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Item type:Publication, Ecohydrological assessment of the water balance of the world's highest-elevation tropical forest (Polylepis)(Elsevier B.V., 2024-09-01)Polylepis trees grow at elevations above the continuous tree line (3000–5000 m a.s.l.) across the Andes. They tolerate extreme environmental conditions, making them sensitive bioindicators of global climate change. Therefore, investigating their ecohydrological role is key to understanding how the water cycle of Andean headwaters could be affected by predicted changes in environmental conditions, as well as ongoing Polylepis reforestation initiatives in the region. We estimate, for the first time, the annual water balance of a mature Polylepis forest (Polylepis reticulata) catchment (3780 m a.s.l.) located in the south Ecuadorian páramo using a unique set of field ecohydrological measurements including gross rainfall, throughfall, streamflow, and xylem sap flow in combination with the characterization of forest and soil features. We also compare the forest water balance with that of a tussock grass (Calamagrostis intermedia) catchment, the dominant páramo vegetation. Annual gross rainfall during the study period (April 2019–March 2020) was 1290.6 mm yr−1. Throughfall in the Polylepis forest represented 61.2 % of annual gross rainfall. Streamflow was the main component of the water balance of the forested site (59.6 %), while its change in soil water storage was negligible (<1 %). Forest evapotranspiration was 54.0 %, with evaporation from canopy interception (38.8 %) more than twice as high as transpiration (15.1 %). The error in the annual water balance of the Polylepis catchment was small (<15 %), providing confidence in the measurements and assumptions used to estimate its components. In comparison, streamflow and evapotranspiration at the grassland site accounted for 63.7 and 36.0 % of the water balance, respectively. Although evapotranspiration was larger in the forest catchment, its water yield was only marginally reduced (<4 %) in relation to the grassland catchment. The substantially higher soil organic matter content in the forest site (47.6 %) compared to the grassland site (31.8 %) suggests that even though Polylepis forests do not impair the hydrological function of high-Andean catchments, their presence contributes to carbon storage in the litter layer of the forest and the underlying soil. These findings provide key insights into the vegetation-water‑carbon nexus in high Andean ecosystems, which can serve as a basis for future ecohydrological studies and improved management of páramo natural resources considering changes in land use and global climate. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Patterns and Drivers of Evapotranspiration in South American Wetlands(Nature Research, 2023-12-01)Evapotranspiration (ET) is a key process linking surface and atmospheric energy budgets, yet its drivers and patterns across wetlandscapes are poorly understood worldwide. Here we assess the ET dynamics in 12 wetland complexes across South America, revealing major differences under temperate, tropical, and equatorial climates. While net radiation is a dominant driver of ET seasonality in most environments, flooding also contributes strongly to ET in tropical and equatorial wetlands, especially in meeting the evaporative demand. Moreover, significant water losses through wetlands and ET differences between wetlands and uplands occur in temperate, more water-limited environments and in highly flooded areas such as the Pantanal, where slow river flood propagation drives the ET dynamics. Finally, floodplain forests produce the greatest ET in all environments except the Amazon River floodplains, where upland forests sustain high rates year round. Our findings highlight the unique hydrological functioning and ecosystem services provided by wetlands on a continental scale. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Governmentality in Evidence? Evolving Rationalities of Forest Governance in Peru(Elsevier Ltd, 2023-06-01)During the recent decades, the effectiveness, sustainability and equity of environmental and resource policies have become increasingly intertwined in governance reforms. This situation with potentially inherent trade-offs has challenged not only the policy planners and implementers, but also the scientific and expert communities to justify the role of specific forms of scientific knowledge in the pursue of multiple and often conflicting objectives. Evidence is a closure of a particular science-policy interface in which the offered scientific knowledge satisfies institutional decision-making criteria. Therefore, for decision-makers evidence is not only information that is judged useful to make their decisions but also a persuasive tool for them to justify the decisions made through giving reasons. We focus on how different prevailing decision-making and administrative rationalities, governmentalities, have shaped the knowledge base and epistemic requirements of forest governance in Peru. We depict a shift from a forester-dominated to legalistic and neoliberal forest governance structure whose main goal has been to foster the forest economy under an economistic sustainable resource use mentality. Increasingly complex administrative processes to support tracing timber extraction, transport and trade have resulted from the institutional adjustments, but, parallelly, also emerging participatory planning processes have challenged and re-politicized the forest governance structure.