There are several ways to sample insects and other invertebrates and the Quantitative Inventory (QI) team are using six of them! The QI team is visiting three different areas of lowland tropical rainforest during this visit to Sabah and we will be sampling in Danum Valley Conservation Area, the SAFE project area and in Maliau Basin Conservation Area.
Both Danum and Maliau are old growth (primary) forest reserves and are good examples of lowland tropical forest. We will be able to compare the invertebrates we find in these two reserves and discover how many species they have in common and how many are unique to one reserve or the other.
(Click images to see them full sized)
By doing this we will be able to tell how many reserves are necessary to conserve all of the diversity found in tropical rainforests. If the reserves have exactly the same species then only one is necessary. But if they have completely different species then two reserves are necessary to retain all of the diversity. Obviously, this is only true for the species we are sampling and this may not be the case for a wide range of other species, e.g. birds, plants, reptiles and so on.
The SAFE project is rather different. This is an area of forest that has already been logged. Much of the forest here is due to be cut down to make way for oil palm plantations. However, some fragments of the forest will be left and this will allow scientists to study the impact that fragmentation has on forest areas. We will be sampling in the areas that will be left behind once the logging takes place later this year; we hope to come back in 5 years and repeat our sampling to find out what has happened to the species in these forests during that period.
In each of these sites we will be sampling in eight, one hectare plots. In each plot we use six methods to sample insects. Three of our methods are done along a 100 m transect through the middle of the plot. Every 7 m we dig a hole and take out any invertebrates we find in there. Termites, beetle larvae and ants are generally what we find in soil.
We also sieve a square metre of litter every 7 m and hang the resulting sieved litter in a Winkler bag. This contraption dries out the litter and, as it does so, the invertebrates fall out of it and collect in a pot below. We have 75 of these Winkler bags hanging up at Danum! In litter, ants and beetles are the most abundant insects.
Along 50 m of the transect we also sample dead wood. Any dead wood that the transect crosses, we break open and remove any invertebrates we find. Again termites and ants are the most common, but also centipedes and scorpions have been found so far.
The other three methods are trapping methods. The first are pitfall traps. These consist of plastic pint glasses buried in the ground so that the opening is flush with the soil surface. Insects run along the ground and fall into the pit. We then come along three days later, empty them out to see what we find. They have been full of ants and cockroaches so far.
We also have two types of Malaise traps. One type is put up at ground level and the other is pulled up in to the lower part of the trees. Both of these traps work by having a barrier that insects fly into. The insects then fly upwards into a funnel and eventually into a pot at the top. These traps are excellent at collecting flies and parasitic wasps (Hymenoptera), but also collect beetles.
Using these methods we collect a lot of material. This material will eventually make it back to the Museum in London so that we can begin to sort and identify it.