scholarly journals Fire and Landscape Dynamics in Yellowstone National Park

1985 ◽  
Vol 9 ◽  
pp. 153-155
Author(s):  
William Romme ◽  
Don Despain
Keyword(s):  
Patch Dynamics ◽  
Landscape Dynamics ◽  
Grizzly Bear ◽  
Quasi Equilibrium ◽  
Successional Stage ◽  
Yellowstone Lake ◽  
Summer Range ◽  
Forest Mosaic ◽  
Successional Stages

This study is an investigation of long-term patch dynamics in the mosaic of forest communities covering the subalpine plateaus of Yellowstone Park. Our specific objectives are the following: 1. We will map the present forest mosaic of a 600,000-ha area, showing the age (number of years since the last destructive fire) and successional stage of each more-or-less homogeneous patch of forest; 2. Usng this map, we will measure the area of each patch created by past fires, determine the size distribution of patches, and estimate the frequency and predictability of formation of patches of each size; and 3. We will reconstruct the changes during the last 200-300 years in individual forest stands and in the entire landscape mosaic, and use these reconstructions to answer the following questions: a. Has the Yellowstone landscape been characterized by quasi-equilibrium conditions, in which the proportion of the total area covered by early, middle, and late successional stages and the diversity of plant communities represented have remained more-or-less constant, or have these parameters fluctuated greatly in the last 200-300 years? b. If we find that the entire landscape has been in a state of equilibrium (which we may not find), then what is the minimum land area necessary for landscape dynamics to approach this condition, i.e., to what extent could the Park be divided into isolated subunits without these subunits losing the quasi-equilibrium state? c. How have the proportions of forest successional stages varied over time in units of the Park that have special ecological interest, such as elk summer range, grizzly bear habitat, or the watershed of Yellowstone Lake?

scholarly journals Fire and Landscape Dynamics in Yellowstone National Park

1987 ◽  
Vol 11 ◽  
pp. 178-180
Author(s):  
William Romme ◽  
Don Despain
Keyword(s):  
Patch Dynamics ◽  
Landscape Dynamics ◽  
Grizzly Bear ◽  
Quasi Equilibrium ◽  
Successional Stage ◽  
Yellowstone Lake ◽  
Summer Range ◽  
Forest Mosaic ◽  
Successional Stages

This study is an investigation of long-term patch dynamics in the mosaic of forest communities covering the subalpine plateaus of Yellowstone Park. Our specific objectives are the following: (1) We will map the present forest mosaic of a 600,000-ha area, showing the age (number of years since the last destructive fire) and successional stage of each more-or-less homogeneous patch of forest. (2) Using this map, we will measure the area of each patch created by past fires, determine the size distribution of patches, and estimate the frequency and predictability of formation of patches of each size. (3) We will reconstruct the changes during the last 200-300 years in individual forest stands and in the entire landscape mosaic, and use these reconstructions to answer the following questions: (a) Has the Yellowstone landscape been characterized by quasi-equilibrium conditions, in which the proportion of the total area covered by early, middle, and late successional stages and the diversity of plant communities represented have remained more-or-less constant, or have these parameters fluctuated greatly in the last 250 years? (b) If we find that the entire landscape has been in a state of equilibrium (which we may not find), then what is the minimum land area necessary for landscape dynamics to approach this condition, i.e., to what extent could the Park be divided into isolated subunits without these subunits losing the quasi-equilibrium state? (c) How have the proportions of forest successional stages varied over time in units of the Park that have special ecological interest, such as elk summer range, grizzly bear habitat, or the watershed of Yellowstone Lake?

scholarly journals Fire and Landscape Dynamics in Yellowstone National Park

1984 ◽  
Vol 8 ◽  
pp. 109-110
Author(s):  
William Romme ◽  
Don Despain
Keyword(s):  
Yellowstone National Park ◽  
National Park ◽  
Patch Dynamics ◽  
Landscape Dynamics ◽  
Forest Communities

This study is an investigation of long-term patch dynamics in the mosaic of forest communities covering the subalpine plateaus of Yellowstone Park.

scholarly journals Effects of post-WWII forced displacements on long-term landscape dynamics in the Polish Carpathians

2021 ◽  
Vol 214 ◽  
pp. 104164
Author(s):  
Andrzej N. Affek ◽  
Jacek Wolski ◽  
Maria Zachwatowicz ◽  
Krzysztof Ostafin ◽  
Volker C. Radeloff
Keyword(s):  
Landscape Dynamics ◽  
Polish Carpathians

Supergene degeneration opposes polymorphism: The curious case of balanced lethals

2021 ◽  
Author(s):  
Emma Berdan ◽  
Alexandre Blanckaert ◽  
Roger K Butlin ◽  
Thomas Flatt ◽  
Tanja Slotte ◽  
...  
Keyword(s):  
Equilibrium State ◽  
Balancing Selection ◽  
Mutation Accumulation ◽  
Small Population ◽  
Quasi Equilibrium ◽  
Deleterious Mutations ◽  
Critical Factors ◽  
Critical Aspect ◽  
Allopatric Divergence

Supergenes offer some of the most spectacular examples of long-term balancing selection in nature but their origin and maintenance remain a mystery. A critical aspect of supergenes is reduced recombination between arrangements. Reduced recombination protects adaptive multi-trait phenotypes, but can also lead to degeneration through mutation accumulation. Mutation accumulation can stabilize the system through the emergence of associative overdominance (AOD), destabilize the system, or lead to new evolutionary outcomes. One such outcome is the formation of balanced lethal systems, a maladaptive system where both supergene arrangements have accumulated deleterious mutations to the extent that both homozygotes are inviable, leaving only heterozygotes to reproduce. Here, we perform a simulation study to understand the conditions under which these different outcomes occur, assuming a scenario of introgression after allopatric divergence. We found that AOD aids the invasion of a new supergene arrangement and the establishment of a polymorphism. However, this polymorphism is easily destabilized by further mutation accumulation. While degradation may strengthen AOD, thereby stabilizing the supergene polymorphism, it is often asymmetric, which is the key disrupter of the quasi-equilibrium state of the polymorphism. Furthermore, mechanisms that accelerate degeneration also tend to amplify asymmetric mutation accumulation between the supergene arrangements and vice versa. As the evolution of a balanced lethal system requires symmetric degradation of both arrangements, this leaves highly restricted conditions under which such a system could evolve. We show that small population size and low dominance coefficients are critical factors, as these reduce the efficacy of selection. The dichotomy between the persistence of a polymorphism and degradation of supergene arrangements likely underlies the rarity of balanced lethal systems in nature.

scholarly journals SOIL SEED BANK IN SEASONAL SEMIDECIDUOUS FOREST AND ABANDONED PASTURE

2016 ◽  
Vol 40 (6) ◽  
pp. 991-1001 ◽  
Author(s):  
Sustanis Horn Kunz ◽  
Sebastião Venâncio Martins
Keyword(s):  
Seed Bank ◽  
Soil Seed Bank ◽  
Life Forms ◽  
Successional Stage ◽  
Semideciduous Forest ◽  
Regeneration Stage ◽  
Significant Difference ◽  
Successional Stages ◽  
Pasture Area ◽  
Seasonal Semideciduous Forest

ABSTRACT The objective of this study was to characterize the seed bank in the soil of different successional stages of Seasonal Semideciduous Forest and abandoned pasture in order to understand the natural regeneration potential of these areas. At each successional stage, 30 samples of soil were collected in the rainy and dry seasons to evaluate the qualitative heterogeneity of the forest, at the regeneration stage (FEA) forest, intermediate regeneration stage forest (ISF) and pasture (PAS). The species were classified according to the life form, successional group and dispersion syndrome. The number of individuals germinated was significantly higher (p < 0.001) in the ISF and in the rainy season (15,949 individuals). Richness was higher in the pasture area (79 species), with a significant difference only between the environments. Most species are herbaceous (49.5%), pioneers (76.5%) and zoocory was the main dispersion syndrome (49% of species). The results show that seed bank in the fragment of the regeneration advanced stage forest presents the highest resilience potential, since it is formed by different life forms and, mainly, by early and late secondary species.

scholarly journals Neighbors consistently influence growth and survival in a frequently burned savanna

2021 ◽  
Author(s):  
Mark Davis ◽  
Richard Condit
Keyword(s):  
Significant Role ◽  
Spatial Arrangement ◽  
Landscape Dynamics ◽  
Positive Interactions ◽  
Successful Management ◽  
Growth And Survival ◽  
Long Term Studies ◽  
Large Grid

Successful management of savannas is challenging and requires knowledge of the causes and consequences of the spatial arrangement of the trees. In savannas, trees are often aggregated, and the ability of trees within the clumps to survive fires plays a significant role in determining the savannas landscape dynamics. Whether or not a tree survives a fire is often dependent on the nature of their interactions with neighboring trees, positive or negative. In cases where disturbances are episodic, detecting these interactions is only going to be possible through long-term studies. Data reported here, from twenty-five years of annual tree censusing of a large grid-plot in a frequently burned savanna, showed consistent neighbor facilitated survival, irrespective as to whether the neighbors were conspecifics or heterospecifics. The positive interactions likely involve the reduction of both herbaceous and woody fuel in denser sites, and possibly mycorrhizal sharing among nearby trees.

scholarly journals Thermal evolution and quiescent emission of transiently accreting neutron stars

2019 ◽  
Vol 629 ◽  
pp. A88 ◽  
Author(s):  
A. Y. Potekhin ◽  
A. I. Chugunov ◽  
G. Chabrier
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Reactions ◽  
Thermal Evolution ◽  
Theoretical Models ◽  
Equilibrium Temperature ◽  
Theoretical Interpretation ◽  
Quasi Equilibrium ◽  
Accretion Rates

Aims. We study the long-term thermal evolution of neutron stars in soft X-ray transients (SXTs), taking the deep crustal heating into account consistently with the changes of the composition of the crust. We collect observational estimates of average accretion rates and thermal luminosities of such neutron stars and compare the theory with observations. Methods. We performed simulations of thermal evolution of accreting neutron stars, considering the gradual replacement of the original nonaccreted crust by the reprocessed accreted matter, the neutrino and photon energy losses, and the deep crustal heating due to nuclear reactions in the accreted crust. We also tested and compared results for different modern theoretical models. We updated a compilation of the observational estimates of the thermal luminosities in quiescence and average accretion rates in the SXTs and compared the observational estimates with the theoretical results. Results. The long-term thermal evolution of transiently accreting neutron stars is nonmonotonic. The quasi-equilibrium temperature in quiescence reaches a minimum and then increases toward the final steady state. The quasi-equilibrium thermal luminosity of a neutron star in an SXT can be substantially lower at the minimum than in the final state. This enlarges the range of possibilities for theoretical interpretation of observations of such neutron stars. The updates of the theory and observations leave the previous conclusions unchanged, namely that the direct Urca process operates in relatively cold neutron stars and that an accreted heat-blanketing envelope is likely present in relatively hot neutron stars in the SXTs in quiescence. The results of the comparison of theory with observations favor suppression of the triplet pairing type of nucleon superfluidity in the neutron-star matter.

scholarly journals From Pre‐Roman Bailo To Roman Baelo: Long‐Term Landscape Dynamics In The Straits Of Gibraltar

2019 ◽  
Vol 38 (2) ◽  
pp. 228-246
Author(s):  
Helena Jiménez‐Vialás ◽  
Ignasi Grau‐Mira
Keyword(s):  
Landscape Dynamics

Population dynamics of canopy trees in New Caledonian rain forests: are monodominant Nothofagus (Nothofagaceae) forests successional to mixed rain forests?

2013 ◽  
Vol 29 (6) ◽  
pp. 485-499 ◽  
Author(s):  
Jennifer Read ◽  
Tanguy Jaffré
Keyword(s):  
New Caledonia ◽  
Single Species ◽  
Secondary Forests ◽  
Rain Forests ◽  
Term Change ◽  
Shade Tolerant Species ◽  
Successional Stages ◽  
Continuous Regeneration ◽  
Canopy Species

Abstract:In New Caledonia, rain forests with an upper canopy dominated by single species of Nothofagus occur next to mixed-canopy forests, without discernible environmental cause. A potential explanation is that they are different successional stages. To test this hypothesis and predict long-term change in canopy dominance, population size structures of 61 canopy species were analysed in six Nothofagus-dominated forests and three adjacent mixed rain forests. Weibull analysis suggests that these Nothofagus forests are secondary forests, with recruitment insufficient to maintain monodominance, except at a high-altitude site. At low- to mid-altitudes the Nothofagus canopy is predicted to develop into a mixed canopy, unless moderate to severe disturbance occurs within its reproductive lifespan. However, adjacent mixed rain forests are also secondary, with 85% of analysed species showing no evidence of continuous regeneration. Fifteen species from both forest types showed reverse-J curves suggesting continuous regeneration, but only Calophyllum caledonicum did so consistently. Since few canopy species showed evidence of high shade tolerance and persistence, a small number of shade-tolerant species is predicted to dominate both forests in the long term, in the hypothetical absence of disturbance. Hence, temporal factors associated with disturbances play a key role in determining dominance in these forests.

Sign in / Sign up

Export Citation Format

Share Document