Water relations, phenology and drought adaptation of understorey trees in tropical lowland rain forest.
1. The ecology of common understorey species associated with ridges was compared with species found on lower-slopes and those species occurring ubiquitously in two 4-ha plots in lowland rain forest at Danum, Sabah, East Malaysia (4″ 58â€™ N, 117â€™ 46â€™ E) over 3 years.
2. During the study period one dry period occurred (psychrometer-measured ridge soil water potential, 20 cm depth -0.67 MPa), but other, more severe, dry periods have occurred since records began in 1985 (estimated ridge water potential -1.21 MPa, March 1992). Lower soil water potentials occurred on ridges which had up to 0.22 MPa lower water potentials than lower-slopes (estimated difference March 1992, 0.40 MPa).
3. At dry times, Dimorphocatyx muricatus (ridge species) had higher pre-dawn (-0.21 v. -0.57 MPa; all quoted differences are significant at p