The spatial structure of soil microbial properties in an upland grassland

TLDR: In this article, the spatial structure of soil microbial properties (microbial biomass1C, microbial biomass1 N, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved inorganic nitrogen (DIN), soil respiration and net nitrogen mineralization, metabolic quotient ( qCO 2) and C/N ratio in the microbial biomass) in an unimproved upland grassland in the Yorkshire Dales, United Kingdom.

Abstract: We characterised the spatial structure of soil microbial properties (microbial biomass1C, microbial biomass1 N, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved inorganic nitrogen (DIN), soil respiration and net nitrogen mineralization, metabolic quotient ( qCO 2) and C/N ratio in the microbial biomass) in an unimproved upland grassland in the Yorkshire Dales, United Kingdom. The grassland was selected because it had been ungrazed for thirty years. A 20 m x 20 m plot was marked and 100 soil samples were taken on a regular grid of 2 m x 2 m. The botanical composition of the vegetation associated with each soil sample was also determined. Both, descriptive statistics parameters and semivariogram analysis were considered for assessing data variability. Soil properties showed very high variability (CV from 50% to 84%). Total plant biomass was rather homogeneous (CV=8%), however, individual plant species distribution was highly skewed. Correlations between soil properties were generally strong. Soil respiration, net N1 mineralization and DIN did not exhibit spatial dependence at the sampled scale, indicating that data for these variables collected at 2m distance are independent. The spatial dependence of the remaining soil properties was described by a nugget component plus a structure, where the proportion of structural variance was highest for DOC and DON. Also the spatial dependence of plant biomass was either absent or scarce. In cases where spatial dependence was found, ranges extended from approximately 3.2 to 8 m, dispersed throughout both soil properties and vegetation; places further apart than this are spatially independent. Furthermore, mapping of the soil properties and vegetation allowed description and interpretation of interaction between them. Our data demonstrate high spatial variation in microbial properties in upland grasslands, and suggests plant cover may influence the different soil microbial properties.