Mixed Conifer Research Articles

Impact of Ice-Storms and Subsequent Salvage Logging on the Productivity of Cunninghamia lanceolata (Chinese Fir) Forests

The impacts of ice-storms on forests have received growing attention in recent years. Although there is a wide agreement that ice-storms significantly affect forest structure and functions, how frequent ice-storms and subsequent salvage logging impact productivity of subtropical coniferous forests in the future still remains poorly understood. In this study, we used the Ecosystem Demography model, Version 2.2 (ED-2.2), to project the impact of salvage logging of ice-storm-damaged trees on the productivity of Cunninghamia lanceolata-dominated coniferous forest and C. lanceolata-dominated mixed coniferous and broadleaved forests. The results show that forest productivity recovery is delayed in coniferous forests when there is no shade-tolerant broadleaved species invasion after ice-storms, and C. lanceolata could continue to dominate the canopy in the mixed coniferous and broadleaved forests under high-frequency ice-storms and subsequent salvage logging. The resistance and resilience of the mixed coniferous and broadleaved forests to high-frequency ice-storms and subsequent salvage logging were stronger compared to coniferous forests. Although conifers could continue to dominate the canopy under shade-tolerant broadleaved species invasion, we could not rule out the possibility of a future forest community dominated by shade-tolerant broadleaf trees because there were few coniferous saplings and shade-tolerant broadleaf species dominated the understory. Our results highlight that post-disaster forest management should be continued after high-frequency ice-storms and subsequent salvage logging in C. lanceolata forests to prevent possible shade-tolerant, late successional broadleaf trees from dominating the canopy in the future.

Persistent composition legacy and rapid structural change following successive fires in Sierra Nevada mixed conifer forests

Mixed conifer forests in the Sierra Nevada, California, USA, face threats from frequent high-severity reburns caused by fuel accumulation and increasingly dry, hot conditions associated with climate change. Stand replacing fire and establishment of expansive shrub patches may result in positive feedbacks causing landscapes to convert to persistent shrubland or grassland. Our objective was to examine changes in mixed conifer forest density and species composition after successive fires across a range of initial and reburn severities. We resampled 134 field plots 5–6 years after the Chips Fire reburned stands initially burned by the Storrie and Rich fires on the Lassen and Plumas National Forests. Generalized Linear Models and post-hoc margins analyses were used to examine the interaction effects of initial and reburn fire severities on changes in conifer tree and seedling densities, percent cover of shrubs, and changes in species composition evaluated using fire tolerance index. We found that successive fires with severities less than high-severity significantly reduced tree densities to values within or close to the natural range of variation for mixed conifer stands. Despite these changes in density, species composition did not shift toward increasing dominance of fire tolerant species; mature trees and seedlings of true firs and other fire intolerant species remained dominant after successive low and moderate severity fires. Seedling establishment pulses were associated with sampling years with abundant precipitation, and unburned, unchanged, and low-severity plots in the reburn sample had significant increases in seedling densities across the range of initial burn severities. Shrub cover increased significantly with only a few reburn severity interactions, but declined significantly with repeated high-severity fire. Although two low- to moderate-severity fires may reduce tree densities to within the natural range of variation, they may not shift species composition towards historical patterns. Selective thinning in areas that burned at low- to moderate-severity may be necessary to restore historical species composition in Sierra Nevada mixed conifer forests.

Late Pleistocene palaeoenvironments and a possible glacial refugium on northern Vancouver Island, Canada: Evidence for the viability of early human settlement on the northwest coast of North America

Multi-proxy palaeoecological analyses of lake cores from two sites on northern Vancouver Island reveal previously undocumented non-arboreal environments in the region during the late Pleistocene. Radiocarbon, pollen, sedimentary ancient DNA (sedaDNA), diatom, and grain size analyses indicate that Topknot Lake on the west coast of northern Vancouver Island was not glaciated in the last 18,500 years, extending into the hypothesized regional glacial maximum. A cold herb-shrub coastal tundra existed at the site from ca. 17,500–16,000 cal BP with species including willows (Salix), grasses (Poaceae), sedges (Cyperaceae), heathers (Ericaceae), and sagebrush (Artemisia). SedaDNA analysis also supports the presence of rare non-arboreal taxa at Topknot Lake during this interval including Jacob's-ladder (Polemonium), bistort (Bistorta), and wild berries (Rubus). After ca. 16,000 cal BP and through the terminal Pleistocene, pine (Pinus), alder (Alnus), and ferns formed open forests under cool and dry conditions. At Little Woss Lake in the mountains of north-central Vancouver Island, fir (Abies) stands dominated from ca. 14,200–14,100 cal BP, then were replaced by open pine woodland with alder and ferns from ca. 14,100–12,000 cal BP. SedaDNA corroborates these plant taxa as well as indicating grizzly bear (Ursus arctos horribilis) and Chinook salmon (Oncorhynchus tshawytscha) in and around the basin by ca. 14,100 cal BP. Mixed conifer forests of pine, western hemlock (Tsuga heterophylla), and alder spread into the island's interior ca. 12,000–11,100 cal BP during the Pleistocene-Holocene transition. The records from these two lakes demonstrate the diachronous development of postglacial ecosystems on northern Vancouver Island. Furthermore, these data provide key evidence for environments that could have supported human populations on the northwest coast of North America for several millennia during the terminal Pleistocene.

Canopy Temperature Is Regulated by Ecosystem Structural Traits and Captures the Ecohydrologic Dynamics of a Semiarid Mixed Conifer Forest Site

AbstractPlant canopy temperature (Tc) is partly regulated by evaporation and transpiration from the canopy surface and can be used to infer changes in stomatal regulation and vegetation water stress. In this study, we used a thermal Unmanned Aircraft Systems in conjunction with eddy covariance, sap flow, and spectral reflectance data to assess the diurnal characteristics of Tc and water stress status over a semiarid mixed conifer forest in Arizona, USA. Diurnal Tc dynamics were closely related to tree sap flow and changes in spectral reflectance associated with stomatal regulation. Consistent with previously reported deviations, we found that on average Tc was 1.8°C lower than the above canopy air temperature (Ta). However, the relationship between Tc and Ta varied significantly according to tree density and tree height classes, with taller and denser trees exhibiting relatively low |Tc‐Ta| (2.4 and 2.1°C cooler canopies, respectively) compared to shorter and less‐dense tree stands (1.7 and 1.5°C cooler canopies, respectively). We used these data to evaluate space‐borne diurnal measurements of Tc and water stress from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission. We found that ECOSTRESS observations of Tc accurately tracked seasonal shifts in diurnal surface temperatures and vegetation water stress, and that site‐level observations of heterogeneity in forest composition and structure could be applied to separate the processes of canopy transpiration and soil evaporation within the ECOSTRESS footprint. This study demonstrates how proximal and satellite remote sensing approaches can be combined to reveal the diurnal and seasonally dynamic nature of Tc and water stress.

Role of forest site type in determining bacterial and biochemical properties of soil

• The biological properties of the soil are determined by the site type. • The tested soils are significant differences in microbiological activity. • Soil from fresh mixed boron is the most fertile soil. The aim of the present study was to investigate the effect of forest site type on the bacterial and biochemical properties of the soil. Data for counts, diversity, and composition of bacterial communities, as well as soil enzymatic activity, was used for the assessment. A determination of the relationships between the parameters was also performed. Soil samples were collected in the Stare Jabłonki Forest Division (north-eastern Poland, Central Europe) from four sites: fresh coniferous forest (Fc), fresh mixed coniferous forest (Fm), fresh mixed forest (Mf), and moist mixed forest (Mm). The tested soils showed significant differences in enzyme activity and microflora. Organotrophic bacteria and actinobacteria proliferated the most in soil from fresh mixed coniferous forest. Organotrophic bacteria grew faster than actinobacteria in the soil, indicating that the former were represented by r-strategists, and the latter – by K-strategists. The soil sampled from site Fc2 (fresh coniferous forest) had the highest values of the diversity index. Alphaproteobacteria (phylum Proteobacteria ) were the dominant bacterial class in the soils, followed by Actinobacteria (phylum Actinobacteria ) and Acidobacteriia (phylum Acidobacteria ). Phyla Proteobacteria , Actinobacteria, and Acidobacteria were most abundantly represented by genera Rhodoplanes, Mycobacterium , and Candidatus Solibacter , respectively. According to the biochemical soil quality index (BA), the soil sampled from site Fc2 (fresh mixed coniferous forest) was the most fertile. The study demonstrates that microbial and biochemical parameters of the soil can serve as an accurate indicator of the status and health of forest ecosystems.

Population structure and dynamics of Pinus koraiensis seedlings regenerated from seeds in a montane region of eastern Liaoning Province, China.

Based on the static life table and survival curve, we explored the population structure and dynamics of Korean pine (Pinus koraiensis) seedlings regenerated from seeds in three different forest belts of Korean pine plantation in a montane region of eastern Liaoning Province. The results showed that the age structure of Korean pine seedlings in three different forest belts (i.e., larch forest belt, mixed coniferous forest belt, and mixed broadleaved forest belt) showed a "∩" type of left skewed distribution. The abundance of seedlings was rich but the mortality rate was high in the early phase, and the abundance of seedlings decreased in the later phase, which indicated that the population was depressing. The survival curve of the population conformed to the Deevey-Ⅱ type. The life expectancy of Korean pine seedlings at each age class in larch forest belt was higher than that in mixed coniferous forest belt and mixed broadleaved forest belt. The survival analysis showed that the survival rate of Korean pine seedlings in three different forest belts decreased but the cumulative mortality rate increased with increasing age. The death density function tended to be flat after the age class of Ⅱ-Ⅲ, while the risk function value showed a decreasing trend with the increases of age. The time series predictive analysis showed that the population showed a certain growth trend with increasing age class, indicating that the population could achieve natural regeneration and have a certain growth potential, but with regeneration obstacles.

Biochar as an Alternative Soil Amendment for Establishment of Northern Highbush Blueberry

Biochar, as a soil amendment, has been reported to improve plant growth by increasing soil moisture and retaining nutrients. In a previous 12-week greenhouse study with highbush blueberry (Vaccinium hybrid), we found that amending soil with biochar alone or in combination with bokashi (fermented wheat bran) increased plant growth relative to unamended soil. The biochar was produced from mixed conifer species during conversion of wood to energy. In the current study, we aimed to validate the greenhouse findings under field conditions in western Oregon. The specific objectives of this 2-year study were to determine the effect of amending soil with biochar or a combination of biochar and bokashi on growth and early fruit production during establishment of northern highbush blueberry (Vaccinium corymbosum L.). To achieve these objectives, we transplanted ‘Duke’ blueberry plants into soil that was either unamended or amended with biochar or 4:1 (v/v) mixtures of biochar and bokashi or biochar and douglas fir [Pseudotsuga menziesii (Mirb.) Franco] sawdust. Each amendment was either applied in the planting hole or incorporated into the row. A treatment with douglas fir sawdust incorporated into the row was also included and represented the industry standard for the region. Plants grown in soil amended with biochar (in the planting hole or row) had 40% to 74% greater total dry weight at the end of the first growing season and 70% to 82% greater fruit yield in the second season than those grown with no amendments or in soil amended with sawdust. However, leaf Mg concentrations were lower with biochar, suggesting it could limit Mg uptake in blueberry. Soil amended with sawdust, on the other hand, was higher in organic matter, microbial activity, and wet stable aggregates than the other soil treatments but resulted in lower leaf N concentrations during the second year after planting. Unlike in the greenhouse study, biochar had no effect on root colonization by mycorrhizal fungi, and there was no benefit to using biochar with bokashi. Adding 4 L of biochar to the planting hole was considerably more economical than applying it to the row and cost $1320/ha less than the industry standard of incorporating sawdust in the row. These findings indicate that biochar is a promising soil amendment for commercial production of highbush blueberry.

Empirically validated drought vulnerability mapping in the mixed conifer forests of the Sierra Nevada

AbstractSevere droughts are predicted to become more frequent in the future, and the consequences of such droughts on forests can be dramatic, resulting in massive tree mortality, rapid change in forest structure and composition, and substantially increased risk of catastrophic fire. Forest managers have tools at their disposal to try to mitigate these effects but are often faced with limited resources, forcing them to make choices about which parts of the landscape to target for treatment. Such planning can greatly benefit from landscape vulnerability assessments, but many existing vulnerability analyses are unvalidated and not grounded in robust empirical datasets. We combined robust sets of ground‐based plot and remote sensing data, collected during the 2012–2016 California drought, to develop rigorously validated tools for assessing forest vulnerability to drought‐related canopy tree mortality for the mixed conifer forests of the Sequoia and Kings Canyon national parks and potentially for mixed conifer forests in the Sierra Nevada as a whole. Validation was carried out using a large external dataset. The best models included normalized difference vegetation index (NDVI), elevation, and species identity. Models indicated that tree survival probability decreased with greenness (as measured by NDVI) and elevation, particularly if trees were growing slowly. Overall, models showed good calibration and validation, especially for Abies concolor, which comprise a large majority of the trees in many mixed conifer forests in the Sierra Nevada. Our models tended to overestimate mortality risk for Calocedrus decurrens and underestimate risk for pine species, in the latter case probably due to pine bark beetle outbreak dynamics. Validation results indicated dangers of overfitting, as well as showing that the inclusion of trees already under attack by bark beetles at the time of sampling can give false confidence in model strength, while also biasing predictions. These vulnerability tools should be useful to forest managers trying to assess which parts of their landscape were vulnerable during the 2012–2016 drought, and, with additional validation, may prove useful for ongoing assessments and predictions of future forest vulnerability.

A floristic survey across three coniferous forests of Kashmir Himalaya, India – a checklist

This study presents a checklist of the flora of three coniferous forests of the Himalayan biodiversity hotspot in Kashmir: low-level blue pine (BP), mixed coniferous (MC) and subalpine (SA) forests. The list includes altitudinal distribution and conservation status of 272 vascular plant species representing 196 genera and 64 families. Excluding neophytes (70 taxa, 62 genera, and 27 families), Magnoliophyta comprised 190 taxa, 139 genera, and 50 families; Pinophyta seven taxa, six genera, and three families; and Pteridophyta three taxa, three genera, and two families. Most speciose families from Magnoliophyta include Compositae, Apiaceae, and Rosaceae. Genera such as Artemisia, Potentilla, Viola, and Saussurea contributed the maximum number of species. In case of Pinophyta, the principal families are Pinaceae with four taxa followed by Cupressaceae (2 taxa), whereas genus Juniperus comprised two species. In Pteridophyta, Pteridaceae (2 taxa) formed the most speciose family. The herbs contributed 177 taxa, followed by tress (15 taxa), shrubs (8) and subshrubs (2). The maximum number of taxa belongs to SA (136 taxa) followed by MC (134 taxa) and BP (83 taxa) forests. The species distribution reveals 20, 30, and 46 taxa are exclusive to BP, MC, and SA forests. More than 16% of taxa are categorized in the International Union for Conservation of Nature (IUCN) Red List, and 24 taxa are endemic to the Himalayan landscape. The checklist provides a roadmap for research, protection and conservation of plant diversity, especially the threatened taxa.

Megafires in a Warming World: What Wildfire Risk Factors Led to California’s Largest Recorded Wildfire

Massive wildfires and extreme fire behavior are becoming more frequent across the western United States, creating a need to better understand how megafire behavior will evolve in our warming world. Here, the fire spread model Prometheus is used to simulate the initial explosive growth of the 2020 August Complex, which occurred in northern California (CA) mixed conifer forests. High temperatures, low relative humidity, and daytime southerly winds were all highly correlated with extreme rates of modeled spread. Fine fuels reached very dry levels, which accelerated simulation growth and heightened fire heat release (HR). Model sensitivity tests indicate that fire growth and HR are most sensitive to aridity and fuel moisture content. Despite the impressive early observed growth of the fire, shifting the simulation ignition to a very dry September 2020 heatwave predicted a >50% increase in growth and HR, as well as increased nighttime fire activity. Detailed model analyses of how extreme fire behavior develops can help fire personnel prepare for problematic ignitions.

Improving Effects of Afforestation with Different Forest Types on Soil Nutrients and Bacterial Community in Barren Hills of North China

Afforestation can improve soil nutrient content and microbial community structure, increase soil carbon sequestration, and reduce greenhouse gas emissions. However, at present, there is a lack of research on the low hills and mountainous areas in North China. In order to scientifically evaluate the effect of afforestation recovery with different forest types on the improvement of the soil ecological system, the Fanggan ecological restoration in North China was taken as the research sample, and the coniferous forests, mixed coniferous and broad-leaved forest quadrats and broad-leaved forests, as well as the contrast of barren hills bushes were set to achieve the research goals. Research results of different forest types on soil nutrient and bacterial community in the Fanggan ecological restoration area have shown that afforestation with broad-leaved forests most obviously improved the nutrition properties and bacterial community of soil. (1) Broad-leaved forest afforestation obviously improved water retention and ammonia nitrogen content but reduced the content of available phosphorus and nitrate nitrogen of surface soil. It also increased available phosphorus, ammonia nitrogen, and nitrate nitrogen content of lower soil. (2) Broad-leaved forest afforestation significantly increased α-diversity of the bacterial community in surface soil, but only enhanced the Chao1 and ACE indices of lower soil. In addition, afforestation has also significantly changed the structure of soil bacterial community and β-diversity index. (3) Proteobacteria, Acidobacteria, Actinobacteria, and Verrucomicrobia accounted for the highest proportion of soil bacterial community. Proteobacteria and Verrucomicrobia occupied higher proportion in broad-leaved forests than in other forest types, while the proportion of Acidobacteria and Actinobacteria was the opposite. (4) Afforestation decreased cooperation and increased competition among bacteria of surface soil as well as increased coexistence and rejection among subsoil bacteria. (5) pH, ammonia nitrogen, organic carbon, and available phosphorus have exhibited a significant impact on the structure of bacterial community in the surface soil, while the bacterial community structure of the lower soil was mainly affected by pH and available phosphorus. Results have fully demonstrated the positive effects of broad-leaved forest on the restoration of soil nutrients and microbial community structure. Meanwhile, the important combinations of soil physical and chemical factors affecting soil bacterial community structure were also explored. The results can provide scientific basis for revealing the mechanism of soil organic matter, nutrient and ecological function restoration by artificial afforestation, and also offer theoretical support and practical reference for the restoration of artificial afforestation in the hilly and mountainous areas of North China.

Impacts of climate and disturbance on nutrient fluxes and stoichiometry in mixed-conifer forests

Elucidating climatic impacts on stream nutrient export and stoichiometry will improve the understanding of forest carbon (C) storage in a warmer world. We analyzed C, nitrogen (N), and phosphorus (P) cycles in four watersheds within a rain-snow transition site and another four within a higher-elevation, snow-dominated site, in California’s mixed-conifer zone. We used these two sites in a space-for-time substitution to assess the potential warming impacts on nutrient cycles in currently snow-dominated areas that will become more rain-dominated. During a non-drought period (water year (WY) 2004–2011), mean annual stream exports of C and N in particulate forms at the transition site were twice that at the snow-dominated site, suggesting sediment-associated nutrient losses may increase with warming. The transition site had 12% lower N but twice P content in mineral horizons, lower N:P mass ratios in organic horizons, and lower stream export of dissolved inorganic N than the snow-dominated site. These differences suggest montane forests may have lower inputs of available N relative to P with warming. In addition, given strong interests in forest thinning to increase drought resiliency, we examined changes in stream nutrient export after thinning and during a major drought period (WY 2013–2015). Stream exports of C, N, and P were similar between unthinned and thinned watersheds during drought, suggesting negligible thinning impacts on stream nutrient export during excessively dry periods. Taken together, our results suggest that as the climate warms, California’s montane forests may lose more nutrients through erosion and increase their N-P nutritional imbalance.

Fractional Vegetation Cover Derived from UAV and Sentinel-2 Imagery as a Proxy for In Situ FAPAR in a Dense Mixed-Coniferous Forest?

The fraction of absorbed photosynthetic active radiation (FAPAR) is an essential climate variable for assessing the productivity of ecosystems. Satellite remote sensing provides spatially distributed FAPAR products, but their accurate and efficient validation is challenging in forest environments. As the FAPAR is linked to the canopy structure, it may be approximated by the fractional vegetation cover (FCOVER) under the assumption that incoming radiation is either absorbed or passed through gaps in the canopy. With FCOVER being easier to retrieve, FAPAR validation activities could benefit from a priori information on FCOVER. Spatially distributed FCOVER is available from satellite remote sensing or can be retrieved from imagery of Unmanned Aerial Vehicles (UAVs) at a centimetric resolution. We investigated remote sensing-derived FCOVER as a proxy for in situ FAPAR in a dense mixed-coniferous forest, considering both absolute values and spatiotemporal variability. Therefore, direct FAPAR measurements, acquired with a Wireless Sensor Network, were related to FCOVER derived from UAV and Sentinel-2 (S2) imagery at different seasons. The results indicated that spatially aggregated UAV-derived FCOVER was close (RMSE = 0.02) to in situ FAPAR during the peak vegetation period when the canopy was almost closed. The S2 FCOVER product underestimated both the in situ FAPAR and UAV-derived FCOVER (RMSE > 0.3), which we attributed to the generic nature of the retrieval algorithm and the coarser resolution of the product. We concluded that UAV-derived FCOVER may be used as a proxy for direct FAPAR measurements in dense canopies. As another key finding, the spatial variability of the FCOVER consistently surpassed that of the in situ FAPAR, which was also well-reflected in the S2 FAPAR and FCOVER products. We recommend integrating this experimental finding as consistency criteria in the context of ECV quality assessments. To facilitate the FAPAR sampling activities, we further suggest assessing the spatial variability of UAV-derived FCOVER to benchmark sampling sizes for in situ FAPAR measurements. Finally, our study contributes to refining the FAPAR sampling protocols needed for the validation and improvement of FAPAR estimates in forest environments.

The Effects of Plant and Soil Characteristics on Partitioning Different Rainfalls to Soil in a Subtropical Chinese Fir Forest Ecosystem

The climate-induced changes in soil water patterns pose a serious threat to subtropical plantations. Mixed species stands have been advocated as an efficient way to enhance ecosystem stability. However, little is known about their possible impact on the soil water-holding capacity in the subtropics. In this study, we employed a stable hydrogen isotope to assess the contribution of rainfall to soil water (CRSW) in a pure Chinese fir (Cunninghamia lanceolata) plantation and in two mixtures of Chinese fir with Cinnamomum camphora or with Alnus cremastogyne after three different magnitudes of rainfall events in subtropical China. Furthermore, we used structure equation modeling (SEM) to quantify the relative importance of vegetation and soil properties on the CRSW. The results indicated that the CRSW did not differ among these three Chinese fir plantations after light rainfall, whereas the CRSW of moderate and heavy rainfall to soil water were 15.95% and 26.06% higher in Chinese fir plantation with Cinnamomum camphora, and 22.67% and 22.93% higher in Chinese fir plantation with Alnus cremastogyne than that in the pure Chinese fir plantation, respectively. SEM analysis showed that the vegetation biomass and soil properties significantly affected the CRSW following light rainfall, but the soil properties were the most important factors influencing the CRSW under moderate and heavy rainfall. Our findings demonstrate that the mixed conifer–broad-leaved plantation is a more effective strategy for improving the soil water-holding capacity than the pure conifer plantation in subtropical regions, which is conducive to coping with the frequent seasonal droughts and extreme precipitation events.

Assessing multi-year-drought vulnerability in dense Mediterranean-climate forests using water-balance-based indicators

Water availability in mountain forests affects vegetation response to drought, which in turn changes evapotranspiration (ET). We investigated water-balance indicators based on precipitation (P) minus ET to assess Mediterranean-climate forest vulnerability to multi-year droughts. We used the drought-vulnerable dense mixed-conifer forests of California’s Sierra Nevada, which includes 78 groves of giant sequoia as study area. With long-term Landsat-based ET data during 1985–2018, water-stress patterns at 30-m resolution during two historical droughts (1987–92 and 2012–15) were analyzed. Canopy moisture loss and tree mortality were used as indices of drought vulnerability. Using cumulative multi-year P–ET as an indicator, groves that were water stressed in 1987–92 were more vulnerable in California’s unprecedented 2012–15 drought. Historical-minimum annual P–ET is an indicator of water stress, explaining 32% and 29% of the variances of canopy moisture loss and tree mortality, respectively. As an extreme test to explore potential vegetation response, we trained a deep-learning Long Short-Term Memory (LSTM) model to project ET during hypothetical extended-drought scenarios. The LSTM model reasonably predicted ET with r2 of 0.72 for the testing period. Annual P–ET using LSTM-based ET agreed (r2 = 0.99) with that using ET values from Landsat. Historical water-stress-prone areas were projected to suffer larger ET decreases and to experience more-severe stress during a 12-yr drought scenario. Water stress is more severe in lower-elevation forests, versus mid-to-high areas that have higher precipitation and shorter growing season under current climate. Our study provides water-balance-based indicators to project drought vulnerability and assess effects of disturbance in forests in a warming climate.

Геохімія ландшафтів історичної місцевості Гірка Крістера (м.Київ)

The study presents the results of ecological and geochemical research of landscapes of the historical area of Krister Hill in Podilsk district of Kyiv. The research aims to identify the current state of pollution of this territory by heavy metals - their content in the components of the landscapes (soils, plants, water environment). The paper characterizes the landscape structure and modern use of the territory. The degree of soil contamination in the sampling points located within the forest-steppe landscapes of the loess-like plain and mixed coniferous forest landscapes is characterized of the moraine-woodland plain was analyzed. For the analysis, the total pollution index (Zc) was used, according to which the study area as a whole has a moderately dangerous level of contamination of soils with heavy metals. The largest part belongs to lead and copper, the content of which in some samples is 2-4 times higher than the maximum allowable concentrations. The content of zinc and nickel is also significant. The total pollution of soils with heavy metals within the landscapes of forest plains is somewhat higher than in moraine-water-glacial landscapes. The results of a study of the microelement composition of the Krister hill vegetation indicate that the plants are characterized by an increased content of manganese, titanium, copper, and lead. Plants with a high ability to accumulate heavy metals include maple, common shingle, and lilac. To analyze the content of pollutants in surface and ground waters, water samples were taken from natural and artificial reservoirs, as well as from the bureaus. An excess of heavy metals content of tens and hundreds of times was detected in the Krister Hill water bodies. Hydrogeochemical peculiarities of drinking groundwater were established. The pump room water meets the requirements of DSTU. Excess of maximum permissible concentrations was detected for the total concentration of sodium and potassium ions and permanganate acidity. The obtained results are essential for substantiating the location of the network of complex environmental and geochemical monitoring and will contribute to the effectiveness of measures to improve the state of the natural environment and improve the living conditions of the population.

The Contribution of Forest Reserves and Managed Forests to the Diversity of Macrofungi of Different Trophic Groups in European Mixed Coniferous Forest Ecosystem

The Contribution of Forest Reserves and Managed Forests to the Diversity of Macrofungi of Different Trophic Groups in European Mixed Coniferous Forest Ecosystem

Effects of fertilization on the growth dominance of Inland Northwest forests of the United States

Large trees have disproportionally large competitive advantage in access to light, which has been proposed to increase growth dominance of large trees (e.g., a larger proportion of volume growth than standing volume is in large trees in a stand). Tree growth may also be limited by the availability of other resources besides light. Nutrient deficiency, especially of nitrogen, is considered common among temperate forests including mixed-conifer forests of the Inland Northwest of the United States. Data from a long-term forest nutrition study across four Inland Northwest states were analyzed to evaluate nitrogen ​× ​potassium fertilization's effects on growth dominance over an eight-year period following treatment. Our results show that growth dominance varied substantially across plots in each vegetation series and fertilization treatment, and its mean values generally were at minuscule magnitudes, negative, and not significantly different from 0. We propose that this lack of a clear pattern in growth dominance was the result of the mixed-species composition where shade-tolerant species remained in lower crown positions, yet their relative growth kept pace with large trees. Limited moisture availability at dry sites may have hampered the development of growth dominance. Growth dominance also was lowered by mortality observed among relatively large trees. The largely negative growth dominance across fertilization treatments indicated that small trees seem to have maintained higher relative growth rates than large trees, even if absolute growth was higher among large trees. In the case fertilization does improve stand growth, a significant part of this improved growth will be lost in density-dependent mortality over time if not captured through thinning/harvesting.

Quantitative dynamics of the early Pliocene climate and vegetation in the Lena River Delta (northern Yakutia, Eastern Siberia)

Early Pliocene climate and vegetation evolution in the Lena River Delta (northern Yakutia, Eastern Siberia) are quantitatively studied for the first time in de­ tail, based on a palaeobotanical record. Palaeobotanical data for this time-interval were obtained on 28 palynofloras from the Sardakhskaya Formation in the coastal cliffs of the Sardakh-Sisse Island (Lena River Delta). In this first integrative study we apply the Coexistence Approach (CA) for quantification of palaeoclimate, the Plant Functional Types (PFT) approach and Integrated Plant Record (IPR) vegetation analysis for quantification of palaeovegetation. Our investigation documents the persistence of temperate climate with two warmer and colder phases. Moreover, our reconstructions show significantly higher mean values of all temperature parameters in comparison to previous estimations. Overall hu­ mid climate conditions (up to 1500 mm) prevailed throughout the early Pliocene correspond to an oceanic climate. Our reconstruction indicates relatively strong temperature and precipitation seasonality. Our data for vegetation show more open vegetation in comparison to previous studies reconstructing mixed conifer- deciduous forests for the early Pliocene of Northeast of Russia. Based on PFT, the early Pliocene vegetation of northern Yakutia in Lena River Delta mainly was presented by more or less open mixed deciduous woodlands of warmer or colder temperate type. The results obtained from the PFT approach generally are in ac­ cordance with our data obtained from IPR approach. However, based on IPR, periodically forests and grasslands were obtained in addition to open woodlands.

Fuel loads and fuel structure in Austrian coniferous forests

Understanding fires in temperate European coniferous forests is hindered by a lack of reliable field observations on fuel load and structure. Fuel load influences the spread, intensity and spotting distance of a surface fire, torching likelihood and potential carbon emissions. We quantified fuel load and structure for Austrian coniferous forests using 93 sample plots across Austria. We compared Austrian fuel types with fuels collected in other regions and biomes. We found significant differences among regions and forest types. Fuel load was more dependent on region and forest type than on age class. Highest fuel load was found in Picea abies stands, lowest in Pinus nigra forests. Dead fuel loads were positively correlated with basal area, while live fuels were negatively correlated, suggesting that basal area drives accumulation of dead fuels and suppresses growth of understorey vegetation. Fuel loads in Austria are similar to published data for other temperate forests. The large variation in observed fuel loads and lack of previous studies highlight the need to further develop fuel models for mixed conifer–broadleaf forests. This pilot study underpins that consistent terminology and fuel classification are important to interpret differences between regions and forest types.