Vegetation patterns associated with nutrient availability and supply in high-elevation tropical Andean ecosystems

• Published in: Biogeosciences 2024-07, Vol.21 (12), p.3075-3091
• Main Authors: Molina, Armando, Vanacker, Veerle, Chadwick, Oliver, Zhiminaicela, Santiago, Corre, Marife, Veldkamp, Edzo
• Format: Article
• Language: English
• Subjects: Alpine environments; Availability; Biogeochemical cycle; Biogeochemical cycles; Biogeochemistry; Carbon sequestration; Cations; Clouds; Cushions; Drainage; Ecosystem management; Ecosystems; Environmental aspects; Essential nutrients; Fog; Forest soils; Forests; Geochemistry; Grasses; High altitude; Hydrology; Lakes; Land use; Leaching; Limiting factors; Mineral nutrients; Moisture content; Mountain lakes; Nutrient availability; Nutrient concentrations; Nutrient deficiencies; Nutrient removal; Nutrient sources; Nutrient uptake; Nutrients; Organic soils; Plant growth; Plant roots; Plants; Rivers; Rock; Rocks; Rooting; Seasonal variations; Soil; Soil chemistry; Soil hydrology; Soil moisture; Soil solution; Soil water; Solutes; Temperature; Topography; Vegetation; Vegetation patterns; Vegetation type; Volcanic soils; Water; Weathering
• ISSN: 1726-4189; 1726-4170; 1726-4189
• DOI: 10.5194/bg-21-3075-2024

Plants absorb nutrients and water through their roots and modulate soil biogeochemical cycles. The mechanisms of water and nutrient uptake by plants depend on climatic and edaphic conditions, as well as the plant root system. Soil solution is the medium in which abiotic and biotic processes exchange nutrients, and nutrient concentrations vary with the abundance of reactive minerals and fluid residence times. High-altitude ecosystems of the tropical Andes are interesting for the study of the association between vegetation, soil hydrology, and mineral nutrient availability at the landscape scale for different reasons. First of all, because of low rock-derived nutrient stocks in intensely weathered volcanic soils, biocycling of essential nutrients by plants is expected to be important for plant nutrient acquisition. Second, the ecosystem is characterized by strong spatial patterns in vegetation type and density at the landscape scale and hence is optimal to study soil-water–vegetation interactions. Third, the area is characterized by high carbon stocks but low rates of organic decomposition that might vary with soil hydrology, soil development, and geochemistry, all interconnected with vegetation. The páramo landscape forms a vegetation mosaic of bunch grasses, cushion-forming plants, and forests. In the nutrient-depleted nonallophanic Andosols, the plant rooting depth varies with drainage and soil moisture conditions. Rooting depths were shallower in seasonally waterlogged soils under cushion plants and deeper in well-drained soils under forest and tussock grasses (>100 cm). Vegetation composition is a relevant indicator of rock-derived nutrient availability in soil solutions. The soil solute chemistry revealed patterns in plant-available nutrients that were not mimicking the distribution of total rock-derived nutrients nor the exchangeable nutrient pool but clearly resulted from strong biocycling of cations and removal of nutrients from the soil by plant uptake or deep leaching. Soils under cushion plants showed solute concentrations of Ca, Mg, and Na of about 3 times higher than forest and tussock grasses. Differences were even stronger for dissolved Si with solute concentrations that were 16 times higher than forest and 6 times higher than tussock grasses. Amongst the macronutrients derived from lithogenic sources, P was a limiting nutrient with very low solute concentrations (