Can we use shelterwoods in Mediterranean pine forests to promote oak seedling development?

The use of shelterwoods to favour the development of natural or underplanted seedlings is common in temperate forests but rare in the pine forests of the Mediterranean area. Our aim was to assess the use of shelterwoods in Aleppo pine (Pinus halepensis) woodlands in southern France to promote the survival and growth of two co-occurring oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex.Twelve Aleppo pine stands were selected and differentially thinned to create a light shelterwood (basal area = 10 m²/ha, irradiance 52%), a medium shelterwood (basal area = 19 m²/ha, irradiance 33%) and a dense shelterwood (basal area = 32 m²/ha, irradiance 13%). A total of 1248 sowing points, half composed of Q. pubescens and half of Q. ilex, were then set up in these three conditions. Seedling survival and growth were monitored for 3 years. Plant stress was assessed by measuring predawn leaf potential and photosynthetic performance through the F_v/F_m ratio. Soil moisture was also recorded at two depths during two growing seasons.Survival was high for both species in all three conditions due to three consecutive wet years. The lowest survival was recorded for Q. pubescens in the dense shelterwoods. Growth in diameter and height increased from the dense to the light shelterwoods. Shrubs developed more strongly in the light shelterwood, and increasing shrub cover enhanced height growth. Photosynthetic performance was lowest for Q. pubescens in dense shelterwoods and highest in light shelterwoods, whereas the reverse was true for Q. ilex. The lowest predawn potentials were recorded in the dense shelterwoods even though higher soil water content values were measured in this treatment during the summer drought.We show that light shelterwoods were more beneficial to growth than denser ones, indicating control mainly by light availability during the 3 years of the study. However, as lower soil moisture at 30-50 cm depth and faster understorey development were also recorded in this condition, more extended observation is needed to determine whether this benefit persists in subsequent years.     

Is collaborative forest management in Nepal able to provide benefits to distantly located users?

Collaborative forest management (CFM) is a joint forest management approach between government and community. It covers distant communities too, who live out of 5-km periphery of the forest and involves them in forest management. This paper assesses whether the distant communities are deriving benefits from CFM in the form of timber, fuelwood and fodder. A total of 350 households was surveyed using a structured questionnaire. The result indicated that distant users were getting more timber compared to the users who lived close to collaborative forest and it was opposite in case of fuelwood and fodder. About 75% and 85% of fuelwood and fodder needs was fulfilled from the private source- trees grown on private farmland. Although CFM approach is able to supply timber to distantly located households, rich and male-headed households are disproportionately receiving high benefits. Provisioning small timber to the poor for house construction in place of sawn timber which is very expensive, may enhance welfare of the poor.     

Does harvest residue management influence biomass and nutrient accumulation in understory vegetation of Eucalyptus globulus Labill. plantations in a Mediterranean environment?

The effect of harvest residue management options on biomass and nutrient accumulation in understory vegetation, as well as the contribution of understory to nutrient cycling, were assessed during the early rotation stage of a Eucalyptus globulus Labill. plantation in Central Portugal. The effects of residue management options on early tree growth were also evaluated. Treatments established at the time of plantation and replicated four times in a simple completely randomised design included removal of harvest residues (R), incorporation of residues into the soil by harrowing (I) and maintenance of residues on the soil surface (S). Understory biomass was sampled in the spring between 2002 and 2006, and every 2 months between March 2006 and March 2007. The latter samples were stratified into biomass, standing dead mass and litter for net above ground primary production (NAPP) assessment. Samples were oven dried, weighed and analysed for nutrient contents. Results showed that understory standing biomass strongly increased from the first to the third year and that quantities of nutrients accumulated in ground vegetation followed similar patterns between the three treatments. Nutrient accumulation in ground vegetation was greater than in tree biomass until at least the second spring after plantation. Bimonthly sampling revealed treatment R to have the largest amounts of standing biomass, standing dead mass, litter and nutrient immobilisation, while treatment S exhibited the lowest values. NAPP (4th–5th year) was 639, 511 and 362 g m⁻² year⁻¹, respectively in R, I and S, corresponding the standing biomass increase to 277, 183 and 143 g m⁻² year⁻¹. These values are comparable to those observed for litter fall in similar stands (age and tree density) in the same area. The contribution of ground vegetation to nutrient accumulation in the system was unaffected by harvest residue management methods, but further research is necessary in order to establish whether slash management options influence long term tree growth and vegetation dynamics.     

Is nitrogen fertilization in the nursery a suitable tool for enhancing the performance of Mediterranean oak plantations?

Mediterranean oaks frequently have poor performance in forest restoration projects. We analyzed if nitrogen (N) fertilization during nursery cultivation enhances the outplanting performance of two ecologically distinct oaks, Quercus coccifera L. an evergreen shrub, and Quercus faginea L., a deciduous tree. Additionally, we compared the sufficiency N levels of both oaks and if root growth capacity (RGC) and photosynthesis testing at low air temperature better discriminated among fertilization treatments than testing at mild temperature. Plants were cultivated under five N fertilization rates (0, 30, 75, 150 and 200 mg N plant^?1) for one growing season. At the end of the cultivation period several plant material and performance attributes were measured. RGC and photosynthesis were assessed at mild temperature and cool conditions in Q. coccifera, while in Q. faginea these attributes were only analyzed at mild temperature conditions. Q. coccifera seedlings were transplanted into four terraces that imposed increasing drought stress, while Q. faginea seedlings were transplanted into an abandoned wheat cropland. Sufficiency level was higher for the tree (150 mg N plant^?1) than for the shrub (75 mg N plant^?1) Nitrogen-deprived Q. coccifera plants had higher frost damage than remaining treatments, which did not differ among them. Fertilization in Q. faginea did not affect photosynthesis rate but it delayed leaf senescence and abscission. RGC increased with fertilization in both species. Testing temperature did not change the effect of fertilization on RGC in Q. coccifera. Photosynthesis in cool conditions discriminated N-deprived seedlings from the remaining treatments, but treatments did not differ in photosynthesis at mild temperature. Fertilization enhanced outplanting survival in Q. coccifera, primarily in the terraces imposing stronger drought stress, while fertilization only increased growth in the terraces imposing mild drought stress. Overall, survival and growth was positively related to seedling size at planting in both oaks. Additionally, Q. coccifera survival was also positively related to RGC in the harsh planting conditions. Field growth was positively related to RGC and plant N concentration in both oaks but the relation was weak or nonexistent under harsh conditions in Q. coccifera. We conclude that fertilization in the nursery is an important tool for improving the success of oak plantations in Mediterranean continental sites, and that large and N-rich seedling have greater field performance than small and low tissue N concentration seedlings, especially in harsh field sites.     

Hydrology-oriented (adaptive) silviculture in a semiarid pine plantation: How much can be modified the water cycle through forest management?

Hydrology-oriented silviculture might adapt Mediterranean forests to climatic changes, although its implementation demands a better understanding and quantification on the water fluxes. The influence of thinning intensity (high, medium, low and a control) and its effect on the mid-term (thinned plots in 1998 and 2008) on the water cycle (transpiration, soil water and interception) and growth [basal area increment (BAI)] were investigated in 55-year-old Aleppo pine trees. Thinning enhanced a lower dependence of growth on climate fluctuations. The high-intensity treatment showed significant increases in the mean annual BAI (from 4.1 to 17.3 cm²) that was maintained in the mid-term. Thinning intensity progressively increased the sap flow velocity (v _s) in all cases with respect to the control. In the mid-term, an increased functionality of the inner sapwood was also observed. Mean daily tree water use ranged from 5 (control) to 18 (high intensity) l tree^?1. However, when expressed on an area basis, daily transpiration ranged from 0.18 (medium) to 0.30 mm (control), meaning that in spite of the higher transpiration rates in the remaining trees, stand transpiration was reduced with thinning. Deep infiltration of water was also enhanced with thinning (about 30 % of rainfall) and did not compete with transpiration, as both presented opposite seasonal patterns. The changes in the stand water relationships after 10 years were well explained by the forest cover metric. The blue to green water ratio changed from 0.15 in the control to 0.72 in the high-intensity treatment, with the remaining treatments in the 0.34–0.48 range.     

Is generalisation of uneven-aged management in mountain forests the key to improve biodiversity conservation within forest landscape mosaics?

Context

Uneven-aged management systems based on selection silviculture have become popular in European mountain forests and progressively replace other silvicultural practices. In time, this trend could lead to a homogenisation of the forest mosaic with consequences on structural indices recognised as beneficial to forest biodiversity.

Aims

This study was conducted to investigate the potential effects of a generalisation of the selection silvicultural system on structural diversity in the forest landscape with consequences for forest biodiversity conservation.

Methods

We compared four structural indices (tree species richness, diameter heterogeneity, deadwood volume and basal area of mature trees) in five different stand types typical of the northern French Alps, using forest plot data in the Vercors mountain range. Through virtual landscape simulations, we then calculated predicted mean proportions of stand types under two different conservation strategies: (i) maximising mean index values at the landscape level and (ii) maximising the number of plots in the landscape with index values above given thresholds.

Results

Multi-staged forests did not maximise all indices, the best solution being to combine the five stand types in uneven proportions to improve biodiversity conservation.

Conclusion

The expansion of selection silviculture in European heterogeneous forest landscapes could enhance biodiversity conservation if other stand types with complementary structural characteristics are maintained.     

Leaf angle responds to nitrogen supply in eucalypt seedlings. Is it a photoprotective mechanism?

We examined the adjustment of leaf angle (L theta) and foliar chlorophyll and xanthophyll chemistry in Eucalyptus nitens (Deane and Maiden) Maiden seedlings maintained in various nitrogen (N)-supply treatments over a 6-month period. Adjustment of L theta toward the vertical was greatest under conditions of foliar N deficiency and became incrementally more horizontal with increasing foliar N concentration. Photochemical efficiency (Fv/Fm) and quantum yield were lower in seedlings with low foliar N (low-N seedlings) in winter, but not in autumn. Low-N seedlings generally had low area-based chlorophyll concentrations and high xanthophyll-cycle conversion ratios, particularly during months of low temperature. Under mild temperature conditions, high concentrations of zeaxanthin and antheraxanthin were associated with lower electron transport rates (ETR). Incident light, Fv/Fm, ETR and total chlorophyll concentration were negatively correlated with L theta, with horizontal leaf orientation measured as 0 degrees and vertical leaf orientation as 90 degrees . Xanthophyll conversion ratio was positively correlated with L theta. Adjustments in L theta may play a role in photoprotection of E. nitens seedlings by assisting the leaf to balance its utilization and dissipation of energy.     

Mexican wolves,elk, and aspen in Arizona: Is there a trophic cascade?

In 1998, Mexican gray wolves (Canis lupus baileyi) were introduced into the Blue Range Wolf Recovery Area (BRWRA) that spans adjacent portions of Arizona and New Mexico. In 2009 we selected three mixed-conifer sites on the Apache National Forest, within the BRWRA of east-central Arizona, to characterize long-term age structure of aspen (Populus tremuloides) and to check for the possible occurrence of a tri-trophic cascade involving Mexican wolves, Rocky Mountain elk (Cervus elaphus nelsoni), and aspen. These mixed-conifer sites included (a) a refugium site, (b) an old-growth site, and (c) a site thinned in 1991–1992. The refugium site was inaccessible to elk and cattle whereas the old-growth and thinned sites were accessible to elk, but not cattle. Age structure results indicated that aspen recruitment (i.e., the growth of sprouts/seedlings into tall saplings, poles, and eventually trees) at the refugium site had been ongoing over a period of many decades. In contrast, aspen recruitment at the old-growth and thinned sites decreased significantly (p < 0.05) during the two most recent decades when elk populations, as indexed by annual harvest levels, were relatively “high”. From 2000 to 2008, only 2.9 Mexican wolves per 1000 elk were present on the Apache National Forest compared to 9.3 western gray wolves (Canis lupus occidentalis) per 1000 elk in Yellowstone National Park where tri-trophic cascades involving wolves, elk, and aspen have been reported. The low number of Mexican wolves relative to their primary prey (elk) suggests that an ecologically effective density of wolves has not become established in east-central Arizona. Furthermore, the lack of recent aspen recruitment in stands accessible to elk indicates an absence, to date, of a tri-trophic cascade.     

Selection of roosting habitats by Nyctalus noctula and Nyctalus leisleri in Białowieża Forest—Adaptive response to forest management?

Tree dwelling bats select cavities in large, old, dying or dead trees. This inevitably brings them into direct conflict with the interests of forest managers, who are trained to fell such trees. Therefore the identification of forest stands providing optimal roosting opportunities for bats is crucial, in order to provide appropriate guidelines for forest management. It is also important to identify the extent to which the roosting ecology of bats changes in response to habitat modification. Bia?owie?a Forest (BF) offers a unique opportunity, in the temperate zone, to observe differences between areas with no direct human intervention and managed areas and in particular to reveal the effect of forest management on the roosting ecology of forest dwelling bat species. We used GIS techniques to evaluate bats’ spatial response to changes in forest structure and to test the hypotheses that the forest dwelling bats Nyctalus noctula and Nyctalus leisleri prefer roost sites within old deciduous or wet woodlands over young and coniferous ones and that roost site preferences reflect the extent to which dead and dying trees are removed. There was a significant difference in the selection of roosting habitat between the managed and pristine areas of the forest. Within the pristine forest, both species displayed a strong preference for roost trees located within old deciduous stands (>100 years), whereas in the managed part of the forest old wet woodland was preferred while all medium and young forest stands were avoided. Our data reveal a high degree of lability in the selection of roosting habitat by bats. It appears that bats are able to respond to changes in their environment by changing their roost site preferences and could therefore occupy habitat previously considered less suitable.     

Do forest policy actors learn through forward-thinking? Conflict and cooperation relating to the past,present and futures of sustainable forest management in Germany

Collaborative participatory policy approaches based on foresight methodology have recently been proposed as promising governance tools to achieve sustainability in general, and address and manage challenges of integrating competing demands on forest land use (e.g., timber production, nature protection, recreation) in particular. Their main argument is that participatory processes will bring policy actors together. Based on long- and short-term future-oriented thinking and actions, they will overcome their previous value-laden and interest-based conflicts through informed communication, deliberation, policy learning and mutual cooperation. But do policy actors learn when they are thinking, debating and shaping the ‘forest futures’ they want to achieve or avoid? To what extent are current beliefs, values, worldviews, and conflict structures projected onto the future? What are their impacts on policy learning today?This paper addresses these research questions from a knowledge-based perspective of relevant policy learning theories. We trace changes and stability in beliefs, values (perception) and behavior (cooperation/conflict) among the involved policy actors. We assess to what extent future-oriented thinking and discussions contribute to, or inhibit, policy learning today.Empirically, the paper is informed by three case studies of regional ‘forest futures’ processes in Germany. They include forest landscapes in Upper Palatinate and South of Munich in Bavaria, and the Black Forest National Park in Baden-Württemberg. They represent different cases in terms of levels of stakeholder conflicts, integrative/segregative forest land use approaches, and the rural/urban divide. The paper is based on a qualitative analysis of interviews and documents about past and future forest land use, and observation of participatory scenario-building and back-casting workshops during 2011–2014.In our analysis, we found that forest policy actors adhered to their pre-existing beliefs and remained divided in terms of present and future aspects of sustainable forest management. That is, we observed no substantial or only strategic policy learning among the involved policy actors. We explain these findings in terms of competing actors' belief systems and worldviews that lead to competing understandings and expectations of ‘forest futures’. We discuss our research against the theoretical propositions and in view of the state-of-the art. We draw conclusions relevant for scholars and policymakers interested in collaborative policy learning processes, and suggest possible topics for further research.     

Unraveling the tripartite interactions among the woolly poplar aphid,its host tree,and their environment: a lead to improve the management of a major tree plantation pest?

Key message

For an optimal deployment of poplar resistance to the gall-inducing aphid Phloeomyzus passerinii , a laboratory susceptibility assay has been developed. The nature of aphid–tree interactions during compatible and incompatible situations has been studied in detail. This should help at identifying specific resistance markers and at testing effects of site conditions on tree–pest interactions.

Context

P. passerinii is a major pest of poplar plantations in Europe, and the plantation of resistant poplar genotypes is regarded as the best long-term management strategy for this pest. This requires a sound knowledge of the interactions among the pest, its host and their environment.

Aims

Here, we review the recent advances aiming at developing an optimal deployment of host resistance versus P. passerinii.

Results

Investigations on aphid-host interactions demonstrated that P. passerinii induces pseudogalls within the bark of susceptible hosts. This results in a reduction of starch bark content during aphid outbreaks, which could be involved in tree death. The constitutive level of starch in the bark could be related to the tolerance level of trees. A susceptibility test has been designed for poplar genotypes, discriminating three categories of susceptibility depending on tree’s ability to totally or partially inhibit pseudogall induction. The test still has several limitations however. It neither takes into account the large level of individual genetic diversity of the aphid in France, nor the environmental modulation of tree resistance and tolerance, while water deficit and fertilization could potentially affect these parameters.

Conclusion

The hypotheses drawn regarding the processes leading to tree death or resistance should help at identifying resistance markers, and at testing effects of site conditions on tree–pest interactions.

     

Is it necessary to change the number of samples for different forest types when evaluating plant species richness? A case study in a forested landscape in central Japan

We demonstrate a method for evaluating the appropriate number of samples required to estimate plant species richness in different forest types within a forested landscape. In each of 36 plots (0.1 ha each) from 5 forest types (deciduous broad-leaved secondary forest and 4 categories of coniferous plantation classified according to stand age) in central Japan, 40 quadrats of 1 × 1 m were set in a regular pattern; the total number of quadrats in each forest type ranged from 200 to 400. In each plot, the number of observed species in 40 quadrats ranged from 60 to 80% of the number of species estimated by the rarefaction method for each forest type. Sampling 30 quadrats detected approximately 90% of the observed species in each plot that were detected using 40 quadrats. In specific functional groups (i.e., tall trees and weed species), the ratios of both tall trees and weed species to all species were at equilibrium for 30 or more quadrats. For fewer than 30 quadrats these ratios were highly variable. No significant differences were found among forest types in the ratio of the observed number of species in each plot to the estimated number of species calculated using the rarefaction method, and in sampling efficiency estimated by use of non-parametric estimators. We concluded that the number of samples does not need to be changed according to forest type or plantation stand age in the studied landscape, and that the method used to evaluate the number of samples could be useful.     

Modelling the management of fragmented forests: Is it possible to recover the original tree composition?: The case of the Maulino forest in Central Chile

In the fragmented Maulino forest (in Central Chile), differences in the relative frequencies of species between seedlings and mature trees are strong indicators of a changing replacement dynamics in the community. Stationary Markov chain models predict that the future tree composition such Maulino forest fragments will differ from that of continuous, intact forest. We found that the persistence probability was highest for Aristotelia chilensis and lowest for Nothofagus glauca. These two tree species are the most affected by fragmentation, and changes in their abundances appear to be the main drivers of the long-term change in stand composition. The aim of our study was to test if the management of just these two species would be sufficient to avoid long-term changes in the composition of forest fragments or would recover their composition toward a state more similar to the continuous forest. For this purpose, we constructed a Markov matrix model from published information, and calculated the future stable stand composition under different management simulations: (1) reduction of A. chilensis recruitment, (2) increased recruitment of N. glauca, and (3) a combined treatment. To evaluate the effectiveness of management treatments, the future composition of fragments was compared with the composition expected for continuous (i.e., undisturbed) Maulino forest. We performed a sensitivity analysis of the stable composition in order to assess the intensity of changes in the future composition driven by the treatments, and to determine to what extend the recruitment of other coexisting species contributes to changes in relative frequencies of A. chilensis and N. glauca.     

Is there a Nordic Model for the treatment of introduced tree species? A comparison of the use,policy, and debate concerning introduced tree species in the Nordic countries

This article compares the use, policy, and debate concerning introduced tree species in the five Nordic countries (Finland, Sweden, Norway, Denmark, and Iceland). These countries have a long common history and are culturally similar. They are often framed under the benchmark of the “Nordic Model” or even the “Nordic Forestry Model”. Therefore, we hypothesize that the Nordic countries’ treatment of introduced tree species share common aspects, and that global environmental agreements and international currents in science and policy have reinforced these similarities. The comparison shows that globalization is strong and it seems, at least at a first glimpse, that the Nordic countries follow a kind of “Nordic Model” in their approach to introduced tree species. However, the history and importance of forestry, ecological conditions, afforestation campaigns, traditions of using introduced trees, understandings, and stakeholder positions have shaped different national and even regional path dependencies and circumstances. This, in turn, has transmuted international policy-making, regulations, and discussions into different specific ways to interpret, control, and implement the use of introduced trees in practice. This article concludes that global environmental agreements and international currents in science and policy adapt to diverse national contexts.