Dendrometric Traits Research Articles

Impact of land-use and climate change on the population structure and distribution range of the rare and endangered Dracaena ombet and Dobera glabra in northern Ethiopia

Dracaena ombet and Dobera glabra are some of the most important rare and endangered tree species in dryland areas. Unfortunately, their sustainability is being compromised by different anthropogenic and natural factors. However, impacts of the on-going land-use and climate change on the population structure and distribution of the species are less explored. This study was carried out in the grazing lands and hillside areas of the Desa'a dry Afromontane-forest, northern Ethiopia, to characterize the population structure of the species and predict the impact of climate change on their potential distributions. In each land-use type, abundance, diameter and height of the trees were collected using 70 sampling plots distributed over seven transects spaced one km apart. The geographic coordinates of each individual tree were also recorded. The results showed that the species populations were characterized by low abundance and unstable population structure. The latter was evinced by a lack of seedlings and mature trees. The study also revealed that the total abundance and dendrometric traits of the trees were significantly different between the two land-uses. The hillside areas had denser abundance with bigger and taller trees than the grazing lands. Climate change predictions using the MaxEnt model highlighted that future temperature increases coupled with reduced precipitation would lead to significant reductions in the suitable habitats of the species in northern Ethiopia. The species suitable habitats were predicted to decline by 48–83% for D. ombet and 35–87% for D. glabra. Hence, to sustain the species populations, different strategies should be adopted, namely the introduction of alternative livelihoods (e.g., gathering NTFP) to reduce the overexploitation of the species for subsistence livelihood, and the protection of the current habitats of the species that will remain suitable in the future using community-based exclosures. Additionally, the preservation of the species' seeds in gene banks is crucial to ensure their long-term conservation.

CO2-assimilation, sequestration, and storage by urban woody species growing in parks and along streets in two climatic zones

Using two cities, Rimini (Italy, Cfa climate) and Krakow (Poland, Cfb), as living laboratories, this research aimed at measuring in situ the capacity of 15 woody species to assimilate, sequester, and store CO2. About 1712 trees of the selected species were identified in parks or along streets of the two cities, and their age, DBH, height, and crown radius were measured. The volume of trunk and branches was measured using a terrestrial LiDAR. The true Leaf Area Index was calculated by correcting transmittance measurements conducted using a plant-canopy-analyser for leaf angle distribution, woody area index, and clumping. Dendrometric traits were fitted using age or DBH as independent variable to obtain site- and species-specific allometric equations. Instantaneous and daily net CO2-assimilation per unit leaf area was measured using an infra-red gas-analyser on full-sun and shaded leaves and upscaled to the unit crown-projection area and to the whole tree using both a big-leaf and a multilayer approach. Results showed that species differed for net CO2-assimilation per unit leaf area, leaf area index, and for the contribution of shaded leaves to overall canopy carbon gain, which yielded significant differences among species in net CO2-assimilation per unit crown-projection-area (AcpaML(d)). AcpaML(d) was underestimated by 6–30 % when calculated using the big-leaf, compared to the multilayer model. While maximizing AcpaML(d) can maximize CO2-assimilation for a given canopy cover, species which matched high AcpaML(d) and massive canopy spread, such as mature Platanus x acerifolia and Quercus robur, provided higher CO2-assimilation (Atree) at the individual tree scale. Land use (park or street), did not consistently affect CO2-assimilation per unit leaf or crown-projection area, although Atree can decline in response to specific management practices (e.g. heavy pruning). CO2-storage and sequestration, in general, showed a similar pattern as Atree, although the ratio between CO2-sequestration and CO2-assimilation decreased at increasing DBH.

The Use of an Airborne Laser Scanner for Rapid Identification of Invasive Tree Species Acer negundo in Riparian Forests

Invasive species significantly impact ecosystems, which is fostered by global warming. Their removal generates high costs to the greenery managers; therefore, quick and accurate identification methods can allow action to be taken with minimal impact on ecosystems. Remote sensing techniques such as Airborne Laser Scanning (ALS) have been widely applied for this purpose. However, many species of invasive plants, such as Acer negundo L., penetrate the forests under the leaves and thus make recognition difficult. The strongly contaminated riverside forests in the Vistula valley were examined in the gradient of the center of Warsaw and beyond its limits within a Natura 2000 priority habitat (91E0), namely, alluvial and willow forests and poplars. This work aimed to assess the potentiality of a dual-wavelength ALS in identifying the stage of the A. negundo invasion. The research was carried out using over 500 test areas of 4 m diameter within the riparian forests, where the habitats did not show any significant traces of transformation. LiDAR bi-spectral data with a density of 6 points/m2 in both channels were acquired with a Riegl VQ-1560i-DW scanner. The implemented approach is based on crown parameters obtained from point cloud segmentation. The Adaptive Mean Shift 3D algorithm was used to separate individual crowns. This method allows for the delineation of individual dominant trees both in the canopy (horizontal segmentation) and undergrowth (vertical segmentation), taking into account the diversified structure of tree stands. The geometrical features and distribution characteristics of the GNDVI (Green Normalized Vegetation Index) were calculated for all crown segments. These features were found to be essential to distinguish A. negundo from other tree species. The classification was based on the sequential additive modeling algorithm using a multi-class loss function. Results with a high accuracy, exceeding 80%, allowed for identifying and localizing tree crowns belonging to the invasive species. With the presented method, we could determine dendrometric traits such as the age of the tree, its height, and the height of the covering leaves of the trees.

The Size of the Assimilatory Apparatus and Its Relationship with Selected Taxation and Increment Traits in Pine (Pinus sylvestris L.) Stands

Studies were carried for 200 trees coming from eight pure pine stands aged 25–95 years, growing in a fresh mixed coniferous forest habitat, in the Murowana Goślina Forest Experimental Station (52°34′ N, 17°00′ E) in western Poland. The aim of the study was to determine the size of the assimilatory apparatus of single pines (Pinus sylvestris L.): weight of leaved twigs (ugc), needle weight (ic), the volume of leaved twigs (ugo) and needle volume (io) and its relationship with selected dendrometric and increment traits of trees. The basic dendrometric traits were determined (height—h and diameter at breast height—d1.3) together with selected increments (heights—Ih5 and Ih10, diameter at breast height—Id5 and Id10, basal area at breast height—Ig5 and Ig10, volume—Iv5 and Iv10). A statistically significant linear correlation and a multiple linear correlation were shown between analysed traits, which confirms a strong relationship of the size of the assimilatory apparatus with tree increment. In this context, the strong correlation with the increment in basal area at breast height (correlation coefficient 0.8731 ÷ 0.9836) and with the increment in diameter at breast height (correlation coefficient 0.7835 ÷ 0.9581), after determining the increment in diameter at breast height requires only simple mathematical transformations to determine the increment in basal area at breast height. For the above-mentioned reasons, the increment in basal area at breast height is predisposed to be commonly used in the determination of the efficiency of the assimilatory apparatus of trees.

Structural characterization and pod yields of populations of the fodder legumes trees <i>Piliostigma thonningii.</i> and <i>Prosopis africana</i> along the toposequence in western Burkina Faso

Plant communities including fodder trees play an important role in livestock production in semi-arid zones of West Africa. This study was carried out at two sites of the western region of Burkina Faso and aimed to provide information on the current status of the natural savanna-woodland pastures and predict the pod production of Piliostigma thonningii and Prosopis africana, two key fodder species of these ecosystems. All woody species were systematically identified and their dbh and height were measured in plots along a toposequence. Pods were collected from 60 trees of P. thonningii and P. africana and the stem circumference at breast height and the crown diameter were also measured. To predict pod production, regression analysis was used to develop predictive allometric equations by selecting tree size variables for fitting to models. Results showed a total of 24 species belonging to 11 families and 22 genera were inventoried with clear tendency to shrub invasion of the toposequence locations. P. thonningii trees had a good regeneration status while P. Africana individuals were old. The two species had good potential for natural regeneration of the stands from seedlings. The pod production prediction equations for both species were significantly correlated to dendrometric traits (P˂0.0001). They were species-specific, and the equations developed for each species were different. It is not advised to apply the same formula to predict pod production of fodder trees species at different savanna-woodland locations throughout West Africa.Keywords: Browse species, dendrometric traits, class distribution, Fodder equation, Natural savannawoodland pastures, Toposequence, West Africa.

Silvicultural Methods Effects on the 82 Year Old Planted <i>Pericopsis elata</i> (<i>Fabaceae</i>) and <i>Entandrophragma cylindricum (Meliaceae) </i> Dendrometry in Yangambi Region, DR Congo

The effects of four silvicultural methods notably Layon, Blanc-Etoc (BE), Martineau and assisted natural regeneration (ANR) have been compared on the dendrometric traits of <i>Pericopsis elata Harms</i> and <i>Entandrophragma cylindricum Sprague</i> planted in 1938 in Yangambi for controlling anthropogenic activities (agricultural deforestation and forest degradation) threatening the species to extinction added to difficult natural regeneration. The sustainable pedo-silvicultural system will preserve Yangambi biosphere reserve. In case of variance analysis significance; the non-parametric test of Kruskal Wallis and the test of Tukey Honest Significant Differences were applied to separate the traits means. Results have revealed that the three plantation methods were significantly different from ANR. BE, Martineau and Layon have determined the Gaussian shape for <i>P. elata</i> diametric structures while Layon, Martineau and ANR presented the inversed J shape for <i>E. cylindricum</i>. BE method convenes for plantations of the two species whose trait values were higher than those of other methods. The difference was significant between the widest average breast height diameter (DBH) of 44.49±10.63cm with the total height mean of 24.46±4.45m for <i>P. elata</i> and DBH of 29.63±11.59cm with the total height mean of 22.04±5.80m for <i>E. cylindricum</i>. The differences were also identified respectively for the two species regarding the basal areas with 25.54±5.6 against 9.474±1.67 m²/ha, the aboveground biomasses with 318.81±77.2 against 94.315±11.59t/ha and the loose volumes with 45069.49±12219.30 against 14 471.348±3 645.692m³/ha. The Layon method did not have significant effect on the <i>E. cylindricum</i>, but has influenced the DBH, AGB and basal area of <i>P. elata</i>. The least productive method ANR has expressed a convenient natural regeneration inversed J shape for the two species, as related to Yangambi reserve preservation.

Linking Dendrometry and Dendrochronology in the Dominant Azorean Tree Laurus azorica (Seub.) Franco

As in many archipelagos, the Azorean primary forest was largely cleared and replaced by secondary forest and grassland, the Azorean tree Laurus azorica (Seub.) Franco being one of the dominant trees in the remaining natural forests. Dendrochronological and dendrometric studies in the Azores mainly focused on non-indigenous trees, either used for timber (e.g., Cryptomeria japonica D. Don) or considered as invasive (Pittosporum undulatum Vent.). Therefore, this study aims to describe the growth ring anatomy of L. azorica, and to understand the relationship between dendrometric traits (e.g., trunk diameter at breast height; tree height), and the number of growth rings. Growth ring anatomy was accessed by wood anatomical preparation of microcore samples while tree age estimation was based on growth ring counts in wood cores taken at breast height and at base. A total of 145 trees were sampled, resulting in 262 increment cores, at six representative stands of laurel forest in São Miguel Island (Azores). The wood anatomical analysis confirmed the presence of clear annual ring boundaries, and a high structural similarity towards Laurus novocanariensis Rivas Mart., Lousã, Fern.Prieto, E.Días, J.C.Costa &amp; C.Aguiar. Age at tree base averaged 33 years, with 60% of the trees between 25 and 50 years old, and only about 15% above 50 years old. This suggests the existence of a secondary forest that is more recent than expected, probably due to human disturbance. The allometric models showed best fit when calculated by stand, suggesting the effect of local environmental conditions on growth rate. Radial growth rate was estimated at 0.68 cm.year−1. Given the known dominance of this species and the threats affecting natural forests, this baseline study will allow a better understanding of forest distribution and dynamics, and support a more effective forest management approach.

Biomass valorization in the management of woody plant invaders: The case of Pittosporum undulatum in the Azores

As one cause for biodiversity loss, invasive alien species are a worldwide threat. However, exotic woodland can also have an enormous biomass potential. The goal of this study was to evaluate the available aboveground biomass (AGB, including trunk, branches and foliage) of the widespread woody plant invader Pittosporum undulatum in the exotic woodland in São Miguel, Terceira and Graciosa islands (Azores archipelago), in order to assess its potential for energetic valorization. We used different modeling approaches in combination with forest inventory data to estimate total AGB. We sampled 127 stands dominated by P. undulatum, estimated stand density, measured diameter at breast height, basal area, tree height, and number of branches at breast height in a total of 5872 trees, and determined the AGB of 674 trees. Allometric equations were used to estimate AGB from dendrometric traits (R2 = 0.88). Although it was possible to predict stand biomass based on stand density and on dendrometric traits, there was no clear relationship between AGB and topographic and climatic variables. Using average estimates of AGB, the areas classified as dominated by P. undulatum in the forest inventory, and a rotation period of 26 years, we calculated a total annual available AGB of 1570, 2594 and 11903 Mg. year−1 for Graciosa, Terceira and São Miguel islands, respectively. The employed methods and the results obtained in this work provide the means for a more accurate evaluation of the woody biomass resources, opening new perspectives for the management of woody plant invaders.

Estimating forest standing biomass in savanna woodlands as an indicator of forest productivity using the new generation WorldView-2 sensor

Accurate and up-to-date information on forest dendrometric traits, such as above ground biomass is important in understanding the contribution of terrestrial ecosystems to the regulation of atmsopheric carbon, especially in the face of global environmental change. Besides, dendrometric traits information is critical in assessing the healthy and the spatial planning of fragile ecosystems, such as the savanna dry forests. The aim of this work was to test whether red-edge spectral data derived from WorldView-2 multispectral imagery improve biomass estimation in savanna dry forests. The results of this study have shown that biomass estimation using all Worldview-2 raw spectral bands without the red-edge band yielded low estimation accuracies (R2 of 0.67 and a RMSE-CV of 2.2 t ha−1) when compared to when the red-edge band was included as a co-variate (R2 of 0.73 and a RMSE-CV of 2.04 t ha−1). Also, similar results were obseved when all WorldView-2 vegetation indices (without the red-edge computed ones), producing slightly low accuracies (R2 of about 0.67 and a RMSE-CV of 2.20 t ha−1), when compared to those obtained using all indices and RE-computed indices(R2 of 0.76 and a RMSE-CV of 1.88 t ha−1). Overall, the findings of this work have demontrated the potential and importance of strategically positioned bands, such as the red-edge band in the optimal estimation of indigeonus forest biomass. These results underscores the need to shift towards embracing sensors with unique and strategeically positioned bands, such as the forthcoming Sentinel 2 MSI and HysPIRI which have a global footprint.