Cechy charakterystyczne i parametryzacje dochodzącego promieniowania fotosyntetycznie czynnego w środkowym basenie Biebrzy = Characteristics and parametrisations of the photosynthetically active radiation incoming in the Middle Biebrza Basin

Abstract

The availability of light is one of the most important factors that determine the photosynthesis process. Wave bands of solar radiation from 400 to 700 nm are called photosynthetically active radiation (PAR) because of their ability to stimulate the process of photosynthesis. The limited data availability and the regional and local PAR dependence cause the need for independent research, especially in areas of high natural value. The main goal of the work is to characterize the incoming photosynthetically active radiation in the Middle Biebrza Basin on the basis of a 9-year measurement series (2013-2021) from the Kopytkowo site (53°35'30.8”N, 22°53'32.4"E). The analysis was carried out for both instantaneous values and daily totals. In addition to the basic statistical characteristics, attention was paid to radiation on clear days and to the relationship between the PAR values on the Earth's surface and at the top of the atmosphere. Due to the limited availability of empirical data, simple parameterizations of PAR radiation were proposed for use in environmental studies. The research was carried out in the north-eastern part of Poland on the outskirts of Biebrza National Park in the Middle Biebrza Basin (Fig. 1). The area can be characterised as natural, almost unchanged, and uninhabited wetlands overgrown by swamp vegetation. The measurement site is located around 350 m north of the small village Kopytkowo with only a handful of permanent residents. The PQS1 PAR Quantum Sensor by Kipp & Zonen mounted at height 2.7 m a.g.l. was used to collect data (Fig. 2). The sensor is part of the eddy-covariance system that measures the exchange of greenhouse gases between the ecosystem and the atmosphere. Data were sampled every 10 seconds and then stored in datalogger (CR500) as 5-minute averages. The results are shown as photosynthetic photon flux density (PPFD) with micromole per square metre per second (µmol∙m⁻²∙s⁻¹) as unit and were collected in Central European Time (CET).