TheThe influenceinfluence ofof herbivoryherbivory onon grasslandgrassland communitycommunity compositioncomposition andand diversitydiversity inin thethe KrugerKruger NationalNational Park:Park: disentanglingdisentangling thethe rolesroles ofof herbherbivoreivore sizesize andand habitathabitat fertilityfertility
Richard W.S. Fynn, Deron E. Burkepile, Alan K. Knapp, Melinda D. Smith, & Navashni Govender
Savanna Convergence Experiment
University of Kwazulu-Natal, Colorado State University, Yale University, Kansas State University, University of New Mexico, Kruger National Park AreAre allall herbivoresherbivores thethe same?same?
DoesDoes herbivoreherbivore richnessrichness matter?matter? TheThe AquariusAquarius
HERBIVOREHERBIVORE SPECIESSPECIES RICHNESSRICHNESS ISIS CRUCIALCRUCIAL TOTO REEFREEF ECOSYSTEMECOSYSTEM FUNCTION!FUNCTION! GrazingGrazing EcosystemsEcosystems DoDo thethe bigbig guysguys runrun thethe show?show? IncreasingIncreasing HumanHuman EncroachmentEncroachment SimulatingSimulating ConsumerConsumer LossLoss
1. Open Areas – No barrier Allows - Elephant, Giraffe, Rhino, Buffalo, Wildebeest, Zebra, Kudu, Impala, Warthog, Steenbok, Duiker
2. Tall Partial Exclosure - Wire fence beginning at 1.8 m Allows – Rhino, Buffalo, Wildebeest, Zebra, Kudu, Impala, Warthog, Steenbok, Duiker
Excludes – Elephant, Giraffe
3. Short Partial Exclosure - Wire fence beginning at 0.9m Allows - Impala, Warthog, Steenbok, Duiker
Excludes - Elephant, Giraffe, Rhino, Buffalo, Wildebeest, Zebra, Kudu
4. Full Exclosure – Diamond Mesh Fence from 0 - 1.2 m Excludes - All Herbivores >0.5 kg EffectsEffects ofof differentdifferent sizesize--classesclasses
AllAll herbivoresherbivores == FullFull ExclosureExclosure vs.vs. OpenOpen AreaArea
LargeLarge herbivoresherbivores == TallTall PartialPartial ExclosureExclosure vs.vs. OpenOpen AreaArea
MediumMedium herbivoresherbivores == TallTall PartialPartial ExclosureExclosure vs.vs. ShortShort PartialPartial ExclosureExclosure
SmallSmall herbivoresherbivores == ShortShort PartialPartial ExclosureExclosure vs.vs. FullFull ExclosureExclosure TallTall PartialPartial ExclosureExclosure
1.8 m ShortShort PartialPartial ExclosureExclosure
0.9 m
ExperimentalExperimental DesignDesign •• ExperimentalExperimental BurnBurn PlotsPlots ((EBP’sEBP’s)) SataraSatara RegionRegion •• Annual,Annual, Triennial,Triennial, UnburnedUnburned PlotsPlots –– nn == 22 •• NestedNested experimentalexperimental designdesign •• nn == 55 forfor eacheach ExclosureExclosure TreatmentTreatment perper burnburn plotplot ResponseResponse MetricsMetrics •• PlantPlant speciesspecies cover,cover, richness,richness, andand diversitydiversity •• PrimaryPrimary productionproduction •• LightLight availabilityavailability •• TreeTree seedlingseedling survivorshipsurvivorship andand growthgrowth TreatmentTreatment EffectivenessEffectiveness •• SpoorSpoor monitoringmonitoring •• DungDung countscounts •• MotionMotion--activatedactivated camerascameras EffectivenessEffectiveness ofof PartialPartial ExclosuresExclosures
Impala Steenbok Wildebeest 15 Zebra Giraffe Elephant
10
5 Tracks/Plot/Survery
closures x Open Areas
Tall Partial E Short Partial Exclosures ImpactImpact andand ContributionContribution
•• ExaminesExamines aa realisticrealistic patternpattern ofof consumerconsumer lossloss fromfrom savannasavanna ecosystemsecosystems
•• BuildsBuilds onon similarsimilar studiesstudies fromfrom HluhluweHluhluwe (Bond(Bond andand OlffOlff),), KenyaKenya (Young(Young etet al.),al.), andand KNPKNP (River/Savanna(River/Savanna Boundaries)Boundaries) examiningexamining effectseffects ofof differentdifferent herbivoresherbivores atat communitycommunity andand ecosystemecosystem levellevel
•• MarineMarine vs.vs. TerrestrialTerrestrial GrazingGrazing Ecosystems:Ecosystems: AreAre ParrotfishParrotfish JustJust WetWet Wildebeest?Wildebeest? ContextContext--dependantdependant effectseffects ofof herbivory:herbivory: thethe importanceimportance ofof habitathabitat productivityproductivity andand herbivoreherbivore sizesize Redrawn from Proulx & Mazumder 1998 (Ecology 79:2581-2592)
30
Low grazing intensity High grazing intensity
20
10 Plant species richness
0 Nutrient-poor Nutrient-rich systems systems Redrawn from Bakker et al. 2006 (Ecology Letters 9:780-788)
Effect of large and small herbivores 80
60 P = 0.003
40
20
0
-20
-40
-60 0 100 200 300 400 500 600
Effect of small herbivores 60 P = 0.45 40
Change in species richness (%) 20
0
-20
-40
-60 0 100 200 300 400 500 600 Primary production (g m-2) Redrawn from Osem et al. 2002 (J. Ecology 90:936-946)
Productivity 500
) Poorly-drained -2 400 Well-drained
300
200
100 Dry Biomass (g m 0
Poorly-drained site
14
12
10 Richness
8
6 Ungrazed Grazed Well-drained site 11
10
9
8
7 Richness
6
5 1996 1997 1998 1999 Year Adapted from Grime (1973)
Stress Optimal Competitive tolerance coexistence exclusion
species richness Light availability Species richness
Environmental stress Habitat productivity Light availability Light availability
Competition intensity Competition intensity
Grazing intensity Productive habitats
Unproductive habitats Stress on plant
Grazing intensity Adapted from Grime (1973)
Stress Optimal Competitive tolerance coexistence exclusion
species richness Light availability Species richness
Environmental stress Habitat productivity Light availability Light availability
Competition intensity Competition intensity
Grazing intensity
AcknowledgementsAcknowledgements
Data collection and Logistics: Beth Amendola Greg Buis Allison Burkepile Catherine Burns Annikki Chamberlain Scott Collins Dave Hoover Kevin Kirkman Dave Thompson
Fencing Crew: Thembi, Wisani, Justice, Conright, Difference
Funding: National Science Foundation, U.S.A.