Sunday, September 9, 2018

What we can learn about ecosystem collapse from Iceland

A large proportion of Iceland is either unvegetated completely or only very sparsely so. This is generally true of highland regions, but also some lowland regions where sand plains may be found.  These are called deserts: not in the sense of a dryland, but in the sense of a deserted place where the paucity of vegetation makes it exceptionally difficult to live. 

This could be the Atacama Desert or Mars. It's a highland desert of Iceland.

A view of Sandvatn, on the way to Langjökull glacier. Notice that little island of green by the lake...more on these islands below.

It is also curious that despite a mild climate for the latitude, the land does not support trees generally. Often, it seems that the dominant vegetation are mosses in rocky areas like lava flows, or grasses where there has been some soil formation. Maybe this isn't so strange in the highlands, where you might have expected more low-growing plants. But, this holds true even in areas closer to the coast which are well within the environmental tolerances of trees.

Your first instinct may be to look at the glaciers and ice sheets, the most extensive in Europe. You might think that after the last ice age, the land never really supported plants because of the recent glaciation. Or you might pin it on the several active volcanoes. And yet old writings, including the sagas, report a vegetated place. Another key to the past is in place names, for example many place names refer to a forest or woodland, yet if you go there there is no such thing present. There's also some hard physical evidence of more extensive vegetation. For example you can go to some nearly barren areas and find charcoal pits. The charcoal would have been made to fuel iron forges (settlers were iron age people), but where are the trees? Surely people didn't drag wood into some barren area just to make charcoal. A sensible person would produce the charcoal where the wood is, then transport the much lighter charcoal.

Then, most informative of all are the rofabörðs. Rofabörðs are actual remnants of vegetated land, usually in small patches with abrupt cliff-like boundaries, that border unvegetated land. I find it poetic that they are sometimes shaped like puzzle pieces. They are that final piece that allows you to solve the puzzle of Iceland's past. You only have to see one to guess the amazing truth: 1. Iceland had vegetation, 2. Now it's mostly gone, 3. The soil, sometimes alot of it, is now gone too. When you start piecing this together with some of the other lines of evidence,  you can further infer that: 4. people were a part of this change. 

A rofabörð at the bottom of a slope at Einifell.

The other side of the hill. Another rofabörð ends abruptly in a cliff-like edge of greater than 1 m.
You can see quite a bit digging into a rofabörð. First, they are deep! Second, they preserve a stratigraphic record of key events like volcanic eruptions. The long term presence of vegetation seems to associated with substantial soil development, and furthermore vegetated patches accumulate rather than lose soil over time, alot of it.

Oli Arnalds opening a soil pit into a nearby rofabörð. Note that the top is vegetated by heath including grasses and low growing shrubs.

We exposed over 1.5m of soil, and still did not reach a marker called the "settlement tephra layer", which is dated to the year 871. This patch must have gained all of that soil in the last 900 years or so. You can see a black tephra layer here, probably one of the more recent (a few centuries ago) Hekla eruptions. 

The scope of the ecosystem collapse is huge. Iceland's vegetation loss led to catastrophic erosion in about one third of the country. The ability of these severely eroded areas to support vegetation ever again is seriously compromised, and it doesn't happen very often without a serious shove from people (future post alert!)

Ok, why did this happen to Iceland? A perfect storm of multiple factors, here's my summary attempt:

1. From the beginning,  Iceland has some unique vulnerabilities. Volcanic ejecta (tephra: ash, cinders, etc.) can, has, and does sometimes bury low-growing vegetation, knocking back the productivity and coverage or snuffing it out completely. This has happened many times to greater or lesser degrees anywhere in the country. The record is captured in soil remnants with datable tephra layers that you can clearly see. Another more localized factor is that many meandering rivers emanating from the ice sheets can render large plains bare (e.g. Skeidarsandur), especially when there is an ice flood. Finally, the soils are andosols, derived from volcanic ash. Such soils may present some nutrient availability challenges, may poorly aggregate without vegetation and organic inputs, and may contain some unusually light mineral particles that can be easily transported by wind or water.

2. Over this fabric of vulnerability, settlers cleared the forests and woodlands to build and heat homes, conduct metal working, and make farmland. The Icelandic birch would have been the dominant species of the lowlands, growing in usually open canopies in small shrub to tree form. this is the only native timber. Such woodlands covered about one third of the country. The highland was likely vegetated with heath with low growing, spreading dwarf shrubs. This heath was not grazed by any native mammalian herbivores, there are none. So the introduction of sheep or goat grazing in the highlands was a new ecological pressure for this system and would further impact recruitment and porductivity of shrubs.

3. Without much tall vegetation anymore (very few trees, fewer shrubs), the former woodlands had lost their resistance to volcanic ash deposition. Some of these areas became deserts after ash fall smothered the rest of the vegetation.

4. Without vegetation, soil erosion is much more prevalent. All of this leads to permanent widespread soil loss, sometimes measurable in meters, and expansion of desert regions. Some sandy deserts also tend to encroach into adjacent areas, compromising vegetation more.

5. A last insult was the Little Ice Age, which was an unconducive period for plant growth, especially with all of these other pressures also occurring.

The prevailing story here is that multiple factors lead to the ecosystem collapse, but new anthropogenic pressures like wood harvest and grazing speeded, expanded and exacerbated natural disturbance regimes. This is difficult to reverse now, but a few ways have been developed by the oldest Soil Conservation Service in the world.

Thursday, August 30, 2018

Exploring Fire Moss in the Northwest

When I tell people that I study mosses in Arizona and New Mexico some folks give me a quizzical look and ask why I’m not working up in the Northwestern US. Thanks to the support of Jason Jimenez from the Colville National Forest and Pete Robichaud from the RMRS Moscow Forest Sciences Laboratory I have been able to heed that advice. Over the past two summers I have traveled to Kettle Falls, Washington to help monitor a Burned Area Emergency Response (BAER) mulching treatment on the 2015 Stickpin Fire. This has also fed my summer wanderlust as I have expanded my natural survey of fire moss colonization to the 2015 fires in Washington and the 2017 fires in Montana.

The Sunrise Fire of 2017, Quartz Montana
It was incredible to see just how important moss is for postfire recovery up there, everything that north westerners had told me was true! I saw the usual suspects Funaria hygrometrica and Ceratodon purpureus, and some new early successional species, Polytrichum juniperinum and the liverwort Marchantia polymorpha. One species that was conspicuously absent from the Northwest was Bryum argenteum. Total bryophyte cover was over 50%! And the speed of natural colonization and succession was incredible. After exploring fires less than one year old, it became apparent that moss was the largest contributor to cover immediately after fire, and thus is an important component of soil stabilization in this region.

Some crispy Marchantia and Funaria both releasing spores prolifically, two years after fire
Moss colonizing the Noisy Creek fire spring 2018, 8 months after fire
To better understand how mulching affected moss colonization on the Stickpin fire, I trained the soils crew from the Colville NF on my methods. Last fall, they sampled straw and wood shred mulched units, as well as an untreated unit. Moss cover was significantly lower on both of the mulches, but seemed to fill in around and under them quite well.
Maddie and Amber demonstrating perfect bryophyte sampling technique. It has been wonderful to share my research with land managers and learning from their experience in a new ecosystem. 
Moss eking out a living under low cover straw mulch.

We were interested in exploring mulching impacts byrophytes in more detail. Additionally we wanted to understand how postfire logging affects moss cover on a logging experiment that had occurred close by. Both mulching and logging are relatively common postfire management techniques and their impacts on vascular plants has been studied in detail. Broyphytes have received much less attention so I submitted a Joint Fire Science Program GRIN proposal to expand our research and it was funded! We will continue to monitor the impacts of postfire treatments on bryophytes this fall and will add some plots in logging units. We will also measure the impacts of mulching and logging on available soil nutrients and relate that to bryophyte cover. Finally, a major component of the GRIN is outreach to the management community so I will be attending BAER workshops, giving a webinar, and creating a fact sheet to continue sharing my research with land managers.

Wednesday, August 22, 2018

Learning a new flora: biocrusts of Geitasandur, Iceland

Geitasandur means "goat sand plain" more or less, which is a pretty cool name. I'll tell you more of its interesting story later. For now, I'm prepping to survey this flora next week. I grabbed over 20 species, mosses and lichens, in a quick visit last week, mostly new to me. So, I'm in that stage of examining, identifying to some degree, and assigning pseudonyms so that I don't have to call everything "unknown lichen 1 - 45". Maybe you can help. Please feel free to suggest some taxa in the comments that I can verify with a key (or an expert) later. By the way, though some species may be shared, this community is totally different from the highlands snow bed community I mentioned previously.

Here's what I grabbed, I imagine there's about 30 species total out there.

Photo 1.Two interesting fruticose lichens. Someone must know the brown one. I've seen the genus before, but don't know it. The white one with a bluish cast is a Stereocaulon. There seem to be multiple species in that genus at the site (S. alpinum is there; but S. arcticum and others are plausible).

Photo 2. I'm curious about that deeply lobed foliose lichen, growing among Polytrichum stems.

Photo 3. Could be Protopannaria, maybe Psoroma. Any other ideas?

Photo 4. Absolutely my favorite! My mind goes to Solorina or Peltigera. It's small, only a couple cm in diameter.

Photo 5. Lots going on here. Good view of a Racomitrium cushion, concealing a Cladonia. But there appears to be two white-rimmed orange things here. 

Photo 6. The little one in the middle. Reminds me of a (miniature) Toninia, maybe Buellia, but probably isn't.

Photo 7. Here's one of the Stereocaulon. Tidy crowded cushion, usually pretty big (3 -5 cm diameter, 1-3 cm tall).

Photo 8. Another beauty. Peltigera for sure, clear dark veins underneath. Reasonably matches P. leucophlebia, but I have not keyed it to be sure.

Photo 9. My second favorite, Very cryptic when standing, but it really pops when you're near the ground. Reminds me of  a Psora, but not one I've met.
The Fulbright Global Scholar program is making it possible for me to spend about the next 3 months in Iceland conducting research and building connections (disclaimer: any views I express in this blog are mine and do not represent the Fulbright Program or the US Government).

Saturday, August 11, 2018

It's alive!

I mean this blog (it's been dormant, not dead), and the biocrust in this picture. There are no rocks in this foreground of this photo. The rolling gray micro-hills are the liverwort Anthelia juratzkana. The orange sporophytes are those of a Polytrichum. Then you can see tufts of another moss. Also present are lichens such as Stereocaulon (not visible in this photo, but they are around). This is one of the prevailing community types in the Icelandic highlands, translating to a moss snow bed community. Apparently highland soils dry out quickly and easily, even though the climate is wet, low lying areas with late snow are needed to support this community. Once these crusts occur, the soil N increases strongly, and also importantly, frost heaving caused by needle ice is reduced. Under these conditions, vascular plants may germinate.

Lest you think this community is something like a moss or lichen carpet typical of boreal regions, I've cut away a small piece here revealing that this is really just a superficial layer (about 1 cm or so) directly over mineral soil. It's not so different from biocrusts of semi-arid regions. Generally, alot of dominant biocrust species tend to have massive multicontinental distributions. This Anthelia also fits this pattern, for example it also forms biocrusts on volcanic soils in Alaska.

The photos below will give you a sense of the habitat. This was from a place called Kaldidalur (translates to cold appropriate name). These are andosols (andisols in USDA system), a type of soil that forms from volcanic ash. You would not be silly to think highlands areas like this one are bare because they were recently glaciated. Actually, they used to support heath vegetation within the last 1000 years. The reason(s) why they are barren now will be the subject of a future post.

I am on sabbatical. I love that phrase. The absolutely wonderful Fulbright Global Scholar program is making it possible for me to spend about the next 3 months here (disclaimer: any views I express in this blog are mine and do not represent the Fulbright Program or the US Government). This is one of the coolest things the Department of State does. Briefly, they support academic exchanges for professors (and students) to spend time in other nations to foster international collaboration and understanding. I am hosted here by the Agricultural University of Iceland. My hosts are Ása Aradóttir, a plant ecologist and restoration ecologist and Ólafur Arnalds, a soil scientist, who were my guides to learning about these highland crusts. My goals for this portion of my sabbatical are to 1. refine the sampling protocol for CrustNet (a global study we are whipping up...more on this in later posts) and conduct the first sampling, 2. learn as much as I can from this unique environment, 3. keep this blog alive.