Transitions and Biomass 1006

7/29/2019 Transitions and Biomass 1006

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State and Transition Models

A Lens For ViewingBiomass ProjectsSherman Swanson,

Rangeland Management State Specialist


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Ecological Site

A kind of land with specific physicalcharacteristics which differs from other kinds ofland in its ability to produce distinctive kinds and

amounts of vegetation and in its response tomanagement.

Over 1000 in Nevada (850+ with sagebrush)

Many of the sagebrush sites may alsosupport pinyon and/or juniper trees at times


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Ecological Site Descriptions

Incorporation of new ecological dynamics theory based

on non-equilibrium ecology:State and Transition Model (Westoby, et al, 1989)

Replaces Range Condition = Seral Stages Model

Multiple stable states


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Range

Condition And

RangeSuccession

Concepts

Range condition / ecological status

0-25% overlap

Poor

Early seral

26-50%

Fair

Mid-seral

51-75% Good

Late Seral

76-100%

Excellent

PNC

Compare current plantcomposition with the reference(potential) composition from thesite description

Overlap = A condition class or

seral stage


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Loamy 8-10 Ecological Site

Site

SHRUBS (45) Description location 1 location 2

Wyoming Sagebrush 25-35 70 (35) 17 (17)

Rabbitbrush 2-5 5 (5) 3 (3) Other 5-10 - -

GRASSES (50) Indian Ricegrass 20-30 9 (9) 15 (15)

Thurber Needlegrass 10-20 6 (6) 27 (20) Squirreltail 2-8 3 (3) 15 (8) Sandbergs Bluegrass 2-5 1 (1) 10 (5) Other 2-8 0 10 (2) Cheatgrass 0 5 (0) 0

FORBS (5)

Globemallow 2-5 1 (1) 2 (2) Other 2-5 T (T) 1 (1)

Total/(Overlap) 100 (60) 100 (73) Condition Good Good Seral Stage Late Late


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Problems With Range Condition And

Succession Concept

Achieve the same range condition or seral stageclassificationwith:

Different species compositions

Different life-form compositions


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Succession Concept




Managers seldom link seral class/ condition scoreswith quantitative species composition


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Succession Concept





With greater deviation from PNC -

less knowledge about community composition

Less is known about the response potential


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Succession Concept





With greater deviation from PNC-

less knowledge about community composition

Less is known about the response potential Class names lose information about response

potential


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State 1

State 2

State 3

Conceptual State and Transition Model

Threshold

Reversible transition

Community pathway

Irreversible transition

Community Phases


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What is a STATE?

A recognizable, resistant and resilientcomplex of 2 components:

soil baseinteraction of climate, abioticsoil characteristics, soil biota,topography

vegetative structureaboveground

communities


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What is a Transition?

A trajectory of system change away from the

current stable state - triggered by natural

events, management actions or both.

Reversible - before transitioning across a threshold

Irreversibleafter crossing a threshold


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What are Thresholds?

Boundary in space and time between states when one or

more ecological processes has been irreversibly changed

beyond the point of self-repair:


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Boundary in space and time between states when one or

more ecological processes has been irreversibly changed

beyond the point of self-repair:

Return to original state - requires management beyond

simple reversal of events that caused the change


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Boundary in space and time between states when one+ecological processes has been irreversibly changed beyondthe point of self-repair:

Return to original state - requires management beyondsimple reversal of events that caused the change

Often associated with high cost/high risk management

actions


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PERENNIAL HERBACEOUS STATE

Succession

Fire or fire surrogate

Herbaceous plantcommunity

Shrubby overstoryWith herbaceous

Understory


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Diminishedperennialherbaceous

understory

Perennial herbaceousunderstory mostly

absent

Requires additional inputsto restore the understory

SHRUB STATE

No fire toBalanceGrazing


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PJ control andnew understorypropagules

Diminished

shrubs

TREE STATE

No

fire

Understory

mostlyabsent

Perennial

Herbaceous

State

Shrub

State


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Nevada Noxious Weed List

A Weeds:

African Rue

Austrian fieldcress

Austrian peaweed

Camelthorn

Common crupina

Toadflax Dyers woad

Giant Salvinia

Goats rue

Houndstongue

Iberian Star thistle

Klamath weed Leafy spurge

Malta Star thistle

Mayweed chamomile

Mediterranean sage

Purple loosestrife

Purple Star thistle

Rush skeletonweed Sow Thistle

Spotted Knapweed

Squarrose star thistle

Sulfur cinquefoil

Syrian Bean Caper

Yellow Starthistle Yellow Toadflax

Leaf Biomass Through Time After Fire


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UNDERSTORY

TREE

Leaf Biomass Through Time After Fire

Phase 1

Phase 2Phase 3

DECREASING

RESILIENCE

RESISTANCE

FLEXIBILITY

INCREASING

RISK

Tree StatePerennial Herbaceous State

and/or Shrub State


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?

ALTERED SITEPOTENTIAL

STATE


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Triage Priorities

Assess rangeland by ecological sitesFind areasapproaching a threshold before they cross it.

Restore their resiliencyuse tools like vegetation

management, fire, grazing management, etc.


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Triage Priorities




Do not focus on areas unlikely to cross a threshold


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Triage Priorities




Do not focus on areas unlikely to cross a threshold

Once across a threshold, manage to prevent the next

threshold

Use fuel breaks to avoid the big fires in PJ

Use livestock to reduce fuels in the annual grassland

Be prepared after fires to seed in the first winter after the

woody plants burn


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Biomass HarvestingWhere and When?


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After higher priority work is assured (not crossing

thresholds)


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thresholds)

In synergy with other tools and budgets to harvest

biomass where the understory can be released


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thresholds)

In synergy with other tools and budgets to harvest

biomass where the understory can be released

To re-create mosaics with fuel breaks (prevent

large fires)


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After higher priority work is assured (not crossingthresholds)

In synergy with other tools and budgets to harvestbiomass where the understory can be released

To re-create mosaics with fuel breaks (preventlarge fires)

To avoid the extreme heat from fire afteraccumulated fuels would kill (not release)

understory perennials.


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After higher priority work is assured (not crossingthresholds)

In synergy with other tools and budgets to harvestbiomass where the understory can be released

To re-create mosaics with fuel breaks (preventlarge fires)

To avoid the extreme heat from fire afteraccumulated fuels would kill (not release)

understory perennials. To harvest a resource (that will otherwise go up in

smoke)


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WYOMING BIG SAGEBRUSH STATE & TRANSITION MODEL

(WITH CHEATGRASS AND/OR OTHER INVASIVE WEEDS)


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PJ control and newunderstory propagules

Diminishedshrubs

TREE STATE

?

ALTERED SITPOTENTIAL ST

ANNUAL GRASS FIRE-

CYCLE STATE

Fire resistantshrubs andcheatgrass

Cheatgrass andother annuals

Fire/ PJcontrol w/osuccessfulseeding

?

PERENNIAL

INVASIVE WEE

STATE

SEEDED PERENNIAL

HERBACEOUS STATE


Succession

Withsagebrush

Succession

Frequent fires

Introduction and explosion ofperennial invasive species

ABUN

DANCE

Early seraldominants

Herbaceousperennials

Sagebrush overstory Dominant treespecies

Sagebrushunderstory

SeededHerbaceous

No fire

Understorymostlyabsent

Diminishedperennialherbaceousunderstory

Perennialherbaceous

understory mostlyabsent

Requiresadditional inputs

SHRUB STATE

No fire to

BalanceGrazing

Annual grass fire cycle state after fire andwithout successful seeding

Perennial invasive weeds dominate if theirPopulations are allowed to explode

No

fir

e

PERENNIAL HERBACEOUS STATE

Succession


Herbaceousplant community

Shrubby overstoryWith herbaceous

Understory


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Priorities for Management

Keep the Perennial Herbaceous State resilient

Prevent fire in the Shrub State

Use fire or fire surrogates to avoid the Tree State

Seed successfully after a Shrub or Tree-State fire

Eradicate invasive weeds before they explode

Break up the landscape to reduce fire frequency in

the Annual Grass Fire-cycle State


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We Cant Continue To Do

Nothing!

Transitions and Biomass 1006

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