Frequencies of annual species of Medicago on brown acid soils of the Macquarie region of New South Wales

Abstract

The distribution of naturalized annual species of Medicago (medics) was studied on the brown acid soils of the Macquarie region of New South Wales, an area approximately 80 miles by 40 miles in extent. Four soil-landscape units were defined and one of these units was subdivided geographically into three parts.

Four medics were found: Medicago minima (L.) Bart. and Medicago laciniata (L.) Mill. were by far the dominant annual legumes, occurring in many places at high frequency; Medicago denticulata Willd. and Medicago praecox DC. occurred at few sites and only at low frequency.

Marked differences with respect to frequencies of medics were found both between soil-landscape units and the geographical subdivisions. On each unit and subdivision the frequency of M. minima in quadrats was consistently higher than that of M. laciniata.

Association between M. minima and M. laciniata in quadrats was variable, but tended to be positive where these two medics occurrcd at low frequency and negative where they occurred at high frequency.