Chemical analysis of rainfall and throughfall in the Tapajós National Forest, Belterra, Pará, Brazil

The Tapajós National Forest (FLONA Tapajós) has 600,000 hectares of protected forest, and is situated 50 km south of the city of Santarém, Pará, Brazil, a port city of 250,000 inhabitants that is located at the confluence of the Tapajós 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 Santarém. 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 Santarém-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 Tapajós at km 67 of Santarém- Cuiabá Highway, south of the city of Santarém. 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 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

Physical, chemical, and biological properties of soil under soybean cultivation and at an adjacent rainforest in Amazonia

Land-use change in the Amazon basin has occurred at an accelerated pace during the last decade, and it is important that the effects induced by these changes on soil properties are better understood. This study investigated the chemical, physical, and biological properties of soil in a field under cultivation of soy and rice, and at an adjacent primary rain forest. Increases in soil bulk density, exchangeable cations and pH were observed in the soy field soil. In the primary forest, soil microbial biomass and basal respiration rates were higher, and the microbial community was metabolically more efficient. The sum of basal respiration across the A, AB and BA horizons on a mass per area basis ranged from 7.31 to 10.05 Mg CO2-C ha-1yr-1, thus yielding estimates for total soil respiration between 9.6 and 15.5 Mg CO2-C ha-1yr-1 across sites and seasons. These estimates are in good agreement with literature values for Amazonian ecosystems. The estimates of heterotrophic respiration made in this study help to further constrain the estimates of autotrophic soil respiration and will be useful for monitoring the effects of future land-use in Amazonian ecosystems

Integrated farming systems influence soil organic matter dynamics in southeastern Brazil

Integrated farming systems are sustainable strategies to intensify land productivity by combining annual crop, livestock and/or forestry activities in different spatio-temporal arrangements. Therefore, they may help tackle global food and energy insecurity and climate change in the coming decades. We investigated the effects of integrated crop-livestock (ICL) and integrated crop-livestock-forestry (ICLF) systems on quantity, quality, and origin of soil organic matter (SOM) in southeastern Brazil. A native forest and an extensive low-grazing intensity pasture system were used as references. In integrated systems, corn (Zea mays) was alternated with two consecutive years of piatã grass (Urochloa bryzantha) for cattle grazing. In ICLF, eucalyptus trees (Eucalyptus urograndis) were planted in simple rows of 15 × 2 m. Soil sampling was performed three times; in 2014, after two years of grazing; in 2015, after crop cultivation; and in 2016, after a successive grazing year, to evaluate chemical and physical composition changes of organic matter (C, N, δ13C, δ15N, and organic matter fractions) with time. Our findings showed that from 2010 to 2016, all systems (extensive grazing, ICL and ICLF) promoted increments on soil C and N stocks. However, land intensification converting extensive low-grazing intensity pasture to ICL was the most promising strategy, increasing soil C stocks at the rate of 0.28 Mg C ha−1 yr−1 from 2010 to 2016. Annual crop cultivation (corn intercropped with piatã grass) promoted high organic matter inputs on the soil, increasing the amount of soil labile organic matter fractions, which presented higher δ13C and lower δ15N values over time. SOM in the integrated farming systems was originated mainly from C4 plants. Therefore, optimizing development of piatã grass and corn increases organic residue inputs and then, soil C and N stocks. In addition, the crop period increased soil fertility parameters, which favors plant growth, thus providing high labile C inputs to the soil. In contrast, land intensification by adding the forestry component into the system (i.e., conversion from ICL to ICLF) reduced soil C (-0.22 Mg C ha−1 yr−1) and N (-0.03 Mg N ha−1 yr−1) stocks from 2010 to 2016, likely due to the reduction of C and N inputs to the soil caused by limited growth of annual crop and grass species under tree shades. In conclusion, land use intensification through ICL system contributes towards a more efficient and low-C agriculture, whereas the studied ICLF system did not bring further benefits to increase the quantity and/or quality of SOM

Estimation of biomass and carbon stocks: the case of the Atlantic Forest

The main objective of this paper is to present and discuss the best methods to estimate live above ground biomass in the Atlantic Forest. The methods presented and conclusions are the products of a workshop entitled "Estimation of Biomass and Carbon Stocks: the Case of Atlantic Rain Forest". Aboveground biomass (AGB) in tropical forests is mainly contained in trees. Tree biomass is a function of wood volume, obtained from the diameter and height, architecture and wood density (dry weight per unit volume of fresh wood). It can be quantified by the direct (destructive) or indirect method where the biomass quantification is estimated using mathematical models. The allometric model can be site specific when elaborated to a particular ecosystem or general that can be used in different sites. For the Atlantic Forest, despite the importance of it, there are only two direct measurements of tree biomass, resulting in allometric models specific for this ecosystem. To select one or other of the available models in the literature to estimate AGB it is necessary take into account what is the main question to be answered and the ease with which it is possible to measure the independent variables in the model. Models that present more accurate estimates should be preferred. However, more simple models (those with one independent variable, usually DBH) can be used when the focus is monitoring the variation in carbon storage through the time. Our observations in the Atlantic Forest suggest that pan-tropical relations proposed by Chave et al. (2005) can be confidently used to estimated tree biomass across biomes as long as tree diameter (DBH), height, and wood density are accounted for in the model. In Atlantic Forest, we recommend the quantification of biomass of lianas, bamboo, palms, tree ferns and epiphytes, which are an important component in this ecosystem. This paper is an outcome of the workshop entitled "Estimation of Biomass and Carbon Stocks: the Case of Atlantic Rain Forest", that was conducted at Ubatuba, São Paulo, Brazil, between 4 and 8 December 2006 as part of the Brazilian project "Ombrophylus Dense Forest floristic composition, structure and function at the Núcleos Picinguaba and Santa Virginia of the Serra do Mar State Park", BIOTA Gradiente