effect of the flood of 1993 on boltonia decurrens, a rare floodplain plant

REGULATED RIVERS: RESEARCH & MANAGEMENT

Regul. Ri6ers: Res. Mgmt. 14: 191–202 (1998)

EFFECT OF THE FLOOD OF 1993 ON BOLTONIA DECURRENS, ARARE FLOODPLAIN PLANT

MARIAN SMITHa,*, THOMAS KEEVINb, PAIGE METTLER-MCCLUREa ANDROBERT BARKAUc

a Biology Department, Southern Illinois Uni6ersity at Edwards6ille, Edwards6ille, IL 62026, USAb US Army Corps of Engineers, St. Louis District, 1222 Spruce Street, St. Louis, MO 63103, USA

c 4965 Eagle Lake Dri6e, Fort Collins, CO 80524, USA

ABSTRACT

Boltonia decurrens (Torrey and Gray) Wood (Asteraceae), a perennial species confined primarily to a 400-km stretchof the Illinois River floodplain, is threatened with extinction due to the destruction of its natural habitat.Construction of a system of levees along the Illinois River has altered flood patterns during the last 100 years,converting wet prairies and natural marshes into cropland. Remaining shore habitats have been modified by alteredflooding regimes. The flood of 1993 exceeded 100-year records on the Mississippi River, but was much less severe onthe Illinois River. A gradient of flood severity on the Illinois River, from the area of confluence with the MississippiRiver to a site 267.5 km upriver, provided an opportunity to study the effects of flooding on the vegetation at threeB. decurrens sites which experienced different flood regimes. A comparison of pre- and post-flood data (1991 and1994) revealed that the flood altered site vegetation. Species richness declined in all three study areas by an averageof 34% and species diversity declined at two sites (11% and 37%). Populations of B. decurrens increased in size at allthree locations (5-, 10- and 400-fold) following the flood, with the greatest increase occurring at the two sites whichhad the most severe flooding. The results suggest that the removal of competing species by flood waters may be animportant factor in maintaining populations of B. decurrens in the floodplain. © 1998 John Wiley & Sons, Ltd.

KEY WORDS: Boltonia decurrens ; Asteraceae; rare plants; flooding; floodplain

INTRODUCTION

Boltonia decurrens (Asteraceae), a perennial plant species endemic to the Illinois River floodplain (Torreyand Gray, 1840), is disappearing from its native habitat (Schwegman and Nyboer, 1985). In spite ofprolific seed production and ability to reproduce vegetatively (Schwegman and Nyboer, 1985), the numberof naturally-occurring populations, which fluctuates annually, continues to decline. In 1988, the US Fishand Wildlife Service placed B. decurrens on the Federal list of threatened species (US Fish and WildlifeService, 1988). It is currently listed as endangered in Missouri (Missouri Department of Conservation,1992) and threatened in Illinois (Herkert, 1991).

The open, wetland habitat suitable for B. decurrens has decreased due to extensive row-crop agriculturein the watershed and the levee system developed in the floodplain (Bellrose et al., 1983; Schwegman andNyboer, 1985; Interagency Floodplain Management Review Committee, 1994; Sparks, 1995). Many areasalong the river that once had regular cyclical flooding, with flood waters receding in late spring, are noweither under water for prolonged periods of time or are no longer flooded (Bellrose et al., 1979, 1983;Sparks, 1995). Extant populations of B. decurrens have become isolated and restricted to human-dis-turbed, alluvial soil habitats, old fields, roadsides and disturbed bottomland lake shores (US Fish andWildlife Service, 1990). Before the record flooding of the Mississippi River and its tributaries in 1993, B.

* Correspondence to: Biology Department, Southern Illinois University at Edwardsville, Room 3331, Science Bldg, Edwardsville, IL62026, USA.

Contract grant sponsor: US Army Corps of Engineers; US National Science Foundation; Illinois Department of Natural Resources,US Fish and Wildlife Service; United States Department of Agriculture (Illinois Groundwater Consortium)

CCC 0886–9375/98/020191–12$17.50© 1998 John Wiley & Sons, Ltd.

Recei6ed 29 August 1996Accepted 24 No6ember 1997

M. SMITH ET AL.192

decurrens was found in seven Illinois counties and one Missouri county and was thought to have beenextirpated from 13 counties in Illinois and three counties in Missouri (US Fish and Wildlife Service, 1990).

Mature plants of B. decurrens are from 1.5 m to 2 m tall, and flower from August through October. Asflowering plants senesce in October, basal rosettes form which overwinter and bolt and flower thefollowing year (Schwegman and Nyboer, 1985). Although B. decurrens is a prolific seed producer (ca.30000 viable seeds per plant; Smith et al., 1993), seedling establishment in the field is low and is restrictedto periods when soil is moist and light levels are high (Redmond, 1992).

Field observations of B. decurrens suggest that its proliferation is dependent upon regular floodingwhich continually recreates open, moist habitat (Schwegman and Nyboer, 1985; US Fish and WildlifeService, 1990). This inference has been supported by studies which indicate that the species is dependentupon regular disturbances which provide high light and moist soil for germination, growth and seedproduction (Smith et al., 1995), and possibly eliminate competing species (Stoecker et al., 1995).

The flood of 1993 heavily impacted the Mississippi River, exceeding 100-year flood levels, but was muchless severe on the Illinois River (US Army Corps of Engineers, 1994). Although flood levels on the lowerIllinois River, from RM 0 to RM 28, exceeded the 100-year record, flood levels approached only the25-year mark at RM 56 and became decreasingly severe along the northern reaches of the river (US ArmyCorps of Engineers, 1994). This provided an opportunity for comparisons of B. decurrens populations inareas with varying degrees of flooding.

Habitat conservation and management must be key elements in any program to minimize or reduce theexpected diminution of the world’s biotic diversity (Shaffer, 1987; Brussard et al., 1992), but to developsound management plans for threatened species, it is necessary to understand the causes for their declineand to develop a data base to help formulate possible management strategies. For wetland species suchas B. decurrens, which seem to be dependent upon flooding for persistence, an understanding of the roleof flooding in regulation of population size is critical. The present study examines the effect of floodingof different magnitude and duration on three populations of B. decurrens along the flooding gradientcreated by the 1993 flood on the Illinois River.

MATERIALS AND METHODS

Population and transect locations (Table I) identified and established in 1991 were used for the currentstudy. In summer 1991, three 20-m transects were established on each site through the area where

Table I. Location and elevation of Boltonia decurrens population study sites in Illinois

Elevation range (m)Location:CountySite name (acronym) Date surveyedRMLatitudeLongitudeDistance from river

135.95–136.64164.5Tazewell 15 August 1994Cooper Park N (CPN)40° 42% 35%% N89° 32% 13%% W0.3 km

Rice Lake (RL) Fulton 138.0 134.15–134.47 16 August 199440° 30% 05%% N89° 54% 30%% N1.2 km

8 June 1994Gilbert Lake (GL) 129.18–129.924.0Jersey38° 57% 57%% N90° 30% 51%% W0.5 km

© 1998 John Wiley & Sons, Ltd. Regul. Ri6ers: Res. Mgmt. 14: 191–202 (1998)

EFFECT OF THE FLOOD OF 1993 ON BOLTONIA DECURRENS 193

individuals of B. decurrens occurred, and all plants which touched the transect were counted. Representa-tives of each species were collected and identified at anthesis (except for B. decurrens, which was left inplace) (see Appendix A for complete list of species). Immediately after flood waters receded from eachsite, in winter 1993 or spring 1994, transects were re-established and plants were again collected andidentified. Data from both years were utilized for a comparison of the following vegetative characteristics:(1) dominant families; (2) species richness (number of species in community; Barbour et al., 1980); and (3)diversity, a product of species richness and evenness. Diversity was calculated according to the formula

H %= (3.3219) %s

i=1

(pi)(log10 pi)

where pi represents the proportion of all individuals in the sample which belong to species i (Shannon andWeaver, 1949).

In summer 1994, all study sites were surveyed and mapped using a Sokkia Set 5 Total Station, SokkiaMAP (Seiler Instruments) and AUTO-CAD Version 12.0. The highest and lowest elevations of thepopulations were compared to stage/duration curves developed for each site. Hydraulic data werecomputed from a model of the Illinois River that was developed for the Rock Island District of the USArmy Corps of Engineers in 1992. Computations were performed using the UNET program (Barkau,1995) which simulates one-dimensional unsteady flow through a network of open channels and lakes. Themodel extends from Marseilles, IL, to Grafton, IL, at the mouth of the Illinois River. Inflow data utilizedin the model are from the streamflow records of the US Geological Survey. Ungauged inflow wasestimated by multiplying the observed flow from a similar drainage basin by the ratio of the ungaugeddrainage to the gauged drainage. The model was calibrated to reproduce water year 1983 (1 October1982–31 September 1983), which includes major flood events in December 1982 and May 1983. Themodel was verified by reproducing water years 1973, 1974, 1979, and 1985. Accuracy of the model is ca.+0.15 m at the observed gaging stations. Data are given as percentage chance exceedance (PCE),indicating the probability of any given location being under water during the time period referenced. Peakflow during the year at each site is given in m3 s−1×103 and the depth of water was extrapolated fromgraphical displays created by the model. None of the three sites discussed in the present study experienceda levee failure which would have contributed to the duration or extent of the floods. Site locations arereferenced by river miles (RM), as this is the unit of measure used by the US Army Corps of Engineersin the original model and because it provides more-easily visualized positions on the river relative to thearea of confluence with the Mississippi River (RM=0) where flooding was more severe. Flood data foreach site are reported for the 1993 water year (1 October 1992–31 September 1993), and separately forthe period considered most critical for seedling emergence, establishment and growth (April, May andJune) (US Fish and Wildlife Service, 1990; Stoecker et al., 1995).

Three population sites were selected to represent the majority of the range of B. decurrens in Illinois(Figure 1 and Table I) and to compare the effects of various degrees of flooding: (1) Cooper Park North(CPN, RM 164.5), close to the northern end of the range; (2) Rice Lake (RL, RM 138.0), an intermediatepopulation; and (3) Gilbert Lake (GL, RM 4.0), at the southern end of the Illinois River. Populationcensuses (1991–1994) were taken by John Schwegman, Illinois Department of Natural Resources, andMarian Smith, SIUE, and included all flowering individuals at each site. Small populations (5250) werecounted individually; however, large populations were estimated visually or by utilizing average counts ofrandomly-placed quadrats multiplied by the total population area.

RESULTS

The sites chosen, from Cooper Park North (Tazewell County), in Peoria, IL, downstream to Gilbert Lake(Jersey County), 3 km N of Grafton, IL, span a 267.5-km stretch of the Illinois River (70% of the entirerange of extant populations) (Table I). From N to S (upstream–downstream), site elevations decreasedfrom a maximum of 136.6 m (CPN) to a minimum of 129.18 m (GL) (Table I). Within sites, elevationsvaried by 0.69 m, 0.32 m and 0.74 m at CPN, RL and GL, respectively (Table I).


M. SMITH ET AL.194

Figure 1. Map of Illinois, USA, with Boltonia decurrens study sites indicated by closed circles



Figure 2. Duration curve depicting flood stage (—) and flow (– – –) for water year 1993 for Cooper Park N, Tazewell County, IL,on the Illinois River (RM 164.5). Parallel dashed lines indicate minimum and maximum elevations of Boltonia decurrens population

Patterns of flooding were similar at CPN and RL (Figures 2 and 3), with three major peaks in floodingwhich inundated populations of B. decurrens ; however, timing differed somewhat between the two sites.At CPN, flood waters inundated the site from mid-January through mid-February, from March tomid-May, from mid-June through mid-July, and a short period during September. Peak flow and waterdepth were somewhat less at CPN compared to RL (Table II). At CPN, PCE was ca. 31% for the wateryear and 65% for the peak growing season (Table II). At RL, flood waters covered the population siteearlier in the water year (November through to mid-February), again from March until mid-May, and,except for a brief subsidance in late August, from mid-June through September. For the water year, PCEwas ca. 70% and 80% for the peak growing season (Table II). Flood pattern and timing were quitedifferent at GL (Figure 4). While there were only two major flood peaks, from April to mid-May and

Figure 3. Duration curve depicting flood stage (—) and flow (– – –) for water year 1993 for Rice Lake, Fulton County, IL, on theIllinois River (RM 138.0). Parallel dashed lines indicate minimum and maximum elevations of Boltonia decurrens population


M. SMITH ET AL.196

Table II. Flood characteristics of Boltonia decurrens study sites in 1993. Values refer to the percentage chanceof exceedance (PCE)

Site Water year 1993 (%) Growing season (%) Maximun flow (m3 s−1×103) Maximum depth(m)

CPN 30.5 65.3 1.6 1.5RL 70.1 84.0 1.8 2.7GL 43.5 80.2 3.9 5.5

Figure 4. Duration curve depicting flood stage (—) and flow (– – –) for water year 1993 for Gilbert Lake, Jersey County, IL, onthe Illinois River (RM 4.0). Parallel dashed lines indicate minimum and maximum elevations of Boltonia decurrens population

from mid-June through to September, peak flow (3.9 m3 s−1×103) and depth of flood waters (5.5 m)were much greater (Table II) than at either CPN or RL. The period of inundation for the water year, PCEof ca. 44%, was intermediate between CPN and RL, and the period of flooding during the growing seasonwas almost equal to that at RL (Table II).

A comparison of pre- and post-flood population sizes at the study sites (Table III) reveals that B.decurrens at CPN was much less affected by the 1993 flood (population size remained relatively steadyfrom 1991 to 1994). Populations at RL and GL, however, which were virtually destroyed in 1993,experienced a large increase in size. Although the number of plants of B. decurrens existing in 1994 wasgreater at RL (50000) compared to GL (20000), the percentage increase was ca. the same at the two sitesfrom 1991 to 1994 (Table III) and greater at GL from 1992 to 1994 (Table III).

In terms of dominant families, vegetation composition at the three sites was altered only slightlyfollowing the flood of 1993 (Table IV). The Asteraceae, of which B. decurrens is a member, was one ofthree dominant families at all sites in 1991, but was replaced by the Primulaceae as a dominantcomponent of the vegetation at CPN in 1994. At RL, the Cyperaceae and Brassicaceae were replaced in1994 by Scrophulariaceae and Malvaceae, but the Asteraceae remained by far the most abundant familyat the site (70%). At GL, the greatest change was an increase in Cyperaceae (from 25 to 78%) and the lossof Verbenaceae from the site. Although relative frequency of the Asteraceae was reduced from 26% to15% at GL, the family’s ranking remained the same (Second).

Species diversity declined (Table IV) at two of the three sites from 1991 to 1994, with greater reductionat GL (37%) than at CPN (11%). Diversity was virtually unchanged at RL. The changes in speciesrichness showed a similar pattern: greater reduction at GL (55%) than at CPN (33%), and a slight increaseat RL (13%) (Table IV).



DISCUSSION

The Illinois River, a component of the Upper Mississippi River System, has suffered severe degradationof habitat as a result of 100 years of human activity (Bellrose et al., 1983; Mattingly et al., 1993). Thenatural regime of regular, moderate flooding (Belt, 1977; Sparks, 1995) has been severely disrupted byflood management efforts that have leveed and channelized the river. Flooding as an integral, beneficialpart of natural river ecosystems is best expressed by the ‘flood-pulse’ concept, which identifies thepredictable advance and retraction of water on the floodplain as the principal agent controlling theadaptations of the biota (Bayley, 1991, 1995; Junk et al., 1989; Sparks, 1995). Flood pulses are, therefore,not to be considered disturbances of the regime, but the natural order (Bayley, 1991, 1995). Floodprevention, conversely, is a disturbance. This principle helps explain the threatened and endangered statusof many floodplain species which have evolved to require the regular flood events natural to the system(Bellrose et al., 1983; Sparks, 1995).

The threatened status of B. decurrens, an endemic of Illinois River wetlands, is an excellent example ofthe consequences of disruption of the natural flooding regime for species adapted to dynamic, riverinehabitats. Boltonia decurrens thrives in hypoxic soils (Stoecker et al., 1995); has morphological andlife-history characteristics that enhance seed production, germination and dispersal in an intermittently-flooded habitat (Smith et al., 1993; Smith et al. 1995); and, in the absence of flooding, is a poorcompetitor with other early successional plants (Schwegman and Nyboer, 1985; US Fish and WildlifeService, 1990).

Analysis of effects of the flood of 1993 on the sites discussed in this study supports the hypothesis thatB. decurrens benefits from flood events. Although flood timing and duration varied among sites, and effectof the flood on B. decurrens was much more pronounced at RL and GL, compared to CPN, populationsize increased at every study site. By all measures of flooding—duration, depth and flow—the two sitesthat had the most severe flooding had the greatest increases in flowering individuals of B. decurrens from1992 to 1994.

Table III. Size of Boltonia decurrens populations, 1991–1994

Number of flowering individuals (date censused)

60 (15 August 1991) 20 (17 September 1992)CPN 104 (9 August 1994)25 (14 September 1993)RL 50 000 (9 August 1994)2000 (15 August 1991) 5000 (17 September 1992) 1 (14 September 1993)

0 (14 September 1993) 20 000 (9 August 1994)750 (15 August 1991)GL 50 (14 September 1992)

When population size exceeds 250 flowering individuals, accuracy is 910%.

Table IV. Comparison of pre- (1991) and post-flood (1994) vegetation at Boltonia decurrens study sites

Richness 1991, 1994Dominant families Diversity 1991, 1994Site(% change) (% change)(% representation on transects)

Year

19941991

CPN Verbenaceae (32) Cyperaceae (28) 1.94, 1.72 (11.3) 15, 10 (33.3)Asteraceae (29) Verbenaceae (24)Cyperaceae (26) Primulaceae (21)

RL Asteraceae (66) Asteraceae (70) 1.26, 1.27 (0.0) 7, 8 (12.5)Cyperaceae (21) Scrophulariaceae (10)

Malvaceae (9)Brassicaceae (12)

Cyperaceae (78)Verbenaceae (28) 22, 10 (54.5)GL 2.27, 1.43 (37.0)Asteraceae (26) Asteraceae (15)Cyperaceae (25) Poaceae (3)


M. SMITH ET AL.198

Populations at RL and GL were virtually eliminated by the 1993 flood, but rebounded withestablishment of thousands of seedlings which flowered in fall 1994. Site inspections throughout autumn1993 revealed that there were no surviving vegetative individuals at either RL or GL, but thousands ofseedlings were observed on the wet mudflats in February 1994 (Smith, personal observation). Soil corestaken in 1991 and 1993 showed a large seed bank (Smith, 1993), but until the sites were flooded, fewseedlings were observed. This is consistent with earlier studies indicating that seeds of B. decurrens do notgerminate unless they are exposed to light (Baskin and Baskin, 1988; Smith et al., 1993, 1995).

Although the net effect of the flood on Boltonia decurrens populations at RL and GL were similar, therewere obvious differences in the nature of the flood at the two sites. Duration of flooding at RL was muchlonger (ca. 69% longer), but intensity, as shown by water depth and flow, was greater at GL. Vegetativerosettes, from which B. decurrens often produces much of the following year’s population, are extremelyflood-tolerant (Stoecker et al., 1995). In 1990, rosettes in a flooded borrow pit at Lock and Dam 26 (onthe Mississippi River near Alton, IL) bolted and flowered after four months of inundation by groundwater (Smith and Keevin, personal observation). Loss of all vegetative plants at both RL and GL in 1993indicates that conditions were more severe than those observed in 1990.

At RL, the population was first flooded in November, 1992, and for almost nine of the following 12months, but the flood was quite moderate in terms of depth of water and flow. Rosettes which arenormally produced at the base of senescing plants from October to December may have failed to form orthe turbidity of the flood water may have prevented photosynthesis and vegetative growth (Smith et al.,1993). At GL, where flooding began in April and persisted for no more than 4 months, rosettes had beenobserved in November, 1992 (Smith, 1993); however, flood waters were extremely deep (5.5 m). This site,at RM 4, is in the area which experienced influx from the flooding Mississippi River (US Army Corps ofEngineers, 1994), so it is possible that the water was also more turbid than at either CPN (RM 164.5) orRL (RM 138) and exacerbated the effects of inundation.

The site with the least severe flooding, CPN, has had a small, slowly-declining population of B.decurrens since 1991, and although it increased from 20 to 104 flowering individuals following the 1993flood, the population remains very small. The area adjacent the B. decurrens population has beencolonized by woody species and the 1993 flood was not severe enough to result in much tree mortality atthis site. In 1991, only one tree species (Acer saccharinum L., Appendix A) was present in the transectssampled in this study and none was present in 1994; however, trees to the south of the population shadethe area in the early morning and late afternoon. It is possible that if flooding were more frequent, ormore severe, and the trees had been submerged as seedlings or young saplings, higher mortality wouldhave kept the entire area cleared of woody species. This is supported by the observation that the few treeswhich were present at GL and RL in 1991 (Appendix A), were apparently eliminated by the flood of 1993.Trees have a negative effect on B. decurrens which requires full sunlight for optimal growth and seedproduction (Smith et al., 1993). Unless the growth of woody species is retarded at CPN, it is unlikely thatthis population will persist.

A comparison of pre- and post-flood data at CPN indicates that the Asteraceae, which had been astrong component of the 1991 community (29%), had disappeared. Other members of the Asteraceae,which often occur at B. decurrens ’ sites, may also be dependent upon adequate flooding to eliminatecompetitors. Aster pilosus Willd. and Aster ontarionis Wieg. which were present at CPN in 1991 (Smith,personal observation), and which occur at RL and GL, are extremely flood-tolerant (Smith, unpublisheddata) and may also be adapted to the same flood regime as B. decurrens. At RL and GL, the Asteraceaeremained relatively unchanged with respect to other dominant families from 1991 to 1994, retaining theirrespective first and second place rankings at the two sites. At both sites, distribution among the threedominant families became much more uneven compared to CPN. It is impossible to say whether thiseffect is associated with differences in flood severity.

Although there is no consensus concerning the interpretation of diversity, diversity generally increasesduring the early stages of secondary succession (Odum, 1969; Barbour et al., 1980) and is often positivelycorrelated with an increase in richness (the number of species in a community) (Barbour et al., 1980).There are many exceptions to these generalities; however, these relationships have been reported for



riparian communities in large river systems (Klein et al., 1975; Kalliola and Puhakka, 1988; Puhakka etal., 1992). Overall, the 1993 flood had a negative effect on diversity and richness at the sites in the presentstudy, and this was correlated with larger populations of B. decurrens. The greatest decrease in diversityand richness occurred at GL which had the greatest percent increase in the number of individuals of B.decurrens (Tables III and IV). The site which consistently had the largest population of B. decurrens, RL,had lower absolute values of diversity and richness (Tables III and IV) than either GL or CPN. The twosites which had population booms following the 1993 flood, RL and GL, were flooded for a largepercentage of the growing season (84.0% and 80.2%, respectively) and produced no flowering plants fromwhich to re-establish after the flood.

Following a major disturbance which completely eliminates flowering individuals, recolonizationdepends upon a large influx of seeds from a nearby source (Egler, 1954) or a substantial soil seed bank(Archibold, 1978) which enable plant species to re-establish quickly and dominate the early vegetationalcommunity (Egler, 1954). In the absence of seed production from native species, riparian habitats may beinvaded by exotics (Decamps et al., 1995). Disruptions in the natural hydrologic cycle have the potentialto disrupt seed production and dispersal of native herbaceous species, reducing the contribution of thenative species to the seed bank (Decamps et al., 1995). In the absence of seed production, recolonizationof the site by native plants is dependent upon an influx of seeds from nearby populations. In the case ofB. decurrens, the disruption of seed production has become particularly problematic: populations whichwere once contiguous are now isolated (Schwegman and Nyboer, 1985; US Fish and Wildlife Service,1990), thus reducing the potential for recolonization of a destroyed site by an influx of seeds fromneighboring populations. A significant influx of seeds would be limited to years with extreme hydrologicevents such as occurred in 1993. As seeds of B. decurrens float for long periods of time (Stoecker et al.,1995), widespread flooding in 1993 may have provided an influx of seeds to the study sites, or seeds of B.decurrens which were in the soil germinated, or both.

Whatever the seed source, the decrease in species diversity and richness at study sites immediatelyfollowing the 1993 flood indicates that competition with seedlings of B. decurrens by other species wasreduced. It has been observed that species richness and diversity are often low where B. decurrens is adominant member of the vegetation (Redmond, 1992). As succession progresses at a site following adisturbance, the number of individuals of B. decurrens declines (US Fish and Wildlife Service, 1990). Itis clear that the removal of competing species, as occurred in 1993, benefits B. decurrens.

Anthropogenic influences on river systems are pervasive worldwide and are accompanied by degrada-tion of riparian habitats (Lean et al., 1990; L’ovitch et al., 1990; Mattingly et al., 1993). There is consensusthat this is the case in the Illinois River floodplain (Bellrose et al., 1983; Interagency FloodplainManagement Review Committee, 1994; Mattingly et al., 1993), and system-wide studies are needed todetermine the extent of the damage and to suggest effective mitigation. Because B. decurrens is adaptedto the dynamic floodplain system, the protection of specific populations from disturbance is not sufficientto ensure its survival. Discing, burning or mowing are possible substitutions for the natural disturbanceprovided by regular flooding, but before any prediction of long-term survival is possible, it is necessaryto understand more about the inter-population dynamics of the species. If B. decurrens and otherthreatened floodplain endemics are studied in the context of the entire river system, rather than as isolatedentities, they may have value as indicator species by which the integrity of the whole system can bemeasured.

ACKNOWLEDGEMENTS

The authors thank Scott Moss, Department of Biology, Southern Illinois University at Edwardsville(SIUE), and John Schwegman, Illinois Department of Natural Resources for their help in collecting thedata for this paper; and Dr Luke Snell, Department of Construction, SIUE, for the use of the surveyingequipment. This work was supported by funds from the US Army Corps of Engineers and grants to MSfrom the US National Science Foundation, Illinois Department of Natural Resources, US Fish andWildlife Service, and United States Department of Agriculture (Illinois Groundwater Consortium).


M. SMITH ET AL.200

APPENDIX A. SPECIES SAMPLED AT STUDY SITES DURING 1991 AND 1994

1991 1994

Species Frequency Species Frequency

Cooper ParkPhyla lanceolata Michx. 0.31 Eleocharis cal6a Torr. 0.27Cyperus strigosus L. 0.16 Phyla lanceolata (Michx.) Greene 0.23Helenium autumnale L. 0.16 Lysimachia nummularia L. 0.20Eupatorium serotinum Michx. 0.10 Veronica peregrina L. 0.14Eleocharis cal6a Torr. 0.09 Aster lanceolatus Willd. 0.09Mimulus ringens L. 0.06 Medicago lupulina L. 0.03Rorippa sinuata (Nutt.) Hitchc. 0.03 Agropyron repens (L.) Beauv. 0.01Acer saccharinum L.a 0.02 Boltonia decurrens (Torr. and Gray) 0.01Asclepias incarnata L. 0.01 Wood

0.01Helenium autumnale L.Boltonia decurrens (Torr. and Gray) 0.01Wood 0.01Plantago major L.Hibiscus lasiocarpos Cav. 0.01Lythrum alatum Pursh 0.01Lobelia cardinalis L. 0.01Physostegia 6irginiana (L.) Benth. 0.01Teucrium canadense L. 0.01

Gilbert LakePhyla lanceolata Michx. 0.27

0.77Cyperus strigosus L. Eleocharis cal6a Torr.0.14Boltonia decurrens (Torr. and Gray) 0.12Aster spp. 0.12WoodCyperus spp. 0.10Cassia fasciculata Michx. 0.020.07 0.02Desmanthus illinoensis (Michx.)

MacM. I6a annua L. 0.02Leersia oryzoides (L.) Sw.I6a annua L. 0.06 0.02Ammania coccinea Rottb.Lycopus americanus Muhl. 0.03 0.01Lindernia dubia (L.) Pennell var.Boltonia decurrens (Torr. and Gray) 0.010.03

Wood dubiaPolygonum lapthifolium L.Xanthium strumarium L. 0.03 0.01

Leersia oryzoides (L.) Sw. Polygonum punctatum Ell.0.02 0.01Asclepias incarnata L. 0.01 Ranunculus aborti6us L. 0.01Cassia fasciculata Michx. 0.01Cephalantus occidentalis L. 0.01Eupatorium serotinum Michx. 0.01Ipomoea lacunosa L. 0.01Lobelia cardinalis L. 0.01Lythrum alatum Pursh 0.01Physostegia 6irginiana (L.) Benth. 0.01Populus deltoidesa Marsh. 0.01Sagittaria latifolia Willd. 0.01Salix interior Rowleea 0.01



Appendix A (continued)

1991 1994

Species Frequency Species Frequency

Rice LakeAster ontarionis Wieg. 0.51 Xanthium spinosum L. 0.57Cyperus spp. 0.21 Boltonia decurrens (Torr. and Gray) 0.13

WoodBoltonia decurrens (Torr. and Gray) 0.15Abutilon theophrastii Medic. 0.09Wood

Rorippa sinuata (Nutt.) Hitchc. 0.12 Lindernia dubia (L.) Pennell var. 0.07Acer saccharinuma L. 0.01 dubia

0.07Campis radicans (L.) Seem. Polygonum pennsyl6anicum L.0.010.04Eleocharis cal6a Torr. 0.01 Amaranthus hybridus L.0.01Veronica peregrina L. Gratiola neglecta Torr.0.01

a Tree species.

REFERENCES

Archibold, O.W. 1978. ‘Buried viable propagules as a factor in postfire regeneration in northern Saskatchewan’, Can. J. Bot., 57,54–58.

Barbour, M.G., Burk, J.H., and Pitts, W.D. 1980. Terrestrial Plant Ecology. The Benjamin/Cummings Publishing Company, MenloPark, CA. p. 140.

Barkau, R.L. 1995. UNET: One-dimensional Unsteady Flow Through a Full Network of Open Channels. Version 3.0. US Army Corpsof Engineers, Hydrologic Engineering Center, Davis, CA.

Baskin, C.C. and Baskin, J.M. 1988. ‘Germination ecophysiology of herbaceous plant species in a temperate region’, Am. J. Bot.,75, 286–305.

Bayley, P.B. 1991. ‘The flood pulse advantage and the restoration of river–floodplain systems’, Regul. Ri6ers: Res. Mgmt, 6, 75–86.Bayley, P.B. 1995. ‘Understanding large river–floodplain ecosystems’, Bioscience, 45, 153–158.Belt, C.B. Jr. 1977. ‘The 1973 flood and man’s constriction of the Mississippi River’, Science, 189, 681–684.Bellrose, F.C., Paveglio, F.L. Jr., and Steffeck, D.W. 1979. ‘Waterfowl and the changing environment of the Illinois River Valley’,

Ill. Nat. Hist. Sur6. Biol. Notes, 32, 4–6.Bellrose, F.C., Havera, S.P., Paveglio, F.L. Jr., and Steffeck, D.W. 1983. ‘The fate of the lakes in the Illinois River Valley’, Ill. Nat.

Hist. Sur6. Biol. Notes, 119, 9–12.Brussard, P.F., Murphy, D.D., and Noss, R.F. 1992. ‘Strategy and tactics for conserving biological diversity in the United States.

Editorial’, Conser6. Biol., 6, 157–159.Decamps, H., Planty-Tabachi, A.M., and Tabachi, E. 1995. ‘Changes in the hydrological regime and invasions by plant species

along riparian systems of the Adour River, France’, Regul. Ri6ers: Res. Mgmt, 11, 23–34.Egler, F.E. 1954. ‘Vegetation science concepts. I. Initial floristic composition, a factor in old-field vegetation development’,

Vegetatio, 4, 412–417.Herkert, J.R. (Ed.) 1991. Endangered and Threatened Species of Illinois: Status and Distribution, 1. Illinois Endangered Species

Protection Board, Springfield, IL. p. 13.Interagency Floodplain Management Review Committee 1994. Sharing the challenge: Floodplain management into the 21st Century,

Report of the Interagency Floodplain Management Review Committee to the Administration Floodplain Management TaskForce. US Government Printing Office, Washington, DC. p. 85.

Junk, W.J., Bayley, P., and Sparks, R.E. 1989. ‘The flood pulse concept in river floodplain systems’, Can. Spec. Publ. Fish. Aquat.Sci., 106, 110–127.

Kalliola, R. and Puhakka, M. 1988. ‘River dynamics and vegetation mosaicism: a case study of the River Kamajohka, northernmostFinland’, J. Biogeogr., 15, 703–719.

Klein, W.M., Daley, R.H. and Wedum, J. 1975. En6ironmental In6entory and Assessment of Na6igation Pools 24, 25, and 26 UpperMississippi and Lower Illinois Ri6ers: A Vegetational Study. Missouri Botanical Gardens, St. Louis, MO. p. 5.

Lean, G., Hinrichsen, D., and Markham, A. 1990. Atlas of the En6ironment. Arrow Books and WWF for Nature, London.194 pp.


M. SMITH ET AL.202

L’ovitch, M.I., White, G.F., Belyaev, A.V., Kindle, J., Koronkevic, N.I., Lee, T.R., and Voropaev, G.V. 1990. ‘Use andtransformation of terrestrial water systems’, in Turner, B.L., Clark, W.C., Kates, R.W., Richards, J.F., Mathews, J.T., and Meyer,W.B. (Eds), The Earth as Transformed by Human Action. Cambridge University Press, Cambridge, UK. pp. 235–252.

Mattingly, R.L., Herricks, E.E., and Johnston, D.M. 1993. ‘Channelization and levee construction in Illinois: review andimplications for management’, J. En6iron. Mgmt, 17, 781–795.

Missouri Department of Conservation 1992. Rare and Endangered Species of Missouri Checklist. Jefferson City, MO. p. 12.Odum, E.P. 1969. ‘The strategy of ecosystem development’, Science, 164, 262–270.Puhakka, M., Kalliola, R., Rajasilta, M., and Salo, J. 1992. ‘River types, site evolution and successional vegetation patterns in

Peruvian Amazonia’, J. Biogeogr., 19, 651–665.Redmond, A. 1992. ‘Population study of Boltonia decurrens, a federally threatened plant species’, MSc Thesis, Southern Illinois

University at Edwardsville, Edwardsville, IL.Shaffer, M.L. 1987. ‘Minimum viable populations: coping with uncertainty’, in Soule, M.E. (Ed.), Viable Populations for

Conser6ation. Cambridge University Press, Cambridge, UK. pp. 69–86.Shannon, C.E. and Weaver, W. 1949. The Mathematical Theory of Communication. University of Illinois Press, Urbana, IL. 139 pp.Schwegman, J.E. and Nyboer, R.W. 1985. ‘The taxonomic and population status of Boltonia decurrens (Torr. and Gray) Wood’,

Castanea, 50, 112–115.Smith, M. 1993. ‘Effects of the flood of 1993 on the decurrent false aster (Boltonia decurrens)’, Report to the US Army Corps of

Engineers, St. Louis, MO. 10 pp.Smith, M., Wu, Y., and Green. O. 1993. ‘Effect of light and water-stress on photosynthesis and biomass production in Boltonia

decurrens (Asteraceae), a threatened species’, Am. J. Bot., 80, 854–864.Smith, M., Brandt, T., and Stone, J. 1995. ‘Effect of soil texture and microtopography on germination and seedling growth in

Boltonia decurrens (Asteraceae), a threatened floodplain species’, Wetlands, 15, 392–396.Sparks, R.E. 1995. ‘Need for ecosystem management of large rivers and their floodplains’, BioScience, 45, 168–182.Stoecker, M.A., Smith, M., and Melton, E.D. 1995. ‘Survival and aerenchyma development under flooded conditions of Boltonia

decurrens, a threatened floodplain species and Conyza canadensis, a widely distributed competitor’, Am. Midl. Nat., 134, 117–126.Torrey, J. and Gray, A. 1840. The Flora of North America. Wiley and Putnam, New York, NY. p. 188.US Army Corps of Engineers 1994. The great flood of 1993, post-flood report, Appendix C, Upper Mississippi Ri6er Basin. St. Louis

District, St. Louis, MO. p. 62.US Fish and Wildlife Service 1988. ‘Endangered and threatened wildlife and plants, determination of threatened status for Boltonia

decurrens (decurrent false aster)’, Fed. Regist., 53, 45858–45861.US Fish and Wildlife Service 1990. Decurrent False Aster Reco6ery Plan. US Fish and Wildlife Service, Twin Cities, MN. 26 pp.


effect of the flood of 1993 on boltonia decurrens, a rare floodplain plant

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