Leaf Physiognomy Offers clues to the Past

By Eric Atkins

There are many techniques that can be used to offer insight to the past–a family of proxies that range from gas found in ice cores to fossilized feces. I have always been interested in fossils. The allure of something so ancient was introduced to me as a child. At the age of eight, I found a veiny imprint of a leaf in a chunk of sandstone. Fossils are a great tool for looking into the past. For nearly a century by paleoclimatologists and paleoecologists have been using leaf physiognomy as a proxy to deduce past climate environments. By looking at leaf mass per area, teeth area, number of teeth, and degree of blade dissection we can extrapolate information about past climates.

Fossilized Platanus leaf, Paleocene, Alberta, Canada. Via Wikimedia Commons.

Fossilized Platanus leaf, Paleocene, Alberta, Canada. Via Wikimedia Commons.

In recent years this type of proxy has evolved along with technology. Continue reading

The Rise of C4 Plants

By Kevin McFadden

Imagine a happy place where you’re laying out in the Caribbean sunshine on a beach with a mojito in hand. You jump into the crystal clear blue bathwater of the sea, then you lay down in your chair under an umbrella and doze off thinking about delicate and beautiful New England winters… you wake up and look over at a little saltbush that hasn’t been consuming delicious beverages, cooling off in the sea or taken cover under an umbrella to take a nap. In fact, this poor plant hasn’t moved an inch. First off, let’s hold the phone here. The truth is, this plant is loving life and it took over 3 billion years of evolution for it to become so happy! Saltbush is one of many plants who has adapted to warm, sunny, and dry conditions.

Long ago, when atmospheric carbon dioxide levels were high and oxygen levels were low, an enzyme called Rubisco started being made in plants which is an important driver in the Calvin cycle, without which food can not be made. Continue reading

Small but Mighty: Insects as Proxies

By Wayne Heideman

Insects have been on the Earth for a long time and their presence can affect their surrounding environment. It is important to look at insects in the past as they can provide us with insight on how they can act in the present and in the future. In a paleoecological sense, insects can be studied in a number of ways. One way is to look at plant-insect interactions through plant fossils (herbivory) and peatlands (habitat). Another technique is through amber and observing the insect in a snapshot of time. Lastly, sediment cores in lakes can capture insect presence, notably Chironomidae (non-biting midges) larvae and Coleoptera (beetles). All three are viable means of observing past insect use but they all have their strengths and weaknesses which should be assessed before using a specific method.

A picture of three different types of insect damage on plants. A) Shows a frass trail as well as an oviposition site marked by the arrow. B) Shows a high degree of herbivory, only leaving fine veins and C) shows areas of leaf case shelter sites. From Wilf 2008.

A picture of three different types of insect damage on plants. A) Shows a frass trail as well as an oviposition site marked by the arrow. B) Shows a high degree of herbivory, only leaving fine veins and C) shows areas of leaf case shelter sites. From Wilf 2008.

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Tree migrations: a matter of scale

By Benjamin Seliger

In everyday life, trees may appear as stationary, permanent fixtures of the landscape, but in reality they are far from it. I will argue that all trees are constantly migrating, and summarize the means by which they do so in this post.

When I tell people I study tree migration, I often get funny looks. After all, how can an organism that cannot even move migrate? The answer to this, like many other phenomena in ecology, is time. Every year, mature trees release thousands of seeds in all directions, and when one of those seeds grows into an adult in a place where others of its own kind were not growing before, the species is migrating. Note that this perspective of migration is not limited to the cyclical movement of animals with the seasons, but rather an adjustment of a species’ range to preferred conditions as climate changes. I will refer to the latter as a range migration and the former as a seasonal migration. The two definitions are really explaining the same process at different scales; seasonal migration being the movement of individuals within their lifespan, and range migration as the movement of populations over the course of multiple generations. The end result for either definition is all the members of a species living in a different place than they did previously due to a change in environmental conditions. Continue reading