Abstract
This report is supposed to address the relationship between the characteristics of Coarse Woody Debris (CWD) and its associated invertebrate community. For the purposes of this report, students will be introduced to data collection methods as well as identification and enumeration of soil invertebrates related to coarse woody debris. Coarse woody debris can be said to be the dead woody particles found mainly above the soil surface. These dead woody materials are always in different stages of decomposition depending on when the dead material started decomposing.
For the purposes of this report, only dead wood above 8 cm diameter will be considered. In groups of 3 students each, the students will be required to classify and collect coarse woody debris from a forested area. They should only focus on CWD size and CWD decay class only.
The main purpose of this study is to determine how the aforementioned variables influence invertebrate abundance, richness, as well as community composition. The results of this field research will help the students determine the different types of coarse woody debris from different parts of the tree, and their relations to the types of invertebrate abundance found in these coarse woody debris.
The results of the study indicate that it is prevalent from the results that the larvae were not as abundant in the CWD samples as compared to the adult of the same species. It was also quite clear that more eggs were found to be present in the sample as indicated by the CWD density (F=3.22, df=50, p=0.0302), length (F=4.08, df=50, p=0.0114), and volume (F=4.90, df=50, p=0.0046) varied by age class.
It can hence be concluded that CWD with a big volume as well as decay level class 5 contain more soil invertebrate abundance as well as richness since they provide the optimum environment for the invertebrates to survive as well as reproduce.
Introduction
Coarse woody debris can be defined as logs as well as chunks of dead wood about 2.5 cm of diameter. However, for this study, only pieces of 8 cm to 20 cm diameter will be used. These coarse woody debris support a wide variety of invertebrate organisms and as such acts as an important source of energy for various ecosystems. The presence of nutrients as well as carbon in coarse woody debris is made available via decomposition and fragmentation, which is aptly facilitated by the invertebrates that infest and exploit them. Coarse woody debris directly improves forest floor systems by increasing spatial complexity a well as stabilizing the soils. Indirectly, the CWD enhances the forest floor by providing nutrients, as well as organic matter through the process of decomposition to the forest floor soil system. Apart from this, presence of CWD also provides food as well as habitation for most soil invertebrates besides maintaining the biodiversity of the forest ecosystems.
CWD occurs in various forms depending on the tree species, decay stage as well as the size. This lab report is out to provide an understanding of the quantitative relations between invertebrate abundance, as well as volume and richness of wood for every decay class of CWD.
For the experiments, the log decomposition will be placed in different classes depending on the level of decomposition they have reached. Other criteria to be observed will be the wood texture, the position in which the CWD is lying on the ground, if there is presence or absence of twigs, presence or absence of a bark, the shape of the woody debris, and finally if there are any invading roots.
After collection of these samples using the criteria explained above. The samples are to be taken to the lab for analysis and data recording. During this stage is when the CWD is split and analyzed under a microscope to see which types of invertebrates exist inside them and the abundance of those invertebrates. This is what forms the basis as well as the purpose of the study.
The study mainly seeks to address various concerns. The most important aim of the study is to find out the relationship between the characteristics of Coarse Woody Debris and its associated invertebrate community. Besides this, other useful data withdrawn from the experiments as well as the analyses can be used to derive useful information that can be used to calculate other information as well as derive a meaningful hypothesis that might be of great use to the students.
Methods
The study location for collecting samples of this study was around the forested area of the campus. This is where each group was required to classify as well as collect coarse woody debris samples. The experiment was set up in such a way that students were randomly placed in groups of three students each. The variables that were relevant to the experiment were two. That is coarse woody debris decay class and CWD size. The study was keen on determining ways in which these two variables influence invertebrate abundance, richness as well as composition.
For the data collection activity, each group was provided with a tape measure, four pin flags, writing instruments, data sheets, and 3 Ziploc bags. With the guidance of the assistant, the students were required to take a careful walk inside the forest trail and choose a suitable position that they desire to collect their samples from. After that, the students were then required to measure out a square measuring 3 m by 3 m using the provided tape measure and then mark each corner using the pin flags provided. Within that square measurement, the students then engaged themselves in finding as well as classifying all coarse woody debris below a measurement of 1 m into the decay class and subsequently record that information on the data sheet. Besides that, students were also encouraged to record any other relevant information about the site that they felt would be of importance in describing the study site. After that, the students were required to select one piece of coarse woody debris from each decay class that were below 30 cm in length and place them in their respective Ziploc bags. Upon leaving the site, the students were instructed to collect all the instruments and tools used on site.
Upon reaching the lab, each group was provided with one microscope to process the three samples of coarse woody debris such that each student processed one sample since each group had three members. For processing purposes, the students were required to remove the samples from the bags and place them in a sorting tray where they were then supposed to collect any fast-moving invertebrates for later identification.
Following activity was measuring the diameter and length of each coarse woody debris and using the measurements to derive the volume of the CWD samples with the help of an equation: V=πr2(l). Where r = half the diameter and l is the length of the log. After this part, the following activity was inspecting as well as dissecting the CWD to locate, identify and record all the invertebrates found in the log keeping them alive since it was a requirement for them to be returned right after the data collection. The next procedure was the no about 10 to 15x magnification to identify the invertebrates' details and to record them in the datasheets.
Upon completion of this process, the students then handed over their findings to the TA but keeping a copy to themselves for later use.
Results
As for the result of the study, one can easily derive them from the sheets submitted to the TA as they contain all the relevant information regarding all the invertebrates found as well as their abundance and occurrence.
Group 1 member seemed to have collected almost similar samples, or their area of collection had fewer invertebrates in the CWD samples collected. Coming to group 2 findings, the results indicate that more and more invertebrates were found in their samples. The abundance, as well as the distribution of invertebrates, in these results, vary. This is because the results project the abundance of invertebrates from one taxonomic group and few other species. This might be so due to the area the group chose to collect their samples. One trend that is emerging from the results is that each group presents different levels of abundance of various invertebrates, which totally differs, from the next group’s findings.
This trend replicates itself throughout the results sheet obtained from the lab analysis. However, it is important to note that apart from the defined invertebrates from the already set taxonomic groups, there were also other invertebrates found by each group that existed or lived inside the coarse woody debris samples that were collected in the forest area of the campus premises.
It is prevalent from the results, where mentioned that the larvae were not as abundant in the CWD samples as compared to the adult of the same species. It was also quite clear that more eggs were found to be present in the sample. This is an indication that the CWD samples provided a breeding ground besides providing a habitat as well as a feeding source for the invertebrates.
Another trend worth noticing is that the bigger the size of the CWD the more the abundance as well as the richness of invertebrates present in the CWD sample collected. In relation to the decaying class, it is noticeable that the CWD class 5 had the most abundance and richness of invertebrates in a specific taxonomic group. This trend is replicated in almost all the group’s findings. It can be concluded from the results that a bigger CWD size as well as more advanced CWD decay class are the two conditions responsible for the most abundance as well as richness of invertebrates in the forest soil ecosystem.
The table below shows the decaying class against the type of CWD
Discussion
The results of this study lived up to the expectations as well as the predictions of the study in many aspects. Just as a reminder, the study was aimed at finding out the relationship between the characteristics of CWD and its associated invertebrate community. By analyzing the results, section it is evident that the relationship between the characteristics of CWD and the associated invertebrate community has been established. From the study results, it is evident that a bigger CWD size is responsible for hosting more invertebrates compared to the smaller sized CWD. This is mainly because a bigger CWD provides more surface area for more invertebrates to find a habitat. Once these invertebrates find these habitats and find that they are suitable for survival since they provide favorable conditions, they begin to multiply therein. This can be explained by the considerable amount of larvae found in bigger sized CWD as compared to the small ones. Another evidence supporting this is the discovery of unidentified eggs that were found by at least each group in the larger sized CWD. This is perfectly in agreement with the predictions as well as the expectations of the study objectives.
The second aspect to consider is the CWD decay class. Referring to table 1.1 above, one can see the decaying class of CWD from class 1 through to class 5. From the study results, it is evident that the CWD decaying class 5 harbors more invertebrates. From the results posted by each group, an emerging trend across all the results indicate that invertebrate richness, as well as abundance increases as the decay class increases. There are fewer invertebrates in the earlier decomposing stages of the CWD since the invertebrates don't find the environment conducive for them. Furthermore, there's little for them to eat in a dry log that has not yet decomposed to an advanced level. Therefore, the invertebrates choose to inhabit the most decomposed CWD since they can find food from it that will support their existence as well as those of the offspring they will have. This explains the abundance and richness of invertebrates in class 5 CWD. The decaying class 5 is also accountable for the abundance of larvae as well as unidentified organisms and eggs of these invertebrates. However, this does not dismiss the smaller and less decayed CWD since they also account for the abundance as well as richness of a number of invertebrates though this number is small.
Conclusion
References
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