Agriculture Reference
In-Depth Information
and slope range from 479 to 800 m a.s.l. and 37 to 73% respectively) of the “El Ventós”
Alicante, SE-Spain (38º 28' N, 0º 37' W). The yearly average rainfall in this area is 291 mm.
The soil is a calcareous regosol (FAO-UNESCO) silt loam developed over marls and
calcareous bedrocks (Chirino 2003).
Table 1. Main environmental characteristics positively (+) and negatively (-) related
with water vapour adsorption by soil (WVA) occurrence in arid and semiarid zones
(information from: Kosmas et al., 1998, 2001; Agam and Berliner 2004, 2006; Verhoef et
al., 2006). The physical attributes affected by the environmental characteristics in the
WVA process were taken from Verhoef et al. (2006) study
Environmental Factors
Effect
Physical Attributes Affected
Soil wetness
-
Surface soil air humidity
Among of potential evaporation
during the period preceding the
WVA period
+
+ *
Clay content
Minimum value of atmospheric
humidity
Diurnal amplitude of atmospheric
humidity
-
Diurnal course of atmospheric vapour
density
+
Proximity of sea
+
- Roughness parameters and localized wind
speed
* Kosmas et al. (2001) found an inverse relationship between accumulated WVA and clay content.
However these author suggested a combined effect with the macro-porosity which affects water
vapor diffusion between atmosphere and soil mass.
Surface cover: mulch, stones,
vegetation
1. Stipa Tenacissima's Water Responses under Water Stress Conditions
In August 22, 2003 our team recorded a surprisingly fast response of dawn leaf water
potential (ψ) after a light rainfall event (1.59 mm day -1 ) in our study area during the only
precipitation event recorded in the summer season of 2003 (Ramírez et al., 2007a). Benefiting
from such small amount of water, S. tenacissima was able to escape of its turgour loss point
(ψ = -3.8 MPa; according to Pugnaire et al. 1996) to move on to a condition of reduced water
stress (ψ = -2.7 MPa) after such a light rainfall. The amount of water that prompted the
response was the lowest available in the literature. For instance, studies like Sala and
Lauenroth (1982) and Ivans et al. (2003) have characterized plant water responses to “short”
( sensu the referred authors) rainfalls in summer. However, the range of rainfall values
assessed in these works was between 5 - 15 mm day -1 , figures notably higher than our
Search WWH ::




Custom Search