12 Year Repeat Photographs of Ferocactus cylindraceus in Plum Canyon
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| Fig. 1. Top: A photograph taken on 12 December 2012 showing 29 numbered barrel cacti, Ferocactus cylindraceus, marked with numbers from 1 to 29 from left to right in the pix. Bottom: A repeat photograph of the same area taken on 8 February 2025. The barrel cacti still present 12 years later are marked with the same number. New barrel cacti, seen only in the 2025 pix, are numbered N1 to N6 from left to right.
In the top photograph, numbered barrel cacti in white rectangular boxes were no longer present in 2025, 12 years later. The other numbered barrel cacti in the pix were still present in 2025. Three Cylindropuntia bigelovii are numbered in each pix, from C1 to C3. The photographs were taken from approximately, but not exactly, the same position, which accounts for a small difference in perspective. For example, in the 2025 pix, you can see a portion of the trail leading to Jim Roberts. But in the 2012 pix, you can only see the lowermost portion of that trail, with the rest obscured by the angle of the photograph. The trail turns left at the position of Jim. James Dillane is on that portion of the trail in the 2012 pix (Kate is climbing up to that portion of the trail). Click on the pictures for larger versions without labeling. Those versions can be used to blink against each other. Due to the difference in perspective, it is best to shift the photographs slightly to line up different portions of the photographs. |
This page presents a photograph taken on 12 December 2012 showing 29 individuals of Ferocactus cylindraceus in Plum Canyon, and a repeat photograph twelve years later of the same field, taken on 8 February 2025.
The original picture was taken just to show the trail where it bypassed a dry waterfall in the main canyon. It was fortuitous that the original photograph showed so many barrel cacti. When we recently hiked Plum Canyon again, Tom dug up the 2012 photograph in order to retake it, to see what happened to the barrel cacti.
A detailed comparison of the two pix reveals:
- 14 of the 29 barrel cacti seen in 2012 are still present 12 years later, 48% of the total. 52% of the original 29 barrel cacti are no longer visible.
- Although the death rate is higher in the left side of the pix than in the right, that could just be due to small number statistics. On the left side, 12 of the 18 barrels died, 67% of the total, compared to 9.4 expected from the overall 52% death rate. The difference of 12 and 9.4 is only a bit less than a one standard deviation deviation (the square root of 9.4 = 3.1), something that happens 32% of the time simply due to chance.
- Six new barrel cacti are seen in the 2025 pix, compared to the 15 that were no longer visible.
- All three Cylindropuntia bigelovii that were alive in 2012 were dead in 2025. While not much can be concluded from the death of three plants, a high death rate has been seen in many places; see Distribution of Cylindropuntia bigelovii and its Recent Death Rate.
- The Agave deserti clumps look pretty much the same in location and size in the two pix. The most noticeable change is that the leftmost Agave single plant in the clump at upper right, below C2 and #29, has flowered and is dying.
Keep in mind that the barrel cacti seen in these pix are only the tallest ones of the population. There are definitely a number of barrels too short to be seen in these photos; we measured some of them in 2025 that cannot be seen in the 2025 pix.
If there was a population with a uniform distribution of ages here, which may not be the case due to episodic establishment, the average lifetime of "tall" barrel cacti in this location would be just 24 years, since half the plants died within a 12 year period. In this context, "tall" means plants that are tall enough to be seen in the photographs. If the population of shorter plants is equal in size to that of the "tall" plants, the average lifetime of the species in this area would be 48 years, close to other estimates of that lifetime. Clearly there is great uncertainty in trying to deduce an average lifetime of barrel cacti from these pix.
Growth rates of barrel cacti. Although 14 of the barrel cacti are seen in both pix, most of them cannot be easily measured to see how much they have grown, since the pix were not taken from the same scale, and in most cases, the base of the barrel cacti is not visible.
We measured some of the barrels in 2025 in the field, but even though we tried to keep track of which barrel measurement corresponded to which numbered barrel, the correspondence was sometimes ambiguous.
Five of the 14 barrel cacti can be compared by using boulders that are nearby to derive a relative height in each photograph:
- Barrels #3 and 4 appear to be unchanged in height.
- Barrel #11 appears to be 40% taller in 2025.
- Barrel #14 appears to be 16% taller in 2025. It was measured as 13" tall in 2025. Its growth rate is 0.17 " / year.
- Barrel #18 appears to be 60% taller in 2025, but this number is uncertain due to the precise location of its base.
- Barrel #21 was 4% taller in 2025. It was measured to be either 44 or 53" (due to uncertainty in knowing which measured barrel corresponded to #21). Its growth rate is either 0.15 or 0.18 " / year.
The two measured growth rates of ~0.17 " / year (0.4 cm / year) are significantly lower than previously-estimated growth rates of ~0.8 to ~2.0 cm / year. It may be that the barrel cacti on this south-facing slope, and possibly in the rain shadow of Sentenac and the North Pinyon Mountains, simply don't grow as quickly as they do elsewhere. Of course, the years between 2012 to 2025 have been rough years, much hotter than normal, with less rainfall, which might account for at least part of the slower growth rate here.