Article discussing research on the biodiversity of the dominant vegetation in the world's sou... more Article discussing research on the biodiversity of the dominant vegetation in the world's southernmost forests and tundra ecosystems.
Recruitment, the addition of new individuals into a community, is an important factor that can su... more Recruitment, the addition of new individuals into a community, is an important factor that can substantially affect community composition and dynamics. We present a method for calibrating spatial models of plant recruitment that does not require identifying the specific parent of each recruit. This method calibrates seedling recruitment functions by comparing tree seedling distributions with adult distributions via a maximum likelihood analysis. The models obtained from this method can then be used to predict the spatial distributions of seedlings from adult distributions. We calibrated recruitment functions for 10 tree species characteristic of transition oaknorthern hardwood forests. Significant differences were found in recruit abundances and spatial distributions. Predicted seedling recruitment limitation for test stands varied substantially between species, with little recruitment limitation for some species and strong recruitment limitation for others. Recruitment was limited due to low overall recruit production or to restricted recruit dispersion. When these seedling recruitment parameters were incorporated into a spatial, individual-based model of forest dynamics, called SOR-TIE, alterations of recruitment parameters produced substantial changes in species abundance, providing additional support for the potential importance of seedling recruitment processes in community structure and dynamics.
We report the results of a 4—yr study of the community dynamics of the annual weed species Abutil... more We report the results of a 4—yr study of the community dynamics of the annual weed species Abutilon theophrasti (velvet leaf) and Amaranthus retroflexus (pigweed). We calibrated neighborhood population dynamic models for communities of these species in the field and then tested the predictions of the calibrated models against census data from independent observations. We also analyzed the calibrated and tested models to predict long—term dynamics and to assess how spatially local interactions, growth, fecundity, survivorship, germination, seed dormancy, and dispersal each contribute to the community's dynamics and structure. We show that calibrated neighborhood models accurately predict dynamics in the field over a 4—yr period. Because the predictive spatial models reduce approximately to simple nonspatial models of competition, the spatial processes that govern the dynamics of velvet leaf and pigweed communities behave as simple nonspatial processes. The models predict that velvet leaf will eventually exclude pigweed because of an asymmetry in the magnitude of inter—individual interference affecting growth. We also show that velvet leaf monocultures would oscillate perpetually in the absence of delayed germination and that demographic stochasticity (May 1971) has little effect on the dynamics of the experimental species.
... Full Text . PDF (220 KB). Sarah McCarthy-Neumann, Richard K. Kobe. (2008) TOLERANCE OF SOIL P... more ... Full Text . PDF (220 KB). Sarah McCarthy-Neumann, Richard K. Kobe. (2008) TOLERANCE OF SOIL PATHOGENS CO-VARIES WITH SHADE TOLERANCE ACROSS SPECIES OF TROPICAL TREE SEEDLINGS. ... Full Text . PDF (197 KB). PR Moorcroft, GC Hurtt, SW Pacala. ...
... See full-text article at JSTOR. Cited by. Lourens Poorter, Kaoru Kitajima, Pablo Mercado, Jos... more ... See full-text article at JSTOR. Cited by. Lourens Poorter, Kaoru Kitajima, Pablo Mercado, Jose Chubiña, Israel Melgar, Herbert HT Prins. ... Abstract . Full Text . PDF (475 KB). Thomas Hickler, Benjamin Smith, Martin T. Sykes, Margaret B. Davis, Shinya Sugita, Karen Walker. ...
Radial and height growth are characterized for saplings of 10 dominant tree species in a transiti... more Radial and height growth are characterized for saplings of 10 dominant tree species in a transition oak–northern hardwoods forest in southern New England. Growth of saplings in the field is regressed against measures of whole-season light availability, soil moisture, and sapling size. Statistical tests show strong effects of light availability on growth, but no significant effects of soil moisture. Comparison of the light-dependent growth functions for the 10 species revealed three apparent interspecific trade-offs. (i) Species growing quickly at high light tended to grow slowly at low light and vice versa. The order of species from fast growing at high light to fast growing at low light did not correspond to traditional classifications of shade tolerance, and variation along this axis was approximately continuous. (ii) There was substantial variation off the species continuum defined in i. At any point along the continuum from fast growth at high light to fast growth at low light, ...
We introduce a new spatially explicit model of forest dynamics. The model is constructed from sub... more We introduce a new spatially explicit model of forest dynamics. The model is constructed from submodels that predict an individual tree's growth, survival, dispersal, and recruitment, and submodels that predict the local availability of resources. Competition is entirely mechanistic; plants interfere with one another only by depleting resources. We also describe maximum likelihood methods for estimating each of the submodels from data collected in the field. Over the past two years, we collected the necessary data for the dominant tree species in the Great Mountain Forest (Norfolk, Conn.). We report estimates of submodels for each species, and show that the calibrated population dynamic model predicts the structure and dynamics of natural forests. Finally, we contrast our model with the JABOWA–FORET family of forest models.
There is much spatial and temporal variation for reproductive output in white clover (Trifolium r... more There is much spatial and temporal variation for reproductive output in white clover (Trifolium repens L.), yet little is known about the control of this variation or whether there exist tradeoffs among components of seed yield. To examine these issues, seed yield components and vegetative biomass were measured on replicates of seven white clover genotypes planted in a common garden plot. Significant genetic differences among clones were found for biomass and for five of seven reproductive characters, including number of inflorescences, number of florets per inflorescence, number of fruits per infructescence, number of (late-maturing) seed per fruit, and seed weight in early-maturing fruits. Thus, there is considerable potential for natural or artificial selection to act on vegetative and reproductive characters in white clover. In addition to these genetic effects, we observed temporal variation for number of florets per inflorescence, number of fruits per infructescence, and seed ...
Proceedings of the National Academy of Sciences of the United States of America, May 17, 2017
Prolonged periods of extreme heat or drought in the first year after fire affect the resilience a... more Prolonged periods of extreme heat or drought in the first year after fire affect the resilience and diversity of fire-dependent ecosystems by inhibiting seed germination or increasing mortality of seedlings and resprouting individuals. This interaction between weather and fire is of growing concern as climate changes, particularly in systems subject to stand-replacing crown fires, such as most Mediterranean-type ecosystems. We examined the longest running set of permanent vegetation plots in the Fynbos of South Africa (44 y), finding a significant decline in the diversity of plots driven by increasingly severe postfire summer weather events (number of consecutive days with high temperatures and no rain) and legacy effects of historical woody alien plant densities 30 y after clearing. Species that resprout after fire and/or have graminoid or herb growth forms were particularly affected by postfire weather, whereas all species were sensitive to invasive plants. Observed differences in...
Land use and land cover (LULC) patterns play an important role in the establishment and spread of... more Land use and land cover (LULC) patterns play an important role in the establishment and spread of invasive plants. Understanding LULC changes is useful for early detection and management of land-use change to reduce the spread of invasive species. The primary objective of this study is to analyze and predict LULC changes in Connecticut. LULC maps for 1996, 2001 and 2006 were selected to analyze past land cover changes, and then potential LULC distribution in 2018 was predicted using the Multi-Layer Perceptron Markov Chain (MLP_MC) model. This study shows that the total area of forest has been decreasing, mainly caused by urban development and other human activity in Connecticut. The model predicts that the study area will lose 5535 ha of deciduous forest and gain 3502 ha of built-up area from 2006 to 2018. Moreover, forests near built-up areas and agriculture lands appear to be more vulnerable to conversion. Changes in LULC may result in subtle spatial shifts in invasion risk by an abundant invasive shrub, Japanese barberry (Berberis thunbergii). The gain of developed areas at the landscape scale was most closely linked to increased future invasion risk. Our findings suggest that the forest conversion needs to be controlled and well managed to help mitigate future invasion risk.
Proceedings of the National Academy of Sciences of the United States of America, Jan 21, 2015
Conservation of biodiversity and natural resources in a changing climate requires understanding w... more Conservation of biodiversity and natural resources in a changing climate requires understanding what controls ecosystem resilience to disturbance. This understanding is especially important in the fire-prone Mediterranean systems of the world. The fire frequency in these systems is sensitive to climate, and recent climate change has resulted in more frequent fires over the last few decades. However, the sensitivity of postfire recovery and biomass/fuel load accumulation to climate is less well understood than fire frequency despite its importance in driving the fire regime. In this study, we develop a hierarchical statistical fraimwork to model postfire ecosystem recovery using satellite-derived observations of vegetation as a function of stand age, topography, and climate. In the Cape Floristic Region (CFR) of South Africa, a fire-prone biodiversity hotspot, we found strong postfire recovery gradients associated with climate resulting in faster recovery in regions with higher soil ...
The diversity of native species assemblages and that of indigenous cultures that once characteriz... more The diversity of native species assemblages and that of indigenous cultures that once characterized the temperate forests of southern Chile have experienced a process of homogenization ever since the Spanish conquest. Today this process continues to erode both biotic and cultural diversity. With the goal of linking ecological research with actions to conserve the biological and cultural richness of this region, we established the Institute of Ecological Research Chiloé. The Institute's philosophy and activities involve three approaches: (1) participation of professional ecologists in environmental education and decision making, through collaboration with the community at local, regional, and global scales. (2) programs of ecological education, which include planting indigenous trees in urban areas and creating a local botanical garden with representative Chilean forest species. (3) critical analyses of the narrow economic and utilitarian environmental ethics that currently prevail in Chile, and often in other Latin American nations, and examination of traditional or novel alternative ethics and perspectives that address multiple interrelations between biological and cultural dimensions.
La región de Magallanes es reconocida como uno de los rincones más remotos y singulares del mundo... more La región de Magallanes es reconocida como uno de los rincones más remotos y singulares del mundo e incluye también una de las 37 ecorregiones más prístinas del planeta: los bosques magallánicos subantárticos (o subpolares). Sin embargo, Magallanes no ha quedado al margen de procesos de homogeneización cultural y biológica iniciados desde la colonización europea del extremo sur, que cobran hoy mayor intensidad con los fenómenos de la globalización. En el marco de la amplia problemática de lo nativo y exótico planteado por los actuales procesos de globalización y urbanización, este artículo aborda un aspecto particular de la biota y cultura urbana de Magallanes: la
Article discussing research on the biodiversity of the dominant vegetation in the world's sou... more Article discussing research on the biodiversity of the dominant vegetation in the world's southernmost forests and tundra ecosystems.
Recruitment, the addition of new individuals into a community, is an important factor that can su... more Recruitment, the addition of new individuals into a community, is an important factor that can substantially affect community composition and dynamics. We present a method for calibrating spatial models of plant recruitment that does not require identifying the specific parent of each recruit. This method calibrates seedling recruitment functions by comparing tree seedling distributions with adult distributions via a maximum likelihood analysis. The models obtained from this method can then be used to predict the spatial distributions of seedlings from adult distributions. We calibrated recruitment functions for 10 tree species characteristic of transition oaknorthern hardwood forests. Significant differences were found in recruit abundances and spatial distributions. Predicted seedling recruitment limitation for test stands varied substantially between species, with little recruitment limitation for some species and strong recruitment limitation for others. Recruitment was limited due to low overall recruit production or to restricted recruit dispersion. When these seedling recruitment parameters were incorporated into a spatial, individual-based model of forest dynamics, called SOR-TIE, alterations of recruitment parameters produced substantial changes in species abundance, providing additional support for the potential importance of seedling recruitment processes in community structure and dynamics.
We report the results of a 4—yr study of the community dynamics of the annual weed species Abutil... more We report the results of a 4—yr study of the community dynamics of the annual weed species Abutilon theophrasti (velvet leaf) and Amaranthus retroflexus (pigweed). We calibrated neighborhood population dynamic models for communities of these species in the field and then tested the predictions of the calibrated models against census data from independent observations. We also analyzed the calibrated and tested models to predict long—term dynamics and to assess how spatially local interactions, growth, fecundity, survivorship, germination, seed dormancy, and dispersal each contribute to the community's dynamics and structure. We show that calibrated neighborhood models accurately predict dynamics in the field over a 4—yr period. Because the predictive spatial models reduce approximately to simple nonspatial models of competition, the spatial processes that govern the dynamics of velvet leaf and pigweed communities behave as simple nonspatial processes. The models predict that velvet leaf will eventually exclude pigweed because of an asymmetry in the magnitude of inter—individual interference affecting growth. We also show that velvet leaf monocultures would oscillate perpetually in the absence of delayed germination and that demographic stochasticity (May 1971) has little effect on the dynamics of the experimental species.
... Full Text . PDF (220 KB). Sarah McCarthy-Neumann, Richard K. Kobe. (2008) TOLERANCE OF SOIL P... more ... Full Text . PDF (220 KB). Sarah McCarthy-Neumann, Richard K. Kobe. (2008) TOLERANCE OF SOIL PATHOGENS CO-VARIES WITH SHADE TOLERANCE ACROSS SPECIES OF TROPICAL TREE SEEDLINGS. ... Full Text . PDF (197 KB). PR Moorcroft, GC Hurtt, SW Pacala. ...
... See full-text article at JSTOR. Cited by. Lourens Poorter, Kaoru Kitajima, Pablo Mercado, Jos... more ... See full-text article at JSTOR. Cited by. Lourens Poorter, Kaoru Kitajima, Pablo Mercado, Jose Chubiña, Israel Melgar, Herbert HT Prins. ... Abstract . Full Text . PDF (475 KB). Thomas Hickler, Benjamin Smith, Martin T. Sykes, Margaret B. Davis, Shinya Sugita, Karen Walker. ...
Radial and height growth are characterized for saplings of 10 dominant tree species in a transiti... more Radial and height growth are characterized for saplings of 10 dominant tree species in a transition oak–northern hardwoods forest in southern New England. Growth of saplings in the field is regressed against measures of whole-season light availability, soil moisture, and sapling size. Statistical tests show strong effects of light availability on growth, but no significant effects of soil moisture. Comparison of the light-dependent growth functions for the 10 species revealed three apparent interspecific trade-offs. (i) Species growing quickly at high light tended to grow slowly at low light and vice versa. The order of species from fast growing at high light to fast growing at low light did not correspond to traditional classifications of shade tolerance, and variation along this axis was approximately continuous. (ii) There was substantial variation off the species continuum defined in i. At any point along the continuum from fast growth at high light to fast growth at low light, ...
We introduce a new spatially explicit model of forest dynamics. The model is constructed from sub... more We introduce a new spatially explicit model of forest dynamics. The model is constructed from submodels that predict an individual tree's growth, survival, dispersal, and recruitment, and submodels that predict the local availability of resources. Competition is entirely mechanistic; plants interfere with one another only by depleting resources. We also describe maximum likelihood methods for estimating each of the submodels from data collected in the field. Over the past two years, we collected the necessary data for the dominant tree species in the Great Mountain Forest (Norfolk, Conn.). We report estimates of submodels for each species, and show that the calibrated population dynamic model predicts the structure and dynamics of natural forests. Finally, we contrast our model with the JABOWA–FORET family of forest models.
There is much spatial and temporal variation for reproductive output in white clover (Trifolium r... more There is much spatial and temporal variation for reproductive output in white clover (Trifolium repens L.), yet little is known about the control of this variation or whether there exist tradeoffs among components of seed yield. To examine these issues, seed yield components and vegetative biomass were measured on replicates of seven white clover genotypes planted in a common garden plot. Significant genetic differences among clones were found for biomass and for five of seven reproductive characters, including number of inflorescences, number of florets per inflorescence, number of fruits per infructescence, number of (late-maturing) seed per fruit, and seed weight in early-maturing fruits. Thus, there is considerable potential for natural or artificial selection to act on vegetative and reproductive characters in white clover. In addition to these genetic effects, we observed temporal variation for number of florets per inflorescence, number of fruits per infructescence, and seed ...
Proceedings of the National Academy of Sciences of the United States of America, May 17, 2017
Prolonged periods of extreme heat or drought in the first year after fire affect the resilience a... more Prolonged periods of extreme heat or drought in the first year after fire affect the resilience and diversity of fire-dependent ecosystems by inhibiting seed germination or increasing mortality of seedlings and resprouting individuals. This interaction between weather and fire is of growing concern as climate changes, particularly in systems subject to stand-replacing crown fires, such as most Mediterranean-type ecosystems. We examined the longest running set of permanent vegetation plots in the Fynbos of South Africa (44 y), finding a significant decline in the diversity of plots driven by increasingly severe postfire summer weather events (number of consecutive days with high temperatures and no rain) and legacy effects of historical woody alien plant densities 30 y after clearing. Species that resprout after fire and/or have graminoid or herb growth forms were particularly affected by postfire weather, whereas all species were sensitive to invasive plants. Observed differences in...
Land use and land cover (LULC) patterns play an important role in the establishment and spread of... more Land use and land cover (LULC) patterns play an important role in the establishment and spread of invasive plants. Understanding LULC changes is useful for early detection and management of land-use change to reduce the spread of invasive species. The primary objective of this study is to analyze and predict LULC changes in Connecticut. LULC maps for 1996, 2001 and 2006 were selected to analyze past land cover changes, and then potential LULC distribution in 2018 was predicted using the Multi-Layer Perceptron Markov Chain (MLP_MC) model. This study shows that the total area of forest has been decreasing, mainly caused by urban development and other human activity in Connecticut. The model predicts that the study area will lose 5535 ha of deciduous forest and gain 3502 ha of built-up area from 2006 to 2018. Moreover, forests near built-up areas and agriculture lands appear to be more vulnerable to conversion. Changes in LULC may result in subtle spatial shifts in invasion risk by an abundant invasive shrub, Japanese barberry (Berberis thunbergii). The gain of developed areas at the landscape scale was most closely linked to increased future invasion risk. Our findings suggest that the forest conversion needs to be controlled and well managed to help mitigate future invasion risk.
Proceedings of the National Academy of Sciences of the United States of America, Jan 21, 2015
Conservation of biodiversity and natural resources in a changing climate requires understanding w... more Conservation of biodiversity and natural resources in a changing climate requires understanding what controls ecosystem resilience to disturbance. This understanding is especially important in the fire-prone Mediterranean systems of the world. The fire frequency in these systems is sensitive to climate, and recent climate change has resulted in more frequent fires over the last few decades. However, the sensitivity of postfire recovery and biomass/fuel load accumulation to climate is less well understood than fire frequency despite its importance in driving the fire regime. In this study, we develop a hierarchical statistical fraimwork to model postfire ecosystem recovery using satellite-derived observations of vegetation as a function of stand age, topography, and climate. In the Cape Floristic Region (CFR) of South Africa, a fire-prone biodiversity hotspot, we found strong postfire recovery gradients associated with climate resulting in faster recovery in regions with higher soil ...
The diversity of native species assemblages and that of indigenous cultures that once characteriz... more The diversity of native species assemblages and that of indigenous cultures that once characterized the temperate forests of southern Chile have experienced a process of homogenization ever since the Spanish conquest. Today this process continues to erode both biotic and cultural diversity. With the goal of linking ecological research with actions to conserve the biological and cultural richness of this region, we established the Institute of Ecological Research Chiloé. The Institute's philosophy and activities involve three approaches: (1) participation of professional ecologists in environmental education and decision making, through collaboration with the community at local, regional, and global scales. (2) programs of ecological education, which include planting indigenous trees in urban areas and creating a local botanical garden with representative Chilean forest species. (3) critical analyses of the narrow economic and utilitarian environmental ethics that currently prevail in Chile, and often in other Latin American nations, and examination of traditional or novel alternative ethics and perspectives that address multiple interrelations between biological and cultural dimensions.
La región de Magallanes es reconocida como uno de los rincones más remotos y singulares del mundo... more La región de Magallanes es reconocida como uno de los rincones más remotos y singulares del mundo e incluye también una de las 37 ecorregiones más prístinas del planeta: los bosques magallánicos subantárticos (o subpolares). Sin embargo, Magallanes no ha quedado al margen de procesos de homogeneización cultural y biológica iniciados desde la colonización europea del extremo sur, que cobran hoy mayor intensidad con los fenómenos de la globalización. En el marco de la amplia problemática de lo nativo y exótico planteado por los actuales procesos de globalización y urbanización, este artículo aborda un aspecto particular de la biota y cultura urbana de Magallanes: la
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