Heterogeneous Agricultural Landscapes Research Articles

Aphid parasitism in winter wheat fields in a heterogeneous agricultural landscape.

The number, timing, and fitness of colonizing parasitoids in fields of ephemeral crops often depend on factors external to the fields. We investigated cereal aphid parasitism in 23 winter wheat fields using sentinel plants infested with bird cherry-oat aphids, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), and we investigated the effect of parasitoids on cereal aphid population growth using exclusion and parasitoid-accessible cages infested with bird cherry-oat aphids. Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae), Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae),and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae), in decreasing order of abundance, parasitized R. padi on sentinel plants. The mean percent parasitism in parasitoid-accessible cages was 5.2% in autumn and 35.0% in spring. Aphid population intensity was greater in complete exclusion than in parasitoid-accessible cages. Measures of landscape composition and configuration were quantified, and aphid parasitism in autumn by L. testaceipes and A. nigritus was positively associated with % landcover by summer crops and patch density. Parasitism by both species was negatively associated with contagion and % woodlands. Parasitism during spring was positively associated with % grassland and fractal dimension and negatively associated with % canola. The number of braconid mummies per sentinel plant was positively correlated to the number of braconid mummies on wheat stems from parasitoid-accessible cages. Results indicate that cereal aphid mortality caused by parasitoids and their ability to exert effective biological control is related to landscape structure. Comparing this study to an earlier study in the same agroecosystem demonstrated temporal stability of the landscape influence on aphid parasitism by L. testaceipes in winter wheat.

Surface energy fluxes and energy balance closure using large aperture scintillometer-based ET station on heterogeneous agricultural landscape in north India

This study was carried out to understand the pattern of surface energy fluxes over a periodical scale and energy balance closure using Large Aperture Scintillometer and Micrometeorological tower. The standalone technique as ‘Scintillometry’ which observes the structure parameter of refractive index based on Monin-Obukhov Similarity theory, has the potential to measure the sensible heat flux precisely. This paper discusses the surface energy balance components and energy balance closure over a period of August 2017 to June 2018. The maximum mean energy fluxes Rn, G, H and LE were observed in September (98.6 Wm-2), May (13.9 Wm-2), June (53.3 Wm-2) and August (82.1 Wm-2), respectively. The overall mean ET was observed at the rate of 1.36 mm day-1 during the study period. This scintillometry technique may further use in evapotranspiration modelling from polar orbiting satellite to geostationary satellite over a heterogeneous and undulated landscape.

Interactive effects of agricultural landscape heterogeneity and weather conditions on breeding density and reproductive success of a diurnal raptor.

Agricultural intensification and climate change are serious threats toward animal populations worldwide. Agricultural intensification reduces the heterogeneity of agricultural habitats by diminishing crop variation and destroying microhabitats, such as small woody features, whereas the effects of climate change range from the growing frequency of weather extremes to disrupted prey-predator dynamics. We collected long-term ringing data from a population of Eurasian kestrels (Falco tinnunculus) located amidst agricultural areas in western Finland during 1985-2021, which we combined with density indices of their main prey species (voles), spatial data consisting of land cover classification of kestrel territories, and weather data, to study the effects of different environmental drivers on breeding density and success. We found that the density of inhabited nests rose with vole abundance and springtime snow depth, with the overall trend of population growth being stronger in areas with more heterogeneous landscapes. Clutch size was influenced negatively by the age of male parent and landscape heterogeneity, and positively by vole abundance, with rainfall having a negative influence conditional to other variables. Likewise, the number of produced fledglings was affected by male age, but it was additionally positively associated with landscape heterogeneity and its interaction with rainfall, with greater fledgling output in heterogeneous landscapes during high precipitation. The discrepancy between factors predicting large clutches and high numbers of fledglings suggests that while kestrels do not prefer heterogeneous landscapes when prospecting for territories, heterogeneous habitats provide better circumstances for foraging during the nestling period, which ensures nestling survival, particularly during adverse environmental conditions. Therefore, breeding in areas under intense agricultural use is more suboptimal to kestrels than their territory preferences would indicate. As changing climate may reduce prey availability and heighten the probability of weather extremities, agricultural intensification may lead to weaker reproductive success in densely populated farmland habitats.

Soil Moisture Mapping in Highly Heterogeneous Agricultural Landscapes

Soil Moisture Mapping in Highly Heterogeneous Agricultural Landscapes

Effects of agricultural landscape heterogeneity on pollinator visitation rates in Mediterranean oilseed rape

Agricultural intensification, by changing land use and modifying the yearly configuration and composition through crop sequences, affects the abundance and diversity of pollinators and, consequently, pollination. This study aims to assess the impact of the characteristics of agricultural landscapes on pollinator abundance in the Mediterranean region. We studied the response of three major wild pollinator groups (hoverflies, bumblebees, and wild bees) to four landscape characteristics: three related to composition, namely, equivalent crop diversity in the sampling year (eRg), previous year equivalent crop diversity (eRgP) and percentage of seminatural habitats (SNH), and one related to landscape configuration, namely, mean field size (MFS). For this evaluation, we selected twenty-two oilseed rape fields (OSRs) differing in surrounding landscape characteristics within a 1-km radius. Multimodel inference indicates that landscape variables affect pollinator groups differently. The percentage of SNH was the most important variable having a positive influence on the abundance of bumblebees, while eRgP and MFS were found to be important for the abundance of wild bees and hoverflies. These data allow us to prioritize actions aimed at specific groups of pollinators, improve agricultural landscape schemes, promote the conservation of wild pollinators, promote crop diversity at the landscape scale and increase the extent of seminatural areas.

Cropland can support high bird diversity in heterogeneous rural tropical landscapes

Summary Land-use change for crop production is one of the key drivers of habitat loss and fragmentation and consequently biodiversity loss and change in tropical regions. This may impact biodiversity-regulated ecosystem services; birds are important to crop health regulating services (e.g. seed dispersal, pest control) and disservices (e.g. seed predation, grain herbivory). However, knowledge is limited on how birds use heterogeneous agricultural landscapes and the consequences for spatial distribution and flow of services and disservices. We studied crop and non-crop–habitat associations of birds in forest–agricultural landscapes of the Kilombero Valley, Tanzania. We focused on dietary preference as a key trait impacting bird responses to land-use change, services, and disservices to crops. We surveyed birds across four main habitat types using repeated point counts, recording a total of 148 species. We found that crop habitats supported higher species richness and larger communities of potentially beneficial species to crop health, whereby 34.5% of invertebrate-feeding species were recorded in cropland. We found that habitat heterogeneity within the landscape supports bird functional diversity and that each habitat type supported unique communities of species. Furthermore, the number of species unique to forest habitats increased with increasing forest canopy closure. Our findings suggest that management strategies for maintaining trees and shrubs, and enhancing tree cover within the crop production landscape, can be effective approaches for maintaining bird diversity and services. However, in-depth studies on trade-offs with disservices need further exploration to mitigate negative impacts of birds on crop yields.

Combining UAV and Sentinel-2 Imagery for Estimating Millet FCover in a Heterogeneous Agricultural Landscape of Senegal

Combining UAV and Sentinel-2 Imagery for Estimating Millet FCover in a Heterogeneous Agricultural Landscape of Senegal

Hierarchical extraction of cropland boundaries using Sentinel-2 time-series data in fragmented agricultural landscapes

Accurately extracting cropland field parcels from satellite data in fragmented agricultural landscapes presents huge challenges due to small field sizes and irregular field shapes. Here, we developed a hierarchical framework for agricultural field boundary extraction from Sentinel-2 satellites based on the concept of the degree in field fragmentation. Our framework focused on three tasks, including a core task for agricultural field extraction and two auxiliary tasks to address special situations in two different fragmented regions, namely the Plains-Basin scenes with relatively regular shapes and diverse crop types, and the Plateau-Hilly scenes, with irregular shapes and small field sizes. First, the field boundaries were delineated using a modified Recurrent Residual Convolutional Neural Network based on U-Net (R2U-Net), and post-processed using morphological filtering and the Douglas-Peucker algorithm (DPA). A rule-based decision fusion strategy assisted with a classification method was developed to address the under-segmentation problem in the Plains-Basin scenes, and an adaptive generalized buffer algorithm (AGBA) was used to address the incomplete-segmentation problem in the Plateau-Hilly scenes. We tested the proposed methods in Yangming County, Heilongjiang Province of China, using time series Sentinel-2 imageries with 10-m spatial resolution. Compared with the results from using R2U-Net or a single-temporal image alone, the fragmented field boundaries show an outstanding performance, with an overall accuracy of 86.42% and 84.15% and F1 score of 0.85 and 0.83 in Plains-Basin scenes and Plateau-Hilly scenes, respectively. Our proposed methods provide a feasible solution to finely extract field boundaries in highly fragmented and heterogeneous agricultural landscapes.

Hedgerows interact with forests to shape the abundance of mesopredators and their predation rate on eggs in farmland landscapes

Nest predation is the main cause of reproductive failure, particularly in ground-nesting birds on farmlands. Understanding the links between nest predation and habitat change can help design effective management schemes to constrain the negative impact of predation pressure on birds. However, the mechanisms underlying the relationships between landscape attributes, predator distribution, and nest predation are still unclear. Here, we use an experimental approach to examine the effects of distance to the hedgerow as well as hedgerow and forest densities on the abundance of major mesopredators of ground nests of our study area (i.e., corvids) and on the predation rate of artificial ground nests (n = 2576). We found evidence that landscape configuration influenced predation patterns differently depending on the predator species. Nest predation by corvids was more likely in homogeneous and open agricultural landscapes with a low density of forest and hedgerows, whereas predation by other predators was more likely close to hedgerows. Nest predation by corvids and the abundance of corvids also tended to be lower in landscapes dominated by grasslands. Other variables such as road density and distance to human settlements had contrasted effects on the likelihood of a nest being depredated by corvids, i.e., no effect with proximity to human settlements and decreasing trend with road density. Altogether, our results suggest that landscape features interact with mesopredator distribution and their predation rates of ground nests. Therefore, from a conservation and management perspective, a heterogeneous agricultural landscape that includes a mixture of crops associated with patches of forests, hedgerows, and grasslands offering alternative food to generalist predators should contribute to reducing ground-nesting bird predation.

Carbon stocks and potential sequestration of Uruguayan soils: a road map to a comprehensive characterization of temporal and spatial changes to assess carbon footprint

Carbon net emission is a critical aspect of the environmental footprint in agricultural systems. However, the alternatives to describe soil organic carbon (SOC) changes associated with different agricultural management practices/land uses are limited. Here we provide an overview of carbon (C) stocks of non-forested areas of Uruguay to estimate SOC changes for different soil units affected by accumulated effects of crop and livestock production systems in the last decades. For this, we defined levels based on SOC losses relative to the original (reference) SOC stocks: 25% or less, between 25% and 50%, and 50% or more. We characterized the reference SOC stocks using three approaches: (1) an equation to derive the potential SOC capacity based on the clay and fine silt soil content, (2) the DayCent model to estimate the SOC stocks based on climate, soil texture and C inputs from the natural grasslands of the area, (3) an estimate of SOC using a proxy derived from remote sensing data (i.e., the Ecosystem Services Supply Index) that accounts for differences in C inputs. Depending on the used reference SOC, the soil units had different distributions of SOC losses within the zones defined by the thresholds. As expected, the magnitude of SOC changes observed for the different soil units was related to the relative frequency of annual crops, however, the high variability observed along the gradient of land uses suggests a wide space for increasing SOC with agricultural management practices. The assessment of the C stock preserved (CSP) belowground and the potential for increasing C accumulation or sequestration (CAP) are critical components of the C footprint of a given system. Thus, we propose a methodological road map to derive indicators of CSP and CAP at the farm level combining both, biogeochemical simulation models and conceptual models based on remote sensing data. We recognize at least three critical issues that require scientific and political consensus to implement the use of this propose: (1) how to define reference C stocks, (2) how to estimate current C stocks over large areas and in heterogeneous agricultural landscapes, and (3) what is a reasonable/acceptable threshold of C stocks reduction.

Biodiversity in landscape mosaics: The roles of local land use and the surrounding landscape on dung beetle assemblages

Abstract Biotic communities in heterogeneous agricultural landscapes can be shaped by both the land use of local patches and the structure of surrounding landscapes. However, studies usually focus on one or the other factor, limiting our ability to propose management guidelines for the conservation of biodiversity in human‐modified landscapes. We used a site‐landscape design and multi‐model inference to assess the effects of land use, landscape structure, and their interactions, on dung beetle assemblages in agricultural landscapes in the Brazilian Cerrado, a biodiversity hotspot. We captured dung beetles in five dominant land uses (savanna, forest, eucalypt, cattle pasture and soybean) and estimated species density, abundance of large and small beetles, and functional richness and dispersion. We measured four landscape structure predictors (savanna cover, forest cover, landscape compositional heterogeneity, and matrix harshness) in circular landscapes around sampling plots. All response variables were affected by land use and by at least one landscape predictor. Relationships between landscape predictors and dung beetle responses were as expected (positive for forest and savanna covers and negative for matrix harshness), except landscape compositional heterogeneity, which had unexpected negative effects. More importantly, land use and landscape predictors interacted in two cases: higher forest cover and lower matrix harshness were related to higher species density and large‐beetle abundance, respectively, but this was mainly observed in eucalypt. Synthesis and applications: To better guide the conservation of mobile organisms in anthropogenic habitat mosaics, we need to consider both landscape characteristics and the land use of local patches. Using this approach, we are able to make some recommendations for the conservation of dung beetles in agricultural landscapes in Cerrado, including the following: (i) ensure, through protection and/or restoration, that natural vegetation patches (even small ones) are interspersed in the agricultural matrix, to increase functional diversity in all land uses and taxonomic diversity in tree plantations, (ii) place eucalypt plantations near forest patches to increase the abundance of sensitive species (forest‐specialists, and some large species); (iii) replace some patches of pasture or soybean with tree plantations, to increase the amount of supplementary habitat for sensitive species.

How landscape characteristics in a heterogeneous oil palm plantation mitigate pest abundance: A case study from Mapiripán, Colombia

The oil palm sector is widely known for its strong impact on biodiversity and human well-being. The United Nations Sustainable Development Goals (SDG) framework calls for a sustainable biodiversity management approach to oil palm plantations and thereby balancing palm oil production and biodiversity conservation. Heterogeneous agricultural landscapes, comprising different vegetation types in a complex spatial pattern, provide habitat to a variety of species and support high biodiversity. Biodiversity can thus offer pest control ecosystem services to agricultural systems. However, so far it remains unclear whether landscape structure and diversity foster or mitigate pest occurrences in plantations. Our case study is the oil palm plantation of Mapiripán in Colombia, which integrates local ecosystems such as secondary forests, relict old-grown forests, riparian forests, and water body remnants in between and around the palm stands of the plantation. With this nature-improved design, we ££pose two main questions: which landscape structural properties characterize the landscape of the oil palm plantation?, and how do specific landscape structural properties foster or mitigate the presence of two main oil palm pests (the butterfly larvae split-banded owlet (Opsiphanes cassina) and the red weevil (Rhynchophorus palmarum))? We first characterize the plantation landscape with a multivariate cluster analysis which led us to identify up to nine different landscape structural types for the Macondo plantation. A mosaic of different landscape types ranging from homogeneous and simple landscapes to heterogeneous, diversified, and connected landscape types. Second, we performed an NMDS ordination to show similarities among the landscape structural types, land cover, and pest occurrence. Our results show that the integration of local ecosystems such as forests and water bodies improves landscape connectivity and suppresses the abundance of the two main oil palm pests.

LAND USE/LAND COVER CLASSIFICATION IN A HETEROGENEOUS AGRICULTURAL LANDSCAPE USING PLANETSCOPE DATA

Abstract. Land use and land cover (LULC) classification has long been an essential topic in Earth Observation research and plays a key role in the sustainable development of agriculture. This study evaluated the accuracy of LULC classification based on an initial clustering step in a heterogeneous agricultural landscape using PlanetScope imagery while checking for variability among their Normalized Difference Vegetation Index (NDVI) temporal signatures. We adopt an object-based image analysis to generate image-objects and then extract statistical information of PlanetScope spectral bands and vegetation indices as input information for classification. The exploratory analysis focused on the double crop class and calculated the distance between NDVI temporal signatures of paired land parcels. We applied an unsupervised clustering technique along with Random Forest algorithm based on multiple tests to classify and analyse gains and losses in accuracies produced by these approaches. Our results showed that the initial clustering method outperformed the non-clustered classification of LULC in overall accuracy measures. The exploratory analysis demonstrated that double crops might present high intra-class variability and diverse crop calendars for neighbour land parcels. The accuracies achieved represent promising opportunities for the sufficiently accurate classification of such areas, and the knowledge of the intra-class variability allows the analyst to infer the temporal dynamics of crop fields. We reinforce that further work could assess other types of classifiers, especially in areas with a large number of crop types and distinct management practices.

Tropical agricultural wooded land uses support high site use of forest birds

Agricultural expansion has been responsible for the large-scale modification of forest ecosystems globally. In many regions, this has resulted in the creation of heterogenous landscapes comprised of cleared agricultural lands, and semi-natural and natural wooded land uses such as agroforests and secondary forests. These wooded land uses can play an important role in supporting forest biodiversity. In a tropical agricultural landscape of Northeast India, we investigate how wooded land uses affect site use by forest specialist, forest generalist and open-country bird species, in comparison to a protected area. We also investigate the effects of site vegetation characteristics, surrounding forest cover and distance to the protected area. Using multi-species occupancy models, we found that wooded land uses support high site use of the three forest specialization groups. We attribute the high site use of forest species in wooded land uses to the similarity in site vegetation characteristics between these land uses and the protected area. In addition, high forest cover at, and neighbouring, our sampling sites, and habitat connectivity also contributed towards supporting high site use of forest species. However, for some species across the three groups, a few site vegetation characteristics and surrounding forest cover had a subtle influence. Our study showcases the supplementary role of low-intensity agricultural landscapes as habitat for forest birds, provided that wooded land uses outside protected areas are well maintained. In so doing, it contributes valuable insights into land management practices that support biodiversity in heterogeneous agricultural landscapes.

Fallow fields and hedgerows mediate enhanced arthropod predation and reduced herbivory on small scale intercropped maize farms – δ13C and δ15N stable isotope evidence

Fallow fields and hedgerows enhance agricultural landscape heterogeneity and boost predatory arthropod diversity, though there is little direct quantitative evidence of their value in mediating pest suppression. Here, stable isotope analyses were used to quantify the influence of fallow field presence, fallow size proportion of farms, hedgerow volume and hedgerow type, on arthropod pest consumption by six predatory taxa. Levels of herbivory by four arthropod taxa on three vegetation groups: maize, beans and non-crops – were also considered. This was achieved through mixing model analysis with δ13C and δ15N stable isotope to identify and estimate food-source proportions incorporated into tissues of arthropod consumers collected from ten maize farms intercropped with beans in western Kenya. Fallow fields’ presence supported predation on Lepidopteran herbivores by attracting predatory bugs and wasps, and mediated lower herbivory levels. Fallow size proportion corresponded to higher taxa-level predation by ants and spiders on phytophagous beetles, and overall increase in bean herbivory, but predicted no difference in maize or non-crop herbivory. Higher hedgerow volumes did not affect overall predation pressure, but supported increased bean herbivory by Lepidoptera, and lower maize consumption by Orthoptera. Exotic hedgerows supported highest wasp predation on Lepidoptera while spiders consumed significantly more Orthoptera and phytophagous beetle pests on indigenous-hedgerow farms. Similarly, exotic hedgerows corresponded to enhanced Lepidoptera bean herbivory while trophic linkage of maize and non-crops to pests overall, were stronger with indigenous hedgerows. Thus, in addition to thicker hedgerows, predatory spillover impacts of wasps, bugs and beetles can be enhanced with fallow presence and exotic hedgerows, and that of spiders and ants, with larger fallows. Overall, the choice, combination and application of farm habitat structural features to maximize predatory arthropods’ contributions to pest biocontrol requires knowledge of focal crops, dominant pest groups and their most important predators. The findings demonstrate that fallow fields and hedgerows are significant in supporting the biological component of integrated crop pest management.

Intercropping shifts the balance between generalist arthropod predators and oilseed pests towards natural pest control

Pest management in intensive crop production currently underutilizes natural biological control, and frequently results in pesticide application. Intercropping modifies physical and ecological conditions in the field and alters the predator-prey dynamics to potentially benefit generalist arthropod predators. We investigated the assemblages of ground-dwelling arthropod predators and crop pests of spring turnip rape (Brassica rapa L. ssp. oleifera) and faba bean (Vicia faba L.) in a replicated two-year field experiment. Pitfall traps and pan traps were used to sample arthropod predators and pests. Arthropod assemblages were compared between intercropping and monocropping systems to illustrate the changes. Intercropping was associated with lower abundance of turnip rape pests compared with monoculture. The total abundance of ground-dwelling predators did not differ between cropping systems. Carabid beetles (Coleoptera: Carabidae) and spiders (Araneae) were the dominant generalist predator taxa. Faba bean monoculture supported the highest abundance of harvestmen (Opiliones) and the lowest abundance of ants (Hymenoptera: Formicidae). The turnip rape monoculture had the highest abundance of spiders in the first year but not in the second. The abundance and species assemblage of carabids indicated a response to season progress but not to cropping system. The abundance of turnip rape pests reflected host crop proportions in each cropping system. Because the cropping method had no significant impact on predator abundance, intercropping potentially facilitated natural biological control resulting from a higher ratio of ground-dwelling predators to pests. Differential within-season dynamics among abundant predator taxa also implied a temporal shift in predation characteristics, and hence, vulnerability of crop production to pest injuries. To utilize natural biological control more effectively at the field scale, intercropping with no shared pests between crops, minimal chemical pest control, and heterogeneous agricultural landscapes are needed.

Valid inferences about soil carbon in heterogeneous landscapes

Using soil organic carbon (SOC) to generate carbon offsets requires reliably quantifying SOC sequestration. However, accuracy of SOC measurement is limited by inherent spatial heterogeneity, variability of laboratory assays, unmet statistical assumptions, and the relatively small magnitude of SOC changes over time, among other things. Most SOC measurement protocols currently used to generate offsets for C markets do not adequately address these issues, threatening to undermine climate change mitigation efforts. Using analyses and simulations from 1,117 soil samples collected from California crop and rangelands, we quantified measurement errors and sources of uncertainty to optimize SOC measurement. We demonstrate that (1) spatial heterogeneity is a primary driver of uncertainty; (2) dry combustion assays contribute little to uncertainty, although inorganic C can increase error; (3) common statistical methods—Student’s t-test and its relatives—can be unreliable for SOC (e.g. at low to medium sample sizes or when the distribution of SOC is skewed), which can lead to incorrect interpretations of SOC sequestration; and (4) common sample sizes (10–30 cores) are insufficiently powered to detect the modest SOC changes expected from management in heterogeneous agricultural landscapes. To reduce error and improve the reliability of future SOC offsets, protocols should: (1) require power analyses that include spatial heterogeneity to determine minimum sample sizes, rather than allowing arbitrarily small sample sizes; (2) minimize the use of compositing; (3) require dry combustion analysis, by the same lab for all assays; and (4) use nonparametric statistical tests and confidence intervals to control Type I error rates. While these changes might increase costs, they will make SOC estimates more accurate and more reliable, adding credibility to soil management as a climate change mitigation strategy.

The importance of landscape heterogeneity and vegetation structure for the conservation of the Ortolan Bunting Emberiza hortulana

Summary Over the last decades, European farmland birds have strongly declined, mainly driven by agricultural intensification. The Ortolan Bunting Emberiza hortulana has suffered one of the most severe declines among farmland specialists. In order to maintain viable populations of the species in the long run, there is a vital need for evidence-based conservation measures. The main goal of this study was to detect the key drivers of breeding-territory selection and mating success of the species in an agricultural landscape in central Europe. We found that the landscape structure within the territories of Ortolan Bunting breeding pairs strongly varied from the overall habitat availability in the study area on both the territory and home-range scales. However, the environmental conditions also differed between the territories of breeding pairs and those of unpaired males. While landscape structure played an important role in breeding-territory selection, it had only weak effects on mating success. In contrast, crop type and vegetation height at potential nesting sites were important drivers of mating success. Overall, our study revealed that Ortolan Bunting has very complex breeding-habitat requirements. Only heterogeneous agricultural landscapes where (1) suitable song posts, (2) appropriate nesting sites, and (3) sufficient foraging habitats occur in close proximity are suitable for breeding. According to the findings of our study, agri-environmental schemes should primarily facilitate low-intensity farming practices that promote landscape heterogeneity, provide suitable nesting sites, and sustain a high abundance of invertebrate prey in farmlands.

Landscape or local? Distinct responses of flower visitor diversity and interaction networks to different land use scales in agricultural tropical highlands

Land use change has been identified as a cause for biodiversity loss and has significant effects on pollinators and their interactions with plants. Interaction network analyses complement diversity estimators by providing information on the stability and functionality of the plant-pollinator community in an ecosystem. However, how land use changes affect insect diversity, and the structure of their plant-insect interaction networks, could depend on the intensity of the disturbance but also may be a matter of scale. Our study was carried out in a tropical highland landscape dominated by intense, yet diverse, small-scale agriculture. We studied the effects of land use, at a landscape scale, and local cover and plant ecological descriptors, at a local scale; on diversity descriptors of insect pollinator communities, the abundance of the most frequent flower visitors, and their interaction networks. Seminatural vegetation favored insect flower visitors at both scales. At the landscape scale, human settlements positively influenced bee diversity, and seminatural areas favored the abundance of frequent hoverfly and bumblebee species. At the local scale, bare soil cover negatively influenced honeybee abundance while flower-rich covers positively related to bumblebee abundance. Only local scale variables had influence on network metrics. Bare soil cover was related to higher network specialization, probably due to a low rate of honeybee interactions. Flower-rich covers negatively influenced network connectance but favored modularity. These results suggest that flower resources, provided by weed areas and flowering crops, promote a high rate of interactions between trophic levels and a non-random structure in the interaction networks that may be helping to sustain network stability. Our results highlight the role of seminatural vegetation, at both scales, in maintaining stable insect pollinator communities and interactions in heterogeneous agricultural landscapes of the tropics.

A roadmap for ladybird conservation and recovery.

Ladybirds (Coleoptera: Coccinellidae) provide services that are critical to food production, and they fulfill an ecological role as a food source for predators. The richness, abundance, and distribution of ladybirds, however, are compromised by many anthropogenic threats. Meanwhile, a lack of knowledge of the conservation status of most species and the factors driving their population dynamics hinders the development and implementation of conservation strategies for ladybirds. We conducted a review of the literature on the ecology, diversity, and conservation of ladybirds to identify their key ecological threats. Ladybird populations are most affected by climate factors, landscape composition, and biological invasions. We suggest mitigating actions for ladybird conservation and recovery. Short-term actions include citizen science programs and education, protective measures for habitat recovery and threatened species, prevention of the introduction of non-native species, and the maintenance and restoration of natural areas and landscape heterogeneity. Mid-term actions involve the analysis of data from monitoring programs and insect collections to disentangle the effect of different threats to ladybird populations, understand habitat use by taxa on which there is limited knowledge, and quantify temporal trends of abundance, diversity, and biomass along a management-intensity gradient. Long-term actions include the development of a worldwide monitoring program based on standardized sampling to fill data gaps, increase explanatory power, streamline analyses, and facilitate global collaborations.