Landscape Function and Disturbance in Arctic Tundra

I Introduction.- 1 Ecosystem Response, Resistance, Resilience, and Recovery in Arctic Landscapes: Introduction.- 1.1 Introduction.- 1.2 NRC Committee Report.- 1.3 The R4D Program.- 1.3.1 Objectives and Conceptual Framework.- 1.3.2 Program Implementation.- 1.3.3 Landscape Function.- 1.4 Summary.- References.- 2 Integrated Ecosystem Research in Northern Alaska, 1947-1994.- 2.1 Introduction.- 2.2 Early Days at NARL.- 2.3 The U. S. Tundra Biome Program.- 2.4 The Meade River RATE Program.- 2.5 Eagle Creek and Eagle Summit.- 2.6 The Arctic LIER Program at Toolik Lake.- 2.7 Other Studies In Alaska and Elsewhere.- 2.8 Summary and Prospects.- References.- 3 Disturbance and Recovery of Arctic Alaskan Vegetation.- 3.1 Introduction.- 3.2 Disturbance and Recovery.- 3.3 Typical Disturbance and Recovery Patterns.- 3.3.1 Small Disturbed Patches.- 3.3.2 Contaminants.- 3.3.2.1 Hydrocarbon Spills.- 3.3.2.2 Seawater and Reserve-Pit Spills.- 3.3.3 Fire.- 3.3.4 Transportation Corridors.- 3.3.4.1 Bulldozed Tundra and Related Disturbances.- 3.3.4.2 Off-Road Vehicle Trails.- 3.3.4.2.1 Summer Travel.- 3.3.4.2.2 Winter Travel.- 3.3.4.3 Permanent Roads and Pads.- 3.3.4.4 Gravel Mines.- 3.3.4.5 Native Species in Revegetation of Gravel Pads and Mines.- 3.3.4.6 Road Dust.- 3.3.4.7 Roadside Impoundments.- 3.3.5 Cumulative Impacts.- 3.4 Conclusions.- References.- 4 Terrain and Vegetation of the Imnavait Creek Watershed.- 4.1 Introduction.- 4.2 Terrain.- 4.2.1 Glacial Deposits.- 4.2.2 Retransported Hillslope Deposits.- 4.2.3 Colluvial Basin Deposits.- 4.2.4 Floodplain Deposits.- 4.3 Vegetation.- 4.3.1 Flora.- 4.3.2 Vegetation Types.- 4.3.2.1 Lichen-Covered Rocks.- 4.3.2.2 Dry Heath.- 4.3.2.2.1 Exposed Sites.- 4.3.2.2.2 Snowbeds.- 4.3.2.3 Tussock Tundra.- 4.3.2.4 Riparian Areas.- 4.3.2.5 Mires.- 4.3.2.6 Beaded Ponds.- 4.4 West-Facing Toposequence.- 4.5 Terrain Sensitivity to Disturbance.- 4.6 Conclusions.- Appendix A. List of Plants for Imnavait Creek, Alaska.- References.- 5 Vegetation Structure and Aboveground Carbon and Nutrient Pools in the Imnavait Creek Watershed.- 5.1 Introduction.- 5.2 Description of Vegetation.- 5.3 Sampling Methods.- 5.3.1 Cover.- 5.3.2 Biomass and Nutrient Pools.- 5.4 Cover.- 5.5 Aboveground Biomass.- 5.5.1 Live Biomass.- 5.5.2 Photosynthetic Biomass.- 5.5.3 Lichen Biomass.- 5.5.4 Organic Litter.- 5.5.5 Watershed Patterns.- 5.6 Nutrient Pools.- 5.6.1 N and P in Heath Cryptogams.- 5.6.2 N and P in Communities.- 5.7 Discussion and Conclusions.- References.- II Physical Environment, Hydrology, and Transport.- 6 Energy Balance and Hydrological Processes in an Arctic Watershed.- 6.1 Introduction.- 6.2 Radiation and Thermal Regimes.- 6.2.1 Surface Energy Balance.- 6.2.2 Snow Cover and Soil Thermal Regime.- 6.3 Hydrological Processes.- 6.3.1 Snowmelt.- 6.3.2 Plot and Basin Water Balance.- 6.3.3 Runoff and Basin Discharge.- 6.3.4 Precipitation, Evaporation, and Evapotranspiration.- 6.4 Energy Balance and Hydrology Models.- 6.4.1 Simulation of the Thermal Regime.- 6.4.2 Simulation of Snowmelt.- 6.4.3 Simulation of Catchment Runoff.- 6.5 Conclusions.- References.- 7 Shortwave Reflectance Properties of Arctic Tundra Landscapes.- 7.1 Introduction.- 7.2 Shortwave Reflectance Studies in Arctic Environments.- 7.2.1 Environmental Considerations.- 7.2.2 Radiometric Data.- 7.2.3 Image Data.- 7.3 Spectral Reflectance.- 7.3.1 Aboveground Biomass.- 7.3.2 Vegetation Composition.- 7.3.3 Landscape Patterns.- 7.3.4 Effects of Dust Deposition.- 7.4 Albedo.- 7.4.1 Undisturbed Tussock Tundra.- 7.4.2 Effects of Dust Deposition.- 7.5 Conclusions.- References.- 8 Isotopic Tracers for Investigating Hydrological Processes.- 8.1 Introduction.- 8.1.1 Units.- 8.1.2 Conservative vs Nonconservative Isotopes.- 8.2 Nonconservative Tracers.- 8.3 Sulfur-35.- 8.4 Oxygen-18.- 8.4.1 Oxygen-18 Content of Snowpack.- 8.4.2 Oxygen-18 Content of Imnavait Creek.- 8.4.3 Oxygen-18 Content of Soil Moisture.- 8.4.4 Covariance of Oxygen-18 and Deuterium in Watershed Compartments.- 8.4.5 Covariance of Oxygen-18 and Deuterium in Plant Water.- 8.5 Long-Lived Radioisotopes: Lead-210 and Cesium-137.- 8.5.1 Distribution of 137Cs on Tundra and in Lake Sediments.- 8.5.2 Cycling of 137Cs in Annual Berries.- 8.5.3 Distribution of 210Pb in Tundra.- 8.6 Conclusions.- References.- III Nutrient and Carbon Fluxes.- 9 Surface Water Chemistry and Hydrology of a Small Arctic Drainage Basin.- 9.1 Introduction.- 9.2 Watershed Instrumentation.- 9.3 Snowmelt Period.- 9.3.1 Snowmelt Hydrology.- 9.3.2 Snowmelt Chemistry.- 9.3.2.1 Overland Flow.- 9.3.2.2 Water Track Flow.- 9.3.2.3 Imnavait Creek Flow.- 9.4 Post Snowmelt Period.- 9.4.1 Atmospheric Inputs.- 9.4.1.1 Rainfall.- 9.4.1.2 Dry Deposition.- 9.4.1.3 Rime.- 9.4.2 Water Chemistry.- 9.4.2.1 Overland Flow.- 9.4.2.2 Active Layer Flow.- 9.4.2.3 Imnavait Creek Flow.- 9.5 Conclusions.- References.- 10 Nutrient Availability and Uptake by Tundra Plants.- 10.1 Introduction.- 10.2 Controls on Mineralization and Nutrient Supply.- 10.2.1 Patterns of Nutrient Supply in the Soil.- 10.2.2 Patterns of Mineralization.- 10.2.3 Controls on N and P Mineralization.- 10.2.4 Controls on Decomposition and Mineralization.- 10.2.4.1 Temperature.- 10.2.4.1.1 Enzyme Activities.- 10.2.4.1.2 Microbial Activity at Low Temperatures.- 10.2.4.1.3 Freeze-Thaw Events.- 10.2.4.2 Effects of Low Oxygen on Microbial Activity and Mineralization.- 10.2.4.3 Substrate Quality.- 10.3 Fate of Available Nutrients.- 10.3.1 Microbial Nutrient Uptake and Competition with Plants.- 10.3.2 Plant Uptake.- 10.3.2.1 Soil Factors Controlling Nutrient Absorption.- 10.3.2.2 Rooting Strategies.- 10.3.2.3 Uptake Characteristics of Tundra Plants.- 10.3.2.4 Retranslocation vs Current Uptake.- 10.4 Disturbances.- 10.4.1 Vehicle Tracks.- 10.4.2 Road Dust.- 10.4.3 Gray Water.- 10.4.4 Climate Change.- References.- 11 Landscape Patterns of Carbon Dioxide Exchange in Tundra Ecosytems.- 11.1 Introduction.- 11.2 Methods.- 11.2.1 Community Types.- 11.2.2 Leaf Photosynthesis.- 11.2.3 Ecosystem Efflux.- 11.2.4 Ecosystem Net CO2 Exchange.- 11.3 CO2 Uptake.- 11.3.1 Factors Affecting CO2 Uptake.- 11.3.1.1 Light.- 11.3.1.2 Temperature.- 11.3.1.3 Phenology.- 11.3.1.4 Water Availability.- 11.3.1.5 Nutrition.- 11.3.2 Landscape Patterns in Leaf Photosynthesis.- 11.4 CO2 Efflux.- 11.4.1 Factors Affecting CO2 Efflux.- 11.4.1.1 Live Plant Biomass.- 11.4.1.2 Soil Quality.- 11.4.1.3 Thaw Depth and Depth to Water Table.- 11.4.1.4 Soil Moisture.- 11.4.1.5 Soil Temperature.- 11.4.2 Landscape Patterns of CO2 Efflux.- 11.4.3 Daily and Seasonal Patterns of CO2 Efflux.- 11.4.4 Dust Deposition Effects on CO2 Efflux.- 11.5 Landscape Patterns in Net CO2 Exchange.- 11.6 Conclusions.- References.- 12 Control of Tundra Methane Emission by Microbial Oxidation.- 12.1 Introduction.- 12.2 Sampling Procedure.- 12.3 Results and Discussion.- 12.3.1 Methane Flux and Environmental Variables in Tundra and Taiga.- 12.3.2 Physiology, Controls, and Potential for Microbial CH4 Oxidation.- 12.3.3 Methane Oxidation by Tundra Soils in a Warmer Climate.- 12.4 Conclusions.- References.- 13 Dynamics of Dissolved and Particulate Carbon in an Arctic Stream.- 13.1 Introduction.- 13.2 Site Description.- 13.2.1 Imnavait Creek Watershed.- 13.2.2 Description of Imnavait Creek.- 13.3 Field and Laboratory Procedures.- 13.4 Physical Regime.- 13.5 Carbon in Imnavait Creek.- 13.5.1 Concentrations.- 13.5.2 Transport.- 13.5.3 Spatial Variability.- 13.5.4 Seasonal Dynamics.- 13.6 Conclusions.- IV Modeling Landscape Function.- 14. Patch and Landscape Models of Arctic Tundra: Potentials and Limitations.- 14.1 Introduction.- 14.2 Modeling Framework.- 14.2.1 Spatial Simulation Units.- 14.2.2 Types of Models.- 14.3 Bottom-Up Models.- 14.3.1 Ecosystem Gas Exchange.- 14.3.1.1 Motivation.- 14.3.1.2 Description.- 14.3.1.3 Potentials and Limitations.- 14.3.2 Plant Growth.- 14.3.2.1 Motivation.- 14.3.2.2 Description.- 14.3.2.3 Potentials and Limitations.- 14.3.3 Nitrogen Uptake.- 14.3.3.1 Motivation.- 14.3.3.2 Description.- 14.3.3.3 Potentials and Limitations.- 14.3.4 Decomposition.- 14.3.4.1 Motivation.- 14.3.4.2 Description.- 14.3.4.3 Potentials and Limitations.- 14.4 Top-Down Models.- 14.4.1 Hydrologic Transport.- 14.4.1.1 Motivation.- 14.4.1.2 Description.- 14.4.1.3 Potentials and Limitations.- 14.4.2 Topographically Derived Vegetation Model.- 14.4.2.1 Motivation.- 14.4.2.2 Description.- 14.4.2.3 Potentials and Limitations.- 14.5 Conclusions.- References.- 15 Modeling Dry Deposition of Dust Along the Dalton Highway.- 15.1 Introduction.- 15.2 Model Fundamentals.- 15.3 Modeling Heavy Particle Dispersion.- 15.4 Estimation of Atmospheric Boundary Layer Parameters.- 15.5 Dust Characterization and Mass Transfer Through the Atmosphere.- 15.6 Theory of Particle Dry Deposition into Vegetation.- 15.7 Numerical Results.- 15.8 Conclusions.- References.- 16 Modeling Decomposition in Arctic Ecosystems.- 16.1 Introduction.- 16.2 Controls on Decomposition.- 16.3 Arctic Decomposition Models.- 16.3.1 ABISKO.- 16.3.2 ARTUS.- 16.3.3 BARK.- 16.3.4 GENDEC.- 16.3.4.1 General Description.- 16.3.4.2 Validation.- 16.4 Model Comparisons.- 16.5 Effects of Environmental Changes.- 16.5.1 Climate Change.- 16.5.2 Effects of Elevated CO2.- 16.5.3 Impacts of Road Dust Deposition.- 16.5.4 Tussock Phosphorus Dynamics.- 16.6 Conclusions.- References.- 17 Hydrological Controls on Ecosystem Gas Exchange in an Arctic Landscape.- 17.1 Introduction.- 17.2 Description of Models.- 17.2.1 Community Gas Exchange.- 17.2.2 Spatial Variation in Water Availability.- 17.3 Coupling of Hydrology and Ecosystem Gas Exchange.- 17.3.1 Vegetation Distribution.- 17.3.2 Spatial Variation in Water Table.- 17.4 Water Balance and Seasonal Changes in Water Fluxes.- 17.4.1 Evapotranspiration.- 17.4.2 Discharge.- 17.4.3 Interception and Surface Water Retention.- 17.5 Carbon Balance and Seasonal Changes in Carbon Fluxes.- 17.5.1 Predicted Water Table and Soil Respiration.- 17.5.2 Predicted Watershed Level Net CO2 Balance.- 17.6 Discussion and Conclusions.- References.- 18 Road-Related Disturbances in an Arctic Watershed: Analyses by a Spatially Explicit Model of Vegetation and Ecosystem Processes.- 18.1 Introduction.- 18.2 Environmental Gradients and Vegetation Distribution.- 18.2.1 Vegetation and Topography.- 18.2.2 Role of Water and Light.- 18.2.3 Role of Nutrients.- 18.3 Description of Model.- 18.3.1 Overview.- 18.3.1.1 T-HYDRO.- 18.3.1.2 T-VEG.- 18.3.1.3 T-NUT.- 18.3.1.4 T-PLT.- 18.3.2 Disturbance Scenarios.- 18.3.2.1 Effects of Altering Discharge.- 18.3.2.2 Effects of Road Dust.- 18.3.3 Model Validation and Limitations.- 18.4 Model Predictions for Undisturbed Watershed.- 18.4.1 Vegetation.- 18.4.2 Discharge.- 18.4.3 N Availability and NPP.- 18.4.4 Model Evaluation.- 18.5 Model Predictions for Disturbed Watershed.- 18.5.1 Discharge Disturbance.- 18.5.1.1 Road #1.- 18.5.1.2 Road #2.- 18.5.1.3 Roads #3 and #4.- 18.5.2 Dust and Discharge Disturbance.- 18.5.3 Effect of Disturbance on Spatial Patterns.- 18.6 Discussion.- 18.6.1 Model Comparisons.- 18.6.2 Patterns of N Availability.- 18.6.3 Extrapolation Potential: Some Cautionary Notes.- 18.7 Conclusions.- References.- V Summary.- 19 Ecosystem Response, Resistance, Resilience, and Recovery in Arctic Landscapes: Progress and Prospects.- 19.1 The NRC Tasks and R4D Accomplishments.- 19.2 Conclusion.- References.