Roundup: Plant Succession, Glacier Surges and Organic Pollutants

Phosphorus, Not Nitrogen, Limits Primary Succession

From Science Advances: “Current models of ecosystem development hold that low nitrogen availability limits the earliest stages of primary succession, but these models were developed from studies conducted in areas with temperate or wet climates. We combine field and microcosm studies of both plant and microbial primary producers and show that phosphorus, not nitrogen, is the nutrient most limiting to the earliest stages of primary succession along glacial chronosequences in the Central Andes and central Alaska. We also show that phosphorus addition greatly accelerates the rate of succession for plants and for microbial phototrophs, even at the most extreme deglaciating site at over 5000 meters above sea level in the Andes of arid southern Peru.”

Read more about the factors affecting plant succession in cold-arid regions here.

Plant succession occurring after the retreat of the Exit Glacier, Alaska (Source: National Park Service).


Tidewater Glacier Surges Initiated at the Terminus

From Journal of Geophysical Research: “There have been numerous reports that surges of tidewater glaciers in Svalbard were initiated at the terminus and propagated up‐glacier, in contrast with downglacier‐propagating surges of land‐terminating glaciers. We present detailed data on the recent surges of two tidewater glaciers, Aavatsmarkbreen and Wahlenbergbreen, in Svalbard. High‐resolution time series of glacier velocities and evolution of crevasse patterns show that both surges propagated up‐glacier in abrupt steps. Geometric changes near the terminus of these glaciers appear to have led to greater strain heating, water production, and storage at the glacier bed. Water routing via crevasses also likely plays an important role in the evolution of surges.“

Find out more about this proposed mechanism of glacier surges here.

Profile of a glacier during normal conditions (left) and during a surge event (right) (Source: Jean-Louis Etienne).


Hexachlorobenzene Accumulation in Svalbard Fjords

From Springer: “In the present study, we investigated the spatial and historical trends of hexachlorobenzene (HCB) contamination in dated sediments of three Svalbard fjords (Kongsfjorden, Hornsund, Adventfjorden) differing in environmental conditions and human impact. HCB concentrations ranging from below limit of quantification (6.86 pg/g d.w.) to 143.99 pg/g d.w. were measured… In case of several sediment cores, the HCB enrichment in surface (recent) sediments was noticed. This can indicate importance of secondary sources of HCB, e.g., the influx of HCB accumulated over decades on the surface of glaciers. Detected levels of HCB were generally low and did not exceed background concentration levels; thus, a negative effect on benthic organisms is not expected.”

Discover more about organic pollutions in Norway here.

The Arctic fox and other living organisms in Svalbard could be affected by hexachlorobenzene contamination (Source: Natalie Tapson/Flickr).

Hunt for Lost Plots in Glacier Bay Yields Key Data

20th century ecologist William Skinner Cooper has a long legacy. He spurred the establishment of Glacier Bay National Park and was one of the first American scientists to use the technique of aerial photography. His name lives on through Alaska’s Mt. Cooper and the biggest award offered by the Ecological Society of America.

William Skinner Cooper returns to Glacier Bay fifty years after his first visit (Source: Robert Howe/NPS).

That legacy continues in new and unexpected ways in Glacier Bay National Park with a treasure hunt to find nine plots established by Cooper there in 1916. Cooper developed the plots in order to study how vegetation develops after glacial retreat. As soil evolved and buried the marker stakes, the plots were lost. A century after Cooper began his experiment, Brian Buma, professor of ecology at University of Alaska Southeast, was determined to relocate the plots and launched the hunt.

Such bridges between the past and present are what national parks are all about, according to Glacier Bay National Park ecologist Lewis Sharman. In 1916, Cooper recognized that Glacier Bay was changing rapidly as its glaciers retreated and exposed new land to primary plant succession.

“Glacier Bay is one of the most dynamic landscapes on earth,” said Lewis. “It’s the quintessential national park in that it encompasses a landscape with great scientific value. Scientists here are like kids in a candy store.”

“It was the most fun I’ve ever had on any science project,” added Buma, who recently published his results in the journal Ecology. “It had everything: adventure, old documents, old-school orienteering.”

The first clues to the plots’ whereabouts came from a paper Cooper published based on his trip to the area in 1916. “The directions literally read “‘From large rock, walk 30 degrees east 40 paces, to small cairn.’ It was very Indiana Jones,” said Buma. The project’s National Geographic funding included a trip to the archives in Minnesota that house Cooper’s original field notes. Some notebooks are stained by water and others burnt by sparks from campfires, according to Buma.

His research in the archives pointed to “Teacup Harbor,” a distinctive round inlet in the West Arm of Glacier Bay. Buma decided to start there, in a search he called “truly for a needle in haystack.” Magnetic north has changed by eleven degrees since Cooper’s day, so the original compass bearings were wrong, and large boulders Cooper used as landmarks are now cloaked by plants.

The plots are located in the West Arm of Glacier Bay. Photo A shows the view from plot Q1 in 1941, and Photo B shows the same view in 2016 (Source: Brian Buma/Ecology).

Isostatic rebound, the rise of land formerly depressed by the weight of a glacier, also transformed Glacier Bay’s landscape and confounded Buma’s search. Rebound has dramatically changed Teacup Bay’s shoreline and the distance of some plots from the water. Undaunted, the team headed to Glacier Bay. Their search process involved scouting from a boat, matching the landscape before them with photographs from the 1970s, and “stumbling around the woods looking at 100-year-old sketches, trying to decipher what a ‘pace’ was,” said Buma. At a likely site, they’d use a metal detector to hunt for the stakes framing the meter square plots.

Cooper’s experience locating the plots would have been far less arduous. A distance Cooper would have tromped in five minutes across the gravel takes thirty minutes or longer today, tortuously zigzagging through brush, according to Buma. “I’d love to know what he’d think if he could come back and see the plots,” said Buma.

Bushwhacking through willows up to five meters tall and staying vigilant for bears, the team found the first three plots fairly quickly, but it took four days to find the next. One plot was lost to erosion in the 1930s, but by the end of their search, the team had found the other eight.

Locating the oldest successional plots in the world came with a wealth of data. In tandem with studying the current plant communities, Buma is analyzing data generated by Cooper and one of his graduate students from as far back as the 1920s. “The collaboration is still going,” said Buma. “This is the longest record of this kind.”

The record shows that whichever species first colonizes the new terrain tends to dominate the landscape. This is the reason for the lack of trees in the area, according to Buma— they can’t establish a hold in the ground that willows colonized first. Today, the plots are surprisingly different in terms of species composition, percent cover, and soil characteristics. Those nearest to the mouth of Glacier Bay, closer to potential seed sources, have the highest species richness.

Each pair of photos is taken from the same spot, facing the same direction. The landscape has changed dramatically (Source: Brian Buma/Ecology).

This experiment is emblematic of the importance of national parks as protected areas, says Lewis. “National parks protect American heritage for present and future generations, and provide the opportunity to conduct long-term scientific research,” said Lewis.

After delving into the past, Buma’s eyes are set on the future. This summer, he’ll return to Glacier Bay with a dendrochronologist and population ecologist to expand the plots, hopefully extending their usefulness another hundred years. Now that succession rates from the last century have been established, the team will seek sites where glaciers receded in the late 20th century in order to compare how rates of succession shift with climate warming. “Is succession moving faster now that the planet is warmer?”  Buma wonders.

As he thinks about the future, he is determined that the plots’ locations will never be lost again and that this important data set will outlast his own research. The GPS points are now on file with the National Park Service, and people will have to apply for access to the coordinates.

First, Glacier Bay was a land of ice, then a land of rock, and now it is a land filled with plants. “As climate warms up, it’s not good news for Glacier Bay,” said Buma, “But it will be interesting to see how the flora changes.”

John Hopkins Glacier has retreated a great deal since Cooper’s time (Source: NPS).

The linkages forged by this study, between landscapes and scientists of the past, present, and future, will be essential to understanding the changing landscape of Glacier Bay.

Roundup: Penguins, Antarctica, and Geological Games

Roundup: Penguins, Antartica, and Geology Board Games

Looking for New Emperor Penguin Colonies

From ScienceDirect: “Knowledge about the abundance and distribution of the emperor penguin is far from complete despite recent information from satellites. When exploring the locations where emperor penguins breed, it is apparent that their distribution is circumpolar, but with a few gaps between known colonies. The purpose of this paper is therefore to identify those remaining areas where emperor penguins might possibly breed. Using the locations of emperor penguin breeding colonies, we calculated the separation distance between each pair of geographically adjacent colonies. Based on mean separation distances between colonies following a circumpolar distribution, and known foraging ranges, we suggest that there may yet be six undiscovered breeding locations with half of these in Eastern and the remainder in Western Antarctica.”

Read more about it here.

A group of Emperor penguins and their chicks (Source: Jenny Varley/Creative Commons).


Patterns of Plant Succession in Antarctica

From Infona: “Maritime Antarctica is severely affected by climate change and accelerating glacier retreat forming temporal gradients of soil development. Successional patterns of soil development and plant succession in the region are largely unknown, as are the feedback mechanisms between both processes. Here we identify three temporal gradients representing horizontal and vertical glacier retreat, as well as formation of raised beaches due to isostatic uplift, and describe soil formation and plant succession along them.”

Learn more about it here.

King George Island, Antartica (Source: Acaro/Creative Commons).


19th Century Geology Board Game

From : “Wonders of Nature in each Quarter of the World was an early nineteenth century educational board game designed to teach children about some of the natural wonders of the world, such as volcanoes. The game was produced at a time of advances in geological thinking and geographical expeditions and this study places such changes and events within the context of the pastime, and presents an interesting window on the way geology was perceived almost two centuries ago.”

Learn more here.

A view of the Wonders of Nature board game (Source: Jane Dove/Geology Today).