Forest Soils & Site Productivity

Nutrition Management:

Fertilization

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Nutrient LimitationsAmount of Nutrients?

• Input (additions)?– Natural

• ppt & wind• deposition• OM decomposition & mineral weathering• manure (deposition & decomposition)• fire (OM & ash)• biological N fixation (eg, legumes, lichens)

• Output (losses)– Erosion– Leaching– Fire– ??

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Nutrient LimitationsAmount of Nutrients?

• Input (additions)?– Natural…..– Management

• fire (OM & ash)• biological N fixation• Crop rotation/alley cropping• fertilizer

– natural….– synthetic

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Soil TexturesSoil pH Sand Loam Clay

6.0 20 35 50

5.5 45 75 100

5.0 65 110 150

4.5 80 150 200

4.0 100 175 230

Pounds of Lime needed to raise soil pH to 6 .5 (lbs/1000ft2)

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Fertilizer Growth Responsedue to?

• (Besides the fertilizer amount and type)

• Stand– species– age– size– stocking– vigor

• Patterns of functions, eg, N immobilization/mineralization

• Availability of other nutrients & water

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Forest Soils &Site Productivity

Nutrition Management:

Biological N-Fixation

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assimilation

assimilation

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ALGAE DiatomsCyanobacteria – N fixing

Lichens (fungi+algae)12

Nitrogen-fixing Bacteria

•Nodules formed where Rhizobium bacteria infected soybean roots.

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Actinomycetes

– Bacterial cells– Grow like fungal hyphae– e.g. Non-legume root nodules having Frankia in Alnus 14

Red Alder nodules – actinomycete fixing atmospheric nitrogen, plant accessing N which limits growth 15

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(Huxley 1999)17

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Forest Soils & Site Productivity

Forest Soil Management

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Multiple States of an Ecosystem

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Resistance and Resiliency

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Low Resistance but High Resiliency

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High Resistance but Low Resiliency

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Forest Management(Disturbances via Tree Planting- Intensive Plantation Forestry)

Tree planting is used in:• Afforestation – open sites w/o trees

for some time• Reforestation – cleared and replanted

(genetically improved?)• Conversion from one forest type to

another type (in sites still supporting considerable forest cover)

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Forest Management and Soil Disturbances

MORE LESS

Wheeled vehicles Track vehicles

Steep slopes Level slopes

Clayey texture Sandy texture

Wet soil Dry soil

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North coast of Papua New Guinea in the Vanimo Timber Area. Creek provided drinking water to the Amoi village but can no longer be used by the villagers!

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Decommissioning and restoration of logging roads

For water erosion, keep soil infiltration high, control overland flow using vegetation, ditches, contour plowing etc.

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Good Forest Management should also be

Good Forest Soil Management

• Planning

• Harvesting?– BD (aeration, percolation,…– OM– Equipment oil spills, ?

• Soil prep - scarification, bedding (temp, H2O table), fertilizer, herbicide

• Planting - species, soil types, …40

Forest Soils & Site Productivity

Long Term Soil Productivity

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Communal Property and the Tragedy of the Commons

• Tragedy of the CommonsOpen access systems - have no rules to manage resource use (1968, Garret Hardin)

• Commonly held resources are degraded and destroyed by self-interest

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Tragedy of the CommonsGarrett Hardin (biologist) 1968

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Tragedy of the Commons

Garrett Hardin (biologist) 1968

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Tragedy of the Commons

Garrett Hardin (biologist) 1968

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Tragedy of the Commons

Garrett Hardin (biologist) 1968

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Long-Term Soil Productivity??

• Sustainability?

(yield)

– The condition of being able to harvest biomass from a system in perpetuity

(several human generations?)

so that

the ability of the system to renew itself (or be renewed) is not compromised

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• the minimization of the number and activity of soilborne plant disease organisms and soilborne insect pests.

(narrow definition?)

• Soil health is the capacity of soil to function as a vital living system with ecosystem and land-use boundaries to:– sustain plant and animal productivity, – maintain or enhance water and air quality, and – promote plant and animal health.

(Doran and Zeiss, 2000, Applied Soil Ecology 15:3-11)

Soil Health?

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Soil Quality

Soil Quality – capacity of the soil :– to sustain plant and biological

productivity, – to maintain environmental quality, and – to promote plant and animal health– AND support human health and habitation.

• Soil Health? – some suggest it is the evaluation of soil quality over time???

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Sensitive indicators of Soil Quality

Indicators?– Physical

– Chemical

– Biological

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ManagementPractices expressed:• locally• regionally, &?

Management affected by ?:• locally,• regionally, • globally

Need to THINK and ACT LONG-TERM54

Sustainability?• Silvicultural (or ecological)but also

• Economic• Socio-politicalHard to quantify!!!

So use term

• Good Forest Management55

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Forest management will affect soil forming factors

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Long-Term Soil Productivity

• Short-Term Use? Still need to consider:

• Long-Term Productivity (crops & SOIL)

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