most widely used stand-level process-based models is the 3-PG model (Physiological Processes Predicting Growth), which is used for applications including estimating wood production, carbon budgets, water balance and susceptibility to climate change. Few 3-PG parameter sets are available for central European species and even fewer are appropriate for mixed-species forests. Here we estimated 3-PG parameters for twelve major central European tree species using 1418 long-term permanent forest monitoring plots from managed forests, 297 from un-managed forest reserves and 784 Swiss National Forest Inventory plots. A literature review of tree physiological characteristics, as well as regression analyses and Bayesian inference, were used to calculate the 3-PG parameters. The Swiss-wide calibration, based on monospecific plots, showed a robust performance in predicting forest stocks such as stem, foliage and root biomass. The plots used to inform the Bayesian calibration resulted in posterior ranges of the calibrated parameters that were, on average, 69% of the prior range. The bias of stem, foliage and root biomass predictions was generally less than 20%, and less than 10% for several species. The parameter sets also provided reliable predictions of biomass and mean tree sizes in mixed-species forests. Given that the information sources used to develop the parameters included a wide range of climatic, edaphic and management conditions and long time spans (from 1930 to present), these species parameters for 3-PG are likely to be appropriate for most central European forests and conditions.ISSN:1612-4677ISSN:1612-466

Presenting a climate-smart forestry evaluation framework based on national forest inventories

Climate-smart forestry (CSF) has gained increasing attention in recent years. Yet, a framework to assess the three pillars of CSF, in terms of mitigation and adaptation to climate change and ecosystem service (ES) provision based on national forest inventory (NFI) data is currently lacking. In this study, we present an assessment framework of CSF based on forest indicators derived from NFI. To quantify the three pillars of CSF we defined 1) mitigation based on the forest carbon stock, 2) adaptation using biodiversity and susceptibility to disturbances caused by storm and bark beetles and 3) ES provision with timber production and protection against avalanches and rockfall. We demonstrate the application of this framework using Swiss NFI data and projections of future forest development under four different management scenarios. Our results show that, in general, the carbon stock is increasing at the national scale when current management practices are maintained. Increases are especially pronounced in the Jura and Southern Alps regions. Trade-offs occur between enhancing mitigation and adaption, and the sustainable provision of ES such as timber production. Scenarios with increased harvesting intensities lead to a higher timber supply in the short-term, while decreasing the carbon stock, biodiversity-related old-growth indicators and the protective function of forests. The indicator framework presented in this study provides a first methodological approach that can support policy making to balance the different forest services in the context of CSF.ISSN:1470-160XISSN:1872-703

Potentials and limitations for estimating daytime ecosystem respiration by combining tower-based remote sensing and carbon flux measurements

Vegetation carbon uptake and respiration constitute the largest carbon cycle of the planet with an annual turnover in the order of 120 GT. Currently, neither ecosystem carbon uptake (through photosynthesis) nor ecosystem carbon release (through respiration) can be measured directly during the daytime. Instead, flux-tower measurements rely on nighttime respiration based on the assumption of zero carbon uptake which are then projected to daytime using an exponential relationship to soil temperature at shallow soil depth. As an alternative to this approach, R could possibly also be determined from combining daytime eddy covariance measurements of net ecosystem production (NEP) and spectral observations of gross primary production (GPP). In previous work, we have shown that multi-angular observations can be used to determine GPP from the absorbed photosynthetically active radiation (APAR) and spectrally obtained observations of light-use efficiency (?). The difference of NEP and GPP suggests that daytime respiration is greater and more dynamic than conventional estimates derived from nighttime flux values. Our findings also suggest that an accelerated ecosystem metabolism results in an exponential increase in respiration which eventually diminishes net ecosystem production. Respiration was also closely related to air and soil temperature. We conclude that tower-level spectral measurements provide considerable new insights into ecosystem fluxes as they allow independent yet complementary measurements of different aspects of the carbon and energy cycl

Use, value, and desire: ecosystem services under agricultural intensification in a changing landscape in West Kalimantan (Indonesia)

A fundamental challenge is to understand and navigate trade-offs between ecosystem services (ES) in dynamic landscapes and to account for interactions between local people and broad-scale drivers, such as agricultural intensification. Many analyses of ES trade-offs rely on static mapping and biophysical indicators while disregarding the multiple uses, values, and desires for ES (UVD-ES) that local people associate with their changing landscapes. Here, a participatory UVD-ES framework was applied to assess differences in the use, values, and desire of ES between three zones with different land-use intensities (with pre-frontier, frontier, and post-frontier landscapes) in West Kalimantan (Indonesia). The analysis revealed that (1) almost the full suite of ES uses has become destabilized as a result of agricultural intensification; (2) ES more closely associated with agricultural intensification were largely desired by local people yet they still valued a diversity of traditional ES, such as those derived from the provision of non-timber forest products, fish, and other ES associated with non-material aspects including those tied to traditional culture; (3) the mismatch in used ES versus valued ES increased with agricultural intensification due to a decrease in the flow of non-timber forest products, aquatic, regulating, and non-material (cultural) ES. Together, exploring UVD-ES patterns in a participatory way helped to reveal locally relevant social-ecological drivers of ES and a multidimensional perspective of ES trade-offs. Our UVD-ES framework offers an opportunity to foster participation as a way to reconnect global environmental research agendas with local and regional landscape contexts. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Research funding was provided by USAID’s Biodiversity Fund, UK Department for International Development (DfID), Spanish Ministry of Economy and Competitiveness under BC3 “Unit of excellence” (MIMECO, MDM-2017-0714) and IJCI-2016-28475, and a Vanier Canada Graduate Scholarship. We thank S. Tomscha, A. Ickowitz, and Y. Laumonier for their comments, L. Leonald for fieldwork contributions, several anonymous reviewers for their constructive reviews, and Jaqueline Loos for editorial suggestions. This work is part of CGIAR Research on Forests, Trees and Agroforestry. We are indebted to workshop participants from Kapuas Hulu