Terrestrial Consumers / Trophic Interactions Structure-Function-Biodiversity LTER VI Planning Workshop 1 September 2007 Anthony Joern
Primary system drivers and grassland consumers? Prairie Structure & Function Grassland Drivers Consumers
Konza Prairie Consumers … • Focus of many long-term core data sets • Major contributors to site biodiversity • Highly variable dynamics, especially densities • Major participants in food webs, contributing to community & ecosystem dynamics • Serve as key indicator species for understanding global environmental change • Major foci of conservation biology
Integration of LTER Research at Konza Prairie New LTER Initiatives Management Issues Climate Change Fire Reversal Exp. Bison/Cattle Rainfall Cross-Site, Network & Manipulations $ Grazing $ International Studies Season of Fire Experimental Land Use / Land Extending the Inference Bud Bank Stream Studies $ Cover Change $ Of Konza Studies Demography $ Flux Towers Invasive Species Insect Biodiversity CO 2 , H 2 0 $ and Ecology $ Restoration $ Climate Gradient Ecological Studies Water Quality $ Genomics $ Plot-Level Spatial and Temporal Mechanistic Studies Heterogeneity Belowground Fire Exp. Plots Tallgrass Prairie Irrigation • Genes Transects • Organisms Grazing P Addition • Populations Experiment • Communities Mycorrhizae & • Ecosystems Soil C Exp $ • Landscapes Climate LINX Studies $
Avian Dynamics Brett Sandercock, Kim With • Long-term LTER core data • Landscape scale habitat use • Long-term lekking activity • Landscape-scale experiments
140 Total Number Caught Peromyscus leucopus 120 100 Small Mammal Dynamics 80 60 D. Kaufman, G. Kaufman 40 20 0 • Long-term core data on small mammals 1980 1985 1990 1995 2000 2005 Year • Temporal dynamics of core species • Responses to key ecosystem drivers & land cover change • Dynamic responses to climate change Stochastic growth rate (log λ ) 0.15 Rapid drying Gradual drying Increased variability 0.10 Total Number Caught 120 Blarina hylophaga 100 0.05 80 0.00 60 40 -0.05 20 Peromyscus maniculatus 0 0.20 0.25 0.30 0.35 0.40 0.45 Frequency of dry years 1980 1985 1990 1995 2000 2005 Year
Small Mammal Responses to Climate and Habitat Drivers Four Research Phases in Konza LTER (since 1981) I Magnitude & causes in temporal/ spatial variation II Season of annual fire effects on populations III Impact of woody invasion (ongoing direction) IV Deer mouse demography (new direction) Key Points & Rationale • Relevant to climate change themes • Woody invasion/ habitat shifts changing communities • Long term population trends provide baseline to link with additional • Critical vertebrate component of trophic structure
Creek chub Orangethroated darter S. redbelly dace Stoneroller Aquatic Consumers 100 (number/ minute e-fishing) K. Gido, C. Paukert, & M. Whiles 10 Abundance 1 10 1 N1B Phoxinus Catch Per Unit Effort 1 0.1 0.1 Discharge 0.1 0.01 0.01 0.01 0.001 95 96 97 98 99 00 01 02 03 04 05 0.001 0.0001 • Long-term core data on fish 10 1 Semotilis Catch Per Unit Effort Discharge 1 0.1 • Focus on stream permanence 0.1 0.01 • Impact of disturbance 0.01 0.001 • Stream macroinvertebrates & fish 0.001 0.0001 98 99 00 01 02 03 04 05 Year • Links to ecosystem processes evident Macroinvertebrates Intermittent Reach Perennial Reach Experimental Steams 25 25 Richness (# taxa) Richness (# taxa) 20 20 15 15 10 10 5 5 0 0 1.0 14 Mean discharge (m3/s) Mean discharge (m3/s) 12 0.8 10 0.6 8 6 0.4 4 0.2 2 Dry 0.0 0 60 80 100 120 140 160 180 200 220 60 80 100 120 140 160 180 200 220 Dry Julian Day (1995) Julian Day (1995)
J. Blair, A. Joern, T. Todd, Terrestrial Arthropods M. Whiles, G. Zolnerowich & Nematodes • Grasshoppers: Long-Term Core Data 250 • Responses to Prairie Drivers Abundance (#/ 200 sweeps) KPBS LTER Acridids 200 • Food Webs & Trophic Cascades 150 100 • Parasitic hymenoptera biodiversity 50 0 2.0 1980 1985 1990 1995 2000 2005 C. calliope Biomass (g AFDM m -2 ) T. aurifera 1.5 1.0 0.5 0.0 0.25 0.20 N flux (g N m -2 ) 0.15 0.10 0.05 0.00 Cont Fert Cont Fert Cont Fert Cont Fert Mowed Unmowed Mowed Unmowed Burned Unburned
Core Long-Term Records Analyses of long-term data are showing interesting insights with respect to role of key grassland drivers • Grasshoppers : ( Jonas & Joern. 2007. Oecologia 153: 699-711) – Dynamics affected by fire, bison and weather at local and regional scales (see Jonas & Joern poster; 25 years) • Fish: ( Franssen et al . 2006. Freshwater Biology 51: 2072-2086) – Seasonality rather than disturbance from floods is best predictor of stream fish assemblages • Birds: (Powell. Auk 123: 183-197) – Variable species-specific responses to annual burning and bison grazing significant; heterogeneous landscape best approach. • Small Mammals: Matlack et al . 2002. Journal of Mammalogy 83:280- 289; Rehmeier et al . 2005. Journal of Mammalogy, 86:670-676. – Strong weather signal and woody vegetation determines temporal dynamics; variable species responses to fire and grazing for spatial variation.
Stoichiometric responses (Viviana Loaiza REU) • N is key, little support for role of P in grasshoppers in P-plots Grasshopper Density (#/m 2 ) 20 0gN/m2 10gN/ m2 15 • Useful to extend stoichiometric 10 approach to understand dynamics 5 of trophic interactions 0 -2.5 0.0 2.5 5.0 7.5 10.0 P-Fertilization (g/m 2 ) Percentage Leaf Damage Andropogon gerardii Andropogon gerardii Solidago missouriensis 30 2.0 0gN 2.5 (a) (b) 10gN 20 % Foliar N 1.5 2.0 % Foliar N 1.5 1.0 10 1.0 0.5 0.5 0 Percentage Leaf Damage 0.0 0.0 0 2 4 6 8 10 Solidago missouriensis 30 0gN 0gN 0.25 0.16 10gN 0gN 10gN % Foliar P % Foliar P 0.20 10gN 0.12 20 0.15 0.08 0.10 10 0.04 0.05 0.00 0.00 0 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 P-Fertilzer (g/m 2 ) P-Fertilizer (g/m 2 ) P-Fertilizer (g/m 2 )
Some New Directions & Syntheses • Synthesize scale-dependent processes affecting consumer responses to canonical prairie drivers • Develop detailed scale-dependent understanding of effects of bison foraging on heterogeneity of vegetation structure, food quality, nutrient cycling, and plant species availability • Determine the critical elements of habitat heterogeneity in response to grazing-fire-climate interactions that underlie different consumer dynamics • Further define the functional contributions of consumers in tallgrass prairie, and their trophic interactions • Develop detailed demographic studies of targeted taxa to track consequences of climate and habitat change
Bison Create Habitats & Heterogeneity • Plant species richness • Vegetation height • Foliar nutritional quality • Variable microclimates & structural microhabitats for smaller consumers
Consumer responses to heterogeneity induced by fire & grazing? Remote sensing & forage quality Vegetation Height Ungrazed Grazed 5 0 6 0 Vegetation Height (cm) Vegetation Height (cm) 1 D T ra n s e c t 2 0 0 5 N 1 B -N T ra n s e c t 2 0 0 5 5 0 4 0 4 0 3 0 1-year 3 0 2 0 2 0 burn 1 0 1 0 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 D is ta n c e A lo n g T ra n s e c t (m ) D is ta n c e A lo n g T ra n s e c t (m ) 6 0 Vegetation Height (cm) N 4 D -E T ra n s e c t 2 0 0 5 Vegetation Height (cm) K 4 B -E fra s s 6 0 5 0 4 0 4-year 4 0 3 0 2 0 burn 2 0 1 0 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 D is ta n c e A lo n g T ra n s e c t (m ) D is ta n c e A lo n g T ra n s e c t (m )
Characterizing & Scaling Effects of Habitat Heterogeneity Grasshopper Rabbits? Voles? Birds? Distribution of Bison depends on bison, fire, soil nutrients
Hierarchical, scale- and size-dependent responses to habitat quality & structure? Ongoing: Konza-Kruger study of top-down effects of grazers/ browsers on vegetation OR dynamics and plant community (Knapp, Smith, Collins, Blair) # Spp/ Individuals Variable heterogeneity determines diversity ? Some Theory: size-dependent fractal relationships of habitat/ resource use by consumers Spatial Heterogeneity (Ritchie & OLff 1998) Small herbivores more likely limited by food quality & habitat structure (ectotherms), large herbivores by quantity
Link Dynamics of Aboveground and Belowground Trophic Structure (Jonas Thesis, In prep) • Use long-term belowground plot experiment to work out role of bottom-up processes determining trophic structure • Link aboveground and belowground dynamics • Have most resources needed to proceed – need conceptual framework and explicit hypotheses • Stable isotope technology may be useful
Climate change affects Mid-Summer biotic interactions: Upper Limit consumer responses Lower Limit Landscape/ Early Summer Management/ Local Conditions State Foliar Precipitation Quality Temperature Nutrients Consumed Plant Topography Biomass & Edaphic Late Spring/ Early Summer Spiders Fire Vegetation Frequency Grasshoppers Structure Plant Grazing Species Time of Day
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