Title: Effects of irrigation on water use and water use efficiency in two fast growing Eucalyptus plantations
Author: Hubbard, Robert M.; Stape, Jose; Ryan, Michael G.; Almeida, Auro C.; Rojas, Juan
Source: Forest Ecology and Management. 259: 1714-1721.
Description: Eucalyptus plantations occupy almost 20 million ha
worldwide and exceed 3.7 million ha in Brazil alone. Improved
genetics and silviculture have led to as much as a three-fold
increase in productivity in Eucalyptus plantations in Brazil
and the large land area occupied by these highly productive ecosystems
raises concern over their effect on local water supplies. As
part of the Brazil Potential Productivity Project, we measured
water use of Eucalyptus grandis x urophylla clones
in rainfed and irrigated stands in two plantations differing
in productivity. The Aracruz (lower productivity) site is located
in the state of Espirito Santo and the Veracel (higher productivity)
site in Bahia state. At each plantation, we measured stand water
use using homemade sap flow sensors and a calibration curve using
the clones and probes we utilized in the study. We also quantified
changes in growth, leaf area and water use efficiency (the amount
of wood produced per unit of water transpired). Measurements
were conducted for 1 year during 2005 at Aracruz and from August
through December 2005 at Veracel. Transpiration at both sites
was high compared to other studies but annual estimates at Aracruz
for the rainfed treatment compared well with a process model
calibrated for the Aracruz site (within 10%). Annual water use
at Aracruz was 1394 mm in rainfed treatments versus 1779 mm in
irrigated treatments and accounted for approximately 67% and
58% of annual precipitation and irrigation inputs respectively.
Increased water use in the irrigated stands at Aracruz was associated
with higher sapwood area, leaf area index and transpiration per
unit leaf area but there was no difference in the response of
canopy conductance with air saturation deficit between treatments.
Water use efficiency at the Aracruz site was also not influenced
by irrigation and was similar to the rainfed treatment. During
the period of overlapping measurements, the response to irrigation
treatments at the more productive Veracel site was similar to
Aracruz. Stand water use at the Veracel site totaled 975mm and
1102mm in rainfed and irrigated treatments during the 5-month
measurement period respectively. Irrigated stands at Veracel
also had higher leaf area with no difference in the response
of canopy conductance with air saturation deficit between
use efficiency was also unaffected by irrigation at Veracel. Results
from this and other studies suggest that improved resource availability
does not negatively impact water use efficiency but increased
productivity of these plantations is associated with higher water
use and should be given consideration during plantation management
decision-making processes aimed at increasing productivity.
Keywords: transpiration, Eucalyptus grandis x urophylla, sap flow, canopy conductance
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Hubbard, Robert M.; Stape, Jose; Ryan, Michael G.; Almeida, Auro C.; Rojas, Juan 2010. Effects of irrigation on water use and water use efficiency in two fast growing Eucalyptus plantations. Forest Ecology and Management. 259: 1714-1721..