Sapling growth and crown expansion in canopy gaps of Nothofagus pumilio (lenga) forests in Chubut, Patagonia, Argentina.

P. M. López Bernal, G. E. Defossé, C.P. Quinteros, J.O. Bava

Abstract


In the province of Chubut in Patagonia, Argentina, Nothofagus pumilio forests (locally known as lenga), are managed through selective cuts, which imply the opening of canopy gaps. This management scheme is carried out without taking into consideration the sapling requirements changes through neither a cutting cycle nor the precipitation gradient in which these forests thrive. To analyze these changes, we inferred the facilitation-competition balance between the canopy and regeneration studying the effects of precipitation levels, gap size and gap age on saplings growth in height on 45 canopy gaps artificially created between 1960 and 1993. Results shown that during the first 20 years since the gap opening, the regeneration growth is determined by light availability in mesic sites and by water availability in dry sites. However, the difference due to the precipitation levels gradually decreases over time. Moreover, in the period between 20 and 35 years after gap opening, in both mesic and xeric sites, light is the limiting factor to growth. This means that in xeric sites, saplings shift from a water-dependent to a light-dependent growth. The average closing rate of gaps due to lateral growth of trees bordering the gap is high enough so that within the proposed gap size range, the gap healing can occur before regeneration reaches the upper stratum. Consequently, in mesic sites the gap opening can be done by a single operation that generates gaps with diameters of approximately twice the average height of the canopy (D/H). While in xeric environments, lenga seedling establishment and initial growth require the cover of small gaps, but advanced regeneration requires bigger gaps to reach the canopy. For this reason, gaps should be opened in two stages: the first gaps should be opened with a D/H between 0.8 and 1, and after a cutting cycle of 35 years, these openings should be enlarged to a D/H between 1.5 and 2. The close relationship is maintained between the new cohort and the upper strata require special considerations regarding the evolution of the balance between positive and negative interactions during development. Our work highlights the need to adjust management practices to these spatial and temporal variations so as to achieve an optimal growth along the entire production cycle.


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References


Bava JO, Puig CJ. 1992. Regeneración natural de lenga. Análisis de algunos factores involucrados. Proc CIEFAP «Actas del Seminario de Manejo forestal de la lenga y aspectos ecológicos relacionados». Esquel, Chubut, Argentina, pp. 85-110.

Carmean WH. 1972. Site index curves for upland oaks in the Central States. Forest Sci. 18, 109-120.

Coates KD, Burton PJ. 1997. A gap-based approach for development of silvicultural systems to address ecosystem management objectives. Forest Ecol. Manag. 99, 337-354. http://dx.doi.org/10.1016/S0378-1127(97)00113-8

Donoso ZC. 1995. Bosques templados de Chile y Argentina. Variación, estructura y dinámica. Editorial Universitaria, Santiago de Chile. 484 pp.

Frelich LE. 2002. Forest dynamincs and disturbance regimes. Studies from temperate evergreen-deciduous forests. Cambridge Univedrsity Press, New York. 266 pp. http://dx.doi.org/10.1017/CBO9780511542046

Heinemann K, Kitzberger T. 2006. Effects of position, understorey vegetation and coarse woody debris on tree regeneration in two environmentally constrasting forests of north-western Patagonia: a manipulative approach. J. Biogeogr. 33, 1357-1367. http://dx.doi.org/10.1111/j.1365-2699.2006.01511.x

Heinemann K, Kitzberger T, Veblen TT. 2000. Influences of gap microheterogeneity on the regeneration of Nothofagus pumilio in a xeric old-growth forest of northwestern Patagonia, Argentina. Can. J. Forest Res. 30, 25-31.

Jobbágy EG, Paruelo JM, León RJC. 1995. Estimación del régimen de precipitación a partir de la distancia a la cordillera en el noroeste de la Patagonia. Ecología Austral 5, 47-53.

Kellman M, Kading M. 1992. Facilitation of Tree Seedling Establishment in a Sand Dune Succession. J. Veg. Sci. 3, 679-688. http://dx.doi.org/10.2307/3235836

Lima RAFd. 2005. Gap size measurement: The proposal of a new field method. Forest Ecol. Manag. 214, 413-419. http://dx.doi.org/10.1016/j.foreco.2005.04.011

López Bernal PM, Arre JS, Schlichter T, Bava JO. 2010. The effect of incorporating the height of bordering trees on gap size estimations: the case of Argentinean Nothofagus pumilio forest. New Zeal. J. For. Sci. 40, 71-81.

López Bernal PM, Bava JO, Antequera SH. 2003. Regeneración en un bosque de lenga (Nothofagus pumilio (Poepp. et Endl.) Krasser) sometido a un manejo de selección en grupos. Bosque 24, 13-21.

Martinez Pastur G, Lencinas MV, Peri PL, Arena M. 2007. Photosynthetic plasticity of Nothofagus pumilio seedlings to light intensity and soil moisture. Forest Ecol. Manag. 243, 274-282. http://dx.doi.org/10.1016/j.foreco.2007.03.034

Pickett STA, Wu J, Cadenasso ML. 1999. Patch dynamics and the ecology of disturbed ground: a framework for synthesis. In: Ecosystems of disturbed ground (Walker, LR, ed.), Elsevier, Amsterdam.

Rechene DC. 1995. Establecimiento y desarrollo de renovales de lenga en situaciones de baja cobertura. In: Regeneración natural de la lenga. Factores ecológicos, CIEFAP, Esquel, Argentina, pp. 75-114.

Runkle JR. 1982. Patterns of disturbance in some old-grwth mesic forests of eastern North America. Ecology 63(5), 1533-1546. http://dx.doi.org/10.2307/1938878

Runkle JR. 1985. Disturbance regimes in temperate forest. In: The ecology of natural disturbance and patch dynamics (Pickett STA, White PS, eds.), Academic Press Inc., Orlando, pp. 17-33.

Runkle JR, Yetter TC. 1987. Treefalls Revisited: Gap Dynamics in the Southern Appalachians. Ecology 68, 417-424. http://dx.doi.org/10.2307/1939273

Rusch V. 1992. Principales limitantes para la regeneración de la lenga en la zona N.E.de su área de distribución. Proc CIEFAP «Actas del Seminario de Manejo forestal de la lenga y aspectos ecológicos relacionados». Esquel, Chubut, Argentina, pp. 61-73.

Schabenberger O and FJ Pierce. 2002. Contemporary statistical models for the plant and soil sciences. CRC Press, Boca Raton.

Schliemann SA, Bockheim JG. 2011. Methods for studying treefall gaps: A review. Forest Ecol. Manag. 261, 1143- 1151. http://dx.doi.org/10.1016/j.foreco.2011.01.011

Trimble GR, Tryon EH. 1966. Crown Encroachment into Openings Cut in Appalachian Hardwood Stands. Journal of Forestry 64, 104-108.

Veblen TT. 1992. Regeneration dynamics. In: Plant succession - Theory and Prediction, Population and Community (Glenn-Lewin, D.C., Peet, R.K., Veblen, T.T., eds.), Chapman & Hall, London, UK, pp. 152-187.

White PS, Pickett STA. 1985. Natural disturbance and patch dynamics: An introduction. In: The Ecology of Natural Disturbance and Patch Dynamics (Pickett STA, White PS, eds.), Academic Press, Orlando, FL, pp. 3-13. PMid:3939877




DOI: 10.5424/fs/2012213-02538

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