Biodiversity and Conservation 12: 1271–1285, 2003. 2003 Kluwer Academic Publishers. Printed in the Netherlands.

Size of nature reserves: densities of large trees anddead wood indicate high value of small conservationforests in southern Sweden

¨ *FRANK GOTMARK and MARIA THORELL*¨ ¨Department of Zoology, University of Goteborg, Box 463, SE 405 30 Goteborg, Sweden; Author for

correspondence (e-mail: f.gotmark@zool.gu.se; fax: 146-31416729)

Received 22 January 2002; accepted in revised form 3 July 2002

Key words: Conservation strategy, Dead wood, Forest, Large trees, Reserve size

Abstract. The optimal size of nature reserves has been debated for some time. Although edge and corehabitats are often recognized, it is commonly assumed in theory and in studies of a particular habitat typethat reserves or patches of different sizes have similar habitat structure. However, for older, highlyfragmented landscapes it has been suggested that small areas are of conservation interest as high-qualityremnants, whereas large areas are more degraded. We studied 49 randomly selected forest reserves in thesize range 5–230 ha (typical for many highly fragmented landscapes) and 3653 sites of key habitat(unprotected deciduous broadleaf forest). Structures in forest that are generally correlated with value forbiodiversity were measured, and reserve objectives were examined from declaration texts. Both thedensity of large trees and the density of dead wood (snags, logs) decreased with increasing reserve size.The mean size of identified key habitats was very small (1.6 ha). A botanical objective for establishmentof reserves was more frequently used for smaller reserves. In contrast, cultural and especially recreationalobjectives were more commonly used when larger reserves were established, suggesting higher values forrecreation in these reserves. For vascular plants, birds and beetles, a literature review indicated that smallforest patches do not contain impoverished communities, but are often rich (per unit of area). Smallreserves and key habitats have several disadvantages, but they are probably important components ofreserve networks for biodiversity in highly fragmented landscapes.

Introduction

For many years, biologists have discussed the optimal size, distribution, and design´of nature reserves (Soule and Simberloff 1986; Shafer 1990; Cowling and Bond

1991; Noss and Cooperrider 1994; Pressey 1994; Shafer 1995; Meffe and Carroll´1997; Soule and Terborgh 1999a, 1999b; Margules and Pressey 2000). The size of

the reserves is one key factor; a large reserve generally contains more species than asmall reserve, and generally supports larger species populations. In addition, largerreserves are more likely to be subjected to natural disturbances such that speciesadapted to different types of patches can survive. Many authors have concluded thatlarge reserves generally are better for biodiversity conservation than smaller ones(reviews in Noss and Cooperrider 1994; Meffe and Carroll 1997).

´Recently, Soule and Terborgh (1999a, 1999b) emphasized the importance ofprotecting very large connected areas with populations of large predators, consid-ered to be keystone species. This strategy may, however, be difficult to implement in

landscapes that are dominated by agriculture and/or forestry. Small protected areas(e.g. ,50 ha) may then be valuable to complement larger areas protected elsewhere(Shafer 1995; Turner and Corlett 1996; Schwartz and van Mantgem 1997; Schwartz1999). Schwartz and van Mantgem (1997) stated that the potential value of smallreserves has been underestimated. They discussed smaller sites of North Americanprairie with high species richness, where isolation in space and time apparently hadnot led to extinction of species (see also Simberloff and Gotelli 1984).

Schwartz and van Mantgem (1997, p. 384) hypothesized that ‘‘Small areas (,10ha) are generally of conservation interest because they are high-quality remnants.Conversely, in chronically fragmented habitats large sites are often already de-graded’’. For prairie habitat, the authors found that larger sites required restorationwork. If their hypothesis concerning patch size is more generally true for un-protected and protected natural areas, this has implications for conservation work.Although edge and core habitats are often recognized, models of reserve design(Diamond 1975; Pelletier 2000), simulation of species richness in forest islands ofdifferent sizes (Wu and Vanka 1991) and various metapopulation models (Hanski1999) assume that different-sized areas have similar habitat composition per unitarea, which may not be true.

We tested Schwartz and van Mantgem’s hypothesis in a study of conservationforests in Sweden. Our study concerned mainly broadleaf temperate forest, thebiome where human exploitation has been most widespread (Hannah et al. 1995;Peterken 1996). We randomly selected forest reserves of different sizes to investi-gate their values in the field. Also, we studied the objectives of these reserves(through declaration texts) and historical trends in reserve sizes. Moreover, weanalysed the size of identified sites of key habitat of broadleaf forest (unprotectedsites). Key habitats were surveyed by forestry boards and we used a database toanalyse their size. Finally, to complement these analyses, we reviewed studieswhere biodiversity (species richness) of three major taxa was related to size ofreserves or patches.

Methods

Study area, reserves, and key habitats

¨Southern Sweden or ‘Gotaland’ (Figure 1) is a lowland area (0–300 m above sea¨level) covering about 25% of the country (Nilsson and Gotmark 1992; Esseen et al.

¨1997; Nilsson 1997). Gotaland mainly belongs to the boreonemoral zone, but three˚counties in the south (Halland, Blekinge and Skane) belong to the nemoral zone of

central Europe (Ahti et al. 1968; Esseen et al. 1997; SEPA (Swedish EnvironmentalProtection Agency) 1997; SOU (Swedish Public Reports) 1997). The forest(dominating habitat) consists mainly of Norway spruce (Picea abies), Scots pine(Pinus sylvestris), and some birch (Betula spp., 8.5% of the wood volume; NationalBoard of Forestry 1997). Forestry has generally disfavoured deciduous (broadleaf)

¨trees. Several deciduous tree species occur mainly or only in Gotaland in Sweden,

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especially oaks (Quercus robur /Q. petraea), beech (Fagus sylvatica), common ash(Fraxinus excelsior), small-leaved lime (Tilia cordata), wych elm (Ulmus glabra)and Norway maple (Acer platanoides), but the abundance of these species is low(National Board of Forestry 1997). Southern deciduous forest is associated withhigh species richness, including red-listed species (Berg et al. 1994; Berg andTjernberg 1996).

¨We studied protected areas in 5 of the 11 counties in Gotaland, the 3 counties in¨¨the nemoral zone and 2 in the boreonemoral zone (Bohuslan and Alvsborg). We

collected information about all nature reserves (380) and national parks (3) with atleast 1 ha of woodland, established up to 1 July 1997 (SEPA (Swedish Environmen-tal Protection Agency) 1997). Below, these sites are referred to as ‘reserves’ or‘protected areas’. Most reserves also contained other habitats, e.g. agricultural landand barren rock. The mean and median sizes of the reserves were relatively small(150 and 50 ha, respectively, including only forest 73 and 22 ha, respectively). Thisis within the typical size range for reserves in landscapes that have been highly

Figure 1. Map of study area and counties in southern Sweden. Forest reserves were studied in the¨¨ ˚counties of Bohuslan, Alvsborg, Halland, Skane, and Blekinge. Key habitats were studied in the counties

¨¨ ¨ ¨of Vastra Gotaland (that is, counties of Bohuslan, Alvsborg, Dalsland, and Skaraborg forming a new¨ ¨ ¨ ¨large county since 1999), Ostergotland, Kalmar, Jonkoping and Kronoberg. The key habitats studied

were partly from different counties than the nature reserves studied, due to availability of data. Halland,˚Skane and Blekinge are situated in the nemoral vegetation zone, the remaining counties mainly in the

boreonemoral zone.

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¨ ¨fragmented for a long time (e.g. Nilsson and Gotmark 1992; Bucking 1997;Schwartz and van Mantgem 1997).

Nature reserves were established for their ‘‘contribution to the knowledge ofnature, for their beauty or remarkable content, or for their importance to outdoorrecreation’’ (Nature Conservation Act, originating from 1909). Based on the IUCN(1994) classification of protected areas, Swedish nature reserves would include: I –Scientific Reserve /Strict Reserve, IV – Nature Conservation Reserve /ManagedNature Reserve /Wildlife Sanctuary, V – Protected Landscape, and partly III –Natural Monument /Natural Landmark.

In 1999, the national and regional forestry boards completed the first part of anextensive survey of key habitats on privately owned (unprotected) properties. Suchproperties comprise as much as 80% of the forest land in southern Sweden (NationalBoard of Forestry 1997). The purpose of the key habitat survey was to identifyforests with high values for biodiversity, in particular red-listed species (Gustafssonet al. 1999; National Board of Forestry 1999). Forest structure (e.g. large trees, deadwood; National Board of Forestry 1995) was a primary criterion used in identifyingkey habitats (forestry board conservation officials E. Sturesson, T. Swerre and S.Adolfsson, personal communication). To some extent also indicator species (‘signalspecies’) were used, mainly cryptogams (National Board of Forestry 1995; Gustaf-sson et al. 1999). Forest key habitats were delimited on the basis of bioticboundaries (for biodiversity) by forestry board personnel in the field.

Collection and treatment of data

Data on reserves were mainly collected in August–November 1997 and May–¨August 1998 in a study of reserves and their potential buffer zones (Gotmark et al.

¨2000; M. Thorell and F. Gotmark, unpublished data). For field work, we randomlyselected 49 reserves from the set of 383 reserves, in the size class 5–225 ha. Theproportion of reserves selected from each county was the same, and selection wasstratified by reserve size, such that 25% of the reserves in each of the following foursize classes were selected randomly: 5–20, 21–50, 51–100, and 101–225 ha.

In forest, the densities of large trees and deadwood are generally correlated withvalue for biodiversity; many cryptogams, invertebrates, birds and mammals use oldand dead trees (e.g. Warren and Key 1991; Berg et al. 1994; Samuelsson et al. 1994;Keddy and Drummond 1996; Nilsson 1997; National Board of Forestry 1997;Jonsell et al. 1998; McComb and Lindenmayer 1999). For forest species withlimited dispersal capacity, many of which are threatened (e.g.Warren and Key 1991;Ranius and Jansson 2000), density of old and dead trees should be one criticalfactor. Using line transects in reserves, we estimated the density of coarse woodydebris (CWD; Harmon et al. 1986; i.e. dead standing trees, called ‘snags’ below, anddowned trees, ‘logs’) and the density of large trees (diameter at breast height, dbh.41 cm). Large trees also contained a second group of .83 cm dbh. Snags were.1.3 m in height and $16 cm in dbh, and logs $16 cm in dbh; other snags were notrecorded. A log was 8 m or longer; logs shorter than 8 m were recorded on the basis

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of 8 m parts (e.g. a 5 m part was a 5/8 or 0.62 log, but a 12 m log was 1.0 log).Single log parts less than 1 m in length were not recorded.

The line transects had a width of 25 m, records being taken 12.5 m from theobserver on both sides along the transect. The transects were laid out systematically,each starting at the reserve border (perpendicular to it) stretching towards the centralpart of the reserve for 100 or 200 m (depending on the size of the reserve). Transectsplaced in this way around (within) reserves were separated by 200–400 m (200 mfor small reserves, 400 m for larger ones). We mapped 4–20 transects per reserve,the number of transects increasing with reserve size (mean 5 10 transects, n 5 49).On average 3.0 ha was sampled per reserve (SD 5 2.1 ha, range 0.56–10.0 ha, n 5

49). The summed investigated area was thus larger in larger reserves, but thepercentage of the reserve forest investigated was higher in small reserves (,30 ha;5–20%) than in large ones (.60 ha; 3–8%).

We analysed the size distribution of 3653 key habitats from five counties in theboreonemoral zone (Figure 1). The data for this analysis were from a large databasefor key habitats (unpublished data from E. Sturesson, Forestry Board of eastern

¨Gotaland). To focus on forests with high biodiversity values, we selected keyhabitats of southern deciduous broadleaf forest types with at least 20% oak (byvolume).

¨Gotmark and Nilsson (1992) used a national database for protected areas toanalyse the objectives (criteria) for initial establishment of protected areas. For thepresent study, we visited the Environmental Units at the County Administrations,reading the texts that the objectives were based upon. We classified the objectivesfor all 383 reserves as ‘human-oriented’ (mostly related to human use of areas) or‘nature-oriented’ (mostly related to biological qualities of areas; e.g. Margules andUsher 1981). The objectives were judged from two sources at the EnvironmentalUnits; (1) the reserve declaration text, and (2) the management plan. The human-oriented objectives were recreational value (RECR; mainly picnics, walks, hiking,nature studies, swimming), landscape value (LAND, aesthetic landscape value) andcultural value (CULT; ancient land use; historical value). The nature-orientedobjectives were botanical values (BOTA, rarity and richness of vascular plants) andzoological values (ZOOL, value for birds mainly, to a minor extent mammals,reptiles, amphibians and invertebrates).

In the statistical analysis we used Spearman’s rank correlation (r ) unlesss

otherwise stated. Lake and sea, covering 12% of the total reserve area of 3158 ha,were not included in the measure of reserve size (protection of water areas was arare objective for the reserves). As we focused on biodiversity in forest, we usedtotal forest area of each reserve as a measure of reserve size instead of total land area(unless otherwise explained). About 70% of the total land area of the reserves wasforest, and forest area and land area of the reserves were correlated (r 5 0.89). Thes

forest area in the reserves varied between 5 and 169 ha (mean 39 ha, n 5 49). Inanalyses of objectives for the reserves we used no statistical tests; all 383 reservescontaining forest in the study area were included, thus they were not a sample butthe whole statistical population.

Finally, we reviewed studies of species richness in three major taxa (herbaceous

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plants, birds and beetles) in highly fragmented temperate forests. Studies of tropicaland northern boreal forests were not included. Using the Institute for ScientificInformation (ISI) database ‘The Web of Science’ we searched for studies publishedbetween 1987 and 2001, especially those reporting measurements per unit area inrelation to forest patch size (or where effect of area was taken into account). Studiesof single species were excluded and we focused on those that studied larger parts ofcommunities of the taxa at several or many sites (of different size). A few oldercomprehensive studies and two earlier reviews (Hanski 1999; Forman 1999) foundin the literature were also included.

Results

Large trees and dead wood in forest reserves

The proportion of deciduous broadleaf forest (in transects) was weakly but notsignificantly negatively correlated with the size (forest area) of the reserves (r 5s

20.22, P 5 0.12, n 5 49 reserves). Of the recorded 3030 large trees, 98.6% had adbh between 41 and 83 cm (thus only 1.4% were thicker than 83 cm). The density oflarge trees (in transects, all species .41 cm dbh) was negatively correlated withreserve size (r 5 20.41, P 5 0.005, n 5 49, Figure 2a). For deciduous trees wes

found a similar relationship between density of large trees and reserve size (r 5s

20.30, P 5 0.041, n 5 49). Of the recorded 2852.5 components of CWD (snags andlogs), 91.8% had a diameter between 16 and 41 cm (thus only 8.2% of the CWDwere thicker than 41 cm). The density of CWD components was negativelycorrelated with reserve size (r 5 20.30, P 5 0.035, Figure 2b).s

Size of key habitats

All but 200 of the 3653 key habitats (broadleaf forest type) identified by the forestryboards in the five counties were smaller than 8 ha (Figure 3). The median size wasonly 1.6 ha (range 0.1–44 ha) and 87% of the sites were smaller than 5 ha.

Objectives in relation to size of reserves

For all protected areas in Sweden (1909–1987), and for the 383 reserves in thepresent data set (1918–1997), we judged that human-oriented and nature-orientedobjectives were about equally important for the establishment of the reserves

¨ ¨(Gotmark and Nilsson 1992; F. Gotmark and M. Thorell, unpublished data). Each¨reserve usually had two or more objectives (Gotmark and Nilsson 1992). Since the

objectives were related also to terrestrial habitats other than forest, we used landarea as a measure of reserve size in the analyses below. For the 49 reserves (studiedin the field), RECR was the most frequently used objective, and its use increasedwith reserve size (Figure 4a). Also CULT was used more often for larger reserves,whereas LAND was about equally frequent for reserves in different size classes. The

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Figure 2. (a) Number of large trees (dbh $41 cm) per hectare in relation to size (forest area) of 49 naturereserves in southwestern Sweden. (b) Number of dead wood components (CWD, snags and logs, dbh$16 cm) per hectare in relation to size (forest area) of 49 nature reserves in southwestern Sweden. Thelines indicate the slope of the relationships (linear regression).

use of the two nature-oriented objectives (BOTA and ZOOL) showed no apparentcovariation with reserve size (Figure 4a).

In the analysis of all 383 reserves (Figure 4b), six instead of four size classescould be used, since this data set included more small and large reserves. To makethe analysis more relevant to forest, we included only reserves where the forestmade up $75% of the land area. Of the 171 reserves included under this restriction,35 were also represented in the sample of 49 reserves. For very small reserves (1–4ha), BOTA was the major objective, whereas for larger reserves (from 21 to 2722ha), RECR was commonly used (Figure 4b). The CULT objective increased slightly,whereas LAND and ZOOL showed no covariation with reserve size.

Since RECR was a common objective for large reserves, the change in foreststructure with increasing reserve size (Figure 2) may be explained by inclusion of

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Figure 3. Number of key habitats (deciduous broadleaf forest) in relation to their size. These key habitatswere identified in a survey of private land (non-industrial private forest owners) by the Swedish forestryboards 1994–1998. Data are from five counties in the boreonemoral zone (Figure 1).

large reserves with only human-oriented objectives (RECR, CULT and/or LAND).In the data set of 49 reserves studied in the field, two reserves contained no clearvalue for biodiversity conservation (no valuable forest habitat, no key habitat, norare species, no red-listed species). We deleted these two reserves, using the newdataset (n 5 47) to re-analyse density of forest structures in relation to reserve size,but found only marginal changes in P-values, and thus no change in conclusions.

We found changes in the size of reserves acquired by conservation agenciesduring the 20th century. The mean size of the forest area of the reserves increased,as did the median size, although the median did not change much between 1968 and1997 (Figure 5). This suggests that larger reserves were considered increasinglyimportant during the period, but the little change in median size between 1968 and1997 showed that small areas also were protected in the five counties.

Studies of taxa in patches of temperate woodland

The criteria set up for our review (see Methods) meant that relatively few studies ofvascular plants, birds or beetles could be included (in addition, investigations ofmany species at several or many sites are quite rare). The studies were from old,highly fragmented landscapes, dominated mainly by agricultural land (USA, UK,Belgium, Denmark) or production forests (Sweden, Finland).

For herbaceous plants, Helliwell (1976) concluded that small, isolated woodlandsof a few hectares in the UK were more valuable than comparable areas forming partof larger blocks of woodland. Simberloff and Gotelli (1984) reported similar results

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Figure 4. Proportion (%) of nature reserves with different protection objectives in relation to reserve size(land area). Each reserve could have several objectives. N values represent the number of reserves in eachsize class. Included in (a) are the 49 reserves that also were studied in the field; (b) shows the result for the171 reserves that contained $75% forest area of the total land area.

for patches of various plant communities in the USA. Helliwell (1976) stated thatone possible explanation could be more intensive management for timber pro-duction in the larger areas. Honnay et al. (1999) found that small forest fragments(1–5216 ha, median 19 ha) in Belgium were important to maintain diversity offorest plants; the size of patches was of little importance, whereas habitat diversityand patch age seemed to be key factors. Similar results were reported by Lawessonet al. (1998) from Denmark, who also found a negative relationship between speciesrichness of herbs (forest species) and patch area, when the effect of area sampled

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Figure 5. Temporal changes in the size (forest area) of nature reserves established during five timeperiods between 1918 and 1997 in southern Sweden (five counties, n 5 383).

was taken into account (size of forests: 1–446 ha, most of them ,100 ha). Thisresult was probably due to less intensive management (cutting) in small forests(Lawesson et al. 1998).

Many beetles, including many red-listed species, depend on CWD or old treescontaining dead wood (Jonsell et al. 1998; Ranius and Jansson 2000). For saproxylic

˚beetles in a mainly forested area in central Sweden, As (1993, 1999) found nodifference in species richness between large (.120 ha) and small (,20 ha)deciduous stands, but he found more species from the surrounding production forestin the small stands. In deciduous stands with many old trees and dead wood insouthern Sweden, the number of red-listed saproxylic beetles was weakly negativelycorrelated (P 5 0.09) with the area of the stands (8–56 ha; Nilsson et al. 1995,species per unit of area sampled not reported). There are several studies of carabids,ground beetles that are less dependent upon old / large trees and CWD. In Belgium,species richness was higher in several small and relatively recent woodlands than inlarger ancient forests, mainly due to the presence of species from the surroundingopen habitat in the smaller fragments (Desender et al. 1999). Typical woodlandcarabids appeared to be strongly linked to larger, ancient woods. Similar results

¨from forest fragments (1–22 ha) in Finland were reported by Halme and Niemela(1993).

Bird species with large area requirements, or those typical of forest interiorconditions, are often absent in smaller forest patches (Table 9.1 in Hanski (1999),and review in Forman (1999), pp. 59–63). Species richness of breeding birds perunit area was higher in small than in larger patches (Forman (1999), pp. 61–62,patch sizes 0–24 ha). This is often referred to as the ‘edge effect’, though otherfactors than the proportion of edge habitat in the patch may also be involved (seebelow). In the UK, Mason (2001) studied birds in 35 woods (0.1–57 ha) in a

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farmland landscape. Species richness per unit area was not reported, but in fourspecies the breeding density increased with decreasing woodland area, and in fourspecies it was unrelated to area (see Mason (2001) for other studies reporting similarresults from the UK). In the southern part of our study area (Sweden), Loman andvon Schantz (1991) studied breeding birds in forest patches in farmland. They foundhigher densities of species and individuals in small than in large forest patches(three classes; ,1, 1–10, and .10 ha). The authors suggested that birds nesting insmaller patches used resources both in the patch and in the surrounding matrix,which might explain the results. Only one vegetation component affected birdspecies richness in the patches; the amount of standing dead trees and bushes. As wefound a higher density of CWD in small reserves, this finding is of particularinterest. The authors concluded that ‘‘for conservation . . . very small habitat islandsmay, per area, be as valuable or even more valuable than medium-size islands’’, andthey suggested that the surrounding matrix also may be productive and worthconservation measures.

To summarize, small or relatively small forest patches in old fragmentedlandscapes in several studies had a valuable flora; the value of small woodlands forbeetles and birds probably varies, depending on stand age, surrounding landscapeand other factors. For southernmost Sweden at least, the evidence suggests thatsmall forest patches contain a rich bird fauna (for similar conclusions, see alsoFischer and Lindenmayer 2002, a study found after the literature review wascompleted). The result of our review does not suggest that small forest patchesgenerally have impoverished species communities.

Discussion and conclusions

Our results are consistent with Schwartz and van Mantgem’s (1997) hypothesis forold, highly fragmented landscapes, that small natural areas are of conservationinterest in having a low proportion of degraded land compared to larger areas.Smaller reserves had, on average, higher densities of large trees and CWD thanlarger reserves. Only land with forest was included in this study, so the result cannotbe explained by the presence of other habitat than forest in the larger areas. Innon-protected forest the key habitats (with broadleaf tree species) consisted of verysmall patches. They were identified by the forestry boards mainly on the basis offorest structure (large trees and dead wood were important criteria) and the resultsuggests that forest stands of this type are very small. Since the key habitats wereprivate land and not protected (delimited to aid land owners in taking environmentalconsiderations), the conclusions are similar for protected and unprotected forest.

Conservation agencies usually survey habitat types (e.g. wetlands, meadows,broadleaf forests) to protect representative and valuable sites. Species richness, plantcommunities, or environmental units are often considered in such work (Howlettand Dhand 2000, and accompanying papers). Our results indicate that both smalland large forest areas should be considered in reserve programmes. However, if weassume that there is a (long) time lag between habitat loss and species loss in forest

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fragments (Nee 1994; Hanski 1999), some species will disappear from smallreserves in the future. This problem needs more study, but at present smallconservation forests in southern Sweden do not seem to contain impoverishedhabitat or species communities.

There are at least four non-mutually exclusive reasons why small forest reservescontained higher density of large and dead trees than larger reserves. First, in earlierdecades dead wood was sometimes removed in the management of reserves, andcutting is still allowed in some reserves. Such management might have been morecommon in larger reserves, where also recreation and aesthetic aspects wereimportant. Second, to establish large reserves, the conservation authorities may haveincluded other, less valuable forest (e.g. production or recreation forest) close tocore areas for biodiversity. If this is true, it should reflect the absence of large woodswith high densities of large and dead trees. Third, a higher proportion of small thanlarge reserves consisted of ground judged inaccessible for forestry machines (i.e.steep area; M. Reinhardt, unpublished data), so cutting could have been difficult insome small reserves. Fourth, the former or present land owners of reserves (allreserves are not fully protected) may have had low demand for timber in smallerforests, while large forest properties were considered more important to cut (cf.Helliwell 1976; Lawesson et al. 1998).

Large reserves were more valuable than small reserves for outdoor recreation, to¨judge from the objectives in the reserve declaration texts (see Gotmark and Nilsson

(1992) for similar results). This was apparently not because the natural setting perse in these reserves had higher aesthetical value (the frequency of LAND did notincrease with reserve size). Rather, larger reserves may provide more space orhabitats for recreational activities. The county administrations usually encouragerecreation in large reserves, whereas this seems to be less common for smallerreserves (personal observation). Remains of pre-industrial agricultural landscapes(CULT) may also contribute to recreational value in large reserves. BOTA predomi-nated for the smallest reserves, so many small sites with interesting vascular plants

¨were apparently protected (see Gotmark and Nilsson (1992) for similar result),indicating botanical values of small reserves.

The result of our literature review might be surprising, given the consensus on theadvantages of large reserves compared to small ones for biodiversity conservation

´(e.g. Noss and Cooperrider 1994; Meffe and Carroll 1997; Soule and Terborgh1999a, 1999b; but see Shafer 1995; Turner and Corlett 1996; Schwartz and vanMantgem 1997). Note that we reviewed species richness (per unit area) and notpopulation sizes, reproductive success, and presence and effects of large mammals(e.g. predators) in relation to patch size, aspects discussed in many papers. More-over, psychological bias might have led to selection of papers from the literature thatare consistent with the result of our test of Schwartz and van Mantgem’s hypothesis.However, even if we assume there is a bias, our review at least shows that highspecies richness of vascular plants, beetles and birds in small forest patches is oftenreported.

In conclusion, large forest reserves are valuable for many reasons (Meffe and´Carroll 1997; Soule and Terborgh 1999a, 1999b). Our results indicate that also small

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conservation forests have values for biodiversity, at least in old fragmentedlandscapes (see Turner and Corlett (1996) for similar conclusions regarding smalltropical rain forest fragments). In areas with many small woodlands, conservationagencies should conduct surveys and consider protection of valuable sites, com-bined with corridors, buffer zones, and other forms of appropriate management ofthe land.

Acknowledgements

˚We are most grateful to Asa Persson, Erik Heyman, Kristina Jungbark, KarinRystedht and Uno Unger for field assistance. We also thank Conny Askenmo,

¨Johnny de Jong, Tommy Ek, Keith Kirby, Rolf Lofgren and anonymous referees foruseful comments on the manuscript. Many persons at the County Administrationsanswered questions and helped in various ways during our visits. The study wasfinanced through grants from the Swedish Council for Planning and Coordination ofResearch, the Swedish Natural Science Research Council, ‘Verner von Heidenstams

¨fond’, ‘Erik och Ellen Sokjer Stipendiefond’, ‘Kungliga Skogs- och Lantbruk-sakademien’, and ‘Adlerbertska Forskningsfonden’.

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