A. Dalmasso

Litter yield in shrubs of larrea in the andean piedmont of Mendoza, Argentina

The production of litter was measured for the piedmont communities of Larrea divaricata ssp. dicaricata (1500 m asl) and L. cuneifolia (1130 m asl) near Mendoza, Argentina. Litter was collected in traps randomly distributed in each stand: herbaceous, shrubby and uncovered soil. The monthly average weight of litter was recorded in each stand during one year and discontineously during other two years more. The material was classified as: leaves and fruits of Larrea sp., fruits of Stipa sp. (by its relative abundance), gramineous and non gramineous material. The litter and the soil in each sample were bromatologically analyzed and the N, Ca and P levels also determined. The annual contribution of nutrients was calculated totally and layer by layer. The L. cuneifolia and the L. divaricata thickets produce 4,71 t.ha-1 year-2 and 2,02 t.ha-1.year-2 of litter respectively, that mean 78,66 kg/ha of N, 4,24 kg/ha of P and 94,2 kg/ha of Ca in the first thicket and 31,14 kg/ha of N, 1,82 kg/ha of P and 34,17 kg/ha of Ca in the second one; in one year of study. In den Larrea divaricata ssp. divaricata und L. cuneifolia Gebüschen des mendoziner Andenvorlandes (1500 m und 1130 m Meereshöhe) wurde die Streuproduktion untersucht. Die Streu wurde getrennt nach Strauchschit, Krauchschit und nacktem Boden in Fallen gesammelt, die stichprobenartig in den Beständen verteilt waren. Ein Jahr lang wurde in jedem Bestand der monatliche Streuanfall ermittelt, wobei die Bläter und Früchte von Larrea von den Stipa-Früchten zwecks Berechnung der relativen Mengen-, grasartige und nicht grasartige, getrennt wurden. Streu und Boden der Bestän wurden bromatologisch analysiert und die Stockstoff, Kalk und Phosphorgehalte bestimmt Derjärliche Nährstoffeintrag wurde schichtweise und als Gesamtmenge berechnet. Das Larrea cuneifolia Gebüsch erzeuchte järlich 4,71 T/ha und das L. divaricata 2,20 T/ha Streu. Diese enthielt 78,66 kg/ha N, 4,24 kg/ha P und 94,20 T/ha Ca im L. cuneifolia-und 31,14 kg/ha N, 1,82 kg/ha P, 34,17 kg/ha Ca im L. divaricata-Gebüsch.

Response to cutting of Larrea divaricata and L. cuneifolia in Argentina

Abstract The response of Larrea divaricata and L. cuneifolia to cutting stems 0–20 cm above the ground was studied in the arid piedmont area west of Mendoza, Argentina. The species occur at different elevations (750–1250m), whileand in vegetation zones: L. cuneifolia < 1250 m ; L. divaricata between 1250 and 2500 m. Four treatments with 10 replicates were analysed in randomly chosen plants: cut at ground level with lopping shears; cut at ground level with a pick; cut at 10 cm with lopping shears; and cut at 20 cm with lopping shears. The initial and final height, volume, and dry matter (above‐ and below‐ground) were determined. The relation between volume and initial and final dry matter and height was analysed through a factorial MANOVA (p< 0,05), and the functional relation between volume, dry matter and height was estimated by adjusting a regression model. In both species, maximum recovery was reached when cut with shears, and predicted recovery (turnover) was 17–18 yr. In the two last treatments height was a useful predictor of dry matter. L. divaricata ‐dominated plots have a lower biomass, growth rate, and allocation to stems and root than L. cuneifolia ‐dominated plots. Regrowth following clipping on an area of 3–10 ha, is sufficient to support the annual needs (cooking and heating) of one family.

Carbon Storage in Larrea Divaricata and L. cuneifolia (Zygophyllaceae) in Drylands of Central-Western Argentina

We studied total stored carbon—aboveground and underground—in Larrea divaricata and L. cuneifolia species, which are the dominant species and form extensive shrublands in both extensive geomorphological units in Mendoza: piedmont and lowlands (45,022 km2). In randomly distributed plots aboveground and underground biomass was assessed using the extractive method. Data on type and distribution of shrublands were obtained from the vegetation map; species cover from field records using the point-quadrat linear method; and biomass of leaves, stems, and roots from randomly distributed plots. Carbon density was calculated using the 0.5 standard factor. Total carbon storage in the two geomorphological units reached 8,237 Tg, of which 36.3% corresponded to L. divaricata and 63.7% to L. cuneifolia. Considering both species together and their distribution, the lowlands store around 98.1% of the carbon, and the piedmont about 1.9%.