Abstract
Pinus pinaster stands in the center of the Iberian Peninsula frequently grow in a unique hydrological system characterized by a variable groundwater table near the soil surface and highly permeable soils (arenosols). Over the last few decades, this superficial aquifer has been overused as a water resource, especially for irrigated crops. Overuse has reached a critical level and has caused various environmental impacts and a water sustainability crisis wherein rainfall variability does not allow for a sufficient level of aquifer recharge by natural means. Within this changing scenario, soil water significantly affects the spatio-temporal ecological response, necessitating more extensive characterization of the complex soil-tree water relationship. The primary goal of the present work was to evaluate the influence of root zone soil moisture on the observed spatial response of Pinus pinaster stands. Volumetric soil moisture content was measured at eleven forest sites, using time-domain reflectometry (TDR), over a two-year observation period. The results demonstrate that the combined effect of groundwater table proximity and dune morphology associated with this area are the main factors driving very different water availability conditions among the monitored hydrological response units, which modulate maritime pine installation and development. Topographically lower areas are more heterogeneous in terms of soil moisture behavior. In these areas, the conifer forests that are connected to the water table may be the most sensitive to land use changes within current environmental change scenarios. Consequently, in these pine ecosystems, the combined influences of geomorphology and water table proximity on variations in root zone soil moisture are essential and must be considered to develop adequate adaptive management models.
Highlights
Soil moisture plays a significant role in many of the biogeochemical processes involved in landscape pattern dynamics (Kimmins, 1997; Barnes et al, 1998; Beldring et al, 1999; Winter, 2001; Paul et al, 2003; Bürgi et al, 2004)
The greatest water availability is present in Site 3, which has the maximum Soil Water Availability (SWA) mean and range
The unique lithology and geomorphology of the sandy flatlands of central Spain strongly influence the spatial variability of soil moisture and, the availability of soil water for vegetation
Summary
Soil moisture plays a significant role in many of the biogeochemical processes involved in landscape pattern dynamics (Kimmins, 1997; Barnes et al, 1998; Beldring et al, 1999; Winter, 2001; Paul et al, 2003; Bürgi et al, 2004) This relationship is emphasized in hydrological systems with special features such as a variable groundwater table near the soil surface or highly permeable soils, which are controlled by a special geological substratum like wind sands (Ronen et al, 2000; Nielsen and Perrochet, 2000; Chen and Hu, 2004). Both of these critical conditions are present in vast areas in the center of the Iberian Peninsula. In areas where fewer good dam sites are available for construction, groundwater is the primary component of the water supply, and its use can be expected to increase as growing populations demand more water
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