Assembling information to develop ecological site and state and transition concepts. Brandon Bestelmeyer, Jornada Experimental Range, Las Cruces, NM

Transcription

1 Assembling information to develop ecological site and state and transition concepts Brandon Bestelmeyer, Jornada Experimental Range, Las Cruces, NM

2 Concepts: Ecological site: division of the landscape based on recurring soil, landform, geological, and climate characteristics that affect use and management Ecological state: division of plant communities (phases) within an ecological site according to the processes needed to produce changes between plant communities Community phase: division of plant assemblages into useful, repeatable units that affect use and management

3 Ecological sites and STMs are information and data supported concepts (models) Community phase what vegetation you have at a point in time Ecological state what vegetation you can attain given novel constraints to recovery Ecological site what vegetation you can attain given climate, soils, and topography

4 General flow of ecological site development Concept development (low intensity or Tier 1 ) Testing of concepts/ concept refinement (medium intensity or Tier 2 ) Characterization/ interpretations (high intensity or Tier 3 )

5 Concept development (and reconnaissance/low intensity sampling) Gather existing information Literature GIS data, other data Define geographic extents Workshop, collective knowledge Rapid field survey/traverse Study extent (LRU/MLRA boundaries) Sampling strata/areas Concepts for ecological sites and states Google Scholar: Scopus database in National Agricultural Library (Digitop) (must be USDA)

6 Climatic variations, geological maps to guide inventory to different landscapes within MLRA/LRU be aware of artificial boundaries

7 Concept development: stratify within landscapes based on imagery or soil map units, collect low intensity traverse data

8 What soil features influence ecological potential? Type Hydrology Soil physical properties Lithology/geology Topography/landform Chemistry Variable (units) Water table depth (m) Flooding duration (days) Soil texture of surface (class or %) Fragment content (%) Argillic horizon development (class) Soil depth to restrictive layer (cm) Bedrock type (class) Landscape position (class) Soil salinity/sodicity (mmhos) Soil gypsum content/distribution in profile (%/cm) Soil carbonate content/distribution in profile (%/cm)

9 What ecological processes can create alternative states? Concept Example 0. Reference Savanna state 1. Native reproduction is limited 2. Native competitors dominant, altered processes 3. Non native species dominant, altered processes 4. Hydrologically impaired 5. Local soil degradation 6. Landscape soil degradation Altered savanna state, former dominant is minor component Shrub dominated state; sod bound state Annual grass dominated state (high frequency of fire) Gullied state Shrubland state (truncated soil); abandoned cropland state Mobile dune/shrubland state

10 Loams Loams shallow to igneous bedrock Saline sediments at surface Sandy soils shallow to saline horizons Sandy soils over other material Deep sand dunes

11 Gather data, develop ecological site concepts Name: Sand plains Concept: > 50 cm of Loamy sand or sand over similar soils or buried soils/bedrock Indicator plants: Caragana Transition processes: wind/water erosion, dune formation (type 5)

12 Gather data, develop ecological site concepts Name: Saline sandy Concept: < 50 cm of loamy sand or sand over saline soil Indicator plants: Acnatherum Transition processes: Erosion exposes saline soil (type 5)

13 Gather data, develop ecological site concepts Name: Saline flats Concept: Silt loam to loam over stratified silty clay loam and loamy fine sand Indicator plants: Nitraria, Sueda Transition processes: Fragile site, changes to soil structure, infiltration, salinity (type 5)

14 Ecological sites within a soil geomorphic system Increasing sand depth Saline flats Saline sandy Sand plains

15 Concept refinement (mediumintensity sampling) Gather existing information Literature GIS data Define geographic extents Workshop, collective knowledge Rapid field survey Sampling and interviews Random stratified samples Targeted samples Interviews with local knowledge holders associated with samples Study extent (LRU/MLRA boundaries) Sampling strata/areas Concepts for ecological sites and states Coupled vegetation and soil samples 1) a sample of gradients/variations 2) rare conditions (reference areas) Information on causes of observed conditions of samples

16 Concept refinement (analysis) Gather existing information Literature GIS data Define geographic extents Workshop, collective knowledge Rapid field survey Sampling and interviews Random stratified samples Targeted samples Interviews with local knowledge holders associated with samples Study extent (LRU/MLRA boundaries) Sampling strata/areas Concepts for ecological sites and states Coupled vegetation and soil samples 1) a sample of gradients/variations 2) rare conditions (reference areas) Information on causes of observed conditions of samples Analysis Specify plant variable types Regression or multivariate Integrate other data, local interviews on processes

17 Medium intensity sampling to firm up state concepts (saline flats) BG = 10% ACSP=46% PHRA=3% NITR=3% AgSt=5.3 BG = 69% ACSP=>1% PHRA=2% NITR=23% AgSt=2.3 BG =40% ACSP=>1% PHRA=32% NITR=8% AgSt=1.7

18 Different states or different sites? Local knowledge, other evidence

19 STM = inventory + mechanisms from the literature + local evidence of reference conditions and transition mechanisms Saline flats ecological site: Natrargid, mm zone (typical steppe) Acnatherum Stipa Acnatherum forbs Patchy Acnatherum Reference State High perennial grass cover, high grass diversity, bare patches small and unconnected. Perennial grasses minimize soil, nutrient and water movement from high-intensity storms. At-risk Community Phase: Perennial cover low in Interspaces between Acnatherum patches, low litter low root mass, some soil movement Restoration pathway: Unknown, may require decades with no grazing. High salinity difficult to reverse. Nitraria Phragmites Transition: Heavy grazing/drought followed by an intense rainfall event to initiate soil degradation. Soil structure loss, reduced inflitration, and/or loss of soil surface horizons, increased salinity, remaining vegetation declines Alternative State Patchy dominance by halophytes, sealed soil surface, no subsoil structure. Reduced infiltration leads to increasing salinity and low available water in rooting zones of grasses, sealed soil prevents grass establishment

20 Data visualization to refine ecological site concepts % cover Larrea Carbonatic gravelly % calcium carbonate Gravelly % clay Gravelly loam Three ecological sites represented in this sample, differences in maximum LATR cover

21 On to ecological site description production Gather existing information Literature GIS data Define geographic extents Workshop, collective knowledge Rapid field survey Sampling and interviews Random stratified samples Targeted samples Interviews with local knowledge holders associated with samples Analysis Specify plant variable types Regression or multivariate Integrate other data, local interviews on processes Study extent (ecoregion) Sampling strata (landforms) Concepts for ecological sites and states Coupled vegetation and soil samples 1) a sample of gradients/variations 2) rare conditions (reference areas) Information on causes of observed conditions of samples Definitions of ecological sites and STMs Identify locations for intensive samples

22 Remember that all models are wrong; the practical question is how wrong do they have to be to not be useful. Box and Draper (1987)