Dynamics of sun-induced chlorophyll fluorescence and reflectance to detect stress-induced variations in canopy photosynthesis

Passive measurement of sun-induced chlorophyll fluorescence (F) represents the most promising tool to quantify changes in photosynthetic functioning on a large scale. However, the complex relationship between this signal and other photosynthesis-related processes restricts its interpretation under stress conditions. To address this issue, we conducted a field campaign by combining daily airborne and ground-based measurements of F (normalized to photosynthetically active radiation), reflectance and surface temperature and related the observed changes to stress-induced variations in photosynthesis. A lawn carpet was sprayed with different doses of the herbicide Dicuran. Canopy-level measurements of gross primary productivity indicated dosage-dependent inhibition of photosynthesis by the herbicide. Dosage-dependent changes in normalized F were also detected. After spraying, we first observed a rapid increase in normalized F and in the Photochemical Reflectance Index, possibly due to the blockage of electron transport by Dicuran and the resultant impairment of xanthophyll-mediated non-photochemical quenching. This initial increase was followed by a gradual decrease in both signals, which coincided with a decline in pigment-related reflectance indices. In parallel, we also detected a canopy temperature increase after the treatment. These results demonstrate the potential of using F coupled with relevant reflectance indices to estimate stress-induced changes in canopy photosynthesis

Experimental warming and precipitation reduction affect the biomass of microbial communities in a Sphagnum peatland

Due to their unique flora, hydrology and environmental characteristics, peatlands are precious and specific habitats for microorganisms and microscopic animals. Their microbial network structure and their biomass are crucial for peatland carbon cycling, through primary production, as well as decomposition and mineralization of organic matter. Wetlands are one of the ecosystems most at risk from anthropogenic activities and climate change. Most recent scenarios of climate change for Central Europe predict an increase in air temperature and a decrease in annual precipitation. These changes may disturb the biodiversity of aquatic organisms, and the peat carbon sink. Considering the above climatic scenarios, we aimed to: i) assess the response of microbial community biomass to warming and reduced precipitation through the lens of a manipulative experiment in a peatland ecosystem ii) predict how global warming might affect microbial biodiversity on peatlands exposed to warmer temperatures and decreased precipitation conditions. Additionally, we wanted to identify ecological indicators of warming among microorganisms living in Sphagnum peatland. The result of a manipulative experiment carried out at Rzecin peatland (W Poland) suggested that the strongest reduction in microbial biomass was observed in heated plots and plots where heating was combined with a reduction of precipitation. The most pronounced changes were observed in the case of the very abundant mixotrophic testate amoeba Hyalosphenia papilio and cyanobacteria. Shifts in the Sphagnum microbial network can be used as an early warning indicator of peatland warming, especially a decrease in the biomass of important phototrophic microbes living on the Sphagnum capitula, e.g. Hyalosphenia papilio.publishedVersio

The full GHG balance of croplands under seven-year rotation scheme and conventional tillage practices in Poland

Greenhouse gases fluxes were measured with chambers on the selected plots of the experimental arable station of Poznan University of Life Sciences in Brody (52o26’N, 16o18’E), Poland. This is a long term experiment, where the same crops are cultivated under the same fertilization treatment schemes (eleven combinations) since 1957. At the blocks of the full 7-year rotation, there are cultivated in permanent rotation: winter wheat ->winter rye -> potato ->spring barley -> triticale and alfalfa (till the second year). GHG fluxes have been measured on plots with the same fertilization level (Nmin-90kg, K2O-120 kg/ha, P2O5-60 kg/ha and Ca), which is very close to the average amount of mineral fertilization applied in western Poland. No catch crops were cultivated between the main crops. The soil was classified as Albic Luviosols according to FAO 2006 classification. CO2 fluxes have been measured monthly since March 2011, while N2O and CH4 fluxes since March 2012 (weekly) and measurements were continued till October 2013. CO2 fluxes were measured with dynamic chambers, while N2O and CH4 fluxes were measured with both static and dynamic chambers approaches (using LOSGATOS gas analyser). Carbon net ecosystem exchange (NEE) and ecosystem respiration (Reco) have been modelled for the entire period based on the measured fluxes (different management treatments were included in the model), while N2O and CH4 fluxes were linearly interpolated between campaigns. Taking into account the accumulation periods between 15th of October and 14th of October of the next year the cumulated NEE was negative only in case of alfalfa, winter rye and winter wheat, reaching in average -3.5 tCO2-C ha-1 for alfalfa and winter rye fields and around -0.4 tCO2-C ha-1 for winter wheat in seasons 2011-2012 and 2012-2013. While, cumulated NEE for spring crops (potato and spring barley) was positive for the same periods and reached in average 1.1 tCO2-C ha-1 and 2.5 tCO2-C ha-1 for spring barley and potatoes, respectively. The fields with spring crops have positive NEE, and hence negative climatic impact, because by more than half of the year the soil was bared and no catch crops were cultivated between main crops. For the entire 12-months period the highest N2O emission rates were recorded at plots of winter wheat and winter rye and reached 2.2 kgN2O-N ha-1 and 2.0 kgN2O-N ha-1, respectively. At plots of alfalfa and potatoes the emission rates were close to 1.5 kgN2O-N ha-1, while at spring barley plots the emission did not exceed 1.1 kgN2O-N ha-1. At the same time, the yearly CH4 uptake reached from -0.9 kgCH4-C ha-1 at plots of alfalfa, -1.5 kgCH4-C ha-1 at plots of winter wheat to around -1.7 kgCH4-C ha-1 at winter rye, potato and spring barley plots

Experimental warming and precipitation reduction affect the biomass of microbial communities in a Sphagnum peatland

Due to their unique flora, hydrology and environmental characteristics, peatlands are precious and specific habitats for microorganisms and microscopic animals. Their microbial network structure and their biomass are crucial for peatland carbon cycling, through primary production, as well as decomposition and mineralization of organic matter. Wetlands are one of the ecosystems most at risk from anthropogenic activities and climate change. Most recent scenarios of climate change for Central Europe predict an increase in air temperature and a decrease in annual precipitation. These changes may disturb the biodiversity of aquatic organisms, and the peat carbon sink. Considering the above climatic scenarios, we aimed to: i) assess the response of microbial community biomass to warming and reduced precipitation through the lens of a manipulative experiment in a peatland ecosystem ii) predict how global warming might affect microbial biodiversity on peatlands exposed to warmer temperatures and decreased precipitation conditions. Additionally, we wanted to identify ecological indicators of warming among microorganisms living in Sphagnum peatland. The result of a manipulative experiment carried out at Rzecin peatland (W Poland) suggested that the strongest reduction in microbial biomass was observed in heated plots and plots where heating was combined with a reduction of precipitation. The most pronounced changes were observed in the case of the very abundant mixotrophic testate amoeba Hyalosphenia papilio and cyanobacteria. Shifts in the Sphagnum microbial network can be used as an early warning indicator of peatland warming, especially a decrease in the biomass of important phototrophic microbes living on the Sphagnum capitula, e.g. Hyalosphenia papilio