Empirical and process-based models predict enhanced beech growth in European mountains under climate change scenarios: A multimodel approach.

Process-based models and empirical modelling techniques are frequently used to (i) explore the sensitivity of tree growth to environmental variables, and (ii) predict the future growth of trees and forest stands under climate change scenarios. However, modelling approaches substantially influence predictions of the sensitivity of trees to environmental factors. Here, we used tree-ring width (TRW) data from 1630 beech trees from a network of 70 plots established across European mountains to build empirical predictive growth models using various modelling approaches. In addition, we used 3-PG and Biome-BGCMuSo process-based models to compare growth predictions with derived empirical models. Results revealed similar prediction errors (RMSE) across models ranging between 3.71 and 7.54 cm2 of basal area increment (BAI). The models explained most of the variability in BAI ranging from 54 % to 87 %. Selected explanatory variables (despite being statistically highly significant) and the pattern of the growth sensitivity differed between models substantially. We identified only five factors with the same effect and the same sensitivity pattern in all empirical models: tree DBH, competition index, elevation, Gini index of DBH, and soil silt content. However, the sensitivity to most of the climate variables was low and inconsistent among the empirical models. Both empirical and process-based models suggest that beech in European mountains will, on average, likely experience better growth conditions under both 4.5 and 8.5 RCP scenarios. The process-based models indicated that beech may grow better across European mountains by 1.05 to 1.4 times in warmer conditions. The empirical models identified several drivers of tree growth that are not included in the current process-based models (e.g., different nutrients) but may have a substantial effect on final results, particularly if they are limiting factors. Hence, future development of process-based models may build upon our findings to increase their ability to correctly capture ecosystem dynamics.

Interrelationships among mountain relief, surface organic layer, soil organic carbon, and its mineral association under subarctic forest tundra.

Efforts to estimate the impact of climate change-induced forest expansion on soil carbon stocks in cold regions are hindered by the lack of soil organic carbon (SOC) concentration data. The presented study addressed the information gap by establishing SOC concentration and its variability in two catchments inside the vast, remote, and rugged Putorana Plateau. Additionally, it explored interrelationships among the terrain relief, vegetation cover, surface organic layer, SOC and its mineral association on the northernmost boundary of the forest-tundra biome traversing the northwestern part of the Central Siberian Tableland. Soil samples were taken from the active layer on the slope base, middle, and below the upper forest boundary. Subsequently, they were analyzed for SOC concentration by dry combustion. Multiple linear regression identified associations between slope angle and surface organic layer thickness and between SOC concentration and surface organic layer thickness, clay content, and dithionite-extracted Al. Clay content and surface organic layer thickness explained 68% of the overall SOC concentration variability. When used with data produced by remote sensing-based multipurpose large-scale mapping of selected biophysical factors, the acquired regression equations could aid the estimation of SOC across the rugged terrain of the Siberian Traps.

Dynamics of internal isoprenoid metabolites in young Picea abies (Norway spruce) shoots during drought stress conditions in springtime.

Currently, large areas of Picea abies (Norway spruce) stands in Europe are increasingly affected by drought and heat waves. Moreover, early spring drought has occurred with much higher frequency. Our work focuses on physiological changes induced by drought in four-year-old spruce seedlings during shoot elongation. We investigated drought effect on photosynthetic rate, concentration of abscisic acid and its metabolites, amount and composition of monoterpenes in needles of seedlings from five different provenances (altitude range 550-1280 m above sea level) in Western Carpathians. Spruce seedlings subjected to one-month drought stress of moderate intensity (about 50% of soil water content at the end of experiment) showed significant reduction of CO2 uptake and increased concentration of ABA related to untreated controls. Induced drought affected needle monoterpene content and composition. Observed changes in drought-induced physiological parameters were influenced by seedling provenance. The provenance from 920 m above sea level showed the greatest sensitivity to drought with significantly highest ABA content and, at the same time, a clear decline of CO2 uptake and amounts of total monoterpenes. Our results indicating intra-specific provenance-related variability in physiological response of spruce seedlings to drought may provide a basis for improved reforestation strategies in drought risk areas.

Modelling Impact of Site and Terrain Morphological Characteristics on Biomass of Tree Species in Putorana Region.

(1) Background: Boreal forests influence global carbon balance and fulfil multiple ecosystem services. Their vegetation growth and biomass are significantly affected by environmental conditions. In the present study we focused on one of the least accessible and least studied parts of the boreal region situated in the western part of Putorana plateau, Central Siberia (Lama and Keta lakes, Krasnoyarsk region), northern Russia. (2) Methods: We derived local height-diameter and crown radius-height models for six tree species. We used univariate correlation and multiple regression analyses to examine the relationships between tree biomass and environmental conditions. (3) Results: Total tree biomass stock (aboveground tree biomass + aboveground and buried deadwood) varied between 6.47 t/ha and 149 t/ha, while total deadwood biomass fluctuated from 0.06 to 21.45 t/ha. At Lama, biomass production decreased with elevation. At Keta, the relationship of biomass to elevation followed a U shape. Stand biomass changed with micro-terrain morphology and soil nutrient content, while the patterns were location-specific. (4) Conclusions: The majority of the derived models were significant and explained most of the variability in the relationships between tree diameter or crown radius and tree height. Micro-site environmental conditions had a substantial effect on tree biomass in the studied locations.

Effects of Phytophthora Inoculations on Photosynthetic Behaviour and Induced Defence Responses of Plant Volatiles in Field-Grown Hybrid Poplar Tolerant to Bark Canker Disease.

Bark cankers accompanied by symptoms of decline and dieback are the result of a destructive disease caused by Phytophthora infections in woody plants. Pathogenicity, gas exchange, chlorophyll a fluorescence, and volatile responses to P. cactorum and P. plurivora inoculations were studied in field-grown 10-year-old hybrid poplar plants. The most stressful effects of P. cactorum on photosynthetic behaviour were found at days 30 and 38 post-inoculation (p.-i.), whereas major disturbances induced by P. plurivora were identified at day 30 p.-i. and also belatedly at day 52 p.-i. The spectrum of volatile organic compounds emitted at day 98 p.-i. was richer than that at day 9 p.-i, and the emissions of both sesquiterpenes α-cubebene and germacrene D were induced solely by the Phytophthora inoculations. Significant positive relationships were found between both the axial and the tangential development of bark cankers and the emissions of α-cubebene and ß-caryophyllene, respectively. These results show that both α-cubebene and germacrene D are signal molecules for the suppression of Phytophthora hyphae spread from necrotic sites of the bark to healthy living tissues. Four years following inoculations, for the majority of the inoculated plants, the callus tissue had already closed over the bark cankers.

Management After Windstorm Affects the Composition of Ectomycorrhizal Symbionts of Regenerating Trees but Not Their Mycorrhizal Networks.

Due to ongoing climate change, forests are expected to face significant disturbances more frequently than in the past. Appropriate management is intended to facilitate forest regeneration. Because European temperate forests mostly consist of trees associated with ectomycorrhizal (ECM) fungi, understanding their role in these disturbances is important to develop strategies to minimize their consequences and effectively restore forests. Our aim was to determine how traditional (EXT) and nonintervention (NEX) management in originally Norway spruce (Picea abies) forests with an admixture of European larch (Larix decidua) affect ECM fungal communities and the potential to interconnect different tree species via ECM networks 15 years after a windstorm. Ten plots in NEX and 10 plots in EXT with the co-occurrences of Norway spruce, European larch, and silver birch (Betula pendula) were selected, and a total of 57 ECM taxa were identified using ITS sequencing from ECM root tips. In both treatments, five ECM species associated with all the studied tree species dominated, with a total abundance of approximately 50% in the examined root samples. Because there were no significant differences between treatments in the number of ECM species associated with different tree species combinations in individual plots, we concluded that the management type did not have a significant effect on networking. However, management significantly affected the compositions of ECM symbionts of Norway spruce and European larch but not those of silver birch. Although this result is explained by the occurrence of seedlings and ECM propagules that were present in the original forest, the consequences are difficult to assess without knowledge of the ecology of different ECM symbionts.

Photosynthetic performance of silver fir (Abies alba) of different origins under suboptimal growing conditions.

Understanding of the intraspecific variability in the physiological stress response of trees may enable to mitigate the impact of climate change on forest ecosystems in the future. We studied the photosynthetic performance of five silver fir (Abies alba Mill.) provenances originating from climatically distinct localities. The study was performed in the trial plot of the silver fir provenance experiment IUFRO 2005 on two dates: in the early summer and in the late summer. Heat waves and a decrease in water availability occurred between the two measurement dates, allowing us to study the response of the provenances to suboptimal growing conditions. The provenances were evaluated at the level of PSII photochemistry and CO2 assimilation by measuring photosynthesis-related pigment content, chlorophyll a fluorescence, and gas exchange parameters. Significant climatic clines were confirmed: the photosynthetic performance before and after the stress period increased with the increasing altitude and precipitation at the site of origin. In contrast, photosynthetic performance declined with the increasing temperature and Ellenberg's quotient of the origin site. We concluded that provenances originating from high altitudes, corresponding well with more humid and colder conditions in Central Europe, showed the greatest photosynthetic performance and were less responsive to moderate heat and drought. This documents inter-population variation in physiological traits, which needs to be considered in setting rules and recommendations for the transfer of forest reproductive materials.

Evaluation of the Carbon Dioxide Production by Fungi Under Different Growing Conditions.

Production of carbon dioxide, as one of the ultimate products of fungal metabolism, can be used to quantify and measure their metabolic rate under different conditions, thus aiding in finding the optimal substrate and environment for cultivation of wood-destroying fungi. This study is focused on species Pleurotus ostreatus and Ganoderma lucidum,. These species are also cultivated for mycorestoration as well as their medicinal and nutritional value. To quantify their metabolical rate on various substrates (agar medium, wood chips, rye straw), multiple custom-built airtight chambers were equipped with CO2 probes (GMP 343, Vaisala, Finland) to measure the production of carbon dioxide. The highest values were measured during the primordial production on rye straw substrate, with the average values of 1.09 g CO2 kg-1 (substrate) h-1. These values varied significantly between various substrates, fungal species and development stages.

Management regime is the most important factor influencing ectomycorrhizal species community in Norway spruce forests after windthrow.

Ectomycorrhizal (ECM) fungi, as symbionts of many tree species in temperate forests, are thought to play an important role in forest regeneration processes after large disturbances. Their reaction to different disturbance and management regimes was studied in spruce forests (Lariceto-Piceetum) 10 years after a severe windthrow in the Tatra National Park (Slovak Republic). ECM community structure was compared between different "management types″-cleared area (EXT), area affected by wildfire (FIRE), uncleared area left for natural development (NEX), and mature forest as a control (REF). Based on Illumina sequencing of soil samples, we determined that the percentage of sequences assigned to ECM fungi decreased with increasing disturbance and management intensity (REF → NEX → EXT → FIRE). Similarly, the total number of ECM species per each of ten sampling points per plot (100 ha) differed between managed (EXT-11 species, FIRE-9) and unmanaged (NEX-16, REF-14) treatments. On the other hand, the percentage of sequences belonging to ericoid mycorrhizal fungi increased. Management type significantly influenced the composition of the ECM community, while vegetation and soil characteristics explained less data variation. The ECM species assemblage of the unmanaged site (NEX) was the most similar to the mature forest, while that of the burnt site was the most different. Thelephora terrestris dominated in all treatments affected by windthrow, accompanied by Tylospora fibrillosa (NEX) and Tylospora asterophora (EXT and FIRE). Management regime was also the most important factor affecting ECM species composition on the roots of spruce seedlings assessed by Sanger sequencing.

Soil microbial characteristics at the monitoring plots on windthrow areas of the Tatra National Park (Slovakia): their assessment as environmental indicators.

This study focused on the responses of soil microorganisms to different management regimes on disturbed windthrow areas. Microbial parameters potentially serving as indicators of environmental changes within a long-term monitoring of forest development after large-scale disturbance events were assessed. Basal and substrate-induced respiration, N mineralisation, catalase activity, microbial biomass as well as functional diversity based on Biolog assay were determined in soil samples from three disturbed plots and an undisturbed reference plot in the Tatra National Park (Slovakia) since 2006. A relative congruence of inter-annual trends of microbial activity indicators at all plots results from a common response of microbiota to changes of climate at the landscape level after forest stands were destroyed. While catalase activity and functional diversity proved to be useful indicators of temporal trends, microbial biomass seems to reflect different management regimes at the disturbed plots.

New international long-term ecological research on air pollution effects on the Carpathian Mountain forests, Central Europe.

An international cooperative project on distribution of ozone in the Carpathian Mountains, Central Europe was conducted from 1997 to 1999. Results of that project indicated that in large parts of the Carpathian Mountains, concentrations of ozone were elevated and potentially phytotoxic to forest vegetation. That study led to the establishment of new long-term studies on ecological changes in forests and other ecosystems caused by air pollution in the Retezat Mountains, Southern Carpathians, Romania and in the Tatra Mountains, Western Carpathians on the Polish-Slovak border. Both of these important mountain ranges have the status of national parks and are Man & the Biosphere Reserves. In the Retezat Mountains, the primary research objective was to evaluate how air pollution may affect forest health and biodiversity. The main research objective in the Tatra Mountains was to evaluate responses of natural and managed Norway spruce forests to air pollution and other stresses. Ambient concentrations of ozone (O(3)), sulfur dioxide (SO(2)), nitrogen oxides (NO(x)) as well as forest health and biodiversity changes were monitored on densely distributed research sites. Initial monitoring of pollutants indicated low levels of O(3), SO(2), and NO(x) in the Retezat Mountains, while elevated levels of O(3) and high deposition of atmospheric sulfur (S) and nitrogen (N) have characterized the Tatra Mountains. In the Retezat Mountains, air pollution seems to have little effect on forest health; however, there was concern that over a long time, even low levels of pollution may affect biodiversity of this important ecosystem. In contrast, severe decline of Norway spruce has been observed in the Tatra Mountains. Although bark beetle seems to be the immediate cause of that decline, long-term elevated levels of atmospheric N and S depositions and elevated O(3) could predispose trees to insect attacks and other stresses. European and US scientists studied pollution deposition, soil and plant chemistry, O(3)-sensitive plant species, forest insects, and genetic changes in the Retezat and Tatra Mountains. Results of these investigations are presented in a GIS format to allow for a better understanding of the changes and the recommendations for effective management in these two areas.

Leukocyte behavior in a free-flap model following chemotherapy and application of granulocyte colony-stimulating factor (GCSF).

Free-flap reconstruction following tumor resection and chemotherapy is used increasingly in sarcoma patients. Granulocyte colony-stimulating factor (GCSF) is used to stimulate polymorphnuclear leukocytes (PMNs). In this study we used a free-flap model to investigate PMN behavior after chemotherapy and GCSF stimulation. Eighteen Lewis rats were divided into three groups: (1) chemotherapy + vehicle; (2) chemotherapy + GCSF; and (3) control. Group 1 received vinblastine; group 2 received vinblastine plus 300 microg rhGCSF. Blood was drawn for total white cell and PMN counts for 9 days. Free-flap surgery was simulated by isolating the cremaster muscle on its pedicle and anastomosing the artery. Leukocyte-endothelium interaction was assessed by observation of leukocytes rolling and sticking. Leukocyte sequestration was measured by counting leukocytes in the lungs and the abdomen. We found that leukocyte rolling and sticking were significantly increased, while sequestration was decreased in the chemotherapy + GCSF group. We conclude that leukocytes-endothelium interaction after chemotherapy and GCSF administration is increased in the microcirculation. This augments the risk of microvascular compromise and subsequent flap failure, as capillary flow may be altered.