Abstract:
We studied water use in a common bamboo species (Bambusa blumeana J.A. and J.H. Schultes) in the Philippines with the aim to (1) estimate bamboo water use and its dependence on environmental factors, (2) evaluate internal water storage and water dynamics and (3) compare water use characteristics of this bamboo species with those of co-occurring tree species. Two thermal sap flow methods were applied and complemented with a deuterium tracing experiment. Sap flow measured using the stem heat balance method (SHB) was in agreement with simultaneous flow measurements from thermal dissipation probes (TDP) which were used for long term measurements in this study. Maximal sap flux densities measured at the culm base using the TDP method were up to 25.7 g cm−2 h−1, but can be 2–3 times higher at other positions along the culm due to changes in the culm wall cross-section. Maximal water use rates of bamboo culms were on average 12 kg d−1, corresponding to a maximal transpiration rate of 1.4 mm d−1 at the clump level. These values are in line with those of co-occurring tree species, but bamboo tends to limit water use more under reduced soil water availability than most co-occurring tree species. Deuterium added to the transpiration stream at the culm base travelled upwards more slowly than in trees, leading to maximal deuterium levels in the canopy at the 3rd or 6th day after labelling, whereas this was the 1st or 2nd day for trees. This may indicate higher water storage capacities in bamboo relative to its water use rates, although diurnal patterns of sap flux density did not support this interpretation.
