Dániel Cserhalmi

Changes in a Wetland Ecosystem: A Vegetation Reconstruction Study Based on Historical Panchromatic Aerial Photographs and Succession Patterns

This paper presents the methodology and results of a vegetation reconstruction method based on botanical sampling, the knowledge of succession pattern, digital photograph-interpretation and automatic delineation via image segmentation. The aim is to provide a methodology for interpretation of archived black-and-white aerial photographs, which can be applied at other study sites. Our study area was the Nyíres-tó mire in the Bereg Plain (NE Hungary). Initially, botanical sampling was carried out, and this was followed by separation and identification of current vegetation types. In our study we selected automatic delineation using multi-resolution image segmentation as the method for vegetation mapping. Based on the present-day vegetation map produced and the known successional pathway of the mire, archive aerial photographs were analyzed separately in reverse chronological order to derive plant associations present at the different photograph acquisition dates. With this method we were able to make a chronological sequence of digital vegetation maps over a period of almost fifty years (1956–2002). The analysis of vegetation maps showed that forest cover increased steadily until 1988. After an artificial water supply was introduced (in 1986), the spread of tree-dominated associations became slower, and the relative cover of the different vegetation types reached a stable state.

The aims and results of the nature-protection management on the North-east Hungarian mires

By our experience the most important practical aspects of the nature-conservation management are the restauration of the surrounding natural vegetation (Fraxino pannonicae-Ulmetum forest) and keep the optimal water supply.

Vegetation change detection of mires with digital aerial photographs

Introduction The application of aerial photos was slightly insufficient in the Hungarian botanical work in the last few decades, and they were mostly used for vegetation mapping. Panchromatic photos were available from the beginning of the twentieth century, but the quality of the first images was fairly poor. GIS and remote sensing applications came to fore in the last years, and the importance of the digital images increased. Nowadays, many botanical researches use multispectral satellite imagery (Landsat TM, SPOT HRVIR/HRG, IKONOS and Quickbird, among others), but the usefulness of the panchromatic images is still contentious and the digital photo interpretation is also a developing field. In most Hungarian researches using aerial photos, the analysis is based on visual photo interpretation (Vona et al. 2006), although several international examples use digital photo interpretation in different territories (Kadmon Harari-Kremer 1999, Jauhianen 2003, Pellerin Lavoie 2003). There are different botanical researches on Hungarian mires (coenological, ecological, floristical, paleobotanical, etc.), but none of them is based on the interpretation of panchromatic images. There also haven’t been any similar researches on the mires of the Bereg plain yet, however several papers dealing with the vegetation changes on these mires (Simon 1992, Nagy et al. 1998a, Nagy et al. 1999, Jakab Magyari 2000, Nagy et al. 2003, Czobel et al. 2005). Mires are ex lege protected habitats, so the investigation of them should be a main objective of nature protection. The purpose of our research was to find out the proper photo interpretation methods that can help to reconstruct the recent vegetation dynamic processes of the mires. These methods could be useful for projecting the management of nature protection, and also for preserving these habitats.

Decomposition Rate, and Carbon and Nitrogen Dynamics of Sphagnum Litter: Lessons from a Peat Bog

ABSTRACT Decomposition rates and changes of carbon and nitrogen contents of Sphagnum litter in mire vegetation can help to explore the ecological effects of climate change and the role of environmental factors from a local to an ecosystem scale. The objective of the study was to determine the relationship between mentioned parameters in small and isolated Sphagnum dominated mires. Measurements had been conducted throughout a year by placing litterbags filled with Sphagnum biomass in three vegetation types (open peat bog, poor fen, alder carr) of a mire ecosystem in Hungary. Peat decomposition rates differed to a great extent; the slowest decomposition rate (39.1±9.52%) was in the alder carr, indicating that slower decomposition could be characteristic for this kind of vegetation type of mire. Between Sphagnum dominated microhabitats, open peat bog showed medium (65.57±4.05) while poor fen the fastest (68.61±5.5) rates in decomposition. The C/N ratio of the Sphagnum litter showed significant decrease (P <0.005) in all studied micro-environments. Slower N release was observed from litter of Alnus dominated association (31.3±6.9%) compared to Sphagnum dominated ones (56.5±8.3%). Our findings showed that the decomposition rates were more dependent on vegetation type than C/N ratio and this relationship was also revealed at a small spatial scale.