Ecosystem processes Ecosystem processes and heterogeneityand heterogeneityLandscape Ecology

TodayTodayGlobal NPPLake positionMoose impacts

Questions/CommentsQuestions/Comments

Ecosystem processesEcosystem processesWhat do we mean? ◦Energy◦Matter

Carbon Nutrients

Spatial Heterogeneity in Spatial Heterogeneity in ecosystem processecosystem processWhat can cause ecosystem processes to vary spatially? ◦Temperature◦Moisture◦Topography

What factors affect NPP? ◦Climate

Temperature Light Precipitation

◦Nutrients

Where is global marine NPP highest?

Why?

Where is global terrestrial NPP highest?

Why?

Paradox…Paradox…How do the factors that drive NPP differ between marine and terrestrial ecosystems?

the basic processes of plant photosynthesis are the same for terrestrial and marine/aquatic plants

the key factors must be the physical and chemical properties of the environments in which plant growth occurs,

or the carbon allocation and life history dynamics of the plants themselves.

Marine NPPMarine NPP“Marine NPP was a major driver of the preindustrial cultures and economies of civilizations in the higher latitudes, and is still a major driver of the global fishing industry”

Driven by:◦Nutrients – upwelling◦Geology

Terrestrial NPPTerrestrial NPP“The most remarkable feature of the terrestrial NPP distribution is that it is the opposite of the pattern of marine NPP”

Driven by:◦Climate?◦Why not nutrients?

Nutrients in TropicsNutrients in TropicsAre the tropics a good place for agriculture?

The basic processes of soil weathering have several inevitable consequences that result in a decline in soil fertility, and thus in the resources available to support plant growth and NPP over time as soils age.

All of these processes occur most rapidly in the tropics.

GlobaGlobal l NutriNutrient ent ConteContentnt

“Why should marine productivity be positively correlated with the availability of mineral nutrients in the oceans and the adjacent continents, while the productivity of the plants growing in the soil on those continents is inversely correlated with nutrient availability?”

ConclusionsConclusionsIn fact, the highest short-term rates of NPP (eNPP) apparently occur in temperate and boreal forests.

These patterns of forest productivity are consistent with the global distribution of soil fertility

as well as the productivity of certain types of crops

and the standardized economic value of agricultural production

Why is might our current Why is might our current paradigm about NPP paradigm about NPP wrong?wrong?Hard to measure NPPSatellites measure green leaves, not necessarily carbon that goes into wood.

Landscape Position and Landscape Position and LakesLakesWhat factors influence the ecosystem functions of a lake?◦Geology◦Size/Depth◦Climate◦Terrestrial inputs

What about the spatial arrangement of lakes can influence functions? ◦Geology◦Climate◦Hydrologic connectivity

What type of ecosystem What type of ecosystem properties could be properties could be influenced? influenced?

How to test? How to test? Observational study..

ConclusionConclusionMany factors change with position◦Ionic composition◦Biota◦Size◦Primary Production

Species and ecosystem Species and ecosystem functionfunctionHow do species influence ecosystem function?

Effects of Moose Browsing on Vegetation and Effects of Moose Browsing on Vegetation and Litter of the Boreal Forest, Isle Litter of the Boreal Forest, Isle Royale,Michigan – McInnis et al. Royale,Michigan – McInnis et al.

Spatial patterns in the moose-forest-soil Spatial patterns in the moose-forest-soil ecosystem on Isle Royale, Michigan USA – J. ecosystem on Isle Royale, Michigan USA – J. Pastor et al. Pastor et al.

BackgroundBackgroundLandscape heterogeneity affects population dynamics and movement.

Animals can alter ecosystem function due to their behavior. ◦Ecosystem engineer?

Large herbivores could have large impacts:◦Large home ranges. ◦Eat a lot.

But only what is tasty.

Background cont. Background cont. With selective feeding, herbivores can affect species composition, nutrient cycling, etc. ◦Obvious on a local scale.

Can herbivores alter ecosystem function at the scale of their home range, or of a valley?

Observations:◦Herbivores change the structure, biomass, production, and species composition of vegetation in heavily browsed or grazed areas

Questions:

Results:

Effects of Moose Browsing on Effects of Moose Browsing on Vegetation and Litter of the Vegetation and Litter of the Boreal Forest, Isle Boreal Forest, Isle Royale,MichiganRoyale,Michigan

Observations:Questions:◦What are the effects of browsing upon the biomass and production of trees, shrubs, and herbs?

◦Does browsing alter species composition of the vegetation?

◦Do changes in species composition affect the quality and quantity of litterfall in browsed areas?

Results:

Effects of Moose Browsing on Effects of Moose Browsing on Vegetation and Litter of the Vegetation and Litter of the Boreal Forest, Isle Boreal Forest, Isle Royale,MichiganRoyale,Michigan

What are the effects of browsing upon the biomass and production of trees, shrubs, and herbs?

Does browsing alter species composition of the vegetation?

Observations:Questions:◦What are the effects of browsing upon the biomass and production of trees, shrubs, and herbs?

◦Does browsing alter species composition of the vegetation?

◦Do changes in species composition affect the quality and quantity of litterfall in browsed areas?

Results:◦Higher biomass, alters species composition, …

Effects of Moose Browsing on Effects of Moose Browsing on Vegetation and Litter of the Vegetation and Litter of the Boreal Forest, Isle Boreal Forest, Isle Royale,MichiganRoyale,Michigan

Observations:

Hypotheses:

Results:

Spatial patterns in the moose-Spatial patterns in the moose-forest-soil ecosystem on Isle forest-soil ecosystem on Isle Royale, Michigan USA – J. Pastor et Royale, Michigan USA – J. Pastor et al. al.

Observations:◦Moose preferentially forage on aspen and avoid conifers.

Hypotheses:◦If moose browsing causes a shift in dominance from hardwoods to conifers across adjacent areas, we should expect corresponding changes in soil nutrient availability over the landscape.

Results:

Spatial patterns in the moose-Spatial patterns in the moose-forest-soil ecosystem on Isle forest-soil ecosystem on Isle Royale, Michigan USA – J. Pastor et Royale, Michigan USA – J. Pastor et al. al.

What was the study What was the study about?about?Examine the large-scale landscape distribution of moose browsing intensity in relation to plant community composition and size structure, as well as soil nitrogen availability.◦Do moose control plant community composition and soil nitrogen at large scales?

What did they measure?What did they measure?Available browse.Annual consumption by moose.Soil nitrogen availability.

They tested three They tested three modelsmodelsRandom Short-range autocorrelationHigher order of regularly arranged patterns

What would these models What would these models look like? look like? Random ◦No autocorrelation – constant variance

Short-range autocorrelation◦Low-variance at short distances

Higher order of regularly arranged patterns◦Low-variance at short distance and low-variances at large distances as well.

Observations:◦Moose preferentially forage on aspen and avoid conifers.

Hypotheses:◦If moose browsing causes a shift in dominance from hardwoods to conifers across adjacent areas, we should expect corresponding changes in soil nutrient availability over the landscape.

Results:

Spatial patterns in the moose-Spatial patterns in the moose-forest-soil ecosystem on Isle forest-soil ecosystem on Isle Royale, Michigan USA – J. Pastor et Royale, Michigan USA – J. Pastor et al. al.

What did Pastor What did Pastor conclude?conclude?Tested hypothesis…

◦Moose causing patterns. Alternative hypotheses?

◦ Slope◦ Aspect◦ Fire◦ Bedrock◦ Geology◦ Beavers

No differences in nitrogen availability or consumption due to slope or aspect.◦Spatial patterns not caused by topographic relief.

◦Nor other factors.

What did Pastor What did Pastor conclude?conclude?Conclusion: ◦Patterns are a result of dynamic interactions between moose foraging and plant communities.

◦Uncommonly strong impact for a large mammal.

◦This patterns has occurred in less than 50 generations.