Effects of density dependence in an evergreen-deciduous broadleaf karst forest in southwest China
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Understory
Density dependence
Temperate rainforest
Temperate forest
Abstract Conspecific negative density dependence (CNDD) promotes tree species diversity by reducing recruitment near conspecific adults due to biotic feedbacks from herbivores, pathogens, or competitors. While this process is well‐described in tropical forests, tests of temperate tree species range from strong positive to strong negative density dependence. To explain this, several studies have suggested that tree species traits may help predict the strength and direction of density dependence: for example, ectomycorrhizal‐associated tree species typically exhibit either positive or weaker negative conspecific density dependence. More generally, the strength of density dependence may be predictably related to other species‐specific ecological attributes such as shade tolerance, or the relative local abundance of a species. To test the strength of density dependence and whether it affects seedling community diversity in a temperate forest, we tracked the survival of seedlings of three ectomycorrhizal‐associated species experimentally planted beneath conspecific and heterospecific adults on the Prospect Hill tract of the Harvard Forest, in Massachusetts, USA. Experimental seedling survival was always lower under conspecific adults, which increased seedling community diversity in one of six treatments. We compared these results to evidence of CNDD from observed sapling survival patterns of 28 species over approximately 8 years in an adjacent 35‐ha forest plot. We tested whether species‐specific estimates of CNDD were associated with mycorrhizal association, shade tolerance, and local abundance. We found evidence of significant, negative conspecific density dependence (CNDD) in 23 of 28 species, and positive conspecific density dependence in two species. Contrary to our expectations, ectomycorrhizal‐associated species generally exhibited stronger (e.g., more negative) CNDD than arbuscular mycorrhizal‐associated species. CNDD was also stronger in more shade‐tolerant species but was not associated with local abundance. Conspecific adult trees often have a negative influence on seedling survival in temperate forests, particularly for tree species with certain traits. Here we found strong experimental and observational evidence that ectomycorrhizal‐associating species consistently exhibit CNDD. Moreover, similarities in the relative strength of density dependence from experiments and observations of sapling mortality suggest a mechanistic link between negative effects of conspecific adults on seedling and sapling survival and local tree species distributions.
Temperate rainforest
Temperate forest
Density dependence
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Abstract In this study, I defined a gap as a small opening formed in a forest canopy (area < 0.1 ha) and tried to synthesize gap-disturbance regimes of primary mature stands in different forest types of Japan, such as warm temperate evergreen broad-leaved (4 stands in 3 localities), cool temperate deciduous broad-leaved (10 in 5) and subalpine evergreen coniferous (3 in 1) forests. Mean percentage of the total gap area within the total forested area (percentage gap area) in each forest type was 17.0% in warm temperate (number of surveyed gaps was 161), 13.8% in cool temperate (278 gaps), and 8.0% in subalpine (100 gaps) forests. Mean gap density (ha-1) and mean gap size (m2) were 19.5 and 77.1 in warm temperate, 16.4 and 92.0 in cool temperate, and 19.1 and 41.9 in subalpine forests, respectively. These figures indicate that gap density is not substantially different among the forest types, but the mean gap size of subalpine forests is smaller than the other two, resulting in lower percentage gap area of this forest type. The gap size distributions were similar among the forest types; smaller gaps were much more frequent than larger ones, and gaps > 400 rrr were rare in warm temperate and cool temperate forests. In subalpine forests gaps > 200 m2 were rare. Gaps formed by multiple gapmakers comprised 19.9% of all gaps in warm temperate, 9.9% in cool temperate, and 44.9% in subalpine forests, which implies that gap formation by simultaneous tree fall or gap enlargement is more frequent in subalpine forests. Canopy trees died less often by uprooting in every forest type; dominant mode for the death of canopy trees was by leaving standing-dead or with broken trunks in every forest type. Since typhoons are obviously a chief agent of forest disturbance in Japan, frequency or magnitude of typhoon disturbance may influence these differences in the gap-disturbance regimes. In addition to the disturbance, tree architectures seem to affect some of these differences; narrower crown size of conifers compared with broad-leaved trees is considered one major cause for smaller gap size of the conifer forest.
Temperate rainforest
Temperate forest
Subalpine forest
Temperate deciduous forest
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PREMISE OF THE STUDY: Timing of budburst ( D BB ) may be related to the functional traits and distributions of woody species in temperate regions. Although many previous studies have investigated D BB in a number of temperate species, it has seldom been linked to multiple plant trait relationships. METHODS: D BB and plant traits were investigated for 24 woody species for 2 years in a warm‐temperate secondary forest in Japan. Particular attention was paid to differences in trait relationships between coexisting deciduous and evergreen broad‐leaved species. KEY RESULTS: D BB was correlated with plant traits in deciduous but not evergreen broad‐leaved species; D BB was later for deciduous species with greater leaf mass, leaf area, vessel diameter, and leaf nitrogen content per unit mass. In addition, D BB was later for species with more northern distributions in deciduous and evergreen species. CONCLUSIONS: Clear differences in the trait relationships between deciduous and evergreen broad‐leaved species might be caused by different selection pressures on D BB ; selection is expected to be more severe in deciduous species. Overall, the continuous variable of vessel diameter might be used as a simple and effective trait to predict D BB of deciduous species regardless of wood anatomy; however, no such traits were detected as effective predictors of D BB in evergreen species at this study site. In addition, D BB was earlier for the species of more southern distributions, suggesting that such species benefit more from warming.
Temperate deciduous forest
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Trait
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Temperate forest ecosystems are most extensively found throughout the Northern Hemisphere, and less extensively in the Southern Hemisphere. The specific regions containing temperate forests include Europe, North America, Asia, South America, Australia, and New Zealand. Northern temperate forests are often composed of deciduous trees that drop their leaves each year, providing a supply of rich nutrients to animals and plants as they decompose. Southern temperate forests, on the other hand, are primarily composed of broad leaved evergreen trees that keep their leaves year round. Most temperate forest ecosystems are heavily exploited and degraded. The underlying bedrock and geology of temperate forests around the world are highly variable, as are the soils, vegetation communities, disturbances, and plant adaptations found within them.
Temperate rainforest
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Temperate deciduous forest
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Temperate rainforest
Temperate forest
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Temperate rainforest
Temperate forest
Temperate deciduous forest
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Temperate forest ecosystems are most extensively found throughout the Northern Hemisphere, and less extensively in the Southern Hemisphere. The specific regions containing temperate forests include: Europe, North America, Asia, South America, Australia, and New Zealand. Northern temperate forests are often composed of deciduous trees that drop their leaves each year, providing a supply of rich nutrients to animals and plants as they decompose. Southern temperate forests, on the other hand, are primarily composed of broad‐leaved evergreen trees that keep their leaves year round. Most temperate forest ecosystems are heavily exploited and degraded. The underlying bedrock and geology of temperate forests around the world are highly variable, as are the soils, vegetation communities, disturbances, and plant adaptations found within them.
Temperate rainforest
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Temperate deciduous forest
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Temperate deciduous forest
Temperate rainforest
Temperate forest
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Abstract The simplification of forest structural complexity, caused by anthropogenic land-use practices, is one of the main threats to understory specialist birds. We examined the association of both single structural attributes and structural complexity, with the density of 4 understory bird species in the Global Biodiversity Hotspot “Chilean Winter Rainfall-Valdivian Forests” of South America. Between 2011 and 2013, we surveyed habitat attributes and conducted bird point counts in 505 plots in Andean temperate ecosystems in Chile. In each habitat plot, we measured understory density, volume of coarse woody debris (CWD), number of snags, diameter at breast height (DBH) of trees, and leaf litter depth. With these attributes, we developed an index of stand structural complexity (ISC). On average, old-growth forests had higher values for understory density, CWD volume, DBH, and litter depth than secondary forests and open fields, and thus greater values of ISC. The density of understory birds was positively correlated with the ISC for the Rhinocryptidae Pteroptochos tarnii, Scelorchilus rubecula, and Scytalopus magellanicus. We also found a positive association between understory density and litter depth, with the density of the Furnariidae Sylviorthorhynchus desmursii. However, this latter species showed a negative association with the density of snags. Our results suggest the utility of using an index of structural complexity, rather than single or even additive habitat attributes, for determining the density of understory specialist birds. We recommend that management plans should promote the retention of habitat attributes that contribute to the structural complexity of temperate forests of South America and beyond.
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Temperate rainforest
Coarse Woody Debris
Temperate forest
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Understory
Temperate deciduous forest
Temperate forest
Temperate rainforest
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