Effects of tillage practices on spider assemblage in rice paddy fields

Appl. Entomol. Zool. 41 (2): 371–381 (2006) http://odokon.org/

Effects of tillage practices on spider assemblage in rice paddy fields Takashi MOTOBAYASHI,1,* Chikara ISHIJIMA,2,† Motonori TAKAGI,1,†† Mihoko MURAKAMI,1 Ayame TAGUCHI,1 Kazumasa HIDAKA3 and Yasuhisa KUNIMI2 1

Field Science Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology; Fuchu 183–8509, Japan Department of Bioregulation and Biointeraction, Graduate School of Agriculture, Tokyo University of Agriculture and Technology; Fuchu 183–8509, Japan 3 University Farm, Faculty of Agriculture, Ehime University; Hojo 799–2424, Japan 2

(Received 7 November 2005; Accepted 3 March 2006)

Abstract To examine the effects of tillage practices on spider assemblages in rice paddy fields, we investigated the abundance and biomass of spiders in untilled and tilled paddy fields over three cropping seasons (from 1999 to 2001). In total, we collected 6,829 spiders, consisting of 13 species in seven families. The family Lycosidae was the most abundant, followed by Tetragnathidae, Linyphiidae, and Salticidae. Spider abundance and biomass were greater in untilled than in tilled paddies during each cropping season. Although we detected no significant effect of tillage on spider abundance, we did observe a significant effect of tillage on spider biomass in 2000 and 2001. No differences were found in the abundance and biomass of tetragnathid and linyphiid spiders during the cropping season. In contrast, the abundance and biomass of lycosid or salticid spiders tended to be larger in untilled paddies than in tilled paddies, especially later in the cropping season. Key words: Paddy fields; spider abundance; spider assemblage; spider biomass; tillage practices

Parmelee, 1985; Robertoson et al., 1994). Notillage practices generate soil-litter conditions that are very different from those of conventionally tilled systems (Gregory and Musick, 1976). The absence of tillage leaves residue from the previous crop on the soil surface, promoting environmental conditions conductive to the proliferation of a robust soil fauna (House and Stinner, 1983). Furthermore, the generalist predator assemblage that is enhanced by no-tillage management may play an important role in reducing pest populations or plant damage in up-land crop fields (Brust et al., 1985; Clark et al., 1994). The importance of generalist predators has also been examined in rice paddy cropping systems (Kenmore et al., 1984; Nakasuji and Dyck, 1984; Kuno and Dyck, 1985; Way and Heong, 1994; Settle et al., 1996). In particular, spiders are one of the most important predators in rice paddy fields because of their abundance and predation activity (Itô et al., 1962; Kiritani et al., 1972; Kawahara et al.,

INTRODUCTION There is a growing interest in the importance of generalist predators in the biological control of insect pests in agro-ecosystems (see review by Hagen et al., 1999). Spiders, carabid beetles, and staphylinid beetles constitute a major and ecologically important group of generalist predators, consuming a wide range of prey species. Comprehensive studies have shown that generalist predators in arable fields reduced pest numbers and may prevent economically important outbreaks (see review by Symondson et al., 2002). Crop management practices, including soil tillage, may affect the survival of beneficial generalist predators. Previous studies have indicated that generalist predators, including ground beetles and spiders, occur in higher numbers in untilled or reduced-tillage systems than in conventionally tilled up-land cropping systems (House and All, 1981; Blumberg and Crossley, 1983; House and

* To whom correspondence should be addressed at: E-mail: [email protected] † Present address: Laboratory of Entomology, Department of Tea, National Institute of Vegetable and Tea Science, Kanaya 428–8501, Japan †† Present address: Plant Biotechnology Institute, Ibaraki Agricultural Center, Ago, Iwama, Nishi-ibaraki 319–0292, Japan DOI: 10.1303/aez.2006.371

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1974; Oraze and Grigarick, 1989). However, studies of habitat manipulation, including no-tillage practices, for the promotion of spider activity, are limited in rice paddy systems (Settle et al., 1996). Hidaka (1993, 1997) and Ishijima et al. (2004) found that lycosid spiders were more abundant in untilled than in conventionally tilled paddy fields. However, whole spider assemblages in untilled paddy fields have not been examined. Thus, the purpose of this study was to clarify the effect of tillage practices on the composition, abundance, and biomass of the spider assemblages. MATERIALS AND METHODS Paddy fields. The study was conducted in rice paddies belonging to Tokyo University of Agriculture and Technology in Fuchu, Tokyo, Japan, during the growing seasons of 1999–2001. Experimental plots were subjected to two different rice paddy tillage systems: untilled and tilled. All fields were irrigated in early May, and 20-d-old rice (Oriza sativa L., variety Tukinohikari) seedlings were transplanted to the field in mid-May at a density of 16.7 hills m2. Each treatment was replicated four times (plot size: 27.510 m) in 1999, and three times (plot size: 27.511 m) in 2000 and 2001 (Fig. 1). Plastic flashing (25 cm in height) was placed on the sides of each plot to prevent spider emigration and immigration. Each plot was fertilized with 40 kg ha1 of nitrogen, phosphate and potassium several days before transplanting the rice seedlings and with 20 kg ha1 of nitrogen and potassium at the panicle-initiation stage in late July. A herbicidal glyphosate solution (RoundUp®, Monsant Co., Ltd.) and esprocarb granule (Sperkstar®, Nissaan Chemical Ind., Ltd.) were applied to each plot 3 wk before and 10 d, respectively, after transplanting the seedlings. No insecticides or fungicides were applied during the experimental period. Spiders and other arthropods. From July to September of each year, the abundance of spiders and other arthropods in each plot was surveyed using the cylinder method (Southwood, 1978). Once every 10 d, ten hills were systematically selected in each plot, and each hill to be sampled was enclosed by forcing a metal frame (0.30.2 1.2 m) into the soil. All spiders and other arthropods within each frame were then collected using a

Fig. 1. Layout of experimental plots in 1999–2001. UT indicates untilled plots; T indicates tilled plots.

suction apparatus. All collected specimens were transferred to glass vials containing 70% ethanol and returned to the laboratory for identification. After identification, spiders were separated at the family level, dried at 60°C for 48 h, and weighed using an electro-balance. Spiders and other arthropod samples were kept in our laboratory (Field Science Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology; Fuchu, Tokyo 183–8509, Japan). Data analysis. All abundance data were (X 0.5)0.5-transformed prior to analysis. Spider abundance and biomass and the abundance of other insects were analyzed using repeated measures analysis of variance (ANOVA). If tillage treatmentsampling time was significant, the data were analyzed using ANOVA with a Bonferroni correction for each sampling time. RESULTS Spider assemblages In total, we collected 6,829 spiders, consisting of 15 species in seven families (3,993 in untilled and

Effects of Tillage Practices on Spiders

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Table 1. Number of spiders collected in untilled and tilled paddy fields in 1999–2001 Number Family

Species Untilled 2,456 (60.9)b 1,811 642 3

1,322 (46.1) 942 376 4

Tetragnathidae Tetragnatha caudicula (Karsch, 1879) Tetragnatha vermiformis Emerton, 1884 Tetragnatha maxllosa Thorell, 1895 Tetragnatha squamata Karsch, 1879 Pachygnatha quadrimaculata Bös et Str., 1906 Pachygnatha clercki Sundevall, 1823 Tetragnatha spp.a Dyschiriognatha spp.a Juveniles of Tetragnathidae

769 (20.0) 104 23 16 14 129 3 240 80 160

892 (32.4) 85 9 6 7 183 5 272 137 188

Linyphiidae Ummeliata insecticeps Bös et Str., 1906 Gnathonarium exsiccatum Bös et Str., 1906 Erigone prominens Bös et Str., 1906 Juveniles of Linyphiidae

434 (10.8) 20 236 5 173

479 (16.6) 35 273 2 169

Salticidae

258 (6.4) 37 221

64 (2.2) 7 57

Clubionidae Clubiona japonicola Bös et Str., 1906 Juveniles of Clubionidae

26 (0.6) 3 23

25 (0.9) 2 23

Thomisidae Misumenops tricuspidatus (Fabricius, 1775) Juveniles of Thomisidae

5 (0.1) 3 2

2 (0.1) 0 2

Theridiidae Coleosoma octomaculatum (Bös et Str., 1906) Juveniles of Theridiidae

9 (0.2) 1 8

13 (0.4) 1 12

Unidentified

36 (0.9)

39 (1.3)

Total number

3,993

2,836

Lycosidae Pardosa pseudoannulata (Bös et Str., 1906) Pirata subpiraticus (Bös et Str., 1906) Juveniles of Lycosidae

Mendoza canestrinii (Ninni in Canestrini & Pavesi 1868) Juveniles of Salticidae

a b

Tilled

Juveniles that were not identifiable to species. Number in parentheses denote the percentages of each family collected in each tillage treatment.

2,836 in tilled paddies; Table 1). Lycosidae was the most abundant family, followed by Tetragnathidae, Linyphiidae, and Salticidae. These families accounted for more than 97% of the captured spiders. The occurrence of species of Culbionidae, Thomisidae and Theridiidae was extremely rare.

Two species of Lycosidae, Pardosa pseudoannulata (Bös. et Str.) and Pirata subpiraticus (Bös. et Str.), were very abundant, particularly in untilled plots. Tetragnatha caudicula (Karsch), Pachygnatha quadrimaculata Bös. et Str., and Gnathonarium exsiccatum (Bös. et Str.) were also abundant.

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increased rapidly in untilled plots and increased slowly in tilled plots, except in 1999. The biomass in untilled plots reached twice the amount in tilled plots in 1999 (Fig. 2B). We found a significant effect of tillage practices on the biomass of spiders in 2000 and 2001 (repeated measures ANOVA; Table 2). A significant interaction was observed between treatment and sampling time for spider abundance in 2000. Thus,

The temporal change in the abundance of spiders was similar during the three years. Although we observed no difference in spider abundance between untilled and tilled plots in early summer, spiders were somewhat more abundant in untilled plots in mid- to late summer except in 1999 (Fig. 2A). In contrast, spider biomass was slightly greater in untilled plots than in tilled plots in early summer. In mid- to late summer, spider biomass

Fig. 2. Temporal changes in the abundance (A) and biomass (B) of spiders in untilled and tilled paddies. Closed symbols indicate untilled plots; open symbols indicate tilled plots; vertical lines indicate standard error; * p0.05.

Table 2. Results of repeated measures analysis of variance to determine differences in spider abundance and biomass among treatments and sampling times in 1999–2001. There were two treatments (untilled and tilled) and seven sampling times in each year Number Year

Biomass

Source d.f.

F

p

d.f.

F

p

1999

Treatment Sampling time TreatmentSampling time

1 6 6

2.31 48.17 1.168

0.179 0.01 0.344

1 6 6

4.099 6.55 0.618

0.089 0.01 0.15

2000


1 6 6

5.451 86.09 5.52

0.079 0.01 0.01

1 6 6

7.99 19.48 4.402

0.047 0.01 0.01

2001


1 6 6

0.757 50.39 1.387

0.433 0.01 0.259

1 6 6

41.3 16.82 2.745

0.01 0.01 0.035

The number of spiders was (X0.5)0.5-transformed prior to analysis.


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Fig. 3. Temporal changes in the abundance of the four most common families of spiders in untilled and tilled paddies. Closed symbols indicate untilled plots; open symbols indicate tilled plots; vertical lines indicate standard error; * p0.05.

we analyzed abundance and biomass using ANOVA with a Bonferroni correction for each sampling time. Significant differences in biomass were detected for collections on 15 September in 2000 (p0.05), and 30 August and 12 September in 2001 (p0.05). Common spider families To examine the effect of tillage practices on spider assemblages more closely, the four most commonly trapped families (Lycosidae, Salticidae,

Tetragnathidae, and Linyphiidae) were analyzed separately. Temporal changes in the abundance of these families collected from the two tillage treatments are shown in Fig. 3. Although we found no difference between untilled and tilled plots in the abundance of lycosid and salticid spiders in early summer, their abundance increased rapidly in untilled plots and increased slowly in tilled plots; therefore, these spiders were more abundant in untilled than in tilled plots in mid- to late summer in each crop-

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Fig. 4. Temporal changes in the biomass of the four most abundant families of spiders in untilled and tilled paddies. Closed symbols indicate untilled plots; open symbols indicate tilled plots; vertical lines indicate standard error; * p0.05.

ping season. The abundance of tetragnathid and lyniphiid spiders also increased slowly in early to mid-summer and increased rapidly in late summer. However, we observed no difference in the trends of abundance for these two families between the two tillage treatments. Temporal changes in the biomass of these families collected from the two tillage treatments are shown in Fig. 4. Each cropping season, the biomass of lycosid spiders was slightly greater in untilled than in tilled plots in early summer. In midto late summer, the biomass of lycosid spiders in-

creased rapidly in untilled plots and increased slowly in tilled plots, so the final biomass of lycosid spiders in untilled plots was two to four times as much as in tilled plots. The biomass of salticid spiders tended to be greater in untilled than in tilled plots in each cropping season; their biomass increased rapidly in untilled plots in mid- to late summer, particularly in 2000 and 2001. The biomass of lyniphiid spiders was extremely low in untilled and tilled plots, and was lower than that of the other three families in each cropping season. The trend in the biomass of tetragnathid spiders


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served in early to mid-summer; whereas, the latter species, relatively smaller in size, increased in late summer. Such changes in species composition within the family during cropping season reflected on the fluctuation in biomass of this family. In both

showed different trends from the other three families. It fluctuated between 5 and 20 mg plot1 in each cropping season. T. caudicula and P. quadrimaculata dominated within this family. The former species, relatively larger in size, was mainly ob-

Table 3. Results of a repeated measures analysis of variance to determine differences in the abundance and biomass of common spider families among treatments and sampling times in 1999–2001. There were two treatments (untilled and tilled) and seven sampling times in each year Number Year

d.f. Lycosidae

Salticidae

Tetragnathidae

Linyphiidae

Biomass

Source F

p

d.f.

F

p

1999


1 6 6

6.453 54.73 1.852

0.044 0.01 0.116

1 6 6

5.647 13.19 1.693

0.055 0.01 0.15

2000


1 6 6

8.219 65.9 5.52

0.045 0.01 0.01

1 6 6

9.269 14.85 3.657

0.038 0.01 0.01

2001


1 6 6

0.602 66.95 4.863

0.481 0.01 0.01

1 6 6

19.96 14.12 2.143

0.011 0.01 0.085

1999


1 6 6

0.818 2.434 0.817

0.4 0.044 0.563

1 6 6

0.855 1.115 1.006

0.39 0.372 0.436

2000


1 6 6

2.096 6.734 1.649

0.221 0.01 0.162

1 6 6

2.228 4.562 1.031

0.209 0.01 0.429

2001


1 6 6

27.961 26.218 18.366

0.01 0.01 0.01

1 6 6

41.301 16.828 2.745

0.01 0.01 0.035

1999


1 6 6

0.742 4.888 2.312

0.422 0.01 0.054

1 6 6

1.381 2.649 0.598

0.284 0.031 0.730

2000


1 6 6

0.415 22.766 2.282

0.555 0.01 0.057

1 6 6

1.539 1.873 0.438

0.283 0.127 0.846

2001


1 6 6

0.178 13.997 1.079

0.695 0.01 0.403

1 6 6

3.893 2.164 1.734

0.120 0.083 0.156

1999


1 6 6

0.142 2.319 0.441

0.719 0.054 0.846

1 6 6

0.638 1.927 0.935

0.455 0.103 0.482

2000


1 6 6

0.236 15.011 0.364

0.652 0.01 0.915

1 6 6

0.434 5.267 0.275

0.546 0.01 0.943

2001


1 6 6

0.751 21.695 1.395

0.435 0.01 0.257

1 6 6

2.267 4.951 0.426

0.207 0.01 0.854

The number of spiders was (X0.5)0.5-transformed prior to analysis.

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tillage treatments, the biomass of lycosid spiders was consistently greater than that of the other families at the sampling times; thus, the biomass of whole spider assemblages followed a trend similar to that of lycosid spiders. We used repeated measures of ANOVA to examine the effect of tillage practices on spider abundance and biomass (Table 3). There was no significant effect of tillage practices on the abundance and biomass of tetragnathid and linyphiid spiders. However, we did find a significant effect of tillage practices on the abundance of lycosid spiders in 1999 (p0.05) and 2000 (p0.05), and on the biomass of these spiders in 2000 (p0.05) and 2001 (p0.05). Moreover, there were significant effects of tillage practices on the abundance and biomass of salticid spiders in 2001 (p0.01). We also found a significant interaction of farming type and sampling time on the abundance of lycosid spiders in 2001 (p0.05). Thus, abundance and biomass were analyzed using ANOVA with a Bonferroni correction for each sampling time. There was a significant effect of tillage treatment on the abundance of lycosid spiders on 5 and 15 September and on the biomass on 15 September in 2000 (p0.05), and abundance and biomass of salticid spiders on

Fig. 5.

29 August and 12 September in 2001 (p0.05). Potential prey abundance Temporal changes in the abundance of potential prey collected from untilled and tilled plots are shown in Fig. 5. Potential prey taxa included insects in the orders Homoptera (mainly Nephotettix cincticeps, Laodelphax striatellus and Sogatella furcifera), Diptera (mainly Chironomidae), and Hemiptera (mainly Microvelia horvathi), which were the three most common, as well as Collembola, and Lepidoptera. We did find a significant effect of tillage treatment on the abundance of dipterans in 2000 and 2001 (repeated measures ANOVA; p0.01 and p0.05, respectively) and hemipterans in 2001 (repeated measures ANOVA; p0.05). A significant effect of tillage treatment was found for dipterans collected on 15 July in 2000 (p0.001) and 17 July in 2001 (p0.05), and for hemipterans collected on 17 and 27 July in 2001. In contrast, the abundance of homopterans tended to be slightly greater in tilled than in untilled plots, particularly in early summer; this has been discussed in a previous report (Ishijima et al., 2004).

Temporal changes in the abundance of potential prey of spiders in untilled and tilled paddies in 1999–2001.


DISCUSSION The rice paddy fields supported diverse spider assemblages that fed on common rice pests such as rice planthoppers and lepidopteran insect pests (Itô et al., 1962; Kiritani et al., 1972; Heong et al., 1992; Way and Heong, 1994). The abundance of spiders was enhanced by the untilled treatment. This agreed with a previous study of the effects of Chinese milky vetch winter mulch and an untilled rice paddy system on predator assemblages (Hidaka, 1993, 1997). Moreover, in this study, the biomass of spiders was enhanced significantly by untilled treatment. Several studies have reported that generalist predators, including spiders, are enhanced in untilled or reduced-tillage cropping systems in upland agro-ecosystems (Brust et al., 1985; Brust and House, 1990; Kendall et al., 1991; Symondson et al., 1996; Clark et al., 1997). Reduced-tillage cropping systems are favorable for spiders because of a richer habitat structure (more weeds and plant residues), lower disturbance, higher soil moisture, and the proliferation of detritivores (see review by Wardle, 1995; Sunderland and Samu, 2000). In conventionally tilled rice paddy systems, spider habitat is destroyed by flooding and puddling before transplanting. In contrast, in untilled paddies, the structural complexity of the spider habitat is maintained by plant residues until transplanting, possibly resulting in the early establishment, reproduction, and enhancement of some spiders. Although no difference was found in the abundance of spiders in both treatments in early to midsummer, the biomass of spiders in untilled plots tended to be greater than that in tilled plots. This was mainly reflected with the larger biomass of lycosid and salticid spiders in untilled plots. Our previous study showed that populations of lycosid spiders were established earlier in untilled plots (Ishijima et al., 2004). Additionally, the abundance of salticid spiders was slightly greater in untilled plots than in tilled plots in early to mid-summer, thus the population of salticid spiders could be established earlier in untilled plots than in tilled plots. We found that dipterans were more abundant in untilled than in tilled paddies, particularly in the early cropping season (Fig. 5). This was mainly due to accumulated rice plant and weed residues on the soil surface acting as food for dipterans (War-

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dle, 1995). Murata (1995) and Settle et al. (1996) suggested that dipterans are important prey for some predators, including spiders, in paddy fields. In the paddies examined here, the taxonomic composition of lycosid spider prey was dominated by dipterans in the early cropping season (Ishijima et al., 2006). Consequently, dipterans may act as an effective alternative prey for some spiders in untilled paddies. The abundance of hemipterans insects, mainly dominated by species of Microvelia, was also slightly greater in untilled than in tilled paddies. Microvelia is an important predator of rice planthoppers (Nakasuji and Dyck, 1984). Lycosid spiders were observed to feed on Microvelia relatively frequently (Ishijima et al., 2006), suggesting that Microvelia is an alternative prey of spiders. These results suggest that no-tillage management in rice paddy systems enhanced spider assemblages through enhancement of the structural complexity of the habitat and thereby providing alternative prey. The composition of spider assemblages differed somewhat between untilled and tilled paddies. The numbers and biomass of lycosid and salticid spiders were greater in untilled than in tilled plots. In contrast, the number of tetragnathid and linyphiid spiders was similar in untilled and tilled plots. Thus, the response of spiders to tillage practices differed among spider families. Kiritani (1985) and Hidaka (1998) proposed that stable habitats with little disturbance supported more non-migratory species, but the unstable habitats were dominated by migratory species. In winter wheat fields, nonmigratory spider species (including Pardosa spp.) were affected by field management practices; however, ballooning species (including Erigone spp.) appeared to be less affected by management (Schmidt et al., 2005). In rice paddies, Pardosa pseudoannulata and Pirata subpiraticus are considered non-migratory (Tanaka and Hamanaka, 1968; Kawahara et al., 1974), while Ummeliata insecticeps, Gnathonarium exsiccatum, and Erigone prominens remain and overwinter in paddy fields during fallow season, emigrate from paddy fields in spring, and then immigrate from surrounding areas in early summer by ballooning (Okuma, 1974; Kawahara, 1975). However, the migratory activity of other species (including salticid and tetragnathid spiders observed in our fields) during

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the fallow season is poorly understood. In general, our results coincide with those of a previous study on spiders (Schmidt et al., 2005). Moreover, several studies have indicated that the response of predatory ground beetles to tillage practices differs among species, and the effects of tillage practices depend on species-specific characteristics and lifecycles (Hance et al., 1990; Cárcamo et al., 1995; Clark et al., 1997). Thus, further investigations of lifecycles, responses to prey, and the migratory activity of each spider species are warranted to understand the mechanisms resulting in the augmentation and organization of spider assemblages in untilled rice paddy fields. ACKNOWLEDGEMENTS This work was supported in part by a Grant-in-Aid from the Japan Society for the Promotion of Science (No. 16380220).

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