Use of Optimization Modeling to Assess the Effect of Timber and Carbon Pricing on Harvest Scheduling, Carbon Sequestration, and Net Present Value of Eucalyptus Plantations

Quantifying the impact of carbon (C) and timber prices on harvest scheduling and economic returns is essential to define strategies for the sustainable management of short-rotation plantations so that they can provide timber products and contribute to C sequestration. In this paper, we present a mixed-integer linear programming model that optimizes harvest scheduling at the forest level, C sequestration, and Net Present Value (NPV) over a planning period of up to 15 years. The model included revenue from the sale of timber (pulplogs) and credits from the net C sequestered during the life of the stands. In addition, plantation establishment, management, harvesting, and transportation costs were included in the analysis. The study area comprised 88 Eucalyptus grandis W. Hill and Eucalyptus dunnii Maiden stands located in Uruguay, totaling a forest area of nearly 1,882 ha. The study investigated the impact of C and timber prices on NPV, harvest schedules, stands’ harvest age, timber flows to customers, and C sequestered per period. The maximum NPV among all the scenarios evaluated (USD 7.53 M) was calculated for a C price of 30 USD t−1, an interest rate of 6%, and a timber price of 75 USD m−3. This was USD 2.14 M higher than the scenario with the same parameters but that included only revenue from timber. C prices also impacted stands’ harvest age, C sequestration, and timber flows delivered to end customers. On average, in scenarios that included C prices, timber flows and C sequestration increased by 15.4 and 12.1%, respectively, when C price increased from 5 to 30 USD t−1. These results demonstrate that harvest scheduling, harvest age, and NPV are very sensitive to C and timber, and that the best economic returns are obtained when the stands are managed to maximize timber production and C sequestration

Stand Characterization of Eucalyptus spp. Plantations in Uruguay Using Airborne Lidar Scanner Technology

Airborne lidar scanner (ALS) technology is used in a variety of applications, including forestry. ALS has enormous potential for the estimation of relevant biometric parameters in forest plantations. This study investigates the use of an object-oriented semi-automated segmentation algorithm for stands delineation, based on modeling ALS data, in plantations of Eucalyptus grandis and E. dunnii in Uruguay. The results show that non-parametric methods delivered more accurate and less biased results for total volume (TV) with R2 0.93, RMSE 20.04 m3 h−1 for E. grandis and R2 0.93, RMSE 18.43 m3 h−1 for E.dunnii; and above ground biomass (AGB) with R2 0.95, RMSE 70.2 kg h−1 for E. grandis and R2 0.96, RMSE: 71.2 Kg h−1 for E. dunnii. Parametric methods performed better for dominant height (Ho) with R2 0.98, RMSE 0.67 m and R2: 0.96, RMSE: 0.8 m for E. grandis and E. dunnii, respectively. The most informative ALS metrics for the estimation of AGB and TV were metrics related to the elevation in parametric models (Elev.70 and Elev.75), while for the non-parametric models (k-NN) they were Elev.75 and canopy density. For Ho, the ALS metrics selected were also related to elevation both in the parametric (Elev.90 and Elev.99) and random forest models (Elev.max and Elev.75). The segmentation methodology proposed here matched closely the segments delineated by human operators, and provides a low-cost, cost-effective, easy to apply and update model aimed at generating AGB or TV maps for harvest tasks, based on rasters derived from ALS metrics. The present research shows the capacity of ALS metrics to improve extensive strategic inventories; validating and promoting the adoption of ALS technology for inventory forest stands of Eucalyptus spp. in Uruguay

Bioethanol production using high density Eucalyptus crops in Uruguay

Experimental scale crops for Eucalyptus grandis, Eucalyptus benthamii, Eucalyptus dunnii and Eucalyptus tereticornis, at 2,220, 4,440 and 6,660 trees ha−1 were established in two soil units, at Paysandú and Tacuarembó, Uruguay. Wood samples were taken from twenty-two-months-old trees, and were used to produce bioethanol by pre-hydrolysis simultaneous saccharyfication and fermentation process (PSSF). Cellulose and lignin content was analyzed. Species and planting density affected biomass production at both sites; the highest value was obtained with E. dunnii at 6,660 trees ha−1 at Paysandú. Cellulose content of wood varied between species at both sites, but only between planting densities at Tacuarembó. The site effect showed that the highest amount of cellulose (14.7 Mg ha−1) was produced at Paysandú. E. benthamii and E. tereticornis wood showed higher lignin contents, conversely, the PSSF yields showed no differences, which led to a bioethanol average of 97 L Mg−1. Bioethanol productivity was associated to the biomass productivity. It was possible to obtain 2,650 L ha−1 of bioethanol using wood from E. benthamii, E. dunnii and E. grandis at 4,440 and 6,660 trees ha−1 at Paysandú, and with E. benthamii at 4,440 and 6,660 trees ha−1, and E. dunnii at 6,660 trees ha−1 at Tacuarembó.ANII: FSE_1_2011_1561

Hybrid mensurational-physiological models for Pinus taeda and Eucalyptus grandis in Uruguay.

There is a consensus that prediction systems should be complex enough to predict yield, and the effect of various combinations of forest management practices on the functioning of interactive natural systems, but at the same time maintain a low level of detail in order to have low implementation costs and facilitate their use. For this reason hybrid mensurational-physiological models have gained importance and attention, and it is expected that their adoption will increase in the near future. This study aimed to explore the potential advantages of a hybrid mensurational– physiological model compared to models currently used in forest plantation management, and provide a better understanding of their capability to improve precision and explanation maintaining a certain level of simplicity as required for forest management. This work also aimed to provide updated tools for managing Pinus taeda and Eucalyptus grandis in Uruguay. In Chapter 2, taper and volume equations were adjusted as those are essential to estimate individual volume and wood products. Emphasis was on testing compatible taper equations, since no models of this type have been developed to date for any species in Uruguay. However, variable exponent equations gave the best performance for predicting diameter at any height with the lowest prediction errors. In Chapters 3 to 5, three systems of stand level equations comprising dominant height, basal area, maximum diameter, standard deviation of diameters, and mortality were developed using differential equations through three approaches: i. Traditional time-based models using sigmoidal difference equations that restricted independent variables to age and parameters as functions of variables for region (base approach). ii. Augmented time-based models that had parameters as linear functions of water holding capacity and physiographical variables such as elevation, aspect and slope. iii. Hybrid physiological-mensurational models based on cumulative light sums since time of planting, with potential radiation-use calculated by modifiers accounting for influences of temperature, vapour pressure deficit (VPD), and water balance. These modified light sums replaced time in sigmoidal growth and yield difference equations. Water holding capacity was the most significant among the surrogate variables tested in the mensurational models for both species (Chapter 3), whereas elevation was seldom significant. Sine and cosine of aspect weighted by the slope, and slope were usually included but to a greater extent to one species than the other. Gains in accuracy of the augmented approach were small compared to the base equations. When adjusting hybrid growth models (Chapter 4), combinations of radiation modifiers were selected that yielded accurate results. It was important to determine whether or not the gains in accuracy were sufficiently high to justify dropping the least representative modifiers and lose flexibility. Differences in global radiation across terrain corresponding to a variety of slopes orientations were tested to see whether or not they significantly affected growth. Radiation-use modifiers related to water balance and vapour pressure deficit (VPD) produced the highest gains in precision; however the complete formulation (including also temperature) was preferred in order to maximize the model utility. Accounting for aspect and slope when computing radiation flux did not improve precision in any of the state variables for either species. For fitting hybrid mortality models (Chapter 5), it was hypothesised that the light-use efficiency approach could better explain the process leading to mortality because it accounts for predisposing site characteristics, recurring perturbations, and aggregation of stress. Extended periods of low water stress and short periods of high water stress were specifically tested as predictors of the probability of mortality. Results suggested that increase in stress did not influence the probability of mortality for Pinus taeda. However, stress helped explain the probability of mortality for Eucalyptus grandis with a negative effect: the accumulation of mild water stress tended to decrease the probability of mortality. For P. taeda, resource availability increased growth and decreased the probability of mortality and mortality rate, but for E. grandis, higher levels of resources increased growth, probability of mortality, and mortality rate. It was hypothesized that the eucalypt species is more sensitive to factors other than water, given a potentially higher tolerance to drought episodes and resilience compared to the pine species. A comparison of the three contrasting systems in terms of precision and bias as well as their capacity to reflect growth rates changes when site conditions vary was conducted. The comparison was extended to explore possible gains in diameter structure estimates. Results showed that precision tended to increase with higher levels of information; however explanatory variables included in the components of each approach and precision gains varied with species. Any of the three systems of equations can be applied for managing forests in Uruguay, especially for projecting diameter distributions, since the three approaches provided diameter distributions of similar accuracy. Nonetheless models based on the hybrid approach were more precise, especially for E. grandis (with precision gains between 9 and 14% among state variables). Biases of the predicted variables were similar between approaches, but consistently less for estimating mortality in long intervals in the hybrid formulation. Along with precision, this approach offered higher utility

Impact of Thinning on the Yield and Quality of <i>Eucalyptus grandis</i> Wood at Harvest Time in Uruguay

Understanding how thinning strategies impact wood quality and quantity for different purposes is of interest, given that plantation management is often based on parameters that require validation under varying growth conditions. Planted forests for solid purposes in the northern region of Urugay, western Argentina and South of Brazil are usually managed in initial stockings ranging from 800 to 1200 trees·ha−1 depending on the use of clones or seeds. Subsequent thinnings are applied (at plantation ages varying from 3 to 11 years) up to final stockings of around 200 trees·ha−1. This study evaluated contrasting thinning regimes applied early in the crop cycle, with an initial tree density of 840 trees·ha−1. Two thinning treatments were applied at 1.5 and 7.3 years, reducing tree densities to 700–400 and 400–100 trees·ha−1, respectively. Growth analyses were conducted from 1.5 to 20.8 years, considering total height, diameter at breast height, individual volume, total and commercial volume per hectare, mean annual increase, and current annual increase. At the final harvest, contrasting tree densities of 100, 250, and 400 trees·ha−1 were sampled to assess wood density and mechanical properties (bending and compression on small-scale clear samples). Individual growth and wood properties were related to a Stand Density Index to understand the effect of competition on these values. The results identified thinning regimes that resulted in the most significant individual and per-hectare growth (both in thinning and clear felling) and the optimal harvest time under specific growth conditions. We assessed the proportions of commercial logs for sawmill and pulp uses, providing valuable inputs for subsequent economic analyses of thinning regimes aiming for the most convenient combination of wood products. Wood’s physical and mechanical properties were relatively little affected by contrasting levels of competition between trees; therefore, the choice of silvicultural system will depend on production and economic criteria

Allometry, Growth and Survival of Three Eucalyptus Species (<i>Eucalyptus benthamii</i> Maiden and Cambage, <i>E. dunnii</i> Maiden and <i>E. grandis</i> Hill ex Maiden) in High-Density Plantations in Uruguay

This study presents a yield model for aboveground biomass production from three species the Eucalyptus in northern and western regions of Uruguay, based on sampling records from intensive crop plantations. High-density eucalyptus plantations represent a forestry alternative for the production of forest biomass. This work assessed the survival and growth of three eucalyptus species (Eucalyptus benthamii Maiden &amp; Cambage, E. dunnii Maiden and E. grandis Hill ex Maiden) planted at densities of 2220, 3330, 4440 and 6660 trees ha&#8722;1, for a period of 57 months in northern (Tacuaremb&#243;) and western (Paysand&#250;) regions of Uruguay. Linear and logarithmic equations of individual volume were fitted by site and species. The survival of E. grandis, E. benthamii and E. dunnii was not related to planting density, and the highest mortality values occurred in Tacuaremb&#243;. The effects of competition among trees were more evident at the highest planting density for E. grandis. In all species, the reduction in diameter was more marked than that of height, as planting density increased. Tree volume showed the same trend, and this was higher with higher planting densities. At Tacuaremb&#243;, the volume was the highest with E. benthamii at 6660 trees ha&#8722;1 (416.4 m3 ha&#8722;1), and, at Paysand&#250;, the highest production was obtained with E. grandis (370.7 m3 ha&#8722;1) and with the densities of 4440 and 6660 trees ha&#8722;1 (305.9 and 315.3 m3 ha&#8722;1, respectively). With all species and planting densities, there was an increase in the accumulated volume during the 57-month study period; however, growth curves indicate that the maximum production per unit time and, therefore, the optimum harvest time occurred at 48 months. In this work, it has been shown that the use of intensive short-rotation plantations of eucalyptus for the production of biomass in Uruguay is suitable in soils prioritized for forestry

Modelling Current and Future Potential Habitats for Plantations of Eucalyptus grandis Hill ex Maiden and E. dunnii Maiden in Uruguay

Eucalyptus grandis and E. dunnii have high productive potential in the South of Brazil, Uruguay, and central Argentina. This is based on the similarity of the climate and soil of these areas, which form an eco-region called Campos. However, previous results show that these species have differences in their distribution caused by the prioritization of Uruguayan soils for forestry, explained by the particular conditions of each site. In this study, the site variables (climate, soil, and topography) that better explain the distribution of both species were identified, and prediction models of current and future distribution were adjusted for different climate change scenarios (years 2050 and 2070). The distribution of E. grandis was associated with soil parameters, whereas for E. dunnii a greater effect of the climatic variables was observed. The ensemble biomod2 model was the most precise with regard to predicting the habitat for both species with respect to the simple models evaluated. For E. dunnii, the average values of the AUC, Kappa, and TSS index were 0.98, 0.88, and 0.77, respectively. For E. grandis, their values were 0.97, 0.86, and 0.80, respectively. In the projections of climatic change, the distribution of E. grandis occurrence remains practically unchanged, even in the scenarios of temperature increase. However, current distribution of E. dunnii shows high susceptibility in a scenario of increased temperature, to the point that most of the area currently planted may be at risk. Our results might be useful to political government and foresters for decision making in terms of future planted areas