Silvopastoral systems: Estimation of understory winter grass productivity by remote sensing.

69. GRANIERI L., CORNAGLIA P., GOLLUSCIO R.A. Y OESTERHELD M

Hohhot, China

Congreso; XXI International Grassland Congress- VIII International Rangeland Congress.; 2008

Internacional Rangeland Society

Introduction Silvopastoral systems combine forest production with pastoral use of the understory. Most rangelands of the Flooding Pampas are dominated by C4 species (Perelman et al. 2001), which determines a low quantity and quality of forage supply during winter, a critical period for livestock production (Paruelo et al. 2001). Clavijo et al. (2005) found a larger proportion of C3 species, with significant winter production, in the herbaceous layers of sites afforested with poplars than in the open grassland. This indicate that planting deciduous trees may constitute an alternative to revert the dominance of warm season grasses  and therefore increase winter productivity. Remote sensing allows for the estimation of biomass, plant cover and productivity of grasslands (Oesterheld et al. 1998; Purevdorj at al. 1998; Paruelo et al. 2001). The objective of this work was to identify and interpret by remote sensing changes in the herbaceous winter productivity associated to the establishment of deciduous trees.   Materials and Methods We obtained NDVI (as a surrogate of primary production) from satellite images, and then we confronted it with the field information obtained on the same grasslands. NDVI was compared in 9 Poplar afforestations (F) with their respective paired plots with original grassland (G).  The plots were located at Castelli, province of Buenos Aires, Argentina (36º05`S; 57º48`W). Multispectral images of Landsat 5 TM satellite (Path: 224-Row: 085), of 30 meters of spatial resolution, during the winter period were used. Satellite data were accompanied with basal cover and other parameters previously obtained in the field (Clavijo et al. 2005). Data were analyzed using ANOVA model with repeated measures.                 Results and Discussion The NDVI from F and G stands were not significantly different (P=0.97). However, F stands had larger NDVI per unit of basal cover of C3 than G stands (P<0.07, Figure 1). These results would explain the increase of relative abundance of C3 grasses below trees due to microenvironmental conditions that enhance its growth (Clavijo et al. 2005).