Contrasting water relations of three coastal tree species with different exposure to salinity

Abstract

This field study examined the ecophysiological responses of three tree species to salinity in the Austin Bay Nature Reserve, adjacent to the Peel-Harvey Estuary in Western Australia (115 46 0 E 32 37 0 S). The area is at increased risk of flooding with saline water during storm surges due to the construction of a channel between the estuary and Indian Ocean in 1994. Banksia attenuata R.Br. occurs on small sandy ridges adjacent to a seasonal wetland, while Melaleuca cuticularis Labill. and Casuarina obesa Miq. occur in a seasonally flooded wetland. Landscape position determined exposure to salinity, with M. cuticularis and C. obesa experiencing high soil and groundwater salinity during summer (electrical conductivity, EC, up to 70 dS m À1 ) while B. attenuata was not exposed to soil or groundwater with EC greater than 20 dS m À1 . B. attenuata had relatively stable leaf water status throughout the year and did not osmotically adjust as root-zone salinity increased. By contrast, M. cuticularis and C. obesa had large variation in stem water potential and exhibited osmotic adjustment during summer. Whereas the sap flow rates of M. cuticularis and C. obesa remained high throughout the year, sap flow of B. attenuata decreased during summer which may have limited uptake of salt. The three species also exhibited differences in traits associated with tissue-level salt tolerance, as M. cuticularis and C. obesa produced compatible organic solutes (methyl proline in M. cuticularis and proline in C. obesa), whereas B. attenuata did not. The distributions of these species within the Austin Bay Nature Reserve are determined in part by their tolerance to salinity, which will influence their responses to hydrological disturbance.

The response of semi‐arid ephemeral wetland plants to flooding: linking water use to hydrological processes

“…Firstly, C. obesa trees growing at Toolibin Lake are likely to be shallow‐rooted, as reflected in our study and shown by work on the same species in an estuarine ecosystem by Carter et al . (). A shallow root system will quickly intercept downward‐flowing water and, at Toolibin Lake, will be less prone to the effects of rising saline groundwater.…”

Spatio‐temporal water dynamics in mature Banksia menziesii trees during drought

“…Leaf-specific conductivities of B. menziesii ranged from 0.9 × 10 −4 to 1.0 × 10 −3 kg m −1 MPa −1 s −1 . Water relations of B. menziesii are very similar to the co-dominant B. attenuata (Canham et al 2009) for which Carter et al (2006) found higher osmotic potential than in co-occurring woodland species and interestingly no osmotic adjustment between summer and winter (always higher than −3 MPa). However, the bulk elastic modulus was 28% higher during summer (less elastic cells) compared to winter suggesting that turgor maintenance relies on changes in cell wall elasticity rather than adjustments in osmotic potential.…”

Tamarix arboreavar.arboreaandTamarix parviflora: Two species valued for their adaptability to stress conditions

“…On the other hand, seasonal effects on plant growth and development may be difficult to detect in field studies where many other sources of variation cannot be controlled [4]. In this comparative study on Tamarix species, photosynthesis showed the most remarkable seasonal differences: T. arborea var.…”