Distribution Of Functional Types Research Articles

Phytoplankton functional community structure in Argentinian continental shelf determined by HPLC pigment signatures

The Patagonian Sea in Argentina is known as an area with high primary production and biodiversity. The complex hydrodynamic environment resulting from the interaction between the Malvinas–Brazil convergence and the waters over the continental shelf and slope enhances the development of high chlorophyll concentrations, especially in frontal and coastal areas. The composition, distribution and variability of several phytoplankton functional types (PFTs) derived from diagnostic pigments were studied in relation to the local hydrographical conditions, using data from a research cruise carried out on board the RV Bio Hesperides at the end of the Summer season (March 2008).Phytoplankton cell size and PFT distributions were found to be highly influenced by the physical and chemical characteristics of the studied environments. Thus large cells, mainly diatoms, were the dominant size fraction in the southern frontal areas, where the SubAntarctic Surface Waters (SASW) from the Malvinas Current meet shelf waters. However, other groups of microphytoplankton (mPF), mainly dinoflagellates, were also detected in the shallow waters zone influenced by the tidal regime near the Valdes Peninsula. Picophytoplankton (pPF) was an important contributor to the floristic composition in the southern frontal zones, while nanophytoplankton (nPF) was dominant in the stations located over the continental slope, and in the oligotrophic area near Mar del Plata.The ratio between photoprotective and photosynthetic pigments (PPC:PSC) and the photoprotection index (PI) indirectly provide information about the environment and its effect on the PFTs composition.

Coupled simulation of climate and vegetation dynamics

Experiments are performed with the climate model of the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), integrated jointly with the Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM). It is shown that the coupled model reproduces the distribution of basic plant functional types around the world quite well. In simulations of climate for the 21st century, this model predicts changes in dominant plant types and in the total area occupied by vegetation regionally. However, it does not reproduce the significant inverse influence that vegetation succession has on the simulated climate.

Global variability of phytoplankton functional types from space: assessment via the particle size distribution

Abstract. A new method of retrieving the parameters of a power-law particle size distribution (PSD) from ocean color remote sensing data was used to assess the global distribution and dynamics of phytoplankton functional types (PFT's). The method retrieves the power-law slope, ξ, and the abundance at a reference diameter, N0, based upon the shape and magnitude of the particulate backscattering coefficient spectrum. Relating the PSD to PFT's on global scales assumes that the open ocean particulate assemblage is biogenic. The retrieved PSD's can be integrated to define three size-based PFT's by the percent volume concentration contribution of three phytoplankton size classes – picoplankton (0.5–2 μm in equivalent spherical diameter), nanoplankton (2–20 μm) and microplankton (20–50 μm). Validation with in-situ HPLC diagnostic pigments resulted in better match-ups for the pico- and micro-phytoplankton size classes as compared to nanoplankton. Global decadal averages derived from SeaWiFS monthly data reveal PFT and particle abundance spatial patterns that are consistent with current understanding. Oligotrophic gyres are characterized by lower particle abundance and higher contribution by picoplankton-sized particles than transitional or eutrophic regions. Seasonal succession patterns for size-based PFT's reveal good correspondence between increasing chlorophyll concentration and percent contribution by microplankton, as well as increasing particle abundance. Long-term trends in particle abundances are generally well correlated with the MEI index indicating increased oligotrophy (i.e. lower particle abundance and increased contribution of picoplankton-sized particles) during the warm phase of an El Niño event. This work demonstrates the utility and future potential of assessing phytoplankton functional types using remote characterization of the particle size distribution.

Changes in plant form and function across altitudinal and wetness gradients in the wetlands of the Maloti-Drakensberg, South Africa

A survey of 93 wetlands in six catchments across the Maloti-Drakensberg is used to assess the distribution of plant functional types across altitudinal and wetness gradients. Altitudes range from 1,000 to 3,200 m a.s.l. Within each catchment, the wetlands were selected to cover the complete range in altitude and wetland types. In each of the selected wetlands, vegetation was sampled in 3 by 3 m quadrats covering the entire range of wetness represented in the wetland, from temporarily wet to permanently inundated soils. Plant species were allocated to one of 11 different functional types (examples are C3 grasses, C4 sedges, rosette plants, and shrubs), and the proportion of the vegetation in each sample occupied by each functional type was calculated from the species’ abundances. Canonical Correspondence Analysis shows that “wetness” clearly has the highest impact on the distribution of functional types, followed by altitude. The most important plant functional types in wetlands are grasses and sedges, however, at higher altitudes, forbs (especially rosette plants) and bulbous plants become a more prominent feature in the wetlands. The total amount of graminoids gradually decreases with altitude. The general trend is that sedges tend to increase with increasing wetness and C3 plants (grasses and sedges) increase with increasing altitude, but these effects are not independent. The distributions of C4 sedges and C4 grasses along an altitudinal gradient are quite different, and C4 grasses grow abundantly at much higher altitudes than C4 sedges. C4 sedges are very scarce at the altitudes represented in the Maloti-Drakensberg area, whereas C3 grasses occur in the permanently wet parts of the wetlands, especially at higher altitudes (normally mostly occupied by sedges). Shrubs are rare in wetlands and tend to be an indication of disturbance. This study complements previous studies on the distribution of grasses and sedges at the lower altitudes within KwaZulu-Natal, which found that at altitudes below 1,000 m a.s.l. C4 sedges were much more prominent, while forbs and rosette plants were largely absent. This confirms that C4 as an adaptation to hotter and warmer climates is sometimes a less favorable metabolism in wet high altitude areas. At high altitudes, rosette plants and bulbous plants become more competitive in wetlands, probably because grasses and sedges present at these altitudes generally grow smaller than they do in low altitude wetlands.

The AMMA-CATCH Gourma observatory site in Mali: Relating climatic variations to changes in vegetation, surface hydrology, fluxes and natural resources

The Gourma site in Mali is one of the three instrumented meso-scale sites deployed in West-Africa as part of the African Monsoon Multi-disciplinary Analysis (AMMA) project. Located both in the Sahelian zone sensu stricto, and in the Saharo–Sahelian transition zone, the Gourma meso-scale window is the northernmost site of the AMMA-CATCH observatory reached by the West African Monsoon. The experimental strategy includes deployment of a variety of instruments, from local to meso-scale, dedicated to monitoring and documentation of the major variables characterizing the climate forcing, and the spatio-temporal variability of surface processes and state variables such as vegetation mass, leaf area index (LAI), soil moisture and surface fluxes. This paper describes the Gourma site, its associated instrumental network and the research activities that have been carried out since 1984. In the AMMA project, emphasis is put on the relations between climate, vegetation and surface fluxes. However, the Gourma site is also important for development and validation of satellite products, mainly due to the existence of large and relatively homogeneous surfaces. The social dimension of the water resource uses and governance is also briefly analyzed, relying on field enquiry and interviews. The climate of the Gourma region is semi-arid, daytime air temperatures are always high and annual rainfall amounts exhibit strong inter-annual and seasonal variations. Measurements sites organized along a north–south transect reveal sharp gradients in surface albedo, net radiation, vegetation production, and distribution of plant functional types. However, at any point along the gradient, surface energy budget, soil moisture and vegetation growth contrast between two main types of soil surfaces and hydrologic systems. On the one hand, sandy soils with high water infiltration rates and limited run-off support almost continuous herbaceous vegetation with scattered woody plants. On the other hand, water infiltration is poor on shallow soils, and vegetation is sparse and discontinuous, with more concentrated run-off that ends in pools or low lands within structured endorheic watersheds. Land surface in the Gourma is characterized by rapid response to climate variability, strong intra-seasonal, seasonal and inter-annual variations in vegetation growth, soil moisture and energy balance. Despite the multi-decadal drought, which still persists, ponds and lakes have increased, the grass cover has largely recovered, and there are signs of increased tree cover at least in the low lands.

Edge effects on plant composition and functional type distribution in renosterveld fragments of the Tygerberg

Edge effects on plant composition and functional type distribution in renosterveld fragments of the Tygerberg

Determination of Critical Conditions of Adsorption for Chromatography of Polymers

Liquid chromatography (LC) at critical conditions of adsorption was used to separate various poly(ethylene oxides), poly(propylene oxides) and their copolymers. For the first time, the determination of the critical conditions by means of Ultra Performance Liquid Chromatography (UPLC) coupled to Electrospray Ionization Time-of-flight Mass Spectrometry (ESI-TOF MS) is reported. In contrast to established, mostly laborious routines to find suitable chromatographic separation conditions, this coupling enables a very fast adjustment of parameters. Similar to LC Matrix-assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (LC/MALDI MS) coupling, a two-dimensional analysis of homo- and copolymers regarding its functionality type and molecular weight distribution, as well as copolymer composition, can be performed simultaneously. Furthermore, there is no need for using polymer standards for the determination of critical conditions or Size Exclusion Chromatography calibration.

Comparing the ability of a genetic algorithm based clustering analysis and a physically based dynamic vegetation model to predict vegetation distribution

This study explores the applicability of data‐driven clustering analysis in predicting vegetation distribution over two continents where water is an important controlling factor for vegetation growth, South America and Africa, and compares the ability of clustering analysis with that of a physically based dynamic vegetation model to predict vegetation distribution. A clustering analysis algorithm based on the genetic‐algorithm‐based K‐means is tested, with the number of clusters determined a priori according to the primary plant functional types observed to exist in the study domain. The most important variables upon which the clustering analysis is based include available water, its seasonality, and evaporative demand. The dynamic vegetation model used is the Community Land Model version 3 coupled with a Dynamic Global Vegetation Model (CLM3‐DGVM) with modifications targeted to address some known biases of the model. Results from both the clustering analysis and the modified CLM3‐DGVM are compared against observations derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). Both methods reasonably reproduced the general pattern of dominant plant functional type distribution. There is no clear winner between the two methods, as the DGVM outperforms the clustering analysis approach in some aspects and is outperformed in others. It is therefore suggested that clustering analysis can be a useful tool in biogeography estimation, although it cannot be used in mechanistic studies as the process‐based DGVMs are.

Ecological indicators for the pelagic zone of the ocean from remote sensing

It is generally accepted that responsible stewardship of the ocean implies ecosystem-based management. A requirement then arises for ecosystem indicators that can be applied in serial fashion with a view to detection of ecosystem change in response to environmental perturbations such as climate change or overfishing. The status of ecological indicators for the pelagic ecosystem is reviewed. The desirable properties of such indicators are listed and it is pointed out that remote sensing (ocean colour, supplemented by sea-surface temperature) is an important aid to achieving them. Some ecological indicators that can be developed from remotely-sensed data on ocean colour are tabulated. They deal with the seasonal cycle of phytoplankton biomass, production and loss terms, annual production, new production, ratio of production to respiration, spatial variances in phytoplankton biomass and production, spatial distribution of phytoplankton functional types, delineation of ecological provinces and phytoplankton size structure.

Single fiber physiology differs between three human leg muscles

While single fiber contractile function within a given fiber type population is largely similar between muscles, fiber type distribution can vary considerably. Because single fiber contractile function and fiber type distribution both contribute to whole muscle function, we generated composite profiles to compare three leg muscles of interest. Eight recreationally active males (5) and females (3) (23 ± 1 yr, 64 ± 3 kg, 51.8 ± 2.6 ml/kg/min) were biopsied from the vastus lateralis (VL) and soleus (S). To make further comparisons, seven recreationally active males (4) and females (3) (22 ± 1 yr, 68 ± 2 kg, 49.5 ± 2.6 ml/kg/min) were biopsied from the gastrocnemius (G). Single fibers were isolated and investigated for size and function, and subsequently processed for myosin heavy chain (MHC) composition (SDS‐PAGE). A composite value, which is a theoretical representation of the entire muscle, was then calculated for each contractile parameter based on the MHC composition of the studied fibers. The VL had higher specific tension (VL 66% > G and 28% > S), shortening velocity (40% > G; 48% > S), peak power (266% > G; 152% > S), and normalized power (276% > G; 221% > S), when compared to the gastrocnemius and soleus. Additionally, the gastrocnemius had lower peak tension (G 37% < VL; G 31% < S) and lower specific tension (40% < VL; 22% < S) when compared to the vastus lateralis and soleus. These findings highlight the unique intrinsic profile of these select muscles, which should be considered when interpreting how they adapt to exercise training.

Mapping plant functional types from MODIS data using multisource evidential reasoning

Reliable information about the geographic distribution and abundance of major plant functional types (PFTs) around the world is increasingly needed for global change research. Using remote sensing techniques to map PFTs is a relatively recent field of research. This paper presents a method to map PFTs from the Moderate Resolution Imaging Spectroradiometer (MODIS) data using a multisource evidential reasoning (ER) algorithm. The method first utilizes a suite of improved and standard MODIS products to generate evidence measures for each PFT class. The multiple lines of evidence computed from input data are then combined using Dempster's Rule of combination. Finally, a decision rule based on maximum support is used to make classification decisions. The proposed method was tested over the states of Illinois, Indiana, Iowa, and North Dakota, USA where crops dominate. The Cropland Data Layer (CDL) data provided by the United States Department of Agriculture were employed to validate our new PFT maps and the current MODIS PFT product. Our preliminary results suggest that multisource data fusion is a promising approach to improve the mapping of PFTs. For several major PFT classes such as crop, trees, and grass and shrub, the PFT maps generated with the ER method provide greater spatial details compared to the MODIS PFT. The overall accuracies increased for all the four states, with the biggest improvement occurring in Iowa from 51% (MODIS) to 64% (ER). The overall kappa statistic also increased for all the four states, with the biggest improvement occurring in Iowa from 0.03 (MODIS) to 0.38 (ER). The paper concludes with a discussion of several methodological issues pertaining to the further improvement of the ER approach.

River Floodplain Vegetation Scenario Development Using Imaging Spectroscopy Derived Products as Input Variables in a Dynamic Vegetation Model

River floodplains are becoming increasingly subject to multifunctional land-use. In this contribution, we are linking imaging spectrometer derived products with a dynamic vegetation model to improve the simulation and evaluation of scenarios for a river floodplain in the Netherlands. In particular, we are using airborne HyMap imaging spectrometer data to derive Leaf Area Index (LAI), spatial distribution of Plant Functional Types (PFT), and model dominant species abundances as input for the ecological model. We use the dynamic vegetation model (DVM) SMART2-SUMO to simulate vegetation succession under scenarios of changing abiotic conditions and management regimes. SMART2 is a soil chemical model whereas SUMO describes plant competition and resulting vegetation succession. We validate all remote sensing derived products and the DVM calibration independently using extensive field sampling. We conclude that the dynamic vegetation models can be successfully initialized using imaging spectrometer data at currently unprecedented accuracy. However, all efforts undertaken for validation in this contribution may significantly exceed capacities for national or continental scale application of the proposed method.

Estimating global distribution of boreal, temperate, and tropical tree plant functional types using clustering techniques

A simple integrated algorithm was developed to relate global climatology to distributions of tree plant functional types (PFT). Multivariate cluster analysis was performed to analyze the statistical homogeneity of the climate space occupied by individual tree PFTs. Forested regions identified from the satellite‐based GLC2000 classification were separated into tropical, temperate, and boreal sub‐PFTs for use in the Canadian Terrestrial Ecosystem Model (CTEM). Global data sets of monthly minimum temperature, growing degree days, an index of climatic moisture, and estimated PFT cover fractions were then used as variables in the cluster analysis. The statistical results for individual PFT clusters were found consistent with other global‐scale classifications of dominant vegetation. As an improvement of the quantification of the climatic limitations on PFT distributions, the results also demonstrated overlapping of PFT cluster boundaries that reflected vegetation transitions, for example, between tropical and temperate biomes. The resulting global database should provide a better basis for simulating the interaction of climate change and terrestrial ecosystem dynamics using global vegetation models.

Synthesis of a macromonomer based on ɛ-caprolactone and 2-hydroxyethyl methacrylate

The mechanism of forming the macromonomer based on ɛ-caprolactone and 2-hydroxyethyl methacrylate under the effect of dibutyltin dilaurate has been investigated. The molecular-mass characteristics and the functional-type distribution of the macromonomer have been determined. It has been established that, as the concentration of the methacrylic component is increased, the contribution of side reactions related to its anionic polymerization rises. It has been shown that macromonomers with caprolactone backbones and terminal methacrylic and hydroxyl groups may be obtained. A method has been proposed for the purification of polymerization products from low-molecular-mass impurities, such as dimethacrylates and diols.

SIMULATING THE EFFECTS OF FREQUENT FIRE ON SOUTHERN CALIFORNIA COASTAL SHRUBLANDS

Fire disturbance is a primary agent of change in the mediterranean-climate chaparral shrublands of southern California, USA. However, fire frequency has been steadily increasing in coastal regions due to ignitions at the growing wildland-urban interface. Although chaparral is resilient to a range of fire frequencies, successively short intervals between fires can threaten the persistence of some species, and the effects may differ according to plant functional type. California shrublands support high levels of biological diversity, including many endangered and endemic species. Therefore, it is important to understand the long-term effects of altered fire regimes on these communities. A spatially explicit simulation model of landscape disturbance and succession (LANDIS) was used to predict the effects of frequent fire on the distribution of dominant plant functional types in a study area administered by the National Park Service. Shrubs dependent on fire-cued seed germination were most sensitive to frequent fire and lost substantial cover to other functional types, including drought-deciduous subshrubs that typify coastal sage scrub and nonnative annual grasses. Shrubs that resprout were favored by higher fire frequencies and gained in extent under these treatments. Due to this potential for vegetation change, caution is advised against the widespread use of prescribed fire in the region.

Terrestrial vegetation redistribution and carbon balance under climate change

BackgroundDynamic Global Vegetation Models (DGVMs) compute the terrestrial carbon balance as well as the transient spatial distribution of vegetation. We study two scenarios of moderate and strong climate change (2.9 K and 5.3 K temperature increase over present) to investigate the spatial redistribution of major vegetation types and their carbon balance in the year 2100.ResultsThe world's land vegetation will be more deciduous than at present, and contain about 125 billion tons of additional carbon. While a recession of the boreal forest is simulated in some areas, along with a general expansion to the north, we do not observe a reported collapse of the central Amazonian rain forest. Rather, a decrease of biomass and a change of vegetation type occurs in its northeastern part. The ability of the terrestrial biosphere to sequester carbon from the atmosphere declines strongly in the second half of the 21st century.ConclusionClimate change will cause widespread shifts in the distribution of major vegetation functional types on all continents by the year 2100.

An NMR study of the structure and molecular characteristics of polyether block copolymers based on propylene oxide and ethylene oxide

The structure of propylene oxide-ethylene oxide block copolymers prepared with the use of glycerol as an initiator and potassium monoglycerate as a catalyst was studied by NMR spectroscopy. The relative amounts of oxypropylene and oxyethylene monomer units, the functionality-type distribution, the number-average molecular mass, and the ratio between primary and secondary terminal hydroxyl groups were determined. The applicability of 1H and 13C NMR techniques to characterization of these copolymers is discussed. The obtained NMR data are compared with results obtained by other techniques.

Reconstructing a lost Eocene paradise: Part I. Simulating the change in global floral distribution at the initial Eocene thermal maximum

This study utilizes the NCAR Land Surface Model (LSM1.2) integrated with dynamic global vegetation to recreate the early Paleogene global distribution of vegetation and to examine the response of the vegetation distribution to changes in climate at the Paleocene–Eocene boundary (∼ 55 Ma). We run two simulations with Eocene geography driven by climatologies generated in two atmosphere global modeling experiments: one with atmospheric pCO 2 at 560 ppm, and another at 1120 ppm. In both scenarios, the model produces the best match with fossil flora in the low latitudes. A comparison of model output from the two scenarios suggests that the greatest impact of climate on vegetation will occur in the high latitudes, in the Arctic Circle and in Antarctica. In these regions, greater accumulated summertime warmth in the 1120 ppm simulation allows temperate plant functional types to expand further poleward. Additionally, the high pCO 2 scenario produces a greater abundance of trees over grass at these high latitudes. In the middle and low latitudes, the general distribution of plant functional types is similar in both pCO 2 scenarios. Likely, a greater increment of greenhouse gases is necessary to produce the type of change evident in the mid-latitude paleobotanical record. Overall, differences between model output and fossil flora are greatest at high latitudes.

Mass Spectrometry of Step-Growth Polymers

For at least two decades different mass spectrometric techniques have been applied for polymer analysis, including the qualitative determination of chemical compositions, end group identification, functionality type distribution and the determination of the cyclisation extend at each degree of polymerisation. Molecular weights exceeding 100 KDa are provable by MALDI-ToF mass spectrometry. Further, molecular weight distributions are determined by MADLI-ToF. However, there are some hints that, there is a discrimination against higher molecular weight species in samples with polydispersity of more than 1.2. Furthermore, pathways for dendritic and hyper-branched polymers, supramolecular polymers and nano condensates are analysed by help of mass spectrometry.

Comprehensive two-dimensional liquid chromatography for the characterization of functional acrylate polymers

Comprehensive two-dimensional liquid chromatography–size-exclusion chromatography (LC × SEC) was investigated as a tool for the characterization of functional poly(methyl methacrylate) (PMMA) polymers. Ultraviolet-absorbance and evaporative light-scattering detection (ELSD) were used. A simple method to quantify ELSD data is presented. Each data point from the ELSD chromatogram can be converted into a mass concentration using experimental calibration curves. The qualitative and quantitative information obtained on two representative samples is used to demonstrate the applicability of LC × SEC for determining the mutually dependent molar-mass distributions (MMD) and functionality-type distributions (FTD) of functional polymers. The influence of the molar mass on the retention behavior in LC was investigated using LC × SEC for hydroxyl-functional PMMA polymers. The critical conditions, at which retention is – by definition – independent of molar mass, were not exactly the same for PMMA series with different end-groups. Our observations are in close agreement with theoretical curves reported in the literature. However, for practical applications of LC × SEC it is not strictly necessary to work at the exact critical solvent composition. Near-critical conditions are often sufficient to determine the mutually dependent distributions (MMD and FTD) of functional polymers.