Growing interest in terrestrial carbon sequestration and increasing demand for water and hydropower have focused international and regional attention on ecosystem services. This project examines those services provided by the high altitude páramo grasslands of the northern Andes. The concept of Payment for Ecosystem Services is being implemented in Ecuador, leading to tree planting in páramo grasslands to sequester carbon and alteration of traditional burning and grazing regimes to enhance water resources. However, the biophysical outcomes of these and related changes in land use and management are poorly understood, and in some cases well-intended changes may not be producing the desired outcomes. In this project, the researchers will systematically investigate the effects of land use change on the production of soil-related ecosystem services, quantify potential tradeoffs among ecosystem services, and evaluate policy implications of different land management strategies. The primary objectives are 1) to determine how land use change affects carbon storage, water storage, and water transmission in Andean páramo soils and 2) to evaluate which land uses maximize ecosystem services related to both carbon and water in páramo grassland soils. The researchers will integrate field observations and in situ experiments at two páramo study sites, Zuleta (northern Ecuador) and the Nudo del Azuay (southern Ecuador), with laboratory analyses of soil samples, and assessment of synergies, trade-offs, and relevant policies to quantify and predict effects of land use change on carbon- and water-related ecosystem services.
This research will provide essential data for predicting ecosystem responses to land use change and will have immediate societal application by improving the scientific basis for Payment for Ecosystem Services programs. The results will provide key data for conservation organizations on the appropriateness of forestation as a form of land restoration in the study region, and will inform policies and programs intended to enhance both terrestrial carbon sequestration and water provision in the Ecuadorian Andes. The research also will provide educational opportunities for several graduate students and a middle-school science teacher from the U.S. and for participating undergraduate students at the University of Azuay in Ecuador, and it will strengthen the collaboration between the investigators and their Ecuadorian partners.
High-elevation Andean paramo grasslands have become a focus of Payment for Ecosystem Services (PES) programs, which compensate land managers for practices expected to promote the production of ecosystem services. However, paramo management recommendations are generally based on assumptions, with little field-derived data to support them. This research investigated the effects of land use/management on the ecosystem services of carbon storage, water storage, and biodiversity in paramo grasslands, focusing on practices currently incentivized by PES programs: afforestation with pine or Polylepis racemosa and reductions in burning. Afforestation WATER. The soil under pine plantations was significantly drier than at grass sites, and tracer tests showed that grasslands regulate the infiltration and subsurface movement of water more uniformly than pine plantations. Polylepis racemosa did not affect soil moisture where the trees were small, but is expected to use more water use as tree size increases. At the northern study area, the pine plantation soil was drier, with less capacity to retain water than that of surrounding grasslands. In the south, surface (upper 12 cm) soils in the two pine plantations evaluated were drier than soil in grass sites but different from each other. Root sizes and architectures also differ significantly between pines and tussock grasses. CARBON. Pines effectively sequester carbon in their biomass, particularly if they remain unharvested for several decades; however, their effects on soil carbon ranged from large negative to small positive impacts. Managing pine plantations to promote a tussock understory could increase soil carbon. Young stands of Polylepis racemosa stored only modest amounts of carbon aboveground and did not alter soil carbon. BIODIVERSITY. Plant species richness in pine plantations, compared to grasslands, was lower in the south but higher in the north, where native forest was adjacent and gaps from harvesting allowed light to enter. Afforestation with Polylepis did not have a pronounced influence on species richness at this stage, though an increase in some native species where Polylepis trees were planted in a former agricultural site demonstrated that, on degraded lands, these plantations may increase biodiversity. Burning WATER. Burning has not reduced the water-retention capacities of paramo soils; moreover, water-retention capacities were highest in recently burned sites. Where grass had remained unburned for 45 years and woody species were becoming established, soil moisture was intermediate between grass and pine, suggesting that, by sustaining the dominance of grasses over woody vegetation, burning promotes moist soil conditions. This result contrasts with current incentives for reducing burning in paramos. CARBON. Our results also suggest that there may be potential for burning on less frequent rotations to maintain or improve carbon sequestration. They also highlight the high soil carbon storage potential of paramo grasslands, where most of the carbon stock is belowground, and the importance of including soil carbon in PES program design. BIODIVERSITY. Our findings challenge the idea that burn exclusion is the optimal way to protect paramo plant diversity and suggest that some burning increases plant species richness, providing openings for small herbaceous species to establish. Burn exclusion in the north led to almost complete domination of tussock grass, while long-term burn exclusion in the south led to a transition to native woodlands. Overall, results suggest a mosaic of burn frequencies likely maximizes landscape diversity. Implications Different relationships found across study areas demonstrated the heterogeneity of Andean paramo ecosystems and the resulting challenge of operationalizing land-use prescriptions to maximize ecosystem services across an environmentally and socio-economically diverse region. Also, the difficulty of obtaining all three ecosystem services (carbon, water, and biodiversity) simultaneously suggests that PES programs should identify one highest priority service while endeavoring to maintain others. Grass paramo supports the production and regulation of fresh water, while afforestation with pine maximizes carbon sequestration but involves important trade-offs and Polylepis plantations do not appear to be highly effective for carbon sequestration. Infrequent burning of grass paramo provides substantial carbon storage without water tradeoffs, and a mosaic of burn frequencies appears to help maximize biodiversity. Because each land use has its own, even local, consequences, no single prescription optimizes the production of all of these services across the region. Broader impacts Broader impacts of this research included the participation of a middle-school science teacher from the U.S. in Ecuadorian fieldwork, and training of eight U.S. graduate students (including one dissertation and one M.S. thesis). The project strengthened relationships between the U.S. PIs (two of whom are female) and five Ecuadorian partner agencies, as well as with other Ecuadorian organizations and individuals. In collaboration with partner organization EcoCiencia, the PIs convened a workshop in Quito, Ecuador at which they presented results of the research, solicited comments from an invited panel of local experts, and discussed Payment for Ecosystem Services programs and management of paramo lands with the 39 participants. They also have a Spanish-language publication in preparation for dissemination in Ecuador.
