Grazing What is grazing? How do opinions vary on the use of grazing? What are overuse and overgrazing? How can controlled grazing manage habitat? What grazing factors influence vegetation & wildlife? Do we need to consider disease transmission? Grazing What is Grazing? Consumption of standing forage Domestic or wild herbivores (e.g., ungulates) Terrestrial v. aquatic Browsing Credit: forestryimages.org Grazing What is Grazing? Herbivores (wild or domestic) Influence vegetation development Alter plant communities Appearance Productivity Composition Structure Disturbance & Succession Affects wildlife & habitat Credit: forestryimages.org Grazing Evolutionary History of Grazing Role of herbivory & subsequent impacts Examples Midcontinent grasslands (prairies) of NA Long history of grazing Semi-desert grasslands No recent history of grazing Plants lack tolerance mechanisms Depends on system Credit: nztec.org Grazing Opinions about Grazing Detrimental to wildlife habitat Livestock conflict with wildlife management Mismanagement Overuse Overgrazing Credit: wordpress.comCredit: wildsonora.com Grazing Mismanagement of Grazing Overuse Excessive removal of current years growth Effects maybe short-lived Overgrazing Continued overuse Changes in plants, soils, & water relationships Altered plant species composition Palatable v. less palatable Some irreversible Reductions in K for grazers (wild & domestic) Grazing Mismanagement of Grazing Ecological costs Inappropriate successional changes Undesirable changes in community composition Unsuitable changes in physical characteristics Loss of biodiversity Reduced densities of various taxa Disrupted ecosystem functions Overgrazing as a habitat management tool? Prairie dogs & black-footed ferrets Grazing Controlled Grazing Managing the degree & timing of removal (including protection) of current years growth Tool for wildlife habitat management Create desirable habitat conditions One of Leopolds Tools - Cow Mimicking a natural process E.g., prairies Ecosystem engineers Rewilding Credit: forestryimages.org Grazing Controlled Grazing Vegetation (restoration & maintenance) Alter composition of plant community Increase productivity of selected species Increase the nutritive quality of forage Increase the diversity (structural) of habitat Credit: forestryimages.org Credit: birdersdigest.com Grazing Controlled Grazing Environmental Protective Grazing Strategic Grazing Credit: sylvandale.com Grazing Environmental Protective Grazing Livestock managed & strictly controlled Protect fragile environments Prevent overuse or overgrazing Particularly in arid & semi-arid systems Credit: extesnion.usu.edu Grazing Environmental Protective Grazing Guidelines Conservative stocking Adequate rest & deferment Appropriate timing around wildlife & plant life cycles Close monitoring Management of cover Exclusion from key areas Grazing Strategic Grazing Livestock managed & strictly controlled Manipulative tool - Leopolds Tool Create specific habitat conditions Credit: humboldtrcd.orgCredit: ansci.wsu.edu Grazing Strategic Grazing Prevent shifts to unsuitable seral stages Cause shifts to earlier seral stages A useful disturbance to affect succession Credit: fw.ky.gov Grazing Strategic Grazing Produce weedy feeding sites Maintain tall grass nesting sites (deferment) Increase structural diversity of the herb layer Create bare feeding, dusting, & display sites Promote re-growth of grasses (nutrition) Grazing Strategic Grazing Reduce unwanted standing dead material Stimulate lateral sprouting of shrubs Create bushier forms of trees & shrubs Increase production of shrubs Credit: rala.is Grazing Strategic Grazing (Payne and Bryant 1994) Grazing Grazing Effects Vegetation Stocking rate* Timing Duration Frequency Rest Animal type Credit: blogs.usak.ca Credit: Sheep101.infoCredit: srcp.org Grazing Stocking Rate Animal units (AUs)/animal unit equivalents (AUEs) AU: Forage consumed by 454 kg (1000 lb) of cow or cow & unweaned calf pair 9 kg/day AUE: Proportion of animal units of different species Based on relative consumption Convenient means of assessing & implementing sticking rates & estimated impacts/forage needs Issues when applied to wildlife Grazing Animal Animal Weight (kg) Daily Dry Matter Intake (% body weight) Daily Dry Matter Intake (kg)AUE Cattle Sheep Goat Horse Bison Elk Moose Bighorn WT Deer Pronghorn (Payne and Bryant 1994) Grazing Stocking Rate Animal unit days/ha/year = number of animals x AU or AUEs x number of days grazing x ha of habitat grazed ~Quantity of vegetation removed Seasonal & annual dynamics Finite amounts Weather important Credit: english-nature.org.uk Grazing Stocking Rate determines Grazing Pressure Influencing vegetation structure & composition Medium stocking Selectively remove vegetation = increased variation High & low stocking All or none of vegetation removed Little effect on variation Depends on type of grazer Grazing Stocking Rate Grazing Pressure influences vegetation by selectively disadvantaging some plants more than others Low stocking Concentrate on most palatable Medium stocking Increasing proportion of palatable High stocking Forced to eat least palatable A tool to remove them? Often a few species become dominant Grazing Stocking Rates Grazing pressure Adjustment takes skill & judgment Introducing grazing Only a portion Low stocking level Increase later Credit: pasture.com Grazing Timing & Duration of Grazing Frequency & rest Suitability of the area for its inhabitants Effect on individual plant species Effect of vegetation removal on fauna Effect of livestock trampling on fauna Grazing Timing & Duration of Grazing (Temperate) Summer grazing- spring to fall Winter grazing- fall to spring Continuous/year round grazing Grazing Timing & Duration of Grazing Summer grazing (tends to maximize ag production) Advantages to wildlife Maintenance of plant species richness Provision of vegetation of suitable height Some wildlife: some breeding birds, winter birds, & invertebrates Credit: flickr.com Grazing Timing & Duration of Grazing Summer grazing Disadvantages to wildlife Removal of nectar sources Prevention of seed development Trampling of bird nests An optimal grazing regime needs planning Even within a season such as summer Grazing Timing & Duration of Grazing Winter grazing Advantages to wildlife Provide conditions for some invertebrates (reduced litter) Maintain specialized plant communities Reduce vigor of unpalatable plants Reduce litter & create bare ground Help maintain short vegetation in spring Credit: worldassoc.com Grazing Timing & Duration of Grazing Winter grazing Disadvantages to wildlife Reduce vigor of desirable plants Allow for colonization of unwanted plants Result in areas of denuded vegetation In many temperate regions Avoided: less ag production with winter grazing Native systems would typically have greater grazing pressure than food resources Grazing Timing & Duration of Grazing Continuous Grazing Advantages & Disadvantages Stocking levels- maximum winter carrying capacity (= 1/3 summer) or overuse Difficult to attain wildlife management goals Wildlife that need short, open conditions in late spring and summer Grazing Timing & Duration of Grazing Grazing Systems Planned grazing & deferment periods Timing Duration Frequency Rest Provide food, cover, diversity, & non-use/undisturbed areas Typically better for wildlife than year-long or season- long continuous grazing systems Grazing Timing and Duration of Grazing Grazing Systems Rotation- moving animals among pastures Deferred rotation- each pasture periodically avoided Provides non-use areas with enhanced food & cover, & less disturbance (Payne and Bryant 1994) Grazing Grazing Systems Rest-rotation Reduced livestock performance Moderate stocking rates Food, cover, disturbance benefits Integrating other treatments such as fire (Payne and Bryant 1994) Grazing Grazing Systems Short-duration grazing (7/60 days) Soil compaction with usually high stocking rates Inappropriate in low resiliency systems (Payne and Bryant 1994) Grazing Grazing Systems High intensity-low frequency system (14/100 days) Soil compaction with usually high stocking rates Inappropriate in low resiliency systems Poor livestock performance (Payne and Bryant 1994) Grazing Animal Type Cattle Sheep Equines (horses, ponies, & donkeys) Goats Wild herbivores Different effects on vegetation & system Grazing Animal Type Pattern & selectivity of vegetation removal Trampling effects Extent to which woody vegetation is browsed Dung fauna Effects will depend on grazing pressure Effects on sward structure, vegetation, etc. typically greatest with medium grazing pressure Grazing Animal Type Cattle (wrap & swing) Feeding unselective at a fine scale Scattered dung deposits Grazing avoidance mosaics Create a bunched/tussocky vegetation structure Medium stocking rates Greater trampling pressure Soil & vegetation Wildlife Best able to digest coarse vegetation Limited browsers Woody plant damage Credit: usda.gov Grazing Animal Type Sheep (nibble) Highly selective feeders Prefer flowers & buds of forbs Limited trampling Create uniform, closely cropped swards High stocking rates Adults able to digest coarse vegetation Poor browsers Scattered dung Credit: ars.usda.gov Grazing Animal Types Equines (nibble) Highly selective feeders Consume grasses & avoid forbs Create variation in vegetation Moderate stocking rates Discrete dung deposits Adults able to digest coarse vegetation Intermediate browsers Donkeys & coarse vegetation (e.g., thistles) Credit:maguirefarm.com Grazing Animal Type Goats Consume a wide variety of vegetation Good browsers Shrub control Damage by grazing sensitive vegetation Agility Credit: senorcafe.com Grazing Animal Type Combinations of grazing animals Effects difficult to predict Open up tall & rank vegetation Reduce selectivity of vegetation removal Facilitate use of grassland by other grazers Credit: flickr.com Grazing Dung Invertebrates Food source, decomposers, nutrient cycling, etc. (Ausden 2007) Grazing Dung invertebrates Anti-parasitic drugs- Avermectins Produce residues in dung Prevent development of larvae Grazing Dung invertebrates Anti-parasitic drugs- Avermectins Treat livestock On basis of need Before or after grazing site of interest With an alternative anti-parasitic drug Grazing Disease Transmission Wild herbivores to livestock Livestock to wild herbivores Credit: fws.gov Grazing What it is Opinions about it How it relates to overuse and overgrazing How it effects vegetation and wildlife How we can use it to manage wildlife habitat The role it plays in disease transmission