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Water and Land
1. Land Use Planning, Forest Cover and Afforestation
Water yield depends on the water and carbon trade-off in forest ecosystems.
Carlos A. Gracia
Center for Ecological Research and Forestry Applications University of Barcelona
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Carbon assimilation and
water use by plants are
tightly coupled…
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
1 g de C 500 g de H2O
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Water use efficiency express how much carbon is fixed in photosynthesis per unit of water lost.
To fix between 2 and 3 g of C, plants have to transpire 1000 g of water so, between 300 and 500 times the carbon
weight.
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Water availability is known to be
the main limiting factor to global
plant photosynthesis, in
particular in arid or semi-arid
ecosystems within
Mediterranean climate regions.
Zaragoza, June 16, 2008
P/PET ~ 0.5
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Monitoring water input and output in l’AVIC (Prades) forested watershed
Continuous recording…
Runoff 28 mm
Stemflow 50 mm
AET 504 mm
Rainfall 560 mm
Throughfall 476 mm
An example of transpiration in Mediterranean forests:
504/560=0.9
Water yield depends on the water and carbon trade-off in
forest ecosystems.
temperate mediterranean
Hubbard Brook TM0 Montseny TM9 Montseny Avic (Prades) Teula(Prades
0
.2
.4
.6
.8
1
1.2 E
a/E0
0 0.5 1 1.5 2 2.5 3 3.5 P/E0 Zaragoza, June 16, 2008
10
0
10
20
30
40
50
Evergreen holm oak at Prades (Tarragona)
NEE annual = 140 gC·m2y1
E = 504 kg H2O·m2·y1
Date
Dec. Jan. Feb. Mar.Apr. May Jun. Jul. Aug.Sept.Oct. Nov.Dec.
NE
E (
g C
m -2
mon
th -1
)
-
10
0
10
30
40
50
20
sink
source
first rainfall
Water yield depends on the water and carbon trade-off in
forest ecosystems.
TToottaall CCoosstt ((ggCC�� mm22 ggrroouunndd�� yy11))
Water Formation Maintenance Total
mm
Leaf Biomass 189 844 1033 281
NPTissues 146 204 350 95
Fine Roots 184 95 279 76
Total 519 1143 1662
Transpiration (mm/y) 141 311 452
Precipitation (mm/y) 178 392 570
Water yield depends on the water and carbon trade-off in
forest ecosystems.
387mm 360mm
In years with low rainfall the mobile carbon stored in the trees decreases to compensate the cost of maintenance respiration of living tissues
387mm 360mm
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Trees are strongly limited by water and it
has been experimentally proved that the
reduction of tree density leads to a higher
transpiration rate by the remaining trees
which is translated in an almost constant
amount of water used by vegetation despite
their population density.
Zaragoza, June 16, 2008
Experimental thinning…
Water yield depends on the water and carbon trade-off in
forest ecosystems. Lea
f Are
a Index
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
600
500
400
300
200
100
0
Tran
spiratio
n (kg/m
2/y)
Control Minimum thinning Maximum thinning
Water yield depends on the water and carbon trade-off in
forest ecosystems.
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
L e a f
A re
a In
de x
0
100
200
300
400
500
600
T ra n s p ira tio n (k g /m 2 /y )
Control Minimum thinning Maximum thinning
Increased resistance to drought in thinned plots
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Strong competition for water…
Constant amount of water used by vegetation despite their population density…
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
All climate models and socioeconomic
scenarios concurred on increasing
precipitation over much of northern Europe
(between 10 and 40 per cent more rainfall)
and decreasing precipitation in the south of
Europe (up to 20 per cent drier), particularly
in summer.
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
LENGTH OF
THE GROWTH PERIOD (days)
1960-1990
<85
[86,100]
[101,115]
[116,131]
[132,146]
[147,161]
[162,177]
[178,192]
[193,207]
[208,223]
[224,238]
[239,253]
[254,269]
[270,284]
[285,300]
LENGTH OF
THE GROWTH PERIOD
A2_HadCM3
2020
<85
[86,100]
[101,115]
[116,131]
[132,146]
[147,161]
[162,177]
[178,192]
[193,207]
[208,223]
[224,238]
[239,253]
[254,269]
[270,284]
[285,300]
LENGTH OF
THE GROWTH PERIOD
A2_HadCM3
2050
<85
[86,100]
[101,115]
[116,131]
[132,146]
[147,161]
[162,177]
[178,192]
[193,207]
[208,223]
[224,238]
[239,253]
[254,269]
[270,284]
[285,300]
LENGTH OF
THE GROWTH PERIOD
A2_HadCM3
2080
<85
[86,100]
[101,115]
[116,131]
[132,146]
[147,161]
[162,177]
[178,192]
[193,207]
[208,223]
[224,238]
[239,253]
[254,269]
[270,284]
[285,300]
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Enlargement of the length of the growth
period by the year 2080 of 50 days for the
Mediterranean region and only 33 in the
Scandinavian countries.
This enlargement of the forest activity will
imply a greater water demand while the
climate projections predict less precipitation
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in forest ecosystems.
A2-HadCM3
GOTILWA+
predicts a
reduction in the soil
water
content
1990 2020
2050 2080
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Among all bioclimatic regions, the
Mediterranean appeared most vulnerable to
global change.
Most of this vulnerability is associated at
the general atmospheric circulation and the
role of water as a limiting resource for
Mediterranean ecosystems
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Water is the most limiting factor of
Mediterranean ecosystems: Med forests
can transpire up to 90 per cent of
precipitation.
The trade off between forest and water
must be addressed from the perspective
of Mediterranean conditions
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Unsustainable projects like the pharaonic Gran Scala, projected in the Monegros, are absolutely inconsistent with the Zaragoza EXPO WORLD objectives and must be discouraged from an environmental perspective.
Zaragoza, June 16, 2008
Water yield depends on the water and carbon trade-off in
forest ecosystems.
Thank you very much !
Zaragoza, June 16, 2008
