Responses Of Functional Groups Research Articles

ASSESSMENT OF PLANT FUNCTIONAL TYPES IN TROPICAL ARID AND SEMI-ARID ECOSYSTEMS OF INDIA USING REMOTE SENSING DATA AND GIS

Abstract. Tropical ecosystems undergo changes caused by season, climate or multiple anthropogenic impacts. Such changes may cause gradual or rapid shifts from one state to another. There has been a focus on functional classifications of plants to find tools for monitoring and assessing species status in changing environments. It has been recognised that plant biological characteristics can be related to their response to predominant environmental factors and interactions between other organisms. These findings have resulted in a search for plant functional types (PFTs) that are user-defined groups of species with similar response to environmental resources and disturbance associated to common biological traits. Now, identification of plant functional types is priority area in the climate change research. Satellite Earth observation data is an important tool in providing considerable information on extracting PFT information at global and regional levels. From the modelling perspective, some of the current needs are the refinement of processes that govern community assembly, such as natural and anthropogenic disturbances. PFTs used in large-scale models are insufficient to represent the diversity of responses in natural plant communities. The currently available MODIS PFT map was generated by re-labeling the IGBP land cover type classes. However, the error magnitudes of the MODIS PFT product and their spatial and temporal distributions have not been fully characterized. Remotely sensed derived information of the phenology, community composition and vegetation structure are the key inputs to integrate with the variability in precipitation and temperature to map the spatial distribution of Plant functional types. PFTs allows accurate representation of the land surface by separately specifying the composition and structure of PFTs within a grid cell. Very little research efforts are discernible in India that explicitly address the PFTs. In the present study five natural vegetation systems were studied along arid, semi-arid and sub-humid regions of Indian Desert and Aravallis of Rajasthan, India, with a distance of 600 km. The annual precipitation decreases from as high as 1600 mm in the south to 700 mm in the north-east and 100 mm in the west. The study is based on the integrated approach of remote sensing, GIS, and phytosociology. In the step 1, vegetation type map was prepared using multi-season IRS P6 LISS III data. Screening of plant traits was done based on field observations and literature. Phytosociological data pertains to 500 sample plots was used to identify plant functional traits of 900 species at morphological level. The vegetation classification scheme at regional level identified thorn forest, dry deciduous forest, broad leaved forest, woodland, shrubland and grasslands. Five plant traits selected in the study were significant for tropical environments. Attributes such as leaf size, leaf texture, spinescence, stem diameter and bark consistency were categorized systematically. Ordination analysis was carried out across the environmental gradient. Plant functional traits were measured on 20 individuals per species at each site. Environmental information was integrated to identify plant trait response. The spatial trends in PFTs were analysed and compared across the vegetation types, along the gradient of land surface temperature, climate, elevation and time integrated NDVI. Results established the occurrence of recurrent patterns of association among selected plant traits. Functional response groups were identified by summarizing results and relating them to individual species. Finally phytoclimatic map was prepared to represent spatial distribution of PFTs. The species with of functional traits of representing microphylls, sclerophyll, rough bark, spinescence and therophyte are demarcated as drought tolerant traits. Drought Intolerant PFTs are represented by macrophyll, malacophyll, smooth Bark, non spinescent stems and leaves. Biological spectrum of Desert national park, Jaisalmer and and Ajmer represents therophytic climate (below 600mm rainfall) while Sariska and Mt. Abu are of therophanerophytic (>600mm rainfall). The higher proportion of microphylls and therophytes are distributed within tropical arid environments. The dominance of the drought tolerant PFTs increased towards west while the dominance of the drought intolerant PFTs increased in southern and northern parts of Rajasthan. Detecting the change of spatial characteristics of plant species under precipitation gradients would be helpful to study species dynamics in a large region under environmental gradient. On the basis of easily-measured plant traits and phytosociological surveys, the present approach summarized the complexity of tropical vegetation into a relatively few PFTs. The present study open up new possibilities for understanding plant trait and environment relationship and developing PFT classification in tropical regions.

Application of Biochemical and Physiological Indicators for Assessing Recovery of Fish Populations in a Disturbed Stream

Recovery dynamics in a previously disturbed stream were investigated to determine the influence of a series of remedial actions on stream recovery and to evaluate the potential application of bioindicators as an environmental management tool. A suite of bioindicators, representing five different functional response groups, were measured annually for a sentinel fish species over a 15 year period during which a variety of remedial and pollution abatement actions were implemented. Trends in biochemical, physiological, condition, growth, bioenergetic, and nutritional responses demonstrated that the health status of a sentinel fish species in the disturbed stream approached that of fish in the reference stream by the end of the study. Two major remedial actions, dechlorination and water flow management, had large effects on stream recovery resulting in an improvement in the bioenergetic, disease, nutritional, and organ condition status of the sentinel fish species. A subset of bioindicators responded rather dramatically to temporal trends affecting all sites, but some indicators showed little response to disturbance or to restoration activities. In assessing recovery of aquatic systems, application of appropriate integrative structural indices along with a variety of sensitive functional bioindicators should be used to understand the mechanistic basis of stress and recovery and to reduce the risk of false positives. Understanding the mechanistic processes involved between stressors, stress responses of biota, and the recovery dynamics of aquatic systems reduces the uncertainty involved in environmental management and regulatory decisions resulting in an increased ability to predict the consequences of restoration and remedial actions for aquatic systems.

Diversity and distribution of benthic macrofauna in the Baltic Sea: Data inventory and its use for species distribution modelling and prediction

This study attempts to model the probability of occurrence of some characteristic macro-invertebrate species of the Baltic Sea from different functional groups (i.e. grazers, deposit and suspension feeders, and predators) in response to major environmental forcing factors (salinity, water depth and seabed substrate type). Analyses were based on the inventory data set compiled by revising the data on macrobenthic species for over 12,000 sampling events in the Baltic Sea. In addition, data on environmental variables are retrieved from the results of modelling and large-scale mapping efforts. A simple logistic regression based modelling technique was applied and the candidate model with highest discriminatory power was selected for habitat suitability mapping. Habitat suitability models allowed to satisfactorily predict the potential distribution of macrofaunal species based solely on modelled salinity, bathymetry and rough sediment class information. Our results indicated that salinity, depth and substrate type are all important in determining the distribution of most characteristic macrobenthic species on the large-scale of the whole Baltic Sea. The present exercise is only a first step. Implementation of other variables (e.g. characterizing oxygen and temperature fluctuations, total organic content, and nutrient supply) would obviously increase the model applicability. Information on the ecological potential of habitat suitability can serve as the utmost important basis for scientifically sound marine spatial planning.

Functional response traits in relation to land use change in the Montado

The socio-economic changes of the last decades have resulted in changes in traditional land uses with consequent abandonment of large farmland areas in the Mediterranean region. We assessed the response of species richness and composition, and species functional traits to decreasing land use intensity in a Montado system, an agro-pastoral system characteristic of the Alentejo, Southern Portugal. Additionally, we investigated whether plant functional types can be established based on the response to decreasing land use intensity in these systems. Consistent with previous studies, species richness decreased sharply after land abandonment, and this was associated with a strong turnover in species composition from grazed to abandoned sites as the vegetation changed from herbaceous to shrub dominated communities. Pronounced differences in functional traits were found for different successional stages. Therophyte life form, short plant height, high specific leaf area (SLA), low leaf dry matter content (LDMC) and small seeds with dispersal structures were dominant in grazed plots. Within abandoned plots, chamaephytes dominated in plots abandoned for 10–15 years and decreased in favour of nanophanerophytes in plots abandoned for 20–30 years. Plant height, LDMC and seed mass increased with abandonment time while SLA decreased. Functional response groups sufficient to describe vegetation change were identified combining life form and SLA. Therophytes with medium SLA were the dominant functional group in grazed areas, while nanophanerophytes with medium or low SLA were associated with later phases of abandonment. At intermediate stages of succession the dominant group was chamaephytes with medium SLA but functional diversity was highest as all the groups, except hemicryptophytes with medium SLA, were represented. These changes in functional composition can be translated into effects on key ecosystem properties. The increase in LDMC indicates an increase in flammability while trends in both LDMC and SLA suggest decreased decomposition, and thereby carbon and nutrient cycling. These will need to be considered in combination with consequences for other ecosystem properties for future management.

Biodiversity benefits of alley farming with old man saltbush in central western New South Wales

Agricultural production systems that also provide opportunities to conserve biodiversity will be a crucial component of integrated and sustainable land use in mixed farming landscapes and should be considered and evaluated. Alley farming is an innovative farming system that aims to increase farm profitability while also enhancing environmental outcomes. Alley farming incorporates belts of woody perennial plants such as trees or shrubs, interspersed with alleys of conventionally rotated cropping and livestock grazing land. In the present study, we assessed the impacts on terrestrial biodiversity of alley farming with the native perennial chenopod shrub old man saltbush (Atriplex nummularia Lindl.) in central western New South Wales. Terrestrial biodiversity conservation status was assessed by site surveys conducted in spring 2005, 2006 and 2007 at 15 old man salt bush alley farming sites (OMSB), 15 conventionally managed sites and three native woodland remnants in and around the Condobolin Agricultural Research and Advisory Station in the central western plains of New South Wales. Biodiversity surveys included an assessment of ‘site condition’ – a metric of biodiversity conservation status at the site scale based on measurement of 10 habitat and vegetation condition attributes, compared against benchmark values for the appropriate native ecosystems with relatively little recent anthropogenic modification. Bird surveys were also conducted to assess the diversity and abundance of birds in OMSB, conventional and remnant woodland sites in four functional response groups. Site condition was significantly higher at remnant woodland sites than at conventional farming and OMSB alley farming sites. Remnant woodland sites had greater native overstorey cover and native ground cover of forbs, more trees with hollows, presence of at least some overstorey regeneration and the presence of fallen logs. Site condition was also significantly higher at OMSB sites than at conventional sites and increased significantly across 3 years. By the third year after establishment, OMSB sites had higher native plant species richness and native mid-storey cover than did conventionally farmed sites. These attributes increased markedly over time at the OMSB sites whereas they did not increase at conventional or remnant woodland sites. Native grasses and forbs established under and around the saltbush plants, indicating that OMSB alley plantings can provide habitat for a wide range of native plant species, enhancing biodiversity values of these areas through improved structure and composition. Improved habitat condition at the OMSB sites after 3 years did not lead to a significantly higher diversity or to a higher overall abundance of birds at the OMSB than at conventional sites. Furthermore, diversity and abundance of birds at both OMSB and conventional sites remained significantly below those of remnant woodland sites. Some decliner bird species were observed using OMSB sites, but not conventional sites. Old man saltbush alley farming can provide direct on-site benefits for native biodiversity by improving the structure, function and composition of vegetation at the site or paddock scale. If proposed as a replacement to conventional crop–pasture rotation, OMSB alley farming can enhance biodiversity conservation values, and where production benefits are likely, could play an important role in the integration of production and conservation as a synergistic ‘win–win’ system in mixed farming enterprises.

Fourth-corner generation of plant functional response groups

Plant functional response groups (PFGs) are now widely established as a tool to investigate plant—environment relationships. Different statistical methods to form PFGs are used in the literature. One way is to derive emergent groups by classifying species based on correlation of biological attributes and subjecting these groups to tests of response to environmental variables. Another way is to search for associations of occurrence data, environmental variables and trait data simultaneously. The fourth-corner method is one way to assess the relationships between single traits and habitat factors. We extended this statistical method to a generally applicable procedure for the generation of plant functional response groups by developing new randomization procedures for presence/absence data of plant communities. Previous PFG groupings used either predefined groups or emergent groups i.e. classifications based on correlations of biological attributes (Lavorel et al Trends Ecol Evol 12:474–478, 1997), of the global species pool and assessed their functional response. However, since not all PFGs might form emergent groups or may be known by experts, we used a permutation procedure to optimise functional grouping. We tested the method using an artificial test data set of virtual plants occurring in different disturbance treatments. Direct trait-treatment relationships as well as more complex associations are incorporated in the test data. Trait combinations responding to environmental variables could be clearly distinguished from non-responding combinations. The results are compared with the method suggested by Pillar (J Veg Sci 10:631–640) for the identification of plant functional groups. After exploring the statistical properties using an artificial data set, the method is applied to experimental data of a greenhouse experiment on the assemblage of plant communities. Four plant functional response groups are formed with regard to differences in soil fertility on the basis of the traits canopy height and spacer length.

Interactions between herbivory and warming in aboveground biomass production of arctic vegetation.

BackgroundMany studies investigating the ecosystem effects of global climate change have focused on arctic ecosystems because the Arctic is expected to undergo the earliest and most pronounced changes in response to increasing global temperatures, and arctic ecosystems are considerably limited by low temperatures and permafrost. In these nutrient limited systems, a warmer climate is expected to increase plant biomass production, primarily through increases in shrubs over graminoids and forbs. But, the influence of vertebrate and invertebrate herbivores has been largely absent in studies investigating the effects of vegetation responses to climate change, despite the fact that herbivory can have a major influence on plant community composition, biomass and nutrient cycling. Here, we present results from a multi-annual field experiment investigating the effects of vertebrate herbivory on plant biomass response to simulated climate warming in arctic Greenland.ResultsThe results after four years of treatments did not give any clear evidence of increased biomass of shrubs in response climate warming. Nor did our study indicate that vertebrate grazing mediated any increased domination of shrubs over other functional plant groups in response to warming. However, our results indicate an important role of insect outbreaks on aboveground biomass. Intense caterpillar foraging from a two-year outbreak of the moth Eurois occulta during two growing seasons may have concealed any treatment effects. However, there was some evidence suggesting that vertebrate herbivores constrain the biomass production of shrubs over graminoids and forbs.ConclusionAlthough inconclusive, our results were likely constrained by the overwhelming influence of an unexpected caterpillar outbreak on aboveground biomass. It is likely that the role of large vertebrate herbivores in vegetation response to warming will become more evident as this experiment proceeds and the plant community recovers from the caterpillar outbreak. Due to the greater influence of invertebrate herbivory in this study, it is advisable to consider both the effect of invertebrate and vertebrate herbivores in studies investigating climate change effects on plant communities.

Relation between macroinvertebrate life strategies and habitat traits in Mediterranean salt marsh ponds (Empordà wetlands, NE Iberian Peninsula)

The influence of water permanence and high intra- and inter-annual hydrological variability on macrobenthos (organisms >1 mm) was studied using a taxonomical and a functional approach. The study was carried out in a Mediterranean salt marsh. Monthly samples of macrobenthic fauna were collected during two consecutive hydroperiods from six ponds with different water permanence (temporary, semi-permanent and permanent waters). Organisms were assigned to five functional response groups based on life-strategies according to their capacity to survive desiccation events, their dispersion capability and the necessity of water for their reproduction. Results from both approaches showed that the benthic community was more related to pond type than to intra- and inter-annual variability. The second aim was to analyse to which extent patterns in functional groups were determined by the existence of succession patterns or to environmental variability. In this sense, a clear succession pattern was not observed. In contrast, in most of the functional groups (4 out of 5), species within each functional group showed similar responses to water fluctuations. However, species of the fifth functional group, which comprised species without any particular adaptation to desiccation survival or avoidance, showed different responses to water level fluctuations.

Agonists of Toll-like Receptor 9 Containing Synthetic Dinucleotide Motifs

Oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs activate Toll-like receptor 9 (TLR9). Our previous studies have shown that ODNs containing two 5'-ends are more immunostimulatory than those with one 5'-end. In the present study, to understand the role of functional groups in TLR9 recognition and subsequent immune response, we substituted C or G of a CpG dinucleotide with 5-OH-dC, 5-propyne-dC, furano-dT, 1-(2'-deoxy-beta- d-ribofuranosyl)-2-oxo-7-deaza-8-methyl-purine, dF, 4-thio-dU, N(3)-Me-dC, N (4)-Et-dC, Psi-iso-dC, and arabinoC or 7-deaza-dG, 7-deaza-8-aza-dG, 9-deaza-dG, N(1)-Me-dG, N(2)-Me-dG, 6-Thio-dG, dI, 8-OMe-dG, 8-O-allyl-dG, and arabinoG in ODN containing two 5'-ends. Agonists of TLR9 containing cytosine or guanine modification showed activity in HEK293 cells expressing TLR9, mouse spleen, and human cell-based assays and in vivo in mice. The results presented here provide insight into which specific chemical modifications at C or G of the CpG motif are recognized by TLR9 and the ability to modulate immune responses substituting natural C or G in immune modulatory oligonucleotides.

Mapping of continuous floristic gradients in grasslands using hyperspectral imagery

Transitions between plant species assemblages are often continuous with the form of the transition dependent on the ‘slope’ of environmental gradients and on the style of self-organization in vegetation. Image segmentation can present misleading or even erroneous results if applied to continuous spatial changes in vegetation. Even methods that allow for multiple-class memberships of pixels presuppose the existence of ideal types of species assemblages that constitute mixtures—an assumption that does not fit the case of continua where any section of a gradient is as ‘pure’ as any other section like in modulations of grassland species composition. Thus, we attempted to spatially model floristic gradients in Bavarian meadows by extrapolating axes of an unconstrained ordination of species data. The models were based on high-resolution hyperspectral airborne imagery. We further modelled the distribution of plant functional response types (Ellenberg indicator values) and the cover values of selected species. The models were made with partial least squares (PLS) regression analyses. The realistic utility of the regression models was evaluated by full leave-one-out cross-validation. The modelled floristic gradients showed a considerable agreement with ground-based observations of floristic gradients ( R 2=0.71 and 0.66 for the first two axes of ordination). Apart from mapping the most important continuous floristic differences, we mapped gradients in the appearance of plant functional response groups as represented by averaged Ellenberg indicator values for soil pH ( R 2=0.76), water supply ( R 2=0.66) and nutrient supply ( R 2=0.75), while models for the cover of single species were weak. Compared to many other vegetation attributes, plant species composition is difficult to detect with remote sensing techniques. This is partly caused by a lack of compatibility between methods of vegetation ecology and remote sensing. We believe that the present study has the potential to increase compatibility as neither spectral nor vegetation information gets lost by a classifying step.

Response of forest plant species to land‐use change: a life‐history trait‐based approach

Summary Classifying species by shared functional characteristics is important if common functional response groups are to be identified among different taxa. We investigated plant traits that determine the response of forest plant species to land use changes using literature data. Sources from eight European countries and four North‐eastern American states, comprising 20 field studies yielded information on 216 forest plant species. For these species, data on 13 life history traits were collected. Trait correlation structure was similar in the European and American data‐sets and corresponded well to those described in the literature. The European and American herbs and the European graminoids were clustered into distinct emergent groups based on their plant traits. The profiles of the European and American emergent groups were similar. Herb species belonging to emergent groups characterized by low dispersability (i.e. large seeds, low fecundity, unassisted dispersal) were relatively slow colonizers. Dispersability (and not recruitment) seems to be a key factor limiting the colonization of some forest plant species. The relationship between dispersability and colonizing capacity was less clear for graminoids. A life history trait‐based approach offers good opportunities to gain insight into the mechanisms behind species response to land‐use change.

Variation in growth rate and ecophysiology among 34 grassland and savanna species under contrasting N supply: a test of functional group differences.

• We tested the hypothesis that biological trait-based plant functional groups provide sufficient differentiation of species to enable generalization about a variety of plant ecophysiological traits or responses to nitrogen (N). • Seedlings of 34 North American grassland and savanna species, representing 5 functional groups, were grown in a glasshouse in an infertile soil with or without N fertilization. • Forbs, C3 and C4 grasses, on average, had similar relative growth rates (RGR), followed in declining order by legumes and oaks, but RGR varied greatly among species within functional groups. All measured attributes differed significantly among functional groups, of these, only RGR and photosynthesis differed among functional groups in response to N. All groups, except the legumes, had significantly greater photosynthetic and respiration rates at elevated N supply. Principal components analyses and cluster analyses yielded groupings that corresponded only moderately well to the biologically based a priori functional groupings. • Variation in RGR among species and treatments was positively related to net CO2 exchange (photosynthesis and respiration) and net assimilation rate, but unrelated to leaf area ratio. Photosynthetic and respiration rates were related to tissue %N among treatments and species. Our data indicate that RGR and related traits differ among the functional groups in significant ways, but in a complex pattern that does not yield simple generalizations about relative performance, controls on RGR, or response to resource supply rate.

Structure of ground-foraging ant assemblages in relation to land-use change in the northwestern Mediterranean region

The abandonment by humans of marginal and less productive zones signifies an important change in land use in North Mediterranean agroecosystems. Human perturbations have led to a highly diversified landscape, with a mosaic made up of patches of land at different stages of succession, from cultivated fields to closed forest. Our aim here is to characterize ant assemblages and their functional groups in response to these land-use changes. This progressive abandonment results in an initial increase in ant richness and abundance, which can reach high levels if the succession proceeds as far as woodland. In terms of the ant functional groups, this land-use change implies: (1) the appearance of Subordinate Camponotini; (2) an increase in Generalized Myrmicinae, Cryptics and Cold-climate specialists in terms of ant species richness, overall abundance and, for Generalized Myrmicinae and Cryptics, an increase in abundance percentage; (3) a decrease in percentage abundance of Opportunists; (4) a progressive decrease in species richness as well as overall and percentage abundance of Hot-climate Specialists throughout the transformation from crops to woodlands; and (5) an initial increase of Dominant Dolichoderinae followed by a decrease in ant species richness, overall abundance and percentage abundance. Using the ant functional group approach for the clearly separate stages of the regeneration process is a promising method for comparing responses of ant communities to human land use.