Shannon's Salamanders: Increasing our amphibian survey with the help of a local graduate student

We started the 2018 season by chopping wood, and lots of it. Slab wood left over from the milling process has been piling up on White Memorial’s property, and we knew exactly who could use it- Amphibians. This summer started out with hauling this wood out into the woods to increase the number of amphibian cover board grids. These grids get surveyed every year to get an idea of amphibian diversity and abundance at White Memorial. This year, it got taken to the next level.

Shannon shown here excitedly showing off a Four-Toed
Salamander she found at one of the grids

Shannon Smith, Litchfield native and Trinity College student, completed her Master’s thesis on White Memorial’s salamanders. Specifically, how Red-Backed salamanders are affected by invasive non-native earthworms. To help Shannon get data for this project, we doubled the amount of cover board grids present on the property, and aided her in field work whenever we could.

Shannon is shown here surrounded by her research
materials. 4 1-Gallons jugs of water mixed with mustard
were brought to each plot, no matter how remote

Her methods required sampling of salamanders, earthworms, leaf litter, and soil invertebrates for each of the 40 grids. Each grid took about 2 hours, a lot of grit, a good sense of direction, and tons of Tecnu to complete.  

Some of the research materials on top of a cover board.
Each grid had 25 of these cover boards that needed
to individually be flipped and analyzed for salamanders

Her research questions evolved as time went on, as is normal for research in this field; so little is known about the earthworm invasion and its implications. Because about half of the cover board grids she sampled had been present for years prior to her project, and the other half had just been dealt out only a few months prior, she had to account for the dispersal rate of these animals to the new grids.

She found that the strongest influences on salamander abundance were leaf litter quality, soil temperature, and invertebrate community diversity.

Red-Backed Salamander found in Shannon's
research

Non-native earthworms decrease the quality of the leaf litter, and also decrease diversity of soil invertebrates. This means that earthworms are indirectly having a negative impact on CT’s Red-backed salamanders.

Red-Backed Salamanders are Connecticut's most abundant amphibian. By consuming large numbers of soil invertebrates which are otherwise unavailable as food for larger animals, Red-Backed Salamanders play a key role in moving nutrients up the food web. They are eaten mainly by songbirds, but also mammals of many sizes and also larger amphibians. 
This study is showing that earthworms may be negatively affecting these amphibian's ability to play that key role in the food web. Earthworms are altering the soil environment for these important amphibians by decreasing the amount/diversity of soil invertebrates and influencing the leaf litter layers.  This could have serious ecological effects reaching far up the food web.  More research is needed to understand the role that non-native earthworms play in our soil, and how they are affecting other soil invertebrates. 

You can help limit the earthworm invasion by not dumping unused "night crawlers" or other worms in the forest but rather the trash bin.  Recognize that earthworms are having huge impacts on forest health, and try not to spread them around. 

Four-Toed Salamander, a species much less
common than the Red-Backed

Ben Vermilyea Wins First Place Scholarship for His Project Titled "Do Invasives Earthworms Impact Water Quality?"

I am pleased to announce that Ben Vermilyea received the first place scholarship from the Natural Resources Conservation Academy for his project titled "Do Invasives Earthworms Impact Water Quality?"  Ben was awarded scholarship yesterday (March 15, 2016) at the Connecticut Conference on Natural Resources at the Unversity of Connecticut.

Congratulations Ben on a job well done!

Do Invasive Earthworms Impact Water Quality?

Ben Vermilyea attended the Natural Resource Conservation Academy (NRCA) at UCONN this past summer 2015.  He approached White Memorial seeking a community partner so that he could apply what he learned at the NRCA.  I have been interested to explore if exotic earthworms could increase soil erosion near headwater streams thereby impacting water quality when they incorporate the mineral layers and consuming leaf litter on the surface.  We've observed leaf litter loss in some areas on the property so severe that by the end of the summer the soils are nearly completely denuded of leaf litter before the next leaf litter crop.  This exposes the soil the air and encourages soil erosion either by the falling water droplets hitting the soil or by sheeting.  Ben and I developed a novel method for measuring soil erosion.  We installed fabric hammocks along the stream bank that collected soil particles before they entered a stream that flowed near an earthworm invaded area and compared that data with another stream that was not impacted by earthworms.  We observed some important patterns.  The earthworms indeed changed the soil properties.  Although we did not observe significant differences between the weights of the soil particles entering both streams, we performed a power analysis which suggested a significant difference could be detected if we increased our sample size to a total of 451 hammocks samples.  We feel this it is feasible to acheive this in future research, so stay tuned.  Obviously, this is based on certain assumptions but we may not need to as many samples if we were to compare headwater streams that flow through regions that are more severely impacted by exotic earthworms.

Ben will present the poster (above) at the Connecticut Conference on Natural Resources on March 14, 2016 at UCONN.

Congratulations Ben!

Naomi Robert Receives First Place Scholarship for Earthworm Research Project!

Naomi Robert collecting earthworms as part of her research project.

Congratualations are well deserved to Naomi Robert for receiving a first place scholarship from UCONN's Natural Resources Conservation Academy for her research on earthworms at White Memorial!  Her poster is below:

White Memorial Posters at the Connecticut Conference on Natural Resources 2015

Monday 16 March 2015 will be the CCNR at University of Connecticut.  We will present two posters at the conference.  Click on the images above to enlarge the poster.

Forest Vegetation Strongly Related to the Earthworm Biomass

Vegetation and earthworm biomass scatterplot.

I investigated the relationship between vegetation and introduced earthworms on the property.  Several important relationships were observed.  Herbaceous vegetation data was collected at 25 randomly selected points on the property within one square meter quadrats.  Native vegetation including tree seedlings in the herbacous layer were negatively correlated with the amount of earthworms in the soil.  Invasive plants were positively correlated with earthworm biomass.  The relative strength of each of these relationships varied.  Invasive plants and  total native plants were the strongests correlations, while native tree seedlings were not as strong.  Tree seedling cover can be influenced by several factors including herbivory, seed production, acid precipitation, as well as many other disturbances.  Neverthess, this data suggests that introduced earthworms are one more important factor that influences our forest ecosystems.

Earthworm Species Inventory and Forest Cover Type Associations

A totalof the 14 earthworm species were detected during the 2014 survey at White Memorial Foundation.  We randomly selected 82 plots throughout the property and collected 993 specimens.  Juvenile or non-clitellate individuals for Megascolecidae family and certain Lumbricid genus are impossible to identify to species using external and internal characters with currently developed keys.  Some cover types were sampled more than others, nevertheless random sampling insured that the frequency distribution reflects the actual proportion of cover type at White Memorial.  The native species Eisenoides lonnbergi was found in only two cover types, oak and mixed conifer, specifically in plots located near wetlands.  The remaining species have exotic origins and were detected in many cover types.  Intially, it appears that the hardwood cover types more species of earthworms than the conifer stands.  Conifer stands tend to have lower soil pH than hardwood cover types, which could influence the species that inhabit the stands.

Bipalium adventitium -- An Introduced Soil Invertebrate

Bipalium adventitium is an introduced terrestrial flatworm that inhabits soils and predates earthworms.

I observed Bipalium adventitium for the second time on the property, yesterday.  I was checking amphibian cover boards and observed two individuals in what looked as if they were copulating.  I collected the specimens and ran back to the office to confirm my identification.  My colleague Jeff Greenwood, WMCC Education Director, ran an errand on the property shortly afterwards and found another individual.  This brought us up to 3 specimens in one day (April 26, 2012) and we weren't even focusing a search for them!

I am not an invertebrate zoologist, so I was quite surprised to learn about this animal last year.  Nicki Hall and I were checking snake cover boards for the last monitoring visit of the season (October 2011) and discovered what looked like a brown "leech".  We didn't think much of it at the time, except that it was on land and that it was after all of the rain we received after Hurricane Irene.  About a week later some colleagues in the state asked me if I had seen this mystery animal and in fact I had!  After a short review from the internet, I found that this organism is introduced to North America from Asia and it is a predator to other soil invertebrates, especially earthworms.  There are a few investigators trying to search for these animals in North America to document the spread.  Peter Ducey, SUNY Cortland, is examining the natural history and the ecological role of Bipalium adventitium as potential competitor to native herpetofauna that consume earthworms.

Blue-spotted x Jefferson Salamander is a state endangered species in CT
 that inhabits White Memorial and eats earthworms.

All of the earthworms that inhabit Connecticut's soils are considered introduced because our region was covered in glaciers only 15,000 years ago.  Therefore, earthworms were not able to colonize this region until humans introduced them.  Several of these species originated from other continents and are now changing our soils.  In forest habitats, these animals are consuming the leaf litter layer that blankets the forest floor so fast that the entire layer is consumed and the soil is exposed to rain, thereby causing extensive erosion.  This lowers water quality and decreases the ability of the forest to regenerate after other disturbances.  Many species of forest dwelling plants depend on the leaf layer as part of their natural history and these species are declining as result of this ecological damage.  I briefly mentioned in a previous blog post how Japanese Barberry, an invasive shrub, is also contributing to this scenario.

If introduced earthworms are doing damage to the forest leaf layer, then wouldn't another predator controlling earthworm populations be a good thing?  John Gorsuch, an undergraduate student at the University of Cincinnati, is examining the effectiveness of B. adventitium as a predator to various earthworm species.  John's preliminary observations suggest that B. adventitium can be an effective predator to some earthworm species but not all.  Amynthas agrestis is an introduced earthworm from Asia and it is one of the few dirty words among forest ecologists (please pardon the pun).  A. agrestis in one of those aforementioned earthworms that are aggressively consuming the leaf litter, but it also has several defense mechanisms to predators, B. adventitium and herpetofauna alike.  Therefore, we are potentially left with several predator species that are generalists consuming every earthworm species except for one species that is causing severe ecological damage to a critical habitat!

What can you do?

Report all of your sightings of B. adventitium to Peter Ducey.  Since these species (earthworms and flatworms) have been introduced to North America from the horticultural industry, it is best to use native species in your garden raised by local growers using local stock for their plants, soils, and amendments.  If you use worms as bait for fishing, throw any remaining worms into the garbage NOT YOUR GARDEN!  And finally, learn as much as you can about this topic (soil, earthworms, invasive species, forest ecosystems, etc.) on your own because soil is one of our vital natural resources that we all need, so take care of it.