Nematode communities on putting greens, fairways, and roughs of organic and conventional cool-season golf courses

Applied Soil Ecology 121 (2017) 161–171

Contents lists available at ScienceDirect

Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil

Nematode communities on putting greens, fairways, and roughs of organic and conventional cool-season golf courses Elisha Allan-Perkinsa, Daniel K. Manterb, Robert Wickc, Scott Ebdona, Geunhwa Junga, a b c

MARK

⁎

Stockbridge School of Agriculture, University of Massachusetts Amherst, 206 Paige Laboratory, 161 Holdsworth Way, Amherst, MA 01003, United States USDA-ARS, 2150 Centre Avenue, Building D, Suite 100, Fort Collins, CO 80526, United States Stockbridge School of Agriculture, University of Massachusetts Amherst, 105 Fernald Hall, 230 Stockbridge Road, Amherst, MA 01003, United States

A R T I C L E I N F O

A B S T R A C T

Keywords: Turfgrass Soil Maturity indicies Ecological indices

Nematodes are an important component of the golf course ecosystem. Many species provide benefits to turfgrass, while others can cause significant damage. Previous studies on golf courses have focused only on herbivore nematodes, mostly on putting greens. This study aimed to characterize all nematode trophic groups and nematode maturity and ecological indices under different management intensities (depicted by roughs, fairways, and putting greens) of three golf courses representing conventional and organic management types over two seasons in 2013 and 2014. The putting greens on all three golf courses had lower diversity and herbivore (plantparasitic) index (PPI) values than the other management areas. The relative abundance of herbivores, bacterivores, and structure index (SI) values differed among organic and conventional management. Canonical correspondence and multiple stepwise regression analyses revealed pH, phosphorous, and organic matter were positively related to increased herbivores and negatively related to increased bacterivores. The results of this study can be used to develop alternative management practices aimed at decreasing problematic herbivore populations on putting greens and increasing potentially beneficial bacterivores.

1. Introduction Nematodes can cause significant damage on golf courses, especially on putting greens, resulting in diminished uniformity on the putting surface. Plant pathogenic nematodes (herbivores) are ubiquitous on golf courses and feed on turfgrass roots, which damages tissues and removes photosynthates from the plant. When herbivore populations reach sufficient densities, they can cause wilting, stunted growth, yellowing, thinning, or death, all of which affect aesthetics and game play (Nelson, 1995). In the past herbivore populations were controlled by nematicides and in extreme cases soil fumigation (Walker et al., 2002). However, many of these products have been banned or have restricted use on turfgrass (Crow, 2007; Martin, 2015). New nematicides are currently being developed, but none have been as effective as previous chemistries, such as fenamiphos, or are only registered in certain states (Martin, 2015; Nelson, 1995). The integration of alternative management strategies is needed to manage herbivore populations. Nematodes also provide many beneficial functions to turfgrasses. Low levels of herbivory promote growth of host plants (Bardgett et al., 1999; Neher, 2010). In addition to the herbivores, the bacterivores, fungivores, carnivores, and omnivores drive important soil ecosystem

processes, such as spreading microbes throughout the soil, aiding in decomposition, and preying on pathogens (Cheng et al., 2008; Neher, 2001, 2010). Bacterivores can increase rhizobacteria in the soil (Briar et al., 2007; Knox et al., 2003). Carnivores and bacterivores increase nitrogen mineralization, thus increasing its availability to plants, promoting plant growth (Briar, 2007; Ekschmitt et al., 1999; Ferris et al., 1998; Ingham et al., 1985). Therefore, there is potential to increase turfgrass health by developing management strategies that encourage beneficial nematodes. Nematodes have been used as indicators of overall soil health since the late 1980’s. These indices may provide insight into how management strategies affect other invertebrates and microbes (Neher, 2010). They have been selected as the ideal soil organism for predicting overall soil community health due to their central position in the soil food web and effect on microbes and decomposition pathways (Bongers and Bongers, 1998; Ferris and Matute, 2003; Freckman, 1988; Moore and de Ruiter, 1991; Neher, 2001, 2010). Additionally, nematodes react to disturbance quicker than larger organisms but slower than microbes (Bongers and Bongers, 1998; Neher, 2001). After identification and classification at the genus or family level, nematodes are assigned to their trophic group and colonizer-persister (cp) value (Bhusal et al.,

⁎

Corresponding author. E-mail addresses: [email protected] (E. Allan-Perkins), [email protected] (D.K. Manter), [email protected] (R. Wick), [email protected] (S. Ebdon), [email protected] (G. Jung). http://dx.doi.org/10.1016/j.apsoil.2017.09.014 Received 13 March 2017; Received in revised form 5 September 2017; Accepted 7 September 2017 0929-1393/ Published by Elsevier B.V.

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

ingredient was Bacillus subtilis, Bayer CropScience, North Carolina, United States of America), Serenade™ (active ingredient was Bacillus licheniformis, Bayer CropScience, North Carolina, United States of America), and Waipuna Weed Control System™ (active ingredients were hot water and foaming detergent, Waipuna Systems LTD, Illinois, United States of America). The conventional courses were established in 1926 and 1939 with native push-up putting greens and have used synthetic pesticides and fertilizers since their construction. The course established in 1939 represents conventional management on the putting greens and reduced input management on the fairways and roughs, so we have designated this course as “hybrid” management. The course had reduced pesticide applications, one synthetic fungicide application in eighteen years, Secure™ (active ingredient was fluazinam, Syngenta Crop Protection, Greensboro, North Carolina, United States of America) on its fairways and applied the biological control product, Pseudomonas aureofaciens TX-1, to the fairways through the irrigation lines. The organic and the two conventional golf courses received sand-based topdressing on the putting greens at least twice per year. The courses were sampled in mid May and early September of 2013 and 2014. The mean temperatures in May 2013 was 11.7 °C and 14.4 °C in 2014. In September of 2013 and 2014 the mean temperatures were 18.9 °C and 22.2 °C, respectively. The grass composition on the putting greens of all three courses was Agrostis stolonifera (creeping bentgrass) with some Poa annua (annual bluegrass) encroachment on the conventional and hybrid courses. The fairways were a mixture of creeping bentgrass, annual bluegrass, and some Lolium perenne (perennial ryegrass). The roughs were a mixture of annual bluegrass, perennial ryegrass, fescues (Festuca spp.), and some weed species.

2014; Bongers, 1990; Bongers and Bongers 1998). Ecological indices, such as free-living maturity including cp1 (MI) and excluding cp1 (MI25), herbivore maturity (PPI), combined maturity (ΣMI25), enrichment (EI), structure (SI), and channel (CI), can be calculated and used to predict soil conditions (Bongers, 1990; Ferris et al., 2001; Korthals et al., 1996; Neher et al., 2004). Additionally, many nematologists calculate nematode trophic diversity, using the Hills N1 equation (N1), to determine how diverse the nematode communities are, which is based on the presence of rare nematode trophic groups (fungivores, carnivores, and omnivores) compared to the dominant nematode groups (bacterivores and herbivores) (Neher, 2001). These indices have been used to understand nematode and soil communities from many different ecosystems including agricultural fields and natural grasslands. Studies have compared organic and conventional management practices to determine if organic practices have positive effects on soil communities. Pesticides have differing effects on nematodes depending on the product and amount used, but studies have found an increase in herbivores and a decrease in bacterivores, fungivores, omnivores, and carnivores following the application of different pesticides (Griffin and Anderson, 1978; Sipes and Schmitt, 1989; Thoden et al., 2011; Yardim and Edwards, 1998; Zhao et al., 2013). Despite the many studies on nematodes in native grasslands and agricultural fields, there have been few studies on nematode communities on golf courses. Past golf course studies have generally focused only on the abundance of herbivores, since they are of economic importance to the turfgrass industry, leaving out the potential beneficial nematodes, such as the bacterivores (Jordan and Mitkowski, 2006; Morris et al., 2013; Walker et al., 2002). However, by understanding how all nematode trophic groups interact under different turf management programs and intensities we may be able to develop new management strategies to decrease herbivores and increase beneficial nematodes. The objectives of this study were to determine if nematode communities differ among highly managed turf areas (represented by the putting greens), moderately managed turf areas (fairways), and lowly managed turf areas (roughs). We chose three golf courses representing organic, reduced input (denoted as “hybrid”), and conventional management programs to see if management program interacted with intensity to change nematode communities. However, since there is only one truly organic golf course in the United States we are only able to draw inferences for the differences among management areas. We hypothesized that the roughs and fairways would contain higher amounts of free-living nematodes than the more intensely managed putting greens. Additionally, the putting greens would show the lowest SI and MI, but a higher PPI than the less disturbed roughs and fairways. Since golf course fairways and putting greens receive high nutrient inputs, we hypothesized that both areas would have high enrichment index values.

2.2. Sampling strategy Three golf course holes (representing one area of play from tee box to putting green) per course were randomly selected and sampled using a 2.5 cm diameter soil core at a depth of 10 cm below the thatch to provide biological replicates of each golf course. All three management areas (roughs, fairways and putting greens) were sampled per hole. Four approximately equidistant transects were used to sample the fairways and roughs (Fig. 1a). Three sampling locations were set up along each transect within the fairway and three samples were taken at each location and pooled for a total of twelve samples per fairway. Each transect extended 4.6 m from the edge of the fairway into one side of the rough. Eight samples were taken at each rough sampling location and pooled for a total of four samples per rough (Fig. 1a). Two concentric circle transects were established on the putting greens (Fig. 1b). The outermost transect was set up 1.5 m from the edge of the putting green and the inner transect was set up 4.6 m from the edge of the putting green (Fig. 1b). Four sampling locations were set up on each transect and four samples were taken at each location and pooled for a total of eight samples per putting green (Fig. 1b). Global positioning system (GPS) coordinates were taken at each sample location and the distances between sample transects and irrigation heads were recorded to ensure repeated sampling at the same locations for May and September of 2013 and 2014. In September of 2014 the organic golf course began the process of renovating their putting greens and we were unable to sample our third hole for a fourth time. Therefore, we sampled a different putting green from a nearby hole. All holes on all the golf courses had similar shade, grass species, and cultural practices with a few exceptions. The roughs had more variable grass species and shade amounts. The organic putting greens were rolled each day, but the conventional and hybrid courses’ putting greens were not. All samples were immediately placed on ice and transported back to the laboratory and were stored at 4 °C.

2. Materials and methods 2.1. Collection sites Three golf courses on Martha’s Vineyard, Massachusetts, United States of America located within 15 km of one another were selected for study. The exact location and identification of the courses is withheld per request of the golf courses’ managers. One golf course has been maintained using an organic program and two golf courses have been maintained using conventional programs. The organic course was built in 2002 and has sand-based putting greens constructed according to United States Golf Association (USGA) specifications (U.S. Golf Association Green Section Staff, 2004). It has never received synthetic pesticides or fertilizers. Fertilizer applications were made using seaweed extract and animal by-products, such as blood and bone meal. The organic pesticides applied were CivitasONE™ (active ingredients were petroleum byproduct, synthetic isoparaffin, and a copper-based pigment, Suncor Energy, Inc., Alberta, Canada), Rhapsody™ (active

2.3. Nematode analysis Soil samples were pooled within a management area per hole for a 162

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

Fig. 1. Sampling schematic for a) fairways and roughs b) putting greens The … indicates transects and * indicates sampling sites where soil cores were taken.

2.5. Statistical analysis

total of three samples per hole, nine samples per golf course, and a total of twenty-seven composite nematode samples per sampling time. Nematodes were extracted in triplicate using the modified Cobb’s sifting and gravitation method followed by centrifugation and sugar flotation (Neher, 1999; Neher and Campbell, 1994), which is the preferred method for recovery of the greatest diversity of nematode genera (McSorley and Walter, 1991; Neher, 2001; Neher et al., 1995). This protocol was modified from extracting 100 cubic centimeters (cc) to 25 cc of soil per sample. Nematodes were counted under a Zeiss Primo Vert inverted compound microscope after identification to genus or family level using the following identification keys (the English translation of Bongers, 1988; Goodey, 1963; Mai and Lyon, 1975; Tarjan et al., 2014). The counts of all three technical replicates were averaged and were not corrected for extraction efficiency as per common practice (Neher, 1999). Nematode genera were assigned to their appropriate trophic groups and cp values (Bongers and Bongers, 1998; Neher, 2001; Neher et al., 2004; Okada et al., 2005; J. LaMondia, personal communication; Sohlenius et al., 1977; Yeates et al., 1993). Members of the Anguinidae often feed as fungivores and herbivores, therefore they were equally split and one half assigned to herbivores and the other to fungivores (Briar et al., 2011). The MI, MI25, PPI, ΣMI25, CI, EI, SI, and Hills trophic diversity (N1) were calculated using weighted abundances for each management area on each hole as described in Neher (1999) and Neher et al. (2004, 2014).

Repeated measures analysis of variance was performed by PROC MIXED in SAS version 9.4 (SAS Institute, Cary, North Carolina, United States of America) for each golf program (organic, hybrid, and conventional) to determine differences among management areas (rough, fairway, putting green) among the three holes using a split–split plot design using years as the split plot and season as the split–split plot for all possible interactions for the total nematode counts, relative abundances of the different trophic groups, the maturity and ecological indices, and the soil properties. These metrics were chosen because previous studies have shown they are more accurate at differentiating among soil ecological conditions than total abundances of individual trophic groups alone (Neher, 1995). Where significant, differences among interactions were determined using PROC GLIMMIX for management area separated by season × year. To meet the criteria for parametric analyses, data for the relative abundances of trophic groups, percent organic matter, and soil texture (percent sand, silt and clay) were transformed with arcsine of the square root of the proportions (Neher et al., 2014). Total nematode data, nematode ecological indices, pH, phosphorus (P), potassium (K), and micronutrients were transformed by taking the natural log of each value and adding 0.1 (Neher et al., 2014). Canonical correspondence analysis, implemented in R (version 3.1.0, R Core Team, Auckland, New Zealand), was performed using edaphic properties and nematode trophic groups, maturity indices, and ecological indices. Multiple regression analysis in R was used to determine the relationship among nematode trophic group relative abundance, maturity indices, and ecological indices to soil properties. All independent variables were removed and entered into the final model using forward and backward eliminations with α set to 0.15.

2.4. Soil analysis Two hundred fifty milliliters of each of the composite soil samples (twenty-seven per sampling time, total one hundred and eight samples) were passed through a 2-mm sieve and oven dried at 35 °C for approximately 48–72 h. The samples were submitted to the University of Massachusetts Amherst Plant Tissue and Soil Testing Laboratory for soil analysis (pH, exchangeable acidity, extractable P, K, Ca, Mg, Fe, Mn, Zn, Cu, B, S, Pb, Al), soil organic matter, and soil texture analysis. 163

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

Fig. 2. a) Total abundance of nematodes and the relative abundance of each trophic group among management areas and sampling dates for b) conventional, c) hybrid, and d) organic courses. The same letters indicate statistically similar counts within a sampling date (P < 0.05) and a lack of letters indicates no significant differences determined by repeated-measures ANOVA. R, F, and P denote roughs, fairways and putting greens, respectively.

3. Results

Rhabditae, Monhysteridae, Panagrolaimidae, and Plectidae. The relative abundance of bacterivores was also significantly different among management areas for all three golf courses (conventional p = 0.0331, hybrid p = 0.0018, and organic p = 0.0146). On the hybrid course, bacterivores were lowest on the putting greens on all sampling dates (Fig. 2c). The relative abundance of bacterivores was generally highest on the fairways of the conventional course and the putting greens of the organic course (Fig. 2b and d). The other three trophic groups were less abundant than the herbivores and bacterivores. The fungivores consisted of the family Anguinidae and they were only significantly different among management areas on the organic course (p = 0.0497), generally being greatest on fairways (Fig. 2d). The omnivores (Nordiidae) were also only significantly different among management areas on the organic course (p = 0.0069) generally being the lowest on the putting greens. The carnivores (Mononchidae and Triplylidae) were significantly different among management areas on all three courses (conventional p = 0.0134, hybrid p = 0.0056, and organic p = 0.0434). They were lowest on the putting greens for the conventional and hybrid course and higher on the putting greens for the organic course, except on the May 2014 sampling date (Fig. 2b, c, and d). Trophic diversity was significantly different among management areas for all courses (conventional p = 0.0109, hybrid p = 0.0012, and organic p = 0.0323) and generally was highest on the fairways and lowest on the putting greens for all three courses (Table 1).

3.1. Nematode community Approximately 60–400 nematodes were counted in each 25 cc of soil per sample, all of which contained every trophic group except for the omnivores, which were not present in the putting greens of the conventional and hybrid golf course programs. The total number of nematodes on the conventional course was significantly different among management areas (p = 0.0331) and management area × season × year (p = 0.0318) with the putting greens generally having the lowest number of nematodes (Fig. 2a). Although all management areas on the organic course had similar total nematodes, the putting greens generally had the fewest nematodes (Fig. 2a). This was not true for the hybrid course. Management areas were significantly different (p = 0.0210), as was management area × season × year (p = 0.0125), and the putting greens generally had the highest number of nematodes (Fig. 2a). Total nematodes were greater in May 2013 than May 2014, most likely due to the more severe winter in 2012–2013 compared to a very mild winter in 2013–2014. The majority of nematodes identified were herbivores and bacterivores. The herbivore families identified were Anguinidae, Criconematidae, Dolichoridae, Heteroderidae, Hoplolaimidae, Longidoridae, Trichodoridae, and Tylenchidae. There were significant differences for the relative abundance of herbivores among management areas on all three golf courses (conventional p = 0.0170, hybrid p = 0.0010, and organic p = 0.0056). Herbivore abundance was greatest on the putting greens for the conventional and hybrid course and lowest on the organic course on almost every sampling data (Fig. 2b, c, and d). The bacterivore families identified were Cephalobidae, Diplogasteridae,

3.2. Nematode maturity and ecological indices The free-living maturity index (MI) was significantly different among management areas for the conventional (p = 0.0029) and 164

165

Sept. 2014

May 2014

Sept. 2013

May 2013

Sept. 2014

May 2014

Sept. 2013

May 2013

Sept. 2014

May 2014

Sept. 2013

May 2013

Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen Rough Fairway PuttingGreen

1.58 1.52 1.26 1.90 1.91 1.41 2.22 2.03 1.54 2.13 1.64 1.58 2.05 2.19 1.53 1.54 1.67 1.49 2.21 2.53 2.32 1.92 1.74 1.79 1.71 2.04 2.70 1.50 1.76 2.86 2.55 2.35 2.47 2.23 2.01 2.27

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.04 0.07 0.02 0.16 0.11 0.05 0.03 0.16 0.18 0.08 0.05 0.05 0.15 0.12 0.03 0.22 0.11 0.06 0.05 0.07 0.07 0.12 0.11 0.02 0.19 0.08 0.03 0.09 0.11 0.07 0.39 0.12 0.14 0.07 0.07 0.12

a ab b a a b a a b a b b a a b – – – – – – – – – b b a b b a – – – – – –

2.52 2.41 2.00 2.89 2.65 2.52 2.63 2.89 2.71 2.78 2.54 2.43 2.70 2.82 2.05 2.48 2.68 2.27 2.68 3.11 2.81 2.67 2.74 2.15 2.97 2.62 2.96 2.78 2.65 3.02 3.41 2.93 2.92 3.06 2.74 2.91

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

MI25§ 0.05 0.10 0.00 0.19 0.12 0.07 0.13 0.17 0.29 0.19 0.06 0.16 0.10 0.04 0.05 0.11 0.18 0.12 0.08 0.06 0.09 0.10 0.11 0.02 0.10 0.10 0.07 0.20 0.21 0.04 0.17 0.17 0.04 0.31 0.11 0.09

a ab b – – – – – – – – – a b b ab a b b a ab a a b – – – – – – – – – – – –

3.27 3.23 2.96 3.83 3.09 2.87 3.25 3.45 2.78 3.17 3.21 2.78 3.01 3.04 2.99 3.04 3.00 2.92 3.01 3.20 2.85 3.13 2.97 2.76 3.71 2.74 2.58 3.06 2.97 2.26 3.03 3.08 2.47 3.02 3.02 2.31

PPI# ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.27 0.15 0.01 0.25 0.16 0.04 0.23 0.05 0.09 0.09 0.02 0.15 0.11 0.07 0.00 0.06 0.13 0.02 0.07 0.03 0.05 0.05 0.05 0.06 0.19 0.07 0.15 0.04 0.11 0.15 0.07 0.18 0.07 0.07 0.19 0.04

– – – a b b ab a b – – – – – – – – – ab a b a ab b a b b a a b a a b a a b 5.78 5.64 4.96 6.72 5.73 5.39 5.88 6.34 5.50 5.95 5.75 5.21 5.71 5.85 5.04 5.52 5.69 5.19 5.69 6.31 5.66 5.80 5.71 4.91 6.68 5.35 5.54 5.84 5.62 5.28 6.44 6.01 5.39 6.08 5.76 5.22

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

ΣMI25†† 0.31 0.24 0.01 0.29 0.28 0.11 0.35 0.17 0.37 0.18 0.04 0.30 0.09 0.04 0.05 0.09 0.25 0.12 0.03 0.03 0.15 0.11 0.11 0.07 0.10 0.17 0.15 0.17 0.31 0.18 0.10 0.31 0.11 0.25 0.15 0.13

– – – a b b – – – – – – a a b ab a b b a b a a b a b b – – – a ab b a ab b 91.30 91.25 92.27 89.10 85.23 93.61 70.54 85.67 92.56 78.03 88.65 87.17 87.56 90.79 80.16 91.29 90.90 89.23 75.38 86.55 76.56 87.00 91.88 74.53 92.45 78.39 84.51 93.92 88.06 62.37 85.60 74.49 86.20 84.06 84.42 89.77

EI‡‡ ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.41 1.92 0.64 0.65 0.14 1.10 6.40 3.31 2.59 8.94 1.36 4.82 3.24 0.46 3.37 3.27 2.06 0.78 3.50 1.49 4.70 1.56 1.51 0.29 4.00 4.28 5.48 2.18 3.95 7.97 6.69 4.24 2.67 6.04 0.95 1.10

– – – – – – b a a – – – ab a b – – – b a b a a b – – – a a b – – – – – – 61.18 ± 4.32 52.88 ± 9.37 0.00 ± 0.00 72.52 ± 6.84 64.12 ± 7.34 50.07 ± 3.43 62.40 ± 7.86 76.62 ± 7.52 60.17 ± 18.22 69.20 ± 8.71 56.80 ± 3.45 40.91 ± 12.62 79.11 ± 6.92 88.20 ± 2.58 6.96 ± 6.96 52.72 ± 8.47 66.67 ± 8.29 30.12 ± 6.61 70.52 ± 4.93 91.18 ± 1.39 74.36 ± 5.33 71.17 ± 5.07 74.50 ± 6.12 22.50 ± 1.31 80.30 ± 2.93 65.34 ± 5.53 93.43 ± 3.17 70.49 ± 7.72 61.51 ± 10.37 91.55 ± 0.97 90.15 ± 4.33 77.45 ± 6.35 92.12 ± 1.94 78.81 ± 9.61 70.84 ± 5.51 88.21 ± 2.62

SI§§ a a b – – – – – – – – – a a b – – – – – – – – – ab b a ab b a – – – – – –

6.07 ± 0.92 7.86 ± 2.57 6.59 ± 1.28 9.59 ± 1.11 12.96 ± 0.98 4.42 ± 1.75 33.92 ± 19.14 15.47 ± 5.01 7.32 ± 3.13 28.94 ± 18.66 11.64 ± 3.62 13.87 ± 8.60 10.95 ± 3.87 7.28 ± 0.34 12.58 ± 4.19 6.10 ± 4.33 7.41 ± 0.88 7.46 ± 0.66 28.33 ± 5.67 11.52 ± 0.12 32.54 ± 11.71 8.52 ± 1.44 6.64 ± 0.99 33.86 ± 0.97 2.91 ± 2.19 20.00 ± 4.77 9.32 ± 3.30 2.28 ± 1.32 10.75 ± 4.78 29.78 ± 9.19 19.66 ± 12.78 18.20 ± 5.31 13.40 ± 3.86 10.95 ± 5.02 8.31 ± 1.11 9.61 ± 1.04

CI## – – – – – – a ab b – – – – – – – – – – – – b b a b a ab b ab a – – – – – –

0.31 0.31 0.28 0.30 0.31 0.30 0.30 0.31 0.31 0.28 0.31 0.31 0.31 0.30 0.27 0.30 0.31 0.27 0.31 0.32 0.29 0.31 0.31 0.29 0.30 0.32 0.29 0.30 0.31 0.30 0.31 0.32 0.30 0.31 0.31 0.30

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.51 0.55 0.51 0.51 0.53 0.53 0.54 0.56 0.52 0.54 0.54 0.53

Hill's Diversity a a b b a b – – – b a a a a b a a b a a b a a b b a b – – – ab a b – – –

†Lowercase letters indicate significant differences (P < 0.05) and − indicates no significant differences among all three management areas within sampling date as determined by repeated measures ANOVA and least mean separation using Tukey's honest signficant differences. ‡ Free-living maturity index. § Free-living maturity index excluding cp1 nematodes. # Herbivore maturity index. †† Combined free-living and herivore matuirty index excluding cp1. ‡‡ Enrichment Index. §§ Structure Index. ## Channel Index.

Organic

Hybrid

Conventional

MI†‡

Table 1 Mean and standard error for nematode maturity indices, ecological indices, and Hill’s Diversity.

E. Allan-Perkins et al.

Applied Soil Ecology 121 (2017) 161–171

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

(R2 = 0.951), and in September 2014 (R2 = 0.840). This correlated with an increase in bacterivores in September 2014 only. Organic matter was negatively correlated with CCA1 in September 2013 (R2 = 0.841) as was the relative abundance of herbivores (R2 = 0.997). On all sampling dates, except September 2014, the organic course clusters separately from the hybrid and conventional courses, and the organic putting greens cluster separately from the organic roughs and fairways (Fig. 4).

organic (p = 00163) courses, but not the hybrid course (Table 1). However, the hybrid course was the only one to have significant differences in MI25 among management areas (p = 0.0029) suggesting that the cp 1 bacterivores were similar among management areas. Generally, the conventional roughs had the highest MI values as did the hybrid roughs for MI25 (Table 1). The organic putting greens had the highest MI values (Table 1). The herbivore index (PPI) was also only significantly different for the conventional (p = 0.0237) and organic (p = 0.0057) courses. Generally, PPI was highest on the roughs and lowest on the putting greens for all three courses (Table 1). The combined maturity index excluding cp 1 (ΣMI25) was significantly different among management areas for all courses (conventional p = 0.0327, hybrid p = 0.0040, and organic p = 0.0097). Generally, it was highest on the roughs and lowest on the putting greens for all of the courses (Table 1). The only ecological index (EI) that was significantly different among management areas for all the golf courses was the structure index (SI) (conventional p = 0.0008, hybrid p = 0.0147, and organic p = 0.0381). Generally, structure was lowest on the putting greens of the conventional and hybrid courses and lowest on the fairways of the organic course (Table 1). The enrichment index was statistically different among management areas on the hybrid course (p = 0.0140) with the putting greens generally being less enriched than the fairways or roughs (Table 1). The interaction of EI and SI predicts overall soil structure and nutrient availability (Ferris et al., 2001). All samples that were taken from the fairways and roughs fell within the upper right quadrant of the scatterplot indicating high structure and nutrient enrichment (Fig. 3a and b). However, for the putting greens, many of the conventional and hybrid samples showed low structure (falling into the upper left quadrant of the plot), whereas all the organic samples remained highly structured (Fig. 3c).

3.5. Regression analysis Since many soil properties showed significant co-linearity, step-wise regression analysis was used to reduce the number of independent variables in the final models and to show the influence of soil properties on nematode communities (Table 3). An increase in pH was positively related (partial R2 = 0.535) to an increase in total nematodes in September 2014, but not in any other season (Table 3). Soil pH was also positively related to an increase in the relative abundance of herbivores (R2 = 0.06–0.65, Table 3). The relative abundance of bacterivores was negatively associated with soil pH (R2 = 0.05–0.22) in September 2013 and May 2014 (Table 3). A positive increase in percent soil organic matter explained an increase in total nematodes, herbivores, and PPI on most sampling dates, and was negatively associated with bacterivores and carnivores in 2013 (Table 3). Percent omnivores were positively associated with percent silt (R2 = 0.12–0.23) on all sampling dates (Table 3). Phosphorous was positively related (R2 = 0.003–0.15) to SI on all sampling dates, except September 2014. A linear regression analysis showed that bacterivore and herbivore were highly negatively related on all sampling dates (Table 4). 4. Discussion

3.3. Soil properties

The results of this study support our hypotheses that the putting greens would contain fewer free-living nematodes and demonstrate a lower structure and maturity on the conventional and hybrid courses. However, on the organic course the putting greens had higher abundances of bacterivores than herbivores and high MI and SI values. The PPI values were lowest on the putting greens regardless of the golf course management program. Putting greens are potentially the most interesting area for studying nematode relationships on golf courses, as this area is where nematode damage is most severe and management inputs are highest in order to maintain uniform and high quality turfgrass. Most differences were observed in the relative abundances of the herbivore and bacterivore nematodes among the three golf course programs. The organic management program had the lowest abundance of herbivores and the highest abundance of bacterivores, omnivores, and carnivores. There are several possible explanations for the increase in herbivores on the conventional and hybrid (managed as conventional) putting greens as compared to the organic course. First, the higher amounts of soil organic matter on the conventional and hybrid putting greens, which Walker et al. (2002) showed positively correlated with an increase in herbivores on putting greens in Ohio (r = 0.37). Organic matter may positively change soil properties to be more conducive for herbivore populations (Thoden et al., 2011). In our study, organic matter was associated with increased herbivores (R2 = 0.030-0.146) and only correlating with herbivores in the CCA from May 2014, suggesting that other factors may be influencing these nematodes. Walker et al. (2002) also reported that organic matter content was confounded by the age of the golf course, which was highly correlated (r = 0.74). Jordan and Mitkowski (2006) found an increase in herbivores associated with course age based on 34 golf courses in the southern New England states of the United States of America. However, they did not measure soil organic matter or other soil properties so the increase in herbivores may or may not have solely been due to course age. In our study, the organic course was younger than the conventional

The conventional and hybrid golf courses had statistical differences in pH (p < 0.0001 and p = 0.0055, respectively) and phosphorous (p = 0.0011 and p = 0.0016, respectively) among management areas and sampling time (Table 2). Generally, pH and phosphorus were highest on the putting greens of both courses (Table 2). Potassium was also significantly different among management areas (p = 0.0060) for the hybrid course, being greater on putting greens (Table 2). Organic matter was significantly (p = 0.0015) lower on the putting greens on the organic course (Table 2). Percent sand differed among management areas for all three courses (conventional p = 0.0365, hybrid p = 0.0366, and organic p < 0.0001) being greatest on the putting greens of the conventional and organic courses and the roughs of the hybrid course. 3.4. Canonical correspondence analysis On all sampling dates, canonical correspondence axes one (CCA1) and two (CCA2) were able to explain over 95% of the variation in the dataset, except for the September 2014 sampling date which explained over 88% (Fig. 4). The relative abundance of bacterivores and herbivores were inversely related on all sampling dates. The relative abundance of bacterivores was positively correlated with CCA1 on all sampling dates, except September 2014, but was only statistically significant in May and September of 2013 (R2 = 0.994 and 0.999, respectively). The relative abundance of herbivores was significantly negatively correlated with CCA1 on all sampling dates (R2 = 0.994, 0.916, 0.997), except September 2014 when it was negatively correlated with CCA2 (R2 = 0.980). The same axes were associated negatively with pH (R2 = 0.925, 0.973, 0.844, 0.828) and phosphorous (R2 = 0.848, 0.895, 0.737, 0.502) on the same sampling dates. Organic matter was positively correlated with CCA1 (R2 = 0.540) in September 2014 and with CCA2 in May 2013 (R2 = 0.876), September 2013 166

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

Fig. 3. Enrichment index versus structure index for a) roughs, b) fairways, and c) putting greens.

programs in this study had higher amounts of phosphorus and potassium as compared to the organic course, which may have contributed to the increased herbivore population. Percent herbivores was positively related and percent bacterivores was negatively related to higher amounts of phosphorus in May 2013, September 2013, and September 2014, which may support the hypothesis that increased nutrients could increase herbivore populations. According to regression analysis, phosphorous was related positively to increased herbivores in May 2013 and September 2014 (Table 4), indicating that although it significantly contributed on some sampling dates, other factors may be more significant. One such factor could be the addition of synthetic pesticides and fertilizers, which may have caused increased herbivore populations on the conventional and hybrid putting greens and selected against the free-living nematodes, especially the bacterivores. Yardim and Edwards (1998) determined that the application of a combination of non-target fungicides, insecticides, and herbicides, as well as insecticides or herbicides alone, caused a significant increase in the number of herbivores and a decrease in the number of bacterivores. We did see a strong inverse relationship among bacterivore and herbivore abundance in our dataset (R2 = 0.872-0.938). Cheng et al. (2008) found no effect of

and hybrid courses, and also had less organic matter on the putting greens. The organic course was fertilized using seaweed extract and animal derived organic fertilizers, which do not provide additional organic matter and are heat-treated so additional nematodes or microbes may be killed before application, unlike the composts used in most organic farms. Therefore, course age and management area would have provided differences in organic matter, rather than organic versus synthetic fertilizers. Since the organic course used in this study is the only course with no synthetic pesticide or fertilizer applications in the United States, the nematode populations on this course would need to be monitored in the future to determine how course age affects nematode communities under organic management. Another factor that may influence herbivore populations are the different management inputs. Thoden et al. (2011) hypothesized that an increase in nutrients may cause plants to produce fewer secondary metabolites that are antagonistic to herbivores or the plants increase root growth, both of which could increase the population of herbivores. In Walker et al.’s (2002) study there was a positive correlation among course age with phosphorus and potassium (r = 0.31 and 0.26, respectively), which may also explain the increase in herbivores with increasing course age. The conventional and hybrid management 167

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

Table 2 Mean and standard error for soil pH, organic matter, macronutrients, and texture. pH† Conventional

May 2013

Sept. 2013

May 2014

Sept. 2014

Hybrid

May 2013

Sept. 2013

May 2014

Sept. 2014

Organic

May 2013

Sept. 2013

May 2014

Sept. 2014

Percent Organic Matter

Phosphorous

Potassium

Percent Sand

Percent Silt

Percent Clay

Rough Fairway PuttingGreen Rough

5.1 5.7 6.6 5.2

± ± ± ±

0.2 0.1 0.1 0.0

c b a c

4.4 4.3 3.5 4.0

± ± ± ±

0.9 0.4 0.2 0.5

– – – –

1.3 ± 0.1 2.2 ± 0.4 16.3 ± 2.9 1.5 ± 0.2

b b a b

50.2 63.0 54.4 37.2

± ± ± ±

7.3 7.7 3.3 6.4

– – – b

83.6 83.0 88.4 83.9

± ± ± ±

2.2 2.8 0.7 2.1

b b a ab

10.6 ± 1.7 10.8 ± 2.1 6.4 ± 0.4 11.1 ± 1.7

a a b a

5.8 6.3 5.3 5.0

± ± ± ±

0.6 0.8 0.6 0.5

– – – –

Fairway PuttingGreen Rough Fairway PuttingGreen Rough

5.8 6.6 5.2 5.6 6.3 5.1

± ± ± ± ± ±

0.1 0.0 0.1 0.1 0.1 0.1

b a c b a c

3.8 3.6 4.4 4.4 3.6 2.9

± ± ± ± ± ±

0.3 0.3 0.7 0.4 0.3 0.2

– – – – – a

2.5 ± 0.4 14.0 ± 2.4 1.1 ± 0.2 2.0 ± 0.5 12.8 ± 1.1 2.0 ± 0.2

b a b b a b

70.6 52.5 42.1 49.6 54.8 21.5

± ± ± ± ± ±

6.5 3.3 5.6 6.3 2.5 3.4

a ab – – – –

82.2 88.2 81.2 82.2 88.4 81.2

± ± ± ± ± ±

3.4 0.9 1.4 3.1 0.8 1.4

b a b b a b

12.5 ± 3.0 6.0 ± 0.5 10.6 ± 1.1 10.8 ± 1.8 6.3 ± 0.4 10.6 ± 1.1

a b a a b a

5.3 5.8 8.2 7.0 5.3 8.2

± ± ± ± ± ±

0.4 0.4 0.3 1.3 0.5 0.3

– – a ab b a

Fairway PuttingGreen Rough Fairway PuttingGreen Rough

5.5 6.4 5.3 5.3 6.6 4.9

± ± ± ± ± ±

0.0 0.0 0.1 0.0 0.1 0.1

b a b b a b

3.4 1.5 3.0 3.9 3.4 2.9

± ± ± ± ± ±

0.2 0.4 0.1 0.1 0.2 0.2

a b – – – –

2.3 ± 0.1 4.9 ± 0.3 1.0 ± 0.1 1.7 ± 0.1 18.1 ± 3.4 1.4 ± 0.0

b a b b a b

18.4 14.3 25.0 22.1 54.7 31.5

± ± ± ± ± ±

1.7 1.0 2.6 1.7 5.5 0.6

– – b b a b

82.2 88.4 93.2 92.6 91.3 92.7

± ± ± ± ± ±

3.1 0.8 0.5 0.2 0.5 0.5

b a a ab b a

10.8 ± 1.8 6.3 ± 0.4 4.5 ± 0.7 4.8 ± 0.6 5.5 ± 0.1 5.3 ± 0.7

a b – – – b

7.0 5.3 2.4 2.6 3.2 2.0

± ± ± ± ± ±

1.3 0.5 0.3 0.3 0.4 0.2

ab b – – – b

Fairway PuttingGreen Rough Fairway PuttingGreen Rough

5.2 6.8 5.2 5.2 6.5 5.6

± ± ± ± ± ±

0.0 0.0 0.1 0.1 0.1 0.4

b a b b a –

3.6 3.6 2.9 3.5 3.1 3.7

± ± ± ± ± ±

0.5 0.3 0.1 0.3 0.7 0.3

– – – – – –

2.0 ± 0.1 17.4 ± 3.3 0.8 ± 0.1 1.2 ± 0.1 16.2 ± 2.1 8.4 ± 6.5

b a b b a b

48.0 58.8 18.2 18.0 39.6 49.3

± ± ± ± ± ±

8.0 1.0 2.0 1.9 1.4 16.2

ab a b b a –

91.3 89.5 91.8 90.8 91.4 91.8

± ± ± ± ± ±

0.3 1.0 0.1 0.8 0.1 0.1

b c – – – –

6.9 5.5 4.5 5.1 4.9 4.5

± ± ± ± ± ±

0.3 0.9 0.3 0.4 0.7 0.3

a b – – – –

1.8 ± 0.3 4.9 ± 0.2 3.7 ± 0.3 4.1 ± 0.5 3.7 ± 0.6 3.7 ± 0.3

b a – – – –

Fairway PuttingGreen Rough Fairway PuttingGreen Rough

5.3 5.1 5.2 5.1 5.2 5.3

± ± ± ± ± ±

0.2 0.1 0.0 0.0 0.1 0.1

– – – – – –

4.2 3.5 2.6 3.3 1.1 2.6

± ± ± ± ± ±

0.2 0.4 0.2 0.1 0.0 0.1

– – a a b a

2.3 ± 0.6 14.6 ± 2.0 1.8 ± 0.2 2.9 ± 0.2 4.7 ± 0.3 2.1 ± 0.1

b a b ab a –

66.7 57.0 27.6 22.8 16.2 20.1

± ± ± ± ± ±

3.9 6.6 1.9 2.1 0.9 3.6

– – a ab b a

90.8 91.4 87.6 88.2 96.6 87.1

± ± ± ± ± ±

0.8 0.1 0.4 0.7 0.7 0.7

– – b b a b

5.1 4.9 9.7 8.1 2.4 9.5

± ± ± ± ± ±

0.4 0.7 0.3 0.6 0.8 0.5

– – a a b a

4.1 3.7 2.7 3.7 1.0 3.5

± ± ± ± ± ±

0.5 0.6 0.2 0.1 0.1 0.3

– – a a b a

Fairway PuttingGreen Rough Fairway PuttingGreen Rough

5.4 5.5 5.1 5.1 5.1 5.9

± ± ± ± ± ±

0.1 0.1 0.0 0.1 0.0 0.4

– – – – – a

2.9 1.2 3.0 3.2 1.3 4.2

± ± ± ± ± ±

0.1 0.1 0.1 0.1 0.1 0.4

a b a a b –

2.4 ± 0.1 4.0 ± 0.3 1.6 ± 0.2 2.0 ± 0.1 3.2 ± 0.2 13.4 ± 5.9

– – – – – a

21.1 12.4 19.8 16.6 15.6 61.3

± ± ± ± ± ±

1.6 0.5 3.1 1.2 0.8 5.5

a b – – – a

87.0 96.2 88.9 88.7 97.3 88.9

± ± ± ± ± ±

1.0 0.2 0.6 1.2 0.2 0.6

b a b b a b

10.6 ± 1.0 1.9 ± 0.1 7.3 ± 0.6 6.9 ± 0.9 1.4 ± 0.5 7.3 ± 0.6

a b a a b a

2.4 1.9 3.8 4.4 1.3 3.8

± ± ± ± ± ±

0.1 0.1 0.1 0.3 0.4 0.1

b b a a b a

Fairway PuttingGreen

5.0 ± 0.2 5.0 ± 0.0

b b

3.6 ± 0.1 4.5 ± 0.6

– –

1.2 ± 0.1 2.0 ± 0.4

b b

32.6 ± 4.0 42.9 ± 5.6

b ab

88.7 ± 1.2 97.3 ± 0.2

b a

6.9 ± 0.9 1.4 ± 0.5

a b

4.4 ± 0.3 1.3 ± 0.4

a b

†Lowercase letters indicate significant differences (P < 0.05) and − indicates no significant differences among all three management areas within sampling date as determined by repeated measures ANOVA and least mean separation using Tukey's honest signficant differences.

The free-living maturity indices (MI, MI25, and ΣMI25) were generally higher on the organic course, supporting that these putting greens were less disturbed and more structured than the conventional courses, as evidenced by the increased abundance of persister nematodes (Bongers, 1990; Neher et al., 2004). The low MI25 may indicate lower pollution stress on the organic course (Neher et al., 2004; Yeates, 1994). In this study, there was an inverse relationship between MI and MI25 compared with PPI. Bongers and Bongers (1998) found the same inverse relationship in areas with high nitrogen fertilization, which they hypothesized was due to the increased carrying capacity of the turfgrass roots for the herbivore nematodes due to the additional nutrients. Since golf courses are nutrient enriched areas, we expected to see the inverse relationship between MI and PPI observed by Bongers and Bongers (1998). All of the courses had high EI, indicating a nutrient rich environment (Ferris and Matute, 2003; Neher et al., 2014). All of the golf course programs had similar enrichment and structure (Fig. 3a and b) on the fairways and roughs. However, the putting greens on the organic course were more structured than the other two courses (Fig. 3c), indicating that the overall soil food web was less disturbed and more connected. Management practices that occur more frequently on putting greens, such as aeration, dethatching, and verticutting, would be expected to reduce the overall structure index on putting greens compared to roughs and fairways. However, we did not see this

organic versus synthetic fertilizers or the use of herbicides on nematode communities, however this study was on turfgrass maintained as home lawns and therefore applied at lower rates than typically used on a golf course putting green. Walker et al. (2002) did not measure specific amount of pesticides applied, but they did correlate the number of herbivores with the pesticide budget for each course. They found an increased fungicide and herbicide budget (0.31 and 0.43, respectively) correlated with more herbivore nematodes. Although all three putting greens were dominated by creeping bentgrass, the perennial ryegrass in the conventional and hybrid courses may have influenced the nematode community. However, studies on host preference indicate more nematode species prefer creeping bentgrass to bluegrasses, so this may have minimally contributed to our results (Martin, 2015). We were limited in our experimental design by the lack of multiple organic golf courses within North America and specifically within a small area with similar climate. The establishment of a long-term golf course field plot to study the effects of organic versus synthetic fertilizers and pesticides on nematode communities would provide better insight on the effect of management program with replication. The benefits of a long-term study would allow us to see temporal shifts in communities with management strategies and to determine how course age and an increase in organic matter and nutrients over time affect nematode communities. 168

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

Fig. 4. Canonical correspondence analysis of soil pH, percent organic matter, phosphorous, potassium, and soil texture for component 1 (CCA1) and nematode trophic groups, maturity indices, and ecological indices as component 2 (CCA2) in a) May 2013, b) May 2014, c) September 2013, and d) September 2014. Biplot vectors for properties with P < 0.05 are displayed.

nematode diversity and herbivore maturity (PPI), with the putting greens of all three golf courses having the lowest values for these metrics. However, there were large differences in nematode communities among organically and conventionally managed putting greens. This is the area of most interest to golf courses, as this is where nematode damage is most severe. This study provides a list of possible factors strongly influencing an increase in herbivores that cause turfgrass damage. Continued monitoring of these three golf courses will help to determine if course age influences nematode communities, especially those under organic management. Additional factors to further investigate would be decreasing organic matter, phosphorus, potassium, and the use of synthetic fertilizers or pesticides. Future studies should focus on examining the effects of these factors on each nematode trophic group and their interactive relationships to determine if they can be integrated into golf course management strategies, and potentially to less managed turf such as home lawns and athletic fields, to reduce herbivores and potentially increase free-living nematode populations, thus reducing disease and increasing turfgrass health through benefits such as increased available nitrogen via bacterivore nematodes.

on the three golf courses we studied, suggesting that these practices minimally effect nematode composition. The results of this study were similar to those of other nematodes studies in many ways. The dominant trophic groups were the herbivores and bacterivores, which is consistent with nematode communities from many different cropping ecosystems. The fungivores were the least abundant group, as in other turfgrass studies (Cheng et al., 2008). This may be due to the removal of the thatch, the layer of decaying plant material underneath the canopy sitting above the soil, during sampling, which is hypothesized to be the area with the highest fungal abundance and therefore it may be the area with the greatest fungivore abundance (Ferris and Matute, 2003; Hendrix et al., 1986; Moore and de Ruiter, 1994). On turfgrass, there is a generally held belief that nematode populations are greatest on the putting greens due to the increased moisture and percent sand, which aid in nematode movement (Jordan and Mitkowski, 2006). Moreover, most studies on turfgrass nematodes have only sampled the putting greens and often only the herbivores. In our study, we determined that fairways have the highest abundance of total nematodes, suggesting that total population is not dependent on percent sand or higher moisture levels from increased irrigation, but perhaps is related to increases in organic matter. However, herbivores were still greatest on putting greens, except on the organic course, suggesting that other inputs may be increasing the nematode populations on the conventional and hybrid putting greens.

Acknowledgements The authors would like to thank the following people for their contributions to nematode identification, statistical analysis, and editing of the manuscript: James Popko, Jr., Hyunkyu Sang, Victoria Kohler, Deborah Neher, Jim LaMondia, and Wes Autio. This research was funded by the United States Golf Association, the New England

5. Conclusion The results of this study show that management intensity affects 169

170

Channel Index (CI)

Structure Index (SI)

Enrichment Index (EI)

Sum of MI25 and PPI (ΣMI25)

Herbivore maturity index (PPI)

MI excluding cp1 (MI25)

Free-living maturity index (MI)

Percent fungivores

Percent carnivores

Percent omnivores

Percent bacterivores

Percent herbivores

0.3101(−) 0.5555(−)

0.2385(−) 0.0039(−)

2014

2014

2013

0.5762(−)

2013

0.0070(+) 0.7674(−) 0.2253(+)

2014

0.0283(+)

0.3563(+)

0.4569(−)

0.0190(+) 0.0858 (−)

0.2141(+) 0.4928(+)

2013

2014

2013

2014

2013

0.0033(−) 0.1553(−) 0.0969(−)

0.1056(−) 0.1213(−) 0.0147(+) 0.3789(−) 0.2403(−) 0.1701(−)

0.0752(−)

0.1005(+)

2014

0.0037(+)

0.0029(−)

0.3567(−)

0.0029(−)

0.0075(−)

0.2025(−)

0.2173(−)

0.2555(−) 0.3275(−) 0.6756(−)

0.2746(+) 0.3283(−)

0.1362(−)

2013

2014

2013

2014

2013

2014

2013

0.0054(+)

2014

0.1139(−)

0.0135(+) 0.4680(−)

0.0356(+) 0.0218(+)

0.2384(−) 0.1766(−) 0.2343(−)

0.0298(+) 0.1824(−) 0.2233(−)

0.2933(+) 0.2786(+) 0.1459(+) 0.3073(+)

0.1461(+)

2013

2014

2013

2014 0.2257(−) 0.0551(−)

0.0400(+) 0.6502(+) 0.2675(+) 0.1928(+) 0.0615(+)

2014

2013

0.5346(+)

May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September May 2013 September May 2014 September

Total nematodes

0.1235(+)

0.0002(−)

0.1459(−)

0.0158(+) 0.1582(−)

0.1107(−)

0.0674(−)

0.0427(−) 0.0287(−) 0.2487(−)

0.0942(−)

0.1895(+)

0.0762(+)

0.0353(−) 0.0259(+)

0.0551(−) 0.0880(−)

0.0263(+) 0.0348(−)

0.0307(−)

0.0606(+)

Potassium

Percent Sand

Percent Silt

Percent Clay

0.1025(+)

0.0551(−) 0.0340(−) 0.0812(−) 0.0002(+)

0.1816(−) 0.0005(+)

0.0113(+)

0.0990(+) 0.0048(−) 0.0438(+)

0.0636(+)

0.0968(−)

0.0603(+) 0.2139(+)

0.0736(+) 0.0012(+) 0.0107(−)

0.0839(+)

0.2241(−)

0.1366(−)

0.0025(−)

0.0024(−)

0.0069(+) 0.1169(−)

0.0864(+)

0.2185(+) 0.0502(+)

0.0360(+) 0.0758(−) 0.1814(+)

0.0705(+)

0.4152(−)

0.2343(+) 0.1241(+) 0.1842(+) 0.1370(+) 0.0089(−)

0.2599(−)

0.0865(−)

0.0122(−)

0.2653(+)

0.1295(−)

0.3075(−) 0.1054(−)

0.2441(−)

0.0830(+)

0.1194(+) 0.0875(−) 0.0297(−)

0.0501(+)

0.0210(−)

0.2387(+) 0.3432(−)

0.0391(−)

0.5308(−)

0.6227(+)

0.0582(−)

0.1461 0.6681 0.2933 0.5664 0.8180 0.5748 0.4476 0.7274 0.6504 0.4490 0.3414 0.6796 0.3182 0.3625 0.3128 0.4081 0.6031 0.5555 0.2628 0.3502 0.2740 0.4735 NA 0.3538 0.7645 0.3567 0.3896 0.5200 0.8107 0.3921 0.2252 0.1794 0.2185 0.4740 0.6618 0.4026 0.4658 0.4554 0.3128 0.6311 0.0812 0.4464 0.1328 0.4093 0.8733 0.5265 0.4043 0.6817 NA 0.3704 NA 0.3927

Final Model

Phosphorous

pH

Percent Organic Matter

R2

Partial R2 and sign of coefficient (b)

2013

Sampling Date

Response Variable

Table 3 Multiple stepwise regression analysis of nematode trophic group abundance, maturity indices, and ecological indices with soil properties.

0.1814 0.6792 0.3920 0.5992 0.8214 0.6165 0.4894 0.7387 0.6785 0.4851 0.3823 0.7050 0.3752 0.3975 0.3180 0.4232 0.6266 0.6008 0.3816 0.4284 0.3754 0.4983 0.0965 0.3726 0.7732 0.4429 0.3952 0.5367 0.8242 0.4319 0.2940 0.2341 0.3407 0.4768 0.6995 0.5308 0.4878 0.5027 0.3655 0.6391 0.1521 0.4899 0.2024 0.4721 0.8806 0.5438 0.4650 0.7123 0.1170 0.4139 0.1072 0.4409

Full Model

E. Allan-Perkins et al.

Applied Soil Ecology 121 (2017) 161–171

Applied Soil Ecology 121 (2017) 161–171

E. Allan-Perkins et al.

golf course greens turf in southern New England. Plant Dis. 90, 501–505. Knox, O.G.G., Killhaim, K., Mullins, C.E., Wilson, M.J., 2003. Nematode-enhanced microbial colonization of the wheat rhizosphere. FEMS Microbiol. Lett. 225, 227–233. Korthals, G.W., de Goede, R.G.M., Kammenga, J.E., Bongers, T., 1996. The maturity index as an instrument for risk assessment of soil pollution. In: van Straalen, N.M., Krivolutsky, D.A. (Eds.), Bioindicator Systems for Soil Pollution. Kluwer Academic Publishers, Dordrecht, Netherlands, pp. 85–93. Mai, E., Lyon, H., 1975. Pictorial Key to Genera of Plant-Pathogenic Nematodes. Cornell University Press, Ithaca, NY. Martin, S.B., 2015. Nematode Control. Clemson University Extension. (accessed 14.6.16). http://www.clemson.edu/extension/horticulture/turf/pest_guidelines/nematodes. html. McSorley, R., Walter, D.E., 1991. Comparison of soil extraction methods for nematodes and microarthropods. Agric. Ecosyst. Environ. 34, 201–207. Moore, J.C., de Ruiter, P.C., 1991. Temporal and spatial heterogeneity of trophic interactions within below-ground food webs. Agric. Ecosyst. Environ. 34, 371–397. Morris, K., Horgan, F.G., Grifin, C.T., 2013. Spatial and temporal dynamics of Meloidogyne minor on creeping bentgrass in golf greens. Plant Pathol. 62, 1166–1172. Neher, D.A., Campbell, C.L., 1994. Nematode communities and microbial biomass in soils with annual and perennial crops. Appl. Soil Ecol. 1, 17–28. Neher, D.A., Peck, S.L., Rawlings, J.O., Campbell, C.L., 1995. Measures of nematode community structure and sources of variability among and within agricultural fields. Plant Soil 170, 167–181. Neher, D., Bongers, T., Ferris, H., 2004. Society of Nematologists Workshop: Computation of Nematode Community Indices. (accessed 13.9.12). http://plpnemweb.ucdavis. edu/nemaplex/FerrisPublications/PublicationsLimitedDistribution/ LD6Neheretal2004.pdf. Neher, D.A., Muthumbi, A.W.N., Dively, G.P., 2014. Impact of coleopteran-active Bt corn on non-target nematode communities in soil and decomposing corn roots. Soil Biol. Biochem. 76, 127–135. Neher, D.A., 1995. Measures of nematode community structure and sources of variability among and within agricultural fields. Plant Soil 170, 167–181. Neher, D.A., 1999. Nematode communities in organically and conventionally managed agricultural soils. J. Nematol. 31, 142–154. Neher, D.A., 2001. Role of nematodes in soil health and their use as indicators. J. Nematol. 33, 161–168. Neher, D.A., 2010. Ecology of plant and free-living nematodes in natural and agricultural soils. Annu. Rev. Phytopathol. 48, 371–394. Nelson, E.B., 1995. Nematode disorders of turfgrasses: how important are they? Turfgrass Trends 4, 1–16. Okada, H., Harada, H., Kadota, I., 2005. Fungal-feeding habits of six nematode isolates in the genus Filenchus. Soil Biol. Biochem. 37, 1113–1120. Sipes, B.S., Schmitt, D.P., 1989. Development of Heterodera glycines as affected by Alachlor and Fenamiphos. J. Nematol. 21 (24), 32. Sohlenius, B., Persson, H., Magnusson, C., 1977. Distribution of root and soil nematodes in a young Scots pine stand in central Sweden. Ecol. Bull. 25, 340–347. Tarjan, A., Esser, R., Chang, S., 2014. Interactive Diagnostic Key to Plant Parasitic, Freeliving, and Predaceous Nematodes. University of Nebraska Lincoln Nematology Laboratory (Accessed 13.05.25). http://nematode.unl.edu/key/nemakey.htm. Thoden, T.C., Korthals, G.W., Thermorshuizen, A.J., 2011. Organic amendments and their influences on plant-parasite and free-living nematodes: a promising method for nematode management? J. Nematol. 13, 133–153. U.S. Golf Association Green Section Staff, 2004. USGA Recommendations for a Method of Putting Green Construction. United States Golf Association, Far Hills, NJ. Walker, N.R., Goad, C.L., Zhang, H., Martin, D.L., 2002. Factors associated with populations of plant-parasitic nematodes in bentgrass putting greens in Oklahoma. Plant Dis. 86, 764–768. Yardim, E.N., Edwards, C.A., 1998. The effects of chemical pest, disease and weed management practices on the trophic structure of nematode populations in tomato agroecosystems. Appl. Soil Ecol. 7, 137–147. Yeates, G.W., Bongers, T., De Goede, R.G., Freckman, D.W., Georgieva, S.S., 1993. Feeding habits in soil nematode families and genera-an outline for soil ecologists. J. Nematol. 25, 315–331. Yeates, G.W., 1994. Modification and quantification of the nematode maturity index. Pedabiologia 38, 97–101. Zhao, J., Neher, D.A., Fu, S., Li, Z., Wang, K., 2013. Non-target effects of herbicides on soil nematode assemblages. Pest Manag. Sci. 69, 679–684.

Table 4 Linear regression analysis of bacterivores (dependent variable) to herbivores (independent variable). Sampling Date

R2 and sign of coefficient (b)

May 2013 September 2013 May 2014 September 2014

0.9042(−) 0.8856(−) 0.8720(−) 0.9377(−)

Regional Turfgrass Foundation, and graduate student support from the University of Massachusetts University Fellowship and Plant Biology Gilgut Fellowship. References Bardgett, R.D., Denton, C.S., Cook, R., 1999. Below-ground herbivory promotes soil nutrient transfer and root growth in grassland. Ecol. Lett. 2, 357–360. Bhusal, D.R., Kallimanis, A.S., Tsiafouli, M.A., Sgardelis, S.P., 2014. Higher taxa vs functional guild vs. trophic group as indicators of soil nematode diversity and community structure. Ecol. Indic. 41, 25–29. Bongers, T., Bongers, M., 1998. Functional diversity of nematodes. Appl. Soil Ecol. 10, 239–251. Bongers, T., 1988. De Nematoden van Nederland. Stichting Uitgeverij van de Koninklijke Nederlandse Natuurhistorische. Vereniging, Netherlands. Bongers, T., 1990. The maturity index: an ecological measure of environmental disturbance based on nematode species composition. Oecologia 83, 14–19. Briar, S.S., Grewal, P.S., Somasekhar, N., Stinner, D., Miller, S.A., 2007. Soil nematode community, organic matter, microbial biomass and nitrogen dynamics in field plots transition from conventional to organic management. Appl. Soil Ecol. 37, 256–266. Briar, S.S., Fonte, S.J., Park, I., Six, J., Scow, K., Ferris, H., 2011. The distribution of nematodes and soil microbial communities across soil aggregate fractions and farm management systems. Soil Biol. Biochem. 43, 905–914. Cheng, Z., Grewal, P.S., Stinner, B.R., Hurto, K.A., Hamza, H.B., 2008. Effects of longterm turfgrass management practices on soil nematode community and nutrient pools. Appl. Soil Ecol. 38, 174–184. Crow, W.T., 2007. Understanding and managing parasitic nematodes on turfgrasses. In: Pessarakli, M. (Ed.), Handbook of Turfgrass Management & Physiology. CRC Press, Boca Raton, FL, pp. 351–374. Ekschmitt, K., Bakonyi, G., Bongers, M., Bongers, T., Boström, S., Dogan, H., Harrison, A., Kallimanis, A., Nagy, P., O’Donnell, A.G., Sohlenius, B., Stamou, P., Wolters, V., 1999. Effects of nematofauna on microbial energy and matter transformation rates in European grassland soils. Plant Soil 212, 45–61. Ferris, H., Matute, M.M., 2003. Structural and functional succession in the nematode fauna of a soil food web. Appl. Soil Ecol. 23, 93–110. Ferris, H., Venette, R.C., van der Meulen, H.R., Lau, S.S., 1998. Nitrogen mineralization by bacterial-feeding nematodes: verification and measurement. Plant Soil 203, 159–171. Ferris, H., Bongers, T., de Goede, R.G.M., 2001. A framework for soil food web diagnostics: extension of the nematode faunal analysis concept. Appl. Soil Ecol. 18, 13–29. Freckman, D.W., 1988. Bacterivorous nematodes and organic matter decomposition. Agric. Ecosyst. Environ. 24, 195–217. Goodey, J., 1963. Soil and Freshwater Nematodes. John Wiley and Sons, Inc., New York. Griffin, G.D., Anderson, J.L., 1978. Effects of DCPA, EPTC, and Chlorpropham on pathogenicity of Meloidogyne hapla to alfalfa. J. Nematol. 11, 32–36. Hendrix, P.F., Parmelee, R.W., Crossley Jr., D.A., Coleman, D.C., Odum, E.P., Groffman, P.M., 1986. Detritus food webs in conventional and no-tillage agroecosystems. Bioscience 36, 374–380. Ingham, R.E., Trofymow, J.A., Ingham, E.R., Coleman, D.C., 1985. Interactions of bacteria, fungi, and their nematode grazers: effects on nutrient cycling and plant growth. Ecol. Monogr. 55, 119–140. Jordan, K.S., Mitkowski, N.A., 2006. Population dynamics of plant-parasitic nematodes in

171