Swamp things 2: saproxylic bugaloos

This post is a sequel to Swamp Things 1: Death, life and nutrient cycling in the peat swamp forest

In January, Sean (me!) returned to the peat swamps of Badas, this time to survey the saproxylic insects in the same plots in which we were studying wood decay. "Saproxylic" sounds super cool but what does it actually mean though? In greek, "sapros" means decayed while "xylon" means wood. "Saproxylic arthropods" generally refers to any species associated with dead or decaying wood (no necessarily directly feeding on it), but for a more specific definition you can refer to Calvin's post on saproxylic insects in Singapore here.

Calvin with a stag beetle (Cyclommatus sp) from the Batu Apoi expedition in June. Stag beetles are considered one of the most charismatic groups of saproxylic insects. Calvin, while charismatic and often associated with dead wood, does not qualify within the scope of our study since he is not an invertebrate.

In each of the plots, two methods were used for sampling of saproxylic arthropods: 1) Hanging flight intercept traps; and 2) Leaf litter sampling and winkler extraction.

Hanging Flight Intercept Traps (FITs)

Flight intercept traps in this design consist of panels with bait (in this case, cotton balls soaked in 70% ethanol which attracts most dead wood lovers) in the centre. Flying insects attracted by the sweet smell of tree death fly into the vertical panels and fall down through the funnel below into a collection jar. After seven days, entomologists (us) return to the sweet smell of insect death to collect the specimens for later sorting and identification.

A hanging FIT under the canopy

Mu'az, Kelvin and Ronnie with our first deployed FIT in the Badas peat swamp

A longhorn beetle (Cerambycidae), Violin ground beetle (Carabidae) and a click beetle (Elateridae) collected from the hanging FITs. All three are known dead wood associates.

Close-up of the violin beetle, Mormolyce castelnaudi, collected from the hanging FIT about 2km deep into the peat swamp. They are predators of other insects and are associated with bracket fungi that are often found growing from dead or decaying trees.

Mu'az doing an impression of a saproxylic insect floating in a collection jar after a long and wet day in the field.

Leaf litter sampling and winkler extraction

In each plot, leaf litter was collected from three 50x50cm quadrats, shaken throroughly through a litter reducer, and collected litter was then brought to Brunei Forestry Department's tropical biodiversity centre to be hung up in winkler extractor bags for seven days. As the litter dries, the critters hiding within start to crawl out, and fall down below into collection jars.

Quadrats before and after leaf litter collection, and Afnan with a plot's worth of leaf reduced leaf litter sample.

Process from litter collection and reducing into sample bag

Leaf litter is first poured out into a tray to remove larger arthropods that cannot escape the mesh bags, before being divided into four "laundry" bags and hung up in the cloth winkler bag.

One winkler bag for each plot hanging at the TBC. Examples of larger invertebrates that were removed into the collection jars before hanging the bags up. Scorpions of the genus Chaerilus are relatively small and feed on other arthropods in the leaf litter.

Ideally, further sampling will be carried out in future for more robust analyses of saproxylic communities between plots of different disturbance levels. These can be compared against wood decomposition data across the same plots to see if there's any effect of saproxylic communities on wood decomposition along the disturbance gradient in the peat swamp. If any students in Brunei would like to contribute to this effort, please feel free to contact Dr Rahayu at UBD or our team over here in the TEE lab!