Surface conductance and energy exchange in an intensively managed peat pasture
نویسندگان
چکیده
Aerodynamic measurements of latent (λE) and sensible heat (H) exchange were made in an intensively managed peat pasture during 2 consecutive years; the fetch was approximately 1.5 km. The surface conductance (gs) was calculated from the Penman-Monteith equation. The analysis focused on 2 successive aspects of gs: gs as a function of environment (primarily vapour pressure deficit [D]) and the energy balance as a function of gs. The effect of D on gs consisted of 2 components: the range of D over which gs was reduced (beyond inflection point Di) and the reducing effect per unit D. As average D increased, so did inflection point Di and the range of D over which gs was reduced; the reducing effect per unit D decreased. gs was a strong mediator in the energy balance. λE increased with D upto the inflection point Di, beyond which gs increasingly offset the positive effect of D. As gs impaired λE, the surface to air temperature difference (∆T) and consequently H increased. With increasing gs, λE and H added up to progressively lower values, suggesting an increasing soil heat flux. Hysteresis in the diurnal patterns of the energy balance showed that the positive effect of D on λE remained stronger than the consequent negative effect of gs. λE was higher after than before noon, whereas ∆T and H were lower.
منابع مشابه
Effect of drainage on CO2 exchange patterns in an intensively managed peat pasture
Eddy correlation measurements of CO2 exchange (F) were made in intensively managed peat pastures at 2 different groundwater tables during most of a growing season. F was separated into a respiratory (Fr) and an assimilatory (Fa) CO2 flux. The fit of the Arrhenius temperature response to Fr showed that Fr was generally higher at low groundwater tables. The fit of a hyperbolic irradiance response...
متن کاملPolicy Time-Inconsistency: A Comparison of Managed Floating Exchange Rate and Controlled Exchange Rate Regimes
Some empirical and theoretical studies have emphasized on fixed exchange rate regime in controlling time inconsistency, while others consider the role of target zone regime as an important factor. Thus there is no general consensus to decide which exchange rate regime may bring about less time-inconsistency. The main purpose of this study is to investigate policy time-inconsistency in exchange ...
متن کاملBiogeochemical indicators of peatland degradation – a case study of a tem- perate bog in northern Germany
Organic soils in peatlands store a great proportion of the global soil carbon pool and can lose carbon via the atmosphere due to degradation. In Germany, most of the greenhouse gas (GHG) emissions from organic soils are attributed to sites managed as grassland. Here, we investigated a land use gradient from near-natural wetland (NW) to an extensively managed (GE) to an intensively managed grass...
متن کاملFeed management practices to reduce manure phosphorus excretion in dairy cattle
Phosphorus (P) is an essential mineral that needs to be supplied in sufficient quantities for maintenance and growth and milk production in dairy cattle. However, over 60% of the P consumed can be excreted in faeces with a potential to cause environmental pollution. Concern over higher levels of P in intensively managed livestock systems has led to legislation such as the Water Framework Direct...
متن کاملDiurnal Variations of Gas Exchange Characteristics in Leaves of Anise Hyssop (Agastache foeniculum) under Normal, Drought Stress and Recovery Conditions
Net photosynthesis rate (Pn), stomatal conductance (gs) and transpiration rate (E) of anise hyssop were measured during the four cloudless days, in reference to diurnal fluctuations of leaf temperature (Tleaf), leaf vapor pressure deficit (VPD leaf) and photosynthetic photon flux density (PPFD) in well watered (WW), stressed (S) and recovered (R) plants. An analysis of measured data showed tha...
متن کامل