Medellín, Colombia
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Emilio T.,National Institute of Amazonian Research | Quesada C.A.,National Institute of Amazonian Research | Costa F.R.C.,National Institute of Amazonian Research | Magnusson W.E.,National Institute of Amazonian Research | And 27 more authors.
Plant Ecology and Diversity | Year: 2014

Background: Trees and arborescent palms adopt different rooting strategies and responses to physical limitations imposed by soil structure, depth and anoxia. However, the implications of these differences for understanding variation in the relative abundance of these groups have not been explored. Aims: We analysed the relationship between soil physical constraints and tree and palm basal area to understand how the physical properties of soil are directly or indirectly related to the structure and physiognomy of lowland Amazonian forests. Methods: We analysed inventory data from 74 forest plots across Amazonia, from the RAINFOR and PPBio networks for which basal area, stand turnover rates and soil data were available. We related patterns of basal area to environmental variables in ordinary least squares and quantile regression models. Results: Soil physical properties predicted the upper limit for basal area of both trees and palms. This relationship was direct for palms but mediated by forest turnover rates for trees. Soil physical constraints alone explained up to 24% of palm basal area and, together with rainfall, up to 18% of tree basal area. Tree basal area was greatest in forests with lower turnover rates on well-structured soils, while palm basal area was high in weakly structured soils. Conclusions: Our results show that palms and trees are associated with different soil physical conditions. We suggest that adaptations of these life-forms drive their responses to soil structure, and thus shape the overall forest physiognomy of Amazonian forest vegetation. © 2014 Copyright 2013 Botanical Society of Scotland and Taylor & Francis.

The tropical Andes store and regulate water outflow that serves nearly 60 million people. Most of the water is for un-managed agricultural irrigation. In this work I report how the drainage of peatlands has adversely affected the development of plant communities and recent carbon accumulation in a páramo massif at 2500 to 3800 m altitude in the northern Andes. I surveyed vegetation and water chemistry in 26 peatlands with differing intensities of drainage. Peat cores to 50 cm from two sites with contrasting drainage histories were dated using 210Pb, and used to compare historical vegetation changes and carbon accumulation rates. (A) Species composition was much affected by drainage, which resulted in a reduction in cover of Sphagnum and other peat-forming species, and the encroachment of sedges and Juncus effusus. The ability of peat to store water and carbon was also reduced in drained peatlands. Vegetation records show a shift towards sedge-Juncus communities around 50 years ago when agricultural use of water increased. (B) Peat and carbon accumulation rates were lower in drained sites, indicating either greater decomposition rates of the upper peat column or lower production by the changed plant communities. The ecological services offered by peatlands to agrarian communities downstream are important. Measures to prevent peatland destruction are needed urgently. © 2014 International Mire Conservation Group and International Peat Society.

Urbina J.C.,Oregon State University | Benavides J.C.,Medellin Botanical Garden
Biotropica | Year: 2015

Tropical alpine peatlands are important carbon reservoirs and are a critical component of local hydrological cycles. In high elevation peatlands slow decomposition rates result from a nutrient-poor substrate resistant to decay. The responses of páramo peatland ecosystems to increased nutrient additions and physical disturbance due to agricultural activities are unknown. Here, we conducted a two-year fertilization and physical disturbance experiment in a Sphagnum-dominated peatland in the Central Andes of Colombia. We hypothesized that fertilization and physical disturbance will diminish the ability of the peat to store organic matter by increasing decomposition and that vascular plants will displace Sphagnum as the dominant plant group. We simulated cattle activity by adding manure as a fertilizer and physical disturbance as a proxy for cattle trampling. Species composition varied in proportion to the intensity of disturbance. Sphagnum cover was reduced under any disturbance treatment. Non-native grasses usually found in cattle pastures invaded treatments with fertilizer additions or physical disturbance. Overall aboveground plant biomass doubled in fertilized treatments, suggesting that plant biomass production was nutrient limited. Decomposition rates tripled in disturbed treatments as compared to controls. This reduces the ability of the peatland to store organic matter. Andean peatlands are prized ecological assets; however, our results show that the El Morro páramo peatland experienced increased decomposition rates over short time periods after small-scale disturbances. This created profound consequences for the ecological services offered by these peatlands. © 2015 The Association for Tropical Biology and Conservation.

Smith R.J.,Oregon State University | Benavides J.C.,Medellin Botanical Garden | Jovan S.,U.S. Department of Agriculture | Amacher M.,U.S. Department of Agriculture | McCune B.,Oregon State University
Bryologist | Year: 2015

Abstract Mat-forming "ground layers" of mosses and lichens often have functional impacts disproportionate to their biomass, and are responsible for sequestering one-third of the world's terrestrial carbon as they regulate water tables, cool soils and inhibit microbial decomposition. Without reliable assessment tools, the potential effects of climate and land use changes on these functions remain unclear; therefore, we implemented a novel "Ground Layer Indicator" method as part of the U.S.D.A. Forest Inventory and Analysis (FIA) program. Non-destructive depth and cover measurements were used to estimate biomass, carbon and nitrogen content for nine moss and lichen functional groups among eight contrasted habitat types in Pacific Northwest and subarctic U.S.A. (N = 81 sites). Ground layer cover, volume, standing biomass, carbon content and functional group richness were greater in boreal forest and tundra habitats of Alaska compared to Oregon forest and steppe. Biomass of up to 22769 ± 2707 kg ha-1 (mean ± SE) in upland Picea mariana forests was nearly double other reports, likely because our method included viable, non-photosynthetic tissues. Functional group richness, which did not directly correspond with biomass, was greatest in lowland Picea mariana forests (7.1 ± 0.4 functional groups per site). Bootstrap resampling revealed that thirty-two microplots per site were adequate for meeting data quality objectives. Here we present a non-destructive, repeatable and efficient method (sampling time: ca. 60 min per site) for gauging ground layer functions and evaluating responses to ecosystem changes. High biomass and functional distinctiveness in Alaskan ground layers highlight the need for increased attention to currently under-sampled boreal and arctic regions, which are projected to be among the most active responders to climate change. © The American Bryological and Lichenological Society, Inc.

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