Cover of fallen tree leaves reduces herbaceous productivity under poplars in silvopastoral systems

Transcription

1 Facultad de Agronomía Universidad de Buenos Aires Cover of fallen tree leaves reduces herbaceous productivity under poplars in silvopastoral systems 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

2 ARGENTINA Delta del Paraná

3 Delta del Paraná Parana River: km Parana River basin: km 2 Delta del Paraná: ha

4 Parana River Uruguay River Gualeguay River La Plata River Delta del Paraná - Floods

5 Formation of islands Formation of islands

6 Delta del Paraná 7500 years ago Codignotto J., 2006

7 Delta del Paraná 7000 years ago

8 Delta del Paraná 6000 years ago

9 Delta del Paraná 4000 years ago

10 Delta del Paraná Current Delta

11 Delta del Paraná 1750

12 Delta del Paraná 1800

13 Delta del Paraná 1850

14 Delta del Paraná 1900

15 Delta del Paraná 1950

16 Delta del Paraná 2005

17 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

18 Delta del Paraná Principal activity: afforestation with Salicaceae (50000 ha)

19 Populus deltoides `Australia years. 400 trees/ha (5 m x 5 m)

20 Silvopastoral with poplar A silvopastoral system is a combination of trees, domestic cattle and forage that can provide increased economic income per unit area.

21 However, herbaceous productivity is reduced beneath deciduous trees as a result of shade, temperature regime and the accumulation of fallen leaves in late autumn.

22 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.

23 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).

24 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.

25 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.

26 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 < ** P*C 0.85 ns

27 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.

28 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.

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30 Thank you

31 Comisión Nacional del Álamo Argentina Mendoza, Argentina April

32 CFM 2009 XIII o Congreso Forestal Mundial XIII th World Forestry Congress XIII e Congres forestier mondial October 2009 Buenos Aires - Argentina Info@cfm2009.org org