Wednesday, March 14, 2018

Borneo as a Carbon Sink

Posted by Richard B. Primack

“The woods I walked in in my youth are cut off. Is it not time that I ceased to sing?” 
-Thoreau in his Journal, 1852 

During the 1980s and 1990s I used long-term forest plots in Malaysian Borneo to determine how so many tree species could co-exist in one place, and how many years forests took to recover from logging. Forest plots from across Borneo are now being combined to examine how the island’s forests are responding to climate change. The results have recently been published as an article in Nature Communications titled Long-term carbon sink in Borneo’s forests halted by drought and vulnerable to edge effects.

Figure 1. Changes in forest biomass in Borneo were studied using 71 long-term plots. 

The main result is that these forests are gaining biomass, meaning they are out of equilibrium and are a net sink for atmospheric carbon dioxide.

Figure 2. Forests in Borneo are showing a net increase in biomass over time in the forest interior; this has also been observed in the Amazon and in Africa. Forests on the edges of fragments are declining in biomass.

Forest fragmentation from human activity has had negative effects as shown by the declining biomass of forests on the edges of fragments. Borneo’s forests are also vulnerable to the effects of climatic variation as a drought in 1997-1998 temporarily halted the increase in biomass and caused an increase in tree mortality. These forest plots will become more valuable in coming decades as a way of documenting the continued impacts of climate change.

Thursday, February 22, 2018

Herbarium specimens show patterns in wild fruiting phenology

Posted by Amanda Gallinat

The timing of fruiting in New England is important for wildlife that eat wild fruits and disperse seeds. However, surprisingly little is known about when different plant species fruit and what environmental variables determine fruiting times.

An American Robin consuming whole fruits in late-autumn (photo by Sam Roberts)

In a paper published last week in the American Journal of Botany, my co-authors and I describe patterns and predictors of fruiting times for 55 woody plant species across New England. Our team recorded fruiting dates and locations for over 3,000 herbarium specimens with ripe fruit, collected in the wild from 1849-2013, and housed at 6 major herbaria. We analyzed variation in fruiting times among 37 native and 18 invasive species, as well as within-species variation.

A Buckthorn (Rhamnus cathartica) specimen with ripe fruits, available through the George Safford Torrey Herbarium digital collections

We found a moderate phylogenetic signal to fruiting dates; in other words, related species tended to fruit at similar times. With phylogeny considered we found that, on average, invasive species fruited 26 days later than native species, and had more variation in their fruiting times. Since some birds are migrating through New England later with warming temperatures, this may increase the likelihood that migratory birds will encounter and consume invasive fruits, and disperse invasive seeds.

Spring temperature and year were significant predictors of fruiting times within species, but explained a very small amount of the variation. We conclude that herbarium specimens are an excellent resource for investigating differences in fruiting times among species, but present unique challenges for analyzing variation within species. Read more about those challenges, potential solutions, and more in the full text.

Friday, February 16, 2018

Chlorophyll content of conifer needles

Post written by Linnea Smith

“Knowledge is to be acquired only by a corresponding experience.”
-Thoreau, A Week on the Concord and Merrimack Rivers

Part of my undergraduate thesis on leaf longevity involves studying how leaf age affects the chlorophyll content of evergreen leaves. We have measured chlorophyll content for broadleaved evergreen species, such as Rhododendrons and hollies, using an AtLeaf+ chlorophyll meter.

Unfortunately, this instrument typically does not work for most conifers, such as firs, spruces, and yews, because the needles are too narrow to cover the width of the measuring window and the results are variable and unreliable. However, with just the tools shown below, we have been able modify the usual procedure for use with narrow conifer needles.

We cut an insert (middle left) out of a sheet of thin plastic; this allows the needles to be precisely placed over the measuring window. We arrange a few needles next to each other to cover the hole in the insert, with no gaps and minimal overlap between leaves, and then tape the leaves down with clear tape.

We then carefully place the insert in the chlorophyll meter so that leaves are over the measuring window, and we’re set to measure chlorophyll content! In effect, this simple procedure is a way to increase the width of the leaf surface area being measured.

Wednesday, February 7, 2018

Happy Tu BiShvat!

Posted by Amanda Gallinat

“Wines of all sorts & qualities of noblest vintages are bottled up in the skins of countless berries for the taste of men & animals.” 
 -Thoreau in his Journal, 1853

Last weekend I visited the Kahal B’raira Humanistic Jewish congregation in Cambridge MA, for their annual celebration of Tu BiShvat. Tu BiShvat, the New Year of the Trees, celebrates the value of trees particularly as providers of fruit and nuts.

We began the morning with a Tu BiShvat seder, during which we ate fruits representing each of the seasons.

One highlight was an interactive activity in which kids and adults acted out parts of a tree from the inside out. We started with the heartwood, and added roots, xylem, phloem, and bark. By the end, the whole congregation was part of the tree!

At the end of the morning, I gave a featured talk entitled Wild Fruits and the Birds that Eat Them. I described the natural history of fruits, their value to wildlife, and human impacts on bird-fruit interactions.

Thanks to Kahal B’raira for the warm welcome, teaching me about Tu BiShvat, and for being such an engaged and curious audience for my talk!

Wednesday, January 31, 2018

Is species richness increasing or decreasing?

Posted by Richard B. Primack, Abraham J. Miller-Rushing, and Vincent Devictor

“It takes two to speak the truth, - one to speak, and another to hear.” 
-Thoreau in A Week on the Concord and Merrimack Rivers

Conservation biologists have argued that we need to protect local species richness (i.e. the number of species found locally) for its value in providing ecosystem services, such as clean water, flood control, and pollination. Yet in a recent editorial in Biological Conservation, we report that many long-term ecological studies have found the surprising result that the number of species at sites around the world has remained stable or is even increasing. We have similarly found that the number of wildflowers in Concord, MA has increased from Thoreau’s time to the present.

A diversity of wildflowers grow in this Romanian meadow

How could this be true when hundreds of species have gone extinct, and thousands more are declining and threatened with extinction? The answer seems to be that the loss of species at the local scale is often balanced by the arrival and establishment of new native or nonnative species.

These findings highlight the need for conservation biologists to avoid oversimplification when selecting management indicators, such as species richness. Targeting only species richness ignores the ethical, cultural, and aesthetic values of certain local species and ecological communities, such as monarch butterflies and redwood forests. These aspects of biodiversity can still be damaged or lost, even as species richness remains steady or increases.

Richard Primack is a professor in the BU Biology Department.
Abraham J. Miller Rushing works for the National Park Service at Acadia National Park (and received his PhD at BU).
Vincent Devictor is a professor at the University of Montpellier in France.
A version of this article was originally published in the journal Biological Conservation.

Thursday, January 25, 2018

Candy-covered Science

Posted by Richard B. Primack

“There are innumerable avenues to a perception of the truth.”
-Thoreau in his Journal, 1851

The Biogeoscience program, which brings together researchers from BU's Biology and Earth & Environment Departments, recently held its Annual Symposium and Winterfest. The event featured short research talks, mostly by grad students, and afterwards grad students enjoyed designing replicas of their research projects using gingerbread, candy, frosting and sprinkles.

Sarabeth Buckley (Earth and Environment) describes her project on the ecosystem ecology of rooftop gardens. 

Mustafa Saifuddin (Biology) uses gingerbread to model fungi and root dynamics in forest soils.

I-Fang Hsieh (Biology) investigates how soil warming (black cable) and the elevation of CO2 levels (from yellow towers) will impact ecosystem processes in Minnesota peatlands. 

Here is a close-up of I-Fang’s project.

Our own Lucy Zipf (Biology) is developing citizen science methods to investigate how noise pollution impacts parks and cities, as shown by this candy-filled model of an iPhone app.

Friday, January 5, 2018

Nantucket faces a rising sea

Posted by Richard B. Primack

“The sea-shore is a sort of neutral ground, a most advantageous point from which to contemplate this world.” 
-Thoreau, in Cape Cod

Over the past half-century the mid-Atlantic coast, including Massachusetts, has experienced a sea level rise that is 3-4 times higher than the global average, according to a report by Sallenger and colleagues in Nature Climate Change. The effects of sea level rise are increasingly felt on Nantucket Island where powerful storm surges dramatically alter beaches and destroy houses.

A storm surge recently eroded the Nantucket coastline in Madaket, leaving this house isolated and vulnerable to being destroyed by the next storm

Homeowners are moving their houses further inland where possible, or building massive sea walls. Such efforts are understandable, but perhaps just delay the inevitable effects of climate change.

Near the town of Nantucket, homeowners build massive walls in front of their houses to keep back the rising sea

Because of its mild oceanic climate, Nantucket gardeners can grow cold-sensitive plants, such as camellias and crepe myrtles that cannot survive Boston winters. As the global climate warms, we will likely be able to grow these beautiful plants in Boston in coming decades.

Camellias are still flowering in early November in protected gardens

The efforts of Nantucket’s people to balance economic development and environmental protection faces new urgency because of rising sea levels and climate change. Some of these same issues have been described in the recent book A Meeting of Land and Sea: Nature and the Future of Martha’s Vineyard by the eminent Harvard Forest ecologist David Foster, that I reviewed for the journal Ecology.