Veg meg midterm

From (Study Guide) & Video quiz

Inventory

systematic collection of information describing the resources at a particular time. (What is here?)

Assessment

Evaluation of current ecological conditions relative to some expectation, reference, objective or criterion (What condition is it in?)

Monitoring

Repeated measurements thru time used to detect change & evaluate progress toward objectives. (Is it changing? Are we meeting our objectives? Did our treatment work?)

Explain how ecological questions are translated into measurable evidence and progression from measurement → analysis → interpretation → informing management decisions

Recognize the importance of distribution, abundance and change thru sapce and time

Distinguish between target population and population of inference

Target population: where we want conclusions to apply

Population of inference: where the sampling design allows conclusions to apply.

How can site selection affect relationship between target population and population of inference?

Poor or restricted site selection can make the population of inference smaller than the target population.

Evaluate factors that should influence site selection and explain why the ecological or management question should determine which variation matters.

Factors include:

• Physical environmental (soils, topo, climate, hydrology, ecological site)

• Vegetation (species composition, distribution, state, rare species, invasive species)

• Animal, Disturbance, management (livestock & wildfire use, timing of grazing, animal concentrations, water & salt locations, fire, treatments, roads, other disturbances)

• Scale and logistics (Size & area of boundaries, acces, management units, fences, sampling feasibility)

These factors might explain the response we are studying so we need to evaluate our question, the differences between study sites and how much those factors might have to do with our question.

Site selection has 2 jobs

1. Represent the population we want to understand

2. Capture or control the variation relevant to our question

Exclusion criteria

Pre-established conditions that make a potential sampling location unsuitable for answering the study/monitoring question.

Should be justified by the question and target population.

EX: Should you include/exclude roads, rocky outcrops, steep slopes??

Explain how selection/exclusion criteria and documentation reduce problems with site selection

It justifies your decisions for choosing not to sample in a certain area. It establishes parameters for site selection which can help with repeatability. And it can help identify and reduce bias because the exclusion criteria explains why you don’t select a site for your study.

Every site selection choice must be

1. Deliberate (tied to criteria)

2. Documented (so others can repeat it)

3. Defensible (in management and in court)

3 types of areas for site selection

Critical area: Areas that should be evaluated separately from other areas in management unit because they have special or unique values.

Key area: Areas that reflect what is happening on a larger area as a result of on-the-ground management actions

Reference area: areas where natural biological and physical processes are functioning normally

How to select a Key Area

Need to

1. Represent the area in which its located

2. Contain key species

3. Be capable of showing a response to management action

Key species

Important part of plant community, indicates change

Key species may change from season to season.

tied directly to objectives

Document criteria for selecting key species

Can be forage oriented, wildlife habitat oriented or indicator only

Why should we stratify

Landscapes can contain a lot of variability which makes it harder to draw reliable statistical inferences so we break down the big landscape into pieces that are similar to one another.

How do we stratify

Geography & topography

similar vegetation, soil type, management, current status

Response to changes in management or disturbances

What should photo monitoring include

Date, location, project, plot/site name, Bearing, coordinates, other details

Vegetation Measurements Toolbox (10)

1. photo monitoring

2. plant species inventory

3. biodiversity

4. cover

5. density

6. frequency

7. biomass/production

8. utilization

9. structure

10. fuel

Photo monitoring

Strengths: permanent visual record, inexpensive, spatial patterns, allows for comparison

Limitations: viewpoint/season differences, difficult to ID species, not quantitative data

Uses: plant abundance, plant/patch size, vegetation cover, spatial distribution shifts

Plant species inventory

Systematic record of the plant species present in defined area

Uses

• Detect important species

• describe community composition

• track change

• inform management

Biodiversity

Variety of species within a community, including both the number of species present and their relative abundances

Uses:

• Describe community structure

• Detect ecological change

• Compare communities

• Inform management

Cover

The proportion of the ground surface occupied by vegetation or other surface features. Expressed as percentage

Uses:

• plant abundance, community composition, ground protection, habitat structure, change thru time, treatment success

Density

The number of individual plants per unit area

Uses:

• population abundance, establishment & recruitment, population change, treatment response, rare or invasive species

Frequency

The proportion of sample units in which a species occurs (yes/no).

How consistently it occurs across an area NOT how many individuals are present.

Uses:

• describe distribution, detect change, evaluate treatment

Biomass & Production

Biomass: amount of plant material present per unit area at a given time

Production: the amount of new plant biomass produced per unit area during specific time

Uses:

• Forage availability, site productivity, treatment & disturbance response, fuel loads

Utilization

Measuring something that has been removed

Tells us what happened during a grazing period but NOT whether grazing was good/bad

Uses:

• evaluate grazing intensity, assess management objectives, understand grazing distribution, inform future management

Vegetation structure

Describes the physical arrangement of vegetation, particularly its height and vertical distribution

Uses:

• wildlife habitat

• grazing/forage condition

• fuel structure

Fuels

Wildland fuels are living and dead plant materials that can ignite and contribute to fire behavior

Uses:

• predict fire behavior, assess fuel continuity & conditions, characterize fuel load

Video quiz questions

why are multiple transects generally preferred over a single transect wihtin a monitoring plot?

They better capture variability within the plot

why might you use more than one monitoring method at a site?

Different methods provide information about different attributes of the ecosystem

What is the first step in developing a monitoring program

Clearly defining the objectives of the monitoring

what is the primary purpose of monitoring rangelands

to detect change and provide information for management decisions

why should the pin be dropped vertically at each sampling point in during a line-point intercept transect

to provide a consistent sampling point and avoid bias in which plants are intercepted

At each point along a line-point intercept transect what is recorded?

Each plant species intercepted verticaly and the soil-surface category

what does the line-point intercept method primarily measure?

vegetation cover and soil surface cover

Why is a plant species inventory often conducted alongside other vegetation measurements?

provides a record of the species present that can help with subsequent monitoring and interpretation

Why are multiple transects generally preferred over a single transect within a monitoring plot?

they better capture variability within the plot

Pros & cons to density

Pros: Fast and easy, Insensitive to seasonal/yearly variation, Works well in sparse vegetation

Cons:

• only gives # individuals present NOT plant size, cover, biomass, vigor.

• defining an individual can be difficult

• may not reflect ecological importance (high density but little biomass/cover)

Sampling design (4)

1. Non-random: we deliberately choose where to sample

2. simple random: anywhere randomly

3. Systematic: regular spacing after random start

4. Stratified random: randomly within predefined groups

You’ll combine these approaches into a defensible sampling design

how many sampling units do we need?

Need to characterize population with precision needed to meet objective.

Variability in population —> desired precision —> available resources

**Bias, accuracy & precision

Bias: tendency for our sample to over/underestimate the true population value

Accurate: how close our estimate to the true population value

Precision: how much uncertainty or variability there is in our estimate

we prefer low accuracy but with high precision over high accuracy low precision

Standard deviation & Standard error

Standard deviation: Describes the variability among samples

• High SD: sample values are more spread out, greater variability

• Low SD: sample values are more similar, less variability

Standard error: describes the uncertainty in our estimate of the population mean

• High SE: more uncertainty in estimate, lower precision

• Low Se: less uncertainty, higher precision

Sampling designs for uniform, random and clumped distribution

Uniform: Systematic & simple random sampling

Random: Systematic & simple random sampling

Clumped: Stratified random sampling (may need more samples to characterize the population)

Quadrat

sampling unit with known area

Quadrat size depends on

• Size of plants: large plants = large quadrat

• spacing/density: Sparse = large

• spatial pattern: clumped = larger/more quadrats

• target species & objectives

Needs to be big enough to capture vegetation and small enough to sample efficiently

Too small / too large quadrat

Too small:

• lots of zero counts

• high variability

• more plants fall on boundaries

• poorly represent sparse/large plants

Too large:

• more time per quadrat

• can average over fine-scale patterns

• inefficient for small, abundant plants

As quadrat size increases

Perimeter:area ratio decreases

More edge = more borderline decisions

(Smaller quadrats have more edge relative to area sampled)

Plant species inventory protocol

1. Mark out standard plot area of 1641 m²

2. search entire plot for 15 minutes with 1 person searching, other recording

3. move systematically thru plot

4. record a plant only if >50% of base is inside plot boundary

5. flag unknown species to identify after 15 min

7 Functional groups

1. Large perennial bunchgrasses (LPBG)

2. Small perennial bunchgrasses (SPBG)

3. Invasive annual grasses (IAG)

4. Annual forbs (AF)

5. Perennial forbs (PF)

6. Shrub

7. Trees

Pros & Cons to Frequency

Pro: repeatable, fast, describes distribution, good for detecting change

Con:

• Doesn’t tell us what changed (density, cover or spatial pattern)

• Dependent on quadrat size & shape

• Can lose sensitivity in the extremes at 0% or 100%

• Requires accurate species ID

Pros & Cons to Cover

Pros:

• ecologically meaningful (related to abundance, community composition, habitat and soil production)

• Efficient and repeatable

• Multiple variables from one method (LPI can give species, function group cover, total cover and ground cover

• Non-destructive

Cons:

• Sensitive to timing & environment conditions (precipitation, phenology, season. Require consistent sampling timing)

• Sensitive to grazing and disturbance

• Method matters (how you define cover; using visual estimates can introduce bias)

Rooted frequency, shoot frequency & mere presence

Rooted frequency: species is present when it’s rooted in the quadrat

Shoot frequency: species is present when at least one rooted shoot is in the quadrat (goof for rhizomatous/stoloniferous species)

Mere presence: Species is present if any of the part occurs in the quadrat even if its rooted outside

Rule must be applied to and consistent across all quadrats & observers

Collecting nested frequency

start with the smallest quadrat, record the species present.

Go to the next largest quadrat and record additional species encountered

(High frequency at small size suggests species is widespread across the sampled area.)

Types of cover

1. basal

2. canopy

3. foliar

4. ground

Basal Cover

Area occupied by plant bases at the soil surface

• more stable year to year, less affected by grazing utilization.

• Good for long-term trend comparisons

Measure for long-term vegetation change

Canopy cover

Area beneath the outer perimeter of plant’s canopy

• based on outer perimeter of the canopy

• includes gaps between stems & leaves

• sensitive to weather, growth and grazing

• Can exceed 100% when cover is summed across species or vegetation layers

Measure for vegetation structure or habit

Foliar cover

Vertical projection of exposed leaf area. Equals the shadow cast by the plant

• overlapping foliage counted once. Openings in canopy excluded

• highly susceptible to yearly fluctuations due to climatic and biotic factors

• difficult to measure for some growth forms. Easiest to measure with broad leaved forbs, shrubs and succulents

Measure if you want actual leaf area or current vegetation response

Ground cover

What is protecting/occupying the soil surface.

Measured to look at soil protection, erosion risk and resistance to invasion.
(plant base, rocks, duff/litter, moss, biocrust, mineral soil)

Methods for estimating cover (3)

1. points

   1. step point, line point intercept

2. Line

   1. line intercept

3. Area

   1. Ocular

   2. Daubenmire

methods for estimating cover

what counts as a hit in a point intercept method

one point can have multiple vegetation hits but only one soil-surface hit

Cover =

(number of points with a hit/total number of points) x 100

Step point technique

select a bearing across landscape and at step intervals, record the cover type at the sampling point

Line intercept

Measure the length of a line intercepted by vegetation.

record where each plant intercept begins and ends or record the total intercepted length

intercepts count as:

• Same species: overlapping canopies only count once

• different species; measure each species separately

• small gaps: use a defined gap rule

Cover = (total intercept length / total line length) x 100

Cover vs composition

Cover: how much of the ground is covered by this vegetation?

• total intercept length/total line length

Composition: of the vegetation present, how much belongs to each group?

• grass canopy cover/total vegetation cover

• composition sums to 100%!!!

Ocular estimates with plots or quadrats

Estimate the proportion of a defined area covered by vegetation

Efficient, good for detecting rare species

How to:

• place quadrat frames along transect at specified intervals

• estimate each species independently

  • species can overlap vertically so summed species canopy cover may be over 100%

**Daubenmire method (type of ocular estimate for cover)

• Semi-quantitative ocular estimate of canopy cover

• Each species is assigned to one of 6 cover classes

• Cover classes are converted to midpoints for analysis

• Use frame markings to calibrate estimates

• Average across quadrats to estimate mean cover for each species

Biomass Pros & Cons

Pros:

• direct & quantitative

• comparable

• ecologically meaningful

  • can indicate dominance based on plant mass. reflects veg structure and resource accumulation.

• useful for management

  • forage availability, fuel load, vegetation productivity

Cons:

• Time & labor intensive

• destructive sampling

• difficult for woody vegetation (trees, belowground biomass)

• highly variable

• timing matters

  • biomass changes with plant growth and herbivory

  • peak standing crop changes according to species & sites

Gross primary production (GPP)

total carbon fixed by plants thru photosynthesis

Plant respiration (R)

Carbon released as CO2 when plants break down sugars

Net primary production (NPP)

The rate at which plants accumulate carbon in new organic material after accounting for plant respiration

Carbon available for building new plant tissue

NPP = GPP - R

Standing biomass (standing crop)

The amount of plant biomass present per unit area at a given time

Peak standing crop

maximum standing biomass observed during a growing season

Residual biomass

plant biomass remaining at a specified time, often following grazing or at the end of a growing season

herbage

aboveground biomass of herbaceous plants (grasses, grass-likes and forbs)

woody biomass

mass of woody plant material. includes stems, branches and twigs

Browse

Leaves & tender shoots of woody plants available for browsing animals

Forage

Herbage or browse that is accessible and suitable for grazing and browsing animals

Necromass

dead plant material. Includes standing dead vegetation, downed woody material and litter

Mast

fruits, nuts and seeds

Methods of measuring biomass (3)

1. Direct measurements

   1. harvesting, drying and weighing vegetation

2. Visual estimation

   1. use reference units or comparative yield

3. Double sampling

   1. combine visual with harvested

Direct measurement - harvest

1. select sampling locations (quadrat size and sampling design)

2. Define what will be harvested (species, plant part, growth period)

3. Clip vegetation

4. dry & weigh

5. calculate biomass per unit area

6. convert dry mass per quadrat to kg/ha or lb/acre

**Fresh weight vs Dry weight

Fresh weight: includes plant tissues and water

• varies with species, growth stage and environmental conditions

Dry weight: plant tissue, no water

• more consistent basis for comparing plant biomass

Ex: 100 g of fresh grass would contain less dry biomass than 100 g of dormant grass

Use the chart to estimate dry mass

Reference unit method

Estimate biomass by comparing vegetation to reference unit with known mass

Estimated biomass = number of units x dry mass per unit

Comparative Yield Method

Estimate biomass by comparing sample quadrats to reference quadrats representing increasing amounts of biomass

1. establish five reference quadrats for range of biomass at the site (1 = lowest, 5 = highest)

2. Assign a rank (1-5) to each sample quadrat based on similarity to reference quadrats

3. Clip, dry and weigh the reference quadrat to determine the biomass associated with each rank

4. estimate biomass in sample quadrats using the calibrated ranks.

Double sampling

1. estimate biomass in all sample quadrats using visual estimate

2. Select a subset of quadrats for harvesting. Use a sampling design that represents the biomass variation

3. clip, dry and weigh the vegetation in the selected quadrats to get measured biomass

4. Develop relationship between estimated and measured biomass. Use it to predict biomass in remaining quadrats. (linear progression)

Remember: quadrats should be estimated first then random procedure should be used to pick plots to be clipped.

Allometric relationships

Used to estimate biomass of shrubs and trees

Crown area (area of circle)

Crown volume (area of cylinder)

Utilization % =

(Forage removed/total forage produced) x 100

ex: Total forage production: 1000 lb/acre

forage removed: 300 lb/acre

utilization = 30%

Relative use vs annual utilization

Relative use: proportion of forage produced to date that has been consumed by animals

We’re looking for just one month so the denominator will be the production for that one month

ex: the relative use for the month of July

100/200 = 50%

Annual utilization is interested in the whole year. Denominator will be the production for the end of the growing season.

harvest efficiency vs utilization

Harvest efficiency: percent of forage production consumed by grazing animals, excluding forage lost thru other ways

Utilization: includes forage removed through trampling, fouling, etc.

50/25/25 guideline

50% remains to support plant growth, recovery and soil

25% is eaten by grazing animals

25% is allocated to other losses (trampling, fouling, inaccessible)

where do we measure utilization

• key areas: representative area used to evaluate grazing

• critical areas: requires special attention due to sensitive resources

utilization measurement methods

• Direct comparisons

  • Paired plots

  • unpaired plots

• Indirect

  • Grazed-Class method

  • landscape appearance method

  • Grazed-plant method

  • Height-weight (using the wheel)

Paired plots

• establish pairs with similar vegetation before grazing starts

  • similar vegetation, comparable site conditions. Repeat it

• Randomly assign 1 plot in each pair to be caged

• clip, dry and weigh current-year biomass in both plots

• Calculate utilization (removed/produced)

unpaired plots

• caged & uncaged plots sampled independently, not in pairs

• Compare mean biomass of protected and grazed plots

Grazed-Class method

• Visually estimate proportion of ofrage removed from individual plants by

  • comparing plants with species-specific photograph guides

  • assigning each plant to a grazed class (0,10,30,50,70 or 90%)

**Landscape Appearance method

visually assess grazing intensity based on appearance of vegetation

• sample at intervals along transect

• assign observations to utilization classes using standardized descriptions

• calculate mean estimated utilization using class midpoints

land PKS

Grazed plant method

• sample plants along transect

• classify as grazed or un-grazed

• find percentage of plants grazed

• use regression to estimate utilization

EX: percent of plants grazed = 60%

Plug into regression equation: y = 0.8377(60) - 3.4316 = 46.8%