Soil organic matter stocks and quality at high altitude grasslands of Apolobamba, Bolivia

In many cases, ecosystems in the puna or grasslands in the Andean plateaus are degraded as a consequence of anthropogenic activities. The Apolobamba Integrated Management National Area is located in the Northwest of La Paz (Bolivia). This grassland ecosystem, with a high biodiversity, is a natural habitat of camelid populations, such as vicuna (Vicugna vicugna), a wild endangered species, and alpaca, a domestic camelid. There is not much information related to carbon reservoirs and camelid influence in these ecosystems. The objectives of this study were to (i) quantify total SOC contents as well as its quality by applying 13C CP/MAS-Nuclear magnetic resonance spectroscopy, and (ii) determine the degree in soil exhaustion in selected zones on the basis of the degradation of SOM, related to vicuna and alpaca populations in Apolobamba. The vicuna densities were considered to select the studied zones as well as other characteristics. The goals of this research were achieved through the analyses of soil organic carbon quantity in soil profiles and in sampling plots. Likewise the 13C CP/MAS-Nuclear magnetic resonance technique was used to gain information about soil carbon quality. Based on Total Organic Carbon contents and functional carbon groups we classified the area into three groups: 1) High, with O-Alkyl-C (50–112 ppm) contents between 44% and 41% (zones 8, 4, 5, 7, 2 and 6), 2) Medium, 39% (zone 1), and 3) Low, 36% (zone 3). These results and the Alkyl-C/O-alkyl-C ratios (above 0.7) indicated Soil Organic Matter with a low stabilization. Overall Nuclear Magnetic Resonance spectra pointed out that the degradation of Soil Organic Matter was higher in zones 1 and 3 than in other studied areas in connection with high alpaca concentration. Although, results showed that some studied zones could be excellent carbon reservoirs we suggest that these three zones should be specifically protected from camelid overexploitation to avoid the soil exhaustion and preserve high grassland ecosystems and its biodiversity in the Apolobamba area.

Research highlights
► High altitude grasslands can be degraded by camelid overexploitation.
► We provide information about soil organic carbon stocks and soil exhaustion degree.
► Studied zones exhibited excellent soil carbon reservoir quantity.
► Protection activities are needed to avoid soil organic matter degradation.