C:N:P stoichiometry associated with biochar in forest soils at historical charcoal production sites in Poland

Abstract

Biochar amendment leads to change of physical, chemical and biochemical properties of soil. The aim of our research was to determine C/N/P stoichiometry of soils with biochar in pine forest in places of historical charcoal production. The research was carried out in the Manowo Forest District, northern Poland (54°08′52″N; 16°27′53″E). The research was carried out in an area where relict charcoal hearths are abundant. The burning of charcoal in this area took place about 200–250 years ago. Pine wood was used in relict charcoal hearths. The samples for analysis were taken from relict charcoal hearths and in the immediate vicinity (background). We determined the enzymatic activity and we recorded the content of C, N and P in testing samples. We also calculated the C/N/P stoichiometry for samples and we used soil enzyme activity stoichiometry for reflects the nutrient availability. Our research confirmed the role of biochar in shaping the C/N/P stoichiometry in forest soils. Soils with biochar were characterized by wider stoichiometry and significantly higher C and P content compared to the control soils. The enrichment of the soil with biochar resulted in a significant increase in the activity of enzymes involved in the carbon cycle (β-glucosidase and β-D-cellobiosidase), nitrogen (N-acetyl-β-D-glucosaminidase) and phosphorus (phosphatase). The enzyme stoichiometry confirmed limited availability of nutrients, especially nitrogen. Biochar in historical charcoal production sites increased total carbon stocks in temperate pine forests. This implied that relict charcoal hearths can significantly promote the carbon sequestration capacity.