For the last couple of weeks, I’ve been grinding litter samples and wrapping them into small tins for elemental analysis. The analyzer here incinerates a 4 mg sample of dried, ground litter and measures the amount of several gases that are formed during the incineration (which is at about 1000 degrees C, by the way!). The gases measured included carbon dioxide and nitrogen gas (I’m not 100% sure about the nitrogen…), and, once we know the amount of those two gases released from a sample, the percent carbon and nitrogen of the sample can be determined. Then, of course, the C:N ratio is calculated, which is what I was after – an index of commonly used in decomposition studies because of it’s relation to decomposition rate and litter quality (in terms of food for microbial decomposers and larger, usually insect, decomposers).
So this was my view for several days.
Overview
Ground litter samples and a 96-well plate to organize tinsWeigh and tare the tinPreparing to fill a tin with ground sample
Ground litter and grinding beads
Filled tinTins are folded into tiny cubes
Weighing the filled tin
The Elemental Analyzer. On top is a loading robot that can hold about 100 samples, minus standards and standards checks.
Software on a connected laptop displays data real-time. The peaks on the screen are results of detection of particular gases (like carbon dioxide) as they are detected leaving the column in the analyzer. The area under the curve is the amount gas detected.
Back in the lab, doing some chemistry on plant litter from Costa Rica. I didn’t think to take photographs until I was almost done with this step in the process – just imagine these 24 vials times, say, 32… that would have made a cooler photograph.
Using a 50:50 mix of methanol and water, I extract a tea from ground litter samples. Each one of the vials has about 0.05 g of powdered litter in it.These samples need to be centrifuged so I can remove the 'tea' extract.
While in Palo Verde last summer, I met Ramsa Chaves, a graduate student at Dartmouth College under Brad Taylor and UCR licenciatura graduate. She used the OTS station in Palo Verde as a headquarters for her research on insect communities associated with streams in the Guanacaste region. Her and one or more assistants traveled to local streams that varied in surrounding land-use and sampled emergent insects during the day, returning to sort and process the catch in PV in the evening. I helped out one of those days to get a taste of her extraordinary and ambitious research project. From memory, Ramsa aimed to examine responses of insect communities to land-use differences and how these responses play-out in aquatic-terrestrial linkages.
We sampled two streams that she and Jereme had set traps in and around three days prior. In Quebrada Amores (lovers stream) within Reserva Biológica Lomas de Barbudal emergence traps were emptied. The floating, triangular traps, as suggested by their name, capture adult insects as the emerge from the stream to breed and feed in the surrounding terrestrial environment.
Quebrada AmoresRamsa and an assistant from Bagatzi cross the streamNo mosquitos, cool air, cool breeze, beautiful stream... why would one choose to work in Palo Verde?Jereme uses an aspirator to collect trapped insects.Ramsa does the same.Without a bottle trap on top of the emergence trap, Ramsa enters into it herself.A trap sits, waiting to be sampled.
Flagging tape labels the traps.
Río Pijije drains agricultural and residential land, in contrast to the protected, forested land-use surrounding Quebrada Amores. Emergence traps had settled ashore after a flash flood, and were not sampled, a common occurrence in the rainy season in dry forest areas. Sticky traps (transparent over-head sheets covered in glue, basically) were placed from 10 to 100 m from the stream edge to sample flying insects as they moved from the stream outward into the the forest or, in this case, cow pasture. In addition to sticky traps, we sampled using butterfly nets, which are not pictured here (probably for two reasons (1) I was sampling and (2) I knocked my net into a large paper wasp next and was promptly stung many, many times. It was an extremely memorable event for me). Both sampling methods have hopefully painted a picture for Ramsa showing how insects respond from and to a stream draining catchment with different land-use patterns.
Emergence traps...ruined.Jereme untangles the a trap.Rio Pijije
A high and low sticky trap were set at several locations along a transect starting from the stream bank.Sticky trap...
Although these were taken during different experiments, the poles remain in the same positions and the height that the photographs were taken was the same – my height. The water depth and vegetation are strikingly different.
Peter has been continuing his monitoring and manipulating of snow cover in his plots this winter, and he has periodically collected samples. Today, sampling didn’t quite go as expected; an off-the-chart flooding event washed through three of his five plots, effectively destroying them by altering organic matter and leaf distribution within the flooded plots. Regardless, Peter salvaged samples from two un-scathed plots and we sample the others just in case there’s something interesting to be found.
Some photos showing riparian flooding:
Showing the extent of the flooding, Peter stands 50 m away at the edge of the stream, and I take a photo from the edge of the flooded area.Riparian zone cleared of most of its leaves and all of its snow.
More leaf and snow clearing
Leaves piles on the base of saplings
Sediment and leaf clearing
A non-flooded plot:
Snow removal plot in the foreground, and the edges of the ambient snow and snow-added plot in the background.
Snow-added
Sampling flooded plots:
The flood waters surrounded and deposited sediment and organic matter around the edges of a snow-added plot
An ambient-snow plot after flooding
Depth of added snow
A quadrat used to remove a sample of litter from a flooded snow-removed plot
Above and here, the story of Peter removing a sample from a snow-added plot
Removing litter
Representing Kent State.
Ariel can't help but smile, even while working in a muddy, frozen, environment.
Another snow-added plot showing evidence of flooding.
Today, with the much-appreciated help of a few volunteers, Jessica’s artificial loaves of leaves were set in the stream. The next couple of weeks will include some intense sampling and processing efforts, but given the work done today, it won’t be a problem.
Nine artificial loaves were attached to stakes set into the stream bed in five different riffles. The nine include two leaf treatments, previously conditioned in the stream and unconditioned. Jessica will be sampling them to examine winter invertebrate colonization and FPOM deposition.
Frigid conditions greeted us.Fun to be had anyway
Scott secures a loaf
Extremely tightly
Ariel put the finishing touches on a few leaf ka-bobsView of a single riffleA few attached leaf packsCompletion
Or artificial loaves of leaves, Jessica, another undergraduate student working in my lab, is investigating leaf pack dynamics in an Ohio stream. She has characterized leaf accumulation in the field, and, unfortunately, seen the rapid washing of her samples during a mild flooding event. The next step is to characterize a few variables that may be important in leaf packs within streams (i.e., invertebrate community succession and FPOM accumulation) using artificially constructed leaf packs… or loaves. Below, leaves where pierced onto a kabob with the help of a couple of volunteers.
KabobsJessica rinses leaves
Ariel, Scott and Mauri construct leaf kabobsSome finished leaf loaves
Peter, an undergraduate student in my lab, is interested in winter ecology – a little studied field that is more or less assumed to be of limited relevance in temperate systems, at least in comparison to warmer seasons. In the winter, ecosystem and community functions slow or stop all together. For example, primary productivity halts in deciduous trees, yet likely still occurs in microorganisms, and invertebrate community interactions (i.e., predation) are simply slowed due to an overall decrease in metabolic rates. Of the multitude of processes or interactions open to investigation, Peter decided to assess decomposition dynamics of leaf litter under the snow, and address effects of snowfall on these dynamics. To do so, five blocks with three treatment plots each were marked and sampled by removing subsamples of leaf biomass from each of the three treatment plots within blocks. Within each block, snow from one treatment plot was removed and added to another, so that there was a treatment plot with ambient snowfall, snowfall removed, and snowfall added. Now, if we could only find enough freezer space…
Peter points out a potential area to set up a blockAn added- and a removed- snow cover plotChris and Peter survey the finished block
Tools of the trade
A sampling area - leaf material was removed from beneath the snow
Three subsamples cleared of leaf materialChris surveys for the next subsample to processSnow is carefully excisedAll in one shot
Sometimes, not all the snow is removed in one shot... this leads to cold hands, since only rubber gloves were used
Or rather, most photographs of a backpack and net hanging from something, while I collected for stable isotopes. Unfortunately, it is extremely difficult to photograph yourself doing field work.
