The contribution of insects to global forest deadwood decomposition

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks. The decomposition of deadwood is largely governed by climate with decomposer groups—such as microorganisms and insects—contributing to variations in the decomposition rates. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect—including the direct consumption by insects and indirect effects through interactions with microorganisms—insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and −0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle

Seven years of follow-up of continuous-cover forestry: responses of saproxylic beetles

Fennoscandian forest management has since 1950s been characterized by forest regeneration through clear cutting, with subsequent top-soil preparation, seeding or planting with conifers, and removals of legacy elements important for biodiversity, such as dead wood. According to national Red Lists, this structural simplification in most Fennoscandian forests has made hundreds of species threatened. One possible way to support these species is continuous-cover forestry, where at least half of a stand is covered by mature or near-mature trees throughout the logging rotation. Such forestry might secure both economic benefits and support specialized forest species, but empirical evidence is largely lacking. Therefore, we collected beetles in Eastern Finnish Scots pine forests that represent a continuum from clear-cuts to different continuous-cover forestry techniques, combined with large-sized dead-wood increment, and unharvested mature forest ("control"). We used flight-intercept window traps one year before (2010) and seven years after logging (2011-17) to collect beetle data. We will present comparisons of the overall community, and specialized groups of saproxylic beetles, and associate these patterns with structural features of forest stands, particularly volume and diversity of live and dead trees and size of cleared gaps. Our results will shed light on relative merits of continuous-cover forestry and legacy elements from an ecological point of view. Such information is crucial not only for conservation of biodiversity in managed forests but also for guidelines of forestry.peerReviewe

Burning harvested sites enhances polypore diversity

Prescribed burning after clear-cut has been used as a silvicultural method, but it has also been found to support biodiversity. We asked what is the impact of fire on polypores that grow on stumps and slash left on clear-cut sites. Eighteen one-hectare study stands were cut with different levels of retention trees and nine of the sites were burned the following summer. The study sites are located in eastern Finland in forests that are dominated by Pinus sylvestris. We sampled stumps and slash for polypores ten years after cuttings and burnings. We sampled 14 235 stumps and 13 345 pieces of slash and counted 7 179 polypore records of 74 species on these. More polypores were found from burned stumps compared to the unburned stumps, but burning had no effect on polypores on slash. We found also some red-listed polypore species both from stumps and slash - more from those sites where the resource had been burned. All red-listed species that were found on unburned sites were found also on burned sites, except for one species. Our results show that stumps and slash can be valuable substrates for wood-decaying fungi, including rare and red-listed species, on clear-cut forest stands. We recommend avoiding full-scale stump and slash harvest. e.g. for the purposes of bioenergy production, on clear-cut areas. Instead, we encourage to retain stumps and to apply prescribed burnings on harvested sites, to enhance polypore diversity in managed forests.peerReviewe

Data from: Combined effects of retention forestry and prescribed burning on polypore fungi

1. Retention forestry and prescribed burning aim to alleviate the negative effects of forestry on biodiversity by maintaining the structural elements of natural forests in managed forests. We present the long-term effects of these methods on polypore fungi, a taxonomic group that has been severely affected by forestry. 2. Using a 10-year, large-scale field experiment, we studied how prescribed burning and two different tree retention levels (10 and 50 m3 ha−1) affect polypore fungi. We monitored polypore sporocarps on 2767 individually marked trees four times over the study period: in the first autumn after the treatments, and again 2, 4 and 10 years after the treatments. 3. The number of polypore species and records initially increased rather slowly but showed a marked increasing trend towards the end of the 10-year monitoring period. After 2 years, the higher retention sites had an average 8·5 species and the low retention sites 4·5 species per site. After 4 years, the difference was 14 vs. 9 species and after 10 years 26 vs. 19 species. Red-listed species were not found often on the trunks earlier than 10 years after the treatments. 4. Prescribed burning increased the number of polypore species and records along with time. Furthermore, 13 species favoured burned sites, while only six species favoured unburned sites, and the differences in the composition of species assemblages between burned and unburned sites were evident 10 years after the treatments. 5. Synthesis and applications. We show, for the first time, that retention trees can host rich polypore assemblages, and even some red-listed species, and, thus, be useful in conservation of forest biodiversity outside protected areas. Higher retention levels maintain more diverse polypore assemblages. Prescribed burning increases the positive effects of retention forestry by creating substrates that are typical in the early-successional natural forests

Polypore fungi on retention trees

Data include fungi occurrences on individual trees in two retention levels in years 2003,2005 and 2011

Data from: Trade-offs in berry production and biodiversity under prescribed burning and retention regimes in Boreal forests

1. Green tree retention and prescribed burning are practices used to mitigate negative effects of forestry. Beside their effects on biodiversity, these practices should also promote non-timber forest products (NTFPs). We assessed: (1) how prescribed burning and tree retention influence NTFPs by examining production of bilberry Vaccinium myrtillus and cowberry; Vaccinium vitis-idaea (2) if there are synergies or trade-offs in the delivery of these NTFPs in relation to delivery of species richness, focusing on five groups of forest dwelling species. 2. We used a long-term experiment located in eastern Finland with three different harvesting treatments: clearcut-logging, logging with retention patches and unlogged, which were combined with or without prescribed burning. Eleven years after the treatment application, we scored plant cover and berry production in different microhabitats within these treatments, while species richness data for five species groups (ground-layer lichens and bryophytes, vascular plants, saproxylic beetles, pollinators – here bees and hoverflies) were collected at the stand level. 3. Logging favoured cowberry production, particularly for plants growing in the vicinity of stumps. Logging was detrimental for cover and berry production of bilberry. Retention mitigated these negative effects slightly, but cover and berry production were still substantially lower compared to unlogged forests. Prescribed burning increased cowberry production in retention patches and in unlogged forest. Bilberry production decreased with burning, except in unlogged forest where the effect was neutral. 4. No single management treatment simultaneously favoured all values - NTFPs and richness - and trade-offs among values were common. Only bilberry production and beetle diversity were higher under retention forestry, or in unlogged stands, compared to logged stands. Prescribed burning favoured many values when performed in combination with retention forestry, or in unlogged stands, but different treatment combinations favoured different species groups. 5. Synthesis and applications. Our results demonstrate that widely-applied conservation practices in managed forests are unlikely to benefit all ecosystem values everywhere. If high multi-functionality is desired, managing at a landscape scale, countering the local trade-offs among values, may be more appropriate than the stand scale conservation practices commonly practiced today

Trade-offs in berry production and biodiversity under prescribed burning and retention regimes in boreal forests

Green tree retention and prescribed burning are the practices used to mitigate negative effects of boreal forestry. Beside their effects on biodiversity, these practices should also promote non-timber forest products (NTFPs). We assessed: (1) how prescribed burning and tree retention influence NTFPs by examining the production of bilberry, Vaccinium myrtillus and cowberry, Vaccinium vitis-idaea; (2) if there are synergies or trade-offs in the delivery of these NTFPs in relation to the delivery of species richness, focusing on five groups of forest-dwelling species. We used a long-term experiment located in eastern Finland, with three different harvesting treatments: clear-cut logging, logging with retention patches and unlogged, which were combined with or without prescribed burning. Eleven years after the treatment application, we scored plant cover and berry production in different microhabitats within these treatments, while species richness data for five species groups (ground layer lichens and bryophytes, vascular plants, saproxylic beetles, pollinators?here bees and hoverflies) were collected at the stand level. Logging favoured cowberry production, particularly for plants growing in the vicinity of stumps. Logging was detrimental for cover and berry production of bilberry. Retention mitigated these negative effects slightly, but cover and berry production were still substantially lower compared to unlogged forests. Prescribed burning increased the cowberry production in retention patches and in unlogged forest. Bilberry production decreased with burning, except in unlogged forest where the effect was neutral. No single management treatment simultaneously favoured all values?NTFPs and richness?and trade-offs among values were common. Only bilberry production and beetle diversity were higher under retention forestry, or in unlogged stands, compared to logged stands. Prescribed burning favoured many values when performed in combination with retention forestry, or in unlogged stands, but different treatment combinations favoured different species groups. Synthesis and applications. Our results demonstrate that widely applied conservation practices in managed boreal forests are unlikely to benefit all ecosystem values everywhere. If high multifunctionality is desired, managing at a landscape scale, countering the local trade-offs among values, may be more appropriate than the stand-scale conservation practices commonly practiced today

Species richness of multiple species groups

Species richness of pollinators, saproxylic beetles, bryophytes, vascular plants and lichens. Collected in experimental plots. See readme file for more info

Plant community data

Plant community data (percent cover) from experimental plots. Ground living vascular plants, macrolichens and bryophytes (mosses and liverworts). Year 2000, 2003 and 2011. See README file for more information

Fruit production and plant cover for two Vaccinium species

Fruit production and plant cover for Vaccinium myrtillus and Vaccinium vitis-idaea collected in experimental plots. See readme file for more info