Archive for August, 2011

Summer in the desert

August 30, 2011

One thing that makes traveling to Portal each month so interesting is the speed at which the desert landscape can change. Southeastern Arizona has recently been in a major drought, but the arrival of summer monsoon rains seems to have helped green things up, at least temporarily.

Desert mushroom

Gopher snake on traps

Below, the first photo was taken on July 2, 2011 and the second photo was taken August 6, 2011. During that month approximately 11.4 cm of rain fell and transformed the dry, dusty ground into a carpet of green seedlings and flowers.

Some areas were covered in orange flowers (e.g., summer poppies, orange flame flower, and showy flame flower), purple flowers (e.g., silverleaf nightshade) and large caterpillars were abundant (I think mostly Sphinx moths).

In addition to the growth of new plant life, the summer rains have also led to flooding in the Chircahua Mountains where the fire left slopes unstable and vulnerable to washing away. Some of the forest roads remain closed and a short drive into Cave Creek Canyon makes it easy to see areas where the forest floor is buried under mud and debris washed down by flash flooding. Some locals, bloggers Azure Gate and Cave Creek Ranch, have posted updates and photos on conditions in the area.

In addition, the dry soil conditions and lack of vegetation on the bajada and in the valley seem to have allowed for increased erosion at our site as well. The gravel roads leading towards the Portal Project were washed out in places and erosion around the fenced plots meant that some gates were left > 12 cm above the actual soil surface or buried underneath mud and debris; both scenarios making it difficult or unlikely for rodents to actually find and use the gates. I’ll have to work at maintaining these gates over the next month as more rains are likely to occur.

Luckily, I had lots of help digging out rodent gates and collecting data by Elita Baldridge, a Ph.D. student in Ethan White’s lab who came to help out before we both headed to present at ESA after field work was finished.

I continue to be amazed at the “sea” of desert pocket mice (Chaetodipus penicillatus) that seem to be taking over–we’re even encountering control plots, where kangaroo rats should be dominant, with no kangaroo rats at all! Amazing.

Oh, and speaking of amazing…

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Portal at ESA 2011

August 4, 2011

If anyone still reads this blog, you may be wondering whatever happened to Portal. Well, rumors of our demise are…mildly exaggerated. Since I last blogged here, intrepid volunteers stepped forward and helped keep the project running on fumes. If you’re a Portal fan and you’re going to be at ESA this year, you should give the following people a hearty pat on the back (or better yet, buy them a beer): Kate Thibault, Karen Mabry, and Sarah Supp  (Glenda Yenni  is also on this list, but she won’t be at ESA this year, so you can just toast her in absentia). From May-December  of last year, we held things together with spit, duct tape, and fervent wishes. I even funded one of the trips by selling  a bunch of books to those used textbook people who seem to habitually lurk  the halls. Fortunately, Mother Nature was working with us and rodent numbers were so low that we could scale back our trips to every other month because rodent pressure on the exclosures was very low. Then the funding deities took some pity on us and we were awarded a 2 year NSF grant to keep the rodent side of things running. We’re still operating on some spit and duct tape, but we’re no longer hyperventilating. The plant side of things are a little more dire, but we’re all doing what we can.

Things at Portal are so not dead, in fact, that we have 4 different Portal presentations occurring at ESA this year. If you’re interested in hearing what’s been going on at the site stop by the following talks/posters (with short promos taken from their abstracts):

Tues: Multi-decadal climate cycles and the dynamics of a Chihuahuan Desert ecosystem. Morgan Ernest, Thomas Valone, James Brown. Poster Session 4:40-6:30 PM in Exhibit Hall 3, Convention Center

One of the greatest challenges facing ecology is understanding shifts in ecosystems that are being reported across the globe. However, understanding whether a particular shift in an ecosystem is the result of directional anthropogenic influences is complicated by the discovery of long-term climate cycles, such as the Pacific Decadal Oscillation (PDO), that fluctuate between alternative phases on decadal timescales. Because many currently operating long-term studies were implemented in the 1970s, 1980s, and 1990s, many of these studies have collected data only under one phase of these decadal-scale climate cycles, making it unclear whether the long-term trajectories documented in some ecosystems represent long-term lagged responses to large-scale shifts in climate due to naturally occurring climate cycles.

Thurs: Small mammal activities decrease soil organic carbon storage in dryland ecosystems. Jane Smith, Heather Throop, Thomas Valone, Morgan Ernest, James Brown. New Mexico State University. 8:20AM Ballroom F, Convention Center

Most of what we know about the terrestrial carbon (C) cycle comes from research conducted in mesic systems and dryland C cycling dynamics are more poorly understood.  However, arid and semi-arid systems cover 40% of Earth’s land surface and may provide an important C sink that will help mitigate the accumulation of CO2 in the atmosphere.  In drylands small mammal disturbances such as digging and burrowing can affect a large proportion of the surface soil, and these disturbances have the potential to influence inputs to and stability of the soil organic carbon (SOC) pool.  We asked how small mammal activity affects SOC pools in dryland ecosystems. 

Thurs: Experimentally altering biotic interactions has different effects on static and dynamic macroecological patterns. Sarah Supp, Xiao Xiao, Morgan Ernest, Ethan White, Utah State University. 4:00 PM Rm 8, Convention Center.

A major focus in recent ecological research has been to elucidate if and when the details of biological interactions play a critical role in producing observed patterns of diversity.  Macroecology has increasingly become an important and popular approach in ecology. However, because it often ignores the inherent complexity within biological systems in its attempt to find generality across systems, its utility has been increasingly questioned. This has generated an important question: are macroecological patterns contingent on the specific networks of interactions among ecological particles or do patterns emerge from interactions regardless of the details of interactions?

Friday: Decline in biotic resistance and the reorganization of an annual plant community by an exotic invader. Ginger Allington & Thomas Valone, Saint Louis University. 8:00 AM Rm 10A Convention Center

Species interactions are considered an important mechanism that limits the abundance and distribution of exotic species, a process known as biotic resistance. Many studies documenting strong biotic resistance have been conducted over short time scales. However, given time-lags inherent in exponential growth and natural population fluctuations, the strength of biotic resistance may change over time.  Here, we use a thirty-year dataset to show an eventual decline in the strength of biotic resistance.