Stand dynamics and tree quality response to precommercial thinning in a northern hardwood forest of the Acadian forest region: 23 years of intermediate results

In the late 1980s, large forest companies began precommercial thinning (PCT) operations in young northern hardwood cutovers in New Brunswick, Canada. To provide supporting growth and yield information, an industrial experiment was established at residual stand densities of 1300, 1600, 1900, and 2200?stems?ha^?1. Stand responses were examined for measurements recorded at 0 (1987), 5 (1992), 10 (1997), 16 (2003), and 23 (2010) years after establishment. Average diameter at breast height, quadratic mean diameter, stand basal area, and stand total volume growth increased as stem density decreased from PCT. There were significant linear differences for many of these variables between treatments and time periods (year). No significant differences were detected in tree height between treatments. In 2010, the four PCT thinning treatments did not exhibit any differences in potential sawlogs at 2.4?m (8?ft) and 3.6?m (12?ft) lengths. Significant differences were observed for 4.9?m (16?ft) sawlogs that were produced at the least dense spacing (1300?stems?ha^?1). Results from this study and recommendations from the European literature suggest that value-added timber products may be produced from more intense PCT treatments than are currently being practiced on sites dominated by yellow birch (Betula alleghaniensis Britt.).     

Integrated pest management of Tuta absoluta: practical implementations across different world regions

Journal of Pest Science - The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), has invaded most Afro-Eurasian countries and is threatening worldwide tomato...     

Does the mutualism between wood ants (Formica rufa group) and Cinara aphids affect Norway spruce growth?

Ant–aphid mutualisms, in which ants tend aphids, which in turn provide honeydew to the ants, are widespread and have been shown to affect plant growth. In boreal forests the effect of ant–aphid mutualism on tree growth can vary with stand age, because forest clear-cutting harms the ecologically most dominant ant partner in such mutualisms, wood ants (Formica rufa group). We studied whether the mutualism between wood ants and Cinara aphids affects the growth of boreal Norway spruces (Picea abies L. Karst.) in stands of different ages. In boreal forests, conifers, unlike deciduous trees, have only few defoliating insects, and therefore we expected the growth loss of conifers due to sap sucking by aphids not to be compensated by reduced insect herbivory due to predation by wood ants. The study was conducted in medium-fertile spruce-dominated stands in eastern Finland. We used stands of four different age classes (5, 30, 60 and 100 years) and selected ten spruces heavily visited and ten spruces lightly visited by ants around five medium-sized ant mounds in each stand age class. The access of ants was blocked on half of the trees in both groups. In the 5-year-old stands, the mean annual height growth of individual heavily visited seedlings was 16.3% greater than in the ones where ant traffic was blocked, but this difference was not significant. In the 30-year-old stands, the mean annual radial growth of the heavily visited spruces was 7.3% smaller than in trees where ant traffic was blocked, and this difference was significant. The mutualism had no significant effect on the radial growth in the 60- and 100-year-old stands. In the 60-year-old stands, however, the spruces that were visited heavily prior to the beginning of the study grew significantly less relative to their past growth than the initially lightly visited trees during the study. This suggests that the ant–aphid mutualism may have long-term effects on tree growth. The ant–aphid mutualism had no significant effect on the growth at the stand level. The results indicate that ant–aphid mutualism can have a significant effect on the growth of individual spruces, but the effect is negligible at ecosystem level.     

Impact of mechanized harvesting on compaction of sandy and clayey forest soils: results of a meta-analysis

Context

Nowadays, harvest operations are predominantly performed fully mechanized using heavy tractors or forestry machines. The resulting soil compaction may negatively affect the soil ecosystem.

Aims

We wanted to draw general conclusions concerning the impact of mechanized harvesting on forest soil bulk density and the influencing factors.

Method

Therefore, we combined the data of several studies using a meta-analysis approach.

Results

The impact decreased from the surface towards deeper soil layers. At 0?C10?cm depth, the impact on clayey soils was highest although not significantly different from the impact on sandy soils. Higher initial bulk densities, i.e., on already compacted forest soils, generally led to smaller extra increases of bulk density after machine traffic. For sandy soils, the impact was also significantly smaller when machines were lighter. No significant relationship was observed between the compaction degree and traffic intensity.

Conclusions

We observed clear compaction on both clayey and sandy soils, especially in case of low initial soil compaction degrees and heavy machines. The compacted initial state of many forest soils, the long recovery period, and the generally high impact of the first passes that is frequently mentioned in literature all count in favour of designated skid trails and an adjustment of the machine type to the job.     

Importance of hedgerows as habitat corridors for forest plants in agricultural landscapes

Hedgerows have been proposed as habitat and conservation corridor for forest plant species, but their importance for the survival of these species is still not clear. The objective of our study was to examine the frequency of occurrence of forest species and total forest species richness in different parts of the hedgerows, and to relate these patterns of occurrence to the species’ habitat requirements and life history traits. We surveyed in total 130 forest-hedgerow transects in North-western Germany, including three age classes.About 77% of all forest plant species (including some endangered taxa) occurring in the neighbouring forests were also found in the adjacent hedgerows. In all age classes, there was a negative relationship between distance from the forest-hedgerow ecotone and the number of species. Ancient hedgerows were not significantly more species-rich than more recent ones. Within 100 m distance from the forest edge, forest species richness increased with an increasing number of species in the nearby forest and with an increasing cover of the tree canopy as well as a decreasing cover of the shrub layer. Species with high frequency had comparatively high Ellenberg indicator values for light, and were mostly associated with anemochorous and epizoochorous seed dispersal.The frequency of occurrence in hedgerows of species with common attributes was partly in agreement, partly in disagreement with the results obtained in previous studies. We conclude that patterns are difficult to generalize, probably due to a strong regional variation in the pool of forest species and in the specific environments of both forests and hedgerows.     

Soil structural responses to alterations in soil microbiota induced by the dilution method and mycorrhizal fungal inoculation

This investigation examines the effect of manipulating soil microbial community composition and species richness on the development of soil structure over a seven month period in planted (with or without mycorrhizal fungi) and in unplanted macrocosms. The dilution method effectively resulted in soil communities with consistently contrasting levels of species (TRF) richness. In particular, the 10^?6 dilution of field soil resulted in less rich communities in bare unplanted soil than did the 10^?1 soil dilution. However, this was not the case in planted soils where root activity was a powerful influence on species richness. After seven months, principal components analysis (PCA) separated bacterial community composition primarily on planting regime; planted mycorrhizal, planted non-mycorrhizal and bare soil treatments all contained different bacterial community compositions. A consistent finding in planted and unplanted soils was that aggregate stability was positively correlated with small pore sizes. Mycorrhizal colonisation decreased plant biomass and also resulted in reduced soil bacterial species richness, lower percentage organic matter and smaller pore sizes relative to planted but non-mycorrhizal soils. However, soil aggregate stability and water repellency were increased in these (mycorrhizal) soils probably due to AMF hyphal activities including enmeshment and/or glomalin production. In contrast, bacterial TRF richness was positively correlated with aggregate stability in the bare and non-mycorrhizal planted soils. Soil organic carbon was an important factor in all treatments, but in the bare soil where there was no additional input of labile C from roots, the percentage C could be directly related to fungal TRF richness. The less species rich bare soil contained more organic C than the more species rich bare soil. This suggests a degree of redundancy with regard to mineralisation of organic matter when additional, more utilisable C sources are unavailable. Understanding the effects of microbial diversity on functional parameters is important for advancing sustainable soil management techniques, but it is clear that soil is a dynamic ecosystem.     

Effect of Dimethyl sulfoxide (DMSO) and egg yolk on sperm motility,fertility and hatching rates of depik Rasbora tawarensis (Pisces: Cyprinidae) eggs after short‐term cryopreservation

Cryoprotectant is the crucial factor in the cryopreservation process. In general, there are two types of cryoprotectant, permeating and non‐permeating cryoprotectants. Dimethyl sulfoxide (DMSO) and egg yolk are common permeating and non‐permeating cryoprotectants respectively. Hence, the objective of the present study was to determine the best proportion of DMSO and egg yolk for the cryopreservation of Rasbora tawarensis sperm. A completely randomized experimental design was used in this study which involves two types of cryoprotectant and their combination at different concentrations, namely 5% DMSO, 5% egg yolk, 5% DMSO + 5% egg yolk and 2.5% DMSO + 2.5% egg yolk. Every treatment was conducted in three replicates. Combination of 5% DMSO + 5% egg yolk gave the best results cryoprotectant treatment had significant effects on sperm motility, fertilization and hatching rate of the R. tawarensis eggs (p < .05). It is concluded that the best proportion of cryoprotectants for sperm cryopreservation in this species is 5% DMSO + 5% egg yolk.