Forest Soils & Site Productivity

Soil Organic Matter and

Organisms

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ESRM 410: Forest Soils and Site Productivity The Role of Soil Invertebrates

(some of the following slides contributed by J Marra-WA Dept of Agric)

(Far Side creator-Gary Larson)2

Heterotrophic Respiration(Energy Flow)

Deciduous Forest

Net Primary

Production

Decomposers95%

Herbivores5%

Invertebrates10%

MicrobesBacteria & Fungi

90%

(Richle 1981)

(Chemoheterotrophs)

Now much research is focused on regulation of nutrient cycling

as well as ‘energy flows’ thus revealing organism/environment interaction! 3

Site and SoilSoil ProductivityProductivity

Comminution - increases surface to volume ratios of litter

Innoculation - transport microbial propagules to new substrates

Grazing - pruning response increases fungal metabolism- releases nutrients contained in microbial

biomass- alters competitive interactions and species

compositionMutualism - coevolved interaction in which both microbes

and invertebrates benefit

Microbial / Invertebrate Interactions in Soil

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Protozoa

Nematodes or roundworms

Major groups of Soil Fauna

The Microfauna < 0.1 mm

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Major groups of Soil Fauna

The Mesofauna 0.1 - 2 mm

Diplura

Featherwing beetle

Springtails

Mites

Protura Pseudoscorpions

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Major groups of Soil FaunaThe Macrofauna > 2 mm

Ants

Ground beetles

Millipedes

Earthworms

TermitesIsopods

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The Earthmovers!!

Ants

Termites

Earthworms

Invertebrate Effects on Soil Productivity

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Earthworms

- earthworms + earthworms

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Termites: Termitidae

Queen

Workers and Soldiers 10

Termite moundFungus farming Termitidae

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Distance NPP Infiltration rate Moisture Bulk Densityto mound (m) (g m-2 yr-1) (cm h-1) (%) (g cm-3)

1-3 728 12.0 29.2 1.2826-28 280 8.0 20.5 1.39

Productivity and soil properties in relation to distance to termite mounds.

(Arshad 1982)

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Leaf Cutter Ants: Atta sp. 13

Leaf-cutter Ant Trail

Photos by Bob Gara

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Leaf cutter AntDefoliation of Pine

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Excavated fungus garden

Vertical distribution of colony 16

NorthCarolina Puerto Rico

Costa Rica

Litterbag StudyComparison of Tropical and Temperate Forests(Heneghan et al. 2000)

NaphthaleneUntreated

P

erce

nt m

ass

rem

aini

ng

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C - without invertebrates F - with invertebrates

stems

roots in mineral soil

roots in humus

leaves

Birch Seedling Growth (Setala and Huhta1991)

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► regulating decomposition and nutrient mineralization processes

► stimulate the activity of microbial organisms, ► altering physical properties such as soil structure

and porosity ► increase moisture holding capacity of soil.

Their effects are generally greater in tropical ecosystems than temperate because of the more moderate climate.

Their effects are generally greater in deciduous forests than coniferous because of higher substrate quality.

Invertebrates contribute to soil productivity by:

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Effects of insects and diseases on forest

productivity

Good or bad?

(some of the following slides from Bob Edmonds)20

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Mountain pine beetle attacks of lodgepole pine in BC.  These pictures were taken east of Quesnel about 25 miles last summer (2005).  22

The current host list includes: California black oak, coast live oak, Shreve oak,tanoak, rhododendron,California bay laurel, big leaf maple, madrone, manzanita, huckleberry, California honeysuckle, toyon,California buckeye, California coffeeberry,Douglas-fir and coast redwoodand Arrow wood (in Germany, the United Kingdom, and the Netherlands).

SUDDEN OAK DEATH An introduced disease? caused by Phytophthora ramorum

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24

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Note height growth reduction in infected Douglas-fir trees over14 year period. Trees were age 24 at beginning of study

MeanCumulativeHeight Growth(inches)

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Impact of diseases and insects – good or bad

a. Mortality

b. Reduced growth

c. Destruction of merchantable wood (decay)

d. Reduction in pulp yield

e. Reduced wood quality - stain

f. Delayed regeneration; inadequate stocking (trees/acre)

g. Site deterioration - build up of pathogens

h. Changes in species succession

i. Creation of biodiversity

j. Decomposition and nutrient cycling27

• We know that land management practices change the soil community. The link between specific changes and soil function is less clear.

• Logging and Farming can reduce organic matter in the soil Reducing tillage tends to result in increased growth of fungi,

including mycorrhizal fungi. Decrease in OM may decrease nutrients, CEC, porosity and

water infiltration, ???

• Fire may also decrease OM, affect soil organisms, etc (direct, indirect, long & short term)

Management affects soil organisms

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• Soil biological crusts are very sensitive to trampling.

• Biosolids – OM, nutrients, water, …

• Soil compaction, lack of vegetation, or lack of plant litter covering the soil surface tends to reduce the number of soil arthropods, fungi, bacteria, etc as well as affecting root growth, aeration and water infiltration (EROSION!).

Management affects soil organisms

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Site and SoilSoil ProductivityProductivity

Physical and Chemical Properties Biological Properties

• soil organic matter• soil moisture balance• soil structure and porosity• nutrient availability• soil volume• microclimates

• mycorrhizas• nitrogen fixation• microbial decomposition• invertebrate regulation

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• A well managed soil is a

Good SoilGood Soil

• A GOOD SOIL is a

LIVE SOILLIVE SOIL

• A LIVE SOIL is a Resilient SoilResilient Soil 31