Soil Change and Soil Quality Indicators on Rangelands

West Regional Cooperative Soil Survey Conference, July 7 – 12, 2002

Arlene J. Tugel Soil Quality Institute Las Cruces, NM How soils change through time:

“Soils are formed by pedogenesis, affected by land-use history, and are currently changing in modern ecosystems that have increasing human influence.”

Richter and Markowitz. 2001, Understanding Soil Change. Outline • Soil change – Time scales, resistance, resilience, rates of change, processes, and function • Indicators for assessing and monitoring soil function – Plant-soil-management interactions, disturbances • Organizing knowledge about soil change – State and transition models • Soil Survey and soil change – Dynamic soil properties Soil Change - Cause and Effect Cause Effect Change in solar radiation Patterns of change

Natural events Natural perturbations (earthquakes, drought)

Use and management Management-induced (disturbance regime) perturbations Temporal Scales of Soil Change Millennia Centuries Entisol

Petroargid

Decades

Richter and Markewitz, 2001 Yearly, Seasonally, Daily Richter and Markewitz, 2001 Resistance, Resilience, Thresholds and Rate of Change Compaction Soil with disturbance high resistance

Low resistance Soil function Low resistance (% of capacity) and high and low resilience resilience

Time (years) (Seybold, etal, 1999) Change in the context of process and function • The importance of change is its affect on function through changes in process. • We need to understand, but N cannot measure P processes directly. C S Linking pedology, ecology and soil function • Pedogenic • Ecological processes processes – Inputs – energy capture – Translocations and flow – Transformations – hydrologic cycle – Removal processes – nutrient cycling

Soil function Capacity to Function

Rangeland health Soil quality • Soil and site • Maintaining biodiversity stability and productivity • Hydrologic • Partitioning water and function solute flow • Biotic integrity • Filtering and buffering • Nutrient cycling • Structural support Indicators for assessing and monitoring soil function

How do we evaluate function?

Measuring stick What is an indicator?

• A key soil (or plant) property that is sensitive to change. – physical, biological or chemical properties – soil surface features – patterns and variability • Reflects complex ecosystem process that are too difficult or costly to measure. • Provides information about the current status of rangeland ecosystems. Qualitative Quantitative Assessment Assessment and monitoring RangelandRangeland HealthHealth IndicatorsIndicators 1717 QualitativeQualitative measuresmeasures Q RillsRills Q LossLoss ofof SoilSoil SurfaceSurface Q WaterWater FlowFlow PatternsPatterns Q Plant/InfiltrationPlant/Infiltration EffectsEffects Q Pedestal/Pedestal/TerracetteTerracette Q CompactionCompaction LayerLayer Q BareBare GroundGround Q Functional/StructuralFunctional/Structural GroupsGroups Q GulliesGullies Q PlantPlant Q WindWind ScourScour AreasAreas Mortality/DecadenceMortality/Decadence Q LitterLitter MovementMovement Q LitterLitter AmountAmount Q ResistanceResistance toto ErosionErosion Q AnnualAnnual ProductionProduction Q InvasiveInvasive PlantsPlants Q ReproductiveReproductive CapabilityCapability Soil Quality Indicators increase the value and accuracy of rangeland assessments • Quantitative measures are less and monitoring subjective. • Provide additional information below the surface.

May 2001 May

function

):

2000, TR 1734-6, BLM 1734-6, TR 2000,

, ,

Rangeland Sheet 2 Sheet Rangeland

of perennial plants perennial of X

Version 3 Version

decadence X

groups X

infiltration and runoff and infiltration X

distribution relative to relative distribution 17. Reproductive capability 17. Reproductive

composition and composition 16. Invasive plants 16. Invasive X

15.production Annual X

degradation X X X 14.amount Litter X X

to erosion to X X X 13.mortality/ Plant

12. Functional/structural

indicatorintegrity logic stability

11. Compaction layer 11. Compaction X X X

terracettes X X

9. Soil surface loss or loss 9.surface Soil 10.community Plant

8. Soil surface resistance 8.surface Soil

7.movement Litter X

6. Wind-scoured areas 6. Wind-scoured X

5. Gullies X X

Rangeland health Biotic Rangeland Hydro- Soil/site

4.ground Bare X X

3. Pedestals and/or 3. Pedestals

2. Water flow patterns 2.flow Water X X

1. Rills X X

The following qualitative assessment indicators and indicators assessment qualitative following The

http://www.ftw.nrcs.usda.gov/glti

(

of Rangeland Health, Health, Rangeland of

the attributes they reflect are from from are reflect they attributes the Interpreting Indicators Interpreting

declines in some patches and increases in others. in increases and patches some in declines

organic matter becomes less uniform, resource availability resource uniform, less becomes matter organic

nutrients and water. Accordingly, as the distribution of soil of distribution the as Accordingly, water. and nutrients

living plants and decaying residue on the soil also affect also soil the on residue decaying and plants living

and deposition. The kinds, amounts, and spatial distribution of distribution spatial and amounts, kinds, The deposition. and

over both short and long distances by such processes as erosion as processes such by distances long and short both over

cycling of water and nutrients in rangeland soils are affected are soils rangeland in nutrients and water of cycling

—Pedestals, exposed plant roots, rills, roots, plant exposed —Pedestals,

—Physical, biological, and chemical soil chemical and biological, —Physical,

—The distribution and distribution —The Spatial patterns and variability. and patterns Spatial

Soil surface features. surface Soil

qualitatively.

as runoff and erosion. These indicators are commonly assessed commonly are indicators These erosion. and runoff as

gullies, wind scours, and soil deposition reflect such processes such reflect deposition soil and scours, wind gullies,

a combination of physical, biological, and chemical processes. chemical and biological, physical, of combination a

Soil properties. Soil to plants. Soil organic matter and soil aggregate stability reflect stability aggregate soil and matter organic Soil plants. to

of soil biota, reflect the availability of both water and nutrients and water both of availability the reflect biota, soil of

infiltration. Other properties, such as the diversity and activity and diversity the as such properties, Other infiltration.

reflect limitations to root growth, seedling emergence, and water and emergence, seedling growth, root to limitations reflect

properties are included. Some properties, such as bulk density, bulk as such properties, Some included. are properties

on rangeland? on

What soil quality indicators are used are indicators quality soil What

vegetation indicators and may be qualitative or quantitative. or qualitative be may and indicators vegetation

system to management. Soil quality indicators complement indicators quality Soil management. to system

Indicators are key soil or plant community characteristics that characteristics community plant or soil key are Indicators measured regularly provide clues about the response of the of response the about clues provide regularly measured

status of rangeland ecosystems. Trends from indicators from Trends ecosystems. rangeland of status

measured directly. They provide information about the current the about information provide They directly. measured

ecosystem processes that are too difficult or expensive to be to expensive or difficult too are that processes ecosystem

are sensitive to change in the environment. They reflect complex reflect They environment. the in change to sensitive are

What are indicators? are What

USDA, Natural Resources Conservation Service Conservation Resources Natural USDA,

Indicators for Assessment and Monitoring and Assessment for Indicators

Rangeland Soil Quality— Soil Rangeland

Soil Quality Information Sheet Information Quality Soil

May 2001 May

Rangeland Sheet 1 Sheet Rangeland

available for plant growth; plant for available

• the availability of nutrients for plant growth; plant for nutrients of •availability the

• runoff, water infiltration, and the potential for erosion; for potential the and infiltration, water • runoff,

• the amount of water from rainfall and snowmelt that is that snowmelt and rainfall from water of •amount the

Changes in soil quality that occur as a result of management of result a as occur that quality soil in Changes

affect:

Why is soil quality important? quality soil is Why

shift may be irreversible, while in others, recovery is possible. is recovery others, in while irreversible, be may shift

accelerated erosion resulting in a change in the soil profile, this profile, soil the in change a in resulting erosion accelerated

resources across the landscape. In some cases, such as such cases, some In landscape. the across resources

properties and processes and/or the redistribution of soil of redistribution the and/or processes and properties

vegetation generally are associated with changes in soil in changes with associated are generally vegetation

changes in soil properties and processes. Significant shifts in shifts Significant processes. and properties soil in changes

abundance. Changes in vegetation may precede or follow or precede may vegetation in Changes abundance.

may disappear, and the less desirable species may increase in increase may species desirable less the and disappear, may

water decreases, plant production declines, some plant species plant some declines, production plant decreases, water

the amount of water available to plants. As the availability of availability the As plants. to available water of amount the

crusting decreases the infiltration capacity of the soil and thus and soil the of capacity infiltration the decreases crusting

Rangeland health and soil quality are interdependent. are quality soil and health Rangeland the cycling of plant nutrients. For example, increased physical increased example, For nutrients. plant of cycling the

storage, and redistribution of water; the growth of plants; and plants; of growth the water; of redistribution and storage,

function affects ecological processes, including the capture, the including processes, ecological affects function

the soil and the plant communities. The capacity of the soil to soil the of capacity The communities. plant the and soil the

Rangeland health is characterized by the functioning of both of functioning the by characterized is health Rangeland

• Rangeland health • Rangeland

• Establishment and growth of invasive plants invasive of growth and • Establishment

• Vegetation changes • Vegetation health related? health

• Carbon sequestration • Carbon

How are soil quality and rangeland and quality soil are How

• Wildlife habitat • Wildlife

• Water yields and water quality water and yields • Water

• Erosion

• Plant production, reproduction, and mortality and reproduction, production, • Plant

rangeland?

What does soil quality affect on affect quality soil does What

habitation.

quality of water and air, and support human health and health human support and air, and water of quality

Introduction

Soil quality is the capacity of a specific kind of soil to soil of kind specific a of capacity the is quality Soil

sustain plant and animal productivity, maintain or enhance the enhance or maintain productivity, animal and plant sustain

function within natural or managed ecosystem boundaries, ecosystem managed or natural within function

What is soil quality? soil is What

change in response to management. to response in change

Soil is a dynamic resource that supports plants. It consists of consists It plants. supports that resource dynamic a is Soil is defined by the inherent soil properties that do not readily not do that properties soil inherent the by defined is

change in response to how the soil is managed. The kind of soil of kind The managed. is soil the how to response in change

biological, chemical, and physical properties, some of which of some properties, physical and chemical, biological,

matter, and numerous species of living organisms. Soil has Soil organisms. living of species numerous and matter,

mineral particles of different sizes (sand, silt, and clay), organic clay), and silt, (sand, sizes different of particles mineral

What is soil? is What

Rangeland health is the degree to which the integrity of the of integrity the which to degree the is health Rangeland

and sustained. and

ecological processes of the rangeland ecosystem are balanced are ecosystem rangeland the of processes ecological

soil, the vegetation, the water, and the air as well as the as well as air the and water, the vegetation, the soil,

What is rangeland health? rangeland is What

Rangeland is land on which the native vegetation is vegetation native the which on land is Rangeland

and wet meadows. wet and

deserts, tundras, areas of alpine communities, coastal marshes, coastal communities, alpine of areas tundras, deserts,

land includes natural grasslands, savannas, shrub lands, most lands, shrub savannas, grasslands, natural includes land

predominantly grasses, grasslike plants, forbs, or shrubs. This shrubs. or forbs, plants, grasslike grasses, predominantly

What is rangeland? is What

USDA, Natural Resources Conservation Service Conservation Resources Natural USDA,

Rangeland Soil Quality— Soil Rangeland Soil Quality Information Sheet Information Quality Soil Information sheets SOM - What is it? Carbon-rich material from plants, animals and soil microbes in various stages of decomposition Soil Organic Matter TYPE RATE OF FUNCTION DECAY

Short term Light Weeks to • Serves as food for soil organisms fraction months • Stores and provides plant nutrients

Physically Decades • Enhances soil structure and protected porosity and water holding capacity

Chemically Hundreds • Hold nutrients Long term stable to • Stabilizes micro-aggregates thousands • Gives soil its dark color of years

Why is it important? • Stable aggregates – resist erosion – reduce crusting – increase infiltration – hold more water – provide pores for growth – physically protect organic matter • Changes may serve as early indicators of recovery or degradation. What effects it? • Environmental factors • Soil properties • Vegetation, roots • Soil organisms • Disturbances – Wind and water erosion – Grazing and traffic – Fire, absence of fire – Invasive weeds, shrub encroachment – Shrub removal Disturbance effects on infiltration (min/in)

Heavy grazing + drought Mesquite Dune 14:24 12:00 Grassland Mesquite establishment 9:36 and increase 7:12 4:48 2:24 Redistribution of 0:00 resources, decrease in e Bar rass grass and increase in G Shrub erosion Herrick, etal, 1999 Soil-plant-management interactions • Roots are primary source of SOM in grassland soils Norfolk, et. al. 2001

Grazing pressure

S1-UG (Intact) S1-LG (Stable) S1-SG (Degrading) S2-HG (Degraded) 0 4 0 20 30 4 0 3 1

Soil depth (cm)Soil depth 0 2 -10 0 0 3 2 0 0 20 1 0 1 1 0 -20 0

-30

-40 0 5 10 15 20 5 10 15 20 5 10 15 20 5 10 15 20 Distance from plant center (cm)

Fig. 4. Root distributions (mm2/cm3 soil) within soils of tropical tallgrass sites in response to accumulated grazing pressure. Information Rangeland Sheet 6

Soil Quality Information Sheet sheets Rangeland Soil Quality—Organic Matter USDA, Natural Resources Conservation Service May 2001

What is soil organic matter? Soil organic matter is carbon-rich material that includes plant, animal, and microbial residue in various stages of • Aggregate stability decomposition. Live soil organisms and plant roots are part of the carbon pool in soil but are not considered soil organic matter until they die and begin to decay. The quantity and composition of soil organic matter vary significantly among major ecosystems. Soil in arid, semiarid, and hot, humid regions commonly has less organic matter than • Compaction soil in other environments. The total content of organic matter ranges from less than 0.5 to more than 8 percent in the surface layer of rangeland soils. Soil organic matter includes three main components (table 1). The light fraction is more biologically active than the other two and includes relatively fresh plant fragments. Physically • Infiltration protected organic matter is locked within aggregates of mineral particles, where it is protected from microbial decomposition. Organic mattter darkens and stabilizes the surface layer in soils. Chemically stable organic matter gives soil its dark color and is generally the largest pool of organic matter in soil. Physically • enhances soil fertility and plant productivity by improving protected organic matter may also be chemically stable. the ability of the soil to store and supply nutrients, water, Table 1.—Soil organic matter and air; • Organic matter • provides habitat and food for soil organisms; Component Rate of Primary function • sequesters carbon from the atmosphere; decay • reduces mineral crust formation and runoff; and • reduces the negative water quality and environmental Light fraction Weeks to • Serves as food for soil effects of pesticides, heavy metals, and other pollutants by months organisms actively trapping or transforming them. • Physical and • Stores and provides plant nutrients • What is it? What affects soil organic matter? Physically Decades • Enhances soil structure, protected porosity, and the water-holding The amount of organic matter in the soil is a balance between capacity additions of plant and animal materials and losses through biological crusts decomposition and erosion. Chemically Hundreds to • Holds nutrients Environmental factors interacting over time affect the stable thousands • Stabilizes microaggregates • Why is it important?amount of organic matter in soil. Rainfall and temperature affect of years plant productivity and the rate of organic matter decomposition. Increasing levels of organic matter promote a higher water- Why is organic matter important? holding capacity, which results in increased plant growth and • Soil biota thus an increased amount of organic matter and plant nutrients. Soil organic matter enhances soil functions and Roots are the primary source of organic matter. Dead roots • Howenvironmental qualityis because it it: measured?and gelatinous materials exuded by plant roots as they grow • binds soil particles together into stable aggregates, thus through the soil are decomposed by soil organisms and improving porosity, infiltration, and root penetration and converted into organic matter. Since much of what is produced • Water erosion reducing runoff and erosion; above ground is lost through photo-oxidation, the amount of • What affects it? • Wind erosion • Management strategies Management strategies to improve the indicator (function) • Maintain or increase vegetation and litter cover. • Decrease the number and size of bare patches. • Promote the growth of species with high root biomass. • Include a mix of species with different rooting depths and patterns. Management strategies

• Reduce soil surface disturbance, especially in arid and sandy areas. • Use prescribed burning appropriately to prevent fuel build-up. Organizing knowledge about soil change How do we present information on processes, soil properties and function? Disturbances and uncoupling of the soil-plant relationship are important keys to predicting plant and soil dynamics and change in function. Soil function (% of capacity) Time (years) State and Transition Ecological Model

Westoby, et. al., 1989 Stringham et.al., 2001

Concept model for predicting vegetation dynamics What the S&T Model provides. Integrates soil-plant-management interactions

1. Potential: historic climax community, states and plant communities 2. Drivers of change: transitions, community pathways (disturbances, stresses, practices and natural events) 3. Boundary of change in process: thresholds for resistance and resilience, early warning indicators What the S&T model provides

4. Temporal scale: management time-scale 5. Spatial scale: ecological site (a grouping of soil map units – functional edaphic unit) La Copita, TX example

1950

1950 (3.59 ha)

100 0 100 200 Meters

Woodland

Groves

1976 1990 Clusters (5.26 ha) (6.52 ha) Herbaceous Archer, et al., 2001 La Copita, TX Soil properties for Runge fine sandy loam ESD: Sandy loam 83c C % Bulk Density (0-10 cm) (gm/cm3) NASIS 1.0-2.0 1.30-1.55

T State 1; A – Tall and 1.2 * Assume 1.1 h re s mid-grass h o ld State 1; C – Short 0.84 1.4 grasses and annuals State 2; D – Clusters 2.2 1.1 and mesquite groves

* Derived from Century model simulation. (Hibbard 1995; Archer et al. 2001) Soil survey and soil change on rangelands

• Soil data needs for interpretation • Integrating dynamic and inherent soil properties • What’s next? Interpret and Predict AA rancherrancher makesmakes aa rangelandrangeland healthhealth assessmentassessment andand findsfinds aa compactioncompaction problem.problem. SoilSoil datadata needsneeds forfor S&TS&T ModelModel Quality criteria or Î What should it be? reference value for Is 1.4; should be 1.1, plant community NASIS: 1.30-1.55 Transitions for STM Î What will it take to (drivers of change, get it there? management regime) Thresholds, resilience Î Will it return and and rate of change how long will it take to get it there? Need to integrate inherent and dynamic soil properties with state and transition models

• Inherent soil features: “Static” and dynamic

• Dynamic soil properties: Susceptible to change on the management time scale Inherent - Result of soil formation; used to make a soil survey. • texture • mineralogy • horizon sequence • soil depth • slope • hourly soil temperature • seasonal pH cycle Dynamic soil properties Dynamic soil properties

All temporal soil properties; Use- includes changes due to dependent Indicators management, natural disturbances (drought, flood, etc), and natural cycles (seasonal, daily, etc); includes use-dependent soil properties. (Relevant to human time scales) Indicators: properties that change in response to management, climate or both and reflect current functional status. What’s next?

• Test soil dynamics in State and Transition Models. • Learn to interpret soil response. • Develop measurement methods for dynamic properties. – What, where, how many, how deep? • Think “soil behavior.” • Rangeland soil quality information sheets – SQ Institute website http://www.statlab.iastate.edu/survey/SQI/ • Interpreting Indicators of Rangeland Health, ver 3. Pellant, M. et.al., 2000. Tech. Ref. 1734-6. – http://www.blm.gov/nstc/library/techref.htm • Understanding Soil Change. 2001. Richter and Markowitz. • States, transitions, and thresholds: Further refinement for rangeland applications. Stringham et al, 2001. – http://www.ftw.nrcs.usda.gov/glti/pubs.html • Dynamic Soil Properties Symposium, SSSA, Nov. 11, 2002, Indianapolis. Soil dynamics

• Dynamics: “The pattern of change or growth of an object; variation and contrast in force or energy.”

• Soil Dynamics: The pattern of change in soil resulting from changes in energy or forces applied to soil. THRESHOLDSTHRESHOLDS

thresholds

trajectory Vegetation attribute(S)

time Questions to be covered

• How are rangeland health and SQ related? • What makes a good indicator? • What is the most important soil-plant interaction? • What affects the capacity of soil to function on rangelands? • How do we document soil dynamics on rangelands?