tailieunhanh - Báo cáo lâm nghiệp: " Soil and tree water relations in mature oak stands of northern Germany differing in the degree of decline"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài:" Soil and tree water relations in mature oak stands of northern Germany differing in the degree of decline. | Ann Sci For 1996 53 697-720 Elsevier INRA 697 Original article Soil and tree water relations in mature oak stands of northern Germany differing in the degree of decline FM Thomas G Hartmann Niedersãchsische Forstliche Versuchsanstalt Grătzelstr2 37079 Gottingen Germany Received 6 September 1994 accepted 27 June 1995 Summary At three sites in northern Germany in which oak decline occurred during the last decade the impact of soil water conditions on oak damage was investigated in one healthy and one declining stand of pedunculate or sessile oak respectively Quercus roburi. and Q petraea Matt Liebl . Soil matric potentials were determined with tensiometers and xylem water potentials as well as relative water content and osmotic pressure of the leaves were measured in oaks differing in the degree of damage. Additionally the distribution and biomasses of fine roots were investigated. More negative soil matric potentials in the declining stand of pedunculate oak and lower relative water contents of the leaves of damaged trees even in a vegetation period with sufficient precipitation indicated a higher risk of drought stress in dry years. At the two sites with sessile oaks the impact of drought on tree water relations seemed to be much smaller. The relative water content of leaves from damaged oaks was not lower than of those from healthy trees even in an extremely warm and dry period. At these sites crown reduction may be a temporary form of adaptation to insufficient water supply and in this case would have to be differentiated from oak decline in its true sense. Generally distinct reductions in fine root biomass and an increased percentage of dead fine roots were detected only in severely damaged trees indicating that root decay is not a primary factor in the complex of oak decline. oak decline Quercus relative water content root soil water potential Resume Regime hydrique du sol et des arbres dans des peuplements de chênes adultes en Allemagne du Nord présentant .