Eucalyptus In Brazil Research Articles

Harvesters’ productivity prediction in Brazilian Eucalyptus plantations: development of a model from machine learning

ABSTRACT Productivity analysis in mechanized harvesting has traditionally relied on statistical expertise and mathematical modeling. However, machine learning tools have emerged as a viable alternative, as they serve the same purpose, utilizing a combination of varied attributes (quantitative and qualitative) and handling large datasets. This study aimed to determine whether the inherent attributes of mechanized timber harvesting of Eucalyptus spp. plantations enable the creation of a high-performance model that can accurately predict productivity from machine learning. For the modeling, we considered five attributes concerning forest inventory, in addition to working hours and the operator experience level. We considered the productivity, timber harvested per working hour, as the target attribute of the modeling. We subjected the database to 17 common algorithms in default mode and compared them according to error metrics and accuracy. We also determined the relative importance of each attribute in the predictive model. The inherent attributes concerning mechanized timber harvesting of Eucalyptus spp. plantations evaluated in this study enable the creation of a high-performance model that can accurately predict productivity from machine learning. The Gradient boosting model in ensemble mode can predict the productivity of harvesters in Eucalyptus spp. plantations with an R2 of 0.81. The attributes that have greater relative importance are operator experience level, average individual tree volume, and stand density with 100%, 76.3%, and 65.8%, respectively.

Unveiling the Potential of Brazilian Eucalyptus for Transparent Wood Manufacturing via the Kraft Pulping Process as a Future Building Material

The emergence of transparent wood as a viable alternative to traditional glass has sparked considerable interest in recent research endeavors. Despite advancements, challenges persist in the delignification methods and wood species utilized in prior studies. Therefore, this study delves into the potential of Brazilian eucalyptus wood for transparent wood production through the kraft pulping process. Delignification was carried out in a laboratory setting, replicating the kraft process with varying reaction times (15, 30, 45, and 60 min). The resulting delignified wood veneers were impregnated with a pre-polymerized PMMA solution. The study encompassed various analyses, including UV-Vis spectroscopy, colorimetry, SEM, optical microscopy, and mechanical property evaluations. The results revealed intriguing trends in terms of transparency, color changes, microstructural modifications, and mechanical properties as a function of delignification time. This work presents valuable insights into the transformative potential of eucalyptus wood, offering a deeper understanding of the interplay between wood modification and PMMA impregnation.

Comparison of thermal, rheological properties of Finnish Pinus sp. and Brazilian Eucalyptus sp. black liquors and their impact on recovery units

Black liquor (BL) is the major bioproduct and biomass fuel in pulp mill processes. However, the high viscosity of BL makes it a challenging material to work with, resulting in issues with evaporators and heat exchangers during its transport and processing. The thermal and rheological properties of BLs from Pinus sp. (PBL) and Eucalyptus sp. (EBL) were studied. FTIR spectra revealed the presence of the characteristic functional groups and the chemical composition in liquors. TGA/DTG curves showed three characteristic degradation stages related to evaporation of water, pyrolysis of organic groups, and condensation of char. Rheologically, liquors are classified as non-Newtonian and with comportment pseudoplastic. Their rheological dynamic shear properties included a linear viscoelastic region up to 1% shear strain, while frequency sweeps showed that storage modulus (Gʹ) > loss modulus (Gʹʹ), thus confirming the solid-like behavior of both BLs. The rheological study demonstrated that increasing the temperature and oscillatory deformations of PBL and EBL decreased their degree of viscoelasticity, which could favor their pumping and handling within the pulp mill, as well as the droplet formation and swelling characteristics in the recovery furnace.

First record of Trichogramma pretiosum parasitizing Iridopsis panopla eggs in eucalyptus in Brazil

Abstract Iridopsis panopla Prout (Lepidoptera: Geometridae) is an important lepidopteran defoliator of eucalyptus. I. panopla eggs were collected naturally in a commercial plantation of Eucalyptus urograndis W. Hill (Myrtaceae) in Três Lagoas, Mato Grosso do Sul, Brazil. After nine days, the natural emergence of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) occurred from I. panopla eggs. Parasitism was evaluated under laboratory and field conditions, this being the first record for eucalyptus in Brazil. Based on the biological characteristics evaluated in the laboratory, I. panopla eggs are suitable for T. pretiosum reproduction. The obtained percentage parasitism, particularly when 72,000 adult females of T. pretiosum per hectare were employed, provide valuable insights regarding the potential of T. pretiosum as an effective biological control agent against I. panopla in eucalyptus plantations.

Economic analysis of the feller buncher in Brazilian Eucalyptus plantations: modeling with time series

ABSTRACTIn the context of increased demand for timber, forest managers must consider best practices in forest management and harvesting operations. Depending on the harvesting systems adopted, the uncertainties of the cost components may reflect the volatility of productivity and the expected value of the project. We investigated whether the uncertainties of the cost components have an influence on the productivity volatility and the expected value of the mechanized timber harvesting investment project with a feller buncher. Monthly feller buncher productivity volatilities were measured based on the absolute value of the percentage variation in the deviation of the cost and productivity components. We modeled productivity and cost components using geometric Brownian motion to estimate project value. Productivity showed a strong positive correlation with the cost components of economic depreciation, supervisor labor, fuel, and operator labor. Lubricating oil and economic depreciation were the most volatile cost components. Considering the deterministic economic analysis, the net present value was USD 3,849,619. When considering the probabilistic economic analysis, the average net present value was USD 187,319 ± USD 1,275,033. We verified that economic depreciation and fuel influenced feller buncher productivity. The uncertainties of these components affect the economic viability of the feller buncher in Eucalyptus plantations.

Potassium limitation of forest productivity – Part 2: CASTANEA-MAESPA-K shows a reduction in photosynthesis rather than a stoichiometric limitation of tissue formation

Abstract. Potassium (K) availability constrains forest productivity. Brazilian eucalypt plantations are a good example of the K limitation of wood production. Here, we built upon a previously described model (CASTANEA-MAESPA-K) and used it to understand whether the simulated decline in C source under K deficiency was sufficient to explain the K limitation of wood productivity in Brazilian eucalypt plantations. We developed allocation schemes for both C and K and included these in CASTANEA-MAESPA-K. Neither direct limitations of the C-sink activity nor direct modifications of the C allocation by K availability were included in the model. Simulation results show that the model was successful in replicating the observed patterns of wood productivity limitation by K deficiency. Simulations also show that the response of net primary productivity (NPP) is not linear with increasing K fertilisation. Simulated stem carbon use and water use efficiencies decreased with decreasing levels of K availability. Simulating a direct stoichiometric limitation of NPP or wood growth was not necessary to reproduce the observed decline of productivity under K limitation, suggesting that K stoichiometric plasticity could be different to that of N and P. Confirming previous results from the literature, the model simulated an intense recirculation of K in the trees, suggesting that retranslocation processes were essential for tree functioning. Optimal K fertilisation levels calculated by the model were similar to nutritional recommendations currently applied in Brazilian eucalypt plantations, paving the way for validation of the model at a larger scale and of this approach for developing decision-making tools to improve fertilisation practices.

Draft Genome Sequence of the Plant Growth Promoter and Biocontrol Agent Bacillus velezensis Strain BIB0110.

Here, we report the draft genome sequence of Bacillus velezensis strain BIB0110, a broad-range biocontrol agent isolated from cultivated eucalyptus in Brazil. The genome has a size of 4.19 Mbp, with a GC content of 45.87%, and it was assembled into 32 scaffolds.

Climate change on Eucalyptus plantations and adaptive measures for sustainable forestry development across Brazil

The main challenges facing the Eucalyptus plantation industry are employing sustainable projects in suitable areas, and using safer forestry strategies, given climate variability and climate change. Brazil is the world’s largest Eucalyptus producer, and more areas have been allocated for Eucalyptus plantations, even in areas that are considered persistent climate change hotspots. Researchers can combine adequate agroclimatic zoning methods with Earth System Model (ESMs) outputs to analyze changes to climate variables, to map suitable areas, and to outline adaptive measures for Eucalyptus plantations. Despite these facts, studies on the Eucalyptus species are still scarce. This study analyzed the impacts of climate change to suitable areas for planting Eucalyptus in Brazil, using proper Agroclimatic Zoning (AZ) method, and outlining effective adaptive measures for sustainable Eucalyptus cultivation under future climate scenarios. Daily precipitation, air temperature (mean and maximum), and global solar radiation data were used from a set of simulations and projections of nine ESMs, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), in two Representative Concentration Pathway scenarios (RCP 4.5 and 8.5). The AZ method was simulated for the current climate (1980–2005), and projected for the near (2021–2050), and far future (2071–2100) climates, in two RCPs. Given intense and persistent changes to precipitation, air temperature, evapotranspiration, and water deficits, i.e., prolonged and continued changes to climate variables resulting from climate change, Eucalyptus plantations will be restricted and economically unfeasible for industrial purposes for about 15 % (RCP 4.5), to 47 % (RCP 8.5), of Brazil in the far future, covering a large part of the North, the north of the Center-West, and the northwestern part of the Northeast, including the new Brazilian agroforestry frontier (MATOPIBA). Only ∼12 % of Brazil, encompassing small areas of the South, the South-Southeast, and a small portion in the Northwest region of the North, will be suitable for Eucalyptus plantations, since these regions are less vulnerable to climate change. As for the rest of Brazil (between ∼42 % and ∼80 %), regular suitability is projected, and the future of Eucalyptus plantations in these places will depend on adopting ‘effective adaptive measures’ and making ‘safe silvicultural decisions’ in order to deal with projected temperature increases and water deficits, including genotypes selection, improvements in hybridization techniques or breeding programs, planting in wider spacings (or lower stockings), and thinning and pruning at shorter intervals.

Effects of pretreatments on the solubilization and theoretical methane production of waste activated sludge from a Brazilian eucalyptus kraft pulp mill

Waste activated sludge (WAS) originating from kraft pulp mill effluent treatment plants represents an important environmental challenge for this industry. Anaerobic digestion is a promising option for WAS treatment, with the added benefit of biogas production. This paper presents the application of thermal, thermal-alkaline, and mechanical pretreatment methods in order to promote the solubilization of organic matter to enhance the anaerobic digestion of the WAS from a Brazilian Eucalyptus bleached kraft pulp mill. A total of 16 pretreatment operating conditions were compared. Chemical analyses showed an improvement in organic matter solubilization, with an increase greater than 7-fold for soluble chemical oxygen demand and 4-fold for biochemical oxygen demand. Nutrient solubilization showed an increase greater than 10-fold for total Kjeldahl nitrogen and 3-fold for total phosphorus. Theoretical biochemical methane potential was improved from 211 mLCH4/gVS for raw sludge to 333-343 mLCH4/gVS after mechanical pretreatment, 314-360 mLCH4/gVS after thermal pretreatment, and 373-378 mLCH4/gVS after thermal-alkaline pretreatment. In general, thermal-alkaline pretreatment showed the best results for all the evaluated parameters, with the advantage of requiring lower temperature and retention time when compared to thermal conditions.

Effect of Feller-Buncher Model, Slope Class and Cutting Area on the Productivity and Costs of Whole Tree Harvesting in Brazilian Eucalyptus Stands

The operational productivity and costs of tree felling operations can be influenced by several factors, among which, the machine characteristics, slope class, the cutting area and the individual volume of the trees stand out. Thus, the main objective of the present study was to analyze the productivity and production cost for two feller-bunchers with different technical characteristics operating in a eucalyptus forest. The productivity was calculated from a time study and the factors analyzed were two feller-buncher models, two slope classes, and two cutting areas. The machine cost per scheduled hour was based on the methodology of the Food and Agriculture Organization of the United Nations. Analysis of the results showed that the felling and turn operational elements occupied the most time in the operational cycle of feller-bunchers. The machine cost per scheduled hour was USD 69.69 h−1 for feller-buncher 1 and USD 102.03 h−1 for feller-buncher 2. In conclusion, the distinct technical characteristics of feller-bunchers were found to influence the productivity and, consequently, the cost, of the felling operation during the harvesting of whole eucalyptus trees.

On-farm assessment of eucalypt yield gaps - a case study for the producing areas ofthe state of Minas Gerais, Brazil.

The concept of yield gaps provides a basis for identifying the main sources of production losses, caused by water or management deficiencies, which may help foresters and forest companies to better plan and make decisions in their areas. Thus, the aim of this study was to identify the magnitude and the major causes of yield gaps of eucalypts, being this the most planted forest genus in Brazil, in different producing regions of the state of Minas Gerais that has the largest planted area. To these ends, potential (Yp) and attainable (Ya) yields were simulated using the agroecological zone model (AEZ-FAO) adapted and calibrated for Brazilian eucalypt clones. Actual yield (Yr) data were obtained from 22 sites located in the state of Minas Gerais from 2009 to 2016, considering an average forest rotation of 6.7 years and plantings occurring between 2002 and 2010. From this, the total yield gap (YGtot), yield gap by water deficit (YGwd), and yield gap by sub-optimal management (YGman) were determined. The YGwd ranged from 37 to 69 m3 ha-1 year-1 across the 22 sites assessed, with an average value of 55 m3 ha-1 year-1. On the other hand, the YGman ranged from zero (optimal management) to 31 m3 ha-1 year-1. The eucalypt yield gap in commercial areas of Minas Gerais state was mainly caused by water deficit, which represented 77% of the total yield gap. On the other hand, the deficiencies in forest management accounted for 23% of the total yield gap.

Farmers' preferences for water-saving strategies in Brazilian eucalypt plantations

In a climate change context, changing temperature and precipitation patterns are expected to have strong impacts on Brazilian eucalypt plantations. Implementing adaptive water-efficient management practices is thus becoming necessary to maintain high levels of productivity while preserving the water resources. This paper investigates the ability of eucalypt farmers to modify their current silvicultural practices in order to adapt to drought in the near future. We ran a choice experiment in the state of Minas Gerais, among 80 eucalypt tree farmers, who were asked to choose from several management options associated with various financial supports. The results show that adaptation by reducing the length of the eucalypt rotation proves to be by far the preferred option, despite the associated costs. On the contrary, reducing density appears to be the least chosen option by the respondents, which may suggest that they underestimate the benefits of this strategy. We moreover find a clear and relevant segmentation of farmers' choice behavior, the general preference for reducing the length of the eucalypt rotation being driven by the most vulnerable farmers of the sample.

Nutrient deficiency enhances the rate of short-term belowground transfer of nitrogen from Acacia mangium to Eucalyptus trees in mixed-species plantations

While a recent study showed that significant amounts of the nitrogen (N) requirements of young Eucalyptus trees can be provided by nitrogen-fixing trees (NFTs) in mixed-species plantations through short-term belowground N transfer, the consequences of soil fertility on this facilitation process remain unknown. We assessed the effect of fertilization on the percentage of N derived from transfer (%NDFT) from Acacia mangium trees to Eucalyptus trees in mixed-species plantations. A complete randomized block design with two treatments (fertilized vs unfertilized) and three blocks was set up in mixed-species plantations of A. mangium and Eucalyptus in Brazil, with 50% of each species at 2.5 m × 2.5 m spacing. Collection of litterfall and forest floor made it possible to estimate the annual N release from forest floor decomposition between 46 and 58 months after planting, close to harvest age. 15N-NO3- was injected into the stem of one dominant Acacia tree in each plot, 58 months after planting. The x(15N) values of Acacia and Eucalyptus fine roots sampled within 1.8 m of the labelled A. mangium tree were determined at 7, 14, 30 and 60 days after labelling. The x(15N) values in wood, bark, branch and leaf samples were also determined for the 6 labelled Acacia trees and their two closest Eucalyptus neighbours, just before and 60 days after labelling. The amount of N released from forest floor decomposition was 31% higher in fertilized (F+) than in unfertilized (F-) plots. Sixty days after labelling, the aboveground compartments of Eucalyptus trees were significantly 15N enriched in both treatments. The x(15N) values of Acacia fine roots were higher than background values from 7 days after labelling onwards in F+ and 30 days after labelling in F-. The x(15N) values of Eucalyptus fine roots were higher than background values in both treatments, from 30 days after labelling onwards. Mean %NDFT values were 18.0% in F+ and 33.9% in F- over the first 60 days after labelling, and 22.8% in F+ and 67.7% in F- from 30 to 60 days after labelling. Fertilization decreased short-term transfer belowground of N from Acacia trees to Eucalyptus trees. Our study suggests that belowground facilitation processes providing N from NFTs to Eucalyptus trees in mixed-species plantations are more pronounced in low-fertility soils than in nutrient-supplied stands.

Quality planning of silvicultural operations in eucalyptus in Brazil

Quality planning of silvicultural operations in eucalyptus in Brazil

Influences of edaphoclimatic conditions on deep rooting and soil water availability in Brazilian Eucalyptus plantations

Brazilian roundwood industry is one of the most important and productive in the world, with Eucalyptus plantations alone representing 73% of the total planted forests. Deep rooting in these plantations represents a more common phenomena than generally expected. However, there is still a lack of information on environmental factors that drive root growth in deep soil layers, with particular emphasis on edaphoclimatic conditions, and related consequence in terms of soil water behavior. As a part of a larger project, this research aimed to investigate soil water and fine root system distribution in deep tropical soils under a commercial Eucalyptus plantation chronosequence. Along a 2800-km gradient (from south- to north-east Brazil), 14 experimental areas were planted with a “plastic” clone (E. urophylla) and investigated in terms of climatic conditions, soil and water features, and plant/stand development for an entire 6-years rotation period. Fine roots distribution were investigated in one site (in Brazil) till to 20 m deep at 3, 9, 24, 48, and 65 months after planting. Results showed a fast displacement of the root front down to 75, 325, 825, 1250, and 1575 cm at month 3, 9, 24, 48, and 65 after planting, respectively. Fine root densities (g cm−3) and proportional water capture exponentially decreased with soil depth. Deep fine roots showed a relativelly higher efficiency in acquiring water than the shallower, denser roots. The relationship between stand height vs root front depth followed an exponential trend, suggesting that these stands developed relatively faster in height rather than in depth during the first 48 months, with the opposite characterizing plantation afterwards. Regardless of stand age, E. urophylla trees rapidly explored a considerable volume of soil at a relatively limited carbon cost. Multivariate statistics showed that edaphoclimatic conditions play a major role in Eucalyptus plant/stand development. This study outlined the major role played by soil development. From poorly developed sandy Entisols, to medium developed Inceptisols, and to most developed fine textured Oxisols, both plant growth and stand productivity greatly improved accordingly. This study suggests that soil type, together with other environmental factors, are likely to influence both the development and behavior of Eucalyptus plantations for an extent greater than commonly anticipated.

How deep can ectomycorrhizas go? A case study on Pisolithus down to 4 meters in a Brazilian eucalypt plantation.

Despite the strong ecological importance of ectomycorrhizal (ECM) fungi, their vertical distribution remains poorly understood. To our knowledge, ECM structures associated with trees have never been reported indepths below2 meters. In this study, fine roots and ECM root tips were sampled down to 4-m depth during the digging of two independent pits differing by their water availability. A meta-barcoding approach based on Illumina sequencing of internal transcribed spacers (ITS1 and ITS2) was carried out on DNA extracted from root samples (fine roots and ECM root tips separately). ECM fungi dominated the root-associated fungal community, with more than 90% of sequences assigned to the genus Pisolithus. The morphological and barcoding results demonstrated, for the first time, the presence of ECM symbiosis down to 4-m. The molecular diversity of Pisolithus spp. was strongly dependent on depth, with soil pH and soil water content as primary drivers of the Pisolithus spp. structure. Altogether, our results highlight the importance to consider the ECM symbiosis in deep soil layers to improve our understanding of fine roots functioning in tropical soils.

Soil Disturbance Effects from Tethered Forwarding on Steep Slopes in Brazilian Eucalyptus Plantations

Traditional timber harvests on steep slopes have been conducted through labor-intensive and sometimes environmentally impactful methods, such as manual felling with chainsaws and extraction using bladed skid trails, winching, or cable yarding. Ground-based mechanized harvesting and primary transportation methods such as cut-to-length harvesters and forwarders have emerged in some parts of the world as low-impact, safe, and efficient alternatives to the aforementioned systems. However, when mechanized operations are used on steep terrain, problems such as poor stability, loss of traction, and increased soil disturbance can occur. Tethered or winch-assisted logging practices are being tested and applied in several countries to adapt to challenges associated with operating equipment on steep slopes while minimizing environmental impact. To better understand the feasibility of these systems, we conducted a designed experiment to quantify changes in soil properties and predicted erosion resulting from varying numbers of passes and payload levels by a forwarder operating on slopes ranging from 27 to 38 degrees. The machine was equipped with two different track configurations, tethered by either a machine-mounted or self-contained winch, in eucalyptus plantations in Brazil. On low slopes, bulk density significantly increased, but it did not increase on steeper slopes; this demonstrates traction winches’ effectiveness at reducing concentrated ground pressures. Rut depths were minimal and decreased with increasing slope classes due to reduced track slippage. Predicted erosion rates were high, primarily due to the extremely steep, long slopes and lack of adequate cover in some portions of the trail, illustrating the importance of proper erosion management practices on steep slopes.

Soil nutrient stocks are maintained over multiple rotations in Brazilian Eucalyptus plantations

Intensive management in tropical plantation forestry has increased global wood production per unit of time and land. Eucalyptus trees in southeastern Brazil grow exceptionally fast, even on the highly weathered and nutrient-poor soils of the Atlantic Forest and Cerrado biomes. By remeasuring plantation soils after twelve years and 1–2 rotations, we investigated how established plantations alter soil stocks of carbon, nitrogen, calcium, potassium, and phosphorus, and whether any changes might limit future plantation productivity. We hypothesized that each harvest cycle would deplete soil stocks of nitrogen, because less nitrogen is often added in fertilizer than is removed in wood, and that the balance between harvest and fertilizer would also dictate changes in stocks of other nutrients. In 2004 and 2016, we sampled soils to a depth of 100 cm in plantations and adjacent pastures and native vegetation reserves, and compared total nutrient stocks across time and vegetation type. We found that nutrients were not significantly depleted over time, and that soil stocks of carbon and nutrients in the plantations all tended to increase, with significant increases in the top 20 cm of 20% for potassium in the Atlantic Forest biome, and 23% for carbon and more than 500% for calcium in the Cerrado. Changes in soil nutrient stocks can be attributed in part to both fertilizer inputs and redistribution from changing stocks of biomass. We also observed changes over time and substantial spatial heterogeneity in nutrient stocks under non-plantation vegetation, highlighting the difficulties of using other vegetation types as static “controls” to assess the effects of plantations on soils. Overall, soil nutrient depletion does not appear to threaten sustainability in these intensive plantation forests over the time period studied.

Distance from the trunk and depth of uptake of labelled nitrate for dominant and suppressed trees in Brazilian Eucalyptus plantations: Consequences for fertilization practices

Climate changes will increase the probability of drought, which is likely to dramatically increase tree mortality. The capacity of trees to withdraw water in deep soil layers is an important trait likely to account for tree survival over prolonged droughts. Our study aimed to gain insight into the maximum distance from the trunk where Eucalyptus fine roots take up water and mobile nutrients in deep sandy soils during dry periods. NO3−-15N was injected in the soil at the end of the rainy season in commercial Eucalyptus stands planted with the same E. urophylla × E. grandis clone. The 15N tracer was applied in the middle of the inter-row (replicated in 3 plots): at 5 depths (from 0.1 to 6 m) at age 0.6 year, at 4 depths (from 0.1 to 9 m) at age 1.2 years, at 5 depths (from 0.1 to 12 m) at age 2.2 years, and at 6 depths (from 0.1 to 15 m) at age 6.4 years. δ15N was determined in leaves sampled in dominant and suppressed trees at different distances from each injection area, 4–5 months after NO3−-15N injection (after the dry season). While dominant trees took up NO3−-15N down to a depth of 6 m between 7 and 12 months after planting, the maximum depth of NO3−-15N uptake for suppressed trees was between 3 and 4.5 m. From 1.5 to 6 years after planting, a foliar enrichment in 15N was mainly detected when the NO3−-15N tracer was injected in the upper soil layers and only for a few trees at a depth of 6 m. Most of the uptake of 15N occurred within 2 m of horizontal distance from the injection site, whatever tree age and tree social status. Low amounts of NO3−-15N were taken up for injection sites located between 2 m and 5 m from the trunk, and 15N uptake was never detected at horizontal distances greater than 6 m from the trunk. Eucalyptus fine roots can take up nitrates at depths between 6 and 8 m the first year after planting. However, the NO3−-15N tracer injected at a depth of 6 m was only taken up by dominant trees and a 15N foliar enrichment of suppressed trees was only detected when the tracer was injected in the upper 3 m. Fertilizers must be applied within 2 m of the trunks in Eucalyptus plantations to be taken up by all trees, regardless of their social status. When fertilizations are concentrated the first months after planting in sandy soils, nutrient leaching in deep layers might increase the heterogeneity of the stands since mobile nutrients could only be taken up by dominant trees.

Life Table Parameters of the Zoophytophagous Predator Brontocoris tabidus (Heteroptera: Pentatomidae) on Introduced and Native Plants.

Brontocoris tabidus Signoret (Heteroptera: Pentatomidae) is a zoophytophagous predator of lepidopteran defoliators of eucalyptus in Brazil. This predator complements its diet with plants, which is fundamental for its population maintenance. The objective was to evaluate the B. tabidus development, reproduction, and life table parameters in the field on Eucalyptus cloeziana F. Muell. (T1), Psidium guajava Linn (Myrtales: Myrtaceae) (T2), or without plants (T3). The parameters estimated were: net reproductive rate (Ro); generation duration (DG); time for the population to double in size (TD); intrinsic population growth rate (rm), survival rate (lX), specific fertility (mx), life expectancy (ex), and mortality risk (qx). Ro, DG, TD, and rm were higher in the T1 and T2 than in T3. Plant presence favored the lx, mx, and qx. Ex values were 36.1 and 56.9 in the T3 and T1, respectively. The B. tabidus fertility, longevity, and life table parameters improvement on E. cloeziana and P. guajava plants are due to the water and nutrients obtained from them. B. tabidus can be reared with Tenebrio molitor Linnaeus (Coleoptara: Tenebrionidae) pupae on E. cloeziana or P. guajava plants in the field.