AGRON 251 EXAM 1

Rangeland management

Energy and input extensive

Cropland management

Energy and input intensive

Pasture

Energy intensive maintenance of introduced/non-native forages

Rangeland

Less management overall. Plant species persist with minimal management

Indigenous Range Management

Use of fire

Homestead Act

Grant Western land for farming 1862

Cattle Boom

Huge profit margins after Civil War

Overgrazing and range degradation

Conservation efforts

US Forest Service 1905

Taylor Grazing Act

1934

Grazing permits on federal land

Climate factors

Precipitation

Temperature

Relative humidity

Wind

Altitude

Effects temperature

Slope aspect

Direction the slope faces

Rain shadow

Slope steepness

Water runoff

Grazing availability

Sandy Soil

Better infiltration

Clay Soil

Better retention

Loamy Soil

Mixed particle size. Best of both worlds

Rangelands cover…

54% of global land

Grasslands cover…

44% of rangelands

Deserts and xeric shrublands cover…

35% of rangelands

Ecocline

gradual transition in community composition

Ecotone

Boundary zone area between two ecosytems

Succession

A community recovers from a disturbance

Community assembly

The species we observe made it through all the different filters

• Dispersal

• Abiotic

• Biotic

Niche

Ecological requirements and functions of an organism

Niche differentiation

different organisms occupy different niches minimizing competition

Temporal Niche differentiation

Different timing

Spatial Niche differentiation

Different spacing

Photosynthetic efficiency

Amount of solar energy converted to chemical energy

Gross Primary Productivity

Rate of chemical energy production

Net Primary Productivity

GPP minus respiration. Maintenance of a plant

Autotroph

Organism that creates its own food

Heterotroph

Living organism that cannot make its own food

Producer

Autotrophs. Plants

Consumers

Heterotrophs. Animals

evaporation

Water from the land lost to the atmosphere

transpiration

water lost from the ground and the plants to the atmosphere

Energy loss between trophic levels

90%. Only ~10% makes it to the next level

Grassland carbon stocks…

mostly in the soil

Nitrogen cycles relies

microbial action in the soil

Ecosystem Services

Supporting services

Regulating Services

Provisioning Services

Cultural Services

Photorespiration

Rubisco picks up O2 instead of CO2

Why does photorespiration matter?

Reduction in potential

Nonstructural Carbs

Monosaccharides, Fructans, Starch

Water-soluble carbs

Monosaccharides and fructans

Where are carbs stored?

The root crown

Rhizomes

Stolons

When are carb reserves the highest? Day and season

At sunset

The fall

When are carb reserves the lowest? Day and season

At sunrise

The spring

When are perennial plants most resistant to defoliation? (Vice versa for least)

During their dormant season

Early in the growing season

How much defoliation can plants handle?

Removing 30-50% of top growth

Plasticity

Individual, no genetic change, relatively fast

Evolution

Population, genetic change, slow

Community shifts

Community, no genetic change, medium timeline

Law of minimum

growth is dictated by the scarcest resource

Ecotypes

locally adapted variety of a species, suited to the local weather, resource availability, etc

Ecological indicators

Optimum range and range of tolerance

Grazers

feed on grasses and sometimes other low-growing vegetation

Browsers

feed mostly on forbs and woody vegetation (shrubs, parts of trees

Ruminants

digest cellulose via a symbiotic relationship with ruminal microorganisms

Forage

herbaceous vegetation that is available and acceptable to grazing animals

Herbage

all herbaceous vegetation

Browse

parts of woody vegetation that are available and acceptable to browsing animals (sometimes included with forage)

Components of forage

Minerals, carbs, fats, proteins, vitamins

When was the US cattle inventory the greatest?

1975

What is proximate analysis?

Testing moisture content, minerals, protein, crude fat, crude fiber.

What are the detergent fiber analyses?

Neutral detergent fiber: hemicellulose, cellulose, lignin, insoluble protein.

Acid detergent fiber: cellulose, lignin, insoluble protein.

What is near reflectance spectroscopy?

measures the reflected light to determine the material's chemical and physical properties

What kinds of plants are most nutritious? When?

Leaves are most nutritious

Young plants, during active growing times

How can managers use diversity to improve livestock diets?

Diverse mixtures will reduce pressure on perennial grasses and provide resources during different seasons

Grazing resistance

Plant survival in grazed system

Grazing avoidance

Plant prevents defoliation

Grazing tolerance

Recovery following defoliation

Secondary metabolites

organic compounds that are not directly involved in the organism’s growth, development, or reproduction

Constitutive vs induced

Always around vs induced by grazing

Quantitative vs qualitative

High concentrations vs low concentrations

Grazing optimization hypothesis

a moderate level of grazing increases plant growth

Overcompensation vs compensation

Compensation is probably more common than overcompensation

Stocking rate

the number of animals (often expressed as animal units) on a given amount of land over a certain period of time

Stocking density

animal units on a given amount of land at one moment in time

Animal Unit

the standard is a 1,000-lb cow with calf

Animal Unit Month

~780 lb dry forage, i.e., the amount of forage that the 1000-lb cow is expected to consume in one month

Animal Unit Equivalent

a number relating the forage dry matter intake of another kind/class of animal to a standard AU

Carrying capacity

Maximum sustainable stocking rate, determined by how much forage a piece of ground can produce in an average year

Harvest coefficient

a safe bet is often around 25%

Continuous grazing

year long

season long

intensive early stocking

seasonal suitability

Fixed stocking

simpler to manage, but can lead to overgrazing during droughts or underutilization during abundant periods

Flexible stocking

theoretically great but challenging in practice

Rotational grazing

Intentional movement of livestock between at least two enclosed areas of pasture/range with recurring periods of grazing and rest (USDA ERS)

Deferred Rotation

Less than 1 year of ungrazed period

systematic rotation of deferment among pastures

Rest Rotation

Long ungrazed periods

Promotes seedling establishment

High intensity - low frequency

medium-short period of grazing at high stocking density then a medium-long ungrazed period. Timing of grazing changes from year to year.

Short duration

like high intensity—low frequency, but shorter grazing periods and ungrazed periods

Adaptive grazing

use monitoring data to adjust the grazing strategy on a seasonal and annual basis.

Integrated Crop-Livestock systems

Using on-site animal services as a resource for crop production

and/or

Using cropland to support livestock production.

Key areas

indicator plots for sampling

Ecological sites

similar soil, climate, and therefore vegetation

Critical areas

unique/special parts of the range: fragile watersheds, rare species habitats, etc.

Herbage utilization

the percentage of the current year’s production that’s consumed or destroyed by herbivores

Vegetation measurements

Biomass, density, frequency, cover, and diversity

grazing intensity measurements

percentage of grazed plants, paired-plot estimates, height-weight methods)

Why are areas grazed unevenly?

Distance from water

Topography

Vegetation type

Temperature and weather

Pests