Examination on the state of health regarding a protected sessile oak stock

It can be observed in more and more fields of science that the results of other disciplines are utilised in order to achieve new results; it is true for nature conservation as well. Global climate change is to be considered as one of the most thoroughly studied topic; scientists pay special attention to the responses given by species and communities to climate change. In case of field examinations the accuracy of samplings and measurements is of key importance. Often solely estimated data is available which deteriorates the accuracy of the assessment. The health status of forests is usually determined by visual observations that imply errors due to human subjectivity. In this examination we surveyed the health status of a protected sessile oak stock within the Botanical Garden of Szent István University in Gödöllő by using not only conventional methods but also instrumental measurements. We have used FAKOPP 3D Acoustic Tomograph. It is an instrument developed in Hungary that is able to determine – in percentage – the extent of deterioration in tree trunks. The method of measurement is the following: this instrument measures the speed of sound propagation in the tree matter, since rotten and healthy tissues conduct sound differently. Prior to the examination we surmised that a predominantly healthy stock would be examined. Nevertheless, instrumental measurements proved that the trees of this stock are considerably decayed; therefore constant instrumental monitoring is required. We found that the extent of decomposition was the most significant in the lowest measurement level (i.e. 40 cm – Layer 1) and it steadily decreased in the higher regions

Influence of soil type on N2O and CH4 soil fluxes in Hungarian grasslands

Soil fluxes of methane and nitrous oxide were determined for grasslands on sandy, loess and clay soils in Hungary. As the direction of methane flux (emission or uptake) depends on the soil characteristics bi-directional fluxes were observed. For sandy and loess grasslands the sink and source processes are practically balanced showing a negligible low mean methane flux for 2006–2007 (−0.04–0.05 kg CH4 ha-1 yr-1 ). In this period the clay grassland functioned as a weak sink for methane (−0.34 kg CH4 ha-1 yr-1 ). Average soil nitrous oxide emission fluxes for the period of 2002–2006 was 0.5 kg N ha-1 yr-1 for sandy and loess while 0.2 kg N ha-1 yr-1 for clay grassland, respectively, with substantial inter-annual variations. Taking into account the total atmospheric N-input 0 to 8 per cent of deposited nitrogen is emitted from the soils in the form of N2O as the intermediate product of soil denitrification processes

Interannual variability of grasslands’ carbon balance depends on soil type

Interannual variation of carbon fluxes of grasslands on sandy (5 years data) and heavy clay soils (4 years data) have been analysed. The sandy grassland was carbon sink in 3 (2004, 2005, 2006) out of the investigated 5 years. Its annual C-balance is precipitation limited, the relation seems strongly conservative, with r2 of 0.83. More than half of the net source activity fell to the summer droughts. The heavy clay grassland was net source of carbon in one year (2007) only with no whole year record from 2003, a drought and heat wave year. Dependence of the C-balance on precipitation was somewhat weaker (r2 =0.57) than in the sandy grassland. Length of growing period showed less variation here compared to the sandy grassland. Recovery of sink activity after rains was much slower for the heavy clay grassland than for the sandy grassland. The reason behind is that the amount of water required to reach optimal soil water content for plant functioning is several times larger for the mountain grassland. This fact and the low conductivity of the clay soil for water decrease the heavy clay grassland’s recovery potential after droughts. Owing to these soil characteristics, the clay grassland may be more vulnerable to droughts in terms of decreased C-assimilation and (soil) carbon losses under the predicted drier summers even if the annual precipitation sum was higher by 10.7% on average for the mountain compared to the sandy grassland. The annual precipitation sum is close to the threshold, below which the grasslands may turn into source of carbon. While in one hand this can be viewed as an example of ecosystem scale adaptation to available water, drought events also involve loss of soil carbon and a potential positive feedback between source activity and decreasing net primary production, on the other

Effects of irrigation on community composition and carbon uptake in Pannonian loess grassland monoliths

Grassland ecosystems in the Carpathian Basin may be particularly vulnerable to current and predicted changes in precipitation, and ecosystem responses to potential effects of water are not well understood. To examine how water addition can affect the species composition and structure, and CO2 -flux of a Central European natural steppe plant community, grassland monoliths were irrigated for three consecutive years at Gödöllő, from 2002 through 2004. The loess grassland studied by ex situ is a characteristic plant association of Hungary and similar vegetation can be found in other temperate regions. The treatment consisted of spray irrigation during night-time only in the growing season as well as aboveground biomass removal twice per year. Interannual and intraannual dynamics of species richness, Shannon Diversity, percentage cover, and different functional groups (monocots/dicots; plant life forms; social behaviour types; C4/C3 plants), and Net Ecosystem CO2. Exchange in treated and untreated permanent plots, were studied simultaneously. To measure NEE and water vapour at stand level a self-developed, portable, non-destructive open chamber system (d=60cm) was used. The majority of the examined parameters varied considerably among years at both irrigated and control, but concerning carbon fluxes water addition effects were evident in dry periods only. At the treated plots, in general species richness, Shannon Diversity, the number of plant life forms and social behaviour types, the ratio of dicots and C4 plants declined with addition of water. Our study proved that decline in species richness and Shannon diversity is not necessarily followed by the reduction of stand physiological (synphysiological) processes