Native Plants, Habitat Restoration, and Other Science Snippets from Athens, Georgia

Monday: 23 December 2013

Let It Rain  -  @ 11:52:05
We've had 4.78 inches of rain in the last 24 hours. At this time, it does look like it's fairly over now. The CoCoRaHS report map showed that Oglethorpe County seemed to be centered on a straight line as drawn through the heaviest rainfall from east central Alabama through north South Carolina. The rainfall totals among the dozen or more CoCoRaHS stations in Oglethorpe County didn't vary by more than 10%.



Anyway, it's been quite a rainfall, with streams rushing down our pathways and ponds overflowing. There were hints of possible tornadoes - the temperatures were warm enough to break high records for two days. But in the end there were no heavy winds to speak of, nor much in the way of thunderstorms. We did have a bit of thunder off to our south late last night. Glenn report roads ponding in places as he went into and returned from Athens last night.

All told we've had almost 62 inches of rain this year, compared to our average 48 inches.

Now I need to run down to Goulding Creek to see what it looks like.

Wednesday: 18 December 2013

Box Turtle Overview  -  @ 11:10:25
Winter is the time for analyzing box turtle data that I took from March until early November. For those who are just joining us, I've been increasingly involved over the last eight years in documenting box turtle encounters and movements on our property here in the northeast Georgia piedmont. For the first five or six years those observations were casual and no particular effort was made to look for turtles. I did take identification photos, though. Then in mid 2011 I began excursions specifically to look for active box turtles. I increased these in 2012, and broadened the study site to include the newly purchased west twenty acres, as well as more of the east portion of the property. In 2013 I further increased the mileage covered, and began to measure dimensions and weights of the turtles I found. You can get more description and rationalization here, and here. I used mark and recapture model to estimate the population size here, at the end of 2012.


So to kick off the data analysis season, here's a representation 1(via Google Earth with a USGS topo overlay) of the overall property, encompassing 60 acres. You can see a larger image (<200 Kb)by clicking on the smaller image below.

The black lines mark the extent of the full 60 acres. There is a quiet road that ends in a cul de sac at the northeast corner. The eastern boundary also marks the transition from young oak-hickory forest to neighboring pasture. The north to west blue line is Goulding Creek, and the south to north thinner blue line is the feeder creek, SBS Creek, that runs through the property. Home is where the house is. I've marked the observed position of several frequently seen box turtles here.



Let's look more closely. Below is portion of the above map including the most frequently walked and best examined part of the property. There are fifteen turtles I've seen more than twice. Here I've included the positions of only 2six often observed turtles (that 1 acre legend may be more like 2-3 acres).



I was interested in estimating the territories and overlaps for each turtle.

For each I've drawn a polygon by connecting the observation sites. A better way would be to calculate a centroid point, and then draw a circle around it with a radius the length from centroid to whichever observation point was at greatest distance. Maybe I'll do that, however see the notes below3.

Sylvia, in red at the northwest end, occupies the smallest territory, probably just an acre or two. I found her first in 2006, and have observed her 17 times since. This year I found her 11 times. She seems to be an older turtle, with her smoothed carapace and blurred markings. I don't go across the creek on a regular basis, but it's possible that she does. Goulding Creek is certainly traversible by box turtles, though it may represent a soft barrier.

Ernest (yellow), who is actually a female, has a territory just a bit bigger than Sylvia's, by this measure. I first found Ernest in 2008, and saw her four times this year. She's a small turtle. At 375 grams, she's 70 grams under the female average. Ernest tends to keep close to lower SBS Creek, but in 2010 the neighbors to our north photographed her close to their house. This year I found her mating with Reuben.

I've seen Reuben, who is in blue, eleven times since I saw him first in 2012. Five of those times were this year. He ranges along SBS Creek similarly to Ernest, but I've found him uphill to the northeast as well, several times.

Megan, in green, has a territory approximately the size of Reuben's, but the two don't overlap. I've never found Megan anywhere except for the south-southeast part of the property. I've found her frequently along upper SBS Creek, and she makes excursions of considerable distance uphill and into the pine woods east. I've seen Megan eight times since 2008, four of those times this year. She's very distinctive, as the above link shows. At 520 grams, she's as much above the average female 445 grams as Ernest is below it.

I've only seen Austin, in white, four times, beginning in 2012. But this year my sole observation had him located far from the other three sightings. In fact, he was mating with Torri, on Nov 2. His territory does not seem to be much larger than the above two. At 460 grams, he's considerably larger than the male average of 402 g.

We'll wind this up with Torri, in purple. She is the largest turtle I've found, at 530 grams. I first found her at the end of turtle season in 2011; since then I've seen her covering great distances. A veritable chelonian Empress, Her territory is much larger than that of any of the others, and overlaps them all. She ranges from upper to lower SBS Creek, and commands the slopes almost to our house.

Earlier in the fall, I documented encounters with timber rattlesnakes. Snakes generally are more active and certainly faster than box turtles, and they have larger ranges as well. The ever helpful Forest Service Fire Effects Information website has an extensive entry on timber rattlers. It tells us that generally timber rattlers will range 0.5-1.0 miles from a central location (often the den). Females have smaller ranges than males, who in search of mates may travel 5 miles from home.

Just for fun I drew two circles around the site of rattler observation this past fall. The smaller one is 0.5 miles diameter (130 acres), and the larger one is 1 mile diameter (500 acres). For comparison, the range for Sylvia, our first box turtle above, closeby is marked as a red circle.



Notes:

1 Anyone who has done hiking will recognize the USGS quad topo maps in the first two figures above. That's the apparent origin of this mapping background. They're crude, old, and use a nauseating shade of green, but they allow for a much larger zoom than Google Earth's default backgrounds. GE gives excellent zoom for satellite views, but it's hard to detect topographic features that way. GE's terrain background, as seen in the third figure above, is great, but you can only use it down to a zoom level that's way below what I want. FYI, in the USGS topo maps the numbered contour at the level of Goulding Creek is 600 feet elevation, and the increments look to be 20 feet per contour.

2 There are nine other turtles I've seen more than twice that I might have included. There are an additional fifteen turtles that I have seen just twice.

3 A circle with a radius the largest distance from the centroid is probably misleading. There exist hard and soft barriers to turtle movements. A soft barrier might be Goulding Creek. Yes, the turtle can cross it, but is perhaps inhibited to some extent. Similarly for steep slopes within a turtle's apparent territory: turtles can certainly climb steep slopes but may opt for easier routes. There aren't many non fatal hard boundaries around here - those that bring a turtle's inclination or crossing success to zero. A large lake might be one, but I don't have a large lake. There is a long deep (10 feet) gully that a turtle would have trouble with, but I've found Reuben on both sides of it. I assume he walked around it.


Tuesday: 10 December 2013

The Month of November  -  @ 08:15:08
It's The Month of November, Number 94 in a series. For us in northeast Georgia, cooler temperatures and continued drier weather (until the end of the month) continued for the second month in a row.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. Displayed is the high and low temperature anomalies.

Click on the image for the high and low anomaly graphic on a new page:



Much of the US was cooler than average, but except for the center of the country the cooler temperatures switched from west to east. Most of the western US was warmer than normal with the Nortwest Pacific maintaining a somewhat cooler than normal monthly pattern. The eastern half of the country began a cool period, except for Florida.

Again, and for at least the fourth month in a row, the high and low anomalies graphic (click on above figure) shows that nights were at least less cool than the days were cooler. This effect was pronounced for most of the country.

We find the National Weather Service Climate Prediction Center's precipitation plots here.



There was some switching in rain patterns, too. The midwestern states, with normal to way above normal last month, dried quite a bit in November. Arizona and the north and western parts of New Mexica, New England got some relief from dry weather by a more normal rainfall during November. However, the southeast continued its dry weather, in large part, as did the Pacific Northwest, much of California except in the extreme south, California, and north Texas.

For the Athens, GA area:

Below is my usual daily rain/temperature plot visualizing the changes in temperatures and precipitation. The spiky lines are temperatures recorded roughly ten times a day, and the lighter blue columns are Wolfskin rainfall measurements.

The black line is the normal average daily temperature, and you can see that we're distinctly on our downward fall toward autumn.



The Athens area mean temperature during November was 5 degF below the average 55.3F. We had two cold night events each lasting a couple of days - we broke the Nov 13 1911 record of 24F when temperatures dropped to 23F. This was repeated the next night, breaking the 1969 record of 25 F. During the 3-5 days surrounding these cold events, daytime temperatures were also quite low.

The rainfall that began in June and continued through August finally came to an end in September, and this dry period continued in November. The official Athens rainfall in November was 2.42 inches, below the 3.82 inches average. It wouldn't have even been that were it not for the near 1.5 inches rain on November 26.

We only had 2 days more than 1 standard deviation above normal highs (average is 5.2 days), but we had 9 nights with temperatures more than 1 standard deviation below normal lows (average 5.1 nights). The number of events outside normality underscores the cooler temperatures the overall average reflects.

The monthly histogram below shows the breakdown of high and low temperature range counts from November 1948 on. The error bars are just plus/minus one standard deviation, which I arbitrarily set as the limits outside of which are "significantly" anomalous.



The high temperature events fall within the error bars (except, perhaps, for the <50 degF days). The nighttime events do show a significant reduction in the number of nights with temperatures above 50F. The number of

And so that does bring us to the rain for our area: in short, not much. The figure below shows the Athens precipitation data which are official for our area. As usual the green line shows our actual rainfall, the red shows the average accumulation expected. The black dots are rainfall over the last 22 years, and the river of peach shows the standard deviation.



We actually flirted a bit with remaining under the river of peach for much of the month, signifying dry weather. But in the last week, we had a good rain that brought us well up into the normal distribution, though still under the average.

So a transition to cooler than average for us, with continued dry weather.


Prognosticator stuff:

What is the prognosticator telling us? For us here in the southeast, it has been accurate over the last five months for temperature and precipitation.

For us in northeast Georgia it will be warmer and drier for the next three months (DJF). At this writing we've had rain every day since Dec 1, but sometime in the next couple of weeks that's going to change to drier over through February. The rain we've been getting has been nicely consistent with last month's forecast.

As of 9 December(yes, I'm late this month), it tells us in the Southeast that we can expect a couple of weeks of warmer temperatures. This has been brought down from a longer period of warm temperatures made last month. Then in late December onward we'll have equal chances of normal temperatures. The picture is quite different elsewhere, so be sure to take a look if you're not close by us.

ENSO stuff:

The folks at CPC have a version of PDF or HTML that is much different from their previous presentations, but at least it's there and the link isn't broken.

As of 9 December, ENSO neutral conditions continue, and are expected to remain neutral, now into the Northern Hemisphere summer. We've remained ENSO neutral now for 19 months. The last time we had such a lengthy period without an El Niño or La Niña was before 2000.

NOAA's Monthly State of the Climate product for October is available. New England states with top 10 dry Octobers, major rain events in the southeast and in Texas, early blizzard in South Dakota and Wyoming, and a rare October tornado in Nebraska top the October list of events.

And last year's annual report for 2012 regionally, nationally, and globally is also available.


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