Agriculture Reference
In-Depth Information
availability and bare soil connection with the root system in this stand allowed the
S.
tenacissima
tussocks to make use of the bare soil water gains from WVA as explained above.
Table 2. Structural and ecophysiological traits of three
Stipa tenacissima
stands in a
South-facing micro-basin located in Alicante, SE - Spain. The ecophysiological
assessment was carried out in August - 2004 (summer season) under high water stress
conditions. Gas exchange measures: E = average transpiration rate, A = average net
photosynthesis, g = average stomatal conductance; chlorophyll fluorescence measure:
F
v
/F
m
= maximum photosystem II photochemical efficiency. CV = variability coefficient.
Different letters mean significant differences detected by Tukey HDS test (p < 0.05)
from one-way ANOVA in each assessed ecophysiologial variable
Traits
Variables
Stand I
Stand II
Stand III
Structure
Altitude (m a.s.l.)
415
640
675
S. tenacissima cover
(%)
41.9
8.9
18.1
Average soil depth (cm)
n = 36
15.5
11.2
9.1
CV soil depth
(%)
65.5
62.0
122.8
Ecophysiology
(± standard error)
E
(mmol H
2
O m
-2
s
-1
)
1.1 ± 0.03
a
0.6 ± 0.01
b
0.3 ± 0.01
c
A
(μmol CO
2
m
-2
s
-1
)
2.0 ± 0.1
a
1.2 ± 0.06
b
0.7 ± 0.1
c
g
(mmol H
2
O m
-2
s
-1
)
25.4 ± 1.3
a
15.0 ± 0.6
b
6.1 ± 0.4
c
Green LAI
(m
2
m
-2
)
2.0 ± 0.1
a
3.1 ± 0.3
b
1.3 ± 0.1
c
Dawn F
v
/F
m
(relative unities)
0.51 ± 0.03
a
0.54 ± 0.01
a
0.33 ± 0.03
b
Midday F
v
/F
m
(relative unities)
0.23 ± 0.02
a
0.35 ± 0.01
c
0.18 ± 0.02
b
C
ONCLUSION
The evidences presented here suggest an important relationship between the water status
of
Stipa tenacissima
and bare soil water dynamic promoted by non-rainfall water (WVA) and
very light precipitation. We acknowledge that specific studies (using isotopic assessment) are
required to thoroughly determinate and quantify a possible physiological integration as the
main mechanism responsible for the transport of the soil-adsorbed water (mainly from bare
soil). Hopefully our study will encourage further works focusing in the dynamics of water,
bare soil and vegetation, a paramount topic in semiarid Mediterranean regions.
