1,721,189 research outputs found
Il principio della dinamica
No full textResoconto del convegno “Analisi strumentali non distruttive a supporto della valutazione di stabilità degli alberi”, svolto il 14 aprile presso il Dipartimento di Scienze Agrarie, Alimentari e Agro-ambientali dell’Università di Pisa
Stima dei consumi idrici e dello stato idrico del pesco
No full textI consumi idrici di piante di pesco innestate su diversi portinnesti sono stati monitorati, per i primi 5 anni successivi dall’impianto, per mezzo di un sistema di misura del flusso xilematico basato sul bilancio di calore (Heat Balance). Le misure del flusso xilematico, eseguite sia su piante irrigate che su piante mantenute in assenza di irrigazione, sono state confrontate con rilievi di potenziale idrico fogliare e con i dati climatici, ed hanno permesso di verificare la sensibilità della tecnica nello stimare lo stato idrico delle piante. I consumi idrici, per pianta e per ettaro, sono risultati fortemente influenzati dal portinnesto, dall’età dell’impianto, dall’andamento climatico e dalle disponibilità idriche del suolo. L’uso del sistema di misura del flusso xilematico ha permesso, inoltre, di determinare, durante tutti gli anni della prova, i coefficienti colturali (Kc) dell’impianto che sono apparsi notevolmente inferiori a quelli riportati nei quaderni FAO ed in letteratura
Comparison of water status indicators for young peach trees
Full text linkWe measured a series of physiological and physical indicators and compared them to xylem sap flow, to identify the most sensitive and reliable plant water status indicator. In the growing season of 1998, 4-year-old peach trees (Prunus persica Batsch cv. 'Suncrest', grafted on 'GF 677' rootstock) were studied under two irrigation treatments, 25 l day(-1) and no irrigation, and during recovery. Trials were conducted near Pisa (Italy) in a peach orchard situated on a medium clay loam soil and equipped with a drip-irrigation system (four 4 l h(-1) drippers per tree). Measurements of leaf water potential (Psi(W)), stem water potential (Psi(S)), and leaf temperature (T-1) were taken over 5 days (from dawn to sunset) and analyzed in conjunction with climatic data, sap flow (SF), trunk diameter fluctuation (TDF) and soil water content (SWC). Physiological indicators showed substantial differences in sensitivity. The first indication of changes in water status was the decrease of stem radial growth. TDF and SF revealed significant differences between the two irrigation treatments even in the absence of differences in pre-dawn leaf water potential (pdPsi(W)), up until now widely accepted as the benchmark of water status indicators. Irrigated trees showed a typical trend in SF rate during the day, while in non-irrigated plants the maximum peak of transpiration was anticipated. Measurements of water potential showed Psi(S) to be a better indicator of tree water status than Psi(W). T-l was found to have poor sensitivity. In conclusion, we found the sensitivity of the indicators from the most to the least was: TDF > SF rate > SF cumulated = pdPsi(W) = Psi(S) > mdPsi(W) > T-l
Estimation of water requirement in a young peach orchard under irrigated and stressed conditions
No full textSap flow measurements on single branches of 8 peach trees (cv. 'Suncrest') were performed for 3 consecutive years after planting (1996-98) to estimate water requirements during the growing season and to evaluate the effect of water stress on growth and productivity of a young peach orchard. Starting from the end of May of each year, irrigation was witheld on half of the trees. Heat balance sap flow sensors (Dynamax Inc., Texas, USA) were applied on a single branch, well exposed to sunlight, of each tree for 4-5 periods of 7-20 days each from May to October. Data on total leaf area per tree and leaf and xylem water potential were also collected during the same periods. At the end of the growing season, total leaf area for each tree was assessed. Data on sap flow showed different water requirements, expressed on a m2 leaf area basis, in different years according to canopy size; in 1996 water consumption appeared to be higher than in the consecutive years. Water consumption per tree was affected by total leaf area and water availability in the soil. Because the type of soil and very large root expansion, the first symptoms of water stress were not recorded until 20-30 days after suspension of irrigation. Water consumption of stressed trees ranged between 80 to 20% of that of irrigated trees depending on vapour pressure deficit and pre-dawn leaf water potential. Data on sap flow during recovery from the stress are also shown for 1997 and 1998
Gli alberi pubblici di Pisa: stima del sequestro di carbonio
No full textIl contributo presenta i risultati di una stima del sequestro del carbonio da parte degli alberi pubblici a dimora nella città di Pisa. Per ognuno dei 19.886 alberi considerati è stato stimato il sequestro del carbonio utilizzando alcuni modelli già presenti in letteratura che richiedevano informazioni relative alla specie, al diametro del fusto misurato a petto d’uomo e all’altezza della pianta
Leaf temperature measured on peach trees growing in different climatic and soil water conditions
No full textIndividual leaf temperatures were measured using a Cyclops Compac 3 (Land Infrared Ltd, Sheffield, England) infrared thermometer on three peach orchards located in Italy, Spain and Portugal during 1997 and 1998. Temperature measurements were performed on 5 single leaves, well exposed to sunlight, in each of 4 stressed and 4 irrigated trees for each location. Diurnal trends of leaf and air temperature and vapour pressure deficit are reported for 6-8 days during stress onset and recovery, both in stressed and irrigated trees. Single leaf temperature appeared to be a good indicator of water stress but showed poor correlation with pre-dawn and midday leaf water potential. Differences between stressed and irrigated trees ranged from 1-2°C in the morning to 5-6°C in the hottest part of the day. These differences diminished rapidly after rewatering. Although simple to use in the field, IR leaf temperature appeared unreliable for water management in fruit tree crops because it is strongly influenced by climatic conditions showing pronounced variations from day to day
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