Species richness and density of ground herbs within a plot of lowland rainforest in north-west Borneo

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Abstract
In a I-ha plot all ground herb species were recorded. Within the plot selected properties were investigated in three 20 m × 20 m subplots. The number of ground herb species and individuals in the subplots were lowest near to a local hilltop and they increased towards the lowest part of the plot. There was no significant difference in canopy openness, or in thickness of leaf litter layer, between the upper and lower subplots. In the upper subplot the soil layer was thin and the weathered bedrock was close to the surface. In the lower subplot the soil was much deeper. The pH and concentrations of Mg were significantly lower and %loss-on-ignition, total P and total N concentrations were significantly higher in the upper subplot. Elevation and soil moisture were significantly correlated in the upper 10 cm of soil. It is not possible to select any one abiotic property as being the critical determinant of the gradient of ground herbs. However, it is suspected that the availability of water in the topsoil, particularly after droughts, may be more important than the soil nutrients in limiting herb distribution.