Bonanza Creek & Andrews LTER GEOG 4401/5401 Soils Geography Fall 2007 – Univ of Colorado, Boulder Kerry Malm & Phil Garcia

Bonanza Creek LTER Alaska The role of soil and Alnus incana subsp. Tenuifolia in landscape succession in the Tanana River floodplain

Why are the soils salty? Shallow Water Table Capillary Rise of Solution Alkaline (Salty) Soil Evaporation of Water Accumulation of Chemicals at Soil Surface (CaCO3 & CaSO4·H2O)

Is this common & Why is this bad? Common in the lowlands of the Tanana River floodplain Not in all AK floodplains Toxic concentrations of ions build up Limit soil processes which supply plants with N and P

Alder to the Rescue Species: Alnus incana subsp. Tenuifolia –Thinleaf Alder Important for: –Soil development –Stand development

Alders Symbiotic actinorhizal bacteria (root nodes) –60-70% of total N accumulation during 200 yrs of floodplain succession –Top 2 m had 4x increase in N in 20 yrs SOM –50% of OM comes from leaves Erosion control –Extensive root system

Results More N in the soil Less erosion Increased terrace height –Decrease flooding –Increased distance to water table –Less salty

And in the end... New plant establishment (succession) Paper BirchTrembling AspenWhite SpruceBlack Spruce Shrubs Time Conifers Climax WillowThinleaf Alder Deciduous Trees

Andrews LTER: The Pacific Northwest Alnus rubra and Pseudotsuga manziesii’s role in forest development

Red Alder and Douglas Fir: A unique relationship over a complex landscape Inceptisols are the dominant soil type Alfisols and Spodosols present also Forests range from young >25yrs to old growth <400yrs An area with considerable potential for C sequestration Major Disturbances: flood, windfall and fire

Red Alders (Alnus rubra) Often first to succeed following disturbance N-fixing because of symbiotic actinomycete frankia Leaf fall is a major source of Nitrogen/humus Erosion Control

2 Soil Types Examined Nutrient rich soil Nutrient poor soil 3 Different Relationships Douglas-fir monoculture Douglas-fir and Alder stand Alder monoculture

Conifer Largest biomass production Conifer + Alder Conifer + Alder Nutrient Rich Soil Alder Straight competition between the 2 species Alder eventually out- competed Slow steady biomass accumulation

Conifer Quick increase in biomass Short lived (50yrs) Conifer + Alder Conifer + Alder Nutrient Poor Soil Alder Largest Biomass production Large fast growth, short lived (70yrs) Overtaken by conifers

Red Alder in H.J. Andrews Increase total stand and conifer growth in ¼ of the forested land Decrease total stand and conifer growth in ½ Most useful on nutrient poor sites Important in Erosion Control

Conclusions In the Tanana River floodplain alders act as an ecosystem engineer to aid in forest succession In the H.J. Andrews experimental forest alders act as ecosystem engineers in nutrient poor soils In both sites alders are important because of their symbiotic relationship with nitrogen fixing bacteria and extensive root systems

Works Cited Chapin, F.S. III, M. Oswood, K. Van Cleve, L.A. Viereck, and D. Verbyla Alaska's Changing Boreal Forest. Oxford University Press. New York. Dyrness, C.T. and K. Van Cleve Control of surface soil chemistry in early-successional floodplain soils along the Tanana River, interior Alaska. Canadian Journal of Forest Research 23: Van Cleve, K., L.A. Viereck and G.M. Marion Introduction and overview of a study dealing with the role of salt-affected soils in primary succession on the Tanana River floodplain of interior Alaska. Canadian Journal of Forest Research 23: Van Cleve, K., J. Yarie, L.A. Viereck and C.T. Dyrness Conclusions on the role of salt-affected soils in primary succession on the Tanana River floodplain, interior Alaska. Canadian Journal of Forest Research 23: Viereck, L.A., C.T. Dyrness and M.J. Foote An overview of the vegetation and soils of the floodplain ecosystems of the Tanana River, interior Alaska. Canadian Journal of Forest Research 23: Binkley, Dan A hypothesis about the interaction of tree dominance and stand production through stand development. Forest Ecology and Management. 190:

More Works Cited… Griffiths, R. P., Bradshaw, G. A., Marks, B., and G. W. Lienkaemper Spatial distribution of ectomycorrhizal mats in coniferous forests of the Pacific Northwest, USA. Plant and Soil 180: Radosevich, S.,Hibbs, D.,Ghersa, C Effects of species mixtures on growth and stand development of Douglas-fir and red alder, Can. J. For. Res. 36: Griffiths, R. P., Bradshaw, G. A., Marks, B., and G. W. Lienkaemper Spatial distribution of ectomycorrhizal mats in coniferous forests of the Pacific Northwest, USA. Plant and Soil 180: