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Preburn and Postfire Prescribed Burn Monitoring

  

Analyses of monitoring data may indicate that the prescribed burn strategy outlined in this document is meeting land management goals, or it may indicate that goals are not being met and management methods need to be adapted to reach them. Monitoring is an essential step in adaptive management.

 

Monitoring, as defined as “the collection and analysis of repeated observations or measurements to evaluate changes in condition and progress towards meeting a management objective.”

 

Monitoring is essential for understanding the relationship between fire and invasive species, whether documenting new invaders following fire, post fire changes in established nonnative populations, recovery of native plant communities after prescribed burning, or its efficacy in controlling nonnative plant species. Monitoring can be used to detect change between sampling periods (before and after fire) or between treatments (burned and unburned areas), and it provides quantitative data for statistically analyzing the probability that the observed differences are due to chance.

 

Vegetation Monitoring

 

Research has shown that there are seven common elements of an effective monitoring program design: objectives, stratification, controls (untreated plots), random sampling, sample size (data quality), statistical analysis, and field techniques.

 

The steps recommended for effective implementation of a prescribed burn strategy include: gathering and reviewing background information on invasive species, fire, and native communities; identifying the priority invasive species and   native communities; and determining resources available for monitoring (for example, funding and personnel with botanical and ecological expertise).

Once priorities are established and amount of available resources is determined, the scale and intensity of monitoring can  be determined. Because resources will likely be limited, the number of priority species and communities to be monitored may be inversely related to the scale and intensity of monitoring. 

Objectives 

Well defined management and monitoring objectives for each individual burn are essential for successful monitoring. Management objectives provide a standard for determining management success and indicate which variables should be measured to determine when success has been achieved.

 

Controls

Controls allow managers to determine whether or not a specific treatment caused the observed change, as opposed to other factors, such as year-to-year variation in weather conditions. Controls should be placed randomly within each monitoring unit rather than in an adjacent unburned area, which may differ in some environmental variables from the treatment unit.

 

Random Sampling 

Random sampling is a requirement for statistical analysis and the basis for defensible monitoring. Simple random sampling requires that each member of a population has an equal chance of being sampled.

 

Sampling plots can be either permanently marked at random locations or randomly located in each sampling period. If  plots are permanently marked and recorded by GIS, then the same plots can be re-measured each sampling period.

 

Sample Size 

Once monitoring objectives are chosen, the easiest way to determine adequate sample size is to collect preliminary data, calculate means and standard deviations, and use established equations to estimate minimum sample size.

 

Field Techniques 

Five monitoring methods are commonly used for estimating vegetation

abundance: frequency, density, and cover—ocular, point-intercept, and line-intercept. Frequency is a measure of the proportion of sample plots that contain the target species. Density is a measure of the number of individual plants or stems per given area. Cover measurements estimate the proportion of ground covered by target species. Each method has its strengths and weaknesses (see table below), and the various methods may or may not give similar qualitative or  quantitative results.

 

Most studies of the impact of fire on nonnative invasive plants are of short duration. Seventy percent of the fire effects studies used in species reviews of nonnative invasive plants written for the Fire Effects Information System from 2001 to 2006 were only followed for 1 year after fire. If post fire effects are ephemeral or delayed, then plant response the first  year after fire may not reflect the true impact of fire on nonnative plants or the ecosystems where they reside. Managers  and scientists agree that monitoring must cover periods long enough to provide results that can inform future management actions.

 

Preburn and postburn vegetation monitoring has been utilized on a number of past PBs in Southern Ontario. At Pinery and Rondeau Provincial Parks, the frequency and density method were utilized. At Pinery, for example, monitoring was used   to evaluate the effectiveness of prescribed burns in reducing the density of planted white pine.

 

 

Comparison of Five Monitoring Methods

Method

 

Advantage

Disadvantage

Frequency

(How many plots contain the target species?)

 

 

• Sensitive to changes in

spatial arrangement

• Effective in monitoring

colonization of invasive

species

• Stable throughout growing

season

• Objective and repeatable

• Easiest and fastest

 

• Affected by spatial

arrangement, size, and

density of vegetation

• Difficult to interpret

biologically

• Sensitive to size and shape

 of sampling frame

Cover

estimates

(How much

ground does

the target

species cover?)

Ocular

(Visual estimate)

• Equalizes contribution of

species

• Most directly related to

biomass

• Does not require

identification of individuals

• Good for diversity and

species richness

• Easy and fast

 

• Changes during growing

season

• Sensitive to changes in

number and vigor

• Not sensitive to reproduction

• Change detection is difficult

with broad cover classes

• Potential observer bias

 

Point intercept

(What proportion of

the points hit the target

species?)

• Least biased and most

objective cover estimate

• Changes during growing

season

• Sensitive to wind

• Sensitive to angle of point

• Overestimation of cover with

large pins

• Not effective for species with

low cover (e.g. SAR)

 

 

Line intercept

(What proportion of a

transect is occupied by

the target species?)

 

• Effective for shrubs

• Effective for mat-forming

plants

• Less effective for single-stem

plants

• Less effective for grasses

• Not effective for species with

low cover

Density

(How many stems per area of

the target species?)

 

• Effective for recruitment

and mortality

• Independent of quadrant shape

• Measurements are repeatable

• Observer bias is low

 

• Less sensitive to changes in

vigor

• More time consuming

• Difficult to use with

prairie grasses

 

 

 

 

 

 

 

 

 

 
 
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