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This study was conducted to improve estimation of concomitant variables for implementation of a stand density management diagram (SDMD) for ponderosa pine (Pinus ponderosa Laws.) in northern California and Oregon. In traditional SDMD, isolines for variables such as stand volume are presented in such a way that uncertainty with estimation is not available. We developed the new top height and stand volume equations, as well as aboveground biomass and percent canopy cover, for building isolines in the SDMD using high-quality data collected from well-managed even-aged stands. The data were selected from the USDA Forest Service’s Pacific Southwest Research Station database. A total of 829 observations (from 113 plots across 15 sites in Oregon and California) were used for model construction. In addition, covariance-variance structures of all of the estimated parameters were provided so that users can evaluate the uncertainty associated with predictions. The model validation results indicated that the predictions made from fixed-effects model forms performed better than the current volume equation of SDMD, as well as those from mixed-effects model forms using the population average effect. The proposed equations provide enhanced predictions and additional useful information about managed ponderosa pine stands, including their uncertainty.

This study was conducted to quantify growth responses of three major commercial conifer species (lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson), interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco), and spruce (white spruce (Picea glauca (Moench) Voss) and hybrid spruce (Picea engelmannii Parry ex. Engelm. × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carrière))) to various fertilizer blends in interior British Columbia, Canada. Over 25 years, growth-response data were repeatedly collected across 46 installations. The fertilizer blends were classified into three groups: nitrogen only; nitrogen and sulfur combined; and nitrogen, sulfur, and boron combined. The growth responses for stand volume, basal area, and top height were calculated through absolute and relative growth rate ratios relative to a controlled group. Fertilizer blend, inverse years since fertilization, site index, stand density at fertilization, and their interactions with the fertilizer blend were used as explanatory variables. The magnitude and significance of volume and basal area growth responses to fertilization differed by species, fertilizer-blend groups, and stand-condition variables (i.e., site index and stand density). In contrast, the response in top height growth did not differ among fertilization blends, with the exception of the nitrogen and sulfur fertilizer subgroup for lodgepole pine. The models developed in this study will be incorporated into the current growth and yield fertilization module (i.e., Table Interpolation Program for Stand Yields (TIPSY)), thereby supporting guidance of fertilization applications in interior forests in British Columbia.

This study developed a stand table projection system for interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco) in British Columbia, Canada. Simulation data, obtained by running PrognosisBC (with 150 year projections) using input derived from 140 permanent sample plots, were utilized for model construction. First, a whole-stand attributes (number of trees per ha, quadratic mean diameter, and arithmetic mean diameter) prediction model was constructed. Weibull parameters for the diameter distribution of the future stand were estimated from the predicted stand attributes using two parameter prediction methods (via seemingly unrelated regression and the cumulative distribution function) and one parameter recovery method. The future stand table was projected with the estimated Weibull parameters and compared with two stand diameter distribution adjustment algorithms, yielding a total of nine parameter estimation-diameter adjustment combinations. The outputs from the stand table projection model were evaluated with repeated measures data covering 20 years from 18 independent plots, as well as compared with the outcomes predicted by PrognosisBC for those plots. The diameter class adjustment procedure applying tree mortality prior to growth, combined with the cumulative distribution parameter prediction method, performed best among the nine combinations we compared. The stand table projection system yielded similar results to PrognosisBC on the evaluation data and is expected to be a useful tool for managing forests sustainably and effectively.

To investigate the long-term impacts of biomass harvesting on site productivity, we remeasured trees in the 1974 Forest Residues Utilization Research and Development Program at Coram Experimental Forest in western Montana. Three levels (high, medium, and low) of biomass removal intensity combined with broadcast burning treatment were assigned after clearcut in western larch (Larix occidentalis Nutt.) stands in 1974. From 1976 to 79, twenty five 2 + 0 bare root seedlings of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were consecutively planted in rows. In 2013, tree height, dbh (diameter at breast height), foliar N and C concentrations were measured. From cross-sectional sapwood area, growth efficiency (the ratio of 5-year-basal area increment to total leaf area) was calculated. Previous measurements from 1980, 1987, 1992, and 2001 were used for dbh and height growth analyses. At this site, none of the response variables were affected by biomass removal level. Only seedling planting year contributed significantly to affect tree mean height, dbh, volume. Growth efficiency was not affected by any treatment. These results indicate no apparent effect of biomass removal on site productivity for the range of biomass harvest levels performed.

Restoration of fire-prone forests is a common practice intended to increase resilience to wildfire, drought, and bark beetles. However, the long-term effects of restoration treatments on understory species, particularly non-native species, are poorly understood. We investigated long-term (23 years) effects of restoration treatments on native and non-native understory vegetation at the Lick Creek Demonstration-Research Forest, a ponderosa pine/Douglas-fir forest in western Montana, USA. Restoration treatments included shelterwood-with-reserves harvesting implemented alone or in combination with prescribed burning under either wet or dry conditions, plus a no-action control. Changes in understory vegetation cover and species richness (measured pre-treatment, 2, 3, 4, 5, 15, and 23 years post-treatment) were analyzed by growth form (forb, graminoid, and shrub) and origin (native vs. non-native) to test how understory dynamics respond to disturbance intensity. We also accounted for basal area of trees to consider how differential overstory conditions affected final treatment responses. Native vegetation cover responses followed predictable successional patterns: after initial declines by grasses and shrubs immediately after disturbance (43% and 40% reduction, respectively), all groups increased, peaked about five years after disturbance (74% greater than pre-treatment on average) and then generally declined to levels similar to pre-treatment. The magnitude of these changes was related to the disturbance intensity (i.e., cut-and-dry-burn > cut-and-wet-burn > cut-and-no-burn > control). For all native groups, variation in tree basal area at year 23 explained remaining differences among treatments. Non-native grasses and forbs followed similar overall trajectories, but cover of these groups increased immediately after treatment and rose more steeply to their peak five years post-treatment (12 times greater than pre-treatment on average), with differences persisting through year 23. While non-native cover responses in year 23 were negatively correlated with tree basal area, as seen for native taxa, overstory conditions alone did not fully account for differences between burned and unburned treatments. This suggests that effects of burning unrelated to tree regeneration favored non-natives. Nonetheless, in the last sampling year treatment-induced increases in non-native cover were modest, suggesting that after 23 years understory responses in this forest type were fairly resilient to restoration treatments. However, because forest structure and composition were reverting to pre-treatment conditions by year 23, retreatment may be necessary at intervals of

We investigated the long-term impact of biomass utilization on shrub recovery, species composition, and biodiversity 38 years after harvesting at Coram Experimental Forest in northwestern Montana. Three levels of biomass removal intensity (high, medium, and low) treatments combined with prescribed burning treatment were nested within three regeneration harvest treatments (shelterwood, group selection, and clearcut). Four shrub biomass surveys (pre-treatment, 2, 10, and 38 years after treatment) were conducted. Shrub biomass for all treatment units 38 years after treatment exceeded the pre-treatment level, and biomass utilization intensity did not affect shrub recovery (ratio of dry biomass at time t to pre-treatment biomass). Species composition changed immediately after harvesting (2 years); however, the species composition of treated units did not differ from the untreated control 38 years after harvesting. Biodiversity indices (Shannon’s and Pielou’s indices) also decreased immediately following harvesting, but recovered 10 years after harvesting. The responses of diversity indices over time differed among biomass utilization levels with the high-utilization level and unburned treatment producing the most even and diverse species assemblages 38 years after harvesting. Our results indicate the shrub community is quite resilient to biomass harvesting in this forest type.

Soil changes associated with forest harvesting, differing utilization levels, and post-harvest prescribed burning were determined using an empirical study to investigate the long-term impacts on soil physical and chemical properties at Coram Experimental Forest in northwestern Montana. In 1974, two replications of three regeneration cuttings (shelterwood, group selection, and clearcut) were installed. In addition, four residue management regimes (high utilization with no burning, medium with no burning, medium with broadcast burning, and low with broadcast burning) were implemented (~74, 63, 65, and 54% wood removal, respectively). Thirty-eight years after harvesting, changes were evaluated in mineral soil and forest floor physical and chemical properties (organic matter [OM], C, N, Ca, K, and Mg pools, soil bulk density, and pH) and in coarse woody debris levels. There were no differences in soil pH and bulk density across all regeneration cuttings and residue treatments, probably due to the minimal soil effects associated with the forest harvesting operations that were used (hand felling and cable yarding). Comparisons between harvest and burning and the control indicate no statistical differences in OM, C, and N contents. Minor differences in extractable cation pools were noted in several comparisons among the treatments; these may be attributed to litter inputs from the differing vegetation compositions of overstory and shrub layers rather than nutrient changes within the mineral soil itself. At this moist-cool forest, intensive biomass utilization, with or without broadcast burning, had few long-term impacts on soil properties of soil C, OM, and nutrients.

Foresters often require an estimation of bark thickness from a reference height (typically breast height) to accurately estimate the bark or wood volume of a tree. Various models for estimating the bark thickness of interior Douglas-fir ( Pseudotsuga menziesii var. glauca ) from measured dbh (diameter at breast height) were evaluated. Sample trees were from northern Rocky Mountain mixed conifer stands that had been subjected to four levels of experimental woody biomass harvesting. Among simple linear, nonlinear, and segmented linear mixed effects models, the segmented linear model performed best. A join point (where the linear equations are linked) for the segmentation was statistically detected at approximately 19.0 cm dbh. The join point seems to indicate the size at which juvenile Douglas-fir trees boost the production of bark tissue, perhaps as those trees express dominance over competing understory vegetation. Woody biomass utilization level had no impact on bark thickness, indicating that the bark:dbh relationship does not depend on biomass utilization intensity. The study results enable accurate bark thickness estimation for interior Douglas-fir in this region, and suggest several silvicultural applications for juvenile Douglas-fir stand management.

To determine the major factor of change in provisioning rates to Varied Tit Parus varius nestlings in relation to increasing elevation, we used video recordings to investigate the number of parent visits and the size of prey carried by parents to their nestlings during the breeding process. Video cameras were installed at the entrances of 35 nests (17 at 300 m a.s.l., 7 at 900 m a.s.l., and 11 at 1,400 m a.s.l.). We also measured air temperature during the breeding season at three study sites. The provisioning rates per nestling showed a significantly negative relationship with prey size provisioned, except during the early nestling stage (days 1 to 4), when small prey were selectively provisioned by the parents. Prey at the higher elevation during days 5 to 15, also, were significantly smaller than at the lower elevation. The mean temperature at each breeding site during the breeding period did not differ significantly due to the delayed onset of breeding at higher elevation. Therefore, we concl...

This study was conducted to address the relationship between socio-economic variables and invasive plant species occurrence in parks and natural areas in two cities of Metro Vancouver, British Columbia, Canada. Invasive plants inventory data in parks and natural areas were acquired from the cities of Surrey (surveyed in 2014–2016) and Coquitlam (surveyed in 2013–2015). Four socio-economic variables were extracted from the 2011 Canada Census, the 2016 National Household Survey, and the 2016 Survey of Household Spending: median household income, population density, single-detached house density, and household expenditure on gardening. Ten topographic/park variables (e.g., elevation, path and trail density) were obtained for each invasive plant observation point. Using an inhomogeneous Poisson point process modelling approach, the relationships between these socio-economic and topographic/park variables and the occurrences of three priority invasive plants—English ivy, knotweed species, and yellow archangel—were evaluated. Population density had positive associations with knotweed species occurrence in both cities as well as English ivy occurrence in Surrey. In Coquitlam, single-detached house density and median household income were identified as significant socio-economic variables for English ivy and yellow archangel, respectively. Results indicate that relationships between socio-economic variables and species occurrence vary with site and target species. This case study demonstrates a possible approach for linking common invasive plant field survey data and socio-economic data to establish relationships. The results can help land managers to establish cost-effective management strategies by providing valuable information needed for monitoring and pro-active management of invasive plants.

With increasing public demand for more intensive biomass utilization from forests, the concerns over adverse impacts on productivity by nutrient depletion are increasing. We remeasured the 1974 site of the Forest Residues Utilization Research and Development in northwestern Montana to investigate long-term impacts of intensive biomass utilization on aspects of site productivity. The historical experiment was implemented in a western larch ( Larix occidentalis Nutt.) forest at three biomass utilization levels (high, medium, and low) combined with prescribed post-harvest burning treatments (burned and unburned) under three regeneration cuttings (clearcut, group selection, and shelterwood). The experiment has two replicates and was designed as a split-plot design with an imbalanced manner. Regenerated tree height and diameter at breast height, shrub root collar diameter, and soil properties (C, N, and total organic matter) of the forest floor and mineral soil layers were measured. Regenerated tree, shrub, and total aboveground biomass and total C, N, and organic matter contents of the soil layers were calculated. Results indicated that total organic matter pools at the ecosystem level were similar across regeneration cutting treatments, and there were no differences among the utilization treatments for either aboveground biomass production or soil properties 38 years after harvest. Minor differences observed among treatments seemed to originate from differences in regeneration dynamics and responses to burning treatment. Our results indicate that site productivity in this forest type was unaffected by these biomass utilization levels.

A spatial analysis was conducted on the characteristics of seedling recruitment and one-year mortality of two temperate deciduous tree species: Quercus serrata Thunb. ex Murray (QUSE) and Carpinus laxiflora (Siebold & Zucc.) Blume (CALA). A systematic grid of 64 seedling plots was established within a typhoon-induced treefall gap in a rare old-growth deciduous stand at Gwangneung Experimental Forest, South Korea. Inverse model, Ripley’s K function, and semivariogram tools were introduced to examine spatial relationships among seedling recruitment, one-year seedling mortality, and trees. Overall QUSE germinant density more than tripled that of CALA. Results suggest that dispersal patterns differ between the two species: for QUSE, 2Dt model yielded the best fit whereas the lognormal model was best fitted to CALA. Those differences may reflect different regeneration strategies between the two species. One-year mortality rates were similar for QUSE (76.15%) and CALA (72.25%). Mortality for both species exhibited substantial variance that was indicated as autocorrelation by the semivariogram, suggesting that mortality was not random for either species. Tree spatial patterns were also shown to be autocorrelated. Together, the observed spatial patterns in germination and first-year mortality indicate that the single treefall gap is among the factors that maintain the community structure associated with this forest type.

Stand structure and spatial distribution of Picea jezoensis (Siebold et Zucc.) Carriere on Mt. Gyebang, Korea was investigated to provide information on the structural characteristics and the maintenance of P. jezoensis population in northern temperate mixed coniferous forests. Height and diameter at breast height (DBH) distribution, age, growth, and spatial distribution patterns of P. jezoensis were examined in thirty nine 100-400 m2 quadrats or circular plots. The overall stand structure attributes in the study sites are stem density of 709 trees ha−1, a mean DBH of 12.8 cm, and a mean height of 5.6 m, with reverse J shapes of DBH and height distributions. The stem density of P. jezoensis population was 81 trees ha−1, a mean DBH of 20.7 cm, and a mean height of 9.1 m, showing bimodal-like shapes in age and DBH distributions. Several growth release periods implied that P. jezoensis stands experienced small disturbances. The radius of patches of similar-sized P. jezoensis in the variogram was equivalent with the height of the tallest trees, indicating that patches were established following the fall of trees in the upper canopy layer. Small windthrows in this region contributed to the maintenance of the P. jezoensis stand by releasing sapling growth and providing nursing logs and space for seedlings.

Stand structure and spatial associations of the dominant tree species in Quercus mongolica stands were investigated to understand interspecific relationships and the persistent dominance of Q. mongolica. We examined the species composition, DBH (diameter at breast height) distribution, and spatial distribution of trees (≥ 2.5 cm DBH) in two permanent 100 m x 100 m plots in Q. mongolica-dominant stands on the western part of Mt. Jiri. Ripley's K-function was used to characterize the spatial patterns and associations of dominant tree species. Q. mongolica showed a continuous and reverse-J shaped DBH distribution with clumped spatial distribution in both study sites. Q. mongolica and Abies koreana exhibited a negative association implying potential interspecific competition. The positive spatial association between Q. mongolica and Alnus hirsuta var. sibirica and Fraxinus sieboldiana were affected by site characteristics: limited habitat conditions with a large proportion of rock surface. Our results suggest that interactions among species were complex and ranged from positive to negative. Differences in stand and site characteristics and regeneration mechanisms among the species play an important role in regulating their spatial distribution patterns, while competition between individuals also contributes to spatial patterning of these communities. The high density and the early developmental stage of spatial distribution and structural characteristics of Q. mongolica and the relatively low importance values of other species in the stands imply that Q. mongolica will remain dominant in the study sites in the near future.

Stand growth and developmental processes were investigated in Pinus densiflora Siebold et Zucc. stands of different ages in the central eastern region of Korea. Stands were inventoried and five trees per stand were sampled for stem analysis, age estimation, and growth analysis. More than 80% of sampled trees in a stand were established within 3-5 years, and most stands had a single cohort structure. The initial growth of pine seedlings was slow, but the height growth accelerated beyond 2-3 m height, 5-10 years after establishment. Linear growth was maintained until 10-12 m height, at which suppressed trees fell behind and might die out. The young stand was composed of pure pines, while few pine seedlings and saplings were found in the understory of older stands. The peak of diameter growth rate occurred around 5-15 years after tree establishment, implying that competition begins during that period. The pine stand development follows four stages: (1) the young stage when the growth rate increases and peaks; (2) the height competition stage when trees focus on height growth for light while maintaining a narrow DBH and height distribution; (3) the differentiation stage when suppressed trees die out, and the DBH distribution becomes wider; and (4) the mature stage when stands have a multi-canopy structure with a wide DBH and height distribution, while the understory is dominated by other tree species. The changes in growth rates and stand structure through forest development would be implemented to predict alterations of above-ground carbon sequestration rates.