The páramo ecosystem is a high-altitude alpine grassland ecosystem found in the northern Andes that is recognized as a biodiversity hotspot for its unique species composition. The Colombian páramo is presently undergoing a dramatic transformation due to activities such as drainage, cattle ranching, coal production, and potato cultivation. Accumulated evidence from studies in high latitude temperate grasslands indicates that continuous soil plowing produces a long-term impact on the composition of microbial communities, soil fertility and soil carbon storage capacity. However, little is known about the effect of agricultural practices on the soil structure, aggregate distribution and carbon storage of páramo soils. To our knowledge, this is the first study to evaluate these properties as a function of soil depth in this ecosystem.
We selected three sites along a precipitation gradient and established soil pits (1 m3 volume) in both relict fragments of páramo and adjacent areas undergoing potato cultivation longer than 40 years. We determined in triplicate the distribution of water stable aggregates (WSA) of different size classes (< 53 μm, 53-250 μm, 250-2000 μm and 2000-8000 μm) at seven points along a 1-m deep profile. In addition, we determined the percent total carbon and nitrogen using a LECO TruSpec CHN elemental analyzer.
Results/Conclusions
Our results revealed significant changes in the distribution of WSA > 53 μm in size for the first 20 cm of soil depth but not for the WSA < 53 μm. In addition, these soils showed very little changes in WSA distribution for depths between 20 to 100 cm suggesting that the effect of continuous plowing did not propagate to the lower profiles. Total Carbon content (%) also varies with soil depth with a major reduction below 80 cm in depth. However, the strongest change in Total Carbon content (%) was observed between sites along the precipitation gradient.
Our results suggest that páramo soils have the potential to accumulate and store great amounts of carbon. Our next step is to perform density fractionation of the Water-Stable Aggregates to distinguish among the functionally different fractions to improve our understanding of the long-term storage of carbon in both cultivated and intact páramo soils.