Streams with Riparian Forest Buffers versus Impoundments Differ in Discharge and DOM Characteristics for Pasture Catchments in Southern Amazonia

Abstract

Forest to pasture land use change following deforestation in Southern Amazonia can result in changes to stream water quality. However, some pasture streams have riparian forest buffers, while others are dammed for farm ponds. Stream corridor management can have differential effects on hydrology and dissolved organic matter (DOM) characteristics. We examined rainfall-runoff patterns and DOM characteristics in a pasture catchment with a forested riparian buffer, and an adjacent catchment with an impoundment. Total streamflow was 1.5 times higher with the riparian buffer, whereas stormflow represented 20% of total discharge for the dammed stream versus 13% with buffer. Stream corridor management was also the primary factor related to DOM characteristics. In the impounded catchment, DOM was found to be less structurally complex, with lower molecular weight compounds, a lesser degree of humification, and a larger proportion of protein-like DOM. In the catchment with a forested buffer, DOM was dominated by humic-like components, with fluorescence characteristics indicative of DOM derived from humified soil organic matter under native vegetation. Our results suggest that differences in stream corridor management can have important implications for carbon cycling in headwater pasture catchments, and that such changes may have the potential to influence water quality downstream in the Amazon basin.

Tracing terrestrial versus marine sources of dissolved organic carbon in a coastal bay using stable carbon isotopes

“…S1 and S2). Based on the comparison with data in the OpenFluor (Murphy et al, 2014), Component 1 (FDOM H ; Ex/Em = 322/405 nm) is associated with a terrestrial humic-like component (Liu et al, 2019;Dalmagro et al, 2019;and Chen et al, 2016). Component 2 (FDOM M ; Ex/Em = 386/450 nm) is also associated with an allochthonous humic-like component (Wünsch et al, 2017).…”

“…The assumed end-member values of DOC and δ 13 C-DOC were 185 µM and −28 ‰ (Raymond and Bauer, 2001), respectively, for the terrestrial endmember (S = 0) and 100 µM and −18 ‰ (Kelley et al, 1998), respectively, for the marine end-member (S = 34). The δ 13 C values from Group 1 fall on the mixing line or are slightly heavier than the mixing line, within 1.5 ‰, indicating conservative mixing between the terrestrial C 3 land plants (−23 ‰ to −32 ‰; Deines, 1980) in freshwater and open-ocean seawater. The slightly heavier values could be produced by in situ biological production during the mixing processes.…”

“…The stable carbon isotopic composition of dissolved organic carbon (δ 13 C-DOC) has been used to distinguish different sources. In general, δ 13 C values derived from C 3 and C 4 land plants are in the range of −23 ‰ to −34 ‰ and −9 ‰ to −17 ‰ (Deines, 1980), respectively, while those derived from marine phytoplankton range from −18 ‰ to −22 ‰ (Kelley et al, 1998;Coffin and Cifuentes, 1999). In addition, the optically active fraction of DOM known as fluorescent DOM (FDOM) has been successfully used for characterizing DOM (Coble et al, 1990;Coble, 1996).…”

Methane, Microbes and Models in Amazonian Floodplains: State of the Art and Perspectives

“…The interest in estimates of CH 4 emission in tropical forests has grown in recent years, particularly in wetlands such as the Amazon basin [10][11][12][13][14][15] and Pantanal [16][17][18]. This is due to the fact that the largest natural sources of CH 4 are wetlands [19], contributing with 177-284 Tg CH 4 per year [7].…”

“…The Colombian wetlands were evaluated and showed that the studied ecosystems are valuable C sinks, and hydrogeomorphology acts as an important factor for the storage of C in these ecosystems [59]. Dalmagro et al [18], when evaluating the largest tropical floodplain area in the world, Pantanal, revealed that they are potentially large C sinks and that the C balance was driven by the seasonal dynamics of precipitation and surface flooding that affected the anaerobic and aerobic phases of the soil. The assessment of the behavior of a freshwater flood area with a usual average flood period of 6 months per year, located in a park in the USA, showed that the environment become a source of CO 2 when it went through a prolonged flood period (17 months).…”