Simulation modeling of phytoplankton dynamics in a large eutrophic river, Hungary – Danubian Phytoplankton Growth Model (DPGM)

Ecological models have often been used in order to answer questions that are in the limelight of recent researches such as the possible effects of climate change. The methodology of tactical models is a very useful tool comparison to those complex models requiring relatively large set of input parameters. In this study, a theoretical strategic model (TEGM ) was adapted to the field data on the basis of a 24-year long monitoring database of phytoplankton in the Danube River at the station of G¨od, Hungary (at 1669 river kilometer – hereafter referred to as “rkm”). The Danubian Phytoplankton Growth Model (DPGM) is able to describe the seasonal dynamics of phytoplankton biomass (mg L−1) based on daily temperature, but takes the availability of light into consideration as well. In order to improve fitting, the 24-year long database was split in two parts in accordance with environmental sustainability. The period of 1979–1990 has a higher level of nutrient excess compared with that of the 1991–2002. The authors assume that, in the above-mentioned periods, phytoplankton responded to temperature in two different ways, thus two submodels were developed, DPGM-sA and DPGMsB. Observed and simulated data correlated quite well. Findings suggest that linear temperature rise brings drastic change to phytoplankton only in case of high nutrient load and it is mostly realized through the increase of yearly total biomass.

Stylization: a method for preserving the character of climate sensitive habitat

Stylization is a method of ornamental plant use usually applied in urban open space and garden design based on aesthetic consideration. Stylization can be seen as a nature-imitating ornamental plant application which evokes the scenery rather than an ecological plant application which assists the processes and functions observed in the nature. From a different point of view, stylization of natural or semi-natural habitats can sometimes serve as a method for preserving the physiognomy of the plant associations that may be affected by the climate change of the 21st century. The vulnerability of the Hungarian habitats has thus far been examined by the researchers only from the botanical point of view but not in terms of its landscape design value. In Hungary coniferous forests are edaphic and classified on this basis. The General National Habitat Classification System (Á-NÉR) distinguishes calcareous Scots pine forests and acidofrequent coniferous forests. The latter seems to be highly sensitive to climate change according to ecological models. The physiognomy and species pool of its subtypes are strongly determined by the dominant coniferous species that can be Norway spruce (Picea abies) or Scots pine (Pinus sylvestris). We are going to discuss the methodology of stylization of climate sensitive habitats and briefly refer to acidofrequent coniferous forests as a case study. In the course of stylization those coniferous and deciduous tree species of the studied habitat that are water demanding should be substituted by drought tolerant ones with similar characteristics. A list of the proposed taxa is going to be given.

Stylization: a method for preserving the character of climate sensitive habitats. A case study of acidofrequent mixed forests

Stylization is a common method of ornamental plant use that imitates nature and evokes the scenery. This paper discloses a not yet proposed aspect of stylization, since the method offers the possibility of preserving the physiognomy of those habitats that seem to vanish due to future climate change. In addition, novelty of the method is founded also on that vulnerability of the Hungarian habitats has been examined by the researchers only from the botanical and ecological point of view so far and not in terms of its landscape design value. In Hungary, acidofrequent mixed forests appear to be highly sensitive to climate change according to ecological models. We are going to discuss the methodology of stylization of climate sensitive habitats and briefly refer to acidofrequent mixed forests as a case study. Those coniferous and deciduous tree species of the studied habitat that are water demanding are proposed to be substituted by drought tolerant ones with similar characteristics, and an optionally expandable list of these taxa is presented. Based on this the authors suggest experimental investigations of those of the proposed taxa for which the higher drought tolerance is based on observations only.

An agro-ecological simulation model system

In this paper five different models, as five modules of a complex agro-ecosystem are investigated. The water and nutrient flow in soil is simulated by the nutrient-in-soil model while the biomass change according to the seasonal weather aspects, the nutrient content of soil and the biotic interactions amongst the other terms of the food web are simulated by the food web population dynamical model that is constructed for a piece of homogeneous field. The food web model is based on the nutrient-in-soil model and on the activity function evaluator model that expresses the effect of temperature. The numbers of individuals in all phenological phases of the different populations are given by the phenology model. The food web model is extended to an inhomogeneous piece of field by the spatial extension model. Finally, as an additional module, an application of the above models for multivariate state-planes, is given. The modules built into the system are closely connected to each other as they utilize each other’s outputs, nevertheless, they work separately, too. Some case studies are analysed and a summarized outlook is given.