Terrestrial Invertebrate Community Structure as an Indicator of the Success of a Tropical Rainforest Restoration Project

Background

With regards to the three broad categories of restoration success indicators  in monitoring (biological diversity, ecological processes and ecosystem services) the aim of this project was to assess the leaf litter invertebrate fauna (diversity) as a sort of “sub-indicator” for measuring the success of the restoration of ecological processes.  Invertebrate were chosen as indicators because the use of vertebrate indicators has been criticized because of the difficulties in relating the abundance of a particular vertebrate species to either habitat quality or its value to other groups or species.  Furthermore, invertebrates are good indicators because they are: 1) sensitive to microclimate indicators 2) critical in nutrient cycling 3) critical food source in the food web. 

Goals & Methods

Here the researchers went back to 0.1 ha plots that were planted in 1988, 1989, and 1990 (6, 5, and 4 years later respectively) and measured canopy cover, canopy height ,  tree species composition and 12 samples of invertebrates from each plot that were filtered through a Berlese filter and light was used to coerce the invertebrates into ethanol.  This sampling was done in all of the plots as well as in adjacent undisturbed rainforest (the ‘reference’ forest) and during both the dry and wet seasons. The invertebrates were placed into functional groups as an indicator of community structure. 

Conclusions & Takeaways

What they found was that the 1988 plot was not significantly different from the two rainforest plots.  And that the 1989 and 1990 plots had significantly fewer invertebrate orders than the two reference plots.  Various statistical procedures were used to tease out a very probable reason for these differences in that the tree species composition of the latter two plots had a much higher proportion of “partially deciduous trees” that resulted in less canopy cover during the driest times of the year which led to less suitable leaf litter and soil microclimates for many of the missing invertebrate orders.