1 The natural regeneration of calcareous grassland at a landscape scale 150 years of plant. 2 community re assembly on Salisbury Plain UK, 3 John W Redhead John Sheail James M Bullock Andrea Ferreruela Kevin J Walker. 4 Richard F Pywell, 6 Redhead J W Corresponding author johdhe ceh ac uk Sheail J Bullock J M Pywell R F. 7 NERC Centre for Ecology and Hydrology Maclean Building Wallingford Oxfordshire OX10 8BB UK. 8 Ferreruela A Forestal Catalana Sabino Arana 34 1r1a 08028 Barcelona Spain Walker K J. 9 Botanical Society of the British Isles 97 Dragon Parade Harrogate HG1 5DG UK. 11 Abstract, 12 Questions What is the timescale for natural regeneration of calcareous grassland Is this timescale. 13 the same for individual plant species plant community composition and functional traits. 14 Location Defence Training Estate Salisbury Plain Wiltshire UK. 15 Methods We investigated the rate of natural regeneration of species rich calcareous grassland. 16 across a 20 000 hectare landscape We combined a large scale botanical survey with historic land use. 17 data 6 150 years before present and examined differences between grasslands age classes in the. 18 occurrence of individual plant species floristic community composition and community functional. 20 Results Many species showed a significant association with grasslands over 100 years in age These. 21 included the majority of those defined elsewhere as calcareous grassland indicators although some. 22 such appeared on grasslands 10 years in age Community composition showed increasing similarity. 23 to the oldest grasslands with increased grassland age with the exception of very recently ex. 24 agricultural grasslands Most functional traits showed clear trends with grassland age with dispersal. 25 ability differing most strongly between recent and older grasslands whilst soil fertility and pH. 26 tolerance were more influential over longer timescales. 27 Conclusions Even in a well connected landscape re assembly of a community resembling ancient. 28 grassland in terms of functional traits and community composition takes over a century although. 29 changes at the level of individual species may occur much earlier These findings confirm the. 30 uniqueness of ancient calcareous grassland They also suggest that the targets of re establishment. 31 efforts should be adjusted to account for the likely timescale of full community reassembly. 33 Key Words, 34 Agri environment chalk grassland chronosequence GIS historic landuse indicator species. 35 restoration, 37 Nomenclature Stace C 2010 New Flora of the British Isles 3rd Edition Cambridge University Press. 39 Running head Natural regeneration on Salisbury Plain UK. 40 Introduction, 41 Calcareous grassland has great conservation value across Europe due to its high floral and faunal. 42 diversity and large number of associated rare and threatened species Poschold WallisDeVries. 43 2002 However calcareous grassland has also undergone one of the most significant declines of. 44 any European grassland habitat since the mid twentieth century Intensification of agriculture has. 45 destroyed or degraded many calcareous grasslands through ploughing fertilizer input and the. 46 sowing of crops Fuller 1987 Van Dijk 1991 Poschlod WallisDeVries 2002 Much of what remains. 47 is now highly fragmented and vulnerable to further degradation from scrub encroachment Redhead. 48 et al 2012 over or under grazing Poschlod WallisDeVries 2002 and the increased risk of species. 49 extinction that isolation brings Matthies et al 2004 Whilst the maintenance and protection of. 50 remnant calcareous grasslands is a vital part of conservation many countries have also set targets. 51 for the re establishment of calcareous grasslands on areas where the land use is or has recently. 52 been primarily agricultural Fagan et al 2008 Strategies to achieve these targets include the use of. 53 options within agri environment schemes which aim to restore agricultural land to semi natural. 54 grassland using a variety of techniques including natural regeneration reduction of soil fertility and. 55 the sowing and management of calcareous grassland species Walker et al 2004. 56 If the re establishment of calcareous grasslands on ex agricultural land is to be successful and. 57 thus cost effective it is important to have information on how best to monitor the progress of. 58 restoration how long it is likely to take and the most effective restoration methods to employ. 59 Whilst a range of studies have contributed towards answering these questions experimentally. 60 Gibson Brown 1991 Wells et al 1994 Stevenson et al 1995 Pywell et al 2002 2003 Kiehl et al. 61 2006 Fagan et al 2008 results have been varied Some authors have suggested that restoration. 62 schemes on ex agricultural land have yet to prove their effectiveness given the severe biotic and. 63 abiotic constraints imposed on re assembly by modern agricultural methods Dobson et al 1997. 64 Walker et al 2004 However many studies have necessarily focussed on the comparatively short. 65 timescales over which grassland restoration projects have been carried out ranging from four years. 66 Pywell et al 2002 to 60 years Fagan et al 2008 Observed rates of regeneration and restoration. 67 are also confounded by the small area and comparative isolation of agri environment sites which. 68 might be expected to act as a constraint by inhibiting colonisation and establishment of calcareous. 69 grassland plants Gibson Brown 1991 Bullock et al 2002 Matthies et al 2004 Butaye et al 2005. 70 Ozinga et al 2009 In addition to this there is little information on the natural rate of plant. 71 community reassembly in landscapes offering good conditions for dispersal colonisation and. 72 establishment Karlick Poschlod 2009 despite some authors advocating natural regeneration as. 73 an effective strategy Fagan et al 2008 This lack of information has often made it difficult to set. 74 appropriate targets which are essential for interpreting the results of restoration efforts McCoy. 75 Mushinsky 2002 Butaye et al 2005, 76 Here we define natural regeneration to mean the re establishment of a calcareous grassland. 77 floristic community following the cessation of agricultural practices in the absence of active. 78 restoration management Fagan et al 2008 Monitoring the progress of natural regeneration can be. 79 achieved using a variety of measures These include the presence or abundance of a set of. 80 calcareous grassland indicator species selected as a proxy for communities of varying degrees of. 81 quality e g Robertson Jefferson 2000 Whilst this approach has the benefit of simplicity and. 82 speed some studies have suggested that indicator species do not necessarily signal more lasting. 83 shifts in total species richness grassland community composition which should be monitored. 84 directly Gibson Brown 1991 Zobel et al 1996 Pywell et al 2003 Walker et al 2004 Fagan et al. 85 2008 A further approach is to assess changes in life history traits of the plant community Using. 86 functional traits may give greater insight into the underlying mechanisms which determine. 87 community composition under different conditions Pywell et al 2003 Marini et al 2012 especially. 88 when analysed in conjunction with data on species composition Kachergis et al 2013 and also. 89 facilitates predictions about the likely fate of regenerating communities Kahmen et al 2002. 90 This study used a variety of response variables including individual species presence community. 91 composition and life history traits to investigate plant community reassembly in a naturally. 92 regenerating grassland landscape over a well characterised 150 year period with the intention of. 93 contributing to a baseline against which to compare the results of restoration experiments. 94 Methods,95 STUDY SITE, 96 The studied landscape the Defence Training Estate Salisbury Plain DTE SP Wiltshire UK is unique. 97 in Western Europe in its extent and minimal fragmentation of calcareous grassland Toynton Ash. 98 2002 The present day extent of DTE SP is the result of land purchases made by the War Office now. 99 the UK Ministry of Defence beginning in the late 1890s and spanning the first half of the twentieth. 100 century The restrictions of access imposed by military training and unexploded ordinance have. 101 limited the extent of intensive cultivation and grazing There are thus large areas which have been. 102 free from significant agricultural influences aside from extensive grazing for over 150 years There. 103 are also widespread areas which were cultivated more recently but then abandoned after military. 104 purchase There are also instances of what was once unimproved grassland i e lacking application. 105 of agricultural fertilizers and pesticides becoming intensively used and managed in the present All. 106 these grassland ages form a largely continuous mosaic covering around 38 000 hectares in total. 107 such that the DTE may represent a best case scenario for natural regeneration in a favourable. 108 landscape, 109 Some 14 000 hectares of DTE SP are currently high quality species rich calcareous grassland. 110 mostly variants of CG3 Bromus erectus Bromopsis erectus grassland as defined by the British. 111 National Vegetation Classification NVC Rodwell 1992 The remainder is typified by other grassland. 112 types including MG1 Arrhenatherum elatius grasslands with gradations towards improved MG7. 113 Lolium perenne leys Current management practices include extensive grazing for full details see. 114 Woodcock et al 2005 There is wide variation in the present and historic extent and intensity of. 115 disturbance from military vehicles Hirst et al 2003 burning Iliffe et al 2000 and encroachment of. 116 scrub species most notably Crategaus monogyna Prunus spinosa and more locally Ulex europaeus. 117 Redhead et al 2012 As is common in the analysis of historical data where many such processes. 118 go unrecorded Sheail 1980 data is lacking on the present and historic extents of these variables. 119 However there is no evidence of systematic bias in these variables in relation to grassland age on. 120 DTE SP,121 GENERATING A LAND USE HISTORY MAP, 122 In the absence of historic records of floral communities we used a chronosequence approach. 123 Pickett 1989 Foster and Tilman 2004 based on historical land use data sets The extent of. 124 unimproved grassland on DTE SP has been mapped on various occasions Suitable land use data. 125 were available for six time periods 1840s 1880s 1930s 1967 1985 and 1996 The earliest two. 126 datasets were derived from tithe maps and first edition Ordnance Survey maps respectively Sheail. 127 1980 Data for the 1930s were drawn from the Dudley Stamp Land Utilisation Survey Stamp 1931. 128 1948 see Hooftman and Bullock 2011 for a description The latter datasets were based on three. 129 grassland surveys Wells 1967 Porley 1986 Walker Pywell 2000 Where maps were not already in. 130 digital form each map was georeferenced and digitized Datasets prior to and including 1930. 131 mapped all areas of non arable grazing land and natural grassland Post 1930 maps refined this to. 132 map only species rich non improved grasslands i e those not showing any signs of agricultural. 133 management beyond traditional grazing or hay cutting Data for the adjacent county of Dorset. 134 Hooftman and Bullock 2011 and for Britain as a whole Fuller 1987 suggest that all mapped. 135 grasslands were agriculturally unimproved prior to the late 1930s It is important to note that even. 136 those grasslands for which there is no evidence of cultivation in this study are likely to have some. 137 history of agricultural influence with archaeological evidence of such up to the post medieval period. 138 Postan 1973 However the available historic data is insufficiently spatially explicit to provide a. 139 meaningful sample of grasslands uncultivated since medieval times. 140 Land use maps were overlain to form a composite map of land use history from 1840 to 1996 Figure. 141 1 Coverage was limited to the western and central areas of DTE SP giving a total area of around. 142 20 000 Ha with full historic land use data The varied land use histories were divided into four. 143 categories the first three of which represent the minimum age of unimproved grassland Old. 144 grassland since 1840 to 1880 136 years old Mid grassland since 1930 1967 50 years old. 145 Recent grassland since 1985 to 1996 6 years old The fourth category Lost denotes areas which. 146 were once unimproved grassland but had been degraded or lost to improvement by 1996 mostly by. 147 conversion to re sown grass leys Georeferencing digitising and analysis of digital maps was. 148 performed in ArcMAP v9 3 1 2011 ESRI Inc Redlands CA USA. 150 Fig 1 Map of estimated grassland age on western and central Defence Training Estate Salisbury. 151 Plain DTE SP Derived from overlay of historic landuse maps Unshaded areas within the DTE are. 152 those lost to improvement lacking historic data or those which are not grassland forest built up. 153 etc Inset map shows location of DTE SP in southern UK. 154 FLORISTIC DATA, 155 Between 1996 and 1997 all vegetation communities present on DTE SP were mapped in the field and. 156 their composition described using the NVC methodology Rodwell 1992 For each discrete. 157 community the cover of vascular plant species was recorded from 2 2 m quadrats to aid. 158 assignation to an NVC community Walker Pywell 2000 However these quadrats were limited in. 159 number and thus did not give an accurate record of total species richness or occurrence of all. 160 species Thus an estimate of abundance for all plants present was made from a walk over survey. 161 using the DAFOR scale Kershaw 1985 The mapped plant communities were captured as digital. 162 polygons and overlain with the land use map As NVC polygons and land use history polygons did. 163 not overlap exactly analyses were restricted to NVC polygons over one hectare in area and having at. 164 least 75 overlap with a single land use history polygon giving 1352 polygons for analysis 484 Old. 165 658 Mid 101 Recent 109 Lost Lists of species presence DAFOR abundance and associated floral. 166 life history traits were compiled for each polygon Traits were selected on the basis of having. 167 information readily available for the majority of species present in the study and of having a clear. 168 potential to characterise ecological function namely the ability of a species to colonise compete. 169 and persist in the landscape concerned functional traits Violle et al 2007 Traits were measured. 170 on either a continuous scale e g height or as ordinal scores e g dispersal ability seedbank. 171 persistence Colonisation ability was represented by a dispersal ability score Traits reflecting. 172 persistence ability included seedbank longevity clonal spread and plant longevity Traits. 173 representing competitive ability were leaf area and typical summer plant height Also included in. 174 the analyses were measures of ecological performance which whilst arguably not traits sensu Violle. 175 et al 2007 are meaningful proxies for multiple traits which affect the ability of species to survive in. 176 the conditions of recently ex agricultural land Pywell et al 2003 These were Ellenberg Ellenberg. 177 et al 1991 tolerance values for light soil reactivity expressed as difference from neutral to correct. 178 for skew towards the acid range Preston et al 2003 and soil fertility Descriptions of all these traits. 179 including values and sources are given in the Supplementary Material Table S1. 180 STATISTICAL ANALYSIS, 181 To investigate how individual species presence related to grassland age Chi squared tests were used. 182 to examine whether presence fitted a null hypothesis of distribution at random across age. 183 categories In order for the assumptions of the test to be met if a species generated expected. 184 values of less than five in any category the Recent and Lost categories were combined If expected. 185 values remained below five the species was excluded from analysis Species showing significant p. 186 0 05 results were grouped according to which land use history categories showed higher than. 187 expected values and contributed the greatest proportion of the significant Chi squared statistic. 188 Although conducting a large number of independent tests we did not apply a sequential Bonferroni. 189 correction but instead examined effect sizes and whether the observed differences were ecologically. 190 explicable following Moran 2003, 191 Differences in grassland community composition between NVC polygons were analysed by. 192 calculating Euclidean distances ED for all pairwise comparisons Euclidean distance is defined as. 193 Equation 1, 194 where EDjk Euclidean distance between samples j and k Xij abundance of individuals of species i. 195 in sample j Xik abundance of individuals of species i in sample k Krebs 1999. 196 The DAFOR scale on which species were recorded across the NVC polygon was converted to a. 197 numeric representation Dominant 5 Abundant 4 Frequent 3 Occasional 2 Rare 1 Present. 198 0 1 to provide a measure of relative abundance Differences in ED between the different age. 199 categories were then analysed by one way Analysis of Variance ANOVA. 200 The weighted mean of each trait was calculated for each NVC polygon with weightings derived. 201 from the numeric representation of the DAFOR scale Differences in traits between grassland age. 202 categories were analysed using analyses of covariance ANCOVA Two covariates were included. 203 Firstly the area of the NVC polygon in order to account for the potential for larger polygons to. 204 support more and rarer species Matthies et al 2004 Secondly the proximity of each NVC. 205 polygon to the nearest old grassland as distance from established calcareous grassland has. 206 previously been found to strongly affect the rate of community reassembly Matthies et al 2004. 207 Fagan et al 2008 Variables giving significant results from ANCOVA were then included in a. 208 Discriminant Function Analysis DFA which classified grasslands to age class using the linear. 209 combinations of traits discriminant functions DFs which best differentiate between categories. 210 Analyses were performed in R R Development Core Team 2008 R A language and environment for. 211 statistical computing R Foundation for Statistical Computing Vienna Austria utilising the MASS. 212 package Venables W N Ripley B D 2002 Modern Applied Statistics with S 4th ed Springer. 213 New York,214 Results,215 SPECIES PRESENCE DATA. 216 Of over 450 plant species recorded on DTE SP in the NVC survey 193 species met the criteria for. 217 analysis and 77 of these 149 species showed a significant p 0 05 associations with grassland. 218 age classes Table 1 full species lists are available in Supplementary Material Table S2 For eight. 219 species small effect sizes or ecologically inexplicable results indicated a possible Type I error the. 220 relationship with grassland age was designated as unclear and the results are not reported further. 221 Table 1 Presence of individual species in response to grassland age category The number of species. 222 showing higher than expected presence for each combination of classes as determined by Chi. 223 squared analysis are given along with the associated approximate age range in years. Grassland Age Classes Species Age of Semi natural Grassland. Old 48 100 years,Old and Mid 11 60 years,Mid 26 30 60 years. Mid and Recent 11 60 years,Mid Recent and Lost 8 100 years. Recent 7 10 years,Recent and Lost 22 10 and improved degraded. Lost 5 Improved degraded, 225 Forty eight species showed a significant association with unimproved grasslands over 100 years. 226 in age Table 1 These included some species entirely restricted to ancient chalk and limestone. 227 grassland in the UK e g Campanula glomerata Carex humilis Picris heiracoides Thesium. 228 humifusum but the majority are confined to species rich communities on infertile soils across a. 229 broader pH range e g Anthyllis vulneraria Filipendula vulgaris Poterium sanguisorba Serratula. 230 tinctoria This group also included species more often associated with disturbed ground e g. 231 Myosotis arvensis Reseda lutea Sinapis arvensis Sonchus asper Species associated with both old. 232 and mid age grasslands included many typical chalk downland species e g Asperula cynanchica. 233 Cirsium acaule Viola hirta whereas those associated with mid or mid and recent age grasslands. 234 included many more species that occur across a broader range of ecological conditions and habitats. 235 e g Centaurea scabiosa Cynosurus cristatus Lathyrus pratensis Leontodon hispidus or more. 236 disturbed conditions on calcareous soils e g Chaenorhinum minus Linum bienne Onobrychis. 237 viciifolia Senecio erucifolius Species associated with recent recent and lost or lost grasslands were. 238 almost entirely species of eutrophic often agricultural habitats including intensively managed. 239 arable land e g Anisantha sterilis Convolvulus arvensis Galium aparine Papaver rhoeas Veronica. 240 persica or improved pasture e g Cirsium spp Rumex spp Taraxacum spp. 241 Of particular interest are the species designated as indicators of calcareous grassland condition. 242 by Robertson Jefferson 2000 from degraded negative indicators to good positive indicators. 243 All six negative indicator species Cirsium arvense Cirsium vulgare Rumex crispus Rumex. 244 obtusifolius Senecio jacobaea Urtica dioica were significantly more common on recent grasslands. 245 and grasslands lost to improvement Of 24 positive indicator species with sufficient sample size for. 246 analysis 13 were associated with old grasslands and a further four with both old and medium age. 247 grasslands Supplementary Material S2,248 GRASSLAND COMMUNITY COMPOSITION. 249 The analysis of ED between plant communities Fig 2 showed that differences showed generally. 250 clear trends along the age gradient a larger ED indicates a bigger difference in community. 251 composition This was indicated by increasing ED when comparing old grasslands against. 252 increasingly younger sites one way ANOVA F 1777 7 p 0 001 and decreasing ED when. 253 comparing lost grasslands against grasslands of increasing age one way ANOVA F 2671 2 p. 256 Fig 2 Bar plot of mean Euclidean distance between grassland communities of four different age. 257 categories Also shown are mean Euclidean distances between grassland communities within the. 258 same age category Age classes are arranged on the x axis in order of decreasing grassland age. 259 Capped lines represent one standard error, 260 Differences were greatest overall between the old and recent categories with mid age grasslands. 261 roughly equidistant between the two The values of ED within each age class indicated variation. 262 among communities of the same age a measure of diversity Newton et al 2012 For such. 263 comparisons within age classes mid age grasslands showed the highest within class ED followed by. 264 old then recent and lost grasslands Fig 2 This suggests variation in community composition. 265 increases from the early to middle stages of reversion and then decreases somewhat as grasslands. 266 age Communities within the lost grassland category showed the lowest mean ED value suggesting. 267 that grasslands lost to agricultural improvement have communities which are comparatively. 268 homogenous across DTE SP,269 COMMUNITY FUNCTIONAL TRAITS. 270 The grassland age categories showed significant differences in all nine traits p 0 01 with many. 271 traits also showing a clear trend with grassland age Fig 3 Even in this landscape of virtually. 272 continuous grassland many traits also varied with the two covariates of polygon area and isolation. 273 Table 2, 274 Table 2 Results of analyses of covariance ANCOVA for 9 plant functional traits Polygon area and. 275 distance from nearest ancient grassland Isolation are covariates and grassland age category is the. 276 factor Also shown are standardised coefficients from discriminant function analysis DFA for each. 277 of the three discriminant functions DFs, Isolation Polygon Area Age Category Discriminant Functions. Trait F p F p F p DF1 DF2 DF3, Ellenberg Fertility 90 376 0 001 13 454 0 001 72 478 0 001 1 183 2 221 1 479. Height 4 970 0 026 5 167 0 023 15 135 0 001 0 895 0 200 1 075. Dispersal Ability 87 049 0 001 18 742 0 001 110 175 0 001 0 551 0 410 1 124. Ellenberg Light 2 354 0 125 19 442 0 001 6 448 0 001 0 418 0 283 0 218. Leaf Area 76 514 0 001 17 861 0 001 33 125 0 001 0 367 0 457 0 437. Ellenberg Difference, 47 783 0 001 15 647 0 001 46 076 0 001 0 315 0 159 0 434. from Neutrality, Clonal Spread 28 891 0 001 24 062 0 001 27 160 0 001 0 118 1 063 0 675. Seedbank Longevity 2 380 0 123 1 089 0 297 40 149 0 001 0 099 0 720 0 451. Plant Longevity 0 834 0 361 22 158 0 001 16 574 0 001 0 046 0 241 0 611. Denotes significance at p 0 05 Denotes significance at p 0 01. 278 Dispersal ability Ellenberg fertility score seedbank longevity and clonal spread all declined with. 279 increasing grassland age Soil pH showed the reverse trend with older grasslands supporting species. 280 which prefer soils further from neutral pH Other traits showed a trend across the three grassland. 281 ages but had intermediate values on lost grassland plant height leaf area or values which were. 282 notably high or low for a single category high plant longevity on old grasslands low light tolerance. 283 on recent grasslands, 285 Fig 3 Bar plot of group standardised means of plant functional traits between communities occurring. 286 on grassland of four different ages classes Capped lines represent one standard error Traits are. 287 weighted by approximate plant abundance 0 1 present 1 rare 2 occasional 3 frequent 4. 288 abundant 5 dominant and scaled for display on the same axis Traits are ordered along the x axis. 289 in order of increasing differentiation between classes according to the results of ANCOVA on each. 290 trait with area and isolation as covariates, 291 Discriminant function analysis gave a classification accuracy proportion classified correctly of. 292 0 614 although classification accuracy varied between age classes Table 3 The most common. 293 misclassifications as proportions of classifications made assigned mid age grassland to the old or. 294 recent classes or recent grassland to the lost or mid age classes Table 3.
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This is a complete walkthrough of Half-Life 2: Episode Two that includes all of the best tips, strategies, and secrets that I've discovered or heard about during the six years I've been playing the game. (As with Half-Life 2, I bought it and installed it the very day it came out back in 2007.)
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Name Year High School, Location College 1 State College 2 Baker, Tom 1977 Jeffersonville H.S., Jeffersonville, IN Eastern Kentucky IN Banks, Gene 1977 W. Philadelphia H.S., Philadelphia, PA Duke PA Budko, Pete 1977 Loyola H.S., Towson, MD North Carolina MD Freeman, Tom 1977 Lynwood H.S., Lynwood, CA Kansas State CA
SCIENCE (Code No. 086 / 090) The subject of Science plays an important role in developing well-defined abilities in cognitive, affective and psychomotor domains in children. It augments the spirit of enquiry, creativity, objectivity and aesthetic sensibility.