Hey there! It's Li Si again! A year ago, I posted about my URECA research project and today, I'm excited to finally share about some of our findings! If you're interested to find Part 1 of this series, do check it out here!
In Part 1, I shared about what I did for field work and some of our interesting encounters. This post will share more about the aftermath of that, the identification and results of this study. But before that, here's a reminder of the hypotheses for this project:
Arthropod diversity and community composition will be different among the four different forest types. We predict that diversity will be greatest in primary forests, followed by secondary, restored then unrestored forest.
Forest restoration will restore soil-leaf litter arthropod diversity and community structure. We predict that restored forests will be most similar in diversity and community composition to secondary forests.
Sample processing
After bringing our samples back to the lab, we'll place our leaf litter and humus samples in the Winkler Extractor and Berlese-Tullgren Funnel respectively to extract the arthropods. The samples are left in the extractors for ~7 days before we collect the specimens from the ethanol jars. Upon collecting the specimens, we brought them to the lab to identify them under the microscope. Using identification keys, we ID'ed each specimen to the Order level and also curated a reference collection for our specimens.
Results
Our sampling efforts yielded 20 626 specimens spanning 30 different orders of arthropods. You can check out our flickr page for our online collection of some of the specimens we got. We found that the leaf litter and humus samples were significantly different from one another, and thus decided to separate the analysis based on the different medium collected.
Firstly, we calculated some of the biodiversity metrics that are usually associated with diversity studies. This includes order richness, abundance, Shannon-Wiener diversity index and Pielou's evenness index. As seen from the box plots, the diversity of arthropod orders increases the more degraded the forest. This is due to low order evenness in less disturbed forest types, i.e. there's a lot of one particular order of arthropods in less disturbed forests. This happens to be the order Acari and Collembola which refer to mites & ticks and springtails respectively.
We then used ordination techniques such as NMDS (nonmetric multidimensional scaling) to visualize how our samples differered from one another to do a community level comparison. For instance, in the plot below, we can see that the primary forest samples were most clustered and nested, followed by secondary, restored then unrestored forest samples being the most dispersed. This means that samples from primary forests were more similar to one another, as compared to samples from unrestored forests. We then conducted further analysis such as PERMANOVA and PERMDISP to better understand if these samples were indeed significantly different from one another.
Our results showed that the diversity and community composition of leaf litter arthropod communities were different across forest types, with those in primary forests being especially distinct from the rest. Secondary forests, despite their reestablishment over the past few decades, still had significantly different communities compared to primary forests. Unrestored forest samples were often extremely varied in their communities, with compositions not observed in other samples at times. Restored forest samples had overlapping leaf litter communities with both the unrestored and secondary forest types, suggesting that although restoration was helping to restore arthropod communities, more time may still be needed for restoration to a state comparable to communities in primary forests.
These results suggest that disturbance of tropical forests from their primary forest state has long-term impacts on the leaf litter arthropod communities. Forest restoration in heavily degraded forests does appear to facilitate re-establishment of leaf litter arthropod communities, albeit at a slow rate. Our study also suggests that restoration of mature secondary forests to facilitate succession to primary forest state may be beneficial for leaf litter communities as well.
Reflections
Moving forward from this project, I will be embarking on my next challenge soon - my Final Year Project. For my Final Year Project, I have decided to focus on the arthropod Orders that were especially abundant in our samples, namely Acari and Collembola. If this URECA project was the Infinity War, this upcoming Final Year Project would be the Endgame. Hopefully, it will turn out as great as Avengers Endgame ;) I will definitely find an opportunity to update my progress here.
Until then, I am extremely grateful for all the support I've gotten for this project, with special shout-outs to Prof Eleanor, Marx and Xin Rui for guiding me throughout this journey! This project evolved into something I became extremely passionate about and it has taught me some important values in life, such as never giving up, being prepared for anything and thinking out of the box.
See you in the next post!