نتایج جستجو برای: irans forests
تعداد نتایج: 39516 فیلتر نتایج به سال:
The woody communities of seven of the most intact bottomland hardwood forests of southeastern Louisiana are described. The seven forests are on old levee ridges associated with past distributaries of the Mississippi River. The communities were divided by diameter size class into overstory (~10.0 cm dbh) and understory (3.0 cm 2 10.0 cm dbh). The overstory (27 species) and understory (24 species...
Temperate forests receive some of the highest rates of nitrogen (N) deposition in the world. While numerous studies have investigated the effects of N enrichment on forests, there is little consensus on why some forests become N saturated while others do not. To investigate this, we used a multi-factor metaanalysis to simultaneously estimate the relative importance of several environmental, exp...
The most popular approach for analyzing survival data is the Cox regression model. The Cox model may, however, be misspecified, and its proportionality assumption is not always fulfilled. An alternative approach is random forests for survival outcomes. The standard split criterion for random survival forests is the log-rank test statistics, which favors splitting variables with many possible sp...
Fire has become a common feature in tropical drained peatlands, and it may have detrimental impacts on the overall biodiversity of the forest ecosystem. We investigated the effect of fire on termite and ant assemblages and the importance of remnant forest in restoring species diversity in fire-impacted tropical peat swamp forests. The species loss of both termites and ants was as high as 50% in...
Tropical forests play a crucial role in regulating regional and global climate dynamics, and model projections suggest that rapid climate change may result in forest dieback or savannization. However, these predictions are largely based on results from leaf-level studies. How tropical forests respond and feedback to climate change is largely unknown at the ecosystem level. Several complementary...
Forests play an important role in environmental protection. There is a long history of protection forests in mountain areas, where they help to prevent soil erosion, landslides and avalanches, and where they are important in maintaining the water quality of rivers draining forested catchments. Special silvicultural methods are required to ensure that these forests are maintained indefinitely. F...
Aim There is increasing concern regarding sustainable management and restoration of planted forests, particuIarly in the Mediterranean Basin where pine species have been widely used. The aim of this study was to analyse the environmental and structural characteristics of Mediterranean planted pine forests in relation to natural pine forests. Specifically, we assessed recruitment and woody speci...
Many forest herbs show reduced frequency in forests growing on former agricultural land (secondary forests) relative to forests that were never cleared for agriculture (primary forests). To explain this pattern, studies of secondary forest colonization by forest herbs have stressed the role of limited seed dispersal, though environmental conditions may also limit colonization. Here I demonstrat...
Examining the fine-scale spatial structure of fungal populations can tell us much about how individual species reproduce and disperse throughout natural landscapes. Here we study the fine-scale genetic structure of Tricholoma matsutake, a prized edible and medicinal mushroom, by systematic sampling of mycorrhizas within fairy rings in 50-y-old and old-growth forests in two villages. Using singl...
From analysis of published global site biomass data (n = 136) from primary forests, we discovered (i) the world's highest known total biomass carbon density (living plus dead) of 1,867 tonnes carbon per ha (average value from 13 sites) occurs in Australian temperate moist Eucalyptus regnans forests, and (ii) average values of the global site biomass data were higher for sampled temperate moist ...
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