The model at the basis of trajectory analysis is conceptually simple.When applied to time series vegetation data,the projectile becomes a surrogate for vegetation state,the trajectory for the evolving vegetation proce...The model at the basis of trajectory analysis is conceptually simple.When applied to time series vegetation data,the projectile becomes a surrogate for vegetation state,the trajectory for the evolving vegetation process,and the properties of the trajectory for the true process characteristics.Notwithstanding its simplicity,the model is well-defined under natural circumstances and easily adapted to serial vegetation data,irrespective of source.As a major advantage,compared to other models that isolate the elementary processes and probe vegetation dynamics for informative regularities on the elementary level,the trajectory model allows us to probe for regularities on the level of the highest process integrity.Theories and a data analytical methodology developed around the trajectory model are outlined,including many numerical examples.A rich list of key references and volumes of supplementary information supplied in the Web Only Appendices rounds out the presentation.展开更多
Ecological practice is telling us that to identify Nature’s rules,we should look for regularities in the resulting effects.Hidden rules are involved and the effects are manifested by compositional,functional,and stru...Ecological practice is telling us that to identify Nature’s rules,we should look for regularities in the resulting effects.Hidden rules are involved and the effects are manifested by compositional,functional,and structural transitions.This paper’s focus is on two conjectures regarding the governance of specific transition compo-nents,the first supposedly under global co-ordination,and the second under superimposed site specific instability oscillations.The reality of any apparent regularity in these is the sole condition for the regularity’s acceptance as a rule.Reality is testable but in retrospect only,based on time series analyses.Since long pollen spectra supply the evidence,the time period involved is measured in thousands of years.For maximal usefulness,a spectrum should have a long period length,dated horizons intensely sampled at short time steps,and precisely identified taxa.Period length and time step width matter because both may have a masking effect on the regularities.There is,of course,a natural limit for period length,which is set by the age of the pollen bearing sediments.We completed the analysis of 23 spectra using techniques deemed suitable for testing the conjectures.The spectra originated from sites in the Americas where we found suitable spectra in sufficient numbers and in geographic contiguity from the Arctic region to the Antarctic.The presented results have clear indications that the two conjectures identify real rules.The main body of the paper narrates the analyses and provides explanations.Informative materials,too voluminous for inclusion in the paper,are made available on the Internet at URL:www.vegetationdynamics.com linking to“Appen-dices Ta”.展开更多
文摘The model at the basis of trajectory analysis is conceptually simple.When applied to time series vegetation data,the projectile becomes a surrogate for vegetation state,the trajectory for the evolving vegetation process,and the properties of the trajectory for the true process characteristics.Notwithstanding its simplicity,the model is well-defined under natural circumstances and easily adapted to serial vegetation data,irrespective of source.As a major advantage,compared to other models that isolate the elementary processes and probe vegetation dynamics for informative regularities on the elementary level,the trajectory model allows us to probe for regularities on the level of the highest process integrity.Theories and a data analytical methodology developed around the trajectory model are outlined,including many numerical examples.A rich list of key references and volumes of supplementary information supplied in the Web Only Appendices rounds out the presentation.
文摘Ecological practice is telling us that to identify Nature’s rules,we should look for regularities in the resulting effects.Hidden rules are involved and the effects are manifested by compositional,functional,and structural transitions.This paper’s focus is on two conjectures regarding the governance of specific transition compo-nents,the first supposedly under global co-ordination,and the second under superimposed site specific instability oscillations.The reality of any apparent regularity in these is the sole condition for the regularity’s acceptance as a rule.Reality is testable but in retrospect only,based on time series analyses.Since long pollen spectra supply the evidence,the time period involved is measured in thousands of years.For maximal usefulness,a spectrum should have a long period length,dated horizons intensely sampled at short time steps,and precisely identified taxa.Period length and time step width matter because both may have a masking effect on the regularities.There is,of course,a natural limit for period length,which is set by the age of the pollen bearing sediments.We completed the analysis of 23 spectra using techniques deemed suitable for testing the conjectures.The spectra originated from sites in the Americas where we found suitable spectra in sufficient numbers and in geographic contiguity from the Arctic region to the Antarctic.The presented results have clear indications that the two conjectures identify real rules.The main body of the paper narrates the analyses and provides explanations.Informative materials,too voluminous for inclusion in the paper,are made available on the Internet at URL:www.vegetationdynamics.com linking to“Appen-dices Ta”.
