Patterns Of Change In Composition Research Articles

Rate-of-change analysis in paleoecology revisited: A new approach

Dynamics in the rate of compositional change (rate-of-change; RoC), preserved in paleoecological sequences, are thought to reflect changes due to exogenous (climate and human forcing) or endogenous (local dynamics and biotic interactions) drivers. However, changes in sedimentation rates and sampling strategies can result in an uneven distribution of time intervals and are known to affect RoC estimates. Furthermore, there has been relatively little exploration of the implications of these challenges in quantifying RoC in paleoecology.Here, we introduce R-Ratepol – an easy-to-use R package – that provides a robust numerical technique for detecting and summarizing RoC patterns in complex multivariate time-ordered stratigraphical sequences. First, we compare the performance of common methods of estimating RoC and detecting periods of high RoC (peak-point) using simulated pollen-stratigraphical data with known patterns of compositional change and temporal resolution. In addition, we propose a new method of binning with a moving window, which shows a more than 5-fold increase in the correct detection of peak-points compared to the more traditional way of using individual levels.Next, we apply our new methodology to four representative European pollen sequences and show that our approach also performs well in detecting periods of significant compositional change during known onsets of human activity, early land-use transformation, and changes in fire frequency.Expanding the approach using R-Ratepol to open-access paleoecological datasets in global databases, such as Neotoma, will allow future paleoecological and macroecological studies to quantify major changes in biotic composition or in sets of abiotic variables across broad spatiotemporal scales.

EFFECTS OF CLIMATE CHANGE ON CENTRAL AMAZONIAN FORESTS: A TWO DECADES SYNTHESIS OF MONITORING TROPICAL BIODIVERSITY

Central Amazon has been subjected to a higher frequency of extreme climatic events, such as very dry or very wet years, in the last decades. Here, we report a 20-year monitoring of 6 biological groups over 100 km 2 of typical terra-firme forest at Ducke Forest Reserve, Manaus. Most assemblages had a decrease in abundance (9 – 35 %) and richness (8 – 25 %) along time, with some taxonomic and functional reorganization. Taxonomic and functional composition changes along time were more extensive in the valleys for trees and ants, and in first-order streams for fish; while bird and small trees had different patterns of composition change in valleys and plateaus. Although the signal of change was not congruent across all assemblages, patterns indicate that the forest and streams are becoming more dynamic as the hydrological cycle intensifies due to climate changes, and these new environments are already filtering species, at least in some well monitored taxonomic groups. Our data, in combination with other studies, suggest that riparian areas in the valleys are hydrological refuges during droughts, although also susceptible to disturbances induced by excessive precipitation and windstorms. In face of the importance of valleys as refuge, its sensibility and the unknown effects of potential migrations from higher topographic areas due to climate change, the conservation of large and extensive riparian areas seems to be of surmount importance to the future of Amazonian biodiversity.

Labor-Market Wedge under Engel Curve Utility: Cyclical Substitution between Necessities and Luxuries

In booms, households substitute luxuries for necessities, e.g., food away from home for food at home. This cyclical pattern of composition changes in the consumption basket has the potential to reduce the volatility of measures of the labor-market wedge, the gap between the marginal rate of substitution and the real wage. Based on household expenditure patterns from the Consumer Expenditure Survey, we show that this composition bias has only a limited impact on the measured labor-market wedge, accounting for 6 percent to 16 percent of its cyclical volatility.

Fine-scale temporal turnover of jarrah forest understory vegetation assemblages is independent of fire regime

BackgroundPrescribed burning is an important management tool in jarrah (Eucalyptus marginata Sm.) forests of southwest Western Australia to reduce the risk of damaging bushfires. In 1986 to 1987, we established long-term study sites in dry (mean annual rainfall ~700 mm) and moist (mean annual rainfall ~1000 mm) jarrah forests to assess the effects of prescribed burning, as well as other fire treatments including fire exclusion, on the composition, richness, and relative abundance of forest understory vegetation.ResultsOver almost 30 years, species assemblages within all fire treatments changed significantly through time, but the changes were independent of treatment. The pattern of change in composition of fire response types over elapsed time was different between sites. At the dry site, changes in species assemblages were initially relatively large in the first decade or so of the study, but slowed thereafter. At the moist site, compositional change driven by obligate seeding shrubs occurred faster and more uniformly with time across all treatments. Species richness was also independent of fire treatment at both sites. Species richness decreased with elapsed time on the moist site but increased with elapsed time on the dry site. The stronger elapsed-time effect rendered the time since fire effect on loss of species richness on the moist site to be insignificant, but there was an inverse relationship with time since fire at the dry site. Within each site, there were clear patterns of changing abundance based on life form and fire response groups, but this was not consistent between sites.ConclusionsAt the scale of the current study, jarrah forest plant communities displayed resilience to imposed experimental fire regimes. Over time, either elapsed time or time since fire, species assemblages across all treatments changed regardless of fire treatment, but changes were mostly associated with specific plant life forms and fire response traits, suggesting that the process is both deterministic and stochastic. While many species changed in abundance over time, no species were lost as a result of the fire treatments. Within the fire frequency and intensity ranges investigated in this study, there was flexibility in the application of prescribed fire to achieve management objectives without loss of plant diversity.

Labor-Market Wedge under Engel Curve Utility: Cyclical Substitution between Necessities and Luxuries

In booms, households substitute luxuries for necessities, e.g., food away from home for food at home. Ignoring this cyclical pattern of composition changes in the consumption basket makes the labor-market wedge- a measure of inefficiency that reflects the gap between the marginal rate of substitution and the real wage- appear to be more volatile than it actually is. Based on the household expenditure pattern across 10 consumption categories in the Consumer Expenditure Survey, we show that taking into account these composition changes can explain 6-15% of the cyclicality in the measured labor-market wedge.

Cabinet Leadership: Does It Mirror Democratic Change in Mexico?

AbstractAn exploration of cabinet leadership in Mexico has always provided insights into political recruitment trends for leading policymakers. An examination of the present cabinet from 2012 through 2016 is valuable for four reasons. First, to what extent does the current leadership reflect changes in compositional patterns of the most influential policymakers as a result of a democratic electoral process dating from 2000? Second, does the return of the PRI reflect traditional patterns established by the last two PRI presidential administrations, or has the present cabinet taken on features that can be attributed to the two previous PAN administrations? Third, have significant patterns emerged, reflected in recent appointments, that suggest influential characteristics exercising broader influences in the future? Fourth, will the most influential cabinet figures under the PRI presidency reestablish their dominance as leading contenders for their party’s presidential election in 2018?

The water footprint of the Spanish agricultural sector: 1860–2010

Since 1860, the Spanish agricultural sector has undergone an intensive process of development resulting in important structural changes, not only in the sector itself, but also in the relationship of the agrarian system to natural resources. This paper studies the evolution of domestic water consumption as a consequence of increasing agricultural production, as well as the impact that the growing need for water had on the construction of infrastructure for irrigation. To that end, we examine the water consumed in the production of vegetable and animal goods for five different years: 1860, 1900, 1930, 1962 and 2010. From these results, a detailed analysis of the trends in water consumption and changes in compositional patterns is carried out. We determine to what extent the development of the agricultural sector conditioned the construction of new irrigation infrastructure. Finally, a Decomposition Analysis (DA) is applied to analytically identify and quantify the main explanatory factors behind that evolution, and to understand the increase in agricultural water consumption over the long term. Our findings show the large pressures on water resources exerted as a result of the expansion of the Spanish agricultural sector during the last 150years.

Application of Bioindicators to Assess Changing Patterns: A Case in the Himalaya

Over the last decade or so biodiversity indicators in the Indian Himalayan Region (IHR) have been variously applied depending upon the objectives of the investigations, for example, selected biodiversity attributes, such as, richness, naturalness, representativeness, uniqueness, endemicity and use value have been effectively applied for prioritization of sites, clusters and grid units in the timberline zone of the Himalaya. An analysis on location specific data sets on endemic elements using various indices as indicators have resulted in the identification of endemic rich grid units in the Himalaya. Likewise, population structure, compositional pattern, sex ratio distribution, habitat heterogeneity, extent of biomass harvesting, litter-fall decomposition rate, etc. help in identifying and assessing changing patterns in composition, structure and function of forest ecosystems. More recently, long time phenological data of selected biodiversity elements using herbarium records is attracting increasing interest to understand how plants respond to global climate change. Such studies attempt to assess the usefulness of phenological patterns as indicators of change focusing on selected high value medicinal alpine/sub-alpine and temperate herbaceous species of IHR, a global hotspot, reportedly sensitive to climatic change. Phenological model using generalized additive models demonstrated early flowering pattern for most species except for Swertia cordata. The paper discusses the usefulness of identifying and applying various types of biodiversity indicators for their value in developing conservation strategies and management options. Moreover, their predictive value in developing future scenarios is also highlighted.

Species Recruitment following Flooding, Sediment Deposition and Seed Addition in Restored Riparian Areas

In recent years an increasing number of streams have been restored to improve conditions for natural fen and meadow vegetation to develop in the associated riparian areas, but with modest success. Here we apply a controlled and replicated approach to investigate the role of flooding, sediment deposition, and seed addition for species recruitment in riparian areas with different types of standing vegetation. We expect that species recruitment is restricted in areas where the vegetation is dominated by fast‐growing productive species because competition for light will make the establishment of new species difficult, especially for low‐productive target species. We found that the naturally recruited species were few, mostly common, and widely distributed species. A majority of the recruited species, including target species added as seeds into the sediments, emerged in all areas independent of the characteristics of the standing vegetation. We observed significant temporal changes in compositional patterns throughout the experimental period (May to October). These changes were especially pronounced in areas with fen/fen‐meadow vegetation and were closely associated with the emergence and growth of species originating from the deposited sediments (e.g. Equisetum pratense, Poa trivialis, Urtica dioica), including the seeded target species (Lychnis flos‐cuculi and Lotus pedunculatus) and with a decline in fen‐associated mosses and small sedges. Compositional changes were also associated with shifts toward more productive species in areas previously dominated by low and intermediately productive species. We infer that flooding and sediment deposition play a limited role for recruitment of target species in riparian areas and that sediment deposition may entail a risk of losing diversity in riparian areas.

Vegetation change and emerging research feedback for Korean National Long Term Ecological Research (KNLTER)

Various responses of forest ecosystems to climate change underscore the need to improve our understanding of the environmentally-driven changes in forests, most effectively by long-term monitoring protocols. We have explored vegetation dynamics based on changes in community structure, species composition, diversity and demographics in four Korean National Long Term Ecological Research (KNLTER) sites--Mt. Nam, Mt. Jeombong, Mt. Worak, and Mt. Jiri--between 2004 and 2009. Most of the sites and forests studied exhibited increments in total basal area, but this was not observed in Quercus mongolica forests in Mt. Nam and Mt. Worak. Stem density exhibited various changes. Altitude gradient was the representative factor in differences in species composition. Two patterns of compositional change--convergence and divergence--were detected. The vegetation of Mt. Nam and Q. mongolica community of Mt. Work showed relatively larger changes in composition. However, in the other sites, few changes were observed. Changes of species richness were not notable except for Mt. Nam, where three species were added in the pine forest, whereas one species disappeared in the oak forest. In the oak forests, mortality rate was as follows (in descending order): Mt. Nam (25.5%), Mt. Jeombong (24.3%), Mt. Worak (16.4%) and Mt. Jiri (0.8%). In the pine forest, the recruitment rate was as follows (in descending order): Mt. Nam (63.7%), Mt. Worak (12.9%), Mt. Jeombong (7.6%) and Mt. Jiri (7.3%). The mortality rate and change rate of basal area were strongly negatively correlated (r = -0.9, P = 0.002), and the recruitment rate and change rate of density were positively correlated (r = 0.77, P = 0.026). In the KNLTER sites, larger vegetation changes were attributed to anthropogenic activities such as salvage logging. Suppression or competition for resources would also affect these changes. Research suggestions such as monitoring to clarify the causes of species mortality were discussed.

Metabolite profiling of doenjang, fermented soybean paste, during fermentation

A fermented soybean paste known as doenjang is a traditional fermented food that is widely consumed in Korea. The quality of doenjang varies considerably by its basic ingredients, species of microflora, and fermentation process. The classification of predefined metabolites (e.g. amino acids, organic acids, sugars and sugar derivatives, and fatty acids) in doenjang samples according to fermentation was performed by using GC-FID and GC-MS data sets with the application of a multivariate statistical method. The predominantly produced amino acids included alanine, valine, leucine, isoleucine, proline, glutamine, phenylalanine and lysine, showing remarkable increases in amounts during the later stages of fermentation. Carbonic acid, citric acid, lactic acid and pyrogultamic acid were identified as the major organic acids. Significant amounts of erythrose, xylitol, inositol and mannitol were detected during fermentation. Regarding fatty acids, relatively higher amounts of palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid were found in the doenjang at each fermentation time point. Principal component analysis (PCA) successfully demonstrated changes in composition patterns as well as differences in non-volatile metabolites according to fermentation period. A set of metabolites could be determined representing the quality of doenjang during fermentation, and which might also be correlated with taste ingredients, flavour, nutrition, and physiology activities that are claimed to be dependent on the quality control of commercial doenjang.

Linking the patterns of change in composition and function in bacterioplankton successions along environmental gradients

The connections that exist between the composition of bacterial communities and their functional attributes are still a matter of intense debate, despite over a decade of intense studies. Here we explored three different facets of the links that may exist between bacterioplankton compositional and functional successions that occurred along the water flow path in a complex watershed in southern Quebec. We analyzed the correlation between composition and function in terms of their absolute patterns, and in terms of their rates of change relative to transit time in environmental transitions, and relative to shifts in resources along the same transitions. Our results showed that the absolute patterns in bacterial community composition (BCC, using DGGE [denaturing gradient gel electrophoresis] profiles) and functional capacities (FC, using BIOLOG profiles) were not correlated, but that the rates of change in BCC and FC along the transitions were strongly correlated to each other. Further, we observed that the strength and shape of the relationship between the changes in BCC and FC varied relative to the type and intensity of gradient considered. Collectively, these results showed that BCC and FC are strongly related but in a very dynamic manner, such that their absolute patterns do not appear to be connected. This in turn suggests a high level of functional redundancy that occurs both within the existing community and in the meta-community from which phylotypes are selected to occupy the new niches that are created along the transitions.

Classification and comparison of oak dominated forests on the eroded fan remnant at the foot of Yatsugatake volcano, central Japan

In order to evaluate the landform-mediated differences in the regeneration of oak ( Quercus crispula), we compared the composition and diameter distribution of 77 stands on an eroded fan remnant at the foot of Yatsugatake volcano in central Japan. In total seven site units were classified on the basis of the combination of the vegetation, topography and soil data. Overall, the patterns of compositional change were strongly related to the topographic and edaphic differences among fluvial landforms. Oak dominated the units on the older-fan surfaces: mounds, depressions, rock outcrops and side slopes, but it was rare in the units on the valley floor: stream terraces, natural levees of coarse rock fragments and seeps. The units on the older-fan surfaces, except for rock outcrops, were covered by fine fertile organic soils (Andisols), while coarser fluvial deposits covered the units on the valley floors. Oak was most abundant on the mounds followed by the depressions, rock outcrops and side slopes. Oak sapling density was low even in oak stands, and it was very low on well-drained sites with high abundances of shade-tolerant trees. Sapling and seedling abundance of these shade-tolerant tree species were high on side slopes and rock outcrops but low on Andisols with thick humus layer and in areas with dense dwarf bamboo ( Sasa nipponica) coverage. Under the current conditions of reduced disturbance frequency, we predict that Q. crispula will be replaced by shade-tolerant tree species, especially on side slopes and rocky outcrops.

DETERMINANTS OF LOCAL EXTINCTION AND TURNOVER RATES IN URBAN BIRD COMMUNITIES

Studying the effects of urbanization on the dynamics of communities has become a priority for biodiversity conservation. The consequences of urbanization are mainly an increased fragmentation of the original landscapes associated with a decrease in the amount of favorable habitats and an increased pressure of human activities on the remaining patches suitable for wildlife. Patterns of bird species richness have been studied at different levels of urbanization, but little is known about the temporal dynamics of animal communities in urban landscapes. In particular, urbanization is expected to have stronger negative effects on migratory breeding bird communities than on sedentary ones, which should lead to different patterns of change in composition. Using an estimation method accounting for heterogeneity in species detection probability and data collected between 2001 and 2003 within a suburban area near the city of Paris, France, we tested whether these communities differ in their local extinction and turnover rates. We considered the potential effects of patch size and distance to Paris' center as a measure of the degree of urbanization around the patches. As expected, local rates of extinction and turnover were higher for migratory than for sedentary species, and they were negatively related to patch size for migratory species. Mean species richness of the sedentary species increased during the study period and their local turnover rate was negatively related to the distance to the urban core, showing a trend to colonize the most urban patches. These results highlight the very dynamic nature of the composition of some local bird communities in fragmented habitats and help to identify factors affecting colonization and extinction.

Vascular plant compositional gradients within and between Iowa fens

Abstract Question: What is the nature and relative importance of compositional gradients within- and between fens? Location: Iowa, USA. Methods: 506 0.5 m × 0.5 m quadrats were sampled from 31 fens across a 550 km extent. Presence/absence of all vascular plant taxa, plus the non-vascular genera Sphagnum and Chara, and values for 24 environmental variables were noted. Global Non-Metric Multidimensional Scaling and Monte Carlo tests were used to describe compositional variation and identify significant environmental co-variables. Model-based cluster analysis was used to identify the optimal number of groups supported by the data, while k-means clustering was used to assign each quadrat to a group. The number of occurrences (and frequency) of each species within each group was calculated. Two-dimensional 95% Gaussian confidence intervals, ANOVA, correlation coefficient homogeneity tests, log-linear modelling, and Fisher's exact tests were used to document patterns of compositional change. Results: Two stable...

Disturbance and Dominance in Tetraphis pellucida: A Model of Disturbance Frequency and Reproductive Mode

The role of disturbance in maintenance of ecological dominance by Tetraphis pellucida Hedw. is examined in field studies and an empirical model. Patterns of compositional change in T. pellucida-dominated communities are summarized in a matrix of transition probabilities. Open substrate patches are most frequently replaced by asexual colonies which gradually change to the sexual state. Most sexual patches persist, or are overcome by competitors, but a significant fraction of the patches experience disturbance. A Markov model is used to predict the effects of varying disturbance frequency on the relative abundance of sexual, asexual, and senescent colonies, as well as on the success ofcompetitors. Experimental reduction in disturbancefrequency causes an increase in competitors and the local extinction of T. pellucida. Tetraphis pellucida maintains ecological dominance by exploiting frequently disturbed microsites. Its dual reproductive modes allow it to perpetuate itself by gemmae in frequent, local disturbances, and to escape to distant disturbances via spore production. Microhabitat preference ofT. pellucida for decayed stumps over adjacent logs may be correlated with differing disturbance frequencies. These findings suggest that disturbance may be an important selective pressure in maintaining dual reproductive modes in this species.

Patterns of composition change in multicomponent batch distillation

A simple dynamic model has been developed to study the behavior of multicomponent batch distillation. The distillate compositions obtained for ideal mixtures behave in accord with intuition since the fractions contain the individual pure components in order of increasing boiling point. Azeotropic mixtures are more complex and counter-intuitive, in some cases displaying non-adjacent distillate fractions which have the same composition. The general behavior of ternary azeotropic batch distillation is described in simple terms based on the nature of the distillate and still composition changes in the phase plane. At large reflux ratio and number of stages, the sequence of distillate fractions generated from any initial composition in the still can be found with little or no computational effort.

Multicomponent exchange and subsurface solute transport: Characteristics, coherence, and the Riemann Problem

When water of one chemical composition is displaced by water of another, there is a change in composition at any point within the flow system which may occur more or less rapidly, depending on both the hydraulics and chemistry of the system. For many applications it is possible to decouple the hydraulic and chemical analyses, and later combine them for prediction of effluent compositions from well fields or concentration histories at observation wells. When an advection‐reaction model is used, the displacement problem is described mathematically as a Riemann problem. In this paper the Riemann problem is solved for the ternary exchange system using the method of characteristics. The pattern of composition changes is found to follow the right eigenvector paths in composition space, and the eigenvalues provide composition‐dependent retardation functions. The hydraulics is treated fairly generally and allows one to consider steady uniform or nonuniform flow fields or stochastic flow models. Both laboratory and field applictions are presented.

Landform-Mediated Differences in Successional Pathways Among Upland Forest Ecosystems in Northwestern Lower Michigan

Abstract Seedling and sapling densities were compared with current overstory composition in 30 upland forest stands in northwestern Lower Michigan to study potential successional pathways. The patterns of compositional change were strongly related to topographic and edaphic differences among glacial landforms. Glaciofluvial landforms, currently dominated by oak, have relatively high densities of oak seedlings (4913 stems/ha) that seldom move into the sapling layer (10 stems/ha). Oak-dominated ecosystems on hilly ice-contact stratified drift exhibited relatively high densities of red maple saplings (48 stems/ha). Oak-dominated ecosystems on extremely well drained outwash plains exhibited sparse sapling regeneration of any species; red maple was typically absent, and oak saplings were usually in an apparent state of decline. Differences in the potential for recruitment of saplings into the overstory among these ecosystems may be attributable to differences in fire history or site-dependent effects on the competitive abilities of species. Morainal landforms, currently supporting relatively diverse northern hardwood overstories, showed little potential recruitment of any species other than sugar maple. Glacial landforms in northwestern Lower Michigan direct compositional change by influencing soil moisture and nutrient availability, and historical patterns of disturbance and species establishment. For. Sci. 33(2):445-457.

Quality of Historical Data on Midwestern Old-Growth Forests

Quality of historical data on species composition in midwestern old- growth forests was assessed for its potential for monitoring long-term vegetation dy- namics. Vectors of compositional dynamics superimposed on ordinations revealed that perceived compositional change owing to sampling error may be similar in size to actual long-term changes. Other data quality problems may arise from big-tree bias, inexact overlap of stand boundaries, varying treatment of stand edges, and in- adequate descriptions of methods and results. To promote an improved long-term monitoring data base, a checklist is given of some commonly overlooked points of de- sign and publication of compositional studies of forests. In 1949 John Potzger received a letter from the editor of the American Midland Natu- ralist soliciting a paper from Potzger's then-recent study of woods near Versailles, Indi- ana (J. E. Potzger archive, Butler University Library, Indianapolis, Ind.). Potzger obliged and the paper was cheerfully accepted by the editor, with the caveat that the ta- bles of species composition should be deleted. Potzger disagreed, writing My experi- ence with omitted tables from published papers has been very unsatisfactory . . . in 25 years, or less, such data would in all likelihood not be available. Furthermore, he of- fered to pay additional typesetting charges to get the tables into print. Potzger's pub- lished tables (Potzger, 1950; and many other papers) have proven useful for later com- parisons. In contrast, most of his unpublished and field data are not present in his archive and are apparently lost forever. We hope that this paper will help spread Potzger's view toward the future. We have assembled published long-term compositional data from midwestern forests to examine the consistency and patterns of compositional change. This compilation re- vealed variation in quality and type of data. If, between two sample dates, composi- tional differences due to sampling error are larger than actual compositional changes, little confidence can be placed in the observed trends. This problem was assessed by comparing the size of long-term changes within stands, as shown by vectors of composi- tional change on an ordination, to compositional variation arising from sampling error. We also compare the influence of broad classes of study methods on the size of per-