Growth of northern deciduous trees under increasing atmospheric humidity: possible mechanisms behind the growth retardation

摘要: Increasing atmospheric humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational impacts various physiological processes, causing growth decline in deciduous trees. We propose, based on the results obtained from long-term free air humidity manipulation experiment, concurrent mechanisms to explain deceleration due increases relative humidity. Reduced evaporative demand diminishes nutrient uptake and leads lower leaf nutritional status an unbalanced foliar phosphorus/nitrogen ratio (P:N), resulting a photosynthetic capacity. Elevated induces readjustment of metabolism: disturbed N metabolism, accumulation starch changes secondary metabolite contents probably impair both performance growth. Increased carbohydrate content leaves suggests that sink strength trees is reduced under elevated As consequence stress, development hindered, observed at individual or whole-tree foliage levels, lowering production potential proportionally their area. Larger investments stem xylem relation cause increase non-photosynthetic tissues, leading larger maintenance respiration costs determined by volume parenchymatous tissue. An proportion living parenchyma cells dead elements sapwood additionally enhances costs. Disproportionate hydraulic versus stomatal conductance become critical factor case weather extremes, which limit canopy may induce dysfunction system. environmental creates favourable conditions pathogens, increasing frequency fungal damage.