The synchronization of microbial and plant phenology in a mountainous watershed and its importance for nutrient retention under changing hydrologic regimes.
EMSL Project ID
49991
Abstract
In mountainous systems that experience seasonal snow-cover, the snowmelt period is characterized by a large pulse of nutrients that originates from microbial mineralization of organic matter beneath the winter snowpack and from microbial biomass turnover associated with melting snow (Schmidt et al. 2007). The snowmelt period is also characterized by high snowmelt infiltration, low evapotranspiration, and low nutrient uptake by dormant vegetation. Consequently, the highest concentrations of nutrients exported during the water year occurs following snowmelt, when water discharge rates are also highest and plants are mostly inactive. Vegetation phenology in these systems is regulated by environmental cues such as photoperiod, soil and air temperature, such that plant nutrient uptake and biomass production are highest, and typically in sync with microbial biomass turnover and nutrient release, during the spring when days become longer, and air and soil temperature increases following snowmelt. The metabolic processes regulating organic matter mineralization and assimilation under-snow by soil bacteria and fungi, as well as the mechanisms of microbial biomass turnover during snowmelt, have not been characterized previously. Similarly, the trajectories of subsequent nutrient transformations and the coupling with plant nutrient assimilation are not well known. In addition, the timing of snowmelt has been occurring earlier in the year and with increasing frequency, which we hypothesize will result in a temporal discontinuity between the coupled behavior of microbial nutrient release and vegetation nutrient demand (greening) (Brooks et al. 1998), with the potential to increase nutrient export from mountainous watersheds in the western U.S.
The Watershed Function Scientific Focus Area (SFA) at the Lawrence Berkeley National Laboratory (LBNL) aims to understand the response of mountainous watersheds to perturbation. This FICUS proposal complements the Watershed Function SFA's broad goals by providing new and extensive field and laboratory observations of the activation of microbial metabolic potential beneath the snowpack during winter and during the snowmelt period, as well as advanced characterization of the chemistry of carbon and nutrient transformations and assimilation by microorganisms and vegetation in response to earlier snowmelt timing.
Project Details
Project type
FICUS Research
Start Date
2017-10-01
End Date
2019-09-30
Status
Closed
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