TAILIEUCHUNG - Báo cáo lâm nghiệp:" Mature trees versus seedlings: Differences in leaf traits and gas exchange patterns in three co-occurring Mediterranean oaks"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí lâm nghiệp đề tài:" Mature trees versus seedlings: Differences in leaf traits and gas exchange patterns in three co-occurring Mediterranean oaks" | Ann. For. Sci. 60 2003 455-460 INRA EDP Sciences 2003 DOI forest 2003038 455 Original article Mature trees versus seedlings Differences in leaf traits and gas exchange patterns in three co-occurring Mediterranean oaks Sonia Mediavilla Alfonso Escudero Departamento de Ecología Facultad de Biología Universidad de Salamanca 37071 Salamanca Spain Received 19 February 2002 accepted 1 August 2002 Abstract - We studied gas-exchange patterns and leaf traits of seedlings and mature trees of three coexisting Mediterranean oaks with contrasting leaf habits the evergreen Quercus ilex and the deciduous Q. faginea and Q. pyrenaica during the well-watered part of the growth season. Leaf life span in Q. ilex seedlings was shorter than in mature trees whereas for the deciduous species the differences in leaf life span between both growth stages were less pronounced. In all species leaves on seedlings displayed a lower mass per unit area and lower nitrogen content than on mature trees. However owing to their larger stomatal conductance leaves on seedlings usually showed larger photosynthetic nitrogen-use efficiency and lower water-use efficiency than on mature trees. Stomatal conductance and CO2 assimilation rate were lower in Q. ilex than in the two deciduous species at the mature stage. However the interspecific differences in gas exchange rates related to differences in leaf longevity disappeared at the seedling stage because in Q. ilex the seedlings showed a much higher stomatal conductance than the adults. Thus seedlings of the three species showed a common strategy regardless of the leaf life span probably as a response to the competition from the herbaceous layer. growth stages leaf gas-exchange leaf traits Quercus sp. Résumé - Arbres adultes versus semis différences de caractéristiques foliaires des types d échanges gazeux chez trois espèces coexistantes de Quercus. Les échanges gazeux et les caractéristiques foliaires des semis et des arbres adultes de trois espèces

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