Ecology of Red Maple Swamps in the Glaciated Northeast: A ...

Fig, 4.3. Relatlvc importance of plants from five wetlrtr.ltf
indicator catgones along a soil xnaisture gradient
between red maple swamps and adjacc~nt uplard
foreeta in southern Fthode Island. Wetland indicator
categories are OBL = obligatcl wetland, FACW =
facultative-wetland, PAC = facultative, FACIJ -
faculhtive-upland, and CJFL = obligate upInnd Soil
moisture categonea are W'Da = very yoorly drained
organic, Vf'b = very prly drairled rnlneral, PI3 =
in the cllnnging coxngmsit ion azid relative abunrtnncc
of krerb-layer species (Fig. 4.3). As one
migbi expect, facultative -wetla~'td(FACW) herbs
declined in abundnlrcc. whilt. facultative-uplaxid
(FACXJ) hcrbs increased along the ~~radierxt fmm
very gmrly rirninor3 to rnodcrakky well drained
soils. Obligate wetlartd (OBIJ) iserbs occurred only
in very poorly draintd soils. Ttle relative cover of
facultativt- (FAC) herbs peaked in ttte poorly
drained and somewhat ~x~,rly drained soil classes,
suggc*stirig that these plants are bst ndapkd to
moisture vo~xditinns neiw the rliiddle of the gradient
exatnix~t~ci.
A moisture-related gradient was evident in the
tree. Iaycr as wt4X (Fig. 4.3). Iteci maple (FAC) was
domirrtr~rt in ttrc wrtlaizd (VPD -PI.)) portions of
the gfradient, and stce~dily dthcliricd in abundance
irz rm upslope direction. White oak (FACU) predomix~nted
in modt~rattily well drained soils and
gcrlc~rally declixred in abu~~c.tnr~c~ z t soil ~ nioisture
increased. This sp~ci~~s wits ztearly as abundant as
red mirplc in ptx~rly drair~ed sn~ls, but decreased
sitarply in1 vc~y poorly dririned soils. 111 the shrub
l:rytbr, tilt. prcrtt al,urlrfirrwr~ of FAC species along
the entire 1cr~gtFI.h of xrlost trwrrscets pig. 4.3) obsctrrcbd
moisture-related trends in vegetation (Allen
et ~1. 1089). Facrzltntivt-1 (FAC) shrubs prcdomirtntcd
at 48 of the 54 sai~~plixlg stations. A
prcpondernncr of swoet popg,crbush throughout
tlic. moisture gradient wrts Irtrgtlly rceporisible fur
these rcsrllts.
l?le shift, irk pretilorninrult irldicat~r status of
herb layer s~>ec*fcs clrstrly sipnled the eharlge
frorrl very paorly draixlcd to lroorly dmined soils;
tiowc>vcr, the rflange frorll hydric to rtonhydric
soils, which occurred betwccrl prly druirxed and
somewtiat poorly drnirled ~tat~ians (Allen et al.
1988), was not accompa~ticxrl by a dietinct chmtgc
irk the wrtla~ld ir~dicator composit+ion csf any of the
vegetation layers (Fig. 11.3).'Rlus, precise localion
af t,hc bouxzdary of rctii rn~i~~lr~ swttrnps rrray bo
prly drained, SE) = aomcwIlat ~worly dram&, ~ n d
= maderahly well drained. Data were collected
&om thee sites (E C. Golct, unpublrshrd data).
'Psthle 4.3. Wetland indirrator ctrtc>goriccs far plant
species tht wru r in turf ka
this study should provide insight inio pattcrris of
species distribution in red maple swamps
throughout the Kortheast.
The moisture gradient, which was well defined
by topographic profiles, groundwater levels, and
soil drainage cimaes at all of the Rhodc Island
sites (Alien et a1. 1989), was most clearly roflecwd
Category cudo wetlands (96)
- -- - -- -
Obligak upland 'tSPJl, < 1
Facultative - upland FACU 2-33
F~culttrve FAG 3-66
Fhm1tatlvc.--wetlmict FACW 87-99