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– ??
2
Nutrient LimitationsAmount of Nutrients?
• Input (additions)?– Natural…..– Management
• fire (OM & ash)• biological N fixation• Crop rotation/alley cropping• fertilizer
– natural….– synthetic
3
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)
7
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
8
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
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)
27
Forest Management and Soil Disturbances
MORE LESS
Wheeled vehicles Track vehicles
Steep slopes Level slopes
Clayey texture Sandy texture
Wet soil Dry soil
28
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!
36
Decommissioning and restoration of logging roads
For water erosion, keep soil infiltration high, control overland flow using vegetation, ditches, contour plowing etc.
37
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
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
43
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
48
• 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?
49
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???
50
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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