Groundwater-dependent wetlands in Western Montana Forests

Jen Chutz, DCI West Biological ConsultingLinda Vance, Montana Natural Heritage

ProgramMontana Wetland Council

March 26, 2014

BackgroundEPA-funded project designed to…Document extent of

Groundwater Dependent Ecosystems (GDEs)• Especially fens, focusing on

Western Montana

Enhance MTNHP’s wetland reference network

Improve recognition of patterns in imagery to assist in USFWS National Wetland Inventory (NWI) mapping

So how do you find GDEs? Expert knowledge

• Many of the largest and richest fens have been identified and surveyed, and are known to botanists and land managers, or described in publications

Trial and error• In theory, in the course of enough wetland surveys,

including getting to and from target wetlands, you’ll encounter GDEs

National Wetland Inventory (NWI) mapping and high-resolution imagery• Our preferred approach!

3.21.2014: 1,726 USGS 24K Quads Mapped2,178,028 Acres

Wetlands: 1,655,061 AcresRiparian: 522,967 Acres

Using the NWI to find GDEs/FensBecause NWI maps are based

on aerial imagery, key indicators like the presence of peat aren’t detectable

However, GDEs generally…• Have no inlet

• Often have no outlet

• Have a fairly distinct “signature” visible to the human eye because they are often saturated through the growing season

Using the NWI to find GDEs/FensAlthough GDEs found from

floodplains to alpine areas in MT…

GDEs generally are found…• At low points in the landscape

OR…

• Near slopes where groundwater intercepts surface

• Associated with glacial till/outwash, alluvial fans/basins, floodplains

• Over limestone deposits

Used NWI mapping in ArcGIS to identify ALL:• Palustrine

Emergent wetlands AND…

• Palustrine Shrub Scrub wetlands WITH…

• Saturated water regimes

• PEMB and PSSB

North of Whitefish, MT

Field surveysRapid assessments (Level 2)• ~ 2 hours

Intensive assessments (Level 3)• Up to 8 hours

Field surveysSet up 0.5 hectare Assessment

Area (AA)• Best represents site• Diversity & proportions

• Usually 40m circle

Site info: • General wetland description• Landscape setting• Physical patch types• AA drawing• Photos & GPS points

Classification of AA• Ecological Systems of MT• Hydrogeomorphic (HGM)

class• Cowardin classification

Field surveysHydrologic

inputs/outlets• If any

Major vegetation zones• Structure and

species composition

Anthropogenic disturbance metrics:• Distance to, degree of, cause

of disturbance/changes to… Landscape Vegetation

GDEs sustained by inputs from local landscape

GDEs are stable, but not resilient

Soil Hydrolog

y

Soil surveysMin. 2 soil pits, each in different

vegetation & hydrology, if possible• Min. 60 cm or until mineral soil

Soil Texture - Organic vs. Mineral • Peat, mucky peat, muck• Ribbon test…Sand Loam Clay Loam

Clay

Other hydric soil indicators• Redox concentrations and depletions (Fe &

Mn)• Hydrogen Sulfide

Soil Color – Munsell Soil Color Chart

Level 3: Intensive assessmentsWithin AA, we lay out ten

10x10m modules

Within 4 selected modules, record…• Vegetation species…• Presence• Stratum• % canopy cover

• Ground Cover…• Type• Deep water, gravel,

litter, woody debris, etc…

• % cover• Depth

50 m

20 m

0 m

#10

#1 #2 #3 #4 #5

#6 #7 #8 #9

50 m

XP1

XP2

AA & Plot Placement

GDEs vs FensNot all GDEs are fens, and not all

fens are GDEs

Fens are defined as having an organic layer with ≥40cm of peat

GDEs rely on groundwater for the majority of their water input• But, we encountered many

flow-through fens, some distinct channels

• Must “dig” for indicators of groundwater dependency• Soil, pH, landscape, etc…

GDE 131 GDE 131, our earlier example, was classified as a wet meadow rather than a fen, although it was a close call.

Soil pits had from 14-25 cm of peat, some with mucky peat underneath, some with a silty loam

Vegetation cover was primarily Carex utriculata, C. atherodes, and Calamagrostis canadensis

Project summaryIn total from 2012 & 2013, we completed intensive

surveys of… • 131 GDEs• 109 fens• 19 wet meadows• 3 emergent marshes

Identified 350 species in the Assessment Areas of these GDEs

Fens• AA vascular plant species richness varied widely

• From 1 to 44 species identified per fen• Mean of 16.4 species

Project summaryNativity was high:

• 77 of the fens had no observed exotic species• Only one –in Glacier National Park– had more than

4

For fens, Mean Floristic Quality Index = 58• This was adjusted for cover weight and native

species• Very near the value of 60.6 MTNHP found for

reference-standard fens in an earlier study

Next stepsSpecies of Concern (SOC) plant data will be entered into

MTNHP databases once all IDs are confirmed

Final report on project will be available from MTNHP by late April

Database and GIS available on request from MTNHP• Contact: Linda Vance livance@mt.gov

Data forms and protocol are available on MTNHP’s website• http://mtnhp.org/wetlands/