by Alain | May 22, 2016
Luquillo Critical Zone Observatory
National Science Foundation, Division of Earth Sciences, Award #0722476
10/2009-9/2013
Principal Investigator (Former PI: Fred Scatena)
This project will establish a monitoring network in two watersheds of the Luquillo National Forest in Puerto Rico to evaluate the physical, chemical, hydrological and biological processes involved in weathering of bedrock and the evolution of the soil environment. This will be an addition to the Critical Zone Observatories (CZO) that are being initiated at various locations in North America. The Luquillo CZO will use the natural laboratory of the Luquillo Mountains to quantify and contrast how critical zone processes in watersheds underlain by granodiorite and volcaniclastic bedrock are affected by climatic conditions and hydrologic, geochemical and biogeochemical cycles. A set of interrelated hypothesis, sampling sites, and a unified data management system will allow critical zone processes to be contrasted by bedrock, landscape position (ridge, hillslope, riparian), depth (surface to bedrock), forest type (Tabonuco, Colorado, Cloud) and location (upland to coastal).
Changing climate affects many processes, and the breakdown of rocks into soil; is one of the most important. In addition, there may be changes in water flow in rivers, as well as erosion of surficial materials. Sediment is already the nation’s largest water quality pollutant and modern land uses are eroding soils and sculpting bedrock in unprecedented ways. The Luquillo Critical Zone Observatory will provide the infrastructure and baseline studies needed to evaluate short and long-term impacts of this erosion on soil and water resources. The Observatory will also support integrated, multi-institutional and multicultural exchanges among a diverse cadre of scientists, who will collaborate to determine the effects of climate change on the terrestrial environment.
by Alain | May 22, 2016
Climate Change Research in the Luquillo Mountains of Puerto Rico: Decision Trees for Evaluating the Potential of Soil Carbon Sequestration Sites for Climate Change Mitigation in Puerto Rico.
United States Forest Service (USFS), United States Department of Agriculture (USDA)
5/2009-4/2011
Co-Principal Investigator (PI: Fred Scatena)
by Alain | Apr 23, 2016
Physico-chemical and bio-chemical controls on soil C saturation behavior. A renewal for: “Soil C Saturation and Steady-State Level Determine C Sequestration Rate and Capacity”.
Department of Energy (DOE), Biological and Environmental Research, Award #ER63912
9/1/2007-8/31/2010
Co-Principal Investigator (PI: Johan Six, University of California, Davis)
Soil organic carbon (SOC) stabilization rates and durations vary across ecosystems, management practices, and climate regimes (West and Six 2007), but how the relationship between physico-chemical and bio-chemical SOC characteristics and the C saturation phenomenon influences the rate, limit and permanence of SOC stabilization has yet to be elucidated. In this renewal proposal we build on the concepts developed and results obtained from previous DOE funded projects to further discern how soil C saturation and deficit govern SOC stabilization and permanence, especially how the physico-chemical and bio-chemical characteristics of SOC play a role in SOC stabilization and saturation. The major hypothesis underlying our newly proposed work is: the rate and permanence of soil C stabilization is determined by the soil C saturation phenomenon, which is itself driven by the physico-chemical and bio-chemical characteristics of the soil minerals and SOC. Many soils, especially those that have been significantly depleted in SOC through cultivation show a linear response between annual C input rates and steady-state SOC levels (Paustian et al. 1997a; Kong et al. 2004; West and Six 2007), suggesting that the mechanisms controlling C accumulation are independent of the amount of C already in the soil, that is, there is no inherent C saturation limit in soils. This assumption of ‘first-order’ kinetics, in which the specific decomposition rate (k) is defined as a constant (e.g., dC/dt = I – kC), forms the basis for nearly all of the current soil organic matter and decomposition models (Paustian et al. 1994; Paustian et al. 1997b). However, some mineral soils with relatively high SOC contents show only a weak or no response to increasing rates of C input, suggesting that there is a dependency between SOC levels and the basic kinetics governing SOC stabilization. These soils exhibit the phenomenon of C saturation (Campbell et al. 1991; Paustian et al. 1997a; Six et al. 2002)1. From these and other observations in the literature (e.g., Hassink 1996) we formalized a concept of soil C saturation (Six et al. 2002) and initiated a suite of laboratory and field studies with funding from DOE. Our DOE-funded results support the following basic tenets of the saturation concept: 1) fundamental kinetics of soil C stabilization are dependent on SOC levels, 2) differences in the relative efficiency by which newly added C is stabilized differs across discrete SOC pools and 3) SOC pool saturation with increasing C input limits responses to global change.
by Alain | Apr 16, 2016
Vulnerability of soil organic matter to temperature changes: Exploring constraints due to substrate decomposability and microbial community structure.
National Science Foundation, Division of Environmental Biology, Award #0444880
1/1/2005-12/31/2007
Co-Principal Investigator (PI: Rich Conant, Colorado State University)
Recent research suggests that even modest temperature increases could cause large releases of CO2 from soils. A one-degree temperature increase could prompt soil carbon losses (as CO2) equivalent to five times the annual CO2 release from all fossil fuel burning. However, such forecasts are based on results from short-term studies that implicitly assume all of the carbon in the soil is uniformly temperature-sensitive. The bulk of applicable research suggests that older, more resistant carbon fractions may be less temperature-sensitive than younger, less resistant carbon fractions. This project will evaluate the extent to which the physical, chemical, and biochemical mechanisms that protect soil carbon from decomposition act to reduce the temperature sensitivity of soil carbon. An important corollary is that soil carbon stocks are less vulnerable to changes in temperature than previously supposed. As a part of this project, we will evaluate temperature sensitivities of soil carbon fractions in soils that differ with regard to their relative abundances of labile versus relatively stable carbon. Results from this work will reduce uncertainty about the vulnerability of soil carbon stocks to changes in temperature, thus improving information available to aid decision makers. This research will also advance our understanding of basic ecosystem dynamics, present a number of unique opportunities for undergraduate and graduate training, and build international collaboration.
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