**4. Random characteristics of Fabaceae of timber importance in the Amazon**

In opposite in the advance of knowledge of the technological properties of wood that defines its potential form of use, forestry research aims to support the recovery of the landscape and the potential of supplying raw material for the future. Historically, the exploitation of native trees is the source of raw material for numerous products and by-products, such as wood, medicines, cellulose and paper, food for fauna and man, fibers, oils and resins, gums, etc. There is a need for research on the silvicultural and economic potential of the species, adding value to biodiversity, especially in planting and reforestation actions, contributing to the conservation of forest resources. Some specific information for 45 random tree species of the Amazon region, with the popular name in Brazil, phylogeny, size characteristic, wood density and N2 fixation ability are presented in **Table 3**.



*Biodiversity of Fabaceae in the Brazilian Amazon and Its Timber Potential for the Future DOI: http://dx.doi.org/10.5772/intechopen.110374*


#### **Table 3.**

*Scientific and popular name, subfamily, tribe, size, wood density and symbiotic n2 nodulation ability of 45 species of Fabaceae native to the Amazon.*

The Fabaceae of wood interest are classified in all subfamilies and many have large size, but also medium or small, varying with the taxon. There are large trees that occupy the upper canopy of the tropical forest in areas of no hydromorphic soil as *Dinizia excelsa* that can reach 55 m high or in flooded forests such as *Mora paraensis*, which grows up to 50 m, but also species such as *Dalbergia spruceana* which, despite the small size, has economic value in the timber market. Some of the largest trees in the Amazon are very old and have an estimated age of up to 1200 years, as verified for *D. odorata*, by dating 14C, in a tree that had trunk diameter of ±120 cm, with an estimated growth rate of ±0.1 cm year−1, while *Parkia pendula*, with trunk diameter of 110 m corresponded to the age of ±200 years with an estimated growth rate of ±0.65 cm year−1 [20].

The timber trade is hampered by the little knowledge of the wood itself and low identification at the species level by the high variation of popular names, yet in the listings of timber exported from the Amazon, angelim, jacarandá, jatobá, sucupira, macacaúba, etc., are frequent presences. The density values of the wood are directly related to its potential for use, so the light woods have density < 0.50 g cm−3, medium density woods have between 0.50 and 0.70 g cm−3 and the stiffest and heavier woods >0.70 g cm−3. The woods of higher density are harder and heavier viable for uses already described, but also for energy production (firewood, alcohol and coal) and

the woods with low density are much lighter and able for the production of pulp and paper, light woods and rich in thin-walled fibers.

For the sustained exploitation of timber resources, it is necessary to consider that in tropical forests, some ecological and economic characteristics can determine the increase or decline of forest species populations. The commercial value, limited geographical distribution, little dispersal ability, slow growth and reduced number of juveniles, will affect the decline of populations if the species is exploited by severe logging [21]. Obtaining more forestry and autecology information of species with greater potential management and cultivation is an important step for the preservation of these natural resources and the main challenge is the great biodiversity and numerical grandeur of wood-producing species.

Additionally, there is a property that also characterizes Fabaceae: the ability to associate with soil bacteria, from the rhizobium group, producing small root nodules, an effective site for biochemical and enzymatic processes that allow the dynamics of biological fixation of N2 - BNF. Numerous tree legumes, but not all, can develop root nodules and fix N2, adding to these species another role besides the productive, that of providing services to increase the entry of NH4+ into ecosystems in imbalance [22]. In soils altered in its organic matter stocks, BNF has a strategic agroecological function. N2 fixer trees in symbiosis with Rhizobia are designated nitrogen-fixing trees – NFTs.

Among the timber species, several with nodulation species of economic importance stand out among the species, they are *Anadenanthera peregrina*, *Campsiandra laurifolia*, *Hymenolobium pulcherrimum*, *Platymiscium trinitatis*, etc. On the other hand in several Fabaceae of wood importance the nodulifiable ability has not been proven, e.g. *Dialium guianense*, *Dinizia excelsa*, *D. odorata*, *Peltogyne paniculata*, etc. It is noted that the fixing ability of N2 in Fabaceae evolved mainly in species of the subfamilies Mimosoideae and Faboideae, and has less representation among Caesalpinioideae, where only species cited for the Caesalpinieae tribes had this natural ability (**Table 3**).

The N2-fixing Fabaceae have advantages over other plants, due to the natural absorption ability of atmospheric N in the form of NH4+, and BNF is an economically and biologically rewarding process, contributing to the productivity of the soil-plantanimal system. The current concepts of Agroecology have emphasized the use of NFTs in forestry or agricultural production systems with particular importance in the composition of species in Agroforestry Systems that seek sustainability in nitrogen. Thus, the Fabaceae of the Amazon emerge as an important element for sustainable production systems in the future.
