Friday, May 6, 2022

Book Review: The Death of Grass by John Christopher

by ISFDB

I admit that I probably would not have read this before my interest in the Poaceae.

I am an ardent science fiction reader, but this post-apocalyptic novel was published in 1956, and I tend not to read older SF. Nevertheless, once I started reading it, I found to my surprise that it was actually quite interesting, although some of the language and viewpoints of the characters were quite dated and made me cringe and roll my eyes.

The story involves the spread of a virus named Chung-Li, which devastates rice crops in China, causing mass starvation. Although confined at first to rice, the virus soon develops variants which attack all members of the grass family. Caught in the backdrop of this ecological catastrophe, a mild mannered British man named John and his family try to safely make it to his brother David, who has started growing potatoes in a farm that is sheltered in a well protected valley. On the way they pick up various other people who can help them, and John slowly transforms into a hardened survivor who will stop at nothing to protect his family.

The Chung-Li virus devastates rice crops

The author does a very good job of emphasizing the importance of the grass family to the very fabric of our lives. Not only does he show the disintegration of governments and societies when the virus expands worldwide, but at various points in the narrative, the characters note the disastrous consequences of the loss of grasses because these make up the vast majority of our food.

"Yes," John said, "wheat is a grass, too, isn’t it?"

"Wheat," David said, "and oats and barley and rye – not to mention fodder for the beasts."

In addition, the author is thoughtful enough to mention the scientific name of the grass family, and even goes so far as to throw in the taxonomic nomenclature of some grass  genera and tribes. 

Roger went on: "The appetite of the Chung-Li virus was for the tribe of Oryzae, of the family of Gramineae. Phase 5 is rather less discriminating. It thrives on all the Gramineae."

"Gramineae?"

Roger smiled, not very happily. "I’ve only picked up the jargon recently myself. Gramineae means grasses – all the grasses."

John thought of David. "We’ve been lucky."

"Grasses," he said, "that includes wheat."

"Wheat, oats, barley, rye, that’s a starter. Then meat, dairy foods, poultry. In a couple of years’ time we’ll be living on fish and chips – if we can get the fat to fry them in."

Wheat is also affected, by Bluemoose

The disappearance of grasses not only impacts the entire food chain that enables civilization, but it also impacts the surroundings, as noted by one of the protagonists:

‘They frightened me. I hadn’t understood properly before quite what a clean sweep the virus makes of a place. Automatically, you think of it as leaving some grass growing, if only a few tufts here and there. But it doesn’t leave anything. It’s only the grasses that have gone, of course, but it’s surprising to realize what a large amount of territory is covered with grasses of one kind or another.’

Although the author has done his botanical homework, he seemingly stumbles at certain points in the narrative. For example, as rationing starts to take its toll on the country, some children complain about the rationing of sweets.

"Potato-cakes,’"John said, "and the empty tin circulating along the tables for you all to have a sniff. Very nourishing too." 

Davey said: ‘Well, I don’t see why they’ve rationed sweets. You don’t get sweets out of grass, do you?’

But of course, most sugar is actually derived from sugarcane (Saccharumn officinarum), which is also a grass!

Overall, I found the novel interesting and entertaining, and the author does not shy away from describing the savagery of man when civilization collapses. In one of the Stephen King novelettes, the phrase "arc of descent" is used, and I think that phrase is quite apt in describing the way the protagonist in this book evolves from beginning to end. 

If you have the time and inclination, give it a go. An electronic version (kindle) is available from amazon.com, and probably from other booksellers worldwide.

Enjoy!

Dying maize/corn


Thursday, April 28, 2022

When Kangaroos Came Down from the Trees

by Rileypie

Kangaroos are marsupials, that unique group of mammals that originated in the Americas, then crossed Antarctica 55 million years ago to end up in Australia by around 25 million years ago. Although kangaroos do not belong to a single species, but to several related species in the family Macropodidae, the group is characterized in the mind of the public as all having disproportionately large hind legs and a propensity to hop along the savannas that it inhabits.

But people today would probably not even recognize the ancestors of these iconic mammals, which were opossum-like critters that spent their lives up in the trees and first ate fruits and then tree leaves. The prevailing view at one time was that the kangaroos did not move down from the trees until around 15-5 million years ago, when growing aridity in Australia caused them to gradually evolve to have the attributes we see in them today.

Modern kangaroos loiter about in their grassland home (by By AWS10)

But a new study disputes that theory.

Researchers studied the teeth of more than 1600 kangaroo specimens, both from modern kangaroos and their fossil ancestors. They focused on the crown height and wear on the teeth, which gave them an indication of what the animals ate. Animals that eat relatively soft foods such as leaves and fruit do not have high crowned teeth, and the wear on the teeth is much less than if the animal ate something abrasive such as grass. This is because grasses are filled with silica bodies called phytoliths, which make eating them akin to eating sand, and the high crowned teeth is an adaptation towards eating such tough food.

Modern Tree Marsupial, who remained in the trees, by By Fred Hsu

When these researchers looked at the changes in teeth from the ancestors of kangaroos to their modern counterparts, they found that the change in dentition (from low crowned to high crowned teeth) and explosive radiation of kangaroo species did not happen as the land first grew arid (15-5 million years ago). Instead, this change only happened 3 million years ago, when C4 grasses started pushing back the trees and forests to create the grasslands and savannas that are now so prevalent in that continent.

This tight correlation between the expansion of grasslands in Australia and the evolution of the kangaroo as we know it today again highlights the importance of our old growth grasslands to the rise of so many iconic and magnificent animals. 

In fact, without the grasslands, our own ancestors would not have done the same thing as the kangaroos did, and we might still be lounging lazily in the treetops today, our minds bereft of the keen intelligence that (allegedly) is a hallmark of Homo sapiens.

Reference:

Couzens AMC, Prideaux GJ. Rapid Pliocene adaptive radiation of modern kangaroos. Science. 2018 Oct 5;362(6410):72-75. doi: 10.1126/science.aas8788. PMID: 30287658.

Monday, April 18, 2022

The Mysterious Origin of Andrews Bald in Great Smoky Mountain National Park

View at Andrews Bald using Panorama setting of Phone Camera

Lying just an hour and a half walk away from one of the most popular tourist destinations in Great Smoky Mountains National Park is a large grassy area that sits atop a mountain. Since it is still below the timberline, all around this open expanse are tall spruce and fir trees, which provide a very shaded environment for hikers who venture out from Clingman's Dome and want to do the 2.5 km trek to this somewhat anomalous area.

The hike itself is moderately easy and quite peaceful, although the almost continuous upward incline on the way back was somewhat strenuous. Recent upgrades to the trail provided nice steps and above-ground planks at certain points that allowed us to move quickly over the sometimes muddy ground.

Narrow boardwalks and steps provide sure footing for hikers

After about an hour and a half we finally burst into the open air and gazed upon an amazing grassy meadow that covered about 1.6 hectares of the mountain top. The change from the dark forested interior to the sunlit top was fairly dramatic, and many people had draped themselves over the lawn-like ground close to the opening, although it was only April and most of the grasses had yet to green and were a dry golden color.

We had finally arrived at Andrews Bald, which at 1800 meters (1.8 km), is the highest so-called "bald" in the Great Smoky Mountains National Park.

Wooden path emerges from forest into Andrews Bald

These "balds" are grassy meadows below the timberline which are found in the southern Appalachian Mountains, and the origins of most are shrouded in mystery. The dominant grass is usually Danthonia compressa, but other grasses such as redtop (Agrostis alba), timothy (Phleum pratense), Canada bluegrass (Poa compressa), Kentucky bluegrass (P. pratense), and red fescue (Festuca rubra) may also be found.

The trail continues, with a view to other parts of the Great Smoky Mountains

Some researchers believe Native Americans originally cleared the areas as hunting grounds or lookouts, and there are historical records that seem to indicate that settlers cleared some of the balds for grazing. There are even some who postulate that the balds had been originally founded by prehistoric herbivores, and then maintained by human hands thereafter.

Whatever the case, there is no doubt that the balds had been used as grazing land during the 1800s. The cattle and sheep that were herded up onto these ridgeline areas during the summer months kept the land open, but after the formation of the national park and the cessation of grazing in the 1930s, trees and shrubs have been slowly reclaiming the land.

Andrews Bald, with visitors (dots on far left) sunning themselves on the golden Springtime grass

A quick look at historical satellite imagery from Google Earth shows that Andrews Bald went from being around 2.5 ha in size in 1995 to around 1.6 ha in 2017 (see image below), and if grazing continues to be excluded from the area, then it is probably inevitable that the bald will continue to shrink in the future. 

But for now, visitors can continue to enjoy the relatively open vista possible in Andrews Bald. It may not be the vast green expanse that it used to be, but I still highly recommend it if you ever visit Great Smoky Mountains National Park.

Area of the meadow shrunk from 2.5 to 1.6 ha from 1995 to 2017

Thursday, April 14, 2022

Rushes are Round: Finding Luzula in Great Smoky Mountain

Although this site is focused on the Poaceae, the other members of the order Poales can oftentimes be mistaken for grasses. This is especially true for members of the families Juncaceae (rushes) and the Cyperaceae (sedges), which are sometimes even given common names that mistakenly identify them as grasses. 

In this case, there is an old adage that might help people separate the three. It goes:

Sedges have edges. Rushes are round. Grasses are hollow. What have you found?

OR

Sedges have edges, rushes are round, Grasses have nodes all the way to the ground.

So, if the stems have corners and edges (roll a stem between your thumb and forefinger), then it's likely what you just thought was a grass is actually a sedge, and if the rounded stems are not hollow and have no nodes spaced along their length, then you probably have a rush.

This rhyme helped me during a hike along the Grotto Falls trail in Great Smoky Mountain a couple days back, when I spied some graminoids near the edge of the wet path that had lots of spiky inflorescence at the top. They were notable because this early in the season, almost none of the grasses had any reproductive structures out yet, 

This particular specimen seemed to be a grass on first look, but when I took macro shots of the flowers and felt around the stems, I decided I was probably mistaken. I could not find any solid nodes along the stems (although granted, this early in the season, everything was still pretty low to the ground), and the round stems seemed to have a solid interior.

Now, I am horrible at identification, but I believe what I found on that day was Luzula multiflora, or the common wood rush, a member of the Rush family. The long white hairs on the leaves and stems indicates it belongs to genus Luzula, and the multiple flowers on variable length stalks separates it out from L. acuminata.

It is a circumpolar species but is listed as relatively scarce in this national park, so if I identified it correctly, then I was quite lucky to see it during that hike!

Long white hairs that is typical of Luzula spp.


Sunday, April 3, 2022

Spreading the New Concept of Alternative Biome States (ABS) to Save Our Old Growth Grasslands

Old-growth grasslands are grass-dominated open biomes which are ancient (some are tens of millions of years old), have high endemism and diversity (they are more diverse than rainforests at some scales), and are slow to reassemble once they have been degraded (more than a millennium according to studies). This ecosystem is one of the most endangered in the world, and misguided efforts to fight climate change by mass tree plantings can only hasten their demise.  

One of the major impediments to the widespread acceptance of the concept of ancient grasslands among the general public is the outdated notion that there is only one natural climax community. This wrong idea that ecological succession is a ladder-like process and that closed canopy forests (e.g. rainforests) are the ultimate goal in nature is deeply entrenched in the public consciousness. It promotes the wrong notion that all grasslands are simply forests that are waiting to happen, and are thus exempt from our protection and conservation.

It must be replaced by the more accurate paradigm of Alternative Biome States (ABS).

African Tropical Grassland (Savanna), by Gossipguy)

What are Alternative Biome States?

New research has shown that open old growth grasslands are a natural alternative to dark shaded forests, and that they can maintain themselves without any human intervention over thousands and even tens of millions of years. Neither grasslands nor forests are the "ultimate" expression and final state of natural succession. Instead, an area whose climactic and soil characteristics can theoretically support both grasses and trees alternates between the two stable biome states depending on other, more local factors.

North American Temperate Grassland (Osage Plains Prairie in Missouri), by Pat Whalen
What local factors keep the two biomes stable over time?

Grasses have harnessed two local factors to help push back forests. Some species have evolved with natural fire, while other grass species have partnered with large herbivores (e.g. elephants, bovids like antelopes, buffaloes, bisons, etc). Both of these "allies" can kill or weaken trees, as well as tree seedlings and saplings. This keeps the grassy biomes sunlit and open, which is the optimum environment for many sun-loving members of the Poaceae.

On the other hand, the dark humid interior of forests is not a welcome environment for most grasses. C4 grasses in particular grow best under the wide open and sunlit skies, and the high humidity and lack of wind also helps keep grass-induced fires from penetrating the inhospitable interior of the forest.

These counteracting forces on both sides stabilize the alternative biomes and allow each one to flourish.

South American Tropical Grassland (Cerrado), by Eliane de Castro)
How are these biomes switched from one state to the other?

Although old growth grasslands and forests are naturally stable over potentially long periods of time, strong perturbations can be enough to tip them over to the alternative state. 

For example, one or two strong forest fires in a region plagued by drought could be enough to quickly turn a closed canopy forest to an open ecosystem, as fire-adapted grasses and other plants colonize the resulting gaps in the forest. This can create a strong feedback mechanism whereby the gaps are widened as the flammable vegetation contributes to more fires going forward, with large herbivores following the grasslands to help keep the trees out.

This scenario created the great savannas in Africa as early as 15 million years ago, when C4 grasses started pushing back the forests to create new and sunlit open landscapes. Evidence of the rise in grass-fueled fires during this period of grass expansion is etched in charcoal deposits, as well as in the phylogeny of savanna-living underground trees, whose lineages increased in response to the rise of the new open biome. It was also around this time when the ancestors of large iconic megafauna like antelopes and other mammalian herbivores radiated into many more species to fill the new ecosystem.
 
The opposite transition from forest to grassland is usually more gradual, but just as inevitable. If fire and mammalian herbivores are somehow excluded from open ecosystems in areas whose climate and soil can support both biomes, then trees will gradually shade out the grasses and other smaller sun-loving plants. 

African Tropical Grassland (Savanna), by Bjørn Christian Tørrissen
What can you do?

Champion and spread the new paradigm of Alternative Biome States (ABS) as a replacement for the outdated concept that ecological succession is a one directional process towards shaded closed canopy forests. The elevation of open ecosystems as a natural alternative to forests will help protect and conserve our ancient and biodiverse grasslands and the countless other plants and animals that live there.

North American Temperate Grassland (Konza Prairie in Kansas), by Jill Knutson Hauko
 References

Pausas JG, Bond WJ. Alternative Biome States in Terrestrial Ecosystems. Trends Plant Sci. 2020 Mar;25(3):250-263. doi: 10.1016/j.tplants.2019.11.003. Epub 2020 Jan 6. PMID: 31917105.

Tristan Charles-Dominique, T. Jonathan Davies, Gareth P. Hempson, Bezeng S. Bezeng, Barnabas H. Daru, Ronny M. Kabongo, Olivier Maurin, A. Muthama Muasya, Michelle van der Bank, and William J. Bond (2016). Spiny plants, mammal browsers, and the origin of African savannas. PNAS DOI: 10.1073/pnas.1607493113

Thursday, March 31, 2022

What happens when an invasive grass parks itself in your parking lot

I had to laugh when I saw this parking lot island invaded by Imperata cylindrica (cogon grass). 

It really wasn't funny, but it does illustrate the problem faced by people who suddenly find masses of cogon grass in their property.

Parking Island with Cogon Grass
Intact Parking Island Flora (with an understory of ornamental grasses and short shrubs)
The persistent rhizomes make it hard to permanently eliminate the species once it encroaches en masse in an area. In this case, I imagine a piece of rhizome (or less likely, a seed?) managed to get into the soil during some activity, and over the years the grass spread throughout the island. Whereas the invaded island was almost entirely covered with the invasive species, the rest of the parking islands with intact flora had healthy looking shrubs and ornamental grasses in them. 

Maintenance crews may have simply pulled individual blades out (which would have done nothing to solve the problem), or perhaps even shrugged in defeat and hoped that the invader would somehow blend in with the rest of the plants.

Shrubs (red arrows) being engulfed by Cogon Grass
Unfortunately, by delaying any aggressive actions against the invader, they simply allowed it to strengthen its grip on the area, and since cogon grass grows very fast and slowly engulfs other plants around it unless it can be shaded out (impossible in this case due to the open nature of the island) the island now sticks out like a sore thumb when compared to the other islands in the parking lot.

The lesson of this story is that when an aggressive invasive shows itself in an area, don't delay in confronting it or you'll end up paying a much larger price later.

Wednesday, March 23, 2022

Grasses in my head and how a C4 grass learned to love the shade

When do you know you think about something way too much? It's when you start dreaming about it!

In my case, I dreamed repeatedly of Microstegium vimineum (Japanese Stiltgrass) last night.

In my dream, there was a hill covered in the small bamboo-like grass, and I was teaching someone how to identify the species by showing them a leaf.

In M. vimineum, a distinctive mark is the silvery midvein on the upper side of the leaves, which you can see by tilting a leaf every which way until the light catches the line.

This species is not only interesting because it is a notorious invasive in the East Coast of the USA, but because it is a C4 grass that is shade tolerant, and it's relatively rare that a C4 grass is efficient in shady conditions.

The C4 photosynthetic pathway allows efficient photosynthesis under hot and arid conditions, but the structural changes needed in C4 grasses can make them less phenotypically pliable, such as when placed in shade. 

In this situation, some are unable to maintain high quantum yields when grown in low-light conditions. Quantum yield refers to how fast the process works relative to how fast photons are being absorbed. Other C4 grasses cannot take advantage of sunflecks because they cannot maintain a high state of photosynthetic induction (increasing CO2 uptake temporarily when light is temporarily increased). Still others fail to reduce carboxylase in the shade, and thus leaves the photosynthetic enzymes  (PEP Carboxylase and Rubisco) with nothing to do (Sage and McKown, 2006).


But it turns out that M. vimineum overcomes the limitations of its photosynthetic pathway by taking advantage of sunflecks. A study showed that it is able to rapidly take in CO2 under flashing lights, and then rapidly close stomata in very low light in order to prevent excess water loss (Horton and Neufield, 1998), although the exact mechanisms of this adaptation has not been elucidated.

I know many people hate this species for being invasive, but one cannot help but admire its adaptability, as well as its ability to overcome the seeming limitations of its kind, and perhaps that is why I dreamed of it. I've been watching X Factor UK auditions on YouTube recently  (don't ask!), and I was awed by the passion and abilities of some of the singers, some of whom surprised the judges - just like M. vimineum surprises me because of its tolerance to shade. 

References

Horton JL, Neufeld HS. Photosynthetic responses of Microstegium vimineum (Trin.) A. Camus, a shade-tolerant, C4 grass, to variable light environments. Oecologia. 1998 Mar;114(1):11-19. doi: 10.1007/s004420050414. PMID: 28307549.

Sage RF, McKown AD. Is C4 photosynthesis less phenotypically plastic than C3 photosynthesis? J Exp Bot. 2006;57(2):303-17. doi: 10.1093/jxb/erj040. Epub 2005 Dec 19. PMID: 16364950.


Saturday, March 12, 2022

The Untold Story Of Grasses

A very nice video that advocates for the saving of old growth grasslands and opposition to the mindless planting of trees everywhere. I particularly like how the narrator mentions that grasslands drew animals out of the forest "to discover the joys of light, infinite food, and the space to see and flee from predators"...because this was probably how our ancestors felt when they themselves moved out of the forest and into the light.

Learn more about grasslands and forests: http://openecosystems.co.za

The story of the underdogs that took out their forest adversaries with powerful allies – fire and the great herds. Grasses created an open sunlit world, rich in plants and animals, including those that nurture and feed us and sustain our cities. Now all are threatened by a trillion trees. Most people don’t think about grass and dismiss ancient grasslands as mere empty space or degraded forests. The open sunlit habitats of half the world have been further neglected in the current tide of media promoting forests and tree planting as a quick fix for climate change. But grassy biomes have been carving a space in forests for millions of years. They created an alternative sunlit world, the inverse of forests – fire-loving and friendly to herds of herbivores. Ancient old-growth grasslands still exist today. Many are extraordinarily rich in plants and animals, which are restricted to their open, sunlit, grassy habitat. Grasslands have provided the world’s major seed crops, staple food for billions of people. Grassland animals were key to the development of our civilizations, providing transport, food and fiber. Global plans to plant billions of trees in vast areas could see the collapse of grasslands in the next decade. Our story was motivated by our concern for this impending disaster. This video gives voice to the sunlit, grassy world, calling for wisdom and understanding rather than policies driven by panic and ignorance.

Credits: Script by William Bond Narration by William Bond


Monday, March 7, 2022

Monoecious Monday: Trypsacum dactyloides

I like taking macrophotographs of grass reproductive structures, and when I was taking some pics of the native ornamental Trypsacum dactyloides (Eastern Gamagrass) I noticed something different. 

Grass flowers are notoriously tiny, and in fact the flowerheads that we see at the macro scale are aggregations of so-called "spikelets", which may contain one to many "florets" (the actual flowers). 

Male (anther) and female (stigma) structures in Imperata cylindrica (cogon grass)

All the florets that I had seen so far have been perfect, with each floret having both male and female parts. 

The male part is the stamen, which is composed of a filament holding up an anther, where the pollen resides. The female part is the pistil, which contains an ovary, a style, and a stigma. The anther and the feathery stigma are what people usually see easily when doing macro of grass flowers.

Feathery stigma and anthers hanging from filaments in Phalaris arundinacea (Reed Canary Grass)

The spikelets of T. dactyloides were surprising to me because at first glance I noticed that the male and female parts seem to be located on different parts, and thus different flowers!

Trypsacum dactyloides is a native grass here in Florida that is widely used as an ornamental, both in city street plantings, and in suburban areas. It is an attractive plant, with wide dark green leaves and a kinda roundish habit.

It turns out that this species, unlike many other grasses, is monoecious, with imperfect (or unisexual) flowers. Monoecious means that there are both male and female flowers on the same individual plant, and unisexual flowers have only either male or female parts. 

Stigma of T. dactyloides

In T. dactyloides, the male florets are situated on the upper part of the grass inflorescence, while the female flowers are located in the lower part of the same inflorescence. This is in contrast to bisexual flowers, which contain both male and female reproductive organs, and which I am more familiar with from my previous photos of other grasses.

Purplish anthers of T. dactyloides
Another grass species which might be more familiar to people and which also is monoecious is maize (Zea mays). In this grass, the male flowers are seen as long "tassels" on the top of the plant, while the female flowers are lower down in the plant and are the ones that form the "ear". The latter is what develops into the corn cob that we all like to eat.

And just to add to the confusion, it should be noted that there are dioecious grasses, although this is even rarer. In this case, the separate male and female flowers are also on separate individual plants! An example of a dioecious grass is Bouteloua dactyloides (buffalo grass). Due to the male and female structures being on different plants, this species needs to cross-pollinate.

But whatever the type, all these species are successful in what they do, given that they are all thriving in today's competitive natural world.

Sunday, February 27, 2022

Expansion of an Invasive Grass Over a Decade as viewed using Satellite Imagery from Google Earth

The field of Imperata cylindrica at ground level (February 2022)
Last year, I found that one can track and view the progress of vegetation over time using Google Street View. This time, I used satellite imagery from Google Earth Pro (Desktop) to examine the expansion of clusters of Imperata cylindrica (cogon grass) as they spread across an open field over almost a decade.

Drone pic of red-hued Imperata cylindrica (cogon grass) clusters from height of 100 m (February  2022)
I used historical satellite imagery from Google Earth Desktop to visualize the progress of the invasion from 2012 to 2021, then made an animated gif (see below) to show clearly how the initial small clusters spread and fused to form contiguous areas of infestation.

Animated GIF showing expansion of I. cylindrica from 2012-2021
As can be seen from the animated gif above, a large cluster slowly expands while multiple smaller clusters develop and grow over the years. Each of the small infestations grows in a circular pattern, which is common during the spread of this rhizomatous species. In 9 years, the area of the field in view that is covered with cogon grass increases to at least five times what it was in 2012, pushing towards 8000 sqm in size  - an area equivalent to almost 2 American football fields!

The gathering of such data shows that the use of online tools like Google Earth and Google Street View holds promise as an informal way of amassing historical data. This is because they allow anyone to derive useful information in an easy and efficient manner. Hopefully, more people learn how to use such tools to advance our knowledge about the world around us.

Thursday, February 24, 2022

Well Hello There Cutie Pie: Melinis repens

Masses of Melinis repens (Natal grass) alongside railroad track

In late January, I was walking near the Kissimmee City Hall, when I noticed pinkish-white flowered plants carpeting the side of the nearby railroad track. Being naturally curious, I wandered over to the tracks (making sure there were no incoming trains!) and marveled at the masses of grasses that lined it. Unfortunately, I did not have my macro lens with me, but I took some pics anyways using my 50 mm lens (although I took an inflorescence and later took macros of the spikelets).

Habit of Melinis repens (Natal grass)

I later identified the grass species as Melinis repens (Natal grass), which is originally from Africa and considered an invasive here in Florida, with the potential to push out native species. However, studies have shown that it is somewhat limited to specific microhabitats, and does not seem capable of really invading intact scrub (David and Menges, 2011).

Pretty flowers of M. repens

Using the macro, I could just make out the purple haired glumes  that surround the two closed flowers, one of which is sterile. 

Overall, even though it is non native and might be invasive, I still found the grass to be quite attractive. One of those small grass species with tiny, but pretty flowers. 

Just don't start planting them in your garden and helping them spread!

2-flowered spikelets of M. repens

Literature Citedn

David, A.S., Menges, E.S. Microhabitat preference constrains invasive spread of non-native natal grass (Melinis repens). Biol Invasions 13, 2309 (2011). https://doi.org/10.1007/s10530-011-0044-5

Sunday, February 20, 2022

Through the Fire: How Grasses Rise Up from the Flames

Aristida beyrichiana (wiregrass), a resprouter
The fact that the Poaceae use fire to create stable ecological states like grasslands and savannas is well known, but resolving the fine details on the mechanisms underlying these processes is a work in progress.

Grass populations can recover from these fire events via two paths or so-called persistence strategies. Some species die back and resprout from underground rhizomes or undamaged crowns. These are the so-called resprouters. For example, both Imperata cylindrica (cogon grass) and Aristida beyrichiana (wiregrass) come back after a fire from surviving remnants (using tough rhizomes in the case of the former). 

Sharp rhizome of Imperata cylindrica, which is a resprouter
The other way to get a population through a fire is by reseeding. These grasses are the so-called seeders, and they include species like Taeniatherum caput-medusae (medusahead grass), Bromus tectorum (cheatgrass), and Microstegium vimineum (stiltgrass). In this case, the population develops to sexual maturity rapidly, and then sets seed, which can survive past the fire event to form a new population and generation.

Dried seedheads of Taeniatherum caput-medusae, a seeder
The two types of persistence strategies significantly affect the various morphological and physiological traits of each species, as listed in the table below.

Trait

Relationship with resprouting ability

Photosynthetic pathway
Resprouters are more likely to be C4 than C3 (Moore et al., 2019). C4 species are highly efficient in fire-prone environments and may therefore have greater stored resources to resprout (Tix & Charvat, 2005; Ratnam et al., 2011)

Bud position

Resprouters are more likely to have buds below the soil surface (rhizome resprouters) where they are protected from intense heat (Pausas & Paula, 2020)

Specific leaf area (SLA)

Resprouters will have lower SLA than seeders (Forrestel et al., 2014). High SLA will aid the rapid growth of seeder species

Leaf nitrogen (N) content

Resprouters will have lower leaf N contents than seeders. Resprouters may experience fire multiple times in their lifetime and thus low-N availability (due to N volatilisation during fire; Reich et al., 2001; Hernández & Hobbie, 2008). In these conditions, a high N-use efficiency (low leaf N content) may be advantageous (Wedin & Tilman, 1990; Reich et al., 2001)

Leaf C : N ratio

Resprouters will have higher leaf C : N ratios than seeders. High leaf C : N ratio, which is linked to low decomposition rates and the accumulation of a highly flammable fuel load (Aerts, 1997), may be advantageous to shade-intolerant resprouting species in maintaining an open canopy (by aiding the removal of standing dead and woody biomass; Everson et al., 1988)

Life history

Resprouters are more likely to be perennial than seeders. Perennial-grass species have buds from which to regrow, which annual species may lack

Table 1. From Simpson et al, 2021

These persistence strategies in grasses have a complex and fascinating relationship with the existing fire regime, but in order to understand it, the different characteristics of an existing fire regime have to be defined.

Fire Frequency is the time between fires in an area. More frequent fires tend to be more damaging to a plant.

Fire Intensity refers to the amount of energy released by the flames. Higher amounts of released energy increases the probability of severe damage or death to a plant.

Fire Severity is an index of the damage caused by a fire by measuring the amount of organic matter lost.

These three attributes are related in a simple manner. The less frequent fire events are, the more biomass can be accumulated, which leads to more intense fires and a corresponding increase in the severity of the event.

Grass seeders proliferate under fire regimes of high frequency and low intensity, whereas resprouters dominate when the fires are more intense after a longer period between fire events. The rapid sexual maturity of seeders allows them to seed quickly, and these grasses can persist even in fire frequencies that are as short as a year!  

However, if fires do not occurs frequently, this leads to a larger accumulation of fuel biomass, and more intense fires. In this case, reprouters have an advantage and will dominate an area because they do not need to pass through the more vulnerable seed and seedling stages. 

The golden hued seeder T. caput-medusae (medusahead) carpets an area
Knowledge about the relationship between fire regimes and persistence strategy is not only fascinating, but can also be used to predict community composition in a habitat given specific changes in the fire regime. For example, changes in fire regimes due to climate change can cause dramatic alterations in the ecology. It may also be possible to use this knowledge to dent the advance of invasive grasses that hew to a particular persistence strategy.


References

Simpson, K.J., Jardine, E.C., Archibald, S., Forrestel, E.J., Lehmann, C.E.R., Thomas, G.H. and Osborne, C.P. (2021), Resprouting grasses are associated with less frequent fire than seeders. New Phytol, 230: 832-844. https://doi.org/10.1111/nph.17069

Saturday, February 12, 2022

What Strange Beasts: The Hidden Armageddon in Sagebrush Country

What strange beasts slither across the hidden landscapes?

There is a war going on. 

It is a war with devastating consequences and monumental importance, but one which slides below the attention of most people who otherwise care about the natural state of the world. It is a war of a scope that beggars the mind, where an entire ecosystem that has existed for millennia is rapidly being destroyed.

Sagebrush covers a huge swath of the American West
The sagebrush ecosystem in the Great Basin of the Western USA is characterized as having a shrub overstory of Artemisia spp, with sagebrush steppe areas having a large component of perennial grasses and forbs, and sagebrush shrublands dominated by larger sage species with fewer grasses and forbs. It spreads over 11 western states and occupies 62 million hectares, and it is home to a multitude of plant and animal species, some of which are threatened or endangered.

Artemisia tridentata (Big Sagebrush). From Wikipedia. 
By Peemus - Own work, CC BY-SA 3.0 
It is in this gargantuan stage that a fight to the death has been ongoing for decades, although mostly hidden from the eyes of people. Hordes of invasive annual grasses are sweeping through the landscape like a scythe, rapidly converting sagebrush into a sea of low lying grasses. One study estimates that more than 200,000 ha of sagebrush are destroyed and replaced by exotic annual grasses every year (Smith et al, 2021). This is a mind boggling number, an area that is twice the size of Los Angeles and nearly triple the land area of New York City!

Intact sagebrush habitat. Wikipedia. By Famartin
Conversion to a sea of exotic annual grasses
Yet typical invasive species groups in social media almost never mention the rapid destruction of these expansive ecosystems, and perhaps this is understandable. People tend to focus on invasives that are closer to home, and those that blight their day to day lives or their recreational activities. The sparsely inhabited and pristine sagebrush areas are thus a blind spot when it comes to most. The most ferocious winter annual grasses that are swallowing up the Great Basin are relative unknowns, and include species such as Bromus tectorum (cheatgrass), Taeniatherum caput-medusae (medusahead grass), and Ventenata dubia

Taeniatherum caput-medusae (medusahead grass) 
Yet the consequences of our blindness may just be as dangerous as the spread of more well known invasives in the suburbs and rural areas. Not only does the sagebrush ecosystems support major endangered species like the Sage Grouse, but this annual grass invasion results in major economic losses as rangeland is lost. 
 
Bromus tectorum (cheatgrass) sprawls along hillside in Bandelier National Monument in New Mexico
In addition, the annual winter grasses use fire as a way to increase and maintain their stranglehold on the land by increasing the frequency and intensity of wildfires (see diagram below). This makes their spread dangerous for human lives and habitation, and in fact these grasses contribute to the huge wildfires that are engulfing the American West and destroying not only our homes but irreplaceable national treasures as well, such as the iconic and ancient Sequoias trees. 

How one winter annual invasive achieves dominance

It is far too late to eradicate these annual winter invasives, and efforts to reclaim land dominated by them have failed to yield fruitful results on a large scale, so land managers are now exploring various other options to mitigate their spread by focusing only on areas that have so far escaped this armageddon  (Maestas et al, 2022). 

We can only hope that it is not too late.

Literature Cited

Jeremy D. Maestas, Mark Porter, Matt Cahill, Dirac Twidwell (2022). Defend the core: Maintaining intact rangelands by reducing vulnerability to invasive annual grasses, Rangelands, ISSN 0190-0528, https://doi.org/10.1016/j.rala.2021.12.008.

Smith, J.T., Allred, B.W., Boyd, C.S., Davies, K.W., Jones, M.O., Maestas, J.D., Morford, S. L., Naugle, D.E., 2021. The elevation ascent and spread of exotic annual grasslands in the Great Basin, USA. bioRxiv 2021, 425458