摘要:

Summary maps presented in this paper depict the current distribution patterns of aboveground woody biomass and carbon content of commercial forests in the southeastern United States. Contour maps of dominance of 10 important southeastern tree taxa are included. These maps were complied from growing—stock volume data available from the Continuous Forest Inventories (CFI) of the United States Department of Agriculture (U.S.D.A.) Forest Service, Southern and Southeastern Forest Experiment Stations. The maps of woody biomass and carbon establish the current for standing crop and carbon storage within forests of the southeastern United States, an area comprising 15% of the temperate forest zone of the earth. The contour maps of tree dominance quantify variation in composition within and between forest types previously mapped only qualitatively by the Forest Service. These dominance maps illustrate the individualistic nature of the distributions in response to gradients of environmental factors and effects of land management practices.

ISSN:0012-9658    

DOI:10.2307/1936984

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

Natural home range features of juvenile Uta stansburiana were measured and compared between socially dominant and subordinate individuals of size— and sex—matched pairs. Dominance was determined via paired encounters in laboratory, neutral arenas. Dominants originated from home ranges with significantly less dense croton and grass vegetation. Dominants showed a slight tendency to inhabit larger home ranges. Dominants' home ranges were significantly more diverse than subordinates' home ranges. A survivorship—based multivariate index of home range quality showed that dominants originated from home ranges of higher overall quality than those subordinates. Home ranges of dominant juveniles resembled home ranges of oversummer survivors of a previous study, and home ranges of subordinates resembled those of nonsurvivors. Subjects were introduced by pairs into outdoor pens with halves of disparate habitat quality. Dominants showed significantly greater occupation of the superior half than subordinates. Dominant juveniles, then, appear to inhabit home ranges different from subordinates; features of these home ranges may convey increased survivorship. The same dominant juveniles are more apt than subordinates to secure superior habitat in a novel situation.

ISSN:0012-9658    

DOI:10.2307/1936985

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

Predation on different—sized Daphnia by the crustacean Neomysis mercedis was examined in the laboratory and the field. Small mysids select the smallest prey available, while adult mysids can consume Daphnia as large as 3.0 mm. Laboratory observations and frequencies of injured Daphnia in the lake indicate that difficulty in handling prey sets the upper limit to the size of Daphnia ingested. The pattern of electivity over the manageable size range of prey is variable for large Neomysis, suggesting that the mysids may alter their feeding behavior in response to changing availability of prey. Freshwater mysids apparently consume prey of a broader size range than most other invertebrate planktivores. The opportunities for evolutionary adjustment of body size and morphology in response to mysid predation are relatively limited for zooplankton prey, especially in lakes where visual predators restrict the sizes that can be attained. This limitation may help to explain the apparent effectiveness of mysids in controlling Daphnia populations.

ISSN:0012-9658    

DOI:10.2307/1936986

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

The 30 smallest seedlings of Ferocactus acanthodes (Lem.) Britton&Rose (Cactaceae) at a canyon site in the northwestern Sonoran desert average 2.5 cm in height. Based on field studies of CO2exchange throughout the year, the estimated time of their germination was late summer 1976. To explain why so little establishment occurred in recent years, the length of lethal drought for seedlings of various ages was calculated from the seedling geometry (volume—to—surface ratio), dehydration tolerance, and transpiration rates. Individual years were identified which had sufficiently long growing seasons relative to the length of the subsequent droughts to allow establishment. Eight of the last 18 yr were found to be suitable for establishment of F. acanthodes, the last year being 1976.

ISSN:0012-9658    

DOI:10.2307/1936987

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

Ideas from ecology, economics, and geography are synthesized into a central—place, space—utilization model which is analytically as well as conceptually useful. Incorporation of social and ecological factors extends common home range models, which incorporate only distance. The patch preference and competition coefficients which are "revealed" by regression on actual use—intensity patterns indicate the importance of these factors by the degree to which the perturb an appropriate distance—decay function. Proximate factors reveal themselves by deforming a Huxleyan "elastic disc." The analytical value of the model is illustrated by an example from my studies of eastern chipmunks.

ISSN:0012-9658    

DOI:10.2307/1936988

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

The structure and dynamics of chipmunk home ranges were characterized by focal—animal observation. Neighboring animals were territorial, but their home ranges overlapped extensively and did not have exclusive core areas. Established neighbors avoided encountering each other. Their pattern of encounter avoidance with extensive spatial overlap resulted in spatial time—sharing. Territorial interference with the timing of space—use did not affect the total utilization of shared areas within a resident's home range. Distance and patch structure were important proximate determinants of space—use intensity. The result suggest that territorial interference is more important as a mechanism for deterring the immigration of nonneighbors than as a continuously operative competitive mechanism between established neighbors. The concept than the proximate object of interference competition is access to space is questioned.

ISSN:0012-9658    

DOI:10.2307/1936989

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

Male Red—winged Blackbird pairing success was studied to determine the role of male quality in female choice of territory and mate. Data on date of first nest, harem size, and proportion of territorial males surviving to subsequent breeding seasons did not support the hypothesis that territory quality alone determines female choice of mate. Male reproductive experience and body size were significantly positively correlated with harem size, but correlations between male age and harem size, and male courtship intensity and harem size, appeared to occur because females preferred territories defended by experienced males. There was no evidence that male aggressiveness tendencies influenced female choice of mate. Although these data indicate that females were influenced by male characteristics, it is suggested that a complex interaction of male and territory quality determines female choice of mate in the Red—winged Blackbird.

ISSN:0012-9658    

DOI:10.2307/1936990

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

This report involves time—series statistical analysis (including concurrent physical and community variables) of the population dynamics of 4737 voles (Microtus californicus) trapped over 19 yr while emigrating from two study enclosures on a Northern California grassland. Population fluctuation of voles, as documented in the literature as well as in this study, generally cannot be described by periodic or regularly cyclic equations, but rather are either random or occasionally pseudoperiodic where autoregressive correlation explains irregular cycles on the basis of the population's previous demographic history. For these two California vole populations, an autoregressive component accounted for approximately a third of the total variability in the population, while random extrinsic environmental variation explained almost all of the remaining variation. Weather played a key determinant role, influencing microtine populations both directly, and indirectly through an effect on vegetation. The distinction between periodic, pseudoperiodic, and random fluctuations in vole populations, and indeed in wildlife populations in general, cannot be dismissed as merely a question of semantics, because each entails a specific ecologic interpretation. The demographic characteristics of microtine rodents, although fluctuating more dramatically, were similar to those of other rodents.

ISSN:0012-9658    

DOI:10.2307/1936991

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

Monthly mist—net censuses were conducted in central Panama to contrast the species richness and composition of the understory avifauna in treefall gaps to that of adjacent, intact forest. We compiled 826 captures of 73 species over a 9—mo period. Species richness was greater in gaps than forest (66 vs. 53 species), but capture rates were nearly identical (gap, 409; forest, 417). Of the 31 species with adequate sample sizes, 5 displayed significant habitat preference (P ° .05): 3 in gaps and 2 in forest. Ordination of all nets by Bray—Curtis analysis indicates that gap and forest bird assemblages are quite distinct. We suggest that treefall gaps contribute to the structural heterogeneity of the forest and influence the composition and richness of the bird community.

ISSN:0012-9658    

DOI:10.2307/1936992

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY

摘要:

The hypothesis that the understory herbs Costus allenii and C. laevis (Zingiberaceae) have converged in floral characteristics to use the same pollinator was investigated in central Panama. Observations and experiments indicated that these species (1) occupy the same habitats, (2) flower synchronously, (3) are identical in flower color, morphology, and nectar secretion patterns, (4) share the same pollinator, the bee Euglossa imperialis, (5) are self—compatible, but not autogamous, and (6) have strong barriers to hybridization. Both grow in low density along streamsides and produce a single flower per day for an extended period (up to 4 mo). Flower density is depressed through extensive predation by the weevil Cholus cinctus, which damaged 31% of all C. allenii and 60% of all C. laevis inflorescences. Direct observation of foraging bees indicated that individuals regularly visit both plant species. An experimental analysis of interspecific pollen transfer using powered paint as a marker verified these results; 97% of the flowers checked had received heterospecific visits. The high probability of interspecific pollination did not affect fruiting success. I suggest that low flower density, exaggerated by extreme floral predation, has selected for floral similarity and pollinator sharing in these species. Floral convergence increases effective flower density and nectar supplies, and probably increases the regularity and rate of pollinator visitation.

ISSN:0012-9658    

DOI:10.2307/1936993

出版商:Ecological Society of America    

年代:1981

数据来源: WILEY