Research Article Journal of Orthoptera Research 2024, 33(2): 255-266 Topographic heterogeneity influences diversity and abundance of Orthoptera in a rewilding scheme Tim GARDINER!, DOROTHY CASEY? 1 Fisheries, Biodiversity and Geomorphology, Environment Agency, Iceni House, Cobham Road, Ipswich, Suffolk, IP3 9JD, UK. 2 Brooke House, Ashbocking, Ipswich, IP6 9JY, UK. Corresponding author: Tim Gardiner (tim.gardiner@environment-agency.gov.uk) Academic editor: Ludivina Barrientos-Lozano | Received 30 January 2024 | Accepted 6 April 2024 | Published 23 September 2024 https://zoobank. org/B828A647-DE53-4D 1 7-8F52-C165315ADF97 Citation: Gardiner T, Casey D (2024) Topographic heterogeneity influences diversity and abundance of Orthoptera in a rewilding scheme. Journal of Orthoptera Research 33(2): 255-266. https://doi.org/10.3897/jor.33.119897 Abstract Rewilding aims to restore ‘self-willed’ ecosystems involving the crea- tion of habitats subject to stochastic disturbance connected by favorable corridors for dispersal of animals, including insects. Reversion of arable land to grassland and scrub habitats adjacent to Arger Fen nature reserve in Suffolk (southeast England) through non-intervention allowed succession to occur largely unmanaged on fields with differing topography, from flat terrain to slopes. Monitoring of Orthoptera revealed statistical evidence that species diversity and richness was greater on the steeper slopes (gradi- ent > 10%), while species varied in their topographic preferences from flat terrain (e.g., long-winged conehead Conocephalus fuscus Fabricius, 1793) to slopes (e.g., field grasshopper Chorthippus brunneus Thunberg, 1815). Lago- morph grazing by the wild brown hare Lepus europaeus (Pallas, 1778) and the rabbit Oryctoloagus cuniculus (Linnaeus, 1758) appeared to be critical in maintaining exposed soil for hillside species such as C. brunneus, which may require the egg-laying and basking habitat. A mosaic of scrub and grassland on a wooded hillside affected by ash dieback Hymenoscyphus frax- ineus (Baral et al. 2014) was also important for Orthoptera. We postulate that rewilding schemes on arable land may be particularly effective when there are topographic undulations incorporating flat and hillside areas to promote the greatest diversity of Orthoptera. Keywords Acrididae, bush-cricket, grasshopper, landscape, Tettigoniidae, topography, wilding Introduction The term rewilding was first used in the 1980s (Noss 1985). Soulé and Noss (1998) proposed three key components of rewild- ing: large core protected areas, ecological connectivity, and key- stone species that translated to the 3Cs of cores, corridors, and car- nivores. Over time, Soulé and Noss’s original concept has shifted into local interpretations but still incorporates self-regulatory eco- systems with minimal or no anthropogenic influence where wild grazers have a critical role (Dempsey 2021). In recent times, the aim of rewilding in Europe has focused on restoring natural processes by creating large areas of habitat sub- ject to stochastic disturbances connected by favorable corridors for species to disperse along (van Klink et al. 2020, Carver and Con- very 2021, Gordon et al. 2021a, b). Hart et al. (2023) provide an overview of the published studies relating to rewilding schemes in Europe, noting that it can take decades if not centuries to have the desired benefits to target species (e.g., Chernobyl Exclusion Zone rewilding site; Dombrovski et al. 2022). The European Green Belt initiative, first discussed in 1989 after the fall of the Berlin Wall, led to the establishment of a 12,500 km long and 50 km wide green corridor from Norway to Greece following the former Iron Curtain (Fraser 2009). The development of naturally vegetated corridors benefits not only apex predators (e.g., the Balkan lynx Lynx lynx balcanicus Bures, 1941 and the brown bear Ursus arctos Linnaeus, 1758 (Sterr et al. 2012)), but also beetles (Coleoptera), flies (Diptera), and some moths (Lepidoptera) of woodland habitats (Thomas et al. 1994, Merckx 2015). Pollinator activity and abundance in horse-grazed areas increased in a Swedish rewilding scheme (Garrido et al. 2019, 2021, 2022), suggesting that introduced herbivores play a role in maintaining rewilded habitats for early successional inver- tebrates. In the Czech Republic, a 26-year experiment revealed that bison, pony, and cattle grazing led to a higher diversity and abun- dance of butterflies (Konvicka et al. 2021). In the UK, reintroduced beavers (Castor fiber Linnaeus, 1758) act as keystone herbivores in rewilding schemes by modifying riparian habitats on farmland, creating ‘beaver meadows’ (Stringer and Gaywood 2016). These structurally diverse wet meadows can form quickly in response to dammed rivers and an absence of active grassland management (e.g., at Spains Hall in Finchingfield, south-east England (Essex County Council 2024)). Ecological restoration that allows habitats to regenerate with a lack of active agricultural (e.g., fertilizer application) or conserva- tion management, such as controlled livestock grazing, is known as rewilding max, a passive strategy (Gordon et al. 2021a, b). Domestic Copyright Tim Gardiner & Dorothy Casey. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unre- stricted use, distribution, and reproduction in any medium, provided the original author and source are credited. JOURNAL OF ORTHOPTERA RESEARCH 2024, 33(2) 256 livestock (cattle, sheep, and ponies) are often used to graze rewilded farmland sites (e.g., Knepp Wildland in West Sussex, UK (Dempsey 2021)) after the initial establishment phase and grassland re-estab- lishment (Casey et al. 2020). This form of conservation interven- tion without sole reliance on natural grazers is known as rewilding lite (Gordon et al. 2021b). However, introduced livestock can have detrimental impacts on Orthoptera when stocking density (number of animals) is too high and the resultant sward height is too short (Gardiner and Haines 2008). The consequences of livestock grazing are largely influenced by the intensity of grazing, type of grazer, and rotational or seasonal aspects of the regime, which in turn have an impact on the characteristics of grasslands, such as leaf litter devel- opment, plant species presence, sward height, and vegetation bio- mass (Marini et al. 2008, Fonderflick et al. 2014, Rada et al. 2014). Rewilding and Orthoptera.—To reverse the decline of insects such as grasshoppers and bush-crickets, the rewilding of arable land may be highly beneficial (Tree 2017, van Klink and WallisDeVries 2018, Garrido et al. 2022). The ideal aim of rewilding is to restore natu- ral processes, often involving the creation of large areas of habitat with stochastic disturbance connected by favorable corridors for species to disperse along (Carver and Convery 2021, Gordon et al. 2021a, b). Rewilding is well established at some UK sites, such as Knepp in West Sussex (Greenaway 2006, Tree 2017, Wallace 2018, Dempsey 2021), Spains Hall in Essex (Essex County Coun- cil 2024), and two sites in Suffolk: Black Bourn Valley and the Somerleyton Estate (Gardiner and Casey 2022a, b). Research at Black Bourn Valley revealed that Orthoptera were found in greatest abundance and diversity in fields > 8 years post-arable cropping cessation (Gardiner and Casey 2022a, b, Broad 2023). The Gar- diner and Casey studies noted the importance of wild lagomorph grazing, anthills, and pond edge habitat, particularly for species such as the field grasshopper Chorthippus brunneus (Thunberg, 1815), which require exposed soil (Waloff 1950). Key aspects of topographic heterogeneity.—Given their importance, various studies have addressed the effects of the topography el- ements of aspect, elevation, and slope gradient on Orthoptera. Landscape heterogeneity is an important factor in insect ecology (Li et al. 2022), such as for butterflies (Kumar et al. 2009, Beirao et al. 2021) and Orthoptera (Batary et al. 2007, Marini et al. 2008, Rada et al. 2014, Joubert-Van der Merwe and Pryke 2018). Topog- raphy of landscapes is characterized by aspect, elevation, and slope gradient (Li et al. 2011) and constitutes a critical influence on envi- ronmental diversity affecting biotic (e.g., taxonomic richness and diversity, population structure, and animal dispersal) and abiotic (e.g., soil structure, micro/macroclimate, and hydrological pro- cesses) factors (Zhang et al. 2017, Amatulli et al. 2018). For exam- ple, plant-level scale microtopography (1 cm to 1 m) incorporates the same elements as broader landscape topography, including as- pect and slope gradient (Diefenderfer et al. 2018). When occurring in any number, anthills at rewilding sites provide significant mi- crotopographic heterogeneity due to the basking and oviposition opportunities provided by the slopes (King 2006, 2020, 2021). i) Aspect.—Orthoptera are affected by significant changes in eleva- tion and microclimatic variations due to north- and south-facing slopes (Voisin 1990, Weiss et al. 2013). South-facing slopes are particularly species rich and important for grasshoppers (Gar- diner 2011). In these scenarios, a hot ‘microclimate’ with high orthopteran abundance can develop (Marshall and Haes 1988). A study of Furze Hills in southeast England found significantly T. GARDINER AND D. CASEY more grasshopper nymphs and C. brunneus adults on the south- facing slope (Gardiner 2022), while a southern aspect appeared to promote higher orthopteran abundance and species richness on Hungry Hill at Lound Lakes (Gardiner 2021). ii) Elevation (altitude).—Elevation, measured in meters above mean sea level (masl), is a common aspect of Orthoptera studies, par- ticularly for species at high altitudes. Studies often record a decline in orthopteran abundance and species richness with increasing el- evation (e.g., Gebeyehu and Samways 2006, Pitteloud et al. 2020), although not exclusively so (see Azil and Benzehra 2020). High- altitude species have adaptations for survival in the colder climate. For example, it appears that egg hatching and adult maturity of the common green grasshopper Omocestus viridulus (Linnaeus, 1758) in the Alps (>2000 masl) are reached much later at high elevations than at low elevations (Berner 2005). Hatching and maturation can also be severely affected by cloudy weather (low amount of sunshine) at high elevations, with cold weather affecting reproduc- tive success (Berner et al. 2004). However, high altitude O. viridu- lus nymphs may have a much shorter period from egg hatching to adult (quicker nymphal maturation) than their lower-altitude counterparts, thereby maximizing their chances of survival (in es- sence, quicker development is necessary due to a more unfavorable climate) (Berner et al. 2004). Smaller hills at low elevations (sum- mits of less than 100 masl) are also likely to have diverse environ- mental conditions depending on aspect and slope gradient. iti) Slope gradient.—Typically, slope steepness is classified by gradi- ent: 0-5% very weak slope, 6-10% weak slope, 10-15% moder- ate slope and > 16% moderately steep and greater (Sikdar et al. 2004). Studies have indicated a declining abundance and diversity of Orthoptera with increasing slope steepness (e.g., Gebeyehu and Samways 2006, Wersebeckmann et al. 2023). Steep slopes are of- ten difficult to actively manage and become abandoned, leading to scrub encroachment and reduced Orthoptera abundance and diversity of open habitats (Marini et al. 2009, Wersebeckmann et al. 2023). In contrast, on small hills in the UK, grassy summits and weak-moderately steep slopes may be particularly susceptible to the burrowing activities of rabbits. This lagomorph digging ac- tivity creates an open mosaic of bare soil and fine-leaved grasses favorable for grasshoppers of shorter vegetation (e.g., C. brunneus) but not bush-crickets (e.g., Conocephalus fuscus Fabricius, 1793), which inhabit taller swards (Gardiner 2022). Interaction between grazing and topography.—On low elevation hill- sides (<100 m), the grazing of grassland by wild lagomorphs (e.g., hare Lepus europaeus Pallas, 1778 and rabbit Oryctoloagus cuniculus Linnaeus, 1758) or targeted livestock (e.g., cattle or sheep) appears to determine the abundance and diversity of Orthoptera in com- bination with aspect (Fonderflick et al. 2014). Two hillside stud- ies suggested lower species richness on rabbit-grazed hill summits. Rabbit grazing leads to an absence of species such as Roesel’s bush- cricket Roeselii roeseliana (Hagenbach, 1822) and dark bush-cricket Pholidoptera griseoaptera (De Geer, 1773) and an abundance of C. brunneus and Pseudochorthippus parallelus (Zetterstedt, 1821) (Gar- diner 2022). There is uncertainty over whether grazing merely ex- pands favorable habitat on hills for species such as C. brunneus or if bare soil lures adults away from nymphal habitats. Soil slippage on hills also appears to provide the bare soil habitat required for adult oviposition and basking for species such as C. brunneus in addition to the trampling hooves of grazing livestock (cattle or sheep) and the burrowing activities of lagomorphs (Gardiner 2022). JOURNAL OF ORTHOPTERA RESEARCH 2024, 33(2) T. GARDINER AND D. CASEY Topography and rewilding schemes.—Variations in landscape topo- graphic features (e.g., slope gradient) can create microclimate heter- ogeneity (e.g., soil drainage and solar radiation), which influences plant and Orthoptera distribution at differing altitudes (Unsicker et al. 2010) and may be important for the selection of rewilding sites. Plant communities are also altered by topographic heterogeneity that influences the height and structure of vegetation as well as the feeding areas of Orthoptera. For example, particularly dense patch- es of coarse grasses (e.g., cock’s-foot Dactylis glomerata Linnaeus, 1753) often form in the moist soil at the base of slopes, which can be important feeding areas for nymphs and adults of species such as the meadow grasshopper P. parallelus (Gardiner and Hill 2004). Re- wilding on former cropland without significant heterogeneity (i.e., mostly flat terrain) can cause the development of an open layer of fine-leaved grasses (e.g., fescue Festuca and bent Agrostis spp.) and a warm microclimate favorable for nymphal and adult development (Gardiner 2022) but limited coarse grasses for feeding (Gardiner and Casey 2022a, b). A mosaic of fine and coarse-leaved grasses is required for all life stages. Movements of grasshopper nymphs and adults between different grass patches may therefore be frequent on post-arable rewilding sites. Topographic heterogeneity, particularly of aspect, elevation, and slope gradient, influences the distribution of these grassland patches (Unsicker et al. 2010). One factor that was not investigated in a recent study of Or- thoptera colonization at Black Bourn Valley was the influence of topographic heterogeneity in rewilding fields (Broad 2023). This was mainly due to the mostly flat topography of the landscape (c. fields 39-52 m elevation) and the absence of any notable slopes (very weak slopes: mean gradient 0.9%, min/max 0.2-2.2%) or small hills. The effect of aspect and slope gradient on weak-mod- erate slopes (5-15%) has not been thoroughly investigated, while its importance for Orthoptera in rewilding schemes is unknown. The aim of this study was to compare the rewilded-grassland Orthoptera on flat and sloping former-arable fields at Arger Fen in Suffolk, UK. The results are discussed in relation to the topograph- ic heterogeneity of the fields, specifically the abundance and diver- sity of Orthoptera in rewilded fields with differing slope gradients. Materials and methods Study site—Arger Fen nature reserve (eastern England, 51°59'14.9856"N, 0°49'9.3504"E) is owned and managed by Suf- folk Wildlife Trust (SWT) and is a mosaic of lowland woodland, dry acid grassland, and fen wetland (110 ha total area) alongside farm- land with slopes varying from very weak to moderately steep (mean gradient 3%, min/max 0.2-10.9%). Each of the four rewilding fields were taken out of arable production between 2004 and 2014 and had been treated with nitrogen (N) fertilizer for a range of annual crops, including winter wheat. Soil types at the reserve vary from clay loams with impeded drainage to freely drained sands/gravels. Much of the rewilding area was once part of Leavenheath, an exten- sive (69 ha) lowland heath that was enclosed and converted into arable farmland after 1817 (Chatters 1985). The intention of rewil- ding the arable fields was to establish a mosaic of rough grassland and scrub similar to that present on Leavenheath before enclosure. A total of four fields were selected for this study due to their differing topographic heterogeneity: two ‘flat’ and two ‘sloping’ (Table 1, Figs 1, 2). The topography of the flat fields was almost completely even with a few very weak slopes (mean gradient 0.2- 0.8%), while the sloping fields had slopes varying from very weak to moderately steep (gradient 1.5- 10.9%). Vertical relief was great- est in the sloping fields (27 m) compared to the flat fields (13 m). 257 All fields were last plowed and cropped before 2014, resulting in maturing grassland swards similar to other ex-arable rewilding sites in Suffolk, such as Black Bourn Valley (Gardiner and Casey 2022a, b). Once cropping ceased, all fields were allowed to natu- rally revert to grassland and scrub through succession with mini- mal intervention apart from mowing of footpaths and occasional light grazing (not during the study period). In the flat and sloping fields in this study, the grasses creeping bent (Agrostis stolonifera Linnaeus, 1753), crested dog's tail (Cynosu- rus cristatus Linnaeus, 1753), D. glomerata, and Yorkshire fog (Hol- cus lanatus Linnaeus, 1753) were frequent, while tufted-hair grass (Deschampsia caespitosa Linnaeus, 1753, Palisot de Beauvois 1812) and red fescue (Festuca rubra Linnaeus, 1753) were often locally abundant. Marsh thistle (Cirsium palustre (Linnaeus 1753), Scopoli 1772) and compact rush (Juncus conglomeratus Linnaeus, 1753) were found in wetter patches in the flat fields. Herbaceous species were scattered throughout all four rewilding fields, including pyramidal orchid (Anacamptis pyramidalis (Linnaeus) Richard 1817), knap- weed (Centaura nigra Linnaeus, 1753), wild carrot (Daucus carota Linnaeus, 1753), perforate St. John’s wort (Hypericum perforatum Linnaeus, 1753), cat’s-ear (Hypochaeris radicata Linnaeus, 1753), ox- eye daisy (Leucanthemum vulgare Lamarck, 1779), and ribwort plan- tain (Plantago lanceolata Linnaeus, 1753). In addition, sheep’s sorrel (Rumex acetosella Linnaeus, 1753) and bracken (Pteridium aquilinum Linnaeus, 1753, Kuhn, 1879) were found to be abundant in a sand- pit on the edge of the sloping Ford’s Heath field. Arable weeds persisting from former cultivation included the annuals field madder (Sherardia arvensis Linnaeus, 1753; Kings- land Lane) and scarlet pimpernel (Anagallis arvensis Linnaeus, 1753; Ford’s Heath). The near threatened (NT; Vascular Plant Red Data List for Great Britain, Cheffings et al. 2005) annual common cudweed Filago vulgaris (Lamarck, 1779) was recorded in the slop- ing Ford’s Heath and Hullback’s Grove fields, indicating a possible initial return of a heathy grassland flora through rewilding on the well-drained soil of the slopes. Filago vulgaris has only been found to be frequent in Suffolk in the acidic, freely draining soils of the Sandlings and Breckland heathlands (Sanford 2005). Post-cropping cessation, scrubland communities have estab- lished in the rewilding fields. Common scrub species observed in- clude hazel (Corylus avellana Linnaeus, 1753), hawthorn (Crataegus monogyna, Jacquin, 1775), broom (Cytisus scoparius Linnaeus, 1753, Link, 1822), (only in Ford’s Heath near sandpit), blackthorn (Pru- nus spinosa Linnaeus, 1753), oak (Quercus robur Linnaeus, 1753), field rose (Rosa arvensis Hudson, 1762), bramble (Rubus fruticosus Linnaeus, 1753), and goat willow (Salix caprea Linnaeus, 1753). A small area (c. 0.2 ha) of ash (Fraxinus excelsior Linnaeus, 1753) saplings affected by Hymenoscyphus fraxineus dieback occurred in Hullback’s Grove. Saplings were interspersed with tall grasses. Table 1. Characteristics of the four fields demarcated by flat and sloping topography. Topography/ Area Linking Mean gradient Elevation min-max field name (ha) habitat % (min-max) (m) vertical relief Flat Kingsland Lane 15.4 H,GL,W _ 0.6 (0.2-0.8) 58-65 Peck’s Piece 160 H,W 0.6 (0.3-0.8) 64-71 Sloping Ford's Heath 30.8 H,M,W__ 5.2 (1.5-10.9) 43-66 Hullback’s Grove 17.0 H,W _ 5.8 (3.5-10.5) 52-70 Key: H = hedge, GL = green lane, M = marsh, W = woodland. JOURNAL OF ORTHOPTERA RESEARCH 2024, 33(2) 258 T. GARDINER AND D. CASEY : a ee § He. 4 ¥ & See a High Road ° ok ae Ford’s Heath we eae ‘ i a4 i Sandpit -sloping Houses at 3 2 att sah bitin” ' we Bi ! a i a ees ' Red Barn Farm i he me ey of » ee \. phones Leavenheath Farm | F < } ( ~\ ( Grove O : Poo aaa a- Track nw wy i 2 \ — Hedgerow an Reservoir At ay €) Woodland oo - VARS. s ae mS Arger Fen / Peck’s Piece -flat Hullback’s Grove -sloping ofe Fen 3 , Kingsland Lane | N x -flat ‘ = ‘en ff a3 Arger Fen Fig. 2. The four study fields demarcated by flat or sloping status and the location of Arger Fen. There was no active conservation management of any of the gether for recording purposes. The surveys were undertaken in veg- fields throughout the 2021 summer study period. All fields were etation sufficiently short (<50 cm) to minimize the possibility of surrounded by dense hedgerows and were adjacent to woodland overlooking nymphs in tall grass or non-stridulating species such (Fig. 2). as groundhoppers (Tetrigidae) (Gardiner et al. 2005). For an ob- server (TG) with 25 years’ experience identifying Orthoptera in the Transect surveys.—A 1 m wide x 400 m long transect was estab- UK, it was relatively easy to ascertain the species of adults without lished in each of the four fields. Transects were arranged in a W_ capture (Gardiner and Hill 2006), although some species, such shape (each arm 100 m) to ensure even coverage of each field and as C. fuscus and R. roeselii, are significantly under-recorded using to avoid any edge habitat effects. The transect method followed visual transects (Gardiner and Hill 2006). It should be noted that the methodology of Gardiner et al. (2005), Gardiner and Hill inexperienced surveyors (<5 years identifying Orthoptera in the (2006), and Gardiner (2021). Adult individuals of all Orthoptera_ field) may produce much lower counts of Orthoptera (Gardiner species along all transects were recorded acoustically and visually 2009b). to determine assemblage composition, species diversity, and spe- A dual visual and acoustic monitoring method has been used cies richness. by Weiss et al. (2013) to ensure complete coverage of the orthop- Each transect was walked at a slow, strolling pace (2 km/h) on _ teran fauna of sites. In the current study, a stridulation monitoring three occasions from May to August 2021. Nymphs detected from technique was used to record adult males of species that stridulated a 1-m wide band in front of the observer were recorded along all along the transects at the same time as visual monitoring. Stridu- transects. The observer walked through the grass and recorded any lation monitoring has been used to record cryptic species in the orthopteran that was disturbed and jumped. As it is difficult to dis- county of Essex and has been found to be effective compared to vis- tinguish between species in the early instars (though not impos- ual sighting transects and pitfall traps (Harvey and Gardiner 2006, sible; see Thommen 2021), nymphs of all species were lumped to- Gardiner et al. 2010, Schirmel et al. 2010). Acoustic signaling was JOURNAL OF ORTHOPTERA RESEARCH 2024, 33(2) T. GARDINER AND D. CASEY used to locate Orthoptera to assess species richness/diversity and preferences between flat and sloping rewilding fields, but acoustic signals were not recorded or analyzed. Bat detectors were not uti- lized in the current study as the first author (TG) was able to detect stridulating males with non-ultrasonic calls up to 20 m away either side of the transect. The weather conditions on survey days were fa- vorable for insect activity, being largely sunny and warm (>17°C). Acoustic detection systems (Diwaker et al. 2007, Penone et al. 2013, Lehman 2014, Jeliazkov et al. 2016, Newson et al. 2017, Tomar et al. 2017, Walcher et al. 2022) are commonly used to obtain data on the presence and abundance of Orthoptera. Acous- tic detectors allow the recording of orthopterans with ultrasonic stridulations not detectable by the human ear. They also provide a strong measure of repeatability between observers and surveys (Diwaker et al. 2007). For the Orthoptera recorded in the Arger Fen study area, the conehead C. fuscus has a peak stridulation fre- quency of 30 kHz (Jorgu and Iorgu 2011), beyond the upper range of human hearing (c. 20 kHz; Diwaker et al. 2007). Other local species, such as C. brunneus (peak frequency 12 kHz) and R. roeselii (peak frequency 17 kHz) (IJorgu and Iorgu 2011), are known by the surveyor (TG) to be easily detected without an acoustic detector based on his 25 years of experience, as their peak frequencies are within the range of human hearing. The use of auditory detection methods by trained surveyors without detection equipment has been found to be reliable for the detection of Orthoptera in tropi- cal regions (Diwaker et al. 2007, Tomar and Diwakar 2020). When identifying species, the results using combined visual- acoustic surveying techniques, such as that used in the current study, can be comparable to those of automated detection systems, particularly in regard to low-frequency calls, and are considerably less time intensive (Walcher et al. 2022). However, the human lis- tener is not effective at detecting species with high frequency calls (>20 kHz, Walcher et al. 2022), such as C. fuscus, which, in the current study, required visual identification. Environmental surveys.—The mean slope gradient for each 100-m arm of all transects was calculated using onthegomap.com. In late May 2021, a total of 40 grass heights were recorded at random po- sitions (selected while walking) along the Orthoptera transects (10 on every 100-m arm) using a 1 m ruler for each of the four fields. In each field, anthills were counted along the 400 m long Orthoptera transects in a 1 m wide band, and the number of wild lagomorph (brown hare and rabbit combined) droppings (dung balls) were recorded on every 100-m arm (positions randomly selected while walking) to ascertain the level of grazing pressure in the fields (Wood 1988, Gibb and Fitzgerald 1998, Millett and Edmondson 2013). To provide further evidence of wild rabbit grazing, the num- ber of burrow excavations was also recorded (positions randomly selected while walking) on the transects for every 100-m arm. Statistical analysis. —All data were square-root transformed to cor- rect for non-normality before analysis (Heath 1995). Significance for all tests was accepted as evidence on the following scale in accordance with Muff et al. (2022): p-value > 0.1, little or no evidence; 0.05-0.1, weak evidence; < 0.05, moderate evidence; < 0.01, strong evidence; or < 0.001, very strong evidence. Slope gradient.—The mean slope gradient for each field was com- pared between flat and sloping fields using a Student's t-test. Cor- rection was made for unequal variance where necessary using Sat- terthwaite’s approximate t test, a method in the Behrens-Welch family (Armitage and Berry 1994, Heath 1995). 259 Orthoptera.—To allow comparison of grasshopper abundance be- tween Arger Fen and other sites (e.g., Black Bourn Valley rewilding site; Gardiner and Casey 2022a), the overall number of grasshop- per adults (of all species combined) per hectare was calculated by dividing the pooled visual detections for the 3 surveys by the transect area searched (e.g., 1600 m* searched for each survey x 3/ number of visual detections). All detections of Orthoptera (visual or acoustic) were summed for each field and survey period (3 surveys) to determine species preferences between flat and sloping rewilding fields. The inde- pendence of field transects was assumed, and data were pooled for each transect for analysis in a way similar to other monitoring studies (Nur et al. 1999). Species richness was calculated for each field and 100-m tran- sect arm. Assemblage diversity estimates were calculated using Species Diversity and Richness software, Version 4.1.2. (Pisces Conservation Ltd., IRC House, The Square, Pennington, Lyming- ton, Hampshire). The Shannon-Wiener Diversity Index (H’, Kent and Coker 1992) was calculated using the total number of indi- viduals recorded for each Orthoptera species in each field and for each 100-m transect arm. Student's t-tests were used to determine whether species rich- ness/diversity, abundance of adults (all species) and nymphs, height of grass, and number of anthills and lagomorph droppings differed between flat and sloping fields. Where necessary, correc- tions for unequal variance were performed using Satterthwaite’s approximate t test, a method of the Behrens-Welch family (Armit- age and Berry 1994, Heath 1995). To test the relationship between different species and slope gradient, all detections of Orthoptera (visual or acoustic) were summed for each 100-m transect arm (the arms had differing gradients). Linear regression models were run to determine whether the number of adults and nymphs of each species, spe- cies richness/diversity, grass height, anthills, lagomorph drop- pings, and rabbit excavations had significant relationships with slope gradient, which varied between the different 100-m tran- sect arms in each field. Results Through the visual surveys, a total density of 1221 adult grasshoppers/ha was recorded at Arger Fen. Six species of Or- thoptera, all widespread and abundant in Suffolk, were recorded in the Arger Fen rewilding fields (Table 2, Appendix 1). The most recorded species (visual and acoustic detections combined) were P. parallelus (n = 409, 34% of adult detections) and R. roeselii (n = 323, 27%), followed by C. fuscus (n = 261, 22%) and C. brunneus (n = 154, 13%). Both the lesser marsh grasshopper Chorthippus albomarginatus (De Geer, 1773, n = 23) and the dark bush-cricket P. griseoaptera (n = 20) were found in much lower abundance (2%). Strong evidence (p < 0.01) was found that the abundance of C. brunneus was significantly higher in sloping fields compared to C. fuscus, which preferred flat fields (Table 2). For nymphs (all spe- cies) and P. parallelus, there was statistical evidence (moderate and weak, respectively) of higher abundance in the flat fields. Contrast- ingly, species diversity was significantly higher (p < 0.05) in the sloping fields. In the flat fields, P. parallelus was the most abundant or- thopteran, comprising c. 41% of the total number, while C. brunneus represented only 1% of detections. However, in the sloping fields, C. brunneus was the most abundant species and JOURNAL OF ORTHOPTERA IRRESEARCH 2024, 33(2) 260 Table 2. Mean number of Orthoptera nymphs, adults of each species, species diversity, and species richness for flat and sloping fields. Student's t-values and significance evidence shown for dif- ferences between means in each row. Species Flat Sloping tvalue p __ Evidence Chorthippus 40 +20 75 #15 -135 0.31 : albomarginatus Chorthippus 2.5 +05 74.5 +9.5 -12.20 <0.01 Strong brunneus Conocephalus fuscus 84.5 +0.5 46.0 +1.0 30.48 <0.01 Strong Pholidoptera O55 205 9.55 27.5_ -57 0.26 - griseoaptera Pseudochorthippus 131.5 +19.5 73.0 +80 2.98 0.09 Weak parallelus Roeseliana roeselii 98.5 410.5 63.0 +0.0 3.72 0.17 - Nymphs (all 56.55 +05 40.5 +2.5 5.69 0.03 Moderate species) Species richness 5.5 +05 6.0 +0.0 -1.00 0.50 - Species diversity 1.2 +00 1.5 +0.0 -15.00 0.04 Moderate Table 3. Natural grazing and habitat variables for flat and sloping fields. Student's t-values and significance evidence shown for dif- ferences between means in each row. Variable Flat Sloping tvalue P Evidence Anthills/field 46.5 419.5 345 +185 0.46 0.69 - Grassheight 37.7 45.9 308 +429 1.06 0.40 - (cm)/field Lagomorph 25.5 43.5 313.0 +51.0 -847 0.01 Moderate droppings Lagomorph 12.0 +3. 605 +05 -9.50 0.01 Moderate excavations represented 27% of the total detections. In these sloping fields, P. parallelus accounted for 26% of adult detections. The two bush-crickets, R. roeselii (flat: 31%, sloping 23%) and C. fuscus (flat: 26%, sloping 17%), were in similar abundance in the slop- ing fields compared to the flat grasslands. All six species were de- tected in the scrubby grassland of the hillside ash dieback area in Hullback’s Grove field. Mean slope gradient was significantly higher in the slop- ing fields compared to the flat grasslands (t value -31, moderate evidence p = 0.02). There was moderate evidence (p < 0.05) that lagomorph droppings and excavations were in higher density in the sloping fields (Table 3). However, there was no evidence that anthill density and mean grass height were different between flat and sloping fields (Table 3). At a more localized level, slope gradient influenced the abundance and diversity of Orthoptera. Linear regression mod- els revealed distinct flat and slope species (Table 4). Moderately significant negative relationships were detected for P. parallelus (Fig. 3) and R. roeselii, and weak ones were detected for C. fus- cus and nymphs, indicating a preference for flatter ground in all cases. However, for C. brunneus (Fig. 3), C. albomarginatus, and spe- cies richness and diversity, statistical evidence revealed significant positive relationships, suggesting a preference for steeper gradient slopes in all cases. There was strong evidence of a significant posi- tive relationship between slope gradient and lagomorph drop- pings/excavations but not between slope gradient and anthills or grass height (Table 4). T. GARDINER AND D. CASEY 60 - @ = Pseudochorthippus parallelus 50 O Chorthippus brunneus - , o —-—-—-Linear (Pseudochorthippus parallelus) oar Linear (Chorthippus brunneus) fi 40 e| ry : x ; ka 30 lo” =a 5 4 rs a Paneer : sae <0.01 5 * So | ee 2 20 4 p = 0.03 Slike te, dee paesta 7 a) ry ee eee ety Bl ape ate ee gee ate e ae Oo 0 +0COO T T T T T 1 0 2 4 6 8 10 12 Slope gradient % Fig. 3. The relationship between slope gradient and the abun- dance of two grasshopper species with contrasting topographic preferences, Chorthippus brunneus (slope species) and Pseudochor- thippus parallelus (flat species); line of best fit shown. Table 4. Linear regression (degrees of freedom (DF) for all mod- els = 1 ) values for slope gradient (independent variable) paired with Orthoptera nymphs, adults of each species, species diversity/ richness, and habitat-dependent variables. Significance evidence shown in the regression model. Species R F p Evidence fepogiapnic preference Chorthippus 0.45 3.62 0.08 Weak Slope albomarginatus Chorthippus brunneus 0.66 11.06 <0.01 Strong Slope Conocephalus fuscus -0.46 3.78 0.07 Weak Flat Pholidoptera griseoaptera 0.32 1.56 0.23 - - Pseudochorthippus -0.54 5.67 0.03 Moderate Flat parallelus Roeseliana roeselii -0.51 4.96 0.04 Moderate Flat Nymphs (all species) -0.48 4.11 0.06 Weak Flat Species richness 0.62 8.86 <0.01 Strong Slope Species diversity 0.78 21.75 <0.001 Very strong Slope Anthills O35. %L.95: +0.18 - - Grass height O07. ."O29< 0:60 - - Lagomorph droppings 0.65 10.10 <0.01 Strong Slope Lagomorph 0.74 17.30 <0.001 Very Slope excavations strong Discussion Rewilding can lead to the return of biodiversity to farmland. Leaving arable fields to revert naturally to grassland, scrub, and woodland without active herbivore introduction is a relatively un- studied aspect of rewilding, with little data available to determine the success of schemes despite theoretical discussion of the ben- efits (Hart et al. 2023). The impact of rewilding on insects in Eu- rope is largely unknown, despite studies conducted in Black Bourn Valley in southeast England (Gardiner and Casey 2022a) and in Sweden (Garrido et al. 2022). Colonisation of rewilded fields. —Rewilding of arable land can lead to rapid colonization by Orthoptera, including species such as C. albomarginatus, C. fuscus, and R. roeselii, which have expanded JOURNAL OF ORTHOPTERA RESEARCH 2024, 33(2) T. GARDINER AND D. CASEY their ranges in the UK due to climate change (Gardiner and Ca- sey 2022a, b). The total of 1221 adult grasshoppers/ha was much higher at the topographically varied Arger Fen than in the flatter fields of Black Bourn Valley (234 adults/ha), another Suffolk re- wilding site 30 km to the north (Gardiner and Casey 2022a). The six species recorded at Arger Fen were all recorded at Black Bourn Valley, which had an overall higher species richness (9 species). Orthoptera inhabiting Black Bourn Valley’s post-arable rewilded fields (Gardiner and Casey 2022a, b) but absent from Arger Fen were the common green grasshopper O. viridulus, the slender (Te- trix subulata Linnaeus, 1758), and the common groundhopper Tetrix undulata (Sowerby, 1806). In contrast to the distant popula- tion of O. viridulus (nearest known site > 4 km distant from fields at Arger Fen), the two groundhoppers have been recorded < 1 km from Arger Fen, making it possible that they could colonize the regenerating grassland and scrub mosaic if the dry, heathy grass- land of Leavenheath continues as part of the rewilding strategy (Chatters 1985). Habitat preferences in flat and sloping fields.—It is important that the mosaic of habitats established at rewilding sites is suitable for a wide range of invertebrate species. The habitat preferences of Orthoptera may relate to the choice of oviposition site, food pref- erences, and vegetation height (Clarke 1948, Richards and Waloff 1954, Gardiner 2006, 2009a). Early colonists of flat post-arable grassland include the range-expanding bush-crickets C. fuscus and R. roeselii (Tables 2, 4). In flat fields, D. glomerata provides the tall grassland (c. 37 cm grass height) both species require as habitat. P. parallelus had a higher abundance in flat fields, perhaps pre- ferring the lush D. glomerata vegetation for feeding, shelter, and oviposition in grass-covered soil (Waloff 1950, Gardiner and Hill 2004), even though the grass height was well above the optimal level (10-20 cm) for this grasshopper (Gardiner et al. 2002). While nymphs were also in higher abundance in the flat fields, C. brunneus preferred the sloping fields (Tables 2, 4, Fig. 3) where lagomorph grazing created patches of bare soil (Tables 3, 4), which may be suitable for oviposition and basking (Clarke 1948, Waloff 1950). Weak evidence was found suggesting that the range-expand- ing C. albomarginatus was a species of the sloping fields (Table 4), perhaps preferring to oviposit at the base of grass blades exposed by rabbit excavations (Waloff 1950). The preference of nymphs for flat fields, with adults of C. brunneus inhabiting sloping fields, suggests that movements of nymphs downhill from egg-hatching (eclosion) sites occurred before adults moved uphill to find the lagomorph-grazed areas to oviposit in the bare soil established by rabbit excavations. Research has shown that early instar grasshop- per nymphs of C. brunneus are often found in short grassland near oviposition sites before moving to taller swards (10-20 cm grass height) as they mature (Gardiner et al. 2002). Exposed soil may offer other benefits for grasshoppers by providing sites where they can bask, as it is often much warmer than surrounding vegetation (Key 2000). However, in this study, the amount of bare soil did not vary between field type, and the number of anthills in flat and sloping fields was similar. Unlike the study at Black Bourn Valley (Gardiner and Casey 2022a, b), microenvironments provided by anthills were evenly distributed between fields, perhaps due to the relatively well-established post- arable grassland (>7 years old) and rapid colonization by ants. Wild lagomorph grazing and interaction with topography.—Wild grazing animals play a significant part in reducing vegetation height and cover (Fargeaud and Gardiner 2018, Gardiner 2018). 261 Rabbits grazed the closed grassland of the sloping fields, creat- ing numerous patches of exposed soil due to their burrowing activities, which were favorable for adult C. brunneus and to a lesser extent C. albomarginatus (Gardiner et al. 2002). Rewilding fields on hillsides may therefore provide a range of topographic conditions and niches that can be utilized by C. brunneus, par- ticularly where there is grazing by wild lagomorphs (Grayson and Hassall 1985). Short sward patches established by lagomorph grazing may have excessively hot temperatures (>40°C) similar to hay mead- ows after cutting (Gardiner and Hassall 2009), which are unlikely to be favorable for grasshoppers in the absence of ‘cool’ tussocks in close proximity. Both the flat and sloping field types had a mean grass height > 30 cm, which may provide grasshoppers with nu- merous sheltered ‘cool’ areas of tall vegetation when temperatures are excessively hot as the climate warms. Such behavioral ther- moregulation may account for the persistence of species such as C. brunneus on slopes where lagomorph excavations (basking and egg-laying sites) were frequently in close proximity to cooler tall vegetation for shade-seeking orthopterans (Fig. 1). Rewilding max: scrub and bare soil provision.—The absence of do- mestic livestock grazing during the study period is akin to rewild- ing max (i.e., more than Rewilding Lite) where active conserva- tion is absent (Gordon et al. 2021a, b) and there is a lack of ‘con- trol’ by site managers (Dempsey 2021). In these situations, large and diverse populations of Orthoptera can build up in the initial phase of grassland regeneration after arable cropping has ceased. As observed at Knepp with satellite remote sensing over two decades, a heterogeneous patchwork of rewilding habitats with scrub and woodland can develop on post-arable land (Schulte to Buhne et al. 2022), removing early successional habitats impor- tant for Orthoptera. Wild grazers such as lagomorphs may create the micro-hetero- geneity in habitat necessary for egg-laying grasshoppers in a rewil- ding max scenario with sloping farmland, although other forms of soil disturbance, such as disc harrowing, may be necessary where bare soil is lost as succession progresses (Gardiner and Casey 2022a, b). Flower-rich grassland swards can also develop with soil disturbance; for example, in the areas of Hullback’s Grove grazed by lagomorphs, an open sward with patches of bare soil has devel- oped, which is favorable for C. brunneus (Fig. 4). It has not been possible to study the effects of domestic livestock grazing (e.g., sheep or cattle) in either flat or sloping post-arable fields, so future studies should investigate the influence of managed grazing on Orthoptera abundance and diversity. All six study species were detected in the hillside ash die- back area in Hullback’s Grove. The mortality of FE. excelsior sap- lings affected by the fungus H. fraxineus led to the maintenance of an open grass and scrub mosaic that would otherwise have been shaded out as the canopy matured (Fig. 5). Such local- scale stochastic variations in habitats outside the control of conservation management may be important for Orthoptera on rewilded hillsides. Survey limitations.—The visual and acoustic surveying technique used at Arger Fen did not utilize acoustic detectors (e.g., those applied to bat detection) to record species in a standardized way (see Newson et al. 2017 and Walcher et al. 2022), which would ensure a strong measure of repeatability between observers and surveys (Diwaker et al. 2007). However, all six species were detect- ed using both visual and acoustic survey techniques at Arger Fen JOURNAL OF ORTHOPTERA IRESEARCH 2024, 33(2) 262 y T. GARDINER AND D. CASEY Ws. be hal Fig. 4. Flower-rich, open sward grazed by lagomorphs in Hullback’s Grove hillside field; © Tim Gardiner. (Appendix 1). The conehead C. fuscus generally has a peak strid- ulation frequency (30 kHz) beyond the upper range of human hearing (c. 20 kHz, Diwaker et al. 2007) and was therefore virtu- ally undetected by ear without acoustic detection equipment in this study (only three acoustic detections, presumably at low fre- quency stridulation, were made). Estimates of C. fuscus abundance are also impacted by visual detection methods where the cryptic nature of the species leads to under-recording and lower species richness estimates (Gardiner and Hill 2006). Other local species, such as R. roeselii (peak frequency c. 17 kHz), were commonly detected by the human listener on the surveys (284 acoustic detec- tions of R. roeselii, Appendix 1), suggesting that the method was useful for the other four study species with call frequencies close to or within the range of human hearing (the three grasshopper species in this study have a peak frequency limit < 21 kHz; Meyer and Elsner 1996). Therefore, visual-acoustic surveying techniques as used in the current study may be comparable to automated de- tection systems where species have low frequency calls (<20 kHz) in addition to being considerably less time intensive in the field (Walcher et al. 2022). For larger studies involving multiple observ- ers and numerous species with ultrasonic stridulation, we suggest the use of an acoustic detection system (e.g., bat detector) for the acoustic component of the surveying technique to ensure stand- ardization and repeatability. Another source of error in this study may be the accuracy of the lagomorph dropping counts. Compared to the taller and moister vegetation present on the lower slopes, droppings may have been easier to locate in shorter, lagomorph-grazed vegetation and would also have dried and been less likely to decay. Thus, the lagomorph dropping counts must be viewed with some caution, and further investigation is required. The choice of random loca- tions on site may also have led to surveyor bias in the sampling of environmental variables in the transects, and it would have been better to locate survey points via random number tables. The pres- ence of only two replicates each for the flat and sloping fields is also a limitation of the current research, and future studies should incorporate more fields where possible. Outlook for Arger Fen.—There is evidence that the heathy grass- land and scrub vegetation of Leavenheath is beginning to re- establish in the sloping fields, following a trajectory similar to nearby Tiger Hill (<1 km distant). At Tiger Hill, the acid grass- land is dominated by Agrostis and Festuca grasses with occasional R. acetosella, moss, and anthills (Kirby et al. 2002). On Ford’s Heath, Agrostis was frequent while R. acetosella was found in a sandpit connecting to the edge of the rewilding field. Along with occasional moss and anthills (Table 3), the presence of P. aquilinum, patches of C. scoparius scrub, and bare ground with JOURNAL OF ORTHOPTERA RESEARCH 2024, 33(2) T. GARDINER AND D. CASEY a uy ‘ ib Fig. 5. Scrub and grassland mosaic in an ash Fraxinus excelsior dieback (Hymenoscyphus fraxineus) area, Hullback’s Grove hillside field, inhabited by six species of Orthoptera; © Tim Gardiner. the threatened annual F. vulgaris indicates the development of heathy vegetation similar to that found on dry, acid soil locally at Tiger Hill. The developing scrub and grassland mosaic on hill- side slopes could be important for species of woody vegetation, such as P. griseoaptera, and those of sparse vegetation, including C. brunneus. The latter species can build up large populations on long-established heathland (1500-3100 adults/ha; Gardiner et al. 2002), which suggests that C. brunneus density in sloping fields (542-700 adults/ha) is on an initial trajectory toward the high abundance of heathy, acid grassland, whereas the flat fields are not (16-25 adults/ha). Conclusion: Importance of topography in rewilding schemes Local species of Orthoptera quickly colonize new habitats created on former arable land, particularly species expand- ing their range due to climate change. In these areas, species diversity and community heterogeneity are improved by differ- ing local topography. This study provides initial evidence that topographic heterogeneity may be important for the diversity of Orthoptera in rewilding schemes on former arable land. Our re- sults suggest that Orthoptera can profit from rewilding schemes on sloping farmland. Acknowledgemenits The authors would like to thank Suffolk Wildlife Trust for supporting the project and giving permission to survey the fields. We would also like to extend our gratitude to the Suffolk Natural- ists’ Society for funding the research through their Morley Grant Scheme. 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