The selection of optimum chock (support) capacity is very crucial for a successful longwall mining. The selection of chock capacity depends on the site-specific geotechnical parameters, constraints and longwall panel ...The selection of optimum chock (support) capacity is very crucial for a successful longwall mining. The selection of chock capacity depends on the site-specific geotechnical parameters, constraints and longwall panel geometry, which are generally not known in detail in priority. Hence, based on the field and laboratory data, various possible combinations should be analyzed to cater for the unforeseeable mining conditions. This paper discusses the use of numerical model for selecting an appropriate chock capacity based on the site-specific geological and geotechnical information and longwall panel geometry. The fracture mechanisms of immediate and main roofs are also discussed for various panel widths and support capacities. For the models considered, the chock convergence is predicted to increase by about 33% due to the increase in face width from 100 to 260 m. Similarly, the massive roof strata are found to yield higher chock convergence compared to bedded strata.展开更多
The lithium sulfur batteries(LSBs) are considered as one of the promising next generation energy storage devices due to the high theoretical specific capacity of sulfur(1675 m Ah g-1), naturally available, low cost.Ho...The lithium sulfur batteries(LSBs) are considered as one of the promising next generation energy storage devices due to the high theoretical specific capacity of sulfur(1675 m Ah g-1), naturally available, low cost.However, the practical LSBs are impeded by the well-known "shuttle effect" combined with other technical drawbacks. The "shuttle effect" causes rapid capacity decay, severe self-discharging and low active material utilization. The polysulfide(PS) which has lone pair electrons in each sulfur atom is considered as Lewis base and shows strong affinity to various polar, Lewis acid and catenation interactive materials but very weakly interacts with the non-polar conductive carbons. The "shuttle effect" occurs due to the diffusion of high order PS from the cathode to the anode and then low-order PS back to the cathode. The PS is polar and, due to a lone pair of electrons associated with the sulfur atom, is considered a Lewis base. As such, the PS shows a strong affinity with various polar and Lewis acid materials. In addition, a more novel trapping can be performance through a catenation reaction. For LSBs to compete with the state-of-the-art lithium ion batteries(LIBs), the LSB areal capacity need to be ~6 m Ah cm-2(which is proportional to sulfur loading). To achieve this target the PS shuttling needs to mitigate, which can be achieved through using functional materials. This review addresses the aforementioned phenomena by considering the PS phase interacts with the various functional materials and how this impacts areal capacity and cycling stability of LSBs.展开更多
Organic phosphorus(P) is an important component of the soil P pool, and it has been proven to be a potential source of P for plants. The phosphorus utilization efficiency(PUE) and PUE related traits(tiller number...Organic phosphorus(P) is an important component of the soil P pool, and it has been proven to be a potential source of P for plants. The phosphorus utilization efficiency(PUE) and PUE related traits(tiller number(TN), shoot dry weight(DW), and root dry weight) under different phytate-P conditions(low phytate-P, 0.05 mmol L^-1 and normal phytate-P, 0.5 mmol L^-1) were investigated using a population consisting of 128 recombinant inbred lines(RILs) at the vegetative stage in barley. The population was derived from a cross between a P-inefficient genotype(Baudin) and a P-efficient genotype(CN4027, a Hordeum spontaneum accession). A major locus(designated Qpue.sau-3 H) conferring PUE was detected in shoots and roots from the RIL population. The quantitative trait locus(QTL) was mapped on chromosome 3 H and the allele from CN4027 confers high PUE. This locus explained up to 30.3 and 28.4% of the phenotypic variance in shoots under low and normal phytate-P conditions, respectively. It also explains 28.3 and 30.7% of the phenotypic variation in root under the low and normal phytate-P conditions, respectively. Results from this study also showed that TN was not correlated with PUE, and a QTL controlling TN was detected on chromosome 5 H. However, dry weight(DW) was significantly and positively correlated with PUE, and a QTL controlling DW was detected near the Qpue.sau-3 H locus. Based on a covariance analysis, existing data indicated that, although DW may affect PUE, different genes at this locus are likely involved in controlling these two traits.展开更多
As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-string...As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.展开更多
The popularization of intelligent healthcare devices and big data analytics significantly boosts the development of Smart Healthcare Networks(SHNs).To enhance the precision of diagnosis,different participants in SHNs ...The popularization of intelligent healthcare devices and big data analytics significantly boosts the development of Smart Healthcare Networks(SHNs).To enhance the precision of diagnosis,different participants in SHNs share health data that contain sensitive information.Therefore,the data exchange process raises privacy concerns,especially when the integration of health data from multiple sources(linkage attack)results in further leakage.Linkage attack is a type of dominant attack in the privacy domain,which can leverage various data sources for private data mining.Furthermore,adversaries launch poisoning attacks to falsify the health data,which leads to misdiagnosing or even physical damage.To protect private health data,we propose a personalized differential privacy model based on the trust levels among users.The trust is evaluated by a defined community density,while the corresponding privacy protection level is mapped to controllable randomized noise constrained by differential privacy.To avoid linkage attacks in personalized differential privacy,we design a noise correlation decoupling mechanism using a Markov stochastic process.In addition,we build the community model on a blockchain,which can mitigate the risk of poisoning attacks during differentially private data transmission over SHNs.Extensive experiments and analysis on real-world datasets have testified the proposed model,and achieved better performance compared with existing research from perspectives of privacy protection and effectiveness.展开更多
科学评价人类活动对水资源的影响是实现水资源可持续利用的前提。对比目前广泛应用的以虚拟水理论为基础的水足迹计算方法,详细介绍了基于生命周期评价(LCA)的产品水足迹计算方法,并以我国小麦生产为例进行实证研究。与虚拟水方法相比,...科学评价人类活动对水资源的影响是实现水资源可持续利用的前提。对比目前广泛应用的以虚拟水理论为基础的水足迹计算方法,详细介绍了基于生命周期评价(LCA)的产品水足迹计算方法,并以我国小麦生产为例进行实证研究。与虚拟水方法相比,LCA方法评价结果体现了水资源利用的环境影响,便于不同产品、不同生产阶段以及不同产地产品间水足迹的比较。实例研究表明:我国黄河、海河流域小麦水足迹平均为1 262 L H2Oe.kg-1,而长江流域仅为31 L H2Oe.kg-1;小麦生产对我国极度缺水的北方造成的压力远高于水资源较为丰富的南方地区。LCA方法能科学评价农产品生产对水资源的影响,为我国保障粮食安全和水资源可持续利用提供科学依据。展开更多
Jasmonates (JAs) are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix (bHLH) transcription factor (TF) MYC2 has recently emerged as a master regulator of most asp...Jasmonates (JAs) are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix (bHLH) transcription factor (TF) MYC2 has recently emerged as a master regulator of most aspects of the jasmonate (JA) signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. MYC2 is required for induced systemic resistance (ISR) triggered by beneficial soil microbes while MYC2 function is targeted by pathogens during effector-mediated suppression of innate immunity in roots. Another notable function of MYC2 is the regulation of crosstalk between the signaling pathways of JA and those of other phytohormones such as abscisic acid (ABA), salicylic acid (SA), gibberellins (GAs), and auxin (IAA). MYC2 also regulates interactions between JA signaling and light, phytochrome signaling, and the circadian clock, MYC2 is involved in JA-regulated plant development, lateral and adventitious root formation, flowering time, and shade avoidance syndrome. Related bHLH TFs MYC3 and MYC4 also regulate both overlapping and distinct MYC2-regulated functions in Arabidopsis while MYC2 orthologs act as 'master switches' that regulate JA-mediated biosynthesis of secondary metabolites. Here, we briefly review recent studies that revealed mechanistic new insights into the mode of action of this versatile TF.展开更多
Porous supramolecular frameworks based on metal-organic cages(MOCs)usually have poor structural stability after activation.This issue narrows the scope of their potential applications,particularly for the inclusion of...Porous supramolecular frameworks based on metal-organic cages(MOCs)usually have poor structural stability after activation.This issue narrows the scope of their potential applications,particularly for the inclusion of guest molecules that demand high porosity.Herein,the authors have reported the stabilization of a mesoporous zirconium MOC-based supramolecular framework with an in situ catalytic polymerization strategy.Due to the passivation effect imparted by this strategy,the introduced polymer is primarily distributed on the surface of the crystals,which results in the hybrid material retaining its crystallinity and permanent porosity.A preliminary application of this type of stabilized mesoporous supramolecular framework shows that among MOC-based supramolecular frameworks,it has the highest high-pressure methane uptake.Such a facile strategy may provide a general way to stabilize fragile porous materials and facilitate exploration of their potential applications.展开更多
Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalm...Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalman filter (KF) is applied to 72-h wind speed forecasts from the WRF model in Zhangbei wind farm for a period over two years. The KF approach shows a remarkable ability in improving the raw forecasts by decreasing the root-mean-square error by 16% from 3.58 to 3.01 m s−1, the mean absolute error by 14% from 2.71 to 2.34 m s−1, the bias from 0.22 to − 0.19 m s−1, and improving the correlation from 0.58 to 0.66. The KF significantly reduces random errors of the model, showing the capability to deal with the forecast errors associated with physical processes which cannot be accurately handled by the numerical model. In addition, the improvement of the bias correction is larger for wind speeds sensitive to wind power generation. So the KF approach is suitable for short-term wind power prediction.展开更多
Seed dispersal and subsequent recruitment is the template on which forest regeneration takes place.Hence,considering the scale over which ecological processes occur is key for understanding the overall impact of vario...Seed dispersal and subsequent recruitment is the template on which forest regeneration takes place.Hence,considering the scale over which ecological processes occur is key for understanding the overall impact of various dispersal agents.To explore leafcutter ant(Atta colombica)dispersal effectiveness in space and time,seed movement and subsequent recruitment of a large-seeded predominately vertebrate-dispersed tree,Simarouba amara(Aubl.Simaroubaceae),was investigated on Barro Colorado Island,Panama.At each of 218 reproductive-sized adults(>20 cm diameter at breast height),presence or absence of a leafcutter ant colony was noted,with extensive checks for Atta activity taking place at or in close proximity to seed and seedling transects,which extended 4 cardinal directions for 30 m from each reproductive female tree(n=74).Only at 2 S.amara trees were nests observed,and in these areas a dense S.amara seedling carpet was observed.Although nearby nest and dump sites might increase local S.amara recruitment in the short term,mortality at these sites is complete or nearly so.Hence,the seed dispersal effectiveness by leafcutter ants appears to be ephemeral and likely contributes inconsequentially to the long-term recruitment and distribution patterns of the species.This finding highlights the importance of evaluating disperser effectiveness at ecologically relevant spatiotemporal scales.展开更多
文摘The selection of optimum chock (support) capacity is very crucial for a successful longwall mining. The selection of chock capacity depends on the site-specific geotechnical parameters, constraints and longwall panel geometry, which are generally not known in detail in priority. Hence, based on the field and laboratory data, various possible combinations should be analyzed to cater for the unforeseeable mining conditions. This paper discusses the use of numerical model for selecting an appropriate chock capacity based on the site-specific geological and geotechnical information and longwall panel geometry. The fracture mechanisms of immediate and main roofs are also discussed for various panel widths and support capacities. For the models considered, the chock convergence is predicted to increase by about 33% due to the increase in face width from 100 to 260 m. Similarly, the massive roof strata are found to yield higher chock convergence compared to bedded strata.
文摘The lithium sulfur batteries(LSBs) are considered as one of the promising next generation energy storage devices due to the high theoretical specific capacity of sulfur(1675 m Ah g-1), naturally available, low cost.However, the practical LSBs are impeded by the well-known "shuttle effect" combined with other technical drawbacks. The "shuttle effect" causes rapid capacity decay, severe self-discharging and low active material utilization. The polysulfide(PS) which has lone pair electrons in each sulfur atom is considered as Lewis base and shows strong affinity to various polar, Lewis acid and catenation interactive materials but very weakly interacts with the non-polar conductive carbons. The "shuttle effect" occurs due to the diffusion of high order PS from the cathode to the anode and then low-order PS back to the cathode. The PS is polar and, due to a lone pair of electrons associated with the sulfur atom, is considered a Lewis base. As such, the PS shows a strong affinity with various polar and Lewis acid materials. In addition, a more novel trapping can be performance through a catenation reaction. For LSBs to compete with the state-of-the-art lithium ion batteries(LIBs), the LSB areal capacity need to be ~6 m Ah cm-2(which is proportional to sulfur loading). To achieve this target the PS shuttling needs to mitigate, which can be achieved through using functional materials. This review addresses the aforementioned phenomena by considering the PS phase interacts with the various functional materials and how this impacts areal capacity and cycling stability of LSBs.
基金supported by the National Natural Science Foundation of China (31401377)the Science and Technology Project of Sichuan Province, China (2017JY0126)the Key Project of Education Department of Sichuan Province, China (14ZA0002)
文摘Organic phosphorus(P) is an important component of the soil P pool, and it has been proven to be a potential source of P for plants. The phosphorus utilization efficiency(PUE) and PUE related traits(tiller number(TN), shoot dry weight(DW), and root dry weight) under different phytate-P conditions(low phytate-P, 0.05 mmol L^-1 and normal phytate-P, 0.5 mmol L^-1) were investigated using a population consisting of 128 recombinant inbred lines(RILs) at the vegetative stage in barley. The population was derived from a cross between a P-inefficient genotype(Baudin) and a P-efficient genotype(CN4027, a Hordeum spontaneum accession). A major locus(designated Qpue.sau-3 H) conferring PUE was detected in shoots and roots from the RIL population. The quantitative trait locus(QTL) was mapped on chromosome 3 H and the allele from CN4027 confers high PUE. This locus explained up to 30.3 and 28.4% of the phenotypic variance in shoots under low and normal phytate-P conditions, respectively. It also explains 28.3 and 30.7% of the phenotypic variation in root under the low and normal phytate-P conditions, respectively. Results from this study also showed that TN was not correlated with PUE, and a QTL controlling TN was detected on chromosome 5 H. However, dry weight(DW) was significantly and positively correlated with PUE, and a QTL controlling DW was detected near the Qpue.sau-3 H locus. Based on a covariance analysis, existing data indicated that, although DW may affect PUE, different genes at this locus are likely involved in controlling these two traits.
基金This work was supported by Guangdong Basic and Applied Basic Research Foundation,China(No.2019A1515110980)research project from the National Natural Science Foundation of China(No.21361162004)China Scholarship Council,and CSIRO.We acknowledge Dr Yesim Gozukara,Dr Malisja de Vries,and Dr Yunxia Yang from CSIRO(Clayton)for their help with material characterization training.
文摘As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.
基金supported by the National Key Research and Development Program of China(No.2021YFF0900400).
文摘The popularization of intelligent healthcare devices and big data analytics significantly boosts the development of Smart Healthcare Networks(SHNs).To enhance the precision of diagnosis,different participants in SHNs share health data that contain sensitive information.Therefore,the data exchange process raises privacy concerns,especially when the integration of health data from multiple sources(linkage attack)results in further leakage.Linkage attack is a type of dominant attack in the privacy domain,which can leverage various data sources for private data mining.Furthermore,adversaries launch poisoning attacks to falsify the health data,which leads to misdiagnosing or even physical damage.To protect private health data,we propose a personalized differential privacy model based on the trust levels among users.The trust is evaluated by a defined community density,while the corresponding privacy protection level is mapped to controllable randomized noise constrained by differential privacy.To avoid linkage attacks in personalized differential privacy,we design a noise correlation decoupling mechanism using a Markov stochastic process.In addition,we build the community model on a blockchain,which can mitigate the risk of poisoning attacks during differentially private data transmission over SHNs.Extensive experiments and analysis on real-world datasets have testified the proposed model,and achieved better performance compared with existing research from perspectives of privacy protection and effectiveness.
文摘科学评价人类活动对水资源的影响是实现水资源可持续利用的前提。对比目前广泛应用的以虚拟水理论为基础的水足迹计算方法,详细介绍了基于生命周期评价(LCA)的产品水足迹计算方法,并以我国小麦生产为例进行实证研究。与虚拟水方法相比,LCA方法评价结果体现了水资源利用的环境影响,便于不同产品、不同生产阶段以及不同产地产品间水足迹的比较。实例研究表明:我国黄河、海河流域小麦水足迹平均为1 262 L H2Oe.kg-1,而长江流域仅为31 L H2Oe.kg-1;小麦生产对我国极度缺水的北方造成的压力远高于水资源较为丰富的南方地区。LCA方法能科学评价农产品生产对水资源的影响,为我国保障粮食安全和水资源可持续利用提供科学依据。
文摘Jasmonates (JAs) are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix (bHLH) transcription factor (TF) MYC2 has recently emerged as a master regulator of most aspects of the jasmonate (JA) signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. MYC2 is required for induced systemic resistance (ISR) triggered by beneficial soil microbes while MYC2 function is targeted by pathogens during effector-mediated suppression of innate immunity in roots. Another notable function of MYC2 is the regulation of crosstalk between the signaling pathways of JA and those of other phytohormones such as abscisic acid (ABA), salicylic acid (SA), gibberellins (GAs), and auxin (IAA). MYC2 also regulates interactions between JA signaling and light, phytochrome signaling, and the circadian clock, MYC2 is involved in JA-regulated plant development, lateral and adventitious root formation, flowering time, and shade avoidance syndrome. Related bHLH TFs MYC3 and MYC4 also regulate both overlapping and distinct MYC2-regulated functions in Arabidopsis while MYC2 orthologs act as 'master switches' that regulate JA-mediated biosynthesis of secondary metabolites. Here, we briefly review recent studies that revealed mechanistic new insights into the mode of action of this versatile TF.
基金the financial support from the Australian Renewable Energy Agency (ARENA)the Australian Centre for Advanced Photovoltaics (ACAP)the ARC Centre of Excellence in Exciton Science
基金This study was financially supported by the National Nature Science Foundation of China(nos.21771177 and 51603206)the Strategic Priority Research Program of CAS(no.XDB20000000)the Key Research Program of Frontier Sciences,CAS(no.QYZDB-SSW-SLH019).
文摘Porous supramolecular frameworks based on metal-organic cages(MOCs)usually have poor structural stability after activation.This issue narrows the scope of their potential applications,particularly for the inclusion of guest molecules that demand high porosity.Herein,the authors have reported the stabilization of a mesoporous zirconium MOC-based supramolecular framework with an in situ catalytic polymerization strategy.Due to the passivation effect imparted by this strategy,the introduced polymer is primarily distributed on the surface of the crystals,which results in the hybrid material retaining its crystallinity and permanent porosity.A preliminary application of this type of stabilized mesoporous supramolecular framework shows that among MOC-based supramolecular frameworks,it has the highest high-pressure methane uptake.Such a facile strategy may provide a general way to stabilize fragile porous materials and facilitate exploration of their potential applications.
基金supported by National Key R&D Program of China(Technology and application of wind power/photovoltaic power prediction for promoting renewable energy consumption,2018YFB0904200)eponymous Complement S&T Program of State Grid Corporation of China(SGLNDKOOKJJS1800266).
文摘Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalman filter (KF) is applied to 72-h wind speed forecasts from the WRF model in Zhangbei wind farm for a period over two years. The KF approach shows a remarkable ability in improving the raw forecasts by decreasing the root-mean-square error by 16% from 3.58 to 3.01 m s−1, the mean absolute error by 14% from 2.71 to 2.34 m s−1, the bias from 0.22 to − 0.19 m s−1, and improving the correlation from 0.58 to 0.66. The KF significantly reduces random errors of the model, showing the capability to deal with the forecast errors associated with physical processes which cannot be accurately handled by the numerical model. In addition, the improvement of the bias correction is larger for wind speeds sensitive to wind power generation. So the KF approach is suitable for short-term wind power prediction.
文摘Seed dispersal and subsequent recruitment is the template on which forest regeneration takes place.Hence,considering the scale over which ecological processes occur is key for understanding the overall impact of various dispersal agents.To explore leafcutter ant(Atta colombica)dispersal effectiveness in space and time,seed movement and subsequent recruitment of a large-seeded predominately vertebrate-dispersed tree,Simarouba amara(Aubl.Simaroubaceae),was investigated on Barro Colorado Island,Panama.At each of 218 reproductive-sized adults(>20 cm diameter at breast height),presence or absence of a leafcutter ant colony was noted,with extensive checks for Atta activity taking place at or in close proximity to seed and seedling transects,which extended 4 cardinal directions for 30 m from each reproductive female tree(n=74).Only at 2 S.amara trees were nests observed,and in these areas a dense S.amara seedling carpet was observed.Although nearby nest and dump sites might increase local S.amara recruitment in the short term,mortality at these sites is complete or nearly so.Hence,the seed dispersal effectiveness by leafcutter ants appears to be ephemeral and likely contributes inconsequentially to the long-term recruitment and distribution patterns of the species.This finding highlights the importance of evaluating disperser effectiveness at ecologically relevant spatiotemporal scales.