Earthworm and soil moisture effects on the productivity and structure of grassland communities

• Published in: Soil biology & biochemistry Vol. 31; no. 4; pp. 517 - 523
• Main Authors: Zaller, J.G, Arnone, J.A
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-04-1999; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Lumbricus; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Switzerland; Zoology (interactions between soil fauna and agricultural or forest soils); Switzerland; Europe; Calcimorphic soil; Monocotyledones; Oligochaeta; Biological productivity; Earthworm; Soil fauna; Rendzinas; Gramineae; Dicotyledones; Angiospermae; Grassland soil; Plant production; Fauna; Plant community; Permanent grassland; Annelida; Lumbricidae; Calcareous soils; Animal activity; Leguminosae; Macrofauna; Animal community; Spermatophyta; Invertebrata; Population density
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/S0038-0717(98)00126-6

The objectives of this study were (1) to evaluate the effect of earthworm activity on aboveground plant biomass production of native calcareous grassland communities in NW-Switzerland and (2) to determine which plant functional types (graminoids, non-legume forbs and legumes) are most responsive as indicators of potential effects on plant community structure. Earthworm activity was manipulated in the field by creating three earthworm densities (low: 37, ambient: 114, high: 169 worms m
−2) and two soil moisture conditions (ambient and 280 mm yr
−1 additional rain) in 30 1×1 m
2 trenched plots (to a depth of 45 cm with nylon screening). Earthworm density was censused and readjusted in the spring and autumn of 1996 and again in the spring of 1997 using the Octet electro-sampling method. Earthworm activity, measured as cumulative surface cast production, was significantly different among worm density treatments (low worm density: 591±49, ambient: 991±87, high: 1469±120 g cast d.m. m
−2 yr
−1),
P<0.001. Cast production increased with increasing worm density, however increased soil moisture, which was significantly higher in plots receiving additional rain, did not affect worm activity at any worm density level. Surprisingly, earthworm activity had no effect on the aboveground biomass production of the plant community or of any plant functional type; however additional rain stimulated aboveground biomass production of graminoids (+30%,
P=0.006) and
Carex spp. (+200%,
P=0.020). The lack of a stimulatory effect of increased earthworm activity on plant biomass production indicates that apparent earthworm-induced increases in plant nutrient availability were insufficient to promote the growth of the perennial plant species in these native grasslands. Our results, taken together with those from earlier studies in these grasslands, suggest that the effects of earthworm activity on plant community structure occur slowly where they relieve soil constraints on plant growth.