You can't understand conservation without understanding conservatism and quality.
A principal goal of conservation is to maintain healthy ecosystems with full complements of the species and genetic diversity. The species that are declining most seriously are "the conservatives."
A conservative plant is the opposite of "a weed." Conservatism can be measured. Common ragweed has a coefficient of 0. The prairie white-fringed orchid has a coefficient of 10. "Coefficients of conservatism" reflect the fidelity of species to high-quality natural areas, on a scale of 0 to 10. If most species at some site are in the 0 to 1 range (dandelions and ragweed, for example) the site has suffered gross degradation. High-quality natural areas are the only ones likely to have plentiful species in the 8 to 10 range, the ones that most indicate health and quality. (See, for example, Endnote 1.)
Floristic Quality Assessment is a way to quantify the plant biodiversity or health of a large or small ecosystem. To compute a Floristic Quality Index (FQI), you first identify the plant species in the area or plot. Then you evaluate the data using a formula that gives higher ratings in proportion to how many plant species are present (diversity) and how well they reflect the now-rare species that made up long-evolved ecosystems – prior to the rise of common “weeds” that now live where plowing, bulldozing, over-grazing, or other mostly-human-caused changes have degraded or eliminated long-evolved species and relationships.
As Dan Carter reminds us under Comments (below), the FQI computation in many cases may not be as helpful as other, related quality indicators. He recommends assessments based on "mean conservatism" or "mean conservatism weighted by relative abundance" as discussed in some of the references, below.
Plants of higher conservatism rankings are rapidly being lost or are already gone in most areas, as habitats degrade. High-quality natural areas typically have large numbers of diverse conservative plants. Two goals of biodiversity conservation are 1) to maintain the health, quality, and species populations in original high-quality natural areas and 2) to restore such populations to larger areas so that evolution and other ecological processes can proceed without biodiversity loss.
The concept of conservatism can also be applied to animals, soil biota, etc. But the concept is most developed for plants.
Floristic quality can be computed for an area of any size from a square foot to a whole site consisting of hundreds or thousands of acres or hectares. One good way to compare natural areas is to sample and then compute average FQIs of many small plots. For example, quarter-meter plots in the original prairie at Somme yield an FQI average of about 20. Unrestored buckthorn thickets have a per-plot FQI of zero.
To see an example of woodland quality rising with restoration (but interrupted by a period of very high deer browsing and another when work was stopped for some years by politics) check out the graph below:
For more details and references, see here and here and here.
If any reader has suggestions for improving this thumbnail explanation, please offer edits in “Comments” below or through an email.
As an example, below is a list of the "most characteristic" "highest quality" (most conservative) species of the classic Illinois black-soil prairie:
Common Name | CC | Scientific name | Scientific name |
cream false indigo | 10 | Baptisia leucophaea | Baptisia leucophaea |
scarlet painted-cup | 10 | Castilleja coccinea | Castilleja coccinea |
white prairie clover | 10 | Dalea candida | Petalostemum candidum |
prairie gentian | 10 | Gentiana puberulenta | Gentiana puberulenta |
prairie white-fringed orchid | 10 | Platanthera leucophaea | Habenaria leucophaea |
prairie lily | 10 | Lilium philadelphicum | Lilium philadelphicum |
prairie panic grass | 10 | Dichanthelium leibergii | Panicum leibergii |
prairie dropseed | 10 | Sporobolus heterolepis | Sporobolus heterolepis |
heart-leaved Alexanders | 10 | Zizia aptera | Zizia aptera |
Acknowledgements
Thanks to Karen Glennemeier for the graph.
Thanks to Christos Economou for proofing and edits.
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ReplyDeleteI would just emphasize that FQI is a function of species richness and conservatism, so it is a function of assessment area size (as richness is), and where degradation is occurring and both weedy species and conservative species co-exist, that higher richness will inflate FQI relative to what it would be if the added richness were conservative species...again because it is a function of richness. Mean coefficient of conservatism (mean C) and Mean C weighted by relative abundance are not vulnerable to those effects. ...so I guess I'm among those that prefers those other metrics to FQI, especially where we are trying to monitor old growth, remnant natural communities or reconstruct the lost complexity of those communities.
ReplyDeleteThe averaging of FQI within a series of quadrat subsamples is a good way to counteract the area-richness relationship, but not so much the bump as richness as weedy vegetation moves in but conservative vegetation still holds on.
DeleteI agree that mean C - especially where weighted by abundance or cover - is a good metric. But I look both at FQI and mean C. It's common with us, these days, to be dealing with areas of woodland sunflower monoculture. If I were to compare such an area (mean C = 5) with another area where, for illustration, there were ten species with a Cs of 4,5 or 6 (C = 5), the much higher FQI would more helpfully indicate meaningfully better quality.
DeleteThat makes sense. The same thing happens in the study of response to management in the Flint Hills. There, extreme overdominance of big bluestem and Indiangrass bump C up. I can picture a situation too where a WI oak woodland herb layer may be taken over by jumpseed (C=7!), but is in fact extremely degraded. That said, if you have richness as it's own metric you can tell whether your mean C is driven by over-dominance of matrix species (or one that perhaps should have a lower C-value) or not. Another promising approach is coarse metrics. There, instead of finding the floristic metric that best aligns with what an experienced steward knows is healthy vs. not, the attributes of a specific community type in terms of structure and are scored. I look at those and have some trouble getting past specific things left out, but they seem to capture site quality very well. In WI we have this for barrens, wet-mesic prairie, and southern sedge meadow. We're starting to work on oak woodlands and savannas, which are tougher, because those communities could each be split up as much as the different types of open prairie are.
ReplyDelete*in terms of structure and composition are scored* in the nonsensical line above.
ReplyDeleteRegarding aggressive composites, I'm starting to wonder if some of the problem in some contexts is lack of the appropriate Orobanche and Cuscuta species.
ReplyDeleteWe harvest and broadcast the seed of dodder (Cuscuta), and it does seem effective at diminishing aggressive species in some areas. Ghost pipes (Orobanche) is common in our woodlands; we haven't noticed much impact in its areas; but it would be great if someone found a way to test that. Wood betony (Pedicularis) and bastard toad flax (Comandra) seem to substantially reduce aggressives.
DeleteOh, not ghost pipes. I'm referring to Orobanche uniflora--not Monotropa uniflora.
DeleteSorry for the confusion. "Ghost pipes" here is a common name for Orobanche uniflora. We call Monotropa "Indian pipes". Perhaps showing questionable judgment, I often use common names, believing that many "learning stage" new conservationists will find them accessible - and the the pros should know both. But "ghost pipes" may be a troublesome common name in that it's about the "third most common." "Broom rape" and "cancer root" seem to be more common, but I'm reluctant to burden this beautiful non-rapist, non-cancerous plant with either of them. I wonder if there's a better, less confusing common name.
DeleteThe use of mean-C and Floristic Quality Index (FQI) has some deficiencies in evaluating the results of ecological restoration/recreation work when accessing the quality of a site. This should not be surprising, because these tools are ones that were created to be used for quickly identifying sites that had indications of little human disturbance. Mean-C and FQI are by design indifferent to the number of a species’ plants that are present; one plant or a hundred is all the same for these two tools. One plant present per species is not really healthy; hundreds of plants are, or at least can be, healthy.
ReplyDeleteA low C-value is not the disparagement of a native species; it is the testament of the species’ ability to survive. High C-value indicates a limited ability to survive. The site with only high C-value species is not necessarily healthier (a human perception) than the site with mainly low C-value species. In fact, it would probably have been unnatural. Sites with many low C-value species and their numbers should be expected. For example, Bell Bowl Prairie, portions of which have been “undisturbed” since the last glacier departed, has a mean-C and an FQI of 4.8 and 46.5, respectively. 15 have a C = 10 (16 if the state endangered Penstemon grandiflorus there is not really a non-native). There the majority of native species (53%) has C-values of less than 5.
https://www.naturalland.org/wp-content/uploads/2021/10/Bell-Bowl-Prairie-Plant-List.pdf
As for “aggressiveness” in a native species, it is a human perception that there is “too much” present. When it occurs, perhaps Nature is really trying to say something about the site’s soil or environment rather than something about the species itself. In such an area does Nature really insist upon a homogeneous dispersion of various species and their numbers or is that just a human perception of need? Perhaps there should be dense patches of a species here and there; Nature should have the final word.
The questions that should be asked and answered are (1) What is it about a site’s soil and environment that are sufficiently “undisturbed” to allow Silene regia or Cimicifuga racemosa to survive and flourish (2) What is it about a site’s soil and environment that creates “aggressiveness” that allows Solidago altissima to suppress its neighbors or Amphicarpa bracteata to smother everything?, and (3) Would a site devoid of non-native species be considered healthy?
Kirk, your comments seem reasonable and helpful. But I'd add this consideration. For purposes of biodiversity conservation, many of us try to restore communities to "ecological health" - meaning a state where all plant and animal species can survive - especially those that do not survive well in the current "modern" landscape. The best research and observation seem to suggest that for most species (especially those that are Endangered or much reduced today) "natural" (or "millennia old") highly-diverse habitats support such species best. Indeed, many of them survive only in communities that seem to reflect their millions of years of evolution.
DeleteYes, diverse communities seem naturally to have species of all levels of conservatism - not just the high conservatives. But degraded communities typically have few or no high conservatives.
And there are studies that suggest that such diverse communities can also help restore "health" to damaged soils.
"High C-value indicates a limited ability to survive" I think that's as much human perception as descriptors like "aggressiveness." Oftentimes conservative species have flourished on a site for at least hundreds of years, likely more. The difference is ability to survive under a novel disturbance regime or colonize disturbed sites.
ReplyDeleteGood point. I agree.
DeleteThis links to a picture of the sod at an ungrazed oak woodland remnant in Walworth County, WI. Surrounding areas that were, are buckthorn. I would contend that this sod, consisting of many relatively conservative plants and the constituent species are plenty tough, but just not when put up against fenced bovines. Granted, the Robin's plantain is a 3. ...but the presence of low C species in a high quality site is antithetical to anything. https://bastardtoadflax.files.wordpress.com/2020/11/image-4.png
ReplyDeleteD.I.Carter: The photo is inspiring. I'd like to go there. Could you say what the major summer and fall species are here? And what the major grasses and sedges are here?
ReplyDelete