Effects of interactive scale-dependent variables on beetle diversity patterns in a semi-arid agricultural landscape

Understanding species-diversity patterns in heterogeneous landscapes invites comprehensive research on how scale-dependent processes interact across scales. We used two common beetle families (Tenebrionidae, detrivores; Carabidae, predators) to conduct such a study in the heterogeneous semi-arid landscape of the Southern Judean Lowland (SJL) of Israel, currently undergoing intensive fragmentation. Beetles were censused in 25 different-sized patches (500–40,000 m²). We used Fisher’s α and non-parametric extrapolators to estimate species diversity from 11,125 individuals belonging to 56 species. Patch characteristics (plant species diversity and cover, soil cover and degree of stoniness) were measured by field transects. Spatial variables (patch size, shape, physiognomy and connectivity) and landscape characteristics were analyzed by GIS and remote-sensing applications. Both patch-scale and landscape-scale variables affected beetle species diversity. Path-analysis models showed that landscape-scale variables had the strongest effect on carabid diversity in all patches. The tenebrionids responded differently: both patch-scale and landscape-scale variables affected species diversity in small patches, while mainly patch-scale variables affected species diversity in large patches. Most of the paths affected species diversity both directly and indirectly, combining the effects of both patch-scale and landscape-scale variables. These results match the biology of the two beetle families: Tenebrionidae, the less mobile and more site-attached family, responded to the environment in a fine-grained manner, while the highly dispersed Carabidae responded to the environment in a coarse-grained manner. We suggest that understanding abiotic and biotic variable interactions across scales has important consequences for our knowledge of community structure and species diversity patterns at large spatial scales.     

The scale of landscape effect on seed dispersal depends on both response variables and landscape predictor

Landscape Ecology - Landscape structure can affect seed dispersal, but the spatial scale at which such effect is maximized (scale of effect, SoE) is unknown. We assessed patterns and predictors of...     

Multi-scale effects of landscape complexity and crop management on pollen beetle parasitism rate

Improving our understanding about how natural enemies respond to semi-natural habitats and crop management scattered in the landscape may contribute to the development of ecologically based pest management strategies maximising biological control services. We investigated how soil tillage and semi-natural habitats influenced the parasitism rates of pollen beetle (Meligethes aeneus F.) larvae at 8 different spatial scales (from 250 to 2000 m radius circular sectors) in 42 oilseed rape (OSR) fields. We used multimodel inference approaches to identify and rank the influence of soil tillage and semi-natural habitats on parasitism rates, and to quantify the importance of each scale. Parasitism rates were due to three univoltine parasitoid species (Tersilochus heterocerus, Phradis morionellus and P. interstitialis) and varied from 0 to 98%. We found that both fine and large scales contributed to explain significantly parasitism rates, indicating that biological control of pollen beetle is a multi-scale process. At the 250 m scale, parasitism rates of T. heterocerus were positively related to the proportion of semi-natural habitats and the proximity to previous year OSR fields. At large scales (1500 to 2000 m), parasitism rates of T. heterocerus were positively related to semi-natural habitats and negatively related to the proportion of previous year OSR fields with conventional soil tillage. Parasitism rates of Phradis spp. were only positively related to the proportion of semi-natural habitats at the 1250 and 1500 m scales. These multi-scale effects are discussed in relation to the influence of semi-natural habitats and soil tillage on parasitoid populations and their movement behaviours within the landscape.     

Organic farming affects the biological control of hemipteran pests and yields in spring barley independent of landscape complexity

Context

Hemipteran pests cause significant yield losses in European cereal fields. It has been suggested that local management interventions to promote natural enemies are most successful in simple landscapes that are dominated by large arable fields.

Objectives

We study how farming category (conventional, new and old organic fields) and landscape complexity affect pests, natural enemies and biological control services in spring barley. We further analyse if yields are related to pest infestation or biological control services.

Methods

The amount of pasture and the length of field borders were used to define landscape complexity around barley fields in Southern Sweden. Arthropods were sampled with an insect suction sampler and predation and parasitism services were estimated by field observations and inspections of pest individuals.

Results

Pest infestation was affected by landscape complexity, with higher aphid, but lower leafhopper numbers in more complex landscapes. Aphid predation was higher under organic farming and affected by effects on predator abundance and community composition independent of landscape complexity. Auchenorrhyncha parasitism was neither significantly affected by landscape complexity nor by farming category. Higher aphid predation rates and lower aphid densities were characteristic for organically managed fields with higher barley yields.

Conclusions

Our results suggest that it is possible to increase both aphid biological control services and barley yield via local management effects on predator communities independent of landscape complexity. However, the success of such management practices is highly dependent on the pest and natural enemy taxa and the nature of the trophic interaction.

     

Effects of landscape structure on avian-mediated insect pest control services: a review

Context

Despite increasing evidence that landscape composition and configuration strongly influence the community structure of potential pest-regulators, landscape structure has seldom been explicitly linked with the rate and magnitude of pest-control services.

Objectives and methods

We conducted a systematic literature review evaluating 158 relevant studies to: (1) characterize our existing understanding of the empirical relationships between landscape structure and avian-mediated insect pest control services in agricultural systems, (2) identify gaps in our current understanding, and (3) develop a conceptual model of landscape structural influences on avian-mediated pest control.

Results and discussion

We found on-farm pest suppression by birds was often higher in landscapes with higher native habitat cover, higher compositional heterogeneity, and in agricultural patches in closer proximity to native habitats. We identified more than 200 bird species that provide pest control services across both temperate and tropical regions. While most avian predators are habitat-generalist species, a substantial fraction of pest control services in tropical regions was mediated by habitat-dependent species, suggesting a link between conservation management and maintenance of pest control services. We identified a three-part research agenda for future investigations of the relationships between landscape structure and avian-mediated pest control, focusing on an improved understanding of mechanisms related to: (1) predator–prey interactions and landscape modulation of trophic relationships, (2) bird dispersal ability and landscape connectivity, and (3) cross-habitat spillover of habitat-dependent avian predators.

Implications

These findings can be applied to efforts to manage and design landscapes capable of supporting both biodiversity and ecosystem services.

     

Effect of growing medium water content on the biological control of root pathogens in a closed soilless system

Summary

The water content of the growing medium and its interaction with a biocontrol agent was studied in a closed soilless culture system in order to identify factors that could increase the efficiency and decrease the variability of biocontrol agents. Pumice was chosen as the growing medium because of its high water-holding capacity and in view of the high water content required for the growth of the root pathogen. The commercial biocontrol agent Binab T (active strains Trichoderma polysporum and T. harzianum) was evaluated at 50% and 70% water content. Studies were carried out in a controlled environment, in a climate chamber, using tomato as the model plant and Pythium ultimum as the model pathogen. Pathogen levels were affected by the water content of the medium and the biocontrol treatment, while the amount of biocontrol agent was not affected by the water content of the growing medium. The Trichoderma strains in Binab T were able to reduce the amount of pathogen and the incidence of disease at both water contents tested. The biocontrol activity of Binab T against P. ultimum, as indicated by the level of glucanase production, was affected by variations in the water content of the growing medium. The pathogen, the biocontrol agent, and the water content of the growing medium, all had an impact on the microbial communities resident in the system.     

Effect of landscape and population variables on immune response in experimentally introduced bush-cricket populations

Despite the growing interest in relationships between ecological variables and individual immune function, few empirical data have been available from wild populations. In this study, I assayed the immune response from 370 wild-caught bush-crickets, Metrioptera roeseli, from 20 experimentally introduced populations, by measuring individual encapsulation responses to a surgically implanted nylon monofilament. Bush-crickets descended from populations introduced into larger habitat patches showed a greater immune response when compared to individuals from smaller habitat-area introductions. Also, there was a significant positive correlation between immune response and the amount of linear elements at the introduction site. However, there was a lack of effect of population variables (i.e., propagule size and rate of population growth) on immune response. These results suggest that large-scale environmental parameters, such as patch size and connectivity, can be important for an individual’s physiological health and its ability to defend against disease-causing agents. Such effects are likely to compound the negative impacts associated with isolation of sub-populations and habitat fragmentation.     

Effects of an early mass-flowering crop on wild bee communities and traits in power line corridors vary with blooming plants and landscape context

Landscape Ecology - Power line corridors have been repeatedly assessed as habitat for wild bees; however, few studies have examined them as bee habitat relative to nearby crop fields and...     

The influence of landscape relative to site and patch variables on primate distributions in the Colombian Llanos

Context

Primates are an important component of biodiversity in tropical regions. However, many studies on the effects of habitat change on primates ignore the relative influence of landscape composition and configuration.

Objectives

This study addresses the question: how important are landscape-scale forest area and composition relative to patch-scale (1–1080 ha) and site-scale (transect of 1 km) habitat variables for the occupancy and abundance of four primate species in the Colombian Llanos.

Methods

Using a randomly stratified survey design, 81 fragments were surveyed for primate occupancy and abundance. We used zero-inflated models to test the relative influence of landscape-scale, patch-scale and site-scale variables on occupancy and abundance for each species. A 95% confidence set of models was constructed using the cumulative Akaike weight for each model and the relative importance of each set of variables calculated for each primate species.

Results

Occupancy was determined by a combination of site-scale, patch-scale and landscape-scale variables but this varied substantially among the primate species.

Conclusion

Our study highlights the importance of managing primates at a range of scales that considers the relative importance of site-, patch- and landscape-scale variables.

     

施用生物质炭对土壤肥力和作物生长的影响

生物质炭是近年来被农业与环境等领域关注的物质,因其有机碳含量高且稳定性强,比表面积较大,负电荷及电荷密度较高,对土壤养分的吸附能力较强,能够提高土壤有机碳含量,改善土壤理化性状,被众多学者推荐为能同时满足农田固碳和增加土壤养分的改良剂。文章总结了生物质炭对土壤结构、土壤肥力和作物产量等方面的研究进展,对需要进一步研究的问题进行讨论。     

The impacts of historical land-use and landscape variables on hollow-bearing trees along an urbanisation gradient

Hollow-bearing trees provide habitat for diverse taxonomic groups and as such they are recognised for their importance globally. There is, however scant reference to this resource relative within urban forest patches. The functional ecology of habitat remnants along an urbanisation gradient plays an important ecological, social and economic role within urban landscapes. Here we quantify the impacts of urbanisation, landscape, environmental, disturbance (past and present) and stand variables on hollow-bearing tree density within urban forest patches. This was undertaken by surveying 45 forest patches on the Gold Coast, south-east Queensland, Australia. Sites were categorised as; urban, peri-urban or rural along an urbanisation gradient, with an additional five control sites. Historical logging practices were found to be the driving factor influencing hollow-bearing tree density along the urbanisation gradient; while the impacts of urbanisation itself are not as yet discernible. These findings highlight the significance of incorporating historical land use practise into current and future urban planning, as these will have continuing impacts on remaining urban biodiversity values. These findings, will benefit natural resource managers and urban planners when making decisions about where and how best to manage for hollow-bearing trees along urbanisation gradients.     

喷施蔗糖对菜薹营养品质及产量的影响

为提高菜薹的营养价值、改善其综合品质,以菜薹‘油绿501’为试材,采用叶面喷施的方式,探究不同浓度的外源蔗糖溶液处理对菜薹营养品质及产量的影响。结果表明,质量浓度为0.1 g·L~(-1)和0.2 g·L~(-1)的蔗糖处理均能显著提高菜薹中可溶性糖含量,0.2 g·L~(-1)和0.4 g·L~(-1)的蔗糖处理均能显著提高其总酚、芥子油苷、花青素含量,且二者间促进效果差异不显著;不同浓度的蔗糖处理对菜薹单株产量的影响不显著。因此,在生产中可采用质量浓度为0.2 g·L~(-1)的蔗糖溶液喷施菜薹幼苗,提高其营养价值。     

The relative importance of local versus landscape variables on site occupancy in bats of the Brazilian Cerrado

Context

Species site-occupancy patterns may be influenced by habitat variables at both local and landscape scales. Although local habitat variables influence whether the site is suitable for a given species, the broader landscape context can also influence site occupancy, particularly for species that are sensitive to land-use change.

Objectives

To examine the relative importance of local versus landscape variables in explaining site occupancy of eight bat species within the Brazilian Cerrado, a Neotropical savanna that is experiencing widespread habitat loss and fragmentation.

Methods

Bats were surveyed within 16 forest patches over two years. We used a multi-model information-theoretic approach, adjusted for species detection bias, to assess whether landscape variables (percent cover and number of patches of natural vegetation within a 2- and 8-km radius of each forest site) or local site variables (canopy cover, understory height, number of trees, and number of lianas) best explained site occupancy in each species.

Results

Landscape variables were among the best models (ΔAIC_c or ΔQAIC_c < 2) for four species (top-ranked model for black myotis), whereas local variables were among the best for five species (top-ranked model for vampire bats). Neither local nor landscape variables explained site occupancy in two frugivorous species.

Conclusion

Species associated with a particular habitat type will not respond similarly to the amount, distribution or relative suitability of that habitat, or even at the same scale. This reinforces the challenge of species distribution modelling, especially in the context of forecasting species’ responses to future land-use or climate-change scenarios.

     

Effects of landscape complexity on the ecological effectiveness of agri-environment schemes

Agricultural intensification is a major cause for biodiversity loss. It occurs at field scales through increased inputs and outputs, and at landscape scales through landscape simplification. Agri-environment schemes (AES) of the European Common Agricultural Policy (CAP) aim at reducing biodiversity loss by promoting extensification of agricultural practises mostly at field scales. We present a conceptual model for the relationship between landscape complexity and ecological effectiveness of AES based on (a) non-linear relationships between landscape complexity and abundance and diversity at field scales and (b) four possible interactive scenarios between landscape- and field scale effects on abundance and diversity. We then evaluated whether and how effectiveness of AES interacted with landscape-scale effects of intensification along a landscape complexity gradient established in central Spain. Pairs of cereal fields with and without AES but with the same landscape context were selected in three regions differing in landscape complexity. Effectiveness of AES was measured as differences between paired fields in species richness and abundance of five target groups (birds, grasshoppers and crickets, spiders, bees and plants). Landscape metrics were measured in 500–m radius circular plots around field centres. Positive, negative and no effects of landscape complexity on effectiveness of AES were found, suggesting that effects of complexity on effectiveness of AES changes from positive to negative along gradients of landscape complexity. Effectiveness of AES for improving biodiversity was then constrained by landscape. Compulsory measures aimed at enhancing or maintaining landscape complexity would enhance the effectiveness of AES for preserving biodiversity in farmed landscapes. For M. Díaz: New address from October 2007: Instituto de Recursos Naturales, Centro de Ciencias Medioambientales–CSIC, Serrano 115, Madrid E-28006, Spain     

Effects of changing spatial scale on the analysis of landscape pattern

The purpose of this study was to observe the effects of changing the grain (the first level of spatial resolution possible with a given data set) and extent (the total area of the study) of landscape data on observed spatial patterns and to identify some general rules for comparing measures obtained at different scales. Simple random maps, maps with contagion (i.e., clusters of the same land cover type), and actual landscape data from USGS land use (LUDA) data maps were used in the analyses. Landscape patterns were compared using indices measuring diversity (H), dominance (D) and contagion (C). Rare land cover types were lost as grain became coarser. This loss could be predicted analytically for random maps with two land cover types, and it was observed in actual landscapes as grain was increased experimentally. However, the rate of loss was influenced by the spatial pattern. Land cover types that were clumped disappeared slowly or were retained with increasing grain, whereas cover types that were dispersed were lost rapidly. The diversity index decreased linearly with increasing grain size, but dominance and contagion did not show a linear relationship. The indices D and C increased with increasing extent, but H exhibited a variable response. The indices were sensitive to the number (m) of cover types observed in the data set and the fraction of the landscape occupied by each cover type (P _k); both m and P _kvaried with grain and extent. Qualitative and quantitative changes in measurements across spatial scales will differ depending on how scale is defined. Characterizing the relationships between ecological measurements and the grain or extent of the data may make it possible to predict or correct for the loss of information with changes in spatial scale.     

On the relative importance of landscape variables to plant diversity and phylogenetic community structure on uninhabited islands,South Korea

Landscape Ecology - Although there have been methodological advances in the analysis of biodiversity and landscape properties, most studies in landscape ecology primarily explore whether certain...     

不同播期对春播大白菜生长发育及产量的影响

针对豫北地区春季气候特点,进行7个春播大白菜品种(组合)2月1日、2月10日和2月20日3个播期栽培筛选试验。结果表明,在温室育苗、小拱棚定植同一栽培模式下,不同播期对春播大白菜的生长影响较大,球叶数、短缩茎长度、病害情况及产量均有明显差异;并且随着播期的延后,球叶数呈递增趋势、短缩茎呈递减趋势、软腐病越来越重;其中在2月10日播种时大白菜产量最高,每667 m~2可达3 794.49 kg。     

东北山樱根浸提液对幼苗生长和根系呼吸代谢的影响

以东北山樱(Cerasus sachalinensis Kom.)为试材,研究其根浸提液对幼苗生长及根系呼吸代谢的影响。结果表明,东北山樱根浸提液对幼苗株高、茎粗、发根数量、茎叶和根的生长量、根系活力、PSⅡ最大光化学效率及呼吸底物含量均表现出低促高抑的化感作用效果。100 g.L-1质量浓度处理对呼吸速率、呼吸途径、呼吸酶活性和中间代谢产物均无显著影响,呼吸代谢顺利进行;200 g.L-1质量浓度使呼吸速率显著升高,激活了HK、PK和G-6-PDH的活性,降低了MDH的表达量,TCA受到抑制,丙酮酸积累,幼苗表现出一定的逆境胁迫状态;400 g.L-1质量浓度使根系呼吸速率下降42.82%;G-6-PDH和6-G-PDH的活性显著提高,调控PPP大量运行,EMP-TCA受阻,丙酮酸和柠檬酸含量显著下降,幼苗呼吸代谢过程紊乱。     

Effects of wind turbines and other physical elements on field utilization by pink-footed geese (Anser brachyrhynchus): A landscape perspective

The effects of wind turbines and other physical landscape elements on field utilization by wintering pink-footed geese (Anser brachyrhynchus) were studied in a Danish farmland landscape. Within the study area geese were feeding on pastures, which together with cereals were the main crop types. Apart from wind turbines a variety of potentially disturbing landscape elements was present, e.g., high-power lines, windbreaks, roads and settlements. Patterns of field use were assessed by measuring goose dropping densities along transects perpendicular to wind farms (with turbines in clusters and in lines) and other landscape elements. Local effects were expressed in terms of `avoidance distance', i.e., the distance from a given landscape element to the point at which 50% of maximal dropping density was reached. The spatial distribution of landscape elements within an eight km radius from the goose roost was determined from aerial photographs. The area occupied by various elements, together with the adjacent zones which were not available to geese due to their associated avoidance distances, were quantified using Geographic Information System (GIS).The avoidance distance of wind farms with turbines in lines and in clusters were ca 100 m and ca 200 m, respectively. Geese did not enter the area between turbines within the cluster. At the landscape level, the combined effect of physical elements other than wind turbines caused an effective loss of 68% of the total field area (40 km²). Wind turbines caused an additional loss of 4% of the field area. However, of the remaining area available to geese (13 km²), wind turbines caused a loss of 13% of the total area. The habitat loss per turbine was higher for the wind farm with turbines arranged in a large cluster than for wind farms with turbines in small clusters or lines. This difference was mainly due to the fact that wind farms in small clusters or with a linear layout were generally placed close to roads or other elements with existing associated avoidance zones, whereas the large cluster was placed in the open farmland area. The avoidance zones associated with physical elements in the landscape do not take into account possible synergistic effects and, hence, actual field areas affected are likely to be minimum estimates. Implications of these findings for planning of wind farms in areas of conservation interest to geese are discussed.     

5种生物药剂对葡萄炭疽病药效研究

为筛选防治葡萄炭疽病安全、高效的生物药剂,采用菌丝生长速率法测定5种生物药剂对葡萄炭疽病菌的毒力,选取其中抑菌活性较好的4种药剂开展田间防效试验。室内毒力测定结果表明,丁子香酚、苦参碱、中生菌素、乙蒜素的EC50分别为0.50、20.03、22.05、33.04 mg/L,均低于对照药剂代森锰锌的EC50值42.66 mg/L,抑菌效果较好,而多抗霉素的EC50为3 420.15 mg/L,抑菌效果差。田间药效试验结果表明,0.3%丁子香酚可溶性液剂1000~1250倍液对葡萄炭疽病的防效最佳,为91.41%~93.49%,显著优于对照药剂80%代森锰锌可湿性粉剂800倍液,0.3%丁子香酚可溶性液剂1 500倍液、80%乙蒜素乳油1 000~1 500倍液防效虽低于对照药剂,但也均在80%以上,可作为与常规化学药剂轮换使用防控炭疽病的有效生物药剂进行推广应用。