Vegetation Matrices Research Articles

Mangroves alter predator-prey interactions by enhancing prey refuge value in a mangrove-marsh ecotone

Black mangroves (Avicennia germinans) are becoming more common along the edges of their range, potentially displacing salt marsh vegetation in transition zones such as the Texas coast in the Gulf of Mexico (USA). Consequences of this shift on trophic interactions within wetland ecosystems are largely unknown. We investigated how increasing mangrove cover might alter predator-prey interactions involving an important consumer in coastal wetlands, blue crabs (Callinectes sapidus), and one of their key prey items, penaeid shrimp (Family Penaeidae). We conducted a series of mesocosm experiments to assess predation rates and prey refuge values in artificial vegetation (AV) matrices simulating flexible marsh grasses (e.g., Spartina patens, Distichlis spicata) and rigid mangrove pneumatophores (aerial root structures). In predation experiments within each of these AV matrices, blue crabs captured 50% fewer penaeid shrimp in the rigid mangrove treatment compared to the flexible marsh treatment, and time between captures was 83% longer among the simulated pneumatophores. In a prey refuge experiment that allowed both predator and prey to move freely among the AV matrices, penaeid shrimp occupied the rigid pneumatophore matrix 30% more often than the grass matrix when blue crabs were present but had no preference when the predator was absent. This study suggests that where A. germinans and marsh grasses co-occur, the mangroves may provide superior refuge for prey items such as penaeid shrimp. Pneumatophores will likely restrict the mobility of predators such as blue crabs, resulting in lower predation efficiency. These results suggest that as mangrove stands continue to increase in cover within mangrove-marsh ecotones, there are likely to be consequences for upper trophic level dynamics.

NATIVE AND EXOTIC SPECIES OF ECONOMICALLY USED PLANTS IN THE SOUTHERN BAHIA ATLANTIC FOREST REGION

The Atlantic Forest is extremely devastated and little remains of its original cover, being a hot spot. Often in the remnants, species not yet described are found, which causes them to become extinct before they are known. Biodiversity inventories in this rich and threatened biome are important. The southern region of Bahia and the IFBA - Campus Ilheus have considerable forest area, highlighting the importance of work aimed at developing biodiversity conservation and preservation activities in these areas. Thus, it is important to know the floristic composition of this biome for a better evaluation of the existing vegetation matrices, as well as access to information about the dynamics of this forest and its local importance. The samples were collected for herborization, identification and incorporation in the UESC herbarium. Subsequently, species cataloging, illustration and morphobotanical characterization were carried out. Eleven different regions were visited, 97 plants were collected, 45 species were identified, 10 plants had only the genus and family identified, 18 were classified only as family and 20 species without identification. The illustrations served as interpretative models of the morphology of these plants. All species collected belong to the group of angiosperms, with a predominance of dicots. It can be concluded that: i) the species collected were planted randomly and are fulfilling the purpose of planting for beautification and composition of cabruca; ii) the endemic landscape of the Atlantic Forest was lost by the introduction of exotic species for ornamental or medicinal use; iii) it was found that the illustration allowed a better understanding of the diversity of shapes of the collected plants; iv) the species are more herbaceous, with sizes ranging from 20 cm to 12 m in length, some plants were characterized by inflorescences and bracts, which shows an important evolutionary aspect.

Role of benthic habitat structure and riverine connectivity in controlling the spatial distribution and ecology of estuarine fish

Estuaries are among the most productive ecosystems per unit area, but this productivity is unevenly distributed across a complex mosaic of habitats. Identifying the qualities of different habitats that influence the composition and productivity of biotic communities is fundamental to understanding the dynamics of these ecosystems. We combined field surveys, hydrological modelling and stable isotope analysis to understand the roles of habitat, hydrological connectivity, salinity and temperature in determining assemblage composition, species abundance and trophic ecology of an estuarine fish community. Hydrodynamics, vegetation matrices of macroalgae and seagrass and the presence of epiphytes on vegetation explained spatial patterns in taxonomic biodiversity, multivariate assemblage structure and the occurrence of juvenile black bream Acanthopagrus butcheri, a species that possesses ecological traits common tomany demersal estuarine fish species. Juvenile bream abundance was related to vegetation composition (particularly epiphyte presence), supporting the hypothesis that juvenile habitats that provided resources or conditions that ex - tended beyond just structure conferredmore ecological advantages. This was further evidenced by stable isotope-based estimates of basal resource contributions of epiphytes. Our findings suggest that hydrodynamic connectivity with riverine water masses acts as a coarse determinant for estuarine fish communities at large spatial scales. At smaller scales, habitat-level associations influence local abundances and the identity and importance of specific trophic resources. Coupling hydro - dynamic modellingwith natural biomarkers provides a powerful approach for assessing the spatial context of habitat use that can help resource managers prioritize monitoring and habitat preservation efforts for coastal fish communities in a changing global environment.

Leaf-deposited semi-volatile organic compounds (SVOCs): An exploratory study using GCxGC-TOFMS on leaf washing solutions

Airborne particulate matter (PM) includes semi-volatile organic compounds (SVOCs), which can be deposited on vegetation matrices such as plant leaves. In alternative to air-point measurements or artificial passive substrates, leaf monitoring offers a cost-effective, time-integrating means of assessing local air quality. In this study, leaf washing solutions from ivy (Hedera hibernica) leaves exposed during one-month at different land use classes were explored via comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS). The composition of leaf-deposited SVOCs, corrected for those of unexposed leaves, was compared against routinely monitored pollutants concentrations (PM10, PM2.5, O3, NO2, SO2) measured at co-located air monitoring stations.The first study on leaf-deposited SVOCs retrieved from washing solutions, herein reported, delivered a total of 911 detected compounds. While no significant land use (rural, urban, industrial, traffic, mixed) effects were observed, increasing exposure time (from one to 28 days) resulted in a higher number and diversity of SVOCs, suggesting cumulative time-integration to be more relevant than local source variations between sites. After one day, leaf-deposited SVOCs were mainly due to alcohols, N-containing compounds, carboxylic acids, esters and lactones, while ketones, diketones and hydrocarbons compounds gained relevance after one week, and phenol compounds after one month. As leaf-deposited SVOCs became overall more oxidized throughout exposure time, SVOCs transformation or degradation at the leaf surface is suggested to be an important phenomenon. This study confirmed the applicability of GCxGC-TOFMS to analyze SVOCs from leaf washing solutions, further research should include validation of the methodology and comparison with atmospheric organic pollutants.

<b>Floristic-structural relationships between Canga ferruginous tree communities and adjacent vegetation types

Our objective was to evaluate the floristic and structural relationships between Canga tree communities and other vegetation types inserted in the physiognomic units set, in order to test the hypothesis that these communities have unique characteristics due to their specific environmental conditions. For this, we compared the structural and floristic attributes of Canga vegetation with adjacent semideciduous seasonal forest, Savanna and ecotone areas, evaluating the similarity in its behavior. Our results demonstrate the existence of distinct relationships among vegetation types in relation to different perspectives, related to macro-scale environmental attributes and to the phytogeographic context. In general, Canga tree vegetation has its structure associated with open vegetation types, such as the Cerrado (Savanna) and its composition associated with forest vegetation types, constituted by a community with specific ecological characteristics. Our results suggest the presence of ferruginous soils as a factor that contributes to environmental and ecological heterogeneity in vegetation matrices.

Predicting Pesticide Volatility Through Coupled Above- and Belowground Multiphysics Modeling

Pesticides are applied to agricultural fields to control unwanted pests but can volatilize and be transported downwind by wind currents to create the potential for non-target organism exposure. Volatilization rates change through the growing season due to pesticide application timing, meteorological differences, and the differential flux rates from soil and vegetation matrices. Field studies quantifying pesticide volatility are expensive and cannot capture the semi-infinite parameter combinations of soil, crop, management, and meteorological conditions encountered under regional agronomic practices. A numerical approach was used to simulate pesticide dissipation above- and belowground to augment field and laboratory experimental observations. Above- and belowground physics are coupled into a single numerical tool using the COMSOL Multiphysics® software package with the current emphasis on pesticide volatility into air from soil and vegetation and resulting near field neighboring air concentrations. Comparison of simulation results against experimental observations for an insecticide (chlorpyrifos) applied to potato and alfalfa fields shows good agreement (R2 0.68–0.98). Chlorpyrifos volatility from plant surfaces drives the overall volatility within the first several days post application. The maximum volatility flux rate simulated and observed were 0.79 and 0.66 μg m−2 s−1 for the alfalfa trial and 2.72 and 2.17 μg m−2 s−1 for the potato field, respectively. This coupled multiphysics tool [computational fluid dynamics (CFD), mass transfer coefficients, and variably saturated flow in soil] can be used to estimate volatility flux rates of pesticides when little or no prior knowledge is available and for extrapolating field study observations to different and diverse scenarios.

Ecological gradients driving the distribution of four Ericaceae in boreal Quebec, Canada.

Understory species play a significant role in forest ecosystem dynamics. As such, species of the Ericaceae family have a major effect on the regeneration of tree species in boreal ecosystems. It is thus imperative to understand the ecological gradients controlling their distribution and abundance, so that their impacts can be taken into account in sustainable forest management. Using innovative analytical techniques from landscape ecology, we aimed to position, along ecological gradients, four Ericaceae found in the boreal forest of Quebec (Canada) (Rhododendron groenlandicum, Kalmia angustifolia, Chamaedaphne calyculata, and Vaccinium spp), to regionalize these species into landscape units relevant to forest management, and to estimate the relative importance of several ecological drivers (climate, disturbances, stand attributes, and physical environment) that control the species distribution and abundance. We conducted our study in boreal Quebec, over a study area covering 535,355 km2. We used data from 15,339 ecological survey plots and forest maps to characterize 1422 ecological districts covering the study region. We evaluated the relative proportion of each ericaceous species and explanatory variables at the district level. Vegetation and explanatory variables matrices were used to conduct redundancy, cluster, and variation partitioning analyses. We observed that ericaceous species are mainly distributed in the western part of the study area and each species has a distinct latitudinal and longitudinal gradient distribution. On the basis of these gradients, we delimited 10 homogeneous landscape units distinct in terms of ericaceous species abundance and environmental drivers. The distribution of the ericaceous species along ecological gradients is closely related to the overlaps between the four sets of explanatory variables considered. We conclude that the studied Ericaceae occupy specific positions along ecological gradients and possess a specific abundance and distribution controlled by the integration of multiple explanatory variables.

Edge type determines the intensity of forest edge effect on epiphytic communities

Edge effect involves microclimatic variations (light, temperature and humidity) in the forest edge that become unsuitable for organisms adapted to forest interior conditions. We speculate that under similar edge types (shrubland matrix), the pattern in the response to forest edge might be different and more hostile for epiphytes in south-oriented edges. Because different matrix types have different effects on microclimate, we hypothesized that the magnitude of the edge effects will depend on the contrast between the physiognomy of the matrix and the forest fragment. The study was carried out in central Spain and consisted of a beech fragment surrounded by different types of vegetation matrices: pine plantation (south orientation), semi-deciduous oak forest (south orientation) and shrubland (north and south orientations). For each type of edge, we established ten transects perpendicular to the edge, running 100 m into the forest patch. Data were collected from three plots placed at 5, 50 and 100 m from the beginning of each transect. The results revealed that variations in the epiphytic composition mainly showed a replacement of forest interior species with generalist light-demanding species at forest edge. Shrubs-bordered edges showed the strongest influence on epiphytic composition, with high species dissimilarity between edge and forest interior, whereas the edge effects were mitigated when the patch was surrounded by other forests. Besides, in the case of shrub-bordered edge, the dissimilarity of species composition between edge interior was higher in the south than in the north-facing edge. We conclude that the magnitude of the edge effect on epiphytic communities is modulated by the physiognomy of the surrounding matrix and the orientation of the forest edge. In the case of a hard contrast matrix, at least 100 m of an edge buffer are required for the conservation of the species with high humidity requirements. Therefore, one of the main problems affecting the loss and even disappearance of shaded species is the decreasing of the amount of core conditions under the increasing forest fragmentation scenarios. This potentially exacerbates forest fragmentation effects linked to livestock use, due to the physiognomically different surrounding matrix compared to forest patches.

염생식물을 이용한 항만 녹색공간 창출기법에 관한 연구

항만생태계 녹색공간 창출을 위해 우리나라 항만에 분포하는 식물상특성, 환경요인분석, 항만유형분석, 적합종, 최소보존면적산출을 통해 식재모식도를 작성하였다. 50개 조사지역에서 44과 174종의 관속식물이 출현하였으며, 그중 염생식물은 19과 48종이 분포하였다. 우점군락은 통보리사초, 갯그령, 좀보리사초, 갯씀바귀, 순비기나무, 갯메꽃, 해당화, 갯완두, 솔장다리, 우산잔디, 번행초, 칠면초, 해홍나물, 갯잔디, 갈대를 포함하여 15개 군락이 분포하였다. 조사지역에 분포하는 식물군락과 환경요인과의 Canonical Correspondence Analysis(CCA) 결과 Clay marsh, Sand marsh, Sand gravel marsh 유형으로 분류되었다. 생육지 유형별 적합종으로 clay marsh는 칠면초, 갈대, 갯잔디, 해홍나물 sand marsh는 갯그령, 갯씀바귀, 통보리사초, 좀보리사초 sand gravel marsh는 갯메꽃, 순비기나무가 선정되었다. 적합종에 대한 최소보전면적을 산출하고 항만생태계 세부 유형별로 가이드라인과 모식도를 작성하였다. To make conservative port and coast ecosystems and creative the greenspace, We were investigated with characteristic of flora, environmental factors, types of port, adaptive species, minimum conservation area and plantation model. In 50 sites of study areas, there are 19 families and 174 species of vascular plants and 19 families and 48 species of halophytes. Dominant communities in port ecosystem contains Carex kobomugi community, Elymus mollis community, Carex pumila community, Ixeris repens community, Vitex rutundifolia community, Calystegia soldandlla community, Rosa rugosa community, Lathyrus japonica community, Salsola komarovi community, Cynodon dactylon community, Tetragonia tetragonioides community, Suaeda japonica community, Suaeda maritima community, Zoysia sinica community and Phragmites communis community. We carried out Canonical Correspondence Analysis(CCA) for ordinations on the vegetation and plant communities-environmental variable matrices in 50 sites. The communities tended to cluster into three types: Clay marsh, Sand marsh, Sand gravel marsh types. Adaptive species in habitate types are selected that sand marsh-type communities in ports contained Elymus mollis community, Ixeris repens community, Carex kobomugi community, Carex pumila community, Clay marsh-type communities contained Suaeda japonica community, Phragmites communis community, Zoysia sinica community and Suaeda maritima community, Sand gravel marsh-type communities contained Vitex rutundifolia community, Calystegia soldandlla community. We are conducted the estimation of minimal area for plantation of adaptive plant species and carried out guide line and plantation model for creation of green space in port ecosystem.

Factors influencing wetland plant communities during a flood-drawdown cycle in the Peace-Athabasca Delta, Northern Alberta, Canada

ABSTRACT I analyzed two sets of the same 583 vegetation plots (0.25–10 m2) and 97 plant taxa sampled in 1993 and 2001 in the Peace-Athabasca Delta (PAD), northern Alberta, Canada. Cluster analyses and Bray-Curtis ordinations were used to examine relationships between environmental and biological factors and wetland community changes over a flood-drawdown cycle. While water regime was key to explaining variation in the vegetation, the vegetation gradients were complex. Vegetation structure, bison grazing, and landscape attributes such as distance to nearest major river, relative elevation, and geographic location within the PAD also played significant roles in explaining variation in the vegetation. Autocorrelations among physical and biological factors indicate that the physical and biological regimes were integrated. The importance of environmental and biological variables in explaining vegetation variation changed from pre- to post-flood. The 1993 and 2001 vegetation matrices were positively associated,...

Forest ecosystems of an Arizona Pinus ponderosa landscape: multifactor classification and implications for ecological restoration

AbstractAim We developed an ecosystem classification within a 110,000‐ha Arizona Pinus ponderosa P. & C. Lawson (ponderosa pine) landscape to support ecological restoration of these forests. Specific objectives included identifying key environmental variables constraining ecosystem distribution and comparing plant species composition, richness and tree growth among ecosystems.Location The Coconino National Forest and the Northern Arizona University Centennial Forest, in northern Arizona, USA.Methods We sampled geomorphology, soils and vegetation on 66 0.05‐ha plots in open stands containing trees of pre‐settlement (c. 1875) origin, and on 26 plots in dense post‐settlement stands. Using cluster analysis and ordination of vegetation and environment matrices, we classified plots into ecosystem types internally similar in environmental and vegetational characteristics.Results We identified 10 ecosystem types, ranging from dry, black cinders/Phacelia ecosystems to moist aspen/Lathyrus ecosystems. Texture, organic carbon and other soil properties reflecting the effects of parent materials structured ecosystem distribution across the landscape, and geomorphology was locally important. Plant species composition was ecosystem‐specific, with C3Festuca arizonica Vasey (Arizona fescue), for instance, abundant in mesic basalt/Festuca ecosystems. Mean P. ponderosa diameter increments ranged from 2.3–4.3 mm year−1 across ecosystems in stands of pre‐settlement origin, and the ecosystem classification was robust in dense post‐settlement stands.Main conclusions Several lines of evidence suggest that although species composition may have been altered since settlement, the same basic ecosystems occurred on this landscape in pre‐settlement forests, providing reference information for ecological restoration. Red cinders/Bahia ecosystems were rare historically and > 30% of their area has been burned by crown fires since 1950, indicating that priority could be given to restoring this ecosystem's remaining mapping units. Ecosystem classifications may be useful as data layers in gap analyses to identify restoration and conservation priorities. Ecosystem turnover occurs at broad extents on this landscape, and restoration must accordingly operate across large areas to encompass ecosystem diversity. By incorporating factors driving ecosystem composition, this ecosystem classification represents a framework for estimating spatial variation in ecological properties, such as species diversity, relevant to ecological restoration.

High-energy polarized-beam EDXRF for trace metal analysis of vegetation samples in environmental studies

The aim of this work was to achieve improved instrumental sensitivity and detection limits for the determination of several trace elements (Cd, Pb, As, Cu, Fe and Zn) in different vegetation species collected at two mining areas in Spain (Aran Valley and Cartagena) by using new instrumentation based on high-energy polarized-beam energy-dispersive x-ray fluorescence analysis. Cd was determined by using its Kα line, while the mutual interference of As and Pb was solved by employing selective excitation conditions with targets of different materials. The use of a standardless fundamental parameter approach (IAEA QXAS) allowed the determination of other metals in the absence of suitable certified reference materials and to compensate accurately for self-attenuation effects in the sample. The proposed methodology provides an alternative analytical tool to classical destructive analytical methods, commonly applied for the determination of these toxic elements in vegetation matrices, with accuracy and precision levels fulfilling the requirements for environmental studies. Copyright © 2006 John Wiley & Sons, Ltd.

Potentiometric determination of fluoride in geological and biological samples following pyrohydrolytic decomposition

A method for the determination of fluoride in coal, coal fly ash, phosphate rock, limestone, mineral clay, fossilised materials, oyster tissue and vegetation using pyrohydrolysis for sample decomposition is proposed. A specific apparatus was constructed and the influence of vanadium pentoxide (V 2O 5) as a catalyst for the pyrohydrolysis reaction was investigated. It was verified that V 2O 5 does not influence the release of fluoride from the vegetation, oyster tissue, coal and coal fly ash matrices analysed. However, the catalyst was necessary for the phosphate rock, fossil bone, mineral clay and limestone samples. Certified and noncertified samples were analysed using an ion selective electrode (ISE) for the analyte detection. Precise (relative standard deviation—R.S.D.<7%) and accurate (recovery in accordance to certified values) results were obtained. The limit of quantification (LOQ) of the method was 5.0 μg g −1 of fluoride using 20 mg of sample and a final dilution to 10 ml. The sample frequency was five samples per hour.

Liquid chromatography–electrospray ionization isotope dilution mass spectrometry analysis of paraquat and diquat using conventional and multilayer solid-phase extraction cartridges

The performance of alkyl-silica sorbent packed solid-phase extraction (SPE) cartridges and a mixed-mode, polymeric sorbent packed SPE cartridge (resin SPE cartridge) were evaluated for the sample preparation of paraquat and diquat in environmental water and vegetation matrices. Also the recoveries of the native and 2H-labeled paraquat and diquat were correlated to validate that the 2H-labeled species can be used for the isotopic dilution mass spectrometry (IDMS) analysis of paraquat and diquat. The results show that the extraction efficiency of alkyl-silica SPE is dependent on the carbon loading of the sorbent and deteriorates with an increasing sample pH. The resin SPE cartridge required no pH adjustment and showed excellent correlation between the native and 2H-labeled species, therefore, allowing us to develop the first liquid chromatography–electrospray ionization IDMS analytical method for the analysis of paraquat and diquat in environmental water and vegetation matrices. Method detection limits derived using standard EPA protocol were 0.2 and 0.1 μg/l for paraquat and diquat in water matrices, and 0.02 and 0.01 μg/g in vegetation matrices, respectively.

A phylogeny of the European lizard genus Algyroides (Reptilia: Lacertidae) based on DNA sequences, with comments on the evolution of the group

AbstractThe four species of Algyroides Bibron &amp; Bory, 1833 form part of the relatively plesiomorphic Palaearctic clade of lacertids comprising Lacerta and its allies. An estimate of phylogeny based on DNA sequence from parts of the 12S and 16S rRNA mitochondrial genes confirms the monophyly of the genus already suggested by several morphological features. The molecular data also indicates that relationships within the clade are: (A. nigropunctatus (A. moreoticus (A. fitzingeri, A. marchi))); this agrees with an estimate of phylogeny based on morphology that assumes the taxon ancestral to Alygroides was relatively robust in body form, and not strongly adapted to using crevices. Initial morphological evolution within Algyroides appears to involve adaptation to crypsis in woodland habitats. The most plesiomorphic form (A. nigropunctatus) is likely to have originally climbed extensively on tree boles and branches and there may have been two subsequent independent shifts to increased use of litter and vegetation matrices with related anatomical changes (A. moreoticus, A. fitzingeri), and one to increased use of crevices (A. marchi). Some members of Algyroides are strikingly similar in superficial morphology to particular species of the equatorial African genus Adolfus. This resemblance results from a combination of many shared primitive features plus a few independently acquired derived ones that are likely to give performance advantage in the relatively similar structural niches that these forms occupy. This study provides evidence that: (1) the use of a combination of molecular and morphological data may sometimes allow the estimation of ancestral anatomical features when these are otherwise unknown; (2) process considerations may permit a choice to be made in cases of character evolution where tree topology means that equally parsimonious alternatives exist; such decisions about character evolution may allow ecological shifts to be similarly assessed; (3) parallel evolution in ecological analogues may involve relatively few characters.

Influence of edaphic factors on the spatial structure of inland halophytic communities: a case study in China

Abstract. In order to understand the influence of edaphic factors on the spatial structure of inland halophytic plant communities, a 2.6 km2 study site, located on the lower fringe of the alluvial fan of the Hutubi River, in an arid region of China, was sampled and mapped. 105 patches were found to be homogeneous in species composition. Plant species and their coverage were recorded in each patch. 45 patches were randomly selected for the measurement of edaphic variables. A map with quadrat locations and boundaries of patches was digitized into a GIS and related to the vegetation and edaphic data matrices. CCA was used to evaluate the relative importance of edaphic factors in explaining the variation of the species assemblages and to identify the ecological preferences of species. The spatial structure of the communities and the main edaphic factors were analyzed using correlograms, Mantel correlograms and clustering under constraint of spatial contiguity.Gradient analysis showed that there are two distinct vegetation gradients in the study area, one of which is determined mainly by soil moisture (determined by depth to the water table), and the other by soil salinity (determined by electrical conductivity and hydrolytic alkalinity of the first soil layer). However, spatial analyses showed that at the sampling scale the halophytic communities in the study area are structured along one main spatial gradient determined by the water table level. Similar spatial autocorrelation structures between the factors related to the first soil layer and the communities, given our sampling scale, could not be detected. Our results suggest that the relative importance of the effects of different edaphic factors on the spatial structure of halophytic communities is scale‐dependent. The partitioning of species variation indicates that in addition to edaphic factors, other factors, such as biotic interactions, may play an important role in structuring these communities.

Microbiological detection and quantitation of bioactive compounds in vegetation matrix by laser light scattering

New approaches have been developed for the assessment of low levels of bioactive substances such as pesticides, organic and inorganic toxicants, as well as growth stimulating substances present in vegetation matrices. The new technology uses a laser /bacterial biossay which is capable off differentiating between various bioactive substances based on their mechanism of action, i.e., toxicity or nutritional fortification at the molecular/cellular level. The system uses a battery of isogeneic Bacillus subtilis mutant strains that were genetically constructed to respond differentially to specific toxicants. The response in terms of growth inhibition/stimulation is monitored by differential light scattering of a laser which is integrated with a computerized system that collects and analyzes the data. Making 1200 measurements on each sample set within 2 to 4 seconds, complete bioresponse data including concentration-related response is obtained on most samples within 60 min. By utilizing a non-toxic cocktail that was developed to solubilize and disperse water insoluble materials into an aqueous matrix, a number of pesticides including carbaryl, malation, chlorsulfuron, glyphosate, tributyltin, and beta-exotoxin could be assayed, specifically characterized, and their concentration directly correlated with the bioresponse of the bacterial strains. Since there was a differential response between mutant bacteria to each compound, a profile unique to each pesticide could be developed and stored in a software recognition library. Finally, the various pesticides could be detected in a vegetation matrix, e.g., citrus leaf, without using a chemical/physical extraction procedure. In addition, the effect of the leaf matrix on the bacterial response could be assessed. Thus, the laser-bacterial assay promises to be a rapid and inexpensive analytical tool for chemical assay in a complex matrix.