Coastal Scrub Vegetation Research Articles

Stimulated photosynthesis of regrowth after fire in coastal scrub vegetation: increased water or nutrient availability?

Fire-prone landscapes experience frequent fires, disrupting above-ground biomass and altering below-ground soil nutrient availability. Augmentation of leaf nutrients or leaf water balance can both reduce limitations to photosynthesis and facilitate post-fire recovery in plants. These modes of fire responses are often studied separately and hence are rarely compared. We hypothesized that under severe burning, woody plants of a coastal scrub ecosystem would have higher rates of photosynthesis (Anet) than in unburned areas due to a transient release from leaf nutrient and water limitations, facilitating biomass recovery post-burn. To compare these fire recovery mechanisms in regrowing plants, we measured leaf gas exchange, leaf and soil N and P concentrations, and plant stomatal limitations in Australian native coastal scrub species across a burn sequence of sites at 1 year after severe fire, 7 years following a light controlled fire, and decades after any fire at North Head, Sydney, Australia. Recent burning stimulated increases in Anet by 20% over unburned trees and across three tree species. These species showed increases in total leaf N and P as a result of burning of 28% and 50% for these macronutrients, respectively, across the three species. The boost in leaf nutrients and stimulated leaf biochemical capacity for photosynthesis, alongside species-specific stomatal conductance (gs) increases, together contributed to increased photosynthetic rates after burning compared with the long-unburned area. Photosynthetic stimulation after burning occurred due to increases in nutrient concentrations in leaves, particularly N, as well as stomatal opening for some species. The findings suggest that changes in species photosynthesis and growth with increased future fire intensity or frequency may be facilitated by changes in leaf physiology after burning. On this basis, species dominance during regrowth depends on nutrient and water availability during post-fire recovery.

A new species of Proterhinus Sharp, 1878 (Coleoptera: Curculionoidea: Belidae)from Miti'aro, Cook Islands, South Pacific.

Proterhinus tauai Brown, new species is described from specimens collected on the island of Miti'aro in the Cook Islands, South Pacific. It differs from congeners by the combination of having a dorsal vestiture of decumbent brown clavate scales, lacking erect elongate setae, anterior pronotal angles projecting forwards, and having short antennae that do not reach the posterior margin of the pronotum. This species shows strong sexual dimorphism in the shape of the rostrum, with males having a large semicircular rostrum, compared with a stout subrectangular rostrum in females. Fitting allometric models to the relationship of morphometric variables with body length show that rostrum width and area have significantly different allometric relationships between the sexes, consistent with hypotheses of sexual selection. Proterhinus tauai was collected from coastal scrub vegetation. Collection data and observation of captive specimens indicate a host relationship with the parasitic vine Cassytha filiformis L. (Lauraceae).