Journal of Threatened Taxa | www.threatenedtaxa.org
| 26 March 2018 | 10(3): 11432–11442
Seasonal distribution and abundance of
earthworms (Annelida: Oligochaeta) in relation to the
edaphic factors around Udupi Power Corporation
Limited (UPCL),
Udupi District, southwestern coast of India
T.S.
Harish Kumar 1, M. Siddaraju 2,
C.H. Krishna Bhat 3 & K.S. Sreepada 4
1,4 Department of
Applied Zoology, Mangalore University, Mangalagangothri,
Mangaluru, Karnataka 574199, India
2 Sri Sathya Sai Loka
Seva P.U. College, Alike, Dakshina Kannada, Karnataka 574235, India
3 KSHEMA, Nitte deemed to be University, Deralakatte,
Mangaluru, Karnataka 575018, India
1 harishsrys@gmail.com,
2 saishreesiddu@yahoo.com, 3 chkrishnabhat1951@gmail.com,
4 srisuchith@gmail.com (corresponding author)
Abstract: Seasonal
distribution and abundance of four species of earthworms belonging to three
families—Rhinodrilidae (Pontoscolex corethrurus), Megascolecidae (Megascolex konkanensis and Metaphire houlleti) and Octochaetidae (Karmiella karnatakensis)—were studied in three habitats (residential, agricultural and
forest) along with edaphic factors around Udupi Power
Corporation Limited (UPCL), Karnataka, India between September 2014 and August
2016. Among the four species, P. corethrurus was collected throughout the year and was most abundant in residential
habitats such as colacasia garden, coconut and banana
pits. M. konkanensis was collected from coconut plantations, banana plantations and forest
soil during monsoon and post-monsoon periods. M. houlleti was collected from manure heaps, coconut and banana pits of residential
habitat, coconut plantations and forest soil. K. karnatakensis was collected from garden soil in residential habitat during the
post-monsoon period, coconut plantations and soil mixed with forest leaf litter
during monsoon and post-monsoon periods.
The soil temperature differ significantly
during different seasons in residential (P= 0.01) and agricultural (P=0.03)
habitats whereas moisture shows highly significant difference in agricultural habitat
(P=0.00037) during different seasons.
P. corethrurus showed
positive correlation with organic carbon during pre-monsoon and C/N ratio
during monsoon in the residential habitat.
It shows negative correlation with pH during the monsoon period. M. houlleti showed positive correlation with organic carbon in residential habitat
during the pre-monsoon and in forest habitat during monsoon periods. M. konkanensis showed positive correlation with electrical conductivity in
agricultural habitats during monsoon period. K. karnatakensis showed positive correlation with moisture during monsoon and with C/N
ratio during post-monsoon period in forest habitats.
Keywords: Earthworm
distribution, edaphic factors, Megascolecidae, Octochaetidae, Rhinodrilidae, Udupi Power Corporation Limited (UPCL).
doi: http://doi.org/10.11609/jott.3806.10.3.11432-11442 | ZooBank:
urn:lsid:zoobank.org:pub:94330186-7D5D-48CF-A4A8-F3B5552E4F46
Editor: J.W. Reynolds, New Brunswick Museum, Saint John, Canada. Date of publication: 26 March 2018 (online & print)
Manuscript details: Ms # 3806 | Received 20 September 2017 | Final received 03 March 2018 |
Finally accepted 10 March 2018
Citation: Kumar, T.S.H., M. Siddaraju,
C.H.K. Bhat & K.S. Sreepada
(2018). Seasonal
distribution and abundance of earthworms (Annelida: Oligochaeta)
in relation to the edaphic factors around Udupi Power
Corporation Limited (UPCL), Udupi District, southwestern coast of India. Journal of Threatened Taxa 10(3): 11432–11442; http://doi.org/10.11609/jott.3806.10.3.11432-11442
Copyright: © Kumar et al. 2018. Creative Commons Attribution 4.0 International
License. JoTT allows unrestricted use of this
article in any medium, reproduction and distribution by providing adequate
credit to the authors and the source of publication.
Funding: SC/ST Research fellowship from Mangalore University.
Competing interests: The authors declare no competing interests.
Author Details: Mr. T.S. Harish Kumar is a
research scholar in the Department of Applied Zoology, Mangalore University
working in the field of earthworm taxonomy and diversity for PhD. Dr. M. Siddaraju
is a lecturer in Sri Sathya Sai
Loka Seva P.U. College, and
he is also a expert in the field of earthworm
taxonomy. Dr. C.H. Krishna Bhat is a retired Biostatistician and currently he
is working as visiting
Professor at Nitte deemed to be
University, Mangaluru. Dr. K.S. Sreepada is a Professor
in Applied
Zoology at Mangalore University.
Author Contribution: All authors have equally contributed.
Acknowledgements: The authors are grateful to Mangalore University for providing the
necessary facilities to undertake this research work. We are thankful to Dr. Raghuramulu Y., Sri. N. Hariyappa,
and Dr. Seetharam, H.G., Central Coffee Research Institute (CCRI),
Coffee Research Station, Chikmagalur District,
Karnataka, India for their support during soil analysis and Mr. Vivek Hasyagar for earthworms
photography.
Introduction
India is a vast country with great diversity of plants and animals
supported with tropical and sub-tropical climates. Soil faunal population is very important
in many agro ecosystems; because the soil organisms
promote soil fertility (Lee 1985; Werner & Dindal
1989). The major soil organisms
include earthworms, centipedes, millipedes and microorganisms. Of these, earthworms are considered as
one of the major soil invertebrates belonging to the phylum Annelida and class Oligochaeta. Oligochaetes are mainly divided into megadriles
and microdriles.
Megadriles live in both terrestrial and
aquatic systems whereas microdriles prefer only
aquatic systems. Globally, there
are about 4,400 different species of earthworms (Reynolds & Wetzel 2017) and from
India 505 species of earthworms (Julka 2014; Ahmed & Julka
2017; Narayanan et al. 2017) have been reported.
Diversity and distribution of earthworms have been studied from
different parts of the world, viz., Bulgaria (Mihailova
1964; Stojanovic et al. 2012), Thrace (Mihailova 1966), Myanmar (Gates 1972; Reynolds 2009),
Australia (Jamieson & Wampler 1979; Blakemore
2000; Blakemore & Paoletti 2006), Argentina (Mischis & Brigada 1985; Mischis 1992, 1993; Mischis &
Righi 1999; Laura & Ines 2001), Turkey (Omodeo & Rota 1991), Australia,
Japan and India (Blakemore 1994, 2004, 2006), Bangladesh (Reynolds 1994;
Reynolds et al. 1995b; Das & Reynolds 2003), northern Neotropical
region (Fragoso et al. 1995), Belize (Reynolds et al.
1995a), Mexico (Fragoso & Reynolds 1997), New
Zealand (Springett et al. 1998), Faisalabad (Ghafoor & Qureshi 1999),
Taiwan (Tsai et al. 2000, 2004), Gujranwala (Rana et
al. 2002), north-west of the Iberian Peninsula (Monrey
et al. 2003), central Terai region (Bisht et al. 2003), Philippines (James 2004), Taiwan (Tsai
et al. 2004), Singapore (Shen & Yeo 2005),
southern and eastern Uruguay (Grosso et al. 2006),
Mexico (Huerta et al. 2007), North America (Reynolds & Wetzel 2008), northwestern England (Chamberlain & Butt 2008),
Nicaragua (Sherlock et al. 2011), Hawaii (Reynolds 2015), Bermuda (Reynolds
& Fragoso 2004), South America (Christoffersen 2008a,b, 2010; De-Assis
et al. 2017), Guadeloupe Islands of West Indies (Csuzdi
& Pavlicek 2009), Serbia and Bulgaria (Stojanovie et al. 2013), and Thailand (Chanbun
et al. 2017).
The reports on Indian oligochaetes include,
Karnataka (Kale & Krishnamoorthy 1978), southern
India (Julka 1983), woodlands of Karnataka
(Krishnamurthy & Ramachandra 1988), Kumaun Himalayan pasture soil (Kaushal
& Bisht 1994), Western Ghats (Blanchart
& Julka 1997), central Himalaya (Bhadauria et al. 2000), Tamil Nadu (Gobi & Vijayalashmi 2004; Kathireswari
et al. 2005, 2008), Chennai (Begum & Ismail 2004), Rajasthan (Tripathi & Bharadwaj 2004),
western Himalaya (Paliwal & Julka
2005), Pondicherry (Sathianarayan & Khan 2006),
northern Indian states (Dhiman & Battish 2006), Tripura (Chaudhuri
et al. 2008), Uttarakhand (Joshi & Aga 2009),
southern Karnataka (Kale & Karmegam 2010), Garhwal Himalaya (Joshi et al. 2010), Kashmir Valley (Ishtiya & Anisha 2011), Dakshina Kannada District of Karnataka (Siddaraju
et al. 2010), Jammu, northeastern India (Rajkhowa et al. 2014), and Kerala (Narayanan et al. 2016).
Earthworms feed on organic matter and litter. They enrich soil fertility by adding
nutrients to the soil through their burrowing activities and are recognized as
ecological engineers due to their strong interaction with soil functioning in
the ecosystem (Jones et al. 1994; Lavelle et al. 1994). Earthworm casts are
highly rich in organic matter compared to the non-ingested surrounding
soil. The effect of earthworms on
the dynamics of soil organic matter depends on the time and space (Mora et al.
2005). Earthworms are known to
increase the transfer of organic carbon and nitrogen into soil through their
gut microbial activities and they facilitate the stabilization and accumulation
of soil organic matter (Desjardins et al. 2003). The cycling process of C and N
in agro- ecosystems depends on the cropping system and management practices (Fonte et al. 2007). The earthworm species and their
interactions also affect the nitrogen mineralization (Brown et al. 1999). They also increase the soil pH and
promote the microbial activity in the soil. In addition, other nutrients such as N,
P, K and Ca derived from earthworm urine and mucus
are also involved in soil fertility (Parmelec et al.
1998).
Understanding the soil factors which control the
abundance of earthworms and their strong interaction in maintaining the soil
ecosystem functioning has gained widespread attention in recent
years. Several studies have shown
that a number of factors control the earthwormÕs density and distribution (Fonte et al. 2009).
Huerta et al. (2007) have observed high earthworm abundance in soil with
high organic matter in tropical rain forests. Management practices, however, alter the
earthworm population density by altering the aggregation of soil organic matter
(Fonte et al. 2009).
Most of the studies focussed on diversity and distribution of earthworms
in natural habitats and agro ecosystems.
A few studies have reported bio-indicator activities for earthworms for
heavy metal pollutions in various habitats (Hook 1974; Spiegel 2002; Hobbelen et al. 2006; Suther et
al. 2008). The present study records the seasonal occurrence and distribution
of four species of earthworms in relation to the edaphic factors around Udupi Power Corporation Limited (UPCL), Udupi
District of Karnataka, southwestern
coast of India.
Study area
Udupi Power Corporation Limited (UPCL)
(14.223055560N & 76.211388890E) is an important coal
based thermal power plant, established in 2008. It is located to the north of Mangaluru, west of Belman and
adjacent to the north-east of Padubidri in the
village of Yellur, Udupi
District, Karnataka, India and it is situated roughly 7–8 km from the
coast (Arabian Sea), very close to the Shambhavi
River. The study area covers the
radius of about 10km around UPCL and the villages included are Bellibettu, Kaup, Kuthyaru, Mudarangadi, Nadsal, Nandikur, Padabettu, Yellur and Tenka-Yermal.
The geographical coordinates in each habitat were noted using a Garmin eTrex GPS and a Google map was constructed using Google
Earth (Image 1). The annual
rainfall in Udupi District ranged from
3,184–3,575 mm. The elevation
ranges from 5–51 m in the study area. The average soil temperature ranged
between 26.5–29.2 0C.
Soil texture varies from fine clay to loamy. The sampling sites were broadly divided
into residential, agricultural and forest habitats. In the residential habitat, the major
plants include: Cocus nucifera (Coconut), Areca catechu (Areca Nut),
Musa
spp. (Banana), Psidium guajava (Common Guava) and Carica
papaya (Papaya). In the
agricultural habitat, the major crops include, Oryza sativa (Paddy), Cocus nucifera, Areca catechu, Musa spp. and in
the forest habitat the tree species include: Tectona grandis (Teak), Millettia pinnata (Indian Beech), Mangifera indica (Mango), Borassus flabellifera (Palmira), Artocarpus heterophyllus (Jack Fruit), Alstonia scholaris (Saptaparna), Tamarindus indica (Tamarind)
and Manikara zapota (Sapodilla).
Methods
Studies on distribution and abundance of earthworms (Pontoscolex corethrurus, Megascolex konkanensis, Metaphire houlleti and Karmiella karnatakensis) was carried
out in residential, agricultural and forest habitats around Udupi
Power Corporation Limited (UPCL) during pre-monsoon (February–May),
monsoon (June–September) and post-monsoon (October–January) periods
of September 2014 to August 2016.
Sampling points were identified and soil was excavated from 30x30x30cm
quadrants in each site in the selected villages. Available earthworms were
collected by hand sorting method and brought to the laboratory along with soil
samples in polythene bags.
Specimens were washed with tap water and anesthetized in 30% ethyl
alcohol, straightened and preserved in 5% formalin. Species were identified based on standard
taxonomic keys of Julka (1988) and Blakemore (2006).
Soil
analysis
In the earthworm sampled habitats such as residential and agricultural
(in all seasons) and forest habitat (monsoon and post-monsoon seasons), edaphic
factors were analysed by using standard protocols (Jackson 1973). Soil temperature was measured by using a
digital thermometer (TP 101 model) at the depth of 10cm. Moisture content was determined
gravimetrically on a wet weight basis by oven drying method (105OC,
12 hours). The air
dried soil sample was sieved and subjected to the following
analysis. The pH (1:2.5) was
detected using digital pH meter (Systronics model EQ
610). Electrical conductivity (EC)
was measured using conductivity meter (Systronics
model EQ 660A). Organic Carbon (OC)
content was determined using Walkley-Black chromic
acid wet oxidation method. Nitrogen (N) content was estimated by Micro Kjeldahl method.
The available Phosphorous (P) content was measured by BrayÕs method for
acidic soil samples (pH<6.5) and OlsenÕs method for alkaline soil samples
(pH>6.5) using Near Infra-Red (NIR) spectrophotometer. The Potassium (K) was measured by Flame
photometer method using neutral normal ammonium acetate as an extractant.
Statistical
analysis
The seasonal abundance of earthworms in relation to edaphic factors was
analysed using Karl PearsonÕs Correlation method. To compare the means of two different
groups, independent student t-test and for comparison of more than two groupÕs one way ANOVA test was used. Statistical analysis was done
using SPSS version 16.
Results and Discussion
The present study records, the
distribution pattern and abundance of four species of earthworms belonging to
three families, viz., Rhinodrilidae (P. corethrurus), Megascolecidae
(M. konkanensis and M. houlleti), and Octochaetidae (K. karnatakensis) (Table 1;
Figs. 1–3). Among
these species P. corethrurus was observed
during all the seasons in the soil of colacasia
gardens, coconut and banana pits of residential habitats, paddy fields and
coconut plantations. More abundance
was observed during the monsoons in the residential habitats (62.0±14.85) and
less abundance during the post-monsoons in agricultural habitats
(3.0±2.60). The species, however,
was not recorded in forest habitats in any of the seasons. M. konkanensis was recorded from coconut gardens
and banana plantations in maximum numbers (51.0±10.82) during the monsoons and
minimum in forest habitats (15.0±7.53) during post-monsoons. M. houlleti was recorded throughout the year except
in the forest habitats during pre-monsoons. The maximum was recorded from coconut
gardens, garden soil and manure heaps in the residential habitats (51.0±0.82)
during the monsoon period; however, fewer numbers were recorded in agricultural
habitats (1.0±1.8, 2.0±1.41, 3.0±2.19). K. karnatakensis was recorded
from all the selected habitats during monsoon and post-monsoon periods except
in residential habitats during the monsoon period and in all the habitats
during the pre-monsoon period. The
maximum number was observed in forest habitats (42.0±3.22) during the monsoon
period and minimum number was observed in agricultural (3.0±2.75) and
residential (3.0±2.92) habitats during monsoon and post-monsoon periods
respectively.
Table 1. Seasonal distribution and abundance of earthworm species (Mean±SD) (n=6).
Seasons |
Pre-monsoon |
Monsoon |
Post-monsoon |
||||||
Habitats |
Residential
habitat |
Agricultural
habitat |
Forest Habitat |
Residential
habitat |
Agricultural
habitat |
Forest
habitat |
Residential
Habitat |
Agricultural
habitat |
Forest
habitat |
Species |
|||||||||
P. corethrurus |
41.0±4.93 |
11.0±3.16 |
- |
62.0±14.85 |
45.0±10.77 |
- |
7.0±2.62 |
3.0±2.60 |
- |
M. konkanensis |
- |
- |
- |
- |
51.0±10.82 |
- |
- |
- |
15.0±7.53 |
M. houlleti |
13.0±4.81 |
1.0±1.8 |
- |
51.0±10.82 |
2.0±1.41 |
22.0±5.83 |
18.0±7.18 |
3.0±2.19 |
9.0±4.09 |
K. karnatakensis |
- |
- |
- |
- |
3.0±2.75 |
42.0±3.22 |
3.0±2.92 |
13.0±5.09 |
13.0±6.19 |
1. Pontoscolex corethrurus (Fr. Muller, 1857) (Image 2)
Distribution: Bellibettu (coconut and
banana pits of residential habitats); Kaup (colacasia garden); Mudarangadi
(banana pits of residential habitats), Padabettu
(paddy field) and Tenka-Yarmal (coconut pits of
residential habitats) villages.
Recorded periods: All the seasons.
Previous records: Bangladesh (Reynolds 1994;
Reynolds et al. 1995b; Das & Reynolds 2003), Mexico (Fragoso
& Reynolds 1997), Taiwan (Tsai et al. 2004), Rajasthan (Tripathi
& Bharadwaj 2004), Singapore (Shen
& Yeo 2005), Tamil Nadu, southern India (Kathireswari
et al. 2005, 2008; Blakemore 2006), Puducherry (Sathianarayan & Khan 2006), Tripura, India (Chaudari et al. 2008), Myanmar (Gates 1972; Reynolds 2009),
Dakshina Kannada, southwestern
coast of Karnataka (Siddaraju et al. 2010), southern
Karnataka (Kale & Karmegam 2010), Nicaragua
(Sherlock et al. 2011), Western Ghats of Karnataka, India (Biradar
et al. 2013), Assam, northeastern India (Rajkhowa et al. 2014), and Kerala, India (Narayanan et al.
2016).
2. Megascolex konkanensis Fedarb, 1898 (Image 3).
Distribution: Adve (Banana
plantation); Kuthyaru (coconut plantation); Nandikur (forest soil) and Yellur
(banana plantation) villages.
Recorded periods: Monsoon and post-monsoon.
Previous records: Southern India (Stephenson 1923; Rao 1979; Oommen 1998; Blakemore
2006; Reynolds et al. 2010), Dakshina Kannada, southwestern coast of Karnataka (Siddaraju
et al. 2010) and Western Ghats of Karnataka, India (Biradar
et al. 2013).
3. Metaphire houlleti
(Perrier, 1872) (Image 4).
Distribution: Adve (banana pits
in residential habitat); Bellibettu (forest soil,
manure heaps, coconut and banana pits of residential habitats) and Nadsal (coconut plantations) villages.
Recorded periods: Monsoon and post-monsoon.
Previous records: Belize (Reynolds et al. 1995a),
Bangladesh (Das & Reynolds 2003), Taiwan (Shen et
al. 2005), Tamil Nadu (Kathireswari et al. 2005),
western Himalaya states (Paliwal & Julka 2005), Australia, Japan and India (Blakemore 1994,
2004, 2006), northern Indian states (Dhiman & Battish 2006), North America (Reynolds & Wetzel 2008),
Tripura, India (Chaudari et al. 2008), Guadeloupe
Islands of West Indies (Csuzdi & Pavlicek 2009), Garhwal Himalaya
(Joshi et al. 2010), southern Karnataka (Kale & Karmegam
2010) and Dakshina Kannada, southwestern
coast of Karnataka (Siddaraju et al. 2010).
4. Karmiella karnatakensis
Julka, 1983 (Image
5)
Distribution: Bellibettu (garden soil
of residential and forest habitats); Nandikur
(coconut plantations) villages.
Recorded periods: Monsoon and post-monsoon.
Previous records: Tirthahalli, Kotegehara, Moodabidri, Bhagamandala, Sakleshpur of
Karnataka State, India (Julka 1988).
Edaphic
factors
As shown in the Table 2 the edaphic factors such as soil temperature
(T), pH, moisture content (MC), electrical conductivity (EC), organic carbon
(OC), nitrogen (N), carbon and nitrogen ratio (C/N), phosphorous (P) and
potassium (K) show the variation range during the study period in selected
habitats. The range of parameters
during pre-monsoon in the residential habitat include, T (27.0–30.2 0C);
pH (5.98–7.63); MC (20.19–41.19 %); EC (0.15– 0.49mS cm-1);
OC (2.87–6.60 %); N (0.14–0.38 %); C/N ratio (9.23–25.38%); P
(99.0–513.0 kg/ha) and K (92.51–609.28 kg/ha). In agricultural habitat, T
(28.2–30.2 0C); pH (5.53–6.51); MC (24.11–27.97
%); EC (0.19–0.36mS cm-1); OC (4.8–5.7 %); N (0.40 to
0.44%); C/N ratio (10.90 to 14.25 %); P (13.0 to 149.0 kg/ha) and K
(76.6–204.73 kg/ha). During
monsoon, in residential habitat, T (24.0–28.0 0C); pH
(4.32–7.52); MC (34.26–64.83%); EC (0.21–0.90mS cm-1);
OC (2.7–6.32 %); N (0.21–0.48 %); C/N ratio (10.36–27.63 %);
P (37.0–480.0 %) and K (50.70–635.60 %). In agricultural habitat, T
(24.5–27.6 0C); pH (5.17–7.37); MC (35.73–51.04
%); EC (0.12–0.38mS cm-1); OC (2.0–7.02 %); N
(0.17–0.48 %); C/N ratio (7.4–20.17 %); P (11.0–175.0 kg/ha)
and K (22.1–348.54 kg/ha) and in forest habitat, T (24.0–27.6 0C);
pH (4.85–7.62); MC (24.33–60.17 %); EC (0.12–0.68mS cm-1);
OC (3.68–7.11 %); N (0.21–0.49 %); C/N ratio (10.65–50.78 %);
P (8.0–499.0 kg/ha) and K (38.75–798.78 kg/ha). During post-monsoon, in residential
habitat, T (26.0–28.0 0C); pH (6.21–6.75); MC
(20.19–41.19 %); EC (0.15–0.49mS cm-1); OC
(2.87–6.60 %); N (0.14–0.38 %); C/N ratio (9.23–25.38 %); P
(99.0–513.0 kg/ha) and K (92.51–609.28 kg/ha). In agricultural habitat, T
(26.5–28.5 0C); pH (4.94–7.86); MC (30.14–35.21
%); EC (0.12–0.36mS cm-1); OC (4.28–5.91 %); N
(0.27–0.30 %); C/N ratio (14.26–20.37 %); P (13.0–94.0 kg/ha)
and K (94.64–251.88 kg/ha) and in forest habitat, T (27.0–28.0 0C);
pH (5.90–5.95); MC (33.86–34.70 %); EC (0.12–0.22mS cm-1);
OC (4.97–5.31 %); N (0.12–0.15 %); C/N ratio(35.40–41.41
%); P (9.0–26.0 kg/ha) and K (85.05–187.82 kg/ha). The soil temperature showed significant
difference in residential (P=0.01) and in agricultural (P=0.03) habitats in all
the seasons. Whereas,
moisture content (P= 0.00037) is found to be highly significant in all the
seasons. In forest habitats,
no significant difference was found between any of the edaphic factors during
monsoon and post-monsoon periods.
The other parameters such as pH, electrical conductivity, organic
carbon, nitrogen, C/N ratio, available phosphorous and potassium also showed no
significant difference during different seasons in the study area.
Table
2. Soil characteristics of different habitats in three
seasons (Mean±SD) (n=6).
Habitats |
Seasons |
Temperature (0C) |
pH |
MC (%) |
EC (mS cm-1) |
OC (%) |
N (%) |
C/N |
P (kg/ha) |
K (kg/ha) |
Residential habitat |
Pre-monsoon |
28.6±1.58 |
6.93±0.63 |
28.06±8.59 |
0.27±0.11 |
4.33±1.29 |
0.27±0.09 |
17.46±6.63 |
213.0±155 |
292.16±213 |
Monsoon |
26.5±1.07 |
6.61±1.13 |
45.79±11.1 |
0.39±0.20 |
4.72±1.32 |
0.29±0.08 |
16.64±6.09 |
145.0±129 |
184±189 |
|
Post-monsoon |
27.4±0.89 |
6.98±0.61 |
35.53±7.32 |
0.23±0.09 |
4.43±1.42 |
0.35±0.06 |
12.87±4.39 |
94.0±92 |
300.91±253 |
|
P value |
0.01* |
0.43 |
0.06 |
0.17 |
0.82 |
0.32 |
0.40 |
0.32 |
0.45 |
|
Agricultural habitat |
Pre-monsoon |
29.2±1.41 |
6.02±0.69 |
26.04±2.72 |
0.27±0.12 |
5.25±0.63 |
0.42±0.02 |
12.57±2.36 |
81.0±96.16 |
140.36±91 |
Monsoon |
26.4±1.19 |
5.99±0.67 |
42.95±5.06 |
0.24±0.09 |
4.11±1.83 |
0.27±0.10 |
15.13±3.83 |
83.0±54.81 |
159.9±93 |
|
Post-monsoon |
27.4±1.07 |
6.10±1.24 |
33.32±2.32 |
0.24±0.13 |
4.79±0.75 |
028±0.01 |
16.68±2.60 |
52.0±33.71 |
193.78±69 |
|
P value |
0.03* |
0.97 |
0.00037** |
0.94 |
0.58 |
0.14 |
0.419 |
0.65 |
0.73 |
|
Forest habitat |
Pre-monsoon |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Monsoon |
26.6±1.23 |
5.79±0.86 |
43.48±10.99 |
0.25±0.19 |
5.33±1.23 |
0.32±0.11 |
19.97±13.8 |
145.0±195 |
190.0± 270.06 |
|
Post-monsoon |
27.5±0.70 |
5.92±0.03 |
34.28±0.59 |
0.17±0.07 |
5.14±0.24 |
0.13±0.02 |
38.40±4.24 |
18.0±12.02 |
136.43±73 |
|
P value |
0.41 |
0.84 |
0.29 |
0.57 |
0.83 |
0.07 |
0.11 |
0.41 |
0.79 |
**P<0.05
(indicates statistically high significant difference), *P<0.01 (indicates
statistically significant difference).
Correlation
between the seasonal abundance of earthworm species with edaphic factors
The correlation analysis of abundance of different species of earthworms
in relation to edaphic factors in different seasons has revealed that, during
pre-monsoon, the abundance of P. corethrurus (r= 0.882;
P=0.02) and M. houlleti (r=0.814; P=0.049) were positively
correlated with organic carbon and are statistically significant in the
residential habitats. During monsoons, P. corethrurus showed
positive correlation with C/N ratio (r=0.732; P=0.01) and is statistically
significant, whereas it shows negative correlation with pH (r=-0.755; P=0.007)
and is statistically highly significant in the residential habitats. M. konkanensis showed positive correlation with
electrical conductivity (r=0.925; P=0.00034) and is statistically highly
significant in the agricultural habitat. In the forest habitat, K. karnatakensis showed statistically highly significant
negative correlation with temperature (r=-0.803;
P=0.029) and positive correlation with moisture content (r=0.770, P=0.043). Whereas, M. houlleti showed positive correlation with
organic carbon (r=0.882; P=0.009) and is highly significant. During post-monsoons,
K.
karnatakensis showed positive correlation with
C/N ratio (r=0.879; P=0.049) and is statistically significant in the
residential habitats.
Diversity,
distribution and abundance of earthworm species
Diversity, distribution and abundance of soil organisms are influenced
by many soil factors. Understanding
the factors which control the earthwormÕs diversity and
population density is a vital process to maintain the soil
ecosystem. Earthworms are important
soil dwelling organisms and are found in a wide range of soil representing
60–80 % of the total soil biomass and they prefer soil
which is rich in organic matter. Diversity is affected due to the loss
of their native habitats (Lavelle et al. 1994; Bhadauria
et al. 2000). Various studies have
reported earlier the distribution of earthworms in relation to habitats (Fonte et al. 2009).
In the earlier reports, P. corethrurus was recorded
from habitats such as manure heaps, garden soil, cultivated land, coconut and
rubber plantations (Julka 2008); nursery stock of
Assam (Rajkhowa et al. 2014), human disturbed forests
of Kerala state (Narayanan et al. 2016), moist soil and cow dung slurry pits of
Dakshina Kannada, Karnataka (Siddaraju
et al. 2010). In the present study P. corethrurus was found to be more widely spread
and was the dominant earthworm species in the study area. The highest population density was
observed during the monsoons followed by post-monsoon period and the same observation was made by Blanchart
& Julka (1997) and Joshi & Aga (2009). This aneciec
earthworm M. konkanensis an endemic species was reported
earlier from forest leaf litter in different parts of South India (Oommen 1998; Kathireswari et al.
2005). Siddaraju
et al. (2010) recorded this species from banana and cashew plantations in Dakshina Kannada district of Karnataka. Siddaraju
et al. (2010) have recorded the same species from manure heaps, coconut, rubber
and cocoa plantations in Dakshina Kannada,
Karnataka. The present study also
records the co-existence of P. corethrurus and M. houlleti in banana and coconut pits of residential
habitats. Julka
(1988) has reported K. karnatakensis from Bhagamandala, Kotegehara, Moodabidri, Sakleshpur and Tirthahalli in Karnataka.
Earthworm
abundance in relation to edaphic factors
The species density was observed where there was the highest litter
degradation in the study area. It indicates that moisture content and food
availability in the habitats influence the distribution of earthworms. It has been observed that, the species
abundance in residential habitats throughout the year is probably due to ideal
soil moisture and rich organic matters as it was reported
earlier by Ghosh (1993). Soil temperature gradually increases
from monsoon to pre-monsoon periods and there is not much variation in
temperature between habitats. Soil pH (5.79 to 6.93) did not show much
difference between the habitats in different seasons. Iordachf &
Borza (2010) opined that earthworm abundance
decreased with increasing soil pH. In the present study, P. corethrurus shows negative correlation with pH
(r=-0.755; P=0.007) in the residential habitats during the monsoon period. M. konkanensis showed the
positive correlation with electrical conductivity (r=0.925; P= 0.00034) in the
agricultural habitats during the monsoon period. Whereas, K. karnatakensis
showed negative correlation with temperature (r=-0.803; P=0.029) and
positive correlation with moisture (r=0.770; P=0.043) in the forest habitats. Organic carbon is very essential for the
normal growth and development of earthworms, which is obtained from litter,
grit and micro-organisms present in the soil. All the soil had high levels of organic
carbon (>2.5%) in the selected habitats during different seasons. Wherever
there is high moisture content and decaying organic matter available easily to
the worms, the rate of decomposition activity is recorded to be more as it was
observed in the study area (Edwards & Bohlen 1996; Joshi & Aga
2009). Hendrix et al. (1992)
reported that earthworm population density is positively correlated with
organic carbon. In the present study also a similar result was observed in the
residential habitats with P. corethrurus (r=0.882;
P=0.02) and with M. houlleti (r=0.814;
P=0.049) during the pre-monsoon and in forest habitats (r=0.882; P=0.009)
during the monsoon period with M. houlleti (Joshi et
al. 2010). Nitrogen content in the
soil is due to the accumulation and decomposition of leaf litter and debris of
the plants. Banana plants add more
nitrogen to the soil after death and decay by decomposition processes. Nitrogen showed no significant
relationship with the distribution of the species. Only P. corethrurus (r=0.732; P=0.01) and K. karnatakensis (r=0.879; P=0.049) showed a positive
correlation with C/N ratio in the residential habitats during monsoon and
post-monsoon periods respectively.
In all the soils, the available phosphorous content was high (52.75 to
213 kg/ha) in all the seasons, except in forest habitats (17.5 kg/ha) during
the post monsoon period. The
available potassium content was medium (136.43 to 193.73 kg/ha) in all the soil
samples, whereas in residential habitats it shows high during pre-monsoon
(292.16 kg/ha) and post monsoon (300.91 kg/ha) periods. In the present study,
that the species didnÕt show the relation with P and K. Phosphorous content in the soil may be
due to the addition of fertilizers in higher doses and also from litter (Singh
et al. 2016). Potassium content in
the soil might be attributed to release of more K from organic residue and
application of K containing fertilizers.
Many reports have shown that industrial discharge deposits on
surrounding areas enters the food chain.
These discharges mainly contain toxic substances such
as organic and inorganic deposits as well as toxic metals and affects
the health of mankind as well as the quality of the soil and its productivity (Chhonka et al. 2000; Ho et al.
2012). Most earthworm species are
very sensitive to the alteration in the soil nutrients;
though some species may survive in altered environments (Suther
et al. 2008). The present study
clearly indicates that there is a species specific
relation with the nutrient availability in the soil. Bio indicator activities of the
earthworm species are being studied to know the impact of industrial discharge
on earthworm species in the study area.
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