Observations of Flowering Plants and the Main Vernal Pools on the Mesa de Colorado, 11/4/00 - 2/23/01

Chronological Observations

Introduction to this page

2000 November 4
2001 January 7
2001 January 28
2001 February 14
2001 February 16
2001 February 18
2001 February 21
2001 February 23
Later Observations

2000 November 4: Vernal Pool Trail, Ranch Road, Trans Preserve Trail. The first significant rain fell on 30 October, and the cycle is beginning again. The plants immediately responded - white-flowered currant is budding out, the mustard flowers are more lush, and the sprouting filaree is turning the Plateau green again.

For months, the grasslands have been tinged yellow due to sticky tarweed, whose bloom has slowly been declining. Suddenly, the grasslands are tinged a brighter yellow, nearly all of it now from mustard.

The pleasure of seeing the new season begin was tempered, however, by the sudden appearance of a framed home on the private property just south of the intersection of Via Volcano and Avocado Mesa Road. The large house looms over the Mesa de Colorado, destroying the solitude of the former wildness. The house can even be seen from the main pool, leaving no spot untouched by its presence. It is a shame that this property could not have been added to the Preserve before a house was built on it, to prevent the serious visual and aesthetic degradation caused by it to the rest of the Mesa de Colorado area. Perhaps somehow the remaining handful of lots can be purchased before building starts. If not, one can only hope that all these new homes will have tall landscaping that will mute their intrusion into this otherwise-natural area. See Threat To The Main Vernal Pool.

Looking ahead to the muddy season, the pea gravel coating of the Vernal Pool Trail has been recently renewed. Enough gravel was left to coat the south ends of the Los Santos and Trans Preserve Trails (about 0.2 mile) for the first time, as well as on a section of the Vernal Pool Trail northeast of the Main Pool (0.06 mile).

As expected, cracks still remain in the ground, and the soil at the bottom of the Vernal Pool is no wetter than elsewhere.

2001 January 7: Vernal Pool Trail, Ranch Road, Punta Mesa Trail, Monument Road, Trans Preserve Trail. The early rain in October, followed by no rain for the next two months, has resulted in an unusual situation. A few areas have plants blooming, whereas in most other areas the plants are not even growing yet! See Detailed Bloom Observations.

The green in October has gradually been muted by the absence of further rain, and in most places the Plateau looks dry and Summer-like again. No moisture remains from the October and November rains in the upper soil, so it most likely no longer "counts" toward filling the pools.

However, the number of people visiting the Plateau is increasing. I met four groups of two people each on this Sunday on the Punta Mesa Trail. I usually never encounter anyone on this remote trail.

The trails have all been recently mowed, and are in good shape. I encountered a few bugs at times, which were only minor annoyances.

2001 January 28: Vernal Pool Trail. The pools still don't have any trace of water, and the clay trail beyond the pea gravel is only muddy in a few places. Only mustard was in bloom on the Mesa de Colorado, with wild cucumber blooming at the drop-off just beyond the Main Pool.

I saw four other groups of hikers on this short hike to just beyond the Pool. One group hiking in was surprised and disappointed to learn that there was no water in the Pool.

We saw two coyotes, one of which had a bad right back leg and did not look nearly as healthy as the other coyotes I've seen this year.

2001 February 14 (Day 1): Vernal Pool Trail. The pools have begun to fill! It was beginning to look like there might be no pools this year, but the 2.3" of rain (as measured in Fallbrook) from the storms of the past five days did the trick. However, the storms just barely filled the pools - the Main Pool is only ~2.3" deep at the boardwalk. The two smaller pools are clearly quite shallow, since waves are only supported on the inner half of the pools.

The pools probably formed overnight, for two reasons. First, a pool of depth 2.3" probably formed from the last ~1" of rain, because any more rain would have resulted in a deeper pool. The amount of rain between 5 p.m. yesterday and 5 a.m. this morning was ~1". Second, the data from previous years show that the rain totals in the last two months are just barely enough to form the Pool, implying again that the pools only formed with the last inch of rain.

The shallowness of the Pool, and the absence of algae now, allowed me to recalibrate the algorithm I use to compute the depth of the Pool. I use the height of the boardwalk at a specific point as a reference point to measure the distance from the boardwalk to the surface of the Pool. In the past, the algorithm I have used to get the Pool depth has been 19" minus that distance. This algorithm gave a depth of 1.75" today. I then made 17 measurements of the actual depth of the Pool in various spots. These measurements averaged 2.3" in depth, and ranged from 1.0-3.25". (The measurements vary because the bottom of the Pool is not a uniform surface, largely consisting of soil, basalt rocks of varying sizes, and clumps of large grasses.) I accordingly will add 0.5" to the results of my algorithm from this time on, making my official measurement for today's depth 2.25". (All of my measurements are only to the nearest 1/4". Of course, the depth at the center of the Pool will be slightly larger, probably only by several inches.)

Birds found the pools quickly. I observed a dozen or so waterfowl gliding along the surface of one of the small pools, and two bluebirds at the Main Pool. The insects I call water fleas have come out of nowhere to fill the surface of the Pool. I observed a maximum density of ~400 per square foot in numerous places. Where do they come from so quickly???

At least one toad or frog wasted no time laying eggs in the Pool. I observed a single cluster of ~9 yellow-green linear eggs, each egg ~5 mm long (~3/16"). The eggs laid haphazardly together, like pick-up sticks tossed at the beginning of a game. Again, how did these eggs get into the Pool so quickly? Was the female carrying the eggs, and waited until the Pool formed before getting the eggs fertilized? Or do females carry around fertilized eggs, and deposit them whenever they encounter water?

In any case, the Pool was no secret to the local toads and frogs. The Pool may be mostly empty, but the air was filled with the croaking of toads and frogs. Although I was surrounded by toads, and looked for them in the half hour I spent at the Pool, I didn't see a single one. Were they all hiding under the boardwalk?

The depth of this year's newborn Pool (2.3") is much shallower than the depth in previous years (7.5, 5.75, and 6.0"). In fact, the lifetime of a 2.3" pool is only ~15 days if there is no further rain, which is too short for any of the Pool's animal inhabitants to complete their life cycle. Nature being quite clever, it is possible that she won't allow the shrimp to hatch in such a shallow pool. Only time will tell...

The trail is quite muddy in places beyond the Pool where the pea gravel ends, and the blooms are still sparse.

2001 February 16 (Day 3): Vernal Pool Trail, Ranch Road, Los Santos Trail, Hidden Valley Road. I was anxious to discover how the depth of the Main Pool has changed in the last two days. It might have gone up, if water had continued to seep into the Pool from higher ground, or gone down, due to evaporation and transpiration. The answer: lower by ~1/8", about that expected without further inflow.

Much to my surprise, the number of water fleas had vastly decreased, from ~400 per square foot to only ~10 per square foot, at best. Where did they all go? Were they hiding due to the bright sun?

There are now four new clusters of toad eggs. These clusters are within a foot or two of the cluster I saw two days ago. Despite careful searching, I couldn't find any eggs in any other location along the boardwalk. The toad or toads must like this spot!

Unlike the pick-up sticks appearance of the cluster seen two days ago, the new egg clusters are the standard spine with ribs double row of eggs. I can now see that the first cluster has the same morphology, but the string of eggs was deposited vertically, making the string of eggs appear quite different.

The chorus of frogs was still serenading visitors in the early afternoon at the Pool, and by sunset their song was everywhere on the Plateau.

I was surprised to see many new species of plants blooming today, although many of them were from only single examples. Among them were a number of lace parsnips near the VP Trailhead, and single examples of checkerbloom, California buttercup and California poppy elsewhere.

On this hike I saw many bobcat prints in the mud. In some places, the bobcat prints outnumbered the bootprints!

I found a tick on me near the end of the Los Santos Trail, and was able to later identify it as a Western Black-Legged Tick (Ixodes pacificus). Furthermore, a much smaller tick I had on me several weeks ago turned out to be the same tick! I was quite surprised to read about the life cycles of this tick, and learn that both sexes need to feed on blood during their development. Hence the same species of tick can vary by over a factor of two in linear length.

2001 February 18 (Day 5): Vernal Pool Trail, Ranch Road, Adobe Loop Trail, Trans Preserve Trail.
The Fairy Shrimp are here! The Fairy Shrimp are here! Those little buggers, at least some of them, decided to go for it and hatch anyway, despite the shallowness of the Pool. There certainly is an argument for some fraction of the shrimp population to adopt that strategy. That strategy allows some shrimp to take advantage of a 2" deep pool that gets augmented by a bit of rain before it dries up, so that it lasts a month, long enough for the shrimp to lay their eggs. Of course, since it is known that only a fraction of the shrimp eggs will hatch even in a deep pool that lasts six months, the species is not placed at risk if those shrimp lose their gamble. I wonder if more shrimp will hatch if the Pool dries up and then reforms?

The Pool continues to evaporate, down another 0.2". The shrimp have significantly less than ten days to win their bet. One of the group of toad eggs laid two days ago has already lost their bet, and are exposed.

But I doubt anyone else saw the shrimp today. You had to have seen them before, and know that the fairy shrimp come before the red and gray shrimp, to know that the little specks moving in the water were the fairy shrimp. And the specks themselves were so hard to find that only those willing to spend five minutes on their stomachs with someone guiding them probably saw them.

I met four people leaving the pool, and none of them had seen the shrimp. Two ladies turned around and walked with me to the Pool after I promised to show them the toad eggs. It took me a minute or two before I saw the shrimp, and another few minutes for the ladies to see the shrimp.

There appeared to be no new toad eggs similar to those laid in previous days. But several strings of a different sort of eggs appeared. These strings are longer, and the eggs look more like fuzzy cotton balls than the well-defined yellow eggs of the previous toad species. These new eggs were laid in the same spot, a relatively clear area, as the previous eggs. Despite a search by myself and the two ladies, no other toad eggs were seen elsewhere along the boardwalk.

The first graffiti now mars the bench at the Pool. Some ignoramuses have scratched some letters into the top of the bench.

Due to my late start, necessitated by brief showers around noon, I only had time to do the Adobe Loop and return. I saw a flock of ~20 of the brilliantly-blue birds near the Vernal Pool Trailhead.

2001 February 21 (Day 8): Vernal Pool Trail, Ranch Road, Lomas Trail, Trans Preserve Trail.
The Plateau received 0.5" of rain on the night of 2/19, which I hoped had raised the Pool level by several inches, ensuring the shrimp's reproductive success this year. Alas, the Pool level was raised only by the amount of the rain, back to 2.4" today, making the end of the Pool 12 days from now, on Day 20. This won't be long enough for the quickest shrimp to lay eggs, and falls far short of the ~60 days needed for the longest-lived fairy shrimp species.

But the shrimp are oblivious to the lifetime of the Pool, and are busy eating and growing. They are 1/16 - 1/12" in length today, and with the largest ones I can just make out their swimming upside-down form, with their legs pointing upward. This was probably impossible to distinguish if you hadn't seen this before, just like knowing the name of the road helps you make out the road sign ahead that can't be seen clearly. They are more numerous today, ~400 per square foot, which is probably simply due to more becoming visible to my eyes.

Unfortunately, it is also now clearer to see the recent graffiti scratched into the pool bench.

The individual eggs of the second species of toad now have become similar to the first species, a bright yellow, both ~3/16" long. The cottony coating has disappeared. Today one could see freshly-laid eggs with the cottony coating next to ones where the coating is gone. The second species has 2 rows of ~22 eggs each, whereas the first species has 2 rows of ~9 eggs each. It appears that all the previous strings of eggs are still in the Pool, meaning none have hatched yet. The strand previously on high ground has been washed back into the Pool.

The water fleas are down once again to ~40 per square foot.

I gave a tour of the pond to ~15 people while I was there, and one of them had sharp enough eyes to spot several groups of toad eggs in another portion of the pool. It was still true that the eggs remain heavily concentrated in one small clear area next to the boardwalk.

More plants are blooming every day. There are now ~10 California buttercups blooming, and ~5 California poppies along my travels today. Lupines are just beginning to bloom east of Poppy Hill, and there are nice clusters of ~30 locoweeds beginning to bloom.

2001 February 23 (Day 10): Vernal Pool Trail. I was fortunate to get this hike in, after the heavy rains all day today. Fallbrook received 0.5" of rain, and the Pool got ~0.5 - 0.75". The Pool is at its highest after this rain; at a depth of 3.4", it is now about 1" deeper than at its formation. The estimated lifetime of the Pool is now 17 more days, making it to day 27. Since heavy rain is predicted for Sunday, it now seems that the shrimp's gamble is going to pay off, and at least the shortest-lived species will reproduce.

The fairy shrimp were more dispersed in the Pool than on previous days, and could be seen in many more places. I estimated their size as unchanged from two days ago. They are now accompanied by these newly visible creatures: two types of "gray shrimp", the paramecium-type worms (~1/4"), water spiders, as well as a large number of springtails (~1400 / square foot) and the very numerous "black fleas" on the side of the boardwalk (many thousands per square foot, making some surfaces entirely black). There are also some very small creatures (~1/32") in the water which cannot be distinguished. (I had the assistance of the sharp eyes of Rob Hicks, Zach Principe, and Blanca Biller to find these assorted new creatures.)

The "gray shrimp" really confused me today. The ones I have seen previously, propelled by rotifers at their head, are about 0.1" long with a triangular-shaped body, widest at the top near their rotors. There aren't many of them, about 1 per square foot at the maximum, so required long periods of observation to find and study them. Much more numerous (~400 / square foot) were a variety I haven't seen before, which are about 1/16" long, fairly linear in body shape, and propelled from the rear. I have no idea whether this new variety will turn red and become the familiar "red shrimp", or whether this is a short-lived nymph phase of some aerial insect. Both these "gray shrimp" move in jerky fashion, compared to the smooth gliding of the fairy shrimp.

There are ~8 clusters of toad eggs in their favorite spot, and still just a handful of clusters visible from all other places along the boardwalk. It does not appear that any of the eggs have begun to hatch.

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Copyright © 2000-2003 by Tom Chester.
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Updated 28 January 2003.