Grassland Ecology Exam 2

Why does range management exist?

We learned our lesson from the Dust Bowl. We have to use land sustainably (crisis science).

What was the Homestead Act of 1862?

This law gave 160 acres of western land to farmers who promised to live on the land for at least 5 years

Immigrants + escaping cities (unsanitary conditions and violence)

What happened to most people who took the Homestead Act?

They died, and their land went back to the government

What did the Homestead Acts of 1909 and 1916 do?

Expanded amount of land offered (320 and 640, respectively)

The 1916 act also gave 50 cows for ranchers to start their operations

Why were open-range systems rough?

There were no fences to define property lines, and plenty of grazing land that had not been claimed. This led to a tragedy of the commons where everyone took advantage of the excess grasses

Cattle were sold by the head, not by the pound, so it was a pure numbers game

What were the Range Wars?

Major conflicts for the control of land and resources in the West. Cattleman and sheep herders engaged in armed conflicts from 1880 to the 1890s.

Who was Arthur Sampson?

The father of rangeland ecology

What was the Taylor Grazing Act of 1934?

An act that intended to "stop injury to the public grazing lands by preventing overgrazing and soil deterioration; to provide for their orderly use, improvement, and development; [and] to stabilize the livestock industry dependent upon the public range."

What was the Soil Conservation Act of 1935?

Established Soil Conservation Service

Now, the Natural Resources Conservation Service

It was the birth of land management, and it aimed to:

1. Minimize soil loss

2. Reduce area with poor range condition

What is the mantra of rangeland management?

Balance forage supply with forage demand

What are the four propers of range management?

1. Stocking rate- how many and for how long? (Moderate)

2. Forage utilization- how much? (even)

3. Animal distribution- where? (even)

4. Kind and class- what type of animal? (most efficient)

What is stock density?

The number of animals per area

What is stocking rate?

amount of land allocated to each animal unit for the grazable period of the year

Stock density/time ((animals/area)/time)

What is an AU?

Animal Unit

1 AU = 1000 pounds of grazing animals

1 cow = 50 jackrabbits

What are AUEs?

Animal Unit Equivalents- a conversion factor reflecting the number of AUs in an average

animal.

Cow = 1

Jackrabbit = 0.02

What are AUMs?

Animal Unit Months- How much dry forage is required to sustain one Animal Unit (AU) for

one month

780 lbs of dry forage for a 1,000 lb cow and calf (1 AU)

What is the "proper" stocking rate?

It differs between introduced/cultivated landscapes and unimproved rangeland (take half, leave half ideal)

Introduced rangelands can tolerate heavier stocking and higher utilization

Unimproved is less tolerant and needs conservative utilization for sustainable production

IT ALSO DEPENDS ON FORAGE BASE AND PRODUCER OBJECTIVES (moderate is the economic optimum for livestock tho)

What does take half, leave half actually mean?

Only 25% of the forage is used for livestock; the other 25% is lost to trampling, insects, defecation, etc.

ONLY USE 25% OF FORAGE AVAILABLE TO CALCULATE 50% UTILIZATION

What are methods for determining available forage?

Field methods: Clipping, drying, and weighing; visual obstruction (POLE METHOD THINGY); ocular estimation (ALL TIME INTENSIVE AND REQUIRE YEARLY DATA)

Digital methods: Web Soil Survey, Ecological site description database, and remote sensing estimates (satellites, airplanes, drones, etc.)

How do you calculate available forage for grazing?

(Average dry matter (lbs/acre)) x (acres) x (utilization factor)

What is important to remember when calculating available forage?

Not all forage is actually available for grazing. Things like slope, animal type, and precipitation amount mean it can't just be an exact number.

What is continous grazing?

Grazing the whole area for the whole grazing season.

What are the pros/cons of continous grazing?

Pros: low input, animals have maximum choice and have high performance

Cons: potential for overgrazing/land degredation, especially for prefered areas and plants

What is deferred rotation grazing?

Don't graze at least one pasture until after it has set seed (deferment). Deferance is rotated among all pastures over subsequent years.

EVERYTHING IS STILL GRAZED EVERY YEAR

What are the pros/cons of deferred rotation grazing?

Pros: rangeland condition can improve as grasses have protection from grazing when sensitive

Cons: increased labor/fencing and can reduce animal performance as there is less opportunity to choose.

What is rest rotation grazing?

Don't graze at least one pasture for a whole year. Rest is roatated among all pastures over subsequent years.

What are the pros/cons of rest rotation grazing?

Pros: rangeland condition can improve as pastures are allowed to rest and set seed

Cons: can reduce animal performance as stocking rate is increased on grazed pasture (stocking rates are usually calculated for whole units) and it is difficult to match grazing timing with forage quality

What is seasonal sutability grazing?

Moving livestock to different areas of range depending on growth patterns of vegetation (following the green)

What are the pros/cons of seasonal sutablity grazing?

Pros: animals have green forage for most of the year, contributing to high growth/performance. Plants are also mostly grazed bfore seedset, which minimizes negative impacts from grazing

Cons: High management/herding input. Also, the summer range may not get deferment

What are the characteristics of decisional/managment intensive grazing?

Consist of one herd with multiple pastures. Grazing decisions are based off of available forage, available water, cover for calving/lambing, and implementation of practices such as haying/prescribed fire.

It's the most common management regime in the world, and it's success depends on THE EXPERIENCE AND DECISIONS OF THE MANAGER + THE LEVEL OF RISK TOLERANCE

What are examples of management intensive grazing?

- Best pasture system: livestock are moved to the pasture that looks the best (designed for arid areas where rain may only improve part of the unit, but miss others)

- Complimentary system: designed in the central plains, animals utilized cultivated/introduced pastures for part of the year, and are moved to native ranges for the rest of the year.

- Seasonal sutability: livestock are moved based on vegetation composition and growth patterns

What is short duration grazing?

Each pasture unit is grazed for a short time and animals are rotated through all available pastures. Each pasture is grazed t least two times per year.

What are other names for short duration grazing?

Rapid rotation, mob grazing, holistic managment, ect.

What are the pros/cons of short duration grazing?

Pros: stocking rate can be set higher because animals eat all plants. Forage quality can be higher because animals are always eating fresh regrowth. Rangeland condition can improve as all areas are evenly grazed (but not the livestocks' favorite forage).

Cons: highly labor intensive, low animal performance because of reduced selectivity/free choice, and condition can decrease because plants never get rest or deferment.

What does light grazing maximize?

Gain per head

What does moderate grazing optimize?

Economic optimum for livestock

What does heavy grazing optimize?

Gain per hectare

What is carrying capacity?

largest number of individuals of a population that a given environment can support (an ecological constraint determined by rainfall, fire, temperature, competition, etc)

Heavy grazing does not relax ecological constraints

K CHANGES OVER TIME

Rank grazing systems on a scale from least uniform to most uniform

pyric herbivory, continous grazing, rotational grazing, intensive rotational grazing

What is the relationship between uniformity and resilency?

Opposite. Intensive rotational grazing is the least resistant technique.

Why are livestock attracted to fire/recently grazed patches?

The new growth is high in nitrogen/protein, which is highly desirable. New growth is high quality. Attraction decreases as time after fire increases.

What is pyric herbivory?

No fenses, but landscape divided up into several patches. A patch is burned every year (rotated). Animals move naturally based on preferences/needs.

Why is heterogeneity important?

Heterogenity is the foundation of biodiversity and stability. It can also stabilize livestock production in a changing climate (insurance).

Species need a range of conditions to thrive in.

Why do we care about climate change?

Climate change has been occuring for billions of years, but we care about the human perspective, so... (new to modern society)

Describe how carbon concentrations have changed.

Carbon content has increased by 31% since 1750.

There is a higher concentration than in the last 650,000 years, probably all the way to the last 20 mil years

The rate of increase in concentration is unprecedented

Describe changes in methane.

Methane is 80 times more potent than CO2 (higher warming potential)

Methane has had runaway warming due to melting permafrost (started with CO2 though, but methane intensified)

It has a shorter-lived warming potential, as it degrades over time (80x CO2 over 20-years, 28x CO2 over 100-years)

Why do we care about climate change in range management?

Climate change got us to where we are today, and will continue to dictate where our future lies.

How does climate change impact plant distribution?

C3 plants thrive in high temps and high CO2 levels. Climate change also increases woody plant encroachment (eastern redcedar, honey mesquite, post oak, etc.) Also cheatgrass invasion.

What can we do about climate change?

The best we can. Promote heterogenity and hedge our bets.

What are the three domains that make up socio-ecological conservation?

The biophysical domain (climate, plant community, landscape size, species, etc.)

The herbivore domain (population density, sex ratio, species, constraint of movement, etc.)

The human domain (social community, population density, belief system, technology, government policy, economics, etc.)

Why is considering the human domain important?

Conservation, rewilding, resoration, and degradation of ecosystems are all human endevors.

What is the historical conservation perspective?

Humans reduce biodiversity

Why is assuming that humans reduce biodiversity problematic?

Humans have ben tied to grasslands for forever (20,000 years). Only looking at the last 75 years is short sighted. Further, failing to address the historical importance of humans and grasslands will lead to insurmountable challenges for conservation.

What was going on 0.01-1.8 million years ago?

The world was at its glacial maximum. C3 plants were dominant.

How is 0.01-1.8 million years ago different from modern day?

Human arrived on scene, and there was a dramatic increase in fire.

However, industrialized agriculture has lead to a dramatic decline in fire, and as such grasslands have altered structure, function, and dominance.

Now there is a mix of C3 and C4 plants, but C4 plants are generally dominant across central US grasslands.

Why are the Great Plains a grassland?

Because of a mix of climate, disturbances, and plate techtonics.

What was going on 84-72 million years ago?

It was the Campanian, and a large ocean seperated the the east and the west. It was still the age of the dinosaurs at this point.

What was going on 70-66 million years ago?

It was the Cenozoic era, and rocky mountain uplift drained the inland ocean.

What was going on 0.01-1.8 million years ago (again)?

It was the Pleistocene, and glaciers were expanding and contracting across North America (including Nebraska). Humans also arrive during this time.

What is the relationship between grasslands and rangelands?

All grasslands are rangelands, but not all rangelands are grasslands (plant community, soil health, usage, etc).

What defines rangelands?

"What unifies rangelands is not so much a biophysical or 'natural' characteristic as a social one: marginality"

(Not farmed/not able to be farmed)

Describe Eastern Redcedar.

Eastern redcedar is native to the great plains. Its distribution has ebbed and flowed. Following human arrival, it was limited to rocky outcrops and other fire limited parts of the landscape. It is very tolerant to landscape variability (hardy).

These trees increase infiltration, but do not necessarily decrease biodiversity (LARGE SCALE).

Altered fire regimes, suppression, and cultural fire aversion have increased juniper spread.

What has been the biggest impact on fire culture?

GOVERNMENT POLICY at state, local, and federal levels (often influenced by agricultural land use intensity).

What is notable about most invasive species studies?

Most studies are performed at small scales, and do not reflect a larger landscape.

58% with treatments 100 m2 or less, 22% omit scale altogether

Cannot capture complexity of heterogeneous grasslands, by design (big studies = hard)

Experimental evidence supporting or rejecting the invasion paradox is lacking across heterogeneous grasslands

What is notable when thinking about invasive species' impact on landscapes?

SCALE MATTERS. Sometimes, invasive species can actually increase biodiversity and species richness. Further, monocultures are incredibly rare. Nature abhores a vaccum.

L. cuneata may not have negative effect on biodiversity or ecosystem function across large, complex grassland landscapes

Scale is the fundamental problem in ecology and for grassland conservation

What are the two types of scale in experiments?

Grain (area divided within total study area) and extent (overall area)

Why do we care about invasive species?

They signal ecological decline, can reduce biodiversity and beauty of areas, cause economic losses, impact all groups equally, and can spread rapidly/silently.

What is important to remember about invasive species management?

IT ALL DEPENDS ON THE MANGERS GOALS. GOALS SHOULD GUIDE THE PROJECT.

Fighting invasive species may not be necessary or economically efficient. However, it could be important for closed system habitats and areas managed for enjoyment/public safety.

BOTH CAN BE TRUE.

How is an invasive species classified?

A species that spreads, establishes, and stays (also one that impacts human health, economics, etc.)

Noxious weeds are designated by the government and are considered injurious. Some species are not considered noxious because it would just be too hard to get rid of them.

What is the main takeaway from Nathan Sayers "The Politics of Scale?"

- Humans went to war with wild animals to ensure the most efficent grazing regime possible (everyone or no one attitude). Jackrabbits and prairie dogs represented competition for forage. Predators represented potential losses (both through death and stress/less productivity).

The paper also discusses the introduction of fencing systems to increase productivity and reduce predator impact. This was the first time in human history property/grazing operations had boundaries. People had to make it work, they couldn't just leave and start over if the going got rough.

What is the main takeaway from "Restoring Heterogeneity on Rangelands: Ecosystem Management Based on Evolutionary Grazing Patterns"

Traditional grazing regimes promote homogeniety through uniform use and distribution. These management practices may have critical impacts on biodiversity and wildlife.

Alternative management approaches an increase heterogenity, including patch burning/grazing. These techniques can create a shifting mosaic that encreases biodiversity and enhances wildlife habitat.

What is the main takeaway from "Rewilding Landscapes through the Recoupling of Fire and Grazing"

The impact of herbivores depends more on management techniques than species. Pyric herbivory could be awesome guys :D Biodiversity and also high productivity :DDDD

(You gotta do species and processes together. Or at least species need processes).

What is the main takeaway from "Perspectives on grassland conservation efforts: should we rewild to the past or conserve for the future?"

Rewildling is a naive idea. We can never get things back to the way they were because of the way the world functions now. Humans are an inherant part of the ecosystem, and we need to consider them in conservation efforts. There is no right answer for whether to rewild species or processes. We need more research.

What is the main takeaway from "What effect does an individual tree in a grassland have on microclimate, soil organic carbon, and water infiltration?"

Trees create cooler, wetter climates within grasslands, especially in extremely hot conditions. Less water runs off, but it is also not retained (transpiration).

Trees do not increase soil organic carbon, nor do they increase carbon sequestration.

OTHER IMPORTANT NOTES?

There is no silver bullet fix-all. We have to accept that things are complex and nuanced. We also have to get off our high horses and understand that we're all a little stupid, and that's okay. :)