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Accueil du site → Doctorat → Espagne → 2016 → La regeneración natural del pino silvestre (Pinus sylvestris L.) en el Valle del Lozoya (Madrid) : germinación y supervivencia inicial

Universidad Politecnica de Madrid (2016)

La regeneración natural del pino silvestre (Pinus sylvestris L.) en el Valle del Lozoya (Madrid) : germinación y supervivencia inicial

Aroca Fernández, Pepa

Titre : La regeneración natural del pino silvestre (Pinus sylvestris L.) en el Valle del Lozoya (Madrid) : germinación y supervivencia inicial

Auteur : Aroca Fernández, Pepa

Université de soutenance : E.T.S.I. Montes (UPM) Universidad Politecnica de Madrid

Grade : Thesis (Doctoral) 2016

Résumé
Seedling establishment is critical for later stand progress because it involves high mortality rates and the surviving saplings constitute the starting material for all the subsequent stages. Restrictions for Scots pine germination and seedling survival may vary greatly across its geographical range, as it is widely distributed within north latitudes. Mediterranean region is a marginal sector within this species range and its ecological conditions differ greatly from those of the bulk of the area. Mortality rates in Mediterranean environments seem to be related to summer weather (mainly drought) and high livestock stocking rather than to cold, light or flooding. Most available information on scots pine regeneration process comes from north European experiences and is not transferable to Spanish forests, whereas studies on Mediterranean region are much scarcer. The present work aims at broadening Scots pine regeneration knowledge within Mediterranean region by analyzing its establishment process in the “Cabeza de Hierro” forest : a Scots pine uneven-aged forest at blocklevel scale, exemplary managed for multi-services purpose. Germination and surviving processes are to be characterized and quantified as to vegetation cover both in trees, shrubs, grass and litter strata. Soil compaction effects on forest sustainability are also assessed and the efficacy of some site preparation techniques on regeneration success is tested and compared (scarification vs. scalping+mounding). Two sampling networks comprising respectively 198 (SN I) and 24 plots (SN II) of 1.5x1.5m have been established over a wide range of vegetal cover conditions within the forest. Soil preparation techniques have been applied only to some of the sampling points ; namely, 1 out of 4 plots have been scarified within Sampling Network I , while 1 out of 2 plots have been object of scalping & mounding within Sampling Network II. After localized sowing prior to growing season, germination and surviving have been periodically sampled for either one (SN II) or three years (SN I). Supplementary measures for micrometeorological variables, stand density, ground vegetal cover and compaction have also been carried out. Results obtained for the studied forest lead to the following insights regarding Scots pine natural regeneration process within this sort of forest and environment : 1) seedling establishment success rate is quite low (0,15% of sowing seeds), due to high mortality during the first summer (>92%), following a prior 17% rate of germination over viable seeds reaching the soil ; 2) mortality rate remains high until the third year after emergence and then decreases to the 50% of surviving ; 3) although vegetal cover significantly affects both seedling germination and survival, lineal correlation between those two processes is rather low, which may indicate that places fit for emergence are not necessarily suitable for summer surviving ; 4) soil scarification improves both germination and survival during the first growing season, but it is associated to higher mortality rates during the next two years ; hence it has no significant medium term effect ; 5) scalping & mounding treatment is more effective than scarification concerning establishment improving during the first summer ; but its effects are only significant under intermediate stand density levels ; 6) soil compaction does not restrict either forest productivity or persistence, despite the area’s long history of high livestock stocking rates and mechanized logging

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Page publiée le 30 septembre 2016, mise à jour le 4 février 2019