*4.3. Management Implications*

SDM are important tools for forest management because these models can reliably predict current and future areas suitable for native and introduced species. This information is crucial in silviculture for the long-term timing of management options [76]. Furthermore, the species responses to environmental variables can provide information to help target for forest management programs at regional and national scales as has been proposed on this study.

The implications for future management are different for both species. With the species *E. dunnii* shows it is possible to visualize a greater potential in the northern and coastal zones in sites that simultaneously combine deep soils and comparatively higher temperatures in the country (Figure 2A). On the other hand, the results obtained with *E. grandis* shows a higher potential to show the advantages of plants to this species in relatively deep soils with little clay and silt content (Figure 2B). This type of soil is concentrated in the coastal and north–north-east regions. Therefore, the effect of the orientation of the slope, although it shows the greatest potential in the north–north-east direction, lacks practical effects, since the plantation takes into account aspects of soil conservation such as contour lines. In turn, the probability values of occurrence of the species associated with this variable are of low magnitude to be taken into account.

Eucalypts plantations will continue to expand in Uruguay, growing in the coming years on soils for regions with forest potential (Figure 1), suitability soils that are still unexplored and this expansion is likely to be different for both species. For the projection of the future surface of *E. dunnii*, it must be taken into account that although the species comes from a relatively small area, it has managed to expand to a wide range of environmental conditions in substitution of *E. grandis*, [77]. However, the predictions of our model and other works carried out in Australia, China and South America show certain vulnerability of this species to changes in temperature, particularly increases in the average temperature above 19 ◦C (considered as the upper limit of climatic suitability) [77,78]. In this sense, future strategy should consider two aspects: (i) to have the widest possible genetic base (field trials and/or germplasm bank) so as to be able to select genotypes tolerant to the eventual increase in temperature, and (ii) have of interspecific hybrids with other species of eucalypts with greater ability to adapt to climate change. With respect to the projection of *E. grandis*, it is expected that it will continue covering an important area (higher than the current one) with the probable scenarios of temperature increase. The wide distribution of that this species shows worldwide, adding to the possibilities of genetic improvement in favor of more extreme weather conditions [8], determine in the long term an optimistic outlook for foresters. The model projections obtained in this study confirm the climatic adaptability of the species and therefore its relative stability against climate change.

Finally, the projections for both species should be taken with caution (particularly with *E. dunnii*) since the future increase of temperature explained by an increase in the concentration of atmospheric CO2 could cause changes in the photosynthetic rate and in the use of water. Studies carried out on these topics with eucalypts species show contrasting results (see for example [8]).

#### **5. Conclusions**

The results obtained in this work indicate that the growth of *E. grandis* is associated basically with soil parameters, while that of *E. dunnii* shows a greater association with the temperatures of the

fall and summer months. The direct relationship of the growth of both species with the depth of the surface horizon of the soil determines the importance of the choice of site with regard to obtaining high levels of growth. From this point of view, the potential of these species is greatest in the northern and coastal soils of the country, which, in general, have a comparatively greater volume of soil to be explored by the roots than the soils of the south-east of the country. With *E. grandis*, the positive effect of the north–north-west orientation on growth, but conditioned by soil conservation practices, must be considered. In this work, the ensemble models of habitat prediction emerge as useful tools to identify the most suitable areas for both species, based on the fitment values obtained. *Eucalyptus grandis* shows greater plasticity than *E. dunnii* regarding the different agroclimatic conditions of the country. Predictions of the future habitat of both species indicate that *E. grandis* is a species that could be used with certainty in the long term, in a wide variety of sites, whereas with *E. dunnii*, there may be areas of higher risk due to the probable climate change. Description of the potential current and future habitat allows selection of the areas with greater value for commercial plantations, which can assist afforestation plans, including the selection of appropriate genetic stock materials.

Despite the results obtained in this study, some limitations should be considered. Restrictions related to the anthropic distribution limits of the species are poorly known and could be insufficient to be effectively used in SDM. This is particularly important for the absence data, which may reduce the geographical extrapolations beyond the sampled area, leading to spurious results [29]. Thus, integrated and comparative survey strategies, including more detailed distribution information, should be considered in future studies. Additionally, an excessive simplification of the variables included in the model may mean that the selected variables limit their ecological interpretation (e.g., over-importance of the edaphic variables in our case). One possible way to avoid this problem is by making models that progressively include the set of environmental variables to interpret their importance step by step (see, for example [79]).

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1999-4907/11/9/948/s1, Figure S1: Reduction in the occurrence area (%) of Euvcalyptus dunnii (A) and E. grandis (B) for 2050 and 2070, considering different scenarios (RCP 2.6, 4.5, 6.0, and 8.5) and the Global Circulation Model CCSM4., Table S1: Soil and climate requirements of E. grandis and E. dunnii., Table S2: Area planted with *Eucalyptus* species (hectares) by department in Uruguay

**Author Contributions:** F.R. and J.D.-L. contributed to the paper equally. F.R., C.R.-C. and L.C.-L. planned and designed the research. F.R., and C.R.-C. conducted fieldwork and performed experiments. R.M.N.-C., J.D.-L. and C.A.-M. contributed to data elaboration and analysis. F.R., R.M.N.-C., J.D.-L. and L.C.-L. wrote the manuscript, with contributions by all authors. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Institute of Agricultural Research (INIA) and the National Agency of Research and Innovation (ANII) through the grant FSE 1 2011 15615 (Evaluación productiva y ambiental de plantaciones forestales para la generación de Bioenergía)

**Acknowledgments:** The authors thank the INIA and ANII for funding this research and are indebted with the Forestry Directorate of the Ministry of Cattle, Agriculture and Fisheries of Uruguay (Dirección General Forestal-Ministerio de Ganadería Agricultura y Pesca de Uruguay) for facilitating the access to the National Forest Inventory.

**Conflicts of Interest:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

#### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
