Peter L. Marshall

Imputing tree-lists from aerial attributes for complex stands of south-eastern British Columbia

The nearest neighbor, k-nearest neighbors, distance-weighted k-nearest neighbor, and class-weighted k-nearest neighbor imputation methods were compared for accuracy in estimating tree-lists (list of species and diameter for each tree) from aerial attributes for complex stands, with up to nine species and a wide range of sizes, in south-eastern British Columbia, Canada. For the four imputation methods, the most similar neighbor distance metric was used, and three neighbors were used for the k-nearest neighbor methods. Ground variables used to represent the tree-list included the number of trees per hectare by species, ranges of diameter by species, and basal area per hectare. Aerial variables included species composition, crown closure (%), elevation, biogeoclimatic ecosystem classification (BEC) zones, height, age, and site class. Sample data were divided, and the imputation methods were compared for accuracy using observed and estimated species composition, stand tables, basal area, and volume per hectare. Also, the imputed tree-list was used to predict yield using a stand level growth model, and this predicted yield was compared to the yield obtained using the actual tree-list. Of the four approaches used, the nearest neighbor was marginally better, but the methods that averaged the three nearest neighbors were somewhat better for the distribution of stems per hectare by diameter for the more sparse hardwood species. Of the three averaging methods, weighting by similarity of the species composition and the BEC zone provided better results. In using the estimated trees lists in a growth and yield model, the average volumes were reasonable at the beginning and end of the period for all methods. However, the volumes for a particular stand could be quite different than that obtained for an observed tree-list.

Allometric equations for integrating remote sensing imagery into forest monitoring programmes

Abstract Remote sensing is revolutionizing the way we study forests, and recent technological advances mean we are now able – for the first time – to identify and measure the crown dimensions of individual trees from airborne imagery. Yet to make full use of these data for quantifying forest carbon stocks and dynamics, a new generation of allometric tools which have tree height and crown size at their centre are needed. Here, we compile a global database of 108753 trees for which stem diameter, height and crown diameter have all been measured, including 2395 trees harvested to measure aboveground biomass. Using this database, we develop general allometric models for estimating both the diameter and aboveground biomass of trees from attributes which can be remotely sensed – specifically height and crown diameter. We show that tree height and crown diameter jointly quantify the aboveground biomass of individual trees and find that a single equation predicts stem diameter from these two variables across the worlds forests. These new allometric models provide an intuitive way of integrating remote sensing imagery into large‐scale forest monitoring programmes and will be of key importance for parameterizing the next generation of dynamic vegetation models.

Evaluating the impact of competition using relative growth rate in red pine (Pinus resinosa Ait.) stands

Abstract The development of red pine ( Pinus resinosa Ait.) stands originating in different spacings was analyzed using absolute growth rate (AGR) and relative growth rate (RGR) in diameter at breast height for several ages. The objectives were to determine whether RGR better reflected the effect of competition than AGR, and to interpret the relationship between RGR and tree size. While AGR was always positively related to tree size, RGR decreased with an increase in tree size before the onset of competition and when competition was not severe, and increased with tree size under severe competitive stress. This implied that small trees were more efficient than large trees at producing new biomass before the onset of competition. The effect of competition was to reduce the efficiency of small trees relative to large trees. It was concluded that RGR expressed the competitive status of stands better than AGR.

Testing site index-site-factor relationships for predicting Pinus contorta and Picea engelmannii × P. glauca productivity in central British Columbia, Canada

Measures of forest productivity for various site conditions are necessary for forest management planning, where timber production is the objective. This study was undertaken to test whether autecological productivity relationships developed for lodgepole pine (Pinus contorta) and interior spruce (Picea engelmannii×P. glauca) using the biogeoclimatic ecosystem classification system of British Columbia are useful as practical field-based procedures to predict site index. Independent data sets consisting of 111 plots for pine and 114 plots for spruce were collected for use in testing the bias and precision of the models. A regression on residuals (predicted minus test values) indicated that the lodgepole pine model was unbiased in estimating site index (p=0.08). However, there was a lack of precision, with a square root of the mean squared prediction error (root-MSPR) of 2.8 m. Only 56% of the test plots had differences from the predicted values of 2.0 m or less. Residual analysis showed that the interior spruce model was biased in estimating site index (p<0.01), generally predicting greater site index than the test values. The model also lacked precision, with a root-MSPR of 3.2 m. Only 44% of the test plots had differences from the predicted values of 2.0 m or less. Forest managers requiring a site-index prediction tool need to decide whether the degree of accuracy precision provided by these models is acceptable.

Height growth pattern of white spruce in relation to site quality

Abstract Using the ratio of height at 60 and 30 years of breast height age ( Z ratio) as a quantitative measure, height growth patterns of 82 white spruce ( Picea glauca (Moench) Voss) stands from the sub-boreal spruce (SBS) zone of British Columbia were examined together with site index, measures of ecological site quality, and site and plant associations. Despite their importance in predicting site index, soil moisture, aeration, and nutrient regimes were not the major determinants of white spruce height growth pattern. There were no significant differences in the Z ratio among strata formed according to biogeoclimatic units and site and plant associations. Although statistically significant, site index and site series only explained a very small proportion of the total variance of the Z ratio. Pattern-specific height curves, developed for each of six groups classified according to the Z ratio, resulted in a significant improvement in prediction precision over conventional height curves. Comparisons among conventional height curves from different regions indicated differences in curve shape, which may imply that climate has an impact on white spruce growth pattern.

Influence of HabItat VarIatIon, nest-sIte selectIon, and Parental beHaVIor on breedIng success of ruddy-caPPed nIgHtIngale tHrusHes (Catharus frantzii) In cHIaPas, MexIco

Abstract We examined the influence of ecological and behavioral factors on breeding success of Ruddy-capped Nightingale Thrushes (Catharus frantzii) in contiguous primary- and secondary-forest habitats during the 2000–2003 breeding seasons in the Central Highlands of Chiapas, Mexico. Breeding density was higher in primary, undisturbed forest than in secondary forest with less understory vegetation. Nest-site selection was related to nest-concealment attributes (visibility, canopy cover, and shrub density) at the nest-site and patch levels. Nest-site selection was stronger in secondary forest, which indicates that preferred nest-site attributes were more limited in that habitat. Overall success per breeding attempt varied annually from 20% to 35%, with a higher mean annual success in primary forest (42%) than in secondary forest (19%). Daily nest survival rates were higher in primary than in secondary forest and varied with nest cover, lateral visibility, and density of ground epiphytes. The number of parental visits to nests was higher in primary than in secondary forest and lower for successful than for failed nests during incubation but did not vary with habitat or fate during the nestling stage. Female nest-attentiveness was higher in primary forest than in secondary forest throughout the nesting attempt and was higher for successful nests during the nestling stage only. Thus, Ruddy-capped Nightingale Thrushes showed habitat-specific breeding performance, with the primary-forest habitats (cloud forest, riparian) supporting higher densities and nesting success than secondary, disturbed habitats.

Combining Multi-Date Airborne Laser Scanning and Digital Aerial Photogrammetric Data for Forest Growth and Yield Modelling

The increasing availability of highly detailed three-dimensional remotely-sensed data depicting forests, including airborne laser scanning (ALS) and digital aerial photogrammetric (DAP) approaches, provides a means for improving stand dynamics information. The availability of data from ALS and DAP has stimulated attempts to link these datasets with conventional forestry growth and yield models. In this study, we demonstrated an approach whereby two three-dimensional point cloud datasets (one from ALS and one from DAP), acquired over the same forest stands, at two points in time (circa 2008 and 2015), were used to derive forest inventory information. The area-based approach (ABA) was used to predict top height (H), basal area (BA), total volume (V), and stem density (N) for Time 1 and Time 2 (T1, T2). We assigned individual yield curves to 20 × 20 m grid cells for two scenarios. The first scenario used T1 estimates only (approach 1, single date), while the second scenario combined T1 and T2 estimates (approach 2, multi-date). Yield curves were matched by comparing the predicted cell-level attributes with a yield curve template database generated using an existing growth simulator. Results indicated that the yield curves using the multi-date data of approach 2 were matched with slightly higher accuracy; however, projections derived using approach 1 and 2 were not significantly different. The accuracy of curve matching was dependent on the ABA prediction error. The relative root mean squared error of curve matching in approach 2 for H, BA, V, and N, was 18.4, 11.5, 25.6, and 27.53% for observed (plot) data, and 13.2, 44.6, 50.4 and 112.3% for predicted data, respectively. The approach presented in this study provides additional detail on sub-stand level growth projections that enhances the information available to inform long-term, sustainable forest planning and management.

Evolution of Canada’s Boreal Forest Spatial Patterns as Seen from Space

Understanding the development of landscape patterns over broad spatial and temporal scales is a major contribution to ecological sciences and is a critical area of research for forested land management. Boreal forests represent an excellent case study for such research because these forests have undergone significant changes over recent decades. We analyzed the temporal trends of four widely-used landscape pattern indices for boreal forests of Canada: forest cover, largest forest patch index, forest edge density, and core (interior) forest cover. The indices were computed over landscape extents ranging from 5,000 ha (n = 18,185) to 50,000 ha (n = 1,662) and across nine major ecozones of Canada. We used 26 years of Landsat satellite imagery to derive annualized trends of the landscape pattern indices. The largest declines in forest cover, largest forest patch index, and core forest cover were observed in the Boreal Shield, Boreal Plain, and Boreal Cordillera ecozones. Forest edge density increased at all landscape extents for all ecozones. Rapidly changing landscapes, defined as the 90th percentile of forest cover change, were among the most forested initially and were characterized by four times greater decrease in largest forest patch index, three times greater increase in forest edge density, and four times greater decrease in core forest cover compared with all 50,000 ha landscapes. Moreover, approximately 18% of all 50,000 ha landscapes did not change due to a lack of disturbance. The pattern database results provide important context for forest management agencies committed to implementing ecosystem-based management strategies.

Population dynamics of the ruddy-capped nightingale thrush ( Catharus frantzii ) in Chiapas, Mexico: influences of density, productivity and survival

We used long-term population data for the ruddy-capped nightingale thrush (Catharus frantzii Cabanis), to examine the influence of forest conditions on annual productivity, survival and growth rate (λ) in a montane forest reserve of Chiapas, southern Mexico, from 1995 to 2003. Productivity was higher in primary, mature forest than in secondary, young forest. More adults were captured in primary forest (n= 132) than in secondary forest (n= 64). Adult survival (Φ = 0.79) and encounter rate (p = 0.36) did not vary across habitats. Males and females had similar survival between primary and secondary forests (Φ = 0.80 vs. 0.83, and 0.77 vs. 0.79, respectively). Juvenile survival (0 = 0.67) was only 12% lower than for adults. Overall, the population of C. frantzii appeared to be declining at 3% y -1 (λ = 0.97, SE = 0.09, 95% CI = 0.88-1.03). Productivity and survival correlated positively with λ across years within habitats, although survival was the primary, significant demographic parameter determining λ. Although habitat alteration may have reduced the carrying capacity and productivity in secondary forest, there was no apparent negative effect on population persistence in this habitat. Thus. secondary forests represent habitats that may facilitate the long-term persistence of C. frantzii populations.

Thinning Intensity and Pruning Impacts on Eucalyptus Plantations in Brazil

A thinning intensity experiment using the Eucalyptus grandis × E. urophylla hybrid was conducted at three sites in Bahia State, Brazil. The treatments were a combination of thinning intensities and pruning: 20%, 35%, and 50% basal area removed with no pruning and 35% basal area removed plus pruning (at 27 months). Plots were measured roughly annually from 27 to 165 months. Thinning was implemented on all sites at 58 months and again at 142 months at two of the sites. One of the sites was harvested at 87 months of age. A linear mixed model was applied separately to each installation to test for differences among treatments for mean increment of height, dominant height, quadratic mean diameter, and volume outside bark at the plot level. Additionally, differences in mean monthly increment of basal area and volume outside bark as a percentage of the value at the beginning of the increment period were examined. Increased thinning intensity increased all tree-level variables except dominant height. Pruning had no impact. Observed mortality on all plots was quite low. Thinning intensity response varied among sites and with time since thinning; however, the thinning intensity response was consistent through time among the installations.