title: Vegetation changes associated with a population irruption by Roosevelt elk.
abstract: Interactions between large herbivores and their food supply are central to the study of population dynamics. We assessed temporal and spatial patterns in meadow plant biomass over a 23-year period for meadow complexes that were spatially linked to three distinct populations of Roosevelt elk (Cervus elaphus roosevelti) in northwestern California. Our objectives were to determine whether the plant community exhibited a tolerant or resistant response when elk population growth became irruptive. Plant biomass for the three meadow complexes inhabited by the elk populations was measured using Normalized Difference Vegetation Index (NDVI), which was derived from Landsat 5 Thematic Mapper imagery. Elk populations exhibited different patterns of growth through the time series, whereby one population underwent a complete four-stage irruptive growth pattern while the other two did not. Temporal changes in NDVI for the meadow complex used by the irruptive population suggested a decline in forage biomass during the end of the dry season and a temporal decline in spatial variation of NDVI at the peak of plant biomass in May. Conversely, no such patterns were detected in the meadow complexes inhabited by the nonirruptive populations. Our findings suggest that the meadow complex used by the irruptive elk population may have undergone changes in plant community composition favoring plants that were resistant to elk grazing.
authors: Department of Biology, Texas State University San Marcos, Texas, 78666.
authors: Heath D
authors: HD
authors: Starns
authors: Department of Biology, Texas State University San Marcos, Texas, 78666.
authors: Floyd W
authors: FW
authors: Weckerly
authors: U.S. Geological Survey, Western Ecological Research Center 800 Business Park Drive, Suite D, Dixon, California, 95620.
authors: Mark A
authors: MA
authors: Ricca
authors: Department of Biology, Texas State University San Marcos, Texas, 78666.
authors: Adam
authors: A
authors: Duarte
keywords: Herbivory; NDVI; plant traits; population regulation; remote sensing; ungulate
references: Ecology. 2006 Feb;87(2):297-303
references: 16637354
references: Oecologia. 1979 Aug;41(2):127-134
references: 28308857
references: Trends Ecol Evol. 1999 May;14(5):179-185
references: 10322530
references: Ecol Appl. 1993 Feb;3(1):35-36
references: 27759229
references: Oecologia. 2001 Aug;128(4):465-479
references: 28547391
references: Proc Biol Sci. 2001 May 7;268(1470):911-9
references: 11370963
references: J Anim Ecol. 2003 Jul;72(4):640-649
references: 30893958
references: Oecologia. 1993 Nov;96(2):157-161
references: 28313410
references: Ecol Appl. 1993 Feb;3(1):2-9
references: 27759225
references: Oecologia. 2013 Nov;173(3):837-47
references: 23719900
references: Trends Ecol Evol. 2005 Sep;20(9):503-10
references: 16701427
references: Oecologia. 1989 Nov;81(3):316-322
references: 28311182
references: Proc Biol Sci. 2000 Sep 7;267(1454):1771-9
references: 12233776
references: Oecologia. 2009 Aug;161(2):303-12
references: 19484268
references: Ecol Appl. 1993 Feb;3(1):30-31
references: 27759233
references: Am J Bot. 1998 Sep;85(9):1266-72
references: 21685013
references: Ecol Appl. 2007 Sep;17(6):1598-606
references: 17913126
references: Biol Lett. 2012 Dec 23;8(6):1002-5
references: 23015455
references: Ecology. 2011 Oct;92(10):1917-23
references: 22073783