Influence of plantation techniques on survival and early growth of poplars (Populus spp) in non-irrigated hapludolls of the Plane Pampas, Argentina.

ACHINELLI, FABIO; ANGELINETTI, SEBASTIÁN; DELGADO, MAXIMIANO; MILLÁN, GUILLERMO J; LUQUEZ VIRGINIA M.C.

Ciudad de Buenos Aires

Congreso; XIII Congreso Forestal Mundial; 2009

FAO- SAGyP

Poplar (P.  deltoides Marsh., P. × canadensis Moench) plantations of Plane Pampas frequently suffer from dry periods during summer. Drought can affect negatively growth and survival during the establishment year, when root systems are being developed and the capacity to explore soil is limited. The standard planting practice (SP) is to use 0.70 m cuttings planted at 0.50 m depth. In this work, we evaluated if using a longer cutting (1.20 m) and a higher planting depth (1 m, DP) could improve survival and growth during the planting year. We hypothesize that the deep planting technique will allow trees to develop more roots and to explore a larger volume of soil, reducing the negative impact of drought on growth and survival.A field experiment (34º 12´ S Lat.; 61º 43´ W Long.; 90 m elevation) was planted in August 2007 with nine clones on a typical hapludoll. The design was a three block split-plot. Main plots consisted of: standard planting (SP) and deep planting (DP); clones were located in 6-plant subplots.A group of soil (gravimetric water content, GWC), and plant growth variables (survival, S; stem volume index; stem dry weight, SDW; individual leaf area, ILA; leaf area, TLA; newly formed leaves, NL; number of coarse roots, RN), were measured from late spring to early autumn.Soil GWC was high during early spring (16,7 %), but in November a dry period began where evaporatranspiration exceeded rainfall.  Soil water holding capacity dropped to 11,5 % mean GWC. Dry period ended with February rains, which replenished upper soil water capacity (15,9 %) but not deeper water storage (9,9 %). We found significant differences between clones for most of growth variables. Clones with highest growth and survival were P. × canadensis `Triplo´, P. × canadensis `Guardi´, P. × canadensis `Ragonese 22 INTA´ and P. deltoides `208/68´, while those with poorer performance were P. deltoides `Catfish 2´ and P. deltoides `Australiano 129/60´.DP planting technique significantly improved growth of poplars till february, but not survival. Despite DP plants produced more RN than SP plants, SP plants recovered growth rates towards late summer to the point that SDW differences were non-significant at the end of the growing season. We found poplar ILA and TLA adjustments to water availability.Growth of both SP and DP trees showed fluctuations associated to soil water availability, and probably differ in the soil depths where they obtain water and nutrients.