Spatial patterns of natural regeneration in stands of English yew (Taxus baccata L.); Negative neighbourhood effects

Understanding the mechanisms underlying spatial patterns of regeneration of tree species can improve the effectiveness of forest management and restoration activities. English yew (Taxus baccata L.) stands have declined across their native range and yew dominated woodlands have priority status under the EU Habitats Directive. Several conservation and restoration programmes for this species have been established. We investigated population structure and spatial distribution of natural regeneration of yew at six woodlands in the south and west of Ireland. Specifically, the influence of adult conspecific neighbourhood density, canopy cover and distance from seed source on regeneration was explored. Within each site, canopy openness, soil and vegetation characteristics were established. Weiner spatial analysis revealed that the density of conspecific adults was negatively related to the recruitment of yew juveniles. In addition, a significant negative relationship between presence of conspecific canopy cover and regeneration density was evident. Although seedlings and saplings were scarce directly beneath conspecifics, regeneration was highest in nearby areas suggesting that intermediate dispersal distance maximises recruitment probability. Yew regeneration was correlated with a number of habitat characteristics, particularly percentage cover of woody shrubs. Management operations should focus on regeneration around the edges of populations to conserve existing yew stand

Conspecific negative density dependence in a long-lived conifer, yew Taxus baccata L.

Conspecific negative density dependence in tree species can have major consequences for structuring of communities, yet in temperate forests this phenomenon remains largely unexplored. We investigated density-dependent recruitment in the long-lived conifer yew (Taxus baccata L.), for which low levels of regeneration have been linked with reduced light availability beneath conspecific canopies and speculative autotoxic effects. We combined in situ assessment of yew regeneration in a temperate forest in southwest Ireland with ex situ pot experiments to assess whether light and/or beneath conspecific canopy conditions inhibit the germination and early growth of yew. In field experiments, recruitment was related to distance from adult conspecifics, with higher levels of regeneration found in areas not beneath yew canopies. However, reduced light availability beneath the dense yew canopy was not responsible for this pattern, with abundant seedlings found in areas of equivalent or even lower light availability. Pot experiments showed that seedling survival was highest in deep shade treatments. Experiments also demonstrated that the addition of yew needles negatively affected seedling growth, but not seed germination. Together, our results suggest that under natural forest conditions, the absence of regeneration beneath mature yew canopies, often attributed to low light availability, may at least be partly related to substances in yew canopy or leaf leachates

Light responses of yew (Taxus baccata L.); does size matter?

Key message Photosynthetic capacity of yew needles depends primarily on light environment, with little evidence that developmental stage is a determinant photosynthetic performance. However, needle morphology is mostly determined by plant size. Abstract Populations of yew Taxus baccata are often characterized by a lack of natural regeneration and stands of this species have been afforded priority conservation status within the European Union. Light availability is known to be a key factor influencing recruitment dynamics in yew. To explore potential size-related responses to light, we investigated the distribution, photosynthetic efficiency and needle morphological traits in yew across a gradient of light availability at Atlantic oak woodland in southwest Ireland. Young plants were more common in shaded areas whereas saplings and juvenile yews were distributed in areas of higher light availability. Photosynthetic capacity of yew needles was found to depend primarily on light environment, with little evidence that the developmental stage is a determinant of photosynthetic performance. Photoinhibition was evident in needles sampled from high light environments across all demographic size classes. However, larger plants also showed particularly strong needle morphological responses (needle length, width, thickness, and specific leaf area) to light levels, which were mostly lacking in seedlings. We conclude that there is a dual control of yew light responses; the efficiency of the photosynthetic light reactions is largely linked to the light environment in which the plants grew, while needle morphology is mostly determined by the size of the plants. The findings of this study highlight the importance of considering all life-history stages and multiple traits when evaluating species response to light availability

Road Decommissioning: Minimising the Adverse Ecological Effects of Roads i9n European Agriculture Landscapes

The field of Restoration Ecology continues to provide an exciting array of new disciplines which focus on the restoration of ecological function and integrity to former habitat areas. Road Restoration Ecology (RRE) is one such discipline which is expanding the possibilities for habitat restoration beyond that which has been provided by the traditional management of roadside vegetation and landscape design.This paper focuses on a particular aspect of RRE - that of road decommissioning. To date even though many hundreds of kilometers of forest roads have been removed in the U.S., virtually no research has addressed the impact of road removal on wildlife. Furthermore, on an international level, even less research has been committed to examining the removal of paved roads despite the fact the road development has been identified in the literature as one of the major causes of habitat fragmentation across landscapes worldwide.In the course of new road planning and design, sections of old road pavement may be abandoned due to (1) the establishment of a new road ecosystem; (2) the realignment of an existing road; (3) the By-Pass of traffic ‘hotspots’; and (4) required road closure for environmental reasons. Occasionally the extent of old road pavement is large enough to significantly extend native habitats adjacent to an old road system.For this reason, road decommissioning can potentially: (1) restore ecological integrity, and function of semi-natural ecosystems (including soil); (2) provide compensatory habitat; (3) maintain and improve quality of existing adjacent habitat by reducing noise disturbance and human access (amongst others); (4) restore connectivity by reinforcing the ecological network of surrounding core habitat areas, and; (5) contribute to the restoration of landscape quality in the vicinity of a new road ecosystem.It can be assumed that, where road pavement is not decommissioned and persists, it may continue to: (1) inhibit the ecological functions and services of semi-natural ecosystems, (2) pose as a barrier to the dispersal of wildlife, (3) in¬hibit the establishment of vegetation cover (and habitat), (4) may continue to have an adverse effect on environmental aesthetics; and (5) contribute to the release of pollutants from surface run-off. It is for one or more of these reasons that the process of road decommissioning is generally carried out.Paved road segments on five national road schemes in Ireland were examined with a view to identifying the potential role of restored vegetation as habitat for wildlife. It has been demonstrated that native vegetation can more readily colonize former road corridors post-decommissioning, especially those roads located adjacent to existing native plant communities e.g. grasslands, hedgerows and woodlands. The resulting decommissioned sections of road generally show rapid recovery through natural recolonisation, where vegetation successional processes are shown to recapture road corridors within a few years, resulting in valuable additional habitat for wildlife, especially birds and nectar feeding invertebrates such as butterflies and bees. Various native mammal species have also been found to utilize old roads as a means of dispersal, therefore providing connectivity in an increasingly intensified agricultural landscape

Phenotypic and genetic analyses of the varroa sensitive hygienic trait in Russian honey bee (hymenoptera: apidae) colonies.

Varroa destructor continues to threaten colonies of European honey bees. General hygiene, and more specific Varroa Sensitive Hygiene (VSH), provide resistance towards the Varroa mite in a number of stocks. In this study, 32 Russian (RHB) and 14 Italian honey bee colonies were assessed for the VSH trait using two different assays. Firstly, colonies were assessed using the standard VSH behavioural assay of the change in infestation of a highly infested donor comb after a one-week exposure. Secondly, the same colonies were assessed using an "actual brood removal assay" that measured the removal of brood in a section created within the donor combs as a potential alternative measure of hygiene towards Varroa-infested brood. All colonies were then analysed for the recently discovered VSH quantitative trait locus (QTL) to determine whether the genetic mechanisms were similar across different stocks. Based on the two assays, RHB colonies were consistently more hygienic toward Varroa-infested brood than Italian honey bee colonies. The actual number of brood cells removed in the defined section was negatively correlated with the Varroa infestations of the colonies (r2 = 0.25). Only two (percentages of brood removed and reproductive foundress Varroa) out of nine phenotypic parameters showed significant associations with genotype distributions. However, the allele associated with each parameter was the opposite of that determined by VSH mapping. In this study, RHB colonies showed high levels of hygienic behaviour towards Varroa -infested brood. The genetic mechanisms are similar to those of the VSH stock, though the opposite allele associates in RHB, indicating a stable recombination event before the selection of the VSH stock. The measurement of brood removal is a simple, reliable alternative method of measuring hygienic behaviour towards Varroa mites, at least in RHB stock

<i>P</i>- value of associations between allele homozygosity and colony phenotypes.

<p>Percentage of <i>Varroa</i>-infested brood removed was calculated as the % change in <i>Varroa</i> infestation of donor combs. Manipulated brood = brood removed + opened brood;</p><p>*reproductive foundress mites = produced one or more progeny; viable progeny = with adult male and young daughter.</p><p>**significant at <i>P</i> < 0.05.</p><p><i>P</i>- value of associations between allele homozygosity and colony phenotypes.</p

Results of the regression analyses relating percentages of <i>Varroa</i>-infested brood removed for whole comb and brood section of donor frames, and brood removal of brood section to different measurements related to hygiene.

<p>Percentage of <i>Varroa</i>-infested brood removed was calculated as the % change in <i>Varroa</i> infestation of donor combs.</p><p>*NR = no progeny produced.</p><p>Results of the regression analyses relating percentages of <i>Varroa</i>-infested brood removed for whole comb and brood section of donor frames, and brood removal of brood section to different measurements related to hygiene.</p

Sample sizes, means (± SE) of different infestation parameters in resident brood of Italian and Russian honey bee colonies, and results of the student’s t-tests.

<p>NR = no progeny. Rows with different letters are significantly different at <i>P</i> < 0.05.</p><p>ns = not significant.</p><p>Sample sizes, means (± SE) of different infestation parameters in resident brood of Italian and Russian honey bee colonies, and results of the student’s t-tests.</p

Light responses of yew (Taxus baccata L.); does size matter?

Key message Photosynthetic capacity of yew needles depends primarily on light environment, with little evidence that developmental stage is a determinant photosynthetic performance. However, needle morphology is mostly determined by plant size. Abstract Populations of yew Taxus baccata are often characterized by a lack of natural regeneration and stands of this species have been afforded priority conservation status within the European Union. Light availability is known to be a key factor influencing recruitment dynamics in yew. To explore potential size-related responses to light, we investigated the distribution, photosynthetic efficiency and needle morphological traits in yew across a gradient of light availability at Atlantic oak woodland in southwest Ireland. Young plants were more common in shaded areas whereas saplings and juvenile yews were distributed in areas of higher light availability. Photosynthetic capacity of yew needles was found to depend primarily on light environment, with little evidence that the developmental stage is a determinant of photosynthetic performance. Photoinhibition was evident in needles sampled from high light environments across all demographic size classes. However, larger plants also showed particularly strong needle morphological responses (needle length, width, thickness, and specific leaf area) to light levels, which were mostly lacking in seedlings. We conclude that there is a dual control of yew light responses; the efficiency of the photosynthetic light reactions is largely linked to the light environment in which the plants grew, while needle morphology is mostly determined by the size of the plants. The findings of this study highlight the importance of considering all life-history stages and multiple traits when evaluating species response to light availability