Fear and Leaching in Michigan or, Dude, where’s my nutrients? Emily Farrer, Joshua Haag, Joel Perkovich, Katherine Windfeldt

Introduction  Properties of Soil Physical Chemical Biological  Synthesis of Lab and Field Data  The Development of a Northern Oak Ecosystem

Physical Properties of Soil  Texture –Sand  H 2 0 Holding Capacity –0.12 cm 3 H 2 O/cm 3 Soil –Lowest of all sites  Bulk Density –1.1 g/cm 3 –2 nd Lowest behind NH

Chemical Analyses CEC - Lowest CEC of all sites at 2.2 cmol c /kg (other sites range cmol c /kg) - Thus, smallest nutrient holding capacity of all soils Base Saturation - Lowest BS of all sites at just 13% (other sites range from 97-99%) pH - Most acidic of all sites at 4.21 (Mixed Oak highest pH at 5.97)

Soil Biological Properties

Ecosystem Biological Properties Ecosystem Biomass Mg/ha% total Aboveground Forest Floor Soil Nitrogen Pools kg/ha% total Aboveground Forest Floor Soil Low ecosystem biomass and N compared to other forests Aboveground and forest floor second lowest (OH lowest) Soil biomass and N pools lowest

Structure / Texture - Well-sorted, sandy PM from former lake bed = larger particle size, weak structure and sandy texture Bulk Density (Db) - Well-sorted (homogenous), loosely packed soil results in second lowest Db `at 1.1 gm/cm 3 (other sites range ) CEC / Base Saturation - Lowest CEC at 2.2 cmol c /kg 90% sand and 3% clay = weak electronegative charge for CEC - Lowest BS at 13% Role of topography / fire and well-drained sandy PM = nutrient loss Available Water Content - Lowest AWC at 0.12 cm 3 H 2 0/cm 3 soil (other sites range ) - well-drained sandy PM, lower elevation and southern aspect = H 2 0 loss pH - Most acidic at 4.21, Non-calcareous PM offers no buffer for soil acidification via weathering Northern Oak Physiography

Soil: Field and Lab Sandy and acidic throughout Lab data supported Little structure Low OM Moderately shallow, weak profile Well-drained – weathering Low OM, no humus accum. O horizon thin A shallow Low biomass in forest floor and soil E weak Bs weak C sand Profile

SOM rules! SOM Water holding capacity Structure Color CEC (& anion EC) Base Saturation pH Microbial biomass Microbial respiration N mineralizationNPP

Vegetation History 1880’s white pine logged, big burn Natural fire regime until 1930 when human fire suppression began Composition Overstory –black oak, white oak, red oak, red maple Understory / Ground Cover –white pine, red maple, sassafras, blueberry, wintergreen, Pensylvania sedge

Vegetation Low Biomass Mg/ha Lowest AWC 0.12 cm 3 H 2 O/cm 3 soil Lowest Nutrient Availability –Nitrogen content of 1584 kg/ha –CEC of 2.2 cmol/kg –BS of 0.13 Species Composition – Dry/Acidic Lowest AWC 0.12 cm 3 H 2 O/cm 3 soil Lowest Nutrient Availability Lowest pH of 4.21 Fire regime Perpetuation of system Fire regime/Dry site Oak species

The Development of a Northern Oak Ecosystem Young soil Limited weathering Low CEC (and non-calcareous parent material) Well drained (low FC and AWC) -> Loss of nutrients by leaching NutrientsCEC

Soil Development and Ecosystem Feedbacks SOM NutrientsCEC Few nutrients -> low biomass Low biomass -> little SOM Little SOM -> Low CEC Loss of nutrients by leaching

Soil Development and Ecosystem Feedbacks NutrientsCEC Nutrients Physiographic and topographic characteristics -> prone to fire Loss of nutrients by burning and leaching

Summary:  Young, relatively unweathered soil  Susceptible to leaching Loss of nutrients Low productivity and biomass  Low SOM and CEC  Susceptible to fire Loss of nutrients Low productivity and biomass  Low SOM and CEC  Positive feedbacks maintain low biomass