mhwh wet hypermaritime subzone - british columbia

Haida Gwaii Field Guide 49

MHwh Wet Hypermaritime subzone

Distribution: MHwh (forested subzone) occurs at higher elevations between approximately 500 and 900 m (depending on location; see below) on the Skidegate Plateau and Queen Charlotte Ranges of Haida Gwaii. The forested MHwh grades into a “parkland” subzone (MHwhp) above ±700 m elevation. MH elevational limits appear to be controlled somewhat by bedrock geology and exposure; the forest/parkland and parkland/alpine boundaries tend to be higher in areas of richer bedrock geology (softer volcanics and limestone) and/or less exposure (higher in the east; lower in the west).

Adjacent biogeoclimatic units: CWHwh2 at lower elevations (below 600 m) on the east side of Haida Gwaii; CWHvh3 at lower elevations (below 500+ m) on the western mountain flanks; the coastal alpine zone (CMA) occurs above the MHwhp (above 800–900 m elevation) on the highest mountains, mainly in the Queen Charlotte Ranges

Distinguishing the MHwh from adjacent biogeoclimatic units—emphasizing zonal sites:

CWHwh2 occurs at lower elevations to the east. It has:• less mountain hemlock (<40–50%) and more western hemlock and

western redcedar• less oval-leaved blueberry• less pipecleaner moss

CWhvh3 occurs at lower elevations to the west. It has:• less mountain hemlock (<40–50%) and more western hemlock and

western redcedar• more salal• less yellow-ladle liverwort and heron’s-bill moss

MHwhp parkland subzone (above ~800 m elevation) and CMA alpine zone (above ~900 m elevation). They have:

• discontinuous forest patches or krummholz/elfinwood with open meadows/heath (MHwh parkland)

• no erect trees, just scattered krummholz within meadows, heath, or rock (CMA)

Haida Gwaii Field Guide50

• more widespread occurrence of a variety of subalpine/alpine plants, such as mountain-heathers and partridge-foot

Common MHwhp and CMA site units are described in Chapter 7. Gen-eral features of the MHwhp (parkland) vegetation are described on page 59 at the end of the MHwh section.

Queen Charlotte twinflower violetViola biflora ssp. carlotttaeEndemic to Haida Gwaii and scattered locations between northern Vancouver Island and southeast Alaska.


Queen Charlotte false rue-anenomeEnemion savileiEndemic to Haida Gwaii and scattered locations between northern Vancouver Island and southeast Alaska.

Calder’s lovageLigusticum calderiEndemic to Haida Gwaii and scattered locations between northern Vancouver Island and southeast Alaska.


Distribution of the MHwh on Haida Gwaii

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MHwh Site Series Flowchart

Driest Forest/Elfinwoodupper slopes and crests; moisture regime slightly dry to fresh

110

101c

101a

Wet , forested seepage slopes of Hm, Ss with Indian hellebore, deer cabbage, shiny liverwort.

Moderately productive forests of Hm, Ss (Hw, Yc). Pacific reedgrass dominant in the understorey.

101b

Stunted Plc, Yc, and Hm and tree cover patchy, may be interspersed with shrubby/herbaceous openings and krummholz/elfinwood; black crowberry and mountain-heathers common, especially in openings.

102

110

Moderately productive forests of Hm, Ss (Hw, Yc). Pacific reedgrass dominant and characteristic in the understorey.

Open herbaceous or shrubby communities at higher elevations with scattered tree islands; transitional to true alpine.

111

More closed forests of Hm, Yc (Hw, Ss) with moderate productivity for MHwh. Blueberries and huckleberries dominate with deer fern and feathermosses.

Forests of Hm, Yc (Hw, Ss) with moderate product-ivity for MHwh. Blueberries and huckleberries dominate with deer fern and feathermosses. Soils moderately well-drained Podzols.

Forests as above but soils imperfectly drained gleyed Podzols (or Gleysols) .

Wet, Yc (Hm, Plc) woodlands with bog and subalpine species (western bog laurel, sundews, lingonberry, peat-mosses).

Very open blanket bogs with above species. Wb54*

Wb53*

ParklandEco-

systems*

Wetter Forestsmoisture regime fresh to wet

Open Forests woodlands or forest patches combined with open, shrubby, or herbaceous communities

* Refer to Chapter 7 for descriptions of wetlands and other non-forested ecosystems on Haida Gwaii.


Description and comparison of site series

Forest productivity in the MHwh is limited by the cold, wet, windy climate and a long-lasting snowpack. The most productive sites gener-ally occur on steep, freely drained colluvial slopes, especially in areas of richer bedrock.

Zonal site series101 HmSs – Blueberry is the dominant site series within the forested portions of the MHwh. The mountainous topography dictates that most sites are moderate to steep, and slope positions are generally upper slopes or crests. Colluvial parent materials are typical, but pockets of glacial till occur, and many sites are shallow to bedrock.

There is considerable range in soil moisture regime/drainage within this site series, but this range is not well expressed in the species com-position of the plant community. For this reason, three phases of the zonal site series are defined. Soils of the Mesic phase (101a) are mostly moderately well-drained Podzols. The Drier phase (101b) typically occurs on better-drained upper slopes and crests with shallow Pod-zols and Folisols (some Regosols). Soils of the Moister phase (101c) are imperfectly drained Gleysols, Folisols, and Podzols. On all phases, Humimor humus forms are often thick (>20 cm) and compacted.

Forests are mixes of mountain hemlock (generally dominating), yel-low-cedar, and Sitka spruce. Western hemlock is often present as well, especially at the lowest elevations of the subalpine zone. Forest produc-tivity is considerably lower than in the CWHwh below. On zonal sites, trees often have considerable girth but a tapered growth form, and main canopies are generally <20–22 m in height. Nevertheless, some quite impressive stands of yellow-cedar extend into the lower MH zone on Haida Gwaii (e.g., along the Sleeping Beauty trail—Slatechuck Moun-tain). Productivity is generally lower on the Subhygric phase (101b).

Oval-leaved blueberry, Alaska blueberry, and red huckleberry domi-nate the shrub layers together with scrubby tree regeneration. Her-baceous cover is restricted by relatively dense canopies (and by deer browsing); spleenwort-leaved goldthread, heart-leaved twayblade, deer fern, bunchberry, and single delight are most consistently present. Step moss, lanky moss, leafy mosses, heron’s-bill moss, and yellow-ladle


liverwort characterize the moss layer. Pipecleaner moss is sometimes abundant. Wet patches of common green peat-moss may occur in the Subhygric phase (101b).

Drier sites 102 YcHm – Crowberry – Mountain-heather is restricted to the most exposed crests and upper slopes where forests are buffeted by cold winds. Topography is generally convex, and soils are well- to rapidly drained Podzols and Folisols overlying rock or fragmental colluvium. Trees are stunted and often well spaced; mountain hemlock dominates with lesser amounts of yellow-cedar, shore pine, and sometimes Sitka spruce.

Tree regeneration dominates the shrub layers, sometimes with scattered red huckleberry, Alaska and oval-leaved blueberry, and false azalea. Crowberry and tufted clubrush (Trichophorum cespitosum) are typical in the understorey, together with the scattered occurrence of many spe-cies that are typical of the 101 (spleenwort-leaved goldthread, bunchber-ry, twayblades). Deer-cabbage and Indian hellebore occur in the wetter pockets. Feathermosses and heron’s-bill moss dominate the bryophyte layer, but large patches of common green peat-moss are also typical.

At higher elevations, transitional to parkland (MHwhp), and in areas where snow lies longer, tree patches (<0 m in height) are interspersed with shrubby or herbaceous openings and elfin forest. These areas have greater understorey species diversity, which includes Pacific reedgrass and a mix of alpine/subalpine species and bog species: white moun-tain-heather, tufted clubrush, tufted hairgrass, partridge-foot, white mountain marsh-marigold (Caltha leptosepela), crowberry, and apar-gidium (Microseris borealis).

Fresh to moist, richer sites110 HmSs – Reedgrass – Lanky moss has been described from only the subalpine areas of Haida Gwaii. This site series occurs mostly on steep slopes where colluvial material gives rise to moderately well-drained Podzols, Folisols, and Regosols. It is unclear why such high-eleva-tion forests with grassy sward understoreys have developed. They are best expressed in areas of richer bedrock geology (softer volcanic and limestone areas), which suggests that their development reflects higher nutrient status.


Stands are typically mountain hemlock–Sitka spruce mixes; some stands have yellow-cedar. Tree productivity is similar to, or slightly higher than 101 sites, with spruce having considerable taper. Shrub composition is similar to zonal sites, with blueberries and huckleberries dominating. The dominance of Pacific reedgrass generally makes this site series easy to identify—even from the air. Grass cover is consis-tently high on the best examples but can be patchy on some sites. Other herbaceous species are the same as those of zonal (101) sites (deer fern and spleenwort-leaved goldthread often dominating), but moister pock-ets tend to have more Indian hellebore, twistedstalks, ferns (lady fern, oak fern), and deer-cabbage. Feathermosses, heron’s-bill moss, and leafy mosses dominate, but, on moister sites, patches of shiny liverwort and peat-mosses occur.

111 HmSs – Reedgrass – Deer-cabbage is restricted to richer seepage slopes and depressions where slope-wash sediments have accumulated. Poorly drained Gleysols are typical soils. The scrubby tree canopy is generally dominated by yellow-cedar and mountain hemlock, but in contrast to the bog woodlands, shore pine is rare or absent and Sitka spruce may be abundant.

Tree regeneration and blueberries and huckleberries dominate shrub layers. Herbaceous communities are dominated by Indian hellebore, Pacific reedgrass, spleenwort-leaved goldthread, deer-cabbage, five-leaved bramble, and twistedstalks. Feathermosses and leafy mosses dominate the bryophyte layer. Peat-mosses and shiny liverwort occupy the wettest portions.

Wet woodlandsWb53 Shore pine – Yellow-cedar – Tufted clubrush bog woodlands extend from sea level to subalpine/alpine environments, especially on the western flanks of the Queen Charlotte Ranges where the CWHvh3 occurs below the MHwh. Open blanket bogs (Wb54) also occur in the MHwh, and many units are intermediate between the two. There are no plots in the Wb54 unit within the MHwh. Wb53 is also described in Chapter 7. The description provided here emphasizes bog woodland characteristics within the subalpine MHwh. The tall shrub variation (Wb53.2) is most typical of the MHwh.

As in the CHWvh3, these blanket/slope bog woodlands occur on considerable slopes—commonly on slopes over 30%, especially over ig-


neous bedrock. Soils range from organic Mesisols that are m or more deep to quite shallow Folisols. Species composition along this 900+ m elevational gradient is surprisingly similar in these bog ecosystems. In the MH zone, yellow-cedar tends to dominate over shore pine and mountain hemlock. Stands are very open, and tree height seldom exceeds 8–0 m.

Shrub layers are dominated by tree regeneration, blueberries and huckleberries (including bog blueberry), false azalea, salal, and western bog-laurel (Kalmia microphylla ssp. occidentalis). Herbaceous/dwarf woody plant communities are diverse, and consist of both lowland and alpine/subalpine species: Indian hellebore; crowberry; sundews (Dro-sera spp.); deer-cabbage; swamp gentian; tufted clubrush; apargidium; lingonberry (Vaccinium vitis-idaea); white, yellow, and Alaskan mountain-heather; bog cranberry (Oxycoccus oxycoccos); Newcombe’s butterweed; and many others. Moss layers are typically peat-moss dominated (several species), though feathermosses and rock-mosses are common as well. Many species of lichens are also typical.

Chapter 7 includes other wetland descriptions.

MHwhp parkland ecosystemsAt elevations above ~700 m (lower in the west; higher in the east), sub-alpine forests become patchier, and eventually small islands of elfin for-est are interspersed with a variety of non-forested communities. As true alpine is approached on the highest peaks (above 800–900 m elevation), dwarf shrub/herbaceous/cryptogam habitats dominate (see Chapter 7).

Subalpine parkland communities have not been extensively sampled on Haida Gwaii (± 0 sample plots). As elsewhere in coastal British Colum-bia, the length of snowpack duration is likely the main determinant of vegetation. Wet sedge habitats (e.g., long-styled sedge [Carex stylosa], many-flowered sedge [C. pluriflora], black alpine sedge [C. nigricans]) occur in moist seeps/late snowpack areas. Richer, moist meadows are dominated by species such as hellebore, white mountain marsh-mari-gold, and Jeffrey’s shooting star; heath communities are characterized by white, club-moss, yellow, and Alaskan mountain-heathers, crowber-ry, and partridge-foot. In addition, all of these habitats typically contain a large diversity of interesting subalpine and alpine flowering plants and cryptogams (see Chapter 7 and Calder and Taylor 968).


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210

1 11

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r inc

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d sp

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MH

wh

Envi

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able

a, b

Site

u

nit

SMR

SNR

Co

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rth

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al s

ites

; LFH

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s co

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act a

nd

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2–3

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ph

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bet

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nal

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5(6)

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Gen

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rs

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ally

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ith

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oft

er v

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d lim

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111

5–6

C–E

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(s)

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(gle

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ors

(M

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epag

e sl

op

es a

nd

dep

ress

ion

s; s

lop

e-w

ash

ed s

edim

ents

may

acc

um

ula

te

a Unl

ess

indi

cate

d ot

herw

ise,

this

tabl

e lis

ts m

ost c

omm

on/t

ypic

al v

alue

s fo

r eac

h at

trib

ute

rath

er th

an e

xtre

mes

/exc

eptio

ns (b

ased

on

sam

ple

plot

s co

mbi

ned

with

the

auth

ors’

expe

rienc

e).

b Cod

es a

re d

escr

ibed

in S

ectio

n 3.

2.2.

SM

R =

soi

l moi

stur

e re

gim

e; S

NR

= s

oil n

utrie

nt re

gim

e.c S

lope

% ra

nge:

leve

l <5%

, gen

tle 5

–25%

, mod

erat

e 25

–70%

, ste

ep >

70%

.

mhwh wet hypermaritime subzone - british columbia

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