Survival and growth of Nothofagus pumilio seedlings under several microenvironments after variable retention harvesting in southern Patagonian forests Guillermo J. Martínez Pastur, Rosina Soler Esteban, Juan Cellini, María V. Lencinas, Pablo L. Peri, Mark G. Neyland To cite this version: Guillermo J. Martínez Pastur, Rosina Soler Esteban, Juan Cellini, María V. Lencinas, Pablo L. Peri, et al.. Survival and growth of Nothofagus pumilio seedlings under several microenvironments after variable retention harvesting in southern Patagonian forests. Annals of Forest Science, Springer Nature (since 2011)/EDP Science (until 2010), 2014, 71 (3), pp.349 - 362. 10.1007/s13595-013-0343-3. hal- 01101533 HAL Id: hal-01101533 https://hal.archives-ouvertes.fr/hal-01101533 Submitted on 8 Jan 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Annals of Forest Science (2014) 71:349–362 DOI 10.1007/s13595-013-0343-3 ORIGINAL PAPER Survival and growth of Nothofagus pumilio seedlings under several microenvironments after variable retention harvesting in southern Patagonian forests Guillermo J. Martínez Pastur & Rosina Soler Esteban & Juan M. Cellini & María V. Lencinas & Pablo L. Peri & Mark G. Neyland Received: 30 July 2013 /Accepted: 30 October 2013 /Published online: 22 November 2013 # INRA and Springer-Verlag France 2013 Abstract forest structure, microclimate, soil properties, and nutrient & Context Variable retention prescriptions for Nothofagus availability. pumilio forests provide for biodiversity conservation and & Methods In the stands harvested by variable retention, five natural regeneration by controlled opening of the canopy. contrasting microenvironments were selected as treatments Harvesting generates different microenvironments which for the experiments and sampling. Environmental variables present dissimilar conditions for seedling establishment, due were related to ecophysiological, seedling survival, and to positive or negative influences over biotic and abiotic performance. factors. & Results The modification of forest structure (crown cover & Aims This study evaluated seedling survival and perfor- and tree density) and the presence of coarse woody debris mance in different microenvironments within the harvested greatly affect the effective rainfall and global radiation stands. Tested hypotheses stated that seedling stress and per- reaching understorey level, influencing seedling stress and formance were influenced by harvesting due to changes in consequently survival and performance. Harvesting also mod- ifies soil properties (e.g., soil bulk density) and coarse woody debris accumulation which in turn influences soil mois- ture and/or solar radiation levels. Analyses showed that Handling Editor: Andreas Bolte seedlings received benefits of microenvironment varia- Contribution of the co-authors G. Martínez Pastur coordinates the tion after harvesting. Areas covered with middle or fine research project, designs the experiments, and writes the paper together woody debris presented regeneration with better eco- with P.L. Peri and M.G. Neyland. R. Soler Esteban and J.M. Cellini physiological response and seedling performance, al- worked in the data taking and data analyses under the supervision of though dispersed retention areas (far away from remnant trees) M.V. Lencinas, who conducted the statistical data analysis. : : and roads could also present suitable conditions for seedling G. J. M. Pastur (*) R. S. Esteban M. V. Lencinas survival and performance. Centro Austral de Investigaciones Científicas (CONICET), & Conclusions The proportion of different microenviron- Houssay 200, (9410) Ushuaia, Tierra del Fuego, Argentina e-mail: [email protected] ments in the harvested forests will determine the amount of natural recruitment of regeneration and consequently the suc- J. M. Cellini cess of proposed silvicultural management. Forest practices Laboratorio de Investigaciones de Sistemas Ecológicos y must be manipulated to increase the proportion of favorable Ambientales (LISEA-UNLP), Diagonal 113 nº 469, (1900) La Plata, Buenos Aires, Argentina microenvironments (e.g., woody debris), allowing greater nat- ural regeneration success during the first years after P. L. Peri harvesting. Instituto Nacional de Tecnología Agropecuaria, Universidad Nacional de la Patagonia Austral - CONICET, cc 332, (9400) Río Gallegos, Santa Cruz, Argentina Keywords Aggregated retention . Dispersed retention . M. G. Neyland Microenvironments . Light availability . Soil moisture . Forestry Tasmania, GPO Box 207, Hobart, Tasmania 7001, Australia Soil properties 350 G.J.M. Pastur et al. 1 Introduction performance, due to their differential influences (positive or negative) on the biotic and abiotic factors described above Current silvicultural prescriptions for the harvesting of (Kupferschmid and Bugmann 2005; Blood and Titus 2010). Nothofagus pumilio forests in southern Patagonia are mainly In this study, the objective was to evaluate seedling survival based on canopy opening that stimulates natural regeneration and performance under different microenvironmental condi- by modifying soil moisture and light availability at ground tions within the harvested stands during the establishment level (Rosenfeld et al. 2006). Seedling growth conditions are stage. Based on such information, silvicultural prescriptions improved when the canopy is gradually opened, as naturally may be developed to successfully regenerate N. pumilio with- occurs in a gap dynamic system (Wardle 1970). However, if out clearing the site and thus completely changing the envi- the opening is increased abruptly in Nothofagus forests, the ronmental conditions. For this purpose, we tested the follow- effective sheltering function of the remnant overstorey can be ing hypotheses: (1) the remnant overstorey following variable diminished (Howard 1973). Also, overstorey canopy cover retention harvesting (comprising both aggregates and dis- determines the effective rainfall that reaches the forest floor persed trees) influences microclimate particularly through and consequently the soil moisture content, which improves rainfall and solar radiation interception at ground level and seedling performance at moderate canopy cover levels (40– consequently affects seedling stress and performance, (2) 60 %) in N. pumilio forests (Martínez Pastur et al. 2011a). harvesting modifies soil properties and nutrient availability However, under extreme canopy opening (>60 %), the solar and consequently affects seedling performance, and (3) ex- radiation intensity at the ground level also increases, which treme values (low and high) of soil water content and/or solar can result in greater evaporation rates, reducing soil moisture radiation negatively affect seedling performance. below critical values. Both effects determine seedling performance during the establishment stage, e.g., in Fagus sylvatica (Ammer et al. 2008). In particular, 2Methods young seedlings of N. pumilio have been demonstrated to be sensitive to soil moisture (Heinemann et al. 2000;Heinemann 2.1 Study site and climate characterization and Kitzberger 2006). Increasingly, structural retention silvicultural systems (e.g., The study site was located in a pure natural N. pumilio forest variable retention) that maintain elements of the original forest on Tierra del Fuego Island (Argentina), harvested using vari- are being designed to meet multiple objectives (e.g., biodiver- able retention (Martínez Pastur et al. 2011b). This method sity conservation, natural cycles, timber production values, retained aggregates (one circular aggregate of 30-m radius and wildlife habitat) (Gustafsson et al. 2012; Lindenmayer per hectare) and dispersed dominant trees (basal area 10– et al. 2012; Neyland et al. 2012). Variable retention harvesting 15 m2 ha−1) evenly distributed between the retained aggre- has been increasingly applied in south Patagonia over the last gates, as remnant overstorey after the harvesting. The forest 10 years in N. pumilio forests, usually as a mix of aggregated was located in Los Cerros Ranch (Fig. 1), and the experiments and dispersed retention. These retention patterns can influence were established in three stands harvested 2–4 years ago microclimate (e.g., radiation, temperature, or soil moisture) (stand 1=2 years, stand 2=3 years, and stand 3=4 years). and other physical processes, which differ substantially be- Stand 1 (15 ha) presented 10 % slope and north aspect, stand 2 tween harvested and non-harvested areas (Heithecker and (22 ha) presented 15 % slope and northeast aspect, and stand 3 Halpern 2007). This harvesting system generates a high spa- (27 ha) presented 9 % slope and east aspect. The studied tial variation in the remnant forest structure within the har- stands were of middle-to-high site quality according to vested stands; however, the heterogeneity of understorey Martínez Pastur et al. (1997), have a total overbark cover, microtopography, and edaphic properties (e.g., volume of 700–900 m3 ha−1, and have total dominant organic