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ABSTRACT: We examined the seed ecology of longisepala as an aid to developing a conserva- tion strategy for this rare endemic forb of northcentral Washington. We conducted field, greenhouse, and laboratory studies to quantify: (1) densities of buried viable seed among sites with different histories of burning, (2) post-fire spatial distributions of germinants relative to reproductive and bum se- verity, (3) seed production and its annual variation, and (4) requirements. Density of seed in the soil was not significantly related to history of burning, but sites that experienced fire 10 years before sampling averaged 10 times as many seeds as sites that burned recently and four times as many seeds as sites that had not burned within 50 years. Density of viable seeds in the soil did not correlate The Seed Ecology of with density of reproductive plants. In a field experiment, germinants appeared after fall burning, but not after spring burning. Germinants were most abundant within 10 m of reproductive plants and were concentrated in areas of high bum severity. Seed production per was significantly correlated to na lor crown diameter, but production varied dramatically from year to year. Experimental germination trials were largely unsuccessful due to low (8%) viability of seeds collected from mature plants. However, (Torr.) Wiggins, field studies illustrate that fire is sufficient to break the dormancy of seeds that have accumulated in the soil. Long-term exclusion of fire may lead to local extinction of populations as the longevity of reproductive plants and seeds are exceeded. However, burning more frequently than every 10 years -- East Cascade could deplete local seed reserves.

Index tern: fire effects, prescribed burning, rare plant, seed ecology

Richy J. Harrodl INTRODUCTION 1940, Pickett and McDomell 1989). As a result, a species that is relatively rare in ( Wenatchet: National Forests Effective conservation of a rare plant the aboveground community may become 215 Melaiy Lane requires an understanding of how habitat dominant after disturbance. We suspected tchee, WA 98801 U$iA requirements, life history, and responses to that I. longisepala maintains a viable seed disturbance shape the population dynamics bank because it has limited dispersal ability Charles B. Halpern of a species (Menges 1986, Schemske et and plant density increases markedly after College of Forest Resources al. 1994). For some rare species, fire may fire (Kuhlmann and Harrod, unpubl. data). Box 35: determine population patterns in space However, knowledge of the frequency of and time. This appears to be the case with disturbance and the ability of I. longisepala ~ersityof 1 , WA 9811 Iliamna longisepala (Tom.) Wiggins (Mal- to develop a seed bank between disturbance vaceae), an endemic herb of northcentral events may be important for understanding Washington. Prior to initiating this work, its population dynamics. our observations suggested a strong, posi- tive effect of wildland fire on the density Fire exclusion has greatly modified his- and vigor of I. bngisepala populations torical patterns of disturbance in dry, (Kuhlmann and Harrod, unpubl. data). ponderosa pine ( Dougl.) Managers have expressed interest in using and Douglas-fir (Pseudotsuga menziesii prescribed fire as a tool to maintain or en- (Mirbel) Franco) forests in the eastern hance populations, but informed decisions Cascade Range, from a regime of frequent, are limited by a paucity of information on low severity fire, to one of infrequent, high the effects of fire. In this paper, we report severity fire (Agee 1994, Everett et al. 2000). on four studies that explore various aspects For I. longisepala, these changes may have of the seed ecology of I. longisepala. These important consequences for the density and contribute to a broader set of experiments persistence of viable seed and ultimately (Harrod 2003) that address the popula- for conservation of the species. The first tion dynamics and possible conservation of our four studies explores the density strategies for this apparent fire-dependent of I. longisepala seed in the soil and how species. it relates to disturbance history and to the abundance of mature, flowering plants. We Corresponding author: Plant species can survive in frequently compare the density of buried viable seed rharrodG3fs.fed.u~;599-664-9331 disturbed environments by forming a among sites that have burned at different persistent seed bank (Cohen 1966). There times in the past and that support different may not be a strong correlation between densities of reproductive plants. Natural Areas Jouml25:246256 plant abundance and density of viable seed in the soil (Oosting and Humphreys Numerous factors can influence the spatial

246 Natural Areas Journal Volume 25 (3), 2005 distributions of buried seeds and how they longisepala have the potential to produce nary observations suggest that seeds of I. respond to disturbance. For many species, large numbers of seeds, we have observed longisepah require fire to break dormancy seeds are often aggregated in the soil considerable annual variability in fruit (Kuhlmann and Harrod, unpubl. data), but (Baskin and Baskin 1998). For species with production. This year-to-year variation its particular germination requirements limited dispersal, seeds are often found in may reflect annual weather patterns (Coffin have not been identified definitively. In close proximity to parent plants (Major and Lauenroth 1992) or other processes. our final study, we compare germination and Qott 1966, Edwards and Whelan Our third study explores the relationship rates among combinations of treatments 1995). Post-fire recruitment may reflect between seed production and plant mor- that vary temperature, duration of heating, these initial distributions, but it may also phological traits (e.g., number of stems, presence of ash, andlor depth of seed burial be influenced by patterns of heating dur- plant height, or crown width) and docu- within the soil. ing fire (Davis et al. 1989). The second of ments annual variation in seed production our four studies examines the distribution within plants. of I. longisepala germinants relative to STUDY AREA AND SPECIES DESCRIPTION reproductive plants and to variation in fire A seed bank strategy-. requires- that seeds severity during experimental burning. remain dormant, but germinate in response Historically, our study area was character- to an environmental cue such as heating ized by a high-frequency, low-severity fire Seed production is fundamental to main- during fire (Harper 1977, Baskin and Baskin regime that maintained an open, park-like taining or replenishing the seed bank after 1998) or leachates from charred wood, ash, forest dominated by I! ponderosa (Agee fire-induced germination or mortality. Seed or smoke (Keeley et al. 1985). Effects of fire 1993, 1994). However, after decades of production tends to vary with plant size on seed germination have been studied in fire exclusion, some forests were burned ' and vigor (Kelly 1984, Harrod et al. 1997). a number of common species (Baskin and by intense, stand-replacing wildfires. We Thus, if seed production can be estimated Baskin 1998), and fire-mediated germina- selected 10 sites representing three distur- from easily measured plant morphological tion has been inferred for three congers of l. bance histories (Table 1) for our studies. traits, it may be possible for managers to longisepala -I. rivularis (Dougl.) Greene, Wildland fire burned three sites in 1994 and predict when seed banks of fire-dependent I. remota Greene, and I. corei (Sherff) four sites in 1988. Where populations of species have been sufficiently augmented SherfT (Brown and DeByle 1989, Steele I. longisepala were present in these areas, for prescribed fire to stimulate popula- and Geier-Hayes 1989, Williams et al. plant density tends to be high. The remain- tion growth. Although mature plants of I. 1992, Baskin and Baskin 1997). Prelirni-

Table 1. Burn history (year of most rant fire), plant amciation, density of I. longiseph plants, and physical chmacteristies of tbe stndy sites.

Most recent fire Plant IIiamna density Elevation Aspect Slope Soil Study site (Year)" associationb (no. m") (m) (deg) (%) texturec Mad River 1994 1 1.24 515 190 35 LS Potato Creek 1994 1 0.52 515 240 10 GFSL Turnwater Mtn. 1994 1 1.44 800 135 35 SL Burch Mtn. 1988 2 1.6 1135 105 25 SSL Mills Canyon 1988 2 0.14 605 70 70 SSL Swakane Canyon 1988 3 0.12 725 200 35 SSL Rattlesnake Spr. 1988 3 1.12 1350 150 40 SFSL Deer Park Spr. - 3 0.12 1210 135 45 LS Red Hill - 4 0.04 725 90 60 SL Mission Creek - 4 0.1 545 200 30 SL

a Dash (-) indicates no fire in the last 50 yr. b Plant associations according to Lillybridge et al. (1995): 1 = Pseudotsuga menziesii /Symphoricarpos albus / Calamagrostis rubescens ,2 = Pinus ponderosa / Agropyron spicatum ,3 = Pseudotsuga menziesii / Calamagrostis rubescens / Agropyron spicatum, 4 = Pinus ponderosa / Purshia tridentata / Agro~ronspicatum . LS = loamy skeletal (<25% rocks in profile), GFSL = gravelly fine sandy loam, SL = sandy loam, SSL = stoney sandy loam, SFSL = stoney fine sandy loam (USDA 1995).

Volume 25 (3), 2005 Natural Areas Journal 247 ing three sites had not experienced wildfire All sites lie on the eastern slope of the in Douglas County), and west to about in the recent past (>50 yr); here densities Cascade Range within the Wenatchee and Lake Wenatchee. Nearly all locations are of I. longisepala are comparatively low. Entiat River watersheds in the Okanogan- on public lands administered by the U.S. Sites burned in 1994 and 1988 had little Wenatchee National Forests, Washington Forest Service. residual overstory cover and were domi- (Figure 1). Elevations range from 515 to nated by Ceamthus velutinus Dougl. and 1360 m, aspects are generally southerly, Iliamna longisepala is a long-lived herba- various grass species (Agrvpyron spicaturn and slopes are (70%. Soils are sandy to ceous, tap-rooted perennial that can reach (Pursh) Scribn. & Smith, Calamagmstis loamy (Table 1). The climate is continental a height of 1-2 m. Leaves are maple-like, rubescens Buck]., and Bmus tectorwn due to the rain shadow produced by the broadly cordate, and 5-7 lobed (~itchcodk L.). Unburned sites were dominated Cascade Mountains; annual precipitation et al. 1969). Plants have dark pink flowers by an overstory of ?! ponderosa and ?! averages dOcm and occurs mostly in the which produce an average of -30 hard menziesii and C. rubescens and Purshia form of snow (Lillybridge et al. 1995). coated seeds per fruit (Kuhlmann and Har- tridentata (Pursh) DC were abundant in rod, unpubl. data). The species appears to the understory. All sites belong to the I! Iliamna longisepala is considered a sensi- depend on out-crossing (mean of 1.8 vs. menziesii forest series and represent hot, tive species in Washington State and has 23.6 seeddfruit in selfed vs. out-crossed dry-shrub or cool, dry-grass plant associa- a global rank of imperiled by The Nature plants, respectively; Harrod, unpubl. data). tions (Lillybridge et al. 1995) (Table 1). Conservancy (WNHP 1997). It occurs from Plants are typically found in upland sites Plant nomenclature follows Hitchcock and just south of Lake Chelan to near Liberty, dominated by perennial herbs and grasses Cronquist (1973). east to the Columbia River (a few popu- with a scattered overstory off! ponderosa lations occur east of the Columbia River or ?! menziesii.In some locations, plants oc-

Fotatmcmek

WASHINGTON

Figure 1. Locations of the study sites. See -lo 1 for details

248 Natural Areas Journal Volume 25 (3), 2005 cur on road-cut banks or old skid trails. during fire (Baskin and Baskin 1997). groups of plants (Figure 2). One plot was Specifically, a drying oven was preheated burned in October 1998 (fall burn) and METHODS to 200°C; each sample was then heated in one in May 1999 (spring bum). Seedling a ceramic dish for -20 min, at which point emergence was monitored between May the temperature at 1 cm depth was - 100°C. and August 1999. We recorded seedling Study 1. Soil Seed Bank Density Heated samples were randomly assigned to presence and distance to the nearest repro- germination flats in the greenhouse on 26 ductive plant, and mapped areas of higher To quantify the density of buried viable January 1999, and observed until 25 May bum severity, where surface vegetation and seed in the soil and its relationship to dis- 1999. Because of limited greenhouse space, the duff layer were consumed, exposing turbance history, we used both the seedling we used 335 randomly selected samples of mineral soil. emergence method (Simpson et al. 1989, the original 450. Gross 1990) and direct seed counts. Direct Study 3. Seed Production counts were made because few seedlings Seedling emergence was again low; and in emerged from untreated or heated soils April 1999, a second set of soil samples In this study, we examined relationships (see below). was collected from sites representing the between seed production and plant size three bum histories. A 5-m x 5-m plot was and morphological traits, and documented Between 27 March and 10 May 1998, soils divided into 1-m x 1-m subplots near the annual variation in seed production within were collected from nine sites represent- center of each I. longisepala population plants. On 10 June 1999 (prior to anthe- ing the three histories of burning: bumed and an 11-cmdeep sample was collected sis), 25 plants were selected at random in 1994, burned in 1988, or not recently with a bulb planter (as above) from each from one population at Swakane Canyon burned (Table 1). Sites were randomly subplot (yielding 25 samples per site).The (Figure 1). For each plant, we recorded selected from a larger pool of sites that number of flowering plants in each sub- number of stems, number of flowering met the following criteria: supporting ex- plot was also recorded. In the laboratory, stems, total plant height, crown diameter tant populations of I. longisepah with at I. longisepala seeds were sifted from the (broadest dimension), and total number of least one flowering individual, located in soil and counted. a relatively undisturbed plant community flowers (on 8 July 1999).Weestimated seed production from a subsample of flowers (no roads or skid trails), and <1 km from A single-factor analysis of variance on each plant. Ten fruits from each plant a road. Near the center of the population (ANOVA) was used to compare mean seed were collected prior to dehiscence on 17-18 at each site, we established a 10-m x 10-m densities (determined from direct seed August 1999 and the number of seeds per plot, grided into 100, 1-m x 1-m subplots. counts) among sites with different bum fruit was counted. The number of seeds per Soil samples were collected from the cen- histories (n = 3); means were considered plant was estimated from the mean number ters of 50 randomly selected subplots per significantly different at P 5 0.05. Tests of seeds per fruit and the total number of plot (yielding a total of 450 total samples) for normality and homogeneity of vari- flowers per plant. The same measurements using a bulb planter (surface area of 23.8 ance indicated that data transformation were taken on the same plants one year cm2) that removed an 11-cm-deep core was not necessary. A Pearson's correlation later (5 July 2000), and seed production (litter plus soil). Samples were bagged coefficient was computed to assess the was assessed on 14-15 August. individually and stored in a cooler for 1- relationship between mean seed density 2 days until they were transported to the and the number of flowering plants at each Multiple linear regression was used to greenhouse. site. Analyses were performed with SPSS model relationships between plant mor- 8.0 (SPSS 1998). Between 1 April and 13 May 1998, soil phological traits (plant height, crown samples were placed in 15-cm x 20-cm diameter, number of stems, and number germination flats and arranged in random Study 2. Spatial Distributions of of flowering stems) and seed production. positions on two greenhouse tables. Soil Seeds and Germinants Morphological and seed production data depth averaged 2 cm. Samples were wa- were assessed for departures from normal- tered daily from above and were exposed In this study, we assessed the spatial dis- ity and for homogeneity of variance, and it to a photoperiod of 16 hr light (natural tribution of emergent seedlings relative to was concluded that transformations were lighting supplemented with 1000-watt, extant plants following experimental burn- not necessary. Independent variables were metal-halide lamps) and 8 hr dark. Flats ing in spring and fall at the Mission Creek entered stepwise into multiple regression were observed for the presence of germi- site (Figure 1). Due to logistical constraints, models and were retained if significant (F nants twice weekly until July 1998. this experiment could not be replicated at test, P 5 0.05). Regression analyses were other locations. The site had not bumed conducted with the linear regression pro- Few germinants emerged and all samples for several decades, and supported three cedures of SPSS 8.0 (SPSS 1998). were then dried, stored for -5 mo at room distinct groups of two to four I. longisepala temperature, and heated in a drying oven plants. Two adjacent rectangular plots (15 to simulate temperatures experienced m x 75 m) were established between two

Volume 25 (3), 2005 Natural Areas Journal 249 uphjll

E Spring 8um V) F A A Globemallow GlobemallowA A~~~~~

E Fall Burn VI F

z I I I 75 m \1 I \ I \ I \ I 1 I f I \ I 1 J \ / \

Figore 2. Schematic illustretion of the plots burned in fell and spring to investigate the spatial dLPtribution of germinnnts relative to reproductive plants and burn severity. The enlargement of the fall-burn plot illustrates locations of IIimnn germinants (duk circles) *ti= to flowering pleots (dark Mangles) and prrps of higher severity burn (shaded regions). No germhants emerged in the spring-burn plots. The dark lines represent slope contours (3-m intervals).

250 Natural Areas Journal Volume 25 (3), 2005 Study 4. Germination Requirements Both sets of experiments yielded few ger- Estimates of seed density were consider- minants (see Results); thus, statistical tests ably greater when soil samples were sifted. In this study, we attempted to isolate the were not conducted. Untreated samples of However, the frequency and density of germination requirements of I. longisepala seed were then sent to the Oregon State seeds varied markedly within and among by employing, in exploratory fashion, University Seed Laboratory, Corvallis, sites (Table 3). Densities in individual sam- combinationsof standard treatments known to test for viability. These included 198 ples ranged from 0-78 (equivalentto 32,830 to stimulate germination in other species. seeds extracted from April 1999 soil m-2) and mean densities at individual sites Tkvo types of experiments were performed samples and 191 and 200 seeds extracted ranged from 0 to >8000 m-2. Despite large with seeds collected in October 2000. from fruits collected in October 2000 and differences in mean seed density, we did not First, sets of five seeds were subjected to September 2001. detect a significant effect of burn history various combinations: oven temperature due to high site-to-site variation (F= 1.93, (70- 120°C), duration of heating (15-60 P = 0.225) (Table 3). However, consistent RESULTS min), and prior stratification (8 days at with germination patterns from the second OTvs. no stratification). Germination was greenhouse emergence trial (Table 2), sites then attempted on wet sand in Petri dishes Seed Bank Density burned in 1988 had the highest frequency in the greenhouse (16 h light, 8 h dark). and density of seeds, and sites burned in Second, sets of 20 seeds were placed in In the first greenhouse germination 1994 had the lowest. soil in aluminum trays (24 cm x 34 cm trial (untreated soils), only three seedlings x 8 cm) and subjected to combinations emerged from the 450 samples. Following Plant densities at sites burned in 1988 and of treatments that contrasted: (1) buming subsequent heating, however, emergence 1994 were 10 times greater than were den- of 150 g of dry F? pondemsa litter vs. no increased substantially (41 seedlings from sities at sites that had not burned recently burning, (2) addition of ash (derived from 335 samples). Most germinants were (-1.1 vs. 0.1 m-2, respectively; Table 1). separately burned litter samples) vs. no ash, from sites that burned in 1988 (Table 2). However, the relationship between density and (3) depth of seed burial (0 vs. 3 cm). In contrast, germinants were absent or of seeds and flowering plants was not sig- Trays were then placed in the greenhouse, infrequent from sites that burned more nificant (n = 9, R~ = 0.068, P = 0.497). watered periodically, and examined weekly recently (1994) or that had not burned for for germinants until 20 March 2001. at least 50 years. Seed Bank Spatial Distribution

Tiventy-nine seedlings appeared in the experimental plot burned in fall 1998 at lsble 2. Frequency and density of I. bngisepah germinants from heated soil samples collected from sites with duperent histories of burning (see lsble 1). Frequency is the proportion of flats (soil Mission Creek. Of these, 72% were found samples) with at least one germbt. within 10 m of reproductive plants and all were located in areas of high bum severity (Figure 2). No seedlings were observed Burn history 1 Site No. of soil Frequency Germinant density (no. m-2) in the plot burned in spring 1999 and no samplesa (%) Mean SE Max. new plants were observed in 2001, two Burned in 1994 summers later. Mad River 40 0 0 0 0 Potato Creek 35 0 0 0 0 Seed Production Turnwater Mtn. 30 3 14 14 42 1 In 1999, the mean number of seeds per Burned in 1988 fruit was 11.2 (n = 250, range of 0-42) . Burch Mtn. 34 21 87 30 42 1 and the mean number seeds per plant was Mills Canyon 28 0 0 0 0 2450 (n = 25, range of 62-11,063). Crown diameter was the best predictor of seed Rattlesnake Spr. 56 50 226 34 1263 production (R2 = 0.696, P = 0.002; seeds Not recently burned per plant = -1249 + 52.3 * crown diameter Deer Park Spr. 38 0 0 0 0 [cm]) (Figure 3). In 2000, plants produced Red Hill 40 0 0 0 0 significantly fewer flowers, and no fruits or seeds were observed. Mission Creek 34 9 37 21 42 1

Germination Requirements a 335 samples were randomly selected from the original set of 450, thus sample sizes vary among sites (see Methods: Soil Seed Bank). Heatinglscarificationtrials and burninglash

Volume 25 (3), 2005 Natural Areas Journal 251 aclditionlseed burial experiments yielded Table 3. Frequency and density of I. longiscpzh & sU'ted Prom soil samples from sites with diP- ferent histories of burning. Frequency is the proportion of samples with seeds. few germinants. In the first set of trials, four of 180 seeds germinated; in the second set, only one of 240 seeds germinated. X-ray Bum history 1 Site Frequency Seed density (no. m-2) and tetrazolium tests indicated that only w) Mean SE Max. 8% of the seeds collected from plants in Burned in 1994 2000 (used for both sets of trials) were Mad River 40 42 1 236 5,893 viable. In contrast, seeds collected from plants in 2001 showed 27% viability, and Potato Creek 52 387 111 2,104 those extracted from soil samples in 1999 Turnwater Mtn. 0 0 0 0 showed 9 1% viability. Burned in 1988 Burch Mtn. 92 2,441 523 10,102 DISCUSSION Swakane Canyon 64 707 161 2,525 Rattlesnake Spr. 92 8,149 1,468 32,830 Seed Bank Density and Spatial Not recently burned Distribution Deer Park Spr. 68 1,818 570 10,943 Many studies have used the seedling emer- Red Hill 24 101 37 42 1 gence method to quantify the density and Mission Creek 60 968 233 2,946 diversity of viable seeds in the soil (e.g., Strickler and Edgerton 1976, Brown 1992, Halpem et al. 1999). However, this method proved to be ineffective for I. longisepala.

12000 -

10000 -

8000- se & 6000- Q 4000- V18

2000 -

0 I I I I I I I .d 50 75 100 125 1SO 175 200 Crown diameter (cm)

Figure 3. The relationship between seed production and crown diameter in Iliumna 'henty-five plants were sampled on 8 July 1999 at the Swakane Cmpn site (see Methods: Seed Production).

252 Natural Areas Journal Volume 25 (3), 2005 Although heating soil samples broke the However, others have observed significant First, annual variation in seed production dormancy of some seeds, this method still relationships between soil seed bank den- can be attributed to patterns of temperature underestimated an apparently large viable sity, plant density, and disturbance history. or rainfall that affect bud formation or seed bank. Although the process is labori- For example, seed density of Adenostomu survival or seed set (Keeley 1977, Coffin ous, direct extraction of seeds followed fasciculatum Hook. &Am. increased with and Lauenroth 1992, Parsons and Whelchel by viability testing is the best method to time after fire occurred in mixed chapar- 2000, Selas 2000). In our study area, timing estimate the density of viable seeds for ral (Zammit and Zedler 1988). Seeds of of rainfall in 2000 may have contributed this species. an Australian grass, Triodia basedowii E. to poor seed production in I. longisepala.

Pritz., were completely absent 3 y after a Although annual precipitation was lower ' Disturbance history appears to be important bum, but seed density returned to initial than average in both 1999 and 2000, only in the seed bank dynamics of I. longisepala. levels after 9 y (Westoby et al. 1988). For in 1999 was August rainfall - at the time of Although we did not detect a statistically I. longisepala, greater replication of sites fruit maturation -close to average (Figure significant effect of burn history on seed and bum histories may be necessary to 4). In 2000, insufficient rainfall in August density, replication was low and site-to-site fully understand the relationships among may have induced fruit abortion (6Selas variation was high, as is often observed in time since disturbance, plant density, and 2000). Annual variation in seed produc- soil seed banks (Halpern et al. 1999, Mor- temporal patterns in the soil seed bank. tion might also be explained by effects gan 2001). However, mean trends for both of weather on the presence or activity of frequency and density were consistent with The results of both direct seed counts and pollinators (Bergman et al. 1996. Parsons a temporal pattern in which seed banks be- field-burning studies indicate that the seed and Whelchel 2000). However, there is come depleted in recently burned sites due bank of I. longisepala is spatially hetero- little evidence in the weather records for to mass germination and possible loss to geneous. Spatial patterns of germination in June, when plants are in flower, to invoke lethal temperatures. Abundant germination the fall-burn plot suggest that seed densities pollination limitation as an explanation for of I. longisepala has been observed after are higher near reproductive plants and that poor seed set. Regardless of its cause, tem- wildfire (Kuhlmann and Harrod, unpubl. long-distance (>lo m) dispersal is fairly poral variation in seed production is likely data), and similar observations have been limited. However, there also appears to be a to play an important role in the dynamics made of its congeners, I. rivularis (Lyon strong effect of bum severity on the spatial of a species that depends on periodic ger- 1971, Brown and DeByle 1989, Steele and distribution of germinants. Germination mination from the seed bank. Geier-Hayes 1989) and I. corei (Baskin and was most common in areas where severe Baskin 1997). Although large declines in fire consumed fine litter that had accumu- Germination Requirements seed bank density can be attributed to the lated under P ponderosa and P. tridentata, stimulatory effect of wildfire on germina- exposing mineral soil. Our observations Because of low viability of seed collected in tion, fire-induced mortality can also lead suggest that differential heating of the soil 2000, we were unable to determine the tem- to depletion of the seed bank. For example, during fall (but not spring) bums effectively perature or heating requirements, or that soil heating by fire in Mediterranean and determined the spatial pattern of seedling ash is necessary to induce germination of I. chaparral ecosystems can deplete soil seed recruitment regardless of the distribution longisepala. Nonetheless, greater viability banks to a depth of 3 cm due to direct of seeds in the soil. Smng relationships of seeds collected in 2001 suggests that, consumption and lethal temperatures (Fer- between the spatial distributions of parent similar to seed production, viability can randis et al. 1999, Odion and Davis 2000, plants, the heterogeneous nature of fire, and vary in time. Further experimentation with Lei 2001). It is likely that for I. longisepala, the spatial pattern of seedling recruitment seeds of known high viability is needed depletion of the soil seed bank in recently have been documented in many other sys- to confirm the physical andlor chemical burned sites reflects a combination of seed tems in which fire is important (Davis et factors that trigger germination. In previ- germination and mortality. al. 1989, Rice 1993, Qler 1995). ous experiments, Fuentes (2000) found that mechanical scarification and heating Density of seed in the soil may also re- Seed Production promoted germination of I. longisepala, flect the density of reproductive plants, which can vary with disturbance history although the significance of these results Seed production in I. longisepala correlates was limited by low treatment replication (generally declining with time since fire). Although the density of reproductive plants well with plant size (crown diameter), but and total germination. The increased rate only when viable seed is produced, and of germination in our second greenhouse in our study was significantly higher on this appears to vary annually. In 1999, emergence trial (after soils were heated) burned sites, seed bank density was not correlated with plant density. In contrast, an average-sized plant at the Swakane is consistent with this result. Fuentes (2000) found a significant correla- Canyon site yielded -2500 seeds, but no Despite poor germination in laboratory tion between seed bank density and plant seeds were formed on the same plants in density at other locations in northeastern 2000. We observed this failure at many and greenhouse trials, there is abundant other locations as well. Several factors evidence from the field to suggest that Washington, but no correlation between wildland fire or prescribed burning is plant density and disturbance history. may contribute to this temporal variability.

Volume 25 (3), 2005 Natural Areas Journal 253 2.5 - +1999 2000 ------30-year average 2.0 -

n E -3 1.5-, s 0 .I C,

.I$ 1.0- Q. .I Ew 0.5-

o.O - a

I I I I I I I April May June July August Sept October Month

Figure 4. Monthly precipitation from the Entiat remote automated weather station during 1999 and 2000 compared to the Syraverage. sufficient to break seed dormancy in I. ate determined by rates of input and loss (granivory, decay, exposure, or transport). longisepala. Localized germination in (Harper 1977, Simpson et al. 1989). For I. Because mature plants are capable of areas of high fire severity in this study, longisepala, seed input derives from local resprouting after prescribed fire (Harrod and abundant germination after fall (but sources (although production and viability 2003), strategies to maintain or enhance not spring) burning in a companion study can vary), and loss, at least historically, existing populations should focus on the (Harrod 2003), strongly suggest that fire, occurred through mass germination or dynamics of the seed bank. Our field ob- and its seasonal timing, are important for mortality from lethal fire temperatures. servations suggest that periodic fire will successful recruitment of seedlings. Field Thus, under a regime of frequent fire, we stimulate seedling emergence from a well- studies of several congeners support this would expect seed density to show an oscil- developed seed bank, and that germination conclusion: heat from fire was the primary lating, but asymmetrical pattern of gradual and subsequent survival will be more likely factor to break seed dormancy in I. corei increase followed by abrupt decline after after fall burning. However, our estimates (Baskin and Baskin 1997), spring burning fire. Density of reproductive plants would of seed bank densities in recently burned induced germination in I. remota (Schwe- mirror this pattern with a slight lag as fire sites suggest that burning at intervals gman 1990), and hot broadcast burning induced abundant recruitment of seedlings

254 Natural Areas Journal Volume 25 (3), 2005 Swanson for fieldwork and laboratory as- and plant reproductive success in an alpine Wenatchee Mountains, Washington. Ph.D. sistance. Carol Baskin provided helpful environment, Swedish Lapland. Arctic and diss., University of Washington, Seattle. guidance early in the study. We thank the Alpine Research 28: 196-202. Harrod, R.J., D.E. Knecht, E.E. Kuhlmann, Leavenworth Ranger District fire crew for Brown, D. 1992. Estimating the composition M.W. Ellis, and R. Davenport. 1997. Effects conducting the prescribed burns at Mission of a forest seed bank: a comparison of the of the Rat and Hatchery Creek Fires on Creek. Jim Agee, Martha Groom, Estella seed extraction and seedling emergence four rare plant species. Pp. 31 1-319 in J.M. methods. Canadian Journal of Botany Leopold, and three anonymous reviewers Greenlee, ed., Proceedings: Fire Effects on 70:1603-1612. Rare and Endangered Species and Habitats provided useful comments that improved Conference, November 13-16.1995, Coeur the manuscript. The USDA Forest Service Brown, J.K., and N.V. DeByle. 1989. Effects of prescribed fire on biomass and plant suc- d' Alene, Idaho. InternationalAssociation of Okanogan-Wenatchee National Forests and cession in western aspen. Research Paper Wildland Fire, Fairlield, Wash. the Wenatchee Forestry Sciences Labora- INT-412, U.S. Department of Agriculture, Hitchcock, C.L.. A. Cronquist, M. Ownbey, tory funded this project. Forest Service, Intermountain Research and J.W. Thompson. 1969. Vascular Plants Station, Fort Collins, Colo. of the Pacific Northwest. Part 3: Saxifraga- Coffin, D.P., and W.K. Lauenroth. 1992. Spa- ceae to Ericaceae. University of Washington Richy Hadis the fire ecologist for the tial variability in seed production of the Press, Seattle. Okanogan-Wenatchee National Forests perennial bunchgrass Bouteloua gmcilis Hitchcock, C.L., and A. Cmnquist. 1973. Flora where he is engaged in restoration plan- (Grarnineae). American Journal of Botany of the Pacific Northwest. University of 79347-353. ning and research. He pratiously served Washington Press, Seattle. as plant ecologist for the Leavenworth Cohen, D. 1966. Optimizing reproduction in a Keeley, J.E. 1977. Seed production, seed popula- randomly varying environment. Journal of tions in soil, and seedling production after Ranger District, Wenatchee National Theoretical Biology 12: 119-129. fire for two congeneric pairs of sprouting Forest. His primary interests are in Jire Davis, F.W., M.I. Borchert, and D.C. Odion. and nonsprouting chapan& shrubs.&logy effects, biological diversity, rare plant 1989. Establishment of micmscale vegeta- 582320-829. biology and conservation, and noxious tion pattern in maritime chaparral after fire. Keeley, J.E., B.A. Morton, A. Pedrosa, and weed management. Vegetatio 8453-67. P. Trotter. 1985. Role of allelopathy, heat Edwards, W., and R. Whelan. 1995. The size, and charred wood in the germination of Charles Halpem is a Research Professor distribution and germination requirements chaparral herbs and suffrutescents. Journal in the College of Forest Resources at the of the soil-stored seed-bank of Grevillea of Ecology 73:445-458. Universityof Washington. His research ex- barklyana (Pmteaceae). Australian Joumal Kelly, D. 1984. Seeds per fruit as a function of plores the successional dynamics offorests of Ecology 20:448-555. fruits per plant in 'depauperate' annuals and and meadows of the PacijSc Northwest, and Everett, R.L., R. Schellhaas, D. Keenum, biennials. New Phytologist 96: 103- 1 14. considers the roles of disturbance, climate D. Spurbeck, and P. Ohlson. 2000. Fire Lei, S.A. 2001. Postfire seed bank and soil change, species' life histories, and biotic history in the ponderosa pin-uglas-fir conditions in a blackbrush (Coleogyne m- forests on the east slope of the Washington interactions in shaping plant community mosissima Torr.) shrubland. Bulletin of the Cascades. Forest Ecology and Management Southern California Academy of Sciences patterns. 129:207-225. 100:100-108. Ferrandis, P., J.M. Hem,and J.J. Martinez- Lillybridge. T.R.. B.L. Kovalchik. C.K. Wil- LITERATURE CITED Sanchez. 1999. ERects of fire on hardated liams, and B.G. Smith. 1995. Field guide for Cistaceae seed banks and its influence on forested plant associations of the Wenatchee Agee, J.K. 1993. Fire Ecology of Pacific techniques for quantifying seed banks. Plant National Forest. General Technical Report Northwest Forests. Island Press. Washing- Ec~l~gy144:103-114. PNW-GTR-359, U.S. Department of Agri- ton, D.C. Fuentes, T.L. 2000. Effects of fire and disease culture, Forest Service, Pacific Northwest Research Station, Portland, Ore. Agee, J.K. 1994. Fire and weather disturbances on Iliomno longisepala (Torr.) Wiggins in terrestrial ecosystems of the eastern (). M.S. thesis, Arizona State Lyon, L.J. 1971. Vegetal development following Cascades. General Technical Report PNW- University, Phoenix. prescribed burning of Douglas-fir in south- GTR-320, U.S. Department of Agriculture, Gross, K.L. 1990. A comparison of methods for central Idaho. Research Paper INT-105, U.S. Forest Service, Pacific Northwest Research estimating seed number in the soil. Journal Department of ~griculture,Forest Service, Station, Portland, Ore. of Ecology 78: 1079-1093. Intermountain Research Station, Fort Col- lins, Colo. Baskin, J.M., and C.C. Baskin. 1997. Methods Halpern, C.B.. S.A. Evans, and S. Nielson. of breaking seed donnancy in the endangered 1999. Soil seed banks in young, closed- Major, J., and W.T. Pyott. 1966. Buried, viable species Iliamna corei (She@ Sherff (Mal- canopy forests of the Olympic Peninsula, seeds in two California bunchgrass sites vaceae), with special attention to heating. Washington: potential contributions to un- and their bearing on definition of a flora. Natural Areas Journal 17:313-323. derstory reinitiation. Canadian Joumal of Vegetatio 13953-282. Baskin, C.C.. and J.M. Baskin. 1998. Seeds: Botany 77:922-935. Menges. E.S. 1986. Predicting the future of Ecology, Biogeography, and Evolution of Harper, J.L. 1977. Population Biology of Plants. rare plant populations: demographic moni- Dormancy and Germination. Academic Academic Press, New York. toring and modeling. Natural Areas Journal 6: 13-25. Press, San Diego, Calif. Hamod, R.J. 2003. Demography and disturbance Bergman, I?, U. Molau, and B. Holmgren. 1996. ecology of IlinmM longisepala and Trifo- Morgan, J.W. 2001. Seedling recruitment pat- Micrometeorological impacts on insect lium thompsonii,two endemic species of the terns over 4 years in an Australian perennial

Volume 25 (3), 2005 Natural Areas Journal 255 grassland community with different fire Schwegman, J. 1990. Preliminary results of 'Qler, C.M. 1995. Factors contributing to histories. Journal of Ecology 89:908-919. a program to monitor plant species from postfire seedling establishment in chaparral: Odion, D.C., and EW. Davis. 2000. Fire, soil management purposes. Pp. 113-1 16 in R.S. direct and indirect effects of fire. Journal of heating, and the formation of vegetation pat- Mitchell, C.J. Sheviak, and D.J. Leopold, Ecology 83:1009-1020. terns in chaparral. Ecological Monographs eds., Ecosystem Management: Rare species U.S. Departmentof Agriculture. 1995. National 70:149-169. and SignificantHabitats, Proceedings of the cooperativesoil survey, Cashmere Mountain 15"~nnualNatural Areas Conference, New Oosting, H.T., and M.E. Humphreys. 1940. soil survey. U.S. Department of Agriculture, York State Museum Bulletin Number 471. Buried viable seeds in a successional series Forest Service, Pacific Northwest Region, [New York State Museum. N.Y.] of old field and forest soils. Bulletin of the Portland, Ore. Torrey Botanical Club 67953-273. Selas, V. 2000. Seed production of a masting Washington Natural Heritage Program. 1997. dwarf shrub, Vaccinium myrtillus, in rela- Parsons, L.S., and A.W. Whelchel. 2000. The Endangered, threatened, and sensitive tion to previous reproduction and weather. effect of climatic variability on growth, vascular plants of Washington - with Canadian Journal of Botany 78:423429. reproduction, and population viability of a working lists of rare non-vascular species. sensitive salt marsh plant species, Lathenia Simpson, R.L., M.A. Leck, and V.T. Parker. Department of Natural Resources, Olympia, glabrata subsp. coulten (Asteraceae). Ma- 1989. Seed banks: general concepts and Wash. droiio 47: 174-188. methodological issues. Pp. 3-8 in M.A. Westoby, M., B. Rice, G. Griffin, and M. Friedel. Leck, V.T. Parker, and R.L. Simpson, eds., Pickett, S.T.A., and M.J. McDonnell. 1989. 1988. The soil seed bank of Modia base- Ecology of Soil Seed Banks. Academic Seed bank dynamics in temperate decidu- dowii in relation to time since fire. Australian Press, San Diego, Calif. ous forest. Pp. 123-145 in M.A. Leck, V.T. Journal of Ecology 13: 161-169. Thomas, and R.L. Simpson, eds., Ecology SPSS. 1998. SPSS Base 8.0 for Windows. SPSS Williams, C.E., T.F. Wieboldt, D.M. Porter. of Soil Seed Banks. Academic Press, San Inc., Chicago, Ill. 1992. Recovery of the endangered Peters Diego, Calif. Steele, R., and K. Geier-Hayes. 1989. The Mountain mallow, Iliamna corei. Natural Rice, S.K. 1993. Vegetation establishment in Douglas-firtninebark habitat type in central Areas Journal 12: 106-107. post-fire Adenostoma chaparral in relation Idaho: succession and management. Genela1 Zammit, C.A., and P.H. Zedler. 1988.Theinflu- to fine-scale pattern in fire intensity and Technical Report INT-252, U.S. Department ence of dominant shrubs, fire, and time since soil nutrients. Journal of Vegetation Science of Agriculture, Forest Service, Intermoun- fire on soil seed banks in mixed chaparral. 4:115-124. tain Research Station, Boulder, Colo. Vegetatio 75:175-188. Schemske, D.W., B.C. Husband, M.H. Ruck- Strickler, G.S., and P.J. Edgerton. 1976. Emer- elshaus, C. Goodwillie, I.M. Parker, and gent seedlings from coniferouslitter and soil J.G. Bishop. 1994. Evaluating approaches in eastern Oregon. Ecology 57:801-807. to the conservation of rare and endangered plants. Ecology 75:584-606.

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