Browsing by Autor "Gladys Soto-Rojas"

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Efecto de la altitud y el micrositio sobre plántulas reforestadas de Polylepis lanata (Rosaceae) en el noroeste de Cochabamba, Bolivia: implicaciones para su restauración ecológica
(2015) Ariel Isaías Ayma-Romay; Gladys Soto-Rojas; Pedro Lovera
The reforestation of Polylepis lanata (Rosaceae) seedlings is limited by the poor knowledge about the environmental conditions that needs to survive and grow. The objective of the study was to determine how altitude and microsite affect seedlings survival and growth. An experiment was implemented with seedlings gathered from the forest and planted on 15 plots distributed in five altitudes (2,690–3,900 m; three replicates per altitude). In each plot, seedlings were planted in heterogeneous microsites. The study was carried out in the community Pajchanti in Northwestern Cochabamba, Bolivia. Survival and growth were assessed 14 and 51 months after planting. We measured altitude of plots and microsites around of each plant (cover shrubs, stones, moss, herbs, grassland, depth of humus and slope). The data analysis was conducted through the fit of generalized linear models, model selection and inference multi-model based in Akaike Information Criteria. The altitude and shrub cover had a positive effect on seedlings increasing their probability of survival; both were the most important variables. The humus, cover of stones and shrubs around the seedlings also improved the growth rates. The reforestations should be carried out in middle altitudes, 3,000 to 3,600 m, but in safe microsites which protect to the seedlings from a possible environmental stress outside of the forest, due to human disturbance of soil and vegetation.
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
(2017) Ariel Isaías Ayma-Romay; Pedro Lovera; Gladys Soto-Rojas
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 different 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 effect 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.