Eucalyptus Plots Research Articles

Unmanned Aerial Vehicle–Light Detection and Ranging-Based Individual Tree Segmentation in Eucalyptus spp. Forests: Performance and Sensitivity

As an emerging powerful tool for forest resource surveys, the unmanned aerial vehicle (UAV)-based light detection and ranging (LiDAR) sensors provide an efficient way to detect individual trees. Therefore, it is necessary to explore the most suitable individual tree segmentation algorithm and analyze the sensitivity of the parameter setting to determine the optimal parameters, especially for the Eucalyptus spp. forest, which is one of the most important hardwood plantations in the world. In the study, four methods were employed to segment individual Eucalyptus spp. plantations from normalized point cloud data and canopy height model generated from the original UAV-LiDAR data. And the parameter sensitivity of each segmentation method was analyzed to obtain the optimal parameter setting according to the extraction accuracy. The performance of the segmentation result was assessed by three indices including detection rate, precision, and overall correctness. The results indicated that the watershed algorithm performed better than other methods as the highest overall correctness (F = 0.761) was generated from this method. And the segmentation methods based on the canopy height model performed better than those based on normalized point cloud data. The detection rate and overall correctness of low-density plots were better than high-density plots, while the precision was reversed. Forest structures and individual wood characteristics are important factors influencing the parameter sensitivity. The performance of segmentation was improved by optimizing the key parameters of the different algorithms. With optimal parameters, different segmentation methods can be used for different types of Eucalyptus plots to achieve a satisfying performance. This study can be applied to accurate measurement and monitoring of Eucalyptus plantation.

Drivers and spread of non-native pests in forests: The case of Gonipterus platensis in Spanish Eucalyptus plantations

Plantations of Eucalyptus species have been widely used in Spain to meet the high demand for wood given their rapid growth and high wood production capacity. Defoliation induced by the invasive eucalypt weevil (Gonipterus platensis (Marelli)), however, has been causing significant economic damage to Spanish Eucalyptus spp. plantations since the 1990s. G. platensis is native to Tasmania, Australia, where populations are controlled by natural enemies including the egg parasitoid Anaphes nitens Girault. In this study, spatio-temporal Universal Kriging was applied to examine the dynamics of defoliation damage caused by G. platensis in Spanish Eucalyptus spp. plantations and to identify the main factors associated with the presence and spread of the pest. The data set combines the Spanish national plots belonging to the network of the European transnational survey of forest condition in Europe (ICP Forest Level I, 16 × 16 km grid) along with regional plots, measured using similar field protocols, in which Eucalyptus spp. are present. A total of 264 Eucalyptus plots were included in the study, G. platensis being present in 167 of these plots at some time during the observed period (2005–2020). Our results show that defoliation damage > 0% and defoliation damage > 5% caused by G. platensis increased over the period 2005–2010 and then decreased between 2010 and 2020. Defoliation damage > 15% incidence steadily decreased from 2005 to 2015, but showed an upturn in 2020. Stands belonging to the Atlantic region are more affected by this pest (76% of the Atlantic sampling plots affected versus just 4% of the Mediterranean plots). The species Eucalyptus globulus Labill. and monospecific stands, as well as spring precipitation of the current year were found to be positively associated with the incidence of G. platensis whereas the relationship with summer temperature of the previous year was negative. Finally, maps showing the degree of incidence over time have been produced to support decision-making for pest prevention and control. This study puts forward a methodology which allows the spread of this pest to be better understood and simulated, thus facilitating risk prevention.

Multi-Temporal Sentinel-2 Data Analysis for Smallholding Forest Cut Control

Land fragmentation and small plots are the main features of the rural environment of Galicia (NW Spain). Smallholding limits land use management, representing a drawback in local forest planning. This study analyzes the potential use of multitemporal Sentinel-2 images to detect and control forest cuts in very small pine and eucalyptus plots located in southern Galicia. The proposed approach is based on the analysis of Sentinel-2 NDVI time series in 4231 plots smaller than 3 ha (average 0.46 ha). The methodology allowed us to detect cuts, allocate cut dates and quantify plot areas due to different cutting cycles in an uneven-aged stand. An accuracy of approximately 95% was achieved when the whole plot was cut, with an 81% accuracy for partial cuts. The main difficulty in detecting and dating cuts was related to cloud cover, which affected the multitemporal analysis. In conclusion, the proposed methodology provides an accurate estimation of cutting date and area, helping to improve the monitoring system in sustainable forest certifications to ensure compliance with forest management plans.

Individual tree crown segmentation from airborne LiDAR data using a novel Gaussian filter and energy function minimization-based approach

Accurate segmentation of individual tree crowns (ITCs) from airborne light detection and ranging (LiDAR) data remains a challenge for forest inventories. Although many ITC segmentation methods have been developed to derive tree crown information from airborne LiDAR data, these algorithms contain uncertainty in processing false treetops because of foliage clumps and lateral branches, overlapping canopies without clear valley-shape areas, and sub-canopy crowns with neighbouring trees that obscure their shapes from an aerial perspective. Here, we propose an approach to crown segmentation using computer vision theories applied in different forest types. First, a dual Gaussian filter was designed with automated adaptive parameter assignment and a screening strategy for false treetops. This preserved the geometric characteristics of sub-canopy trees while eliminating false treetops. Second, anisotropic water expansion controlled by the energy function was applied for accurate crown segmentation. This utilized gradient information from the digital surface model and explored the morphological structures of tree crown boundaries as analogous to the maximal valley height difference from surrounding treetops. We demonstrate the generality of our approach in the subtropical forests within China. Our approach enhanced the detection rate of treetops and ITC segmentation relative to the marker-controlled watershed method, especially in complicated intersections of multiple crowns. A high performance was demonstrated for three pure Eucalyptus plots (a treetop detection rate r ≥ 0.95 and crown width estimation R2 ≥ 0.90 for canopy trees; r ≥ 0.85 and R2 ≥ 0.88 for sub-canopy trees) and three plots dominated by Chinese fir (r ≥ 0.95 and R2 ≥ 0.87 for canopy trees; r ≥ 0.79 and R2 ≥ 0.83 for sub-canopy trees). Finally, in a relatively complex forest park containing a wide range of tree species and sizes, a high performance was also achieved (r = 0.93 and R2 ≥ 0.85 for canopy trees; r = 0.70 and R2 ≥ 0.80 for sub-canopy trees). Our method demonstrates that methods inspired by the computer vision theory can improve on existing approaches, providing the potential for accurate crown segmentation even in mixed forests with complex structures

Étude comparative de la diversité des macrochampignons dans les plantations forestières matures d'eucalyptus et de pins en zone de savanes tropicales à l'Ouest du Cameroun

To meet the need for wood in the African savanna zone, forest plantations have been established since the 1930s. Exotic tree species of the genera Pinus and Eucalyptus are the major groups planted in the Western Highlands of Cameroon where they form artificial forests whose mycoflora is not yet documented. This study aimed at comparing the macro-fungi diversity in mature eucalyptus and pine plantations in tropical savannas, particularly in the Melap Forest Reserve. Four permanent plots of 1000 m2 were installed in each plant community, sporophores were collected and identified from April to June 2016; species richness and generic diversity were calculated. A total of 125 species were inventoried. Taxonomic diversity was significantly higher in Eucalyptus communities than in Pinus communities, with 107 and 33 species respectively. The number of ectomycorrhizal species was higher in the eucalyptus plots where a few locally consumed species were found. The mycofloral abundance in Eucalyptus communities is explained by the presence of local tree species hosting ectomycorrhizal fungi, such as Uapaca guineensis.

Brachiaria physiological parameters in agroforestry systems

ABSTRACT: This study aimed to assess the effects of Eucalyptus and maize shading on characteristics related to water use by Brachiaria in agroforestry systems. Treatments were arranged in a split-split-plot design, with plots consisting of different spacing between Eucalyptus plants (12.0×2.0m and 12.0×4.0m), split-plots of different distances between Brachiaria and Eucalyptus (6.0, 4.0, and 2.0m), and split-split-plots of Brachiaria sowing sites (maize row and inter-row). One treatment with Brachiaria under full sunlight was included. Bread grass intercropping in maize inter-rows associated with the densest Eucalyptus spacing and bread grass proximity to Eucalyptus tree crowns adversely affected the stomatal conductance, internal carbon, and transpiration rate of bread grass. Water use efficiency of bread grass intercropped in maize rows decreased, regardless of the Eucalyptus plot design and distance between forages and trees.

Effects of silvicultural treatments on temporal variations of spatial autocorrelation in Eucalyptus plantations in Brazil

We examined the change in spatial structures of Eucalyptus plantations across different types of silvicultural treatments over a full rotation. Clonal and seed-origin Eucalyptus plots applied with differing levels of fertilization (high vs. traditional) and irrigation (irrigated vs. non-irrigated) treatments were investigated. Additionally, for the clonal plots, uniform vs. heterogeneous stand structure treatments were created using staggered planting dates. The heterogeneous structure of the clonal plots aimed to mimic the seed-origin plots. Spatial structures were characterized by assessing the spatial autocorrelations of diameters, heights, and biomass. We also applied two distance-based neighborhood structures to look at the degree of change in spatial autocorrelations with different numbers of neighboring trees being defined as neighbors. The results suggest that spatial autocorrelations of diameters, heights, and biomass of Eucalyptus plantations were mostly insignificant at an alpha level of 0.05 over the rotation. However, spatial autocorrelations in most plots after the middle of the rotation were predominantly negative, indicating the occurrence of size differences among neighboring trees. In particular, general declining patterns from positive to negative spatial autocorrelations in diameters and biomass, except for plots with the heterogeneous stand structures, were noted at plots treated with high levels of fertilizer. This suggests that high fertilization may have influenced the realizations of microsite effects in the early stage of stand development. General trends in spatial autocorrelations between the two neighborhood structures considered were mostly similar except for several plots differing in intensities of spatial autocorrelations over the rotation.

MASSIVE-SCALE TREE MODELLING FROM TLS DATA

Abstract. This paper presents a method for reconstructing automatically the quantitative structure model of every tree in a forest plot from terrestrial laser scanner data. A new feature is the automatic extraction of individual trees from the point cloud. The method is tested with a 30-m diameter English oak plot and a 80-m diameter Australian eucalyptus plot. For the oak plot the total biomass was overestimated by about 17 %, when compared to allometry (N = 15), and the modelling time was about 100 min with a laptop. For the eucalyptus plot the total biomass was overestimated by about 8.5 %, when compared to a destructive reference (N = 27), and the modelling time was about 160 min. The method provides accurate and fast tree modelling abilities for, e.g., biomass estimation and ground truth data for airborne measurements at a massive ground scale.

Calcium biominerals in typical Argiudolls from the Pampean Plain, Argentina: An approach to the understanding of their role within the calcium biogeochemical cycle

The aims of this work are: (a) to describe the presence of calcium oxalate crystals from fungus and vegetal origin; (b) to determine the contribution from leaves; and (c) to assess the role they could play within the calcium biogeochemical cycle, in typical Argiudolls with different vegetal cover in the Pampean Plain, Argentina. Two plots with different vegetation were investigated: Acacia melanoxylon– Celtis tala and Eucalyptus globulus– Celtis tala. Leaves of the vegetation species were diaphanized and cleared with sodium hypochlorite (50%). Leaves and mycelial mats of the organic horizons were analyzed by optical, petrographic and scanning electronic microscopy. Soil samples were taken to determine particle size distribution and mineralogy, and to test calcium concentration by UV–vis spectrophotometry both in the soils’ saturated paste extract and in leached soil. Different morphologies of weddellite (i.e., primary nuclei, rosettes and druses) in the fungus hyphae were observed. Calcium oxalate crystal production was highest in A. melanoxylon and C. tala. Ca–Na feldspars are the only minerals that could release calcium to the system, but show no features of weathering. Calcium concentration in soil solution was higher in the Eucalyptus plot than in the Acacia, and it decreased from the organic to the mineral soil horizons. Fungus and vegetal calcium biomineral production, in addition to their higher susceptibility to weathering than minerals of inorganic origin, represents an important contribution to the calcium biogeochemical cycle.

Estimation of Forest Plantation Productivity Using a Physiologically Based Model Driven with Meteorological Data and Satellite-derived Estimates of Canopy Photosynthetic Capacity

Within the framework of Kyoto protocol, carbon sink concept is a major topic for the global climate change. There is an urgent need to collect some necessary data on the forest plantations. Therefore, there is a clear need to develop methods for estimating the biomass at diverse sites simply with non- destructive methods. Modeling is one of effective approaches and Process Based Models (PBMs) can provide a better understanding of stand growth and dynamics. A one simplified model of PBMs is 3PG model and modified one is 3PGS model; Physiological Principles Predicting Growth with Satellite data (1). The model enables to use parameters derived from satellite data such as Fraction of absorbed Photosynthetically Active Radiation (FPAR) as well as meteorological data. The objective of this study is to compare between 3PG model and 3PGS model by estimating above ground biomass (Wabv). Landsat Enhanced Thematic Mapper-Plus (ETM+) data were used for the model implementation. The estimated parameters were validated with the ground-measured values. Field measurements were conducted in Eucalyptus camaldulensis and Acacia mangium plantation. The 3PGS model outputs showed that there was very good relationship between measured (ground-based measurements) and simulated (modeled) values. Root mean square errors (RMSE) of 3PGS model results were less than the RSME of 3PG model results in Eucalyptus plot. The result applied for Acacia mangium showed it had higher RMSE between measured and simulated values than the result applied for Eucalyptus camaldulensis. The results indicate that the 3PGS model can provide reasonable estimates of Wabv.

Hydrological implications of soil water-repellency in Eucalyptus globulus forests, north-central Portugal

Soil water-repellency (hydrophobicity) is a widespread property of Eucalyptus globulus and Pinus pinaster forest soils in central and north littoral Portugal and is particularly severe during the summer dry conditions. This paper attempts to assess the impact of water repellency on overland flow and runoff generation at plot and catchment scales for two types of terrain with differing land management and degree of soil hydrophobicity: (i) highly hydrophobic land with regenerating eucalyptus forest following fire; and (ii) largely hydrophilic land on which deep-ploughing prior to planting eucalyptus seedlings had eliminated hydrophobicity. Overland flow responses were monitored over a 40-month period for two 8m×2m plots and streamflow was recorded continuously at gauging stations for two small catchments of predominantly regrowth eucalyptus and ploughed/planted eucalyptus, respectively. Soil hydrophobicity was assessed using the Water Drop Penetration Time (WDPT) test. Seasonal variations in the factors influencing plot overland flow response were assessed for each land management type using multivariate analysis. For the regrowth eucalyptus plot, overland flow generation was found to be negatively correlated with antecedent soil moisture in summer (suggesting that hydrophobicity-linked Hortonian overland flow is then dominant), but positively related to throughflow in winter (suggesting that saturation overland flow generation in a hydrophilic-phase soil was at that time the dominant mechanism). In the ploughed/planted areas, negative correlations with soil moisture were found neither in summer nor winter. Rainfall amount (and in winter also antecedent precipitation) were found to be the variables most strongly and positively related to overland flow volume. The plot results are compared with streamflow responses for the small catchments.

Soil phosphorus pools and supply under the influence of Eucalyptus saligna and nitrogen-fixing Albizia facaltaria

Replicated plantations of Eucalyptus saligna (Sm.) and Albizia falcataria (L.) Fosberg were examined for patterns in soil phosphorus (P) fractions and soil P availability. The supply of P was assessed in the field with anion exchange resin bags, which indicated that P supply was about twice as high under Eucalyptus as under Albizia. In the laboratory, solution P extracted with iron oxide-impregnated paper strips was also 45% higher under Eucalyptus. The effects of mixtures of the two species were intermediate between the pure-species effects. Overall, P supply either increased with Eucalyptus or decreased under Albizia. Despite significantly lower soil P availability, the Albizia plots appeared to take up and cycle as much P as the Eucalyptus plots, indicating that P supply was not independent of P demand. High rates of P uptake by Albizia may depend on higher allocations of carbohydrate to belowground production.

Change in soil macrofauna and vegetation when fast-growing trees are planted on savanna soils

Many forest species can be found in understory vegetation of old plantation plots, despite the fact that the native vegetation was a poor savanna growing on highly nonfertile sandy soils. The aim of the present paper is to describe the changes that occur in the environmental conditions when savanna is planted with fast-growing trees, and is particularly concerned with vegetation and soil macrofauna. The study was carried out in industrial eucalyptus plantations, and in experimental Acacia and pine plantations. Most plots were located on sandy soil, but some measurements were also carried out on clay soil planted with the same species in order to assess the influence of soil type. A strong correlation was shown between the age of the eucalyptus trees and the percentage of forest species in undergrowth, emphasizing the progressive change from savanna vegetation towards forest vegetation. Biomass and density of macrofauna were very low in both sandy and clayey savanna soils, total biomass being 3.3 and 5.8 g/m 2 respectively. Soil macrofauna became more important as the age of plantations increased, and biomass reached 29 g/m 2 in the 20-year-old eucalyptus plot on sandy soil, and 74 g/m 2 in 26-year-old eucalyptus plantation on clay soil, compared to 33 g/m 2 in the natural forest plot on sandy soil; however, frequency of occurrence and number of taxa were lower in old eucalyptus plot as compared to forest. Large differences in the abundance of macrofauna were observed in relation to planted species. Acacia was most favourable to soil macrofauna, with a total biomass of 60 g/m 2 on sandy soil and many taxa present. Pine plantations had a poor macrofauna and several taxa were lacking, particularly in the sandy soil. Total macrofauna frequency was significantly correlated with the percentage of forest species in understory vegetation. Both were correlated with soil pH and soil organic-matter content. The results suggest that soil organic matter and litter quality are of main importance in changing the above- and below-ground habitat in plantations.

Short-rotation biomass trial of mixed and pure stands of nitrogen-fixing trees and Eucalyptus grandis

Summary Mixtures with nitrogen-fixing tree species may alleviate the need for N fertilizer in Eucalyptus plantations, but questions remain as to how growth and yield are affected. In this five-year trial grown at sea level, Eucalyptus grandis was planted alone and in combination with an N-fixing species; either a Leucaena hybrid, Paraserianthes falcataria, or Enterolobium cyclocarpum, by alternating tree types within rows. The N-fixing species were also grown in pure stands. All trees were initially coppiced after the first year and then harvested on one, two and four-year rotations. Mean annual increments (MAI) at one, two and four-year rotations averaged 8.2, 15.6, and 15.5 Mg ha−1 yr−1 total biomass dry matter, respectively. Several mixed plantings equalled or exceeded the pure Eucalyptus plots in yield. Two-year old P. falcataria plots had the highest MAI at 21.6 Mg ha−1 yr−1. Stem diameter (DBH) was the best predictor of tree biomass, and height explained significant additional variation only for leucaena. Separate allometric equations were developed for each Eucalyptus treatment to account for differences in height, DBH, leaf biomass, and leaf+stem biomass. Separate equations to predict biomass were required because of differences in Eucalyptus morphology related to inter-specific competition with E. cyclocarpum. It is concluded that mixtures of Eucalyptus with N-fixing trees can equal biomass yields of pure Eucalyptus.