What You Should Know About Dark Matter

This is a really nice infographic about dark matter. You can find more over at SPACE.com including some great links to more information.

Source SPACE.com: All about our solar system, outer space and exploration

Claim Your Place in Space!

KLM is running a particularly awesome contest. You can win a trip to space!

Besides having a ridiculously cool contest website, this is a completely legit contest to win a trip to space worth more than $95,000 (£60,000). You could be part of a revolutionary space project that will see the first commercial space trip take off from Curacao on January 1, 2014.

So how does this work?

On April 22, KLM will launch a special high altitude balloon from the Nevada desert in the US, carrying cameras and a GPS to monitor its exact progress. When you go on to their website you go through a few easy steps to predict how high this balloon will get before it pops. The closest predictor to the actual pop-site wins! KLM will will fly you and a friend to Curacao to stay at a luxury hotel before getting on board the SXC Lynx spaceship.

If you choose to register with a social media account, your friends can even help up your chances to win!

Speaking of which, I posted my entry on Science Storiented's Facebook page. Feel free to help me win!

You only have 6 more days to enter. So hurry!

Here's the contest website:

http://space-origin.klm.com/

Om Nom Nom: The Links Between Plant Diversity and Herbivory

I usually start a post with the reason why a particular article caught my eye. Today, I’m not sure why my eyeballs glommed on to this paper, but they did. As it turns out, they have a pretty good taste in articles. Who knew?

An early view paper from the Journal of Ecology looks at how the large herbivores of the African savanna affect the diversity and community structure of plants. More and more studies these days are taking a phylogenetic approach to community ecology questions. That is, they are looking at the evolutionary development and history of a species or taxonomic group to explain the patterns that we currently see. This new study takes this approach in the subtropical woodland biome, or “bushveld,” of the Kruger National Park (KNP) in northeast South Africa. This area is home to 148 mammal species, of which 30 are large herbivores such as elephants, rhinos, and giraffes. The vegetation of this area consists of 1974 species, including 458 species of trees and shrubs. KNP varies from dense thicket, savanna woodlands to forests characterized by tall trees and a closed canopy. These plant communities are under occasional pressure from periodic fire and under constant pressure from large herbivores. This study looks at the impacts of these herbivores on the phylogenetic structure of woody plant assemblages and evaluates the impacts of their removal on plant community composition and structure.

The researchers used DNA sequencing to reconstruct the phylogeny of 448 species of trees and shrubs (using Amborella as an outgroup), representing 246 genera, 71 families and 31 orders. ... Let’s pause for a second to say “Wow!” ... Then they calculated divergence times and used speciation models on these data. Next was the community sampling along a north-south transect through KNP. This transect has enclosures situated along it where large herbivores are partly or fully excluded. These enclosures have been established in the park for between 8 and 43 years. Within 15 defined “ecozones,” the researchers surveyed 110 50x50 meter unrestricted herbivory plots and 15 50x50 meter plots in each of the five herbivore exclusion enclosures. Within these plots they recorded all species of trees and shrubs and the number of individuals per species (abundance). Then they evaluated various physical and mechanical plant defense traits (not including chemical defenses), using wood density of quantify plant resistance to physical damage and specific leaf area (SLA) as a proxy for leaf nutrient content.

All sorts of indices (MPD, MNTD, SR, Shannon, NRI, NTI) and statistics were used that I’m not going to go into because they will just confuse everyone. But when all the statistics were done, they found a latitudinal gradient in diversity with the highest diversity in the south and extreme north and low diversity in the center (which matches rainfall patterns). In parallel, they found shifts in community phylogenetic structure comparable to these changes in community diversity, indicating that the communities in the center are more highly phylogenetically clustered (composed of more closely related species). Plant diversity in the KNP is strongly spatially structured and this clustering is reflective of generalist browsing, the geomorphology of the area, and the patchy distribution of large herbivores. In plots where herbivory is unrestricted they found significant phylogenetic clustering of plant communities, likely the result of the heavy pressure from the herbivores. They also found that plant defense traits had a weak but significant phylogenetic signal, suggesting that they do not fit well into the simple model they used. When the researchers compared the enclosures to the unrestricted areas they found “that when megaherbivores are excluded, species diversity generally decreases, but changes in phylogenetic diversity [vary] by spatial location.” When large herbivores are excluded, plant community structure is contingent upon the initial community structure. If a community was initially overdispersed then the shift towards a more clustered community would occur by excluding large herbivores and vice versa. Ultimately, they conclude that the exclusion of large herbivores results in impoverished species communities.

I think that it is important to mention that these researchers were limited by the study design they had to work with. These enclosures had already been set up by other people. As such, the scientists encountered some issues that they would have been able to control for if they had set up the site themselves. Issues like enclosure age and location. For example, one enclosure was located on a river that periodically floods, altering local plant diversity. Such issues make it difficult for them to predict how specialist vs. generalist herbivores impact community structure and prevents them from drawing strong conclusions about the underlying causes for the patterns they saw.

On the upside, their results add valuable knowledge critical for predicting the impacts of overall herbivore decline on African ecosystems and local increases of these animals in protected reserves. This study “shows not only that large herbivores are key to maintaining woody plant diversity, but also that they may impose specific phylogenetic structure on plant communities.” Shifts in this structure have downstream consequences in that phylogenetic diversity can capture genetic and functional diversity, which has been linked to ecosystem productivity. And, ultimately, we want to keep our ecosystems happy and productive, right?


Kowiyou Yessoufou, T. Jonathan Davies, Olivier Maurin, Maria Kuzmina, Hanno Schaefer, Michelle van der Bank, & Vincent Savolainen (2013). Large herbivores favour species diversity but have mixed impacts on phylogenetic community structure in an African savanna ecosystem Journal of Ecology : 10.1111/1365-2745.12059


(image via Animals Time)

Epic Battle of Electricity

If you haven't watched Epic Rap Battles of History then you need to hop on that train. It is hysterical! Here's a recent rap battle featuring two epic minds of their time and their actual battle over electricity.

Unraveling Spider Silk

An interesting infographic about spider silk.

(via The Guardian)

Getting to the Roots (and Fungi) of Carbon Sequestration

This week, I found a paper that I’m calling the best of both worlds. Well, for me at least. This paper combines my past (and lingering) interest in island biogeography with a current interest in climate change and carbon storage.

If you have been reading my blog long enough then you already know my love of islands. They are just so darn useful. In the past, I have focused on oceanic islands, but lake islands are also really neat. These types of islands typically form when lower lying land areas fill with water, effectively cutting off higher areas from the mainland and making them into islands. As such, these islands usually already contain forest as opposed to an oceanic island that emerges from the ocean and must be colonized. A new study, published in journal Science, looks at a fire-driven boreal forest chronosequence on forested lake islands in northern Sweden. Such a chronosequence allows the study of soil carbon sequestration over time scales of centuries to millennia.

This new study looks at roots and their associated fungi (mycorrhizae) as sources of this stored carbon. I’m not going to spend the space to describe mycorrhize, but will, instead, send you over to my Free Market Fungi post for more information, if you need it. It is known that 16 percent of the global carbon stock is sequestered in soils. To date, most carbon studies of this type focus on aboveground leaf litter as the fundamental determinants of this carbon accumulation. But a large portion of photosynthetically fixed carbon is actually directed belowground to the roots and, subsequently, the mycorrhizae. Now, let’s add fire. It has been shown that when a forest doesn't burn, the soil and ecosystem carbon accumulate unabated, and in a linear fashion. Add this information together and it becomes a big deal when it comes to correctly allocating carbon, calculating the long term sequestration rates, and predicting how forests will respond to climate change and other environmental shifts.

The study sites were in two adjacent lakes, Lake Hornavan and Lake Uddjaure, in northern Sweden. The islands in these lakes were formed after the most recent glaciation and come in a variety of sizes. In terms of fire, larger islands burn more frequently because they are larger targets for lightning strikes. As a result, several of the large islands in these lakes have burned in the last century, whereas some of the small islands haven’t burned in at least 5000 years. This lack of fire leads to very thick humus layers (or organic layers towards the top of the soil column) on smaller islands, up to 1 meter thick!

The researchers divided islands into three size classes of 10 islands each: large (over 1 ha), medium (0.1-1.0 ha), and small (less than 0.1 ha). They took soil samples from these islands to look at the organic soil profiles and found that large islands accumulated 6.2 kg of C per square meter belowground with a mean time since fire of 585 years, medium islands accumulated 11.2 kg of C per square meter with a mean time since fire of 2180 years, and small islands 22.5 kg of C per square meter with a mean time since fire of 3250 years. Then they looked at the carbon dynamics across this chronosequence by analyzing bomb 14C. This allowed them to determine the age since fixation of soil carbon. Then they fitted a mathematical model to measurements of carbon mass and age distribution across the soil profiles for six of the islands (3 large, 3 small). This model revealed that the distribution of carbon mass and age could only be predicted when they included carbon from roots. This root-derived carbon accumulation was found to be larger on small islands (70 percent, that's a LOT!) than large islands (47 percent). They were able to explain the entire carbon sequestration difference on small islands from these root-derived inputs. The model also showed that small islands store a major proportion of their soil carbon in the deeper soil layers, those over 100 years old. However, below 20 cm depth, the root-derived carbon inputs were shown to be low and to decompose slowly. So the root-derived carbon input into the upper layers probably contributes to the long-term buildup of humus that is seen on these islands. But, as usual, that's not the end of the story.

We know that fungi play very important roles in forest ecosystems, both as decomposers and in root-assoicated carbon transport and respiration. So the researchers also profiled the relative abundance of major groups of fungi by depth in the soil profiles. They found that the upper soil layers are dominated by free-living saprotrophs (fungi that obtain their nutrition heterotrophically from non-living organic materials), and greater depths were dominated by mycorrhizal and other root-associated fungi. Their model suggests that these mycorrhizae live at the spots where the largest difference in carbon sequestration between the island size classes exists, which also tends to be the areas of highest root mass. When they ran tests for fungal biomass throughout each soil profile they found greater mycelial (the vegetative part of a fungus, consisting of a mass of branching, threadlike hyphae) production on large islands, but less mycelial necromass (dead stuff) on small islands. This suggests that the large production is counterbalanced by faster decomposition of mycelial remains. “Correspondingly, the 14C model indicated faster decomposition of root-derived [carbon] on large islands, despite inputs being conservatively constrained to be equal across all islands.”

I found these conclusions to be interesting because of the amount of soil carbon from roots and mycorrhizal fungi, especially on small islands. And although they saw less carbon accumulation on large islands, these islands have a greater root density and so should have more carbon allocation to roots and the associated fungi. Did you catch the contradiction? Well, in response to increased carbon dioxide, there will be an increase of carbon inputs to the roots which will accelerate the turnover of soil organic matter. This counteracts carbon accumulation and enhances nitrogen cycling through the microbial pools, an effect these researchers observed when they tested the C:N-ratios in the humus of large islands. This is much lower on small islands, possibly because of impared mycorrhizal nitrogen mobilization and the accumulation of nitrogen in fungal remains. This leads to progressive nutrient limitations, then leads to changes plant productivity, leading to changes in community composition, which leads to changes in total belowground carbon allocation, that leads to changes in fungi.

Definately starting to grasp the importance of the belowground dirty stuff. There’s a whole lot of carbon down there that we need to start looking at, accounting for, and seeing where it goes. We know that changes in the environment such as climate change, soil fertilization, fire suppression, and forest management make big differences to the aboveground stuff. It only makes sense that the belowground stuff is impacted as well.


Clemmensen, K., Bahr, A., Ovaskainen, O., Dahlberg, A., Ekblad, A., Wallander, H., Stenlid, J., Finlay, R., Wardle, D., & Lindahl, B. (2013). Roots and Associated Fungi Drive Long-Term Carbon Sequestration in Boreal Forest Science, 339 (6127), 1615-1618 DOI: 10.1126/science.1231923

If you would like some follow-up reading I suggest:

Treseder, K. K. (2013-03-29) Fungal Carbon Sequestration. Science, 339(6127), 1528-1529. (DOI: 10.1126/science.1236338) 

Also check out the write-up in Nature "Fungi and roots store a surprisingly large share of the world's carbon"

(image via Forest Keepers)

The Mockingbird Problem

In the past, I've had this exact problem with a mockingbird. Currently, I'm having a problem with a Carolina wren that isn't aware that it isn't supposed to be singing outside my bedroom window at 3 a.m.

(via Bird and Moon)