Spectroscopic Assessment of Soil Organic Matter in Wetlands from the High Andes

Abstract

Wetlands are valuable for their function as C sinks, water conservation and filtering, flood control, and as a recreational landscape. In the Central and Southern Andes, peatlands (a.k.a., bofedales) are also a source of good quality pastures for wild and domestic South American camelids (Vicugna pacos, Lama glama, and Vicugna vicugna). In the present study, whole soil samples from seasonally and permanently flooded bofedales were analyzed using laser‐induced fluorescence spectroscopy (LIFS) and electron paramagnetic resonance (EPR) to assess soil organic matter (SOM) stability. The results obtained by both techniques were comparable (R2 = 0.88) and proven to be reliable indicators of increased or reduced SOM stability and thus suitable methods for assessing its humification index. The humification values determined in the permanently flooded bofedal were lower than for the seasonally flooded one. Deeper in the soil profiles of both bofedal types, the humification process of SOM attains more advanced stages, with a relative increase of more recalcitrant organic compounds. An important factor is the presence of water in permanently flooded bofedales, which slows down organic matter decomposition due to anaerobiosis. Results from a portable LIFS system also showed significant correlations when compared with both the bench LIFS system (R2 = 0.88) and the EPR (R2 = 0.62). The portable system constitutes an affordable option for the in situ characterization of SOM. This assessment is of outmost importance in agroecosystems acting as green house gases sink or sources under variable climatic conditions.

Soil carbon stock and humification in pastures under different levels of intensification in Brazil

“…Samples were excited by a continuous wave (cw) laser, at a wavelength of 405 nm radiation, emitted by diode laser equipment (labassembled instrument) with a power source of approximately 200 mW. Experimental procedures were conducted according to Segnini et al (2010). The measurement range was from 475 nm to 800 nm, the integration time 500 ms, and the average and boxcar five and four, respectively, for all evaluations.…”

Key ecosystem services and ecological intensification of agriculture in the tropical high-Andean Puna as affected by land-use and climate changes

“…Muñoz García and Faz Cano (2012) reported a carbon stock of 2-3.8 kg C m À2 in the soil surface (5 cm depth) of a managed Bolivian Wet Puna grassland grazed by vicuñas above 4500 m asl. Furthermore, it has been shown that SOC stocks in high Wet Puna wetlands largely exceed native grasslands C stocks, reaching values of 30.6 kg C m À2 in the 0-30 cm soil profile of seasonally flooded wetlands (Segnini et al, 2010).…”

“…An archetypal case of a high altitude region is the tropical high-Andean Puna (hereafter Puna). High biological diversity, agrobiodiversity, and endemism (Buytaert et al, 2011;de Haan, 2009), large reservoir of soil organic carbon (SOC) stocks Segnini et al, 2010), and water provision to mining, agricultural, energetic, and urban demands (Buytaert et al, 2011;Buytaert and de Bièvre, 2012;Vuille et al, 2008b) confer a special ecological relevance to this region. Nevertheless, high-altitude ecosystems are among the most fragile of the Earth as they show low recovery rates after disturbance (Bierman-Lytle, 2015).…”

Carbon stock and humification index of organic matter affected by sugarcane straw and soil management

“…Soil C humification index determination by LaserInduced Fluorescence Spectroscopy Laser-Induced Fluorescence Spectroscopy (LIFS) of the soil samples was used to assess the SOM humification (Milori et al, 2006;González-Pérez et al, 2007;Segnini et al, 2010Segnini et al, , 2011Milori et al, 2011). Homogenized soil samples were used to produce pellets.…”