Assessing vulnerability to embolism and hydraulic safety margins in reed-like Restionaceae.

The African Restionaceae (Poales), the dominant graminoid layer in the megadiverse Cape Floristic Region of South Africa, are distributed across a wide range of moisture availability, yet currently there is very little known about the underlying hydraulics of this group. We tested two methods for measuring culm vulnerability to embolism, the optical and pneumatic methods, in three species of Cannomois ranging in habitat from semi-riparian (Cannomois virgata) to dryland (Cannomois parviflora and C. congesta).

Post-fire summer rainfall differentially affects reseeder and resprouter population recovery in fire-prone shrublands of South Africa.

Summer rainfall can have strong effects on post-fire mediterranean-type shrubland recovery patterns, with potentially long-lasting implications on communities. Our three-year field rainfall manipulation experiment tested post-fire survival and physiological responses of reseeders and resprouters to contrasting summer rainfall patterns in Fynbos and Renosterveld shrublands in South Africa. Climate projections are uncertain for this region but indicate that increased convective summer rainfall events could occur.

Does a trade-off between growth plasticity and resource conservatism mediate post-fire shrubland responses to rainfall seasonality?

Growth plasticity may allow fire-prone species to maximize their recovery rates during temporary, sporadic periods of rainfall availability in the post-fire environment. However, moisture-driven growth plasticity could be maladaptive in nutrient-limited environments that require tighter control of growth and resource use. We investigated whether a trade-off between plasticity and conservatism mediates growth responses to altered rainfall seasonality in neighbouring shrubland communities that occupy different soils.

Ramification has little impact on shoot hydraulic efficiency in the sexually dimorphic genus (Proteaceae).

Despite the diversity of branching architectures in plants, the impact of this morphological variation on hydraulic efficiency has been poorly studied. Branch junctions are commonly thought to be points of high hydraulic resistance, but adjustments in leaf area or xylem conduit abundance or dimensions could compensate for the additional hydraulic resistance of nodal junctions at the level of the entire shoot. Here we used the sexually dimorphic genus (Proteaceae) to test whether variation in branch ramification impacts shoot hydraulic efficiency.

The iodine content of fresh milk samples in Natal and the effect of iodophor teat dips on milk iodine content.

The iodine content of fresh milk samples from bulk milk transport vehicles (tankers) and from bulk tanks on individual farms was determined. Approximately 75 percent of all the samples fell within the normal range of 25 to 300 micrograms iodine/l of milk. The mean iodine concentration in the tanker samples was 257 micrograms/l and in the farm tank samples 294 micrograms/l, while the medians of the iodine concentrations in the surveys were 214 and 218 micrograms/l respectively.