Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 4, 2000
Publication Date: N/A
Interpretive Summary: Many rangelands on the southwestern U.S. support an extensive cover of woody plants and weeds, a problem that must be managed for successful range animal production and for best use of the land for other purposes. Determining the extent of noxious plant populations on rangelands by ground surveys is difficult because of the generally great expanse and inaccessibility of these areas. Studies were conducted to determine the light reflectance characteristics of several weed and brush species found on rangelands in the southwestern U.S. and Mexico. Color-infrared (CIR) and conventional color (CC) aerial photos were evaluated for detecting the noxious species. Plants studied were silverleaf sunflower, broom snakeweed, Big Bend locoweed, Wooton locoweed, huisache and Chinese tamarisk. Phenology of the plants had an important influence on their light reflectance and detection on aerial photographs. Canopy architecture, vegetative density and leaf pubescence were also important for distinguishing some species. Reflectance measurements were related to the plant species color tonal responses on CIR and CC photographs. These findings should be useful to rangeland resource managers.
Technical Abstract: This paper demonstrates the use of field reflectance measurements and aerial photography [color-infrared (CIR) and conventional color (CC)] for distinguishing noxious plant species on rangelands. The visible/near -infrared (0.45- to 0.90-um) reflectance characteristics of several brush and weed species found on rangelands in the U.S. and Mexico are presented. The phenological stage of plants has an important influence on their spectral characteristics and subsequent detection on aerial photographs. Canopy architecture, vegetative density and leaf pubescence are also important for distinguishing some species. Reflectance measurements are related to the plant species color tonal responses on CIR and CC photographs. Plant species addressed include silverleaf sunflower (Helianthus argophyllus Torr. and Gray), broom snakeweed [Gutierrezia sarothrae (Pursh.) Britt. and Rusby], huisache [Acacia smallii (L.) Wild.], ,Big Bend locoweed [Astragalus mollissimus var. earlei: (Rydb.) Tidestr.], Wooton locoweed (Astragalus wootonii Sheld.), and Chinese tamarisk (Tamarix chinensis Lour.).