Home About us Contact
|
Home About us Contact | ||
|
|
||
Chiloé Island (chiloé + island)
Selected AbstractsNon-symbiotic nitrogen fixation during leaf litter decomposition in an old-growth temperate rain forest of Chiloé Island, southern Chile: Effects of single versus mixed species litterAUSTRAL ECOLOGY, Issue 2 2010CECILIA A. PÉREZ Abstract Heterotrophic nitrogen fixation is a key ecosystem process in unpolluted, temperate old-growth forests of southern South America as a source of new nitrogen to ecosystems. Decomposing leaf litter is an energy-rich substrate that favours the occurrence of this energy demanding process. Following the niche ,complementarity hypothesis', we expected that decomposing leaf litter of a single tree species would support lower rates of non-symbiotic N fixation than mixed species litter taken from the forest floor. To test this hypothesis we measured acetylene reduction activity in the decomposing monospecific litter of three evergreen tree species (litter C/N ratios, 50,79) in an old-growth rain forest of Chiloé Island, southern Chile. Results showed a significant effect of species and month (anova, Tukey's test, P < 0.05) on decomposition and acetylene reduction rates (ARR), and a species effect on C/N ratios and initial % N of decomposing leaf litter. The lowest litter quality was that of Nothofagus nitida (C/N ratio = 78.7, lignin % = 59.27 ± 4.09), which resulted in higher rates of acetylene reduction activity (mean = 34.09 ± SE = 10.34 nmol h,1 g,1) and a higher decomposition rate (k = 0.47) than Podocarpus nubigena (C/N = 54.4, lignin % = 40.31 ± 6.86, Mean ARR = 4.11 ± 0.71 nmol h,1 g,1, k = 0.29), and Drimys winteri (C/N = 50.6, lignin % = 45.49 ± 6.28, ARR = 10.2 ± 4.01 nmol h,1 g,1, k = 0.29), and mixed species litter (C/N = 60.7, ARR = 8.89 ± 2.13 nmol h,1g,1). We interpret these results as follows: in N-poor litter and high lignin content of leaves (e.g. N. nitida) free-living N fixers would be at competitive advantage over non-fixers, thereby becoming more active. Lower ARR in mixed litter can be a consequence of a lower litter C/N ratio compared with single species litter. We also found a strong coupling between in situ acetylene reduction and net N mineralization in surface soils, suggesting that as soon N is fixed by diazotroph bacteria it may be immediately incorporated into mineral soil by N mineralizers, thus reducing N immobilization. [source] Environmental controls and patterns of cumulative radial increment of evergreen tree species in montane, temperate rainforests of Chiloé Island, southern ChileAUSTRAL ECOLOGY, Issue 3 2009CECILIA A. PÉREZ Abstract We investigated the local environmental controls on daily fluctuations of cumulative radial increment and cambial hydration of three dominant, evergreen tree species from montane, Coastal rainforests of Chiloé Island, Chile (42° 22, S). During 2 years (1997,1998 and 1998,1999) we recorded hourly cumulative radial increments using electronic band dendrometers in the long-lived conifer Fitzroya cupressoides (Cupressaceae), the evergreen broad-leaved Nothofagus nitida (Nothofagaceae), and the narrow-leaved conifer Podocarpus nubigena (Podocarpaceae). We also measured soil and cambial tissue hydration using capacitance sensors, together with air and soil temperature and rainfall during the period of the study. In addition, we collected cores of these tree species to evaluate how dendrometer measurements reflect annual tree ring width. One-year long daily time series of cumulative radial increments suggests that radial growth of Fitzroya cupressoides was initiated slowly in early spring, with a maximum in early summer. Multiple regressions showed positive relations between daily precipitation and radial index (i.e. the difference in cumulative radial increment of two consecutive days) in the three species. According to path analysis there was a significant direct effect of changes in tree hydration on radial index of the three focal species. In emergent, pioneer species such as Nothofagus and Fitzroya, radial index was negatively affected by changes in maximum air temperature and photosynthetically active radiation, probably because of high evapotranspiration demand on warm sunny days. The shade-tolerant species Podocarpus nubigena was positively affected by photosynthetically active radiation. Our diel scale findings support the use of tree ring widths for reconstructing past climate in these southern temperate forests and provide evidence that rainforest trees may be highly sensitive to future declines in rainfall and temperature increases during summer. [source] Mating success of the endemic Des Murs' Wiretail (Sylviorthorhynchus desmursii, Furnariidae) in fragmented Chilean rainforestsAUSTRAL ECOLOGY, Issue 1 2006IVÁN A. DÍAZ Abstract: We studied the effects of fragment size, vegetation structure and presence of habitat corridors on the reproductive success of the Des Murs' Wiretail (Sylviorthorhynchus desmursii Des Murs, Furnariidae), a small (10 g) understorey bird, endemic to South American forests. In a rural landscape of Chiloé Island, southern Chile (42°S; 70°W), we determined the mating and nesting success of wiretails in 28 territories distributed in seven small (1,20 ha) and two large (>300 ha) forest fragments during the 1997,1998 breeding season. Wiretails inhabited dense bamboo thickets in the understorey of forest patches, dense shrublands covering old fields, and dense early successional forest vegetation. Wiretails avoided open pastures. Reproductive success depended solely on the probability of finding mates, and the main factor affecting mating success was the presence of corridors. Mated individuals occupied 72% of the territories in forest patches <20 ha connected by corridors, 73% of the territories in large (>300 ha) fragments, but only 20% of territories in isolated fragments surrounded by pastures. Because of the rapid expansion of pastures in southern Chile, the conservation of wiretails and other understorey birds will depend on the maintenance of travel corridors with dense understorey vegetation between forest fragments. [source] Seedling Mortality and Herbivory Damage in Subtropical and Temperate Populations: Testing the Hypothesis of Higher Herbivore Pressure Toward the TropicsBIOTROPICA, Issue 2 2010Ek Del-Val ABSTRACT Herbivory rates are generally thought to be higher in tropical than in temperate forests. Nevertheless, tests of this biogeographic prediction by comparing a single plant species across a tropical-temperate range are scarce. Here, we compare herbivore damage between subtropical and temperate populations of the evergreen tree Aextoxicon punctatum (Olivillo), distributed between 30° and 43° S along the Pacific margin of Chile. To assess the impact of herbivory on Olivillo seedlings, we set up 29 experimental plots, 1.5 × 3 m: 16 in forests of Fray Jorge National Park (subtropical latitude), and 13 in Guabún, Chiloé Island (temperate latitude). Half of each plot was fenced around with chicken wire, to exclude small mammals, and the other half was left unfenced. In each half of the plots we planted 16 seedlings of Olivillo in December 2003, with a total of 928 plants. Seedling survival, leaf production and herbivory by invertebrates were monitored over the next 16 mo. Small mammal herbivores killed ca 30 percent of seedlings in both sites. Nevertheless, invertebrate herbivory was greater in the temperate forest, thus contradicting the expected trend of increasing herbivore impact toward the tropics. Seedling growth was greater in subtropical forest suggesting better conditions for tree growth or that higher invertebrate herbivory depressed seedling growth in the temperate forest. Invertebrate herbivory increased toward temperate latitudes while small mammal herbivory was similar in both sites. We suggest that comparison of single species can be useful to test generalizations about latitudinal patterns and allow disentangling factors controlling herbivory patterns across communities. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source] | ||||||||||