We find it enlightening to reread material written by naturalists in the middle 1800s as they began to study evolution and the origin of species. Most commonly read are the two books written by Charles Darwin: Origin of Species and Voyage of the Beagle. There were many others studying the science of plant and animal development during this time and Darwin made good use of their studies in crafting his theories.
In these two books, especially in the Origin of Species, he makes the point that every generation produces variations in the makeup of the species--all due to natural causes. The variations are too small to be observed in just one generation, but these changes, accumulated over time result in either more adaptability to the environment or less. In other words, if the variation makes survival more likely, they make it, otherwise... Some make it some do not. The process can lead to overpopulation or to extinction.
These old writings make the reader realize that we live in an ever-changing world of living things and the change is happening right before our eyes. But we don't notice the change as our span of observation is our lifetime and these genetic changes occur over a much greater time period.
This constant change sets up the contest for survival of the fittest and the struggle for existence.
Hundreds of years ago, the native Live Oaks of the gulf coastal region grew only in the heavy soil and warmer conditions along the coast. Oaks are known for their ability to readily produce variation and some variations adapted to the soil and conditions of the Hill Country. Because of these adaptabilities of the Oak species, we have the Plateau Live Oak that lives here but not on the coast.
It may seem to us that the Plateau Live Oak is well established, but we ask, is it really?
Let's take the reseeding of the Plateau Live Oak, as just one of the factors that determine its existence. Our variety of Live Oak (Quercus Fusiforma) received a kick it the rear end last year in February when we had that severe cold downdraft from the polar region. Many of the oaks had trouble leafing out on time and from my observation, they did not produce many acorns that year. Without acorns we get no new oaks. During normal winters and springs, the oaks produce a good crop of acorns. When I first began experimenting with live oak propagation, I collected handfuls of acorns at random and spread them out over the grassy fields expecting to see a forest of new trees develop. How many did I see? None.
Then I started testing the acorns to determine if they were alive and found that in a typical handful, I might find one that was alive, all others having had their cores eaten out by worms while still on the tree. The little hole in the acorn that shows up later after the acorn has fallen to the ground is the telltale sign that the acorn is dead. The worm consumes the heart of the acorn, develops and escapes it leaving a hole in the acorn.
So then, I only planted known live acorns in the grassy fields where I monitored them with a marker. How many did I get? None. In disbelief, I started to inspect the planting site and found that the acorn did sprout but deer or some other animal found the new leaves so tasty that the sprout was consumed and without starter leaves, the new plant died for lack of nourishment.
Extrapolating the grazing process, it becomes apparent that this is the cause of most of our live oaks having Y-shaped trunks, where the grazer has nipped off the leader but left enough to allow the plant to live and to ultimately form two trunks in the absence of the leading stem.
So now to have more live oaks, I plant live acorns in pots and when they come up and live in a pot for a year, then they are transplanted with screen guards to prevent grazing. It's the only way. So, if you were to depart (we all do sooner or later) and come back in a hundred years, the botany of the area would look just like it does today, open grasslands and mottes of oaks, but perhaps with filled in areas of Ashe Juniper. What gives Ashe Juniper the edge to expand its territory? New sprouts are not attractive to browsing animals, perhaps due to their prickly exterior. And even if the new sprouts are browsed, if the browser does not get every bit of green, the new seedling continues to grow. Ashe Junipers are like that. That browsing also leads to the Ashe Juniper growing up without a main trunk and looking much like a shrub.
Live Oak acorns have other factors in their struggle to create the next generation of trees. Live acorns are a prime source of food for squirrels, turkeys and hogs.
And there is Oak Wilt, a disease that can decimate whole stands of live oaks.
In summary, about the only way for a Live Oak to reproduce naturally in our immediate environment is to germinate in the brush among the mature trees. The predators find it not worth their effort to probe the brush where the new sprout is hiding. Acorns from live oaks standing in the open have no chance to produce seedlings. This situation is one of the causes of our oaks forming mottes as commonly occur here.
I would like to see the data on the odds of a single tree producing a single successful descendant--it must be very low. As Darwin has pointed out, there is a struggle for existence.
