Definitions for invasive plants People use different words for invasive species AlienExotic InvasiveNon-indigenous ImportedWeedy IntroducedNon-native ImmigrantColonizer Naturalized

Definitions for invasive plants LEGAL DEFINITIONS State: NRS 555 “Noxious weed” means any species of plant which is, or is likely to be, detrimental or destructive and difficult to control or eradicate. Federal: Plant Protection Act of 2000 Noxious weed means any plant or plant product that can directly or indirectly injure or cause damage to crops (including nursery stock or plant products), livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment. Federal: Executive Order (a)“Alien species” means, with respect to a particular ecosystem, any species … that is not native to that ecosystem (e) “Introduction” means intentional or unintentional escape, release…of a species…as a result of human activity (f) “Invasive species” means an alien species whose introduction does or is likely to do harm to public health

Definitions for invasive plants ECOLOGICAL DEFINITIONS (1) Nevada’s Coordinated Invasive Weed Strategy Noxious weeds are “species of plants that cause disease or are injurious to crops, livestock or land, and thus are detrimental to agriculture, commerce or public health” Invasive weeds often share characteristics such as Highly competitiveCause environmental degradation ExoticEasily spread Highly aggressiveAre difficult to control Cause economic lossAugment wildfires “Species of concern” are species that have potential to cause greatest impact on Nevada’s ecosystem and economic well being (2) The Nature Conservancy Invasive species are: Spread from human settings into wild Once wild, continue to reproduce Displace native species; reduces biodiversity Usually non-native

Definitions for invasive plants ECOLOGICAL DEFINITIONS (3) Davis & Thompson (2000) 8 ways to be a colonizer, but only 2 ways to be an invader Dispersal: Short Long Uniqueness: Common Novel Common Novel Impact:Small Great Small Great Small Great Small Great SC SC NNC NIC SC SC NNC NIC

Definitions for invasive plants ECOLOGICAL DEFINITIONS ( (4) Richardson et al. (2000) Alien plants = plant taxa in a given area whose presence is due to intentional or accidental introduction as a result of human activity Casual alien plants = alien plants that flourish but do not form self-replacing populations. Continued presence depends on re-introductions. Naturalized plants = alien plants that reproduce consistently and sustain populations over many life cycles without direct intervention by humans Invasive plants = naturalized plants that produce reproductive offspring (often in largenumbers) at considerable distance from parent plants >100m & <50 years for seed dispersing species >6 m & >3 years for vegetatively reproducing species Weeds = plants that grow in sites where they are not wanted; usually have economic or environmental effects Transformers = subset of invasive plants that change ecosystems

How are they located? Eyewitness account Darwin in 1833 during trip through the Argentinean pampas “… very many (probably several hundred) square miles are covered by one mass of these prickly [variegated thistle] plants, and are impenetrable to man or beast. Over the undulating plains, where these great beds grow, nothing else can now live.”

Remote sensing Satellite imagery: spectral signatures (from Eric Peterson, NV Natural Heritage Program,

Bromus tectorum greens up early Remote sensing

Bromus tectorum greens up early, and also senesces early compared to native species Remote sensing

From a spectral perspective Fall Winter Spring Summer O N D J F M AM J J A S Remote sensing

From a spectral perspective Fall Winter Spring Summer O N D J F M AM J J A S Peak greenness Min. greenness Remote sensing

From a spectral perspective Fall Winter Spring Summer O N D J F M AM J J A S Peak greenness Min. greenness NDVI = greenness index based on chlorophyll reflectance in infrared relative to red. Remote sensing

From a spectral perspective Fall Winter Spring Summer O N D J F M AM J J A S Peak greenness Min. greenness NDVI = greenness index based on chlorophyll reflectance in infrared relative to red. Does change in NDVI (ΔNDVI) correspond with Bromus abundance? Remote sensing

Imagery from Landsat 5; 8 scenes over Owyhee Uplands from 2 times during year Remote sensing

But also need ground truthed data Remote sensing

Ground truthed data: 262 training plots Measured Bromus cover Relative ΔNDVI Remote sensing

Ground truthed data: 262 training plots plus 75 validation plots 9.7% error for validation plots Remote sensing

Map of Bromus tectorum abundance in Owyhee Uplands Remote sensing

Invasive annual grasses across entire state Remote sensing