Dendrological Characterization as Inspection Resources of Caatinga Wood Market

This study aimed to distinguish five native forest species of the Caatinga Biome from the exotic invasive algaroba (Prosopis juliflora (Sw.) DC.), considering dendrologic characteristics of bark and wood, in order of providing subsidies for the inspection of the wood market in this Biome. The native species studied were jurema-preta (Mimosa tenuiflora (Willd.) Poir.), angico branco (Anadenanthera colubrina var. colubrina (Vell.) Brenan), angico vermelho (Anadenanthera colubrina var. cebil (Gris.) Alts.), aroeira (Myracrodruon urundeuva Allem) and braúna-do-sertão (Schinopsis brasiliensis Engl.). Studied species were recognized using dendrology identification records, containing characteristics of bark, heartwood and sapwood coloration; and the organoleptic proprieties like color, smell and taste, used for safe wood logs identification. The macroscopic characteristics, organized in dichotomous key, allowed the differentiation among the species, available in logs, during inspection.


INTRODUCTION
In the Brazilian semi-arid region, the unsustainable exploitation and commercialization, often illegal, of woody species from Caatinga Biome, is used to subsidize the local economy, supplying biomass for energy purposes, and non-wood forest products (Paes et al., 2013;Medeiros et al., 2014;Campello, 2015).Firewood and charcoal account for 30% of the states and municipalities energy matrix; in addition to meeting the domestic demand for cooking of 70% of families in the Brazilian Northeast Region (Campello, 2015).
The three main forest exploitation methods in the Caatinga are illegal deforestation and forest management for wood production, and legal deforestation for alternative land use; the latter two being authorized by competent bodies (Pareyn, 2010).Thus, the Caatinga Biome forest resources have been intensively exploited, as a result of the anthropic action in the region (Medeiros et al., 2014).It is necessary to enforce mitigating measures (Pereira et al., 2014) such as the requirement that commercialized wood originates from managed areas or reforestation, as recommended by the Brazilian Forest Code, Brasil (2012), Article 31, Law 12.651.
Wood can be obtained also from the exploration of exotic species, without the need for authorization (Ndagijimana et al., 2015), among these species exploited commercially in the Caatinga, stands Prosopis juliflora (Sw.)DC., known as algaroba (Pegado et al., 2006;Farias et al., 2013).This species was introduced and disseminated as an economic alternative, by adapting it in several semi-arid regions of the world and by its versatile use as firewood, wood and forage (Pegado et al., 2006).
As a result, and with the frequency in which commercially banned native trees are illegally exploited, it is necessary to develop scientific-based strategies in order to differentiate native species from the Caatinga Biome exotic species, especially the Prosopis juliflora, contributing to the efficiency of inspection by the responsible organs and technicians (Alves et al., 2012).
Dendrology as an identification tool uses knowledge based on botany, taxonomy and wood macroscopic anatomy to recognize the wood.The tree is studied from vegetative features, such as the bark color, structure, appearance, trunk size and shape, presence of aculeus and or thorns, fruits, leaves shapes and types, seeds, exudations, and the existence of peculiar smell (Panshin & De Zeeuw, 1980;Gonzales, 2008;Rotta et al., 2008;Castillo, 2010;Silva & Costa e Lima, 2010;Alves et al., 2012).
Knowledge of the dendrological characteristics of native species marketed is essential for various purposes, including a practical subsidy and inspection by regulatory agencies to differentiate native and exotic forest species.
Therefore, this work aimed to identify, from the bark and wood characteristics, five native forest species of the Caatinga Biome and to distinguish them from the exotic species Prosopis juliflora, elaborating a dichotomous key, which provides subsidies for inspection the wood market in this Biome.

Species selection and material collection for dendrological analysis
The sample of native species included: Mimosa tenuiflora (Willd.),Anadenanthera colubrina var.colubrina (Vell.)Brenan, Anadenanthera colubrina var.cebil (Gris.)Alts., Myracrodruon urundeuva Allem, Schinopsis brasiliensis Engl.The group of exotic species was composed by Prosopis juliflora (Sw.)DC.Even though the Myracrodruon urundeuva and Schinopsis brasiliensis species are threatened with extinction, they are often illegally marketed in the region.All species were selected taking into account the indications of technicians responsible for the forest division of the Superintendency of Environmental Management -SUDEMA, João Pessoa, Paraíba.
We analyzed dendrological characteristics of five specimens of each forest located in the municipalities of Patos, Maturéia, São José de Espinharas, São José dos Cordeiros and Santa Terezinha, Paraíba State.We cut and analyzed one tree per location.The species Anadenanthera colubrina var.colubrine, Andaenanthera colubrina var.cebil, and Myracrodruon urundeuva were obtained in an area of forest management located at Agro Mercantil Urtigas S.A, Santa Terezinha; Mimosa tenuiflora and Prosopis juliflora from the Health Center and Rural Technology (CSTR), Federal University of Campina Grande (UFCG), Patos, and Schinopsis brasiliensis was provided by a rural owner in the São José dos Cordeiros municipality, with the authorization of Superintendence of Environment Administration -SUDEMA.

Dendrological description and bark characteristics
Information regarding the diameter at breast height (DBH), characteristics of bark and organoleptic were obtained in the field before cut.Characteristics within and among species with registration in different growth stages were evaluated.We evaluated the specimens' mentioned organs features descriptions.Information from the cross-section such as wood color and distinction between heartwood and sapwood were evaluated in the Forestry Product Laboratory, of the Academic Unit of Forest Engineering -UAEF located in the CSTR of the UFCG, Patos, Paraíba.
The rhytidome was removed with a knife to analyze the color and its internal surface, followed by the same analysis to characterize the inner bark.As to the presence of exudates, or liquids released when the plant is cut, its presence or absence and, when present, its consistency, flow velocity, viscosity and color after exposure to air were observed.

Characteristics of heartwood and sapwood, organoleptic and dichotomous key
Characteristics such as color and the possible distinction between heartwood and sapwood were studied.For this, 24 transverse discs, 4 cm thick, were prepared; two from the basal and two from the apical portions of each specimen.Color was defined from the samples comparison with the Munsell soil color charts, Munsell Color (2005), to avoid personal subjective evaluation.
The following organoleptic characteristics were observed: smell and taste, analyzed according to the protocol contained in Zenid & Ceccantini (2007).Smell and taste were recorded only as present or absent, with no details (subjective assessment).We analyzed only the color of the rhytidome and the cross section.
Digital photographic records were made for the rhytidome, inner bark, heartwood and sapwood to illustrate the dendrological characteristics and the differences among them.The wood macroscopic characteristics were recorded in a dendrological record, following recommendations by Ramalho (1979), Ribeiro et al. (1999) and Silva et al. (2005), which provided subsidies for the dichotomous key elaboration.

RESULTS AND DISCUSSION
The observed dendrological characteristics were taken from individuals with different DBHs, reflecting distinct life stages, which may influence their characteristics (Table 1).Variations in the trees characteristics with different DBHs were observed both among species and among individuals.

Characteristics and distinctions among forest species
Tables 2, 3 and 4 present the macroscopic characteristics of rhytidome, inner bark and wood, respectively.The comparison, in pairs, among the native species and the Prosopis juliflora, indicated that there is greater similarity between them and Mimosa tenuiflora, regarding the rhytidome of both forest species (Table 2, Figure 1), which may complicate the distinction in the absence of more details.The most relevant dendrological characteristics for this distinction consisted of the inner bark color, the presence of exudation and the distinction among heartwood and sapwood (Tables 3 and 4, Figure 2).
In the Prosopis juliflora, the inner bark color is orange (Figure 2a), with no exudation (Figure 2c), and there is a clear distinction between the heartwood and sapwood (Figure 2e), which are dark brown -7.5YR 4/6 and light yellow-gray-5y 8/3, respectively, according to the classification obtained in the color chart of Munsell Color (2005).In Mimosa tenuiflora, the inner bark has intensely red when freshly cut (Figure 2b), yellow fast flowing exudation (Figure 2d), and less clear distinction between the heartwood and sapwood (Figure 2f).
(Meliaceae), with precision, only from the rhytidome pattern.The main dendrological characteristics found to distinguish the Prosopis juliflora from Myracrodruon urundeuva were rhytidome dehiscence, inner bark structure and the exudation presence (Tables 2 and 3, Figure 4).In the Myracrodruon urundeuva, the rhytidome is dehiscent, detaching itself in irregular and concave blades (Table 2, Figure 4b).The inner bark has exudation close to the sapwood, with a yellowish color and uniform appearance (Table 3, Figure 4f).The Prosopis juliflora rhytidome is indehiscent (Figure 4a), the inner bark shows no exudation (Figure 4e) and the structure is laminated (Table 3; Figure 4c).

The distinction between Schinopsis brasiliensis
and Prosopis juliflora is possible by the presence of exudation and the inner bark structure, since the first is present in the Schinopsis brasiliensis and absent in the Prosopis juliflora (Table 3, Figure 5).The exudation flow in the Schinopsis brasiliensis is fast, viscous, transparent, and becomes light brown with time (Figure 5b).Regarding the inner bark structure, the Schinopsis brasiliensis has a non-laminated structure (Figure 5d) and the laminated Prosopis juliflora (Figure 5c) that separates when it is handled.For rhytidome, we observed difference in the stretch marks, present in both species (Table 2).In the Schinopsis brasiliensis, the stretch marks are more superficial, with lenticels in their area (Figure 5e), while in the Prosopis juliflora these are deeper and with generally light brown streak (Figure 5e).In the Schinopsis brasiliensis, this characteristic was observed in individuals with DBH ≤18 cm, with a change in the rhytidome characteristics with increasing DBH (Table 1), behavior also reported for Schinopsis quebracho (Giménez et al., 2000).
We estimate that the time between the species cut and the transports for commercialization is of only a few days, and might not affect the studied characteristics.Also, with time, we observed modifications such as darkening in the inner bark color and exudation absence, although the latter could be visible in the form of crystallized resin in places that suffered mechanical damages (without modifications in the other characteristics).
Studies of recognition and identification from forest species using dendrological characteristics were developed for individual species and specific biomes.In Tahuamanu and Alto Huallaga areas, in Lima, Peru, for example, studies were developed for 26 forest species of commercial importance (Castillo & Nalvarte, 2007).For the phytophysiognomies of the Brazilian Cerrado, identification keys of tree species were constructed from dendrological characteristics

CONCLUSION
The dendrological characteristics of the rhytidome, inner bark and wood available at the time of inspection (wood in logs), along with the elaborated dendrological characteristic key, allow the precise identification and distinction among the studied species, avoiding confusion among the studied native species and the Prosopis juliflora, in the act of inspection.
DBH = Diameters at Breast Height.