Carbon and nitrogen stock and fluxes in coastal Atlantic Forest of southeast Brazil: potential impacts of climate change on biogeochemical functioning

Benefits of Blue Carbon Stocks in a Coastal Jazan Ecosystem Undergoing Land Use Change

Coastal ecosystems are characterized by high content of soil carbon storage; however, they experience severe land conversions in the past decades. The current study aims to examine how different land use/land cover (LU/LC) impact carbon stock in coastal ecosystem along Jazan coast, Saudi Arabia. In this study, impacts of LU/LC on carbon stocks in the coastal zone of Jazan, Saudi Arabia in 2009, 2013, and 2021 were assessed. Also, the LU/LC dynamics were evaluated using data provided by the land use dynamic model. The carbon stocks were modelled based on LU/LC using the InVEST program. Our study results showed that the decrease in mangroves from 2013 to 2021 reflects the high atmospheric emissions of carbon dioxide (CO2). Also, the increase in built-up areas might negatively impact total carbon stock. The estimated carbon stocks for the coastal zone of Jazan biome were 7279027.42 Mg C in 2009 (1Mg = 106 g). It decreased to 2827817.84 Mg C in 2013, with a total loss of − 4450675.40 Mg C, and an average of annual loss of − 1,112,669 Mg C in the study period with net value of − 461240790.53 US$. On the other hand, the total estimated carbon stock was increased from 2013 to 2021 with a 3772968.31 Mg C in 2021 (a total gain 944840.87 Mg C). Based on the current findings, we recommend that land-use-policy makers and environmental government agencies should implement conservation policies to reduce land use change at Jazan coastal ecosystems.

Carbon and nutrient stocks of three Fabaceae trees used for forest restoration and subjected to fertilization in Amazonia

Amazonia is crucial to global carbon cycle. Deforestation continues to be one of the main causes of the release of C into the atmosphere, but forest restoration plantations can reverse this scenario. However, there is still diffuse information about the C and nutrient stocks in the vegetation biomass. We investigated the carbon and nutrient stocks of Fabaceae trees (Inga edulis, Schizolobium amazonicum and Dipteryx odorata) subjected to fertilization treatments (T1 - no fertilization; T2 - chemical; T3 - organic; and T4 - organic and chemical fertilization) in a degraded area of the Balbina Hydroelectric Dam, AM - Brazil. As an early successional species, I. edulis stocked more C and nutrients than the other two species independent of the fertilization treatment, and S. amazonicum stocked more C than D. odorata under T1 and T4. The mixed species plantation had the potential to stock 4.1 Mg C ha-1 year-1, while I. edulis alone could stock 9.4 Mg C ha-1 year-1. Mixing species that rapidly assimilate C and are of significant ecological and commercial value (e.g., Fabaceae trees) represents a good way to restore degraded areas. Our results suggest that the tested species be used for forest restoration in Amazonia.

Carbon accumulation rates recorded in the last 150years in tropical high mountain peatlands of the Atlantic Rainforest, SE - Brazil

Peatlands are environmental matrices that store large amounts of organic carbon (TOC) and work as records of environmental changes. Recent record of organic carbon accumulated were assessed in two Forest National Parks, Itatiaia and Serra dos Órgãos in the Southeastern of Brazil. Based on organic and inorganic characterization, the cores from peatlands presented a predominance of organic material in an advanced stage of decomposition and those soils were classified as typical Haplosaprists Histosols. The combination of favorable topographic and climatic conditions led to rapid C accumulation across coastal mountain in the tropical peatlands studied, presenting an average accumulation rate of C, in the last century, of 194gCm^-2yr^-1 about 7 higher times than the rate found in boreal and subarctic peatlands, those higher values may be related to changes in the hydrological cycle occurred since 1950s.

Influence of hydrological pathways on dissolved organic carbon fluxes in tropical streams

Water flow pathways and water balance are fundamental components for understanding the dynamics of C in the soil/water interface of small basins. The objective of this study was to describe the seasonal variations and estimate the annual balance of dissolved organic carbon (DOC) by comparing two tropical microbasins (preserved forest—PF and cacao plantation—CP). Twenty‐one weekly collections were conducted from September to December 2012 and from April to June 2013. The calculation of the partial balance considered precipitation (P) as inflow and the stream as outflow. The samples were filtered and analyzed using a TOC analyzer. Overall, the DOC was higher CP compared with FP. The behavior of both venues showed that rainy season caused an increase in concentrations in the overland flow (OF) and in the stream, and a decrease in the precipitation (P) and in the throughfall (T). In the CP, the outflow and the soil were chiefly responsible for the high DOC concentrations in the stream, when compared to the PF, which is the result of constant OM decomposition. Soil composition contributes to the control of DOC consumption in each type of soil. The balances were negative in both microbasins, although losses were higher in the AFS (agroforestry systems) when compared to the PF, especially during rainy seasons (−8.98 and −3.05 kg ha⁻¹ year⁻¹, CP and FP, respectively). Thus, the high annual loss of DOC in the CP of the microbasins during the rainy season indicates changes in ecosystem metabolism due to the vegetation cover and to the interactions with the soil.

Evaluation of nutrients and major ions in streams-implications of different timescale procedures

Small watersheds are characterized by a high degree of sensitivity to changes observed in their environment, making them important sampling and management units. Due to this high sensitivity, several studies have shown that intensive collecting may be more effective in these systems compared to other timescale procedures. The aim of this study was to evaluate the concentration of organic and inorganic nutrients and major ions dissolved in two small watersheds with different land uses to determine whether there are differences between these watersheds with different levels of impact and to identify the most appropriate timescale procedure for the variables under analysis. Therefore, monthly, daily, and hourly samples were taken in the two streams in the northeast of Brazil. One of the streams is located in an undisturbed area (environmental protected area) (S1) and one in a disturbed area (S2). The results showed significant differences for conductivity, temperature, pH, dissolved oxygen (%), sodium (Na(+)), and chloride (Cl(-)) ions and higher values presented in the anthropogenic stream. Dissolved inorganic nitrogen (DIN) in S2 mainly comprised ammonium (NH4 (+)), while nitrate (NO3 (-)) predominated in S1. The considerable increase in the concentration of NO3 (-) and dilution of Na(+) and Cl(-) after rain in April in S1 shows how precipitation may change the chemical composition of the water in a 1-day period. No changes were observed in the concentrations of major ions and nutrients that could be related to the cyclical variation of the hours during the day in both small watersheds. Daily collections allow better monitoring of the dynamics of streams and greater robustness of the data.