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field_methods:vegetation_plant_height [2014/01/29 18:00]
field_methods:vegetation_plant_height [2014/02/09 15:21] (current)
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 ====== Vegetation (Plant) Height ====== ====== Vegetation (Plant) Height ======
 [[http://​​about/​get_involved|{{:​abstract_in_dev.gif|}}]]\\ [[http://​​about/​get_involved|{{:​abstract_in_dev.gif|}}]]\\
-from the USDA-ARS //​Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems//​+prepared by Grant Hamilton 
 +===== Method Type ===== 
 ===== Introduction ===== ===== Introduction =====
-Vegetation height is measured as the height ​of the tallest plant part within ​a 30 cm (12 in) diameter cylinder projected tangent to the transect. ​ It is measured vertically from the soil surface at the center of the cylinder (Figure 17).  Vegetation height provides plot-level vertical structure information necessary to predict soil erosion from wind and characterize wildlife habitat. ​ Vegetation height is usually measured at the same time as [[line_point_intercept|line-point intercept]] because it is more efficient, but can be measured separately.  +Vegetation height is one of the methods contained ​within the //Monitoring Manual for GrasslandShrubland and Savanna Ecosystems//​ and is intended ​to support ​the additional methods described ​in the manual.  ​Click [[protocols:monitoring_of_grassland_shrubland_and_savanna_ecosystems|here]] ​to for more information about the all of the methods ​in the //​Monitoring Manual//.
- +
-===== Materials Required ===== +
-  * Measuring tape (length of transect)—if using a tape measure in feet, use one marked in tenths of feet +
-  * Two steel stakes for anchoring tape +
-  * Graduated survey rod or height measuring stick with graduations in centimeters (or 0.5 in) and meters (or ft) +
-  * 30 cm (12 in) diameter disc or ruler (optional) +
-  * Clinometer or extendable range pole +
-  * Electronic device for paperless data collection (preferred) OR clipboard, Line-point Intercept with Height Data Sheet OR Vegetation Height Data Sheet (available in the USDA - ARS Monitoring Manual) and pencil(s)  +
- +
-===== Standard Method ===== +
-== 1. Measure plant heights at regular intervals (5 m [10 ft] recommended) ​for a minimum of 30 height measurements per plot.  Distribute the total number of height measurements evenly among all transects. == +
-  * At each designated transect markhold the edge of the disc on the opposite side of the tape. Using the disc as a guide, determine the tallest living or dead woody (when present) AND living or dead herbaceous plant (when present) parts intersecting a projected 30 cm (12 in) diameter cylinder tangent to the line (Figure 15).  +
-  * All plant materials existing inside the projected cylinder are considered, whether they are rooted inside or outside the 30 cm (12 in) circular area (Figure 16).  It doesn'​t matter where plants are rooted, only plant materials within the cylinder are observed. +
-  * Do not stretch or move any plant parts. ​ Ignore any part of the plant that is outside the cylinder. +
-  * Height is determined as the perpendicular distance (relative ​to the earth'​s center, regardless of slope) from the soil surface at the center of the cylinder to the tallest plant element contained within the cylinder.  +
-  * Record height from the center of the cylinder at the soil surface, even if the soil surface is uneven, mounded or bumpy (Figure 17, Table 17).  Woody or herbaceous litter are not measured.  +
- +
-== 2. Record the height of plants 0-2 m (6 ft) tall to the nearest centimeter (0.5 in).  Record the height of plants that exceed 2 m (6 ft) in height to the nearest 30 cm (~1 ft)== +
-  * Record the height of the tallest part of the plant inside the cylinder. ​ Record only one height for each plant type (woody or herbaceous) if present. ​ Where no woody or herbaceous vegetation is present, mark "​0"​ on the data sheet.  +
-  * If vegetation is taller than 3 m (~10 ft), a clinometer, phone application,​ or geometric technique can be used to estimate height. ​ For the geometric option, step back from the cylinder far enough so the tallest point of the plant in the cylinder can be seen.  Measure (a) the horizontal distance to that point and (b) the angle (from the soil surface where the observer is standing) to that point. ​ Calculate the height using the following formulaHeight = (distance ​to plant) x (tangent of angle from soil surface). ​ Be sure to measure and set calculators to ‘degrees’ when using this equation.  +
- +
-== 3. Optional: Species names can be recorded ​for projects that require species identification of the plant element measured. ==  +
- +
-== 4. Optional: Record if the plant element is alive or dead. ==  +
- +
-{{:​field_methods:​veg_height_1.png}} +
- +
-===== Vegetation Height Indicator Calculations ===== +
-Vegetation height calculations are computed for two reasons: (1) to describe overall height structure on a plot and (2) to describe the heights of the vegetation on the plot.  Overall height structure on a plot, described in Steps 1, 2, and 3, is the average height recorded at all measurement intervals including measurements where no vegetation was present and height was recorded as "​0"​. ​ To describe the vegetation height by structural group (woody or herbaceous) or by species, average the heights recorded when those species or groups occur. ​ Keep in mind that estimating vegetation height only where vegetation was measured (height > 0) may result in variable number ​of height measurements between plots. +
- +
-== 1. Calculate ​the average vegetation height (vertical structure) for all measurements. An example is shown in Table 18. == +
-  * Add together all height measurements,​ regardless of species. ​ Divide this sum by the number of samples in this group. ​ Record this value as average overall height on your data sheet.  +
- +
-== 2. Calculate the average woody height for all measurements (woody vertical structure). == +
-  * Add together all woody species height values. Divide this sum by the number of samples in this group. ​ Record this value as the average woody height on your data sheet+
-== 3. Calculate the average herbaceous height (herbaceous vertical structure). ​== +===== Method ===== 
-  Add together all herbaceous species ​height ​measurements. ​ Divide this sum by the number of samples in this group. ​ Record this value as average herbaceous height on your data sheet+{{:​field_methods:​veg_height_1a.png}}\\ 
 +*A graduated rod and disc is used measure vegetation ​height. ​**
-== 4Optional: Calculate average ​of woody or herbaceous ​heights including only heights > 0. ==+Plant height is measured with a graduated survey rod or measuring stick with a 30cm disc affixed to the top of the measuring tool An imagery cylinder extends from the disc's circumference to the ground. ​ The highest point of any plant (living or dead) that falls within this cylinder is recorded. ​ Woody and/or herbaceous ​plants are differentiated. ​  If both woody and herbaceous plants are present underneath the disc, the tallest point of each type of plant is recorded. ​ If no plants are present, a value of "0" is recorded. ​ Transects are established at regular intervals (5m is recommended) with a minimum of 30 height measurements per plot 
-{{:​field_methods:​veg_height_2.png}}+{{:​field_methods:​veg_height_2a.png}} ​\\ 
 +** Example plots. ​ The black silhouette represents a woody species and the grey silhouette represents an herbaceous species. ** \\
-===== Vegetation Height Basic Interpretation ===== +Once the data is collected, an average ​height of all species is calculated as well as an average height of woody species ​and herbaceous species.  ​Values ​of (no vegetation presentcan be discarded when calculating average heights if desired.
-Woody and herbaceous ​height ​can be important indicators ​of vertical vegetation structure, especially when interpreted together with [[basal_gap_intercept|Gap intercept]] ​and [[line_point_intercept|Line-point intercept]] data.  ​Woody and herbaceous vegetation structure, together with [[canopy_gap_intercept|canopy gap size]] and distribution,​ are used to characterize wildlife habitat to determine if the site provides adequate thermal, hiding, and/or nesting cover for species ​of management interest ​(Table 19). +
-Vegetation height ​and canopy gaps are also indicators ​of potential wind erosion on a site.  ​A site with large canopy gaps and short vegetation ​is more susceptible to wind erosion than a site with smaller canopy gaps and taller vegetation.  ​Models have been developed that predict wind erosion based on vegetation ​height, ​foliar cover and canopy gaps (e.g., Okin 2008*).  ​+===== Data Entry and Management =====    
 +Electronic record keeping is recommended. ​ The [[databases:​rangeland_database|Database for Inventory, Monitoring & Assessment (DIMA)]] contains data entry forms which can be downloaded as part of an MS Access database.  ​DIMA is compatible ​with PDAs and tablets.  ​Alternatively,​ a paper version of the plant height ​inventory form can printed from the appendix of the //​Monitoring Manual for GrasslandShrubland ​and Savanna Ecosystems//​.
-{{:​field_methods:​veg_height_3.png}}+===== Related Methods ===== 
 +Vegetation height is often measured with [[field_methods:canopy_gap_intercept|gap intercept]] and [[field_methods:​line_point_intercept|line-point intercept]] to provide a complete picture of vegetation structure. ​ This data can be useful in wildlife habitat suitability analysis. ​ Vegetation height and canopy gaps are also indicators of a site's vulnerability to erosion. ​ See Okin 2008 for a description of using vegetation height data to predict the impact of wind erosion. 
 +===== References ===== 
 +  * Okin, G.S. 2008. A new model of wind erosion in the presence of vegetation. //Journal of Geophysical Research// 113: F02S10.
-===== Manual ===== 
   * USDA-ARS Jornada Experimental Range. (2014). //​Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems//​. Volume I: Core Methods. 2nd Ed. pp. 36-40. http://​​monit-assess/​manuals/​monitoring ​   * USDA-ARS Jornada Experimental Range. (2014). //​Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems//​. Volume I: Core Methods. 2nd Ed. pp. 36-40. http://​​monit-assess/​manuals/​monitoring ​
field_methods/vegetation_plant_height.1391043631.txt.gz · Last modified: 2014/01/29 18:00 by jgh