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• We carried out vegetation studies in the ancient oak forest Hasbruch in Germany. • We analysed drivers of changes in vascular plant species richness. • We analysed the effect of management and vegetation type on these changes. • The main drivers for changes in species richness were light and water availability. • Effects of the drivers strongly depended on the vegetation type. We carried out vegetation studies in the ancient Hasbruch forest, which provided the unique conditions of unmanaged (UM) and managed (M) stands in two vegetation types Stellario-Carpinetum loniceretosum (POOR) and stachyetosum (RICH) stands in one closed forest allowing us to study (1) the changes in species composition and richness over 20 years considering the entire forest as well as (2) group-specific changes. Hasbruch forest in the lowlands of Lower Saxony, Germany. In 2016 we resurveyed the vascular plant species composition of 79 semi-permanent plots analysed in 1996. General and group-specific trends as well as drivers of changes were analysed using DCA, PCA, LM, t -test, U test, ANOVA. Tree and shrub layer coverage increased significantly in the entire forest. Herb layer species richness decreased significantly only in group RICH_UM. While the pH-value increased significantly in group POOR, it decreased significantly in group B. EIV F increased significantly in group POOR_M and decreased significantly in group RICH_UM. EIV L increased significantly in both of the managed groups, while it decreased significantly in group RICH_UM. An increase was found for EIV N in group POOR_M, whereas a decrease was found in group RICH_M. Strongly increasing species were Ilex aquifolium , Rubus fruticosus agg. and Hedera helix ; strongly decreasing species Geum urbanum and Primula elatior. The change in species richness was positively affected by ΔpH and negatively affected by ΔT1cov in the entire forest. The main drivers for changes in species richness and composition in the Hasbruch forest were light and water availability. The effects of the drivers strongly depended on the vegetation type. Changes in species composition were more pronounced in nutrient-rich forests than on nutrient-poor sites. In nutrient-rich forests, decreased groundwater influence led to decreased soil pH which especially affected typical woodland plants in a negative way. Management positively affected light-demanding species as well as some N-demanding species. Thus, unmanaged, nutrient-rich stands displayed the highest losses in species diversity. In the nutrient-poor stands, changes in species composition were not significantly related to changes in soil and management. However, increasing pH as well as increased Ellenberg L, F, and N values suggest a tendency towards eutrophication. This is possibly a consequence of N deposition and recovery from soil acidification. [ABSTRACT FROM AUTHOR]

Highlights • Black locust plantations are always lighter, warmer and less humid. • Contain more non-forest, ruderal and significantly higher number of alien species. • The largest impact of black locust was recorded on the mixed oak-hornbeam forests. • The smallest impact was recorded on the floodplain forest. Abstract Information about invasive alien species and their interactions with the environment and native ecosystems is very important to prevent widespread loss of original habitats and biodiversity. Black locust (Robinia pseudoacacia) is one of the most widespread alien plant species in Europe and has become a dominant forest tree species, which is frequently planted. We analysed how environmental factors (light, temperature and humidity), species composition and level of invasion changed in black locust stands compared with those in different neighbouring native forest types (floodplain, oak and mixed oak-hornbeam forests). The aims of this study were to determine (i) how the microclimatic conditions of the native forests changed after replacing the native trees with black locust, (ii) how black locust changed species composition and level of invasion of the understory and (iii) whether black locust equally influenced the three types of native forests. The results showed that compared with those of the other forest types, the conditions of black locust stands were always warmer and drier with more light from the sparse canopy of trees. In the black locust forests, we recorded more non-forest and ruderal species with significantly higher percentage number and cover of alien species in the understory vegetation than in the native forest stands. Different native forest types and their black locust twins were mutually influenced in a different way. The mixed oak-hornbeam forest was the type most influenced by replacement with black locust, whereas floodplain forest changed the least. Black locust plantations replacing native forests cause decreasing native species biodiversity, because of the occurrence of alien, ruderal and non-forest species. The dry and warm character of black locust stands contributed to an acceleration of microclimate change. This information can be useful for forest managers and planners participating in the replacement of native forest stands by alien tree species, which has ecological and economic impacts with consequences for nature and society. [ABSTRACT FROM AUTHOR]

Highlights • We carried out vegetation studies in the currently largest CWS project in Germany. • We analysed coppicing induced changes in vascular plant species richness. • CWS restoration led to an increase in species richness, particularly tree regeneration. • "Nitrogen time bomb" scenario after canopy opening did not happen in our study area. • True forest species are not negatively affected by coppicing. Abstract Aims Coppice-with-standards (CWS) management was one of the most important disturbances in Central European forests in the past. As our knowledge about the effects of coppicing on species richness and composition needs to be enhanced, we carried out vegetation studies in the currently largest CWS project in Germany. In this article we focus on two issues: 1. Coppicing induced changes and trends in species richness and composition from year to year and 2. Development of species richness and composition in 19 years of CWS restoration. Location Salzgitter Höhenzug mountains between Liebenburg and Goslar, Lower Saxony, Germany. Climate: subatlantic to subcontinental; soil: Limestone rendzina with low water storage capacity. Methods In 2013 we resurveyed the plant species composition of 12 permanent plots analysed every year from 1994 till 2002. The dates of coppicing were recorded for all of these plots, which enabled us to analyse the dynamics of species richness and composition after coppicing on a year to year basis. Differences in species richness and composition were analysed using ANOVA, H-test, DCA and GLMM. Results In 19 years of CWS restoration mean plot species richness increased significantly, mainly attributed to the increase in woody species, such as Quercus robur and Sorbus torminalis. The Ellenberg indicator value for nutrients decreased significantly, whereas the indicator value for light increased significantly. The typical dynamic after coppicing consists of a continuous increase in shrub layer coverage and an increase in herb layer coverage with a maximum in years 3 and 4 after coppicing. Total species richness as well as richness of open habitat and forest species and true forest species also showed an increase with its maximum in years 3 and 4 after coppicing. Conclusions Our results showed that the alternation of light and shaded phases had a positive impact on species richness, particularly on tree regeneration. Considering the trend of decreasing species richness level in Central European forests, CWS forests play a major role in the conservation of vascular plant species diversity. In contrast to other studies, the increase in species richness after coppicing did not result from an increase in weedy, nitrogen-demanding species. The so called "nitrogen time bomb" scenario (which other authors assumed to be happening after opening the canopy) did not occur in the studied area. The low water storage capacity of the limestone rendzina soil may be one reason, as there was not sufficient water and nitrogen for the more demanding species. [ABSTRACT FROM AUTHOR]

Glomalin-related soil proteins (GRSP) are glycoproteins abundantly produced by arbuscular mycorrhizal fungi in roots and soil. They can be a significant component of soil organic matter, which effectively acts to bind mineral particles together, so improving soil structure. Although it is known that high temperatures and tillage both have a negative impact on GRSP, there is no study aimed at comparing and contrasting the effects of fire and enduring cultivation on GRSP content in contiguous areas undergoing the two forms of soil disturbance. We studied such a situation in Kurdistan, Iran, where the top 5 cm of soil was sampled in i ) an unmanaged and unburned oak sparse forest, both inside and outside sprout clumps, ii ) a vineyard, both under and outside the canopy, and iii ) a burned portion of the forest in between. In the latter, the samples were collected from areas burned with high and moderate severity inside sprout clumps, and areas burned with low severity outside sprout clumps. All soil samples were air-dried and sieved to obtain four aggregate size fractions (8–2, 2–1, 1–0.25, and <0.25 mm in diameter). Total organic carbon (TOC), easily extractable glomalin (EEG) and residual glomalin (RG) were determined in all fractions. Both TOC and GRSP were significantly lower in the cultivated soil than in the unburned forest. Fire did not change the content of TOC, although GRSP increased with increasing fire severity. The relative amount of small aggregates was higher in the burned and cultivated soils, likely because of the breakdown of macroaggregates by heating and tillage, respectively. TOC, EEG, and RG generally increased in concentration with decreasing aggregate size. The linear regression analysis revealed significant relations between GRSP and TOC in all studied treatments; however, the GRSP/TOC ratio was significantly higher in the soil burned with the highest severity and in the vineyard compared to the unburned soil . Overall, this study demonstrated that GRSP in soil is significantly affected by both severe fire and cultivation, and suggests that total amount of GRSP and GRSP distribution between the aggregate size fractions might be two reliable indicators of these types of perturbations of the soil environment. [ABSTRACT FROM AUTHOR]

Forest soil microbial community is easily modified by changes in plant composition. Therefore, differences in the assembly of soil microbial community within different forest types should be evaluated to gain a deeper understanding of microbial biodiversity and forest system functioning. In the present study, pine, oak, and pine-oak mixed forests at different developmental stages (young, immature, and mature forests) were evaluated to explore the assembly, co-occurrence network, and influencing factors of bacterial and fungal community. The assembly of bacterial community was dominated by deterministic processes (homogeneous selection), whereas the assembly of fungal community was dominated by stochastic processes (dispersion limited). At the young forest stage, the proportion of deterministic processes in bacterial community assembly among the three forest types differed less. In contrast, the proportion of deterministic processes at the immature and mature forest stages in the bacterial community assembly in the pine-oak mixed forest was larger than that in the pure forests. The proportion of stochastic processes in the assembly of fungal community in the pine-oak mixed forest was greater than that in the pure forests and was observed at all forest stages. Network analysis showed that the links and average degree of bacteria in the pine-oak mixed forest were lower than that of the pure forests, whereas the network topological features of fungi in the pine-oak mixed forest were higher than that of the pure forests. The stochastic processes increased microbial co-occurrence. The results of the random forest indicated that Pielou's evenness index (E) of plant was the most important predictor of fungal community assembly, and Shannon's diversity index (H) of plant also was the critical factor influencing bacterial community assembly. Our study demonstrated the importance of plant diversity in the assembly of forest soil microbial community. • Bacterial community assembly was dominated by deterministic processes. • Fungal community assembly was dominated by stochastic processes. • Bacteria community in mixed forest were most affected by deterministic processes. • Fungal community in mixed forest were most affected by stochastic processes. • Plant played an important role in the assembly of forest soil microbial community. [ABSTRACT FROM AUTHOR]

The responses of soil respiratory components to global warming are poorly understood particularly in high altitude forest ecosystems. To examine the different responses of soil respiration ( R S ) components, i.e., autotrophic ( R A ) and heterotrophic ( R H ) respirations, in a mountainous temperate forest to elevated temperature, we conducted an open-field soil warming experiment combined with trenching treatments in a 60-year-old cool-temperate deciduous broadleaved forest in central Japan. Here we particularly focused on the temporal variations of respirations under remarkable seasonal change of air and soil temperatures in the region. R S was divided into R A and R H by trenching method in both warmed and control plots (three subplots for each treatment). We installed heating cables at 5 cm below the soil surface to increase soil temperature by 3.0 °C during snow-free seasons in the four experimental years from 2012 to 2015. The soil warming significantly increased R S , however, the soil warming did not alter fine root biomass, carbon concentrations nor nitrogen availability in the soils, which were positively related to R S . The magnitude of the warming effects on R H was negatively correlated to both soil temperature and soil moisture content. In this cool-temperate forest characterized by monsoon climate in summer, the high soil moisture level may not be a limiting factor for the soil warming effect on R H . The effect of soil warming on R S did not vary throughout the daytime, but the effect on R S varied seasonally because R H showed more sensitive response to soil warming in the late-growing season when compared to other seasons. We demonstrated that the season-specific Q 10 model is able to quantify the warming impacts on annual respiration rates more accurately than apparent annual Q 10 model. The soil warming increased annual R S , R H , and R A for the second year by 18.1%, 25.6%, and 5.3%, respectively, but the magnitude of those increments declined in the fourth year to 9.9%, 19.5%, and −2.8%, respectively. Our results suggest that soil warming did not alter the temperature sensitivity of R H in this forest soil, but might have induced thermal acclimation of R A . This 4-year soil warming study in a mountainous forest contributes to the better understanding of the different responses of R H and R A to changing soil temperature conditions, and we highlight that the seasonal variations in the warming effects on R H and R A to future climate conditions should be taken into consideration in projecting the future soil carbon cycle. [ABSTRACT FROM AUTHOR]

Sun-induced fluorescence (SIF) has been proven to serve as a proxy of photosynthesis activity and therefore, as an early indicator of physiological alterations for global monitoring of vegetation. However, the interpretation of SIF over different spatial resolutions is critical to bridge the existing gap between local and global scales. This study provides insight into the influence of scene components, and forest structure and composition on the quantification of the red and far-red fluorescence signal as an early indicator of forest decline. The experiments were conducted over an oak forest ( Quercus ilex ) affected by water stress and Phytophthora infection in the southwest of Spain. SIF retrievals through the Fraunhofer Line Depth (FLD) principle with three spectral bands F (FLD3) was assessed using high resolution (60 cm) hyperspectral imagery extracting sunlit crown, full crown and aggregated pixels. Results showed the link between F (FLD3) extracted from sunlit crown pixels and the tree physiological condition in this context of disease infection, yielding significant relationships (r 2 = 0.57, p < 0.01) for midday xylem water potential (ψ), (r 2 = 0.63, p < 0.001) for the de-epoxidation state of the xanthophyll cycle (DEPS), and (r 2 = 0.74, p < 0.001) for leaf-level measurements of steady-state fluorescence yield (F s ). In contrast, a poor relationship was obtained when using aggregated pixels at 30 m spatial resolution, where the relationship between the image-based F (FLD3) and F s yielded a non-significant relationship (r 2 = 0.25, p > 0.05). These results demonstrate the need for methods to accurately retrieve crown SIF from aggregated pixels in heterogeneous forest canopies with large physiological variability among individual trees. This aspect is critical where structural canopy variations and the direct influence of background and shadows affect the SIF amplitude masking the natural variations caused by physiological condition. FluorFLIGHT, a modified version of the three dimensional (3-D) radiative transfer model FLIGHT was developed for this work, enabling the simulation of canopy radiance and reflectance including fluorescence at different spatial resolutions, such as may be derived from proposed satellite missions such as FLEX, and accounting for canopy structure and varying percentage cover. The 3-D modelling approach proposed here significantly improved the relationship between F s and F (FLD3) extracted from aggregated pixels (r 2 = 0.70, p < 0.001), performing better than when aggregation effects were not considered (r 2 = 0.42, p < 0.01). The FluorFLIGHT model used in this study improved the retrieval of SIF from aggregated pixels as a function of fractional cover, Leaf Area Index and chlorophyll content yielding significant relationships between F s ground-data measurements and fluorescence quantum yield estimated with FluorFLIGHT at p < 0.01 (r 2 = 0.79). The methodology presented here using FluorFLIGHT also demonstrated its capabilities for mapping SIF at the tree level for single tree assessment of forest physiological condition in the context of early disease detection. [ABSTRACT FROM AUTHOR]

Although being well described at the landscape level, patterns in species composition of forest herb layer are rarely studied at smaller scales. Here, we examined fine-scale environmental determinants and spatial structures of herb layer communities in thermophilous oak- and hornbeam dominated forests of the south-eastern part of the Czech Republic. Species composition of herb layer vegetation and environmental variables were recorded within a fixed grid of 2 × 2 m subplots regularly distributed within 1-ha quadrate plots in three forest stands. For each site, environmental models best explaining species composition were constructed using constrained ordination analysis. Spatial eigenvector mapping was used to model and account for spatial structures in community variation. Mean Ellenberg indicator values calculated for each subplot were used for ecological interpretation of spatially structured residual variation. The amount of variation explained by environmental and spatial models as well as the selection of variables with the best explanatory power differed among sites. As an important environmental factor, relative elevation was common to all three sites, while pH and canopy openness were shared by two sites. Both environmental and community variation was mostly coarse-scaled, as was the spatially structured portion of residual variation. When corrected for bias due to spatial autocorrelation, those environmental factors with already weak explanatory power lost their significance. Only a weak evidence of possibly omitted environmental predictor was found for autocorrelated residuals of site models using mean Ellenberg indicator values. Community structure was determined by different factors at different sites. The relative importance of environmental filtering vs. spatial processes was also site specific, implying that results of fine-scale studies tend to be shaped by local conditions. Contrary to expectations based on other studies, overall dominance of spatial processes at fine scale has not been detected. Ecologists should keep this in mind when making generalizations about community dynamics. [ABSTRACT FROM AUTHOR]

In the midwestern and eastern U.S., oaks ( Quercus spp.) have been a dominant component of forests for at least the last 10,000 years, providing vital habitat for numerous wildlife and plant species that have adapted to oak forest conditions. However, the current state of these oak systems, in which there has been a general lack of successful oak regeneration and recruitment and an increase in the relative dominance of mesophytic species, may be nearing critical thresholds. If reached, restoring oak systems through natural regeneration and other methods, such as prescribed fire, may become especially challenging if not impossible. An understanding of spatial variation in oak dominance over time can inform and potentially improve the efficacy of intervention strategies. Using Public Land Survey and Forest Inventory and Analysis (FIA) inventories, we evaluated changes in the composition of timberland across ecoregional subsections in the Driftless Area of the Midwest at three time periods (pre-settlement 1800s, 1990s, and 2000s). We identified an overall decrease in oak dominance, and particularly dominance of the white oak ( Quercus alba L., Q. macrocarpa Michx., and Q. bicolor Willd.) species group since the pre-settlement era, and an increase in other eastern soft hardwoods. Within the last 20 years, both the red oak ( Q. rubra L., Q. ellipsoidalis E.J. Hill and Q. velutina Lam.) and white oak species groups decreased in dominance, with an increase in hard maple-basswood ( A. saccharum Marsh., A. nigra L., and Tilia americana L.) species group dominance, indicating further mesophication of forests in the region. However, we found a notable decrease in hard maple-basswood relative dominance within the small diameter class across most of the regions within the last 10–20 years, with an increase in dominance of other, non-oak, species. Our findings complement qualitative evidence from interviews with natural resource professionals from the region and offer further information on the potential for forest conversion to “undesirable” forest conditions, as identified as a source of concern by some professionals. There was spatial variation in these trends, however, with some pronounced differences across adjacent state boundaries. The variation in forest change across state boundaries suggests the role of state-level socioeconomic and policy factors in affecting forest conditions, and thus the potential for a targeted and timely approach to promoting preferred pathways of change. [ABSTRACT FROM AUTHOR]

Wildfires are a major disturbance in forest ecosystems around the world and may lead to changes in vegetation succession trajectories. This study examined the impact of time since wildfires on the successional gradients of the degraded Zagros semi-arid oak forest in Iran. Here, we investigated the role of soil seed bank in postfire understory vegetation successional trajectories after wildfires and how time-since-fire influenced plant recovery of this disturbed site. Three adjacent high severity burned areas with different fire histories and the same physiographic conditions were considered. In sampling, we surveyed both aboveground understory vegetation and soil seed bank in all the 96 plots taken along the transects of each area. Soil samples were also collected from each plot and physicochemical properties were analysed in the laboratory. Species composition in the seed bank showed divergent successional trajectories compared to the aboveground vegetation after wildfire. The diversity of soil seed banks followed a gradual decrease, while aboveground understory plants revealed an increasing trend of diversity over time. In addition, the physical and chemical composition of soils was significantly altered by fire. This study presents important insights into soil seed bank dynamics compared to the corresponding aboveground vegetation during postfire succession. The observed changes in diversity and vegetation composition after wildfire can give important insights to management strategies involving prescribed fire in the restoration efforts of highly disturbed semiarid oak forest. [ABSTRACT FROM AUTHOR]

Oak forests around the world have been widely used to obtain firewood and produce charcoal and like other habitats have been affected by the increasing development of livestock activities. Oak forests from western Mexico are one of the five priority habitats for the conservation of birds at a continental level and are the repository of the highest number of endemic bird species in this megadiverse country. We studied how charcoal extraction and the use of oak forest for cattle grazing affect bird communities. We focused our work on oak forest patches with four different management units that include three successional stages that occur after most of the trees have been removed for charcoal production and cattle-grazing is conducted, and mature oak forest patches with little wood extraction and no cattle-grazing. We used unlimited radius point counts to survey avian communities, and compared their richness, composition, density, structure and similarity among the different management units. We found that resident bird species, summer migrants and Neotropical migrant bird species used the four management units differently. Resident bird species used all habitat units similarly. Winter migrants as a group were present in the different management units, however while some species used habitats with cattle, other species used habitats with no cattle-grazing. Finally, summer migrants used habitat units with tall trees and high values of tree and shrub richness, and tended to avoid the early successional unit. Both charcoal extraction and cattle grazing worked in synergy decreasing the species richness and the equity of the bird communities. Management strategies should include active conservation of undisturbed oak forest areas because they play an essential role to maintain resident bird species in the landscape. [ABSTRACT FROM AUTHOR]

In a Quercetum petraeae-cerris forest in northeastern Hungary, we examined effects of litter input alterations on the quantity and quality soil carbon stocks and soil CO2 emissions. Treatments at the Síkfőkút DIRT (Detritus Input and Removal Treatments) experimental site include adding (by doubling) of either leaf litter (DL) or wood (DW) (including branches, twigs, bark), and removing all aboveground litter (NL), all root inputs by trenching (NR), or removing all litter inputs (NI). Within 4 years we saw a significant decrease in soil carbon (C) concentrations in the upper 15 cm for root exclusion plots. Decreases in C for the litter exclusion treatments appeared later, and were smaller than declines in root exclusion plots, highlighting the role of root detritus in the formation of soil organic matter in this forest. By year 8 of the experiment, surface soil C concentrations were lower than Control plots by 32% in NI, 23% in NR and 19% in NL. Increases in soil C in litter addition treatments were less than C losses from litter exclusion treatments, with surface C increasing by 12% in DL and 6% in DW. Detritus additions and removals had significant effects on soil microclimate, with decreases in seasonal variations in soil temperature (between summer and winter) in Double Litter plots but enhanced seasonal variation in detritus exclusion plots. Carbon dioxide (CO2) emissions were most influenced by detritus input quantity and soil organic matter concentration when soils were warm and moist. Clearly changes in detritus inputs from altered forest productivity, as well as altered litter impacts on soil microclimate, must be included in models of soil carbon fluxes and pools with expected future changes in climate. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied seasonal and interannual variation in fine-root dynamics in forest. [•] Temperature controlled fine-root production. [•] Leaf phenology, especially of understory bamboo, related to the fine-root production. [•] Mass-based fine-root production was 589 or 726gm− 2 yr− 1. [•] Fine-root production accounted for 36% or 41% of total net primary production. [Copyright &y& Elsevier]

Abstract: The aim of the study was to determine the effect of soil and canopy on the understory vegetation of Quercus robur stands in Latvia, located in the boreo-nemoral zone. To determine the main processes regulating formation of the plant communities, the understory vegetation of Q. robur stands was described using plant traits. Vegetation and soils were described in 24 plots representing contrasting soil types and tree species composition. Redundancy analysis was used to determine the relation between vegetation, described using plant traits (proportion of species with each trait), and soil and canopy factors. About 50% of the variation in vegetation described by plant traits was explained by soil factors, which were collinear with canopy factors. Species characteristic of ancient forest were generally abundant. A smaller proportion of autochorous species, which have limited seed dispersal distances, occurred in secondary forest on previous agricultural land with higher soil pH in the upper soil horizon. A typical nemoral herb layer with greater proportion of ant-dispersed species and hemicryptophytes was associated with soils that had higher clay content. Forest management for conservation to maintain the nemoral aspect of deciduous woodland should focus on woodland that has developed on silty clay loam soils. [Copyright &y& Elsevier]

Abstract: Although oaks (Quercus spp.) have historically dominated many forests in eastern North America, forest composition is changing due to anthropogenic impacts on disturbance regimes. Silvicultural practices, such as partial harvesting, are one component of management to promote oak regeneration. From 2007 to 2009 our research examined nest-site selection and nesting success for a guild of five canopy songbirds in upland mixed-oak forests in southeastern Ohio, USA. We monitored >700 nests across three state forests in both open canopy shelterwood stands harvested to approximately 50% stocking, and closed-canopy mature second-growth. Habitat attributes, including topography, canopy structure, and floristics, were measured at nest sites and random plots ⩽100m from nests representing microhabitat available within the territory. Canopy songbirds selected specific topographic microclimates: Eastern Wood-pewees (Contopus virens) nested on xeric ridgetops, Blue-gray Gnatcachers (Polioptila caerulea) favored valleys, and Cerulean Warblers (Dendroica cerulea) preferred productive northeast-facing slopes. Nest sites differed among species in terms of concealment, nest support, topographic position on the slope, and basal area of trees >38cmdbh. Four of the five focal species selected Quercus alba as the nest substrate more than twice as much as available, and three species avoided Quercus rubra. Daily survival rates of nests were negatively associated with basal area of red oak species (both Quercus velutina and Q. rubra) for several species individually and across the canopy-nesting guild. Additional factors related to success included time of season for Eastern Wood-pewees, nest age for Cerulean Warblers, and concealment and size of the support branch for Scarlet Tanagers (Piranga olivacea). In the long-term management for oak regeneration could benefit canopy songbirds, but our results indicate that white oaks, especially Q. alba, may be preferable to red oak species. [Copyright &y& Elsevier]

Abstract: Nitrogen mineralisation in soils of various forest sites (pine plantation, natural and thinned oak) at Uludağ University campus in Bursa, Turkey was investigated continuously over a year by the field incubation method. Net nitrogen mineralisation and nitrification rates varied depending on sampling dates. Although nitrogen mineralisation and nitrification rates increased in the spring and summer months, there was no seasonal variation in the soils of the examined forests. Annual net nitrate (NO3 −–N) accumulation in the upper soil layer (0–5 cm) was higher in Oak I and Oak II (14 kg ha y−1 and 12 kg ha y−1) than in the pine plantation (8 kg ha y−1). While annual net NO3 −–N accumulation (0–5 cm) varied between the oak forests (possibly due to forest management practices), annual net N min values were similar in these forests. No significant correlation was found between the examined soil parameters and net nitrification and mineralisation rates in the soils (P > 0.05). These results indicate that tree species and forest management practices play important roles in N cycling in forest ecosystems. [Copyright &y& Elsevier]

Abstract: The impact of past Roman occupation on the composition of ectomycorrhizal (ECM) communities was analysed in 12 Roman settlements in an oak forest in Central France. At each Roman settlement, soils and ECM roots were sampled from two plots (600 m2 each), one plot close to the remains of the buildings (<100 m), supposed to be impacted by ancient Roman agriculture, and the second plot 250–500 m away from the remains of the buildings, supposed to be less intensively influenced by previous cultivation. Soils were analysed and ECM fungal taxa were identified by morphotyping and sequencing the rDNA ITS region. The soil properties were significantly affected by the past Roman occupation, in terms of nutrient availability, especially for P, N and Mg. The enhancement of soil nutrient levels by past Roman land-use had significantly modified alpha diversity and species composition of ECM communities. Among the 67 determined ECM morphotypes, 40 were shared by the occupied and non-occupied plots, 17 were found only in the occupied plots and 10 only in the non-occupied plots. Six morphotypes were significantly more frequent near the antique remnants. Our study showed, for the first time, that ectomycorrhizal communities are impacted by previous Roman land-use, even after nearly two thousand years of forest state. [Copyright &y& Elsevier]

Abstract: The study sought to achieve the broadest possible spatial and temporal predictions by examining genetic variations in the timing of flowering between populations of the Iberian Quercus species using pollen data from 15 sites in Spain. The specific objective of the study was to develop and fit regional phenological model to predict the flowering start and flowering peak of Quercus species in the Iberian Peninsula by ascertaining whether potentially significant genetic variations in the timing of flowering required different phenological models or if, on the contrary, regional models for several localities can explain the variability detected in Quercus phenology in Spain. Model estimates did not vary greatly as a function of environment within similar climate areas where the same species grew; thus, model estimates of the temperature response of individuals growing in similar climate areas did not differ significantly. The percentage of variance explained by models was greater in models fitted with local data (75–97%). Nevertheless, acceptable results were also obtained using regional models (55–85%). The lowest value was found for the Simplifed Model including all Spanish sites together (51%). [Copyright &y& Elsevier]

In Iberian Mediterranean ecosystems holm-oak acorn production is of vital ecological and economic importance. Economically these fruits are the major component in the feeding systems of high-quality domestic pigs. As in most Quercus species, the chief feature of holm-oak acorn production is its high variability among individuals and years. Many hypotheses have been put forward to explain these fluctuations, but the variables influencing this alternating behavior remain unknown. From 1998 to 2003 we studied floral phenology, fruit production, fruit size, airborne pollen emission and meteorology in a holm-oak natural area of South Spain. The results obtained by using a Principal Components Factorial Analysis indicated that pollen emission, up to the day where maximum pollen data are recorded, was the most important factor determining final acorn harvest. With regard to the influence of the weather, temperature, relative humidity and rainfall of January, March and September were the most influencing variables. Our results support the “wind pollination” hypothesis proposed by other authors in some North-American Quercus studies. Integration of aerobiological, field phenological and meteorological data could represent an important step forward in forest fruit production research. [Copyright &y& Elsevier]

Abstract: Two sandy soil profiles under oak forest were examined for their phenolic composition using 13C labelled tetramethylammonium hydroxide (TMAH) thermochemolysis, the first application of this method to soils. Lignin, demethylated lignin, hydrolysable tannin, and other phenolic acids could be distinguished, and as such indications of the relative distribution of these sources among the soil horizons was determined. Some compounds extracted from soils using TMAH thermochemolysis, all of which are permethylated phenols, can have multiple structural and botanical sources, such as 3,4-dimethoxybenzoic acid methyl ester from vanillic acid or demethylated vanillic acid derived from lignin, or protocatechuic acid as the initial compound. Correcting the common lignin proxies for contributions of non-lignin phenols and altered lignin, it was found that Λ (yield of monomers upon thermochemolysis), F/P (ferulic acid/p-coumaric acid), Ac/Al (acid/aldehyde) ratios, and Γ (indicator of side chain shortening) were severely influenced by non-lignin phenols. By contrast, the S/G (syringyl/guaiacyl) and C/G (cinnamyl/guaiacyl) ratios remained rather similar. The proxies that changed the most were those that affect interpretations of lignin patterns in terms of source, alteration and preservation. From L to Ah horizons, a progressive lignin alteration was found for both soils, but the differences in litter input among plant materials (leaves, bark, branches, roots) also potentially affected the lignin patterns within and between both profiles. Therefore, important insights into the rapid changes in lignin chemistry between organic and mineral horizons were provided as this method permitted enhanced distinction between fresh source input and decomposition. Even with the corrections to lignin proxies, the soil lignin and polyphenol chemistry remained complex and highlights the limitations of using a few or only one lignin proxy in assessing soil organic matter dynamics. [Copyright &y& Elsevier]

Abstract: In northeastern India, subtropical forests are over-exploited for timber, fuel wood and common agricultural practice like shifting cultivation, which are responsible for the degradation of natural forest. In degraded areas, large-scale plantations of different species of Quercus have been raised since 1980 for the production of economic Tasar silk. Conversion of natural forest into plantation affects the process of nutrient cycling due to management practices. Thus, it would be of importance to study the litterfall, litter decomposition process and the factors regulating the rate of litter decay in these ecosystems to improve recommendations for their management and conservation. We recorded litterfall by using litter traps and decomposition of leaf litter by nylon net bag technique to understand the amount of organic matter and nutrient return and their release in soils of forest and plantation in Manipur, northeast India. Total litterfall was 419.9gm−2 year−1 in plantation and 547.7gm−2 year−1 in forest. Litter decomposition rate was faster at plantation site than the forest in the early stage of litter decomposition whereas the reverse was observed at later stages of decomposition. Stepwise regression analysis showed the significant role of relative humidity and mean temperature on mass loss rates in the forest. Relative humidity, maximum temperature, population of fungi and actinomycetes were the best predictor variables for mass loss rates in plantation. Nutrient retranslocation efficiency and the immobilization of N and P in forest litter were higher than plantation. This suggests that Q. serrata growing in natural ecosystem in oligotrophic condition adapted strong nutrient conservation mechanisms to compete with the other plant species for the meager soil nutrients. The same species in plantation loses these adaptive capabilities because of exogenous supply of nutrients and in the absence of intense competition with other plant species. Thus, the optimization of organic and chemical fertilizer input in plantation is recommended for maintaining the soil fertility level to produce quality leaf for silkworm by conserving essential nutrients in the system. [Copyright &y& Elsevier]

Abstract: We studied the effects of traditional forest management practices (i.e. forest exploitation activities such as burning, cutting and livestock grazing) on carabid beetle (Coleoptera, Carabidae) assemblages in Pyrenean oak forests of NW Spain. A total of 11370 carabid individuals representing 61 species were collected by pitfall trapping from May to October 2004 in four types of traditionally managed oak ecosystems: “dehesa”, “mature open”, “mature closed” and “young”. These four management types experienced a variety of anthropogenic activities, resulting in differences in the structure and composition of the tree and understorey vegetation layers. We showed that the four management types were quite similar at the carabid assemblage level, mainly supporting open habitat and generalist species. The “dehesa” system was most distinct with a higher species richness (not significantly) and with several unique species, probably travelling from the adjacent grassland. However, many species responded significantly to the type of management, depending on the habitat associations of the species. We also found strong responses of some of the species to one type of management, either positive (exclusively collected from one management type) or negatively (completely absent). Shrub cover and soil organic matter content were the main environmental variables determining the carabid assemblage structure. At the regional scale, the four management types accounted for a high carabid beetle diversity. This diversity appears to be threatened by landscape homogenization, since traditional management practices are disappearing due to recent land-use changes in the area. [Copyright &y& Elsevier]

Abstract: Although it is known that many plant species that are sensitive to solar UV radiation exist in low radiation environments, little is known about the sensitivity of young tree seedlings and herbaceous forest vegetation that inhabits the low radiation environment of the forest understory. Furthermore, little is known about the UV radiation environment of this vegetation during the deciduous forest leaf-out period when solar radiation levels are the highest. The development of the forest canopy and the penetration of solar UV radiation through the canopy to the understory of a deciduous upland forest was studied between 15 April and 1 June of 2004. During the early part of the leaf-out period, the mean canopy transmittance in the PAR exceeded that in the UV-A or UV-B. By 20 days into the leaf-out period, the PAR transmittance was nearly equal to that of the UV. As the leaves in the canopy reached full expansion, the PAR, UV-A and UV-B penetration was essentially equal and small. Canopy transmittance during leaf-out was not dependent on cloud cover. Greater penetration of solar radiation in longer wavelengths within the UV was probably a result of scattering of direct beam radiation off tree bark in the canopy. The effective canopy transmittance from 15 March through the canopy leaf-out was 47%. For an expected period of UV exposure for the herbaceous layer of 15 March through 15 May, the tree seedlings and herbaceous plants received 41kJm−2 of biologically effective UV-B radiation. It is projected that the herbaceous layer vegetation will receive approximately 27% more UVBBE radiation on clear days with a decreased stratospheric ozone of 20DU and approximately 3% more UVBBE radiation with increased temperatures causing leaf-out to begin 10 days earlier than 2004. More research is needed to understand the potential interactions of these and other climate change components on the deciduous forest. [Copyright &y& Elsevier]

Studying land degradation through a soil quality approach, which reveals soil functioning within the ecosystem, is necessary for sustainable management of land resources. This investigation was conducted to understand the changes of soil functions, resulting from exploitive management, using some soil quality indicators and their statistical and geostatistical measures. Undisturbed and disturbed sites were identified in each of two study areas, including an oak forest and a semiarid rangeland in central Iran. Soil organic carbon (OC), total nitrogen (TN), microbial respiration (MR), aggregate stability (AS), and hydraulic properties of the sites were determined. Statistical comparisons of frequency distribution functions of OC and MR revealed that these functions are normal in protected forest, while in the disturbed forest distributions deviate from normality. In the rangeland sites, the results were exactly the opposite. Spatial variability of the two variables in forest sites demonstrated pure nugget and spherical pattern in protected and disturbed sites, respectively. As for the rangeland ecosystem, pure nugget pattern was observed for both sites. According to our findings, protection of rangeland has resulted in higher OC and MR with no effect on the amount of TN and infiltration rate. The negative effect of this management system was a decrease in aggregate stability due to the formation of crust as a result of complete grazing exclusion. By contrast, improvement in all soil quality indicators in protected forest indicated the success of conservative management in this region. [Copyright &y& Elsevier]

The effects of prescribed burning, herbicide application, and thinning treatments were examined in upland Quercus stands with a replicate block field study. Two site types were analyzed: (1) nonsuccessional with a Quercus overstory and Quercus understory, and (2) successional with a Quercus overstory and an Acer saccharum understory. Treatments were examined for their effects on vegetation structure and composition, especially with respect to altering the natural succession from Quercus communities to mesophytic species. In addition, impacts of burning on soil nutrients were examined prior to and immediately following burn treatments. Results from the study indicate that fire had little effect on A horizon soil nutrients following burns. The data suggest fire plays a more important role as a decomposer for nutrient release in February burns than in November burns. Natural precipitation and leaching from the litter layer in the fall rendered similar nutrient dynamics as burning in November.The structural changes to vegetation following fire were more noticeable than compositional changes. Thinning of the canopy was generally necessary for the understory to respond to burning treatments. Burning did not affect stems >3.8 cm dbh (diameter at breast height). Density of most woody species <3.8 cm dbh decreased with burning, but increased with burning and thinning, indicating the stress of shaded conditions. Thus, burning prior to thinning may be an effective method for controlling an A. saccharum invasion into Quercus stands.Herbaceous, seedling, sapling, and overstory strata diversity were unaffected by the treatments. Data indicated that the community responds with species extant at the time of treatment. Thus, the initial conditions prior to disturbance were important factors in the response of the stand to disturbance.Although fire has played a major role in upland forest dynamics prior to settlement, forest structure and composition can no longer be maintained by fire. Succession without fire has resulted in a different structure and composition to oak forests, altering both fuels and fuel moisture levels. Species normally considered intolerant of fire have reached size classes large enough that they tolerate cool to moderate burns. More severe disturbance techniques, or combinations of techniques, are necessary for sustainable oak forest management in the central hardwood region. [Copyright &y& Elsevier]

The current work deals with the use in a Mediterranean environment of a simulation model of forest ecosystem processes which was originally created for temperate areas (FOREST-BGC). The model was calibrated and applied on two deciduous forest stands in Tuscany (Central Italy) by using conventional and remote sensing data as inputs. First, information on the two stands needed to initialise the model was derived from different sources, while meteorological data were extrapolated from a nearby station by an existing procedure (MT-Clim). Temporal profiles of leaf area index (LAI) were then derived both from direct ground measurement and from the processing of NOAA-AVHRR NDVI data. The model was calibrated using stand transpiration values obtained for 1997 by a sap flow method. Next, its performances were tested against the same transpiration values measured in 1998. The results obtained indicate that FOREST-BGC is capable of simulating water fluxes of Mediterranean forests when suitable LAI profiles are considered. Moreover, the derivation of these profiles from NDVI data can improve the model performance probably due to an enhanced consideration of the effects of the typical Mediterranean summer water stress. These results support the final objective of the work, which is the development of a procedure capable of integrating conventional and remote sensing data to operationally simulate water and carbon fluxes on a regional scale. [Copyright &y& Elsevier]

Quercus pollen and meteorological data for several years from eight sites in Spain have been statistically analysed to select the threshold temperature and calculate the mean heat accumulation for predicting the Quercus pollination start in different climatic areas. The growing degree days method, which assumes the daily temperature varies as a sine wave, was used for heat accumulation calculations. Threshold temperatures between 4 and 12 °C were chosen using linear regression equations forced through the origin and their root mean square error (RMSE) of predicted against the observed dates for each observation site. Above the threshold, the average growing degree days (up to 1999) for the studied years was taken as the predictor value. Results showed a relationship between the selected threshold and elevation and a stronger and statistically significant correlation between threshold and yearly mean temperature, for each site. Regression analysis indicated that the selected threshold and the calculated heat accumulation were optimum for most of the localities. The validity of the results was tested using the meteorological data for the year 2000 as independent variable and this confirmed that there were only a few days difference between the predicted and observed day of the first pollen release for most of the studied localities. [Copyright &y& Elsevier]

• The highest accumulation of microbial necromass C at the interface of litter and mineral soil. • Microbial necromass C accounted for <50% of bulk SOC in oak forest mineral soils. • The proportion of microbial necromass to SOC increased significantly from Oi1 to Ah2. • Soluble C, N, and P significantly affected microbial necromass decomposition/accumulation. • The ratio of fungal to bacterial necromass C decreased significantly from Oi1 to Ah2. Microbial necromass plays an essential role in soil organic carbon (SOC) accumulation. Nevertheless, how microbial necromass carbon (C) concentrations and their contributions to SOC sequestration change from litter to mineral soil and what factors influence its accumulation remain poorly understood. To address this knowledge gap, we performed a field experiment to investigate the compositional distribution characteristics of microbial necromass C and its contributions to SOC sequestration in an oak forest (Quercus wutaishanica) litter-mineral soil profile of the Chinese Loess Plateau. The present study estimated the microbial necromass C concentrations based on the microbial cell wall's biomarker amino sugars. Our results demonstrated that microbial necromass C increased from the Oi1 to Oa layers but decreased from the Ah1 to AB horizons. The highest accumulation of microbial necromass C was found at the litter-mineral soil interface (i.e., total microbial necromass in the Oa layer was 39.5 Mg ha−1, and Ah1 was 22.8 Mg ha−1). The contribution of total microbial necromass C to SOC increased from Oi1 to Ah2. Specifically, the total microbial necromass C accounted for 40.7%, 47.7%, and 37.0% of the average bulk SOC in the Ah1, Ah2, and AB horizons of the oak forest mineral soil, respectively. The ratio of fungal to bacterial necromass C decreased from litter to mineral soil, indicating that the relatively higher bacterial necromass C increasingly accumulated in the deeper litter layers and upper mineral soil horizons. Fungal and bacterial necromass C increased with increasing labile organic C, nitrogen (N), and labile inorganic phosphorus (P), suggesting that higher easily accessible soluble nutrients lead to higher microbial biomass levels, which in turn lead to higher microbial necromass accumulation. Overall, our findings suggested that microbial demand for C or N influences the quantity of soluble nutrients and further lead to changes in microbial necromass C decomposition/accumulation. [ABSTRACT FROM AUTHOR]

Air pollution from industrial areas is an environmental stress on trees that can seriously endanger the future of forests. Ancient Persian oak trees (Quercus brantii Lindl.) in the semi-arid forests of the Zagros are exposed to various environmental stresses such as air pollution from the Ilam gas refinery, which causes many challenges in forest regeneration and afforestation, thus jeopardizing forest sustainability or restoration. The aim of this study was to investigate the effect of toxic pollutants emitted from a gas refinery operation on seed germination and morphological characteristics of seedlings from maternal trees that are located at different distances (1000, 1500, 2000, 2500 and 10,000 m) and directions (east and west) from the facility. The results showed that oak seedlings grown from acorns collected at a distance of 10,000 m had the highest values in various seed germination and seedling developmental measures and morphological traits such as leaf and root mass, number and length compared to other distances of 1000, 1500, 2000 and 2500 m from the gas refinery. Highest values in seed germination, and seedling emergence and growth occurred at distances furthest from the refineries. Also, direction from the refinery significantly (p < 0.05) effected root growth, with larger seedlings occurring from acorn collected west of the refinery. The results of principal component analysis and discriminate analysis showed that, of the traits observed, various seed germination traits were most sensitive to gaseous toxic pollutants emitted from this source. Based on all studied traits, seedlings from acorns collected at 10,000 m from the facility were easily distinguished from seedlings of acorns collected at closer distances. It can be concluded that refinery toxic pollutants caused significant adverse changes in germination and seedling growth from acorns collected from oak trees located near (less than 10,000 m) to the source of air pollution. It is recommended that such pollution sources should be established far away from forest areas, and if constructed, be equipped with appropriate technologies such as flare gas recovery (FGR) to reduce emission of toxic pollutants and other emissions such as sulfur dioxide (SO 2) and hydrogen sulfide (H 2 S) from the gas refinery. It is also strongly recommended that acorns collected for restoration measures come from maternal trees growing at a distance >10,000 m, and especially to the west of gas refineries. • The highest values in oak seed germination and seedling morphological traits occurred at distances furthest from the refinery. • Various seed germination traits were most sensitive to gaseous toxic pollutants emitted from this source. • Such pollution sources should be established far away from forest areas, and if constructed, be equipped with appropriate technologies such as flare gas recovery (FGR). [ABSTRACT FROM AUTHOR]

• Although extraction is recognized as a threat for orchids, its effects are unknown. • Extraction increases the abundance of old plants but diminishes that of the young. • Plant sections extraction diminishes the biomass of the plants and their flowering. • Fallow periods are required in populations under extraction. Chronic anthropogenic disturbance caused by the extraction of plant sections or entire individuals from wild populations can modify the population structure of the plants. Population structure, plant biomass capital and reproductive probability were compared in five Laelia autumnalis populations under different extraction intensities. For each plant, the number of pseudobulbs was counted and the biomass of each pseudobulb estimated and its live/dead status recorded along with the presence of inflorescence remnants. The live biomass of each plant was related to its total number of pseudobulbs. In populations under greater levels of extraction, the plants accumulate less biomass as they become larger. In populations under lower extraction, there was a greater abundance of small plants (1–9 and 10–18 pseudobulbs). In contrast, populations under higher extraction presented a structure with a greater abundance of large individuals (>19 pseudobulbs). In all populations, the frequency of the remains of inflorescences increases with plant size. In contrast, the development of inflorescences in the study season decreased as the intensity of extraction increased. In conclusion, extraction of Laelia autumnalis plants causes them to accumulate less biomass and become less likely to develop inflorescences as they age, and ultimately modifies their population structure toward an abundance of large, old plants. [ABSTRACT FROM AUTHOR]

• Effect of wild boar grubbing on forest soil CO 2 emission was assessed. • Grubbing activity increased soil CO 2 emission across two-year investigation. • Grubbing activity increased soil basal respiration. • Topsoil and subsoil organic carbon together explained the elevated soil CO 2 emission. Soil disturbances by large animals are known to affect soil carbon (C) storage and thus have the potential to change ecosystem functioning in forests. However, little is known about the effects of wild boar grubbing on soil CO 2 emission in forest ecosystems. Here we investigated soil respiration and soil physico-chemical properties of top- (0–10 cm) and sub-soil (10–20 cm) on the paired grubbed and non-grubbed plots in an oak forest for a 2-year period. Wild boar grubbing substantially increased soil respiration by 69.5% in 2015 and 32.9% in 2016, respectively. Wild boar disturbance considerably elevated soil basal respiration but showed no effect on its temperature sensitivity. In addition, we found that the grubbing-induced increases in soil organic carbon and microbial biomass activity from both top- and sub-soil contributed to the stimulated soil respiration after the disturbance. Our 2-year experiment indicates that soil bioturbation could lead to a strong positive effect on soil CO 2 emission in oak forest ecosystems, but the stimulation tends to reduce with recovery time. The finding also highlights the importance of soil depth and time effect while quantifying the effect of wild boar grubbing on soil C storage in forest ecosystems. [ABSTRACT FROM AUTHOR]

We estimated above-ground biomass, nutrient content, litterfall and nutrient return to the soil in deciduous and evergreen Quercus pyrenaica Will., Quercus lanuginosa Lamk and evergreen Quercus ilex L. oak forests, respectively, near Salamanca (Spain) and Montpellier (France). The calculated biomass ranged from 64 to 121Mgha-1. Perennial material (trunks and branches) represented 96-97% in the four Spanish Q. pyrenaica stands and 93% in the French Q. lanuginosa and Q. ilex stands. Q. pyrenaica had higher P, Mg, Fe and Mn contents thanthe other two species from southern France. In contrast, these latter species had higher N and Ca concentrations. All of these differences were related to soil nutrient availability, especially Ca, Mg, P, Fe and Mn. Comparison of the chemical composition of leaves on trees with that of leaf litter indicated retention and translocation of N, Pand K from leaves to perennial biomass and recycling of Ca and Mg from trees to the soil. [ABSTRACT FROM AUTHOR]

Soil and soil water chemistry under three different vegetation-typeson a former heath area were investigated in Jutland, Denmark. An unmanaged heathland left undisturbed since the start of this century is now invaded by the oaks. Together with a small Sitka plantation (age 60 years), soil development due to vegetation changes was investigated. The typical heathland podzol soil had changed within decades underthe oak trees towards an acid brown soil. The soil under the Sitka spruce had changed towards a more strongly podzolized soil compared tothe former heath soil. Present processes occurring within the soil were investigated by analysis of soil solution chemistry. The leachingof inorganic ions and soluble organic matter had increased manifold under Sitka spruce. Nitrification increased markedly with soil depth probably due to effects of higher pH. The increase of nitrate with soil depth was followed by a similar increase in dissolved aluminium. The equivalence of the dissolved organic carbon varies under oak and heath between 6 and 10 m eqv g-1. TOC and under Sitka the equivalence of the dissolved carbon was between 10 and 15 m eqv g- 1. No nitrate and only traces of ammonium were found in soil water from the upper 30 cm of the soil under heath. Soil nitrogen was almost exclusively (more than 90%) connected to the carbon cycle. Under Sitka spruce generally less than 20% of soil water nitrogen was coupled to the carbon cycle, i.e. most of the nitrogen in the soil water leaving the rooting zone under Sitka spruce was nitrate. In the oak forest, nitrate only appeared as traces in the soil water in the winter periodand in the summer period in relatively higher amounts. Generally, between 80% and 90% of the nitrogen was coupled to the carbon cycle in the winter and in the summer only 50%. (c) 1999 Elsevier Science B.V. [ABSTRACT FROM AUTHOR]

The influence of atmospheric nitrogen deposition on mixed-oak forestvegetation along a deposition gradient in south Sweden was studied using multivariate methods. The main vegetation gradients were largelycontrolled by soil acidity, nitrogen supply, canopy composition and the location of the sample plots. The results suggest that nitrogen deposition has affected the field layer vegetation directly by increased nitrogen availability and indirectly by accelerating soil acidification. A close correlation between nitrogen deposition and longitude/latitude does not allow a sharp separation between effects of deposition and other geographically controlled factors. However, according to time series studies, 20 of the 30 field layer species that are mostclosely associated with high nitrogen deposition in our study have increased in frequency in areas with high deposition during the past decades. This group of field layer species includes many species generally considered as nitrophilous, but also several acid-tolerant species. [ABSTRACT FROM AUTHOR]