Linking spatio-temporal dynamics of earthworm populations to nutrient cycling in temperate agricultural and forest ecosystems

摘要

Numerous laboratory and small plot-scale studies have highlighted the importance of earthworm populations in decomposition and nutrient cycling. However, the simple scaling up of such results to explain conditions on a large field scale, across agricultural landscapes under varied management scenarios, or across landscapes made up of different types of ecosystems (agricultural, grassland, forest), is very much constrained by a lack of information about the spatiotemporal distribution of earthworm populations. This study documents the spatiotemporal variation in earthworm populations in temperate ecosystems. A mixed deciduous forest, grass-dominated hayfield and corn agroecosystern were each fitted with a single 50 m x 50 m sampling grid, consisting of twenty-five 10 m x 10 m cells. Earthworms were collected at distinct single georeferenced locations in each of the 25 cells. Locations varied according to the sampling date (May, July or September). The earthworms collected by hand-sorting and formalin extraction, were first separated by species, then counted and weighed. The soil characteristics (temperature and moisture content, extractable nutrients, organic matter, pH) were also assessed for each time and location. Geostatistical and correlation analyses served to generate spatial maps of earthworm populations and to assess which soil factors most closely paralleled the numerical distribution of earthworms. This provided some insight into small-scale heterogeneity in earthworm populations, possibly allowing for the future extrapolation of laboratory and controlled field study results to larger scales, and in turn a more accurate estimation of the role of earthworms in nutrient cycling at the ecosystem and landscape levels.