Landscape-scale connectivity and fragment size determine species composition of grassland fragments

As a consequence of agricultural intensification and habitat fragmentation since the mid-20th century, biological diversity has declined considerably throughout the world, particularly in Europe. We assessed how habitat and landscape-scale heterogeneity, such as variation in fragment size (small vs. large) and landscape configuration (measured as connectivity index), affect plant and arthropod diversity. We focused on arthropods with different feeding behaviour and mobility, spiders (predators, moderate dispersal), true bugs (mainly herbivores and omnivores with moderate dispersal), wild bees (pollinators with good dispersal abilities), and wasps (pollinators, omnivores with good dispersal abilities). We studied 60 dry grassland fragments in the same region (Hungarian Great Plain); 30 fragments were represented by the grassland component of forest-steppe stands, and 30 were situated on burial mounds (kurgans). Forest-steppes are mosaics of dry grasslands with small forests in a matrix of plantation forests. Kurgans are ancient burial mounds with moderately disturbed grasslands surrounded by agricultural fields. The size of fragments ranged between 0.16–6.88 ha (small: 0.16–0.48 ha, large: 0.93–6.88 ha) for forest-steppes and 0.01–0.44 ha (small: 0.01–0.10 ha and large: 0.20–0.44 ha) for kurgans. Fragments also represented an isolation gradient from almost cleared and homogenous landscapes, to landscapes with relatively high compositional heterogeneity. Fragment size, connectivity, and their interaction affected specialist and generalist species abundances of forest-steppes and kurgans. Large fragments had higher species richness of ground-dwelling spiders, and the effect of connectivity was more strongly positive for specialist arthropods and more strongly negative for generalists in large than in small fragments. However, we also found a strong positive impact of connectivity for generalist plants in small kurgans in contrast to larger ones. We conclude that besides the well-known effect of enhancing habitat quality, increasing connectivity between fragments by restoring natural and semi-natural habitat patches would help to maintain grassland biodiversity.     

人工固沙植被恢复对地表节肢动物群落组成及多样性的影响

人工绿洲是干旱区主要的自然景观之一,为了维护绿洲稳定而营建的防护林强烈改变地表生态水文过程,进而影响着地上和地下生物多样性。然而,以往的研究对地上植被关注较多,而对土壤动物研究较少。以张掖绿洲外围人工固沙植被群落和天然固沙植被群落为研究对象,探讨人工固沙植被恢复对荒漠地表节肢动物群落组成及多样性的影响及不同动物类群对植被变化的响应模式。研究表明,天然固沙植被群落转变为人工固沙植被群落显著降低了地表节肢动物数量,但提高了地表节肢动物类群丰富度和多样性,这在5月份表现尤为明显。植被类型对地表节肢动物群落的影响不同,8月人工柽柳林群落地表节肢动物活动密度、类群丰富度和多样性均显著高于人工梭梭林群落。人工固沙植被恢复显著降低了适应荒漠环境的拟步甲科甲虫,而蚁科和部分蜘蛛的数量显著增加,它们对人工固沙植被恢复的响应模式不同决定了群落结构及多样性的变化规律。此外,研究还发现一些地表节肢动物类群对不同生境具有强烈的指示作用,如拟步甲科等可指示荒漠生境,潮虫科等可指示梭梭林生境,而蠼螋科和狼蛛科等可指示柽柳林生境。综上所述,人工栽植固沙灌木形成的固沙植被群落导致了一些适应荒漠环境的地表节肢动物类群的数量降低,但也为更多的地表节肢动物类群提供了适应栖居环境和充足的食物资源等,从而提高了地表节肢动物的多样性。     

Impacts of large herbivorous mammals on bird diversity and abundance in an African savanna

Large native mammals are declining dramatically in abundance across Africa, with strong impacts on both plant and animal community dynamics. However, the net effects of this large-scale loss in megafauna are poorly understood because responses by several ecologically important groups have not been assessed. We used a large-scale, replicated exclusion experiment in Kenya to investigate the impacts of different guilds of native and domestic large herbivores on the diversity and abundance of birds over a 2-year period. The exclusion of large herbivorous native mammals, including zebras (Equus burchelli), giraffes (Giraffa camelopardalis), elephants (Loxodonta africana), and buffalos (Syncerus caffer), increased the diversity of birds by 30%. Most of this effect was attributable to the absence of elephants and giraffes; these megaherbivores reduced both the canopy area of subdominant woody vegetation and the biomass of ground-dwelling arthropods, and both of these factors were good predictors of the diversity of birds. The canopy area of subdominant trees was positively correlated with the diversity of granivorous birds. The biomass of ground-dwelling arthropods was positively correlated with the diversity of insectivorous birds. Our results suggest that most native large herbivores are compatible with an abundant and diverse bird fauna, as are cattle if they are at a relatively low stocking rate. Future research should focus on determining the spatial arrangements and densities of megaherbivores that will optimize both megaherbivore abundance and bird diversity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Structure of ground-dwelling arthropod assemblages in vegetation units of Área Natural Protegida Península Valdés,Patagonia, Argentina

Knowing the spatial variation of insect and arachnid assemblages and their relationship with habitat variables is critical to understand the structure and dynamics of these communities in arid environments. The aim of this paper was to analyze the variation in ground-dwelling arthropod assemblages across three representative vegetation units of the Área Natural Protegida Península Valdés (Patagonia, Argentina). We asked whether environmental differences among representative vegetation units were associated to distinct arthropod assemblages. We selected three plant communities: grass, dwarf-shrub, and shrub steppes, and established three sampling sites within each of them. We measured variables of vegetation structure and soil characteristics and collected the arthropods using 10 pitfall traps per site. We analyzed the structure of arthropod assemblages at both family and ant species taxonomic levels. Each plant community displayed a distinctive assemblage, with differences in diversity, taxa abundance, trophic structure and functional groups of ants. Vegetation variables explained a higher proportion of the variation in the structure of the ground-dwelling arthropod assemblages than the soil variables. This work highlights the importance of the different vegetation units for the conservation of ground-dwelling arthropod biodiversity in Península Valdés.     

Effects of vegetation management by mowing on ground-dwelling arthropods

Species-rich grasslands are rare in the Netherlands and need consistent vegetation management to retain their characteristic biodiversity. Roadside verges are important refuges for grassland plants since the mowing management no longer aims at traffic safety only but also strives for botanical diversity. Although arthropods are highly abundant in roadside verges, the effect of different mowing practices on this group is largely unknown. During 4 years, we studied ground beetles, weevils, ants and ground-dwelling spiders with pitfall traps in experimental plots in roadside verges with five different mowing treatments: (i) no management, (ii) and (iii) mowing once a year with and without hay removal, (iv) and (v) mowing twice a year with and without hay removal. This was done in a plant productivity gradient; the experiment was repeated in low-, medium- and high-productive verges. In the low-productive site, the effect of management on the arthropods only existed in a higher abundance in plots mown twice per year with hay removal. In the medium- and high-productive sites, mowing twice a year with hay removal resulted not only in highest abundances but also in highest arthropod species richness. Mowing twice without hay removal and mowing once with removal showed intermediate values, while mowing once per year without removal and particularly the absence of management resulted in low diversity and low abundance. To promote ground-dwelling arthropods in medium-to-high-productive grassland verges, we recommend a management of mowing twice a year with the removal of hay. It is reasoned that some form of rotational management, aiming at leaving some vegetation refuges intact after mowing events, may further promote arthropod survival. However, caution should be taken that these refuges are not too large, as overall suitability for ground-dwelling arthropod decreases rapidly in such patches. Out of several studied vegetation characteristics, the number of flowering plant species (medium-productive verge) and total flower abundance (high-productive verge) appeared to represent suitable, and easily monitored, proxies that significantly mirror arthropod diversity.     

Effects of bird predation on canopy arthropods in wandoo Eucalyptus wandoo woodland

Abstract: As top predators, birds may have significant effects on arthropod abundances and affect the trophic structure of arthropod communities through predation of lower order predators (e.g. spiders) and by competition for prey. We investigated the effects of bird predation on canopy arthropods in south‐western Australia by using plastic bird mesh to exclude insectivorous birds from the foliage of wandoo Eucalyptus wandoo saplings. Exclosure resulted in an increase in the number of herbivorous and predatory arthropods. Total arthropods (with and without ants), spiders, adult Coleoptera, and larval Lepidoptera were significantly more abundant on meshed than unmeshed saplings. All size‐classes of arthropods, taxa grouped, were more abundant on meshed than unmeshed saplings, but with no evidence of a disproportionate increase of the largest arthropods on meshed saplings. All size‐classes of spiders increased in abundance on saplings from which birds were excluded. There were significant differences in the total abundance of arthropods (with and without ants), spiders (Araneae), sucking bugs (Homoptera), adult beetles (Coleoptera), larval moths (Lepidoptera), and wasps and ants (Hymenoptera) for both unmeshed and meshed saplings between sample periods. These seasonal patterns of abundance and differences between sample periods appeared to be determined by seasonal weather patterns, with the lowest numbers associated with drier and hotter conditions in summer and autumn than in winter and spring. The conclusion reached is that eucalypt forest birds have limited effects on temporal variation in canopy arthropod abundances, but depress abundances, and affect the size and trophic composition of the fauna. Given the cascading effects of birds as predators on arthropods, successful conservation management of eucalypt ecosystems, including plantations and revegetation, should be planned to maximize bird numbers and diversity.     

Biological consequences of invasion by reed canary grass (<Emphasis Type="Italic">Phalaris arundinacea</Emphasis>)

Although they are typically assumed to be negative, the consequences of plant invasions for native diversity or biological integrity are seldom broadly quantified (i.e., for multiple taxa or across large regions). We investigated the impacts associated with invasion of wetlands by reed canary grass (Phalaris arundinacea L.; RCG) on plants and several animal groups. In a local study, we compared plants, arthropods, and small mammals on treatment plots with reduced RCG dominance to those on highly invaded plots. We also conducted a companion study, where we measured RCG dominance and plants, arthropods, and birds in 82 randomly selected wetlands across Illinois (USA) to determine if our experimental results were consistent in communities across the region. Plant diversity, floristic quality, and diversity and abundance of Homopteran insects decreased with RCG dominance in all instances. Richness and abundance of all other arthropods decreased with increasing RCG in the local study, but no trend was detected in communities statewide. No relationship between total abundance or richness of small mammals (local) or birds (statewide) with RCG was detected. However, voles and shrews were more abundant, and mice less abundant, in RCG-dominated plots. These results support the hypothesis that there are negative effects for multiple taxa from RCG invasion. Because negative effects observed in the local study either corroborated, or were neutral with respect to results from statewide surveys, they suggest that native biodiversity and biological integrity are being dampened across wide areas of this invader’s range.     

Effects of landscape connectivity on the spatial distribution of insect diversity in agricultural mosaic landscapes

European agricultural landscapes are mosaics of intensively cultivated areas and semi-natural elements. Although comprising only a small fraction of the total area, semi-natural elements provide habitat for most of the landscape biodiversity. Agricultural intensification has increasingly fragmented semi-natural elements and species numbers are in decline. Insights into the effects of landscape structure on species’ distributions within and among semi-natural habitats are needed to conserve biodiversity in agricultural landscapes more effectively. We investigated the landscape- and habitat-specific diversity partitions of wild bees, true bugs, and carabid beetles in two differently structured agricultural landscapes in Switzerland. In each landscape, we partitioned the total species diversity (γ) into its additive components within (_P) and among patches (β_P) and among habitats (β_H). In the landscape characterized by a patchy, isolated distribution of habitat elements, among-patch diversity (β_P) explained 44% of the total species richness (γ) and was significantly higher than expected under a random distribution of samples among habitat patches; in the landscape with higher habitat connectivity, among-patch diversity (β_P) comprised 32% of the total species richness (γ) and did not differ from the random expectation. Habitat-specific within-patch contributions to species richness were similarly low across habitat types (_P=23–24%) in the patchy landscape, whereas in the more connected landscape within-patch partitions tended to be higher and differed among habitat types (_P=22–38%). Functionally different groups of bees, true bugs, and carabids also responded differently to landscape structure in a manner that was consistent with known differences in resource specialization and dispersal ability. Differences in diversity partitions among landscapes and taxa indicate the need for flexible conservation strategies. Conservation of habitat-specific diversity may require more habitat patches in landscapes that have lower habitat connectivity and low within-patch diversity (_P) than in landscapes with higher within-patch diversity (_P).     

Plant genotypic diversity and environmental stress interact to negatively affect arthropod community diversity

Many studies have found positive relationships between plant diversity and arthropod communities, but the interactive effects of plant genetic diversity and environmental stress on arthropods are not well documented. In this study, we investigated the consequences of plant genotypic diversity, watering treatment, and its interaction for the ground-dwelling arthropod community in an experimental common garden of quaking aspen (Populus tremuloides Michx.). We found that varying plant genotypic diversity and watering treatment altered multivariate arthropod community composition and structure. Arthropod biodiversity and richness showed a distinct response to the plant diversity × watering treatment interaction, declining sharply in water-limited genotypic mixtures. Abundance of arthropod functional groups did not show any response to diversity or the plant diversity × watering treatment interaction, but varied in their response to watering treatment, with predator and detritivore abundance increasing and parasitoid abundance decreasing in well-watered blocks. Our results conflict with most previous studies, and suggest that environmental stress can substantially change the nature of the plant-arthropod diversity relationship. Additionally, we suggest that the plant-arthropod diversity relationship is dependent on the type of plant and arthropod species sampled, and that the association between tree diversity and ground-dwelling arthropods may be much different than more commonly studied grassland species and herbivorous arthropods.     

Roadside habitats: effects on diversity and composition of plant, arthropod, and small mammal communities

Road edge effects cover extensive areas and exert a wide range of ecological influences on nearby plants and animals. Most studies have focused on individual and population level effects of the road edge; less is known about how communities and their functionality are altered in proximity to roads. Here, we studied the effect of road edges on species richness, rarity, endemism, composition, and functional (trophic) classification of communities of plants, ground-dwelling arthropods (beetles, spiders, scorpions, diplopods), and small mammals. The study, conducted in a Mediterranean ecosystem in central Israel, included sampling of these taxa in 10 plots adjacent to a regional road, and in 12 nearby control plots located in a typical shrubland habitat. We found a variety of community level road edge effects on the structure, composition, and function of the studied communities. The extent of effects varied among taxa, but they were generally positive or neutral. For the species-rich taxa (plants, beetles, and spiders), distinct road edge communities characterized by higher richness and altered species composition were found. Rarity and endemism were lower, and the proportion of disturbance-associated plant species was higher at the road edge. Among the species-poor taxa, scorpions and small mammals were more abundant along road edges than in control plots, while diplopods, the only negatively affected taxon, showed decreased abundance along the road. No ecologically meaningful changes in richness or composition were detected for the species-poor taxa along the road edge. Road edges profoundly affect floral and faunal communities, with possible implications for biodiversity conservation.     

Measuring the Short‐term Success of Grassland Restoration: The Use of Habitat Affinity Indices in Ecological Restoration

Agricultural intensification threatens grasslands worldwide and the restoration of grasslands from arable lands can at least partially counter this threat. We studied grassland restoration by following early successional changes of arthropod assemblages (spiders, Araneae; true bugs, Heteroptera; orthopterans, Orthoptera; and ground beetles, Carabidae) on 1‐ and 2‐year‐old restorations using arable lands and native grasslands as two ends of the succession timescale. To examine the changes in species composition among the habitat types, we used habitat affinity indices based on fidelity and/or specificity of the species. We found that the number of species did not differ between habitat types, while species composition changed markedly with time. Species richness was thus not adequate to detect favorable changes after grassland restoration. Habitat affinity indices, on the other hand, were useful to detect compositional changes caused by the increasing numbers of species characteristic of target grasslands as early as the second year after restoration. Habitat affinity indices are easy‐to‐use, easy‐to‐interpret measures of restoration success; therefore, we recommend their use as measures complementary to species richness and simple similarity. Our results show that sowing low‐diversity seed mixture followed by mowing and grazing can be particularly successful in grassland restoration in time periods as short as 2 years.     

River drying lowers the diversity and alters the composition of an assemblage of desert riparian arthropods

Summary 1. Many studies have shown negative effects of river drying on in‐stream animals. However, the influence of river drying on riparian animals remains poorly studied. We examined ground‐dwelling riparian arthropod assemblages along a drying section of the semi‐arid San Pedro River in southeastern Arizona, U.S.A. 2. We found strong differences in assemblage composition, taxon diversity and the abundance of key taxa between dry and flowing sites, with higher diversity and abundance of most taxa at flowing sites. 3. Changes in assemblage composition, taxon diversity and abundance of representative taxa were associated with a combined measure of water availability that included distance to water and type of water. Other environmental variables showed a weaker association with changes in these arthropod assemblages. 4. Thus, we found evidence that desert riparian arthropods are sensitive to river drying and to reduction in water resources. Increases in drying along this river may reduce the diversity and the abundance of many groups of ground‐dwelling arthropods, leading to marked shifts in community composition.     

Plant diversity effects on arthropods and arthropod-dependent ecosystem functions in a biodiversity experiment

Biodiversity-ecosystem function experiments test how species diversity influences fundamental ecosystem processes. Historically, arthropod driven functions, such as herbivory and pest-control, have been thought to be influenced by direct and indirect associations among species. Although a number of studies have evaluated how plant diversity affects arthropod communities and arthropod-mediated ecosystem processes, it remains unclear whether diversity effects on arthropods are sufficiently consistent over time such that observed responses can be adequately predicted by classical hypotheses based on associational effects. By combining existing results from a long-term grassland biodiversity experiment (Jena Experiment) with new analyses, we evaluate the consistency of consumer responses within and across taxonomic, trophic, and trait-based (i.e. vertical stratification) groupings, and we consider which changes in arthropod community composition are associated with changes in consumer-mediated ecosystem functions.Overall, higher plant species richness supported more diverse and complex arthropod communities and this pattern was consistent across multiple years. Vegetation-associated arthropods responded more strongly to changes in plant species richness than ground-dwelling arthropods. Additionally, increases in plant species richness were associated with shifts in the species-abundance distributions for many, but not all taxa. For example, highly specialized consumers showed a decrease in dominance and an increase in the number of rare species with increasing plant species richness. Most ecosystem processes investigated responded to increases in plant species richness in the same way as the trophic group mediating the process, e.g. both herbivory and herbivore diversity increase with increasing plant species richness. In the Jena Experiment and other studies, inconsistencies between predictions based on classic hypotheses of associational effects and observed relationships between plant species richness and arthropod diversity likely reflect the influence of multi-trophic community dynamics and species functional trait distributions. Future research should focus on testing a broader array of mechanisms to unravel the biological processes underlying the biodiversity-ecosystem functioning relationships.     

胜山阔叶红松林蚂蚁巢穴对其他地表节肢动物多样性的影响

为了阐明蚂蚁巢穴对其他地表节肢动物群落组成和多样性的影响,于2019年在胜山自然保护区的原始阔叶红松林内开展实验,并采用陷阱法收集地表节肢动物.共捕获地表节肢动物92266只,分别为蜈蚣目、盲蛛目、马陆目、蜘蛛目,大头蚁属和步甲科、隐翅虫科、葬甲科这8个类群;蚂蚁巢穴存在及到蚂蚁巢穴的不同距离对其他地表节肢动物个体数量...     

Declines in a ground-dwelling arthropod community during an invasion by Sahara mustard (Brassica tournefortii) in aeolian sand habitats

Sahara Mustard (Brassica tournefortii; hereafter mustard), an exotic plant species, has invaded habitats throughout the arid southwestern United States. Mustard has reached high densities across aeolian sand habitats of southwestern deserts, including five distinct sand habitats in the eastern Coachella Valley, California. We examined trends in ground-dwelling arthropod community structure concurrent with mustard invasion in 90 plots within those habitats from 2003 to 2011 (n = 773 plot·years). We expected arthropod communities to respond negatively to mustard invasion because previous work documented significant negative impacts of mustard on diversity and biomass of native plants, the primary resource base for many of the arthropods. Arthropod abundance and species richness declined during the study period while mustard cover increased, and arthropod metrics were negatively related to mustard cover across all plots. When controlling for non-target environmental correlates (e.g. perennial frequency and precipitation) and for potential factors that we suspected of mediating mustard effects (e.g. native cover and sand compaction), negative relationships with mustard remained statistically supported. Nevertheless, arthropod richness’s relationship decreased slightly in strength and significance suggesting that mechanistic pathways may be both direct (via habitat structure) and indirect (via native cover suppression and sand compaction). However, mechanistic pathways for mustard effects, particularly on arthropod abundance, remain unclear. Most arthropod taxa, including most detritivores, decreased through time and were negatively related to mustard cover. In contrast, many predators were positively related to mustard. In total, our study provides substantial evidence for a negative effect of Sahara mustard on the structure of a ground-dwelling arthropod community.     

Even the Smallest Non-Crop Habitat Islands Could Be Beneficial: Distribution of Carabid Beetles and Spiders in Agricultural Landscape

Carabid beetles and ground-dwelling spiders inhabiting agroecosystems are beneficial organisms with a potential to control pest species. Intensification of agricultural management and reduction of areas covered by non-crop vegetation during recent decades in some areas has led to many potentially serious environmental problems including a decline in the diversity and abundance of beneficial arthropods in agricultural landscapes. This study investigated carabid beetle and spider assemblages in non-crop habitat islands of various sizes (50 to 18,000 square metres) within one large field, as well as the arable land within the field, using pitfall traps in two consecutive sampling periods (spring to early summer and peak summer). The non-crop habitat islands situated inside arable land hosted many unique ground-dwelling arthropod species that were not present within the surrounding arable land. Even the smallest non-crop habitat islands with areas of tens of square metres were inhabited by assemblages substantially different from these inhabiting arable land and thus enhanced the biodiversity of agricultural landscapes. The non-crop habitat area substantially affected the activity density, recorded species richness and recorded species composition of carabid and ground-dwelling spider assemblages; however, the effects were weakened when species specialised to non-crop habitats species were analysed separately. Interestingly, recorded species richness of spiders increased with non-crop habitat area, whereas recorded species richness of carabid beetles exhibited an opposite trend. There was substantial temporal variation in the spatial distribution of ground-dwelling arthropods, and contrasting patterns were observed for particular taxa (carabid beetles and spiders). In general, local environmental conditions (i.e., non-crop habitat island tree cover, shrub cover, grass cover and litter depth) were better determinants of arthropod assemblages than non-crop habitat island size, indicating that the creation of quite small but diversified (e.g., differing in vegetation cover) non-crop habitat islands could be the most efficient tool for the maintenance and enhancement of diversity of ground-dwelling carabids and spiders in agricultural landscapes.     

Ants and plants as indicators of biodiversity,ecosystem services,and conservation value in constructed grasslands

Grasslands are constructed for soil and wildlife conservation in agricultural landscapes across Europe and North America. Constructed grasslands may mitigate habitat loss for grassland-dependent animals and enhance ecosystem services that are important to agriculture. The responses of animal species richness and abundance to grassland habitat quality are often highly variable, however, and monitoring of multiple taxa is often not feasible. We evaluated whether multiple animal taxa responded to variation in constructed grassland habitats of southwest Ohio, USA, in ways that could be predicted from indicators based on quality assessment indices, Simpson diversity, and the species richness of ants and plants. The quality assessment indices included a widely used Floristic Quality Assessment (FQA) index, and a new Ant Quality Assessment (AntQA) index, both based on habitat specificity and species traits. The ant and plant indicators were used as predictor variables in separate general linear models of four target taxa—bees, beetles, butterflies and birds—with response variables of overall species richness and abundance, and subsets of taxa that included the abundance of ecosystem-service providers and grassland-associated species. Plant Simpson diversity was the best-fitting predictor variable in models of overall bee and beetle abundance, and the abundance of bees classified as ecosystem-service (ES) providers. FQA and plant richness were the best predictors of overall butterfly species richness and abundance. Ant species richness was the best predictor of overall bird species richness and abundance as well as the abundance of ES birds, while the AntQA index was the best predictor for the abundance of grassland bird and butterfly species. Thus, plant Simpson diversity and ant species richness were the most effective indicators for complementary components of grassland animal communities, whereas quality assessment indices were less robust as indicators and require more knowledge on the habitat specificity of individual ant and plant species.     

The influence of habitat structure on arthropod diversity in Argentine semi-arid Chaco forest

Abstract. The Argentine Chaco is a mosaic of grassland and open forest habitats maintained by natural disturbance activities such as fire. Since the introduction of domestic livestock and other human activities, the balance of this mosaic has been significantly altered, both in plant species and structural composition. This study focuses on the impact of such changes on the diversity of ground-dwelling arthropods within semi-arid Chaco forest. Quantitative measures of habitat structure and arthropod diversity were taken in forest areas previously subjected to grazing, logging and ploughing. Results indicated that arthropod diversity was smaller on sites with reduced structural complexity, with marked changes in arthropod family composition. The habitat components relating to plant architectural and vertical diversity were particularly influential on arthropod diversity. The guild size ratio of predatory to non-predatory arthropods also differed significantly between habitats suggesting a change in the resource base available to some groups. The latter suggests a shift in the functional organisation of the forest ecosystem which could have important repercussions for the diversity of other trophic levels.     

Plant diversity and habitat structure affect tree growth,herbivory and natural enemies in shelterbelts

Shelterbelts have become a refuge and source of food for wildlife because of habitat loss in farmlands. However, effects of shelterbelt attributes such as plant diversity and habitat structure on different trophic levels within shelterbelts are unclear. Effects of shelterbelt woody plant diversity and habitat structure (lower vegetation strata, logs, litter and rocks) were measured on the growth and herbivory of Eucalyptus blakelyi saplings that were caged from birds, caged from birds and arthropods and un-caged. Arthropod diversity of E. blakelyi saplings and shelterbelts was evaluated. Height and stem diameter of saplings in all treatments was positively correlated with plant diversity. Habitat structure was negatively correlated with numbers of leaves on E. blakelyi saplings and positively correlated with herbivory, which was greater in saplings caged from birds. The overall abundance of arthropods inhabiting shelterbelts correlated positively with plant diversity, but negatively with habitat structure. Araneae and Formicidae were the most common taxa on E. blakelyi saplings and were more numerous on saplings caged from birds, suggesting an important role of these vertebrates as predators of shelterbelt arthropods.     

Birds as surrogates for mammals and reptiles: Are patterns of cross-taxonomic associations stable over time in a human-modified landscape?

Cross-taxonomic surrogates can be feasible alternatives to direct measurements of biodiversity in conservation if validated with robust data and used with explicit goals. However, few studies of cross-taxonomic surrogates have examined how temporal changes in composition or richness in one taxon can drive variation in concordant patterns of diversity in another taxon, particularly in a dynamic and heavily modified landscape. We examined this problem by assessing changes in cross-taxonomic associations over time between the surrogate (birds) and target vertebrate taxa (mammals, reptiles) that demand high sampling effort, in a heterogeneous mosaic landscape comprising pine monoculture, eucalypt woodland remnants and agricultural land. Focussing on four study years (1999, 2001, 2011, 2013) from a dataset spanning 15 years, we: (1) investigated temporal changes in cross-taxonomic congruency among three animal taxa, (2) explored how temporal variation in composition and species richness of each taxon might account for variation in cross-taxonomic congruency, and (3) identified habitat structural variables that are strongly correlated with species composition of each taxon. We found the strength of cross-taxonomic congruency varied between taxa in response to both landscape context and over time. Among the three taxa, overall correlations were weak but were consistently positive and strongest between birds and mammals, while correlations involving reptiles were usually weak and negative. We also found that stronger species richness and composition correlations between birds and mammals were not only more prevalent in woodland remnants in the agricultural matrix, but they also increased in strength over time. Temporal shifts in species composition differed in rate and extent among the taxa even though these changes were significant over time, while important habitat structural correlates were seldom shared across taxa. Our study highlights the role of the landscape matrix and time in shaping animal communities and the resulting cross-taxonomic associations in the woodland remnants, especially after a major perturbation event (i.e. plantation establishment). In such dynamic landscapes, differing and taxon-specific shifts in diversity over time can influence the strength, direction and consistency of cross-taxonomic correlations, therefore posing a ‘temporal’ problem for the use of surrogates like birds in monitoring and assessments of biodiversity, and conservation management practices.