Lecture 16 April 12, 2005 Ecosystem Processes & Land-Water Interactions

Ecosystem ecology = study of the flow of energy and materials through organisms and their environment (systems). Landscape ecology = study of the interactions among patches or different landscape elements through the redistribution of energy, matter, or information. Respiration Herbivore Detritus Decomposer Primary Producer Predation Growth & Reproduction Growth & Reproduction Death, Excretion Consumption Predation Death, Excretion Grazing Growth & Reproduction Respiration Carbon Fixation Energy Ecosystem Processes and Landscapes

Ecosystem ecology historically has not been concerned with spatial heterogeneity and pattern! Pre early-1970s: Assumptions of spatial homogeneity, equilibrium, and closed systems. Post- 1970s: Ecosystem responses to Disturbances. Recently, spatial heterogeneity has been more explicitly addressed, first by varying the sampling approach, then by addressing adjacency effects. Ecosystem Processes and Landscapes

Fine Scale Heterogeneity Studies that have examined spatial heterogeneity at the scale of individual patches, or ecotones between patches. Plant-scale feedbacks with hydrology and biogeochemistry. Others include edge effects on microclimate and productivity. Riparian zones as erosional buffers. Ecosystem Processes and Landscapes

Running et al Coarse scale heterogeneity Studies that have examined spatial heterogeneity at very large scales – often subcontinental or larger. Often concerned with feedbacks between climate and land cover – and are often conducted in the context of global climate change. Issue is often how to “scale up.” Ecosystem Processes on Landscapes

Early limnology assumed lakes to be closed systems. Recent studies have recognized interactions between rivers/lakes and their surroundings. Groundwater flow, precipitation inputs, and ionic concentrations are affected by hydrological position and spatial placement of rivers/lakes. Webster et al Ecosystem Processes on Aquatic Landscapes

What can terrestrial landscape ecology tell us about rivers and lakes? Matter: Water volume, anions, cations, particulates, other? Energy: Flow velocity Information: NA? The Landscape spatial processes Patch sizes, shapes, configuration, etc.

What can terrestrial landscape ecology tell us about rivers and lakes? Pathways The movement of water from land to water body significantly alters hydrology and chemistry Particulate accumulation/removal Magnitude of flow Chemical transformations (biogeochemistry) Movement across the landscape alters stream flow, lake inputs, the amounts of physical, chemical change in transit.

source pathway destination Patch composition Patch size Patch arrangement Variations in landscape pathways The Landscape The Landscape The Landscape The Landscape

A major emphasis in “biocomplexity” studies of late. Past research has focused on nonpoint source pollution and the role of riparian buffers. Current studies focus on cycling of carbon and nutrients between terrestrial and aquatic systems. Weller et al Land-Water Interactions

The Landscape sourcepathwaydestination Stream ecology Landscape ecology precipitation Land-Water Interactions: Discipline boundaries

Effects of the landscape on water chemistry Sandstone + dolomite dolomite Mixed granites Dolomite, shale, limestone Parent geology Variation in parent geology & weathering causes chemical variation in water.

Effects of the landscape on water chemistry: Parent geology Cations Ca, Mg, Si Anions Carbonates Affects productivity, acidification risk Nutrients Phosphorus all from rock weathering Slow rate of weathering  widespread P limitation Geological effects exist both within and between drainages.

From: Holloway et al Nature 395: Effects of the landscape on water chemistry: Parent geology

Parent geology affects the path that water takes Preferential flow paths Land forms

Effects of the landscape on water chemistry Land Use/Land Cover Variation in land use/land cover causes variation in water quality. Best studied landscape effect on water quality.

Effects of the landscape on water chemistry: land use/land cover NO3-N (mg/L) SRP (mg/L) South West Central % Agriculture in the basin (Stanley unpublished) NitratesSoluble Reactive Phosphorus

Effects of the landscape on water chemistry: land use/land cover % agriculture The signal of agricultural, urban land cover is often strong and direct –Nutrient enrichment –Classic pollutants –Organic C But not always…

Effects of the landscape on water chemistry Why aren’t land use/land cover always good predictors of water chemistry?

What we see… What actually happens Deep groundwater sources by-passing land cover. Why less effect of the landscape on water chemistry: Why less effect of the landscape on water chemistry: Hydrologic pathways can by-pass land cover The Landscape

There are many ways for water to flow downhill! Why less effect of the landscape on water chemistry: Why less effect of the landscape on water chemistry: Hydrologic pathways can by- pass land cover

Why less effect of the landscape on water chemistry: Flow paths vary as a function of landscape position E.g., water quality varies among lakes despite similar land cover. Different lakes fed by water from different sources = the effect of Landscape Position. Precipitation Input Groundwater Input “Highland” lake “Lowland” lake

High (little GW) Low (lots of GW) Cond (µS cm -1 ) Landscape position Chl a (µ g L -1 ) Landscape position High (little GW) Low (lots of GW) From: Riera et al Freshwater Biology 43: Why less effect of the landscape on water chemistry: Flow paths vary as a function of landscape position

Why less effect of the landscape on water chemistry: Hot spots Definition 1: Sites where water moves quickly from land to lake/stream. Patches that have a disproportionately large influence on water quality Hot spot effects Addition of particles, solutes Removal of particles, solutes

Why less effect of the landscape on water chemistry: Hot spots Definition 2: Sites where water is subject to distinct physical/biogeochemical environment and transformation.

Why less effect of the landscape on water chemistry: Hot spots From:Soranno et al Ecological Applications 6: Example: P derived from small hotspots. However, the extent of hotspots is affected by land use Example: Urban cover accounts for 10% of cover and 20-55% of P input to L. Mendota.

Effects of the landscape on water chemistry: Riparian zones

Aquatic/terrestrial interface Soils often saturated (anoxic), rich in organic matter Water velocity slows Rapid biogeochemical change, particle trapping High rates of denitrification!

Effects of the landscape on water chemistry: Riparian zones Riparian Zone Benefits:

Effects of the landscape on water chemistry: Riparian zones The solution to non- point source pollution? May or may not be effective in reducing nutrient loads in groundwater. Dependent upon: Pathways Size Shape of RZ

From: Weller et al Ecological Applications 8: Spatial configuration of riparian zone affects nutrient retention Effects of the landscape on water chemistry: Riparian zones

The challenge: Determining when water does/does not pass through the riparian zone. Determining where we can restore natural filtering functions. Effects of the landscape on water chemistry: Riparian zones Alteration of water flow due to agricultural drainage and urbanization.

Landscape influence on water quality determined by: Relative importance of different flow paths What happens along these flow path Lots of research opportunities for questions: Effect of patch arrangement, patch size? Precipitation deep ground water Effects of the landscape on water chemistry: Summary