Phosphorus Supply by Deep Rock Weathering Sustains Temperate Forest Ecosystem Functioning
Abstract
Primary productivity of forest ecosystems depends on the availability of the most plant-essential mineral nutrient phosphorus. Because phosphorus demand of trees exceeds phosphorus supply from rock, tree nutrition is sustained by efficient re-utilisation of organic-bound phosphorus, which is continuously returned from trees to soil. However, where soil phosphorus is permanently lost by drainage and erosion, phosphorus limitation may develop over millennia. It has been suggested that the development of such a deficit is prevented if, in eroding landscapes, advection of unweathered bedrock continuously supplies mineral nutrients. However, observations of the mechanisms and the depth range for this advective model are missing. We show that in two montane temperate forest ecosystems phosphorus originates from several meters depth, beneath which minor primary phosphate minerals have not yet been weathered. As evidence we use the depth distribution of calcium-bound phosphorus, and the concordance of the isotope ratios 87Sr/86Sr and 10Be(meteoric)/9Be between plant tissue and the regolith. We conclude that nutrient supply from deep regolith is critical for forest ecosystem functioning, and should be considered in global carbon models assessing, for instance, the contribution of forest ecosystems as natural sinks for anthropogenic carbon dioxide emissions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP11D2085U
- Keywords:
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- 0416 Biogeophysics;
- BIOGEOSCIENCESDE: 1826 Geomorphology: hillslope;
- HYDROLOGYDE: 1835 Hydrogeophysics;
- HYDROLOGYDE: 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS