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1.
We investigated successional trends on windthrow mounds in two old-growth Tsuga heterophylla-Picea sitchensis forests in northern southeast Alaska to determine the influence of windthrow disturbance on the maintenance of plant diversity. We were particularly interested in assessing the value of mosses in detecting long-term effects of disturbance in temperate rainforests. Mosses established a dense carpet on windthrow mounds within the first few decades after the disturbance. No consistent changes were noted in total moss and vascular plant cover, moss biomass, or species diversity between young mounds (±50 yrs), intermediate mounds (±150 yrs) or old mounds (> 200 yrs), or between mounds and the undisturbed forest floor, despite consistent differences in soils development.Classification and ordination of the vegetation data did not show a consistent relationship between soil surface age or soil depth and overall species composition on the two sites. Young mounds were the most compositionally distinctive, primarily due to moss species. Pogonatum alpinum var. sylvaticum, P. contortum and Polytrichum formosum were generally confined to young mounds with unstable substrata, while Dicranum majus and Sphagnum girgensohnii were associated with old soil surfaces and deep organic soils. Vascular plant species with affinities for riparian or deep shade habitats (Tiarella trifoliata, Coptis asplenifolia and Dryopteris expansa) showed a general preference for the forest floor. Gymnocarpium dryopteris was the only vascular plant with a significant association with young mounds.Mosses comprised approximately 25% of understory plant biomass and as much as 50% of understory productivity. In cool temperate forests, the inclusion of mosses in vegetation analysis may provide valuable insights into the nature of vegetation patterns over subtle environmental gradients. The distinctiveness of the temperate rainforest type and the unique ecological effects of windthrow disturbance in this type are also suggested by this study.Abbreviations HR =
Heintzleman Ridge (study site)
- OP =
Outer Point (study site) 相似文献
2.
Population structure and spatial patterns for trees in a temperate old-growth evergreen broad-leaved forest in Japan 总被引:9,自引:0,他引:9
The population structure and spatial pattern of major tree species in a warm-temperate old-growth evergreen broad-leaved forest in the Tatera Forest Reserve of Japan were investigated. All stems 5 cm in diameter at breast height (DBH) were mapped on a 4 ha plot and analyses were made of population structure and the spatial distribution and spatial association of stems in different vertical layers for nine species. This was done in the context of scale dependency. The plot was located on a very gentle slope and 17.1% of its canopy layer was in gaps. It contained 45 woody plant species and 4570 living stems with a basal area of 63.9 m2 ha–1. Castanopsis cuspidata var. sieboldii, the most dominant species for the basal area, had the maximum DBH among the species present, fewer smaller stems and a lower coefficient of statistical skewness of the DBH distribution. The second most dominant species, Dystilium racemosum, had the highest stem density (410 ha–1), more abundant smaller stems and a relatively higher coefficient of skewness. Most stems in different vertical layers showed a weakly aggregated distribution with loose colonies as basic units. Gap dependency for the occurrence of stems under the canopy layer was weak. Maximum slope degree of the plot also weakly affected the occurrence of stems. Spatial associations varied among intra- and interspecific cohorts in the different layers and spatial scales examined, and positive associations among cohorts were found more frequently as the scales examined became larger. This tendency suggests that key factors forming observed spatial associations might vary with the spatial scales. 相似文献
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Abstract: In most temperate deciduous forests, windstorm is the main source of dead wood. However, the effects of this natural disturbance on ambrosia and bark beetle communities are poorly known. In managed oak‐hornbeam forests storm‐damaged in France in 1999, we sampled ambrosia (and second bark beetles) by ethanol‐baited window‐flight traps in 2001. By comparing uncleared gaps, undisturbed closed‐canopy controls and seedling‐sapling stands, we investigated the short‐term effects of gap formation, gap size and surrounding landscape to provide a snapshot of scolytid response. Contrary to expectations, neither the abundance nor the richness of ambrosia beetle species was significantly higher in gaps than in undisturbed stands. Few responses in abundance at the species level and only a slight difference in assemblage composition were detected between gaps and closed‐canopy controls. Gaps were more dissimilar from seedling‐sapling stands, than from closed‐canopy controls. More scolytid individuals and species were caught in gaps than in seedling‐sapling stands. Mean local and cumulative richness peaked in mid‐size gaps. Only mid‐size gaps differed from closed‐canopy controls in terms of species composition. We identified generalist gap species (Xyleborus saxesenii, X. cryptographus), but also species significantly more abundant in mid‐size gaps (Platypus cylindrus, Xyloterus signatus). The faunistic peculiarity of mid‐size gaps seemed to be partly related to a bias in oak density among gap size classes. Few landscape effects were observed. Only the scolytids on the whole and X. dispar were slightly favoured by an increasing density in fellings at the 78 ha scale. We did not find any correlation between scolytid abundance and the surrounding closed‐forest percentage area. We confirmed that temperate, deciduous, managed stands did not come under threat by ambrosia and bark beetle pests after the 1999 windstorm. Nonetheless, our data stressed the current expansion in Western Europe of two invasive species, X. peregrinus and especially X. germanus, now the predominant scolytid in the three oak forests studied. 相似文献
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The distribution and regeneration strategy of the major canopy dominants in species-rich subtropical/warm temperate rainforests
in south-western Japan was studied in a hilly zone below 1100 m a.s.l. Using the patch sampling method, four dominance-community
types were numerically identified and they corresponded to four habitats which represented a combination of topography and
altitude (i.e. ridgesvs slopes, and belowvs above 500 m a.s.l.) Seven major canopy dominants had their respective distributional core in one of these topo-altitudinal
habitats. The seven canopy dominants could be classified into three species groups according to their size structure and growth
habits. Group A (Tsuga sieboldii andQuercus gilva) and group B (Quercus acuta, Quercus salicina, Machilus thunbergii) were restricted to the emergent and canopy layer, respectively. These two groups had only a few subcanopy trees and saplings.
Saplings of group B showed a rapid growth rate in canopy gaps. Group C (Distylium racemosum) was characterized by many subcanopy trees and saplings that grew steadily under the closed canopy.Castanopsis sieboldii showed intermediate characteristics between group B and C in the size structure and growth habit of its saplings. The density
ofD. racemosum canopy trees was markedly reduced on ridges and slopes above 500 m and on slopes below 500 m. In these marginal habitats,
the three species groups coexisted by sharing different strata within a community. This situation was possible due to the
differences in regeneration strategies among the canopy species. 相似文献
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Hiroshi Tanaka 《植被学杂志》1995,6(6):887-896
Abstract. Seed demography of three co-occurring Acer species in an old-growth mixed deciduous forest in Japan was studied. Almost all of the seeds of A. mono germinated in the first spring, while those of A. palmatum var. amoenum showed a delay in germination of almost one year. A. rufinerve showed a rather opportunistic germination habit. Both A. palmatum var. amoenum and A. rufinerve form short-term persistent seed banks, but without input of newly dispersed seeds they may become extinct in about one year. The seed bank for these two species is not as significant as for a typical pioneer species, and the seedling bank is important for all three species. Only a small proportion of the dispersed propagules contained viable embryos, mainly due to pollination failure or abortion (A. mono and A. palmatum var. amoenum), and invertebrate predation (A. rufinerve). For all three species, larger seed crops had a higher percentage of viable seeds. Even for these relatively small, wind-dispersed seeds, the predation pressure was very high. A large part of the dispersed seeds was eaten by wood mice during the first winter (30–80 %). Estimation from the 5-yr average of seed dispersal and seedling emergence showed that only 7–16 % of the dispersed viable seeds succeeded in germinating. 相似文献
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Cecilia Smith-Ramírez 《Biodiversity and Conservation》2004,13(2):373-393
Temperate forests of southern South America are globally important because of their high level of endemism. I argue here that within southern South America, rainforests of the Chilean Coastal Range should be the primary target for new conservation efforts. Historically, most protected areas in southern South America have been designated to preserve forests above 600 m, mainly in the Andes. However, Coastal Range forests have higher species richness and are under greater threat than Andean forests at similar latitudes. Coastal forests are characterized by the presence of numerous narrow-range endemics, among them two monotypic plant families. The higher frequency of endemic species in Coastal Range forests is attributed to its more stable biogeographic history compared to the Andes, particularly during the glacial events of the Quaternary. Due to the extent of human impact, the remaining fragments of coastal forests are quite distant from one another, and are disconnected from the larger protected areas of Andean forests. Only 439000 ha of Valdivian coastal forest still remain, including some remnants of primary forest. New private or public reserves should be created to protect the last remnants of continuous forest remaining on the Coastal Range of the Valdivian region (40–42° S). A different conservation strategy should be applied north of 40° S, where protected areas are too small and fragments are too scattered to maintain viable populations of most vertebrates. In this latter area, I recommend expanding existing reserves, restoring native forests, and interconnecting remnant forests through a corridor network. 相似文献
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M. S. Fontanarrosa G. Chaparro P. de Tezanos Pinto P. Rodriguez I. O’Farrell 《Hydrobiologia》2010,646(1):231-242
Dense mats of free floating plants (FFP) often produce severe underwater light attenuation and strong oxygen depletion in
the water column. In this study, we experimentally assessed the zooplankton response to artificial shading using field mesocosms.
During 30 days, we simulated three different light scenarios by mimicking the persistence, absence, and fluctuation of FFP
typically encountered in vegetated shallow subtropical lakes. We used dark meshes to simulate the abiotic effects engineered
by FFP. Both in the permanently covered and fluctuating situations, anoxia impaired zooplankton development. Anoxia constituted
a major driving force in shaping the zooplankton response, whereas the feeding resource availability (phytoplankton) seemed
to play a minor role; no top down effect on phytoplankton occurred in anoxic situations. In the fluctuating cover regime (periodic
darkness and anoxia), the temporal variation of nanophytoplankton was not affected by zooplankton; once again oxygen availability
seemed the main force shaping the zooplankton dynamics. Either periodical or permanent shading, associated to anoxic conditions,
impaired the success of small herbivores. Large herbivores and microphytoplankton were negatively affected only under persistent
shade and anoxia. In contrast, when neither light nor oxygen limitation occurred, such as in the scenario without shading,
top-down control occurred. This study highlights the importance that the oxygen dynamics driven by the presence of FFP exert
on the structure and dynamics of zooplankton assemblages and on the top down cascading effects on phytoplankton in warm temperate
or subtropical shallow lakes. 相似文献
12.
Deborah Lawrence Dana Richards Laura Schneider John Rogan Birgit Schmook Henry Wilbur 《Biotropica》2011,43(6):676-684
Hurricanes are an important part of the natural disturbance regime of the Yucatán Peninsula with the potential to alter forest structure and composition, yet investigations of species‐level responses to severe winds are limited in this region. The effect of a category 5 hurricane (Hurricane Dean, 21 August 2007) on dry tropical forests across the southern Yucatán was examined with respect to tree damage, mortality, and sprouting. Damage was assessed 9–11 mo following the hurricane in 92 (500 m2) plots stratified by wind speed and normalized difference vegetation index (NDVI) change classes over a 25,000 km2 study area. We investigated the relative importance of biotic (i.e., species, size, and wood density) and abiotic (i.e., wind speed) factors to better explain patterns of damage. Overall mortality was low (3.9%), however, mortality of less common species (8.5%) was elevated more than fourfold above that of 28 common species (1.8%), indicating immediate selective consequences for community composition. Species varied in the degree and type of damage experienced, with susceptibility increasing with tree diameter and height. Wood density influenced damage patterns only in areas where a critical threshold in storm intensity was exceeded (wind speeds ≥210 km/h). Although overall, damage severity increased with wind speed, common coastal species were more resistant to damage than species distributed farther inland. Our findings suggest that selective pressure exerted by frequent hurricane disturbance has, and will, continue to impact the floristic composition of forests on the Yucatán Peninsula, favoring certain wind‐resistant species. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp . 相似文献
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We studied the effects of the timing of urea treatment on the succession of ammonia fungi. In two evergreen Castanopsis cuspidata forests and in one deciduous Quercus serrata forest, we applied 343g urea to 25 and 15 plots of 0.5m2, respectively, at three different times of the year. Ten of the early-phase (EP) species, considered to be saprotrophic, and 6 of the late-phase (LP) ones, considered ectomycorrhizal, fruited. In both phases, the commencement, peak, and cessation of fruiting took place simultaneously among all the plots treated at the same time. The fruiting occurred in summer and autumn. Quantity and size of the fruit bodies was larger in the LP than in the EP species. Fruiting of EP species was affected by the treatment time and that of LP species by interaction of the treatment time and vegetation type. EP was short and occurred as one period, whereas LP was long and occurred as two or more fruiting seasons. We found that species composition, dominant species, and degree of its dominance in fruiting of the ammonia fungi are predictable for different treatment times of the year and different vegetation types. 相似文献
14.
Information has been obtained as a part of a wider study of leaf structure, water relations and mineral status, which is to include work on a considerable variety of evergreen forests. Fifteen structural features have been investigated in well-lit leaves of 60 dicotyledonous species of Japanese Warm Temperate Rain Forest, this sample giving an 81% cover of the relevant species (Table 1). The salient features of the average leaf are summarised on p. 200. The leaves of shrubs and small trees have been compared with those of tall and medium trees; some of the differences were unexpected. For example, the leaves of the lower growing species tended to be thicker and to have thicker outer walls. The leaves of the whole Japanese sample were compared with those of 40 species in Tropical Lowland Rain Forest in New Britain. Although the average leaf area of the Japanese species was less than one tenth of that of the species from New Britain, the thickness and internal structure of the leaf and the size and density of the stomata were quite similar in the two sets of leaves (Table 2). The Japanese leaves were somewhat more xeromorphic in that they had thicker outer walls in the upper and lower epidermis. 相似文献
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Tomás A. Altamirano José Tomás Ibarra Kathy Martin Cristian Bonacic 《Biodiversity and Conservation》2017,26(10):2453-2472
South American temperate rainforests, a global biodiversity hotspot, have been reduced to nearly 30% of their original extent and most remaining stands are being degraded. Cavity-nesting vertebrate communities are dependent on cavity-bearing trees and hierarchically structured within nest webs. Evaluating the actual degree of cavity dependence (obligate, non-obligate) and the preferred attributes of trees by cavity nesters is critical to design conservation strategies in areas undergoing habitat loss. During three breeding seasons (2010–2013), we studied the cavity-nesting bird community in temperate rainforests of Chile. We found the highest reported proportion of tree cavity nesters (n = 29 species; 57%) compared to non-cavity-using birds for any forest system. Four species were excavators and 25 were secondary cavity nesters (SCNs). Among SCNs, ten species were obligate and 15 were non-obligate cavity nesters. Seventy-five percent of nests of SCNs were located in cavities produced by tree decay processes and the remaining 25% were in cavities excavated mainly by Pygarrhichas albogularis and Campephilus magellanicus. Nest web structure had a low dominance and evenness, with most network interactions occurring between SCNs and large decaying trees. Tree diameter at breast height (DBH) was larger in nest-trees (57.3 cm) than in available trees (26.1 cm). Cavity nesters showed a strong preference for dead trees, both standing and fallen (58% of nests). Our results stress that retaining large decaying and standing dead trees (DBH > 57 cm), and large fallen trees, should be a priority for retention in forest management plans in this globally threatened ecosystem. 相似文献
17.
We observed spawning behaviors of the haremic cleaner wrasse Labroides dimidiatus at a rocky reef in southern Japan. Females released pelagic eggs daily from June to September after a spawning ascent by
pairs. When the high tide occurred between noon and evening (quarter moon to new or full moon), they spawned around the time
of the tide providing fast offshore currents. For the rest of the lunar cycle, spawnings occurred during late afternoon independent
of the state of the tide at the time of day. This spawning pattern is quite different from that of conspecifics on coral reefs
that always spawn around the high tide at all lunar stages to avoid potential egg predators. The wrasse ascended high in the
water column, probably because of its predator-immune characters as a cleaner. The steep slope of the study site seemed to
contribute to releasing gametes far above aggregating planktivores. Thus, gametes were not subject to heavy predation. Current
direction might not always affect survival of spawned pelagic eggs on the temperate reefs so crucially as it does on coral
reefs. We conclude that spawning during unfavorable tidal conditions during the daytime may be better than spawning during
the best tidal condition in the crepuscular period when predation pressure on adults will be high. Intraspecific variation
in the timing and location of spawning of the wrasse may result from different conditions for larval survival.
Received: February 6, 2000 / Revised: June 16, 2000 / Accepted: July 17, 2000 相似文献
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The specialization of herbivores among tree species is poorly understood despite its fundamental importance as a factor regulating
diversity. To examine the effect of tree species on larval community structure, the larval communities in 10 temperate deciduous
tree species that differed in leaf emergence pattern (flush- vs. intermediate-type) were seasonally surveyed. The newly developed
soft, nitrogen-rich leaves of all species became tough and nitrogen-poor as the season progressed. Following the changes in
leaf quality, two distinct seasonal lepidopteran larval communities emerged, with a marked turnover in early July. The beta
diversity, or dissimilarity, of species composition in the larval communities among tree species was higher in summer than
in spring. These results imply that the lepidopteran larval communities as a whole were supported by alpha diversity in spring
and by beta diversity in summer, demonstrating that the plant diversity of this forest could support a caterpillar community.
We examined the importance of spatio-temporal variations in leaf quality within and among tree species in promoting herbivore
diversity, although other factors, such as tree species phylogeny and predators, may also have a large effect on lepidopteran
larval communities. 相似文献
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