Influence of the tropical millipede, Glyphiulus granulatus (Gervais, 1847), on aggregation, enzymatic activity, and phosphorus fractions in the soil

Abstract

Soil macrofauna contribute to soil aggregation, as well as to enzymatic and nutrient dynamics in soils. Few studies have investigated the influence of millipede species from tropical regions on these soil variables. The objective of this study was to investigate the influence of the millipede Glyphiulus granulatus (Gervais, 1847), on aggregation, enzymatic activity, and phosphorus (P) fractions in a subtropical soil under controlled conditions. The present study was performed using 0, 2, 6, and 12 individuals per microcosm with five replicates of each density. After an incubation period of 28days, the increase in G. granulatus population density reduced the proportion of aggregates between 1.00‐2.00mm (y=236.16−1.4921x, P<0.05). The aggregates between 1.00‐2.00 and 2.00‐4.76mm were negatively correlated (r=−0.95, P<0.05). The increase population densities resulted in increased nitrogen (N) levels in the soil. The greatest population density (12 millipedes per microcosm) increased soil N content by 7%. The activity of β-glycosidase increased with densities of 6 and 12 millipedes per microcosm as compared to the control. However, the acid phosphatase activity was reduced in the presence of the millipedes, particularly at high densities, reaching 341μgp-nitrophenolg−1soilh−1 while 489μgp-nitrophenolg−1soilh−1 was found in the control treatment. The millipedes had no influence on available inorganic P fractions (H2O-Pi and NaHCO3-Pi). However, the amount of readily labile P (H2O-Pi+NaHCO3-Pi+NaHCO3-Po) was greater at the highest millipede density (12 individuals) and was mainly related to the increase of NaHCO3-Po. This indicated that the available P in soils may be conserved by cycling of organic P with high densities of such macroinvertebrates.