IJERD – International Journal of Environmental and Rural Development (2020) 11-1

Research article
erd

Evaluation of Soil Ecosystem Health in Different Farming
Systems by Observing Diversity of Soil Arthropods
MARISOL TERASHIMA
Graduate School of Agriculture, Tokyo University of Agriculture, Japan
Email: chamiter@hotmail.com

MACHITO MIHARA*Faculty of Regional Environment Science, Tokyo University of Agriculture, Japan
Email: m-mihara@nodai.ac.jp
Received 22 January 2020

Accepted 30 April 2020(*Corresponding Author)

Abstract Organic or natural farming practices are known to promote soil fertility as well as
biological diversity. Organic matter recycling, multiple cropping and ecological corridors areavailable as reservoirs for biological control agents such as predators or parasitic insects.
These practices allow ecosystem services to reduce the presence of phytophagous insects andmicroorganisms. The objective of this study is to analyze the effect of the different farming
systems on the diversity of arthropods. The sampling of arthropods was performed by pitfall
trap method. The traps buried at surface level of the ground were set at 3.5 m intervals for 24hours in the line of the cultivated crops. In addition to this method, Tullgren funnel method
is applied in this study. In the experimental results, there were no significant differences inrichness and abundance of observed arthropods. In the natural farming system, taxonomic
group of Araneae, Acari and Coleoptera was observed. In the conventional farming system,
the group of Formicidae was dominant. Using the Simpson’s (inverse) index and ShannonWeaver’s index, the diversity was calculated. The results indicated there was more diversityof arthropods in the natural farming compared to conventional farming system. It is evident
that agricultural practices (natural or conventional) may affect the diversity of arthropods
within an agroecosystem.
Keywords beneficial arthropods, pitfall traps, pest management

INTRODUCTION
Soil health is associated with biological diversity and stability. Plant and animal diseases outbreaks
can be considered as indicators of instability and poor ecosystem health. Therefore, there is likely
also to be a link between soil health, the ability of the biological community to suppress plant
pathogens, the population density of plant pathogens in soil, and ultimately disease incidence andseverity (van Bruggen and Grunwald, 1996). The organic and natural farming is a production systemthat promotes processes which improve soil fertility and biological activity. Pest population density
is related to factors such as climate and population of predators. The climate generates immediate
and drastic changes in the population of the pests, but the control through natural enemies is more
complex. In a successful biological control of pest, the natural enemy reduces the pest to a level that
does not cause harm, but does not eliminate it completely, since the natural enemy requires aminimum population of pest for its survival (Nicholls, 2008). The idea of biological control is tokeep the natural community in balance, and unlike chemical control it is safe, selective, efficient andworks for long term. Those practices such as buffer zones, rotation and intercropping system,
promote biodiversity and it would provide more shelter, food and reproductive possibilities, allowing
the natural enemies to establish themselves as a tool for biological control of pests. And thesepractices also will make the production system more stable and productive in the medium and longterm. Therefore, this study focuses on analyzing the richness and abundance of arthropods in twodifferent production systems. By measuring the diversity of arthropods, it could indicate the stability
and health of the soil ecosystem of the farms.
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MATERIALS AND METHODS
The study was conducted at a natural farm in Saitama prefecture and a conventional farm in Tokyo
City, both located in Kanto region of Japan. The difference between them is that the natural farm
does not use chemical products and uses a system of rotation and intercropping. Which means thatto control pests and diseases they have a complex vegetation structure in the farm to distract insects
and prevent them from attacking their production. The macro or meso arthropods were collectedusing pitfall traps and microarthropods were extracted using Tullgren funnel method. The samples
were preserved in 70% ethyl alcohol and were identified at taxonomic order.
Data Analysis
For all the statistical analyses EstimateS 9.1.0 (Colwell, 2013) was used. For estimates of speciesrichness, Abundance based Coverage Estimator of species richness (ACE) was used (Chao and Lee,1992; Chao et al., 1993). ACE is based on relative abundance data, those species with ≤ 10
individuals in the sample (Chao et al., 1993; Chazdon et al. 1998). Ace takes the form
Srare

F1

ace

ace

Sace=Scommon+ C + C γ2ace(1)where Scommon is number of common species, Srare is number of rare species, Cace is the sample
abundance coverage estimator and ϒace is the estimated.
And for indices of species diversity, Shannon – Weaver’s coefficient of variation of F1 for rare
species. This estimator has been found to give good results and is highly recommended (Chazdon etal. 1998; Hortal et al. 2006). diversity index (H´) and Simpson´s (inverse) diversity (D) index wereused.
𝐻ʼ = − ∑𝑠𝑖=1(𝑝𝑖)(ln𝑝𝑖)(2)where Hʼ is species diversity index, s is number of species and 𝑝𝑖 is proportion of the total sample
belonging to 𝑖 th species. Shannon-Weaver’s index (H´) considers the relative abundance andnumber of species and expresses the uniformity of the values of importance across all the species inthe sample. In addition, it assumes that individuals are randomly selected, and that all species arerepresented in the sample (Magurran, 2004).
𝑛𝑖(𝑛𝑖−1))
𝑁(𝑁−1)

𝐷 = ∑((3)

where ni is the number of individuals in the i th species and N is the total number of individuals. As
D increases, diversity decreases. Simpson’s index is therefore usually expressed as 1-D or 1 ⁄ D(Magurran, 2004). This index is heavily weighted towards the most abundant species in the sample,
while being less sensitive to species richness. For comparing both diversity indices, t-test was used
(Hutcheson, 1970). This test was developed to compare the diversity of two communities samples
for Shannon-Weaver’s index and Simpson’s index.
RESULTS AND DISCUSSION
Richness and Abundance of Species between Natural and Conventional Farming System
The arthropods collected in conventional system are represented by 7 taxa of arthropods. They were:
Acari, Araneae, Collembola, Coleoptera, Hymenoptera, Orthoptera and Thysanoptera. In naturalagroecosystem in addition to those named, 6 taxa more were recorded: Dermaptera, Diptera,Chilopoda, Hemiptera, Homoptera and Lepidoptera. In the conventional agroecosystem, 21 species
and an abundance of 174 individuals were found, whereas in the natural agroecosystem 47 species
and 270 individuals were registered. Figure 1 shows the distribution of total abundance among thedifferent taxonomic groups registered in both farming systems. The most abundant taxonomic groupin natural farming were Formicidae (33%), Orthoptera (14%) and Acari (12%). In the conventionalⒸ ISERD141

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one the Collembola (45%), Orthoptera (16.7 %), Formicidae (18.4 %) and Other Hymenoptera(11.5 %) were the taxa with greater abundance of individuals.

Fig. 1 Percentage of abundance of individuals per taxonomic group for both systems
With these results, we could discuss the significance of the different taxonomic groups inagroecosystems. Ground beetles predators (Carabidae and Staphylinidae) were found because they
are usually found in arable lands. These species as well as spiders (Araneae) are non-specificpredators, unlike parasitic wasps that are specific predators. Mites (Acari) are important in the soil
as fungivores, bacterivores and nematode predators (Largerlof and Andren, 1988). In addition, they
are related with the decomposition of organic residue in the soil.

Fig. 2 Number of families per order for both systems
Figure 2 shows the distribution of the total richness among the taxonomic groups recorded inboth evaluated sites. In natural agroecosystem the taxa with the highest number of families were:
Coleoptera (17%), Araneae (17%) and Other Hymenoptera (15%). In contrast, in the conventional
agroecosystem the taxa with the highest percentage of species were: Formicidae (29%), Araneae(19%), Other Hymenoptera (19%) and Collembola (14%). An advantage of species richness is thatit provides a broad measure of the complexity of communities and perhaps their resilience to change.
Its disadvantage lies in the practical difficulty of distinguishing invertebrate species and how little itreveals about species interactions. However, species richness has the potential to tell us more aboutⒸ ISERD

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invertebrate communities and soil quality than straight biomass, density or abundance (Stork andEggleton, 1992).
Diversity Functional Group between Natural and Conventional Farming System
Although there was no significant difference in richness and abundance in both cropping systems, inan agroecosystem, we can discuss the function that has each arthropod. From an ecological system
it is important to know this since not all invertebrates that we find in the system could have differentfunctions. That is, although there is more diversity, it could not mean that there are more functionalgroups. In Fig. 3, we can see that in the two systems, we could find a higher percentage of predators
abundance in the natural system than in the conventional one.

Fig. 3 Percentage of the abundance for functional group in both systems
Species Accumulation Curves (ACE) between Natural and Conventional Farming System
In order to understand the correlation between the observed and the estimated, Fig. 4 could be used
to analyze the scenarios. In this figure we can see that the effort of the samples was insufficient inboth systems. But we could conclude that despite that, in both systems the natural one is more diverse
than the conventional one, since it is estimated that in the natural system, there are more than twice
as many species as in the conventional one.

Sobs: observed species, ACE: estimatedFig. 4 Species accumulation curves in natural system (A) and conventional system (B)Diversity Indices between Natural and Conventional Farming SystemⒸ ISERD

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Both diversity indices indicate a higher value in natural system than conventional system. Diversity
in agroecosystem, or agro biodiversity, promotes the presence of beneficial fauna, optimizing theecological processes that favor stability, and consequently favoring their sustainability (Altieri andNicholls, 2000). But it should be clarified that it could not be quantified how an agroecosystem isonly considering the relation that exists in the same space and time by a determined number of species.
This is because the interaction between the same amounts of species in different conditions can vary
(Ewel, 1986, 1999). The diversity indices give us an indication of the stability of the system,indicating that the farm of natural agriculture is more stable. And this indices at the same time
coincides with the abundance and richness of the arthropods found in the two systems. A strong pointof Simpson’s index is that it considers rare species. These arthropods could indicate that they arespecific to the system. In other words, rare arthropods include predators with general habits andparasitoids that are more specific, such as the parasitoid wasps which in total collected 11 species, 7of which were in natural farm and 4 in conventional farm. Predators such as spiders and beetles
recorded 18 species in natural agriculture and 4 species in the conventional.

(*) denotes significant difference at P<0.05(**) denotes significant difference at P<0.01

Fig. 5 Simpson Inverse Index in both
farming system

Fig. 6 Shannon – Weaver Index inboth farming system

These results would support the hypotheses of Altieri and Letourneau (1984) and Altieri andNicholls (2000) that diverse systems stimulate a greater diversity of arthropods. The first hypothesisis that more complex systems mean more diversity of species. And the diversity of species andstructural plants would be associated with the diversity and abundance of insects because it wouldgenerate more food resources and temporary shelters. Increased abundance of predators andparasitoids in diverse plant associations reduces prey / host density (Root, 1973), so competition
between herbivores is reduced, which in turn allows for the addition of new species of herbivores
that support more species of natural enemies. And finally, they assume that the productivity ofpolycultures is greater, stable and predictable than in monocultures. Increased productivity andheterogeneity of the agroecosystem would mean that in a temporal and spatial environment, more
species of arthropods could coexist.
CONCLUSION
There was no significant difference in richness and abundance, but more predators were observed in
the natural system. Among the predators, the spiders and beetles population were dominant. The
diversity indices were higher in the natural system, which means the distribution and abundance inthe community is more equitable.
The farming system influences the diversity of arthropods in an agricultural environment.
Therefore, if a system cannot conserve or increase the biodiversity of the farmland, it will be more

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unstable and with poor soil ecosystem health. However, more research is needed to better understandthe interaction and roles of arthropods in a soil ecosystem.
ACKNOWLEDGEMENTS
I would like to express my gratitude to Nakamura farm as well as the people of the NPO Tagayasu,
who gave me the opportunity to take the samples from their farms.
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