István Fekete

The effect of temperature and moisture on enzyme activity in Síkfőkút site

Seasonal effects have been observed in case of all the three examined enzymes which were influenced by soil moisture content and litter amount falling down to the soil surface. The effect of the soil temperature proved to be various. Sensibility of the enzymes occured in different ways. The above mentioned effects were observed in all enzymes but the degree of the regulation was uneven. The results obtained suggest, that a sustainable forest ecosystem may be exposed to various physiological effects induced by seasonal effects.

Effects of Climate Change on Litter Production in a Quercetum petraeae-cerris Forest in Hungary

Abstract - Climate change is a global problem. During the last century the increase of annual average temperature was 0.68°C, while the decrease of annual average of precipitation was 83 mm in Hungary. According to the long term meteorological data of Síkfőkút forest ILTER site the annual average temperature increased while average of yearly precipitation decreased, the forest climate became warmer and dryer. These processes could considerably contribute to forest decline, not only in the Quercetum petraeae-cerris stand of Síkfőkút, but everywhere in the country. Species composition and structure of the forest have changed considerably, as 68% of sessile oak (Quercus petraea) and 16% of Turkey oak (Quercus cerris) have died. Forest decline resulted in the breaking up of the formerly closed canopy, and consequently, in the formation of gaps in the forest. In the gaps, a secondary canopy developed with tree species of less forestry value. As a consequence, mass regeneration of field maple (Acer campestre) appeard in the gaps. The formation of gaps accelerated the warming and aridity of forests. In the article we answer the following question: how did climatic change and changing forest structure influence the leaf-litter production in the last four decades? Kivonat - A klímaváltozás hatása egy Magyarországi cseres-tölgyes erdő avarprodukciójára. Napjainkban a klímaváltozás egy globális probléma. Magyarországon az elmúlt évszázad folyamán az évi átlagos hőmérséklet 0,68 °C-ot emelkedett, az évi csapadék átlag 83 mm-t csökkent. A Síkfőkút Project korábbi, közel 20 éves meteorológiai adatsorai is bizonyítják a klímaváltozást, az erdő klímája melegebbé és szárazabbá vált. Mindezen folyamatok is hozzájárulhattak ahhoz a fapusztulási folyamatokhoz, amely nem csak a Síkfőkúti tölgyes állományt, de az ország számos állományát érintette. Az erdő fafaj összetétele és struktúrája jelentős mértékben megváltozott, a kocsánytalan tölgy 68%-a, a csertölgy 16%-a kipusztult. A fapusztulás következtében a korábbi zárt lombkorona felnyílt, az elpusztult fák helyén kisebb nagyobb lékek alakultak ki, amelyekben erdészeti szempontból kevésbé értékes fafajok nőttek fel és hozták létre a második lombkoronaszintet. Ennek köszönhető a mezei juhar tömeges megjelenése és térhódítása a lombkoronaszintben. A lékek kialakulása, a klímaváltozás hatását fokozva, felgyorsította az erdő felmelegedését és szárazodását. Jelen dolgozatunkban arra kerestük a választ, hogy a klímaváltozás, és ezen keresztül az erdő struktúrájának a változása hogyan befolyásolta az avarprodukciót az elmúlt négy évtized folyamán.

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

Background and aimsWe examined the influence of litter quality and litter depth on soil microclimate in the detrital manipulation plots in the Síkfőkút 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.MethodsDIRT manipulations include two litter addition and three litter removal treatments, and one Control.ResultsThere 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.ConclusionClimate 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.

An optimized HPLC method for soil fungal biomass determination and its application to a detritus manipulation study.

The goal of this research was to develop modified analytical method for the quantitative analysis of ergosterol, which is highly effective marker for fungal biomass. We suggest that our optimized method for the determination of ergosterol is an effective way to monitor changes in fungal biomass under different environmental conditions.

The Effects of Climate Change on Element Content and Soil pH (Síkfőkút DIRT Project, Northern Hungary)

In the Detritus Inputs and Removal Treatment (DIRT) field experiments established at the Sikfőkut Site (northern Hungary) in October 2000, an experimental approach was applied to study long-term effects of litter quality and quantity on pH and nutrient mobility of soil in a Quercetum petraeae-cerris forest. Our previous results have suggested that decreases in organic matter content, total N, Ca2+ and Mg2+ concentrations in the soil are the consequence of the reduction in forest litter production induced by climate change and the resultant soil degradation over a longer period. An eight-year litter manipulation demonstrated a relation between soil pH and Mg2+ and Ca2+ concentrations in the soil. The reduction of litter production resulted in a decrease of the soil pH which occurred due to the decreasing Mg2+ and Ca2+ inputs into the soil, and consequent reduction of soil buffering capacity against the acidifying effects of the acidic intermediates of litter decomposition and humus compounds. If the litter production increases as a result of climate change, it should be accompanied by increasing C, total N, Ca2+ and Mg2+ contents in the soil and soil pH, with a positive effect on the soil organic matter and fertility. However, this scenario is rather unlikely as our results indicated decreasing litter production in the measurement period.

The detrital input and removal treatment (DIRT) network: Insights into soil carbon stabilization

Ecological research networks functioning across climatic and edaphic gradients are critical for improving predictive understanding of biogeochemical cycles at local through global scales. One international network, the Detrital Input and Removal Treatment (DIRT) Project, was established to assess how rates and sources of plant litter inputs influence accumulations or losses of organic matter in forest soils. DIRT employs chronic additions and exclusions of aboveground litter inputs and exclusion of root ingrowth to permanent plots at eight forested and two shrub/grass sites to investigate how soil organic matter (SOM) dynamics are influenced by plant detrital inputs across ecosystem and soil types. Across the DIRT network described here, SOM pools responded only slightly, or not at all, to chronic doubling of aboveground litter inputs. Explanations for the slow or even negative response of SOM to litter additions include increased decomposition of new inputs and priming of old SOM. Evidence of priming includes increased soil respiration in litter addition plots, decreased dissolved organic carbon (DOC) output from increased microbial activity, and biochemical markers in soil indicating enhanced SOM degradation. SOM pools decreased in response to chronic exclusion of aboveground litter, which had a greater effect on soil C than did excluding roots, providing evidence that root-derived C is not more critical than aboveground litter C to soil C sequestration. Partitioning of belowground contributions to total soil respiration were predictable based on site-level soil C and N as estimates of site fertility; contributions to soil respiration from root respiration were negatively related to soil fertility and inversely, contributions from decomposing aboveground litter in soil were positively related to site fertility. The commonality of approaches and manipulations across the DIRT network has provided greater insights into soil C cycling than could have been revealed at a single site.

Long-term effects of climate change on carbon storage and tree species composition in a dry deciduous forest

Abstract Forest vegetation and soils have been suggested as potentially important sinks for carbon (C) with appropriate management and thus are implicated as effective tools in stabilizing climate even with increasing anthropogenic release of CO2. Drought, however, which is often predicted to increase in models of future climate change, may limit net primary productio (NPP) of dry forest types, with unknown effects on soil C storage. We studied C dynamics of a deciduous temperate forest of Hungary that has been subject to significant decreases in precipitation and increases in temperature in recent decades. We resampled plots that were established in 1972 and repeated the full C inventory by analyzing more than 4 decades of data on the number of living trees, biomass of trees and shrubs, and soil C content. Our analyses show that the decline in number and biomass of oaks started around the end of the 1970s with a 71% reduction in the number of sessile oak stems by 2014. Projected growth in this forest, based on the yield tables data for Hungary, was 4.6 kg C/m2. Although new species emerged, this new growth and small increases in oak biomass resulted in only 1.9 kg C/m2 increase over 41 years. The death of oaks increased inputs of coarse woody debris to the surface of the soil, much of which is still identifiable, and caused an increase of 15.5%, or 2.6 kg C/m2, in the top 1 m of soil. Stability of this fresh organic matter input to surface soil is unknown, but is likely to be low based on the results of a colocated woody litter decomposition study. The effects of a warmer and drier climate on the C balance of forests in this region will be felt for decades to come as woody litter inputs decay, and forest growth remains impeded. &NA; The distribution of dry, extreme dry, and wet years from 1953 to 2014 (Bases: 1950–1980 average precipitation). The shaded area represents the time frame of the oak decline. Dry conditions in forest, forest stand composition and diversity change, net primary production, and oak decline. Figure. No caption available.

Application of a Stir Bar Sorptive Extraction sample preparation method with HPLC for soil fungal biomass determination in soils from a detrital manipulation study.

Ergosterol is a sterol found ubiquitously in cell membranes of filamentous fungi. Although concentrations in different fungal species span the range of 2.6 to 42μg/mL of dry mass, many studies have shown a strong correlation between soil ergosterol content and fungal biomass. The analysis of ergosterol in soil therefore could be an effective tool for monitoring changes in fungal biomass under different environmental conditions. Stir Bar Sorptive Extraction (SBSE) is a new sample preparation method to extract and concentrate organic analytes from liquid samples. SBSE was here demonstrated to be a simple, fast, and cost effective method for the quantitative analysis of ergosterol from field-collected soils. Using this method we observed that soil ergosterol as a measure of fungal biomass proved to be a sensitive indicator of soil microbial dynamics that were altered by changes in plant detrital inputs to soils in a long-term field experiment.

The Detrital Input and Removal Treatment (DIRT) Network

Abstract Ecological research networks functioning across climatic and edaphic gradients are critical for improving predictive understanding of biogeochemical cycles at local through global scales. Geographically broad networks can also test the generality of results seen at an individual site, and mixed results in different ecosystems can help with the discovery of unrecognized controls on ecosystem properties. One such international network, the Detrital Input and Removal Treatment (DIRT) Project, was established to assess how rates and sources of plant litter inputs influence accumulations or losses of organic matter in forest soils. DIRT employs chronic enhancements and exclusions of aboveground litter inputs and exclusion of root ingrowth to investigate how soil organic matter (SOM) dynamics are influenced by plant detrital inputs across ecosystem and soil types. Across the DIRT network described here, SOM pools decreased slightly in response to chronic exclusion of aboveground litter, but responded only slightly, or not at all, to chronic doubling of aboveground litter inputs. Explanations for the slow or even negative response of SOM to litter additions include increased decomposition resulting in greater soil respiration, priming (increased microbial utilization of old soil organic matter following inputs of new organic matter inputs), and increased dissolved organic carbon (DOC) output. Partitioning of belowground contributions to total soil respiration was predictable based on site-level soil C and N as estimates of site fertility. Contributions to soil respiration from root respiration were negatively related to soil fertility and contributions from decomposing aboveground litter in soil were positively related to site fertility. Finally, aboveground litter exclusion had an effect on C levels similar to that of root exclusion, thus we did not see evidence that root-derived C is more critical to soil C sequestration.