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Applied Soil 121 (2017) 161–171

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Applied Soil Ecology

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Nematode communities on putting greens, fairways, and roughs of organic MARK and conventional cool-season golf courses ⁎ Elisha Allan-Perkinsa, Daniel K. Manterb, Robert Wickc, Scott Ebdona, Geunhwa Junga, a Stockbridge School of Agriculture, University of Massachusetts Amherst, 206 Paige Laboratory, 161 Holdsworth Way, Amherst, MA 01003, United States b USDA-ARS, 2150 Centre Avenue, Building D, Suite 100, Fort Collins, CO 80526, United States c Stockbridge School of Agriculture, University of Massachusetts Amherst, 105 Fernald Hall, 230 Stockbridge Road, Amherst, MA 01003, United States

ARTICLE INFO ABSTRACT

Keywords: Nematodes are an important component of the golf course . Many provide benefits to turfgrass, Turfgrass while others can cause significant damage. Previous studies on golf courses have focused only on Soil nematodes, mostly on putting greens. This study aimed to characterize all nematode trophic groups and ne- Maturity indicies matode maturity and ecological indices under different management intensities (depicted by roughs, fairways, Ecological indices 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 (- parasitic) index (PPI) values than the other management areas. The relative of , bacter- ivores, and structure index (SI) values differed among organic and conventional management. Canonical cor- respondence and multiple stepwise regression analyses revealed pH, phosphorous, and organic matter were positively related to increased herbivores and negatively related to increased . 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 processes, such as spreading microbes throughout the soil, aiding in , and preying on pathogens (Cheng et al., 2008; Neher, Nematodes can cause significant damage on golf courses, especially 2001, 2010). Bacterivores can increase rhizobacteria in the soil (Briar on putting greens, resulting in diminished uniformity on the putting et al., 2007; Knox et al., 2003). and bacterivores increase surface. Plant pathogenic nematodes (herbivores) are ubiquitous on nitrogen mineralization, thus increasing its availability to , pro- golf courses and feed on turfgrass roots, which damages tissues and moting plant growth (Briar, 2007; Ekschmitt et al., 1999; Ferris et al., removes photosynthates from the plant. When herbivore populations 1998; Ingham et al., 1985). Therefore, there is potential to increase reach sufficient densities, they can cause wilting, stunted growth, yel- turfgrass health by developing management strategies that encourage lowing, thinning, or death, all of which affect aesthetics and game play beneficial nematodes. (Nelson, 1995). In the past herbivore populations were controlled by Nematodes have been used as indicators of overall soil health since nematicides and in extreme cases soil fumigation (Walker et al., 2002). the late 1980’s. These indices may provide insight into how manage- However, many of these products have been banned or have restricted ment strategies affect other invertebrates and microbes (Neher, 2010). use on turfgrass (Crow, 2007; Martin, 2015). New nematicides are They have been selected as the ideal soil for predicting overall currently being developed, but none have been as effective as previous soil health due to their central position in the soil chemistries, such as fenamiphos, or are only registered in certain states and effect on microbes and decomposition pathways (Bongers and (Martin, 2015; Nelson, 1995). The integration of alternative manage- Bongers, 1998; Ferris and Matute, 2003; Freckman, 1988; Moore and de ment strategies is needed to manage herbivore populations. Ruiter, 1991; Neher, 2001, 2010). Additionally, nematodes react to Nematodes also provide many beneficial functions to turfgrasses. quicker than larger but slower than microbes Low levels of herbivory promote growth of plants (Bardgett et al., (Bongers and Bongers, 1998; Neher, 2001). After identification and 1999; Neher, 2010). In addition to the herbivores, the bacterivores, classification at the genus or family level, nematodes are assigned to , carnivores, and drive important soil ecosystem 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. E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

2014; Bongers, 1990; Bongers and Bongers 1998). Ecological indices, ingredient was Bacillus subtilis, Bayer CropScience, North Carolina, such as free-living maturity including cp1 (MI) and excluding cp1 United States of America), Serenade™ (active ingredient was Bacillus (MI25), herbivore maturity (PPI), combined maturity (ΣMI25), en- licheniformis, Bayer CropScience, North Carolina, United States of richment (EI), structure (SI), and channel (CI), can be calculated and America), and Waipuna Weed Control System™ (active ingredients were used to predict soil conditions (Bongers, 1990; Ferris et al., 2001; hot water and foaming detergent, Waipuna Systems LTD, Illinois, Korthals et al., 1996; Neher et al., 2004). Additionally, many nema- United States of America). The conventional courses were established in tologists calculate nematode trophic diversity, using the Hills N1 1926 and 1939 with native push-up putting greens and have used equation (N1), to determine how diverse the nematode communities synthetic pesticides and fertilizers since their construction. The course are, which is based on the presence of rare nematode trophic groups established in 1939 represents conventional management on the put- (fungivores, carnivores, and omnivores) compared to the dominant ting greens and reduced input management on the fairways and roughs, nematode groups (bacterivores and herbivores) (Neher, 2001). so we have designated this course as “hybrid” management. The course These indices have been used to understand nematode and soil had reduced pesticide applications, one synthetic fungicide application communities from many different including agricultural in eighteen years, Secure™ (active ingredient was fluazinam, Syngenta fields and natural . Studies have compared organic and Crop Protection, Greensboro, North Carolina, United States of America) conventional management practices to determine if organic practices on its fairways and applied the biological control product, Pseudomonas have positive effects on soil communities. Pesticides have differing ef- aureofaciens TX-1, to the fairways through the irrigation lines. The or- fects on nematodes depending on the product and amount used, but ganic and the two conventional golf courses received sand-based top- studies have found an increase in herbivores and a decrease in bac- dressing on the putting greens at least twice per year. terivores, fungivores, omnivores, and carnivores following the appli- The courses were sampled in mid May and early September of 2013 cation of different pesticides (Griffin and Anderson, 1978; Sipes and and 2014. The mean temperatures in May 2013 was 11.7 °C and 14.4 °C Schmitt, 1989; Thoden et al., 2011; Yardim and Edwards, 1998; Zhao in 2014. In September of 2013 and 2014 the mean temperatures were et al., 2013). Despite the many studies on nematodes in native grass- 18.9 °C and 22.2 °C, respectively. The grass composition on the putting lands and agricultural fields, there have been few studies on nematode greens of all three courses was Agrostis stolonifera (creeping bentgrass) communities on golf courses. with some Poa annua (annual bluegrass) encroachment on the con- Past golf course studies have generally focused only on the abun- ventional and hybrid courses. The fairways were a mixture of creeping dance of herbivores, since they are of economic importance to the bentgrass, annual bluegrass, and some Lolium perenne (perennial rye- turfgrass industry, leaving out the potential beneficial nematodes, such grass). The roughs were a mixture of annual bluegrass, perennial rye- as the bacterivores (Jordan and Mitkowski, 2006; Morris et al., 2013; grass, fescues (Festuca spp.), and some weed species. Walker et al., 2002). However, by understanding how all nematode trophic groups interact under different turf management programs and 2.2. Sampling strategy intensities we may be able to develop new management strategies to decrease herbivores and increase beneficial nematodes. Three golf course holes (representing one area of play from tee box The objectives of this study were to determine if nematode com- to putting green) per course were randomly selected and sampled using munities differ among highly managed turf areas (represented by the a 2.5 cm diameter soil core at a depth of 10 cm below the thatch to putting greens), moderately managed turf areas (fairways), and lowly provide biological replicates of each golf course. All three management managed turf areas (roughs). We chose three golf courses representing areas (roughs, fairways and putting greens) were sampled per hole. organic, reduced input (denoted as “hybrid”), and conventional man- Four approximately equidistant transects were used to sample the agement programs to see if management program interacted with in- fairways and roughs (Fig. 1a). Three sampling locations were set up tensity to change nematode communities. However, since there is only along each transect within the fairway and three samples were taken at one truly organic golf course in the United States we are only able to each location and pooled for a total of twelve samples per fairway. Each draw inferences for the differences among management areas. We hy- transect extended 4.6 m from the edge of the fairway into one side of pothesized that the roughs and fairways would contain higher amounts the rough. Eight samples were taken at each rough sampling location of free-living nematodes than the more intensely managed putting and pooled for a total of four samples per rough (Fig. 1a). greens. Additionally, the putting greens would show the lowest SI and Two concentric circle transects were established on the putting MI, but a higher PPI than the less disturbed roughs and fairways. Since greens (Fig. 1b). The outermost transect was set up 1.5 m from the edge golf course fairways and putting greens receive high nutrient inputs, we of the putting green and the inner transect was set up 4.6 m from the hypothesized that both areas would have high enrichment index values. 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 2. Materials and methods pooled for a total of eight samples per putting green (Fig. 1b). Global positioning system (GPS) coordinates were taken at each sample loca- 2.1. Collection sites tion and the distances between sample transects and irrigation heads were recorded to ensure repeated sampling at the same locations for Three golf courses on Martha’s Vineyard, Massachusetts, United May and September of 2013 and 2014. In September of 2014 the or- States of America located within 15 km of one another were selected for ganic golf course began the process of renovating their putting greens study. The exact location and identification of the courses is withheld and we were unable to sample our third hole for a fourth time. per request of the golf courses’ managers. One golf course has been Therefore, we sampled a different putting green from a nearby hole. All maintained using an organic program and two golf courses have been holes on all the golf courses had similar shade, grass species, and cul- maintained using conventional programs. The organic course was built tural practices with a few exceptions. The roughs had more variable in 2002 and has sand-based putting greens constructed according to grass species and shade amounts. The organic putting greens were United States Golf Association (USGA) specifications (U.S. Golf rolled each day, but the conventional and hybrid courses’ putting Association Green Section Staff, 2004). It has never received synthetic greens were not. All samples were immediately placed on ice and pesticides or fertilizers. Fertilizer applications were made using sea- transported back to the laboratory and were stored at 4 °C. weed extract and by-products, such as blood and meal. The organic pesticides applied were CivitasONE™ (active ingredients were 2.3. Nematode analysis petroleum byproduct, synthetic isoparaffin, and a copper-based pig- ment, Suncor Energy, Inc., Alberta, Canada), Rhapsody™ (active Soil samples were pooled within a management area per hole for a

162 E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

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

total of three samples per hole, nine samples per golf course, and a total 2.5. Statistical analysis of twenty-seven composite nematode samples per sampling time. Nematodes were extracted in triplicate using the modified Cobb’s Repeated measures analysis of variance was performed by PROC sifting and gravitation method followed by centrifugation and sugar MIXED in SAS version 9.4 (SAS Institute, Cary, North Carolina, United flotation (Neher, 1999; Neher and Campbell, 1994), which is the pre- States of America) for each golf program (organic, hybrid, and con- ferred method for recovery of the greatest diversity of nematode genera ventional) to determine differences among management areas (rough, (McSorley and Walter, 1991; Neher, 2001; Neher et al., 1995). This fairway, putting green) among the three holes using a split–split plot protocol was modified from extracting 100 cubic centimeters (cc) to 25 design using years as the split plot and season as the split–split plot for cc of soil per sample. Nematodes were counted under a Zeiss Primo Vert all possible interactions for the total nematode counts, relative abun- inverted compound microscope after identification to genus or family dances of the different trophic groups, the maturity and ecological in- level using the following identification keys (the English translation of dices, and the soil properties. These metrics were chosen because pre- Bongers, 1988; Goodey, 1963; Mai and Lyon, 1975; Tarjan et al., 2014). vious studies have shown they are more accurate at differentiating The counts of all three technical replicates were averaged and were not among soil ecological conditions than total abundances of individual corrected for extraction efficiency as per common practice (Neher, trophic groups alone (Neher, 1995). Where significant, differences 1999). Nematode genera were assigned to their appropriate trophic among interactions were determined using PROC GLIMMIX for man- groups and cp values (Bongers and Bongers, 1998; Neher, 2001; Neher agement area separated by season × year. To meet the criteria for et al., 2004; Okada et al., 2005; J. LaMondia, personal ; parametric analyses, data for the relative abundances of trophic groups, Sohlenius et al., 1977; Yeates et al., 1993). Members of the Anguinidae percent organic matter, and soil texture (percent sand, silt and clay) often feed as fungivores and herbivores, therefore they were equally were transformed with arcsine of the square root of the proportions split and one half assigned to herbivores and the other to fungivores ( Neher et al., 2014). Total nematode data, nematode ecological indices, (Briar et al., 2011). The MI, MI25, PPI, ΣMI25, CI, EI, SI, and Hills pH, phosphorus (P), potassium (K), and micronutrients were trans- trophic diversity (N1) were calculated using weighted abundances for formed by taking the natural log of each value and adding 0.1 (Neher each management area on each hole as described in Neher (1999) and et al., 2014). Canonical correspondence analysis, implemented in R Neher et al. (2004, 2014). (version 3.1.0, R Core Team, Auckland, New Zealand), was performed using edaphic properties and nematode trophic groups, maturity in- 2.4. Soil analysis dices, and ecological indices. Multiple regression analysis in R was used to determine the relationship among nematode trophic group relative Two hundred fifty milliliters of each of the composite soil samples abundance, maturity indices, and ecological indices to soil properties. (twenty-seven per sampling time, total one hundred and eight samples) All independent variables were removed and entered into the final were passed through a 2-mm sieve and oven dried at 35 °C for ap- model using forward and backward eliminations with α set to 0.15. proximately 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), , and soil texture analysis.

163 E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

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 3.1. Nematode community management areas for all three golf courses (conventional p = 0.0331, hybrid p = 0.0018, and organic p = 0.0146). On the hybrid course, Approximately 60–400 nematodes were counted in each 25 cc of bacterivores were lowest on the putting greens on all sampling dates soil per sample, all of which contained every trophic group except for (Fig. 2c). The relative abundance of bacterivores was generally highest the omnivores, which were not present in the putting greens of the on the fairways of the conventional course and the putting greens of the conventional and hybrid golf course programs. The total number of organic course (Fig. 2b and d). nematodes on the conventional course was significantly different The other three trophic groups were less abundant than the herbi- among management areas (p = 0.0331) and management area × vores and bacterivores. The fungivores consisted of the family season × year (p = 0.0318) with the putting greens generally having Anguinidae and they were only significantly different among manage- the lowest number of nematodes (Fig. 2a). Although all management ment areas on the organic course (p = 0.0497), generally being areas on the organic course had similar total nematodes, the putting greatest on fairways (Fig. 2d). The omnivores (Nordiidae) were also only greens generally had the fewest nematodes (Fig. 2a). This was not true significantly different among management areas on the organic course for the hybrid course. Management areas were significantly different (p = 0.0069) generally being the lowest on the putting greens. The (p = 0.0210), as was management area × season × year carnivores (Mononchidae and Triplylidae) were significantly different (p = 0.0125), and the putting greens generally had the highest number among management areas on all three courses (conventional of nematodes (Fig. 2a). Total nematodes were greater in May 2013 than p = 0.0134, hybrid p = 0.0056, and organic p = 0.0434). They were May 2014, most likely due to the more severe winter in 2012–2013 lowest on the putting greens for the conventional and hybrid course and compared to a very mild winter in 2013–2014. higher on the putting greens for the organic course, except on the May The majority of nematodes identified were herbivores and bacter- 2014 sampling date (Fig. 2b, c, and d). Trophic diversity was sig- ivores. The herbivore families identified were Anguinidae, nificantly different among management areas for all courses (conven- Criconematidae, Dolichoridae, Heteroderidae, Hoplolaimidae, Longidoridae, tional p = 0.0109, hybrid p = 0.0012, and organic p = 0.0323) and Trichodoridae, and Tylenchidae. There were significant differences for generally was highest on the fairways and lowest on the putting greens the relative abundance of herbivores among management areas on all for all three courses (Table 1). three golf courses (conventional p = 0.0170, hybrid p = 0.0010, and organic p = 0.0056). Herbivore abundance was greatest on the putting 3.2. Nematode maturity and ecological indices greens for the conventional and hybrid course and lowest on the or- ganic course on almost every sampling data (Fig. 2b, c, and d). The The free-living maturity index (MI) was significantly different families identified were Cephalobidae, Diplogasteridae, among management areas for the conventional (p = 0.0029) and

164 .AlnPrise al. et Allan-Perkins E.

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

†‡ †† ‡‡ MI MI25§ PPI# ΣMI25 EI SI§§ CI## Hill's Diversity

Conventional May 2013 Rough 1.58 ± 0.04 a 2.52 ± 0.05 a 3.27 ± 0.27 – 5.78 ± 0.31 – 91.30 ± 0.41 – 61.18 ± 4.32 a 6.07 ± 0.92 – 0.31 ± 0.00 a Fairway 1.52 ± 0.07 ab 2.41 ± 0.10 ab 3.23 ± 0.15 – 5.64 ± 0.24 – 91.25 ± 1.92 – 52.88 ± 9.37 a 7.86 ± 2.57 – 0.31 ± 0.00 a PuttingGreen 1.26 ± 0.02 b 2.00 ± 0.00 b 2.96 ± 0.01 – 4.96 ± 0.01 – 92.27 ± 0.64 – 0.00 ± 0.00 b 6.59 ± 1.28 – 0.28 ± 0.00 b Sept. 2013 Rough 1.90 ± 0.16 a 2.89 ± 0.19 – 3.83 ± 0.25 a 6.72 ± 0.29 a 89.10 ± 0.65 – 72.52 ± 6.84 – 9.59 ± 1.11 – 0.30 ± 0.00 b Fairway 1.91 ± 0.11 a 2.65 ± 0.12 – 3.09 ± 0.16 b 5.73 ± 0.28 b 85.23 ± 0.14 – 64.12 ± 7.34 – 12.96 ± 0.98 – 0.31 ± 0.00 a PuttingGreen 1.41 ± 0.05 b 2.52 ± 0.07 – 2.87 ± 0.04 b 5.39 ± 0.11 b 93.61 ± 1.10 – 50.07 ± 3.43 – 4.42 ± 1.75 – 0.30 ± 0.00 b May 2014 Rough 2.22 ± 0.03 a 2.63 ± 0.13 – 3.25 ± 0.23 ab 5.88 ± 0.35 – 70.54 ± 6.40 b 62.40 ± 7.86 – 33.92 ± 19.14 a 0.30 ± 0.00 – Fairway 2.03 ± 0.16 a 2.89 ± 0.17 – 3.45 ± 0.05 a 6.34 ± 0.17 – 85.67 ± 3.31 a 76.62 ± 7.52 – 15.47 ± 5.01 ab 0.31 ± 0.00 – PuttingGreen 1.54 ± 0.18 b 2.71 ± 0.29 – 2.78 ± 0.09 b 5.50 ± 0.37 – 92.56 ± 2.59 a 60.17 ± 18.22 – 7.32 ± 3.13 b 0.31 ± 0.00 – Sept. 2014 Rough 2.13 ± 0.08 a 2.78 ± 0.19 – 3.17 ± 0.09 – 5.95 ± 0.18 – 78.03 ± 8.94 – 69.20 ± 8.71 – 28.94 ± 18.66 – 0.28 ± 0.01 b Fairway 1.64 ± 0.05 b 2.54 ± 0.06 – 3.21 ± 0.02 – 5.75 ± 0.04 – 88.65 ± 1.36 – 56.80 ± 3.45 – 11.64 ± 3.62 – 0.31 ± 0.00 a PuttingGreen 1.58 ± 0.05 b 2.43 ± 0.16 – 2.78 ± 0.15 – 5.21 ± 0.30 – 87.17 ± 4.82 – 40.91 ± 12.62 – 13.87 ± 8.60 – 0.31 ± 0.00 a Hybrid May 2013 Rough 2.05 ± 0.15 a 2.70 ± 0.10 a 3.01 ± 0.11 – 5.71 ± 0.09 a 87.56 ± 3.24 ab 79.11 ± 6.92 a 10.95 ± 3.87 – 0.31 ± 0.00 a Fairway 2.19 ± 0.12 a 2.82 ± 0.04 b 3.04 ± 0.07 – 5.85 ± 0.04 a 90.79 ± 0.46 a 88.20 ± 2.58 a 7.28 ± 0.34 – 0.30 ± 0.00 a PuttingGreen 1.53 ± 0.03 b 2.05 ± 0.05 b 2.99 ± 0.00 – 5.04 ± 0.05 b 80.16 ± 3.37 b 6.96 ± 6.96 b 12.58 ± 4.19 – 0.27 ± 0.00 b Sept. 2013 Rough 1.54 ± 0.22 – 2.48 ± 0.11 ab 3.04 ± 0.06 – 5.52 ± 0.09 ab 91.29 ± 3.27 – 52.72 ± 8.47 – 6.10 ± 4.33 – 0.30 ± 0.01 a Fairway 1.67 ± 0.11 – 2.68 ± 0.18 a 3.00 ± 0.13 – 5.69 ± 0.25 a 90.90 ± 2.06 – 66.67 ± 8.29 – 7.41 ± 0.88 – 0.31 ± 0.00 a PuttingGreen 1.49 ± 0.06 – 2.27 ± 0.12 b 2.92 ± 0.02 – 5.19 ± 0.12 b 89.23 ± 0.78 – 30.12 ± 6.61 – 7.46 ± 0.66 – 0.27 ± 0.00 b May 2014 Rough 2.21 ± 0.05 – 2.68 ± 0.08 b 3.01 ± 0.07 ab 5.69 ± 0.03 b 75.38 ± 3.50 b 70.52 ± 4.93 – 28.33 ± 5.67 – 0.31 ± 0.00 a Fairway 2.53 ± 0.07 – 3.11 ± 0.06 a 3.20 ± 0.03 a 6.31 ± 0.03 a 86.55 ± 1.49 a 91.18 ± 1.39 – 11.52 ± 0.12 – 0.32 ± 0.00 a 165 PuttingGreen 2.32 ± 0.07 – 2.81 ± 0.09 ab 2.85 ± 0.05 b 5.66 ± 0.15 b 76.56 ± 4.70 b 74.36 ± 5.33 – 32.54 ± 11.71 – 0.29 ± 0.01 b Sept. 2014 Rough 1.92 ± 0.12 – 2.67 ± 0.10 a 3.13 ± 0.05 a 5.80 ± 0.11 a 87.00 ± 1.56 a 71.17 ± 5.07 – 8.52 ± 1.44 b 0.31 ± 0.00 a Fairway 1.74 ± 0.11 – 2.74 ± 0.11 a 2.97 ± 0.05 ab 5.71 ± 0.11 a 91.88 ± 1.51 a 74.50 ± 6.12 – 6.64 ± 0.99 b 0.31 ± 0.00 a PuttingGreen 1.79 ± 0.02 – 2.15 ± 0.02 b 2.76 ± 0.06 b 4.91 ± 0.07 b 74.53 ± 0.29 b 22.50 ± 1.31 – 33.86 ± 0.97 a 0.29 ± 0.01 b Organic May 2013 Rough 1.71 ± 0.19 b 2.97 ± 0.10 – 3.71 ± 0.19 a 6.68 ± 0.10 a 92.45 ± 4.00 – 80.30 ± 2.93 ab 2.91 ± 2.19 b 0.30 ± 0.51 b Fairway 2.04 ± 0.08 b 2.62 ± 0.10 – 2.74 ± 0.07 b 5.35 ± 0.17 b 78.39 ± 4.28 – 65.34 ± 5.53 b 20.00 ± 4.77 a 0.32 ± 0.55 a PuttingGreen 2.70 ± 0.03 a 2.96 ± 0.07 – 2.58 ± 0.15 b 5.54 ± 0.15 b 84.51 ± 5.48 – 93.43 ± 3.17 a 9.32 ± 3.30 ab 0.29 ± 0.51 b Sept. 2013 Rough 1.50 ± 0.09 b 2.78 ± 0.20 – 3.06 ± 0.04 a 5.84 ± 0.17 – 93.92 ± 2.18 a 70.49 ± 7.72 ab 2.28 ± 1.32 b 0.30 ± 0.51 – Fairway 1.76 ± 0.11 b 2.65 ± 0.21 – 2.97 ± 0.11 a 5.62 ± 0.31 – 88.06 ± 3.95 a 61.51 ± 10.37 b 10.75 ± 4.78 ab 0.31 ± 0.53 – PuttingGreen 2.86 ± 0.07 a 3.02 ± 0.04 – 2.26 ± 0.15 b 5.28 ± 0.18 – 62.37 ± 7.97 b 91.55 ± 0.97 a 29.78 ± 9.19 a 0.30 ± 0.53 – May 2014 Rough 2.55 ± 0.39 – 3.41 ± 0.17 – 3.03 ± 0.07 a 6.44 ± 0.10 a 85.60 ± 6.69 – 90.15 ± 4.33 – 19.66 ± 12.78 – 0.31 ± 0.54 ab Fairway 2.35 ± 0.12 – 2.93 ± 0.17 – 3.08 ± 0.18 a 6.01 ± 0.31 ab 74.49 ± 4.24 – 77.45 ± 6.35 – 18.20 ± 5.31 – 0.32 ± 0.56 a PuttingGreen 2.47 ± 0.14 – 2.92 ± 0.04 – 2.47 ± 0.07 b 5.39 ± 0.11 b 86.20 ± 2.67 – 92.12 ± 1.94 – 13.40 ± 3.86 – 0.30 ± 0.52 b Sept. 2014 Rough 2.23 ± 0.07 – 3.06 ± 0.31 – 3.02 ± 0.07 a 6.08 ± 0.25 a 84.06 ± 6.04 – 78.81 ± 9.61 – 10.95 ± 5.02 – 0.31 ± 0.54 – Fairway 2.01 ± 0.07 – 2.74 ± 0.11 – 3.02 ± 0.19 a 5.76 ± 0.15 ab 84.42 ± 0.95 – 70.84 ± 5.51 – 8.31 ± 1.11 – 0.31 ± 0.54 – PuttingGreen 2.27 ± 0.12 – 2.91 ± 0.09 – 2.31 ± 0.04 b 5.22 ± 0.13 b 89.77 ± 1.10 – 88.21 ± 2.62 – 9.61 ± 1.04 – 0.30 ± 0.53 –

†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 Applied SoilEcology121(2017)161–171 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. E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171 organic (p = 00163) courses, but not the hybrid course (Table 1). (R2 = 0.951), and in September 2014 (R2 = 0.840). This correlated However, the hybrid course was the only one to have significant dif- with an increase in bacterivores in September 2014 only. Organic ferences in MI25 among management areas (p = 0.0029) suggesting matter was negatively correlated with CCA1 in September 2013 that the cp 1 bacterivores were similar among management areas. (R2 = 0.841) as was the relative abundance of herbivores Generally, the conventional roughs had the highest MI values as did the (R2 = 0.997). On all sampling dates, except September 2014, the or- hybrid roughs for MI25 (Table 1). The organic putting greens had the ganic course clusters separately from the hybrid and conventional highest MI values (Table 1). The herbivore index (PPI) was also only courses, and the organic putting greens cluster separately from the significantly different for the conventional (p = 0.0237) and organic organic roughs and fairways (Fig. 4). (p = 0.0057) courses. Generally, PPI was highest on the roughs and lowest on the putting greens for all three courses (Table 1). The com- 3.5. Regression analysis bined maturity index excluding cp 1 (ΣMI25) was significantly different among management areas for all courses (conventional p = 0.0327, Since many soil properties showed significant co-linearity, step-wise hybrid p = 0.0040, and organic p = 0.0097). Generally, it was highest regression analysis was used to reduce the number of independent on the roughs and lowest on the putting greens for all of the courses variables in the final models and to show the influence of soil properties (Table 1). on nematode communities (Table 3). An increase in pH was positively The only ecological index (EI) that was significantly different among related (partial R2 = 0.535) to an increase in total nematodes in Sep- management areas for all the golf courses was the structure index (SI) tember 2014, but not in any other season (Table 3). Soil pH was also (conventional p = 0.0008, hybrid p = 0.0147, and organic positively related to an increase in the relative abundance of herbivores p = 0.0381). Generally, structure was lowest on the putting greens of (R2 = 0.06–0.65, Table 3). The relative abundance of bacterivores was the conventional and hybrid courses and lowest on the fairways of the negatively associated with soil pH (R2 = 0.05–0.22) in September 2013 organic course (Table 1). The enrichment index was statistically dif- and May 2014 (Table 3). A positive increase in percent soil organic ferent among management areas on the hybrid course (p = 0.0140) matter explained an increase in total nematodes, herbivores, and PPI on with the putting greens generally being less enriched than the fairways most sampling dates, and was negatively associated with bacterivores or roughs (Table 1). The interaction of EI and SI predicts overall soil and carnivores in 2013 (Table 3). Percent omnivores were positively structure and nutrient availability (Ferris et al., 2001). All samples that associated with percent silt (R2 = 0.12–0.23) on all sampling dates were taken from the fairways and roughs fell within the upper right (Table 3). Phosphorous was positively related (R2 = 0.003–0.15) to SI quadrant of the scatterplot indicating high structure and nutrient en- on all sampling dates, except September 2014. A linear regression richment (Fig. 3a and b). However, for the putting greens, many of the analysis showed that bacterivore and herbivore were highly negatively conventional and hybrid samples showed low structure (falling into the related on all sampling dates (Table 4). upper left quadrant of the plot), whereas all the organic samples re- mained highly structured (Fig. 3c). 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 The conventional and hybrid golf courses had statistical differences lower structure and maturity on the conventional and hybrid courses. in pH (p < 0.0001 and p = 0.0055, respectively) and phosphorous However, on the organic course the putting greens had higher abun- (p = 0.0011 and p = 0.0016, respectively) among management areas dances of bacterivores than herbivores and high MI and SI values. The and sampling time (Table 2). Generally, pH and phosphorus were PPI values were lowest on the putting greens regardless of the golf highest on the putting greens of both courses (Table 2). Potassium was course management program. also significantly different among management areas (p = 0.0060) for Putting greens are potentially the most interesting area for studying the hybrid course, being greater on putting greens (Table 2). Organic nematode relationships on golf courses, as this area is where nematode matter was significantly (p = 0.0015) lower on the putting greens on damage is most severe and management inputs are highest in order to the organic course (Table 2). Percent sand differed among management maintain uniform and high quality turfgrass. Most differences were areas for all three courses (conventional p = 0.0365, hybrid observed in the relative abundances of the herbivore and bacterivore p = 0.0366, and organic p < 0.0001) being greatest on the putting nematodes among the three golf course programs. The organic man- greens of the conventional and organic courses and the roughs of the agement program had the lowest abundance of herbivores and the hybrid course. highest abundance of bacterivores, omnivores, and carnivores. There are several possible explanations for the increase in herbivores on the 3.4. Canonical correspondence analysis conventional and hybrid (managed as conventional) putting greens as compared to the organic course. On all sampling dates, canonical correspondence axes one (CCA1) First, the higher amounts of soil organic matter on the conventional and two (CCA2) were able to explain over 95% of the variation in the and hybrid putting greens, which Walker et al. (2002) showed posi- dataset, except for the September 2014 sampling date which explained tively correlated with an increase in herbivores on putting greens in over 88% (Fig. 4). The relative abundance of bacterivores and herbi- Ohio (r = 0.37). Organic matter may positively change soil properties vores were inversely related on all sampling dates. The relative abun- to be more conducive for herbivore populations (Thoden et al., 2011). dance of bacterivores was positively correlated with CCA1 on all sam- In our study, organic matter was associated with increased herbivores pling dates, except September 2014, but was only statistically (R2 = 0.030-0.146) and only correlating with herbivores in the CCA significant in May and September of 2013 (R2 = 0.994 and 0.999, re- from May 2014, suggesting that other factors may be influencing these spectively). The relative abundance of herbivores was significantly nematodes. Walker et al. (2002) also reported that organic matter negatively correlated with CCA1 on all sampling dates (R2 = 0.994, content was confounded by the age of the golf course, which was highly 0.916, 0.997), except September 2014 when it was negatively corre- correlated (r = 0.74). Jordan and Mitkowski (2006) found an increase lated with CCA2 (R2 = 0.980). The same axes were associated nega- in herbivores associated with course age based on 34 golf courses in the tively with pH (R2 = 0.925, 0.973, 0.844, 0.828) and phosphorous southern New England states of the United States of America. However, (R2 = 0.848, 0.895, 0.737, 0.502) on the same sampling dates. Organic they did not measure soil organic matter or other soil properties so the matter was positively correlated with CCA1 (R2 = 0.540) in September increase in herbivores may or may not have solely been due to course 2014 and with CCA2 in May 2013 (R2 = 0.876), September 2013 age. In our study, the organic course was younger than the conventional

166 E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

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

and hybrid courses, and also had less organic matter on the putting programs in this study had higher amounts of phosphorus and po- greens. The organic course was fertilized using seaweed extract and tassium as compared to the organic course, which may have con- animal derived organic fertilizers, which do not provide additional tributed to the increased herbivore population. Percent herbivores was organic matter and are heat-treated so additional nematodes or mi- positively related and percent bacterivores was negatively related to crobes may be killed before application, unlike the composts used in higher amounts of phosphorus in May 2013, September 2013, and most organic farms. Therefore, course age and management area would September 2014, which may support the hypothesis that increased have provided differences in organic matter, rather than organic versus nutrients could increase herbivore populations. According to regression synthetic fertilizers. Since the organic course used in this study is the analysis, phosphorous was related positively to increased herbivores in only course with no synthetic pesticide or fertilizer applications in the May 2013 and September 2014 (Table 4), indicating that although it United States, the nematode populations on this course would need to significantly contributed on some sampling dates, other factors may be be monitored in the future to determine how course age affects ne- more significant. matode communities under organic management. One such factor could be the addition of synthetic pesticides and Another factor that may influence herbivore populations are the fertilizers, which may have caused increased herbivore populations on different management inputs. Thoden et al. (2011) hypothesized that the conventional and hybrid putting greens and selected against the an increase in nutrients may cause plants to produce fewer secondary free-living nematodes, especially the bacterivores. Yardim and Edwards metabolites that are antagonistic to herbivores or the plants increase (1998) determined that the application of a combination of non-target root growth, both of which could increase the population of herbivores. fungicides, , and herbicides, as well as insecticides or her- In Walker et al.’s (2002) study there was a positive correlation among bicides alone, caused a significant increase in the number of herbivores course age with phosphorus and potassium (r = 0.31 and 0.26, re- and a decrease in the number of bacterivores. We did see a strong in- spectively), which may also explain the increase in herbivores with verse relationship among bacterivore and herbivore abundance in our increasing course age. The conventional and hybrid management dataset (R2 = 0.872-0.938). Cheng et al. (2008) found no effect of

167 E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

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

† pH Percent Organic Matter Phosphorous Potassium Percent Sand Percent Silt Percent Clay

Conventional May 2013 Rough 5.1 ± 0.2 c 4.4 ± 0.9 – 1.3 ± 0.1 b 50.2 ± 7.3 – 83.6 ± 2.2 b 10.6 ± 1.7 a 5.8 ± 0.6 – Fairway 5.7 ± 0.1 b 4.3 ± 0.4 – 2.2 ± 0.4 b 63.0 ± 7.7 – 83.0 ± 2.8 b 10.8 ± 2.1 a 6.3 ± 0.8 – PuttingGreen 6.6 ± 0.1 a 3.5 ± 0.2 – 16.3 ± 2.9 a 54.4 ± 3.3 – 88.4 ± 0.7 a 6.4 ± 0.4 b 5.3 ± 0.6 – Sept. Rough 5.2 ± 0.0 c 4.0 ± 0.5 – 1.5 ± 0.2 b 37.2 ± 6.4 b 83.9 ± 2.1 ab 11.1 ± 1.7 a 5.0 ± 0.5 – 2013 Fairway 5.8 ± 0.1 b 3.8 ± 0.3 – 2.5 ± 0.4 b 70.6 ± 6.5 a 82.2 ± 3.4 b 12.5 ± 3.0 a 5.3 ± 0.4 – PuttingGreen 6.6 ± 0.0 a 3.6 ± 0.3 – 14.0 ± 2.4 a 52.5 ± 3.3 ab 88.2 ± 0.9 a 6.0 ± 0.5 b 5.8 ± 0.4 – May 2014 Rough 5.2 ± 0.1 c 4.4 ± 0.7 – 1.1 ± 0.2 b 42.1 ± 5.6 – 81.2 ± 1.4 b 10.6 ± 1.1 a 8.2 ± 0.3 a Fairway 5.6 ± 0.1 b 4.4 ± 0.4 – 2.0 ± 0.5 b 49.6 ± 6.3 – 82.2 ± 3.1 b 10.8 ± 1.8 a 7.0 ± 1.3 ab PuttingGreen 6.3 ± 0.1 a 3.6 ± 0.3 – 12.8 ± 1.1 a 54.8 ± 2.5 – 88.4 ± 0.8 a 6.3 ± 0.4 b 5.3 ± 0.5 b Sept. Rough 5.1 ± 0.1 c 2.9 ± 0.2 a 2.0 ± 0.2 b 21.5 ± 3.4 – 81.2 ± 1.4 b 10.6 ± 1.1 a 8.2 ± 0.3 a 2014 Fairway 5.5 ± 0.0 b 3.4 ± 0.2 a 2.3 ± 0.1 b 18.4 ± 1.7 – 82.2 ± 3.1 b 10.8 ± 1.8 a 7.0 ± 1.3 ab PuttingGreen 6.4 ± 0.0 a 1.5 ± 0.4 b 4.9 ± 0.3 a 14.3 ± 1.0 – 88.4 ± 0.8 a 6.3 ± 0.4 b 5.3 ± 0.5 b Hybrid May 2013 Rough 5.3 ± 0.1 b 3.0 ± 0.1 – 1.0 ± 0.1 b 25.0 ± 2.6 b 93.2 ± 0.5 a 4.5 ± 0.7 – 2.4 ± 0.3 – Fairway 5.3 ± 0.0 b 3.9 ± 0.1 – 1.7 ± 0.1 b 22.1 ± 1.7 b 92.6 ± 0.2 ab 4.8 ± 0.6 – 2.6 ± 0.3 – PuttingGreen 6.6 ± 0.1 a 3.4 ± 0.2 – 18.1 ± 3.4 a 54.7 ± 5.5 a 91.3 ± 0.5 b 5.5 ± 0.1 – 3.2 ± 0.4 – Sept. Rough 4.9 ± 0.1 b 2.9 ± 0.2 – 1.4 ± 0.0 b 31.5 ± 0.6 b 92.7 ± 0.5 a 5.3 ± 0.7 b 2.0 ± 0.2 b 2013 Fairway 5.2 ± 0.0 b 3.6 ± 0.5 – 2.0 ± 0.1 b 48.0 ± 8.0 ab 91.3 ± 0.3 b 6.9 ± 0.3 a 1.8 ± 0.3 b PuttingGreen 6.8 ± 0.0 a 3.6 ± 0.3 – 17.4 ± 3.3 a 58.8 ± 1.0 a 89.5 ± 1.0 c 5.5 ± 0.9 b 4.9 ± 0.2 a May 2014 Rough 5.2 ± 0.1 b 2.9 ± 0.1 – 0.8 ± 0.1 b 18.2 ± 2.0 b 91.8 ± 0.1 – 4.5 ± 0.3 – 3.7 ± 0.3 – Fairway 5.2 ± 0.1 b 3.5 ± 0.3 – 1.2 ± 0.1 b 18.0 ± 1.9 b 90.8 ± 0.8 – 5.1 ± 0.4 – 4.1 ± 0.5 – PuttingGreen 6.5 ± 0.1 a 3.1 ± 0.7 – 16.2 ± 2.1 a 39.6 ± 1.4 a 91.4 ± 0.1 – 4.9 ± 0.7 – 3.7 ± 0.6 – Sept. Rough 5.6 ± 0.4 – 3.7 ± 0.3 – 8.4 ± 6.5 b 49.3 ± 16.2 – 91.8 ± 0.1 – 4.5 ± 0.3 – 3.7 ± 0.3 – 2014 Fairway 5.3 ± 0.2 – 4.2 ± 0.2 – 2.3 ± 0.6 b 66.7 ± 3.9 – 90.8 ± 0.8 – 5.1 ± 0.4 – 4.1 ± 0.5 – PuttingGreen 5.1 ± 0.1 – 3.5 ± 0.4 – 14.6 ± 2.0 a 57.0 ± 6.6 – 91.4 ± 0.1 – 4.9 ± 0.7 – 3.7 ± 0.6 – Organic May 2013 Rough 5.2 ± 0.0 – 2.6 ± 0.2 a 1.8 ± 0.2 b 27.6 ± 1.9 a 87.6 ± 0.4 b 9.7 ± 0.3 a 2.7 ± 0.2 a Fairway 5.1 ± 0.0 – 3.3 ± 0.1 a 2.9 ± 0.2 ab 22.8 ± 2.1 ab 88.2 ± 0.7 b 8.1 ± 0.6 a 3.7 ± 0.1 a PuttingGreen 5.2 ± 0.1 – 1.1 ± 0.0 b 4.7 ± 0.3 a 16.2 ± 0.9 b 96.6 ± 0.7 a 2.4 ± 0.8 b 1.0 ± 0.1 b Sept. Rough 5.3 ± 0.1 – 2.6 ± 0.1 a 2.1 ± 0.1 – 20.1 ± 3.6 a 87.1 ± 0.7 b 9.5 ± 0.5 a 3.5 ± 0.3 a 2013 Fairway 5.4 ± 0.1 – 2.9 ± 0.1 a 2.4 ± 0.1 – 21.1 ± 1.6 a 87.0 ± 1.0 b 10.6 ± 1.0 a 2.4 ± 0.1 b PuttingGreen 5.5 ± 0.1 – 1.2 ± 0.1 b 4.0 ± 0.3 – 12.4 ± 0.5 b 96.2 ± 0.2 a 1.9 ± 0.1 b 1.9 ± 0.1 b May 2014 Rough 5.1 ± 0.0 – 3.0 ± 0.1 a 1.6 ± 0.2 – 19.8 ± 3.1 – 88.9 ± 0.6 b 7.3 ± 0.6 a 3.8 ± 0.1 a Fairway 5.1 ± 0.1 – 3.2 ± 0.1 a 2.0 ± 0.1 – 16.6 ± 1.2 – 88.7 ± 1.2 b 6.9 ± 0.9 a 4.4 ± 0.3 a PuttingGreen 5.1 ± 0.0 – 1.3 ± 0.1 b 3.2 ± 0.2 – 15.6 ± 0.8 – 97.3 ± 0.2 a 1.4 ± 0.5 b 1.3 ± 0.4 b Sept. Rough 5.9 ± 0.4 a 4.2 ± 0.4 – 13.4 ± 5.9 a 61.3 ± 5.5 a 88.9 ± 0.6 b 7.3 ± 0.6 a 3.8 ± 0.1 a 2014 Fairway 5.0 ± 0.2 b 3.6 ± 0.1 – 1.2 ± 0.1 b 32.6 ± 4.0 b 88.7 ± 1.2 b 6.9 ± 0.9 a 4.4 ± 0.3 a PuttingGreen 5.0 ± 0.0 b 4.5 ± 0.6 – 2.0 ± 0.4 b 42.9 ± 5.6 ab 97.3 ± 0.2 a 1.4 ± 0.5 b 1.3 ± 0.4 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. organic versus synthetic fertilizers or the use of herbicides on nematode The free-living maturity indices (MI, MI25, and ΣMI25) were gen- communities, however this study was on turfgrass maintained as home erally higher on the organic course, supporting that these putting lawns and therefore applied at lower rates than typically used on a golf greens were less disturbed and more structured than the conventional course putting green. Walker et al. (2002) did not measure specific courses, as evidenced by the increased abundance of persister nema- amount of pesticides applied, but they did correlate the number of todes (Bongers, 1990; Neher et al., 2004). The low MI25 may indicate herbivores with the pesticide budget for each course. They found an lower pollution stress on the organic course (Neher et al., 2004; Yeates, increased fungicide and herbicide budget (0.31 and 0.43, respectively) 1994). In this study, there was an inverse relationship between MI and correlated with more herbivore nematodes. MI25 compared with PPI. Bongers and Bongers (1998) found the same Although all three putting greens were dominated by creeping inverse relationship in areas with high nitrogen fertilization, which bentgrass, the perennial ryegrass in the conventional and hybrid they hypothesized was due to the increased of the courses may have influenced the nematode community. However, stu- turfgrass roots for the herbivore nematodes due to the additional nu- dies on host preference indicate more nematode species prefer creeping trients. Since golf courses are nutrient enriched areas, we expected to bentgrass to bluegrasses, so this may have minimally contributed to our see the inverse relationship between MI and PPI observed by Bongers results (Martin, 2015). We were limited in our experimental design by and Bongers (1998). All of the courses had high EI, indicating a nutrient the lack of multiple organic golf courses within North America and rich environment (Ferris and Matute, 2003; Neher et al., 2014). All of specifically within a small area with similar . The establishment the golf course programs had similar enrichment and structure (Fig. 3a of a long-term golf course field plot to study the effects of organic versus and b) on the fairways and roughs. However, the putting greens on the synthetic fertilizers and pesticides on nematode communities would organic course were more structured than the other two courses provide better insight on the effect of management program with re- (Fig. 3c), indicating that the overall was less disturbed plication. The benefits of a long-term study would allow us to see and more connected. Management practices that occur more frequently temporal shifts in communities with management strategies and to on putting greens, such as aeration, dethatching, and verticutting, determine how course age and an increase in organic matter and nu- would be expected to reduce the overall structure index on putting trients over time affect nematode communities. greens compared to roughs and fairways. However, we did not see this

168 E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

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. on the three golf courses we studied, suggesting that these practices nematode diversity and herbivore maturity (PPI), with the putting minimally effect nematode composition. greens of all three golf courses having the lowest values for these me- The results of this study were similar to those of other nematodes trics. However, there were large differences in nematode communities studies in many ways. The dominant trophic groups were the herbi- among organically and conventionally managed putting greens. This is vores and bacterivores, which is consistent with nematode communities the area of most interest to golf courses, as this is where nematode from many different cropping ecosystems. The fungivores were the least damage is most severe. This study provides a list of possible factors abundant group, as in other turfgrass studies (Cheng et al., 2008). This strongly influencing an increase in herbivores that cause turfgrass da- may be due to the removal of the thatch, the layer of decaying plant mage. Continued monitoring of these three golf courses will help to material underneath the canopy sitting above the soil, during sampling, determine if course age influences nematode communities, especially which is hypothesized to be the area with the highest fungal abundance those under organic management. Additional factors to further in- and therefore it may be the area with the greatest abundance vestigate would be decreasing organic matter, phosphorus, potassium, (Ferris and Matute, 2003; Hendrix et al., 1986; Moore and de Ruiter, and the use of synthetic fertilizers or pesticides. Future studies should 1994). On turfgrass, there is a generally held belief that nematode focus on examining the effects of these factors on each nematode populations are greatest on the putting greens due to the increased trophic group and their interactive relationships to determine if they moisture and percent sand, which aid in nematode movement (Jordan can be integrated into golf course management strategies, and poten- and Mitkowski, 2006). Moreover, most studies on turfgrass nematodes tially to less managed turf such as home lawns and athletic fields, to have only sampled the putting greens and often only the herbivores. In reduce herbivores and potentially increase free-living nematode popu- our study, we determined that fairways have the highest abundance of lations, thus reducing disease and increasing turfgrass health through total nematodes, suggesting that total population is not dependent on benefits such as increased available nitrogen via bacterivore nema- percent sand or higher moisture levels from increased irrigation, but todes. perhaps is related to increases in organic matter. However, herbivores were still greatest on putting greens, except on the organic course, Acknowledgements suggesting that other inputs may be increasing the nematode popula- tions on the conventional and hybrid putting greens. The authors would like to thank the following people for their contributions to nematode identification, statistical analysis, and 5. Conclusion editing of the manuscript: James Popko, Jr., Hyunkyu Sang, Victoria Kohler, Deborah Neher, Jim LaMondia, and Wes Autio. This research The results of this study show that management intensity affects was funded by the United States Golf Association, the New England

169 .AlnPrise al. et Allan-Perkins E.

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

Response Variable Sampling Date Partial R2 and sign of coefficient (b) R2

pH Percent Organic Matter Phosphorous Potassium Percent Sand Percent Silt Percent Clay Final Model Full Model

Total nematodes May 2013 0.1461(+) 0.1461 0.1814 September 2013 0.5346(+) 0.0606(+) 0.0025(−) 0.0122(−) 0.0582(−) 0.6681 0.6792 May 2014 0.2933(+) 0.2933 0.3920 September 2014 0.0400(+) 0.2786(+) 0.0356(+) 0.1366(−) 0.0865(−) 0.5664 0.5992 Percent herbivores May 2013 0.6502(+) 0.1459(+) 0.0218(+) 0.8180 0.8214 September 2013 0.2675(+) 0.3073(+) 0.5748 0.6165 May 2014 0.1928(+) 0.0307(−) 0.2241(−) 0.4476 0.4894 September 2014 0.0615(+) 0.0298(+) 0.0135(+) 0.6227(+) 0.7274 0.7387 Percent bacterivores May 2013 0.1824(−) 0.4680(−) 0.6504 0.6785 September 2013 0.2257(−) 0.2233(−) 0.4490 0.4851 May 2014 0.0551(−) 0.0263(+) 0.2599(−) 0.3414 0.3823 September 2014 0.1139(−) 0.0348(−) 0.5308(−) 0.6796 0.7050 Percent omnivores May 2013 0.0839(+) 0.2343(+) 0.3182 0.3752 September 2013 0.2384(−) 0.1241(+) 0.3625 0.3975 May 2014 0.0551(−) 0.0736(+) 0.1842(+) 0.3128 0.3180 September 2014 0.1766(−) 0.0054(+) 0.0880(−) 0.0012(+) 0.1370(+) 0.4081 0.4232 Percent carnivores May 2013 0.2343(−) 0.3101(−) 0.0107(−) 0.0089(−) 0.0391(−) 0.6031 0.6266 September 2013 0.5555(−) 0.5555 0.6008 May 2014 0.2025(−) 0.0603(+) 0.2628 0.3816 September 2014 0.1362(−) 0.2139(+) 0.3502 0.4284 Percent fungivores May 2013 0.0353(−) 0.2387(+) 0.2740 0.3754 September 2013 0.0075(−) 0.0259(+) 0.0968(−) 0.3432(−) 0.4735 0.4983 170 May 2014 NA 0.0965 September 2014 0.2746(+) 0.0029(−) 0.0762(+) 0.3538 0.3726 Free-living maturity index (MI) May 2013 0.3283(−) 0.4152(−) 0.0210(−) 0.7645 0.7732 September 2013 0.3567(−) 0.3567 0.4429 May 2014 0.2555(−) 0.0636(+) 0.0705(+) 0.3896 0.3952 September 2014 0.3275(−) 0.0029(−) 0.1895(+) 0.5200 0.5367 MI excluding cp1 (MI25) May 2013 0.6756(−) 0.0990(+) 0.0360(+) 0.8107 0.8242 September 2013 0.2173(−) 0.0942(−) 0.0048(−) 0.0758(−) 0.3921 0.4319 May 2014 0.0438(+) 0.1814(+) 0.2252 0.2940 September 2014 0.0037(+) 0.1005(+) 0.0752(−) 0.1794 0.2341 Herbivore maturity index (PPI) May 2013 0.2185(+) 0.2185 0.3407 September 2013 0.2141(+) 0.1056(−) 0.0427(−) 0.0113(+) 0.0502(+) 0.0501(+) 0.4740 0.4768 May 2014 0.0190(+) 0.4928(+) 0.1213(−) 0.0287(−) 0.6618 0.6995 September 2014 0.0858 (−) 0.0147(+) 0.2487(−) 0.1816(−) 0.4026 0.5308 Sum of MI25 and PPI (ΣMI25) May 2013 0.3789(−) 0.0005(+) 0.0864(+) 0.4658 0.4878 September 2013 0.0283(+) 0.2403(−) 0.0674(−) 0.1194(+) 0.4554 0.5027 May 2014 0.1701(−) 0.0551(−) 0.0875(−) 0.3128 0.3655

September 2014 0.4569(−) 0.1107(−) 0.0340(−) 0.0297(−) 0.6311 0.6391 Applied SoilEcology121(2017)161–171 Enrichment Index (EI) May 2013 0.0812(−) 0.0812 0.1521 September 2013 0.3563(+) 0.0002(+) 0.0069(+) 0.0830(+) 0.4464 0.4899 May 2014 0.0158(+) 0.1169(−) 0.1328 0.2024 September 2014 0.0070(+) 0.1582(−) 0.2441(−) 0.4093 0.4721 Structure Index (SI) May 2013 0.7674(−) 0.0033(−) 0.1025(+) 0.8733 0.8806 September 2013 0.2253(+) 0.1553(−) 0.1459(−) 0.5265 0.5438 May 2014 0.0969(−) 0.3075(−) 0.4043 0.4650 September 2014 0.5762(−) 0.0002(−) 0.1054(−) 0.6817 0.7123 Channel Index (CI) May 2013 NA 0.1170 September 2013 0.2385(−) 0.0024(−) 0.1295(−) 0.3704 0.4139 May 2014 NA 0.1072 September 2014 0.0039(−) 0.1235(+) 0.2653(+) 0.3927 0.4409 E. Allan-Perkins et al. Applied Soil Ecology 121 (2017) 161–171

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