Ecosystem services and invasive plants - Invasive Plant Council of BC

Ecosystem services – the 

significance of contributions by 

invasive plant species 

Invasive Plant Council of British Columbia 

Research Forum 

October 18, 2011 

S t e v e Yo u n g , P h D 

We e d E c o l o g i s t 

U n i v e r s i t y o f N e b r a s k a - L i n c o l n

Outline 

• Discuss invasive plant species impacts 

• Define ecosystem services 

• Present information on: 

◦ A theoretical framework for assessing invasive plant 

species and ecosystem services 

◦ The practical considerations for reducing invasive 

plant species impacts on ecosystem services 

• Summary

Bromus tectorum 

Spartina alterniflora 

Tamarix spp. 

Myrica faya 

Genista 

monspessulana

Invasive plant species 

• Present in nearly every region and most habitat types 

Fraction of flora that is exotic for 184 sites around the world, broken down by: 

Region 

Biome 

Source: Lonsdale 1999



• Economic impact > $120 billion per year in US 

(Pimental et al. 2005)



• Economic impact > $120 billion per year in US 

(Pimental et al. 2005) 

• Invasion frequencies 

are increasing

Ecosystem Services

Biodiversity 

Ecosystem services 

• Millennium ecosystem assessment (2005) 

Supporting 

Nutrient cycling, Seed dispersal, Primary Productivity 

Provisioning 

Food, fresh 

water, pharmas, 

energy, fiber 

Regulation 

C sequestration, 

flood control, 

pest control 

Cultural 

Aesthetics, 

heritage, 

recreation, 

spiritual 

• MANY categories declining under current 

scenarios

Outline 








• Summary

How do we assess ecosystem services 

• Indicators must be: 

◦ Representative 

◦ Reliable 

◦ Feasible 

• Current assessments: “…because ecosystem services can 

be difficult to measure directly, scientists have tended to 

use land use ⁄ land cover as a proxy for the provision 

of services even though the relationships between land use ⁄ 

land cover and service provision are largely untested 

for most services in most regions of the world.” 

(Bennett et al. 2009)

What do we need to understand to manage 

ecosystem services 

• Who are the key ecosystem service providers 

• What are the components of community structure 

that influence function at landscape level (e.g. 

compensatory mechanisms) 

• What are the key environmental factors 

• What are the spatio-temporal scales over which 

providers and services operate 

Kremen 2005

% precip available 

Mark and Dickinson 2008

Water quantity Forage production Carbon storage Flood control 

High precip- ET climate, NPP, Plant biomass land use, 

forage quality, (AG+ BG) veg. type 

grazing tolerance 

distribution 

sales livestock 

products 

Low Chan et al. 2006

Ecosystem processes that impact water supply 

Braumann et al 2007

How are ecosystem services different from 

functions 

• Services often integrate across multiple ecosystem 

functions and attributes 

• Emphasis on scale & location 

• Emphasis on multiple services and tradeoffs 

• Distribution of services depends on distribution of 

functions as well as human demands

Assessment and prediction of ecosystem services 

impacted by IPS 

• Can we use ecosystem functions as proxies for services 

• How strong are our broad generalizations about the 

ecosystem impacts of invaders 

• How do we move beyond these generalizations to consider: 

◦ Context- dependence: environment 

◦ Abundance 

◦ Community interactions 

◦ Temporal scale 

◦ Spatial scale 

Heterogeneity within vegetation types 

Heterogeneity across landscape 

Scale at which services are regulated 

Scale at which ecosystem functions are needed for human use 

• How do we integrate all of these factors



• Can we use ecosystem functions as proxies for 

services 

◦ We have a good understanding of many species effects on 

ecosystem functions. 

◦ Ecosystem functions used as proxies for services 

Must consider integration of component functions over space and 

time 

◦ Predictions based on functions an improvement over current 

assessment techniques, especially when incorporating the 

mechanisms

How do invaders impact services 

Charles & Dukes 

2007






• How do we move beyond these generalizations to 

consider: 


◦ Abundance 









Moving from “all invaders” to functional-type 

generalizations 

• Invaders that provide novel functional types have 

large impacts 

◦ N fixers (increase decomposition, nitrogen cycling) 

◦ Woody invasion into grasslands (tend to decrease water 

provision, increase carbon sequestration) 

◦ High biomass producers near waterways (WUE and 

spread rate compared to native vegetation)

Soil C impacts of woody invasion into grasslands 

Increase C 

Decrease C 

Jackson et al 2002

What about less obvious changes 

(when invasions are similar vegetation structure)

What about less obvious changes 

(water use by „vegetation‟) 

Johns 1989

Russian olive 

‣Seasonal ET 

(May 1 Through September 1, 2005) 

‣26.7 Inches OR 2.23 Acre-feet Water, AVERAGE 

Equals 23.8 Gallons Water Per Plant Per Day* 

‣Seasonal LOW Of 11.8 Inches Water 

10.5 Gallons Water Per Plant Per Day* 

‣Seasonal HIGH Of 41.5 Inches Water 


OR 

OR 

Hergert et al., 2010

Saltcedar 

‣Seasonal ET 

(May 1 Through September 1, 2005) 

‣26.8 Inches OR 2.23 Acre-feet Water, AVERAGE 

Equals 21.6 Gallons Water Per Plant Per Day* 

‣Seasonal LOW Of 13.8 Inches Water 


‣Seasonal HIGH Of 37.8 Inches Water 


OR 

OR 

Hergert et al., 2010





◦ Broad generalizations are a good first step 

◦ Management and updated theory should be based on 

Measurements of individual invaders across space and time 

Collectively, these measurements can build a better predictive 

framework







consider: 


◦ Abundance 












consider: 


Different traits regulate functions in different environments 

A given species alters its traits in response to its environment 

◦ Abundance/community interactions 

Ecosystem effects vary with abundance (linear vs. non-linear) 

Impact of abundance depends on similarity in function

What density does a plant need to be at to have an ecosystem effect 

Fyles & Fyles1993 

100% fir 100% alder 100% fir 100% alder

Non-natives impact soils even at less than 

3% of community biomass 

Invaders present 

Soil C (%) .27 + .024 .2 + .008 

Microbial activity (μg 

CO 2 -C g −1 soil h −1 ) 

.56 + .14 .28 + .08 

Invaders removed 

Natives + invaders Natives only Invaders only 

Peltzer et 

al. 2009




consider: 


Different traits regulate functions in different environments 

A given species alters its traits in response to its environment 

◦ Abundance/community interactions 

Ecosystem effects vary with abundance (linear vs. non-linear) 

Impact of abundance depends on similarity in function 

◦ Spatiotemporal scale 

Heterogeneity within vegetation types and across landscapes 

Scales at which services and functions are regulated and needed 

for human use, respectively

Spatiotemporal scales 

• Variability 

◦ Annual (e.g. cheatgrass NPP varies 10-fold year to year) 

◦ Seasonal 

• “Hot moments” 

• Thresholds 

• Directional 

shifts over 

time 

MEA 2005

• Different 

patches of 

landscape 

provide 

different 


• Invasions 

may alter 

services by 

making 


more 

homogenous 

• Location of 

invasion on 


matters 

MEA 2005



• Requires integration across complexity : 

◦ The effects of invaders on ecosystem functions changes with 

environment, abundance, community interactions, space and 

time. 

◦ Current trait-based predictive frameworks can be expanded, 

and coupled with landscape theory to predict these variations

Outline 








• Summary

The practicality of invasive plant species and 


• How have invasive species affected ecosystem 


• Can we restore ecosystem services following 

invasion



• Not all exotic species are equal – need to prioritize 

• Species impacts driven by species traits and habitat 

characteristics, among other factors 

• Removal is often not enough - legacies

Significant community changes 

California grasslands 

Semi-arid shrublands 

Freshwater wetlands 

Forest understories

Biodiversity 

• Wilcove et al. (1998) - >49% of listed species in U.S. 

affected by invasive species 

• Gurevich and Padilla (2004) – Multiple factors: 

land-use, invasive species, among others, can‟t be 

separated 

• Sax and Gaines (2008) – Species invasions may 

increase biodiversity 

• The role of invasive species in extinctions of plants 

may be overstated, but significant shifts are 

occurring in community composition

Supporting services 

• Provide indirect benefits to humans, through other 


• Invasive species often (not always) increase net 

primary productivity and net N cycling rates 

• Invasive plant species have increased some measures, 

but this is not necessarily beneficial

Provisioning services 

Water hyacinth in Lake Victoria, Kenya 

Agricultural 

run-off and 

nutrient-rich 

sediment 

• 1998: >20,000 ha 

• 2005 – Nearly 

absent 

• 2006 – Reinvasion 

following heavy 

rains and nutrient 

influx 

Source: NASA


Water hyacinth in Lake Victoria, Kenya 

Agricultural 

run-off and 

nutrient-rich 

sediment 

• 1998: >20,000 ha 

• 2005 – Nearly 

absent 

• 2006 – Reinvasion 

following heavy 

rains and nutrient 

influx 

• Consequences: 

“Dead zones” and 

loss of fishing 

productivity 

Source: NASA


• Food, fresh water, pharmaceutical products, energy, 

fiber 

• Agricultural pests – weeds, pathogens, diseases 

• Weeds decrease agricultural productivity by ~12% 

• Degrade pasture land – e.g. leafy spurge, St. John‟s 

wort 

• Well-established negative impacts of invasive plant 

species on provisioning services

Regulating services 

• C sequestration 

Meta-analysis of effects of invasion on ecosystem C 

pools (Liao et al. 2008) 

Carbon pool 

% increase in 

pool size 

(native 

exotic) 

Shoots 133 ± 2 84 

Roots 5 ± 3 60 

Litter 49 ± 9 16 

Soil 6 ± 1 83 

Soil microbes 34 ± 6 14 

n



• Flood control - Tamarix spp. in southwest

Tamarix spp. 

• Shrub or small tree 

introduced from Eurasia 

• Invades riparian habitat 

• Widespread in arid and 

semi-arid North America

Tamarix spp. - Impacts 

• Displaces native vegetation 

• Increases fire frequency 

• Increases water transpiration – depleting 

groundwater 

- Consumes 3000-4500 m 3 ha -1 yr -1 more water than native veg 

- (Annual precipitation < 4500 m 3 ha -1 yr -1 ) 

• Increases flooding, erosion rates



• Flood control - Tamarix spp. in southwest 

• A number of examples for plants, but better 

documentation exists for all invasive species

Lupines in California (native) 

What is aesthetic

What is aesthetic 

Lupines in California (native) 

Purple loosestrife in CT (exotic)

Cultural services 

• Aesthetic beauty, heritage, recreation 

• Maybe the most difficult to quantify or generalize, 

but local, state and national policy initiatives 

indicate that invasive [plant] species threaten 

things widely accepted as important (e.g., boating, 

hiking, fishing, bird watching).





- Significant effects on all categories 


invasion







invasion

Restoring ecosystem services 

• Removal of invasive species – Manual, chemical, 

biological methods

Restoring ecosystem services 

• Removal of invasive species – manual, chemical, 

biological methods 

• Removal alone is not enough 

◦ Legacies of invasion exist 

◦ Legacies can have an impact on ecosystem services (restoring 

and maintaining) 

◦ Legacies established during invasive plant species occupancy 

◦ Legacy effects retained (long) after invasive plant species have 

vacated

Legacies of invasive species 

• Community legacies 

• Changes in nutrient or resource “pools”

Pools vs. fluxes 

• Nitrogen cycle: 

◦ Pools: Vegetation, soil organic matter, inorganic N 

◦ Fluxes: Plant uptake, mineralization, nitrification, leaching



• Changes in nutrient or resource “pools” 

- N-fixers increase soil N pools 

- California non-native grasses increase N leaching losses 

- Tamarix increases sedimentation, narrows stream channels




- N-fixers increase soil N stocks 


- Tamarix increases sedimentation, narrows stream channels 

• Changes in soil biota

Changing soil biotic communities 

• Soil from garlic mustard 

stands has lower 

mycorrhizal fungi 

colonization 


stands has lower tree 

seedling growth 

Stinson et al. 2006

Changing soil biotic communities 


stands has lower 

mycorrhizal fungi 

colonization 


stands has lower tree 

seedling growth 

• Mechanism – Garlic 

mustard disrupts plantfungi 

mutualism Stinson et al. 2006




- N-fixers increase soil N stocks 


- Tamarix increases sedimentation, narrows stream channels 

• Changes in soil biota 

• To be successful, restoration must consider such 

legacies and their ‘costs’ to the ecosystem







invasion 

- Yes, but must do more than just remove target 

species 

- Legacies of invasion may limit restoration

Summary 

• Current and Future Directions: 

◦ Continue to fill knowledge gaps on the processes 

underlying ecosystem services and impacts by 

invasive plant species – theoretical and practical 

◦ Evaluate benefits of ecosystem services and trade-offs 

among management actions related to invasive plant 

species that affect these services 

◦ Determine the value of ecosystem services to more 

accurately direct the decision making process in the 

management of invasive plant species 

◦ Incorporate technology to identify and quantify 

ecosystem services at the landscape scale

Acknowledgements 

• Collaborators: 

• Val Eviner, UC Davis, California 

• Jeff Corbin, Union College, New York 

• Funding: 

• Early Career Grant - North Central Regional 

Center for Rural Development (NCRCRD), 

Michigan State University 

• National Academies KECK Futures Initiative 

(NAKFI)

Ecosystem services and invasive plants - Invasive Plant Council of BC

Create successful ePaper yourself

Delete template?

Save as template?