Abundance and diversity of the coleopterous fauna of a calcareous grassland under different cutting regimes

Published source details Morris M.G. & Rispin W.E. (1987) Abundance and diversity of the coleopterous fauna of a calcareous grassland under different cutting regimes. Journal of Applied Ecology, 24, 451-465.
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Summary

The type of semi-natural grassland management may greatly influence the occurrence and abundance of many invertebrate animals. In this study the effects of cutting on oolitic limestone grassland at different times of year on the abundance and diversity of coleoptera was examined.

Study site: Coleoptera were sampled from an oolitic limestone grassland dominated by false oat-grass Arrhenatherum elatius at Castor Hanglands National Nature Reserve, Cambridgeshire, southeast England.

Treatments and experimental design: Four grassland treatments were initiated on long-unmanaged grassland in 1973: annual cutting in May or July, or both months, with an uncut control, with four replicates of each in a randomized block design. The 16 plots (each 16 x 12 m) were separated by 2 m-wide unmown grassland strips. As much mown vegetation as possible was removed from cut plots by raking.

Sampling: In October 1972, and at 2-4-weekly intervals throughout April 1973 to December 1975, standard samples of invertebrates were taken from 1.1 1 m² of grassland in each plot using a D-Vac insect vacuum net to sample mostly vegetation-living species.

Heat extraction of turves in Berlese-type funnels was also used. Samples (using 20 funnels) were taken in five periods from November 1973, after cutting had been undertaken once, to August 1974, following the second annual cut. In each period, four successive weekly samples of a single, randomly selected 0.071 m² turf were taken from each plot. Extracted beetles were identified to species and data pooled for each of the five sampling periods for most analyses.

A comparison of beetle numbers showed the D-Vac samples to contain only 1-17% of that in the sample turves, the control plots generally having the higher proportions recorded. Due to the higher efficiency of turf extraction and the uniform trimming of each turf, it was assumed that D-Vac sampling had differential efficiencies in extracting Coleoptera from plots under different cutting treatments. The data from the D-Vac sampling were therefore discarded for most purposes.

A total of 9,947 beetles of 149 species (22 families) were taken from the turve samples, with a further 23,580 individuals and an additional 68 species from vacuum samples. The most abundant and species-rich family extracted from turves was the Staphylinidae (58 species recorded - 39% of the total) with the 8,627 individuals making up 87% of the turve fauna. Carabidae and Curculionidae were the next most species-rich, but together accounted for only 21% of the species and 8% of the individuals recorded. The average density of coleopterans was 435/m².

Significant differences were recorded in the number of species, diversity and evenness of the beetle fauna summed over the year, with values highest on the control plots and then, though less clearly, on the July-cut plots.

The small staphylinid Amischa analis, was especially abundant on the May and May/July plots and strongly influenced diversity and eveness values.

Significantly more species and individuals of predacious and saprophagous families
were recorded on the control plots and also on the May-cut plots, but less so. No significant differences were recorded for phytophagous groups.

Significant differences between treatments for number of species and diversity were recorded in some periods, particularly in August post-treatment, but there were no differences in the abundance of individuals.

Compared with earlier work on Hemiptera sampled from the same plots and with other studies of the grassland Coleoptera abundance and diversity, there was little similarity between the effects of the May and control treatments, between these two groups. This was partly attributed to a lack of vertical stratification of the beetle fauna in grassland.

Conclusions: The authors recommend the use of rotational management to maintain the features of tall and short grassland, essential for the maintenance of species populations of different plants and animals.

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