Effects of Surface Fire on Hydraulic Characteristics of the Larch Trees in Eastern Siberia

Massive and frequent wildfires hit larch forests around Yakutsk region (eastern Siberia) in the spring of 2002. The base of larch tree suffered significant damage by surface fire, and scorched forest floors were observed after the wildfires. In the present study, we discuss the effects of spring surface fires on hydraulic characteristics of larch tree by comparing leaf, stem and soil water potentials, soil water content and sap fluxes observed at damaged larch tree by surface fire, intact or intact and watered larch trees. The field observations were conducted at a larch forest located at about 25 km northwest of Yakutsk, Russia. Seven test stands of larch were selected from three different plots in the larch forest; the first was a burnt plot, the second was an intact plot and the last one was intact and watered plot. The observation period was from 21 July to 2 August 2002. The leaf water potential of burnt larch trees was always 0.2 to 0.5 MPa less than that of intact larch trees, although the soil water content at burnt plot showed relatively higher than that at intact plot. We also observed that the sap flux of burnt larch tree was about 75 percent of that of intact larch tree. There was no obvious difference in the relationships between sap flux, and difference of water potential between stem and leaf for the burnt and intact larch trees. These results showed that the hydraulic conductivity of the burnt larch tree has been reduced due to the significant damage of water flow tissues around the base of burnt tree by surface fire. The thresholds of transpiration and leaf water potential of the intact larch tree in summer season were also discussed by the variation in sap fluxes and leaf water potentials observed at burnt, intact and watered plots.