Effects of water addition on above- and below-ground processes in montane meadows
Abstract
The carbon balance of a system is particularly sensitive to water availability because carbon availability drives both the mechanisms of photosynthesis and decomposition (Huxman et al. 2004 b, Ignace et al. 2007). The carbon balance of terrestrial plants is mainly a function of (i) carbon fixation through photosynthesis, (ii) carbon release via respiration from autotrophs, and (iii) heterotrophic (microbial and fungal) decomposition of soil organic matter. Soil microbes, (bacteria, fungi) first respond within hours of an irrigation event, while above-ground autotrophs generally do not increase photosynthetic activity until days later (Huxman et al. 2004b). Studying community function at both the species-level and community level over different time scales is needed to reveal the mechanisms controlling carbon balance and the potential impacts of a changing climate on montane systems. I tested the hypotheses that (1) water is a limiting factor for decomposition of organic matter and for net carbon assimilation in montane plant communities over the course of a growing season and that (2) changes in the rates of carbon uptake and release after a water pulse will differ on a fine temporal scale for three components of a subalpine plant community: below- ground processes, shallow-rooted plant species, and deep rooted plant species. Results from this study suggest that water is one limiting factor to carbon inputs and plant photosynthesis. Below- ground processes respond to added water on a shorter time scale than do above-ground plant processes. More studies like this run concurrently with accurate precipitation modeling will provide greater predictive power for understanding system responses to a changing climate. 2 Potter
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