Importance of nurse logs as a substrate for the regeneration of pioneer tree species on Barro Colorado Island, Panama

Factors associated with seedling establishment on logs of different fungal decay types-A seed-sowing experiment

Wood decay fungi alter the abiotic and biotic properties of deadwood, which are important as nurse logs for seedling regeneration. However, the relationship between fungal decay type and seedling performance has not been evaluated experimentally. In this study, we examined the germination, growth, and survival of six arbuscular mycorrhizal (AM) and six ectomycorrhizal (ECM) tree species on three substrates (pine logs with brown and white rot and soil) by conducting seed-sowing experiments in a mixed forest dominated by Pinus densiflora and Quercus serrata. Analysis using ribosomal DNA internal transcribed spacer 1 (rDNA ITS1) sequencing revealed that the fungal community was significantly different across three substrates. The richness of operational taxonomic units (OTUs) of AM and ECM fungi was the largest on brown rot logs and soil, respectively. The substrate significantly affected the seedling performance when comparing wood decay types, but these were not consistent across the mycorrhizal status of the seedlings. Nevertheless, seedlings of some AM trees showed better growth and enhanced mycorrhizal colonization on brown rot logs than on white rot logs. The wood decay type influenced fungal communities in the logs and the performance of some seedling species partly by different mycorrhizal colonization rates. However, the effect was seedling species dependent and showed no apparent difference between AM and ECM trees.

The nutritional status and root development of silver fir (Abies alba Mill.) seedlings growing on decaying deadwood in temperate forest ecosystem

The study aimed to compare two substrates, soil and deadwood, for the regeneration of silver fir (Abies alba Mill.) seedlings. Three-year-old fir seedlings growing both on deadwood and in the soil were collected. The examination involved determining the physical, chemical, and biochemical properties of soil and deadwood, as well as assessing the morphology of the roots and the nutrition of seedlings growing on the soil and deadwood. The examined substrates differed in physical, chemical and biochemical properties. It was shown that strongly decomposed fir logs are a good substrate for the growth of fir seedlings, mainly due to the high content of exchangeable cations (especially calcium, magnesium and potassium) and high phosphorus and nitrogen content. The type of substrate had a significant impact on the root morphology of fir seedlings. In our study, the most responsive root traits to differences in growing substrates were specific root area (SRA) and specific root length (SRL). Our analyses did not confirm significant differences in the stoichiometry of C, N and P in the roots and needles of seedlings grown on different substrates. The stoichiometry of roots and needles suggests no limitations in the uptake of nutrients by seedlings growing on deadwood. This study validated that heavily decomposed wood can provide favourable microhabitats for the growth of the young generation of fir.

Nurse logs: A common seedling strategy in the Permian Cathaysian flora

Nurse logs are common in modern forests from boreal to temperate and tropical ecosystems. However, the evolution of the nurse-log strategy remains elusive because of their rare occurrence in the fossil record. We report seven coniferous nurse logs from lowermost to uppermost Permian strata of northern China that have been colonized by conifer and sphenophyllalean roots. These roots are associated with two types of arthropod coprolites and fungal remains. Our study provides the first glimpse into plant—plant facilitative relationships between late Paleozoic gymnosperms and sphenopsids. Detritivorous arthropods and fungi appear to have been crucial for the utilization of nurse logs in Permian forests. The phylogenetically distant roots demonstrate that nurse-log interaction was a sophisticated seedling strategy in late Paleozoic humid tropical forests, and this approach may have been adopted and developed by a succession of plant groups leading to its wide representation in modern forest ecosystems.

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Diverse nurse-log interactions are documented in the Permian Cathaysian flora.

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Conifer wood served as substrates for seed plants and sphenopsids at the time.

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Arthropods and fungi were crucial for utilization of nurse logs in ancient forests.

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Nurse logs probably first occurred in swamps then expanded to various habitats

Evaluation of Deadwood Characteristics and Carbon Storage under Different Silvicultural Treatments in a Mixed Broadleaves Mountain Forest

The deadwood (DW) of the forest is in the following two forms: standing (snag) and fallen (log). The DW categories and decay stage are important functional and structural components of forest ecosystems. We used a field-based assessment to quantify how the relative contribution of deadwood to total above-ground carbon stock changes across a silvicultural method and stand altitude gradient in mixed broadleaves stands. The characteristics of DW and carbon stock in selection-cutting managed stands (Sc), shelter-wood managed stands (Sh) and protected stands (Pr) were examined in three altitude ranges (low, <600; medium, 600–1200; and high, >1200 m a.s.l.) in a mixed broadleaves high forest. The results showed that with increasing altitude, the volume of DW increased. The volume of DW in Pr stands was about three times higher than Sh stands and twice higher than Sc stands. The volume of the standing DW was greater than that of the fallen DW in all stands. The highest volume ratio of fallen DW to standing DW was found in the medium altitude in the Sc stand. The amount of carbon stock by DW in the Sh, Sc, and Pr stands was 1.53–2.22, 2.29–3.19, and 5.03–6.80 t ha−1, respectively. The DW share of C-stock of above ground biomass was 4%–4.6% in Sh stand, 4.3%–4.8% in Sc stand, and 7.4%–7.9% in the Pr stand. Deadwood assessment and management, in terms of volume, type, species composition, diameter distribution, spatial allocation and decay stage, is one of the new challenges for a proper sustainable forest management.

Non-negligible role of dead organic matter in a rainforest remnant in Northeast Brazil

Abstract Dead organic matter represents an essential reservoir of carbon, especially that allocated in standing dead trees, coarse woody debris, and fine litter, playing a pivotal role in nutrient cycling and habitat provisioning. However, necromass is frequently disregarded in forest assessments. Here, we aimed to perform the first assessment of multiple necromass compartments in the Atlantic Forest of Northeast Brazil, providing a basis for future integrative studies related to necromass in this region. We registered 17 standing dead trees in 0.5 hectare and 239 logs of coarse woody debris. Necromass had 3.9 Mg.ha-1 of standing dead trees, 54.24 Mg.ha-1 of coarse woody debris and 7.2 Mg.ha-1 of litter. We indicate that standing dead trees and coarse debris were mostly in the intermediate and final stages of decomposition. Leaves were the dominant component of litter, and drier months had more litterfall. Finally, we highlight that assessing standing dead trees and coarse woody debris adds 25.6% on top of aboveground tree mass, improving information about organic matter storage in rainforest ecosystems. Our findings emphasize that the necromass compartment must be considered in forest assessments, also including small pieces of coarse woody debris, which could inform better practices of forest management.

Coarse Woody Debris Variability Due to Human Accessibility to Forest

Coarse woody debris (CWD) plays an important role in supporting biodiversity and assisting ecological processes. Sometimes local people intervene modifying the expected distribution of CWD components, harvested as fuel wood. The effect of the human accessibility (HA) on the volume and characteristics of CWD (snag, downed log and stump) was investigated in the natural uneven-age mixed hardwood stands of the Hyrcanian forests of Iran to quantify the impact on CWD. The HA was classified into three classes (easy, medium and difficult) on the basis of slope class, slope direction to the nearest road and road type. As expected, a negative relationship between the degree of accessibility was found with respect to the main qualitative and quantitative indices referring to CWD. The results showed that the volume of CWD decreased with an increase in human accessibility class (HAC), thus the mean volume of CWD in the difficult, medium and easy accessibility classes were 14.87 m3 ha−1, 8.84 m3 ha−1 and 4.03 m3 ha−1, respectively. The decrease in CWD volume was more associated with the decreasing volume of small diameter of low decayed downed logs. The ratio of snag volume to standing volume, the ratio of downed log volume to the volume of trees and the ratio of CWD volume to standing volume increased with a decrease in HAC, while the ratio of downed log volume to snag volume decreased with a decrease in HAC. No selective behaviour on the botanical species of CWD was recorded. For ecological forest management, the effect of HAC on CWD should be considered. A constant supply of snags and downed logs must be preserved to assure a high level of biodiversity. To balance social needs and biodiversity requirements, an increased level of CWD retention might be needed in areas with easy accessibility. The obtained results may be useful when ecological and socio-economical needs have to be taken into consideration in future policy-making decisions.