Abstract

AYMA-ROMAY, Ariel Isaías; LOVERA, Pedro  and  SOTO-ROJAS, Gladys. Sobrevivencia y crecimiento de plántulas reforestadas de Podocarpus glomeratus (Podocarpaceae) en diferentes altitudes y micrositios en ecosistemas de pastizales de los Andes bolivianos después de cuatro años. Ecol. austral [online]. 2017, vol.27, n.1, pp.63-71. ISSN 1667-782X.

Altitude and microsite are key factors for the establishment of seedlings in mountain ecosystems. In this study, we evaluated how seedling survival and growth of Podocarpus glomeratus, a native tree vulnerable to extinction, varied across diferent altitudes and microsites. As part of a four-year reforestation program, 150 seedlings were planted in 15 experimental plots along an altitudinal gradient of five levels (2747, 3005, 3300, 3590 and 3850 m a.s.l.) and three repetitions by altitude (nested plots) in a grassland ecosystems from the community of Pajchanti (Cochabamba, Bolivia). Plant survival, growth and microsite around each seedling, such as slope and ground cover (rock outcrops, grasses, shrubs, mosses and herbs) were measured three times during the reforestation program. Generalized linear mixed models (GLMM) and Tukey tests were used in order to evaluate the influence of altitude on seedling survival and growth (including nested plots as random factor). The influence of each component biotic or abiotic in the microsites on the survival and growth was analyzed also with GLMM, for each altitude separately. Thus, we avoided confusing effect of altitude and microsite. Seedlings survival was significantly greater at the intermediate altitude and lower at both altitudinal extremes, but seedlings growth was greater at the lower altitude range (from 2700 to 3300 m a.s.l.), while smaller at higher altitudes. Seedlings survival was not influenced by abiotic or biotic components of the microsite. However, high shrub cover was related to higher seedlings growth at the lowest altitude. High rock outcrops cover had a negative effect on growth in the intermediate altitude, while more rock outcrops and higher slope percentage had positive efect on the growth at a higher altitude (3590 m a.s.l.). Reforestation of P. glomeratus in grassland ecosystems should be carried out at 2700 to 3300 m a.s.l. Nonetheless, shrubs, rock outcrops and slope of the microsite influenced the establishment of the seedlings, depending on cover percentage and interactions with the altitude. These microsite components must be managed in future reforestations.

Keywords : Forestation; Mountain; Facilitation.