Lab News

In October, the Battles Lab participated in the 2nd Annual STEMposium as a part of the Youth Speaks Inc Life is Living Festival in West Oakland, CA. The purpose of the event was to engage the community at large, with an emphasis on youth, in discussions about how science, technology, engineering, and math (STEM) impacts their community and can be used to make changes in their community.The event engaged and encouraged youth in STEM research through hands on activities and career exploration, with a special emphasis in areas such as environmental science, urban gardening and agriculture, transportation and urban design. Our exhibit showcased a career as a forest ecologist, with examples of the types of questions we try to answer about the environment. We demonstrated how dendrochronology can be used as a tool to answer environmental questions ranging from climate change, historical disturbances (fire, land slides, hurricanes), to effects of air pollution on forest health. Both kids and adults were fascinated with tree rings and how trees grow, particularly when they got to practice coring a real tree trunk and looking at tree cores under the microscope! We also interacted with educators from local schools, sparking discussion and ideas for classroom activities. Click to learn more about the Life is Living Festival, and the STEMposium.

In a recent paper (Ecology, Vol 92, Issue 6), Anne Eschtruth and John Battles investigated the widely held belief that riparian communities are highly invasible to exotic plants. This idea is based primarily on comparisons of the extent of invasion in riparian and upland communities. However, because differences in the extent of invasion may simply result from variation in propagule supply among recipient environments, true comparisons of invasibility require that both invasion success and propagule pressure are quantified. In this study, Eschtruth quantified propagule pressure in order to compare the invasibility of riparian and upland forests and assess the accuracy of using a community’s level of invasion as a surrogate for its invasibility. Extent of invasion was found to be a poor proxy for invasibility. The higher level of invasion in the studied riparian forests resulted from greater propagule availability rather than higher invasibility. Further, this study suggests that failure to account for propagule pressure may confound our understanding of general invasion theories. Ecological theory suggests that species-rich communities should be less invasible. However, Eschtruth and Battles found significant relationships between species diversity and invasion extent, but no diversity–invasibility relationship was detected for any species. Study results demonstrate that using a community’s level of invasion as a surrogate for its invasibility can confound our understanding of invasibility and its determinants.

Natalie van Doorn and colleagues report on a 10-year resurvey of a valley-wide plot network (371 plots across 3,160-ha) in Hubbard Brook Valley, New Hampshire (online in advance of print in the Canadian Journal of Forest Research). The goal of this project was to quantify recent trends in tree biomass and demography. The results from this paper confirm earlier reports that the forest at Hubbard Brook is no longer aggrading. There was no significant change in live tree biomass between 1995/6 and 2005/6. However, there were salient shifts in relative dominance of the canopy species (in particular, significant drop in yellow birch biomass was matched by increases in balsam fir and red spruce). A look into the tree demography revealed that mortality significantly exceeded recruitment for yellow birch and paper birch. For the major tree species, there was no instance of recruitment significantly exceeding mortality. Relative growth rates were greater than 1.5% per year for sugar maple, red spruce, and beech. Although effects of novel disturbances documented on a regional level have not led to directional changes in tree demography at Hubbard Brook, the authors suggest that these novel stressors are depressing the biomass potential of the forest.

Read more about the long-term Hubbard Brook Valley plot network

Maya Hayden and colleagues highlight the conservation importance of abandoned channels as refugia for sustaining pioneer riparian forest ecosystems (online in advance of print in the journal Ecosystems). Recognizing that organisms in disturbance-prone environments often persist in spatial refugia during stressful periods, they explore the importance of abandoned channels as potential refugia for a foundation tree species (Fremont cottonwood, Populus fremontii) within the riparian corridor of a large meandering river (Sacramento River in central California). They quantified the total proportion of cottonwood-dominated forest that initiated as a result of channel abandonment for a 160-km reach of the river via GIS analysis of historical air photos, and found that over 50% of the total extant cottonwood forest area was associated with channel abandonment. Tree-ring evidence showed that cottonwood stands commonly developed immediately following channel abandonment, and the recruitment window was less than 10 years at most sites (4-40 yrs). They connected patterns of tree establishment with floodplain accretion and sedimentation history, showing rates of floodplain rise and fine sediment accumulation to be higher in young sites and decreasing logarithmically over time. These results suggest that abandoned channels are an important refuge for cottonwood recruitment and that sedimentation processes influence the duration of the colonization window for cottonwood trees. They suggest that on rivers where tree recruitment along the active channel is severely limited by hydrologic regulation and/or land management, abandoned channel refugia may play an even more important role in sustaining an ecologically functional riparian corridor. Preserving bank erosion, active meander corridors, and forest regeneration zones created by cutoff events are therefore key conservation measures in shifting rivers.

In February, the Battles Lab participated in the 1st Annual Science, Engineering, Math and Technology (STEM) Career Fair in Oakland, CA, put on by the non-profit SEM Link, Inc. The goal of the event was to expose K-12 youth (particularly underrepresented minorities) to real-world applications of math and science by connecting them to STEM professionals and promoting hands-on learning experiences. The fair brought in over 45 Bay Area youth, mostly middle-school aged and younger, including a large group from Girls Inc. of Alameda County. Our exhibit showcased a career as a forest ecologist, with examples of the types of questions we try to answer about the environment. We demonstrated how dendrochronology can be used as a tool to answer environmental questions ranging from climate change, historical disturbances (fire, land slides, hurricanes), to effects of air pollution on forest health. The kids were really excited to learn about tree rings and how trees grow, particularly when they got to practice coring a real tree trunk and looking at tree cores under the microscope! 

Learn more about SEM Link, Inc

In a recent paper (In press at the Canadian Journal of Forest Research), Natalie Cleavitt and her colleagues charted the impact of calcium amendments on the survival and growth of sugar maple seedlings. Depletion of the soil calcium pool in the eastern deciduous forests due to acid precipitation has been linked to region-wide decline of sugar maple trees. Natalie tracked the fate of 5,400 sugar maple seeds for three years. These seeds were planted across the environmental gradients in the calcium treated and reference watershed. Calcium amendments clearly improved first-year survival of seedlings and this initial increase persisted for three years. However there was no calcium effect on seed germination or seedling growth. It seems that the population-level response to the watershed-scale fertilization is dissipating as calcium availability is decreasing with time since addition.