Central European Deciduous Forests Research Articles

Dominant herbaceous plants contribute to the spatial heterogeneity of beech and riparian forest soils by influencing fungal and bacterial diversity

Understanding of factors that shape diversity patterns in forest ecosystems is a main challenge in forest ecology and management practices. Although herbaceous plants are known to contribute to the maintenance of the structure and function of temperate forests, their impact on fungal and bacterial communities in soils is largely unknown. Therefore, we conducted a comparative study of soil fungal and bacterial diversity in two Central European deciduous forests, focusing on plots with dominant herbaceous species of contrasting morphology, phenology, reproduction, and ecology, including Allium ursinum and Dentaria enneaphyllos in a beech forest, as well as Aegopodium podagraria and Ficaria verna in a riparian forest. Plots with a mixture of herbaceous species and without plant cover were also studied. In both forests, fungal communities showed the strongest association with spatial location, part of which was explained by between-site variability in soil chemistry and was also influenced by herbaceous vegetation. The community composition of saprotrophic fungi depended on the presence and type of herbaceous vegetation in both forests. In addition, herbaceous plants affected the composition of arbuscular mycorrhizal fungi community in the beech forest, while in the riparian forest they affected endophytes and plant pathogens. For bacteria, soil chemistry played the most important role. Our results showed that dominant herbaceous vegetation is one of the drivers shaping microbial community composition, contributing to spatial heterogeneity of forest sites. Given that herbaceous species, especially those forming monospecific patches, affect the soil biotic properties in temperate forests, they should be included in forest management practices.

Water retention of the organic soil horizon in a central European deciduous forest

Water retention of the organic soil horizon in a central European deciduous forest

The role of vernal species in vegetation classification: a case study on deciduous forests and dry grasslands of Central Europe

The very short lifespan of some therophytes and geophytes growing in Central European deciduous forests and dry grasslands may be a source of inconsistencies in vegetation data analyses. Based on data provided by the Czech National Phytosociological Database (CNPD) we identified frequently occurring vernal species, using species life-form strategies and species response curves. We also studied vernal species richness in respect to particular vegetation units. Using two data sets of permanent plots (Deciduous Forests and Dry Grasslands; each recorded in spring and summer), we tested whether partitions of spring releves have a higher similarity to partitions of summer releves if we exclude the vernal species. The same question was addressed using large data sets compiled from the CNPD. We found 21 frequent vernal species in forests and 36 in dry grasslands. Many of them are included in the Red List of the Czech Republic. Richest in vernal species were the phytosociological class of mesic and wet forests (Carpino-Fagetea), pioneer vegetation of the Koelerio-Corynephoretea and dry grassland vegetation of the Festuco-Brometea. When we excluded the vernal species before classification of spring releves, we got a significant increase in partition similarity of the summer data. We conclude that exclusion of vernal species helps to get more consistent and comparable results, except of data analyses focused on the spring period and vernal species as vegetation indicators. Application of intra-seasonal stratification might be a way to obtain more balanced data sets suitable for comparison, analyses and classification.

The effects of litter production and litter depth on soil microclimate in a central european deciduous forest

We examined the influence of litter quality and litter depth on soil microclimate in the detrital manipulation plots in the Sikfőkut Detrital Input and Removal Treatments (DIRT) experiment in northeastern Hungary. We measured the soil temperatures from 06.01.2001 to 06.16.2008 and air temperature from 06.17.2004 to 06.16.2008. DIRT manipulations include two litter addition and three litter removal treatments, and one Control. There were significant differences detected among plots in winter and summer soil mean temperatures (p < 0.001) as well as in the number of frost-free days. The highest annual soil temperature variation was detected in litter removal treatments, while the lowest variation was in Double Litter plots with the thickest litter layer. The root exclusion treatments had significantly greater soil moisture contents than other treatments due to loss of transpiration. Plots wetter and lower in organic matter showed lower winter temperatures. Climate change influences soil temperature and moisture content not only directly, but also through the change of litter production. Litter thickness can reduce the effects of soil temperature extremes and moderate minimum and maximum temperature values. These differences in soil microclimate may have a highly significant, but unrecognized effect on soil carbon balance through effects on microbial processing of litter and soil carbon.

Alterations in forest detritus inputs influence soil carbon concentration and soil respiration in a Central-European deciduous forest

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.

When beech strikes back: How strict nature conservation reduces herb-layer diversity and productivity in Central European deciduous forests

Current nature conservation policy is going to alter the tree-layer composition of many Central European deciduous forests. As a consequence of ceasing silvicultural management, the competitive ecosystem engineer European beech (Fagus sylvatica L.) will spread and the proportion of secondary tree species will considerably decrease. Thus, changes can also be expected in herb-layer diversity, productivity and composition. To predict these changes, we analysed relationships between tree- and herb-layer diversity and composition along tree-diversity gradients in the Central German woodland areas of the Hainich National Park (unmanaged) and the Göttinger Wald (managed by close-to-nature forestry).The flora of both study areas was dominated by typical forest species. In the Hainich, the herb-layer vegetation in beech-dominated stands was less diverse compared to stands richer in canopy species. Herb-layer productivity was also lower in beech-dominated stands. In the Göttinger Wald, herb-layer diversity and productivity were not related to tree-layer diversity and beech proportion, instead to the light transmissibility of the canopy layer. The different results can be explained by logging effects in the Göttinger Wald, which promoted the light factor as significant for herb-layer diversity and productivity. In the consistently darker stands of the Hainich, soil variables, particularly influenced by the ecosystem engineer beech, were decisive. Areas of high canopy diversity in the Hainich result from former management practices and can, in the future, be expected to decrease with the spread of beech.We conclude that forest management cessation will result in decreasing herb-layer diversity and productivity in many Central European deciduous woodlands, especially in landscapes where historical management practices led to unnaturally low proportions of beech. The short-term consequence of management cessation is a loss of herb-layer diversity due to reduced light availability; in the long-term, herb-layer diversity is expected to decrease due to the expansion of beech.If the key aim of nature conservation policy is to preserve and develop the typical diversity of near-natural beech forests, then a complete cessation of forest management can be advised. However, if the typical forest herb diversity of the semi-natural, century-old cultural landscape is to be maintained, close-to-nature forestry management is necessary.

Different reactions of central and marginal provenances of Fagus sylvatica to experimental drought

Climate extremes are expected to increase in frequency and magnitude as a consequence of global warming, threatening the functioning, services and goods of forest ecosystems. Across Europe, the ecologically and economically important tree species Fagus sylvatica is expected to suffer particularly under such conditions. The regional introduction of provenances from drier and warmer climates is one option to adapt beech forest ecosystems to these adverse effects of climate change. Marginal populations from the drought-prone southern and north-eastern edges of the species’ distribution come into focus in search of suitable candidates for Central European deciduous forests. Here, we test three marginal provenances (Spain, Bulgaria and Poland) and three provenances from the centre of the distribution range (Germany) for their response to drought in two different soil types (sand, loam) in a full factorial common garden experiment in Landau, Germany. Drought impacted all growth parameters negatively (leaf damage +22 % (percentage points), height −40 % and diameter increment −41 %), and the sandy substrate exacerbated this effect. However, provenances differed in their response to drought and soil type. Evidence for a local adaptation to summer drought was detected, especially in terms of mortality rates. The Bulgarian and Spanish provenance showed a stable performance under drought conditions (BG −27 % in diameter increment; ES −32 %), compared to the Polish (−48 %) or the most sensitive German provenances (−57 %), yet for Bulgaria on a low level of total increment. This may indicate a trade-off between drought tolerance and growth. Therefore, a sole focus on drought-resistant marginal provenances seems to not be conducive, as they might be less adapted to other climatic factors, e.g. frost, as well. However, intermixed with local Central European provenances, these may act as functional insurance in future drought-prone forest stands.

Variability of Organic Matter Inputs Affects Soil Moisture and Soil Biological Parameters in a European Detritus Manipulation Experiment

Over the last three decades, increased temperatures and reduced annual precipitation have resulted in significant changes in several Central European deciduous forests. These effects include changes in soil moisture content and detritus production. Within the framework of a detritus manipulation experiment carried out in an old-growth Quercetum petraea–cerris community, we examined how changes in detritus inputs affect soil moisture content and microbial activity within six treatments. CO2 release and microbial enzyme activities are known to be highly sensitive to environmental factors such as soil moisture and detritus inputs. We applied three detritus removal (No Litter, No Roots and No Input) and two detritus addition (Double Litter and Double Wood) treatments. Although the plots received the same amount of precipitation, the various detritus inputs caused significant differences in soil moisture. Treatments excluding living roots had the highest moisture levels, while the treatment excluding only aboveground detritus inputs had the lowest. CO2 release, arylsulphatase activity and saccharase activity showed significant seasonal differences with the highest values occurring in spring. Moisture content had a significant positive correlation with CO2 release, and enzyme activities of the plots were affected by the quantity and quality of detritus inputs. Arylsulphatase activity showed the strongest correlation with soil moisture content (R = 0.62 in the control plot) followed by CO2 release (R = 0.61) and finally saccharase activity (R = 0.42). We observed that there was a remarkably weaker correlation between soil moisture content and the three parameters in the detritus removal treatments (R values between 0.56 and 0.13) than in the Control and detritus addition treatments (R values between 0.72 and 0.42). The correlation between the three parameters of interest and soil moisture content weakens considerably under drought conditions relative to the optimal moisture range of soil moisture content for microbial activity. If the amount of precipitation in the area continues to decrease as anticipated, then litter production and soil microbial activity may be reduced.

The relation between various detritus inputs and soil enzyme activities in a Central European deciduous forest

Within the framework of Síkfőkút DIRT (Detritus Input and Removal Treatments) Project, we have been examining the extent to which microbial activities of soils are influenced by detritus inputs of diverse quantities and qualities. The experimental site is located in the south part of the Bükk Mountains in North Eastern Hungary. This forest is a semi-natural stand ( Quercetum petraeae-cerris community) without forest management. The six treatments established are as follows: three treatments involving detritus removal (No Litter, No Roots, No Inputs), two treatments involving detritus duplication (Double Litter, Double Wood) and a control treatment. The study intends to present the results of saccharase and arylsulphatase activity examinations. Our hypothesis was that detritus reduction causes significantly greater influence on soil enzyme activities than detritus increase of the same extent. The general purpose of the project is to reveal the connection between modifications of detritus production and changes of climatic conditions and land use. It also studies how the modifications, decreases or increases in detritus production influence organic material content, and physical, chemical or biological processes of soils. Saccharase and arylsulphatase activities were measured three and a half years after the establishment of the plots; thus having enough time for the development of different ecological conditions at our disposal. Significant differences were detectable between the treatments for both enzymes. Two separate groups of treatments could be distinguished. The treatments with additional aboveground inputs (Double Litter, Double Wood) and the control (C) revealed higher activities, while a lower – sometimes significantly lower – enzyme activity characterized the other three, removal treatments (No Litter, No Roots, No Inputs). As for the Double Litter, Double Wood and Control treatments, no significant difference was detectable, although the latter two revealed higher values of enzyme activities than the former one. We found that soil moisture content was correlated with the two soil enzyme activities, especially that of the arylsulphatase. A much weaker correlation was found between the enzyme activities and soil moisture content in the soils that were wetter and poorer in substrates (No Roots and No Inputs treatments). Seasonal differences also involved the diverse moisture contents, while the effect of temperature could hardly be observed during the examinations (due to the nature of methods). In the case of both enzymes, the highest activities were detected during the wetter period, in spring. The three detritus removal treatments influenced enzyme activities in different ways. As for saccharase, it was the removal of belowground detritus that caused the greatest influence. However, in the case of arylsulphatase, it was the soil moisture content that influenced activity to the greatest extent in detritus removal treatments.

Controls on the dynamics of dissolved organic carbon and nitrogen in a Central European deciduous forest

Despite growing attention concerning therole of dissolved organic matter (DOM) inelement cycling of forest ecosystems, thecontrols of concentrations and fluxes of bothdissolved organic carbon (DOC) and nitrogen(DON) under field conditions in forest soilsremain only poorly understood. The goal ofthis project is to measure the concentrations and fluxes of DON, NH4 +, NO3 −and DOC in bulkprecipitation, throughfall, forest floorleachates and soil solutions of a deciduousstand in the Steigerwald region (northernBavaria, Germany). The DOC and DONconcentrations and fluxes were highest inleachates originating from the Oa layer of theforest floor (73 mg C L−1, 2.3 mg NL−1 and about 200–350 kg C, 8–10 kg Nha−1 yr−1). They were observed to behighly variable over time and decreased in themineral topsoil (17 mg C L−1, 0.6 mg NL−1 and about 50–90 kg C, 2.0 to 2.4 kg Nha−1 yr−1). The annual variability ofDOC and DON concentrations and subsequentialDOC/DON ratios was substantial in allsolutions. The DOC and DON concentrations inthroughfall were positively correlated withtemperature. The DOC and DON concentrationsdid not show seasonality in the forest floorand mineral soil. Concentrations were notrelated to litterfall dynamics but didcorrespond in part to the input of DOC and DONfrom throughfall. The throughfall contributionto the overall element fluxes was higher forDON than for DOC. Concentrations and fluxes ofDON were significantly correlated to DOC inthroughfall and the Oi layer. However, thecorrelation was weak in Oa leachates. Inaddition, seasonal and annual variation ofDOC/DON ratios indicated different mechanismsand release rates from the forest floor forboth components. The concentrations of DOC andDON in forest floor leachates were in mostcases dependent neither on the pH value orionic strength of the solution, nor on thewater flux or temperature changes. As aconsequence, the DOC and DON fluxes from theforest floor into the mineral soil werelargely dependent on the water flux if annualand biweekly time scales are considered.