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Pasture rehabilitation on, and management of degraded areas in the Andes of South Ecuador

Applicant Professor Dr. Erwin Beck, since 4/2014
Subject Area Ecology and Biodiversity of Plants and Ecosystems
Term from 2013 to 2019
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 227674295
 
Final Report Year 2020

Final Report Abstract

Pastoralism is the main land use in the tropical Andes of Ecuador. Mountain rainforests have been widely replaced by pastures with exotic grasses, mainly Golden Millet (Setaria sphacelata). However, many pastures have been abandoned because of heavy infestation by weeds, in particular by the tropical bracken fern (Pteridium spp.). Ecophysiological studies showed a delicate equilibrium between the grass and the weed in which temperature and moisture play an important role. Modelling of the competition over an altitudinal range from 1800 to 2800 m elevation, including also the different UV-sensitivity of Setaria and bracken explains the observation that at lower elevation the grass dominates over the fern whereas in the higher regions the opposite is the case. A second aspect of the competition between both species is a higher nutrient acquisition capacity of the fern, explaining why fertilization of the poor soils shifts the equilibrium in favor of the grass. A third factor is grazing which can stimulate growth of the grass while damaging the fern by trampling, both effects depending however on the intensity of pasture management. Golden Millet is known for a high content of soluble oxalate that can cause the severe cattle disease Hypocalcemia ("milk fever", lameness). Fertilization increases the oxalate content. A joint study with the Universidad Tecnica Particular de Loja (UTPL) showed that fertilization with 100 kg N per ha and year combined with bimonthly cutting the grass (simulating grazing greatly promotes growth but did not increase the oxalate content beyond the toxic threshold. More fertilization and less frequent grazing however, resulted in a toxic oxalate content. In a field experiment on a heavily bracken-infested slope at about 2000 m elevation, control of the bracken fern and subsequent pasture rehabilitation could be achieved and a demonstration area has been prepared with an information booth. Several combinations of fertilization and grazing intensity (simulated by mowing) were investigated with respect to growth of the grass and sustainable suppression of the fern. For information of the local farmers the common management (no fertilization, intense grazing, allowing 0.8 piece of cattle per ha and year) was contrasted with our recommendation (high fertilization, at least during the first years after restoration of the pasture, and low to moderate intensity of grazing, allowing at least two pieces of cattle). With fertilization and proper management the need to create new pastures by clearing the natural forest can thus be mitigated. Since the project was part of the German-Ecuadorian Platform for knowledge transfer, information of knowledge conveyors and potential applicants was an essential program point. The approaches were: Publications in Spanish, oral and poster presentations at meetings, visits of the demonstration area and of individual farms and the provision of plant material. Our data have been used for a holistic ecological and socio-economical assessment of several options for using abandoned pastures in the research area: Afforestation or pasture farming with high or low/no input. The investigation showed that afforestation and intense pasture farming improve the ecological value compared to the abandoned pasture, but low input pasture management does not. This also holds for the economic values of the land use options. A representative poll showed that the local people are more inclined towards afforestation but with subsidies would also prefer intense pasture farming. These studies have been published in 2 papers in Nature Communications triggering press releases from the Technical University of Munich and the Universities of Bayreuth and Marburg.

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