Species Basal Area Research Articles

Influence of Edaphic and Phytosociological Attributes on Semideciduous Remnants Vegetation

Atlantic forest biome in Brazil has high biodiversity that is threated due to fragmentation and its remnants retain important residual flora that should be preserved. Studies of environmental conditions that influence species occurrence in those areas are very important to preserve them. This study characterized two remnants vegetation in the Biological Reserve, Pindorama-SP, Brazil, classified as seasonal semideciduous forest sampled in 65 plots of 400 m2, using soil attributes and vegetation data. Soil attributes altitude, basal area, height and number of trees with diameter at breast height (DBH) ≥ 5 cm were evaluated in the plots and non-arboreous species infestation was evaluated in a randomly drawn quadrant of 100 m2. The hierarchical clustering, based on soil attributes, separated plots in two major groups and five subgroups of similarity used to characterize the vegetation and the species diversity, by the Shannon Index (H') and the Pielou Equitability Coefficient (J). Soil attributes influenced endemic trees and non-arborous vegetation showing that preservation of native vegetation should consider these species relationships. Plots with higher clay percentage and higher fertility had higher infestation of non-arboreous plants as bamboo, lianas and different grasses species and had lower species diversity, basal area and height of tree species.

Predicting site productivity of the timber tree Pterocarpus angolensis

Pterocarpus angolensis is an important timber tree of the miombo woodlands of sub-Saharan Africa. The species only grows in natural mixed forests and little is known about is productivity potential. This study aimed at investigating productivity of P. angolensis on a local scale in Namibia and Angola and on a regional scale in southern Africa. The most commonly accepted productivity indicator is stem diameter increment and this was used to study productivity at a regional scale. Indicators of productivity used at the local scale were basal area, proportional basal area and site form, which were derived from 217 forest inventory plots in Namibia and Angola. The productivity measures were modelled with abiotic site factors; biotic factors were added for the local scale. Results indicated that the most consistent site factors at local and regional scale were not related to climate but to forest cover, with the species having a competitive advantage in more open forests. Mean annual diameter increment in the open forests of Namibia was 0.51 cm after 50 years. Boosted regression tree models at a local scale showed that species presence can be modelled more successfully than species basal area, proportional basal area (correlation of 0.72 vs 0.56 and 0.45, respectively) and site form. The sites with the highest productivity of P. angolensis at the local scale had a temperature seasonality below 34.5 °C, a slope of less than 1.5°, tree cover less than 20% and stand basal area higher than 9 m2 ha−1. The results can assist in establishing a site-dependent growth model for the species and direct forest and fire management towards the most productive areas.

Modeling and predicting solar radiation transmittance in mixed forests at a within-stand scale from tree species basal area

Light under tree canopy cover is essential for the study and understanding of plant diversity, regeneration, plant growth and many other forest ecosystem processes; however, quantifying light is difficult and requires specialized equipment. That is why proxies or models predicting light availability can help scientists to obtain estimates of transmittance and forest managers to better assess and adjust silvicultural practices at a reasonable cost. The main objective of our research was to develop a model to predict local solar radiation transmittance from species basal area in mono-specific and mixed stands of sessile oak (Quercus petraea) and Scots pine (Pinus sylvestris). Models based on the Beer-Lambert law were fitted and compared using 163 measures of solar radiation transmittance obtained from hemispherical photographs and light sensors. In mono-specific stands, local transmittance was predicted by local basal area considered on a radius equaling approximately tree height. In mixed stands, the same model broken down into its mono-specific components (local basal area of each species multiplied by their own extinction coefficients) predicted transmittance well. The extinction coefficients we obtained were very close to those previously established for these species and did not differ between mono-specific and mixed stands. Our model explained 77% of the variation in transmittance when random effects were included and 64% of the variance without taking into account these random effects. The predictive value of the model was good with high accuracy (mean signed deviation not significantly different from zero) and a fairly high precision (relative mean absolute error=20%). The fact that tree canopy transmittance in mixed stands can be predicted by extinction coefficients obtained from mono-specific stands indicates that modifications in crown structure and leaf distribution are only slight, or even non-existent, when the two species grow in a mixture.

Functional antagonism between nitrogen-fixing leguminous trees and calcicole-drought-tolerant trees in the Cerrado

The Cerrado is the largest savanna of South America and its physiognomy varies from savanna to woodlands. There are two main types of woodlands in the Cerrado: dystrophic woodlands, dominated by N-fixing leguminous trees (LEG), and mesotrophic woodlands dominated by non-leguminous drought-tolerant trees (DRY), which are calcicoles and sensitive to Al3+. The working hypothesis is that LEG and DRY are functional antagonists in terms of the acidification/alkalization processes involving different forms of inorganic nitrogen and pH, Ca2+ and Al3+ in soil. Tree species basal area and soil properties were used to investigate the antagonism between LEG and DRY using generalized linear models. The results suggest that LEG and DRY are antagonists. The LEG were positively associated with Al3+, NO3- and NH4+ content and negatively related to increasing Ca2+ content, whereas the DRY were negatively associated with Al3+, NO3- and NH4+ and positively associated with increasing Ca2+ content. The upper soil layer in plots dominated by LEG species became more acidic and the upper soil layer in plots dominated by DRY species became more alkaline. The results suggest that LEG and DRY are functional antagonists and their preferences for NH4+ or NO3- might influence the way the Cerrado woodland changes.

Assessing Soil-Related Black Spruce and White Spruce Plantation Productivity

This article focuses on modelling and mapping the productivity of black (Picea mariana) and white spruce (Picea glauca) plantations across the Black Brook forest management area in northwestern New Brunswick, Canada, encompassing about 200,000 ha. This effort involved establishing 3500 50 m2 survey plots, each informing about: plantation age (15 to 43 years), planted species type, stem count, tree height, basal area, and wood volume. All of this was supplemented with location-specific productivity predictors, i.e., xy location and specifications pertaining to soil type, soil drainage (established through digital elevation modelling by way of the depth-to-water index DTW), and years since thinning (pre-commercial and commercial), and. The DTW index, as it emulates the elevation rise away from open water features such as streams, rivers and lakes, allowed the re-mapping of existing soil borders by topographic position and drainage association. Non-linear regression analysis revealed that plantation height, basal area and volume all increased with plantation age, as to be expected. Pre-commercial thinning in plantations <30 years old had a positive while the more recent commercial thinning still had the negative effect on standing wood volume and mean annual volume increment (MAI). White spruce MAI generally exceeded black spruce (MAI) by a factor of 1.25. Poor and excessive soil drainage reduced MAI. Best growth performances occurred on plantations established on well-drained calcareous soils. The best-fitted results so obtained allowed for generating black and white spruce MAI maps across the forest management area by ridge-to-valley soil and DTW location at 10 m resolution. These maps were subsequently used for site-by-site silvicultural evaluation and ranking purposes.

Influence of fire disturbance and biophysical heterogeneity on pre‐settlement ponderosa pine and mixed conifer forests

AbstractFire frequency is assumed to have exerted a strong influence on historical forest communities in the inland Pacific Northwest. This study reconstructs forest structure and composition in the year 1890 and fire frequency from 1760 to 1890 at 10 sites spanning a broad productivity gradient in the southern Blue Mountains of eastern Oregon. We tested for the relative influence of fire frequency, climate, soils, and topography by fitting variables to ordinations of forest structural and compositional configurations. We also built formal statistical models using non‐parametric permutational multivariate analysis of variance. Because fire disturbance and biophysical influences on forest structure and composition may vary depending on the scale at which relationships are examined, we tested the influence of variables at the scale of 4‐ to 12‐ha sites and at the scale of three equal‐sized areas within each site. The proportion of fire‐intolerant species basal area reconstructed within sites in the year 1890 ranged from 0% to 43%. The proportion of fire‐intolerant species basal area reconstructed within equal‐sized areas within sites ranged from 0% to 75%. Despite significant differences in historical species composition between and within sites, fire frequencies were relatively similar. Mean fire return intervals (MFRIs) calculated for sites ranged from 10.6 to 21.2 yr. MFRIs calculated for equal‐sized areas within sites ranged from 10.6 to 28.8 yr. Fitting fire frequency and biophysical variables to ordinations and model building with perMANOVA showed that topographic position index and vapor pressure deficit had stronger influences on site‐scale forest structure and composition than fire frequency metrics. Available soil water was the most important influence on forest structure and composition within equal‐sized areas within sites. Relatively frequent fire across a broad range of forest types in the southern Blues appears to have been a relatively uniform influence on forest dynamics modulated by fine‐scale biophysical heterogeneity. If return to historical conditions is a goal of management, treatments to reduce fuel and restore frequent fire are appropriate across a broad productivity gradient in the southern Blues.

Charcoal production through selective logging leads to degradation of dry woodlands: a case study from Mutomo District, Kenya

Provision of woodfuel is an important ecosystem service of dry forests and woodlands. However, charcoal production through selective logging of preferred hardwood species has the potential to alter the physiognomic composition of the residual or re-growth woodlands and may lead to their deterioration and degradation. This study, conducted through forest inventory in Mutomo District in Kenya, assessed the impact of charcoal production on unprotected dry woodlands in terms of tree density, targeted species basal area, species richness, evenness and Shannon diversity. The parameters of the disturbed woodlands were evaluated for significant differences with those of the neighbouring protected Tsavo East National Park, which served as a reference for an ecologically undisturbed ecosystem. By evaluating a consequence of tree harvesting for charcoal production, this study confirmed the overall significant differences between the protected and unprotected woodlands in all the tested parameters. To confirm if the differences in the land-covers of the woodlands had any influence on their degradation, all mentioned parameters were compared between the four differentiated classes and their respective control plots in the protected areas. At the “land-cover level”, the statistically significant difference in the basal area of tree species preferred for charcoal production between the protected and unprotected open trees confirms that the class with a high density of large mature trees is the prime target of charcoal producers. In addition, there seems to be a general trend of lower values of tree species richness, evenness and Shannon diversity for the unprotected woodlands subjected to charcoal production. On the other hand, the disturbed woodlands display the potential to recover through their comparably high saplings density. The findings make an important contribution to the discourse on the impact of charcoal production in dry woodlands, a topic that is highly controversial among researchers.

Using codispersion analysis to quantify and understand spatial patterns in species-environment relationships.

The analysis of spatial patterns in species-environment relationships can provide new insights into the niche requirements and potential co-occurrence of species, but species abundance and environmental data are routinely collected at different spatial scales. Here, we investigate the use of codispersion analysis to measure and assess the scale, directionality and significance of complex relationships between plants and their environment in large forest plots. We applied codispersion analysis to both simulated and field data on spatially located tree species basal area and environmental variables. The significance of the observed bivariate spatial associations between the basal area of key species and underlying environmental variables was tested using three null models. Codispersion analysis reliably detected directionality (anisotropy) in bivariate species-environment relationships and identified relevant scales of effects. Null model-based significance tests applied to codispersion analyses of forest plot data enabled us to infer the extent to which environmental conditions, tree sizes and/or tree spatial positions underpinned the observed basal area-environment relationships, or whether relationships were a result of other unmeasured factors. Codispersion analysis, combined with appropriate null models, can be used to infer hypothesized ecological processes from spatial patterns, allowing us to start disentangling the possible drivers of plant species-environment relationships.

Tree Species Diversity and Dominance in Ketumbeine Forest Reserve, Tanzania

Ketumbeine Forest Reserve, an isolated forest on a small protruding hill located in the dry area of northern Tanzania has unknown tree species diversity and dominance. Using a systematic grid of 390 m by 780 m in 77 randomly selected plots of 0.071 ha, located along nine transects, botanical names of tree species, diameter above breast height (dbh), regenerants and key shrub species were recorded in order to determine species diversity index, dominance index, number of shrubs and regenerants, forest stocking and tree basal area, respectively. A total of 26 tree species and 17 shrubs were recorded. The tree species with the highest importance values were Cassipourea malosana (37%), Nuxia congesta (20%), Olea europaea (10%), and Juniperus procera (10%), among others. The Simpson index value ranged between 0.0 and 0.0925 with Cassipourea malosana and Nuxia congesta having the highest index with 0.0925 and 0.0278, respectively. The Shannon index of tree species diversity ranged between 0.0177 and 0.3620 with Cassipourea malosana having the highest index. Forest stocking was 435 stems per ha with a mean species basal area of 30.49 m2 per hectare with Nuxia congesta occupying the highest (259.443 m2 per ha) area and Flacoutia indica the lowest (0.0044 m2 per ha), respectively. The estimated wood volume per hectare was 395.07 m3 . The mean total density of regenerants was 97 ± 30 stems per hectare with Urtica masaica (90), Lippia javonica (30), Rhus vulgaris (20), being the dominant shrubs. In conclusion, the forest has high tree species diversity which is a good stand characteristic of a natural forest. The forest basal area is quite good for the montane forest which normally ranges between 20-60 m2 / ha. However, if unchecked, human disturbance may alter the tree species composition. This survey established a baseline for future monitoring of the forest performance.

Characteristics of the Psidium cattleianum invasion of secondary rainforests

AbstractStrawberry guava (Psidium cattleianum) is a shade‐tolerant shrub or small tree invader in tropical and subtropical regions and is considered among the world's top 100 worst invasive species. Studies from affected regions report deleterious effects of strawberry guava invasion on native vegetation. Here we examine the life history demographics and environmental determinants of strawberry guava invasions to inform effective weed management in affected rainforest regions. We surveyed the vegetation of 8 mature rainforest and 33 successional sites at various stages of regeneration in the Australian Wet Tropics and found that strawberry guava invasion was largely restricted to successional forests. Strawberry guava exhibited high stem and seedling densities, represented approximately 8% of all individual stems recorded and 20% of all seedlings recorded. The species also had the highest basal area among all the non‐native woody species measured. We compared environmental and community level effects between strawberry guava‐invaded and non‐invaded sites, and modelled how the species basal area and recruitment patterns respond to these effects. Invaded sites differed from non‐invaded sites in several environmental features such as aspect, distance from intact forest blocks, as well as supported higher grass and herb stem densities. Our analysis showed that invasion is currently ongoing in secondary forests, and also that strawberry guava is able to establish and persist under closed canopies. If left unchecked, strawberry guava invasion will have deleterious consequences for native regenerating forest in the Australian Wet Tropics.

A stand-level tool for predicting the natural regeneration density of black spruce and jack pine following fire and salvage

A tool was developed to allow managers and foresters to quickly assess reforestation needs following forest fire and salvage logging at the stand level in both pure and mixed black spruce and jack pine stands. This on-site operational assessment tool was created using a forest regeneration model that simulates the natural regeneration densities of black spruce and jack pine following fire and salvage. Tree species basal areas used for simulations represent the natural range expected in the field. Additional parameters include the abscission schedule of the species, the percentage of optimal (exposed mineral soil or humus) post-fire seedbeds, and the timing of the salvage operation. The tool also allows for rapid planning of both salvage operations and planting. It has important advantages over conventional seedling surveys in that it can be employed immediately following fire, can guide management decisions about the planning of road construction and the harvest sequence, and takes into account the entire establishment phase. Using the tool to adjust the harvesting schedule to minimize replanting, the likely final cost of reforestation can be estimated for an entire burn. The tool shows that a higher percentage of optimal seedbeds are necessary following salvage: (1) for black spruce to regenerate adequately compared to jack pine (i.e., planting of black spruce will almost always be necessary); (2) as basal area of the species of interest decreases; and, (3) to adequately regenerate burned intact and salvaged stands in late-season fires compared with those from early-season fires.

Termitaria as preferred browsing patches for black rhinoceros (Diceros bicornis) in Chipinge Safari Area, Zimbabwe

Abstract:This study tested the hypothesis that the black rhinoceros browses more on termitaria than off termitaria vegetation due to elevated soil and foliar nutrient levels on termitaria. We investigated the role of termitaria in providing nutrient-rich forage for the black rhinoceros, by comparing the preference (selection ratio) for vegetation occurring on and off termitaria, and then testing its relationship with foliar nutrient concentrations. Soil nutrients, bite intensity, tree species diversity, vegetation density, canopy cover and basal area were also surveyed on and off termitaria. We sampled 25 termite mounds together with their corresponding control plots in Chipinge Safari Area, Zimbabwe. Soil and foliar N, P, K, Ca and Na concentrations were greater on termitaria than off termitaria, with approximately twice the concentration of these nutrients. Browse preference followed the between-site differences in soil and foliar nutrient concentrations, with higher selection ratios and bite intensities for vegetation on termitaria than off termitaria. Diospyros quiloensis was the most preferred browse species whilst Combretum imberbe, Kigelia africana and Strychnos innocua were the least. In conclusion, the black rhino preferred vegetation on termitaria to that in the surrounding matrix, and utilization of vegetation can be influenced by the soil substrate on which tree species grow.

Tree Response to Experimental Watershed Acidification

Forest ecosystems in the Eastern USA are threatened by acid deposition rates that have increased dramatically since industrialization. We utilized two watersheds at the Fernow Experimental Forest in West Virginia to examine long-term effects of acidification on ecological processes. One watershed has been treated with ammonium sulfate (approximately twice the ambi- ent deposition rate) since 1989 to simulate elevated acidic deposition, while the other served as a control. Prior to treatment, both watersheds were similar in age and species composition. Ten dominant overstory Prunus serotina and Liriodendron tulipifera trees were selected and cored from each watershed to measure bolewood concentrations of essential elements through time. In addition, changes intree species basal area were analyzed utilizing 50 long-term growth plots. Results of this experiment show lower calcium and magnesium concentration and increased acidic cation concentration for both species in the treated watershed, indicating a negative treatment effect. Growth response, measured through relative growth rates of cored trees and changes in basal area from growth plots, was not as conclusive and appeared to differ by species. The resulting differ- ence in species response indicates that acidification sensitivity is something that land managers should con- sider when managing forests affected by acidification.

Floral Composition and Diversity Pattern in Open and Closed Dry Deciduous Forest

Forests are the important source of subsistence, employment, revenue earning and raw material to various industrial uses. Above all they are most important component of life support system on the earth. The present study was conducted to analyze the impact of biotic disturbance on composition and diversity of dry deciduous forests of Barnawapara wild life sanctuary, Chhattisgarh, India. For this, two sites viz. open canopy forest and closed canopy forest were selected. Floristic analysis of tree vegetation was done and density, Important Value Index, diversity index etc. were determined for both the sites. Regeneration status of tree species was analysed by developing population structures. Species number was high in closed canopy forest as compared to open canopy forest. Tree density (1520 trees ha−1) and basal area (50.35 m2ha−1) were higher in closed canopy forest than in open canopy forest (650 trees ha−1 density and 48.29 m2ha−1 basal area). In sapling layer species number (14), density (590 saplings ha−1) and basal area (2.46 m2ha−1) were higher in closed canopy forest as compared to open canopy forest. Seedling layer also follow the similar trend. Generally, Shannon index, species richness and equitability were higher in closed canopy forest than open canopy forest. Thus, it can be concluded that biotic disturbance adversely affect the forest composition and diversity.

Tree Species Diversity and Dominance in Gelai Forest Reserve, Tanzania

Tree species diversity and dominance of Gelai Forest Reserve, an isolated montane forest located in an arid area of Northern Tanzania remains unknown. A systematic grid of 390 m x 780 m between 100 plots of 0.02 ha, along nine transects was used during the forest survey. The tree species present, location, diameter above breast height (dbh) and botanical names were recorded including regenerants of tree species and key shrub species. These parameters were then used to determine species diversity index, dominance index, number of tree species regenerants, number of stems per ha and tree basal area per ha. A total of 39 tree species were recorded. The tree species with the highest importance values were Nuxia conjesta (70.7), Olea europaea (44.4) and Crotalaria stulhmanii (40.4). The Simpson index value ranged between 0.0 and 0.034; with Crotalaria stulhmanii having the highest (0.034) index. The tree species diversity index ranged between 0.016 and 0.313. Forest stocking was 377 stems per ha while species basal area ranged between 0.098 m2 and 439 m2 per ha, with Nuxia congesta occupying the highest (439.07 m2 per ha) area and Acacia rovumae the lowest (0.098 m2 per ha), respectively. Seventy nine regenerants were recorded on 9% of the plots. Shrubs, herbs and grasses were found on 55% of the plots mainly without trees dominated by Vernonia galamensis, Leonatis leonorus, Ocimum suave and Solonum incanum. In conclusion, the forest has high tree species diversity which is a good stand characteristic of a natural forest. This survey established a baseline for future monitoring of the forest performance after mitigation of human activities.

Characterizing forest species composition using multiple remote sensing data sources and inventory approaches

The purpose of the study was to evaluate tree species composition estimated using combinations of different remotely sensed data with different inventory approaches for a forested area in Norway. Basal area species composition was estimated as both species proportions and main species by using data from airborne laser scanning (ALS) and airborne (multispectral and hyperspectral) imagery as auxiliary information in combination with three different inventory approaches: individual tree crown (ITC) approach; semi-individual tree crown (SITC) approach; and area-based approach (ABA). The main tree species classification obtained an overall accuracy higher than 86% for all ABA alternatives and for the two other inventory approaches (ITC and SITC) when combining ALS and hyperspectral imagery. The correlation between estimated species proportions and species proportions measured in the field was higher for coniferous species than for deciduous species and increased with the spectral resolution used. Especially, the ITC approach provided more accurate information regarding the proportion of deciduous species that occurred only in small proportions in the study area. Furthermore, the species proportion estimates of 83% of the plots deviated from field measured species proportions by two-tenths or less. Thus, species composition could be accurately estimated using the different approaches and the highest levels of accuracy were attained when ALS was used in combination with hyperspectral imagery. The accuracies obtained using the ABA in combination with only ALS data were encouraging for implementation in operational forest inventories.

Tree species diversity and abundance as indicators of understory diversity in French mountain forests: Variations of the relationship in geographical and ecological space

Trees are one of the main components of forest ecosystems; they modify resource levels (light, nutrients, water) that affect understory vegetation composition and diversity. Tree species diversity is used as a biodiversity indicator in various European and French monitoring schemes for sustainable forest management. Moreover, tree species basal area has been found to better indicate floristic biodiversity than tree species richness or diversity. Herein we empirically check this finding by analyzing data from mountain spruce-fir forests in France with Bayesian statistical models. We insist on the magnitude of the relationship and its variation in geographical and ecological space. Our results indicate that both tree species abundance (based on cover or basal area) and tree species richness and dominance are good indicators of some parts of understory vascular plant species richness. The effect of dendrometric indicators on floristic biodiversity varied among ecological groups and along ecological gradients such as aspect, soil acidity, region and altitude. As a result, plots with north-facing and south-facing slopes exhibited opposite relationships of species richness with tree species abundance, and so did plots located on acidic and basic sites. We discuss these results in light of other empirical results relating positive interactions between species and abiotic stress. Our study supports evaluating biodiversity indicators to determine when they actually have non-negligible relationships with biodiversity, i.e. for which ecological groups and in which ecological contexts.

Species diversity and regeneration of native species in Pennisetum ciliare (buffelgrass) pastures from the thornscrub of Sonora, México

To examine the influence of buffelgrass land conversion and pasture management on native species diversity and regeneration patterns, we describe community attributes and population structure in four different active pastures in thornscrub vegetation from eastern Sonora, Mexico. We compare a relatively undisturbed thornscrub community with a contiguous five years old active pasture, to identify species able to regenerate under current management practices. Buffelgrass conversion has a significant influence on species diversity and other community attributes. Active pastures have lower species diversity, crown cover and basal area of native species than the studied native thornscrub. An active pasture subjected to heavy grazing and without management of the thorny legume, Acacia cochliacantha, showed the lower species diversity and an almost monospecific stand of this legume. It is likely that the reduction in species diversity is caused by the conversion process, inadequate management and regeneration barriers that limit seedling establishment in active pastures. Our data recorded eight native species (13%) that were able to regenerate in active pastures. However, the great majority of native species were unable to regenerate under pastures. This study shows that under current management, active buffelgrass pastures maintain only a small fraction of native species with regenerating populations in the thornscrub.

Evaluation of Forest Recovery over Time and Space Using Permanent Plots Monitored over 30 Years in a Jamaican Montane Rain Forest

Conservation of tropical forest biodiversity increasingly depends on its recovery following severe human disturbance. Our ability to measure recovery using current similarity indices suffers from two limitations: different sized individuals are treated as equal, and the indices are proportionate (a community with twice the individuals of every species as compared with the reference community would be assessed as identical). We define an alternative recovery index for trees – the Tanner index, as the mean of the quantitative Bray-Curtis similarity indices of species composition for stem density and for basal area. We used the new index to compare the original (pre-gap) and post-gap composition of five experimental gap plots (each 90–100 m2) and four control plots over 24–35 years in the Blue Mountains of Jamaica. After 24–35 years, these small gaps surrounded by undisturbed forest had recovered 68% of the sum of per species stem density and 29% of the sum of per species basal area, a recovery index of 47%. Four endemic species were especially reduced in density and basal area. With the incorporation of basal area and stem density, our index reduces over-estimations of forest recovery obtained using existing similarity indices (by 24%–41%), and thus yields more accurate estimates of forest conservation status. Finally, our study indicates that the two kinds of comparisons: 1) over time between pre-gap and post-gap composition and 2) over space between gap plots and spatial controls (space-for-time substitution) yield broadly similar results, which supports the value of using space-for-time substitutions in studying forest recovery, at least in this tropical montane forest.

A nearest-neighbor imputation approach to mapping tree species over large areas using forest inventory plots and moderate resolution raster data

The paper describes an efficient approach for mapping multiple individual tree species over large spatial domains. The method integrates vegetation phenology derived from MODIS imagery and raster data describing relevant environmental parameters with extensive field plot data of tree species basal area to create maps of tree species abundance and distribution at a 250-m pixel size for the entire eastern contiguous United States. The approach uses the modeling techniques of k-nearest neighbors and canonical correspondence analysis, where model predictions are calculated using a weighting of nearest neighbors based on proximity in a feature space derived from the model. The approach also utilizes a stratification derived from the 2001 National Land-Cover Database tree canopy cover layer. Data pre-processing is also described, which includes the use of Fourier series transformation for data reduction and characterizing seasonal vegetation phenology patterns that are apparent in the MODIS imagery.A suite of assessment procedures is applied to each of the modeled dataset presented. These indicate high accuracies, at the scales of assessments used, for total live-tree basal area per hectare and for many of the most common tree species found in the study area. The end result is an approach that enables the mapping of individual tree species distributions, while retaining much of the species covariance found on the forest inventory plots, at a level of spatial detail approaching that required for many regional management and planning applications. The proposed approach has the potential for operational application for simultaneously mapping the distribution and abundance of numerous common tree species across large spatial domains.