The Glaciation Fascination

By Rayna Campbell

The Earth’s history shows a wild mix of climates. Ranging from the toxic CO2-filled atmosphere of the earliest years, to global tropical conditions, to periods of intense and violent volcanic disturbances. In the incredibly short period of time humans have inhabited the earth, the climate has not had much time to change. But if we look back into our history, the last glacial maximum, or “The Ice Age” only occurred about  21,500 years ago (Editors). On the scale of geological time, this is very recent. So recent, in fact, we are still able to look to our paleoecological records and “see” evidence of the changes the environment went through during the presence of these huge ice masses.

Fig. 1) Glacial striations. Image courtesy of GNS Science (2009)

On the rocky coasts of lovely Maine in the summer, trips to the seaside provide not only a relaxing retreat from the summer heat, but a wealth of information about glacial movement thousands of years ago. Continue reading

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Dendrochronology: the trees tell stories too

By Erin Hayes-Pontius

To add to the seemingly never-ending list of proxies paleoecologists use to study the past, here’s another one: trees. If you have been following this blog for a little while, you probably read about what pollen can tell us, but using the trees themselves, rather than their pollen, can tell an entirely different story. Studying the pollen that accumulates in lake sediments has the distinct advantage of providing a record that is as old as the lake itself, which can sometimes be up to millions of years old. However, because of how long it takes lake sediments to accumulate, we cannot always be very confident of the date a particular layer of sediment represents. In contrast, trees generally provide a much shorter record than pollen, but because of their annual rings, give us an annual record to work with.

treecore

A device used to extract thin cores from trees (Wikimedia Commons: Beentree 2006).

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Through the looking glass: how diatoms can reconstruct wind

By Kelsey

Few object are more beautiful than the minute siliceous cases of the diatomaceae: were these created that they might be examined and admired under the high powers of the microscope? ~ Charles Darwin

As Darwin remarks, diatoms are beautiful.  They have unique, intricate cell walls that help in their identification, because in addition to their beauty, they can tell a lot about past environmental conditions.  My research uses diatoms as a proxy (a preserved item that acts as a ‘natural archive,’ capable of telling us something about climate in the past) to explore past environmental conditions in lakes.  Diatoms are a type of single celled organisms called algae.  These organisms are found in many wet environments including soils, but I focus on diatoms in lakes.

Figure 1: Images of various species of diatoms. Image from Wikimedia Commons.

Figure 1: Images of various species of diatoms. Image from Wikimedia Commons.

Diatoms are unique from other types of algae because they have siliceous or glass-like cell walls, and therefore are well preserved in lake sediments.  This makes them good proxies of past climates.  Additionally, diatom species, like other algae have a variety of environmental preferences.  These preferences can range from mixed or stable water conditions, to high nutrient or light levels and provide the basis for climate inferences. Continue reading

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

Humans: where we have been and where are we going

By Gloria Lima

When looking at how humans have change throughout the year one may simply think in the past hundred years or maybe even a bit further to medieval times or to ancient Rome and Greece. But nonetheless, humans have been around for longer than that– try around 100,000 years! To understand the idea that human ancestors may have been around longer than today’s humans have though is a bit mind blowing.  To think that we have been on this earth for that long is pretty amazing.  Continue reading

Wildfire through time: shaped by climate and people

By Dulcinea Groff

Picture the landscape of a tropical savanna, composed of grasses, shrubs and a sparse number of trees.  The savanna biome is dominated by a wet season supplying thousands of herbivores with forage and a dry season accompanied by intense lightning and fire.  These wildfires maintain the savanna as grassland by killing the saplings (suppressing tree growth) and the grasses quickly regenerate.  Imagine early hominids in the fire-constructed savanna, they begin to use fire, control fire and even make it!  Fire is a permanent link now between biome and human.

Fire was used by humans for presumably many reasons:  communication, prepare food, drive and corral prey, warmth during cold periods, etc.  Humans have long suppressed and ignited fires for various reasons.  In fact, as a source of ignition, humans have been shaping landscapes since the earliest known hominids were thought to use fire one million years ago in South Africa (Berna et al. 2012). Continue reading