Archivos de diario de febrero 2019

12 de febrero de 2019

Hints for identifying Carex using photos.

This blog started as a response on this website to an observation. However, I'm glad I copied and pasted the text into a document prior to posting. The software wiped out my note at "too long" and exceeding the 1000 character limit (it has more than 5000). So, I'll try posting it here.

As for Carex photos, photos of just the flowers (spikelets) are certainly helpful and often diagnostic. The insect is also interesting but would be a separate observation. It is hard to say exactly what works best with sedges, but here are a few general rules of thumb.

(1) Roots may be required. I used to identify Carex frankii throughout Arkansas. However, the closely related C. aureolensis has very long rhizomes. So, without a photo of rhizomes I can't tell you which is which. Someone might, but I can't as I've not studied other characteristics or researched it. Similarly, if memory serves me well, C. floridana has long rhizomes and C. nigromarginata forms large circular clones. Varieties of C. albicans may also require looking for rhizomes. Some taxa such as C. hyalinolepis have large and distinctive rhizomes. So, when I collect, I try to get rhizomes or roots of any Carex. The same would apply to photos in general.

(2) In the next two months from Louisiana north with climate, look for very short stalked carices such as C. umbellata, C. tonsa, C. reznicekii, and others. I love the C. umbellata story in Arkansas as an example. The state had listed it as S1 (six or fewer sites or subject to other hazards of extirpation). I started collecting Carex in 1990 and for a few years walked over it every year. Why? These look like a circular clump of grass all year long. When I did discover it, I started finding it everywhere. A few weeks later, I added six county records in about ten minutes of field time outside my car! The perigynia are on very short stalks, 1-3 cm tall. They bloom early, late Feb. to March in Arkansas. L. L. Gaddy found ants like the oil bodies (eliasomes?) at the base of the perigynia (same is true for C. nigromarginata) and I'd often find plants covered with ants. By April, the plants would be sterile and by the end no sign of perigynia were left. But botanists don't hunt them in March! In the east (NC, GA, et al.) there's C. tonsa which tends to be found in tiny clumps with a few culms less than 2 inches high on disturbed muddy edges of gravel parking lots, which I might call its preferred habitat! Trails also work. It seems to like disturbance. For identification, some species will require careful and clear photos of the length of the culms and peduncles.

(3) Leaf sheaths are often important and without a clear view of sheathless or sheathed species, a person gets stuck in the keys. Leaf width is important in some species, so taking a photo with a millimeter ruler would help with that and many other characteristics.

(4) The leaves themselves can be important. Several species have distinctive glaucous leaves or hairy leaves. For example, C. oxylepis var. oxylepis is (more or less?) glabrous while var. pubescens is quite hairy. Hairs may not be easy to see or even photograph. On rare occasions, I found hairs on supposedly glabrous plants only to be told "Ignore the sparse hairs at the base of the stem."

(5) Spikelet length and shape is often important. You had great photos for that.

(6) Perigynia and achenes are often important at the species level. To be honest, if I was going to regularly photograph sedges, I'd have to come up with a good method. A scope with a camera would of course be ideal, but as you will see below, I've always had other ideas.

Conclusions:

Despite being a regional ecologist for the US Forest Service before I retired and collecting thousands of Arkansas Carex specimens, I've always considered myself someone of a naturalist more than a scientist. That is, I don't conduct my laboratory or even field research. I like to find things and let others deal with the specifics. I've always wanted to be like my professor, Dr. Douglas James at the U of Arkansas, who seemed to be able to pick up anything and give it a name. I took the same approach to Carex. So, you will see me taking photos of sedges out of season without fruit or some diagnostic characters shown. Here's a recent example: https://www.inaturalist.org/observations/20071014. Based on field experience, I feel 99.9% sure of this ID despite the sterile plant! When I look at a sedge in the Section Ovales, I still want to be able to identify it on sight without using a scope. Most people fear any attempt to identify them accurately. However, I found some very easy to determine. C. longii has a particular look to it that is hard to define (and a unique perigynium shape). C. festucacea also has a hard to define look to it. C. ozarkana is very easy to identify on sight, but can be confused with C. festucacea at first. C. molesta (upland wet spots) and C. molestiformis (riverine wet spots) have slightly overlapping habitats (such as upland wet spots near rivers!) but it really takes looking at the achenes to easily nail the ID (which is done very easily). These latter two I studied in about 1992 or 1993 by making about 25 collections in Baxter County. If I recall correctly, Tony (A. A.) Reznicek agreed with all my IDs. Then, I compared the collection sites and defined the habitats!

So, have fun! Otherwise, it is like work!

Ingresado el 12 de febrero de 2019 por sedgehead sedgehead | 13 observaciones | 2 comentarios | Deja un comentario