查看更多>>摘要：? 2022 The AuthorsPasture is a globally important managed habitat providing both food and income. The way in which it is managed leads to a wide range of impacts on soil microbial communities and associated soil health. While there have been several studies comparing pasture farming to other forms of land use, we still have limited understanding of how the soil microbial communities vary between pasture farms and according to management practices. Here we present the results of a field survey across 56 UK livestock farms that are managed by members of the Pasture fed Livestock Association, using amplicon sequencing of the 16S and ITS regions to characterise the soil bacterial and fungal community within fields that have been under pasture for differing durations. We show that grazing management intensity has only limited effects upon microbial community structure, while the duration of pasture since ploughing (ranging from 1 year to over 100 years) impacted the fungal community structure. The impact of management duration was conditional upon soil physicochemical properties, particularly pH. Plant community effects on upon soil bacterial and fungal composition appear to also interact with the soil chemistry, highlighting the importance of plant-soil interactions in determining microbial community structure. Analyses of microbial indicators revealed proportionally more fungal taxa that responded to multiple ecosystem health associated properties than bacterial taxa. We also identified several fungal taxa that both acted as indicators of soil health related properties within our dataset and showed differentiation between grassland types in a national survey, indicating the generality of some fungal indicators to the national level. Members of the Agaricomycetes were associated with multiple indicators of soil health. Our results show the importance of maintaining grassland for the development of plant-soil interactions and microbial community structure with concomitant effects on soil and general ecosystem health.
查看更多>>摘要：? 2022 Elsevier B.V.The plant productivity and species richness (P-SR) relationship has been a central topic in ecology for decades. It is increasingly recognized that climate resources (CR, temperature and precipitation) might affect the P-SR relationship as (1) the response of plant productivity and species richness to CR are different; (2) plant-plant interactions change along the CR gradient. However, little is known about how these effects mediate the shape and strength of the P-SR relationship from local-site to regional scales. Here, we proposed a cross-scale framework to disentangle the climatic control over the P-SR relationship in grasslands using the HerbDivNet dataset, which covers 28 natural grasslands in 19 countries and 6 continents with wide precipitation and temperature gradients. Our results showed that, at the local-site scale, a humped-back P-SR relationship is common at sites under poor and rich CR conditions, whereas both the shape and strength of the P-SR relationship strongly vary among sites under moderate CR condition. However, at the regional scale, the humped-back P-SR relationship is only observed under poor CR condition. We suggested that the asynchronous responses of productivity and species richness to increasing CR is an abiotic driver of the inconsistent P-SR relationships along the climatic gradient in addition to the changing plant-plant interactions suggested by the stress-gradient hypothesis. These findings help to reconcile the long-standing debate over the P-SR relationship and highlight the importance of CR conditions in developing or comparing grassland ecosystem theories and management at small scales.
查看更多>>摘要：? 2022 Elsevier B.V.The benefits of maintaining soil organic matter in agroecosystems have long been recognized, although there are many open questions with respect to the controls on crop residue decomposition and the consequences for carbon and nutrient cycling. The large extension of intensively cropped agriculture in the Argentine Pampas of soybean, sunflower, wheat, and maize motivates the need for a broader understanding of these controls. In modern no-till agriculture, post-harvest crop residues may remain upright as standing or on the soil surface for extended periods of time; nevertheless, the effects of sunlight exposure and its interaction with soil biota on decomposition of crop residues have not been evaluated. We established a manipulative experiment using soybean, sunflower, wheat and maize crop residues with treatments of full or attenuated sunlight exposure and presence or absence of soil biota. Species identity was significant in determining rates of leaf residue decomposition with mass loss of soybean ≥ sunflower > wheat ≥ maize. Sunlight exposure significantly accelerated decomposition of leaf residues in the absence of soil biota, while soil biota significantly contributed to increased leaf residue decomposition with and without sunlight exposure. In contrast, stem residue decomposition was modest under all conditions and differences in decomposition were determined by species identity. Surface area for leaf and stem residues across species was the strongest litter quality predictor for the variation in crop residue decomposition. Our results suggest that sunlight exposure, duration of fallow period with or without rotation or cover crops, and the proportion of leaves vs. stems in crop residues interacting with soil biota may be fundamental elements in determining carbon turnover in these intensively cropped agroecosystems. There would be great value in incorporating the impacts of sunlight exposure and unexplored aspects of crop residue quality in models for sustainable agriculture in the region and globally.
查看更多>>摘要：? 2022 Elsevier B.V.Enclosure lake aquaculture causes lake eutrophication and emits CH4 to the atmosphere. So far, little is known about the rate of CH4 emission from lake aquaculture and about how ecological restoration (or aquaculture abandonment) affects the emission. In this study, the eddy covariance (EC) technique was deployed to quantify the CH4 flux in an enclosure lake aquaculture farm and to investigate the flux response to ecological restoration. The lake site under aquaculture farming emitted 36.0 g C-CH4 m?2 yr?1 to the atmosphere, an amount that is comparable to the global mean value of semi-intensive aquaculture systems. The annual CH4 emission decreased from the pre-restoration level by 34% and 37% to 23.7 and 22.8 g C-CH4 m?2 yr?1 in the first and second year of ecological restoration, respectively, but was still much higher than that at a reference lake site not impacted by aquaculture farming (6.12 g C-CH4 m?2 yr?1). The high emission values after aquaculture abandonment suggest that aquafeed input in the decades of farming may have caused accumulation of a large amount of organic carbon in the sediment that continues to fuel CH4 production and that it may take a long time for the system to recover to a natural state. After aquaculture abandonment, floating-leaved plants expanded rapidly within the EC flux footprint, resulting in a high net ecosystem productivity (NEP) in the growing season. These plants appeared to be able to transport CH4 to the atmosphere through aerenchyma tissues and stomata.
查看更多>>摘要：? 2022Pollen limitation studies are scarce in entomophilous crops, as it can be very tedious to supplement plants with hand pollination at the relevant plant scale. To overcome this, recent studies have used pollinator gradients over several fields to assess whether crops were pollen limited. But the plant maternal resources and thus the yield potential may vary between fields of the same crop. If these resources are not properly controlled, it may affect the conclusions of the study. We investigated the relationship between yield, measured as seed number, seed mass, and seed oil content per head, and pollinator density in sunflower (Helianthus annuus L.) by using a gradient of pollinator densities set both across and within fields. We analyzed the yield and the % of yield potential, the latter being assessed with pollen supplementations applied at the whole plant scale. We analyzed the data both with and without random effects including year, cultivar, field and sampling plot. We also compared the yields of open and pollen-supplemented sunflowers to sunflowers isolated under tulle bags to assess autonomous self-fertilization and self-production rates in each field. Without random effects included in models, yields increased with pollinator density but only up to 0.3 bees per head, implying pollen limitation only below this threshold, while with random effects included, the yields were marginally pollen limited across the whole range of pollinator densities observed (P = 0.072 and 0.037). Yet, on the other hand, there was no relationship between bee density and % of yield potential (assessed with pollen supplementation treatments), with or without random effects included, implying no pollen limitation across the complete range of bee densities observed in our study (0.1–1 bees per sunflower head). These last results are explained by variation in the yield potential between and within fields, and by the positive correlation found between yield potential and pollinator density. Insect pollination contributed on average to 53.7% and 42.8% of the seed number and mass per head, respectively, and also increased the seed oil content by 5.5% on average. Our study showed that plant maternal resources and random effects are crucial to consider when quantifying pollen limitation using pollinator gradients and yields. Pollinator gradients on a per flower basis are a useful tool to identify target pollinator densities to maximize yields, but should be combined with pollen supplementation treatments at the relevant scale in order to correctly assess pollen limitation.
查看更多>>摘要：? 2022 Elsevier B.V.Thanks to the intense efforts over the past decades to reduce nutrient losses, the annual average nitrate (NO3-) concentrations in the European surface waters have decreased between 1990 and 2010, but the reduction has levelled off since then. Nitrogen (N) mitigation measures adapted to the local conditions are needed to further reduce the N pressure from agriculture on surface water quality. The NO3--N residue measured before the onset of winter has been used as a simple indicator of the N pressure from agriculture. However, the vulnerability of a stream to NO3- inputs depends on dilution and reduction of NO3- during its transport towards the surface water, which can be expressed by the attenuation factor for surface water (AFsw), i.e. the ratio of the average NO3- concentration at the bottom of the rooting zone and the average NO3- concentration in the surface water. In this study, we combined NO3--N measurements in the soil in autumn, NO3- concentrations measured in the surface water during the winter period and a relatively simple soil-crop model to calculate AFsw at subcatchment level, in order to estimate the effect of mitigation measures without collecting detailed information on the subsoil and groundwater processes. Simulations demonstrated that in Flanders (the northern part of Belgium) the further optimisation of the N fertilisation rate is the most effective measure to reduce surface water NO3- concentrations. Maximising the acreage of catch crops had a limited additional effect on the NO3- concentrations in surface water given that this is already widely practiced at present. Although the removal of N rich crop residues is highly effective at field level, it contributed little to the reduction of NO3- concentrations in the surface water because of the small acreage of these crops. The implemented scenarios show that in subcatchments with low AFSw, targeted and subcatchment-specific combinations of measures, but including the trade-off with the potential economic and other negative effects, may not be sufficient to obtain acceptable NO3- concentrations in the surface water at subcatchment level. In regions with low AFsw, end–of-pipe technologies might be more cost-effective and even imperative to avoid the risk of eutrophication and a low surface water quality.
查看更多>>摘要：? 2022 Elsevier B.V.Coffee berry borer (CBB) (Hypothenemus hampei; Coleoptera: Curculionidae: Scolytinae) is a major insect pest affecting coffee cultivation that causes large economic losses worldwide. Characteristics related to its life cycle makes it very difficult to control. Usually, CBB control measures are carried out at plot scale, with almost no actions taken at wider landscape scales. It is unclear how plot level control strategies and landscape factors act alone or in combination to influence CBB infestation levels. We evaluated the joint effects of crop management at the plot level, of farm features, and of landscape structure at different spatial scales on CBB infestation in 50 Costa Rican coffee farms. On five plants in each farm, we estimated the maximum number of infested berries during the fruiting period. We measured three separate groups of variables related to plot management practices, farm features and landscape structure. To assess their single and joint contributions, their relative importance and the effects of these variables on the number of infested berries we used the variance partitioning approach of the RandomForest algorithm. When evaluating the groups of factors separately, we found that crop management explained 35% of the variability of number of infested berries, farm features 42% and landscape structure 27%. The joint contribution of all three groups of variables explained 48% of variability of the number of infested berries. However, when we assessed the single contributions of each set of variables, i.e., when controlling the other two set of variables, we found that farm features explained 17% of the variance of the number of infested berries, landscape structure 6% and crop management practices only 3%. The larger amount of the variance explained by the joint effect of crop management practices, farm features, and landscape structure suggests that to develop a pest management strategy at a local scale it is important to consider the effect of both local and landscape factors affecting pest abundance. The integrated CBB management plan should consider influences at multiple spatial scales and a coordinated action among farmers that share the same landscape would be beneficial.
查看更多>>摘要：? 2022 Elsevier B.V.Monitoring ecosystem processes resulting in ecosystem services (ESs) and disservices (EDs) is crucial in agricultural ecosystems. Traditionally, ESs/EDs provided by arthropods have been estimated indirectly by measuring arthropod abundance and diversity, overlooking the recognised limitations of such approach. Using a consistent methodology based on the sentinel approach, we quantified the intensity of five ecological processes leading to four ESs and two EDs in vineyards and citrus orchards on Terceira Island, Azores. We assessed herbivory rates on lettuce plants (ED), predation rates on green plasticine caterpillars by vertebrates and invertebrates (ES), the intensity of insect pollination on strawberry plants (ES), the rates of predation on wheat and dandelion seeds (ED and ES, respectively) by rodents and invertebrates, and decomposition rates using tea and rooibos leaves (ES). Herbivory rates after 2 weeks were significantly lower in vineyards (mean ± SD; 0.5 ± 0.6%) than in citrus orchards (3.6 ± 2.9%). Vertebrate predation rates in vineyards (4.0 ± 13.6% d-1) were significantly higher than in citrus orchards (2.4 ± 10.7% d-1), while no differences were observed for overall and invertebrate predation rates. Pollination efficiency in vineyards (214.5 ± 23.9 seeds/fruit) was significantly higher than in citrus orchards (162.0 ± 14.7 seeds/fruit). Seed predation rates were higher, although not significantly so, in citrus orchards (2.0 ± 5.8% d-1) than in vineyards (0.3 ± 0.8% d-1). Decomposition was significantly higher on tea than on rooibos leaves, both in vineyards (1.15 ± 0.11 g vs. 0.72 ± 0.16 g) and citrus orchards (1.34 ± 0.06 g vs. 0.78 ± 0.13 g); no differences between mass loss in the two habitats were observed. Our results demonstrated the suitability of simple, direct monitoring tools for a quantitative comparison of agricultural habitats, confirm that landscape complexity does not always support ESs, and that the same agro-ecosystem characteristics that support ESs could occasionally also favour EDs.
查看更多>>摘要：? 2022 Elsevier B.V.Rice paddy fields are important sources of atmospheric methane (CH4) and nitrous oxide (N2O). Dissolved organic matter (DOM) is one of the most reactive organic matter fractions in the soil. However, the relationships between greenhouse gas emissions and DOM properties associated with different rice varieties in paddy fields are unclear. Here, a two-year field experiment was conducted to investigate the relationships between DOM characteristics and microbial gene abundance on CH4 and N2O emissions in seven rice varieties. The dissolved organic carbon, dissolved sugar, and NH4-N and NO3-N contents were positively correlated with CH4 and N2O emissions, and dissolved phenol was negatively correlated with CH4 and N2O emissions. Fourier transform infrared (FTIR) and three-dimensional fluorescence (EEM) spectroscopy analysis further indicated that DOM includes more O-H and C[dbnd]O phenol and protein content, of which tryptophan-like and tyrosine-like protein materials were positively correlated with CH4 and N2O emissions. In addition, CH4 and N2O emissions were significantly correlated with microbial functional genes (mcrA, pmoA, AOA, AOB, nirS, and nosZ). The redundancy analysis indicated that dissolved organic carbon, dissolved sugar, NH4-N, NO3-N, and tyrosine-like and tryptophan-like proteins in the DOM were significantly correlated with soil microbial functional gene abundance, suggesting that DOM could regulate CH4 and N2O emissions by influencing microbial abundance. The rice variety with lower greenhouse gas emissions (YY 1540) had the highest yield. These results demonstrated that the differences in greenhouse gas emissions among different rice varieties were dependent on DOM properties and microbial abundance, providing a theoretical basis for mitigating greenhouse gas emissions in rice paddy fields.
查看更多>>摘要：? 2022 The AuthorsIn Denmark, agriculture is the largest source of anthropogenic methane emissions (81%), mainly from cattle (dairy and beef) farms. Whole-farm methane emissions were quantified at nine Danish cattle farms, using the tracer gas dispersion method. Five to six measurement campaigns were carried out at each farm, covering a full year. Of the nine cattle farms, seven were home to dairy cows and two to beef cattle. The farms represented typical breeds, housing and management systems used in Denmark. Whole-farm methane emission rates ranged from 0.7 to 28 kg h?1, with the highest measurements seen at locations with the highest number of animals. Emissions tended to be higher from August to October, due to elevated temperatures and high amounts of stored manure during this period of the year. The average emission factor (EF) for dairy cow farms was 26 ± 8.5 g Livestock Unit (LU)?1 h?1, whereas it was 16 ± 4.1 LU?1 h?1 for beef cattle farms, i.e. 38% lower for the latter. The use of deep litter house management explained some of the differences found in the EFs for dairy cows. Methane emission rates estimated using IPCC models and national guidelines tended, on average for all farms and measurements, to be underestimated by 35% in comparison with the measured methane emissions, for all models and farms. The results suggest that future improvements to inventory models should focus on enteric methane emissions from beef cattle and manure methane emissions for both dairy cows and beef cattle, especially from deep litter management.
NSTL
Elsevier