Oak Woodlands
 Home

The Problem

The Word "Acorn"

Oak Flowers

Leaf Galls

Acorns

Natural Planting

Seedlings
    Gophers
    Annual Weeds
    Cattle
    Deer

Life in Mature Trees
    "Spanish Moss"
     Mistletoe
     Leaping Lizards
     Diseases, Decline
     Sudden Oak Death
     Insects
     Fire

Key to Oak Species

Restoration
     Planting Trees

The Newsletter of the Official California Acorn Counting Team: Walt Koenig and Jean Knops,

Vol. 2 28 Sept. 1998

Author/Editor:Walt Koenig

THE WARMUP

Greetings once again from the California Acorn Counting Team. As in previous years, we practiced up for the California acorn count in Minnesota when Walt flew to Minneapolis the last weekend in August to count the six plots we have at Cedar Creek. This fourth year of midwest acorn counting revealed a very good pin oak and very poor bur oak acorn crop, corresponding to a good crop of the major 2-year species and poor crop of the major 1-year species. Might this match the situation in California? We were dripping with antici...pation. Our thoughts began to wander toward chartering a small plane for future acorn surveys so as to allow us to survey on a larger geographic scale, and probably would have continued to do so had Walt not become totally distracted at the Minnesota State Fair, which was happening only a few blocks from Jean and Ann's house. Several dozen deep-fried cheese curds and minidonuts later, I'd forgotten exactly what I was there for beyond indulging in sickening quantities of inimitable midwestern delicacies and contemplating signing myself up for the Catapult, sort of a reverse bungee jump in which one is literally shot up 100 feet or so in the air. Maybe next year we'll stay motivated enough to start planning a world-wide acorn survey on the scale it deserves.

....AND BACK TO CALIFORNIA

Fortunately, it all came back to us a couple weeks later in time for Jean to fly in from some sort of strange NSF panel in Washington. Thanks to much-appreciated efforts on the part of Barry Garrison at Cal Fish and Game, we again had support for this, the 5th edition of the California Acorn Survey, allowing Jean to rent a car at the Monterey Airport when he arrived. The car, a white Dodge Stratus that we quickly nicknamed "the Mattress", introduced us to a variety of incredible features that are apparently built into modern American cars, none of which, best we could tell, were desirable or necessary. Jean found its habit of automatically locking the doors shortly after driving off especially annoying, while I found the ability of its seat belts to tie Jean up in a knot after sitting for less than 5 minutes extremely amusing.

Since Jean came in late Friday night, we passed up on our usual xylem water potential party and started directly in with the Hastings acorn survey. As usual, Bill Carmen came down for the event, although he was held up a bit longer than usual to tend to his family's pet tortoise, whose hind leg had ended up as part of the meal of one of the local raccoons up in Mill Valley the night before he was to come down to Hastings. While waiting, Jean and I amused ourselves trying to remember how to use the HP palmtop computer and finally went ahead and did School Hill, not letting the fact that it was only 10 in the morning and near the beginning of the survey get in the way of the traditional gin and tonics at Red House. Fortunately, it took Bill several hours to arrive, so we had time to sober up in time to head up to the Arnold for the first and longest transect of the survey. Despite the late start, we finished on Sunday, in time for Bill to get stuck in what I suspect was an ungodly traffic jam heading back to the Bay Area while Jean and I attempted to pack for the statewide survey. By the way, I forgot to mention what was by far the most important and exciting event of the weekend: Bill brought along a revised version of his long-awaited California Scrub-jay thesis. Needless to say, we all eagerly await the day, hopefully in the near future, when the manuscript will caste off its legendary "in press" status and be reincarnated as a real-live monograph. Go Bill!

THE NORTHERN ROUTE

As usual, the excitement was palpable as Jean and I rolled out of Hastings at 05:30 Monday morning trying to remember which direction to turn onto Carmel Valley Road. After only 2 or 3 false starts, we figured it out and zipped up to Jasper Ridge for the traditional start of the Statewide Survey. We arrived at Jasper Ridge just in time to miss the Rush Limbaugh show on the radio, a benefit we unfortunately were not afforded during several of the remaining mornings of the survey. In any case, Jasper Ridge cemented the dismalness of this year's blue and valley oak acorn crops, added to our overall depression concerning the extent to which yellow star-thistle is taking over the world, and was most notable for the fact that it was cool and foggy for most of our 3 mile hike around the Reserve-a first for the 10 years we've now done this site.

This prompts me to answer one of the most frequently asked questions of we, the California Acorn Counting Team, namely, how, exactly, do we count acorns? After many years of experimentation we've come to the conclusion that counting by ones is clearly superior to all alternatives of which we are aware. Even more importantly, we strongly recommend counting in base 10. Why, you ask, in this era of binary and hexadecimal, would we even suggest this anachronistic means of counting? Simply put, we have found that keeping track of those 1s and 0s is too complicated (we dare you to try counting to 60 in base 2 real fast) and hexadecimal was too hard to write down on our datasheets without confusing the numbers with one or another passwords associated with Jean's e-mail accounts. So, just remember: base 10, count by ones. Say it several times just to be sure. Believe me, forget these simple rules for counting acorns and you'll be sorry!

[Note: two people count as many acorns as they can see on the selected tree in 15 seconds (with our without binoculars-as needed), add the numbers counted, (= n) and report ln (n). For more detail see: Koenig et al. 1994. Estimating acorn crops using visual surveys. Can. J. Forestry 24:2105-2112]

Where was I? The remainder of the Northern trip went by too quickly, although with inevitably way too much driving. Hopland was populated by a larger-than-normal complement of sheep biologists and one of the first llamas we've noted on the survey. Otherwise, the station is lovely as always. The trip north to Tower House was way too long, while Dye Creek confirmed our suspicions that yellow star-thistle is not only taking over the world but the result of some communist plot. Seriously, in the space of a single year the stuff had taken over the riparian area where we survey valley oaks to the extent that it was painful and difficult to walk to the trees. This was not helped by the fact that Jean had stubbed his toe several days earlier and thus was trying to negotiate the transect in sandals, but even I had a hard time making my way through the head-high thistles in search of our trees. It was scary. Don't underestimate how obnoxious yellow star-thistle is, or can become in a very short time.

Next was Sierra Foothills, where we stayed the second night and briefly met with Jerry Tecklin, the man who discovered that Black Rails, a bird thought to only occur in California in the salt marshes primarily around San Francisco Bay back when I was in grad school, is actually remarkably common in relatively undisturbed streams in the foothills of the Sierras in the vicinity of the station, if not beyond. I like to think that this discovery is analogous to finding that Coelocanths are fairly abundant in San Francisco Bay. In any case, we didn't go off in search of rails this year but instead went to see some blue oaks whose catkins had apparently misformed into tiny, aborted acorns. This is a bizarre anomaly Jean and I have noted in an Engelmann oak down at the Santa Rosa Plateau but had failed to follow up on. What exactly is going on is still a mystery, but may have something to do with the additional flushes that many trees appear to have experienced this year due to the unseasonably late rains and cool weather that have marked the extraordinary El Niño year of 1998.

Sierra Foothills was followed, as always, by the excruciating drive down to Yosemite Valley, after which we were just able to make it to the San Joaquin Experiment Station and survey the blue oaks there prior to sunset. Once again we failed to find a decent place to eat on the way home; Taco Bell in Los Banos was passable but not exactly a dinner to write home about. Perhaps next year we'll succeed in arranging a stop that ends the trip on a higher note; Lorna Colton, a biologist with Cal Fish and Game in Oakhurst, has promised us some help in achieving this long-time goal of the survey in 1999 and we hope to take her up on this offer.

THE ANNUAL XYLEM WATER POTENTIAL PARTY

Unfortunately, our attempt to skip measuring xylem water potential on our 40 litter trees came to an end the Thursday afternoon after our return from the Northern Route. Our prior results had indicated that water potential was significantly less negative in wet years, but since this result was based only on a single data point (1995), we figured we had better do it all again during a second wet year. The 1.03 m of rain Hastings had this year provided this opportunity, so off we went. We were joined this year by Lars Pierce from Cal State Monterey Bay, an ecologist interested in modeling carbon use in the central coast. Part of what he needs for this effort is a lot of xylem water potential measurements, so he came along to see whether our data might be of use to him. He also brought along his own pressure bombs, which are a whole lot lighter and easier to use than our 1968 model, left over from Jim Griffin's classic work with valley oaks here at Hastings. Lars didn't indulge in the predawn trips, but otherwise added a lot to what has never been our favorite oak project. He even helped deflect some of the hornets that nailed us but good while trying to get at some leaves in one of the valley oaks down by the gate. They were truly vicious, and left Jean with a remarkable sting on his arm that took most of the remainder of the trip to disappear.

THE SOUTHERN ROUTE

Monday, 21 September saw us repeating the quandary of the prior week. 5:30 just isn't a good time to have to decide whether to turn north or south on Carmel Valley Road. Much to our surprise, we scored almost 100% and eventually headed south to donuts and coffee in King City. This was only the beginning of what is always an impressively long day. First stop was Liebre Mountain, where it was foggy and cold-yet another first. Liebre Mountain, for those of you who aren't familiar with it, is near Gorman and includes both one of the southernmost populations of blue oaks and an absolutely fantastic black oak woodland. The black oaks here-unlike those at Hastings-are generally loaded with acorns, and although this year was not a record, there were still lots of acorns to be counted in this unparalleled site.

After Liebre Mountain and a stop at the Valencia Trader Joe's, we went on to Switzer's Camp in the San Gabriel Mountains just north of Pasadena. After a brief stop at a couple of Pasadena antique stores (Jean's appetite for collectible beer cans and license plates have reached almost insatiable proportions) we toured the eastern LA basin and headed for Mount Palomar. This year, for a change, we decided to eat before going up the mountain, which saved us the necessity of cooking after dark in what is often a pretty cold place even in a normal year, whatever that is. This turned out to be a good choice, although it wasn't as cold as we'd feared up on the mountain. Nonetheless, we still left some food out overnight, giving us the opportunity to fend off raccoons from the picnic table at night and Steller's Jays in the morning.

The second day of the Southern Route includes counting at Palomar Mountain State Park, a drive up to the always-lovely Santa Rose Plateau where we met Zack Principe and a grad student studying those much-neglected insects on acorns, and then on to the no-longer virtual Sedwick Reserve in Santa Barbara County. This year found Mark and Shorty moved to the Big House on the reserve itself, which afforded us a wonderful opportunity to envision how the other 0.2% once lived here in the wilds of the Santa Ynez Valley. Thanks, as always, to Mark and Short for a lovely dinner and an entertaining evening.

The third, and final, day of the Southern Route includes counting at Sedgwick followed by the drive up to Pozo. This year for a change we took the shortcut, which involves a 15 mile drive on a paved road inland from Arroyo Grande followed by a 10 mile ordeal on a dirt road heading over the mountains to the Pozo Ranger Station. We'd done this once before without incident, but this year, after a horrendous winter, there was no telling what we'd find. And an adventure it was: one large sinkhole pretty much as large as The Mattress itself covering most of the road and several gullies made it unclear whether we'd make it or not. Jean, however, turned out to be fearless and would simply not take "let's go back" for an answer. In the end, not only did we make it, but it only took about 10 minutes longer than we figure the other longer route takes. What a deal! The only participant that suffered was The Mattress, but what the heck; we figure that's what rental cars are for. Presumably most of the damage was hidden underneath the car where the rental folks are unlikely to find it for a few months at least.

THIS IS ALL VERY NICE, BUT WHAT ABOUT THE ACORN CROP?

In the midst of all the excitement getting from one site to the next, it's pretty easy to forget why we're presumably doing all this. But yes, we did count acorns at all the sites. For the record, this was the 19th year for Hastings, the 10th year for Jasper Ridge and Pozo, and the 5th year for the complete statewide survey including Hopland, Tower House, Dye Creek, Sierra Foothills, Yosemite Valley, San Joaquin Experiment Station, Liebre Mountain, Switzer's, Mount Palomar, the Santa Rosa Plateau, and Sedgwick Ranch. As always, the survey includes some 34 populations of 6 species (valley, blue, Engelmann, coast live, canyon live, and California black) of oaks. Most sites involve 20 or so individuals of each species, and the total number of trees we count numbers 847 (Table 1). Incredibly enough, this pathetically small sample of the hundreds of millions of oaks in California appears to give us a pretty good idea of what's going on in the oak world around the state.

So what is going on? As many of you know, we have previously documented that the acorn crops of valley and blue oaks are correlated with conditions during the spring flowering period: warm dry springs correlate with large acorn crops, while cold, wet springs are generally followed by poor acorn crops (Can. J. For. Res. 26: 1677-1683; 1996). With El Niño rearing his ugly head, it was nothing but cold and wet last spring, and consequently we expected things to be poor for those two species. And poor it was. Values are summarized in Table 2, where mean log-transformed counts are indexed from 0 (no acorns counted) to 1 (= to the maximum number of acorns ever counted at a site, which was, by the way, the black oaks at Liebre Mountain in 1994). Values were all quite low (<0.27), with a couple of populations, including valley oaks at Sedgwick and blue oaks at Jasper Ridge, yielding total busts-an event we had never before encountered for either of these species. Meanwhile, coast live oaks, which are more closely correlated with how wet things are, not necessarily in the prior winter but in the winter before that, did reasonably well, with modest (0.23 < LN30 < 0.59) for most localities and very good (LN30 = 0.74) at Pozo.

As many of you know, these three species all mature acorns in a single season, whereas both canyon live oaks and black oaks require two years to mature acorns. One of the generalizations we appear to be coming up with in our work is that things are much "simpler" in the 1-year species: not only are their acorn crops directly correlated with a simple environmental variable, but they are also geographically quite synchronous. In contrast, neither of these necessarily seem to hold for the 2-year species. This year was no exception. Canyon live oaks did very well in most localities (LN30 > 0.72) except for Hopland, where it was poor, and Hastings, where it was moderate. California black oaks did moderately well in three sites and poor in 2 sites. As usual, generalizations are much harder to come by for these species; about the best we can say is that they had a fairly good year in most sites, certainly much better than the 1-year species.

SPATIAL AUTOCORRELATION IN ACORNS

One of the primary reasons we're going through all this every year is to figure out the extent to which acorn production patterns are synchronized geographically. With only 5 years of data on a statewide scale, we can't give you the final word on this as yet. However, I thought we should present some of our preliminary findings, which we doubt will change too much in the next couple of years. Geographic synchrony can be measured by calculating the correlation between the acorn production at sites on a pairwise basis and then plotting the values against the distance between the sites. The results thus far for blue oaks and California black oaks are graphed in Fig. 1. All blue oak populations that we survey are highly correlated with one another, and thus far there doesn't even appear to be any dropoff with distance (Fig. 1, top). This indicates that pretty much every blue oak in California (and thus the world) pretty much produces acorns synchronously. This is not the case for California black oaks (Fig. 1, bottom); several populations are highly correlated, but others are all over the map.

Our working hypothesis is that these patterns are related to the environmental correlates of acorn production. As mentioned earlier, for the one year species these are straightforward and also (most likely) geographically synchronous around the state, whereas neither is apparently true for the 2-year species. Interestingly enough, everything seems to change when one goes through the Tehachapis and into southern California, as evidenced by the fact that the correlations between all our blue oak populations and the one Engelmann oak population we survey at the Santa Rosa Plateau are all highly negative, rather than positive (Fig. 1, top). Unraveling these sorts of problems are what the project is all about. Our current plan is to let things sit, more or less, for another 2 years and then write the statewide survey up for the millennium in the year 2000.

That's about it for now. For those of you who wish to keep up with our published papers relevant to the acorn survey, the last year has seen the emergence of a preliminary paper discussing geographic synchrony in acorns published in the Oak Woodlands Symposium Proceedings (Koenig, W. D. and J. M. H. Knops. 1997. Patterns of geographic synchrony in growth and reproduction of oaks within California and beyond. Pp.101-108 in Proceedings of the Symposium on Oak Woodlands: Ecology, Management, and Urban Interface Issues. Pacific SW Forest & Range Exp. Station Gen. Tech. Rep. PSW-GTR-160.) and a paper on statistically testing for spatial autocorrelation (Koenig, W. D. and J. M. H. Knops. 1998. Testing for spatial autocorrelation in ecological studies. Ecography 21: 423-429). In press include a paper on acorns, oak species diversity, and Acorn Woodpecker biogeography (Koenig, W. D. and J. Haydock. Oaks, acorns, and the geographical ecology of the acorn woodpecker. Journal of Biogeography), a review of spatial autocorrelation in ecology (Koenig, W. D. Spatial autocorrelation in ecological studies. Trends in Ecology & Evolution) and, most excitingly, a brief report on the large geographic synchrony and tradeoffs between growth and reproduction that occur in boreal coniferous trees (Koenig, W. D. and J. M. H. Knops. Geographic and taxonomic scale of mast-seeding in Northern hemisphere boreal trees. Nature ). Stay tuned right here for the latest information on the cutting edge of acorn production ecology!

See you next year, and as always,

May all your acorns be counted.