Abstract

Páramos are highly biodiverse ecosystems in the northern Andes, providing essential services such as water provision and carbon sequestration. However, increasing anthropogenic pressures are altering their ecological functions, particularly their carbon storage capacity. Soil organic carbon stocks are relatively well understood in páramo systems, however, the above and below ground plant biomass stocks have been less studied, especially under varying levels of disturbance. This study quantifies biomass stocks and concentrations in the Ponce-Paluguillo Water Protection Area (APHP) in northern Ecuador, across a gradient of anthropogenic disturbance. Vegetation plots were categorized into four disturbance classes: Overgrazed Páramo, Recovering Areas, Páramo Grassland, and Shrubby Páramo Grassland. Species biomass concentrations were estimated using allometric models developed from representative species via destructive sampling, then generalized to similar species. Biomass stocks were calculated by multiplying species-specific biomass concentrations by their coverage areas, aggregated by quadrant. Our results showed that tussock grasses and sclerophyllous shrubs had the highest biomass concentrations, with the Andean fescue, Festuca andicola, surpassing all other species. Recovering Areas exhibited the highest total and aboveground biomass stocks (61.41 ± 24.48 Mg/ha and 43.93 ± 4.28 Mg/ha), followed by Shrubby Páramo Grasslands (30.30 ± 0.26 Mg/ha and 27.78 ± 0.02 Mg/ha). We also found that Overgrazed Páramo had the lowest values (22.10 ± 2.42 Mg/ha and 14.01 ± 2.15 Mg/ha). Species diversity followed a similar pattern, with disturbed sites showing higher diversity than undisturbed sites. This suggests that pasture fallowing in páramo grasslands follows a successional pattern consistent with the mass ratio hypothesis (MRH). The biomass estimates we report are similar to several other paramo plant biomass studies, suggesting that the methodology we employed is accurate and can be used to estimate and monitor aboveground and total plant biomass in páramo ecosystems under different land use types. Our results indicate that in this páramo system, the highest biomass gains occur early in succession under relatively high disturbance levels, suggesting that natural recovery alone may not maximize long-term carbon sequestration. Therefore, active management strategies might be more appropriate, such as controlled pasture fallowing, could be employed to maintain intermediate disturbance levels, thereby promoting both biodiversity and biomass accumulation.