Upscaling key ecosystem functions across the conterminous United States by a water-centric ecosystem model

We developed a water-centric monthly scale simulation model (WaSSI-C) by integrating empirical water and carbon flux measurements from the FLUXNET network and an existing water supply and demand accounting model (WaSSI). The WaSSI-C model was evaluated with basin-scale evapotranspiration (ET), gross ecosystem productivity (GEP), and net ecosystem exchange (NEE) estimates by multiple independent methods across 2103 eight-digit Hydrologic Unit Code watersheds in the conterminous United States from 2001 to 2006. Our results indicate that WaSSI-C captured the spatial and temporal variability and the effects of large droughts on key ecosystem fluxes. Our modeled mean (±standard deviation in space) ET (556 ± 228 mm yr−1) compared well to Moderate Resolution Imaging Spectroradiometer (MODIS) based (527 ± 251 mm yr−1) and watershed water balance based ET (571 ± 242 mm yr−1). Our mean annual GEP estimates (1362 ± 688 g C m−2 yr−1) compared well (R2 = 0.83) to estimates (1194 ± 649 g C m−2 yr−1) by eddy flux-based EC-MOD model, but both methods led significantly higher (25–30%) values than the standard MODIS product (904 ± 467 g C m−2 yr−1). Among the 18 water resource regions, the southeast ranked the highest in terms of its water yield and carbon sequestration capacity. When all ecosystems were considered, the mean NEE (−353 ± 298 g C m−2 yr−1) predicted by this study was 60% higher than EC-MOD\u27s estimate (−220 ± 225 g C m−2 yr−1) in absolute magnitude, suggesting overall high uncertainty in quantifying NEE at a large scale. Our water-centric model offers a new tool for examining the trade-offs between regional water and carbon resources under a changing environment

Making Service-Learning Work for You

Consensus emerges about defining characteristics and transformative potential of service-learning. The challenge is to design effective service-learning experiences that nurture connections at the intersections of learning and service goals, disciplines, and institutional units. Individuals can attend any or all parts of this workshop; discussion will occur during each part. Part 1 (30 min): Overview of the pedagogy, its non-traditional nature, benefits, and challenges. Service-learning integrates learning and service goals; academic and civic learning; collaboration between campus and community; and structured reflection. Community partnerships and critical reflection are key elements of intentional design for maximum impact. Part 2 (60 minutes): Examples of service-learning in natural resources courses at NC State, from single-class activities to multi-course sequences. (1) We integrated service-learning into a three-course forest measurement sequence. A “one-shot” service-learning activity acclimates students to the approach during the first course; they advance to a semester-long service-learning project in the third course. (2) Natural Resources Measurements is built around a service-learning project. Students have worked with county government to estimate local trends in impervious surface levels, providing data used in drafting new storm water regulations. (3) We are assessing the ecological value of Raleigh’s forests with several partners during a three-semester process in which data and information are passed from one course to the next. Part 3 (90 minutes): Clinic to help faculty see how to incorporate service-learning effectively into their courses and curricula. Working in small, facilitated groups, participants will engage in focused discussion of service-learning possibilities for their courses. We will offer an instructional design process and support participants in applying it collaboratively to their situations. Participants will leave with concrete ideas and a list of resources. The session will be relevant to instructors new to and experienced with service-learning

Interactive effects of nocturnal transpiration and climate change on the root hydraulic redistribution and carbon and water budgets of southern United States pine plantations

International audienceDeep root water uptake and hydraulic redistribution (HR) have been shown to play a major role in forest ecosystems during drought, but little is known about the impact of climate change, fertilization and soil characteristics on HR and its consequences on water and carbon fluxes. Using data from three mid-rotation loblolly pine plantations, and simulations with the process-based model MuSICA, this study indicated that HR can mitigate the effects of soil drying and had important implications for carbon uptake potential and net ecosystem exchange (NEE), especially when N fertilization is considered. At the coastal site (C), characterized by deep organic soil, HR increased dry season tree transpiration (T) by up to 40%, and such an increase affected NEE through major changes in gross primary productivity (GPP). Deep-rooted trees did not necessarily translate into a large volume of HR unless soil texture allowed large water potential gradients to occur, as was the case at the sandy site (S). At the Piedmont site (P) characterized by a shallow clay-loam soil, HR was low but not negligible, representing up to 10% of T. In the absence of HR, it was predicted that at the C, S and P sites, annual GPP would have been diminished by 19, 7 and 9%, respectively. Under future climate conditions HR was predicted to be reduced by up to 25% at the C site, reducing the resilience of trees to precipitation deficits. The effect of HR on T and GPP was predicted to diminish under future conditions by 12 and 6% at the C and P sites, respectively. Under future conditions, T was predicted to stay the same at the P site, but to be marginally reduced at the C site and slightly increased at the S site. Future conditions and N fertilization would decrease T by 25% at the C site, by 15% at the P site and by 8% at the S site. At the C and S sites, GPP was estimated to increase by 18% and by > 70% under future conditions, respectively, with little effect of N fertilization. At the P site, future conditions would stimulate GPP by only 12%, but future conditions plus N fertilization would increase GPP by 24%. As a consequence, in all sites, water use efficiency was predicted to improve dramatically with future conditions. Modeling the effect of reduced annual precipitation indicated that limited water availability would decrease all carbon fluxes, including NEE and respiration. Our simulations highlight the interactive effects of nutrients and elevated CO2, and showed that the effect of N fertilization would be greater under future climate conditions

Upscaling key ecosystem functions across the conterminous United States by a water-centric ecosystem model

States by a water‐centric ecosystem mode