Nutrient cycling in riparian canebrakes in southern Illinois

Transcription

1 Nutrient cycling in riparian canebrakes in southern Illinois Amanda Nelson Karl Williard Jon Schoonover Department of Forestry

2 Giant Cane [Arundinaria gigantea] Was dominant component of lower Midwest and southeastern United States riparian areas, including southern Illinois (Brantley and Platt, 2001, Platt and Brantley, 1997, Platt et al., 2009) Classified as threatened Photo by Devin Mannix

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4 Giant Cane Communities Formerly vast monotypic canebrakes now small patches Lost due to urban and agricultural conversion, altered fire regime, grazing

5 Giant Cane Native bamboo Has a relatively dense rhizome/rooting network (Brantley and Platt, 2001) Photo by Devin Mannix

6 Wildlife Benefits Provides cover for wildlife throughout the year as an evergreen species (Platt et al., 2001) Provides sanctuary to many species of insects, birds, reptiles and mammals (Platt et al., 2001, Rose, 1981) Swainson s Warbler (Limnothylpis swainsonii) inhabit giant cane stands almost exclusively (Hoover et al., 2000, Eddleman et al., 1980)

7 Unique Features of Riparian Areas in Southern Illinois Relative absence of tile drainage Presence of unique native species; giant cane

8 Riparian Benefits Good candidate to include in multispecies riparian buffers designs Promotes infiltration of surface runoff and deposition of sediment and associated nutrients (Schoonover et al., 2005, Schoonover et al., 2006) Performed as well as, or better than, forest vegetation in reducing nitrogen levels in surface and ground water (Schoonover et al., 2010)

9 Giant Cane Research at SIUC: Riparian Buffers and Water Quality 3 Riparian studies comparing giant cane and forest buffers 1. Overland flow, soil water, and groundwater nutrient and sediment attenuation 2. Effects on groundwater nitrogen and phosphorus 3. Soil phosphorus dynamics Schoonover et al., 2010

10 Percent Reduction of Sediment and Nutrients in the Initial 3.3 m of Riparian Buffers Parameter Giant Cane Forest Overland Flow Sediment Total PO 4 80 (14)+ Total NH 4+ -N Dissolved NH 4+ -N Dissolved NO 3- -N Schoonover et al., 2010

11 Conclusions / Study Implications Relatively narrow buffers can yield significant water quality benefits Overland Flow: promotes infiltration Groundwater: plant assimilation and microbial processing Giant cane buffers performed better than forest buffers in terms of water quality benefits Schoonover et al., 2010

12 Objectives Comparing giant cane soil nutrient cycling with adjacent row crops and forests Nitrogen content and form Net mineralization

13 Methods Six study sites each with cane, forest, and crops (corn/soybean rotation) Monthly soil samples Bulk Density Soil C:N Seasonal net mineralization sampling 28 day incubations

14 Net mineralization Twenty-eight day in-situ incubation Extracted within 24 hours Flow Solution IV Autoanalyzer NH 4 NO 3

15 Net Mineralization Ammonification NH 3 + H 2 O NH 4 OH (NH 4 ) + + (OH) - Nitrification NH O 2 NO H + + H 2 O Calculate Net Subtract pre-incubation values from postincubation values

16 Bulk Density Mean Bulk Density (g cm -2 ) a a b cane crop forest Forest is significantly lower than crop and cane 0.2 0

17 Soil C:N Crop is significantly lower than forest and cane a b a Ratio guidelines Under indicates nitrogen mineralization Over 30 indicates immobilization Mean C:N cane crop forest 2 0

18 Soil Carbon a Soil carbon (g m -2 ) b c 5 0 cane crop forest

19 Soil Nitrogen 2.5 a Soil Nitrogen (kg m -2 ) b b 0 cane crop forest

20 Leaf Litter Leaf Litter (g m -2 ) July August September October November December January February March April May June July August Month Lower Cache Access Garage 1 Garage 2 Hickory Bottoms 1 Hickory Bottoms 2 Johnson Dairy

21 Extractable Nitrate (aka Nitrogen Pool) b 2000 b NO 3 (mg m -2 ) cane crop forest 500 a 0-500

22 Net mineralization a Net mineralization (mg kg -1 ) a a cane crop forest -10

23 Ammonification Change in NH 4 (mg kg -1 ) NH 3 + H 2 O NH 4 OH (NH 4 ) + + (OH) - 20 a 10 ab b cane crop forest

24 Nitrification NH O 2 NO H + + H 2 O Change in NO 3 (mg kg -1 ) a b a cane crop forest

25 Conclusions Forest soils have significantly lower bulk density than crop or cane C:N ratio is significantly lower in crop than in forest and cane due to the carbon levels Crop < forest < cane for carbon Crop < forest, cane for nitrogen

26 Conclusions Crop soils had the highest amounts of extractable nitrate Immobilized in microbial biomass Cane soils had the least amount of extractable nitrate There was no significant difference among net mineralization rates

27 Future Research Further analyses Canebrake ages Seasonal variation Continue sampling Other sampling Monthly for N 2 O Leaf litter decomposition

28 Acknowledgements NSF IGERT WaSP program McIntire-Stennis Graduate committee Fellow graduate students Jackie Crim US FWS