Showing papers by "Swiss Federal Institute for Forest, Snow and Landscape Research published in 2007"

Specific root length as an indicator of environmental change

Abstract: Specific root length (SRL, m g(-1)) is probably the most frequently measured morphological parameter of fine roots. It is believed to characterize economic aspects of the root system and to be indi ...

Long‐term drought severity variations in Morocco

Abstract: [1] Cedrus atlantica ring width data are used to reconstruct long-term changes in the Palmer Drought Severity Index (PDSI) over the past 953 years in Morocco, NW Africa. The reconstruction captures the dry conditions since the 1980s well and places this extreme period within a millennium-long context. PDSI values were above average for most of the 1450-1980 period, which let recent drought appear exceptional. However, our results also indicate that this pluvial episode of the past millennium was preceded by generally drier conditions back to 1049. Comparison of PDSI estimates with large-scale pressure field reconstructions revealed steady synoptic patterns for drought conditions over the past 350 years. The long-term changes from initially dry to pluvial to recent dry conditions are similar to PDSI trends reported from N America, and we suggest that they are related to long-term temperature changes, potentially teleconnected with ENSO variability and forced by solar irradiance changes.

Field observations of basal forces and fluid pore pressure in a debris flow

Abstract: [1] Using results from an 8 m2 instrumented force plate we describe field measurements of normal and shear stresses, and fluid pore pressure for a debris flow. The flow depth increased from 0.1 to 1 m within the first 12 s of flow front arrival, remained relatively constant until 100 s, and then gradually decreased to 0.5 m by 600 s. Normal and shear stresses and pore fluid pressure varied in-phase with the flow depth. Calculated bulk densities are ρb = 2000–2250 kg m−3 for the bulk flow and ρf = 1600–1750 kg m−3 for the fluid phase. The ratio of effective normal stress to shear stress yields a Coulomb basal friction angle of ϕ = 26° at the flow front. We did not find a strong correlation between the degree of agitation in the flow, estimated using the signal from a geophone on the force plate, and an assumed dynamic pore fluid pressure. Our data support the idea that excess pore-fluid pressures are long lived in debris flows and therefore contribute to their unusual mobility.

A strategy to assess river restoration success

Abstract: Summary 1. Elaborate restoration attempts are underway worldwide to return human-impacted rivers to more natural conditions. Assessing the outcome of river restoration projects is vital for adaptive management, evaluating project efficiency, optimising future programmes and gaining public acceptance. An important reason why assessment is often omitted is lack of appropriate guidelines. 2. Here we present guidelines for assessing river restoration success. They are based on a total of 49 indicators and 13 specific objectives elaborated for the restoration of low- to mid-order rivers in Switzerland. Most of these objectives relate to ecological attributes of rivers, but socio-economic aspects are also considered. 3. A strategy is proposed according to which a set of indicators is selected from the total of 49 indicators to ensure that indicators match restoration objectives and measures, and that the required effort for survey and analysis of indicators is appropriate to the project budget. 4. Indicator values are determined according to methods described in detailed method sheets. Restoration success is evaluated by comparing indicator values before and after restoration measures have been undertaken. To this end, values are first standardised on a dimensionless scale ranging from 0 to 1, then averaged across different indicators for a given project objective, and finally assigned to one of five overall success categories. 5. To illustrate the application of this scheme, a case study on the Thur River, Switzerland, is presented. Seven indicators were selected to meet a total of five project objectives. The project was successful in achieving ‘provision of high recreational value’, ‘lateral connectivity’ and ‘vertical connectivity’ but failed to meet the objectives ‘morphological and hydraulic variability’ and ‘near natural abundance and diversity of fauna’. Results from this assessment allowed us to identify potential deficits and gaps in the restoration project. To gain information on the sensitivity of the assessment scheme would require a set of complementary indicators for each restoration objective.

Cover effect in bedrock abrasion : A new derivation and its implications for the modeling of bedrock channel morphology

Abstract: The sediment load of a bedrock river plays an important role in the fluvial incision process by providing tools for abrasion (the tools effect) and by covering and thereby protecting the bed (the cover effect). We derive a new formulation for the cover effect, in which the fraction of exposed bed area falls exponentially with increasing sediment flux or decreasing transport capacity, and explore its consequences for the model of bedrock abrasion by saltating bed load. Erosion rates predicted by the model are higher than those predicted by earlier models. In a closed system, the maximum erosion rate is predicted to occur when sediment supply is equal to transport capacity for a flat bed. By optimizing the channel geometry to minimize the potential energy of the stream and using representative values for both discharge and grain size, we derive equations for the geometry of a bedrock river and explore how predictions for width, slope, and bed cover vary as functions of drainage area, rock uplift rate, and rock strength. The equations predict a dependence of channel width on drainage area similar to the relations using a simple shear stress incision law. The slope-area relationship is predicted to be concave up in a log-log regime, with a curvature dependent on uplift rate. However, this curvature does not deviate sufficiently from a straight line to allow discrimination between models using empirical data. Dependence of channel width and slope on rock uplift rate can be separated into two domains: for low uplift rates, channel geometry is largely insensitive to uplift rate due to a threshold effect. At high uplift rates, there is a power law dependence. Bed cover is predicted to increase progressively downstream and to increase with increasing uplift rate. In our model, the width-to-depth ratio is a function of both tectonic and climatic forcing. This indicates that the scaling between channel width and bed slope is neither a unique indicator of tectonic forcing at steady state nor a signature of transience or steady state. We conclude that sediment effects need to be taken into account when modeling bedrock channel morphology.

The Swiss agri-environment scheme enhances pollinator diversity and plant reproductive success in nearby intensively managed farmland

Abstract: Summary 1. Agri-environment schemes attempt to counteract the loss of biodiversity and associated ecosystem services such as pollination and natural pest control in agroecosystems. However, only a few studies have evaluated whether these attempts are successful. 2. We studied the effects of managing meadows according to the prescriptions of ecological compensation areas (ECA), the most widely adopted agri-environment scheme in Switzerland, on both pollinator species richness and abundance, and the reproductive success of plants in nearby intensively managed meadows (IM). 3. We established arrays of four pots, each containing individuals of three insectpollinated, non-autogamous ‘phytometer’ species ( Raphanus sativus , Hypochaeris radicata and Campanula glomerata ), in ECA and adjacent IM at increasing distances from the ECA at 13 sites. 4. Species richness and abundance of hoverflies, solitary bees and large-sized pollinators (mainly social bees and butterflies) were significantly higher in ECA than in adjacent IM. Species richness and abundance of small-sized pollinators in IM declined significantly with increasing distance from ECA, whereas large-sized pollinators were not significantly affected by distance. Plant species richness and flower abundance were the major drivers of pollinator species richness and abundance; the area of an ECA had no significant influence. 5. Individual plants of R. sativus and C. glomerata produced more and heavier seeds in ECA than in IM. Furthermore, the number of seeds of these two phytometer species was positively correlated with species richness and abundance of bees. No such effects were observed for individual plants of H. radicata . The number of fruits and seeds per plant of R. sativus in IM decreased with increasing distance from ECA. 6. Synthesis and applications. We conclude that establishing ECA is an effective method of enhancing both pollinator species richness and abundance and pollination services to nearby intensely managed farmland. Our study emphasizes the importance of connectivity between ECA in maintaining diverse pollinator communities and thereby providing pollination services in agricultural landscapes.

Variation in fine root biomass of three European tree species: Beech (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst.), and Scots pine (Pinus sylvestris L.)

Abstract: Fine roots (<2 mm) are very dynamic and play a key role in forest ecosystem carbon and nutrient cycling and accumulation We reviewed root biomass data of three main European tree species European beech, (Fagus sylvatica L), Norway spruce (Picea abies L Karst) and Scots pine (Pinus sylvestris L), in order to identify the differences between species, and within and between vegetation zones, and to show the relationships between root biomass and the climatic, site and stand factors The collected literature consisted of data from 36 beech, 71 spruce and 43 pine stands The mean fine root biomass of beech was 389 g m−2, and that of spruce and pine 297 g m−2 and 277 g m−2, respectively Data from pine stands supported the hypothesis that root biomass is higher in the temperate than in the boreal zone The results indicated that the root biomass of deciduous trees is higher than that of conifers The correlations between root biomass and site fertility characteristics seemed to be species specific

Stomatal regulation by microclimate and tree water relations: interpreting ecophysiological field data with a hydraulic plant model.

Abstract: Dynamics in microclimate and physiological plant traits were studied for Pubescent oak and Scots pine in a dry inner-alpine valley in Switzerland, at a 10 min resolution for three consecutive years (2001-2003). As expected, stomata tended to close with increasing drought in air and soil. However, stomatal aperture in oak was smaller than in pine under relatively wet conditions, but larger under dry conditions. To explore underlying mechanisms, a model was applied that (i) quantifies water relations within trees from physical principles (mechanistic part) and (ii) assumes that signals from light, stomatal aperture, crown water potential, and tree water deficit in storage pools control stomata (systemic part). The stomata of pine showed a more sensitive response to increasing drought because both factors, the slowly changing tree water deficit and the rapidly changing crown water potential, closed the stomata. By contrast, the stomata of oak became less drought-sensitive as the closing signal of crown water potential was opposed by the opening signal of tree water deficit. Moreover, parameter optimization suggests that oak withdrew more water from the storage pools and reduced leaf water potentials to lower levels, without risking serious damage by cavitation. The new model thus suggests how the hydraulic water flow and storage system determines the responses in stomatal aperture and transpiration to drought at time scales ranging from hours to multiple years, and why pine and oak might differ in such responses. These differences explain why oaks are more efficient competitors during drought periods, although this was not the case in the extremely dry year 2003, which provoked massive leaf loss and, from July onwards, physiological activity almost ceased.

Adjustment for proxy number and coherence in a large-scale temperature reconstruction

Abstract: [1] Proxy records may display fluctuations in climate variability that are artifacts of changing replication and interseries correlation of constituent time-series and also from methodological considerations. These biases obscure the understanding of past climatic variability, including estimation of extremes, differentiation between natural and anthropogenic forcing, and climate model validation. Herein, we evaluate as a case-study, the Esper et al. (2002) extra-tropical millennial-length temperature reconstruction that shows increasing variability back in time. We provide adjustments considering biases at both the site and hemispheric scales. The variance adjusted record shows greatest differences before 1200 when sample replication is quite low. A reduced amplitude of peak warmth during Medieval Times by about 0.4°C (0.2°C) at annual (40-year) timescales slightly re-draws the longer-term evolution of past temperatures. Many other regional and large-scale reconstructions appear to contain variance-related biases.

Interaction diversity within quantified insect food webs in restored and adjacent intensively managed meadows.

Abstract: 1. We studied the community and food-web structure of trap-nesting insects in restored meadows and at increasing distances within intensively managed grassland at 13 sites in Switzerland to test if declining species diversity correlates with declining interaction diversity and changes in food-web structure. 2. We analysed 49 quantitative food webs consisting of a total of 1382 trophic interactions involving 39 host/prey insect species and 14 parasitoid/predator insect species. Species richness and abundance of three functional groups, bees and wasps as the lower trophic level and natural enemies as the higher trophic level, were significantly higher in restored than in adjacent intensively managed meadows. Diversity and abundance of specific trophic interactions also declined from restored to intensively managed meadows. 3. The proportion of attacked brood cells and the mortality of bees and wasps due to natural enemies were significantly higher in restored than in intensively managed meadows. Bee abundance and the rate of attacked brood cells of bees declined with increasing distance from restored meadows. These findings indicate that interaction diversity declines more rapidly than species diversity in our study system. 4. Quantitative measures of food-web structure (linkage density, interaction diversity, interaction evenness and compartment diversity) were higher in restored than in intensively managed meadows. This was reflected in a higher mean number of host/prey species per consumer species (degree of generalism) in restored than in intensively managed meadows. 5. The higher insect species and interaction diversity was related to higher plant species richness in restored than in intensively managed meadows. In particular, bees and natural enemies reacted positively to increased plant diversity. 6. Our findings provide empirical evidence for the theoretical prediction that decreasing species richness at lower trophic levels should reduce species richness at higher trophic levels, and in addition lead to even stronger reductions in interaction diversity at these higher levels. Species at higher trophic levels may thus benefit relatively more than species at lower trophic levels from habitat restoration in the grassland ecosystems studied. We also demonstrate enhanced compartment diversity and lower interaction evenness in restored than in intensively managed meadows, both of which are theoretically positively associated with increased ecosystem stability in restored meadows.

Radial growth responses to drought of Pinus sylvestris and Quercus pubescens in an inner‐Alpine dry valley

Abstract: Question: Lower montane treeline ecotones such as the inner Alpine dry valleys are regarded as sensitive to climate change. In the dry Valais valley (Switzerland) the composition of the widespread, low altitude Pinus forests is shifting towards a mixed deciduous state. The sub-boreal P. sylvestris shows high mortality rates, whereas the deciduous sub-mediterranean Quercus pubescens is spreading. These species may act as early indicators of climate change. We evaluate this hypothesis by focusing on their differences in drought tolerance, which are hardly known, but are likely to be crucial in the current forest shift and also for future forest development. Methods: We used dendroecological methods to detect species-specific patterns in the growth response to drought. The relationship between radial growth of 401 trees from 15 mixed stands and drought was analysed by calculating response functions using yearly tree-ring indices and monthly drought indices. PCA was applied to the response ratios to ...

Horizontal and vertical distribution of saproxylic beetles (Col., Buprestidae, Cerambycidae, Scolytinae) across sections of forest edges

Abstract: We evaluated the preferred home ranges of three saproxylic beetle taxa along transects from the open field into the forest interior, and from the forest floor up to the canopy. By means of trap sets on metal scaffolds, vertical and horizontal strata were sampled across two types of forest edges: soft-edge ecotones with a gradual transition from the field into the forest and hard edges with an abrupt transition. The forest edges consisted of different strata such as herbaceous fringe, shrub belt, unmanaged forest and managed forest. The thermophilic buprestids were mainly caught in the open land (herbaceous fringe and agricultural land) and in the upper forest mantle. In general, the cerambycids were most abundant in the open land and the lower forest mantle, but a few species favoured the forest interior. The bark beetles (Scolytinae) were equally distributed in all habitats. These distribution patterns of the taxa were observed in terms of both species numbers and abundances. Each species with at least five collected specimens was assigned to one of the three habitat types: open land, forest mantle and forest interior. Of 74 ranked species, only 16% were prevalent in the forest interior and are thus considered to be true forest species. The other 84% of the species were attributed to open land or the forest mantle and are, therefore, forest edge species. Soft forest edges generally supported a higher species richness than hard edges, particularly as regards Cerambycidae and Scolytinae. In terms of Shannon diversity, soft edges tended to be more diverse in buprestids and cerambycids. Overall, the forest interior showed the least species richness and diversity. Therefore, for the conservation of saproxylic beetles, not only the amount and quality of dead wood is important, but also the presence and design of forest boundary structures.

Linking increasing drought stress to Scots pine mortality and bark beetle infestations.

Abstract: In the dry Swiss Rhone Valley, Scots pine forests have experienced increased mortality in recent years. It has commonly been assumed that drought events and bark beetles fostered the decline, however, whether bark beetle outbreaks increased in recent years and whether they can be linked to drought stress or increasing temperature has never been studied. In our study, we correlated time series of drought indices from long-term climate stations, 11-year mortality trends from a long-term research plot, and mortality probabilities modeled from tree rings (as an indicator of tree vitality) with documented occurrences of various bark beetle species and a buprestid beetle, using regional Forest Service reports from 1902 to 2003 and advisory cases of the Swiss Forest Protection Service (SFPS) from 1984 to 2005. We compared the historical findings with measured beetle emergence from a 4-year tree felling and breeding chamber experiment. The documented beetle-related pine mortality cases increased dramatically in the 1990s, both in the forest reports and the advisory cases. The incidents of beetle-related pine mortality correlated positively with spring and summer temperature, and with the tree-ring based mortality index, but not with the drought index. The number of advisory cases, on the other hand, correlated slightly with summer drought index and temperature, but very highly with tree-ring-based mortality index. The tree-ring-based mortality index and observed tree mortality increased in years following drought. This was confirmed by the beetle emergences from felled trees. Following dry summers, more than twice as many trees were colonized by beetles than following wet summers. We conclude that increased temperatures in the Swiss Rhone Valley have likely weakened Scots pines and favored phloeophagous beetle population growth. Beetles contributed to the increased pine mortality following summer drought. Among the factors not addressed in this study, changed forest use may have also contributed to increased beetle populations and Scots pine mortality, whereas air pollution seems to be of lesser importance.

Objectives of public participation: Which actors should be involved in the decision making for river restorations?

Abstract: [1] River restoration as a measure to improve both flood protection and ecological quality has become a common practice in river management. This new practice, however, has also become a source of conflicts arising from a neglect of the social aspects in river restoration projects. Therefore appropriate public involvement strategies have been recommended in recent years as a way of coping with these conflicts. However, an open question remains: Which stakeholders should be involved in the decision-making process? This, in turn, raises the question of the appropriate objectives of public participation. This study aims to answer these questions drawing on two case studies of Swiss river restoration projects and a related representative nationwide survey. Our findings suggest that public involvement should not be restricted to a small circle of influential stakeholder groups. As restoration projects have been found to have a substantial impact on the quality of life of the local population, avoiding conflicts is only one of several objectives of the involvement process. Including the wider public provides a special opportunity to promote social objectives, such as trust building and identification of people with their local environment.

Exudation of organic acid anions from poplar roots after exposure to Al, Cu and Zn

Abstract: We studied the effects of a 2-day exposure to aluminum (Al), copper (Cu) and zinc (Zn) stress on root exudates and root apices of aseptically grown poplar (Populus tremula L.) cuttings. Aluminum induced root exudation of oxalate and citrate, Cu induced root exudation of oxalate, malate and formate, and Zn induced root exudation of formate. The threshold treatment concentrations were 100 microM for Cu and 500 microM for Al and Zn, corresponding to about 30 microM Cu2+, 140 microM Al3+ and 290 microM Zn2+. Simultaneous with the increase in organic acid anion exudation, sulfate and the nutrient cations K+, Ca2+ and Mg2+ were released into the solutions. Significant positive correlations between the organic acid anions and the cations indicate possible co-release. Toxicity symptoms of the poplar roots included browning of the root apices, which occurred at Cu concentrations of 50 microM and above, at Zn concentrations of 500 microM and above, and at an Al concentration of 1000 microM, and callose formation, which was observed solely in response to Al concentrations of 500 microM or higher. The results indicate that the composition of the exuded organic acid anions from poplar roots and the toxicity symptoms are specific to each of the applied heavy metals.

Methodical study of nitrous oxide eddy covariance measurements using quantum cascade laser spectrometery over a Swiss forest

Abstract: . Nitrous oxide fluxes were measured at the Lageren CarboEurope IP flux site over the multi-species mixed forest dominated by European beech and Norway spruce. Measurements were carried out during a four-week period in October–November 2005 during leaf senescence. Fluxes were measured with a standard ultrasonic anemometer in combination with a quantum cascade laser absorption spectrometer that measured N2O, CO2, and H2O mixing ratios simultaneously at 5 Hz time resolution. To distinguish insignificant fluxes from significant ones it is proposed to use a new approach based on the significance of the correlation coefficient between vertical wind speed and mixing ratio fluctuations. This procedure eliminated roughly 56% of our half-hourly fluxes. Based on the remaining, quality checked N2O fluxes we quantified the mean efflux at 0.8±0.4 μmol m−2 h−1 (mean ± standard error). Most of the contribution to the N2O flux occurred during a 6.5-h period starting 4.5 h before each precipitation event. No relation with precipitation amount could be found. Visibility data representing fog density and duration at the site indicate that wetting of the canopy may have as strong an effect on N2O effluxes as does below-ground microbial activity. It is speculated that above-ground N2O production from the senescing leaves at high moisture (fog, drizzle, onset of precipitation event) may be responsible for part of the measured flux.

Leaf responsiveness of Populus tremula and Salix viminalis to soil contaminated with heavy metals and acidic rainwater.

Abstract: Fast-growing trees such as Salix viminalis L. and Populus tremula L. are well suited to phytoremediate heavy metal contaminated soils. However, information on tree performance, particularly leaf function, under conditions of heavy metal contamination is scarce. We used yearly coppiced saplings of S. viminalis and P. tremula growing in model ecosytems to test four hypotheses: (1) heavy metal contamination impairs photosynthesis by injuring leaf structure; (2) the effects of heavy metal contamination are enhanced by acidified rainwater and low soil pH; (3) heavy metal contamination increases dark respiration and, thus, repair processes; and (4) heavy metal contamination is tolerated and remediated better by S. viminalis than by P. tremula. We investigated heavy metal accumulation, tissue injury and gas exchange in leaves of plants subjected to controlled soil contamination with heavy metal dust. Additional treatments included acidic and calcareous natural forest subsoils in combination with irrigation with rainwater at pH 5.5 or 3.5. In both provenances of P. tremula that were studied, but not in S. viminalis, heavy metal treatment reduced photosynthesis and transpiration by varying amounts, except in the hot and dry summer of 2003, but had no effect on dark respiration. At light saturation, net CO(2) uptake and water-use efficiency were reduced by heavy metal contamination, whereas the CO(2) concentration in the leaf intercellular air space was increased. Rainwater pH and subsoil pH only slightly modified the effects of the heavy metal treatment on P. tremula. Gas exchange responses of P. tremula to heavy metals were attributed to leaf structural and ultrastructural changes resulting from hypersensitive-response-like processes and accelerated mesophyll cell senescence and necroses in the lower epidermis, especially along the transport pathways of heavy metals in the leaf lamina. Overall, the effects of heavy metals on P. tremula corroborated Hypothesis 1, but refuted Hypotheses 2 and 3, and were inconclusive for Hypothesis 4. Both P. tremula and S. viminalis showed appreciable potential for storing heavy metals in aging foliage.

State of the art in rockfall – forest interactions

Abstract: To effectively prevent rockfall related disasters below forested slopes, silvicultural, eco-engineering, civil engineering or mixed techniques can be used. To do this in a cost-efficient manner it is necessary to know the following: 1) where rockfall events occur and which magnitudes are likely, 2) to what extent the forest reduces the run-out distances, the jump heights and the energies of rocks falling downslope, and 3) how the protective function of forests could be improved. This paper gives an overview of the current scientific knowledge and methods that are applied by practitioners who deal with rockfall and forests protecting against it. Efficient ways to derive information on the probable magnitude and frequency of future rockfall events from the source and deposit area are described. Subsequently, the scientific knowledge on the energy absorption capacity of single trees and the currently available knowledge on the protective function of forest stands against rockfall are presented. Then easy-to-...

Controls on dissolved organic matter leaching from forest litter grown under elevated atmospheric CO2

Abstract: The aim of our study was to identify controls on initial dissolved organic matter (DOM) leaching from decomposing forest litter and to estimate how it is affected by increasing atmospheric CO 2 . Using microcosms, we measured initial C mineralization and leaching rates of DOC, DON and biodegradable DOC from litter of eight tree species from CO 2 enrichment experiments in a 100 year-old broadleaf forest and a 30 year-old treeline ecosystem. Over 11 weekly leaching cycles, between 2.5% (Pinus uncinata, Fagus sylvatica) and 15% (Carpinus betulus) of litter C were leached as DOC, corresponding to 9–36% of the total mass loss. Significantly less, 0.9% (Pinus) to 4.5% (Tilia platyphyllos) of litter N was leached as DON. Leaching of DOC was not correlated to C mineralization, which ranged between 12% (Fagus) and 32% (Tilia) of litter C. While C mineralization increased with decreasing litter C/N ratios and lignin contents, DOC leaching particularly the initially leached DOC was significantly related to concentrations of non-structural carbohydrates (NSC) and phenolics. DOC leached after the third leaching cycle did not correlate with any of the measures of litter quality, but with the molar UV absorptivity of DOC, suggesting that DOC production is linked to lignin degradation. Previous CO 2 enrichment increased NSC and phenolics in the litter and decreased lignin contents, which resulted in significantly greater initial C mineralization ( + 5 % ) and DOC leaching rates ( + 16 % ) . However, these CO 2 effects were only significant during the initial leaching phase and much smaller than the differences between tree species. Initially leached DOC was less biodegradable when its parent litter was grown under elevated than under ambient CO 2 (38% vs. 42% of DOC across all species, P 0.05). Therefore, leaching of ‘refractory’ DOC was increased under elevated CO 2 , which will rather accelerate DOC inputs into mineral soils than further stimulate microbial activity. In summary, our study shows (1) that initial DOM leaching is controlled by other factors than C mineralization; and (2) that CO 2 enrichment of forests can stimulate initial mineralization and leaching of C from litter by altering its quality, but these effects will be short-term and much smaller than any change in species composition.

Palaeoecological evidence for anthropogenic acidification of a kettle-hole peatland in northern Poland:

Abstract: We studied the Holocene developmental history of a small kettle-hole peatland in northern Poland using radiocarbon dating and analyses of pollen, plant macrofossils, and testate amoebae with the aim to sort out the influences of climate change, autogenic succession, and human impact. The mire followed the classical succession from lake to a Sphagnum-dominated peatland, but peat accumulation only started about 3000 years before present. A rapid shift to wetter conditions, lower pH, and higher peat accumulation rate took place about 110-150 years before present, when the vegetation shifted to a Sphagnum-dominated poor fen with some bog plants. While the first shift to a peat-accumulating system was most likely driven by climate, the second one was probably caused by forest clearance around the mire. This shift towards a Sphagnum-dominated vegetation mirrors both in pattern and timing the changes observed in similar situations in North America and New-Zealand. While human activities have overall caused the loss of vast expanses of peatlands worldwide in recent centuries, locally they may have also allowed the development of communities that are now ironically considered to have a high conservation value. However, in the case of the site studied and possibly elsewhere the likely anthropogenic shift to bog vegetation was at the expense of a species-rich poor fen, which today has even higher conservation value than ombrotrophic bogs. Thus this study also illustrates the value of palaeoecology for peatland management and biodiversity conservation.

Deadwood volume assessment in the third Swiss National Forest Inventory: methods and first results

Abstract: The Swiss National Forest Inventory (NFI) is expected to provide reliable data about the current state of the Swiss forests and recent changes. Since the first Swiss NFI (1982–1986) a deadwood assessment has been part of the inventory. However, the definition of deadwood used was restricted and only parts of the total deadwood volume were assessed. A broader definition was therefore used in the second NFI (1993–1995) and coarse wood debris (CWD) was also assessed using line intersect sampling in the third NFI (2004–2006). This paper discusses the development of the definition of deadwood from the first to the third Swiss NFI, as well as the tally rules and estimators used in assessing deadwood in the ongoing third NFI. Different definitions of deadwood were applied in two Swiss regions and the resulting volume estimates were compared. The definition of deadwood appears to be crucial for the estimate of deadwood volumes, which were significantly underestimated in the first and second Swiss NFI. The minimum diameter and other limits applied must be chosen with special care. Up to 30 m3/ha of deadwood was found in Swiss forests varying with the region. There was little evidence of significant correlations between deadwood volume and such forest parameters as management, site or stand attributes. The proposed target values for the volume of deadwood have been generally reached, whereas the number of snags per hectare has not.

Tree fine root Ca/Al molar ratio – Indicator of Al and acidity stress

Abstract: High soil acidity and elevated soil Al concentrations limit plant growth in many terrestrial ecosystems. Aluminium toxicity can be ameliorated by Ca. Thus, Ca/Al molar ratios in soil solution and in plant tissues have been proposed as superior indicators than Al concentration itself for evaluating the Al toxicity stress to trees (Cronan & Grigal, J Environ Qual 1995;24:209 – 226). This article presents an overview of publications since 1995 where the reduced Ca/Al ratio in fine tree roots has been used as an indicator of stress for Al and/or soil acidity. The main aim of this review was to evaluate the use and the critical threshold of the fine root Ca/Al ratio as a potential indicator for Al toxicity stress to trees in acid soils. Based on the reviewed literature, the fine root Ca/Al molar ratio was strongly negatively related to Al stress in small tree seedlings in controlled environments, whereas the response was not clear under field conditions where other environmental factors interact. Fine...