Eucalyptus Plantations In Brazil Research Articles

Green deserts, but not always: A global synthesis of native woody species regeneration under tropical tree monocultures.

Tree monocultures constitute an increasing fraction of the global tree cover and are the dominant tree-growing strategy of forest landscape restoration commitments. Their advantages to produce timber are well known, but their value for biodiversity is highly controversial and context dependent. Therefore, understanding whether, and in which conditions, they can harbor native species regeneration is crucial. Here, we conducted meta-analyses based on a global survey of the literature and on a database created with local, unpublished studies throughout Brazil to evaluate the regeneration potential of native species under tree monocultures and the way management influences this regeneration. Native woody species regeneration under tree monocultures harbors a substantial fraction of the diversity (on average 40% and 68% in the global and Brazilian surveys, respectively) and abundance (on average 25% and 60% in the global and Brazilian surveys, respectively) of regeneration observed in natural forests. Plantations with longer rotation lengths, composed of native tree species, and located adjacent to forest remnants harbor more species. Pine plantations harbor more native individuals than eucalypt plantations, and the abundance of regenerating trees is higher in sites with higher mean temperatures. Species-area curves revealed that the number of woody species under pine and eucalypt plantations in Brazil is 606 and 598 species, respectively, over an aggregated sampled area of ca. 12 ha. We highlight that the understory of tree monocultures can harbor a considerable diversity of regenerating native species at the landscape and regional scales, but this diversity strongly depends on management. Long-rotation length and favorable location are key factors for woody regeneration success under tropical tree monocultures. Therefore, tree monocultures can play a role in forest landscape restoration and conservation, but only if they are planned and managed for achieving this purpose.

Developing indicators for biodiversity monitoring in short rotation tree plantations

Global biodiversity loss has increased societal expectation to businesses to assess and manage their dependencies on biodiversity and transparently report their biodiversity impacts. Various global frameworks have been developed to manage risks and|or report the impacts. The metrics and indicators of the global frameworks are generic in nature and do not necessarily capture local biodiversity impacts. Stora Enso has publicly declared in our Sustainability Strategy an ambition to have a net positive impact on biodiversity. For short rotation plantations Stora Enso has set an objective to develop granular, yet practical and applicable indicators for monitoring and reporting biodiversity impacts and developments over time. The selection of indicators needs to reflect the connection between biodiversity management actions and outcomes, i.e. that: i) there are purposeful biodiversity measures in place that ii) result in monitorable outcomes. Hence Stora Enso in collaboration with the joint venture partners in Veracel and Montes del Plata has developed biodiversity indicators adapted to the local conditions for the Eucalypt plantations in Brazil and Uruguay, respectively. The overarching goal is to have indicators that reflect that the environmental and biodiversity measures that are integrated in the management of the plantations have real and measurable effects promoting landscape level biodiversity. The selected biodiversity indicators meet the following criteria: Science-based, measurable and quantifiable, reliable, recurrent, and cost-effective monitoring to follow trends over time. With biodiversity indicators in place, Stora Enso wishes to further the development of adaptive biodiversity management. This means to continuously monitor biodiversity management performance, via the indicators, to enable further adaptation and development of biodiversity positive actions. The indicators will be publicly published to provide full transparency. In preparation for launching the indicators in the fall 2023, the intention at this conference is to present the indicators and consult with the audience on their purposefulness.

Light use efficiency declines with water deficit and age in Eucalyptus plantations across Brazil

Eucalyptus plantations in Brazil are among the world’s most productive forests. We examined how differences in growth across an 1100 km environmental gradient related to light use and light use efficiency for 11 tropical Eucalyptus plantations, with the same 11 clones planted at each site. The long geographic gradient led to differences in precipitation, temperature, and soils, giving annual water deficits ranging from 40 to 500 mm yr−1. Mean annual increment (MAI) declined by about 2.2 Mg ha−1 yr−1 for each 100 mm yr−1 increase in water deficit. Across sites, about one-fourth of the differences in MAI related to light use (absorbed photosynthetically active radiation, APAR), and three-fourths to light use efficiency (LUE, wood growth per unit of light absorbed),. Light use did not relate to water deficit, so the decline in MAI resulted from a 0.1 g MJ−1 decline in LUE for each 100 mm yr−1 increase in water deficit. Though APAR accounted for a minor part of the decline in growth across sites, differences in both APAR and LUE among clones were important within each site. The pattern in wood growth per unit of light use likely includes the effects of water deficit on both total carbon (C) gain per unit of light use and partitioning of C belowground. A next step in harnessing production ecology insights for silviculture and breeding may be direct assessments of belowground partitioning (and perhaps respiration), and how opportunities vary with site conditions.

A system lock-in blocks the uptake of mixed sustainable Eucalyptus plantations in Brazil

Forest plantation areas across the globe are increasing in size and in 2019 Eucalyptus monocultures in Brazil covered 6.97 million hectares (0.8%). These monocultures hardly provide ecosystem services and do not support wildlife habitats. A transition towards more sustainable Eucalyptus plantations is urgently needed to support the provisioning of ecosystem services and conserve biodiversity. This transition requires the development of sustainable business models. We studied the upscaling of sustainable Eucalyptus plantation alternatives in Brazil, by analysing the potential barriers that need to be overcome using the Technological Innovation Systems perspective and semi-structured interviews of relevant stakeholders across the Eucalyptus value chain. Although the provisioning of ecosystem services is improved by alternative plantation management, we identified four blocking mechanisms that inhibit the functioning of the innovation system and as such hamper upscaling; 1) the productivist approach by incumbent actors on plantation management that is focussing only on short-term profit maximisation and results in a strong resistance to change current practices, 2) the weak societal and governmental vision that does not put sufficient pressure to change practices, 3) additional certification to support alternatives is in its infacy to develop niche markets which also hampers the development of financial support, and 4) failed demonstration projects in the past that have led to a lack of proof of concept for further experimentation and knowledge development. These barriers combined lead to a system lock-in, resistant to change and not capable for a diffusion of sustainable alternatives. We conclude that the directionality of a sustainability transformation should be enhanced by formulating long-term goals and strong commitment of public and private actors. We discuss how a mission oriented approach could foster such directionality for the urgently needed regime transformation in Eucalyptus paper and pulp production.

Potassium limitation of forest productivity – Part 1: A mechanistic model simulating the effects of potassium availability on canopy carbon and water fluxes in tropical eucalypt stands

Abstract. The extent of the potassium (K) limitation of forest productivity is probably more widespread than previously thought, and K limitation could influence the response of forests to future global changes. To understand the effects of K limitation on forest primary production, we have developed the first ecophysiological model simulating the K cycle and its interactions with the carbon (C) and water cycles. We focused on the limitation of the gross primary productivity (GPP) by K availability in tropical eucalypt plantations in Brazil. We used results from stand-scale fertilisation experiments as well as C flux measurements in two tropical eucalypt plantations to parameterise the model. The model was parameterised for fertilised conditions and then used to test for the effects of contrasting additions of K fertiliser. Simulations showed that K deficiency limits GPP by more than 50 % during a 6-year rotation, a value in agreement with estimations in K-limited eucalypt stands. Simulations showed a decrease of modelled canopy transpiration of around 50 % and a decrease in modelled water-use efficiency WUEGPP of 10 %. Through a sensitivity analysis, we used the model to identify the most critical processes to consider when studying K limitation of GPP. The inputs of K to the stands, such as the atmospheric deposition and weathering fluxes, and the regulation of the cycle of K within the ecosystem were critical for the response of the system to K deficiency. Litter leaching processes were of lower importance, since residence time of K in litter was low. The new forest K-cycle model developed in the present study includes multiple K processes interacting with the carbon and water cycles, and strong feedbacks on GPP were outlined. This is a first step in identifying the source or sink limitation of forest growth by K.

From the dual cyclone harvest performance of single conidium powder to the effect of Metarhizium anisopliae on the management of Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae).

Insect pests introduced in eucalyptus plantations in Brazil are mostly of Australian origin, but native microorganisms have potential for their management. High quality biopesticide production based on entomopathogenic fungi depends on adequate technologies. The objective of this study was to evaluate Mycoharvester® equipment to harvest and separating particles to obtain pure Metarhizium anisopliae conidia to manage Thaumastocoris peregrinus Carpintero & Dellapé, 2006 (Hemiptera: Thaumastocoridae). The Mycoharvester® version 5b harvested and separated M. anisopliae spores. The pure conidia were suspended in Tween 80® (0.1%) and calibrated to the concentrations of 1 x 106, 107, 108 and 109 conidia/ml to evaluate the pathogenicity, lethal concentration 50 and 90 (LC50, LC90) and lethal time 50 and 90 (LT50, LT90) of this fungus to T. peregrinus. This equipment harvested 85% of the conidia from rice, with production of 4.8 ± 0.38 x 109 conidia/g dry mass of substrate + fungus. The water content of 6.36% of the single spore powder (pure conidia) separated by the Mycoharvester® was lower than that of the agglomerated product. The product harvested at the concentrations of 108 and 109 conidia/ml caused high mortality to T. peregrinus third instar nymphs and adults. The separation of conidia produced by solid-state fermentation with the Mycoharvester® is an important step toward optimizing the fungal production system of pure conidia, and to formulate biopesticides for insect pest management.

Rethinking the nature of intraspecific variability and its consequences on species coexistence.

Intraspecific variability (IV) has been proposed to explain species coexistence in diverse communities. Assuming, sometimes implicitly, that conspecific individuals can perform differently in the same environment and that IV increases niche overlap, previous studies have found contrasting results regarding the effect of IV on species coexistence. We aim at showing that the large IV observed in data does not mean that conspecific individuals are necessarily different in their response to the environment and that the role of high-dimensional environmental variation in determining IV has largely remained unexplored in forest plant communities. We first used a simulation experiment where an individual attribute is derived from a high-dimensional model, representing "perfect knowledge" of individual response to the environment, to illustrate how large observed IV can result from "imperfect knowledge" of the environment. Second, using growth data from clonal Eucalyptus plantations in Brazil, we estimated a major contribution of the environment in determining individual growth. Third, using tree growth data from long-term tropical forest inventories in French Guiana, Panama and India, we showed that tree growth in tropical forests is structured spatially and that despite a large observed IV at the population level, conspecific individuals perform more similarly locally than compared with heterospecific individuals. As the number of environmental dimensions that are well quantified at fine scale is generally lower than the actual number of dimensions influencing individual attributes, a great part of observed IV might be represented as random variation across individuals when in fact it is environmentally driven. This mis-representation has important consequences for inference about community dynamics. We emphasize that observed IV does not necessarily impact species coexistence per se but can reveal species response to high-dimensional environment, which is consistent with niche theory and the observation of the many differences between species in nature.

Assessing the nutritional status of Southern Brazilian Eucalyptus plantations by the CND method

Genus Eucalyptus can be grown in different soils worldwide, although it is not always ready to fulfill plants’ nutrient demands. Whenever such nutrient shortage happens, it is necessary applying the nutrients missing, which can be established based on the critical levels and sufficiency ranges (SRs) of nutrients in leaves or by multivariate mathematical models, such as the composition nutrient diagnosis (CND). This study aimed to investigate the nutritional status of Eucalyptus plantations in Brazil, based on the CND method. A total of 119 12-month-old Eucalyptus saligna (E. saligna) plantations were sampled in the Rio Grande do Sul State (RS), Southern Brazil. Nutrient concentration in leaves and the diameter at breast height (DBH) was measured. The E. saligna nutritional status was calculated through the CND method. High- and low-yield populations were set based on DBH of 4.2 cm. The SRs proposed by the CND method were narrower than the ones proposed by official recommendations for Eucalyptus, especially for magnesium (Mg), boron (B), and iron (Fe). The CND-r2 index recorded for each nutrient generated a limitation order for nutrients. The greater accuracy of the recommendations proposed by the CND method, compared with univariate and bivariate methods, contribute to reducing the use of fertilizers.

Low nutrient losses by deep leaching after clearcutting and replanting Eucalyptus plantations in Brazil

Sustainable management of highly productive eucalypt plantations requires the application of fertilizers to balance nutrient exports associated with biomass removal every 6-7 years. Although deep leaching after clear-cutting is an important component of input-output budgets of nutrients in forest soils, accurate quantifications are rare in tropical plantations. Our study aimed to assess the consequences of management practices in highly productive eucalypt plantations on nutrient losses by deep leaching in two hillslope positions with contrasting soil types. Soil solutions were continuously collected using lysimeters down to a depth of 3 m, in the last year before the clear-cutting, then in the first 3.5 years after replanting. Concentrations of the main cations and anions were determined monthly and fluxes of gravitational solutions at the depths where the lysimeters were installed were estimated using the Hydrus 1D model, calibrated in situ. Stand productivity was high in both landscape positions with a mean basal area at harvest of 35 m2 ha-1 at the bottom of the slope and 27 m2 ha-1 at the top of the slope. Soil solution chemistry in the topsoil was highly responsive to management practices with sharp increases in ionic charges after clearcutting and fertilizer applications. While leaching fluxes of mobile ions (especially N-NO3-, K+ and Mg2+) reached values greater than 30 kg ha-1 yr-1 at a depth of 1 m after clear-cutting, they remained lower than 3 kg ha-1 yr-1 at a depth of 3 m both in the upper and lower hillslope positions throughout the rotation. Our study suggests that splitting fertilizer applications may not be necessary in tropical Eucalyptus plantations established in very deep tropical soils.

Potassium fertilization enhances xylem plasticity and growth recovery of Eucalyptus grandis trees in response to drastic changes in water availability

Most Eucalyptus plantations in Brazil are located in regions currently experiencing periods of water shortage, where fertilizers such as potassium (K) are intensively used to achieve high productivity. In a changing environment, improving our understanding of the effects of K nutrition on tree growth rates and xylem plasticity across tree ages as a function of climate is crucial for forest management. The objective of this study was to gain insight into the interactive effects of K fertilization, water availability, and tree age on stem growth and changes in xylem traits of E. grandis trees over a full rotation. Changes in growth and xylem traits in response to a severe drought that occurred in 2014 were also studied. An experimental plantation of E. grandis trees was established in São Paulo, Brazil and monitored over a full 6-year rotation period. The experiment consisted of a split-plot design with two water supply regimes (37 % throughfall reduction vs undisturbed throughfall) and two fertilization regimes (K supply vs control). Basal area increment (BAI) was monitored using band dendrometers at 14-day intervals from 1 to 6 years after planting. Xylem traits including wood density (WD), cell wall fraction (CWF), cell density (CDen), theoretical xylem specific hydraulic conductivity (Kst), vessel diameter (VD), vessel density (VDen), vessel area (VA), and the vulnerability index (VI) were measured in 6-month periods (rainy and dry seasons) throughout the rotation. K fertilization increased BAI by a factor of 3 in plots where throughfall was not disturbed but led to an interruption of tree growth during the severe drought in 2014. The growth patterns showed a positive effect of K for growth recovery following drought. Throughfall reduction affected growth only in K-fertilized trees and up to 30 months of age. K fertilization also increased changes in xylem traits in response to drought in E. grandis trees. The main changes occurred in vessel traits, with a 53 % decrease in Kst during the drought but recovery was rapid after the first rainfall events. High plasticity was also observed for WD, CWF, CDen, and VI.

Draft Genome Sequence of Calonectria pteridis, the Causal Agent of Calonectria Leaf Blight on Eucalyptus.

ABSTRACTHere, we report the draft genome sequence of Calonectria pteridis, the causal agent of Calonectria leaf blight in eucalyptus plantations in Brazil. The 58,373,473-bp genome assembly consists of 1,167 scaffolds, with a GC content of 50.21%. These genomic data can contribute to future studies involving the biology, adaptability, and pathogenicity of C. pteridis.

Using multi-temporal tree inventory data in eucalypt forestry to benchmark global high-resolution canopy height models. A showcase in Mato Grosso, Brazil

The global monitoring of forest structure worldwide is increasingly being supported by refined and enhanced satellite mission datasets. Forest canopy height is a global metric to characterise and monitor dynamics in forest ecosystems worldwide. Satellite mapping missions as NASA's Global Ecosystem Dynamics Investigation (GEDI) are creating opportunities to refine global forest canopy height models adding forest structural information to time-series satellite imagery. A recent global canopy height model presented by Lang et al., (2022) using GEDI and 10-m Sentinel-2 and the map from Potapov et al., (2020) using GEDI and Landsat are both tested in this study using multi-temporal tree-level data collected over eucalypt plantations in Brazil. Our results at plot-level showed Lang et al., (2022)’s estimates of canopy height came short compared to 2020 maximum and mean tree height records in the plots, 7.6 and 3.6 m, respectively, but adding CHM standard deviation improves the agreement of ground records for maximum tree height. Higher errors were computed for the plots in 2019 using the Potapov's 30-m CHM: 14.2 and 9.5 m, respectively. Averaged stand values were more similar between the three sources tested. We report improvement from the 30-m CHM to the 10-m, but still height saturation problems were observed when accounting for height differences in tall eucalypt trees. As more global products for forest height and biomass are becoming available to users, more validation exercises as presented in this study are needed to assess the suitability of CHM products to forestry needs, and facilitate the uptake and actionability of the next generation of global height and biomass products. We provide recommendations and insights on the use of GEDI laser data for global mapping and on the potential of commercial forestry areas to benchmark the accuracy of satellite mapping missions focusing on tree height estimation in the tropics.

Growth and canopy traits affected by myrtle rust (Austropuccinia psidii Winter) in Eucalyptus grandis x Eucalyptus urophylla

AbstractAustropuccinia psidii Winter, causal agent of myrtle rust, is one of the main pathogens in Eucalyptus plantations in Brazil. We investigated the effects of the pathogen on wood yield and light use efficiency (LUE) in a Eucalyptus grandis x Eucalyptus urophylla clone in a field trial at the end of a five‐year rotation. The study comprised two treatments that are commonly adopted by managers. One treatment with curative fungicide spray (Triadimenol 250 g l−1) seven months after planting and another with five preventive sprays of the same fungicide, from the 1st to 7th month age of saplings. At 5 years old, the control plots attained a mean annual increment of 35 m³ ha−1 yr−1, the curative and preventive treatments were 39 and 47 m³ ha−1 yr−1 (11% and 34% higher, respectively). LUE was also higher when fungicides were applied, 8% and 26% higher in curative and preventive treatments (1.06 and 1.24 g MJ−1) compared with the control plots (0.98 g MJ−1). To confirm the negative effect of rust at a larger scale, we tracked 102 inventory plots (from 1,234 ha) from 2 to 6 years old with the same clone, half infected and half with rust corrective control. Growth difference decreased with time, from an average of 41% at age 2%–5% at age 6. These results highlight the importance of managing myrtle rust in Eucalyptus plantations by selecting a disease‐tolerant genotype or adopting other strategies for disease control.

Changes in microbial biomass and activity of tropical soil submitted to successive Eucalyptus rotations in the semi-arid region of Brazil

Soil microbial biomass (SMB) is considered an important indicator of changes in the soil organic carbon dynamics. Although there are several studies on SMB in Eucalyptus plantations in Brazil, there are still no records of investigations which have evaluated the effect of successive crop rotations on soil microbial biomass. Therefore, the aim of this study was to evaluate changes in the biomass and microbial activity of tropical soil submitted to successive Eucalyptus cultivation rotations. The study was carried out in commercial plantations of Eucalyptus urophylla in the first, second and third rotations (area cultivated 4, 9 and 15 years ago, respectively) using a fragment of native forest as a reference. Soil collections were performed at a depth of 0–10 cm. The carbon and nitrogen contents of the soil microbial biomass were determined by the fumigation-extraction method and the soil microbial activity was based on the amount of CO2 evolved. The increase in Eucalyptus cultivation time caused increases in litter accumulation and soil organic carbon, which represented an increase of 50% in rotation 1 compared to rotations 2 and 3. This was reflected in increases in C immobilization in microbial biomass (MB-C) and in the efficiency of converting organic carbon to MB-C and reducing soil carbon losses. Following a similar pattern, the microbial biomass carbon (MB-C) levels showed increases of 52 and 47% in rotation 3 in relation to rotation 1 and 2, respectively. Only the metabolic quotient among the microbiological indices was sensitive to the Eucalyptus cultivation time, with a significant reduction in rotation 3 (131.0 mg g−1 day) compared to rotations 1 and 2 (average of 269.1 mg g−1 day). The change imposed by the progressive increase in the Eucalyptus cultivation time positively influenced the activity and C transformation of SMB.

Very Low Nutrient Losses by Deep Leaching after Clearcutting Commercial Eucalyptus Plantations in Brazil

Very Low Nutrient Losses by Deep Leaching after Clearcutting Commercial Eucalyptus Plantations in Brazil

Prognosis of forest production using machine learning techniques

Forest production and growth are obtained from statistical models that allow the generation of information at the tree or forest stand level. Although the use of regression models is common in forest measurement, there is a constant search for estimation procedures that provide greater accuracy. Recently, machine learning techniques have been used with satisfactory performance in measuring forests. However, methods such as Adaptive Neuro-Fuzzy Inference System (ANFIS) and Random Forest are relatively poorly studied for predicting the volume of wood in eucalyptus plantations in Brazil. Therefore, it is essential to check whether these techniques can provide gains in terms of accuracy. Thus, this study aimed to evaluate the use of Random Forest and ANFIS techniques in the prognosis of forest production. The data used come from continuous forest inventories carried out in stands of eucalyptus clones. The data were divided into 70% for training and 30% for validation. The algorithms used to generate rules in ANFIS were Subtractive Clustering and Fuzzy-C-Means. Besides, training was done with the hybrid algorithm (descending gradient and least squares) with the number of seasons ranging from 1 to 20. Several RFs were trained, varying the number of trees from 50 to 850 and the number of observations by five leaves to 35. Artificial neural networks and decision trees were also trained to compare the feasibility of the techniques. The evaluation of the estimates generated by the techniques for training and validation was calculated based on the following statistics: correlation coefficient (r), relative Bias (RB), and the relative root mean square error (RRMSE) in percentage. In general, the techniques studied in this work showed excellent performance for the training and validation data set with RRMSE values <6%, RB < 0.5%, and r > 0.98. The RF presented inferior statistics about the ANFIS for the prognosis of forest production. The Subtractive Clustering (SC) and Fuzzy-C-Means (FCM) algorithms provide accurate baseline and volume projection estimates; both techniques are good alternatives for selecting variables used in modeling forest production.

First record of a new microsporidium pathogenic to Gonipterus platensis in Brazil

Microsporidia are naturally occurring fungal-related parasites that can infect nearly all animal hosts, but their biocontrol potential of insect pests is routinely overlooked in agriculture and forestry. This research brings the first report describing the natural occurrence of a microsporidium causing disease in field-collected populations of the invasive eucalyptus snout beetle, Gonipterus platensis (Coleoptera: Curculionidae), a major destructive pest of eucalyptus plantations in Brazil. Adult beetles were collected during field surveys in commercial eucalyptus plantations in southern Brazil to be examined and dissected with typical symptoms to verify presence of microsporidian spores in haemolymph. From 14 plantations in different sites, the natural infection occurrence in these populations ranged from 0 to 65%, while a lab colony exhibited an infection incidence of 70%. Spore density in haemolymph of symptomatic insects averaged 2.1 (± 0.4) × 107 spores/beetle. Symptoms in infected adults were identified by an abnormal abdomen with malformation of the second pair of wings, impairing their flight activity. Electron transmission microscopy of the pathogen showed morphological features similar to species belonging to the genus Nosema or Vairimorpha. Phylogenetic analysis of the full-length small subunit ribosomal RNA gene suggests this pathogen’s placement in the genus Vairimorpha, but with a sequence identity of ~ 94% with the nearest neighbours. The low level of sequence identity suggests this pathogen may represent a novel taxon in the genus and further requires whole genome sequencing for definitive taxonomic resolution. These findings provide insights on the natural occurrence of this novel pathogen of this invasive pest in Eucalyptus plantations in Brazil. Further studies are needed to determine potential of this microsporidium in the design of conservative or augmentative biological control programs for this invasive pest.

Assessment of GEDI's LiDAR Data for the Estimation of Canopy Heights and Wood Volume of Eucalyptus Plantations in Brazil

Over the past two decades spaceborne LiDAR systems have gained momentum in the remote sensing community with their ability to accurately estimate canopy heights and aboveground biomass. This article aims at using the most recent global ecosystem dynamics investigation (GEDI) LiDAR system data to estimate the stand-scale dominant heights ( <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> ), and stand volume (V) of Eucalyptus plantations in Brazil. These plantations provide a valuable case study due to the homogenous canopy cover and the availability of precise field measurements. Several linear and nonlinear regression models were used for the estimation of <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> and V based on several GEDI metrics. <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> and V estimation results showed that over low-slopped terrain the most accurate estimates of <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> and V were obtained using the stepwise regression, with an root-mean-square error (RMSE) of 1.33 m (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 0.93) and 24.39 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .ha <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 0.90) respectively. The principal metric explaining more than 87% and 84% of the variability (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> and V was the metric representing the height above the ground at which 90% of the waveform energy occurs. Testing the postprocessed GEDI metric values issued from six available different processing algorithms showed that the accuracy on <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> and V estimates is algorithm dependent, with a 16% observed increase in RMSE on both variables using algorithm a5 vs. a1. Finally, the choice to select the ground return from the last detected mode or the stronger of the last two modes could also affect the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dom</sub> estimation accuracy with 12 cm RMSE decrease using the latter.

Quantifying turgor loss point and leaf water potential across contrasting Eucalyptus clones and sites within the TECHS research platform

Understanding the mechanisms governing drought tolerance in highly productive clonal Eucalyptus plantations in Brazil will become increasingly important with climate change driven increases in temperature and drought events. We quantified how leaf water potential, hydraulic safety margin (mid-day – pre-dawn leaf water potential, Ψδ) and the physiological parameters obtained from standard pressure–volume curves differed between four contrasting Eucalyptus genotypes across a temperature and water availability gradient in Brazil. We hypothesized that genotypes developed in dry areas were more drought tolerant and would exhibit lower mid-day leaf water potentials and turgor loss points than clones developed in wetter regions. Recognizing that standard pressure volume curves are time consuming and may not be a suitable screening tool for forest managers, we also tested if a key physiological parameter from the pressure–volume curve (turgor loss point, πtlp) could be accurately estimated from an osmometer as has been found in other species. We found no support for our first hypothesis; physiological parameters determined (including turgor loss point) from the pressure volume curves were not associated with the supposed drought tolerance of any of the clones. Similarly, mid-day leaf water potentials were not directly correlated with drought tolerance. The lack of support for our hypothesis may be because our measurements were taken during periods of minimum water stress. However, we did find that, overall, turgor loss point tended to be lower at the dry compared to wetter sites we studied suggesting that it may be a useful tool for assessing drought tolerance of Eucalyptus plantations in the future. We also found that estimates of osmotic potential at full turgor were similar between the pressure volume curve and osmometer techniques and that turgor loss point can be accurately estimated with an osmometer in highly productive Eucalyptus genotypes (R2 = 0.79).

Quantifying losses in productivity by the rust in eucalypt plantations in Brazil

The eucalyptus plantations in Brazil have been great importance in economy with 1.3% of the Gross Domestic Product, so their productivity has recently been extensively researched by the forestry. This productivity is affected by abiotic and biotic factors. Among the biotic factors we can highlight the rust, which attacks and generates large long-term losses in large scale. The aim of this paper is to measure the effect of the rust disease in eucalyptus stand by the statistical-models approach. Firstly, a new index named Rust Severity Index – RSI has been proposed. The index is a weighted average of the severity scale by the inverse of age in days. The generalized linear model has been used to model the effect of region/farm and severity of disease in maximum sample volume (m3) of the plantations. We also fit a generalized linear regression model to maximum sample volume (m3) of the plantations by the rust severity index. Finally, Gompertz nonlinear regressions models were fitted to the volume growth according to region/farm and rust severity. Then, it has been possible to measure the losses in volume (m3) due the rust severity by the percentage difference between the rust severity categories at 51st and 72nd months.