This post explores new research on the critters, including humans, who help shape forests.
Meet the Mice Who Make the Forest
Brandon Keim wrote a fascinating article in the New York Times about research that is exploring the role of small mammals in tree seed dispersal. Ivy Yen, a biologist at the University of Maine, uses fluorescent markers on seeds to study how deer mice and voles move these seeds across landscapes. Her focus is specifically on the role that the animals’ personalities play in their willingness to move seeds. If one is interested in the future of a forest — which tree species will thrive and which will diminish, or whether those threatened by a fast-changing climate will successfully migrate to newly hospitable lands — one should look to these seed-dispersing animals. “The only way they’re (trees) going to move with the shifting temperatures is with the animals,” Ms. Yen said of the trees. “Will personality affect that? Will there be individuals who are more likely to help?”
Ms. Yen is a doctoral student in the lab of Alessio Mortelliti, a wildlife ecologist with a peculiar interest: how seed dispersal intersected with the emerging study of animal personality. Each summer for the past seven years, Dr. Mortelliti’s students trap deer mice and southern red-backed voles in their study plots — about 2,000 animals in all — and test them to measure where they fall on a spectrum between bold and shy. Before being released, each is tagged with a microchip like those used to identify lost pets.
Over the years, Mortelliti’s teams have developed intricate protocols for tracking the small mammals and determining what they do with different species of tree seed. Acorns are especially useful because they can be easily marked and discovered from wherever the animals hide them. Many seeds will be eaten, of course, but some will stay hidden, eventually growing into new trees.
The work has produced numerous papers, but one published in Ecology Letters, Dr. Mortelliti describes as a “proof of concept”. The researchers showed that the personalities of small mammals influence their choice of seeds. Earlier this year the team described how some deer mice, depending on their personality, were more likely than others to cache red oak, white pine and American beech nuts in ways that promoted germination.
This fascinating article is lushly illustrated by Tristan Spinski’s gorgeous photographs.
The role of ants in forest regeneration
Walk through an old-growth forest in early spring, and you’ll be dazzled by wildflowers, their jewel-like tones shining from the forest floor. But in newer forests, spring ephemerals such as trillium, wild ginger, violets and bloodroot are in shorter supply. The reason may lie with some less-flashy forest residents: Aphaenogaster sp., or the woodland ant. “Not a lot of people have heard of them, but they are the powerhouse of moving seeds and called ‘keystone dispersers,'” explained Carmela Buono, a Binghamton University doctoral candidate in biological sciences. Buono is the lead author of a paper recently published in Ecology that measured understory plants and seed dispersal by ants in 20 New York state forests, half old-growth and half-regenerated. More than 95% of New York state forests—including the Binghamton University Nature Preserve—are secondary forests, which have sprung up on land once cleared for agriculture. While parts of these regenerated forests, such as the overstory, have recovered well, they are missing other aspects of biodiversity—particularly when it comes to understory plants such as native wildflowers. Many plant species rely on a mutual relationship with ants to disperse their seeds. In fact, northeastern North America is one of the major hotspots of ant-plant mutualism. “These plants evolved with seeds that have an appendage rich in fats attached to them, and that’s very attractive to woodland ants,” she said. “Ants need fats just as much as protein and sugar, and it’s hard to find foods rich in fats in the forest. Ants are beneficial. They’re not as charismatic as butterflies or bees that help pollinate flowers, but they are just as important,” Buono said.
How humans shape global forests
Climate change and human activities strongly influence forests, but researchers have not fully understood the pervasiveness of these stressors and how they will shape future forest structure. Forests are expected to be mostly intact in protected areas (PAs) and so-called intact forest landscapes (IFLs). However, human impacts are expanding and intensifying to affect even these areas, and the global importance of such effects remains poorly understood. Now, researchers led by Dr. Li Wang from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences (CAS) have provided, for the first time, a panoramic view of global patterns in the multidimensional structure of forests. As part of their work, the researchers have discerned the relative importance of climate and human impacts as well as other environmental factors in shaping global forest structure, particularly that of PAs and IFLs. The study was published in Nature Sustainability.