Agriculture, Ecosystems & Environment最新文献

Phosphorus is a nonrenewable source of fertilization, which will challenge the future of food production and cropland sustainability worldwide. Crop diversity is known to promote greater productivity, yet the capacity of crop diversity to alleviate productivity dependence on nonrenewable fertilization and promote multiple ecosystem services remains virtually unknown. Here, we conducted a field experiment to quantify the contribution of maize-alfalfa intercropping to soil biodiversity and multiple ecosystem services under contrasting phosphorus fertilization levels. Results showed that unfertilized intercropping can support higher levels of ecosystem services such as soil microbial habitat, plant-soil mutualism, nutrient cycling, and soil carbon storage compared to phosphorus-fertilized monoculture. Intercropping could optimize the delivery of soil diversity and multiple ecosystem services override phosphorus, including microbial diversity, weighted ecosystem services, productivity stability and sustainability, and soil microbial habitat were 5–30 times higher, respectively. Unfertilized intercropping also helped to reduce important tradeoffs between productivity and soil microbial diversity compared with fertilized monoculture. Together, our results provide evidence that intercropping can optimize crop use of phosphorus, and promote multiple important ecosystem services, which can help alleviate global dependence on nonrenewable, and often environmentally deleterious fertilizer inputs.

Weeds are a major threat in tropical regions where climate conditions favor their growth and development. This is particularly true in low-input rice-based cropping systems in the Malagasy highlands, where weed management is mainly done by manual removal. Crop rotation is often promoted as an efficient way to control weed infestations, while the role of fertilization is more controversial. In this study, we compared rice monoculture to three rainfed rice-based two-year rotations: rice followed by groundnut, rice followed by sorghum-cowpea mixture, and rice followed by a velvet-bean crotalaria mixture. Each rotation was tested with two levels of fertilization (5 t DM ha⁻¹ organic manure, sole or in combination with mineral fertilizer - 400 kg ha⁻¹ NPK + 200 kg ha⁻¹ urea). We assessed the effect of rotation and fertilization on weed composition, diversity, biomass and rice yield. Additionally, the farmers’ perception of weed harmfulness and the relation between their assessment of weed harmfulness and rice production was tested. Our results showed that weed biomass significantly decreased rice yield but only under the low fertilization level. The rotation of rice with the velvet bean-crotalaria mixture was efficient in reducing weed biomass, modified weed community composition and allowed to achieve the highest rice yield. A significant negative relationship was found between weed community harmfulness index and weed species richness. Yet, the lowest rice yield was observed under rice monoculture despite a higher species richness over years and under high fertilization level. The lack of significant correlation between the harmfulness index and the actual rice yield is probably because our index is partly based on farmer’s perception, and only on major weeds. More studies on tropical weed harmfulness are needed to support the design of ecologically intensified cropping systems.

The fluxes of methane (CH₄) and carbon dioxide (CO₂) between soils and atmosphere play vital roles in regulating climate change and global carbon cycling. There is evidence that CH₄ uptake and CO₂ emission are correlated on the plot scale. However, it remains unclear whether the fluxes of these two greenhouse gases are tightly linked on temporal and large spatial scales in upland ecosystems. Here, through three independent approaches (in-situ observation, data extracted from ten typical field experiments, and a global meta-analysis), we found that soil CH₄ uptake rate was positively associated with soil CO₂ emission rate on a temporal scale over two years in our in-situ experiments. Data extracted from other typical field experiments verified that the tight linkage between soil CH₄ uptake and CO₂ emission on a temporal scale was common, even after the effects of soil temperature and moisture were removed. Moreover, a global meta-analysis further confirmed that the tight linkage between the fluxes of these two greenhouse gases also exists on a large spatial scale. Model selection analysis and structural equation modelling all verified that soil CO₂ emission rate was the key predictor for soil CH₄ uptake rate after accounting for several important factors, such as climate and soil properties. The estimated annual global forest soil CH₄ sink based on our findings is 19.70 ± 6.37 Tg C yr⁻¹. The tight linkage between soil CH₄ uptake and CO₂ emission rate on temporal and spatial scales we found in this study open new insights to easily model soil CH₄ uptake based on soil CO₂ emission measurement, since it is easier and more cost-efficient to measure than CH₄ flux. Overall, our study highlights the role of soil CO₂ emissions in predicting soil CH₄ uptake, which should be taken into consideration for global CH₄ budget quantification.

Artificial water bodies in agricultural landscapes (hereafter ‘farm dams’) are established primarily to support livestock and crop production but also provide habitats for a wide range of native species. Managing water quality in farm dams is essential to animal production and biodiversity. Farm dam enhancement, which includes restricting direct access of stock to dams, can improve water quality in farm dams, by reducing soil erosion and direct faecal contamination, as well as reducing the trampling, grazing, and browsing of vegetation in the immediate catchment. We tested farm dam enhancement as a tool to improve and maintain water quality in 109 farm dams across 34 farms over three years in the sheep-wheat belt of southeast Australia. Using Bayesian Linear Mixed Models, we found that farm dam enhancement significantly reduced levels of phosphorus, nitrogen, turbidity, thermotolerant coliforms, Escherichia coli, and pH. Furthermore, our study revealed links between dam enhancement, increases in vegetation cover, and improved water quality. Our results show that restoration efforts in the surrounds of dams can have positive results on water quality. They highlight the importance of restoration in agricultural landscapes to both agricultural production and biodiversity.

Agriculture intensification is one of the most impacting drivers of European biodiversity decline. The Natura 2000 (N2000) network constitutes a key tool for conservation of species and natural habitats in Europe. Its action to counteract negative impacts of agriculture is mainly based on implementation of Agri-environment schemes (AES) in the N2000 sites. As economical resources are usually limited, spatial targeting is essential for such conservation policy. Here we evaluated whether AES distribution was in spatial coordination with species and habitat conservation states, and agriculture-driven pressures in the French N2000 network. Using the Pressure-State-Response framework, we tested the hypothesis that AES were mainly implemented in sites mostly exposed to pressures, having higher representativeness of species and habitats and higher degradation levels. We combined different sources of information (i.e., standard data forms of the N2000 policy, data collected by the observatory of rural development and national geographical information) to produce pressure, state and response spatial indicators. We declined the analysis per category of pressures related to agricultural activities and considered species and habitat vulnerability to each pressure category. We found limited spatial coordination between AES, pressure and state variables: only 37 % of the fitted models were significant. Significant relationships between AES implementation and agricultural intensification pressure were mostly negative. Considering all indicators, our hypotheses were disproven for more than half of the significant relationships. The results revealed a spatial mismatch between AES distribution and the ecological needs within the N2000 network, as more resources were devoted to sites less exposed to pressure. Our results raise the need of a more strategic approach for the N2000 policy. Indeed, the state of biodiversity conservation and the level of human pressures should be automatically considered a-priori of any implementation of management measures to effectively focus the efforts on the causes of current biodiversity crisis.

Nitrogen pollution has increased dramatically over the last decades, becoming a major contributor to biodiversity loss and compositional changes globally. While the main effects of excessive nutrients on plant communities are well established, Mediterranean grasslands have been less studied despite their high levels of biodiversity. Moreover, evidence has shown that the impacts of nutrients may depend on additional factors, namely soil conditions and grazing, increasing the uncertainty about the effects of increasing nutrient availability in these systems. In this work, we assessed the short-term effects (1 year) of fertilization in an extensively grazed oak open woodland (called montado, or dehesa), in Spain. Plots comprised a complete randomized design with four treatments: control (not fertilized), fertilization with nitrogen at a rate of 100 kg N ha⁻¹, fertilization with phosphorous (50 kg P ha⁻¹) and fertilization with both N and P (100 kg ha⁻¹ N + 50 kg ha⁻¹ P). We assessed changes in plant species composition and functional diversity and evaluated the association between species and fertilization treatments with an indicator species analysis. Our results showed that species diversity increased with NP fertilization and that forbs in particular increased in cover and richness. SLA and seed mass also showed differences compared to the control. The Community-weighted mean and functional dispersion of groups based on growth form and N-fixing ability were not influenced by fertilization. Two species were significantly associated with fertilized plots: the spiny forb Carlina racemosa and the latex-producing forb Tolpis barbata. Our study suggests that short-term fertilization may alleviate nutrient limitations in these systems, increasing plant diversity, although longer-term studies are needed to understand the effects of a continuous increase in nutrient availability.

Fall armyworm (FAW) is a multi-generational invasive insect pest of maize. Field experiments were conducted in diverse ecologies at Hyderabad, Telangana (Location 1); Dholi, Bihar (Location 2); Kolhapur, Maharashtra (Location 3) during the rainy season from July-November, 2023 to assess the impact of maize intercropping with legumes and leafy vegetables on FAW damage, abundance of beneficial insects, weed dynamics, and yield. In the present study, location-specific intercrops were selected for the experimentation. In location 1, maize intercropped with cowpea followed by groundnut reduced the level of FAW infestation compared to sole maize. The increased natural enemy population (coccinellids, spiders, earwigs); weed suppression, and higher yields were observed in maize when intercropped with cowpea followed by groundnut and red amaranthus. In location 2, maize intercropped with cowpea followed by green gram and black gram reduced the FAW damage and higher natural enemy population. Maximum yield was obtained in maize intercropped with black gram followed by green gram and cowpea. However, concerning weed suppression and cost-benefit ratio, green gram followed by black gram was found to be superior. Minimum FAW infestation, abundant natural enemy population, weed suppression, and improved economic returns were observed in maize when intercropped with cowpea followed by groundnut and fenugreek in location 3. Each intercrop had its advantages concerning pests, weed suppression, an abundance of natural enemy populations, and higher yields. Therefore, it is suggested that the selection of plants as intercrops with maize should be based on the location-specific importance of particular aspects to attain multifunctional benefits. The present results revealed that crop diversification with location-specific intercrops can reduce significant yield losses caused by FAW and promote higher yields in maize.

Understanding soil biodiversity response to land use change is crucial for predicting and preserving soil ecological functions and health under anthropogenic influence. Yet, the overall effect of land use changes and climate conditions on belowground biodiversity remains insufficiently explored at large scales. Here, we studied the effect of conversion from natural soils to agricultural soils on soil nematode diversity and community assembly across the Mollisol zone in northeast China. We found that nematode alpha diversity decreased in agricultural soils, and nematode alpha diversity did not exhibit a regular change with latitudinal variation. For beta diversity, we found that nematode community structures were significantly affected by land use change. Furthermore, climatic factors and geographic distance significantly impacted the beta diversity of soil nematodes, but not the alpha diversity. Mean annual temperature was a primary climatic determinant of soil nematode communities, while the effect of mean annual precipitation on soil nematode beta diversity was only observed in agricultural soils. Stochastic processes dominated soil nematode community assembly, but agricultural soils increased the importance of deterministic processes compared to natural soils. There is no any expected variation in soil nematode alpha diversity along the Mollisol zone. Our findings highlight the crucial role of temperature in driving soil nematode communities.

Non-point source pollution water erosion caused by sugarcane planting on sloping land is a serious environmental problem in tropical and subtropical regions. The adjustment of sugarcane planting patterns (ratio of perennial to new planting areas) will affect slope soil erosion. However, the relationship between the contribution of sugarcane land to river pollution load and the planting years of ratoon sugarcane remains unclear. To quantitatively analyse the contribution of sugarcane fields to eroded sediment nitrogen (N) and phosphorus (P) loads into the river in different ratoon years and growing seasons, this study was conducted in the intensive sugarcane cultivation area of the southern subtropical Guangxi Nala sub watershed, using the specific compound specific stable isotope (CSSI) traceability technology and real-time monitoring in the watershed. The changes of N and P loading of sugarcane soil erosion and sediment into the river was determined at different ratoon years (RS₀-RS₃) in addition to the related influencing factors. The results showed that the influence of different ratoon years on the N and P input loads of eroded sediment from sugarcane fields was significantly greater than that of runoff. The contribution of different ratoon sugarcane planting years (including root density) to the loads of sediment N and P into the river was 67.1 % (p < 0.01), which was 2.8 times that of runoff (24.3 %) (p < 0.05). With increasing ratoon sugarcane planting years, the N and P loads of sediment into the river from the sugarcane land decreased significantly; the ratoon sugarcane planting years showed a highly significant negative correlation with the N loads of sediment into the river from the sugarcane fields (p < 0.01), and a significant negative correlation with P (p < 0.05) was observed. Newly planted sugarcane contributed the most to the N and P sediment loads into the river at the seedling stage and the least at the maturity stage. Therefore, in the intensive sugarcane planting areas, to effectively control erosion-induced non-point source pollution, perennial sugarcane planting areas should be rationally in the newly planted sugarcane fields, especially at the seedling stage, to increase land surface cover.

Establishing multi-species swards is a common objective in agricultural forage production systems around the world. Managing pasture productivity and sward resilience is especially challenging in semi-arid environments where mixtures of perennial and self-regenerating annual species are expected to co-exist while growing in competition under water-limited conditions. This review explores the implications of competition dynamics and the practice of changing row configuration at sowing as a prospective approach to managing the composition and productivity of multi-species swards. It uses three test case species representing different functional groups, including the perennial legume, lucerne (alfalfa; Medicago sativa L.), the perennial grass, phalaris (harding grass; Phalaris aquatica L.) and the self-regenerating annual legume, subterranean clover (Trifolium subterraneum L.). Early field studies showed consistent benefits of separating subterranean clover from other sward components at sowing, in terms of foliage dry matter and regeneration density of that species. However, total sward productivity either remained unchanged or declined compared to where all species were planted in the same drill row, especially where forage species were sown with grain cover crops. This is explained by a basic principle of ecology where dominant species drive total production in a short-term ecosystem such as a phased pasture. Constraining dominant species to fewer drill rows at sowing limited their production due to a transient restriction in resources, such as light. It is concluded that separating species in drill rows is a useful strategy for improving the abundance of transient or subordinate species when grown in mixtures with dominant species. However, to avoid perverse outcomes, care is required to ensure that the productivity of the dominant species is not compromised. Practical implications point towards maintaining the number of drill rows to which dominant species are sown. Further research is required to minimise drill row spacing, thus maximising the number of drill rows and increasing early plant coverage on a given area of land. The legacy effect of the pasture drill row is also highlighted, with most species remaining close to the original drill row for the life of a 3-year pasture phase in semi-arid environments. Increased concentration of plants led to enduring benefits in soil fertility, microbial diversity and abundance compared to the inter-row area, findings that warrant closer examination under a greater range of soil and climatic conditions.