Tree Height Diversity Research Articles

The effect of leaf-on and leaf-off forest canopy conditions on LiDAR derived estimations of forest structural diversity

Forest structural diversity metrics describing diversity in tree size and crown shape within forest stands can be used as indicators of biodiversity. These diversity metrics can be generated using airborne laser scanning (LiDAR) data to provide a rapid and cost effective alternative to ground-based inspection. Measures of tree height derived from LiDAR can be significantly affected by the canopy conditions at the time of data collection, in particular whether the canopy is under leaf-on or leaf-off conditions, but there have been no studies of the effects on structural diversity metrics. The aim of this research is to assess whether leaf-on/leaf-off changes in canopy conditions during LiDAR data collection affect the accuracy of calculated forest structural diversity metrics. We undertook a quantitative analysis of LiDAR ground detection and return height, and return height diversity from two airborne laser scanning surveys collected under leaf-on and leaf-off conditions to assess initial dataset differences. LiDAR data were then regressed against field-derived tree size diversity measurements using diversity metrics from each LiDAR dataset in isolation and, where appropriate, a mixture of the two. Models utilising leaf-off LiDAR diversity variables described DBH diversity, crown length diversity and crown width diversity more successfully than leaf-on (leaf-on models resulted in R² values of 0.66, 0.38 and 0.16, respectively, and leaf-off models 0.67, 0.37 and 0.23, respectively). When LiDAR datasets were combined into one model to describe tree height diversity and DBH diversity the models described 75% and 69% of the variance (R² of 0.75 for tree height diversity and 0.69 for DBH diversity). The results suggest that tree height diversity models derived from airborne LiDAR, collected (and where appropriate combined) under any seasonal conditions, can be used to differentiate between simple single and diverse multiple storey forest structure with confidence.

Land-use intensity indirectly affects soil multifunctionality via a cascade effect of plant diversity on soil bacterial diversity

Land-use intensification impairs multiple soil ecosystem functions and services (hereafter ‘soil multifunctionality’; SMF) crucial to human wellbeing by influencing plant diversity and soil microbial communities. However, available information is limited on the contrasting and interaction effects of plant diversity and soil microbial communities on SMF under a gradient of land-use intensity (LUI). We measured five soil ecosystem functions associated with effective soil nutrients and water retention along 15 LUI gradients on Hainan Island, where land-use change and biodiversity loss has been severe. We used phospholipid fatty acid (PLFA) method to determine the diversity and composition of soil microbial communities. The relationships among LUI, plant diversity (species and functional diversity), soil microbial diversity (bacterial and eukaryotic diversity), and soil microbial composition (fungi/bacteria and Gram-positive/Gram-negative bacteria ratios), and SMF were examined. The LUI affected SMF indirectly by reducing plant diversity and its interaction with soil bacterial diversity. Specifically, with increase in LUI, loss of plant species diversity indirectly reduced SMF via reduction of soil bacterial diversity. In contrast, loss of tree height diversity reduced SMF directly and indirectly through decrease in soil bacterial diversity. Importantly, the indirect effect of LUI mediated by tree height diversity was stronger than that mediated by plant species diversity and soil bacterial diversity. These results provide evidence that the cascade effect of plant diversity to soil bacterial diversity mediates the impacts of land-use intensity on soil multifunctionality, and further suggest that focusing on tree height diversity may be helpful for sustainable ecosystem management and predicting the impacts of land use changes.

Large-eddy simulation of the optimal street-tree layout for pedestrian-level aerosol particle concentrations – A case study from a city-boulevard

Abstract Street vegetation has been found to have both positive and negative impacts on pedestrian-level air quality, but the net effect has remained unclear. In this study, the effect of street trees on aerosol mass (PM10 and PM2.5) and number in a boulevard-type street canyon with high traffic volumes in Helsinki is examined using the large-eddy simulation model PALM. Including a detailed aerosol module and a canopy module to comprise permeable trees, PALM allows to examine the effect of street trees in depth. The main aim is to understand the relative importance of dry deposition and the aerodynamic impact of street trees on the different aerosol measures at pedestrian-level and to find a suitable street-tree layout that would minimise the pedestrian-level aerosol particle concentrations over the boulevard pavements. The layout scenarios were decided together with urban planners who needed science-based knowledge to support the building of new neighbourhoods with boulevard-type streets in Helsinki. Two wind conditions with wind being parallel and perpendicular to the boulevard under neutral atmospheric stratification are examined. Adding street trees to the boulevard increases aerosol particle concentrations on the pavements up to 123%, 72% and 53% for PM10, PM2.5 and total number, respectively. This shows decreased ventilation to be more important for local aerosol particle concentrations than dry deposition on vegetation. This particularly for PM10 and PM2.5 whereas for aerosol number, dominated by small particles, the importance of dry deposition increases. Therefore the studied aerosol measure is important when the effect of vegetation on pedestrian-level air quality is quantified. Crown volume fraction in the street space is one of the main determining factors for elevated mass concentrations on the pavements. The lowest pedestrian-level mass concentrations are seen with three rows of trees of variable height, whereas the lowest number concentrations with four rows of uniform trees. The tree-height variation allows stronger vertical turbulent transport with parallel wind and largest volumetric flow rates with perpendicular wind. Introducing low (height The results show how street trees in a boulevard-type street canyon lead to decreased pedestrian-level air quality with the effect being particularly strong for larger aerosol particles. However, with careful planning of the street vegetation, significant reductions in pedestrian-level aerosol particle concentrations can be obtained.

Coppicing improves the growth response of short-rotation hybrid aspen to elevated atmospheric humidity

Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens’ northern range, climate models predict an increase in precipitation and, consequently, in atmospheric humidity. Our aim was to clarify the long-term effect of elevated air humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p < 0.001): negative in 4 years, positive also in 4 years and non-significant in 3 years. Mean basal area of humidified (11.6 ± 0.8 cm2) and control trees (15.0 ± 1.0 cm2) differed significantly (p = 0.035) at the end of the first but not the second rotation period (9.3 ± 0.9 cm2 and 9.3 ± 1.2 cm2, respectively). Average growth differences levelled out already in the beginning of the second rotation, suggesting that some root-level acclimation must have taken place. The annual size-growth relationships (SGR) indicated a more size-symmetric growth in humidified (SGR = 1.00 ± 0.05) and a size-asymmetric growth (SGR = 1.12 ± 0.04) in control stands, implying a greater role of root-competition in humidified stands. In humidified stands, the growth of re-sprouting trees was more strongly determined by parent tree size, indicating a stronger carry-over of size hierarchy. The tree height diversity fluctuated more in control stands, where mortality was higher, especially after dry years. To summarise, short- and long-term responses of hybrid aspen to elevated air humidity varied, emphasizing the importance of long-term climate manipulations with trees. Generally, hybrid aspen short-rotation coppice forests showed promising acclimation capacity with future more humid climate predicted for northern latitudes.

Linking vegetation and soil functions during secondary forest succession in the Atlantic forest

Secondary forest succession can be an effective and low-cost strategy to increase forest cover and the associated biodiversity and soil functions. However, little is known about how soil functions develop during succession, and how vegetation attributes influence soil functions, especially in highly biodiverse and fragmented landscapes in the tropics. Here we assessed a wide range of indicators of taxonomic (e.g. number of tree species), structural (e.g. basal area, canopy openness) and functional diversity (e.g. community weighted means of functional traits) of tree species, as well as indicators for soil functions related to soil organic matter accumulation, nutrient cycling and soil cover in secondary forest patches ranging from 5 to 80 years. Two recently abandoned agricultural fields were included as the starting point of forest succession and two primary forest patches served as references for the end point of forest succession. Four ecological hypotheses, centred around the role of functional diversity, structural diversity and biomass, were tested to explore mechanisms in which forest vegetation may influence soil functions. Most measures of structural, taxonomic and functional diversity converged to values found in primary forests after 25–50 years of succession, whereas functional composition changed from acquisitive to conservative species. Soil carbon and nutrient cycling showed a quick recovery to the levels of primary forests after 15 years of succession. Although soil cover also increased during succession, levels of primary forests were not reached within 80 years. Variation in tree height and trait dominance were identified as aboveground drivers of carbon and nutrient cycling, while aboveground biomass was the main driver of litter accumulation, and the associated soil cover and water retention. Our results indicate that secondary forest succession can lead to a relative fast recovery of nutrient and carbon cycling functions, but not of soil cover. Our findings highlight the essential role of secondary forests in providing multiple ecosystem services. These results can be used to inform management and reforestation programmes targeted at strengthening soil functions, such as soil cover, nutrient and carbon cycling.

The Influence of Vegetation Characteristics on Individual Tree Segmentation Methods with Airborne LiDAR Data

This study investigated the effects of forest type, leaf area index (LAI), canopy cover (CC), tree density (TD), and the coefficient of variation of tree height (CVTH) on the accuracy of different individual tree segmentation methods (i.e., canopy height model, pit-free canopy height model (PFCHM), point cloud, and layer stacking seed point) with LiDAR data. A total of 120 sites in the Sierra Nevada Forest (California) and Shavers Creek Watershed (Pennsylvania) of the United States, covering various vegetation types and characteristics, were used to analyze the performance of the four selected individual tree segmentation algorithms. The results showed that the PFCHM performed best in all forest types, especially in conifer forests. The main forest characteristics influencing segmentation methods were LAI and CC, LAI and TD, and CVTH in conifer, broadleaf, and mixed forests, respectively. Most of the vegetation characteristics (i.e., LAI, CC, and TD) negatively correlated with all segmentation methods, while the effect of CVTH varied with forest type. These results can help guide the selection of individual tree segmentation method given the influence of vegetation characteristics.

Do climate and human disturbance determine the sizes of endangered Metasequoia glyptostroboides trees in their native range?

Under global change scenarios, climate change and habitat loss or alteration as a result of human activities are regarded as two important factors affecting species’ distributions and in situ conservation. Metasequoia glyptostroboides Hu et Cheng, a living fossil, occurs naturally only in a small region in Central China, with most individuals now growing near human settlements. The climate in the native range is poorly characterized, and little is known regarding what potential factors (e.g. climate variables) explain variation in the sizes of M. glyptostroboides trees. Here, we found that climate variables were not, or only very weakly, related to three measures of tree sizes: canopy sizes, DBHs (diameter at breast heights) and heights. As elevations increased, tree heights and canopy sizes decreased significantly, but no relationship was found with DBHs. On average, M. glyptostroboides trees were larger, in terms of DBHs and heights, when growing within 30 m of a house, road or farmland versus more than 30 m from one or more of these features; however, canopy sizes showed the opposite trend for trees growing near roads and farmlands. Climate variables, elevations, and human disturbance explained little variations in tree canopy sizes, DBHs or heights, though human disturbance was the most important factor of the tree for DBHs. Elevations, mean annual temperature, and precipitation in the wettest quarter explained the most variation in tree heights, while elevations, precipitation in the wettest quarter and the distance to farmland affected canopy sizes. Due to its poor natural regeneration in the native range, more effective in situ conservation is urgently needed for the existing small M. glyptostroboides populations.

Drivers of the growth–survival trade‐off in a tropical forest

AbstractQuestionsThe growth–survival trade‐off is a central concept for the conflicting strategies of acquisitive species that grow quicker and conservative species that grow slower. Understanding which, and how, cross‐species functional traits contribute to the growth–survival trade‐off is a key topic for understanding the functioning of tropical forests. The present study aimed to: (a) determine if leaf traits, wood density and fruit size influence the growth–survival trade‐off at the community level; and (b) test the hypothesis that averaged leaf traits, averaged wood density and averaged fruit size among all trees of subplots explain tree height in a 50‐ha plot of secondary Atlantic Forest in Brazil.MethodsAll trees with DBH &gt; 3 cm had their heights estimated and were taxonomically identified. The functional traits used were leaf length (LL), leaf width (LW), petiole length (PL), petiole width (PW), leaf width/petiole width (LW/PW), leaf length × leaf width (LL*LW), wood density (WD), fruit length (FL) and fruit width (FW).ResultsA total of 74,335 trees of 178 species were recorded in 5,076 subplots of 100 m2. Associations between functional traits and mean height (Hmean) and height mode (Hmode) were congruent with expected trends of LW, LL, LW/PW, WD and FW with the top‐ranked global model explaining most of the found variance suggesting that Hmean and Hmode are the best averaged response variables. The growth response represented by Hmean and Hmode had the most distinctive, congruent and consistent association with LW/PW, WD and FW.ConclusionsHigher LW and higher LW/PW indicated higher dependence of leaf blade on local microclimatic conditions, and lower dependence on petiole support for plant growth, which is beneficial for the acquisitive strategy. Smaller fruits and higher WD were also associated with the acquisitive strategy. Therefore, LW, LW/PW, WD and FW influenced the growth–survival trade‐off at the community level and explained tree height variation in the studied tropical forest.

Adaptation Capacity of Norway Spruce Provenances in Western Latvia

In Europe, numerous Norway spruce (Picea abies L. Karst.) provenance trials have been established and evaluated at a juvenile age. Still, information about the adaptation potential and long-term fitness of transferred seedlots in the Baltic Sea region is lacking. The aim of the study was to evaluate the adaptation capacity of provenances and assess the patterns of their long-term reaction to environmental transfer. We examined a 32-year-old provenance trial in the mild Baltic Sea coastal climate of Western Latvia. Significant differences in height and stem volume were observed among provenances. Growth superiority for certain local and Carpathian provenances was maintained over more than one-third of the rotation period. The best predictor of climate transfer functions was minimum temperature of the coldest month at the place of origin, explaining 28% variation in tree height. Populations from sites with more frost days and a colder mean annual temperature, minimum temperature, and lower annual heat-moisture index than the planting site were generally taller.

Geographic variation of tree height of three pine species (Pinus nigra Arn., P. pinaster Aiton, and P. pinea L.) gathered from common gardens in Europe and North-Africa

This datapaper collects individual georeferenced tree height data from Pinus nigra Arn., P. pinaster Aiton, and P. pinea L. planted in common gardens in France, Germany, Morocco, and Spain. The data can be used to assess genetic variation and phenotypic plasticity with further applications in biogeography and forest management. The three datasets are available at (Vizcaino-Palomar et al. 2018a), (Vizcaino-Palomar et al. 2018b), and (Vizcaino-Palomar et al. 2018c), and the associated metadata are available at , and for P. nigra, P. pinaster and P. pinea, respectively.

Local Adaptation and Response of Platycladus orientalis (L.) Franco Populations to Climate Change

Knowledge about the local adaptation and response of forest tree populations to the climate is important for assessing the impact of climate change and developing adaptive genetic resource management strategies. However, such information is not available for most plant species. Here, based on 69 provenances tested at 19 common garden experimental sites, we developed a universal response function (URF) for tree height at seven years of age for the important and wide-spread native Chinese tree species Platycladus orientalis (L.) Franco. URF was recently used to predict the potential growth response of a population originating from any climate and growing in any climate conditions. The developed model integrated both genetic and environmental effects, and explained 55% of the total variation in tree height observed among provenances and test sites in China. We found that local provenances performed better than non-local counterparts in habitats located in central, eastern, and southwestern China, showing the evidence of local adaptation as compared to other regions. In contrast, non-local provenances outperformed local ones in peripheral areas in northern and northwestern China, suggesting an adaptational lag in these areas. Future projections suggest that the suitable habitat areas of P. orientalis would expand by 15%–39% and shift northward by 0.8–3 degrees in latitude; however, the projected tree height of this species would decline by 4%–8% if local provenances were used. If optimal provenances were used, tree height growth could be improved by 13%–15%, along with 59%–71% suitable habitat expansion. Thus, assisted migration with properly selected seed sources would be effective in avoiding maladaptation in new plantations under a changing climate for P. orientalis.

Inferring phenotypic plasticity and population responses to climate across tree species ranges using forest inventory data

AbstractAimTo test whether intraspecific trait responses to climate among populations across species distribution ranges can be untangled using field observations, under the rationale that, in natural forest tree populations, long‐term climate shapes population responses while recent climate change drives phenotypic plasticity.LocationEurope.Time period1901–2014.TaxaSilver fir (Abies alba Mill.) and sessile oak [Quercus petraea (Matt.) Liebl.].MethodsWe estimated the variation of individual tree height as a function of long‐term and short‐term climates to tease apart provenance effects (variation among populations of different geographical origin), plasticity and their interaction, using mixed‐effect models calibrated with national forest inventory data (in‐situ models). To validate our approach, we tested the ability of in‐situ models to predict independently tree height observations in common gardens experiments where provenance and plastic effects can be measured and separated. In‐situ model predictions of tree height variation among provenances and among planting sites were compared to observations in common gardens and to predictions from a similar model calibrated using common garden data (ex‐situ model).ResultsIn Q. petraea, we found high correlations between in‐situ and ex‐situ model predictions of provenance and plasticity effects and their interaction for tree height (r &gt; .80). We showed that the in‐situ models significantly predicted tree height variation among provenances and sites for A. alba and Q. petraea. Spatial predictions of phenotypic plasticity across species distribution ranges indicate decreasing tree height in populations of warmer climates in response to recent anthropogenic climate warming.Main conclusionsOur modelling approach using national forest inventory observations provides a new perspective for understanding patterns of intraspecific trait variation across species ranges. Its application is particularly interesting for species for which common garden experiments do not exist or do not cover the entire climatic range of the species.

Multi‐scale effects of habitat structure and landscape context on a vertebrate with limited dispersal ability (the brown‐throated sloth, Bradypus variegatus)

AbstractAs human population, food consumption, and demand for forest products continue to rise over the next century, the pressures of land‐use change on biodiversity are projected to intensify. In tropical regions, countryside habitats that retain abundant tree cover and structurally complex canopies may complement protected areas by providing suitable habitats and landscape connectivity for a significant portion of the native biota. Species with low dispersal capabilities are among the most at risk of extinction as a consequence of land‐use change. We assessed how the spatial distribution of the brown‐throated sloth (Bradypus variegatus), a model species for a vertebrate with limited dispersal ability, is shaped by differences in habitat structure and landscape patterns of countryside habitats in north‐central Costa Rica using a multi‐scale framework. We quantified the influence of local habitat characteristics and landscape context on sloth occurrence using mixed‐effects logistic regression models. We recorded 27 sloths within countryside habitats and found that both local and landscape factors significantly influenced their spatial distribution. Locally, sloths favored structurally complex habitats, with greater canopy cover and variation in tree height and basal area. At the landscape scale, sloths demonstrated a preference for habitats with high proportions of forest and nearby large tracts of forest. Although mixed‐use areas and tree plantations are not substitutes for protected forests, our results suggest they provide important supplemental habitats for sloths. To promote the conservation and long‐term viability of sloth populations in the tropical countryside, we recommend that land managers retain structurally complex vegetation and large patches of native habitat.

Species, functional, structural diversity of typical plant communities and their responses to environmental factors in Miao Archipelago, China.

Island vegetation plays an important role in biodiversity research across the world. The study of plant diversity in island is helpful for understanding the mechanism of plant diversity maintenance under land-sea interaction. Here, four typical plant communities (Quercus acutissima community, Robinia pseudoacacia community, Pinus thunbergii community and Vitex negundo community) in Miao Archipelago were selected to examine the species, functional and structural diversities and their responses to environmental factors at the community scale by using species diversity indices, functional diversity indices, as well as structural diversity indices. The results showed that the species richness and Rao index of P. thunbergii community was higher than that of Q. acutissima community and R. pseudoacacia community, but the structural diversity was lower. The species diversity and structural diversity of V. Negundo shrub were lower than that of forest community, but the functional diversity was higher than some forest communities. The relationship between the diversity of typical plant communities in island area illustrated a significant positive correlation between species richness with Rao index and tree height diversity, however the correlation with functional evenness was significantly negative. The structural diversity and functional evenness were determined by slope with negative and positive relationships, respectively. Functional heterogeneity, functional divergence and species diversity were affected largely by soil physical and chemical properties, displaying the positive relationship with soil bulk density and soil total carbon content, and a negative relationship with soil water content. In conclusion, diversity pattern of plant community in Miao Archipelago reflected not only the characteristics in mainland vegetation but also the special nature of the sea island.

Research Article Genetic and phenotypic association of the carnauba palm tree evaluated by inter-simple sequence repeat and biometric traits

The carnauba palm Copernicia prunifera is the third most important non-timber forest species in Brazil; it is mainly known for the production of carnauba wax. We examined intrapopulation genetic diversity and correlated genotypic and phenotypic traits of 28 trees from a coastal location in Rio Grande do Norte state. Phenotypic variables tree height, diameter at breast height, curvature of the stem, fresh mass of fruits and seeds, and length and diameter of fruits and seeds were evaluated. Genotypic parameters were examined based on inter-simple sequence repeat (ISSR) polymorphisms. The eight ISSR primers detected 79 loci, of which 76% were polymorphic. The polymorphic information content ranged between 0.408 and 0.500, the Nei's diversity index h was 0.327, and Shannon index was 0.470. Although there was no significant association between the matrices of genotypic and phenotypic traits, stepwise multiple regression analysis identified ISSR markers that can be used in a marker-assisted breeding program. The ISSR loci 881(2), 880(1), and M1(4) were significantly and positively associated with plant height. The sMRA also identified a positive association between DBH and 842(5) and a negative association between the curvature of the stem and 857(1). The fresh mass of fruits had a significant negative correlation with ISSR locus 840(1). The other traits showed positive and negative associations when the marker(s) of the previous step(s) were included in the succeeding step in sMRA analyses. These results are relevant for breeding programs, with the perspective of obtaining intra specific hybrids that are superior for desirable characters.

Multi-scale analysis of relationship between imperviousness and urban tree height using airborne remote sensing

The relationship between impervious land cover and tree development is an important component to understanding urban ecological systems. While impervious surfaces are associated with degraded soil conditions, rerouted hydrological networks and urban microclimates, the overall impact of these effects on tree development is highly variable. This study examines this relationship at two spatial scales: within the individual tree's local environment and across the broad-scale urban landscape. Using a fusion of airborne hyperspectral imagery and light detection and ranging (LiDAR) data, a 1.0m spatial resolution classified land cover map (accuracy of 88.6%) was produced for the city of Surrey, British Columbia, Canada, from which landscape imperviousness was then derived. The stem heights of 1914 trees were estimated from the LiDAR data, to which species-specific height models were fit using planting dates recorded by city authorities. Having accounted for the age of the trees, the residuals from these models (i.e.: the difference between modelled and measured height) were then used as indicators of tree development. When aggregated to 0.5km2 spatial units, negative relationships (r2 between 0.292 and 0.753) were found between height model residuals and the degree of land cover imperviousness. These relationships did not persist when examined at the individual tree level, for which imperviousness was measured within the direct vicinity of each tree using the same imperviousness map. We conclude that, using this approach, imperviousness does not appear to be a significant driver of tree height variation, with broad-scale relationships likely due to correlations with other environmental variables associated with the urban-rural gradient. Despite some limitations, the integration of hyperspectral and LiDAR data proved to be a powerful tool for mapping imperviousness, with LiDAR metrics being particularly important for distinguishing between types of urban land cover.

Varying selection differential throughout the climatic range of Norway spruce in Central Europe.

Predicting species distribution changes in global warming requires an understanding of how climatic constraints shape the genetic variation of adaptive traits and force local adaptations. To understand the genetic capacity of Norway spruce populations in Central Europe, we analyzed the variation in tree heights at the juvenile stage in common garden experiments established from the species' warm‐dry to cold‐moist distribution limits. We report the following findings: First, 47% of the total tree height variation at trial sites is attributable to the tree populations irrespective of site climate. Second, tree height variation within populations is higher at cold‐moist trial sites than at warm‐dry sites and higher within populations originating from cold‐moist habitats than from warm‐dry habitats. Third, for tree ages of 7–15 years, the variation within populations increases at cold‐moist trial sites, whereas it remains constant at warm‐dry sites. Fourth, tree height distributions are right‐skewed at cold‐moist trial sites, whereas they are nonskewed, but platykurtic at warm‐dry sites. Our results suggest that in cold environments, climatic conditions impose stronger selection and probably restrict the distribution of spruce, whereas at the warm distribution limit, the species' realized niche might rather be controlled by external drivers, for example, forest insects.

Abiotic Controls on Macroscale Variations of Humid Tropical Forest Height

Spatial variation of tropical forest tree height is a key indicator of ecological processes associated with forest growth and carbon dynamics. Here we examine the macroscale variations of tree height of humid tropical forests across three continents and quantify the climate and edaphic controls on these variations. Forest tree heights are systematically sampled across global humid tropical forests with more than 2.5 million measurements from Geoscience Laser Altimeter System (GLAS) satellite observations (2004–2008). We used top canopy height (TCH) of GLAS footprints to grid the statistical mean and variance and the 90 percentile height of samples at 0.5 degrees to capture the regional variability of average and large trees globally. We used the spatial regression method (spatial eigenvector mapping-SEVM) to evaluate the contributions of climate, soil and topography in explaining and predicting the regional variations of forest height. Statistical models suggest that climate, soil, topography, and spatial contextual information together can explain more than 60% of the observed forest height variation, while climate and soil jointly explain 30% of the height variations. Soil basics, including physical compositions such as clay and sand contents, chemical properties such as PH values and cation-exchange capacity, as well as biological variables such as the depth of organic matter, all present independent but statistically significant relationships to forest height across three continents. We found significant relations between the precipitation and tree height with shorter trees on the average in areas of higher annual water stress, and large trees occurring in areas with low stress and higher annual precipitation but with significant differences across the continents. Our results confirm other landscape and regional studies by showing that soil fertility, topography and climate may jointly control a significant variation of forest height and influencing patterns of aboveground biomass stocks and dynamics. Other factors such as biotic and disturbance regimes, not included in this study, may have less influence on regional variations but strongly mediate landscape and small-scale forest structure and dynamics.

Prediction of Height, Breast Height Diameter and Volume of Eucalyptus microcorys of Sri Lanka

Eucalyptus microcorys is the most valuable Eucalyptus species growing in Sri Lanka. Although the extant of government owned E. microcorys plantations is comparatively small, the attention of private sector planters has been drawn by this species. Therefore the present study was conducted with the objective of predicting the variation of tree height, breast height diameter (dbh) and total stem volume with the tree age. Fourteen E. microcorys plantations were selected for this study from Halgranoya and Nuwara Eliya Forest Ranges of Nuwara Eliya Forest Division. Those plantations were three to 24 years old and the extents varied from 4.5 to 32.5 ha. Circular sample plots of 0.02 ha drawn at random were used for data collection. The number of sample plots varied with the extents of the selected plantations. Total height and dbh of each tree were measured using standard methods. Then each tree stem was visually divided into a few sections and the length, bottom diameter, mid diameter and top diameter of each section were measured. Using these measurements, volume of each section was estimated by Newton‟s formula and the total stem volume was calculated by adding all section volumes. The shape of the final section was assumed to be a cone. When tested, the selected plantations did not indicate significant site quality differences. The tree height and dbh prediction models were constructed assuming them as functions of the age. Tree volume model was built as a function of tree height and dbh. All possible transformations of the candidate variables were tested in constructing those models and the best models were selected based on R2 values and distribution of standard residuals. The selected best three models for height-age, diameter-age and volume-dbh and height relationships had R2 values of 80.1%, 79.5 % and 98.2% respectively. Further, the standard residual distributions of the selected models did not indicate significant biases. Using those models, a two-parameter volume prediction model for E. microcorys was also constructed. Keywords: Eucalyptus microcorys, Stem volume prediction, Two-parameter volume table

Forest-atmosphere BVOC exchange in diverse and structurally complex canopies: 1-D modeling of a mid-successional forest in northern Michigan

Foliar emissions of biogenic volatile organic compounds (BVOC)—important precursors of tropospheric ozone and secondary organic aerosols—vary widely by vegetation type. Modeling studies to date typically represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height variation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homogeneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting foliage (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.