Limestone Hills
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Restoration pathway R2A More details
- Restoration pathway R3A More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
State 1
Reference State
Description
1.1 Warm season grasses/shrubs/succulents (diagnostic plant community)
A mix of grasses, shrubs and succulents are present. Total foliar cover is > 65%, depending on the amount of rock outcrop.
1.1A Community Pathway: This pathway represents time between fires, during which natural processes increase shrub and succulent vigor and decrease grass production and composition.
1.1B Community Pathway: This pathway represents fire. Fire suppresses succulents and many shrubs, giving grasses a competitive advantage.
1.2 Shrubs/succulents/warm season grasses: Over time, foliar cover of shrubs and succulents increases and that of warm season grasses decreases.
1.2A Community Pathway: This pathway represents intervals between fires which are longer than the historic range of variability. Fire suppression, whether through loss of fuel load due to herbivory or from fighting natural wildfires, has increased shrub and succulent vigor and decreased grass production and percent composition.
1.2B Community Pathway: This pathway represents fire. Fire suppresses succulents and many shrubs, giving grasses a competitive advantage.
1.2C Community Pathway: This pathway represents a growing competitive advantage for nitrogen fixing shrubs due to slow changes in soil chemistry and hydrology.
1.3 Warm season grasses/scattered shrubs: This plant phase exists after fire. Grasses respond well to fire, while many shrubs and succulents decrease.
1.3A Community Pathway: This pathway represents intervals between fires, during which natural processes increase shrub and succulent vigor and decrease grass production and composition. Over time, plant community 1.3 shifts to 1.1.
1.4 At risk: shrubs/warm season grasses/succulents/nitrogen fixing shrubs: Due to gradual changes in hydrologic function and soil chemistry, succulents and shrubs increase over time. The increased abundance of native nitrogen fixing shrubs such as whitethorn and catclaw mimosa is a key indicator that this community phase is “at risk.”
1.4B Community Pathway: This pathway represents fire. Fire sets back succulents and many shrubs, giving grasses a competitive advantage.
1.4D Community Pathway: A change in livestock grazing management promotes grass vigor and decreases shrub competition. This accelerates the turnover of fine roots, causing an increase in labile carbon, acceleration in decomposition, and a resulting increase in plant available water.
T1A Transition one: Slow variables: Continued encroachment by whitethorn acacia, coupled with the loss of herbaceous plant species, causes a decrease in soil organic matter, leading to a decrease in plant available water. Trigger event: A severe drought causes loss of soil organic carbon. Threshold: A hydrologic function/soil chemistry threshold is crossed.
1.5 At risk: shrubs/succulents/warm season grasses: This plant phase is the result of gradual changes in species composition to a shrub and succulent dominated community. There has been a decrease in hydrologic function as grasses are weakened in this community. This is a different plant community than 1.4, as nitrogen fixing plants are not present.
1.5B Community Pathway: This pathway represents fire. Fire sets back succulents and many shrubs, giving grasses a competitive advantage.
1.5D Community Pathway: A change in livestock grazing management to allow for decreased shrub competition, improved litter accumulation, an increase in labile carbon, and acceleration in decomposition resulting in an increase in plant available water.
T1B Transition two: Slow variables: Continued decrease in grasses and overall canopy cover, causing a decrease in soil organic matter, leading to a decrease in plant available water, decomposition, and plant available nutrients. Trigger event: A severe drought, causing a loss of organic carbon. Threshold: A hydrologic function threshold was crossed.
2.0 Nitrogen fixing shrubs/succulents/shrubs/warm season grasses state
2.1 Whitethorn Acacia/succulents/shrubs/warm season grasses: Whitethorn acacia has become a prominent plant on the site. Foliar cover has decreased to < 40%. A higher Nitrogen turnover rate increases the invasiveness and stability of whitethorn. This community has a mix of shrubs, succulents, and warm season grasses.
R2A Restoration Process: An increase in the competitive advantage of non-nitrogen fixing species through physical, chemical, and biological management practices.
3.0 Shrubs/succulents state
3.1 Shrubs/succulents: This plant community has crossed a threshold where shrubs and succulents dominate the canopy and grasses are very limited. Due to fire suppression and continuous herbivory a change in the hydrologic cycle has occurred. This community is very similar to 2.1 except for the presence of whitethorn and other nitrogen fixing shrubs.
R3B Restoration Process: Organic matter needs to be increased in the system to stimulate decomposition, mineral cycling, and water storage. Fine root systems from grass species are important for increasing organic matter.
Submodel
Description
Whitethorn acacia has become a prominent plant on the site. Foliar cover has decreased to < 40%. A higher Nitrogen turnover rate increases the invasiveness and stability of whitethorn. This community has a mix of shrubs, succulents, and warm season grasses.
Submodel
Description
This plant community in this state has crossed a threshold where shrubs and succulents dominate the canopy and grasses are very limited. Due to fire suppression and continuous herbivory a change in the hydrologic cycle has occurred. This community is very similar to 2.1 except for the presence of whitethorn and other nitrogen fixing shrubs.
Submodel
Transition T1A
Mechanism
This transition moves the site across a threshold to state two. Slow variables: Continued encroachment by whitethorn acacia, and catclaw mimosa, coupled with the loss of the herbaceous plant community. Both chemical and hydrological shifts occur as the C:N decreases creating an increase in the nitrogen turnover rate and creating an on-going competitive advantage for nitrogen fixing shrubs.
Trigger event: A severe drought, causing a loss of organic carbon. Threshold: A hydrologic function/soil chemistry threshold is crossed.
Mechanism
This transition moves the site across a threshold to state three. Slow variables: A continued competitive advantage and increase of shrubs and succulents, coupled with the loss of the herbaceous plant community. A hydrological shift occurs as shrubs and succulents out-compete herbaceous plants for water resources.
Trigger event: A severe drought, causing a loss of organic carbon. Threshold: A hydrologic function threshold is crossed.
Restoration pathway R2A
Mechanism
An increase in the competitive advantage of non-nitrogen fixing species through physical, chemical, and biological management practices.
Various facilitating and management practices can be used to restore this ecological site back to reference. Chemical, mechanical, and biological practices can all be used to suppress whitethorn and other leguminous thorny plants in the plant community. Also, range seeding, winter feeding, browsing, and high intensity-short duration livestock grazing can help bring grass seed and organic matter back into the system and start restoring soil carbon and microbial levels. Eventually, prescribed burning will also help reduce shrub competition and improve grass vigor, once fuel loads can carry fire.
Monitoring foliar cover by species will help inform the land manager if plant composition is responding to management.
Mechanism
An increase in the competitive advantage of herbaceous species through prescribed burning and grazing management practices.
Various facilitating and management practices can be used to restore this ecological site back to reference. Prescribed burning is important to help reduce shrub competition for nutrients and water resources. Chemical, mechanical, and biological practices can also be used to suppress shrub competition. Also, range seeding, winter feeding, browsing, and high intensity-short duration livestock grazing can help bring grass seed and organic matter back into the system and start restoring soil carbon and microbial levels.
Monitoring foliar cover by species will help inform the land manager if plant composition is responding to management.
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.