查看更多>>摘要：ABSTR A C T Farmers are increasingly looking to cover crops to provide ecosystem services to support yields, while reducing off-farm inputs. Research evidence in both unmanaged and agricultural ecosystems suggests that increased plant diversity can improve ecosystem service outcomes. The use of diverse cover crops as a practice to increase ecosystem service delivery has potential, though knowledge gaps remain regarding the types and levels of di-versity that are most effective, and how environment may impact the desired outcomes. Using six species of legumes (hairy vetch, field pea, crimson clover) and of grasses (cereal rye, common wheat, ryegrass) along with multiple cultivars of each, we conducted an annual field experiment repeated twice during the winter fallow season. We tested the effect of a gradient of diversity in intraspecific mixtures, interspecific mixtures, and functional group (grass and legume) mixtures. We measured aboveground biomass production, weed biomass, soil-derived and fixed nitrogen in the shoots, and the C/N ratio of the aboveground biomass to evaluate corre-sponding ecosystem services relating to C and N cycling and weed suppression. Species mixtures, especially those composed of both grasses and legumes tended to have the most significant ecosystem service benefits suggesting that functional diversity is more significant than species richness. Where soil nutrients were less available, the diversity effect tended to be stronger, though this was significant in only two instances. These results lend some support to the stress-gradient hypothesis in that in more stressful conditions the diversity benefit was greater. Diverse mixtures may not consistently produce substantial service improvements, but there is little risk, and they may be most useful in marginal or depleted field conditions.
查看更多>>摘要：Arable plants and wild bees are negatively affected by agricultural intensification, one of the major drivers of global biodiversity loss. However, it remains unclear how endangered and low competitive arable plants (rare arable plants) contribute to the persistence of flower-visiting wild bees by providing additional flower resources in agricultural landscapes. Thus, the effects of sowing 10 rare arable plant species on wild bees were investigated in an experimental field and on 10 different arable farms on nutrient-poor soils. Sowing of rare arable plants on cropped and uncropped plots was compared to annual and perennial wildflower strips. Results showed that rare arable plants on uncropped plots attracted as many wild bees as wildflower strips. Wild bee abundance and species richness increased in the autumn-sown crops in the second year, likely because winter annual rare arable plants were preferred. In particular, rare arable plants provided flowers preferred by long-tongued bumblebees, which are often lacking in intensively managed arable fields. Our study shows that sowing of rare arable plants can increase niche diversity and therefore resource availability for wild bees, and it can also conserve diversity of arable plants in degraded agricultural landscapes. Conservation of arable plants through sowing can also support wild bee communities and may become an important tool in pollinator-friendly management of arable land.
查看更多>>摘要：Environmental management often lacks a harmonization across scales and beyond boundaries of the land with changed use. As an example, extensive areas of Uruguayan grassland have been transformed into crop and timber plantations in the past decades, but little is known about the possible impacts of these changes on neighboring native forests. We explore how the diversity of native forests differs in relation to land-use change trajectories, from grassland to monocultures, in the surrounding landscapes. We recorded woody species in 32 different native forest plots in Uruguay. Using Landsat images, we created land-use maps in a buffer of 3 km around each plot for the years 1986/1987, 1996/1997, 2006/2007 and 2016/2017. We calculated trajectories of changes regarding the percentage of cover per land use, the landscape shape and aggregation index for native forests, grassland, timber plantations and crops. Trajectories were explored based on the slope of the generalized linear model correlated with woody species composition. Landscape covered by native forests, timber plantations and crops increased whereas grassland cover decreased. Large and interconnected native forests in a landscape dominated by grasslands harbor a high diversity of woody species. Disaggregation of grassland resulted in a decrease in richness and diversity of woody species. The history of surrounding landscape determines diversity of native forests. We observed cross boundary effects of neighboring land uses on native forests. These effects have to be considered in all measures of environmental management to reduce the trade-offs between biodiversity con-servation and economic profit. Nevertheless, other parameter such as climate and soil interplay, override and alter the effects of land use history and management.
Cole, Lorna J.Baddeley, John A.Robertson, DuncanTopp, Cairistiona F. E....
10页
查看更多>>摘要：Insect-pollinated legumes are rich in plant-based proteins making them a vital constituent of sustainable healthy diets for people and livestock. Furthermore, they deliver or support a range of ecosystem services that underpin agricultural production and their prevalence in agricultural landscapes is likely to increase. Under typical implementation and management, the value of legumes to pollinators has, however, been questioned. Through exploring a range of legume crops, grown as monocultures and mixtures, this study aims to identify multifunctional legume cropping systems that optimise forage availability for a diversity of wild pollinators whilst delivering a wide range of agronomic and environmental benefits. This study innovatively explores legume mixtures concurrently with monocultures of the component species using replicated small-plot field trials established in two geographical locations. Observational plots assessed the richness and abundance of floral resources, and wild pollinators (i.e. bumblebees and hoverflies) throughout the peak flowering period. Densely flowering, highly profitable legumes (e.g. Trifolium incarnatum and Trifolium mixes) supported abundant and rich pollinator assemblages. The functional makeup of floral visitors was strongly influenced by flower structure and hoverflies, with their shorter proboscises, were largely constrained to legumes with shallower corolla and open weed species. Floral richness was not a key driver of pollinator assemblages; however, clear intra-specific differences were observed in flowering phenology. Combining functionally distinct legumes with respect to flower structure and phenology, will support a wider suite of pollinating insects and help stabilise the temporal availability of forage. For highly competitive legumes (e.g. Vicia faba and Vicia sativa), planting in discrete patches is recommended to reduce the risk of less competitive species failing in mixtures. Legumes can provide valuable forage for pollinators; however, they fail to meet all resource requirements. They should therefore be used in combination with agri-environmental measures targeted to promote early-season forage (e.g. hedgerows and farm woodlands), open flowers for hoverflies, saprophytic hoverfly larval resources (e.g. ditches and ponds) and nesting habitats (e.g. undisturbed field margins).
查看更多>>摘要：Increases in the input of chemical fertilizer and rapid decline of soil organic matter have increased serious demand for sustainable agriculture. Cellulose is an important component of soil organic matter, which strongly affects global carbon cycle and crop yields in the agroecosystem. beta-glucosidases (BG) convert cellobiose to glucose, providing carbon for soil microorganisms and plants. However, little is known about the structure of beta-glucosidase gene (GH3)-harboring microbial community and its functions in response to long-term intensive cropping with frequent fertilization. In this study, quantitative PCR (qPCR) and high-throughput sequencing were used to determine the abundance of bacterial and fungal GH3 gene as well as the diversity of GH3-harboring community in intensified citrus orchards of different ages (5-year, 15-year and 30-year), or under different management practices (straw application on the surface, peanut planting between rows and control) for 15 years. The adjacent natural forest and grass soils were used as reference to investigate the effect of intensive citrus plantation on soil BG enzyme activity and the GH3 gene. The results revealed that citrus plantation significantly reduced soil GH3 gene abundance, especially for the bacterial GH3 gene. The higher abundance of bacterial GH3 gene than that of fungal GH3 gene in the soil highlighted the key role of bacterial GH3 gene in regulating soil BG enzyme activity. Among the reservoirs of the GH3 gene, Proteobacteria, Acidobacteria, Fir-micutes and Actinobacteria were the main bacterial phyla, while Ascomycota was the only dominant fungal phylum. Citrus plantation caused soil bacterial community varied from Proteobacteria-dominant to Acidobacteria-dominant and reduced BG enzyme activity. The higher diversity of the bacterial community indicated that bacteria play a dominant role in the conversion of cellobiose to glucose. Citrus plantation and plantation age strongly influenced the diversity and structure of beta-glucosidase gene-harboring community. A significant decline occurred in bacterial diversity along with increasing citrus plantation age. The community diversity exhibited a clear land-use specific pattern, as indicated by the obviously different community structure between the forest soil and citrus soil. Among the detected environmental factors, SOC, bacterial beta-glucosidase gene abundance and the community diversity were the most important factors controlling soil BG enzyme activity. These results indicate that citrus plantation with long-term fertilization suppresses the abundance of the beta-glucosidases gene, and the bacterial beta-glucosidase gene contributes more to the BG enzyme activity than the fungal gene.
Moreaux, CelineMeireles, Desiree A. L.Sonne, JesperBadano, Ernesto, I...
12页
查看更多>>摘要：Animal pollinators are globally threatened by anthropogenic land use change and agricultural intensification. The yield of many food crops is therefore negatively impacted because they benefit from biotic pollination. This is especially the case in the tropics. For instance, fruit set of Coffea arabica has been shown to increase by 10-30% in plantations with a high richness of bee species, possibly influenced by the availability of surrounding forest habitat. Here, we performed a global literature review to (1) assess how much animal pollination enhances coffee fruit set, and to (2) examine the importance of the amount of forest cover, distance to nearby forest and forest canopy density for bee species richness and coffee fruit set. Using a systematic literature review, we identified eleven case studies with a total of 182 samples where fruit set of C. arabica was assessed. We subsequently gathered forest data for all study sites from satellite imagery. We modelled the effects of open (all forest with a canopy density of >= 25%), closed (>= 50%) and dense (>= 75%) forests on pollinator richness and fruit set of coffee. Overall, we found that animal pollination increases coffee fruit set by similar to 18% on average. In only one of the case studies, regression results indicate a positive effect of dense forest on coffee fruit set, which increased with higher forest cover and shorter distance to the forest. Against expectations, forest cover and distance to open forest were not related to bee species richness and fruit set. In summary, we provide strong empirical support for the notion that animal pollinators increase coffee fruit set. Forest proximity had little overall influence on bee richness and coffee fruit set, except when farms were surrounded by dense tropical forests, potentially because these may provide high-quality habitats for bees pollinating coffee. We, therefore, advocate that more research is done to understand the biodiversity value of dense forest for pollinators, notably assessing the mechanisms underlying the importance of forest for pollinators and their pollination services.
查看更多>>摘要：Non-bee insects have been identified as important crop pollinators globally. However, strategies to protect pollinators and enhance crop pollination usually focus on supporting bees. This study examined the effects of landscape structure, location within field, and floral resources on pollinators' visits on mass-flowering caraway (Carum carvi L.) in boreal farmland, and the effects of the visits on caraway yield. Pollinator visits on caraway flowers were monitored and caraway yield measured in 30 fields at landscapes ranging from field-dominated to forest-dominated landscapes. Hoverflies were the most abundant flower-visitors of caraway, followed by honeybees. Hoverflies and other flies made more flower visits on caraway than all bee species combined. Pollinator groups differed in their responses to landscape and local factors. Flies were most abundant near field edges and in landscapes with high forest cover. Non-syrphid flies and solitary bees responded positively to the cover of flowering herbs in the adjacent field margins. Flower visits by honeybees, instead, were positively related to the flowering crop cover in the study fields. Caraway seed yield increased with increasing number of flower visits by honeybees, hoverflies and all pollinators together. Pollinator exclusion reduced caraway fruit set (i.e. the number of fruits per flower) by 13% and seed yield by 40%. Our study is the first to report the high importance of flies to crop pollination in boreal farmland, where caraway is an important export crop. The results highlight the need of taking flies and their habitat requirements into account when developing strategies to enhance crop pollination.
Momesso, LetusaCrusciol, Carlos A. C.Bossolani, Joao W.Kuramae, Eiko E....
14页
查看更多>>摘要：Forage grasses used in cropping no-till systems in tropical regions alter soil chemical properties, but their longterm impact on soil microbial processes of the nitrogen (N) cycle and microbial community abundance, composition and structure are unknown. Here, microbial functions related to nitrogen fixation, nitrification and denitrification as well as bacterial, archaeal and fungal populations were evaluated in a long-term field experiment in which tropical forage grasses palisade grass (Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster) and ruzigrass (U. ruziziensis (R. Germ. and C.M. Evrard) Crins) were cultivated with or without N fertilization. Uncultivated soil was used as a control. Forage grasses, especially palisade grass, increased soil bacterial and fungal abundances, whereas the archaeal population was highest in uncultivated soil. In soils cultivated with forage grasses, N fertilization favored N-cycle-related genes; however, cultivation of palisade grass increased the abundances of amoA bacteria (AOB) and amoA archaea (AOA) genes associated with soil nitrification and decreased the abundances of genes nirS, nirK and nosZ genes related to denitrification, compared to ruzigrass and control, regardless of N input. In addition, abundances of total bacteria and total fungi were associated with the N cycle and plant biomass in soils cultivated with forage grasses. Forage cultivation clearly benefitted the soil nutrient environment (S-SO42-, Mg2+, total-C and -N, N-NO3- and N-NH4+) and microbiome (bacteria and fungi) compared with uncultivated soil. In soil cultivated with palisade grass, the microbial community composition was unresponsive to N addition. The high N uptake by palisade grass supports the competitive advantage of this plant species over microorganisms for N sources. Our results suggest that palisade grass has advantages over ruzigrass for use in agriculture systems, regardless of N input.
查看更多>>摘要：Phosphorus (P) mineralization from organic matter is one of the most important microbially-driven soil processes in natural ecosystems. However, little is known about how long-term fertilization affect the abundance, diversity and community composition of these important organisms in croplands wherein P is directly supply via fertilizers. Here, we investigated the fate of phosphorus-mineralizing bacteria in a citrus plantation chronosequence (5-30 years) including information on management practices (no covering, straw covering and peanut covering after 15 years). We found that the diversity and abundance of phoD-harboring bacteria and the activity of phosphatase was largely suppressed after 30 years of fertilization. Moreover, long-term fertilization altered the bacterial community associated with P mineralization, decreasing the relative abundance of Methylobacterium, Aquabacterium and Rhizobacter in comparison with adjacent natural forests. Remarkably, land management practices associated with land covering helped to increase the diversity of phoD-harboring bacteria, after 15 years of experiment. This result is likely associated with the entrance of organic matter to the system. Our results provide new evidence that long-term fertilization drastically suppressed the abundance and diversity of bacteria associated with P mineralization, with implications for soil health and sustainability.
查看更多>>摘要：Soil organic carbon (SOC) sequestration by improved agricultural practices is an acclaimed strategy to combat climate change. Nevertheless, the aim of increasing of SOC encounters limitations, e.g. with regards to permanence of carbon storage or leakage effects in food production. Agmforestry systems (AFS) are a promising land use option that is able to sequester substantial amounts of SOC while addressing these challenges. With a focus on temperate climate zones worldwide, available information on SOC in AFS was reviewed to determine their SOC sequestration potential and respective controlling factors. From a total of 61 observations, SOC sequestration rates in soils of AFS were derived for alley cropping systems (n = 25), hedgerows (n = 26) and silvopastoral systems (n = 10). The results showed that AFS have a potential for substantial SOC sequestration in temperate climates. SOC stocks were higher in the topsoil (0-20 cm) than in the control in more than 70% of the observations, and higher within the subsoil (20-40 cm) for 81% of all observations, albeit large variation in the data. The mean SOC sequestration rates were slightly higher at 0-20 cm (0.21 +/- 0.79 t ha(-1) yr(-1)) compared to 20-40 cm soil depth (0.15 +/- 0.26 t ha(-1) yr(-1)). Hedgerows revealed highest SOC sequestration rates in topsoils and subsoils (0.32 +/- 0.26 and 0.28 +/- 0.15 t ha(-1) yr(-1), respectively), followed by alley cropping systems (0.26 +/- 1.15 and 0.23 +/- 0.25 t ha(-1) yr(-1)) and silvopastoral systems showing a slight mean SOC loss (-0.17 +/- 0.50 and -0.03 +/- 0.26 t ha(-1) yr(-1)). Moreover, SOC sequestration rates tended to be higher for AFS with broadleaf tree species compared to coniferous species. We conclude that temperate AFS sequester significant amounts of SOC in topsoils and subsoils and represent one of the most promising agricultural measures for climate change mitigation and adaption.
NSTL
Elsevier