DOI: 10.5061/dryad.m0cfxpp2j
title: Data from: Carbon flux and forest dynamics: increased deadwood decomposition in tropical rainforest tree-fall gaps

description: This study was carried out within an area of lowland, old growth
 dipterocarp rainforest in the Maliau Basin Conservation Area, Sabah,
 Malaysia (4° 44' 35" to 55" N and 116° 58' 10" to
 30" E; mean annual rainfall 2838 mm ± 93 mm). On the 20th of July
 2017, there was a storm at the study site, which generated winds speeds of
 8.4 m/s (Fig. S1). These were among the strongest winds normally
 experienced in inland forests of the region, which placed extreme sheer
 stress on trees. Consequently, a large number of trees fell within the
 same 24-hour period in the study location. Ten tree-fall gaps (mean
 length: 32 m ± 2.8, mean width: 24.5 m ± 3; see table S1 for gap
 characteristics) created during this event were selected for use in this
 investigation, along with ten adjacent closed canopy sites, located 20 m
 from the edge of each gap. We took 10 hemispherical photos in each gap and
 closed canopy sites to quantity canopy openness at each location.
description: <i>Decomposition
 assay</i> In October 2017, we established a
 wood decomposition assay. Using a termite suppression experiment combined
 with macroinvertebrate accessible and inaccessible mesh bags, Griffiths
 <i>et al.</i> (2019) demonstrated that non-termite
 macroinvertebrates did not contribute significantly to the decomposition
 of a standardised wood substrate, <i>Pinus radiata
 </i>blocks<i>, </i>at this site. Therefore, to assess
 the rate of decomposition within these paired gap and closed canopy sites
 and determine the relative contributions of termites versus microbes to
 the process, we used the same assay of mass loss from untreated
 <i>P. radiata</i> wood within macroinvertebrate accessible and
 inaccessible bags. Wood blocks (9 x 9 x 5 cm, 161.2 ± 1.3 g; wood density
 of 0.40 g cm<sup>-3 </sup>[Zanne et al., 2009]; wood C:N ratio
 of 462 ± 48 [Ganjegunte, Condron, Clinton, Davis, & Mahieu, 2004])
 were dried at 60 ºC until they reached a constant weight and placed inside
 “open” (accessible to macroinvertebrates, principally termites, and
 microbes), or “closed” (accessible to microbes only) bags, which were all
 made with 300 micron nylon mesh (Plastok™, Merseyside, UK). The open
 woodblocks had ten 1 cm holes cut into the top and bottom of the bags to
 avoid confounding effects of using mesh of different sizes in
 decomposition assays (Stoklosa et al., 2016). The edges of the closed bags
 were folded several times and sealed with staples to prevent access by
 invertebrates. In each gap and closed canopy site, we ran a 50-m transect
 and randomly placed 5 open and 5 closed wood blocks 5 m apart along the
 transect (n = 10 per site; n = 200 woodblocks in total: 10 x forest sites
 x 2 canopy treatments [closed canopy or gap] x 2 mesh treatments [open or
 closed] x 5 replicates). Because the gaps were irregular in shape
 (Appendix table S1), we placed the transects along the longest axis of
 each gap. In all but one of the gap sites, we were unable to establish a
 50 m transect, therefore, we placed an additional line perpendicular to
 the first, ensuring that each block was always at least 5 m apart from its
 nearest neighbouring block (Fig. 1). A hemispherical photograph was
 taken by placing an iPhone 6 with a fisheye lens attachment directly on
 top of each wood block. Photographs were analysed using the function
 <i>Hemiplot </i>in R to calculate canopy openness, which was
 twice as high within the gaps compared with closed canopy sites (t = 9.67,
 <i>P</i> &lt; 0.001, mean openness in gap sites = 0.24 ±
 0.03; mean openness in closed canopy sites = 0.12 ± 0.02; Fig. S2). When
 placing the woodblocks, the top layer of leaf litter was removed, and the
 blocks were put directly on the humus layer. Wood blocks were left on the
 forest floor for 12 months (October 2017 to October 2018), after which
 they were collected and dried at 60 ºC until they reached a constant
 weight. Once dried, wood material was separated from termite soil. The
 remaining deadwood and termite material (carton and soil) was then
 re-weighed separately to calculate the proportion of mass loss from each
 block and the mass of soil brought into the mesh bags by termites. Given
 that termites are the only invertebrates known to translocate soil into
 deadwood (Oberst, Lai, & Evans, 2016), the mass of soil moved into
 the experimental woodblocks provides additional information on the termite
 activity compared with non-termite wood-feeding invertebrates.
 <i>Soil conditions
 and termite communities</i> Every month for the 12-month
 duration of the study, soil moisture percentage and soil temperature were
 measured within 5 cm of each wood block using a Delta-T Devices HH2
 moisture metre (precise to 0.01 %) and a digital soil thermometer.
 Measurements were taken in dry conditions, between 8 AM and 10 AM.  To
 assess termite communities located within the gap and closed canopy sites,
 we carried out termite transects in September 2018 using the Jones and
 Eggleton transect method (Jones & Eggleton, 2000). This method
 uses a 100 m x 2 m belt transect which is divided into twenty 5 m x 1 m
 sections. Each section is sampled for 30 minutes by two trained collectors
 searching for termites in twelve 12 cm x 12 cm x 10 cm soil pits and
 examining all dead wood, leaf litter and trees for the presence of
 termites. When encountered, termite specimens were collected in 70%
 ethanol and taken to the laboratory for identification. Because our gap
 sites were not big enough to place a 100 m transect, we carried out the
 same method but two using smaller transects to equal a 50 m transect
 combined. Therefore the sampling effort was half that of the Jones
 & Eggleton (2000) method. <i>Dead wood surveys
 </i> To
 estimate the volume of deadwood found on the forest floor in areas
 affected by tree-fall, compared with undisturbed areas, we carried out
 deadwood surveys in December 2017. To avoid disturbing our decomposition
 assays, these surveys were carried out in areas within the forest
 surrounding experimental plots. We established eight 50 m transects, four
 of which were within 5 m of a tree that had fallen during the storm in
 July 2017 and four that were in areas of forest at least 20 m from the
 nearest tree fall. Along each transect, we recorded the diameter of each
 piece of deadwood that intersected with the line, and these values were
 used to calculate the volume of dead wood using the following equation
 (Van Wagner 1968): <i>V=
 </i><i>π</i><sup><i>2</i></sup><i>8L</i><i>d</i><sup><i>2</i></sup> Where <i>V</i> is the volume of deadwood (cm<sup>3</sup>/50 m), <i>d </i>is the diameter of the deadwood item at the intersection and <i>L </i>is the length of the sample line.
description: 1. Proportion mass loss
 from pinus radiata blocks that were accessible to invertebrates
 and micobes or microbles only in canopy gaps and intact forest in an old
 growth rainforest.  2. Monthly soil mositure and
 temperature beneath tree fall canopy gaps and closed canopy
 sites. 3. Termite
 communities sampled within tree fall canopy gaps and closed canopy
 sites. 4. The
 volume of deadwood on the forest floor close to or more than 20 m from a
 tree fall gap.