CWT-VI (2008-2015) involved 28 Project Investigators and 12 Affiliated Investigators from 9 institutions who collectively published 268 peer-reviewed publications and successfully advised 26 graduate students in research to produce an equal number of dissertations and thesis. The overall project objective was to examine ecosystem processes, water quantity, water quality and biodiversity as impacted by land use, climate change and the interactions between them.

Our analysis of long-term tree phenology shows advancing spring leaf-out and more variable, drought-dependent leaf fall although phenological responses along topographic gradients vary in function of the climate variability measured along the same gradient. We showed how forest diversity is promoted by individual responses to landscape variation in moisture, temperature and competition for light and moisture, demonstrating that the most important variables linked to forest change operate at the scale of the individual not the forest. We furthermore demonstrated the variability in response to these forces across species and size classes.

It is known that species loss and land management decisions can alter hydrologic and biogeochemical processes, but we showed, for example, how forest conversion reduces infiltration, soil storage, and hence baseflow. We also demonstrated how the rapid loss of eastern hemlock from riparian forests through its infestation by the hemlock wooly adelgid affects carbon, water and nutrient cycling, terrestrial and aquatic litter decomposition as well as stream temperature and trophic processing. We also showed how soil resource heterogeneity depends on disturbance history so that previous agricultural lands have more invasive plants than comparable sites that were never cultivated. The higher invasibility of former agricultural lands is also associated with thinner leaf litter, higher soil moisture and more abundant tulip poplar.

The terrestrial and aquatic ecosystem models we are developing provide new insight on the dynamics of water, C and N in watersheds of the Little Tennessee River Basin and the Ring of Asphalt expanding across the region. We show how landowner riparian zone management practices at the parcel level affect channel structure, wood loading and sedimentation. Steep slope development, in particular, contributes to high stream nitrate levels and other watershed-scale changes to biogeochemical processes. While urban development increases debris flow, runoff and erosion hazards, topography can nevertheless be as significant as land use and cover in controlling watershed hydrology. When we combined such results with a stream metabolism model, we were able to show that nitrogen export was especially sensitive to in-stream processes when terrestrial inputs are low, whereas high N loading saturates in-stream processes.

Our model of hillslope hydrology, biogeochemistry and productivity reveals how debris flowing into streams from upper slopes is exacerbated by recent increases in extreme precipitation events and the expansion of rhododendron that reduces net root cohesive strength in forest soils. Additional results indicate that private conservation increases land prices by creating amenity effects and removing land from a market that distinguishes between conservation in fee versus conservation in easement. The direct implication is that land management strategies must be careful to avoid promoting development near conserved parcels. With work in progress we are extending the model and implications to predict the effects of mountainside development on N export in the Little Tennessee River, and the ability to evaluate the roles and interactions of residential development and buffer zone protection in determining N export.

Beyond the noted intellectual contributions, their implications for land management and the benefit to gradu...

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