Sphagnum bogs…

Louise Kulzer

            Water quality specialist, Aquatic ecologist

            King County Department of Natural Resources

 

           

CTo understand the unique characteristics of sphagnum bogs

CTo understand how human influences can adversely impact sphagnum bogs

CTo see a peat system first-hand

 

What you’ll learn about...

•Where & how bogs are formed

•How sphagnum moss creates it’s own niche

•Physical & chemical gradients in wetlands & where bogs fit in

•Plant & animal communities in bogs

•How human activities can disrupt bogs

Definitions (after Bridgham, 1998)

Peatland is a generic term applied to wetlands in which the rate of accumulation of organic matter exceeds the rate of decomposition, and where at least 1 foot ( 30 - 40 cm) of peat has accumulated (Glaser, 1987)

(Mire is the European name for peatlands)

Two basic divisions in peatlands:

            bogs -- acidic peatlands, Sphagnum moss forms dense mat

            fens-- depends on  classification-- usually more sedges, less acidic

Definitions, cont’d
 Other peatland types

muskeg-- northern peatlands covered with stunted black spruce (Crum, 1992) rooted in Sphagnum

moors-- in Britain, bleak, uncultivated land, not necessarily peaty.  “High-moor” is characterized by calcium poor substrates and Sphagnum mosses.

heath--in Britain, areas of infertile, often peaty soils supporting shrubby vegetation. Typically over-grazed historically.

carr-- a peat system, usually not Sphagnum-dominated,  supporting deciduous trees

 

Types of bogs

•lake-fill or kettle-hole bogs

–flat basin                              

–plateau  or raised bogs

•Blanket bogs                        

–flat valley

–slope bogs

carpets, lawns (use differs with authors)

open hummock/hollow, usually w/ shrubs

forested

 

Bogs form in specific environmental situations

Precipitation exceeds evaporation
 

Bogs form in specific environmental situations

•Drainage is poor (plateaus, drainage divides)

•Poor soils, often glaciated

•Kettle holes

•Cool temperatures

•Oceanic influence common-- rainfall higher in Na & Cl

•Northern latitudes

•in lakes, protected from wind, upstream flowpaths

Sequence /age  of peat profile

 

Puget Sound region

–Often underlain by blue clay

–sedge peat

–pumicite layer (laid down 6,700 yr b.p. (151 obs.))

–sphagnum peat

•11,900 yr. b.p. average for beginning of peat accumulation

•41 years/ inch of peat accumulation (151 obs, Puget Sound lowlands)

Other NW bogs: 49 years / inch (55 obs in NE Wa, Idaho, BC)

Northern Minnesota-- 4,000 yr. BP (mid-holocene)

 

Characteristics of sphagnum bogs

•form mats which are at least somewhat buoyant

•mats often form hummocks & hollows, support a unique assemblage of plants

•water acidic

•bacterial communities severely depressed, but aquatic fungi thrive

•lack of dissolved oxygen, minerals and nutrients in water

•typically have a moat or “lagg” at periphery

 

Gradients operating in peatlands

•source of water

                        rainΰ runoff ΰ groundwater

•water mobility

                        stagnant ΰ flowing

•water chemistry (pH, cations, anions, nutrients) 

             low ΰ high

•water levels

                        stable ΰ fluctuating

 

More gradients

•sunlight                                shade

•summer                                  winter

•hummock                   hollow

•mat                             lagg or moat

 

                       

Generally

 

water source

mobility

chemistry

            pH

            cations

            anions

             nutrients

water level

    bogs                        fens  

rainwater             surface & groundwater

stagnant               flowing       

 

acid                     neutral or basic

scarce      abundant

Cl  dominant    CO3, HCO3 dominant           

low                      high

stable                   stable or fluctuating           

 

Bottom line:

Sphagnum bogs are isolated from the influences of groundwater &/or surface water runoff in some way

•topography (small watershed, flat area)

•impermeable layers

–blue clay

–decomposed peat itself

•raised character of hummocks or plateau

•moat or lagg

 

 

Sphagnum moss

•Indeterminate growth

•upper portion actively grows,bottom portion sloughs away, may sink to bottom or be suspended

•dozens of species, w/ own growth habits, tolerances for pH, light, wetness

•leaves thin, only 1 cell thick

•cell walls w/ perforations, high concentrations of polyuronic acid, an active cation exchanger

•high water-holding capacity (15-23X dry weight)

 

 

Sphagnum ecology

•Numerous species, 61 in European mires

•wide range of pH tolerances

•some species are specialists, some generalists

•Coastal BC-- 6 species groups

–degree of shading

–height above water table

–surface water chemistry

•No definitive local taxonomy done for WA, OR

Profile through a sphagnum hummock

 

Sources of acidity in bogs

•decomposition of peat in the acrotelm yields organic acids

–humic acids

–fulvic acids

•redox reaction of sulfur compounds yields acids

•Cation exchange by sphagnum -- H+

Bog/fen gradient

Cation exchange

 

                                                                                                           

Chemistry of waters:  cations
data from Puget Sound area (typical)

hardness (Ca + Mg)

alkalinity (...    mg/L CaCO3)

1    10    20    30    40    50    60    70    80    90

 

Common bog plants

(Based on fall 1998 survey, 30 Puget Sound bogs)

30    Ledum groenlandicum (Labrador tea)

25        Tsuga heterophylla (hemlock)

20        Kalmia microphylla (bog laurel)

17        Spirea douglasii

17        Vaccinium oxycoccus (cranberry)

15        Thuja plicata (w. red cedar)

Pink font = family Ericaceae

Other common bog plants

Drosera rotundifolia (sundew)

Cladium (reindeer lichen)

Rhynchospora alba (beakrush)

stunted Sitka spruce, shorepine, white pine

crabapple, cascara, willow, birch

blueberry, huckleberry

Eriophorum (cottongrass), Menyanthes (bogbean) 

Scirpus atrocinctus (= cyperinus)

skunk cabbage

 

Uncommon bog plants

Carex pauciflora (few-flowered sedge)

Olympic peninsula

Myrica gale (sweet gale)

Rhododendron macrophyllum

Gentianan sp. (bog gentian)

Habenaria dilatata (bog orchid)

British Columbia

Andromeda sp. (bog rosemary)

Rubus sp. (cloudberry)

 

 

Unique bog beetles--
WA state sensitive status

Effects of human activity

Uses of sphagnum

•soil amendment

•fuel source, ancient times to present

•acid-loving crops

–cranberries

–blueberries

•truck farms (Ravenna P-patch)

•paleo-botanical record

•historical record

•absorbent material -- bandages WW1, diapers

 

Historical changes in sphagnum acreage -- King County, WA

              24 King County Bogs, 1930s to 1990

                                    Sphagnum acres

                                    1930     1980    1990

Total      458                140         132    

                                    » 71% reduction in acreage   

 

1930 acres from Rigg, Peat Resources of Washington

1980, 90 acres estimated from from air photos

Urbanization of watershed

•volume of annual runoff increased ~ 40%

•increases winter high

    water level

•increases water level fluctuation

•concentration of cations, nutrients

greatly increases ( changes buffer equilibrium)

•bacterial concentration increase

•physical disturbance increases (pets, people)

 

Responses to urban runoff

•Binding of cations+ greatly increased, may use up exchange sites and kill moss

•buffering system equilibrium disturbed

•WLF causes

–increased depth of D.O., increased area of acrotelm, more decomposition of mat

–higher winter, lower summer  water levels

•increased bacteria, more decomposition

•higher nutrients favor typical emergents

 

Recent changes in sphagnum acreage -- King County

Recent changes in sphagnum acreage -- King County

Of the 50 remaining bogs in King Co. WA

most show damage

–draining

–dirt paths, roads

–cuts for ROW, ditches

–invasion by non-acid loving plants

            (more overland runoff)

–erosion of mat (increased O2, WLF)

–trampling

 

 

Recent changes in sphagnum acreage -- King County

Impacts of recent drainage, LCR14

ihemlock growth taller near cut face of  bog

i# years of accelerated growth increase      closer to the cut face

iheight of Ledum increases, little Kalmia

    near cut face

iDry hummocks, no bog beetles near

    cut face

 

King County Surface Water Design Manual

Sphagnum bog protection menu applied throughout watershed

Goals:  reduce TP by 50%

           reduce  N by 40%

                    alkalinity < 10 mg/L

                            pH < 6

3-facility WQ treatment train

facilities which contribute organic acids

ALSO:  match pre-developed volumes

So what to do?

•Keep entire catchment forested-- no logging

•Keep roads out of catchment

•Limit any construction/ land disturbance to dry season

•No cement use in catchment

•Don’t give mining permits, stop using peat

•Construct modest, low-impact trails

•Show people!  You can’t long protect what people don’t value.

LCR16 from moat looking to bog mat