(i) The effect of environmental characteristics (distance to seed source, % vascular plant cover, % woody debris, altitude and soil pH) selleck products on the tree regeneration densities
were examined using Spearman rank correlation coefficients. The analyses were carried out separately for the dominant species that were identified (birch, alder, rowan, willow and oak). Ground flora characteristics in each quadrat were analysed as: (i) Total number of species, S, (ii) % vascular plant cover of each species, and (iii) linear regression analysis was used to examine the difference in vascular plant coverage with time since clearfelling. A total of 14 tree and shrub species were found to be regenerating, of which 10 were species native to Great Britain. The non-native species consisted of three conifers (Sitka spruce, Pinus contorta (lodgepole pine) and larch) and one broadleaved species (Alnus
incana (grey alder)). The native species were birch, oak, PI3K inhibitor rowan, willow, common alder, Fraxinus excelsior (ash), holly, Fagus sylvatica (common beech), Corylus avellana (common hazel) and Juniperus communis (common juniper). The mean density of regeneration of native species on clearfelled sites varied from 0 stems/ha to >5000 stems/ha ( Table 2). While the regeneration density of non-native tree species is shown in Table 2 it is important to note that in a number of study sites regenerating non-native conifers had been felled, making it difficult to draw any conclusions about the frequency of non-native regeneration. The linear regression of time since clearfelling on regeneration density of native species was not found
to be significant (r2 = 0.26, n.s.). Table 3 shows the density of regeneration for native species and the fraction of clearfelled sites where each species was recorded. Regeneration was dominated by birch and rowan. Whilst the regeneration of holly and oak were recorded infrequently (<20% of sites), relatively high regeneration densities were recorded at specific sites for these species (for example, 723 stems/ha in the case of oak). The regeneration density of birch and alder was found to be negatively correlated with oxyclozanide distance from seed source (see Table 4). In the case of birch, for example, 63% of regeneration occurred within 20 m of a seed source. No significant relationship was found for rowan or oak. No significant relationship between plant cover and regeneration density was seen for any species. However, when the regenerating trees were divided into sapling (taller than 0.5 m) or seedling (shorter than 0.5 m) categories then a significant negative correlation was seen between birch seedling density and vascular plant cover. Birch also showed a significant negative correlation with the percentage of brash (woody debris). No such effects were noted for alder, willow, oak or rowan.