We sampled twenty populations of the vulnera- ble endemic shrub or tree, Arbutus pavarii Pampan., at different elevations and aspects within the A1-Akhdar mountainous region of Libya. Our sampling sites were at elevat...We sampled twenty populations of the vulnera- ble endemic shrub or tree, Arbutus pavarii Pampan., at different elevations and aspects within the A1-Akhdar mountainous region of Libya. Our sampling sites were at elevations ranging from 285 to 738 m above sea level, and several different habitats： vallies （locally known as wadis）, north- and south-facing slopes, and mountaintops. All individuals within each quadrat were studied. Population size and structure, and plant functional traits were assessed. None of the populations had a stable distribution of size classes. Some consisted mostly of small plants, with little or no fruit production; others consisted only of mid-sized and large plants, with high fruit production, but no juvenile recruitment. There was a significant increase in percent cover with increasing elevation; reproductive output （the number of fruits per branch and total number of fruits per individual） also generally increased with elevation. In some of these populations the lack of recruitment, and in others the failure to produce fruit, together constituted serious demographic threats. In light of these results, recommen- dations are made for conservation of this vulnerable endemic species.展开更多
Habitat transformation is identified as major threat to biodiversity loss globally,affecting threatened raptors.Changes in land use can alter the abundance and distribution of birds of prey by affecting habitat availa...Habitat transformation is identified as major threat to biodiversity loss globally,affecting threatened raptors.Changes in land use can alter the abundance and distribution of birds of prey by affecting habitat availability and quality.In this study,we used multivariate analyses to investigate the effect of habitat alteration on the demography of a declining Eastern Imperial Eagle(Aqufla heliaca),making assumptions for future population trajectories.We used the Generalized Linear Mixed Models with Poisson distribution and Log link function,searching a relationship between the demographic parameters and the landscape structure and possible effects of fragmentation.In our study area,habitat change affected dramatically permanent grasslands,shrinking their availability.As we expected,the share of grasslands in eagles’territories significantly affected occupancy rate,but not productivity and breeding frequency.We found that occupancy rate decreased significantly,while productivity and breeding frequency showed no trend.Modeling the effect of habitat alteration on Eastern Imperial Eagle demography,we found out that territory quality was a more powerful factor driving the response of a top predator to the alteration of favorite foraging habitats.Only the habitat quality in source territories had a significant positive effect on eagle productivity.We found that simple rules to predict adverse agricultural impact on territory abandonment or breeding productivity of a top predator were not reliable.Our results could be used for planning conservation of other large territorial raptors,facing the same type of threat.展开更多
Background: Documenting the entire lifetime of long-lived organisms requires splicing together short-term observations. Matrix demography provides a tool to calculate lifetime statistics, but large samples from juveni...Background: Documenting the entire lifetime of long-lived organisms requires splicing together short-term observations. Matrix demography provides a tool to calculate lifetime statistics, but large samples from juvenile to adult are needed, and few such studies have been done in tropical trees because high species diversity limits sample sizes. The 50-ha plot at Barro Colorado in Panama was designed to provide large samples, and with 30years of censuses, accurate population matrices can be constructed.Methods: In 31 abundant species, I divided all individuals≥1 cm dbh into 4 or 5 size class in each of seven censuses. Movements of stems between size classes over two censuses are termed transitions, and I constructed complete transition matrices for each species. From the matrices, I derived analytic solutions for lifetime demographic statistics. Expected adult lifespan from the sapling stage was the key statistic.Results: Expected adult lifespan from the sapling stage varied 100-fold over the 31 species, from 0.5 to 50 years,and maturation time varied from 19 to nearly 200 years. Species with the highest growth rates also had high death rates, and theoretical calculations of reproductive lifespan show that the fast-growing pioneer species have short expected adult lifespans relative to the average slow-growing, shade-tolerant species. Within the slowgrowth category, however, there was high variation in expected adult lifespan, and several shade-tolerant species under-performed the pioneers in terms of adult lifespan.Conclusions: Analytical solutions from population matrices allow theoretical analyses that integrate short-term growth records into lifespans of tropical trees. The analyses suggest that pioneer species must reproduce more successfully than shade-tolerant species to persist in the Barro Colorado forest. My next goal is to incorporate seed production and germination into lifetime matrix demography to test this hypothesis.展开更多
In the context of historical Palestine, the Palestinian and Jewish demography are deeply embedded （Goldsheider, 1991; Freidlander, 2002）. The growth and structure of the populations are one of the most important too...In the context of historical Palestine, the Palestinian and Jewish demography are deeply embedded （Goldsheider, 1991; Freidlander, 2002）. The growth and structure of the populations are one of the most important tools for the control of the territory （Dahlan, 1989）. Jewish immigration was and is still considered as the single most important mean for the conquest of the land （Courbage, 2005）. Yet this is only a partial truth （Fargues, 2000）. Fertility, especially when it is natural at its peak or still very high is also a very significant asset, which is likely to reverse internal equilibrium among the different forces shaping the two societies （Courbage ＆ Todd, 2011; Ettinger, 2011）. Hence, Jews and Palestinians have embarked since decades into a demographic competition （Faraoune, personal communication, December 19, 1992; Anson ＆ Avinoam, 1996）, with this extraordinary result, that in a matter of a century （1948-2048） this small piece of land will have undergone the highest population growth on earth, equivalent to sub Saharan Africa （Faitelson, 2008; Courbage ＆ Fargues, 1997）. It is likely output is not less important to define the future nature of historical Palestine： one or two states （Baskin, 2005; Courbage, 2008）？ And if the two states solution is in effect, what kind of states would it be？ After presenting the recent trends of Palestinian demography in the context of historical Palestine since the first intifada and the aftermath of the second intifada, this essay will focus on future developments, i.e. the likely population dynamics of the Palestinian territory from 2011 until 2048, and of its different components, namely fertility. Palestinian population growth during the next four decades will be compared to that of the future Israeli population and the policy components of this differential population growth will be evaluated both in the context of historical Palestine and in the context of the Jewish State in its 1948 borders （Jews and Palestinians of 1948）. The most serious demographic challenges, （which are not those of an overall ＂equilibrium＂ between Palestinian and Jewish populations as very often claimed）, are very precisely delineated in the ground. These are, first, the question of the peopling of the settlements （Be-Tselem, 2002）. their population is likely to explode from 560,000 settlers now to 1.7 million in 2048, thanks to their extremely high fertility, low mortality, high immigration and ＂population momentum＂ （Central Bureau of Statistics, 2013; Courbage, 2006）. From 18% of the overall population of the West Bank they could reach 29% in 2048, a clear defiance to the possibility of statehood in Palestine. Besides, statehood in Palestine is also threatened by the fact that East-Jerusalem, the likely capital of the Palestinian state is also threatened by the expansionist demography of the Jewish settlers, both in the so-called ＂neighborhoods＂, those settlements close to Jerusalem but which are according to international law an integral part of the West Bank （annexed by Israel in 1967）, and inside the Old city. In Jerusalem, besides Jewish immigration to the neighborhoods from the densely and poor areas of West Jerusalem, fertility trends have now been reversed to advantage of the Jews as compared to the Palestinians in the Holy city （Della Pergola, 2001）. This presentation will deal also with the population trends of the Palestinian population from now on until 2048 （Dalen ＆ Petersen, 2004; Courbage, 1999）. Under the impact of a higher fertility, and a population momentum clearly to its benefit, the population of Gaza （all Palestinians） could approach the Palestinian population of the West Bank： 4.0 in Gaza, 4.3 in the WB （Clarens, 2011）. Yet, the slight majority in the West Bank comes from the Palestinians in Jerusalem, whose political status is still vague. A larger share of the Palestinian population living in the Gaza strip rather than in the West bank is probably not devoid of political implications. For the policy makers it is not easy to run against demographic trends, especially when they are largely guided and decided by the other State which shares the same land. Yet, it is of utmost importance to be fully aware of the likely evolution of the demographic landscape in Palestine and to prepare the demographic but mostly non-demographic policy measures to counterbalance their effects.展开更多
The purpose of this study is to correlate demography and socio-economic aspects at Irrigated Smallholder Agricultural Enterprises and their association with the Cultivation of Maize in order to determine its positive ...The purpose of this study is to correlate demography and socio-economic aspects at Irrigated Smallholder Agricultural Enterprises and their association with the Cultivation of Maize in order to determine its positive impacts at irrigated smallholders’ agricultural entrepreneurs’ household. Chi-square test was used as descriptive analysis method. The Fischer Exact tests were employed to test demography (gender, age, education, and income) in winter and summer production season of irrigated smallholder agricultural enterprises and their association with the cultivation of selected field crop (i.e. maize). The results show that gender results were not being statistically significant, as measured by the Phi measure of effect size, φ = 0.149, p = 0.011, and φ = 0.05, p = 0.392 in summer. As far as age is concern, it appears to be a statistically significant association between cultivating maize and age in winter, φ = 0.046, p = 0.730 in winter and φ = 0.172, p = 0.013. Education winter result not being statistically significant, the effect size showed a weak association, as measured by the Phi measure of effect size, φ = 0.112, p = 0.305 and φ = 0.035, p = 0.948 in summer. Income result not being statistically significant, as measured by the Phi measure of effect size, φ = 0.049, p = 0.399 and φ = 0.081, p = 0.166 in summer. In conclusion, the study shows that the development of best management practices must be based on a comprehensive analysis of the livelihoods and irrigated smallholder agricultural enterprise farming styles of participating irrigated smallholder agricultural entrepreneurs.展开更多
The attack by the Islamist group Hamas against Israel on October 7,2023,and the immediate Israeli offensive in the Gaza Strip,with the thousands of deaths and the devastation that we are witnessing daily in one of the...The attack by the Islamist group Hamas against Israel on October 7,2023,and the immediate Israeli offensive in the Gaza Strip,with the thousands of deaths and the devastation that we are witnessing daily in one of the most densely populated areas of the world,have pushed further away the prospect of a solution of coexistence between Israelis and Palestinians through the establishment of two peoples-two states,a solution that is viewed favorably in non-holy Palestinian and Israeli circles by many Western countries and by the Holy See.To complicate the socio-political picture,we recall that in the last decades,in the territories occupied by Israel in the West Bank,there has been an incessant work of human settlements and the construction of roads and infrastructures,facilitated by Israel’s rapid population growth.According to many analysts,in order to dominate the Palestinians,Israel is now implementing a real system of apartheid that is spreading from the occupied territories to the Palestinian Arab citizens of Israel.Based on the available data,which are not always reliable for political and organizational reasons of the existing statistical systems,this study attempts to grasp the strategic role that differential demography has had and continues to have in this complex conflictual reality.展开更多
Demography plays a fundamental role in shaping the landscape of human resources.The interdependent relationship between these two fields is observable in the workforce composition,labor market trends,talent management...Demography plays a fundamental role in shaping the landscape of human resources.The interdependent relationship between these two fields is observable in the workforce composition,labor market trends,talent management strategies and on learning.Changes perceived in demographic changes are shaping and transforming human resources management.In an era marked by demographic shifts,technological advancements,and evolving work preferences,organizations are facing the need to understand and adapt to the changing demographics to effectively manage their human resources.This article explores how demography influences human resource(HR)with a special highlight on the management of multigenerational workforce.展开更多
Temperate rainforests have historically been considered highly vulnerable to disturbance.Climate change,which is expected to increase the intensity,frequency,and impacts of disturbance events,is consequently a signifi...Temperate rainforests have historically been considered highly vulnerable to disturbance.Climate change,which is expected to increase the intensity,frequency,and impacts of disturbance events,is consequently a significant threat to their long-term persistence.However,data describing the long-term response of temperate rainforests to disturbance is rare.In the cool temperate rainforests of northern New South Wales,Australia,Nothofagus moorei is considered especially vulnerable to climate change due to a decreasing number of mature individuals,limited remaining suitable habitat,and low rates of sexual regeneration.In this study,we used over 50 years of empirical data from silvicultural experiments with multiple thinning intensities to characterise the demographic responses(i.e.,growth,mortality,and recruitment)of cool temperate rainforest species,including N.moorei,to disturbance over time.Cool temperate rainforest species showed resilience to disturbance,predominantly through their widespread ability to basally coppice.Nothofagus moorei,in particular,demonstrated higher rates of successful sexual and vegetative recruitment and grew faster in response to higher intensities of disturbance,in comparison to very low rates of recruitment pre-disturbance.These results challenge successional models that position rainforests as disturbance-sensitive ecosystems and identify N.moorei as a species that requires large-scale disturbance to successfully regenerate.Management regimes that actively exclude disturbance from these forests risk the local loss of disturbance-dependent rainforest species such as N.moorei.展开更多
Background The full lifespan of long-lived trees includes a seedling phase,during which a seed germinates and grows to a size large enough to be measured in forest inventories.Seedling populations are usually studied ...Background The full lifespan of long-lived trees includes a seedling phase,during which a seed germinates and grows to a size large enough to be measured in forest inventories.Seedling populations are usually studied separately from adult trees,and the seedling lifespan,from seed to sapling,is poorly known.In the 50-ha Barro Colorado forest plot,we started intensive censuses of seeds and seedlings in 1994 in order to merge seedling and adult demography and document complete lifespans.Methods In 17 species abundant in seedling censuses,we subdivided populations into six size classes from seed to 1cm dbh,including seeds plus five seedling stages.The smallest seedling class was subdivided by age.Censuses in two consecutive years provided transition matrices describing the probability that a seedling in one stage moved to another one year later.For each species,we averaged the transition matrix across 25 censuses and used it to project the seedling lifespan,from seed until 1cm dbh or death.Results The predicted mean survival rate of seeds to 1cm dbh varied 1000-fold across species,from 2.9×10^(−6)to 4.4×10^(−3);the median was 2.0×10^(−4).The seedling lifespan,or the average time it takes a seed to grow to 1cm dbh,varied across species from 5.1 to 53.1 years,with a median of 20.3 years.In the median species,the 10%fastest-growing seeds would reach 1cm dbh in 9.0 years,and the slowest 10%in 34.6 years.Conclusions Combining seedling results with our previous study of lifespan after 1cm dbh,we estimate that the focal species have full lifespans varying from 41 years in a gap-demanding pioneer to 320 years in one shade-tolerant species.Lifetime demography can contribute precise survival rates and lifespans to forestry models.展开更多
文摘We sampled twenty populations of the vulnera- ble endemic shrub or tree, Arbutus pavarii Pampan., at different elevations and aspects within the A1-Akhdar mountainous region of Libya. Our sampling sites were at elevations ranging from 285 to 738 m above sea level, and several different habitats： vallies （locally known as wadis）, north- and south-facing slopes, and mountaintops. All individuals within each quadrat were studied. Population size and structure, and plant functional traits were assessed. None of the populations had a stable distribution of size classes. Some consisted mostly of small plants, with little or no fruit production; others consisted only of mid-sized and large plants, with high fruit production, but no juvenile recruitment. There was a significant increase in percent cover with increasing elevation; reproductive output （the number of fruits per branch and total number of fruits per individual） also generally increased with elevation. In some of these populations the lack of recruitment, and in others the failure to produce fruit, together constituted serious demographic threats. In light of these results, recommen- dations are made for conservation of this vulnerable endemic species.
基金funded by the LIFE Program of the European Union under the project’Restoration and sustainable management of Imperial Eagle’s foraging habitats in key Natura 2000 sites in Bulgaria’LIFE14 NAT/BG/001119。
文摘Habitat transformation is identified as major threat to biodiversity loss globally,affecting threatened raptors.Changes in land use can alter the abundance and distribution of birds of prey by affecting habitat availability and quality.In this study,we used multivariate analyses to investigate the effect of habitat alteration on the demography of a declining Eastern Imperial Eagle(Aqufla heliaca),making assumptions for future population trajectories.We used the Generalized Linear Mixed Models with Poisson distribution and Log link function,searching a relationship between the demographic parameters and the landscape structure and possible effects of fragmentation.In our study area,habitat change affected dramatically permanent grasslands,shrinking their availability.As we expected,the share of grasslands in eagles’territories significantly affected occupancy rate,but not productivity and breeding frequency.We found that occupancy rate decreased significantly,while productivity and breeding frequency showed no trend.Modeling the effect of habitat alteration on Eastern Imperial Eagle demography,we found out that territory quality was a more powerful factor driving the response of a top predator to the alteration of favorite foraging habitats.Only the habitat quality in source territories had a significant positive effect on eagle productivity.We found that simple rules to predict adverse agricultural impact on territory abandonment or breeding productivity of a top predator were not reliable.Our results could be used for planning conservation of other large territorial raptors,facing the same type of threat.
基金Numerous grants from National Science Foundation (US), the Smithsonian Institution, the Mac Arthur Foundation, and Earthwatch supported census work in the Barro Colorado 50-ha plotThe Center for Forest Science at the Morton Arboretum provided support for the author while writing
文摘Background: Documenting the entire lifetime of long-lived organisms requires splicing together short-term observations. Matrix demography provides a tool to calculate lifetime statistics, but large samples from juvenile to adult are needed, and few such studies have been done in tropical trees because high species diversity limits sample sizes. The 50-ha plot at Barro Colorado in Panama was designed to provide large samples, and with 30years of censuses, accurate population matrices can be constructed.Methods: In 31 abundant species, I divided all individuals≥1 cm dbh into 4 or 5 size class in each of seven censuses. Movements of stems between size classes over two censuses are termed transitions, and I constructed complete transition matrices for each species. From the matrices, I derived analytic solutions for lifetime demographic statistics. Expected adult lifespan from the sapling stage was the key statistic.Results: Expected adult lifespan from the sapling stage varied 100-fold over the 31 species, from 0.5 to 50 years,and maturation time varied from 19 to nearly 200 years. Species with the highest growth rates also had high death rates, and theoretical calculations of reproductive lifespan show that the fast-growing pioneer species have short expected adult lifespans relative to the average slow-growing, shade-tolerant species. Within the slowgrowth category, however, there was high variation in expected adult lifespan, and several shade-tolerant species under-performed the pioneers in terms of adult lifespan.Conclusions: Analytical solutions from population matrices allow theoretical analyses that integrate short-term growth records into lifespans of tropical trees. The analyses suggest that pioneer species must reproduce more successfully than shade-tolerant species to persist in the Barro Colorado forest. My next goal is to incorporate seed production and germination into lifetime matrix demography to test this hypothesis.
文摘In the context of historical Palestine, the Palestinian and Jewish demography are deeply embedded （Goldsheider, 1991; Freidlander, 2002）. The growth and structure of the populations are one of the most important tools for the control of the territory （Dahlan, 1989）. Jewish immigration was and is still considered as the single most important mean for the conquest of the land （Courbage, 2005）. Yet this is only a partial truth （Fargues, 2000）. Fertility, especially when it is natural at its peak or still very high is also a very significant asset, which is likely to reverse internal equilibrium among the different forces shaping the two societies （Courbage ＆ Todd, 2011; Ettinger, 2011）. Hence, Jews and Palestinians have embarked since decades into a demographic competition （Faraoune, personal communication, December 19, 1992; Anson ＆ Avinoam, 1996）, with this extraordinary result, that in a matter of a century （1948-2048） this small piece of land will have undergone the highest population growth on earth, equivalent to sub Saharan Africa （Faitelson, 2008; Courbage ＆ Fargues, 1997）. It is likely output is not less important to define the future nature of historical Palestine： one or two states （Baskin, 2005; Courbage, 2008）？ And if the two states solution is in effect, what kind of states would it be？ After presenting the recent trends of Palestinian demography in the context of historical Palestine since the first intifada and the aftermath of the second intifada, this essay will focus on future developments, i.e. the likely population dynamics of the Palestinian territory from 2011 until 2048, and of its different components, namely fertility. Palestinian population growth during the next four decades will be compared to that of the future Israeli population and the policy components of this differential population growth will be evaluated both in the context of historical Palestine and in the context of the Jewish State in its 1948 borders （Jews and Palestinians of 1948）. The most serious demographic challenges, （which are not those of an overall ＂equilibrium＂ between Palestinian and Jewish populations as very often claimed）, are very precisely delineated in the ground. These are, first, the question of the peopling of the settlements （Be-Tselem, 2002）. their population is likely to explode from 560,000 settlers now to 1.7 million in 2048, thanks to their extremely high fertility, low mortality, high immigration and ＂population momentum＂ （Central Bureau of Statistics, 2013; Courbage, 2006）. From 18% of the overall population of the West Bank they could reach 29% in 2048, a clear defiance to the possibility of statehood in Palestine. Besides, statehood in Palestine is also threatened by the fact that East-Jerusalem, the likely capital of the Palestinian state is also threatened by the expansionist demography of the Jewish settlers, both in the so-called ＂neighborhoods＂, those settlements close to Jerusalem but which are according to international law an integral part of the West Bank （annexed by Israel in 1967）, and inside the Old city. In Jerusalem, besides Jewish immigration to the neighborhoods from the densely and poor areas of West Jerusalem, fertility trends have now been reversed to advantage of the Jews as compared to the Palestinians in the Holy city （Della Pergola, 2001）. This presentation will deal also with the population trends of the Palestinian population from now on until 2048 （Dalen ＆ Petersen, 2004; Courbage, 1999）. Under the impact of a higher fertility, and a population momentum clearly to its benefit, the population of Gaza （all Palestinians） could approach the Palestinian population of the West Bank： 4.0 in Gaza, 4.3 in the WB （Clarens, 2011）. Yet, the slight majority in the West Bank comes from the Palestinians in Jerusalem, whose political status is still vague. A larger share of the Palestinian population living in the Gaza strip rather than in the West bank is probably not devoid of political implications. For the policy makers it is not easy to run against demographic trends, especially when they are largely guided and decided by the other State which shares the same land. Yet, it is of utmost importance to be fully aware of the likely evolution of the demographic landscape in Palestine and to prepare the demographic but mostly non-demographic policy measures to counterbalance their effects.
文摘The purpose of this study is to correlate demography and socio-economic aspects at Irrigated Smallholder Agricultural Enterprises and their association with the Cultivation of Maize in order to determine its positive impacts at irrigated smallholders’ agricultural entrepreneurs’ household. Chi-square test was used as descriptive analysis method. The Fischer Exact tests were employed to test demography (gender, age, education, and income) in winter and summer production season of irrigated smallholder agricultural enterprises and their association with the cultivation of selected field crop (i.e. maize). The results show that gender results were not being statistically significant, as measured by the Phi measure of effect size, φ = 0.149, p = 0.011, and φ = 0.05, p = 0.392 in summer. As far as age is concern, it appears to be a statistically significant association between cultivating maize and age in winter, φ = 0.046, p = 0.730 in winter and φ = 0.172, p = 0.013. Education winter result not being statistically significant, the effect size showed a weak association, as measured by the Phi measure of effect size, φ = 0.112, p = 0.305 and φ = 0.035, p = 0.948 in summer. Income result not being statistically significant, as measured by the Phi measure of effect size, φ = 0.049, p = 0.399 and φ = 0.081, p = 0.166 in summer. In conclusion, the study shows that the development of best management practices must be based on a comprehensive analysis of the livelihoods and irrigated smallholder agricultural enterprise farming styles of participating irrigated smallholder agricultural entrepreneurs.
文摘The attack by the Islamist group Hamas against Israel on October 7,2023,and the immediate Israeli offensive in the Gaza Strip,with the thousands of deaths and the devastation that we are witnessing daily in one of the most densely populated areas of the world,have pushed further away the prospect of a solution of coexistence between Israelis and Palestinians through the establishment of two peoples-two states,a solution that is viewed favorably in non-holy Palestinian and Israeli circles by many Western countries and by the Holy See.To complicate the socio-political picture,we recall that in the last decades,in the territories occupied by Israel in the West Bank,there has been an incessant work of human settlements and the construction of roads and infrastructures,facilitated by Israel’s rapid population growth.According to many analysts,in order to dominate the Palestinians,Israel is now implementing a real system of apartheid that is spreading from the occupied territories to the Palestinian Arab citizens of Israel.Based on the available data,which are not always reliable for political and organizational reasons of the existing statistical systems,this study attempts to grasp the strategic role that differential demography has had and continues to have in this complex conflictual reality.
文摘Demography plays a fundamental role in shaping the landscape of human resources.The interdependent relationship between these two fields is observable in the workforce composition,labor market trends,talent management strategies and on learning.Changes perceived in demographic changes are shaping and transforming human resources management.In an era marked by demographic shifts,technological advancements,and evolving work preferences,organizations are facing the need to understand and adapt to the changing demographics to effectively manage their human resources.This article explores how demography influences human resource(HR)with a special highlight on the management of multigenerational workforce.
基金supported by the Bushfire and Natural Hazards Cooperative Research Centre and New South Wales National Parks and Wildlife Service.
文摘Temperate rainforests have historically been considered highly vulnerable to disturbance.Climate change,which is expected to increase the intensity,frequency,and impacts of disturbance events,is consequently a significant threat to their long-term persistence.However,data describing the long-term response of temperate rainforests to disturbance is rare.In the cool temperate rainforests of northern New South Wales,Australia,Nothofagus moorei is considered especially vulnerable to climate change due to a decreasing number of mature individuals,limited remaining suitable habitat,and low rates of sexual regeneration.In this study,we used over 50 years of empirical data from silvicultural experiments with multiple thinning intensities to characterise the demographic responses(i.e.,growth,mortality,and recruitment)of cool temperate rainforest species,including N.moorei,to disturbance over time.Cool temperate rainforest species showed resilience to disturbance,predominantly through their widespread ability to basally coppice.Nothofagus moorei,in particular,demonstrated higher rates of successful sexual and vegetative recruitment and grew faster in response to higher intensities of disturbance,in comparison to very low rates of recruitment pre-disturbance.These results challenge successional models that position rainforests as disturbance-sensitive ecosystems and identify N.moorei as a species that requires large-scale disturbance to successfully regenerate.Management regimes that actively exclude disturbance from these forests risk the local loss of disturbance-dependent rainforest species such as N.moorei.
基金funded by the Environmental Seed Arrival and Interspecific Associations in Seedling Sciences Program of the Smithsonian Institutionthe National Science Foundation (DEB-0075102,DEB-0823728,DEB-0640386,DEB-1242622,DEB-1464389)the Andrew Mellon Foundation,The Ohio State University,and Yale University
文摘Background The full lifespan of long-lived trees includes a seedling phase,during which a seed germinates and grows to a size large enough to be measured in forest inventories.Seedling populations are usually studied separately from adult trees,and the seedling lifespan,from seed to sapling,is poorly known.In the 50-ha Barro Colorado forest plot,we started intensive censuses of seeds and seedlings in 1994 in order to merge seedling and adult demography and document complete lifespans.Methods In 17 species abundant in seedling censuses,we subdivided populations into six size classes from seed to 1cm dbh,including seeds plus five seedling stages.The smallest seedling class was subdivided by age.Censuses in two consecutive years provided transition matrices describing the probability that a seedling in one stage moved to another one year later.For each species,we averaged the transition matrix across 25 censuses and used it to project the seedling lifespan,from seed until 1cm dbh or death.Results The predicted mean survival rate of seeds to 1cm dbh varied 1000-fold across species,from 2.9×10^(−6)to 4.4×10^(−3);the median was 2.0×10^(−4).The seedling lifespan,or the average time it takes a seed to grow to 1cm dbh,varied across species from 5.1 to 53.1 years,with a median of 20.3 years.In the median species,the 10%fastest-growing seeds would reach 1cm dbh in 9.0 years,and the slowest 10%in 34.6 years.Conclusions Combining seedling results with our previous study of lifespan after 1cm dbh,we estimate that the focal species have full lifespans varying from 41 years in a gap-demanding pioneer to 320 years in one shade-tolerant species.Lifetime demography can contribute precise survival rates and lifespans to forestry models.
