Using facilitation microsites as a restoration tool for conversion of degraded grasslands to Nothofagus forests in Southern Patagonia

Abstract

In Southern Patagonia, introduction of exotic grasses after forest fires strongly restricts restoration of Nothofagus spp forests. The use of polycarbonate shelters to shield Nothofagus seedlings has been not enough for getting restoration success. Selection of natural facilitation microsites (i.e. logs, rocks, pioneer plants) for seedling outplanting may improve early performance of Nothofagus pumilio (Poepp. et. Endl.) Krasse (N. pumilio), by reducing the incidence of limiting factors such as soil water and light stress. In 2012, seedlings of N. pumilio shielded with polycarnonate shelters were planted close to log piles, nurse plants of native shrubs, and open areas to evaluate the effect of natural facilitation microsites on early performance of the species. After three growing seasons, soil measurements, seedlings survival, stem diameter and height of plants, electronic transport rate, stomatal conductance, and the chlorophyll index were evaluated to explore leaf photochemistry and any possible limitation to photosynthesis associated to microsite conditions. Seedling survival was significantly lower in open sites in comparison to the other microsite conditions. Seedling height was highest both under nurse plants and log piles microsites. Stomatal conductance was higher for seedlings in nurse plant microsites despite the fact that the soil water content was similar across all conditions. Soil penetration resistance and electron transport rate were higher, but chlorophyll index was lower, in open sites when compared to the other microsites. Our results show that the use of facilitation microsites such as pioneer nurse shrubs and logs for N. pumilio reforestation or restoration plans in degraded grassland areas in Southern Patagonia should be considered even when plants are protected with polyethylene shelters.