Petermann16_artificial tree holes

Petermann16_artificial tree hole

Experimental design.

<p>In the two regions (Alb and Hainich), we set up six artificial tree holes in each of 29 and 24 plots, respectively. In the Alb, three of the holes in each plot had openings at the side, three at the top. In the Hainich, all tree holes had top openings. Tree holes were installed in April. In the Alb, all tree holes were collected in June, in the Hainich, three were harvested in June, three remained until September. Tree holes in the Alb had a maximum volume of 10l, in the Hainich a substantially lower maximum volume of 600ml. For further information on tree-hole characteristics and measurements in the two regions, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.s007" target="_blank">S1 Table</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.s002" target="_blank">S2 Fig</a>. Table numbers in the figure refer to tables with the respective statistical analyses for the data sets: <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.t001" target="_blank">Table 1A and 1B</a> for data sets involving June data in the Alb and June and September data in the Hainich, respectively, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.s008" target="_blank">S2 Table</a> for June data (and additional environmental variables) in the Hainich. Grey areas depict forests, white areas non-forest habitats. Maps reprinted with permission from Landesamt für Geoinformation und Landentwicklung Baden-Württemberg (17.03.2016, Az.: 2851.2-D/7537 <a href="http://www.lgl-bw.de" target="_blank">www.lgl-bw.de</a>) for the Alb and from GeoBasisDE / TLVermGeo (2016) for the Hainich.</p

Effect of forest management intensity on difference in detritus volume.

<p>Difference in volume of detritus in the artificial tree holes was calculated between the start of the experiment and harvesting time (June or September). Values above zero represent a net gain, below zero a net loss of detritus from the tree hole. Data are from the Hainich region (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.s010" target="_blank">S4 Table</a>) from June (closed symbols and solid lines) or from September (open symbols and dashed line). Symbols represent means per plot, error bars show ±SE. Forest management intensity was calculated according to Kahl and Bauhus [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.ref030" target="_blank">30</a>]. For results of statistical analyses see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155549#pone.0155549.s010" target="_blank">S4 Table</a>.</p

Comparison of macroinvertebrate communities of artificial and natural tree holes in the two regions in June.

<p>A) abundance (square-root transformed), B) species richness and C), D) composition. Artificial holes are depicted by black bars and symbols, natural holes by grey bars and symbols. Average water volume differed between artificial and natural tree holes (artificial tree holes had larger average volume). However, the differences in abundance and richness between artificial and natural tree holes were still significant after fitting water volume as a covariate (for results of statistical analyses see text). Raw abundance and species richness (i.e. not adjusted for differences in volume) are shown here. The low overlap between artificial and natural communities in the composition plots (C, D) shows that community composition differed between artificial and natural tree holes in both regions. Only taxa with more than five occurrences per region across both tree-hole types were used for the nonmetric multidimensional scaling (NMDS) plots in C and D. Stress = 0.17, n = 214 for Alb, stress = 0.21, n = 124, for Hainich. Please note that experimental set-up and the volume of artificial tree holes also varied between the two regions, so they cannot be compared directly.</p

Insect communities in water-filled tree holes

collected in the fiel

Mixed model results for abundance and richness.

<p>Mixed model results for abundance and richness.</p

Insect community composition.

<p>Nonmetric multidimensional scaling (NMDS) plot showing the composition of insect communities in artificial tree holes in the two regions in June: A) Alb, B) Hainich. Red symbols in A represent artificial holes with a side opening, symbols in black are artificial tree holes with a top opening. The size of the symbols represents the density of natural tree holes in the respective plots. Forest management intensity affected community composition in the Alb and in the Hainich as shown by the arrow drawn by fitting forest management intensity <i>post hoc</i> and indicating tree holes in plots with high and low forest management. Opening type and tree-hole density had an effect on community composition in the Alb only (shown by the clustering of similar symbols). For results of statistical analyses, see text. Only taxa with more than five occurrences per region across both tree-hole types were used for the plots. Stress = 0.16, n = 137 for Alb, stress = 0.19, n = 134, for Hainich.</p