The reservoir area of the Corumbá IV power plant, located in the Central region of Brazil, is delimited by the border between a permanent preservation area and the neighboring properties. It was formed by the impoundment of the Corumbá River, which flooded an extensive native riparian forest area and required rerouting the main highway in the area. The water partially or totally flooded the bordering properties. It forced some rural inhabitants to move to urban areas and transformed the surrounding landscape of the municipalities directly affected by the reservoir, among them Abadiânia and Alexânia (
Figure 1). The municipality is the local administrative unit in Brazil. It is akin to a county, except that government is by a single mayor and municipal council. Municipalities range from lightly populated rural ones with one or two small towns to heavily populated urban ones that are part of greater metropolitan regions. During the construction period of the Corumbá IV power plant reservoir, illegal charcoal makers and cattle breeders extracted the vegetation in the region, eliminating virtually all its wildlife. The riparian forest disappeared and most of the vegetation remaining around the reservoir’s borders was pasture, mainly consisting of
Brachiaria sp. grass. Moreover, different forms of illegal fishing combined with wastewater discharge have decimated the fish population [
44].
The state of Goias, where the reservoir is located, is characterized by public policies strongly oriented to agricultural production and livestock breeding. The inexistence of soil conservation techniques and the removal of gallery forests have contributed to the disappearance of entire species native to the Brazilian Cerrado. The few initiatives to restore the forests have been limited to the planting of high-performance exotic trees. Reforestation with exotic tree species in Brazil is mainly with species of Eucalyptus and Pinus, widely used in South America [
45,
46,
47]. Although they have fair resistance against environmental threats, insects, and microorganisms and provide satisfactory forest yield, they do not add value to ecosystems, mainly because they upset the balance between flora and fauna, favorably biased to the exotic trees [
48]. First developed in Queensland, Australia [
49], the framework species method involves the planting of indigenous trees that attract wild animals, which in turn are responsible for seed dispersion and germination, rapidly reestablishing the forest structure and revitalizing the ecosystem [
20].
The experimental sites are identified as ES-1 and ES-2 (
Figure 1), both located on the margins of the reservoir of the Corumbá IV hydroelectric power plant, located in central Brazil. They were in an advanced state of degradation caused by native tree deforestation, partial reforestation with exotic species like Eucalyptus, livestock grazing, and reservoir pollution due to indiscriminate discharge of untreated wastewater. The heterogeneity of soil between these sites was the primary factor for their choice among several location alternatives. The predominant types of soil in the study area are Dystroferric Red Latosol and Dystroferric Haplic Cambisol.
Table 1 shows the granulometric and chemical compositions for the soils of the two experimental sites. The soil samples were analyzed for pH (0.01 M CaCl
2; 1:5 soil: solution), Al, Mg, K, P, Fe, and C according to procedures recommended by Silva [
50]. The Ca
2+, Mg
2+ and Al
3+ were extracted using 1 mol L
−1 KCl solution (Al
3+ by tritation with 0.2 mol L
−1 NAOH; Ca
2+ and Mg
2+ by atomic absortium spectrophotometry); and available K, P, and Fe were extracted with Mehlich-I. Concentration of K
+ was determined by flame spectrophotometry, P was determined by calorimetry using an UV-Vis spectrometer, and Fe was determined by atomic absortium spectrophotometry. The (H + Al) was extracted by calcium acetate pH 7.0 and determined by titration with 0.2 mol L
−1 NAOH. Organic carbon was determined by Walkley-Black (Na
2Cr
7O
7 + H
2SO
4). Sum of base (SOB = Ca + Mg + K) and CEC ph 7.0 (CEC pH 7.0 = Ca + Mg + K + (H + Al)) were also determined. Organic matter was calculated considering the C content of 58%. Four samples were extracted, and the averages of the compositions were calculated for ES-1 and ES-2 sites. The granulometric composition is the determining factor for their differentiation, as they have relatively higher proportions of sand and silt, respectively. These soils are acidic with a pH approximately equal to 5 and have a low level of nutrients such as phosphorus, calcium, and sodium. The soil organic carbon (SOC), a critical indicator of soil health because it reflects the level of soil functionality associated with soil structure, hydraulic properties, and microbial activity, has a composition level considered medium, in both types of soils [
51]. The sum of bases (SB) of the soil represents the sum of the exchangeable cation contents (SB = Ca
2+ + Mg
2+ + K
+), except for H
+ and Al
3+. Base saturation (V%) is an excellent indicator of the general conditions of soil fertility, being used even as a complement in soil nomenclature. Both soils at ES-1 and ES-2 sites are considered dystrophic, or poorly fertile, as they present V% less than 50%, in this case 20% and 18%, respectively. A low V% index means that there are small amounts of cations, such as Ca
2+, Mg
2+, and K
+, saturating the negative charges of the colloids and that most of them are being neutralized by H
+ and Al
3+. These dystrophic soils are poor in Ca
2+, Mg
2+, and K
+ and have a very high exchangeable aluminum content, with aluminum saturation (Al sat%) above 50%. They have also a high content of iron and aluminum, which cause clogging of particles and a reduction in soil permeability. High levels of iron prevent the fixation of phosphorus in the particles, whose content is poor in these soils, hindering root absorption and the energy source of adenosine triphosphate (ATP), essential for photosynthesis, cell division, and growth. Excess aluminum, in turn, hinders the regular absorption of water and nutrients by the deeper roots, causing superficial rooting and limiting the growth of trees [
39]. The aluminum saturation of 61% and 62% for ES-1 and ES-2, respectively, confirms the high toxicity of both soils.
The accessibility of the sites and the commitment of the farmer to performing daily inspection were taken into consideration as well [
52]. Experimental site ES-1 has a total area of 9379 m
2, which includes the firebreak perimeter and the access road. Its geographic coordinates for one vertex are S: 16°16′51.6″ and WO: 48°29′7.8″, and for the opposite vertex are S: 16°16′55.0″ and WO: 48°29′4.4″. The soil classification is Dystroferric Red Latosol, here called Latosol, rich in iron, with a clayey structure [
53]. Experimental site ES-2 has a total area of 9655 m
2, with firebreak and access road. Its geographic coordinates for one vertex are south: 16°12′55.7″ and west: 48°18′22.2″, and for the opposite vertex are S: 16°13′1.4″ and WO: 48°18′20.2″. The soil classification is Dystroferric Hapli Cambisol, here briefly called by Cambisol, with a light sandy loam structure [
53].
2.1. Sampling Procedure
A phytosociological analysis considering the possible adaptation to the two types of soil initially identified 15 native fruit tree species as being viable [
54]. All these fruits are juicy and sweet and make up part of the basic diet of many native species of birds and mammals. The protection of the two experimental sites against animal and human invasions was achieved with fences of barbed wire supported by autoclaved eucalyptus stakes erected along their perimeters. In order to evaluate the plants’ ability to survive in the presence of
Brachiaria sp., the grass was not removed, and the seedlings were planted in holes spaced three meters apart [
55]. Finally, three organic elements were added: fertilizer made from chicken excrement, a compound of aquatic macrophytes applied on the crown of the plants, and a pesticide against ants. The fertilizer is plentiful and available without charge from local poultry farms and the aquatic macrophytes were harvested directly from the reservoir. A total of 1942 seedlings of the 15 species were planted in a randomized block design in the experimental sites ES-1 and ES-2, but since six species were excluded from the study, the remaining number of seedlings planted was reduced to 1248. However, two years after the seedlings were planted, six species were unable to adapt to the aggressive conditions of the soil and competition with
Brachiaria sp. grass, having an average survival rate of only 8.6%, significantly different from the remaining group of nine species, with an average survival rate of 56% (
p-value < 0.001). The nine species selected for the present study are listed in
Table 2. The binomial name and the Brazilian common name of the six species not considered in the present study are:
Cheiloclinium cognatum (Bacupari da Mata),
Anacardium humile St.Hilaire (Cajuí),
Eugenia dysenterica (Cagaita),
Brosimum gaudichaudii Tréc (Mama Cadela),
Hancornia speciosa Gomes (Mangaba) and
Caryocar brasiliense Cambess (Pequi).
The first measurements were carried out two years after planting. The researchers responsible for site inspection, measurement, and reporting were a forest engineer, an agriculture technician, and one of the authors. The inspections were performed in sunny and dry weather. The dry season from May to September is particularly severe in Central Brazil. On the other hand, the wet season in the summer receives almost 50 times more than the average precipitation [
56]. Although the planting in both experimental sites was done in the beginning of the wet season, the hot weather and intense rainstorms influenced the survival capacity of some species. Moreover, the presence of
Brachiaria sp. grass covering the entire experimental sites posed additional challenges to the seedlings. This exotic African grass was introduced by farmers in the Brazilian Cerrado for pasture. Due to its high dispersion capacity for vegetative seedling reproduction, fast reproductive cycle, high photosynthesis efficiency for nutrient usage, fast growth, resistance against livestock trampling, and fire tolerance, this grass has been a successful invader of natural ecosystems [
57]. The competition between native plants and exotic grasses for soil nutrition resources changes the vegetation morphology. It also reduces the quantity and changes the composition of nutrients available for plant consumption, increasing plant vulnerability [
58,
59].
2.2. Data Analysis
For the problem analyzed here, the comparison of the four morphological features—trees’ percentage of survivors (SUR), average diameter at breast height (DBH), average total height (HEI), and average number of leaves per branch (LEA)—by means of the fuzzy analytic hierarchy process (FAHP) allowed the assignment of weights to them. Then, the comparison of the species measurements for each criterium resulted in the species performance metrics as shown in
Figure 2. The analytic hierarchy process (AHP) is a MCDA method based on priority theory whose main characteristic is the decomposition of a problem into two elements, the criteria, and the alternatives. The criteria are compared to each other in terms of their relative importance to achieve a certain result and then the alternatives are compared to each other according to their performance in relation to each of the criteria. The main limitation of this method is that it is not able to reproduce inaccuracy and uncertainty [
60,
61]. Fuzzy AHP allows including a measure of inaccuracy in any step of the analysis. This measure is represented by α-cuts delimitating a fuzzy membership function (FMF), which defines a range over a set of possible values for the fuzzy variables. Thus, inaccuracy is incorporated into the assessment procedure, allowing a more coherent approach to the real world, thus influencing the conclusion. Chang [
62] proposed a method for synthesizing the model solution and tested the respective algorithm to solve hierarchy problems associated with fuzzy logic.
The SIMOS elicitation method [
63] was used to obtain comparison scores of the degree of importance between the criteria. An expert received four cards containing identification of the four criteria and twelve blank cards. He was asked to place the cards containing the criteria identifications in descending order of importance. Each blank card inserted between two criteria indicated the degree of importance of that criterion over the next one. The greater the number of blank cards, the greater the degree of importance, with the absence of cards meaning that the criteria are equally important. The cards with the criteria occupy a certain position, which divided by the total number of cards results in the normalized weight by the SIMOS procedure. To convert these weights into scores according to the Saaty procedure, the change to base eight plus one was used [
64]. In this study, the cards’ order represented the importance of the criteria that influence the survival of the species in the long run.
To apply the fuzzy AHP technique for the ranking of the tree species, we used the base eight plus one method, referring to the tree with the best performance. The result of the numerator or denominator, depending on the direction, must be rounded to the nearest integer. Therefore, the variable scores of relative survival rates are converted to the Saaty scale. The advantage of this approach is that it meets the format requirement of the input data established by Saaty and Vargas [
65] and the resulting matrix is transitive.