Succession Influences Wild Bees in a Temperate Forest Landscape: The Value of Early Successional Stages in Naturally Regenerated and Planted Forests

<div><p>In many temperate terrestrial forest ecosystems, both natural human disturbances drive the reestablishment of forests. Succession in plant communities, in addition to reforestation following the creation of open sites through harvesting or natural disturbances, can affect forest faunal assemblages. Wild bees perform an important ecosystem function in human-altered and natural or seminatural ecosystems, as they are essential pollinators for both crops and wild flowering plants. To maintain high abundance and species richness for pollination services, it is important to conserve and create seminatural and natural land cover with optimal successional stages for wild bees. We examined the effects of forest succession on wild bees. In particular, we evaluated the importance of early successional stages for bees, which has been suspected but not previously demonstrated. A range of successional stages, between 1 and 178 years old, were examined in naturally regenerated and planted forests. In total 4465 wild bee individuals, representing 113 species, were captured. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056678#s3">Results</a> for total bees, solitary bees, and cleptoparasitic bees in both naturally regenerated and planted conifer forests indicated a higher abundance and species richness in the early successional stages. However, higher abundance and species richness of social bees in naturally regenerated forest were observed as the successional stages progressed, whereas the abundance of social bees in conifer planted forest showed a concave-shaped relationship when plotted. The results suggest that early successional stages of both naturally regenerated and conifer planted forest maintain a high abundance and species richness of solitary bees and their cleptoparasitic bees, although social bees respond differently in the early successional stages. This may imply that, in some cases, active forest stand management policies, such as the clear-cutting of planted forests for timber production, would create early successional habitats, leading to significant positive effects for bees in general.</p> </div

Effects of different successional stages on the abundance and species richness of bees, showing total (A and B), social (C and D), solitary (E and E), and cleptoparasitic (G and H) assemblages, in naturally regenerated and conifer (<i>Cryptomeria japonica</i>) planted forests.

<p>Y axes indicate the numbers of collected individuals for abundance and the number of collected species for species richness, respectively. Solid circles represent naturally regenerated forest, and open circles represent planted conifer forest.</p

Model comparisons, for the abundance and species richness of bee groups (all, social bees, solitary bees, and cleptoparasitic assemblages) in natural regenerated forest.

<p>The table shows values of AIC and of ΔAIC calculated as the difference from AIC values of the null models.</p

Comparison of methodologies for isolation of MOTUs.

<p>Fifty one MOTUs and five morphospecies were recognized during the surveys. Within these MOTUs, 19 and 42 were found in culturing (left circle; blue and red) and dissection (right circle; black and red) survey, respectively, and 10 were recognized by both types of surveys (center; red). *: Hand-picked during dissection analysis; **: Both sequencing and culturing not successful for five morphospecies (right bottom; green).</p

Molecular phylogenetic relationship among MOTUs and the SSU sequences stored in the GenBank database.

<p>The 100001st Bayesian tree inferred from MOTUs and SSU sequences under GTR+I+G model (lnL = 30163.4492; freqA = 0.2367; freqC = 0.2089; freqG = 0.2585; freqT = 0.2959; R(a) = 1.1766; R(b) = 2.7362; R(c) = 1.8858; R(d) = 0.6747; R(e) = 4.2046; R(f) = 1; Pinva = 0.1854; Shape = 0.57). Posterior probability values exceeding 50% are given on appropriate clades. Successfully cultured species are written in bold. *: Identified solely by molecular sequence; ** : identified based on morphological observation.</p

Unmanned Aerial Survey of Fallen Trees in a Deciduous Broadleaved Forest in Eastern Japan

<div><p>Since fallen trees are a key factor in biodiversity and biogeochemical cycling, information about their spatial distribution is of use in determining species distribution and nutrient and carbon cycling in forest ecosystems. Ground-based surveys are both time consuming and labour intensive. Remote-sensing technology can reduce these costs. Here, we used high-spatial-resolution aerial photographs (0.5–1.0 cm per pixel) taken from an unmanned aerial vehicle (UAV) to survey fallen trees in a deciduous broadleaved forest in eastern Japan. In nine sub-plots we found a total of 44 fallen trees by ground survey. From the aerial photographs, we identified 80% to 90% of fallen trees that were >30 cm in diameter or >10 m in length, but missed many that were narrower or shorter. This failure may be due to the similarity of fallen trees to trunks and branches of standing trees or masking by standing trees. Views of the same point from different angles may improve the detection rate because they would provide more opportunity to detect fallen trees hidden by standing trees. Our results suggest that UAV surveys will make it possible to monitor the spatial and temporal variations in forest structure and function at lower cost.</p></div

Relationship between lengths of ground-surveyed and visually identified fallen trees.

<p>Relationship between lengths of ground-surveyed and visually identified fallen trees.</p

Location of the Ogawa Forest Reserve (OFR).

<p>Location of the Ogawa Forest Reserve (OFR).</p

Genetic Structure and Potential Environmental Determinants of Local Genetic Diversity in Japanese Honeybees (<i>Apis cerana japonica</i>)

<div><p>Declines in honeybee populations have been a recent concern. Although causes of the declines remain unclear, environmental factors may be responsible. We focused on the potential environmental determinants of local populations of wild honeybees, <i>Apis cerana japonica</i>, in Japan. This subspecies has little genetic variation in terms of its mitochondrial DNA sequences, and genetic variations at nuclear loci are as yet unknown. We estimated the genetic structure and environmental determinants of local genetic diversity in nuclear microsatellite genotypes of fathers and mothers, inferred from workers collected at 139 sites. The genotypes of fathers and mothers showed weak isolation by distance and negligible genetic structure. The local genetic diversity was high in central Japan, decreasing toward the peripheries, and depended on the climate and land use characteristics of the sites. The local genetic diversity decreased as the annual precipitation increased, and increased as the proportion of urban and paddy field areas increased. Positive effects of natural forest area, which have also been observed in terms of forager abundance in farms, were not detected with respect to the local genetic diversity. The findings suggest that <i>A</i>. <i>cerana japonica</i> forms a single population connected by gene flow in its main distributional range, and that climate and landscape properties potentially affect its local genetic diversity.</p></div

Close-up image of part of the forest floor.

<p>Two fallen trees are detectable.</p