Increased nutrient availability, especially nitrogen and phosphorus from fertilization and pollution, affects plant communities. Nutrient concentrations in plant tissues and their stoichiometric ratios can indicate nutrient availability. This study aimed to evaluate the use of nutrient concentrations and stoichiometric ratios as indicators of nutrient addition effects on productivity, species composition, and functional group proportions in a mountain meadow. In a long-term grassland experiment in the Polish Carpathians, various fertilizer combinations (90NPK, 180NPK, N, P, PK, control) and liming were applied. Over 39 years, species composition was assessed, and nitrogen, phosphorus, and potassium concentrations in plant biomass were measured. Liming had no effect on vegetation parameters or nutrient concentrations. The N:P ratio remained low across all treatments, ranging from 4.9 in 90NPK to 11.7 in 90N, suggesting nitrogen limitation. Despite significant variations in species composition and productivity between the NPK-fertilized treatments and the remaining treatments, the N:P ratio varied only slightly. The N:P ratio was influenced not only by nutrient availability but also by other factors, such as the capacity of some species characteristic of oligotrophic habitats to accumulate excess nitrogen in the 90N treatment, and the increase in the proportion of nitrogen-fixing legumes following potassium application in the PK treatment. Conclusion: Stoichiometric ratios may serve as useful indicators of nutrient effects on vegetation; however, they should be interpreted with caution because they are also affected by various environmental factors.
Coffee is one of the most widely consumed beverages worldwide, and its mineral composition varies significantly depending on roasting parameters and product form. This study aimed to assess the content of macronutrients (K, Mg, Ca, Na, P) as well as trace and potentially toxic elements (Al, Co, Cr, Fe, Mn, Ni, Sr, Zn) in brews made from coffee beans roasted to five levels (5/10-9/10) and from two variants of freeze-dried instant coffee (5/10 and 6/10). Brews were prepared at a standardized coffee-to-water ratio of 6:100 (m/v), at 92 degrees C for 5 min, digested with HNO3 and H2O2, and then the concentrations of elements were determined by the ICP-OES method. Potassium was the predominant element in all brews, with mean concentrations of 287 mg L-1 in whole bean coffees and 688 mg L-1 in freeze-dried coffees. The concentrations of macronutrients in freeze-dried coffees were 1.51-2.36 times higher than in whole-bean coffee, reflecting the greater content of soluble solids in the instant product. In contrast, iron concentrations were practically identical in both product forms regardless of the degree of roasting, suggesting differences in the physicochemical form in coffee beans. It was demonstrated that roast degree affects element concentrations in a curvilinear manner, with maximum extraction occurring at 7/10-8/10, while intense roasting (9/10) led to a 35-55% reduction in concentrations relative to maximum values. The results indicate that dark-roasted coffee contains lower concentrations of minerals than medium-roasted coffee, which may have nutritional implications for consumers who regularly drink coffee as a source of magnesium and potassium in their diet. Concentrations of arsenic, cadmium, and lead remained below the method's limit of quantification in all samples, confirming the safety of the analysed brews with respect to toxic metal content.
