Abstract
Abstract. 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 (<1 µM) for all three vegetation types. In contrast K showed greater solute concentrations under forest soils with values that were 2 to 3 times higher than under cushion-forming plants or tussock grasses. Our findings have important implications for future management of Andean páramo ecosystems where vegetation type distributions are dynamically changing as a result of warming temperatures and land use change. Such alterations may lead not only to changes in soil hydrology and solute geochemistry but also to complex changes in weathering rates and solute export downstream with effects on nutrient concentrations in Andean rivers and high-mountain lakes.
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Claims 10
Claim · model-written summary
Rooting depth varied with drainage and soil moisture in nonallophanic Andosols.
Not reportedDirection
Verbatim
e0“In the nutrient-depleted nonallophanic Andosols, the plant rooting depth varies with drainage and soil moisture conditions.”
Claim · model-written summary
Roots were shallower in seasonally waterlogged soils under cushion plants.
Verbatim
e0“Rooting depths were shallower in seasonally waterlogged soils under cushion plants and deeper in well-drained soils under forest and tussock grasses (>100 cm).”
Claim · model-written summary
Roots were deeper, exceeding 100 cm, in well-drained soils under forest and tussock grasses.
Verbatim
e0“Rooting depths were shallower in seasonally waterlogged soils under cushion plants and deeper in well-drained soils under forest and tussock grasses (>100 cm).”
Claim · model-written summary
Vegetation composition indicated rock-derived nutrient availability in soil solutions.
- Taxon
- Vegetatione0
- Outcome
- rock-derived nutrient availability in soil solutionse0
- Setting
- soil solutionse0
Not reportedDirection
Verbatim
e0“Vegetation composition is a relevant indicator of rock-derived nutrient availability in soil solutions.”
Claim · model-written summary
Plant-available solute nutrient patterns differed from total and exchangeable rock-derived nutrient pools.
Verbatim
e0“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.”
Claim · model-written summary
Soils beneath cushion plants had about threefold higher calcium, magnesium and sodium solute concentrations than soils beneath forest and tussock grasses.
Verbatim
e0“Soils under cushion plants showed solute concentrations of Ca, Mg, and Na of about 3 times higher than forest and tussock grasses.”
Claim · model-written summary
Dissolved silicon under cushion plants was 16 times higher than under forest.
Verbatim
e0“Differences were even stronger for dissolved Si with solute concentrations that were 16 times higher than forest and 6 times higher than tussock grasses.”
t0“Vegetation patterns”
Claim · model-written summary
Dissolved silicon under cushion plants was six times higher than under tussock grasses.
Verbatim
e0“Differences were even stronger for dissolved Si with solute concentrations that were 16 times higher than forest and 6 times higher than tussock grasses.”
t0“Vegetation patterns”
Claim · model-written summary
Phosphorus was limiting, with solution concentrations below 1 µM across three vegetation types.
Verbatim
e0“Amongst the macronutrients derived from lithogenic sources, P was a limiting nutrient with very low solute concentrations (<1 µM) for all three vegetation types.”
Claim · model-written summary
Potassium in forest soils was two to three times higher than under cushion plants or tussock grasses.
Verbatim
e0“In contrast K showed greater solute concentrations under forest soils with values that were 2 to 3 times higher than under cushion-forming plants or tussock grasses.”