Xylem cavitation vulnerability influences tree species' habitat preferences in miombo woodlands
Vinya, R and Malhi, Y and Fisher, JB and Brown, N and Brodribb, TJ and Aragao, LE, Xylem cavitation vulnerability influences tree species' habitat preferences in miombo woodlands, Oecologia, 173, (3) pp. 711-720. ISSN 0029-8549 (2013) [Refereed Article]
Although precipitation plays a central role in structuring Africa’s miombo woodlands, remarkably little is known about plant-water relations in this seasonally dry tropical forest. Therefore, in this study, we investigated
xylem vulnerability to cavitation for nine principal tree species of miombo woodlands, which differ in habitat preference and leaf phenology. We measured cavitation vulnerability (Ψ50), stem-area specific hydraulic conductivity (KS), leaf specific conductivity (KL), seasonal variation in predawn water potential (ΨPD) and xylem anatomical properties [mean vessel diameter, mean
hydraulic diameter, mean hydraulic diameter accounting for 95 % flow, and maximum vessel length (VL)]. Results show that tree species with a narrow habitat range (mesic specialists) were more vulnerable to cavitation than species with a wide habitat range (generalists). Ψ50 for mesic specialists ranged between -1.5 and -2.2 MPa and that for generalists between -2.5 and -3.6 MPa. While mesic specialists exhibited the lowest seasonal variation in ΨPD,
generalists displayed significant seasonal variations in ΨPD suggesting that the two miombo habitat groups differ in their rooting depth. We observed a strong trade-off between KS and Ψ50 suggesting that tree hydraulic architecture is one of the decisive factors setting ecological boundaries for principal miombo species. While vessel diameters correlated weakly (P > 0.05) with Ψ50, VL was positively and significantly correlated with Ψ50. ΨPD was significantly correlated with Ψ50 further reinforcing the conclusion that tree hydraulic architecture plays a significant role in species’ habitat preference in miombo woodlands.