{"id":3717,"date":"2010-03-23T16:00:00","date_gmt":"2010-03-23T16:00:00","guid":{"rendered":"https:\/\/cnhp.colostate.edu\/field-techniques-frequency\/"},"modified":"2021-06-09T14:49:47","modified_gmt":"2021-06-09T14:49:47","slug":"field-techniques-frequency","status":"publish","type":"post","link":"https:\/\/cnhp.colostate.edu\/cnhpblog\/2010\/03\/23\/field-techniques-frequency\/","title":{"rendered":"Field techniques &#8211; Frequency"},"content":{"rendered":"<p>CNHP ecologists use frequency of occurrence as a measure of plant community composition, especially if we want to know how the community is changing over time.<\/p>\n<div style=\"clear: both;text-align: center\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-6994\" src=\"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/april-and-steve-sg69-2003b.jpg\" width=\"320\" height=\"240\" srcset=\"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/april-and-steve-sg69-2003b.jpg 320w, https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/april-and-steve-sg69-2003b-300x225.jpg 300w\" sizes=\"auto, (max-width: 320px) 100vw, 320px\" \/><\/div>\n<div style=\"text-align: center\"><span style=\"font-size: x-small\">Reading a frequency frame placed along a transect.<\/span><\/div>\n<p>\nFrequency is usually expressed as a percentage, such as the percent of all plots in which a species is present, or the percent of cells in a grid that contain the species. It is a presence\/absence measurement, and does not reflect the number of individuals or the area they cover. A little reflection tells us that frequency is highly dependent on the size of the area being observed \u2013 if our sample frame is the size of the earth, every species has a frequency of 100%!<\/p>\n<p>Since we don&#8217;t always know in advance what size frame will be appropriate for detecting changes in species frequencies, and because some species are much bigger than others, it is common to use a &#8220;nested&#8221; frequency frame like this, placed at many different locations in the area being studied:<\/p>\n<div style=\"clear: both;text-align: center\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-6995\" src=\"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/freq_frame.jpg\" width=\"400\" height=\"301\" srcset=\"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/freq_frame.jpg 400w, https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/freq_frame-300x226.jpg 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/div>\n<p>\nThis frame can easily be made out of plastic pipe and elbow fittings. Divisions can be marked with strings, or marks along the frame edge. To read the frame, record a 1 if the species is in the smallest square, a 2 if it is in the 1\/10th m square but not the 1\/100th, and a 3 if it is only in the largest square outside the other two squares. A species that gets a 1 is present in all three frame sizes, but a species with a 3 is only present at the largest frame size. Calculate the percent of &#8220;present&#8221; frames for each species at each size frame. To detect change over time, a frame size that gives a percentage between 20 and 80 is best.<\/p>\n<div style=\"clear: both;text-align: center\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-6996\" src=\"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/dog-in-plot.jpg\" width=\"320\" height=\"240\" srcset=\"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/dog-in-plot.jpg 320w, https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-content\/uploads\/sites\/12\/2018\/11\/dog-in-plot-300x225.jpg 300w\" sizes=\"auto, (max-width: 320px) 100vw, 320px\" \/><\/div>\n<div style=\"text-align: center\"><span style=\"font-size: x-small\">Quiz time! Assuming the nested corner is upper left in the photo,<\/span><br \/>\n<span style=\"font-size: x-small\">is the dog is a 1, 2, or a 3?<\/span><\/div>\n<div style=\"text-align: center\"><span style=\"font-size: x-small\">(A: we&#8217;re sampling plants here, shoo!)<\/span><\/div>\n","protected":false},"excerpt":{"rendered":"<p>CNHP ecologists use frequency of occurrence as a measure of plant community composition, especially if we want to [&hellip;]<\/p>\n","protected":false},"author":9,"featured_media":6994,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[19],"tags":[],"class_list":{"0":"post-3717","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-field-techniques","8":"entry","9":"override"},"_links":{"self":[{"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/posts\/3717","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/comments?post=3717"}],"version-history":[{"count":0,"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/posts\/3717\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/media\/6994"}],"wp:attachment":[{"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/media?parent=3717"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/categories?post=3717"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cnhp.colostate.edu\/cnhpblog\/wp-json\/wp\/v2\/tags?post=3717"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}