Secondary succession: changes in relative abundance of tree species at Hubbard Brook Experimental Forest

34 invertebrate communities in streams A, B, C, D indicate community types determined by classification

Classification

Primary succession: colonization of concrete blocks in intertidal zone by algae

Keystone species Sea otter urchins kelp

Heterotrophic succession: fungal populations colonizing pine litter

No disturbance Periodic density-dependent disturbance

Enteromorpha Chondrus Preferred food Poor food source Dominant competitor Poor competitor Littorina littorea

Ecosystem: Tansley (1935) “The more fundamental conception is… the whole ecosystem including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment… We cannot separate the organisms from their special environment with which they form one physical system…. It is the system so formed which provides the basic units of nature on the face of the earth.”

Precipitation

Temperature

temperature Rate of photosyn or respiration Net photosynthesis Gross photosynthesis respiration temperature Net photosynthesis Topt

Water deficit: Potential evapotranspiration (PET) - precipitation (PPT)

Length of growing season

Limiting nutrient availability

NPP along transect from coast of Georgia to edge of continental shelf

Consumption efficiencyEnergy ingested at trophic level n Energy produced at trophic level n-1

Assimilation efficiencyEnergy assimilated at trophic level n Energy ingested at trophic level n

Production efficiencyEnergy produced at trophic level n Energy assimilated at trophic level n

Trophic level transfer efficiency

forest lake grassland stream

Decomposer Amino acids, Carbohydrates, Lipids, Nucleic acids Proteins, etc. Inorganic Nutrients NO3-, SO4--, PO4--- Mg, Mn, Fe, Ca, K, etc immobilization H 2 O + CO 2 O2O2 respiration mineralization Dead animal or plant matter Organic C, E, nutrients

Limiting nutrients Immobilized Decay rate increased by increased content of limiting nutrients All nutrients mineralized Decay rate decreased by increased content of limiting nutrients % remaining Time

Stages of decomposition Early: – Autolysis – Leaching of dissolved OC, minerals – Colonization by bacteria and fungi – Decomposition of sugars and amino acids > starch > cellulose – Population explosion of early colonizers

Stages of decomposition Intermediate/Late – Microorganisms specializing in using resistant material colonize > high diversity 1 g soil: 10,000 genetically distinct bacteria – Degrade cellulose, complex proteins, lignins – Physical contact required (e.g., membrane surface enzymes)

Time (weeks)Time (weeks)Time (weeks) % Original remaining Nutrient dynamics during decomposition in a Scots pine forest, Sweden

Time (weeks)Time (weeks)Time (weeks) % Original remaining Nutrient dynamics during decomposition in a Scots pine forest, Sweden

Concentrations of solutes in streams draining Hubbard Brook experimental catchments W2 (deforested and treated with herbicides in 1965) and W6 (control)