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Nothofagus Forests (nothofagus + forest)
Selected AbstractsSeparating host-tree and environmental determinants of honeydew production by Ultracoelostoma scale insects in a Nothofagus forestECOLOGICAL ENTOMOLOGY, Issue 4 2007ROGER J. DUNGAN Abstract 1.,Sugar-rich honeydew excreted (,produced') by insects feeding on phloem sap is a key energy flow in a range of temperate and tropical ecosystems. The present study measured honeydew produced by Ultracoelostoma sp. (Homoptera: Coelostomidiidae) scale insects feeding on Nothofagus solandri var. solandri (Hook f.) Oerst. trees in a temperate evergreen forest in New Zealand. Simultaneous measurements of environmental variables and canopy photosynthesis were conducted to allow separation of host-tree and environmental determinants of honeydew production. These relationships were further examined in experiments where canopy photosynthesis was manipulated by shading or plant nitrogen levels increased by foliar spray. 2.,Rates of honeydew production varied nine-fold from a maximum (± 1 SE) of 64.4 ± 15.2 mg dry mass m,2 bark h,1 in early summer (December) to a minimum of 7.4 ± 4.2 mg m,2 h,1 in winter (August). Rates of production measured 1.4 m from the base of the trees' stems varied significantly with stem diameter, and were higher on medium-sized (18 cm diameter) than small or large stems. 3.,Rates of production were significantly related to environmental conditions over the hours preceding measurement (air temperature and air saturation deficit averaged over the preceding 24 and 12 h respectively). There was no evidence that rates of production were directly related to short-term changes in the supply of carbohydrates from the canopy (either when compared with measurements of unmanipulated photosynthetic rate, or after sugar levels were manipulated by shading 80% of host-trees' leaf area), or to changes in phloem nitrogen content. 4.,The results show that there is no clear effect of host-tree carbon supply on honeydew production; if production is related to photosynthesis, the effect of this is much less important that the large and significant direct effect of environmental conditions on honeydew production. [source] Does soil determine the boundaries of monodominant rain forest with adjacent mixed rain forest and maquis on ultramafic soils in New Caledonia?JOURNAL OF BIOGEOGRAPHY, Issue 6 2006J. Read Abstract Aim, To determine the soil characteristics of Nothofagus -dominated rain forests in an ultramafic region (i.e. soils having high concentrations of metals including Mg, Fe and Ni), and whether soil characteristics may explain the location of monodominant rain forest in relation to adjacent mixed rain forest and maquis (shrub-dominated vegetation). Location, New Caledonia. Methods, Soil characteristics were compared among six Nothofagus -dominated rain forests from a range of altitudes and topographic positions. At four of these sites, comparisons were made with soils of adjacent mixed rain forest and maquis. Results, Soil characteristics varied among the monodominant Nothofagus forests, largely due to differences between ultramafic soils and soils influenced by non-ultramafic intrusions. The soils of all vegetation types had low concentrations of nutrients, particularly P, K and Ca (both total and extractable/exchangeable), and high total concentrations of Ni, Fe, Cr and Mn. There were significant differences between the rain forests and adjacent maquis in soil concentrations of several elements (N, P, Ca, Mg and Mn), more so in surface soils than at depth, but much of this pattern may be caused by effects of vegetation on the soil, rather than of soil on the vegetation. However, there were no significant differences in soil concentrations of any mineral elements between Nothofagus forest and adjacent mixed rain forest. Main conclusions, We found no evidence for soil mediation of boundaries of Nothofagus rain forest with mixed rain forest, and little evidence for the boundaries of either forest type with maquis. We suggest that the local abrupt boundaries of these monodominant Nothofagus forests are directly related to temporal factors, such as time since the last wildfire and frequency of wildfire, and that disturbance is therefore a major causal factor in the occurrence of these forests. [source] The abundance, distribution and structural characteristics of tree-holes in Nothofagus forest, New ZealandAUSTRAL ECOLOGY, Issue 8 2008TANYA J. BLAKELY Abstract Tree-holes provide an important microhabitat that is used for feeding, roosting and breeding by numerous species around the world. Yet despite their ecological importance for many of New Zealand's endangered species, few studies have investigated the abundance or distribution of tree-holes in native forests. We used complementary ground and climbed tree surveys to determine the abundance, distribution and characteristics of tree-holes in undisturbed Nothofagus forest in the Lewis Pass, New Zealand. We found that hole-bearing trees were surprisingly abundant compared with many other studies, including Australian Eucalyptus species and American beech. In fact, we estimated as many as 3906 tree-holes per hectare, of which 963 holes per hectare were potentially large enough to provide roost sites for hole-nesting bats in New Zealand, while only eight holes per hectare were potentially suitable for specialist hole-nesting birds. This was of great interest as primary cavity-excavating animals are absent from New Zealand forests, compared with North America and Australia. Moreover, tree-hole formation in New Zealand is likely to be dominated by abiotic processes, such as branch breakage from windstorms and snow damage. As has been found in many other studies, tree-holes were not uniformly distributed throughout the forest. Tree-holes were significantly more abundant on the least abundant tree species, Nothofagus fusca, than on either N. menziesii or N. solandri. In addition to tree species, tree size was also an important factor influencing the structural characteristics of tree-holes and their abundance in this forest. Moreover, these trends were not fully evident without climbed tree surveys. Our results revealed that ground-based surveys consistently underestimated the number of tree-holes present on Nothofagus trees, and illustrate the importance of using climbed inspections where possible in tree-hole surveys. We compare our results with other studies overseas and discuss how these are linked to the biotic and abiotic processes involved in tree-hole formation. We consider the potential implications of our findings for New Zealand's hole-dwelling fauna and how stand dynamics and past and future forest management practices will influence the structural characteristics of tree-holes and their abundance in remnant forest throughout New Zealand. [source] Does soil determine the boundaries of monodominant rain forest with adjacent mixed rain forest and maquis on ultramafic soils in New Caledonia?JOURNAL OF BIOGEOGRAPHY, Issue 6 2006J. Read Abstract Aim, To determine the soil characteristics of Nothofagus -dominated rain forests in an ultramafic region (i.e. soils having high concentrations of metals including Mg, Fe and Ni), and whether soil characteristics may explain the location of monodominant rain forest in relation to adjacent mixed rain forest and maquis (shrub-dominated vegetation). Location, New Caledonia. Methods, Soil characteristics were compared among six Nothofagus -dominated rain forests from a range of altitudes and topographic positions. At four of these sites, comparisons were made with soils of adjacent mixed rain forest and maquis. Results, Soil characteristics varied among the monodominant Nothofagus forests, largely due to differences between ultramafic soils and soils influenced by non-ultramafic intrusions. The soils of all vegetation types had low concentrations of nutrients, particularly P, K and Ca (both total and extractable/exchangeable), and high total concentrations of Ni, Fe, Cr and Mn. There were significant differences between the rain forests and adjacent maquis in soil concentrations of several elements (N, P, Ca, Mg and Mn), more so in surface soils than at depth, but much of this pattern may be caused by effects of vegetation on the soil, rather than of soil on the vegetation. However, there were no significant differences in soil concentrations of any mineral elements between Nothofagus forest and adjacent mixed rain forest. Main conclusions, We found no evidence for soil mediation of boundaries of Nothofagus rain forest with mixed rain forest, and little evidence for the boundaries of either forest type with maquis. We suggest that the local abrupt boundaries of these monodominant Nothofagus forests are directly related to temporal factors, such as time since the last wildfire and frequency of wildfire, and that disturbance is therefore a major causal factor in the occurrence of these forests. [source] Effects of natural disturbance and selective logging on Nothofagus forests in south-central ChileJOURNAL OF BIOGEOGRAPHY, Issue 7 2002William Pollmann Aim Changes in stand structure, floristic composition and tree population dynamics during the last four centuries were described in southern temperate rain forests. The impacts of natural and anthropogenic disturbance since the late 1560s were examined for old-growth and logged forests. Location The study was conducted in montane Nothofagus alpina forests in the Andean Range of south-central Chile. Study sites were located at a range of altitudes between 1000 and 1250 m a.s.l. Methods Temporal variation in species recruitment and annual dendroecological data were used to determine the historical development and disturbance history of three old-growth forests, and three stands after selective logging in the late 1880s to early 1900s. Considering the spatial structure of evergreen vs. deciduous elements, the forests are a mixture of deciduous and evergreen tree species. Results Stem density, maximum stem diameter and basal area differed between the old-growth and logged stands, but species composition did not. At lower altitudes, N. alpina was the dominant canopy species in both old-growth and logged stands, but regeneration of N. alpina was significantly different in these stands. At higher altitudes, N. alpina and N. dombeyi were the dominant canopy species in both old-growth and logged stands, and here regeneration patterns of these Nothofagus species were similar. After selective logging, in mixed forests of shade-intolerant Nothofagus and more shade-tolerant trees (such as Laurelia philippiana) there has been a shift in regeneration from more shade-tolerant resprouting species towards Nothofagus. Major and moderate releases in radial growth, indicative of disturbance, occurred in most of the older trees during the last four centuries, and especially during the last 100 years. Growth rates of N. alpina are higher than those of associated shade-tolerant trees, and apparently increase after disturbances. Main conclusions Results suggest that under disturbance regimes dominated by treefall gaps, and additionally canopy openings by selective logging, maintenance of Nothofagus species appears to be associated with complementary differences in growth rate, sprouting capacity, canopy residence time, and longevity. Such small-scale canopy openings may help explain the relative abundance of N. alpina in montane mixed rain forests in the Andean Range, where the maintenance of Nothofagus species in many stands has been attributed to a high frequency of coarse-scale disturbance. My results serve to emphasize that understanding the species coexistence and forest dynamics in Nothofagus forests may require attention to interspecific differences in life-history characteristics. [source] Structural and floristic characteristics of some monodominant and adjacent mixed rainforests in New CaledoniaJOURNAL OF BIOGEOGRAPHY, Issue 2 2000J. Read Abstract Nothofagus spp. dominate the upper canopy of some rainforests on ultramafic soils in New Caledonia. These monodominant forests typically occur within, or contiguous with, larger areas of mixed-canopy rainforest. In this study the structure, diversity and composition of six Nothofagus -dominated plots were investigated, and comparisons were made with three adjacent mixed rainforest plots. Stand density and basal area (all stems , 1.3 m high) in the Nothofagus plots were in the range 16,056,27,550 stems/ha and 43.1,69.9 m2/ha, respectively. There was no significant difference (P , 0.05) in total stand density or basal area between the paired Nothofagus and mixed rainforests, but there were consistently fewer trees and less basal area of trees , 40 cm d.b.h. in the Nothofagus forests. Species richness, species diversity (Shannon-Wiener, based on basal area) and equitability (based on basal area) of trees , 20 cm d.b.h. on 0.1 ha Nothofagus plots were in the range 4,17, 0.96,3.76 and 0.45,0.87, respectively. No significant differences (P , 0.05) were recorded in these three parameters between the paired Nothofagus and mixed rainforests, although species diversity was consistently lower in the paired Nothofagus forests. Comparison of dominance by density and basal area indicated that although the uppermost canopy of the Nothofagus forests was dominated by Nothofagus (70,95%), the basal area and density contribution was , 55% except at Col de Yaté (, 85%). Analysis of similarity indicated no significant difference in stand composition of trees , 20 cm d.b.h. (following removal of Nothofagus from the data set) between Nothofagus and mixed rainforests using basal area, density or presence-absence data. It is concluded that the Nothofagus -dominated forests differ from the adjacent mixed rainforests mainly by (1) dominance of the uppermost canopy, without necessarily dominance of the stand by basal area or density, and (2) the smaller basal area contributed by large trees (all species). [source] Influence of fire severity on stand development of Araucaria araucana,Nothofagus pumilio stands in the Andean cordillera of south-central ChileAUSTRAL ECOLOGY, Issue 6 2010MAURO E. GONZÁLEZ Abstract Fire is the prevalent disturbance in the Araucaria,Nothofagus forested landscape in south-central Chile. Although both surface and stand-replacing fires are known to characterize these ecosystems, the variability of fire severity in shaping forest structure has not previously been investigated in Araucaria,Nothofagus forests. Age structures of 16 stands, in which the ages of approximately 650 trees were determined, indicate that variability in fire severity and frequency is key to explaining the mosaic of forest patches across the Araucaria,Nothofagus landscape. High levels of tree mortality in moderate- to high-severity fires followed by new establishment of Nothofagus pumilio typically result in stands characterized by one or two cohorts of this species. Large Araucaria trees are highly resistant to fire, and this species typically survives moderate- to high-severity fires either as dispersed individuals or as small groups of multi-aged trees. Small post-fire cohorts of Araucaria may establish, depending on seed availability and the effects of subsequent fires. Araucaria's great longevity (often >700 years) and resistance to fire allow some individuals to survive fires that kill and then trigger new Nothofagus cohorts. Even in relatively mesic habitats, where fires are less frequent, the oldest Araucaria,Nothofagus pumilio stands originated after high-severity fires. Overall, stand development patterns of subalpine Araucaria,N. pumilio forests are largely controlled by moderate- to high-severity fires, and therefore tree regeneration dynamics is strongly dominated by a catastrophic regeneration mode. [source] Variable strength of top-down effects in Nothofagus forests: bird predation and insect herbivory during an ENSO eventAUSTRAL ECOLOGY, Issue 4 2009C. NOEMI MAZIA Abstract Predators are thought to play a key role in controlling herbivory, thus having positive indirect effects on plants. However, evidence for terrestrial trophic cascades is still fragmentary, perhaps due to variation in top-down forces created by environmental heterogeneity. We examined the magnitude of predation effects on foliar damage by chewing insects and mean leaf size, by excluding birds from saplings in ,dry' and ,wet'Nothofagus pumilio forests in the northern Patagonian Andes, Argentina. The experiment lasted 2 years encompassing a severe drought during the La Niña phase of a strong El Niño/Southern Oscillation event, which was followed by unusually high background folivory levels. Insect damage was consistently higher in wet than in dry forest saplings. In the drought year (1999), bird exclusion increased folivory rates in both forests but did not affect tree leaf size. In the ensuing season (2000), leaf damage was generally twice as high as in the drought year. As a result, bird exclusion not only increased the extent of folivory but also significantly decreased sapling leaf size. The latter effect was stronger in the wet forest, suggesting compensation of leaf area loss by dry forest saplings. Overall, the magnitude of predator indirect effects depended on the response variable measured. Insectivorous birds were more effective at reducing folivory than at facilitating leaf area growth. Our results indicate that bird-initiated trophic cascades protect N. pumilio saplings from insect damage even during years with above-normal herbivory, and also support the view that large-scale climatic events influence the strength of trophic cascades. [source] Litterfall of epiphytic macrolichens in Nothofagus forests of northern Patagonia, Argentina: Relation to stand age and precipitationAUSTRAL ECOLOGY, Issue 3 2006MAYRA S. CALDIZ Abstract: The objective of this study was to analyse how stand age and precipitation influence abundance and diversity of epiphytic macrolichens in southern beech Nothofagus forests, estimated by lichen litter sampling. Five sites of Nothofagus dombeyi (Mirbel) Oersted were selected in Nahuel Huapi National Park, Argentina. At each site, lichen fragments from the forest floor were collected at 12.5 m2 plots in pairs of young and mature N. dombeyi forest. Additionally, two sites with multi-aged subalpine Nothofagus pumilio (Poepp. et Endl.) Krasser forest were investigated in a similar manner. Average litterfall biomass per stand varied from less than 1 kg ha,1 in a young low-precipitation stand to a maximum of 20 kg ha,1 in a mature high-precipitation stand. In places with higher precipitation, litterfall biomass in N. dombeyi forest was considerably higher in old stands as compared with young ones. In places with less than 2000 mm of precipitation, differences in biomass were less pronounced. Old humid stands contained about twice as many taxa in the litter as old low-precipitation stands and young stands in general. Mature stands in low-precipitation sites only contained 17% of the litter biomass as compared with mature stands in high-precipitation sites. Epiphytic lichen composition changed from predominating fruticose lichens (Usnea spp. and Protousnea spp.) in low-precipitation stands to Pseudocyphellaria spp., Nephroma spp. and other foliose lichens, in the high-precipitation stands. There were no clear differences in the proportion of fruticose and foliose lichens between young and old stands. Fruticose lichens dominated litter biomass in both N. pumilio sites. [source] A long-term record of Nothofagus dominance in the southern Andes, ChileAUSTRAL ECOLOGY, Issue 1 2005William Pollmann Abstract The general model of regeneration dynamics in Nothofagus forests of southern South America could have value in community ecology if predictive relationships between disturbance history, functional traits and site attributes could be identified. Examined here is the proposal that on favourable sites shade-intolerant Nothofagus are likely not to survive in competition with shade-tolerant, broad-leaved evergreen taxa of temperate rain forests, and persistence, thus, is dependent on periodic coarse-scale disturbance. Comparison of stand dynamics of three old-growth Nothofagus forests at different elevations in the southern Andes, Chile where deciduous Nothofagus alpina dominates the upper canopy, and examination of the life history trade-offs of this variation were made. Stem density of all stems ,5.0 cm d.b.h. was 233,303 stems per hectare, and basal area was 123.9,171.0 m2ha,1. Maximum lifespan of N. alpina was found to be greater than ca 640 years, exceeding all previously reported ages for this species in the region. Forests had a stable canopy composition for this long-term, but some appeared to lack effective regeneration of N. alpina in recent years. Regeneration of N. alpina was generally greater in disturbed stands and higher elevation than in undisturbed stands and at lower elevation. Recruitment emerged to be strongly affected by competitive over- and understorey associates. There was a gradient of increasing dependence of N. alpina on disturbance towards the more productive end of the environment gradients, and hence less dependence of N. alpina on disturbance for its regeneration towards higher elevation. The study confirms that changes in forest composition may be explained by processes occurring in accordance with the predictions of the existing model of Nothofagus regeneration dynamics, providing stronger evidence specifically directed at mid-tolerant N. alpina, and by factoring out regeneration dynamics on favourable sites. Thus, for N. alpina, trait differences probably contribute to the competitive advantage over its associates in productive habitats, and may be linked to small-to-intermediate-sized disturbances which inevitably occur as older trees die, enabling N. alpina to persist in forests and therefore maintain species coexistence for the long-term. [source] | ||||||||||