Der hochdiverse tropische Regenwald weist eine Fülle verschiedener struktureller Parameter auf, die sich je nach Exposition und Meereshöhe graduell oder abrupt ändern. Schichtung, Bestandesarchitektur, Lebensformenanteile (Palmen, Baumfarne, Hochstauden, Epiphyten etc.), Diversitätsgrößen, Durchwurzelung, Nähr- und Spurenelementverteilung ändern sich entlang von Höhengradienten oder auch entsprechend unterschiedlicher Störungsregime. Beispiele dieser Kenngrößen und ihrer Funktion sollen erfasst werden und insbesondere mit dem Auftreten der Baumlücken verknüpft werden. Baumlücken ('gaps') spielen für die Regeneration und damit Erhaltung der hohen Biodiversität und heterogenen Bestandesstruktur in Primärwäldern eine entscheidende Rolle. Wahrscheinlich lässt sich in Primärwäldern ein großer Teil der für jede Art wesentlichen Kennfaktoren, wie Regenerationsdynamik, Keimung, Jungwuchs, Alterspyramide, Zuwachsraten, etc. aus der Baumlückendynamik ableiten. Für Bergregenwälder muß dies allerdings erst noch aufgezeigt werden. Die Einbeziehung verschiedener Störungsursachen rezenter Baumfallücken gibt Hinweise auf mögliche Entwicklungsrichtungen der Waldlücken, also auch auf ihre mögliche weitere Sukzession. Je nach Artenzahl an vorkommenden Baumarten sind vergleichende Untersuchungstransekte notwendig, die in Ecuador einerseits, in Costa Rica andererseits zur Verfügung stehen und damit ideale Vergleichsmöglichkeiten bieten.
The timing of diel stem growth of mature forest trees is still largely unknown, as empirical data with high temporal resolution have not been available so far. Consequently, the effects of day-night conditions on tree growth remained uncertain. Here we present the first comprehensive field study of hourly-resolved radial stem growth of seven temperate tree species, based on 57 million underlying data points over a period of up to 8 years. We show that trees grow mainly at night, with a peak after midnight, when the vapour pressure deficit (VPD) is among the lowest. A high VPD strictly limits radial stem growth and allows little growth during daylight hours, except in the early morning. Surprisingly, trees also grow in moderately dry soil when the VPD is low. Species-specific differences in diel growth dynamics show that species able to grow earlier during the night are associated with the highest number of hours with growth per year and the largest annual growth increment. We conclude that species with the ability to overcome daily water deficits faster have greater growth potential. Furthermore, we conclude that growth is more sensitive than carbon uptake to dry air, as growth stops before stomata are known to close.
The timing of diel stem growth of mature forest trees is still largely unknown, as empirical data with high temporal resolution have not been available so far. Consequently, the effects of day-night conditions on tree growth remained uncertain. Here we present the first comprehensive field study of hourly-resolved radial stem growth of seven temperate tree species, based on 57 million underlying data points over a period of up to 8 years. We show that trees grow mainly at night, with a peak after midnight, when the vapour pressure deficit (VPD) is among the lowest. A high VPD strictly limits radial stem growth and allows little growth during daylight hours, except in the early morning. Surprisingly, trees also grow in moderately dry soil when the VPD is low. Species-specific differences in diel growth dynamics show that species able to grow earlier during the night are associated with the highest number of hours with growth per year and the largest annual growth increment. We conclude that species with the ability to overcome daily water deficits faster have greater growth potential. Furthermore, we conclude that growth is more sensitive than carbon uptake to dry air, as growth stops before stomata are known to close.
RESPECT aims to unveil for the mountain rain forest in South Ecuador how major ecosystem functions, (i) ecosystem biomass production, and (ii) water fluxes, are affected by ongoing and future environmental changes through alterations in response and effect traits of relevant biota. The research question is addressed with two approaches: (i) A newest generation Land Surface Model (LSM) and (ii) a statistical response–effect framework (REF). By including (i) specific Plant Functional Types (PFTs) for the megadiverse biodiversity hotspot, (ii) introducing trait diversity, (iii) new modules for tree hydraulics and (iv) new modules of focal biological processes (seed dispersal and PFT establishment, herbivory) we will conduct a biodiversification of LSMs.