Subject development

The loss and reduction of forest cover alters the functioning and capacity of forest ecosystems to provide ecosystem services such as soil erosion control, carbon capture and storage, rainwater harvesting, aquifer recharge, and food production, among others (^{ONUAA, 2012}). In the state of Guanajuato, land use change, overexploitation of species, overgrazing, introduction of exotic taxa, illegal logging, and fires are the main causes of forest ecosystem degradation (^{SMAOT, 2021}). According to ^{Semarnat and CP (2002)}, environmental degradation is the deterioration of the environment due to the depletion of natural resources (air, water, soil, or vegetation), which leads to the destruction of ecosystems.

In the last decade, more than 250 000 ha have been reforested in Mexico to counteract the negative effects of deforestation and degradation (^{Burney et al., 2015}). Reforestation allows the latter to be reversed, changing moderate-degradation areas to a low-degradation status (^{Semarnat and CP, 2002}). However, in the best of cases, the survival rate in these plantations barely exceeds 60 % (^{Burney et al., 2015}), and in some entities it is less than 40 % due, among other things, to the use of species that are poorly adapted to the environmental conditions of the plantation site, the lack of protection of these areas, and their conversion to agricultural land (^{Torres, 2021}).

Ecological niche modeling by means of Geographic Information Systems (GIS) and ecological niche algorithms is a tool for assessing the actual or potential spatial distribution of species (^{Soberón et al., 2017}) and generating land suitability maps for its development, which in turn are the basis for determining potential areas for reforestation, restoration, or taxon conservation (^{Garza-López et al., 2016}; ^{Manzanilla-Quijada et al., 2020}).

Genetic (GARP), climate envelopes’ (BIOCLIM), and maximum entropy (MaxEnt) algorithms are used to model the ecological niche; these utilize ecogeographic variables such as latitude, longitude, altitude, slope, climate, and soil in the form of raster layers (^{Guisan and Zimmermann, 2000}; ^{Castellanos-Acuña et al., 2018}).

Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst., Albizia occidentalis Brandegee, Acacia farnesiana (L.) Willd. (synonym of Vachellia farnesiana (L.) Wight & Arn.), Lysiloma divaricata (Jacq.) J. F. Macbr. (synonym of Lysiloma divaricatum (Jacq.) J. F. Macbr.), Leucaena esculenta (DC.) Benth. and Acacia pennatula (Schltdl. & Cham.) Benth. (synonym of Vachellia pennatula (Schltdl. & Cham.) Seigler & Ebinger) are tree legumes native to the state of Guanajuato that can be used in reforestation programs. Therefore, the objective of this research was to identify and quantify the areas susceptible of reforestation with these species through the modeling of the ecological niche with Geographic Information Systems and the BIOCLIM analysis system, according to their environmental requirements.

The study covered the entire surface of the state of Guanajuato, located between 20°50'22" and 19°54'46" N, and 99°40'17" and 102°05'49" W. From a political-administrative point of view, the entity is made up of 46 municipalities and has a territorial area of 30 460 km² (^{Inegi, 2017}). Guanajuato has a rugged landscape with mountains and plateaus, which is why it is part of three physiographic provinces: the Eastern Sierra Madre, the Central Plateau, and the Transversal Neovolcanic Axis (^{Inegi, 2017}). According to ^{García's (2004)} classification, the predominant climates are semi-warm sub-humid (type (A)C(w₀)), semi-arid temperate (BS₁kw), and sub-humid temperate (C(w₁)).

The following activities were carried out for the development of the work: (a) Description of the habitat with data provided by the Comisión Nacional Forestal (National Forest Commission) (^{Conafor, 2018}) for reforestations in the last ten years in areas of Guanajuato, Mexico, (b) Bibliographic review of the requirements of forest species with respect to the altitude and slope of the terrain, precipitation and mean annual temperature, soil type, texture and depth, (c) Construction of a database of the environmental requirements of each taxon with the information obtained in steps (a) and (b), (d) Stratification of digital layers of environmental information according to the requirements of each species, (e) Using the BIOCLIM algorithm with the DIVA GIS software version 4 (^{Hijmans et al., 2004}) to generate an ecological interval and the potential distribution of the taxa, and (f) Editing of the resulting layers and generation of the maps of potential suitability of the territory for each species, excluding agricultural areas, bodies of water, and urban areas of the state.

Table 1 describes the environmental variables and intervals used in the identification and quantification of potential areas for reforestation with the six tree taxa. Figure 1 shows the maps generated based on BIOCLIM.

Acacia farnesiana (L.) Willd. (synonym of Vachellia farnesiana (L.) Wight & Arn.), Acacia pennatula (Schltdl. & Cham.) Benth. (synonym of Vachellia pennatula (Schltdl. & Cham.) Seigler & Ebinger), Lysiloma divaricata (Jacq.) J. F. Macbr. (synonym of Lysiloma divaricatum (Jacq.) J. F. Macbr.).

Figure 1 Potential areas for reforestation with the six studied tree species. 

With the BIOCLIM ecological niche model, it was possible to determine the potential distribution of the six taxa analyzed, which are similar to the species studied by ^{Martínez-Méndez et al. (2016)}. The areas of potential distribution identified in the state correspond to areas of lowland rainforest, scrubland, and grasslands. The similarity in the delimitation of the potential areas responds to the fact that species such as Acacia farnesiana, Prosopis laevigata, Albizia plurijuga (Standl.) Britton & Rose, Eysenhardtia polystachya (Ortega) Sarg., Lysiloma microphylla Benth. and Senna polyantha (Moc. & Sessé ex Collad.) H. S. Irwin & Barneby are associated with the plant formations present in the entity (^{Guevara-Escobar et al., 2008}).

The largest potential area was for P. laevigata, due to its wide adaptive capacity, which agrees with the results obtained by ^{Palacios et al. (2016)} and ^{Palacios et al. (2021)}. According to ^{Rodríguez-Sauceda et al. (2019)}, it is tolerant to drought and to soils of low physical and chemical quality. Furthermore, from an environmental point of view, its inclusion in reforestation activities is key due to its great capacity to retain soil and improve its fertility, which helps to prevent desertification.

The mapping generated is a useful tool for planning reforestation strategies that consider the six native Fabaceae. In this sense, according to ^{Guevara-Escobar et al. (2008)}, the percentage of survival in reforestation activities increases if the ecological niche factor is taken into account.

Of the six species considered in the study, Prosopis laevigata has the largest area suitable for use in reforestation programs.

The mapping generated for each of the six species is a guide to direct reforestation actions that will guarantee the increase of their survival and thus, the success of the plantations.