**2. Atlantic Forest biome**

devastation ofthe Atlantic Forest, atlarge, has been attributed to intensive use oftimber species of interest (mainly *Caesalpinia echinata*, popularly known as Brazilwood), and the establishment of areas for agriculture, pasture and urbanization. The advancement and establishment of agricultural areas and, consequently, fallen forests have reduced native forest massifs to fragmented forests, which has greatly compromised biological diversity and conservation of these forest ecotypes [1]. Even with the intense land‐use change, with only 12.5% of the original cover remaining (only fragments larger than 3.0 ha), the Atlantic Forest currently shows more than 15,000 plant species and more than 2000 species of vertebrate animals [2]. The biome has high diversity of endemic species, and is considered a priority area for conservation (hotspots). In it, 383 species of animals threatened with extinction are found

114 Tropical Forests - The Challenges of Maintaining Ecosystem Services while Managing the Landscape

Studies on native forests are of vital importance for a better understanding of the behavior of intrinsic characteristics to the ecosystem and must be performed before these ecosystems have all their original area changed by men [3]. The understanding of intrinsic characteris‐ tics aids to adopt proper programs for the recovery of degraded ecosystems. Therefore, a significant part of the areas that were changed due to changes in land use can be recovered. They can present again the ecological interactions necessary to ensure the biodiversity of fauna and flora. The recovery of ecosystems as a strategy to reverse the degradation process and enhance biodiversity conservation and provide ecosystem goods and services is already

Mainly in tropical and subtropical regions, it is of utmost importance to have further infor‐ mation concerning the dynamics of nutrients in different compartments of a forest ecosystem. It is important in order to employ silvicultural practices to effectively ensure sustainable long‐ term management of altered ecosystem by land‐use change. Nutrient cycling occurs naturally, in part, by the throughfall of tree canopies and trunks by rainfall and through the deposition of senescent tissues (litter) and after their decomposition [5]. This process, nutrient cycling (plant‐soil‐plant), enables the development of forests in soils with low nutritional levels [6]. The organic material that accumulates under the forest works as a big sponge able to retain water, reduce evaporation and sudden variations of soil temperature, thus preventing erosion,

In addition to these benefits, the understanding of nutrient cycling through litterfall in forests is one of the key aspects to be studied for planning the use of tree species to recover degraded areas or for timber production [7]. The content of nutrients supplied to the forest soil can influence production capacity as well as the potential of environmental recovery, because the nutrients resulting from organic material cause changes to the chemical and physical charac‐

In this chapter, we will present some information about the nutrients cycling in the Atlantic Forest biome, the most important biome in socio‐economic terms of Brazil. We will show the current status and characterization of existing forest types in the biome, description of nutrient cycles and factors affecting cycling in forests and indication and analysis of results of studies carried out throughout the biome and the potential of practical use of the data in areas with

improving soil structure and promoting the cycling of nutrients [7].

[2].

being implemented [4].

teristics of the soil [3].

land‐use change.

The Atlantic Forest biome consists of forest formations [Dense Ombrophilous Forest, Mixed Ombrophilous Forest (also known as Araucaria Forest), Open Ombrophilous Forest, Semide‐ ciduous Seasonal Forest, Deciduous Seasonal Forest and Evergreen Seasonal Forest] and pioneer formations, such as Sandbanks, Mangroves and Grassland [8]. The biome represents 13.04% of the Brazilian territory of which only 22% are in native vegetation at different regeneration stages [9].

The significant biodiversity of the Atlantic Forest biome is related to geographical variations in this region. Longitude, latitude and altitude affect the climatic variables, forming regions with distinct characteristics, increasing species diversity. The area of the Brazilian Atlantic Forest covers a large latitudinal extent (from 3°S to 30°S) and longitudinal (approximately 17°) and significant altitudinal variations (from sea level to altitudes above 2700 m in the Manti‐ queira Hills) [10, 11] (**Figure 1**).

**Figure 1.** Distribution of Atlantic Forest Biome in Brazil. Adapted from Ref. [9].

The main forest types found in the Atlantic Forest biome are classified according to the floristic composition and environmental variables, such as precipitation and temperature. In the following section, we show some features of the main forest formation in the Atlantic Forest according to Veloso [12] and the Brazilian Institute of Geography and Statistics [13, 14].

The Ombrophilous Forest is classified as Dense, Open and Mixed formation. Dense Ombro‐ philous forest is characterized by the presence of medium and large trees, in addition to lianas and epiphytes in abundance, due to the constant moisture from the ocean. The coastline extends from the Northeast to the extreme South of Brazil. Its occurrence is connected to hot and humid tropical climate without dry season, with rainfall well distributed throughout the year (eventually there may occur in some regions dry periods until 60 days) and average temperature is 25°C. In Open Ombrophilous Forest, we find arboreal vegetation more sparse and with lower shrubby density. It occupies areas with climatic gradients ranging between two and four dry months. Average temperatures range between 24°C and 25°C. Finally, Mixed Ombrophilous Forest is strongly characterized by the predominance in the upper stratum of *Araucaria angustifolia* and genera of the family Lauraceae (e.g., *Ocotea* and *Nectandra*). It consists of 2776 forest species, and 946 are endemic [10]. The physiognomy occurs in areas of wet climate and without water deficit. The average annual temperature is around 18°C. The Dense and Open Ombrophilous Forests had most forest species (9661) as well as most endemic species (5164) [10].

Seasonal Forest is classified as Deciduous, Semideciduous and Evergreen. For the first, De‐ ciduous Seasonal Forest, it is characterized by a large number of deciduous trees, account‐ ing for more than 50% of individuals of the forest component. It consists of 165 endemic forest species of the total of 1113 found in the forest typology [10]. In the tropical region, its occurrence is conditioned to a long dry period (more than seven months). In the subtropical region, however, this forest formation occurs in areas with long cold periods, for more than five months with average temperatures below 15°C. On the other hand, Semideciduous Sea‐ sonal Forest is composed of deciduous trees, which represent 20–50% of individuals of the forest component. It has the second largest number of forest species (3841) of the Atlantic Forest of which 1081 are endemic [10]. Their occurrence in the tropical region is defined by two well‐defined pluviometric periods, one dry and one rainy with average annual temper‐ ature around 21°C. However, in the subtropical region, this formation occurs in a short dry period followed by a sharp drop in temperature, with averages below 15°C in the cold peri‐ od. The last type is the Evergreen Seasonal Forest, which is composed of deciduous trees, which account for less than 20% of individuals of the forest component. This forest occurs under tropical climate with a rainy and dry season, with about four to six months of dry weather. Still, the arboreal component does not seem to undergo water stress, which causes low leaf shedding.

Currently, approximately 7% of the biome natural areas are well preserved in fragments larger than 100 ha [15]. The biome consists of about 20,000 plant species of which 8000 (i.e., 40%) are endemic [16]. The analysis of species distribution in the different forest formations [10] showed that more than half of the wealth (60%) and most endemics (80%) are found in the Atlantic Forest. Due to their high levels of richness and endemism, the Atlantic Forest is among the top five hotspots in the world [16].

This region is of great importance for Brazil, because more than half of the national population is spread across the Atlantic Forest biome and this region accounts for much of the economic activity in the country. In addition, water resources that serve about 70% of the Brazilian population are located in this biome [17]. However, with the intense land‐use change and the consequent fragmentation of this biome, biodiversity loss is noticeable and there is an eminent need for conservation. Due to the importance of this vegetation component, law n. 11,428 was enacted in 2006 [8] to regulate the use of native plants in the Atlantic Forest biome.
