General information Data from: Lehtilä, K., Vinter, T., Dinnetz, P. (2020). Plant response to habitat amount and configuration in Swedish forests. Diversity and Distributions. -------------- Abstract Aim: There is an intense debate about whether habitat fragmentation has a negative or positive effect on biodiversity. We examined whether species richness and incidence of forest plants were negatively or positively associated with fragmented forest configuration. We also analysed whether the results support the fragmentation threshold hypothesis with fragmentation effects only in landscapes with small habitat amount. Location: Södermanland province, south-eastern Sweden (8388 km2). Methods: Data consisted of plant distribution maps and landscape data on forest amount and configuration in 2.5 km × 2.5 km quadrats. We carried out models including forest area together with clumpiness index (CL models) or edge density (ED models) as the measure of habitat configuration. We focused on plant taxa with positive association between incidence and forest area (163 taxa in CL models; 119 taxa in ED models). Results: Responses to fragmented configuration were negative more often than by random (33 and 22 taxa in CL and ED models, respectively; includes only models without significant forest area × configuration interaction), whereas positive responses were rare (four taxa in both models). When forest area × configuration interaction was significant, the most common response had a negative effect of fragmented configuration when forest area was low and no effect of configuration when forest area was high, which agrees with the fragmentation threshold hypothesis. Species richness also had this type of response. In another common interactive response, the effect of fragmented configuration was negative at low forest area and positive at high forest area. Main conclusions: Responses to fragmented forest configuration, when significant, were usually negative. When responses to fragmented configuration were modulated by forest area, they were negative when forest area was low. The findings of complex interaction between forest area and configuration has implications for selection of appropriate patch sizes in sustainable forest management. -------------- Contact information: Kari Lehtilä, Tiina Vinter and Patrik Dinnetz, Södertörn University, School of Natural Sciences, Technology and Environmental Studies, SE-14189 Huddinge, Sweden. Corresponding author: Kari Lehtilä, Södertörn University, School of Natural Sciences, Technology and Environmental Studies, SE-14189 Huddinge, Sweden. email: kari.lehtila@sh.se -------------- Methods of data processing and analysis: Data were analysed in R 3.6.0. Script for the analyses: Lehtila_et_al_R_script_Plant_response_to_habitat_amount_and_configuration_Diversity_and_Distribution_2020.R. The script includes the analyses of the Result section, starting with the analysis of the clumpiness text, followed by the edge density tests. A description of production of the figures is also included. Data files: clumpydata.csv. Data file for the analyses of forest area and clumpiness interactions. To minimize correlation between forest area and clumpiness, the 2.5 km x 2.5 km quadrats with forest area between the range 15% ... 75% were included in the analysis. Variables: RT90E, RT90N: Middle coordinates of the 2.5 km x 2.5 km quadrats, Swedish RT90 coordinate system. The coordinates represent distance in metres towards east and north from the RT90 reference point. forestarea: forest area as percent forest of total area in the 2.5 km x 2.5 km quadrats. clumpy: clumpiness of forest in the 2.5 km x 2.5 km quadrats. sprichness: number of forest taxa occurring in the 2.5 km x 2.5 km quadrats. occ: Occupancy data of one species (Lycopodium annotinum) is included to give an example of a single-species analysis. Copyright of the occupancy data is owned by the authors of Rydbeck and Wanntorp 2001, Sörmlands flora. Stockholm, Sweden: Botaniska sällskapet i Stockholm. The occupancy data is available at www.artportalen.se. forestarea.z: standardized values of forest area. clumpy.z: standardized values of clumpiness. edgedensity.csv. Data file for the analyses of forest area and edge density interactions. To minimize correlation between forest area and edge density, the forest area between the range 20% ... 85% were included in the analysis. Variables: RT90E, RT90N: Middle coordinates of the 2.5 km x 2.5 km quadrats, Swedish RT90 coordinate system. The coordinates represent distance in metres towards east and north from the RT90 reference point. forestarea: forest area as percentage of forest in the 2.5 km x 2.5 km quadrats. ED: edge density of forest in the 2.5 km x 2.5 km quadrats. sprichness: number of forest taxa occurring in the 2.5 km x 2.5 km quadrats. occ: Occupancy data of one species (Lycopodium annotinum) is included to give an example of a single-species analysis. Copyright of the occupancy data is owned by the authors of Rydbeck and Wanntorp 2001, Sörmlands flora. Stockholm, Sweden: Botaniska sällskapet i Stockholm. The occupancy data is available at www.artportalen.se. forestarea.z: standardized values of forest area. ED.z: standardized values of edge density. speciesnames.csv. A list of all taxa from Rydbeck and Wanntorp (2001) that were included in the analyses. These taxa fulfilled the criteria set up for inclusion in the analysis. Cultivated and aquatic plants were excluded. For details, see Lehtilä et al. (2020). Most of the taxa were used in both clumpiness and edge density analyses. However, because forest area ranges of the data frames clumpydata and edgedensity differ, they do not cover exactly the same 2.5 km x 2.5 km quadrats. Ten species of clumpiness tests were absent in the data set used for the edge density tests. Similarly, ten species of edge density tests were absent in the data set used for the clumpiness tests. Variables: species: the taxon name. clumpinesstest: the variable showing whether the taxon was included in the clumpiness tests (NA=not included). EDtest: the variable showing whether the taxon was included in the ED tests (NA=not included).