Oak-hickory Forest Research Articles

Vegetation History and Human Activity in 2nd Millennium AD in NW Turkey: Pollen Analysis of a Peat Bog

The vegetation history of the Agi Dagi region in the Ida Massif (NW Turkey) was reconstructed on the basis of pollen analysis of a topogenic peat bog. The analysis provided evidence of human impact on the woodland environment in Byzantine times and the centuries that followed. The bog was probably formed as a result of extremely wet conditions due to excessive forest degradation. It appears that the initial chestnut—oak forest, after a period of intensive clearings, recovered at first artificially and then naturally. A sequence of events: deforestation-afforestation continues to the present day. Chestnut woodland displayed an optimal development between the 11th and 14th centuries due to human influence. However, due to negligence and destruction, the gradual destruction of the initial chestnut-oak forest at the mountain vegetation level resulted in the extension of black pine forests at this level, leading to acidification of the soil and disappearance of the ephemeral flora of the original leafy forest....

Per-segment Aboveground Forest Biomass Estimation Using LIDAR-Derived Height Percentile Statistics

An outbreak of red oak borer, an insect infesting red oak trees, prompted the need for a biomass model of closed-canopy oak-hickory forests in the rugged terrain of the Arkansas Ozarks. Multiple height percentiles were calculated from small-footprint aerial LIDAR data, and image segmentation was employed to partition the LIDAR-derived surface into structurally homogeneous modeling units. In situ reference data were incorporated into a machine-learning algorithm that produced a regression-tree model for predicting aboveground woody biomass per segment. Model results on training data appear adequate for prediction purposes (mean error 2.38 kg/m2, R 2 = 0.83). Model performance on withheld test data reveals slightly lower accuracy (2.77 kg/m2, R 2 = 0.72).

Successional trends and apparent Acer saccharum regeneration failure in an oak-hickory forest in central Missouri, USA

Permanent vegetation plots established in 1968 at the Baskett Research and Education Area (BREA) were remeasured in 2004/2005 to assess trends in canopy composition, vegetation–environment relationships, and regeneration patterns. Quercus spp. [particularly Quercus alba (white oak)] remained dominant in BREA forests. However, Nonmetric Multidimensional Scaling Ordination of a dataset composed of tree importance values from both samples indicated the two most common community types (Dry Ridge and Slope; Mesic Slope) were shifted away from Quercus spp. abundance toward greater importance of Acer saccharum (sugar maple) in ordination space. Plots in glade-like environments shifted toward greater Juniperus virginiana (eastern redcedar) importance. Environmental analysis indicated that soil properties (pH, organic matter, Ca, Mg, and K) and slope position were highly correlated with ordination axes. Saplings of Quercus spp. exhibited greatly reduced abundance in the most recent sample and the reduction in Quercus spp. density was highest in plots with greatest canopy cover. While Acer saccharum saplings were still quite abundant in BREA forests, smaller sapling size classes were becoming notably depleted, reflecting growth of a cohort of plants established before the 1968 sample toward and into tree-sized individuals. Seedlings surveys emphasized that A. saccharum seedlings have become very rare in BREA forests, while Quercus spp. seedling densities are higher, but likely below those needed for eventual adequate recruitment to the canopy. Although a number of mechanisms to explain apparent A. saccharum regeneration failure can be developed, herbivory, recent climate trends (warming late-winter conditions) and increased litter layer depth are the most plausible explanations for the observed scarcity of A. saccharum seedlings. Although increasing importance of A. saccharum in the canopy of BREA forests appears inevitable in coming decades, longer-term trends are unclear given the shortage of seedling regeneration.

Topsoil Seed Bank of an Oak-Hickory Forest in Eastern Kentucky as a Restoration Tool on Surface Mines

Typical reclamation practices in the central Appalachian coal region often use compacted spoils as a topsoil replacement, and these soils are revegetated with aggressive grasses and legumes. This restoration approach results in an herbaceous-dominated landscape with limited natural succession by native flora. An alternative restoration method is to save topsoil prior to mining, stockpile it during mining, and then replace it on uncompacted spoils to “inoculate” the site with native plant species. In an effort to test this approach, vegetation assessments were performed at a relatively undisturbed forested site in Clay County, Kentucky, U.S.A. Eight 15 × 15–m plots were established, and soils from individual plots were used in seed bank studies both in the greenhouse and on loose-dumped mine spoils. Bulk soil samples were removed from the plots and subjected to cold stratification for 13 weeks, after which seeds were allowed to germinate under greenhouse conditions for 1 year. Additional topsoil (approximately 1.5 m3 from the upper 0–20 cm) was removed from the plots and replaced on fresh spoil in eight 2 × 5–m plots. Controls consisted of uncompacted spoil material substrate only. A total of 105 species emerged in the greenhouse from the seed bank. On the relocated topsoil, 69 species were recorded of which 39 were also observed in pre-mine vegetation surveys. Ten of the 17 most important pre-mine forested site species emerged from the relocated topsoil treatments on the mine site. Our results indicate that application of topsoil could enhance plant diversity and native species reestablishment on surface-mined lands.

Occurrence of Carpenter Ants in Ozark Forests in Relation to Prescribed Fire and Stand Variables

Abstract Fire is a natural abiotic disturbance agent that is important in determining the vegetation patterns observed in many hardwood forests. Although natural fire was suppressed through much of the 20th century, in the late 20th century, fire was reintroduced into many ecosystems in the form of prescribed burning. The effects of fire on insect populations are not well understood. The objective of this study was to assess the effects of prescribed fire, tree species, and tree size on black carpenter ant abundance and distribution. The effects of prescribed fire, tree species group, and tree dbh on black carpenter occurrence were studied using a presence–absence baited test on 3,556 trees in the oak–hickory forests of the Ozark Mountains of Arkansas. Trees were distributed over unburned areas and areas burned in the dormant seasons of 2005, 2006, and 2007. Black carpenter ants occurred most frequently at baits on large red oaks and least frequently at baits on small hickories, suggesting that they preferentially forage on certain tree species and sizes. Occurrence of black carpenter ants varied by fire treatment. Habitat alterations are likely to be a cause of ant occurrence patterns in oak–hickory forests, but additional studies are necessary to understand the mechanism behind this trend.

The Role of Microhabitats in the Desiccation and Survival of Anurans in Recently Harvested Oak–Hickory Forest

Juvenile survival is an important life history feature, because recent modeling efforts suggest that modest changes in juvenile survival rates due to habitat change may greatly affect population growth rates. We compared water loss and survival rates of recently metamorphosed American Toad (Anaxyrus americanus), Green Frog (Lithobates clamitans), and Wood Frog (Lithobates sylvaticus) juveniles contained within four microhabitats, two of which occur in uncut control forest (i.e., forest ridgetop, forest drainage) and two within recently harvested forest (i.e., clearcut open, clearcut brushpile). Survival was higher in forest drainage than forest ridgetop, indicating that microhabitats within continuous forest are not equally suitable. Brushpiles of coarse woody debris reduced desiccation risks in clearcuts as indicated by survival differences between clearcut open and clearcut brushpile and survival in clearcut open was very low for all species in both years. We found species differences in survival as well as a species by microhabitat interaction in water loss rates. These results are best explained by observed behavioral differences as opposed to physiological differences among species. We conclude that desiccation can be a major source of mortality for juveniles entering terrestrial habitats, especially habitat altered by anthropogenic land-use. Desiccation risks are greatest in areas with low soil moisture conditions, which for our study included microhabitats within clearcuts without coarse woody debris, forested ridgetops, and years with below average rainfall.

Spatial Structure of Forest Lepidopteran Communities in Oak Hickory Forests of Indiana

The response of forest insect communities to disturbances such as timber harvest will likely depend on the underlying spatial structure of species assemblages before the disturbance occurs. Unfortunately, many studies of forest management implicitly assume homogeneity of community structure before harvest; postlogging communities are inferred to be a direct product of the imposed management. The goal of this study is to examine variation in the community structure of forest Lepidoptera using the pretimber harvest data on Lepidoptera from 20 forest sites within three watersheds at Morgan Monroe State Forest, IN. A total of 14,537 individuals representing 324 species of Lepidoptera were sampled from Morgan-Monroe State Forest in 2007. Sampling efficiency was not a function of management unit, and, surprisingly, we found little evidence that management units differed in overall community composition. Diversity partitioning suggested that >99% of Simpson diversity (species dominance) was determined at the local scale, and each site contained the same 10 dominant taxa in rank order. Variation in species richness seemed to be more a problem of sampling bias than underlying differences in habitat preference by moth feeding guilds. Finally, Mantel tests suggested that forest moth communities at Morgan-Monroe are not spatially autocorrelated. The results here are encouraging because they strongly suggest that shifts in lepidopteran community structure should reflect the community response to disturbance rather than inherent spatial heterogeneity of species composition.

Spatial Structure of Forest Lepidopteran Communities in Oak Hickory Forests of Indiana

The response of forest insect communities to disturbances such as timber harvest will likely depend on the underlying spatial structure of species assemblages before the disturbance occurs. Unfortunately, many studies of forest management implicitly assume homogeneity of community structure before harvest; postlogging communities are inferred to be a direct product of the imposed management. The goal of this study is to examine variation in the community structure of forest Lepidoptera using the pretimber harvest data on Lepidoptera from 20 forest sites within three watersheds at Morgan Monroe State Forest, IN. A total of 14,537 individuals representing 324 species of Lepidoptera were sampled from Morgan-Monroe State Forest in 2007. Sampling efficiency was not a function of management unit, and, surprisingly, we found little evidence that management units differed in overall community composition. Diversity partitioning suggested that > 99% of Simpson diversity (species dominance) was determined at the local scale, and each site contained the same 10 dominant taxa in rank order. Variation in species richness seemed to be more a problem of sampling bias than underlying differences in habitat preference by moth feeding guilds. Finally, Mantel tests suggested that forest moth communities at Morgan-Monroe are not spatially autocorrelated. The results here are encouraging because they strongly suggest that shifts in lepidopteran community structure should reflect the community response to disturbance rather than inherent spatial heterogeneity of species composition.

The Vascular Plants of the Berea College Forest in Madison, Jackson, and Rockcastle Counties, Kentucky

ABSTRACT The vascular plants of the Berea College Forest (BCF), the oldest managed forest in Kentucky, are presented as an annotated species list. BCF is comprised of 3,380 ha in Madison, Jackson, and Rockcastle counties of east-central Kentucky. Forests and diverse habitats include western mesophytic forest, mixed mesophytic forest, oak-hickory forest, mixed oak-Virginia pine forest, secondary succession areas, wetland habitats, and many anthropogenic-influenced areas. The known vascular plants consist of 1,017 specific and infraspecific taxa, 513 genera, and 139 families. Classification divisions with species are Equisetophyta (2), Lycopodiophyta (4), Polypodiophyta (33), Pinophyta (13), and Magnoliophyta (965). One hundred ninety-six taxa (19.27%) are naturalized, persisting, adventive, or cultivated exotics. The Asteraceae (141), Poaceae (100), Cyperaceae (64), and Fabaceae (56) are the largest families.

Seasonal Terrestrial Microhabitat Use by Gray Treefrogs (Hyla versicolor) in Missouri Oak-hickory Forests

It is important to identify and understand the critical habitat components of organisms inhabiting landscapes that are increasingly altered by human activities to adequately predict the effects of habitat alteration on natural populations. Our study identifies terrestrial habitats that are important to the gray treefrog (Hyla versicolor) during the nonbreeding season using radiotracking and mark-recapture/release of individuals captured in artificial arboreal refugia. High humidity and rainfall were associated with decreased captures in artificial refugia, while high ambient air temperatures were correlated with increases in the number of treefrog captures. Refugia placed in small trees recorded more small individuals than those in larger trees, and refugia in white oaks (Quercus alba) contained females more frequently than expected at random. We found that space-use estimates encompassing foraging and overwintering locations of gray treefrogs were relatively small and typically included only a few adjace...

Estimating components of forest evapotranspiration: A footprint approach for scaling sap flux measurements

Forest evapotranspiration (ET) estimates that include scaled sap flux measurements often underestimate eddy covariance (EC)-measured latent heat flux (LE). We investigated potential causes for this bias using 4 years of coupled sap flux and LE measurements from a mature oak-hickory forest in North Carolina, USA. We focused on accuracy in sap flux estimates from heat dissipation probes by investigating nocturnal water uptake, radial pattern in flux rates, and sensor-to-stand scaling. We also produced empirical functions describing canopy interception losses (measured as the difference between precipitation and throughfall) and soil evaporation (based on wintertime eddy covariance fluxes minus wintertime water losses through bark), and added these components to the scaled sap flux to estimate stand evapotranspiration (ET S). We show that scaling based on areas in which the leaf area index of predominant species deviates from that of the EC footprint can lead to either higher or lower estimate of ET S than LE (i.e. there is no bias). We found that accounting for nocturnal water uptake increased the estimate of growing season transpiration by an average of 22%, with inter-annual standard deviation of 4%. Annual ET S estimate that included sap flux corrected for nocturnal flux and scaled to the EC footprint were similar to LE estimates (633 ± 26 versus 604 ± 19 mm, respectively). At monthly or shorter time scales, ET S was higher than LE at periods of low flux, similar at periods of moderate flux, and lower at periods of high flux, indicating potential shortcomings of both methods. Nevertheless, this study demonstrates that accounting for the effects of nocturnal flux on the baseline signal was essential for eliminating much of the bias between EC-based and component-based estimates of ET, but the agreement between these estimates is greatly affected by the scaling procedure.

Long-term spatial dynamics of Acer saccharum during a population explosion in an old-growth remnant forest in Illinois

Species richness and evenness have greatly declined in oak–hickory forests in the central hardwood region in the U.S.A. in the past 100 years due to the rapid population growth of Acer saccharum. This study used a 50-year record of spatial dynamics to examine how demographic processes, particularly recruitment, may have contributed to this increase in an old-growth forest remnant, Brownfield Woods, Urbana, Illinois, U.S.A. The impact of canopy disturbance, including the outbreak of Dutch elm disease, on this increase was also evaluated. Historical maps of trees (≥7.6 cm DBH) from 1951, 1988, and 2001 in a 180 m × 280 m area were used to develop a series of univariate Ripley's L( d) functions to study changes in spatial patterns of three size classes of A. saccharum over time. Bivariate Ripley's L( d) functions were also utilized to evaluate spatial associations between recruitment and canopy disturbance. Our results indicated that A. saccharum was aggregated at most spatial scales up to 80 m during 1951–2001. Such aggregation arose mainly from small individuals. Furthermore, newly recruited individuals were aggregated at multiple spatial scales, and were significantly associated with canopy disturbance in general, as well as gaps created by Ulmus trees killed by Dutch elm disease. The aggregation of the 1951 initial group of small individuals changed via mortality to a random distribution over time. The results indicate that tree deaths caused by disturbances of different scales and types were the main cause of increased recruitment of A. saccharum in Brownfield Woods. The occurrence of Dutch elm disease further accelerated its population increase. This study demonstrated a direct spatial link between recruitment of A. saccharum and disturbance, and provided a long-term case study of a population explosion.

Breeding and Recruitment Phenology of Amphibians in Missouri Oak-Hickory Forests

ABSTRACT Knowing the phenologies of species in a region helps guide management and conservation activities in breeding ponds and surrounding terrestrial habitats. We examined the phenology of pond-breeding amphibians in central Missouri oak-hickory forests. Two ponds were monitored for 4 y from 2000–2003 and five other ponds were monitored for 1 y during 2004 using drift fences with pitfall traps. We found 15 species of pond-breeding amphibians, nine of which we captured in sufficient abundance to evaluate breeding phenology. Among the nine species, breeding migrations occur from Feb. to Nov., while subsequent metamorph emigration occurred primarily from May to Oct.. Our ponds were nearly permanent, resulting in salamander-dominated communities in these oak-hickory forests. Pond-use was partitioned by species that differed in their timing of reproduction and post-metamorphic emergence. For example, breeding in the fall gives larval ringed salamanders a potential size advantage over the spring-breeding spo...

Vascular Flora of Middle Fork Woods Nature Preserve

The vascular flora of Middle Fork Woods Nature Preserve, Vermilion County, Illinois, was studied during the growing seasons of 1999–2002. A total of 376 species were found: 12 ferns, fern-allies, and gymnosperms; 99 monocots; and 265 dicots. The three families with the largest number of species were the Poaceae (44), Asteraceae (39), and Cyperaceae (34, 29 of which were members of the genus Carex). The overstory and woody understory of six forest communities were surveyed: a mature second growth dry-mesic upland forest dominated by Quercus alba (white oak) and Q. velutina (black oak); an old growth, dry-mesic savanna dominated by Q. alba with a dense understory of Acer saccharum (sugar maple); SW-facing and NE-facing forested slopes of a mesic ravine, both dominated by A. saccharum and Q. alba; a southern flatwood forest/ ephemeral pond community dominated by Q. bicolor (swamp white oak); and an immature second growth dry-mesic upland forest dominated by Q. alba and Carya ovata (shagbark hickory). Ground layer plants were surveyed in spring and fall in the dry-mesic upland forest communities, and for each species the relative cover, relative frequency, and importance values were determined. The preserve, comprised mostly of oak-hickory forest communities, was found to be in relatively good ecological condition. Mature and maturing second-growth oaks were present throughout much of the preserve. Sugar maples dominated the understory and, along with the dense overstory, were apparently limiting oak regeneration. The non-natives Lonicera spp. (bush honeysuckles), Elaeagnus umbellata (autumn olive), Alliaria petiolata (garlic mustard), and the native sugar maple, will continue to need to be controlled. Prescribed fire is recommended to limit populations of these species.

Lichen Checklist from the Liking Lichens Teacher Workshops at the Charlie Elliott Wildlife Center, Georgia, USA

Abstract The lichen flora of the Charlie Elliott Wildlife Center in the Georgia Piedmont was explored during successive Liking Lichens Teacher Workshops in July 2006 and 2007. Habitats surveyed include mesic mixed hardwood forest, Oak-Hickory forest and granitic flatrock. A checklist of 146 species in 64 genera from this workshop is presented. This report represents only the second lichen checklist from Georgia, USA, and is one of the first field-based checklists for the Piedmont physiographic province of eastern North America.

A Vascular Flora of Lynch's Woods Park, Newberry County, South Carolina

Lynch's Woods Park (Newberry County, South Carolina) was floristically surveyed between 2002 and 2005. The Park features north-facing slopes, granite outcrops, and several small streams within the Piedmont physiographic province. A total of 528 vascular plant species were documented within the 101.2 ha, including 91 (17%) nonnatives. Three species, Anemone berlandieri, Eurybia mirabilis, and Rhododendron eastmanii were rare species. Analysis of community structure revealed that most of the area was a mixed mesophytic forest, with the upland sites developing toward an oak-hickory forest.

Oak mortality associated with crown dieback and oak borer attack in the Ozark Highlands

Oak decline and related mortality have periodically plagued upland oak–hickory forests, particularly oak species in the red oak group, across the Ozark Highlands of Missouri, Arkansas and Oklahoma since the late 1970s. Advanced tree age and periodic drought, as well as Armillaria root fungi and oak borer attack are believed to contribute to oak decline and mortality. Declining trees first show foliage wilt and browning, followed by progressive branch dieback in the middle and/or upper crown. Many trees eventually die if severe crown dieback continues. In 2002, more than 4000 living oak trees ≥11 cm dbh in the relatively undisturbed mature oak forests of the Missouri Ozark Forest Ecosystem Project (MOFEP) were randomly selected and inventoried for tree species, dbh, crown class, crown width, crown dieback condition (healthy: <5% crown dieback, slight: >5–33%, moderate: 33–66%, and severe: >66%) and number of emergence holes created by oak borers on the lower 2.4 m of the tree bole. The same trees were remeasured in 2006 to determine their status (live or dead). In 2002, about 10% of the red oak trees showed moderate or severe crown dieback; this was twice the percentage observed for white oak species. Over 70% of trees in the red oak group had evidence of oak borer damage compared to 35% of trees in the white oak group. There was significant positive correlation between crown dieback and the number of borer emergence holes ( p < 0.01). Logistic regression showed oak mortality was mainly related to crown width and dieback, and failed to detect any significant link with the number of oak borer emergence holes. Declining red oak group trees had higher mortality (3 or 4 times) than white oaks. The odds ratios of mortality of slightly, moderately, and severely declining trees versus healthy trees were, respectively, 2.0, 6.5, and 29.7 for black oak; 1.8, 3.8, and 8.3 for scarlet oak; and 2.6, 6.5 and 7.1 for white oaks.

Postbreeding Habitat Use of Wood Frogs in a Missouri Oak-hickory Forest

Fitness benefits to individuals from using a particular habitat during the non-breeding season are likely species- and habitat-specific. Our goal was to define the postbreeding habitat use of adult Wood Frogs (Rana sylvatica) within continuous oak-hickory forest in Missouri. We used radio-telemetry to determine whether adult Wood Frogs are evenly spaced throughout this forest type or clumped at a particular resource. In addition, we determined microhabitat selection using conditional logistic regression that compares the microhabitat at frog locations to paired points located 2 m from the frog. Adult frogs migrated from breeding sites located on ridgetops into ephemeral, rocky ravines. Use of drainages by Wood Frogs depended on the distance between the breeding site and drainage, and the orientation of drainages relative to the pond edge influenced whether migratory paths of frogs are funneled or spaced apart. The most supported model of microhabitat selection indicated that frogs selected locations with increased leaf litter depth and air temperature and with decreased humidity and light compared to paired points. Persistence of Wood Frog populations along the southwestern edge of their range requires successful annual migrations between breeding sites and forested drainages, which are important nonbreeding habitat for Wood Frogs in a Missouri oak-hickory forest.

Forest Changes in the Great Lakes Region at 5-7 ka BP

Pollen stratigraphy from 90 sites in and bordering the Great Lakes record the 5-7 ka history of forest development of the Great Lakes region. By 7 ka beech (Fagus grandifolia) had invaded the oak-hickory (Quercus-Carya) forest of lower Michigan and hemlock (Tsuga canadensis) and beech the white pine (Pinus strobus)-dominated forest of southern Ontario. At the same time, white pine replaced jack pine (P banksiana) as it expanded northward to the Clay Belt beyond its present-day range. Forest changes at 6 and 5 ka were dominated by range extensions of beech and hemlock in a northwesterly direction, by northward expansion of eastern white cedar (Cupressineae), and southward migration of white pine into the Michigan basin. The beech and hemlock migrations (160 m yr-1and 280 m yr-1, respectively) may have been influenced by the cool-moist climate generated by the Nipissing Great Lakes in combination with enhanced regional warming. White pine and eastern white cedar responded to regional warming and reduced precipitation, whereas birch (Betula) and alder (Alnus) may have been influenced more by fire activity caused by the warm-dry climate. The boreal-mixed forest ecotone was displaced 140 km northward at 5-7 ka compared to 60-70 km for the mixed-deciduous forest ecotone.

Factors Associated With Variation in Home-Range Size of Appalachian Ruffed Grouse (Bonasa Umbellus)

Abstract From 1996 to 2001, researchers at 10 Appalachian study sites collected radiotracking data sufficient to delineate 1,054 seasonal home ranges of Ruffed Grouse (Bonasa umbellus; hereafter “grouse”). Using information-theoretic model selection and paired comparison of home ranges from individual grouse, we evaluated individual, local, and landscape factors hypothesized to affect grouse home-range size. Females and juvenile males occupied home ranges that averaged &gt;2× larger than those of adult males, and home ranges of females averaged 2.6× larger during successful breeding seasons than during years of reproductive failure. Clearcuts and forest roads are considered high-quality covers, and both were more prevalent in smaller home ranges. Several factors operating at a regional and landscape scale were also important. Previous studies have reported that southern grouse use relatively large home ranges, and we observed a continuous decline in home-range size with increasing latitude across the 710-km range spanned by our study sites. Home-range size of males, particularly juvenile males, was positively related to an index of population density. Given the species' “dispersed lekking” mating system, we interpret this as evidence of competition for preferred display sites. As has been reported for other game birds, all sex and age classes of grouse used smaller home ranges following closure of sites to hunting. Grouse inhabiting oak-hickory forests used larger home ranges than conspecifics in mixed mesophytic forests, and other factors interacted with forest type. In oak-hickory forests, female home-range size was inversely related to use of mesic bottomlands, which support important forage plants, and home ranges of adult grouse increased 2.5× following poor hard-mast crops. By contrast, home ranges of grouse inhabiting mixed mesophytic forests were unrelated to use of bottomlands, and the influence of hard mast was reduced. This is in line with the view that in Appalachian oak-hickory forests, grouse are under strong nutritional constraint. However, this constraint is reduced in mixed mesophytic forests, likely because of the presence of high-quality alternative foods (e.g., cherry [Prunus spp.] and birch [Betula spp.]). Facteurs associés à une variation de la taille du domaine vital de Bonasa umbellus dans les Appalaches