Short description
(English)
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Our project aims at assessing the impact of the ongoing climatic warming on carbon cycling in alpine treeline ecosystems. We will experimentally warm soil surfaces by 3K and study the response of plant growth, soil respiration, and leaching of dissolved organic carbon. By measuring C and O isotopes in tree rings we will identify how and why does tree growth changes to the increasing temperatures. By tracing the 13C label originating from an ongoing CO2 enrichment experiment in soil-respired CO2 and leached DOC, we will estimate if young and old soil organic matter pools respond differently to the increasing temperatures. In addition, we intend to conduct a 13C pulse-labelling experiment to estimate how warming affects the C partitioning and C cycling rates in the plant and soil system.
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Partners and International Organizations
(English)
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AT, BA, BA, BG, CH, CZ, DE, DK, EE, ES, FI, GR, HU, IE, IL, IT, LT, NL, NO, PT, RO, SE, SI, SK, TR, UK
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Abstract
(English)
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The effect of nine years of elevated CO2 concentration and three years of soil warming (+4°C above current soil temperatures) on the carbon, water relation and plant soil interaction of Larix decidua and Pinus mugo ssp uncinata above timberline is investigated in Stillberg (near Davos) is investigated. In 2010 we studied the above mentioned treatment effects on the carbon allocation from the needles via twigs and stems to the roots. To study the effects on the carbon dynamics in different tree compartments (phloem, xylem and wood, then twigs, stems and roots) tree twigs were enclosed in plastic bags and exposed to 1000 ppm of highly 13C-enriched CO2 (99.8%). High irradiation and average temperatures between 20°C - 25°C ensured a maximum CO2 uptake. Compound specific isotope analysis for different sugars (Sucrose, Fructose, Glucose and Pinitol) extracted from samples of the above mentioned tissues at various intervals after the labeling (one, four, 24 hours two weeks and 2 months) showed no significant effects, caused by any of the mentioned treatments. Only in the plants, which were exposed to soil warming we found a slight trend, where the 13C-label disappeared faster, which indicates an increased carbohydrate transport. The analysis of PLFA (Phospho-lipid-fatty acids) in combination with soil respiration indicates an increased turnover of the soil CO2 release, where preferably old carbon is decomposed. Perspectives: After all the samples have been analyzed and most of the data evaluated, three papers are in preparation to publish the results on a) leaf level responses on instantaneous gas exchange and stable C and O isotopes, effects of elevated CO2 and soil warming on carbon allocation within the trees and c) Tree soil interaction in a warmed soil and elevated CO2. The final synthesis of this study will be published in a PhD thesis.
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