Showing papers in "Annals of Forest Science in 2019"

Forest adaptation to climate change—is non-management an option?

Abstract: Climate change is posing a considerable challenge to foresters. The intensity of required adaptive measures and the relevance of old-growth forests as benchmark for managed forests are debated. Forest managers need to make decisions on stand treatment that are based on climatological and biological parameters with high uncertainties. We provided the conceptual basis for adaptive forest management and provide a number of case studies that reflect the options and limitations of ways of coping with climate change. The examples are derived from the experience of the authors. We conclude that only few forest types are either not strongly affected by climate change or do not require immediate adaptations of forest management. Many productive forests have stand properties that are decisively shaped by past management decisions, such as tree species composition, age distribution, rotation period, and stand structure. Maintaining these properties under the influence of climate change requires continuous and even increasing efforts of forest managers.

Implementing forest landscape restoration under the Bonn Challenge: a systematic approach

Abstract: There is no one-size-fits-all way to successfully implement forest landscape restoration (FLR). Complex socio-ecological systems present challenges and opportunities that can best be met with a systematic framework for designing, planning, steering, and monitoring FLR projects to meet diverse needs. Project cycle management is an iterative, adaptive, hierarchical framework with recurring consultations among stakeholders that can enhance the likelihood of FLR success.

Climate change and mixed forests: how do altered survival probabilities impact economically desirable species proportions of Norway spruce and European beech?

Abstract: Economic consequences of altered survival probabilities under climate change should be considered for regeneration planning in Southeast Germany. Findings suggest that species compositions of mixed stands obtained from continuous optimization may buffer but not completely mitigate economic consequences. Mixed stands of Norway spruce ( Picea abies L. Karst . ) and European beech ( Fagus sylvatica L.) (considering biophysical interactions between tree species) were found to be more robust, against both perturbations in survival probabilities and economic input variables, compared to block mixtures (excluding biophysical interactions). Climate change is expected to increase natural hazards in European forests. Uncertainty in expected tree mortality and resulting potential economic consequences complicate regeneration decisions. This study aims to analyze the economic consequences of altered survival probabilities for mixing Norway spruce (Picea abies L. Karst.) and European beech (Fagus sylvatica L.) under different climate change scenarios. We investigate whether management strategies such as species selection and type of mixture (mixed stands vs. block mixture) could mitigate adverse financial effects of climate change. The bio-economic modelling approach combines a parametric survival model with modern portfolio theory. We estimate the economically optimal species mix under climate change, accounting for the biophysical and economic effects of tree mixtures. The approach is demonstrated using an example from Southeast Germany. The optimal tree species mixtures under simulated climate change effects could buffer but not completely mitigate undesirable economic consequences. Even under optimally mixed forest stands, the risk-adjusted economic value decreased by 28%. Mixed stands economically outperform block mixtures for all climate scenarios. Our results underline the importance of mixed stands to mitigate the economic consequences of climate change. Mechanistic bio-economic models help to understand consequences of uncertain input variables and to design purposeful adaptation strategies.

The 10% wind speed rule of thumb for estimating a wildfire’s forward rate of spread in forests and shrublands

Abstract: The collective analysis of a relatively large number of wildfire observations documented in conifer forests, dry eucalypt forests and temperate shrublands revealed that the forward rate of fire spread is roughly 10% of the average 10-m open wind speed, provided both are expressed in the same units (e.g. km h −1 ). Knowledge of a wildfire’s forward spread rate is a prerequisite for defining adequate fire suppression strategies and to ensure timely public warnings. We wanted to investigate the possibility that a simple relationship exists that could be used as a first approximation for quickly estimating a wildfire’s spread rate simply from the open wind speed alone. We analysed data from a number of high-intensity wildfire observations (n = 118) documented in temperate shrublands, Australian dry eucalypt forests and North American conifer forests to examine the suitability and soundness of a relationship between wind speed and rate of fire spread. We also contrasted the performance of the best function against established fire spread rate models for the three fuel types. The resulting rule of thumb is that the forward rate of spread of wildfires burning in forests and shrublands in relatively dry conditions is approximately equal to 10% of the average 10-m open wind speed, where both values are expressed in the same units. The rule of thumb gives the most accurate results for dry fuel and high wind speed conditions with reduced bias and mean relative errors lower than 50%. Under these conditions, the error statistics are comparable to those obtained by the established fire spread rate models. The rule is not applicable to grasslands.

On the need to consider wood formation processes in global vegetation models and a suggested approach

Abstract: Dynamic global vegetation models are key tools for interpreting and forecasting the responses of terrestrial ecosystems to climatic variation and other drivers. They estimate plant growth as the outcome of the supply of carbon through photosynthesis. However, growth is itself under direct control, and not simply controlled by the amount of available carbon. Therefore predictions by current photosynthesis-driven models of large increases in future vegetation biomass due to increasing concentrations of atmospheric CO 2 may be significant over-estimations. We describe how current understanding of wood formation can be used to reformulate global vegetation models, with potentially major implications for their behaviour.

Evidence of climate effects on the height-diameter relationships of tree species

Abstract: The mean temperature from March to September affects the height-diameter relationship of many tree species in France. For most of these species, the temperature effect is nonlinear, which makes the identification of an optimal temperature possible. Increases in mean temperature could impact the volume supply of commercial species by the end of the twenty-first century. Height-diameter (HD) relationships are central in forestry since they are essential to estimate tree volume and biomass. Since the late 1960s, efforts have been made to generalize models of HD relationships through the inclusion of plot- and tree-level explanatory variables. In some recent studies, climate variables such as mean annual temperature and precipitation have been found to have a significant effect on HD allometry. However, in these studies, the effects were all considered to be linear or almost linear, which supposes that there is no optimal temperature and no optimal precipitation. In this study, we tested the hypothesis that an optimum effect of temperature and precipitation exists on tree heights. We fitted generalized models of HD relationships to 44 tree species distributed across France. To make sure that the climate variables would not hide some differences in terms of the local environment, the models included explanatory variables accounting for competition, tree social status and other plot-level factors such as slope inclination and the occurrence of harvesting in the last five years. It turned out that the temperature effect was significant for 33 out of 44 species and an optimum was found in 26 cases. The precipitation effect was linear and was found to be significant for only seven species. Although the two climate variables did not contribute as much as the competition and the social status indices to the model fit, they were still important contributors. Under the representative concentration pathway (RCP) 2.6 and the assumptions of constant form factors and forest conditions in terms of competition and social statuses, it is expected that approximately two thirds of the species with climate-sensitive HD relationships will generally be shorter. This would induce a decrease in volume ranging from 1 to 5% for most of these species. Forest practitioners should be aware that the volume supply of some commercial species could decrease by the end of the twenty-first century. However, these losses could be partly compensated for by changes in the form factors and the species distributions.

Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought

Abstract: Key messageAbundant Neotropical canopy-tree species are more resistant to drought-induced branch embolism than what is currently admitted. Large hydraulic safety margins protect them from hydraulic failure under actual drought conditions.ContextXylem vulnerability to embolism, which is associated to survival under extreme drought conditions, is being increasingly studied in the tropics, but data on the risk of hydraulic failure for lowland Neotropical rainforest canopy-tree species, thought to be highly vulnerable, are lacking.AimsThe purpose of this study was to gain more knowledge on species drought-resistance characteristics in branches and leaves and the risk of hydraulic failure of abundant rainforest canopy-tree species during the dry season.MethodsWe first assessed the range of branch xylem vulnerability to embolism using the flow-centrifuge technique on 1-m-long sun-exposed branches and evaluated hydraulic safety margins with leaf turgor loss point and midday water potential during normal- and severe-intensity dry seasons for a large set of Amazonian rainforest canopy-tree species.ResultsTree species exhibited a broad range of embolism resistance, with the pressure threshold inducing 50% loss of branch hydraulic conductivity varying from − 1.86 to − 7.63 MPa. Conversely, we found low variability in leaf turgor loss point and dry season midday leaf water potential, and mostly large, positive hydraulic safety margins.ConclusionsRainforest canopy-tree species growing under elevated mean annual precipitation can have high resistance to embolism and are more resistant than what was previously thought. Thanks to early leaf turgor loss and high embolism resistance, most species have a low risk of hydraulic failure and are well able to withstand normal and even severe dry seasons.

The relation between pressure–volume curve traits and stomatal regulation of water potential in five temperate broadleaf tree species

Abstract: Key message In the five temperate tree species, leaf turgor loss point and the stringency of stomatal regulation are not related to each other and to the drought sensitivity of radial growth, suggesting that additional factors exert a large influence on the species’ drought tolerance.

Harmonisation of stem volume estimates in European National Forest Inventories

Abstract: Volume predictions of sample trees are basic inputs for essential National Forest Inventory (NFI) estimates. The predicted volumes are rarely comparable among European NFIs because of country-specific dbh-thresholds and differences regarding the inclusion of the tree parts stump, stem top, and branches. Twenty-one European NFIs implemented harmonisation measures to provide consistent stem volume predictions for comparable forest resource estimates. The harmonisation of forest information has become increasingly important. International programs and interest groups from the wood industry, energy, and environmental sectors require comparable information. European NFIs as primary source of forest information are well-placed to support policies and decision-making processes with harmonised estimates. The main objectives were to present the implementation of stem volume harmonisation by European NFIs, to obtain comparable growing stocks according to five reference definitions, and to compare the different results. The applied harmonisation approach identifies the deviations between country-level and common reference definitions. The deviations are minimised through country-specific bridging functions. Growing stocks were calculated from the un-harmonised, and harmonised stem volume estimates and comparisons were made. The country-level growing stock results differ from the Cost Action E43 reference definition between − 8 and + 32%. Stumps and stem tops together account for 4 to 13% of stem volume, and large branches constitute 3 to 21% of broadleaved growing stock. Up to 6% of stem volume is allocated below the dbh-threshold. Comparable volume figures are available for the first time on a large-scale in Europe. The results indicate the importance of harmonisation for international forest statistics. The presented work contributes to the NFI harmonisation process in Europe in several ways regarding comparable NFI reporting and scenario modelling.

A dataset of forest volume deadwood estimates for Europe

Abstract: ICP-Forests relies on a representative pan-European network based on a 16 × 16 km grid-net covering around 6,000 plots. Dead wood volumes for 3,243 plots, related to 19 European Countries, are presented in this data paper as a result of harmonised sampling procedure, and under compliance with FAIR Data Principles. Dataset access is at . Associated metadata are available at .

The effect of thinning on mechanical properties of Douglas fir, Norway spruce, and Sitka spruce

Abstract: The first author was supported in undertaking this work by a Teagasc Walsh Fellowship. This work was also supported by grant aid from the Forest Sector Development Division of the Department of Agriculture, Food and the Marine, Ireland.

Phenology of wood formation in larch (Larix decidua Mill.) trees growing along a 1000-m elevation gradient in the French Southern Alps

Abstract: Spring temperature increase is the main driver of larch tree wood formation onset along a 1000-m elevation gradient in the Southern Alps, while its cessation is more probably controlled by water stress at the lowest elevation and photoperiod at higher ones. The survival of perennial plants depends on their adaptation to changing environment and specially temperature, which in trees is notably implemented through wood formation process. Our main objective is to understand how the phenology of wood formation is related to environmental factors and to temperature in particular. We monitored the xylogenesis of 60 larch trees, distributed in four stands along an elevation gradient of 1000 m in the French Southern Alps. Cambial activity started around mid-May at the lowest site (1350 m) and around mid-June at the highest one (2300 m), showing a delay of 5.4 days per °C. The onset of wall-thickening and mature phenophases followed the same linear trend with a delay of 5.2 and 3 days per °C, respectively. Phenophase cessations followed a parabolic trend with trees from the lowest site finishing their growth the first, while those from 1700 m finished the last. Our results show that the onset of xylem formation is mainly driven by spring temperature increase, while its cessation is more related to photoperiod, with water shortage being able to hasten it. Future climatic changes will most probably increase growing season length (but not necessarily wood production) and shift upwards the optimal elevation for larch growth in the Southern Alps.

Inbreeding depression and differential maladaptation shape the fitness trajectory of two co-occurring Eucalyptus species

Abstract: The fitness trajectory of long-lived forest species with mixed mating systems is shaped by a dynamic interplay between endogenous (inbreeding depression) and exogenous (environmental maladaptation) factors. Using two eucalypt species, we show that the timing and translation of inbreeding depression from growth to survival through size-dependent mortality may vary between species and may intensify under climate stress. Inbreeding is an important issue in evolutionary biology and breeding, as it can reduce genetic diversity and fitness and ultimately limit the adaptive response of populations to environmental stress. This is particularly relevant to forest tree species, such as eucalypts, which have a mixed mating system and long-generation intervals. Examine the role of inbreeding depression on the fitness trajectory of two eucalypt species, Eucalyptus globulus and E. ovata. Survival, growth, and reproduction of controlled-crossed self and outcross, as well as open-pollinated progeny of each species grown in a common garden field trial were assessed over a 28-year period and analysed using mixed effect models. Inbreeding depression resulted in the purging of inbred progeny through size-dependent mortality with the most death of inbreds occurring between 4 and 13 years. After this period, differential maladaptation of the species was the dominant cause of mortality, associated with a period of drought and high temperatures, and it was evident first in the selfed populations. This study demonstrates the dynamic nature of the selective process in purging inbred progeny from a population, with inbreeding depression the dominant factor early in stand development, leading to older stands being dominated by outcrosses.

Fire activity and burned forest lands decreased during the last three decades in Spain

Abstract: Fire activity has decreased in the last decades in Spain as a whole and in most provinces. However, fire risk factors have increased. Wildfires are burning preferentially treeless areas. Flammable pine areas burn less, while the less flammable oak forests burn more. This decreasing fire activity coincides with increasing fire suppression resources. Climate and other fire risk factors are changing across the world, including the Mediterranean region. It is important to determine how fire activity is responding to such changes. To identify spatio-temporal changes in fire frequency and size, main tree species burned, and their association with changes in climate, land-use and land-cover, and fire suppression. Analysis of trends, breakpoints, and association among the time series of fire variables and fire risk factors during 1980–2013 in Spain at country and provincial levels. Wildfires in Spain have been decreasing in number, burned area, mean, and largest fire sizes. Fires are more frequently burning treeless areas than forests. Pine forests are burning less, while oak forests are burning more. Fire suppression resources, particularly aerial ones, increased significantly. Risk factors like the mean summer fire weather index, and the forested and the artificial areas all increased. Despite increasing fire risk factors, wildfires have decreased at the country as a whole and in most provinces in Spain during the last 34 years.

Forest stand productivity derived from site conditions: an assessment of old Douglas-fir stands ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) in Central Europe

Abstract: Douglas-fir growth correlates with the climate, the soil moisture regime, and the soil nutrient status, reflecting a broad physiological amplitude. Even though planting this non-native tree species is suggested as a viable strategy to improve adaptiveness of European forests to a more extreme climate and to assure future productivity, the expected temperature increase may induce a decline in forest stand productivity for Douglas-fir in already warm and dry regions. Tree species selection is one of the most important forest management decisions to enhance forest productivity and stand stability on a given site. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), a non-native species from north-western America, is seen as an important additional species option for adapting Central European forests to a changing climate. This study assesses Douglas-fir forest productivity derived from site conditions. We investigate climatic and physico-chemical soil characteristics and productivity of 28 mature Douglas-fir stands growing on siliceous, as well as carbonate bedrock material in southern Germany and north-eastern Austria. The importance of climatic and physico-chemical soil characteristics was analyzed with the machine learning method Random Forests. The results show that Douglas-fir growth correlates with climate, soil moisture, and soil nutrient availability derived from ten climatic and physico-chemical soil parameters. The broad pH optimum between 4.5 and 7.2 reflects the broad physiological amplitude of Douglas-fir, and no significant differences were detectable between carbonate and siliceous bedrock. We also conclude that climate change may induce a forest stand productivity decline, because lower productivity with the highest mean summer temperature across our study range was observed at the warmest sites in Eastern Austria.

Secondary disturbances of low and moderate severity drive the dynamics of eastern Canadian boreal old-growth forests

Abstract: Both low- and moderate-severity secondary disturbances are drivers of eastern Canadian boreal old-growth forests dynamics. Moderate-severity disturbances reflect mainly spruce budworm outbreaks. Low-severity disturbances are produced by both spruce budworm outbreaks and random events such as windthrow. Each level of disturbance severity has a specific impact on stand dynamics, and both shape the diversity of boreal old-growth forests. A regular succession of low-severity disturbances is seen as determining the dynamics of the old-growth stage (gap dynamics); however, recent studies suggest that moderate-severity secondary disturbances also play an important role in the dynamics of eastern Canadian boreal forests. This study aims to determine if eastern Canadian boreal old-growth forests are driven by a combination of low- and moderate-severity secondary disturbances. We reconstructed the 200-year disturbance history of 20 boreal old-growth stands using dendrochronological analysis. We discriminated low- from moderate-severity disturbances based on their respective influence on mean stand growth. The secondary disturbance regime of eastern Canadian boreal old-growth forests varies highly over time, reflected by disturbance peaks in the chronological record. Most peaks occurred during spruce budworm outbreaks related to both low- and moderate-severity disturbances. Between each peak, low-severity disturbances dominate. Each level of disturbance severity has specific consequences for stand dynamics. Both low and moderate secondary disturbances are drivers of forest dynamics in eastern Canadian boreal old-growth stands and shape the structural diversity of these stands. The complexity of these dynamics should be recognized in management planning to ensure the efficiency of old-growth forest conservation policies.

Global change impacts on forest and fire dynamics using paleoecology and tree census data for eastern North America

Abstract: The tree census, paleopollen, fossil charcoal, human population, and climate data presented here provide unique support for important anthropogenic influences on fire over the last 2000 years in the eastern USA. This includes multiple instances of climate fire anomalies that may be best explained by the role of human-caused burning. The coupling of paleoecological and tree census data to address larger global change questions is a novel research approach to describe and ascribe recent vegetation dynamics vis-a-vis the climate versus disturbance debate. The aims of the study are to (1) compile and compare pre-European settlement versus modern upland arboreal pollen and tree survey data from a large number of studies in various forest regions in the eastern USA, (2) analyze fossil charcoal dating back 2000 years for the northern versus central/southern tiers of the eastern USA, and (3) compare and contrast compositional and ecophysiological attributes for both datasets and temporal changes to known climate or disturbance phenomena to elucidate global change impacts and the drivers of forest change. We analyzed paleoecological (pollen and charcoal) and tree census studies to compare protohistoric and modern vegetation assemblage for eastern North America, including the drivers of forest change. A total of seven forest types in the north and central regions of the eastern USA were used to co-analyze fossil pollen, fossil charcoal, and tree survey data. Disparities and consistencies existed when independently assessing witness tree and pollen records. Although forests north of the tension zone line (TZL) contained mostly Fagus, Pinus, Tsuga, and Acer witness trees, pollen records were dominated, as expected, by high-pollen-producing Pinus, Quercus, Tsuga, and Betula. Here, present-day pollen and tree survey data revealed significant declines in Fagus, Pinus, Tsuga, and Larix and increases in Acer, Populus, Fraxinus, Quercus, and Abies. South of the TZL, both witness tree and pollen records pointed to Quercus and Pinus domination, with declines in Quercus and Castanea and increases in Acer and Betula based on present-day data. Modern assemblages comprise tree genera that are increasingly cool-adapted, shade-tolerant, drought-intolerant pyrophobes. Paleocharcoal data from 1 to 1750 AD indicate a slight increase in burning in southern forests and stable levels in the north, despite the increasing cold associated with the Little Ice Age. The most significant increase in burning followed the dramatic increase in human population associated with European settlement prior to the early twentieth century. Post-1940, fire suppression was an ecologically transformative event in all datasets. Our analysis identifies multiple instances in which fire and vegetation changes were likely driven by shifts in human population and land use beyond those expected from climate alone.

Temporal and spatial high-resolution climate data from 1961 to 2100 for the German National Forest Inventory (NFI)

Abstract: Keymessage The “NFI 2012 environmental data base climate” is part of the environmental database of the German National Forest Inventory. It contains climate information for 26,450 inventory points generated from gridded daily climate data for 1961–2100 at a spatial resolution of 250 m. Grids are based on DWD-Observations and REMO EURO-CORDEX climate projections. Access to the databases is provided via the URL: https://doi.org/10.3220/DATA/20180823-102429. Associated metadata are available at https://agroenvgeo.data.inra.fr/geonetwork/srv/fre/ catalog.search#/metadata/d0789030-c94e-4883-8d38-2a7332c98673.

Hardwood injury and mortality associated with two shot hole borers, Euwallacea spp., in the invaded region of southern California, USA, and the native region of Southeast Asia

Abstract: We assessed the impact of the polyphagous shot hole borer (PSHB), Euwallacea whitfordiodendrus (Schedl), and Kuroshio shot hole borer (KSHB), E. kuroshio Gomez and Hulcr, on hardwood trees in southern California, southwestern China, and northwestern Vietnam. The highest levels of mortality were recorded from 10 of 39 tree species in the survey, and these were primarily native tree species. Two invasive shot hole borers represent relatively recent introductions in southern California, USA, and continue to spread and cause injury and mortality to several native and ornamental tree species. They originate from Southeast Asia. Knowledge of tree species susceptibility to these wood-boring beetles is essential to inform better pest management and to evaluate future risk for urban and wildland forests. From 2012 to 2016, ground surveys were conducted in the invaded and native regions at PSHB/KSHB-infested and PSHB/KSHB-uninfested sites to record levels of tree injury and mortality on native and ornamental tree species. In California, several native species of maple, Acer, willow, Salix, and sycamore, Platanus, were infested by either PSHB or KSHB at high rates (> 70%), and comparative rate of infestation by KSHB in all trees and in native trees surpased that by PSHB, whereas rate of infestation by PSHB in ornamental trees surpassed that by KSHB. Mortality of two maple species caused by PSHB exceeded 20%, whereas background mortality rate of hardwoods was 2% in uninfested areas. These data should inform land managers about the tree species at most risk to injury and mortality, facilitate detection ground surveys, and direct prophylactic treatments for these invasive woodborers.

Acorn size is more important than nursery fertilization for outplanting performance of Quercus variabilis container seedlings

Abstract: Small acorns are usually discarded for seedling cultivation because they reduce plant quality. This, however, can potentially reduce genetic diversity of plantations. The use of small acorns will result in the production of a higher proportion of small seedlings containing low nutrient levels and having poor outplanting performance in oak container seedlings. Nursery fertilization partially offsets the negative effect of small acorns on seedling attributes in the nursery but not on outplanting performance. Small acorns result in low-quality seedlings and so are usually discarded in artificial regeneration programs of oak species. This can potentially reduce genetic diversity of plantations. Nursery fertilization may compensate for the low quality of small-acorn seedlings. To assess whether nursery fertilization interacts with Quercus variabilis acorn size to determine seedling morphology and nutrition in the nursery and outplanting performance. Acorns of three size classes were used to cultivate seedlings with or without fertilization. Seedling emergence, nursery morphology and nutrient status, and outplanting survival and growth were measured. Small acorns represented 41% of the seed batch. Most acorn size variation occurred within trees rather than among trees. Smaller acorns were associated with lower emergence and resulted in smaller seedlings that had lower nutrient content levels. Nursery fertilization slightly increased seedling growth for all acorn sizes; it also strongly increased nutrient content, especially in small-acorn seedlings. Two years after planting, survival of small-acorn seedlings was 32% lower than the survival of medium- and large-acorn plants. Fertilization did not affect survival, but it did increase size, especially of small-acorn seedlings, though they did not achieve the growth of large-acorn seedlings. Nursery fertilization increases growth and nutrient status, but not outplanting performance, of small-acorn seedlings.

Increased tolerance to Phytophthora cinnamomi in offspring of ink-diseased chestnut ( Castanea sativa Miller) trees

Abstract: Increased tolerance to Phytophthora cinnamomi was observed in small-sized offspring of ink-diseased chestnut trees, suggesting that a virulent pathogen can trigger a defence response of trees in the subsequent generation. Increased tolerance to water stress was not observed in offspring of chestnut trees. In sweet chestnut (Castanea sativa Miller), P. cinnamomi Rands is responsible for the widespread and destructive ink disease. We investigated if the susceptibility of C. sativa to water stress and P. cinnamomi depends on the health status of mother trees. Plants were grown from seeds collected from healthy and ink-diseased chestnut trees. Leaf wilting after drought exposure and plant mortality after pathogen inoculation were assessed. Offspring of ink-diseased trees had poorer performance in plant height and root biomass than offspring of healthy trees, with allocation of biomass to seeds mediating this effect. Leaf wilting due to water stress was similar in offspring of healthy and P. cinnamomi-infected trees. However, increased tolerance to P. cinnamomi was observed in small-sized seedlings, suggesting that tolerance in C. sativa may involve growth costs. This is the first report of increased tolerance to P. cinnamomi in plants germinating from a diseased tree. The results suggest that an invasive pathogen can regulate the performance and prime a defence response of a forest tree species in the subsequent generation, and generate conflicting selection pressures related to plant size.

Opportunities and challenges for an Indonesian forest monitoring network

Abstract: Permanent sampling plots (PSPs) are a powerful and reliable methodology to help our understanding of the diversity and dynamics of tropical forests. Based on the current inventory of PSPs in Indonesia, there is high potential to establish a long-term collaborative forest monitoring network. Whilst there are challenges to initiating such a network, there are also innumerable benefits to help us understand and better conserve these exceptionally diverse ecosystems.

Quantifying the risk mitigation efficiency of changing silvicultural systems under storm risk throughout history

Abstract: Silvicultural adaptations throughout history resulted in an increasing mitigation efficiency towards storm risk, quantifiable through an increasing conditional value at risk and decreasing average damage loss. Recently recommended silvicultural systems for spruce stands in Central Europe, like the group selection system, showed the highest mitigation efficiency towards storm, compared to past thinning from below or thinning from above systems. Storms may affect forests and their productivity. Silvicultural systems adapted throughout history to maintain economic performance of forests under storm risk. This paper aims to (i) determine the conditional value at risk (CVaR) as the expected value of the lower 5% quantile of the simulated economic performance distribution of different silvicultural systems under storm risk, (ii) demonstrate the effect of historical cost and price changes on their performance, and (iii) assess their performance considering revenues from multiple ecosystem services. We used an individual-tree growth model to simulate three silvicultural systems, namely thinning from below, thinning from above and group selection. An additive land expectation value is introduced to reflect long-term timber and carbon sequestration revenues. The performance of silvicultural systems under storm risk is assessed, using an empirical storm model combined with Monte Carlo simulations. The group selection system showed the highest CVaR and therefore highest mitigation efficiency towards storm risk. Moreover, it showed the least sensitivity towards historical cost and price changes. Inclusion of other ecosystem services (carbon sequestration) showed minor sensitivity to storm risk. Silvicultural adaptations throughout history resulted in increasing mitigation efficiency towards storm risk. Integration of silvicultural adaptation is crucial in the further development of forest management, especially approaching risks from climate change.

Tree and stand level estimations of Abies alba Mill. aboveground biomass

Abstract: We provided a complete set of tree- and stand-level models for biomass and carbon content of silver fir Abies alba . This allows for better characterization of forest carbon pools in Central Europe than previously published models. The best predictor of biomass at the stand level is stand volume, and the worst are stand basal area and density. Among European forest-forming tree species with high economic and ecological significance, Abies alba Mill. is the least characterized in terms of biomass production. To provide a comprehensive set of tree- and stand-level models for A. alba biomass and carbon stock. We hypothesized that (among tree stand characteristics) volume will be the best predictor of tree stand biomass. We studied a chronosequence of 12 A. alba tree stands in southern Poland (8–115 years old). We measured tree stand structures, and we destructively sampled aboveground biomass of 96 sample trees (0.0–63.9 cm diameter at breast height). We provided tree-level models, biomass conversion and expansion factors (BCEFs) and biomass models based on forest stand characteristics. We developed general and site-specific tree-level biomass models. For stand-level models, we found that the best predictor of biomass was stand volume, while the worst were stand basal area and density. Our models performed better than other published models, allowing for more reliable biomass predictions. Models based on volume are useful in biomass predictions and may be used in large-scale inventories.

The utility of terrestrial photogrammetry for assessment of tree volume and taper in boreal mixedwood forests

Abstract: This study showed that digital terrestrial photogrammetry is able to produce accurate estimates of stem volume and diameter across a range of species and tree sizes that showed strong correspondence when compared with traditional inventory techniques. This paper demonstrates the utility of the technology for characterizing trees in complex habitats such as boreal mixedwood forests. Accurate knowledge of tree stem taper and volume are key components of forest inventories to manage and study forest resources. Recent developments have seen the increasing use of ground-based point clouds, including from digital terrestrial photogrammetry (DTP), to provide accurate estimates of these key forest attributes. In this study, we evaluated the utility of DTP based on a small set of photos (12 per tree) for estimating stem volume and taper on a set of 15 trees from 6 different species (Populus tremuloides, Picea glauca, Pinus contorta latifolia, Betula papyrifera, Picea mariana, Abies balsamea) in a boreal mixedwood forest in Alberta, Canada. We constructed accurate photogrammetric point clouds and derived taper and volume from three point cloud–based methods, which were then compared with estimates from conventional, field-based measurements. All methods were evaluated for their accuracy based on field-measured taper and volume of felled trees. Of the methods tested, we found that the point cloud–derived diameters in a taper curve matching approach performed the best at estimating diameters at the lowest parts of the stem ( 50% of total height). Using the field-measured DBH and height as inputs to calculate stem volume yielded the most accurate predictions; however, these were not significantly different from the best point cloud-based estimates. The methodology confirmed that using a small set of photographs provided accurate estimates of individual tree DBH, taper, and volume across a range of species and size gradients (10.8–40.4 cm DBH).

Impact of deadwood decomposition on soil organic carbon sequestration in Estonian and Polish forests

Abstract: The deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests. In warmer conditions (Poland), the deadwood decomposition process had a higher rate than in cooler Estonian forests. Soil organic matter fractions analysis can be used to assess the stability and turnover of organic carbon between deadwood and soil in different experimental localities. Deadwood is an important element of properly functioning forest ecosystem and plays a very important role in the maintenance of biodiversity, soil fertility, and carbon sequestration. The main aim was to estimate how decomposition of deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests. The investigation was carried out in six forests in Poland (51° N) and Estonia (58° N). The study localities differ in their mean annual air temperature (of 2 °C) and the length of the growing season (of 1 month). The deadwood logs of Norway spruce (Picea abies (L.) Karst.), common aspen (Populus tremula L.), and silver birch (Betula pendula Roth) were included in the research. Logs in three stages of decomposition (III–V) were selected for the analysis. There were differences in the stock of soil organic carbon in two experimental localities. There was a higher soil carbon content under logs and in their direct vicinity in Polish forests compared to those in the cooler climate of Estonia. Considerable differences in the amount of soil organic matter were found. The light fraction constituted the greatest quantitative component of organic matter of soils associated with deadwood. A higher carbon content in surface soil horizons as an effect of deadwood decomposition was determined for the Polish (temperate) forests. More decomposed deadwood affected soil organic matter stabilization more strongly than less decayed deadwood. This relationship was clearer in Polish forests. Higher temperatures and longer growing periods primarily influenced the increase of soil organic matter free light fraction concentrations directly under and in close proximity to logs of the studied species. The slower release of deadwood decomposition products was noted in Estonian (hemiboreal) forests. The soil organic matter mineral fraction increased under aspen and spruce logs at advanced decomposition in Poland.

Nitrogen addition accelerates the nitrogen cycle in a young subtropical Cunninghamia lanceolata (Lamb.) plantation

Abstract: The nitrogen (N) cycle is likely to accelerate under future climate change. Leaf δ 15 N enrichment factor is an indicator of N status in young Cunninghamia lanceolata (Lamb.) plantation ecosystems. Given that N dynamics across the plant-soil continuum respond more strongly to N addition during the dry season when N leaching is minimal, fertilization during this period represents an optimal strategy for improving soil fertility. The effects of N deposition on N dynamics across the plant–soil continuum in subtropical regions are poorly understood. We investigated the effects of N addition on the N dynamics across the plant–soil continuum in young C. lanceolata plantations in different seasons as well as the effects of N addition on the soil microbial community. During the dry and wet seasons, we measured the concentrations of soil inorganic N, dissolved organic N in soil solution, leaf and root N concentrations, and stable isotope abundances, and soil microbial community characteristics. Short-term N addition decreased the levels of inorganic N, dissolved organic N, and leaf N concentration in the dry season; root N concentration was significantly higher in the high N and low N addition plots. Irrespective of treatment, the NH4+/NO3− ratio was higher in the wet season than in the dry season. The δ15N enrichment factors of the leaf and root in our experiments were closer to zero for all N addition treatments. Redundancy analysis revealed that the variation in the soil microbial community had low correlation with pH. Nitrogen dynamics across the plant–soil continuum respond more strongly to N addition in the dry season. High N deposition in N-saturated subtropical forest soil may rapidly increase leaching, particularly during the wet season. Nutrients in roots are more sensitive to changes in soil nutrient availability than those in leaves. The microbial community is primarily regulated by nutrient availability in the soil rather than by pH.

Is tree age or tree size reducing height increment in Abies alba Mill. at its southernmost distribution limit

Abstract: Conventional methods for estimating the current annual increment of stand volume are based on the uncertain assumption that height increment decreases with tree age. Conversely, size, rather than age, should be accounted for the observed senescence-related declines in relative growth rate and, consequently, implemented in silvicultural manuals. Results stem from a study on Abies alba Mill. at its southern limit of distribution. Many factors limit height increment when age and size increase in large-statured tree species. Height–diameter allometric relationships are commonly used measures of tree growth. In this study, we tested if tree age was the main factor affecting the reduction in height increment of silver fir trees (Abies alba Mill.), verifying also whether tree size had a significant role in ecophysiological-biomechanical limitations to tree growth. The study was carried out in a silver fir forest located in Southern Italy, at the southernmost distribution limit for this species. Through a stratified random sampling, 100 trees were selected. All the selected trees were then felled and the total tree height, height increments (internode distances), diameter at breast height, and diameter increments (ring widths) were measured. The analyses of allometric models and scaling coefficients showed that the correlation between tree age and height increment was not always significant. We may conclude that tree age did not statistically explain the decrease in height increment in older trees. Instead, the increase in tree size and related physiological processes (expressed as product between diameter at breast height and tree height) explained the reduction in height increment in older trees and was the main factor limiting height growth trends in marginal population of silver fir.

Forest-water interactions in the changing environment of south-western Australia

Abstract: In a major Australian city, water supply has been decoupled from forests as a result of management and climate change. Water yield and quality are closely related to forest cover and have been manipulated through broad-scale intervention. The forests remain important for biodiversity protection and considering water as a forest product will fund interventions that maintain the forest’s environmental values. Perth, an Australian city of 2 million people and a potable water demand of 300 GL/year, occurs in a region that has experienced a decline in rainfall and a major reduction in surface runoff to water supply reservoirs over the last 40 years. This has led to a major impact on water policies, with the collapse of surface water supply from forested watersheds resulting in the almost complete substitution of Perth’s water supply with groundwater and desalinated water. Thus, water supply has been decoupled from forests and forest management processes. In this paper, we review the interactions between forest cover and water supply in the drying environment of south-western Australia, exploring studies on the hydrological effects of extensive deforestation for agricultural development, widespread reforestation, forest management, and reduced annual rainfall. We draw conclusions applicable to other regions that are experiencing the combined impacts of climate change and pressures from land-use intensification. We find that streamflow and water quality are clearly linked to forest cover and this is affected by both climate and forest management. Streamflow increases with a reduction of forest cover (through deforestation or thinning) and decreases with reforestation and reduced rainfall. Stream salinity increases with deforestation and decreases with reforestation. Hydrological responses occur where forest cover treatments have been applied and maintained at watershed-scales. Surprisingly, where water yield or quality has been improved, this has not been rewarded financially and there is a need to develop methods of financing treatments to maintain streamflow. Whereas forests were initially maintained for water and timber supply, with biodiversity protection as a co-benefit without a defined value, the decoupling of forests from water supply has substantially reduced the financial resources for any form of direct forest management. As the forests remain important for biodiversity protection, a key recommendation is to consider water as a forest product and thus provide funds for watershed-scale treatments, such as forest thinning, that maintain the forest’s environmental values in a drying climate.

Phosphorus availability in relation to soil properties and forest productivity in Pinus sylvestris L. plantations

Abstract: Pinus sylvestris L. productivity in Spanish plantations is driven by P availability, which, in turn, is determined by the activity of soil microorganisms, responsible for inorganic P solubilization; Fe and Al contents, responsible for P retention; and organic matter, which is source of organic P, inhibits its precipitation as insoluble compounds, and reduces P retention. Phosphorus is often a limiting nutrient in forest ecosystems mainly due to the low solubility of P compounds and the sorption processes occurring in soils. The main aims of this work were to evaluate soil P availability, to assess which soil properties are driving P availability, and to study whether soil P availability is determining forest productivity in Pinus sylvestris L. plantations in Northern Spain. Soil properties and forest productivity were studied in 34 plots located in monospecific P. sylvestris plantations. Tiessen and Moir (Canadian Society of Soil Science 75–86, 1993) sequential fractionation method was carried out to determine different forms of soil P and to provide a comprehensive assessment of available P in soils. To explore the relationships between these variables, canonical correlation analyses and Pearson’s correlations were studied. Significant correlations were found between P fractions and soil properties related to Fe and Al contents, organic matter, and microbial biomass. Besides, significant correlations were found between site index and the studied P fractions except for P extracted with anion exchange membrane (PAEM) and the recalcitrant P fraction. In the studied soils, P availability is low and the predominant fractions of P are the recalcitrant forms. Aluminum and iron contents in the soils studied play an important role in sorption processes related to the highly and moderately labile P fractions and the organic phosphorus. P availability seems to be regulated by both processes: biochemical mineralization, where phosphatase activity is relevant, and biological mineralization of the soil organic matter. Phosphorus availability affects forest productivity in the Pinus sylvestris plantations studied.