Abstract
The Tapajos National Forest (FLONA Tapajos) has 600,000 hectares of protected forest, and is situated 50 km south of the city of Santarem, Para, Brazil, a port city of 250,000 inhabitants that is located at the confluence of the Tapajos and Amazon Rivers. There is a lot of farmland in the region, which offers many opportunities to study changes in land use. Selective wood harvesting is one type of land use that is particularly important to the economy of Santarem. Wet and dry deposition of organic material can be an important source of nutrients for plants, and this is especially true when the soil is poor, which is the case in Santarem-Belterra plateau region, the study area of this research. In this region, the natural atmospheric deposition of nutrients is often enhanced by the burning of biomass, which releases a large part of the above-ground biomass nutrients into the atmosphere. The objectives of this study were: 1 - estimate the total wet deposition via direct precipitation and through the canopy, including dry deposition; 2 - verify potential sources of nutrients found in the total wet deposition and dry deposition; and 3 - investigate the effects of coverage vegetation on nutrient content in precipitation and throughfall. The study was conducted in FLONA Tapajos at km 67 of Santarem- Cuiaba Highway, south of the city of Santarem. The study area consisted of a portion of 100 x 100 m transects divided into 10 x 10 m plots. The area was located next to a meteorological tower 65 m tall that measures various climate parameters such as rainfall, wind speed and direction, solar radiation, temperature and humidity, among others. Direct precipitation (PD) and internal precipitation (IP) collectors consisted of 2 L polyethylene bottles with a 115 mm diameter funnel. Samples were collected weekly from April 2003 to March 2006. The volume of the sample was measured individually for each collector (25 traps for internal precipitation and 4 for direct precipitation). The conclusions that can be drawn from this study are: 1 - the dry season has the highest variation
Highlights
The Tapajós National Forest (FLONA Tapajós) has 600,000 ha of protected forest, and is situated 50 km to the south of the city of Santarém, Pará, Brazil, a port city of 250,000 habitants situated at the confluence of the Tapajós and Amazon Rivers.The Santarém-Belterra Plateau, an area of 400,000 hectares (Oliveira Junior and Correa, 2001), has experienced land use change for the last 15 years due to the conversion of forest to grassland or forest to grain agriculture, and most commonly, of pasture to grain agriculture (Cohenca, 2005; Gardner et al, 2013)
In ion flux; 2 - seasonality has a strong influence on the concentration of basic cations; 3 - dry deposition is one of the most important ways that nutrients are acquired in FLONA Tapajos; 4 - there is a significant inflow of nutrients Cl and Na due to intensive grain farming nearby; 5 - dry deposition is the most important process for the enrichment of water that reaches the forest floor; 6 - principal component analysis facilitates the interpretation and characterization of rainwater and in this study shows the influence of anthropogenic sources such as agriculture, biomass burning, and dust
3.2. pH and electrical conductivity The results show that the pH of rainfall and throughfall slightly decreases at the beginning of the dry season and increases during the wet season (Table 1)
Summary
The Tapajós National Forest (FLONA Tapajós) has 600,000 ha of protected forest, and is situated 50 km to the south of the city of Santarém, Pará, Brazil, a port city of 250,000 habitants situated at the confluence of the Tapajós and Amazon Rivers.The Santarém-Belterra Plateau, an area of 400,000 hectares (Oliveira Junior and Correa, 2001), has experienced land use change for the last 15 years due to the conversion of forest to grassland or forest to grain agriculture, and most commonly, of pasture to grain agriculture (Cohenca, 2005; Gardner et al, 2013). Today the region has about 47,000 ha with mechanized agriculture of rice, soy and corn (Pará, 2011). According to Venturieri et al (2007), from the late 90s and early 2000s, the region of the Lower Amazon, the municipalities of Santarém and Belterra, began to experience a new occupational process based on the use of mechanized agriculture. Tropical rainforests represent a type of ecosystem that has a large influence on hydrologic processes (Jeten, 1996). The trees intercept a large part of the rainfall on the forest, a portion of which evaporates, and the portion that reaches the forest floor is determined by the intensity of the canopy and by its drainage characteristics (Jeten, 1996)
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