Abstract
Abstract. Plant ecosystems in arid and semiarid climates show high complexity, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development and its dynamic evolution. The available water-soil content results from the water balance in the system, where the key issues are the soil, the vegetation and the atmosphere. However, it is the vegetation, which modulates, to a great extent, the water fluxes and the feedback mechanisms between soil and atmosphere. Thus, soil moisture content is most relevant for plant growth maintenance and final water balance assessment. A conceptual dynamic vegetation-soil model (called HORAS) for arid and semi-arid zones has been developed. This conceptual model, based on a series of connected tanks, represents in a way suitable for a Mediterranean climate, the vegetation response to soil moisture fluctuations and the actual leaf biomass influence on soil water availability and evapotranspiration. Two tanks were considered using at each of them the water balance and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process, whereas the second one models the evolution of moisture by the upper soil. The model parameters were based on soil and vegetation properties, but reduced their numbers. Simulations for dominant species, Quercus coccifera L., were carried out to calibrate and validate the model. Our results show that HORAS succeeded in representing the vegetation dynamics and, on the one hand, reflects how following a fire this monoculture stabilizes after 9 years. On the other hand, the model shows the adaptation of the vegetation to the variability of climatic and soil conditions, demonstrating that in the presence or shortage of water, the vegetation regulates its leaf biomass as well as its rate of transpiration in an attempt to minimize total water stress.
Highlights
Water-controlled ecosystems are complex, evolving structures, whose characteristics and dynamic properties depend on many interrelated links between climate, soil and vegetation (Rodriguez-Iturbe et al, 2001)
Our results show that HORAS succeeded in representing the vegetation dynamics and, on the one hand, reflects how following a fire this monoculture stabilizes after 9 years
This paper presents a Conceptual Vegetation-Soil model based on a tank type schematization
Summary
Water-controlled ecosystems are complex, evolving structures, whose characteristics and dynamic properties depend on many interrelated links between climate, soil and vegetation (Rodriguez-Iturbe et al, 2001). Process-based ecosystems models were developed mainly focusing on the simulation of the photosynthesis, autotrophic and heterotrophic respiration, allocation, turnover, mortality, recovery after disturbance (i.e. fire or land-use changes) recovery, plant competition, etc These models involve the plant physiological processes from regional to global scales, paying special attention to the energy balance and CO2 exchanges to evaluate climate changes (White et al, 2000; Arora and Boer, 2005). The Soil-Vegetation-Atmosphere Transfer schemes (SVAT) were thought to simulate, energy and carbon fluxes These models take into account the water balance, but they still consider static vegetation (Federer, 1979; Dawes et al, 1997; Arora, 2002). Leaf biomass evolution was included in the model as a state variable considering the vegetation water demand, water-soil availability and the vegetation water-stress concept
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