Perennial biomass feedstocks enhance avian diversity

Federal mandates to increase biofuel production in North America will require large new tracts of land with potential to negatively impact biodiversity, yet empirical information to guide implementation is limited. Because the temperate grassland biome will be a production hotspot for many candidate feedstocks, production is likely to impact grassland birds, a group of major conservation concern. We employed a multiscaled approach to investigate the relative importance of arthropod food availability, microhabitat structure, patch size and landscape‐scale habitat structure and composition as factors shaping avian richness and abundance in fields of one contemporary (corn) and two candidate cellulosic biomass feedstocks (switchgrass and mixed‐grass prairie) not currently managed as crops. Bird species richness and species density increased with patch size in prairie and switchgrass, but not in corn, and was lower in landscapes with higher forest cover. Perennial plantings supported greater diversity and biomass of arthropods, an important food for land birds, but neither metric was important in explaining variation in the avian community. Avian richness was higher in perennial plantings with greater forb content and a more diverse vegetation structure. Maximum bird species richness was commonly found in fields of intermediate vegetation density and grassland specialists were more likely to occur in prairies. Our results suggest that, in contrast to corn, perennial biomass feedstocks have potential to provide benefits to grassland bird populations if they are cultivated in large patches within relatively unforested landscapes. Ultimately, genetic improvement of feedstock genets and crop management techniques that attempt to maximize biomass production and simplify crop vegetation structure will be likely to reduce the value of perennial biomass plantings to grassland bird populations.     

Bird Communities and Biomass Yields in Potential Bioenergy Grasslands

Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes.     

Perennial Agroenergy Feedstocks as En Route Habitat for Spring Migratory Birds

Increased production of bioenergy crops in North America is projected to exacerbate already heavy demands upon existing agricultural landscapes with potential to impact biodiversity negatively. Grassland specialist birds are an imperilled avifauna for which perennial-based, next-generation agroenergy feedstocks may provide suitable habitat. We take a multi-scaled spatial approach to evaluate the ability of two candidate second-generation agroenergy feedstocks (switchgrass, Panicum virgatum, and mixed grass–forb plantings) to act as spring migratory stopover habitat for birds. In total, we detected 35 bird species in mixed grass–forb plantings and switchgrass plantings, including grassland specialists and species of state and national conservation concern (e.g., Henslow’s Sparrow, Ammodramus henslowii). Some evidence indicated that patches with higher arthropod food availability attracted a greater diversity of migrant bird species, but species richness, total bird abundance, and the abundance of grassland specialist species were similar in fields planted with either feedstock. Species richness per unit area (species density) was relatively higher in switchgrass fields. The percent land cover of forest in landscapes surrounding study fields was negatively associated with bird species richness and species density. Habitat patch size and within-patch vegetation structure were unimportant in predicting the diversity or abundance of spring en route bird assemblages. Our results demonstrate that both switchgrass and mixed grass–forb plantings can attract diverse assemblages of migrant birds. As such, industrialized production of these feedstocks as agroenergy crops has the potential to provide a source of en route habitat for birds, particularly where fields are located in relatively unforested landscapes. Because industrialization of cellulosic biomass production will favor as yet unknown harvest and management regimes, predicting the ultimate value of perennial-based biomass plantings for spring migrants remains difficult.     

Avian use of perennial biomass feedstocks as post-breeding and migratory stopover habitat

Increased production of biomass crops in North America will require new agricultural land, intensify the cultivation of land already under production and introduce new types of biomass crops. Assessing the potential biodiversity impacts of novel agricultural systems is fundamental to the maintenance of biodiversity in agricultural landscapes, yet the consequences of expanded biomass production remain unclear. We evaluate the ability of two candidate second generation biomass feedstocks (switchgrass, Panicum virgatum, and mixed-grass prairie) not currently managed as crops to act as post-breeding and fall migratory stopover habitat for birds. In total, we detected 41 bird species, including grassland specialists and species of state and national conservation concern (e.g. Henslow's Sparrow, Ammodramus henslowii). Avian species richness was generally comparable in switchgrass and prairie and increased with patch size in both patch types. Grassland specialists were less abundant and less likely to occur in patches within highly forested landscapes and were more common and likely to occur in larger patches, indicating that this group is also area-sensitive outside of the breeding season. Variation in the biomass and richness of arthropod food within patches was generally unrelated to richness and abundance metrics. Total bird abundance and that of grassland specialists was higher in patches with greater vegetation structural heterogeneity. Collectively, we find that perennial biomass feedstocks have potential to provide post-breeding and migratory stopover habitat for birds, but that the placement and management of crops will be critical factors in determining their suitability for species of conservation concern. Industrialization of cellulosic bioenergy production that results in reduced crop structural heterogeneity is likely to dramatically reduce the suitability of perennial biomass crops for birds.     

Long-term variability of root production in bioenergy crops from ingrowth core measurements

用内生长法测定的生物能源作物根生产的长期变化 对于土地用途转为种植生物燃料作物后的根系产量,还很少进行过长期的测定。为了评价此前的土地用途对地下生物量积累的影响,我们在“美国休耕保护项目”(Conservation Reserve Program, CPR)下生长了22年的草地(CRP草地)和使用期超过50年的农业用地(AGR农地)转为种植生物燃料作物玉米(Zea mays, Corn, C)、柳枝稷(Panicum virgatum, Switchgrass, Sw)和恢复性草原植被(Prairie, Pr)。我们将一块CPR草地维持为对照。我们的假设是土地利用历史和作物类型对根系密度有显著的影响;其中,原CRP草地上种植的多年生作物具有较高的根系生产力,而在原农业用地上种植的玉米的根系生产力最低。通过内生长土芯法对内生长根系生物量进行了原位测定,同时对地上净初级生产力(ANPP)进行了测量。包括气温、生长季长度和降水量在内的辅助测量则被用来考查它们对根系生产量的影响。根系生产力在未转变的CRP草地最高(1716 g m⁻² yr⁻¹),而在玉米田中最低(526 g m⁻² yr⁻¹)。由CRP草地和AGR农田转变而来的多年生作物种植地在第一年都具有较低的根系生物量和ANPP,但柳枝稷在2011年达到峰值,恢复后的草原植被也在一年后达到峰值。恢复后的草原生态系统稳定性较高(AGR-Pr: 4.3 ± 0.11; CRP-Pr: 4.1 ± 0.10),而仅种植单一作物的生态系统稳定性都较低。根系生产量与ANPP呈正相关性(R² = 0.40)。总体而言,对生物燃料作物大规模种植过程中的根系生物量积累应予以重视,因为这是固碳的一种主 要来源。     

Grass Invasion into Switchgrass Managed for Biomass Energy

Switchgrass (Panicum virgatum) is a C₄ perennial grass and is the model herbaceous perennial bioenergy feedstock. Although it is indigenous to North American grasslands east of the Rocky Mountains and has been planted for forage and conservation purposes for more than 75 years, there is concern that switchgrass grown as a biofuel crop could become invasive. Our objective is to report on the invasion of C₄ and C₃ grasses into the stands of two switchgrass cultivars following 10 years of management for biomass energy under different N and harvest management regimes in eastern Nebraska. Switchgrass stands were invaded by big bluestem (Andropogon gerardii), smooth bromegrass (Bromus inermis), and other grasses during the 10 years. The greatest invasion by grasses occurred in plots to which 0 N had been applied and with harvests at anthesis. In general, less grass encroachment occurred in plots receiving at least 60 kg of N ha^?1 or in plots harvested after frost. There were differences among cultivars with Cave-in-Rock being more resistant to invasion than Trailblazer. There was no observable evidence of switchgrass from this study invading into border areas or adjacent fields after 10 years of management for biomass energy. Results indicate that switchgrass is more likely to be invaded by other grasses than to encroach into native prairies or perennial grasslands seeded on marginally productive cropland in the western Corn Belt of the USA.     

Switchgrass for bioethanol and other value-added applications: a review

Switchgrass is a promising feedstock for value-added applications due to its high productivity, potentially low requirements for agricultural inputs and positive environmental impacts. The objective of this paper is to review published research on the conversion of switchgrass into bioethanol and other value-added products. Environmental benefits associated with switchgrass include the potential for carbon sequestration, nutrient recovery from runoff, soil remediation and provision of habitats for grassland birds. Pretreatment of switchgrass is required to improve the yields of fermentable sugars. Based on the type of pretreatment, glucose yields range from 70% to 90% and xylose yields range from 70% to 100% after hydrolysis. Following pretreatment and hydrolysis, ethanol yields range from 72% to 92% of the theoretical maximum. Other value-added uses of switchgrass include gasification, bio-oil production, newsprint production and fiber reinforcement in thermoplastic composites. Future prospects for research include increased biomass yields, optimization of feedstock composition for bioenergy applications, and efficient pentose fermentation to improve ethanol yields.     

Ecology and conservation of grassland birds in southeastern South America: a review

ABSTRACT The grasslands of southeastern South America (SESA), comprising one of the most extensive grassland ecosystems in the Neotropics, have been negatively impacted by the development of the livestock industry, arable agriculture, and forestry. SESA grasslands have a rich avifauna that includes 22 globally threatened and near‐threatened species, and many other species have suffered local population extinctions and range reductions. In addition to habitat loss and fragmentation, grassland birds in SESA are threatened by improper use of agrochemicals, unfavorable fire management regimes, pollution, and illegal capture and hunting. Studies to date have provided information about the distribution of grassland birds, the threats populations face, and the habitat requirements of some threatened species, but more information is needed concerning dispersal and migration patterns, genetics, and factors that influence habitat use and species survival in both natural and agricultural landscapes. There are few public protected areas in the region (1% of original grasslands), and many populations of threatened grassland birds are found on private lands. Therefore, efforts to preserve grassland habitat must reconcile the interests of land owners and conservationists. Current conservation efforts include establishment of public and private reserves, promotion of agricultural activities that reconcile production with biodiversity conservation, development of multilateral conservation projects across countries, and elaboration of action plans. Measures that result in significant losses to private land owners should include economic compensation, and use of economic incentives to promote agriculture and forestry in native grassland areas should be discouraged, especially in priority areas for grassland birds. Although more studies are needed, some actions, particularly habitat protection and improved management of public and private lands, should be taken immediately to improve the conservation status of grassland birds in SESA.     

Influence of Patch Factors and Connectivity on the Avifauna of Fragmented Polylepis Forest in the Ecuadorian Andes

Human‐induced alteration of habitat is a major threat to biodiversity worldwide, especially in areas of high biological diversity and endemism. Polylepis (Rosaceae) forest, a unique forest habitat in the high Andes of South America, presently occurs as small and isolated patches in grassland dominated landscapes. We examine how the avian community is likely influenced by patch characteristics (i.e., area, plant species composition) and connectivity in a landscape composed of patches of Polylepis forest surrounded by páramo grasslands in Cajas National Park in the Andes of southern Ecuador. We used generalized linear mixed models and an information‐theoretic approach to identify the most important variables probably influencing birds inhabiting 26 forest patches. Our results indicated that species richness was associated with area of a patch and floristic composition, particularly the presence of Gynoxys (Asteraceae). However, connectivity of patches probably influenced the abundance of forest and generalists species. Elsewhere, it has been proposed that effective management plans for birds using Polylepis should promote the conservation of mature Polylepis patches. Our results not only suggest this but also show that there are additional factors, such as the presence of Gynoxys plants, which will probably play a role in conservation of birds. More generally, these findings show that while easily measured attributes of the patch and landscape may provide some insights into what influences patch use by birds, knowledge of other factors, such as plant species composition, is essential for better understanding the distribution of birds in fragmented landscapes.     

Integrating future scenario‐based crop expansion and crop conditions to map switchgrass biofuel potential in eastern Nebraska,USA

Switchgrass (Panicum virgatum) has been evaluated as one potential source for cellulosic biofuel feedstocks. Planting switchgrass in marginal croplands and waterway buffers can reduce soil erosion, improve water quality, and improve regional ecosystem services (i.e. it serves as a potential carbon sink). In previous studies, we mapped high risk marginal croplands and highly erodible cropland buffers that are potentially suitable for switchgrass development, which would improve ecosystem services and minimally impact food production. In this study, we advance our previous study results and integrate future crop expansion information to develop a switchgrass biofuel potential ensemble map for current and future croplands in eastern Nebraska. The switchgrass biomass productivity and carbon benefits (i.e. NEP: net ecosystem production) for the identified biofuel potential ensemble areas were quantified. The future scenario‐based (‘A1B’) land use and land cover map for 2050, the US Geological Survey crop type and Compound Topographic Index (CTI) maps, and long‐term (1981–2010) averaged annual precipitation data were used to identify future crop expansion regions that are suitable for switchgrass development. Results show that 2528 km² of future crop expansion regions (~3.6% of the study area) are potentially suitable for switchgrass development. The total estimated biofuel potential ensemble area (including cropland buffers, marginal croplands, and future crop expansion regions) is 4232 km² (~6% of the study area), potentially producing 3.52 million metric tons of switchgrass biomass per year. Converting biofuel ensemble regions to switchgrass leads to potential carbon sinks (the total NEP for biofuel potential areas is 0.45 million metric tons C) and is environmentally sustainable. Results from this study improve our understanding of environmental conditions and ecosystem services of current and future cropland systems in eastern Nebraska and provide useful information to land managers to make land use decisions regarding switchgrass development.     

Modelling pink-footed goose (Anser brachyrhynchus) wintering distributions for the year 2050: potential effects of land-use change in Europe

Feeding on farmland by overwintering populations of pink-footed geese ( Anser brachyrhynchus ) conflicts with agricultural interests in Northern Europe. In order to forecast the potential future of this conflict, we used generalized linear models to relate the presence and absence of pink-footed geese to variables describing the contemporary landscape, and predicted their future distributions in relation to two land-use scenarios for the year 2050. One future scenario represented a global, economically orientated world (A1) and the other represented a regional, environmentally concerned world (B2). The probability of goose occurrence increased within cropland and grassland, and could be explained by their proximity to coast, elevation, and the degree of habitat closure. Predictions to future scenarios revealed noticeable shifts in the suitability of goose habitat evident at the local and regional scale in response to future shifts in land use. In particular, as grasslands and croplands give way to unsuitable land-use types (e.g. woody biofuel crops, increased urbanization, and forest) under both future scenarios, our models predicted a decrease in habitat suitability for geese. If coupled with continued goose population expansion, we expect that the agricultural conflict will intensify under the A1 and particularly the B2 scenarios.     

Agroenergy Crops Influence the Diversity, Biomass, and Guild Structure of Terrestrial Arthropod Communities

Expanded production of contemporary bioenergy crops (e.g., corn) is considered a threat to the conservation of biodiversity, yet next-generation perennially based crops (switchgrass, mixed-grass?Cforb prairie) may represent an opportunity for enhancing biodiversity in agricultural landscapes. We employed a multi-scaled approach to investigate the relative importance of feedstock selection, forb content, patch size, and landscape-scale habitat structure and composition as factors shaping the diversity and abundance of terrestrial arthropod communities and the biomass of functional groups of arthropods associated with the provisioning of ecosystem services. Compared to intensively managed annual corn fields, switchgrass and mixed-grass?Cforb prairie plantings were associated with a 230% and 324% increase in arthropod family diversity and a 750% and 2,700% increase in arthropod biomass, respectively. Biomass of arthropod pollinators, herbivores, predators, and parasites were similarly the highest in mixed-grass?Cforb prairie, intermediate in switchgrass plantings, and the lowest in cornfields. Community-wide biomass and that of several functional arthropod groups were positively linked to increasing forest cover and land cover diversity surrounding biomass plantings, while pollinator and detritivore biomass was lower in smaller fields. Results not only suggest that the choice of biomass feedstock will play an important role in shaping within-field arthropod diversity but also indicate an important role for the composition of this surrounding landscape. Collectively, our results suggest that selection of perennially based biomass feedstocks along with careful attention to crop placement have important potential to enhance biodiversity conservation and the provisioning of ecologically and economically important arthropod-mediated ecosystem services in future agricultural landscapes.     

Close association between grasshopper and plant communities in suburban secondary grasslands and the indicator value of grasshoppers for conservation

Semi-natural grasslands in Japan have decreased due to management abandonment and urbanization over the last 100 years, but they remain in suburban areas in addition to rural areas. Because suburban grasslands have various land-use histories and disturbance regimes, plant and herbivorous insect communities are likely to differ among grassland types. To identify grasslands with high conservation value, we conducted a comprehensive survey of grasshoppers and plants in 150 grasslands with 5 grassland types differing in land-use history and current management in northern Chiba prefecture, Japan. We then analyzed the association of the distributions of grasshopper and plant species compositions. Our results showed that grasshoppers were classified into habitat specialists and generalists. Three out of four habitat specialists were almost exclusively found in semi-natural grasslands and vacant lots, while habitat generalists were commonly observed at the cropland margins. This habitat specialist–generalist distribution gradient corresponded well to that found in plant communities, which was probably due to current disturbance regimes. We suggest that vacant lots as well as semi-natural grasslands have high conservation value for grassland organisms of various taxa in suburban areas, and grasshoppers are candidate indicator species for monitoring grassland environments.

     

Energy Potential of Biomass from Conservation Grasslands in Minnesota,USA

Perennial biomass from grasslands managed for conservation of soil and biodiversity can be harvested for bioenergy. Until now, the quantity and quality of harvestable biomass from conservation grasslands in Minnesota, USA, was not known, and the factors that affect bioenergy potential from these systems have not been identified. We measured biomass yield, theoretical ethanol conversion efficiency, and plant tissue nitrogen (N) as metrics of bioenergy potential from mixed-species conservation grasslands harvested with commercial-scale equipment. With three years of data, we used mixed-effects models to determine factors that influence bioenergy potential. Sixty conservation grassland plots, each about 8 ha in size, were distributed among three locations in Minnesota. Harvest treatments were applied annually in autumn as a completely randomized block design. Biomass yield ranged from 0.5 to 5.7 Mg ha⁻¹. May precipitation increased biomass yield while precipitation in all other growing season months showed no affect. Averaged across all locations and years, theoretical ethanol conversion efficiency was 450 l Mg⁻¹ and the concentration of plant N was 7.1 g kg⁻¹, both similar to dedicated herbaceous bioenergy crops such as switchgrass. Biomass yield did not decline in the second or third year of harvest. Across years, biomass yields fluctuated 23% around the average. Surprisingly, forb cover was a better predictor of biomass yield than warm-season grass with a positive correlation with biomass yield in the south and a negative correlation at other locations. Variation in land ethanol yield was almost exclusively due to variation in biomass yield rather than biomass quality; therefore, efforts to increase biomass yield might be more economical than altering biomass composition when managing conservation grasslands for ethanol production. Our measurements of bioenergy potential, and the factors that control it, can serve as parameters for assessing the economic viability of harvesting conservation grasslands for bioenergy.     

Bird assemblages in fragmented agricultural landscapes: the role of small brigalow remnants and adjoining land uses

Agricultural intensification typically leads to changes in bird diversity and community composition, with fewer species and foraging guilds present in more intensively managed parts of the landscape. In this study, we compare bird communities in small (2–32 ha) brigalow (Acacia harpophylla) remnants with those in adjacent uncultivated grassland, previously cultivated grassland and current cropland, to determine the contribution of different land uses to bird diversity in the agricultural landscape. Twenty remnant brigalow patches and adjacent agricultural (‘matrix’) areas in southern inland Queensland, Australia were sampled for bird composition and habitat characteristics. The richness, abundance and diversity of birds were all significantly higher in brigalow remnants than in the adjacent matrix of cropping and grassland. Within the matrix, species richness and diversity were higher in uncultivated grasslands than in current cultivation or previously cultivated grasslands. Forty-four percent of bird species were recorded only in brigalow remnants and 78% of species were recorded in brigalow and at least one other land management category. Despite high levels of landscape fragmentation and modification, small patches of remnant brigalow vegetation provide important habitat for a unique and diverse assemblage of native birds. The less intensively managed components of the agricultural matrix also support diverse bird assemblages and thus, may be important for local and regional biodiversity conservation.     

Community composition of butterflies and bumblebees in fallows: niche breadth and dispersal capacity modify responses to fallow type and landscape

Fallows (i.e. fields temporarily taken out of production) provide important habitat for flower-visiting insects in intensively cultivated agricultural landscapes. Cost-efficiency of fallowing schemes could be enhanced through improved understanding of key characteristics of fallows and surrounding landscape that determine community composition and provide support for species of conservation concern. Impacts of fallow characteristics and landscape structure on the species composition of butterflies and bumblebees were studied in two types of perennial fallows in boreal farmland. To understand species’ responses to environmental factors from a conservation perspective, community composition was examined with respect to two species traits—niche breadth and dispersal capacity. Whereas overall species composition of butterflies and bumblebees was strongly affected by forest cover in the surrounding landscape, the studied species traits were most related to fallow type and the cover of perennial grasslands. Habitat breadth of butterflies was narrowest in long-term grassland fallows in landscapes with high grassland cover. Dispersal capacity of butterflies was also lowest in grassland-rich landscapes. Diet breadth of bumblebees was narrower in long-term grassland fallows than in short-term fallows. The results confirm that the diversity of butterflies and bumblebees can be enhanced by establishing and managing fallows both in open and forested landscapes. For conservation of habitat specialists and less mobile species, retention of long-term fallows in grassland-rich landscapes is apparently the best option. The results provide no justification for exempting forested regions or farms with high grassland cover from the ecological focus area requirement under the European Union’s current agricultural policy.     

Simulating Strategic Implementation of the CRP to Increase Greater Prairie-Chicken Abundance

The Conservation Reserve Program (CRP) has the potential to influence the distribution and abundance of grasslands in many agricultural landscapes, and thereby provide habitat for grassland-dependent wildlife. Greater prairie-chickens (Tympanuchus cupido pinnatus) are a grassland-dependent species with large area requirements and have been used as an indicator of grassland ecosystem function; they are also a species of conservation concern across much of their range. Greater prairie-chicken populations respond to the amount and configuration of grasslands and wetlands in agriculturally dominated landscapes, which in turn can be influenced by the CRP; however, CRP enrollments and enrollment caps have declined from previous highs. Therefore, prioritizing CRP reenrollments and new enrollments to achieve the greatest benefit for grassland-dependent wildlife seems prudent. We used models relating either lek density or the number of males at leks to CRP enrollments and the resulting landscape structure to predict changes in greater prairie-chicken abundance related to changes in CRP enrollments. We simulated 3 land-cover scenarios: expiration of existing CRP enrollments, random, small-parcel (4,040 m²) addition of CRP grasslands, and strategic, large-parcel (80,000 m²) addition of CRP grasslands. Large-parcel additions were the average enrollment size in northwestern Minnesota, USA, within the context of a regional prairie restoration plan. In our simulations of CRP enrollment expirations, the abundance of greater prairie-chickens declined when grassland landscape contiguity declined with loss of CRP enrollments. Simulations of strategic CRP enrollment with large parcels to increase grassland contiguity more often increased greater prairie-chicken abundance than random additions of the same area in small parcels that did not increase grassland contiguity. In some cases, CRP enrollments had no or a negative predicted change in greater prairie-chicken abundance because they provided insufficient grassland contiguity on the landscape, or increased cover-type fragmentation. Predicted greater prairie-chicken abundance increased under large-parcel and small-parcel scenarios of addition of CRP grassland; the greatest increases were associated with large-parcel additions. We suggest that strategic application of the CRP to improve grassland contiguity can benefit greater prairie-chicken populations more than an opportunistic approach lacking consideration of the larger landscape context. Strategic implementation of the CRP can benefit greater prairie-chicken populations in northwestern Minnesota, and likely elsewhere in landscapes where grassland continuity may be a limiting factor. © 2020 The Wildlife Society.     

Can switches in disturbance type improve habitat for grassland birds in semi-arid grasslands of South-Eastern Australia?

Grasslands are one of the most endangered and degraded ecosystems globally. Switches in disturbance type can restore grassland function and improve conservation outcomes for fauna, but land-use legacies can limit the capacity of biota to respond positively to shifts in disturbance type, making it difficult to predict ecological outcomes. In semi-arid grasslands of South-Eastern Australia, habitat for grassland birds is managed using livestock grazing, a practice that has continued for >150 years. It is unknown if outcomes for birds can be improved by a switch in disturbance type as alternatives to livestock grazing have not been explored. We compare the effects of status-quo livestock grazing with alternative biomass management tools (no management, ‘crash’ grazing, planned fire) on birds, vegetation structure, and food resources using a BACI design across 3 years (2017–2019). We found crash grazing and fire produced more open, shorter grassy swards, with less exotic grass cover, compared to status-quo grazing or disturbance exclusion. Preferred habitat structure for the critically endangered plains-wanderer (Pedionomus torquatus) was maximized by status-quo grazing. Grassland birds responded in opposing ways to a disturbance switch. Brown songlarks (Megalurus cruralis) and Horsfield's bushlarks (Mirafra javanica) responded positively to disturbance exclusion, while stubble quail (Coturnix pectoralis) responded negatively to crash grazing. Australasian pipits (Anthus novaeseelandiae) were more frequent in response to status-quo grazing. Our findings suggest that multiple disturbance types should be used if the aim is to promote the spectrum of vegetation structures and food sources required to support a diverse grassland bird community in semi-arid grasslands of Australia.     

Implications of Three Biofuel Crops for Beneficial Arthropods in Agricultural Landscapes

Production of biofuel feedstocks in agricultural landscapes will result in land use changes that may have major implications for arthropod-mediated ecosystem services such as pollination and pest suppression. By comparing the abundance and diversity of insect pollinators and generalist natural enemies in three model biofuel crops: corn, switchgrass, and mixed prairie, we tested the hypothesis that biofuel crops comprised of more diverse plant communities would support increased levels of beneficial insects. These three biofuel crops contained a diverse bee community comprised of 75 species. Overall, bees were three to four times more abundant in switchgrass and prairie than in corn, with members of the sweat bee (Halictidae) and small carpenter bee (Ceratina spp.) groups the most abundant. Switchgrass and prairie had significantly greater bee species richness than corn during the July sampling period. The natural enemy community at these sites was dominated by lady beetles (Coccinellidae), long-legged flies (Dolichopodidae), and hover flies (Syrphidae) which varied in their response to crop type. Coccinellids were generally most abundant in prairie and switchgrass, with the exception of the pollen feeding Coleomegilla maculata that was most abundant in corn. Several rare or declining coccinellid species were detected in prairie and switchgrass sites. Dolichopodidae were more abundant in prairie and switchgrass while Syrphidae showed no significant response to crop type. Our results indicate that beneficial insects generally responded positively to the increased vegetational diversity of prairie and switchgrass sites; however, when managed as a dedicated biofuel crop, plant and arthropod diversity in switchgrass may decrease. Our findings support the hypothesis that vegetationally diverse biofuel crops support higher abundance and diversity of beneficial insects. Future policy regarding the production of biofuel feedstocks should consider the ecosystem services that different biofuel crops may support in agricultural landscapes.     

Hybrid ecosystems can contribute to local biodiversity conservation

Calcareous grasslands have become severely threatened habitats in Europe. The aim of this study was to investigate the changes in plant species richness, and functional and phylogenetic diversity in northern Estonian calcareous (alvar) grasslands resampled after 90 years of land-use change. Functional traits characterizing species that have benefited most from decreased habitat area and altered environmental conditions, and additional species that can potentially inhabit the remaining grassland patches were identified. Also changes in the relative amount of habitat-specific species were studied to detect a possible decrease in habitat integrity. Although grasslands in the studied region had lost most of their original area (~90 %), species richness had substantially increased due to invasion by more competitive, nutrient-demanding native species. Functional diversity generally increased, whereas phylogenetic diversity showed no response to altered conditions. Overall, these grasslands have lost their integrity as calcareous grassland habitat type in the region, because the relative amount of habitat-specific characteristic species has declined significantly. However, although the grasslands have transformed to a ‘hybrid’ habitat type and restoration to their previous state is likely not reasonable, such degraded species-rich grassland fragments can still be recognized as important habitats to preserve high local biodiversity and several characteristic species of calcareous grasslands. As current landscapes consist of an increasing number of hybrid and novel communities, new tools to supplement traditional conservation or restoration practices are necessary to recognize and maintain regions and habitats of high local biodiversity.