Effects Of Land-use Intensity Research Articles

Effects of land-use intensity on vegetation dynamics across elevation in Savanna Grassland, Southern Ethiopia

The rangeland ecosystem is currently one of the area’s most sensitive to biodiversity because of both natural and human effects. There is still much to learn about the sustainable management of dry and semi-arid rangelands in order to protect their rich biodiversity resources. This is due to the uncertain indirect effects of environmental factors, such as dryness, on vegetation species, which are mediated by shifting both living and non-living components. The purpose of this project was to ascertain the effects of land use intensity (LUI) on the various species of rangeland flora along the elevation gradient in the Borana Rangeland. We gathered a total of 37 plant species, comprising 22 grasses, 7 graminoids, and 8 forbs, from the nine sampling locations, which were exposed to LUI and included three locations within each elevation range of 500–900, 1000–1400, and 1500–1900 m.a.s.l. At every sampling site, we evaluated the dynamics of the plant species, taking into account their diversity, richness, percentage of undesirable species, and properties of the soil. We used structural equation modeling (SEM) to examine the effects of LUI on the different vegetation species along the elevation gradient. We found that the density and diversity of vegetative species decreased and the fraction of undesired species increased as elevation climbed (from lower to higher). Because of the heavy livestock grazing, these impacts were substantially linked with high LUI at lower elevations. According to our research, the complex relationships between elevation gradient and LUI have a big influence on the diversity and density of the flora. This demonstrates that we need to account for environmental gradients in order to generalize LUI's effects on rangeland biodiversity. This study sheds important light on the complex interactions between vegetation dynamics and LUI in savanna grasslands. To create practical strategies for maintaining ecosystem health and biodiversity in the Southern Ethiopian Savanna Grasslands, policymakers, environmentalists, and land managers should take these findings into account.

Effect of land-use intensity and adjacent semi-natural habitats on wild and honey bees of meadows

Most terrestrial ecosystems are shaped by the pollination service provided by insects, foremost bees. As bees are also important pollinators of crop plants, they are key for both the pollination of wild plants and for agricultural production. Meadows and semi-natural habitats (SNHs) are important habitats for bees. However, there is limited knowledge on how land-use intensity of meadows affects wild bees and managed Western honey bees. Further, it is unknown whether SNHs adjacent to meadows affect bees in meadows. Here, we examined in a landscape dominated by grasslands, the effects of land-use intensity (nitrogen input, grazing intensity, mowing frequency), flower availability and adjacent SNHs on bee communities in meadows. We recorded more than 5000 individuals of 87 species of bees and found no effect of land-use intensity on wild and honey bees. Flowering plant species richness had a positive effect on bee species richness in one study year. Though we recorded more bee species in SNHs than meadows, overall and specifically in ecologically specialized bee species (e.g. parasitic bees, oligoleges), the availability of adjacent SNHs did not affect bee abundance and richness in meadows. We discuss why land-use intensity and SNHs adjacent to meadows did not affect bees in meadows and conclude that SNHs are important in sustaining functionally diverse bee communities in landscapes dominated by grasslands.

Stressors affecting the ecological status of temporary rivers in the Mediterranean region

Temporary rivers are widespread in the Mediterranean region and impose a challenge for the implementation of the Water Framework Directive (WFD) and other environmental regulations. Surprisingly, an overarching analysis of their ecological status and the stressors affecting them is yet missing. We compiled data on the ecological status of 1504 temporary rivers in seven European Mediterranean region countries and related their ecological status (1) to publicly available data on pressures from the European WISE-WFD dataset, and (2) to seven more specific stressors modelled on a sub-catchment scale. More than 50 % of the temporary water bodies in the Mediterranean countries reached good or even high ecological status. In general, status classes derived from phytobenthos and macrophyte assessment were higher than those derived from the assessment of benthic invertebrates or fish. Of the more generally defined pressures reported to the WISE-WFD database, the most relevant for temporary rivers were ‘diffuse agricultural’ and ‘point urban waste water’. Of the modelled more specific stressors, agricultural land use best explained overall ecological status, followed by total nitrogen load, and urban land use, while toxic substances, total phosphorus load and hydrological stressors were less relevant. However, stressors differed in relevance, with total nitrogen being most important for macrophytes, and agricultural land use for phytobenthos, benthic invertebrates and fish. For macrophytes, ecological quality increased with stressor intensity. The results underline the overarching effect of land use intensity for the ecological status of temporary water bodies. However, assessment results do not sufficiently reflect hydrological stress, most likely as the biological indicators used to evaluate these systems were designed for perennial water bodies and thus mainly target land use and nutrient impacts. We conclude that biomonitoring systems need to be updated or newly developed to better account for the specific situation of temporary water bodies.

Little evidence for land-use filters on intraspecific trait variation in three arthropod groups

Abstract. Declines in species richness and abundance of insects over the last decades are often driven by anthropogenic land use and can have severe consequences for ecosystem functioning. Many studies investigated the effects of land-use intensification on the distribution of phenotypic traits across species at the community level, often with mixed results. However, biotic and abiotic environmental filters and potential selection act on individuals within each species, i.e., at the species' population level, and thus drive the extent of intraspecific phenotypic variation. Here, we compare the morphological trait variation within selected species of dung beetles, bees and grasshoppers and link this variation to land-use intensity in forests and grasslands. Selected traits included absolute body size measures and relative leg, wing or eye size, or shape and are often interpreted as “functional traits” in the context of specific ecological responses or effects. We predicted that trait variability among individuals of arthropod species is reduced in intensively used ecosystems (with pronounced environmental filtering) compared to low-intensity ones, particularly for arthropod species that were more abundant in intensively used sites (“land-use winners” compared to “losers”). In general, only few effects of land-use intensity on trait variation were found showing a decreasing variation with increasing land-use intensity in forests but an increasing variation in grasslands. Although many studies confirmed strong land-use impacts on species composition, diversity and trait distribution, including evidence from the same land-use gradients, we were not able to confirm consistent effects at the intraspecific level. However, the choice of which traits are included in analyses and the linkage between phenotypic variation and genetic variability can strongly influence the conclusions drawn on ecological processes. Therefore, we suggest extending the use of intraspecific trait variation on other, more specific response or effect traits and a broader range of species in future studies.

Effects of land-use intensity, grazing and fire disturbances on soil bacterial and fungal communities in subtropical wetlands

Bacteria and fungi are primary components in wetland soil microbial communities and provide essential ecosystem functions and services. Understanding responses of bacterial and fungal communities to multiple drivers of environmental change and their interactions is crucial for wetland conservation and management, particularly for those embedded in agricultural landscapes. Yet little is known about effect of agricultural land use and wetland management on soil microbial communities in subtropical seasonal wetlands. Here, we used a long-term whole-ecosystem wetland experiment to examine individual and interactive effects of upland land-use intensification, livestock grazing, and prescribed fire on soil bacteria and fungi. We asked: (1) How do land-use intensification, grazing and fire disturbances interact to alter taxonomic composition and functional potential of wetland soil bacterial and fungal communities? (2) To what extent would these management and disturbance effects on wetland microbial communities manifest through alterations in soil properties? Our results showed that both microbial taxonomic and functional composition are responsive to agricultural land use and wetland management. Upland land-use intensification was the strongest driver (as compared to fire and grazing) in shaping bacterial and fungal community composition. Specifically, land-use intensification increased functional richness of both bacteria and fungi, whereas grazing and fire only interactively affected bacterial functional richness. In addition, responses of bacterial and fungal species diversity to wetland management varied, where grazing and fire reduced fungal species diversity in wetlands embedded in low-intensity managed pastures, but none of these management practices altered bacterial species diversity. Further, we found that pH and secondary nutrients (i.e., Ca and Mg) availability were the most important soil properties that explain how agricultural land use and wetland management drive the composition of bacterial and fungal communities. Our findings suggest that integration of lime application into intensified land uses to neutralize soil pH could facilitate maintenance of microbial diversity and associated functions. Our results highlight the need to comprehensively assess management impacts on soil microorganisms, rather than using a single or few indicators, due to inconsistent responses of bacterial and fungal communities, as well as their varied taxonomic and functional responses.

Eco-Environmental Effects and Spatial Heterogeneity of “Production-Ecology-Living” Land Use Transformation: A Case Study for Ningxia, China

Spatio-temporal changes to the eco-environmental quality index (EQI) and determination of their spatial differentiation characteristics are important bases for land management and ecological environment protection. This study evaluates the changes in EQI and its spatial distribution characteristics with reference to the three dominant functions of land use, namely “production-ecology-living” (PEL), based on the interpretation of land use remote sensing data in 2000, 2010 and 2018. The spatial diversity of ecological environment quality and its driving factors were quantitatively analyzed by gravity center transfer, cold and hot spot analysis, and the GeoDetector model. The results showed that: (1) The transformation of land in Ningxia from 2000 to 2018 mainly manifested by the increase in industrial and mining production land (IMPL), urban living land (ULL) and rural living land (RLL), and the decrease of grassland ecological land (GEL), especially in the north of Ningxia. (2) The ecological environment quality decreased slightly during the research period, but there was an improvement trend in the north. High environment quality values were concentrated in the Liupan Mountain area in the south of Ningxia, while the low values were mainly in the desert areas of Shapotou County and Zhongning County in the west. (3) The interaction between land use intensity and topographic factors led to spatial change in EQI in the research area. Effects of land use intensity are the dominant factor, reflecting the degree of impact of human activities on natural ecosystems. Our results suggest that topographic factors and human disturbances should be fully taken into account in future land and spatial development decisions to minimize human-ecological conflicts.

Depth-differentiated, multivariate control of biopore number under different land-use practices

Earthworms and (tap-)roots impact the soil structure by creating large biopores, affecting infiltration capacity, seepage, nutrient cycling, and soil aeration. Despite the importance of biopores for the functions of soils and the fact that several hundreds of biopores >2 mm in diameter may occur on one square meter of soil, knowledge on the interdependence of soil properties, land-use intensity, and biopore number is still rudimentary. In this study, we investigate the linkage of the number of biopores (>2 mm i.d.) with the earthworm community, root biomass, and soil properties, including pH, water content, soil organic carbon (SOC), as well as the land-use intensity (pasture vs. cropland) as a function of the soil depth (15, 30 and 50 cm). Hypothesized causal relationships among these factors were analyzed by piecewise structural equation modelling (SEM). We found various and novel linkages between roots, earthworms, biopores, and soil properties depending on soil depth. In topsoil (at 15 cm depth), roots directly affected the number of small-sized biopores, and anecic earthworms were related to medium-sized biopores. These effects diminished with depth. We identified land-use intensity as the factor preponderating the relations between biopores, root biomass, and earthworm number in the topsoil horizons, thereby masking other interactions among variables. This appeared as high multicollinearity among variables in the SEM of the topsoil. Land-use intensity effects were found to impact the whole soil profile but decreased with soil depth. To further elucidate the single effects of soil properties on biopore-forming biota and number of biopores in the topsoil, we excluded land-use intensity as a variable in subsequent analyses. Biopores increased with soil pH and soil water content but decreased with increasing SOC. Based on our SEM analysis, we conclude that the occurrence, frequency, and persistence of biopores are the consequence of intricate interdependencies between earthworm communities, roots, and site-specific soil properties, governed by land-use intensity.

Natural forest regrowth under different land use intensities and landscape configurations in the Brazilian Atlantic Forest

Natural forest regrowth is considered the most cost-effective strategy to promote large-scale forest restoration, but regrowth trajectories and their consequences for nature and people can be highly variable. This uncertainty may obstruct devoting land, time and resources in promoting this restoration approach. Process-based models allow to simulate forest regrowth under different scenarios and may thus support decision making to manage areas in ways that maximize forest restoration based on natural forest regrowth. In the present study, we used the process-based model LandClim to assess the following questions:1) How does land use intensity affect forest growth, aboveground biomass (AGB) and tree species diversity in agricultural landscapes in the long term? 2) How do different land use configurations affect the structure and expansion of second-growth forests? We based our study on six 4 × 4 km agricultural landscapes, dominated by pastures and sugarcane, in the Brazilian Atlantic Forest region. We parameterized and validated LandClim for the study region by comparing model outputs with published estimates and information from field data collected across the six landscapes. We then simulated natural forest regrowth under different land use intensities in the six landscapes and analyzed how land use intensity and landscape configuration affect AGB, tree species diversity and the spatial dynamics of second-growth forests. Our results showed negative effects of increased land use intensity on landscape biomass accumulation due to limited forest cover expansion. Landscapes dominated by sugarcane had lower forest regrowth potential than pasture-dominated landscapes due to lower likelihood of abandonment, and limited rates of seed availability and seedling growth. Land use intensity and landscape configuration were also important factors for tree diversity changes. However, temporal patterns differed, and while AGB reached a plateau after 100–150 years, tree diversity peaked between 30 and 70 years. Thus, the effects of land use intensity and landscape configuration on forest AGB and tree diversity take decades to be fully expressed, highlighting the importance of a long-term commitment in restoration projects.

Soil Nutrient Depletion and Tree Functional Composition Shift Following Repeated Clearing in Secondary Forests of the Congo Basin

The Congo Basin's rapidly growing population still largely depends on shifting cultivation for both energy and food security. This nexus of population growth and ecological impact will continue to exacerbate landscape degradation in the coming decades. To quantify the effects of land-use intensity on soil nutrient stocks and the functional composition of young regrowth forest in the Congo Basin, we used fallows of different ages that had been subjected to a varying number of clearing cycles. We show that repeated clearing substantially affected soil cation stocks, reducing total K, Mg and Ca in the upper 20 cm of soil by roughly 20% per clearing cycle. Additionally, we show that plant-available nitrogen (ammonium and nitrate) and phosphorus decline in the topsoil with increasing land-use intensity. Furthermore, the tree functional composition of young fallows changed after repeated clearing cycles: we observed a decrease in abundance of pioneer species and an increase in nitrogen fixing species early in succession. Variation in soil total nutrient stocks was decoupled from changes in vegetation, and soil plant-available nutrients only marginally explained tree functional composition changes. We conclude that land-use intensity substantially affects both soil total and plant-available nutrients in a shifting cultivation system, as well as the functional composition of the regenerating vegetation. However, compositional changes of the tree community are only partly driven by land-use intensity effects on soil plant-available nutrients.

Forest habitat parameters influence abundance and diversity of cadaver-visiting dung beetles in Central Europe.

Dung beetles provide crucial ecosystem services and serve as model organisms for various behavioural, ecological and evolutionary studies. However, dung beetles have received little attention as consumers of large cadavers. In this study, we trapped copronecrophagous dung beetles on above-ground exposed piglet cadavers in 61 forest plots distributed over three geographically distinct regions in Germany, Central Europe. We examined the effects of land use intensity, forest stand, soil characteristics, vascular plant diversity and climatic conditions on dung beetle abundance, species richness and diversity. In all three regions, dung beetles, represented mainly by the geotrupid species Anoplotrupes stercorosus and Trypocopris vernalis, were attracted to the cadavers. High beetle abundance was associated with higher mean ambient temperature. Furthermore, A. stercorosus and T. vernalis were more abundant in areas where soil contained higher proportions of fine sand. Additionally, an increased proportion of forest understorey vegetation and vascular plant diversity positively affected the species richness and diversity of dung beetles. Thus, even in warm dry monocultured forest stands exploited for timber, we found thriving dung beetle populations when a diverse understorey was present. Therefore, forestry practices that preserve the understorey can sustain stable dung beetle populations and ensure their important contribution to nutrient cycles.

Ant biodiversity and ecosystem services in bioenergy landscapes

Most strategies for limiting global climate change invoke the use of bioenergy, but biofuel crops vary in climate mitigation potential and in the provision of other ecosystem services. The predominant biofuel in North America is ethanol produced from corn Zea mays. Corn is grown on ∼360,000 km2 of land in the U.S. and ∼40 % of the yield is used for ethanol production. Despite its prevalence, corn ethanol is a poor climate change mitigator and the spread of intensive corn agriculture also leads to the loss of biodiversity and an unknown complement of associated ecosystem services. To test for effects of land use intensity on the provision of ecosystem services from biofuel crops, we compared insect communities inhabiting long-term experiments in which land use intensity varied from annual corn production to less intensive native perennial biofuel crops (switchgrass and restored prairie) and unmanaged native forests. Within the experiments we focused on ants (Formicidae: Hymenoptera), including their diversity, abundance, functional traits, and predation of biofuel crop pests. Native perennial biofuel crops supported up to 185 % more ant species than corn fields and provided up to 55 % more natural pest suppression. They also contained higher functional richness by supporting social parasites and seed dispersing ants that were absent in corn. Biofuel crops did not differ in ant activity or the prevalence of introduced ants. Our results highlight tradeoffs in bioenergy production and suggest ways to maximize benefits for wildlife and people. Converting some corn fields to prairie or other native vegetation could restore landscapes while mitigating climate change and meeting energy needs.

The effects of increasing land use intensity on soil nematodes: A turn towards specialism

Abstract The ecosystem services that humans obtain from the soil are strongly linked to the soil's biota. There is ample evidence that intensive agriculture has a negative effect on the soil's biological diversity. While in other ecosystems, habitat specialists are at a higher risk of extinction due to human impacts than generalists, we have no evidence of whether this holds true for soil biota. We calculated the realized niche width for soil nematodes using co‐occurrence data. We compared these with ecological traits. We then calculated an index of community specialization and tested whether land use intensity leads to decreases in the index of community specialization, taxon richness, diversity and to changes in nematode abundance. The resulting realized niche widths did not correlate with ecological traits such as feeding group, body mass or c‐p class. While it is possible that there are no relationships between these traits and the realized niche width, it is likelier that food availability, pH tolerance, or host breadth are more important factors in explaining niche width. Contrary to our expectations, the lowest community specialization levels were found in soils with the lowest human intervention (shrubland–woodland ecosystems), while grasslands, dairy farms and arable farms had an overall higher level of specialization. Weather variables and land use intensity explained 66% of the variation in the index of community specialization in sandy soils. We found highest richness and diversity at intermediate levels of disturbance (grasslands and dairy farms). The lowest abundances were found on shrubland–woodland systems. Dairy farms on sand and clay had similar indices of community specialization, whereas peaty soils fostered a higher proportion of habitat specialists. We argue that farmland supposes a stable environment for organisms with shorter life spans. Agricultural management strives to lower disturbances, allowing shorter lived organisms to escape pressures otherwise present in nature, such as drought or nutrient deficiencies during the growing season. In very disturbed systems, however, specialists may also suffer from negative effects of land use intensity. This co‐occurrence method to assess niche width opens the door to estimating the soil community's niche breadth, for which resource‐based methods are difficult to implement. A free Plain Language Summary can be found within the Supporting Information of this article.

Polycultures, pastures and monocultures: Effects of land use intensity on wild bee diversity in tropical landscapes of southeastern Mexico

The conservation of pollinator diversity is fundamental to maintaining sustainable agricultural systems and food security. Some agricultural systems support pollinator diversity, while others may lead to their decline. Previous studies have evaluated the impacts of agricultural intensification on pollinators in temperate climates regions, but in tropical regions these impacts have been evaluated by only very few studies. We conducted a study in southeastern Mexico, in order to understand the effects of three agricultural systems on bee diversity in a tropical landscape. We compared 18 sites at two different scales (plot scale and landscape scale). We found a link between agricultural system intensity level at the plot scale and forest proportion at the landscape scale: land use intensity was low at both scales in 7 polycultures, low at plot scale and high at landscape scale in 4 pastures, and high at both scales in 7 monocultures. We collected bees at all sites, and found an overall high bee richness, with a total of 127 species. Bee richness was compared across agricultural systems using diversity accumulation curves with iNEXT package. Both polycultures and pastures had significantly higher richness as monocultures. We constructed bee species guilds according to ecological and life-history traits (i.e. size, sociality and nesting) and found that whatever the trait considered, the species richness in the different agricultural systems was most often affected in the same way than the complete community richness. Our results show, for the first time in tropical conditions that agricultural systems with low-intensity farming practices and forested landscape allow the preservation of a significantly higher diversity of bees than agricultural systems with high-intensity farming practices and highly deforested landscape. Considering that bee diversity is key to maintaining crop productivity, these findings can help scientists, policy-makers, and community members design policies that support both agricultural production and biodiversity conservation in the tropics.

Functional diversity overrides community-weighted mean traits in linking land-use intensity to hydrological ecosystem services

Land-use intensification can importantly influence terrestrial ecosystem services by altering plant functional traits. Although we know that functional traits influence both ecosystem properties and services, we do not fully understand the mechanistic pathways governing these relationships nor how they will respond to global climate change. To identify the impact pathways of land-use intensity on hydrological services under changing precipitation regimes, we monitored hydrological services in 15 plots of different land-use types during 25 precipitation events (6 light, 8 moderate, and 11 heavy rains). Bayesian structural equation modeling was used to quantify the direct and indirect effects between land-use intensity, functional trait components (community weighted mean [CWM] and functional diversity [FD]), ecosystem properties (canopy density, litter fall and fine-root density), and hydrological services under different rainfall intensities. The impact of land-use intensity on hydrological service provisioning was regulated by plant functional traits regardless of intensity rainfall. Under light and moderate rain, FD significantly influenced hydrological services by altering canopy density and fine-root density, but we found no significant effect of CWMs. Under heavy rain, FD had significant, and greater, impacts on hydrological services than CWM of traits, although CWM of traits influenced hydrological services provision indirectly by altering canopy density and fine-root density. Land-use intensity indirectly affected hydrological services mainly by altering FD regardless of rainfall intensification, suggesting that the reduction of niche differentiation caused by land-use intensity is the main mechanism of hydrological services degradation. Our results suggested that the effect of land-use intensity on hydrological services are likely to change with increasing frequency of extreme precipitation events because of the different underlying mechanism at play and emphasize the importance of FD in maintaining hydrological services in respond to global environmental changes.

Landscape-scale effects of land use intensity on birds and butterflies

Although today there is ample evidence that biodiversity is affected by agricultural land use intensification, little is known about how species respond to different land use intensity gradients at landscape scale. To properly describe the relationship between biodiversity and land use intensity, intensity indicators need to account for land cover, management intensity, and be assessed at landscape scale. The study was conducted in 91 landscapes of 1 km2 in Switzerland. Three different land use intensity indicators were calculated: indicator 1 was defined as the ratio between agricultural and natural area; indicator 2 as the ratio between arable land and permanent grassland; and indicator 3 as the ratio between agricultural area and biodiversity promotion areas (BPA, i.e. wildlife-friendly managed areas under Swiss agri-environment schemes). Species richness and abundance of birds and butterflies were used as biodiversity indicators and trait-based community indices were used to describe bird community changes. Overall, we found that birds were affected by landscape composition and agricultural management, while butterflies were mainly affected by agricultural management. Specifically, from natural (e.g. forest dominated) to agriculture-dominated landscape, bird species richness showed a sharp decrease when 80% or more of the landscape was farmed. Butterfly species richness followed a hump-shaped curve. None of the species groups was significantly correlated with the proportion of arable land versus permanent grassland. Yet species richness of birds and butterflies significantly changed with the proportion of BPA: the lower the proportion of BPA, the lower the observed richness. Finally, when the proportion of agricultural land increased, populations of migratory birds and hedge/tree breeders decreased. We conclude that to further promote farmland biodiversity, natural areas, such as forests, hedges and waterbodies, should cover at least 20% of the agricultural landscapes and the proportion of BPA should be increased.

Effects of abiotic environmental factors and land use on the diversity of carrion-visiting silphid beetles (Coleoptera: Silphidae): A large scale carrion study.

Anthropogenic land use causes global declines in biodiversity. Despite the knowledge that animal carrion is the most nutrient-rich form of dead organic matter, studies on landscape and local scales determining whether and the means by which land use intensity influences the diversity of the carrion-associated insect fauna are globally scarce. We investigated the effects of land use intensity and abiotic and biotic environmental factors on the abundance, species richness, and diversity of the important ecosystem-service-providing silphid beetle taxon (carrion beetles) in three regions of Germany. In 61 forest stands distributed over three geographically distinct regions in Central Europe, we trapped silphid beetles on exposed piglet cadavers during late summer. In all three regions, higher ambient temperatures and higher fine sand contents were associated with the abundance of the silphid beetle taxa. The carrion community silphid diversity was negatively affected by an increase in mean ambient temperature in all three regions. Although management intensity in forests did not affect the overall abundance of Silphidae, the abundance of Nicrophorus humator decreased significantly with higher forest management intensity across all three regions. Unmanaged and age-class forests showed a higher abundance of N. humator compared with extensively managed forest stands. These findings indicate that N. humator has potential as an indicator species for anthropogenic disturbances in forests. Overall, the direct responses of the silphid beetle community to diverse soil characteristics underline soil as an important factor determining the abundance and diversity of necrophagous carrion beetles in Central Europe. To protect these valuable ecosystem-service providers, forest-management-induced soil modifications need to be paid close attention.

Direct and indirect effects of agricultural intensification on a host-parasitoid system on the ribwort plantain (Plantago lanceolata L.) in a landscape context

Intensification of land use is known as a major driver of worldwide decline in biodiversity. Trophic interactions might be especially affected by a changing landscape structure due to agricultural intensification. In this study we investigated the effects of increasing land use intensity on a tritrophic system at different spatial scales in a landscape context. We examined two weevil species, Mecinus labilis Herbst and M. pascuorum Gyllenhal, as well as their common parasitoid, Mesopolobus incultus Walker, living on a common native herb, the ribwort plantain (Plantago lanceolata L.), at 76 sites in three geographic regions in Germany. The effect of land use intensity on species abundances was analysed across a range of spatial scales (100–2000 m) around the study sites. In all three regions and across most spatial scales, an increasing proportion of intensively managed grasslands in the surrounding landscape directly negatively influenced herbivore abundance. An increasing proportion of semi-natural habitats had a direct positive influence on herbivore abundance. The abundance of M. labilis was best explained at radii of r = 1500–2000 m, that of M. pascuorum at r = 100–500 m. The parasitoid, M. incultus, was indirectly influenced by land use intensity via the density of its two hosts. Agricultural intensification of grasslands can profoundly affect the abundance of their herbivorous and entomophagous fauna at landscape scale. This may have important implications for landscape management and the conservation of higher trophic level organisms in agricultural landscapes.

The Influence of Land Use Intensity on the Plant-Associated Microbiome of Dactylis glomerata L.

In this study, we investigated the impact of different land use intensities (LUI) on the root-associated microbiome of Dactylis glomerata (orchardgrass). For this purpose, eight sampling sites with different land use intensity levels but comparable soil properties were selected in the southwest of Germany. Experimental plots covered land use levels from natural grassland up to intensively managed meadows. We used 16S rRNA gene based barcoding to assess the plant-associated community structure in the endosphere, rhizosphere and bulk soil of D. glomerata. Samples were taken at the reproductive stage of the plant in early summer. Our data indicated that roots harbor a distinct bacterial community, which clearly differed from the microbiome of the rhizosphere and bulk soil. Our results revealed Pseudomonadaceae, Enterobacteriaceae and Comamonadaceae as the most abundant endophytes independently of land use intensity. Rhizosphere and bulk soil were dominated also by Proteobacteria, but the most abundant families differed from those obtained from root samples. In the soil, the effect of land use intensity was more pronounced compared to root endophytes leading to a clearly distinct pattern of bacterial communities under different LUI from rhizosphere and bulk soil vs. endophytes. Overall, a change of community structure on the plant–soil interface was observed, as the number of shared OTUs between all three compartments investigated increased with decreasing land use intensity. Thus, our findings suggest a stronger interaction of the plant with its surrounding soil under low land use intensity. Furthermore, the amount and quality of available nitrogen was identified as a major driver for shifts in the microbiome structure in all compartments.

Intensification of Upland Agriculture in Thailand: Development or Degradation?

AbstractThe large scale conversion of extensive swidden agriculture to intensive market oriented production of maize in upland areas of South East Asia is a cause of environmental concern. This study investigates how intensive maize cultivation affects soil quality in an upland area of Northern Thailand by comparing commonly used indicators of soil quality in soils from maize fields used at various intensities. Relations between these indicators and concentration of permanganate oxidizable carbon (Pox‐C) – a low cost proxy for soil quality – are also examined. The extent, type and drivers of land use changes between 2002 and 2012 are investigated by classification of high resolution satellite images, interviews, participatory mapping and questionnaires. We document a widespread change from traditional swidden agriculture to intensive cultivation of maize that is mainly brought about by economcic and political drivers. We show that the concentration of Pox‐C in the top soil of the maize fields is closely related to common indicators of soil quality and to farmers' perceptions of soil quality. Most of the other soil quality indicators are negatively – albeit not significantly – related to intensity of maize cultivation. There is a strong negative correlation between intensity of maize cultivation and concentration of Pox‐C in the upper 5 cm of the soil where the Pox‐C concentration declines with a rate of 40 mg year under maize−1. We conclude that Pox‐C is a sensitive indicator of effects of land use intensity on the soil and a useful integrative measure of soil quality. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of land use on taxonomic and functional diversity: a cross-taxon analysis in a Mediterranean landscape.

Land-use change is the major driver of biodiversity loss. However, taxonomic diversity (TD) and functional diversity (FD) might respond differently to land-use change, and this response might also vary depending on the biotic group being analysed. In this study, we compare the TD and FD of four biotic groups (ants, birds, herbaceous, woody vegetation) among four land-use types that represent a gradient of land-use intensity in a Mediterranean landscape (Mediterranean shrublands, dehesas, mixed-pine forests, olive groves). Analyses were performed separately at two different spatial scales: the sampling unit scale and the site scale. Land-use intensity effects on TD and FD were quite different and highly varied among the four biotic groups, with no single clear pattern emerging that could be considered general for all organisms. Additive partitioning of species diversity revealed clear contrasting patterns between TD and FD in the percentage of variability observed at each spatial scale. While most variability in TD was found at the larger scales, irregardless of organism group and land-use type, most variability in FD was found at the smallest scale, indicating that species turnover among communities is much greater than functional trait turnover. Finally, we found that TD and FD did not vary consistently, but rather followed different trajectories that largely depended on the biotic group and the intensity of land-use transformation. Our results highlight that the relationship of land use with TD and FD is highly complex and context-dependent.