Ecotype – Problematic Concept in a Changing World

Iowa is the most altered state in the U.S. Nowhere have natural communities been more thoroughly destroyed. I started thinking about ecotypes when I was in my early twenties collecting seeds on little “postage stamp” prairies in Iowa. Ecotypes can be thought of as plants from a particular geographic area that tend to share similar genes and also observable structural characteristics (morphology), though often the concept is simplified to geographic sources, regardless of the magnitude of any real differences between plants. For that reason, I’ll use “ecotype” and “source” interchangeably here.

Often restoration and reconstruction projects for natural communities limit themselves to local ecotypes, which often means, on the conservative end, using only seed gathered within the immediate vicinity of a project area, or on the more liberal end, sourcing seeds from within a county, adjacent counties, or perhaps up to 100 miles or so away.

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Myself in youth using a leaf blower in reverse to suck up and pulverize ground plum (Astragalus crassicarpus) pods on an Iowa prairie. For those with PPE concerns, I will add that this was a staged photo.

The seeds I was harvesting on those Iowa prairies were either going directly to market after cleaning, or they were going into restorations or plantings, which would subsequently be harvested for use in other restoration projects. As I moved from one small and geographically isolated population to the next, the following questions increasingly weighed on my mind:

1. What is missing? Often the bags strapped to my waist were heavy with seeds, but what about genes? Would the ghosts of prairies past in the surrounding seas of corn and soy haunt our success?

2. How good of a match are native populations in remnant prairies, more often than not located on marginal, rocky or sandy ground, for prairie reconstruction projects located in cool-season pastures or cultivated fields? Such sites might be geographically close, but they are often situated on different soils, which have seen their structure deteriorated and their nutrients and microbial communities altered by more than a century of agricultural use.

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Typical postage stamp prairie surrounded by horizons of corn in western Iowa. 

3. What about climate change? Plants on those postage stamp prairies surrounded by miles of corn and beans are going nowhere fast. Already, temperature and precipitation patterns have changed enough in much of the Midwest and Great Plains that you would have to travel a hundred miles or more to find the same/similar climate in terms of average temperature and precipitation at the time of European settlement, and that ignores the extremes of our new climate. Still, we often use climate to make guesses about how to define ecotypes. Not only have native plant populations passed through extreme genetic bottlenecks, but the prairie landscape has been fragmented to such an extreme degree that if there were other suitable sites on the landscape, the plants would not be able to disperse their seeds to them. Not even Donald Trump could build a better wall than what an 80- or 160-acre Iowa cornfield is to a compass plant. Note: Donald Trump never crossed my mind once back in those days. It was an age of reason.

4. Given these things, how much does the ecotype concept, particularly when interpreted narrowly, really help us?

Here is a brief synopsis, admittedly simplistic, of what we know. Plants from different locations, whether separated by altitude, latitude, longitude, etc. differ in terms of both their structures and genes. The timing of flowering and growth (phenology), the size of all or parts of individual plants, and tolerance of extremes of heat or cold are all things that can vary. We know this, in large part, due to common garden experiments. What we observe when we look at a plant is the result of genes and the environment. If plants from locations A, B, and C, are all grown together in one place, it can be assumed that their differences are genetic and not based on environment alone , because the environment is held constant. This ignores epigenetics, which could be very important, but methods to suss out its effects haven’t really been developed as far as I know. Phenological events like flowering time and time of emergence can affect how plants interact with consumers (e.g. pollinators) and one-another. A classic scenario is the one where a flower emerges earlier due to a warming climate, but its pollinator is not able advance its emergence to the same degree, leading to an asynchrony that harms both species. In such a case, environmental conditions are the cause. However, use of an ecotype that differs in phenology from a local source could cause similar asynchronies.

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A monarch butterfly visits meadow blazingstar (Liatris ligulistylis). 

For those reasons, “local is best” is the mantra, if not the dogma, of many in the conservation and restoration community. It’s a cautious and logical approach. However, in recognition of the altered and changing world we live in and recognizing that ecological restoration and reconstruction projects are  essentially the only way many species can move across today’s fragmented landscape, I would urge people to be a little more liberal in how they apply the ecotype concept.

I will start by briefly summarizing my research on the topic. I was not only concerned with whether plants from points A and B were a little different from one-another. I was concerned with whether or not any differences they might have actually affected how well they established in a realistic prairie reconstruction setting. Additionally, I was not concerned with one species, but with a dozen, all of which I sourced from three distant locations (one in Nebraska, one in Kansas, and one in Oklahoma). Thus, I was planting twelve species together, all sourced from the same location  (a twelve-species, single-source seed mix). The mix from Nebraska was sown next to a mix with the same species in the same amounts from Kansas, and another from Oklahoma. In turn, at each site from which I sourced the twelve species (NE, KS, and OK), I established common gardens of prairie reconstructions so that differences in outcomes would be due largely to the seed sources rather than the particular environmental conditions they were grown under.

What did I find? There was no consistent local advantage. Sure, there were cases where the local source performed best (measured as species-specific biomass 1,2, and 3 years after planting), but those cases were no more common than one would expect from chance. Sources often performed similarly, and in some cases non-local sources performed best. In addition, seed source did not affect the number of sown species that ultimately established 1, 2, or 3 years after planting. Two articles from this research are available open access at:

Seed Source and Prairie Establishment

Seed Source and Prairie Seedling Survival

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Stiff goldenrod (Oligoneuron rigidum) seedling marked and tracked for survival on a research plot in Nebraska. There, the local Nebraska source did have the highest initial seedling density, but there were no differences in the survival of emerged seedlings between the Nebraska, Kansas, and Oklahoma sources. 

 

Now, is that work conclusive? Absolutely not. It followed reconstructed prairies for three years, and it used only a small subset of possible species, sources, and growing sites. However, its results should give pause. It illustrates how focus on one species or one site could have led to false support of a general local advantage. In addition, initial establishment is critical for many prairie species in a restoration / reconstruction setting.  In perennial plants, the most important demographic parameter for maintaining stable populations is usually  year-to-year survival rather than seed production, so getting plants growing is the most critical step. Initial establishment also impacts the extent to which invasive species can get a toehold.

Was I surprised the results? No. The plots that were seeded were different from even the nearby prairies from which the seeds were sourced, our climate has changed, and the genes I gathered as I collected seeds from remnant prairies, even though they were  big prairies with fairly large populations of many species, were most likely just a subset of what was once available in each region.

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Stiff goldenrod in its second year from seed on one of my research plots in Kansas. In Kansas, the Nebraska source for stiff goldenrod established better (grams biomass / square meter) than the local Kansas source and the Oklahoma source. 

What does other research say? There is very little work that goes beyond whether or not plants have genetic or other measurable differences by taking the additional step of quantifying how well they actually perform in a realistic setting. However, similar work, which focuses on only single species or a few species, is mixed or equivocal on local vs. non-local sources.

Local Sources VS. Cultivars (Paywall)

Local VS Non-Local Along Longitudinal Gradient (Paywall)

That said, we still know that ecotypes can differ in measurable traits, including phenology, and that has the potential to be a big deal.

Let me return to my suggestion to conservation and restoration professionals to be more liberal about ecotypes. The ecotype concept was developed under a view that assumes stasis in the natural world, but everything these days is rapidly changing. Certainly, when local sources are available, they should be used. However, in order to conserve biodiversity, we should also look more regionally, take sources that may be geographically more distant, and use those in combination with our local sources. I’m not saying that that a project in Wisconsin should use seeds from Texas, but it may be worthwhile to consider sources from Iowa or Illinois. Below are the reasons I find most compelling.

1. The effects of source location vary by species such that there is no one-size-fits-all rule or relationship for sourcing plant material.

2. If any one source performs poorly, it will tend not to survive and reproduce, and it may then be compensated for by better performers in a mix that includes a variety of sources.

3. Ecological asynchronies can be caused by sourcing geographically distant plants, but they can also be caused by climate change. It is not, therefore, clear that including distant sources that differ from local sources in phenology  will, with the backdrop of climate change, always lead to asynchrony. In fact, when different sources are mixed, a broader phenological range (e.g. more variation in flowering dates) might reduce asynchrony.

4. Best practice in restoration/reconstruction is to utilize as many native species as appropriate and practicable, which often diminishes the importance of any one species through redundancy. This increases community resistance to and resilience from disturbances. Since many specialist consumers specialize on genera or families rather than species, potential asynchronies in phenology can be minimized by including multiple species from families and genera that are native to the same region but that grow or flower at different times from one another, thus extending the season.

5. A regional perspective provides the seed buyer more options in the market, both to locate purveyors of desired species and to control costs, both of which can be leveraged towards creating a seed mix more diverse in species, which has known benefits.

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Drought parches Konza Prairie in 2012 after a spring of unprecedented warmth that caused big bluestem (Andropogon gerardii) and heath aster (Symphyotrichum ericoides) to flower in May. Fluke, or more to come?

6. There is simply no other way for many species to move over the landscape as quickly as they need to in response to climate change. It’s a forgone conclusion that natural communities are going to profoundly change; some already have. The contemporary fight is to maintain biodiversity. Unfortunately, we don’t know enough to confront this task with clarity, but we also don’t have time.

At the very least, people should think more critically their sourcing procedures in the narrow context of single projects and the broad context of regional biological and genetic diversity. This is not a topic where reality lends simple, repeating, and unthinking procedure.

 

 

Posted in Conservation, gardening, native plants, Phenology, Prairie, restoration, Savanna, Uncategorized | Tagged , , , , , , , | 4 Comments

Winter Identification of Native and Exotic Phragmites Subspecies in SE Wisconsin

BACKGROUND

Originally from Eurasia, exotic Phragmites australis ssp. australis (Figure 1) invades high quality and disturbed wetlands alike, reducing biodiversity by excluding other plant life and disrupting ecological function. It’s spread has been rapid, and land managers are hard-pressed to keep up.

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Figure 1. Phragmites australis ssp. australis seen crossing a driveway. Its capacity to spread rapidly by vegetative means (stolons and rhizomes) and form large, dense patches that exclude other plant species is exceptional, even among invasive species in Wisconsin. It’s seeds are also dispersed by wind, water, or by adhering to people, equipment, or animals.

In contrast, native Phragmites australis ssp. americanus has co-evolved with other native flora and fauna, has existed in Wisconsin for thousands of years, and does not typically reduce biodiversity or cause ecological disruption where it occurs. It most often forms either loose or localized colonies, which allow for the co-occurrence other species. The growth form of native Phragmites lends a unique element of physical structure to wetlands and the tissues of the plant support a number of insect species.

For these reasons, resources need to be directed towards the eradication of the exotic subspecies and not wasted eradicating stands of the native subspecies. The eradication of native Phragmites may simplify wetland food webs and the associated disturbance may create opportunities for truly harmful invaders.

IDENTIFICATION

While some may think otherwise, efficient identification of native and exotic subspecies isn’t especially difficult, if you know what to look for. Here I focus on characteristics most easily observed during the fall and winter. Fall and winter are arguably the best time to identify the native and exotic subspecies, because some of the most reliable characteristics for identification are most clearly observed on dormant plants.

Investigation of several characteristics is strongly advised, because interpretations of certain more qualitative characteristics can vary from person to person, and some plants may be ambiguous or atypical with respect to any single characteristic. However, if one considers several characteristics the determination will almost always be clear and direct. Hybrids between native and exotic subspecies would be problematic for identification, but hybrids are exceedingly rare (documentation in North America is in the low single digits).

Below I use material from a patch of exotic Phragmites australis ssp. australis and a patch of native Phragmites australis ssp. americanus, both from Scuppernong Springs in Waukesha County, Wisconsin, to illustrate winter differences between the subspecies.

1) The lower stems (culms) of the exotic subspecies are tightly covered in a leaf sheath that remains well into winter (Figures 2). In contrast, by late summer or early fall, the lower culms of native plants are without sheaths or any remaining dry sheaths are loose and very easily removed (Figure 3). This distinction should be a component of any identification taking place late enough in the growing season that remaining leaf sheaths have dried and are no longer green (middle/late summer through winter).

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Figure 2. Winter photos of exotic Phragmites australis ssp. australis. Left) Culm prior to removal of the leaf sheath. Right) Culm with leaf sheath partially torn away.

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Figure 3. Winter photo of native Phragmites australis ssp. americanus culm with no sheaths remaining.

2) The lower stems (culms) of the native species TEND to be shinier in appearance and smoother in feel than the exotic (Figure 4). In the exotic, parallel ridges running up and down exposed culms give a slightly rough or textured feel. While these ridges are present in the native, they are less obvious.

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Figure 4. Native and exotic Phragmites australis culms side by side showing the relative difference in shininess and smoothness.  Mildew may occur on culms or sheaths of both the native and the exotic and is not a useful characteristic for identification.

3) Occasionally, the culms of the native will have distinct black spots formed by a fungus (Figure 5). This fungus is not known to colonize the exotic. The absence of these spots indicates nothing about whether the Phragmites is native or exotic, but the presence of spots indicates that the Phragmites is native. It is worth investigating several culms in a given patch for spots. These very distinct spots should not be confused with dark / black blotches caused by mildew (Figures 4 and 5) or injuries caused by insects, which may leave spots that are brown in color and / or irregular in shape.

Paul Mozina filmed me talking about this.

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Figure 5. Distinct black spots caused by a fungus only known to infect the native Phragmites australis ssp. americanus.

4) Certain floral parts in the spikelets of the inflorescence tend to differ in average size between the native and exotic subspecies. The native tends to have first (lower) glumes between 3 mm and 6.5 mm in length, with most longer than 4 mm (Figure 7) and the exotic tends to have first (lower) glumes between 2.5 mm and 5 mm in length, with most shorter than 4 mm (Figure 8).  Always measure several first glumes, ideally from a few different seed / flower heads) and take an average to avoid basing a decision on a potential outlier. This practice also helps ensure that you’ll notice if structures on one particular spikelet are damaged or missing in a potentially misleading way. 

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Figure 7. A spikelet from native Phragmites australis ssp. americanus with the first glume nearly 6 mm long.

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Figure 8. A spikelet from exotic Phragmites australis ssp. australis with the first glume about 3 mm long.

5) The native also tends to have longer second glumes than the exotic. Its second (upper) glumes tend to be between 5.5 mm and 11 mm in length, with most longer than  6 mm (Figure 9), and the exotic tends to have second (upper) glumes between 4.5 mm and 7.5 mm long, with most shorter than 6 mm (Figure 10).  In Figure 10, the lower glume on the exotic spikelet is ambiguous, because it measures almost exactly 6 mm and falls within the range of both subspecies! This illustrates why, for second glumes just like first glumes, we should always measure several, ideally from a few separate seed / flower heads) and take an average to avoid basing a decision on a potential outlier. This plant happened to have about 50% glumes that were almost exactly 6 mm in length, but the remainder were 4-5.5 mm, so I considered the second glumes to be consistent with the exotic subspecies, particularly in the context of the first glumes, sheaths, and culms shown above.

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Figure 9. A spikelet from native Phragmites australis ssp. americanus with the second glume about 8 mm long.

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Figure 10. A spikelet from exotic Phragmites australis ssp. australis with the second glume about 6 mm long.

Care needs to be taken to measure the glumes and not the lemmas, which are often still present in fall and winter. In addition, other floral parts may be present in the spikelet above glumes and lemmas, particularly in the fall. The first glume is nearest the base of the spikelet, and the second glume attaches immediately above and opposite the first glume. I recommend use of a hand lens to ensure measurement of the correct parts. The discussion of grass morphology in a field guide, such as Judziewicz and others’ Field Guide to Wisconsin Grasses should be helpful for learning these parts. Learning them in order to identify Phragmites will also expand your ability to identify grasses in general. Figure 11 shows exotic and native spikelets side by side.

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Figure ll. Comparison of exotic and native spikelets.

6) The native tends to form loose stands in which other species of plants are able to grow (Figure 12). The exotic tends to form dense stands that are nearly monocultures or that greatly reduce the growth and vigor of co-occuring species (Figure 13). This is why the exotic is a problem. Apply this characteristic with caution, however, because exceptionally nutrient-rich sites, nutrient poor sites, and sites that generally cause the plants stress can lead to altered stand density and vigor.

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Figure 13. View from within the middle of a large patch of native Phragmites australis ssp. americanus. Note how there is a continuous layer of vegetation, though partially snow-covered, beneath the Phragmites. This patch was easy to walk through, and the canopy cover of Phragmites here was likely less than 20% during the growing season.

Don’t judge the density of Phragmites patches from far away. A large patch of native Phragmites australis ssp. americanus can appear to be more dense than it truly is when viewed from the side and from a distance (Figure 14). Instead, get up close.

 

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Figure 14. The same patch of native Phragmites australis ssp. americanus in figure 11 viewed from far away. It only appears to be dense, because of the size (depth) of the patch, and because there are some cattails mixed in that are similar in winter color.

The below table summarizes and lists, from what I consider to be the most reliable (top) to least reliable (bottom), the characteristics for fall and winter identification of Phragmites discussed above. Phrag_table.jpgThe size of the ligules is another distinguishing characteristic, but ligules are better used in summer, because they have largely deteriorated or the leaves they are on have been shed by late fall and winter, so that’s another post for another season.

Finally, some might be familiar with the tendency of the native to develop strikingly red lower culms during the growing season after the sheaths split open and / or fall off (Figure 15). This red color disappears when plants go dormant in fall, and it only develops in the first place as a consequence of the sheaths falling off and exposing the culms to sunlight. Therefore, I would stress observing the sheaths above all else, because the red coloration may be less apparent if the lower culms are shaded, and because, even with sheaths adhering tightly, the exotic strain can have reddish coloration in small exposed areas between the sheaths.

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Figure 15. The striking red coloration that may be visible on the lower culms of native Phragmites australis ssp. americanus before plants go dormant in fall.

Conclusion

All of this for two subspecies of one species. Identification really does become quite simple with practice. After a while, you’ll feel like you can make the ID from a speeding car on the freeway. Resist that temptation. It’s usually best to get up close and personal the plants. Good luck!

Part I of a video Paul Mozina took of me discussing the exotic

Part II of a video Paul Mozina took of me discussing the exotic

Part I of a video Paul Mozina took of me discussing the native

Part II of a video Paul Mozina took of me discussing the native (distinct culm spots, same link as the one under culm spot description above)

Sources

Price, A.L., J.B. Fant, and D.J. Larkin. 2013. Ecology of Native vs. Introduced Phragmites australis (Common Reed) in Chicago-Area Wetlands. Wetlands DOI 10.1007/s13157-013-0504-z

Saltonstall, K., P.M. Peterson, and R. Soreng. 2004. Recognition of Phragmites australis subsp. americanus (Poaceae: Arundinoideae) in North America: evidence from morphological and genetic analyses. Sida 21(2):683-692.

Swearingen, J. and K. Saltonstall. 2010. Phragmites Field Guide: Distinguishing Native and Exotic Forms of Common Reed (Phragmites australis) in the United States. Plant Conservation Alliance, Weeds Gone Wild. http://www.nps.gov/plants/alien/pubs/index.htm

 

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Beulah Bog

Bogs are old places that evoke the passage of time. Beulah Bog in SE Wisconsin consists of a series of kettle depressions formed when great boulders of ice that were mixed with the till of the Wisconsin Glacier melted. These depressions became large ponds. As boreal forests retreated northward and were replaced by hardwood forest and then oak savannas, woodlands, and prairies, the relentless annual growing and dying of floating mat-forming sedges and sphagnum moss have slowly closed over and filled these ponds.

Each depression containing a bog is surrounded by a “moat.” This is the area of tension between the bog and the surrounding uplands. When groundwater levels rise, the floating bog mat follows with it, creating a zone of separation that is often inundated early in the year or during wet times. Recent weeks have been exceptionally dry, so my entry into the bog was fairly straightforward.

This is the

This is the “moat” zone that separates the uplands from the bog. Here it is dense with arrowheads, lake sedge, and wool-grass sedge. In wetter times, this would be a thigh-deep mire of roots and muck.

There is still a small area of open water in one of the depressions, surrounded on all sides by floating-mat forming sedges and other vegetation. Left undisturbed, this will eventually be sealed over.

There is still a small area of open water in one of the depressions, surrounded on all sides by floating-mat forming sedges and other vegetation. As the mat thickens, it supports shrubs and tamaracks. Left undisturbed, this pond will be sealed over in short geological time. There is a boardwalk here. I would never be this close to open water, if I were on a floating mat!

Bogs in SE Wisconsin don’t pack as many species into a given area as some of our other natural communities, but they are among the most interesting. The water that feeds the depressions containing the bogs consists of recent rainwater that has had little opportunity to pass through mineral rich soils or glacial till, and the decaying spagnum moss acidifies the environment. This leads to the development of a plant community dominated by specialized plants, including a number sedges, ericaceous shrubs like huckleberry and leather leaf, and carnivorous plants like sundews, pitcher plant, and bladderwort.

Some open areas of the bog are absolutely covered with minute round-leaved sundews, a carnivorous plant that snares insects with the  sticky drops held on stalks from their modified leaves.

Some open areas of the bog abound with round-leaved sundew, a carnivorous plant that snares insects with the sticky drops held on stalks from its modified leaves.

A purple pitcher plant in sphagnum moss- Pitcher plants digest insects in their liquid-filled, modified leaves, which are lined with downward pointing hairs.

A purple pitcher plant (Sarracenia purpurea) in sphagnum moss- Pitcher plants digest insects in their liquid-filled, modified leaves, which are lined with downward pointing hairs.

Bladderwort (here, Utricularia gibba) trap invertebrates in small bladders.

Humped bladderwort (Utricularia gibba) traps invertebrates in small bladders held on small leaves that float in shallow depressions or sit on top of recently exposed mucky or peaty shores.

Beak-rush (here, Rhyncospora alba) is not a rush at all. It's a sedge sedge that occurs in open areas of bogs and fens.

White beak-rush (Rhynchospora alba) is not a rush at all. It’s a sedge sedge that occurs in open areas of bogs and fens.

Tawny cotton grass (Eriophorum virginicum) is not a grass. It's a sedge that is extremely abundant at Beulah Bog and typical of bogs in SE Wisconsin.

Tawny cotton grass (Eriophorum virginicum) is not a grass. It’s a sedge that is extremely abundant at Beulah Bog and typical of bogs in SE Wisconsin.

Three-way sedge (Dulichium arundinaceum) reproduces mostly asexually by rhizomes, despite what the name might imply. The name refers to the three-ranked leaves that form three perfet rows when viewed from above.

Three-way sedge (Dulichium arundinaceum) reproduces mostly asexually by rhizomes, despite what the name might imply. Rather, the name refers to the three-ranked leaves that form three perfect rows when viewed from above.

Huckleberry (Gaylussacia baccata) and tamarack (Larix laricina) dominate much of the bog interior.

Huckleberry (Gaylussacia baccata) and tamarack (Larix laricina) dominate much of the bog interior.

The fruits of water arum (Calla palustris), which occurred throughout the bog.

The fruits of water arum (Calla palustris), which occurrs throughout the bog.

Few-seeded sedge (Carex oligosperma) is the dominant sedge at Beulah bog.

Few-seeded sedge (Carex oligosperma) is a dominant plant in the bog.

Viewed today was the result of thousands of years of slow, undending change. There is something soothing to me about that kind of change, the same kind of change, but on a different scale, as the brightening dawn or waxing moon. It certainly beats the abruptness of the change wrought by agriculture and development on the landscape or the sudden turning on of a lamp in the dark of early morning.

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