Orchards productivity and thus nut yield is strictly dependent on plant growth (Baldwin, 2010), which is in turn influenced directly by water availability. However, when introducing a species in a new ecosystem the sole watering might not be sufficient, but rather a study on the local climate and on the responsiveness of the target species is necessary to assess eventual limitations of the new plantations sites. The project took place in Dellapool, Sandigo, NSW, Australia and lasted for two growing season from February 2015 to April 2017, including an initial period for instrument testing in the field. The continuous monitoring of sap flow, soil water content and stem growth together with meteorological parameters allowed to assess more precisely the ecological dynamics of C.avellana and its response in the local climate. From the research point of view, it was extremely valuable to record multiple growing seasons under continuous monitoring. This allowed to assess the variation in the growing season length based on sap flows (about 200 days of positive sap flow) and to calibrate the maximum conductance of trees according to the favorable climatic conditions. Among the main points that emerged from the study, the limitation exerted by the evaporative demand of the atmosphere (VPD) revealed to be the strongest. At comparable average soil water content, the canopy conductance (Grel) was severely depressed by high frequency of VPD >15hPa, which decreased in the first year the Grel of six times respect to the second. The tree based calculation of daily water loss also reported 0.27mm day-1 in the first year and 0.56mm day-1 in the second, suggesting that high VPD caused stomata closure and reduced water loss. A further highlight regards the LAI that was directly calculated through allometric relationships in the field. The value attributed to the site presented here is of 1.32, similar to that predicted by the HET model. Field data also served to verify the HET model. HET had a slight overestimation that will be adjusted according to the site and VPD effect. The amount of water for 2015-2016 was 3.28Ml ha-1 (3.51 in the HET) while for 2016-2017 3.59 Ml ha-1 (3.97 in the HET). Finally, the Lci gas analyzer reported a tight correlation between stomatal conductance and carbon assimilation providing the basis for further consideration that link water loss at leaf and canopy level and carbon availability for yield production. According to these findings, some technical recommendation should be taken in account. Aiming at closing the canopies would limit soil evaporation. For the same reason the bush-habit shall be preferred to the tree. To increase the presence in the orchard of high tree species either as wind breaks or as a companion species will limit the VPD increase and keep the cultivated surface cooler. Moreover, the light saturation point of hazelnut is low (660 μmol m-2 s-1), thus a slight shading will provide great benefit and avoid leaf burning which was often observed by local staff.

Final Report Monitoring water relations in hazelnut plantations located in Dellapool, Narrandera (NSW, Australia)

PASQUALOTTO, GAIA
Writing – Original Draft Preparation
;
Vinicio Carraro
Methodology
;
Tommaso Anfodillo
Supervision
;
2018

Abstract

Orchards productivity and thus nut yield is strictly dependent on plant growth (Baldwin, 2010), which is in turn influenced directly by water availability. However, when introducing a species in a new ecosystem the sole watering might not be sufficient, but rather a study on the local climate and on the responsiveness of the target species is necessary to assess eventual limitations of the new plantations sites. The project took place in Dellapool, Sandigo, NSW, Australia and lasted for two growing season from February 2015 to April 2017, including an initial period for instrument testing in the field. The continuous monitoring of sap flow, soil water content and stem growth together with meteorological parameters allowed to assess more precisely the ecological dynamics of C.avellana and its response in the local climate. From the research point of view, it was extremely valuable to record multiple growing seasons under continuous monitoring. This allowed to assess the variation in the growing season length based on sap flows (about 200 days of positive sap flow) and to calibrate the maximum conductance of trees according to the favorable climatic conditions. Among the main points that emerged from the study, the limitation exerted by the evaporative demand of the atmosphere (VPD) revealed to be the strongest. At comparable average soil water content, the canopy conductance (Grel) was severely depressed by high frequency of VPD >15hPa, which decreased in the first year the Grel of six times respect to the second. The tree based calculation of daily water loss also reported 0.27mm day-1 in the first year and 0.56mm day-1 in the second, suggesting that high VPD caused stomata closure and reduced water loss. A further highlight regards the LAI that was directly calculated through allometric relationships in the field. The value attributed to the site presented here is of 1.32, similar to that predicted by the HET model. Field data also served to verify the HET model. HET had a slight overestimation that will be adjusted according to the site and VPD effect. The amount of water for 2015-2016 was 3.28Ml ha-1 (3.51 in the HET) while for 2016-2017 3.59 Ml ha-1 (3.97 in the HET). Finally, the Lci gas analyzer reported a tight correlation between stomatal conductance and carbon assimilation providing the basis for further consideration that link water loss at leaf and canopy level and carbon availability for yield production. According to these findings, some technical recommendation should be taken in account. Aiming at closing the canopies would limit soil evaporation. For the same reason the bush-habit shall be preferred to the tree. To increase the presence in the orchard of high tree species either as wind breaks or as a companion species will limit the VPD increase and keep the cultivated surface cooler. Moreover, the light saturation point of hazelnut is low (660 μmol m-2 s-1), thus a slight shading will provide great benefit and avoid leaf burning which was often observed by local staff.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11577/3274856
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