The Overstory
The Overstory #190 Silvopastoralism
12th June, 2007
The Overstory #190--Silvopasture: An Agroforestry Practiceby Ned B. Klopfenstein, W.J. Rietveld, Richard C. Carman,
Terry R. Clason, Steven H. Sharrow, Gene Garrett,
and Bruce E. Anderson
DEFINITION
Although some form of silvopasture management has been practiced for
centuries, silvopasture as an agroforestry practice is specifically
designed and managed for the production of trees, tree products, forage,
and livestock. Silvopasture results when forage crops are deliberately
introduced or enhanced in a timber production system, or timber crops
are deliberately introduced or enhanced in a forage production system.
As a silvopasture, timber and pasture are managed as a single integrated
system.
OBJECTIVES
Silvopastoral systems are designed to produce a high-value timber
component, while providing short-term cash flow from the livestock
component. The interactions among timber, forage, and livestock are
managed intensively to simultaneously produce timber commodities, a high
quality forage resource, and efficient livestock production. Overall,
silvopastures can provide economic returns while creating a sustainable
system with many environmental benefits. Well-managed silvopastures
offer a diversified marketing opportunity that can stimulate rural
economic development.
PLANNING CONSIDERATIONS
Before new silvopastoral systems are established, implications of
merging forestry and agricultural systems should be explored thoroughly
for economic and environmental considerations along with local land use,
zoning, cost-share program, and tax regulations. Forest and agricultural
land may have separate zoning and land-use regulations accompanied by
divergent tax assessments. Environmental requirements (e.g., planting
trees, stream-side protection, wildlife habitat maintenance, etc.) also
may vary with land use.
PLANT CONSIDERATIONS
When making tree and forage crop selections, consider potential markets,
soil type, climatic conditions, and species compatibility.
The timber component should be:
* marketable,
* high quality,
* fast growing,
* deep-rooted,
* drought tolerant, and
* capable of providing the desired products and environmental services.
On marginally productive lands, conifers are well-suited for
silvopastures because they can adapt to diverse growing sites, respond
rapidly to intensive management, and permit more light to reach the
forest floor. Select and use trees and planting/harvesting patterns that
are: a) suitable for the site; b) compatible with planned silvopastoral
practices; and c) provide desired economic and environmental returns.
The forage component should be a perennial crop that is:
* suitable for livestock grazing,
* compatible with the site (soil, temperature, precipitation),
* productive under partial shade and moisture stress,
* responsive to intensive management, and
* tolerant of heavy utilization.
LIVESTOCK SELECTION
Potential livestock choices include: cattle, sheep, goats, horses,
turkeys, chickens, ostriches, emu, rhea, or game animals such as bison,
deer, elk, caribou, etc. The selected livestock system must be
compatible with tree, forage, environment, and land use regulations. In
general, browsing animals such as sheep, goats, or deer are more likely
to eat trees; whereas, large grazing animals such as cattle or elk or
more likely to step on young trees. Younger livestock are more prone to
damage trees than are older, more experienced animals. Livestock are
more likely to impact hardwood trees than conifers.
DESIGN AND ESTABLISHMENT
Silvopastures can be established on any land capable of simultaneously
supporting tree and forage growth. However, silvopastoral systems can
require a relatively large land base to sustain timber and livestock
production continuity. A source of local technical assistance is
essential to develop a silvopastoral system matched to local conditions
and landowner objectives. Appropriate establishment methods depend on:
1) woodland/forest type (e.g., site conditions, and tree species, age,
pattern, and spacing) or existing pasture situation; 2) whether
even-aged or uneven aged silviculture is practiced; and 3) landowner
objectives (e.g., timber products, environmental benefits, wildlife,
etc.). Appropriate grazing systems depend on climate, terrain, tree
species, tree age, other vegetation, kind of livestock, labor
requirements, and extent of fencing, water supplies, and supplementary
equipment.
Tree pattern is an important factor for silvopasture success. Trees can
be evenly distributed over the area to optimize growing space and light
for both trees and forage. Alternatively, grouping trees into rows or
clusters concentrates their shade and root effects while providing open
spaces for pasture production. Trees are typically pruned to increase
light penetration and develop high-quality sawlogs. Silvopastures of
varying ages can be merged and managed on a landscape basis.
The establishment of forage in even-aged or uneven aged silvicultural
situations may require thinning and some type of tillage to provide a
favorable seedbed for germination and growth. On rangeland or pasture
sites, forage suppression (e.g., herbicide, tillage, mulch, etc.) may be
required for 2-3 years to establish tree seedlings, but suppression
methods must be carefully selected to avoid damaging desirable plants.
MANAGEMENT
Livestock grazing should be intensively managed. A successful
silvopasture requires understanding forage growth characteristics and
managing the timing and duration of grazing to avoid browsing of young
tree seedlings or elongating shoots. Livestock should be excluded from
tree plantings during vulnerable periods. Similar approaches can
minimize damage by trampling or rubbing. Improper management of
silvopastures can reduce desirable woody and herbaceous plants by
over-grazing and soil compaction. Thus, proper management is the key to
success.
Available management tools include:
* tree harvesting, thinning, or pruning;
* fertilization to improve both forage and tree production;
* planting legumes for nitrogen fixation and forage production;
* multi-pasture, rotational grazing;
* rotational burning;
* supplemental feeding;
* developing water sources (e.g., stock tanks, windmills, photovoltaic
pumps, hydraulic rams, ridge reservoirs, etc.);
* locating salt/mineral licks, and walkways to encourage uniform
livestock distribution; and
* fencing (e.g., standard or electric), tubing, plastic mesh,
repellents, and seasonal livestock exclusion to reduce damage to young
seedlings.
BENEFITS
--> Economic
Integrating trees, forage, and livestock creates a land management
system to produce marketable products while maintaining long-term
productivity. Economic risk is reduced because the system produces
multiple products, most of which have an established market. Production
costs are reduced and marketing flexibility is enhanced by distributing
management costs between timber and livestock components. Comprehensive
land utilization in silvopastoral systems provides a relatively constant
income from livestock sale and selective sale of trees and timber
products. Well-managed forage production provides improved nutrition for
livestock growth and production. Potential products of the tree
component include: sawtimber, veneer logs, pulpwood, firewood, pine
straw, posts and poles, harvested game, nuts, fruit, ornamental flowers
and greenery, maple syrup, mushrooms, organic mulches, and other
secondary products.
--> Woodland and forage
Grazing can control grass competition for moisture, nutrients, and
sunlight, thereby enhancing tree growth. Well managed grazing provides
economical control of weeds and brush without herbicides, maintains fire
breaks, and reduces habitat for gnawing rodents. Fertilizer applied for
forage is also used by trees. In addition, livestock manure recycles
nutrients to trees and forage.
--> Livestock
Some forage species tend to be lower in fiber and more digestible when
grown in
a tree-protected environment. Trees that provide shade or wind
protection can have a cli-mate-stabilizing effect to reduce heat stress
and windchill of livestock. Protection from trees can cut the direct
cold effect by 50% or more and reduce wind velocity by as much as 70%.
Livestock require less feed energy, so their performance is improved and
mortality is reduced.
--> Environmental and aesthetic
Silvopastures can increase wildlife diversity, and improve water
quality. The forage protects the soil from water and wind erosion, while
adding organic matter to improve soil properties. Silvopastures provide
an attractive landscape with an aesthetically pleasing "park-like"
setting. In contrast to concentrated livestock operations, silvopastoral
systems are less likely to raise environmental concerns related to water
quality, odors, dust, noise, disease problems, and animal treatment.