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17 - Water relations and water transport in coppice vs. single stem Quercus cerris L. trees
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- By M. Sabatti, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy., G. E. Scarascia Mugnozza, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy., R. Valentini, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy., A. del Lungo, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy.
- Edited by M. Borghetti, J. Grace, A. Raschi
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- Book:
- Water Transport in Plants under Climatic Stress
- Published online:
- 04 August 2010
- Print publication:
- 13 May 1993, pp 191-204
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- Chapter
- Export citation
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Summary
SUMMARY
The coppice and coppice-with-standards treatments are still widely applied in broadleaf forest stands, especially in Southern Europe. These sylvicultural systems are also promising for the management of fast growing tree crops and for multilayer agroforest stands in tropical regions.
Coppice sprouts show a higher productivity on a per leaf area basis compared to trees grown from seed and allowed to develop naturally as ‘standards’. Evidence is presented that coppice trees had also improved water relations and greater water transport on a per leaf area basis.
INTRODUCTION
Forests are naturally regenerated either via sexual reproduction or by vegetative propagation. In the first case, the production of seeds, their germination and the establishment of seedlings can be encouraged by several silvicultural techniques.
On the other hand, regeneration of many species can occur by growth and development of the meristematic centres located at the stump or root levels. The sprouts and suckers thereby produced give rise to a forest stand called coppice; sometimes, within coppice stands some trees are left uncut for a maximum of three to four consequent harvests, to provide some regeneration from seeds, in order to replace the declining stumps. These trees left for sexual reproduction are called standards. Coppice and coppice-with-standards are old silvicultural systems, widely used for firewood and timber production in Southern Europe. They have received renewed attention in recent years because they represent a valid option for new silvicultural goals such as fast growing biomass plantations (Ferm & Kauppi, 1990) and tropical agroforestry systems (Stewart, 1980).
10 - Relations between sap velocity and cavitation in broad-leaved trees
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- By M. Borghetti, Istituto Miglioramento Genetico delle Piante Forestall, Consiglio Nazionale delle Ricerche, via S. Bonaventura 13, 50145 Firenze, Italy; Present address: Dipartimento di Produzione Vegetale, Universita della Basilicata, Potenza, Italy., P. de Angelis, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo De Lellis, 01100 Viterbo, Italy., A. Raschi, Istituto di Analisi Ambientale e Telerilevamento applicati all'Agricoltura, Consiglio Nazionale delle Ricerche, p.le delle Cascine 18, 50144 Firenze, Italy., G. E. Scarascia Mugnozza, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo De Lellis, 01100 Viterbo, Italy., R. Tognetti, Istituto Miglioramento Genetico delle Piante Forestall, Consiglio Nazionale delle Ricerche, via S. Bonaventura 13, 50145 Firenze, Italy., R. Valentini, Dipartimento Scienze dell'Ambiente Forestale e delle sue Risorse, Universitá della Tuscia, via S. Camillo De Lellis, 01100 Viterbo, Italy.
- Edited by M. Borghetti, J. Grace, A. Raschi
-
- Book:
- Water Transport in Plants under Climatic Stress
- Published online:
- 04 August 2010
- Print publication:
- 13 May 1993, pp 114-128
-
- Chapter
- Export citation
-
Summary
SUMMARY
Concurrent measurements of cavitation by the ultrasound acoustic emission technique and sap velocity by the thermoelectric heat pulse method were carried out in the field on three woody species (Quercus pubescens, Quercus ilex and Alnus cordatd) characterized by different wood structure. The plant water status was assessed by measuring xylem water potential and stomatal conductance. A good correspondence was found between the patterns of sap velocity and cavitation rate. A threshold-type relationship was observed, in Alnus cordata, between water flow and cavitation rate. In some cases temporal lags between ultrasound emission and sap velocity were observed: several factors may account for these lags, including the possibility that cavitation of xylem conduits may be a rather patchy phenomenon and that different xylematic volumes might have been sensed by the ultrasound and heat pulse transducers.
INTRODUCTION
The formation and spreading of gaseous emboli through the xylem are recognized as common events in water stressed plants (Milburn, 1979; Tyree & Sperry, 1989a). In particular, it is widely held that the increase of xylematic tension, which is caused by the drop of water potential between the soil and the atmosphere, frequently induces cavitation, i.e. the breakage of water columns and the formation of gas bubbles in the lumina of xylem conduits.
The mechanism of cavitation is still being debated, although the hypothesis that cavitation is caused by the aspiration of air bubbles through the intervessel pit membranes (the so-called air seeding hypothesis) is widely supported by experimental evidence (Sperry & Tyree, 1988; Sperry, Tyree & Donnelly, 1988).