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Introduction

Ecological communities can be defined as a group of species that are interacting with each other and are residing in a same place. a community is said to be interlinked with each other by the network of the influences that the species have on one another. If one of the species gets affected, then the effect is evident in other species as well and this is felt due to the balance in nature. In a community development there exists different kinds of interactions: herbivory, parasitism, predation (here one species gets the benefits and the other species is disadvantaged); competition (each of the species gets affected negatively); commensalism (one species remains unaffected, while one species is benefitted); mutualism (both the species gets benefitted from the interaction) (Allouche et al., 2012). The factors that affect the diversity of a community are: climate change, invasive species, habitat loss, overexploitation. Community diversity can be measured through the species richness and species diversity. Majority of the invertebrates are found in the leaf litter, the little invertebrates feed on the litter and they break it down to simpler pieces. The various invertebrates that are found in the leaf litter are beetles, spiders, centipedes, millipedes, worms, snails and slugs. Some of the invertebrates are found in certain point of the year and only at certain point of the year. Some of the invertebrates either use for hibernating or for besting (Strong Jr et al., 2014). The aim of the study is to find the hw diverse is the leaf litter invertebrate community in the Toohay forest and the how does the diversity varies between the two different locations (riparian and ridge) in Toohay forest.

Methods

1. Study area: the study area (Toohay forest) which is located 10 km South of the Central Business District of Brisbane. The area is a260 hectares of bushland. The region is classified as an open eucalyptus forest and it contains 400 different types of flora and fauna. The forest in managed and for this reason it is sequentially burned to prevent bushfire hazards intro the urban area.

2. Collection: The leaf litter was collected from an area of approximately 100x100 cm of the forest floor. A total of the 33 samples were collected from the riparian and ridge area. Among both the areas, 16 samples were collected from the ridge area of Toohay Forest, whereas 17 samples were collected from the riparian area of Mimosa creek. Invertebrates are extracted from the leaf litter by placing the samples in separate Fulgren funnel. The samples are put inside the bottle containing 70% ethanol and the base is enclosed in an alfoil. The samples were then left for about 48 hours after that the samples bottles are removed. In the laboratory the invertebrates are from each of the sample were identified and sorted to morphospecies. In the final step the abundance of the each of the morphospecies were counted and recorded.

3. Analysis: The raw species data are collected from the 33 samples and are collated in a dataset. A species accumulation curve was used to explore the efficiency of the data. The three summary community metrics were calculated from the class data which consisted of the Species evenness, species diversity, species richness. The difference in the each of the summary metrics was calculated between the ridge and the riparian habitats and it was explore using a t-test. The following are the hypotheses for the study:

H0= there was no difference in the mean community metric of leaf litter invertebrates between ridge and riparian habitats.

H1= there was a significant difference in the mean community metric of leaf litter invertebrates between ridge and riparian habitats.

Results


Figure 1: Species accumulation curve

The species accumulation curve shows that the 33 sampling sites does not have the equal distribution of species. Only 5 sampling sites are found to be to be near the trendline or on the trendline. The sapling sites ranging from the 1 to 19 are found to be clustered near the trendline and does not show major variation. Whereas, the sampling sites ranging from 20 to 34 is showing larger variation in data. The graph shows the dispersed species accumulation.

Figure 2: comparison of mean of diversity, evenness, abundance, richness for Riparian habitat


Figure 3: comparison of mean of diversity, evenness, abundance, richness for Ridge habitat


Figure 4: comparison of standard error of diversity, evenness, abundance, richness for Riparian habitat


Figure 5: comparison of standard error of diversity, evenness, abundance, richness for Ridge habitat

The riparian and the ridge habitats are found to be exhibiting different types of species abundance, species richness and species diversity (Shannon). The riparian habitat exhibits larger values of species richness, species abundance, species diversity in comparison to the ridge habitat. While, the species evenness is found to be similar in both the riparian and the ridge habitats. The total number of the species in the riparian habitat is 17 while, the total number of the species in the ridge habitat is 16.

The comparison of standard error of diversity, evenness, abundance, richness for Riparian habitat has revealed that the species richness and the species abundance data are higher in comparison to the ridge habitat data. while the species diversity and the species evenness data for both the riparian and the ridge habitat are more or less similar.

Table 1: t-test data

t-test

 

t value

1.54

 

0.11

 

2.59

 

2.64

degrees of freedom (df)

31

 

31

 

31

 

31

t critical value

0.133707

 

0.913118

 

0.014494

 

0.012863

Reject HO at p=0.05 ?

NO

 

NO

 

YES

 

YES

From the table 1 it has been found that the null hypotheses for both the Shannon diversity and species evenness is accepted. This means that the species evenness and species diversity for both the riparian and ridge habitat shows no difference in the mean community metric of leaf litter invertebrates. While, the null hypotheses have been rejected for the species abundance and species richness. This means that the species richness and species abundance for both the ridge and the riparian habitat shows a significant difference in the mean community metric of leaf litter invertebrates.

Discussion

The following are the hypotheses for the study:

H0= there was no difference in the mean community metric of leaf litter invertebrates between ridge and riparian habitats.

H1= there was a significant difference in the mean community metric of leaf litter invertebrates between ridge and riparian habitats.

The results have clearly pointed the fact that the null hypothesis is rejected for the for both the species abundance and species richness when the leaf litter invertebrates of both the riparian and the ridge habitats are considered. While, the null hypothesis has been accepted for both the species evenness and species diversity when the leaf litter invertebrates of both the riparian and the ridge habitats are considered. Both the figure 2 and 3 highlight the fact that there is no difference between the leaf litter invertebrates in the riparian and the ridge habitats in terms of species evenness and species diversity. Similarly, there is the presence of significant between the riparian and the ridge habitats in terms of the species abundance and species richness. Thus, the hypotheses are in accordance with the findings.

The 33 sampling sites selected for the study and the evaluation do provide adequate number of samples for the proper conduct of the study. The sapling sites provided the species richness that was evident during the sampling study. However, it has been noticed that that not all the sampling sites had the uniform number of the leaf litter invertebrates. From the samples data only certain invertebrates like amphipoda, ant, isopoda, mite, spider, springtail, termite, thrip, tick is found in larger number in comparison to the 33 different invertebrates that were sampled. The four metrics that were used by the in the study are the species richness, species diversity, species evenness and species abundance.

According to Olson (1994), the tropical forest management species that are confined to the narrow altitudinal belts are highly sensitive to fragmentation and habitat loss. It has been see that the moisture conditions, high temperature, lack of the landscapes are highly responsible for the movement of the species within the same altitudinal contour. This also accelerates the species and population decline. Furthermore, the negative effect of deforestation has also led to loss of species over a wider altitudinal ranges. Studies conducted by this author have shown that the 55 percent of the species are confined in a place or region. It has been found that the with the increase of 500 meter of altitude, there is a reduction of 50 percent of the characteristic species. The number of the leaf litter invertebrate species drop when there is a lack of the zonation of the invertebrate assemblages. Uniform decline in the species richness is noticed in the with the increase in elevation and physical parameters are the constant determinants of the local diversity of leaf litter invertebrates. The cool temperatures have been found to be inhibiting the normal metabolic process as well as the development of the larvae or egg. Along with it, the tough pachyphyll leaves, cool temperatures, and waterlogged substrates prevent the decomposition of the leaves in the cloud forests. According to, Lange et al. (2011), the intensification of the land use pattern is the key reason for the global diversity loss. It has been found through this study that the diversity of the lead litter invertebrate is valid for the higher taxonomic resolution. The species richness is not affected by the intensity of the land use that exist in the temperate and the subtropical regions. The tropical and the subtropical regions have different taxonomic compositions. A study conducted by Sayer (2006), revealed that the litter plays a major role in the forest ecosystem and it is a major part of the carbon and nutrient cycling. Litter can be considered to be protective layer on the surface of the soil and it regulates the microclimate conditions on the soil. Thus, litter manipulation both removes and adds the organic matter in and out of the soil. This also directly impacts the rates of soil respiration and rates of decomposition. According to York (1999), has highlighted that the low intensity fires are considered to be patchy in nature and the controlled forest fires have impacted both the litter and the soil invertebrates. It has been found that the frequent fires have the potential to impact the habitat heterogeneity and also affects the survival of the invertebrate population. This is an important aspect as it affects the major role played by the invertebrates in the maintaining biological diversity.

Conclusion

From the above discussion it can be concluded that the ecological communities are a group of species that are interacting with each other and are residing in a same place. a community is said to be interlinked with each other by the network of the influences that the species have on one another. If one of the species gets affected, then the effect is evident in other species as well and this is felt due to the balance in nature. The results have clearly pointed the fact that the null hypothesis is rejected for the for both the species abundance and species richness when the leaf litter invertebrates of both the riparian and the ridge habitats are considered. While, the null hypothesis has been accepted for both the species evenness and species diversity when the leaf litter invertebrates of both the riparian and the ridge habitats are considered.

Reference

1. Allouche, O., Kalyuzhny, M., Moreno-Rueda, G., Pizarro, M., & Kadmon, R. (2012). Area–heterogeneity tradeoff and the diversity of ecological communities. Proceedings of the National Academy of Sciences, 109(43), 17495-17500.
2. Lange, M., Weisser, W. W., Gossner, M. M., Kowalski, E., Türke, M., Joner, F., & Fonseca, C. R. (2011). The impact of forest management on litter-dwelling invertebrates: a subtropical–temperate contrast. Biodiversity and Conservation, 20(10), 2133-2147.
3. Olson, D. M. (1994). The distribution of leaf litter invertebrates along a Neotropical altitudinal gradient. Journal of tropical Ecology, 10(2), 129-150.
4. Sayer, E. J. (2006). Using experimental manipulation to assess the roles of leaf litter in the functioning of forest ecosystems. Biological reviews, 81(1), 1-31.
5. Strong Jr, D. R., Simberloff, D., Abele, L. G., & Thistle, A. B. (Eds.). (2014). Construction Ecological communities: conceptual issues and the evidence (Vol. 613). Princeton University Press.
6. York, A. (1999). Long-term effects of frequent low-intensity burning on the abundance of litter-dwelling invertebrates in coastal blackbutt forests of southeastern Australia. Journal of Insect Conservation, 3(3), 191-199.