A comparison of the application of different waste products to a lettuce crop: Effects on plant and soil properties

A romaine-type lettuce (Lactuca sativa L.) was cultivated during three successive crop seasons in an agricultural land near the Wastewater Treatment Plant (WWTP) of Alcázar de San Juan. Four fertilization treatments were compared, including: two different organic fertilizer treatments consisting of (i) air-dried sewage sludge (SS), and (ii) municipal solid waste compost (MSWC), (iii) an inorganic treatment of commercial fertilizer (FER), and (iv) a control treatment in which no fertilizer was applied (CONT). The highest yield was observed in the SS treatment in all crop seasons. In the organic treatment plots there was an increase in macronutrients and organic matter in the soil. An accumulation of heavy metals in the soil was not observed but there was an increase in microbial population in the organic treatment plot, especially in the SS treatment plot. In plant tissue, the continued addition of fertilizers did not produce an accumulative effect of macro- and micronutrients. Low heavy metal content (Cr, Cd, Pb and Hg) was observed in all treatments and crop seasons. Microbiological content was more numerous in the first crop season in SS-treated plants, mainly in lettuce leaves but also in the soil.     

Effects of high salinity and the exogenous application of an osmolyte on growth,photosynthesis, and mineral composition in two ornamental shrubs

A greenhouse experiment was carried out to determine the growth, photosynthetic activity, and mineral composition in two ornamental shrubs [Viburnum lucidum L. (arrow-wood) and Callistemon citrinus (Curtis) Stapf. (red bottlebrush)] that had been treated or not treated with 2.5 mM glycine betaine (GB) or 5.0 mM proline (Pro). Plants were supplied with a non-salinised or salinised nutrient solution containing 200 mM NaCl. Salinity caused reductions in plant growth parameters, shoot biomass production, and net CO₂ assimilation in both species. Neither Pro nor GB were able to mitigate the adverse effects of salinity in bottlebrush, whereas GB reduced the deleterious effects of salt stress on arrow-wood, indicating a differential species-specific response to these osmolytes. The application of GB to salt-stressed arrow-wood increased apical and lateral shoot lengths, the number of leaves per plant, and shoot dry biomass by 222%, 113%, 238%, and 49%, respectively, compared to untreated or Pro-treated plants. The improved performance of salt-stressed arrow-wood plants whose roots were treated with 2.5 mM GB was attributed to partial suppression of Na uptake, higher chlorophyll concentrations, and the better nutritional status (higher K) of shoots.     

Walkability in urban landscapes: a comparative study of four large cities in China

Context

Walkability is an important element for assessing the sustainability of urban landscapes. There are increased concerns that as the world becomes more urbanized, cities become less walkable.

Objectives

We aim to develop a composite walkability index to evaluate the spatio-temporal pattern of the walkability of cities. By using the index to evaluate four major cities China, we also aim to provide policy implications.

Methods

A comprehensive walkability index is developed to integrate five aspects of the urban built environment: dwelling density, street connectivity, land-use mix, access to public transit, and flatness. Shanghai, Hangzhou, Chongqing, and Lanzhou are chosen as case studies to evaluate the spatio-temporal patterns and changes of walkability in the context of rapid urban expansion.

Results

Great variations exist among the four cities in terms of speed, scale, and locations of changes of walkability. During 2000–2010, the inner cities of Hangzhou, Chongqing, and Lanzhou and the entire cities of Shanghai and Chongqing increased their walkability index, whereas the inner city of Shanghai had decreased walkability. Furthermore, while inner cities of Shanghai and Hangzhou experienced decreased or stable walkability, the inner cities of Lanzhou and Chongqing enjoyed moderate to high increases in walkability. For inner cities, Shanghai had the highest average walkability index, whereas Lanzhou held the lowest in 2010.

Conclusions

The spatiotemporal changes in walkability seem to be closely associated with governmental policies and planning. The walkability index method can be widely implemented for any urban landscape because of its comprehensiveness, simplicity, and flexibility.

     

Protocol: a rapid and economical procedure for purification of plasmid or plant DNA with diverse applications in plant biology

Research in plant molecular biology involves DNA purification on a daily basis. Although different commercial kits enable convenient extraction of high-quality DNA from E. coli cells, PCR and agarose gel samples as well as plant tissues, each kit is designed for a particular type of DNA extraction work, and the cost of purchasing these kits over a long run can be considerable. Furthermore, a simple method for the isolation of binary plasmid from Agrobacterium tumefaciens cells with satisfactory yield is lacking. Here we describe an easy protocol using homemade silicon dioxide matrix and seven simple solutions for DNA extraction from E. coli and A. tumefaciens cells, PCR and restriction digests, agarose gel slices, and plant tissues. Compared with the commercial kits, this protocol allows rapid DNA purification from diverse sources with comparable yield and purity at negligible cost. Following this protocol, we have demonstrated: (1) DNA fragments as small as a MYC-epitope tag coding sequence can be successfully recovered from an agarose gel slice; (2) Miniprep DNA from E. coli can be eluted with as little as 5 μl water, leading to high DNA concentrations (>1 μg/μl) for efficient biolistic bombardment of Arabidopsis seedlings, polyethylene glycol (PEG)-mediated Arabidopsis protoplast transfection and maize protoplast electroporation; (3) Binary plasmid DNA prepared from A. tumefaciens is suitable for verification by restriction analysis without the need for large scale propagation; (4) High-quality genomic DNA is readily isolated from several plant species including Arabidopsis, tobacco and maize. Thus, the silicon dioxide matrix-based DNA purification protocol offers an easy, efficient and economical way to extract DNA for various purposes in plant research.     

Diel leaf growth of soybean: a novel method to analyze two-dimensional leaf expansion in high temporal resolution based on a marker tracking approach (Martrack Leaf)

Background

We present a novel method for quantitative analysis of dicot leaf expansion at high temporal resolution. Image sequences of growing leaves were assessed using a marker tracking algorithm. An important feature of the method is the attachment of dark beads that serve as artificial landmarks to the leaf margin. The beads are mechanically constricted to the focal plane of a camera. Leaf expansion is approximated by the increase in area of the polygon defined by the centers of mass of the beads surrounding the leaf. Fluctuating illumination conditions often pose serious problems for tracking natural structures of a leaf; this problem is circumvented here by the use of the beads.

Results

The new method has been used to assess leaf growth in environmental situations with different illumination conditions that are typical in agricultural and biological experiments: Constant illumination via fluorescent light tubes in a climate chamber, a mix of natural and artificial illumination in a greenhouse and natural illumination of the situation on typical summer days in the field. Typical features of diel (24h) soybean leaf growth patterns were revealed in all three conditions, thereby demonstrating the general applicability of the method. Algorithms are provided to the entire community interested in using such approaches.

Conclusions

The implementation Martrack Leaf presented here is a robust method to investigate diel leaf growth rhythms both under natural and artificial illumination conditions. It will be beneficial for the further elucidation of genotype x environment x management interactions affecting leaf growth processes.

     

Dry-matter partitioning in a tomato crop: Comparison of two simulation models

SUMMARY

TOMSIM(l.O) and TOMGRO(I.O) are two dynamic models for tomato growth and development. Their sub-models for dry-matter distribution between leaves, stem and fruits were compared and discussed. In both models the simulated dry-matter distribution is regulated by the relative sink strengths of the plant organs. These sink strengths are quantified by the potential growth rates of individual organs, i.e. the growth rates under conditions of non-limiting assimilate supply. This approach is general and not limited to the tomato crop. In TOMGRO(J.O), fruits, leaves and internodes stay within age classes and move from class to class during development, whereas in TOMSIM (1.0), record is kept of every fruit truss separately but leaves and internodes are lumped together (i.e. no record of weight or leaf area per age class as in TOMGRO(l.O)). In TOMSIM(1.0), vegetative sink strength is a constant, whereas in TOMGRO(l.0) it is calculated from potential area expansion rate of leaves and specific leaf area. In both models, the ratio between leaf growth and stem growth is constant. In TOMGRO(l.O) there is a feed-back mechanism which controls the vegetative/generative balance: a higher demand/supply ratio for assimilates induces higher fruit abortion rates. In TOMSIM(l.O) the number of fruits set per truss is not simulated, but is an input to the model. TOM SIM (1.0) functions representing flowering rate, fruit growth period, vegetative sink strength and fruit sink strength were compared with similar TOMGRO(l.O) functions, in their dependence on temperature and physiological plant age. A sensitivity analysis was made for the effects of temperature, flowering rate, and fruit and vegetative sink strengths on dry-matter distribution for both models. A validation of both models was based upon periodic destructive harvests in: 1) a greenhouse experiment in Wageningen, using a round tomato cultivar, consisting of a control treatment and a treatment where every second truss was removed at anthesis, and 2) two greenhouse experiments conducted in Montfavet, using a beefsteak tomato cultivar. Daily shoot dry-weight increase, average 24 h greenhouse temperatures and numbers of fruits set per truss (in TOMGRO(l.O) numbers of flowers per truss) were inputs to the models. In general dry-matter distribution was simulated well by both models for the cultivar and conditions where they were developed. TOMGRO(1.0)'s poor performance in one of the validations resulted from the absence of an assimilate storage pool. To achieve reasonable agreement between measurements and simulations for situations other than where the models were developed, parameter adjustments had to be made, most likely reflecting cultivar differences. Strong and weak points of both models are discussed.     

Dry-matter production in a tomato crop: comparison of two simulation models

TOMSIM(l.O) and TOMGRO(l.O) are two dynamic models for tomato growth and development. Their submodels for dry matter production are compared and discussed. In TOMSIM(l.O), dry matter production is simulated by a modified version of SUCROS87 (Spitters et al., 1989). Single leaf photosynthesis rates are calculated separately for shaded and sunlit leaf area at different depths in the canopy, according to the direct and diffuse components of light; daily crop gross assimilation rate (A) is computed by integration of these rates over the different depths and over the day. In TOMSIM(l.O) leaf photochemical efficiency (e) and potential leaf gross photosynthesis rate at saturating light level (Pgmax) both depend on temperature and C02 level. In TOMGRO(l.O) crop gross photosynthesis rate is calculated by the equation of Acock et al. (1978); e is a constant and Pg max is a linear function of C02. In both models leaf photosynthesis characteristics are assumed to be identical in the whole canopy. Maintenance respiration (Rm) and conversion efficiency (Cf) are taken into account in the same way, except that root maintenance respiration is neglected in TOMGRO(l.O). For both models a sensitivity analysis was performed on the input variables (light intensity, temperature, C02 and leaf area index (LAI)) and on some of the model parameters. Under most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(l.O) than in TOMGRO(l.O). At temperatures above 18°C Rm was also higher in TOMSIM(l.O), and C, was 4% higher in TOMGRO(l.O). The two models were very sensitive to changes in e and to a lesser extent to changes in the light extinction coefficient, whereas the scattering coefficient of leaves had hardly any effect on the simulated A. TOMGRO(l.O) appeared to be rather sensitive to the C02 use efficiency, whereas at ambient C02 level mesophyll resistance was quite important in TOMSIM(l.O). Four sets of experimental data (differences in cultivar, C02 enrichment and planting date) from Wageningen (The Netherlands) and Montfavet (southern France) were used to validate the models. Average 24 h temperature and average daily C02 concentration values were used as input to the models. For the Wageningen experiments, hourly PAR values were calculated from the daily global radiation sum by TOMSIM(l.O) and used as input in both models. For the Montfavet experiment, average hourly PAR measurements were used. Also measured LAI, dry matter distribution and organ dry weights (for calculation of Rm) were input to the simulation. In the Wageningen experiments, total dry matter production was simulated reasonably well by both models, whereas in the Montfavet experiment an under-estimation of about 35% occurred. TOMGRO(l.O) and TOMSIM(l.O) simulated almost identical curves in all four experiments. Strong and weak points of both models are discussed.     

RhizoTubes as a new tool for high throughput imaging of plant root development and architecture: test,comparison with pot grown plants and validation

Background

In order to maintain high yields while saving water and preserving non-renewable resources and thus limiting the use of chemical fertilizer, it is crucial to select plants with more efficient root systems. This could be achieved through an optimization of both root architecture and root uptake ability and/or through the improvement of positive plant interactions with microorganisms in the rhizosphere. The development of devices suitable for high-throughput phenotyping of root structures remains a major bottleneck.

Results

Rhizotrons suitable for plant growth in controlled conditions and non-invasive image acquisition of plant shoot and root systems (RhizoTubes) are described. These RhizoTubes allow growing one to six plants simultaneously, having a maximum height of 1.1 m, up to 8 weeks, depending on plant species. Both shoot and root compartment can be imaged automatically and non-destructively throughout the experiment thanks to an imaging cabin (RhizoCab). RhizoCab contains robots and imaging equipment for obtaining high-resolution pictures of plant roots. Using this versatile experimental setup, we illustrate how some morphometric root traits can be determined for various species including model (Medicago truncatula), crops (Pisum sativum, Brassica napus, Vitis vinifera, Triticum aestivum) and weed (Vulpia myuros) species grown under non-limiting conditions or submitted to various abiotic and biotic constraints. The measurement of the root phenotypic traits using this system was compared to that obtained using “classic” growth conditions in pots.

Conclusions

This integrated system, to include 1200 Rhizotubes, will allow high-throughput phenotyping of plant shoots and roots under various abiotic and biotic environmental conditions. Our system allows an easy visualization or extraction of roots and measurement of root traits for high-throughput or kinetic analyses. The utility of this system for studying root system architecture will greatly facilitate the identification of genetic and environmental determinants of key root traits involved in crop responses to stresses, including interactions with soil microorganisms.

     

Influence of forest cover on in-stream large wood in an agricultural landscape of southeastern Brazil: a multi-scale analysis

Large wood (LW) is critical to the structure and function of streams and forests are the main LW source to stream channels. To assess the influence of forest cover changes at different spatial scales on in-stream LW quantity, we selected eighteen catchments (2nd–4th order) in Southeastern Brazil with forests at different levels of alterations. In each catchment we quantified the pattern of forest cover (% cover and relative catchment position), the physical characteristics of catchments (elevation and slope), the characteristics of channels (wetted channel width and depth), the abundance and volume of in-stream LW, and the frequency of LW pools. We used simple and multiple linear regression to assess the response of LW variables to landscape and stream reach variables. Most of the LW was relatively small; 72 % had a diameter <20 cm, and 66 % had a length <5 m. Although percent forest cover at reach scale had substantial support to explain LW variables, the best predictors of LW variables were forest cover at broader scales (LW abundance and LW pool frequency were best predicted by forest at intermediate distance at the catchment scale and LW volume was best predicted by forest cover at the drainage network scale), suggesting that downstream transport is an important process in addition to local processes in our study area. These findings have important management implications because although low forested reaches receive less LW from local forests (or no LW in the case of deforested stream reaches), they are receiving LW from upstream forested reaches. However, the material is generally small, unstable and likely to be easily flushed. This suggests that not only should riparian forest conservation encompass the full drainage network, but forests should also be allowed to regenerate to later successional stages to provide larger, higher quality LW for natural structuring of streams.     

Integration of invasion ecology theories into the analysis of designed plant communities: a case study in Southern Germany

Theories regarding the establishment and persistence of self-naturalising alien species can help in interpreting these processes in designed plant communities with their combination of exotic species and native plant communities. Thus, they may provide a theoretical basis for this kind of landscape design. A case study investigated the influence of plant community conditions (invasibility), species-specific traits (invasiveness), and gap diameter size on the establishment of selected North American prairie forbs in Central European horticultural meadows. Experimental sites were located in Freising, Bavaria. Introduced forbs included Aster laevis, Aster novae-angliae, Aster x salignus, and Aster x versicolor. Establishment success was measured as survival rate and total aboveground dry biomass. Invasibility of the investigated horticultural meadows was strongly related to resource availability, as most influences of plant community traits could ultimately be attributed to this factor. Leaf area and specific leaf area above canopy height of the resident meadow species appear to be the traits that best explained differences in establishment success of the Asters. Gap size influenced species performance mainly on the less productive site, again due to higher availability of resources in the larger gaps. These results are consistent with findings of studies on self-naturalising alien species. By applying this interdisciplinary approach, valuable insights in the functioning of designed plant communities could be gained. Horticultural meadows can be one important tool in designing the highly dynamic urban landscape. In choosing suitable sites, resource availability should be strongly considered.     

Protocol: high throughput silica-based purification of RNA from Arabidopsis seedlings in a 96-well format

Background

The Arabidopsis thaliana-Pseudomonas syringae model pathosystem is one of the most widely used systems to understand the mechanisms of microbial pathogenesis and plant innate immunity. Several inoculation methods have been used to study plant-pathogen interactions in this model system. However, none of the methods reported to date are similar to those occurring in nature and amicable to large-scale mutant screens.

Results

In this study, we developed a rapid and reliable seedling flood-inoculation method based on young Arabidopsis seedlings grown on MS medium. This method has several advantages over conventional soil-grown plant inoculation assays, including a shorter growth and incubation period, ease of inoculation and handling, uniform infection and disease development, requires less growth chamber space and is suitable for high-throughput screens. In this study we demonstrated the efficacy of the Arabidopsis seedling assay to study 1) the virulence factors of P. syringae pv. tomato DC3000, including type III protein secretion system (TTSS) and phytotoxin coronatine (COR); 2) the effector-triggered immunity; and 3) Arabidopsis mutants affected in salicylic acid (SA)- and pathogen-associated molecular pattern (PAMPs)-mediated pathways. Furthermore, we applied this technique to study nonhost resistance (NHR) responses in Arabidopsis using nonhost pathogens, such as P. syringae pv. tabaci, pv. glycinea and pv. tomato T1, and confirmed the functional role of FLAGELLIN-SENSING 2 (FLS2) in NHR.

Conclusions

The Arabidopsis seedling flood-inoculation assay provides a rapid, efficient and economical method for studying Arabidopsis-Pseudomonas interactions with minimal growth chamber space and time. This assay could also provide an excellent system for investigating the virulence mechanisms of P. syringae. Using this method, we demonstrated that FLS2 plays a critical role in conferring NHR against nonhost pathovars of P. syringae, but not to Xanthomonas campestris pv. vesicatoria. This method is potentially ideal for high-throughput screening of both Arabidopsis and pathogen mutants.     

A new approach to varietal identification in plants by microsatellite high resolution melting analysis: application to the verification of grapevine and olive cultivars

Background  

Microsatellites are popular molecular markers in many plant species due to their stable and highly polymorphic nature. A number of analysis methods have been described but analyses of these markers are typically performed on cumbersome polyacrylamide gels or more conveniently by capillary electrophoresis on automated sequencers. However post-PCR handling steps are still required. High resolution melting can now combine detailed sequence analysis with the closed-tube benefits of real-time PCR and is described here as a novel way to verify the identity of plant varieties such as grapevine and olive.     

Distinguishing between human-induced and climate-driven vegetation changes: a critical application of RESTREND in inner Mongolia

Changes in the spatiotemporal pattern of vegetation alter the structure and function of landscapes, consequently affecting biodiversity and ecological processes. Distinguishing human-induced vegetation changes from those driven by environmental variations is critically important for ecological understanding and management of landscapes. The main objectives of this study were to detect human-induced vegetation changes and evaluate the impacts of land use policies in the Xilingol grassland region of Inner Mongolia, using the NDVI-based residual trend (RESTREND) method. Our results show that human activity (livestock grazing) was the primary driver for the observed vegetation changes during the period of 1981?C2006. Specifically, vegetation became increasingly degraded from the early 1980s when the land use policy??the Household Production Responsibility System??led to soaring stocking rates for about two decades. Since 2000, new institutional arrangements for grassland restoration and conservation helped curb and even reverse the increasing trend in stocking rates, resulting in large-scale vegetation improvements in the region. These results suggest that most of the degraded grasslands in the Xilingol region can recover through ecologically sound land use policies or institutional arrangements that keep stocking rates under control. Our study has also demonstrated that the RESTREND method is a useful tool to help identify human-induced vegetation changes in arid and semiarid landscapes where plant cover and production are highly coupled with precipitation. To effectively use the method, however, one needs to carefully deal with the problems of heterogeneity and scale in space and time, both of which may lead to erroneous results and misleading interpretations.     

The impact of urban expansion on the regional environment in Myanmar: a case study of two capital cities

Context

This study examines the spatio-temporal patterns of urban expansion for Yangon and Nay Pyi Taw, the former and new national capitals of Myanmar, and its impact on the regional environment between 2000 and 2013.

Objectives

The objective is to examine different driving forces of urban expansion for Yangon and Nay Pyi Taw, and their environmental consequences during Myanmar’s transitional economy.

Methods

Classified time-series Landsat images are used to evaluate urban expansion processes. Environmental parameters being evaluated in this study include five sets of remotely sensed MODIS land products that are land surface temperature (LST), percent tree cover (PTC), evapotranspiration (ET), terrestrial ecosystem net primary productivity (NPP), and aerosol optical depth (AOD). A time-series trend analysis technique is used to examine the environmental consequences.

Results

The built-up areas in Nay Pyi Taw and Yangon exhibit exponential and polynomial increase, respectively. A 1% increase of built-up area could potentially cause an increase of daytime LST of 0.7 °C, a PTC loss of 2.3%, a decrease in NPP of 34.3 kg/m², and an ET decrease of 42.2 mm for Yangon. Similarly, for Nay Pyi Taw, a 1% increase in built-up area could potentially cause a daytime LST increase of 0.3 °C, a nighttime LST increase of 0.06 °C, a PTC loss of 2.5%, a decrease in NPP of 15.1 kg/m², and a decrease of 19.2 mm ET. No significant change was observed for AOD for either city.

Conclusions

Both cities have experienced extensive urban expansion but with different spatial and temporal characteristics, and their effects on the regional environment are different. Urban expansion of Nay Pyi Taw mainly was government-induced municipal infrastructure development. Yangon’s expansion is mainly caused by population pressure and migration from rural areas. The urban expansion in Yangon was mainly due to reconstruction and renovation, as well as infill development during the study period.

     

How key habitat features influence large terrestrial carnivore movements: waterholes and African lions in a semi-arid savanna of north-western Zimbabwe

Within a landscape where prey has an aggregated distribution, predators can take advantage of the spatial autocorrelation of prey density and intensify their search effort in areas of high prey density by using area-restricted search behaviour. In African arid and semi-arid savannas, large herbivores tend to aggregate around scarce water sources. We tested the hypothesis that water sources are a key determinant of habitat selection and movement patterns of large free-ranging predators in such savannas, using the example of the African lion. We used data from 19 GPS radio-collared lions in Hwange National Park, Zimbabwe. Maps of lions’ trajectories showed that waterholes are key loci on the lions’ route-maps. Compositional analyses revealed that lions significantly selected for areas located within 2 km of a waterhole. In addition, analysis of lions’ night paths showed that when lions are close to a waterhole (<2 km), they move at lower speed, cover shorter distances per night (both path length and net displacement) and follow a more tortuous path (higher turning angle, lower straightness index and higher fractal dimension) than when they are further from a waterhole. Hence, our results strongly suggest that lions adopt area-restricted searching in the vicinity of waterholes, and reduce their search effort to minimize the time spent far from a waterhole. They provide an illustration of how key habitat features that determine the dispersion of prey (e.g. waterholes in this study) have an influence on the spatial ecology and movement patterns of terrestrial predators.     

Plant establishment on a green roof under extreme hot and dry conditions: The importance of leaf succulence in plant selection

Plant selection for extensive green roofs has largely been based on cool, temperate climate research. However, as green roof implementation in hotter and drier climates increases, there is a need to evaluate plant performance under these climatic conditions. Succulents have been shown to be successful in hot and dry green roofs, although survival differs between species and the role of leaf succulence in survival has not been fully explored. For non-succulent plants, habitats with conditions similar to green roofs (‘habitat templates’) have been used to select plants, although few studies have discussed the performance of these selections under green roof conditions. Therefore, we evaluated establishment of 32 plant species on an unirrigated extensive (125 mm deep) green roof in Melbourne, Australia over a 42 week period (from winter through summer into autumn). Plants were selected on the basis of life-form, succulence, appropriate habitat templates and/or successful use on green roofs internationally. Climatic conditions during the experiment were often extreme, with evaporation regularly exceeding rainfall and a hot and dry summer (mean maximum air temperature 35 °C and 80.6 mm total rainfall), leading to roof temperatures of 65 °C. After 42 weeks, only succulent plants remained alive and only three of the succulent species had 100% survival. Survival was positively related to the degree of leaf succulence (g H₂O leaf area cm⁻¹) making this a useful trait for plant selection for unirrigated green roofs in hot, dry climates. The failure of most species, despite being chosen from appropriate habitats, demonstrates the need to evaluate potential plants on green roofs under extreme climatic conditions. Supplementary irrigation may be essential to sustain non-succulent species during extreme weather in hot and dry climates.     

Modelling the impacts of agriculture in mixed-use landscapes: a review and case study involving two species of dabbling ducks

Context

This study synthesizes evidence from three separate surveys of American Black Duck and Mallard breeding habitat usage to quantify the effects of agriculture at the landscape scale.

Objectives

To assess duck breeding activity in agricultural landscapes within the Canadian maritimes in order to measure the overall impact of agricultural land use, the response to particular agricultural activities, and the influence of landscape configuration.

Methods

Models, constructed using a long-term census (SURVEY1), were used to predict habitat selection for two other independent surveys (SURVEY2, SURVEY3). Predictions incorporated information about wetland area and diversity, as well as anthropogenic factors, allowing subsequent analyses to focus on the remaining residual error attributable to agricultural effects.

Results

SURVEY2 results demonstrated that the proportion of active agriculture is an important indicator of the severity of human disturbance, yielding threshold estimates of 39% for Mallards and 60% for Black Ducks, with an overall average of 50%. Agricultural conversion beyond these thresholds deterred breeding ducks independently of other factors. SURVEY3 land cover information demonstrated that the presence of cropland intensified this deterrence effect, even at levels as low as 10%. Woodland cover (in excess of 30%) was important for both species, but its configuration was not.

Conclusions

In addition to quantifying threshold effects, this study reaffirms that woodland is an important part of the maritime landscape matrix, and contributes positively to habitat diversity in mixed use, moderate intensity agricultural regions. Wetland restoration in agricultural landscapes should monitor and promote less crop-intensive, mixed-use practices.