Vegetation Sampling Key concepts Types of vegetation sampling Methods of vegetation sampling Definitions Density Cover Growth Vigor Utilization Transect Macroplot Quadrat Physiological status Why Sample Vegetation? Detect changes in plants is response to environmental change or management action (monitoring) Determine quantity of resource for utilization timber, range forage (inventory) Determine quality of habitat for wildlife or other plant species (inventory and monitoring) Determine population status of plant species (inventory and monitoring) Vegetation Sampling Metrics Enumeration Density Cover Growth Vigor stress, reproductive success Physiological status (census) counts? Depends on objectives!!! 1
(census) Macroplots and Quadrats Macroplot Quadrats Transect and Quadrats Quadrats Baseline Transects 2
Boundary or Edge Effects Use two edges as in Count every other boundary plant as in Count only plants 50% or more in plot Variable Circular Plot Method Prism view in out Small tree plot Medium tree plot Large tree plot Distance based measures (not recommended) 3
Distance Based Measures Problems with Distance-based Methods for Density estimation and enumeration Most methods assume random distribution of plants this is rarely the case. Even methods designed to work with nonrandom plant distributions (wandering quarter distance measure) are biased and not as effective as quadrats. Measurements can be time consuming and less efficient than quadrats. Distance based measures (not recommended) Aerial photos Aerial Photos Enhance with various filters (e.g., near infrared) Enumeration and density: Count all plants Count plants in quadrats 4
Distance based measures (not recommended) Aerial photos Frequency Frequency Portion of quadrats containing plant species Plants Quadrats Frequency Methods Use frequency of occurrence within quadrats to determine percent of area occupied. Easily conducted simply determine whether plant is in quadrat or not. Sensitive to changes in distribution (e.g., expansion or contraction of distribution) Must standardize quadrat size or comparisons over time or between areas not possible. Not as effective in determining changes in density. Measuring Cover What is cover? Vertical projection of vegetation as viewed from above Why measure cover? Difficult to enumerate individual plants May reflect greater change Depends on objectives How is cover measured? Quadrat Line intercept Point intercept Aerial photos 5
Quadrat Estimate of Cover Line Intercept Estimate of Cover Estimate % cover Measure plant dimensions Point Intercept for Measuring Cover Aerial Photos Enhance with various filters (e.g., near infrared) Cover Use pixel count by color Polygons of plant crowns 6
Estimating Growth and Vigor What is growth? Incremental change in biomass Production is annual output of vegetative biomass What is vigor? Health of plant can include growth, decline, reproductive rate, disease Why measure growth and vigor? Determine amount of plant for grazing Determine growth rate as related to environmental conditions Determine disease status of plants Estimating Growth and Vigor Measuring growth Clipping of sample quadrats Visual estimates in sample quadrats Measurements of individual plants (e.g., trees: height, DBH) Utilization amount of foliage removed by herbivores Before vs. after Exclosures Measure number of seeds reproductive output In seed heads On ground Estimate portion of individuals with disease Physiological Status What is Physiological Status? Rate of photosynthesis, transpiration Plant water or nutrient status Why measure physiological status? Can help predict plant performance Can help determine nutritional status for grazing Can help determine water availability in soil Estimating Physiological Status Usually conducted on sample of individual plants or plant parts Photosynthesis measures: Gas-exchange of CO 2 and water vapor, chlorophyll fluorescence, eddy flux Nutrient status Measured on tissue samples Water status Measured with moisture sensors in plant and soil (water potential or content) Measured on tissue samples (water content) 7