Facultad de Agronomía Universidad de Buenos Aires Cover of fallen tree leaves reduces herbaceous productivity under poplars in silvopastoral systems borodows@gmail.com ARGENTINA Monlezun, S.J., Cornaglia, P.S., Pincemin, J.M., Zunino, H., Clavijo, M.P. and Borodowski, E.D. Dirección de Forestación Secretaría de Agricultura, Ganadería, Pesca y Alimentos
ARGENTINA Delta del Paraná
Delta del Paraná Parana River: 4.000 km Parana River basin: 2.600.000 km 2 Delta del Paraná: 1.750.000 ha
Parana River Uruguay River Gualeguay River La Plata River 2 3 2 4 3 2 Delta del Paraná - Floods
Formation of islands Formation of islands
Delta del Paraná 7500 years ago Codignotto J., 2006
Delta del Paraná 7000 years ago
Delta del Paraná 6000 years ago
Delta del Paraná 4000 years ago
Delta del Paraná Current Delta
Delta del Paraná 1750
Delta del Paraná 1800
Delta del Paraná 1850
Delta del Paraná 1900
Delta del Paraná 1950
Delta del Paraná 2005
Profile of an island in the Lower Delta of Parana. a) Afforestation. b) Forest ceibo with Pajonal of Cortadera. c) Pajonal of Cortadera. d) Secondary forest. Autors: Kandus y Quintana
Delta del Paraná Principal activity: afforestation with Salicaceae (50000 ha)
Populus deltoides `Australia 129. 7 years. 400 trees/ha (5 m x 5 m)
Silvopastoral with poplar A silvopastoral system is a combination of trees, domestic cattle and forage that can provide increased economic income per unit area.
However, herbaceous productivity is reduced beneath deciduous trees as a result of shade, temperature regime and the accumulation of fallen leaves in late autumn.
Objective: This study aimed to evaluate the effect of the cover of dead tree leaves on the herbaceous productivity of two seeded temperate perennial grasses during the year of establishment.
Material and Methods: The experiment was conducted in a 13-year-old commercial plantation of Populus deltoides `Stoneville 71' (323 plants per hectare), in the low delta of the Parana River, Argentina (34º 06 S; 58º 47 W).
Material and Methods: The evaluated forage species were Festuca arundinacea (FA) and Dactylis glomerata (DG). A randomized complete block experimental design was used, with three replications and two factors: position inside the plantation (north, centre and south) and cover of fallen poplar leaves (with and without). Annual grasses: Bromus unioloides var. I, B. unioloides var. II, Lolium multiflorum and Avena sativa. Perennial grasses: Dactylis glomerata and Festuca arundinacea. Legume: Trifolium repens.
Forage species were sown in lines 15 cm apart, at a density of 500 seeds per m 2, at the end of March (autumn in the Southern Hemisphere). Biomass was clipped to 2 cm above the ground at 4 dates: July, September, October and December. Data were analyzed by ANOVA with repeated measures, and Tukey s Test (α = 0.05) was used to analyse differences in treatment means and interactions.
Results Average total productivity (g/m 2 /yr) for FA and DG in plots without and with fallen poplar leaves. ANOVA p values Position 0.71 ns Cover of fallen poplars leaves < 0.001 ** P*C 0.85 ns
Final considerations: Temperate forage grasses are the best adapted to grow beneath trees because of their ability to sustain positive carbon gains at low irradiance rates. However, our results suggest that the excessive shading of understory forage by dead tree leaves would drastically affect the performance of C 3 grasses.
The productivity of a silvopastoral system is a consequence of the balance between the positive and negative interactions among their components. The design of this type of system should focus on minimizing negative interactions: removal and/or grazing fallen poplar leaves seems to be a tool to minimize their negative effect on herbaceous productivity.
Thank you
Comisión Nacional del Álamo Argentina Mendoza, Argentina 15 17 April 2009 www.jornadasalicaceas.com jornadasalicaceas@gmail.com
CFM 2009 XIII o Congreso Forestal Mundial XIII th World Forestry Congress XIII e Congres forestier mondial 18 25 October 2009 Buenos Aires - Argentina www.cfm2009.org Info@cfm2009.org org