Definitions for invasive plants

People use different words for invasive speciesAlien ExoticInvasive Non-indigenousImported WeedyIntroduced Non-nativeImmigrant ColonizerNaturalized

Definitions for invasive plants

LEGAL DEFINITIONSState: 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 2000Noxious 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 13112(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 asHighly competitive Cause environmental degradationExotic Easily spreadHighly aggressive Are difficult to controlCause 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 ConservancyInvasive 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 invaderDispersal: 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 activityCasual 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 humansInvasive plants = naturalized plants that produce reproductive offspring

(often in large numbers) 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 accountDarwin 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 sensingSatellite imagery: spectral signatures (from Eric Peterson, NV Natural

Heritage Program, http://heritage.nv.gov/reports.htm)

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 SummerO N D

J F MA M J

J A S

Remote sensing

From a spectral perspective

Fall Winter Spring SummerO N D

J F MA M J

J A S

Pea

k gr

eenn

ess

Min

. gr

eenn

ess

Remote sensing

From a spectral perspective

Fall Winter Spring SummerO N D

J F MA M J

J A S

Pea

k gr

eenn

ess

Min

. gr

eenn

ess

NDVI = greenness index based on chlorophyll reflectance in infrared relative to red.

Remote sensing

From a spectral perspective

Fall Winter Spring SummerO N D

J F MA M J

J A S

Pea

k gr

eenn

ess

Min

. gr

eenn

ess

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

0 20 40 60 80 100

02

04

06

08

01

00

Measured Annual Grass Cover

Est

ima

ted

An

nu

al G

rass

Co

ver

Measured Bromus cover

Rel

ativ

e Δ

ND

VI

Remote sensing

Ground truthed data: 262 training plots plus 75 validation plots9.7% error for validation plots

Remote sensing

Map of Bromus tectorumabundance in OwyheeUplands

Remote sensing

Invasive annual grassesacross entire state

Remote sensing