Here in southern Califas it is winter. This basically means that on the colder days, shorts are not really an option. In the opinion of people from more northern or inland parts of the country- the California winter is not really a winter at all, and there is some truth to this. At best the winter months are described as a hybrid of spring and fall. When you look at the vegetation it is in a state of both decay and regrowth. This simultaneous juxtaposition of seasons is best evinced when you go explore the native chaparral vegetation as opposed to the imported non-native landscape.
|La Jolla Canyon. Ventura County. N Santa Monica Mtns|
|Nasturtium exploding after winter rains. Oxnard CA.|
|Unknown ferns. La Jolla Canyon CA.|
Another observation I made during my winter walk through the semi-desert chaparral was the ubiquity and abundance of moss. Now as I have discussed earlier with ferns in xeric habitats, moss is not what immediately comes to mind when imagining desert vegetation. But I did find lots of the stuff, oftentimes in shaded, wet areas- but not always, some of the larger patches were in full sun.
|Patches of moss. La Jolla Canyon CA.|
Check out this video from Geodermatophilia.
While we still have much to learn about soil crusts, recent research indicates that these mosses go into carbon deficit when exposed to frequent small rainfall events as opposed to infrequent large rainfall events. So they actually thrive in deserts with long dry spells and then heavy rains.
|Zelikova 2012. Loss of crust from|
frequent small rain events
Lack of competition from angiosperms. Grasses were not widespread even by the end of the Cretaceous. The pattern of angiosperm spread was from wetlands to more arid habitats.
Dinosaur feet. The feet of dinos had a lot more in common with large flightless birds, kangaroos, and camels than sharp hoofed ruminants. Ratites, camels and kangaroos coexist with soil crusts but sharp hoofed herbivores cut into the slow growing crusts and erode the thin desert soils. The largest dinosaurs would have been rare in desert environments.
Monsoonal climatic regime characterized much of the Mesozoic. This pattern of seasonal, heavy precipitation events would have favored mosses as opposed to sporadic, light rainfall events as discussed above.
The study of these crusts is still in its infancy, the study of these crusts in the context of deep time- well that is an even more unexplored vista. Until we have a well preserved in situ Mesozoic desert ecosystem this area is just informed speculation.
Until then here is a little thought experiment. Imagine that caribou and their habitat, the arctic tundra, were extinct. Researchers discovering the skeleton of the dominant herbivore of the arctic, but lacking a proper proxy for its tundra habitat, may have assumed it dined in a manner not too dissimilar to other cervids- a mix of browsing and grazing on various shrubs, trees and grasses. The researchers likely would have failed to realize that the most important forage for caribou is not a plant at all- but slow growing lichen, which accounts for up to 90% of its winter forage. Through no fault of their own, these
|Cladonia rangiferina. Reindeer lichen|
Now imagine strange dinosaurian herbivores dug from Africa. Their ecosystem is construed as an equatorial arid region, dominated by gymnosperms, for which we have no modern equivalent. Angiosperms were rare and grasses not yet on the scene. Yet the skulls of these dinosaurs are most aptly compared to "Mesozoic lawnmowers" and abundant grit marks on the teeth suggests a mode of feeding near ground level. The consensus view is that without grasses, these dinos likely grazed ferns and horsetail- both types of vegetation commonly construed as groundcovers during the Mesozoic. But maybe, like caribou, this dinosaur- let's call it Nigersaurus, was not your typical herbivore at all but subsisted predominantly on mosses
Was Nigersaurus, and other dinosaurs, perhaps specialists in cropping moss, lichens, soil crusts? I don't know for sure and I am just putting this theory out there. What I do know is that it is an area worth exploring and we should not be limited in imagining how these animals/ecosystems functioned based on what we see today.
and here is some more (Kate) Moss in the desert...
Physiological Ecology of Desert Moss
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