Photosynthetic response to different light intensities and water status of two main Nothofagus species of southern Patagonian forest, Argentina

Abstract

Net photosynthetic rate (A) and stomatal conductance (gs) of leaves of Nothofagus pumilio and N. antarctica seedlings were measured at different photosynthetic photon flux densities (PPFDs, 20, 150, 250, 500, 750, 1,000, 1,500 and 2,200 µmol/m 2 /s) and after 60 minutes of shade to determine the rate of photosynthetic induction after seedling transition from low to high PPFD. A and gs were also measured to evaluate the responses to water stress and the tolerance to waterlogging. N. pumilio had higher A values than N. antarctica for all light intensities measured with the maximum value of 16.8 µmol CO 2 /m 2 /s saturated at 1,000 µmol/m 2 /s PPFD. Values of gs for both Nothofagus species also declined as light intensity decreased. The times required for full induction of A were 18 and 27 minutes after the increase of PPFD (full sun) for N. pumilio and N. antarctica, respectively. There was a negative relationship between A and water stress, expressed as pre-dawn leaf water potential (ψ lp ), where the reduction in gs was the main factor that reduced A in both species. Tolerance to waterlogging was related with changes in A and gs where N. antarctica was more tolerant. These photosynthetic results of Nothofagus leaves to fluctuating light, water stress and waterlogging could be used to estimate the responses of regeneration to environmental conditions under the dynamics of natural stands, after silvicultural practices and for restoration plans.

Seedling drought stress susceptibility in two deciduous Nothofagus species of NW Patagonia

“…These reductions may be due in part to a decrease in gs, especially if VPD is high, but an additional effect of some degree of damage of the photosynthetic apparatus must be considered for both species to explain photosynthesis reductions. Considering the results from seedlings under suitable water conditions, both species had mean values of net photosynthetic rate similar to those found in other species of the genus (Read and Hill 1985;Martinez Pastur et al 2007;Piper et al 2007;Peri et al 2009) and related genera (e.g. Leuzinger et al 2005;Gallé and Feller 2007).…”

“…For example, the physiological responses of European species of the genus Quercus and Fagus are well known (Cochard et al 2000;Corcuera et al 2002;Lemoine et al 2002;Aranda et al 2004;Lendzion and Leuschner 2008), while the knowledge of the drought response of species in many other regions with Mediterranean-type climate, including northern Patagonia on the western rim of South America, is limited to just a few species (Suarez et al 2004;Gyenge et al 2007;Martinez Pastur et al 2007;Piper et al 2007;Peri et al 2009), or even non-existent for other important forest species.…”

State and transition model approach in native forests of Southern Patagonia (Argentina): linking ecosystem services, thresholds and resilience

“…It is also important to highlight that survival of seedlings and saplings depends on the species' ecophysiological traits. Notofagus antarctica is considered less 'shade tolerant' from a physiological perspective compared to other closely related species such as N. pumilio (Peri et al 2009b). It provides competitive advantages for this tree species to grow in open areas.…”

Natural dynamics and thinning response of young lenga (Nothofagus pumilio) trees in secondary forests of Southern Patagonia

“…Similarly, Martínez Pastur et al (2011) reported a superior height growth of N. pumilio regeneration beneath the protection of older residual seed trees (45 % crown cover). According to Peri et al (2009) andMartínez Pastur et al (2007), N. pumilio seedlings have higher photosynthetic rates in big gaps or when light availability increases due to silvicultural treatments, and when water is non-limiting. However, when soil moisture becomes a limiting environmental factor (pre-dawn leaf water potential less than -1.7 MPa), the photosynthetic response (and therefore growth) is reduced regardless of light availability.…”