Browsing by Author "Weber, Michael"

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Comparison of natural regeneration in natural grassland and pine plantations across an elevational gradient in the páramo ecosystem of southern Ecuador
(2019) Quiroz Dahik, Carlos Alberto; Marín Molina, Franklin Geovanny; Arias Chumbi, Ruth Eulalia; Crespo Sánchez, Patricio Javier; Weber, Michael; Palomeque Pesántez, Fanny Ximena
During the 1980s, reforestation programs using exotic species (Pinus spp.) were established in the páramo ecosystem of Ecuador. The aims of this study were: (1) to compare the natural regeneration between pine plantations (Pi) and natural grassland (NG) across an elevational gradient and (2) to identify the attributes of Pi and soil properties that were influencing herbaceous and woody plant composition and their plant cover. In total, six independent Pinus patula (Schltdl. & Cham. plantations (two per each elevation) were selected and distributed in an elevational range (3200–3400, 3400–3600, 3600–3800 m a.s.l.). Adjacent to Pi, plots in NG were established for recording natural regeneration. Both, namely the attributes and the soil samples, were measured in Pi. The results showed that natural regeneration differs significantly between both types of vegetation. As expected, NG holds more plant diversity than Pi; the elevational range showed a clear tendency that there was more herbaceous richness when elevation range increases, while the opposite was found for woody species. Moreover, attributes of Pi influenced herbaceous and woody vegetation, when saturated hydraulic conductivity (Ksat) in the soil, basal area (BA) and canopy density (CD) increased, herbaceous species richness and its cover decreseased; and when Ksat and the acidity in the soil increased, woody plants richness and its cover decreased. The plantations have facilitated the establishment of shade tolerant species. More studies are needed to evaluate if removal with adequate management of pine plantations can improve the restoration and conservation of the native vegetation of the páramo ecosystem.
Impacts of pine plantations on carbon stocks of páramo sites in southern Ecuador
(2021) Quiroz Dahik, Carlos; Crespo Sánchez, Patricio Javier; Stimm, Bernd; Mosandl, Reinhard; Cueva, Jorge; Hildebrandt, Patrick; Weber, Michael
ackground: Since the 1990’s, afforestation programs in the páramo have been implemented to offset carbon emissions through carbon sequestration, mainly using pine plantations. However, several studies have indicated that after the establishment of pine plantations in grasslands, there is an alteration of carbon pools including a decrease of the soil organic carbon (SOC) pool. The aim of this study is to investigate the impact of the establishment of pine plantations on the carbon stocks in different altitudes of the páramo ecosystem of South Ecuador. Results: At seven locations within an elevational gradient from 2780 to 3760 m a.s.l., we measured and compared carbon stocks of three types of land use: natural grassland, grazed páramo, and Pinus patula Schlltdl. & Cham. plantation sites. For a more accurate estimation of pine tree carbon, we developed our own allometric equations. There were significant (p < 0.05) differences between the amounts of carbon stored in the carbon pools aboveground and belowground for the three types of land use. In most of the locations, pine plantations revealed the highest amounts of aboveground and belowground carbon (55.4 and 6.9 tC/ha) followed by natural grassland (23.1 and 2.7 tC/ha) and grazed páramo sites (9.1 and 1.5 tC/ha). Concerning the SOC pools, most of the locations revealed significant lower values of plantations’ SOC in comparison to natural grassland and grazed páramo sites. Higher elevation was associated with lower amounts of pines’ biomass. Conclusions: Even though plantations store high amounts of carbon, natural páramo grassland can also store substantial amounts above and belowground, without negatively affecting the soils and putting other páramo ecosystem services at risk. Consequently, plans for afforestation in the páramo should be assessed case by case, considering not only the limiting factor of elevation, but also the site quality especially affected by the type of previous land use. © 2021, The Author(s).
Improvement of forest management key strategies: a contribution to conservation and sustainable land use
(Universitat Bayreuth, 2017) Manchego, Carlos
Reforestation is a key strategy for restoration and rehabilitation of degraded lands in the tropical mountain forest ecosystem. The experiences with Alnus acuminata are promising and further research about reforestation with native tree species in mountain regions is desirable; highly relevant topics like the selection of suitable sites and reproductive material, efficient seedling production, and silvicultural management in the field should be addressed in order to ensure successful reforestation projects. Plantations of native Alnus acuminata or exotic Pinus patula can also serve as nurse trees for enrichment planting with native tree species.
Natural or assisted succession as approach of forest recovery on abandoned lands with different land use history in the Andes of southern Ecuador
(2017) Palomeque Pesántez, Fanny Ximena; Günter, Sven; Siddons David, Christopher Null; Hildebrandt, Patrick; Stimm, Bernd; Aguirre, Nikolay; Arias Chumbi, Ruth Eulalia; Weber, Michael
Forest recovery on disturbed areas is of special significance in the Ecuadorian Andes, where deforestation is a serious problem. Natural diachronic succession was evaluated on three large plots or sites, differing in their land use and vegetation composition, one is dominated by grass species on an abandoned pasture (Pasture site), the other two are post-fire vegetation dominated by bracken (Bracken site) and various shrubs (Shrub site). Additionally, we assessed the effectiveness of manual removal of competitive herbaceous species to accelerate forest recovery. Monitoring was done in 2003, 2005 and 2007 on 48 subplots of 116 m2 each recording species richness and woody-species density. Results showed that the Pasture site demonstrated a competitive effect of exotic grasses on woody species recruitment with much lower species recruitment and density, suggesting serious inhibition of natural forest regeneration and an unclear successional trajectory. The Bracken and Shrub sites became significantly similar floristically and there is evidence for a marked facilitation of woody plant recruitment correlated with light availability on the ground. Both sites showed characteristics of classic succession, with Shrub showing a higher species richness and density while late-successional species are poorly represented on the Bracken site. However, NMDS ordination using species density showed that the two trajectories may not be converging towards a common “final state”. Manual weeding was ineffective for accelerating forest recovery. These results suggest that the main limiting factor for the recruitment of woody species on the Pasture site is strong grass competition and must be addressed before seed availability, while seed availability seems to be the constraining factor for Bracken and Shrub site development, thus direct seeding or planting may be effective in accelerating forest recovery.
Reforestación con especies nativas y exóticas: caso del valle de San Francisco, Zamora Chinchipe
(FLACSO, 2020) Weber, Michael; Palomeque Pesántez, Fanny Ximena; Günter, Sven; Hildebrandt, Patrick; Stimm, Bernd; Aguirre Mendoza, Nikolay
A pesar de la riqueza florística de especies arboreas nativas que se encuentran en los bosques andinos con potencial para la restauración activa (reforestación), los paisajes intervenidos se encuentran dominados por especies exóticas. Pocos estudios se han llevado a cabo para comparar el crecimiento y supervivencia entre especies nativas y exóticas en sitios con diferente cobertura vegetal como son: Pastizales recientemente abandonados, Llashipal y Arbustiva. Se establecieron parcelas puras de monitoreo para seis especies nativas (Cedrela montana, Handroanthus chrysanthus [syn. Tabebuia chrysantha], Juglans neotropica, Alnus acuminata, Morella pubescens y Heliocarpus americanus) y dos especies exóticas (Pinus patula y Eucalyptus saligna) en cada sitio, con un total de 384 parcelas y 9600 plántulas al inicio del experimento. La mitad de las parcelas fueron sometidas a tratamiento de remoción de vegetación competitiva. El monitoreo se realizó cada año durante cinco años, excepto para M. pubescens que se monitoreo por solo cuatro años. Los resultados indicaron que en general las especies nativas rinden bien dependiendo del sitio. Por ejemplo, al igual que las especies exóticas, A. acuminata resultó ser una de las especies más competitivas en los pastizales. M. pubescens tuvo un buen crecimiento en la cobertura tipo llashipal, mientras que H. chrysanthus tuvo alta supervivencia, aunque un crecimiento lento, en cobertura tipo arbustiva. La información generada en este estudio demuestra la importancia de las especies nativas en procesos de recuperación de sitios degradados. Adicionalmente indica cómo el monitoreo a mediano y largo plazo aporta a las decisiones sobre el uso de especies más adecuadas dependiendo de la cobertura vegetal predominante en el paisaje.
Variabilidad intraespecífica en la calidad de semillas de especies forestales nativas en bosques montanos en el sur del Ecuador: Implicaciones para la restauración de bosques
(2017) Palomeque Pesántez, Fanny Ximena; Maza Leon, Andrea Paola; Iñamagua Uyaguari, Juan Pablo; Günter, Sven; Hildebrandt, Patrick; Weber, Michael; Stimm, Bernd
One of the most important aspects in efficient plant production for restoration purposes is seed quality and its variability. The main goal of this study was to evaluate seed parameters according to the rules of “International Seed Testing Association” among different mother trees or individuals of seven native tree species (Cedrela montana, Morella pubescens, Inga acreana, Tabebuia chrysantha, Ocotea heterochroma, Oreocallis grandiflora and Myrcianthes rhopaloides) in two mountain forests in the Southern of Ecuador. These species were selected based on the ecological, socioeconomic importance, and their high potential for restoration. From a total of 35 mother trees for all species, seeds were collected in their fructification periods, and in the laboratory the following seed parameters were analyzed: purity, seed weight, moisture content, and germination; in addition, the coefficient of velocity of germination was determined as well. The results showed an intraspecific similarity in each species for the majority of seed parameters. However, the seed weight showed a high intraspecific variability for all species. The germination parameter showed differences among individuals for C. montana, T. chrysantha, O. heterochroma and M. rophaloides. In regard to the coefficient of velocity of germination, individual of species such as O. grandiflora and I. acreana showed a high coefficient in contrast to the individuals of O. heterochroma and M. pubescens. The information generated in this study could be a first step in the formulation of guidelines for the mass plant production for restoration purposes.