Agriculture, Ecosystems & Environment最新文献

Dissolved organic carbon (DOC) in agricultural soils is a pivotal indicator of soil carbon response to management practices, facilitating substance transport, energy transfer, and information exchange. Despite its importance, there is limited understanding of the global impact of these practices on the magnitude, drivers, and functionality of soil DOC. Here, we conducted a meta-analysis of 3539 paired DOC, 196 paired soil carbon dioxide (CO₂) emissions, and 1424 paired crop yields from cropland soils to fill this knowledge gap. Management practices included conservation tillage (CT), nitrogen fertilizer, straw, manure, nitrogen combined with straw (NS), nitrogen combined with manure (NM), and biochar. DOC under NM, manure, NS, straw, nitrogen fertilizer, biochar, and CT increased significantly by 78.21%, 49.91%, 41.02%, 25.68%, 18.4%, 14.89%, and 9.74%, respectively. Except for biochar and CT, the other management practices also led to an increase in the DOC/SOC ratio, ranging from 7.66% to 15.79%. Biochar application decreases the DOC/SOC ratio by 25.02%, indicating its soil carbon stability and the potential for carbon sequestration. The intensity and duration of management practices emerged as driving factors influencing the DOC. Each unit increase of DOC under nitrogen fertilizer, straw, and NM not only effectively decreased the effect size of CO₂ emissions, but also increased the effect size of crop yields in contrast to CT, manure, NS, and biochar. Overall, this study highlighted the importance of the intensity and duration of management practices on DOC. The regulation of DOC through management practices is also required to account for both environmental aspects and crop yields for sustainable agricultural development.

Apples are a highly pollinator-dependent crop that require a minimum number of accumulated chill hours to break dormancy in preparation for bud development and blooming. In the Indian Western Himalayas, apple production is shifting to higher elevations to counteract climate change-associated temperature increases. But it is unclear if and to what extent pollinators are able to match these shifts, or how these altitudinal shifts impact pollinator contribution to apple production. To address these knowledge gaps, we manipulated pollination conditions for apple blossom clusters in 13 orchards distributed along an elevational gradient (1680–2360 m) and measured early fruit set. Fruit set was significantly impacted by pollination treatment and elevation, and in some cases by their interaction. Averaged across elevations, fruit set in the pollinator exclusion treatment was only 6% of that observed under open pollination conditions, but fruit set in the open pollination treatment decreased markedly with elevation. Predicted pollinator contribution to fruit set also decreased with elevation, from 0.96 at the lowest modeled elevation to 0.76 at the highest modeled elevation. Fruit set was enhanced by supplementary hand pollination, demonstrating pollination limitation. We found that pollination deficit increased with elevation, ranging from 0.05 at the lowest modeled elevation (1650 m) to 0.24 at the highest modeled elevation (2400 m). Our findings demonstrate that at least some of the productivity gains realized with increased availability of chilling units at higher elevations might be compromised by pollination limitation. Future studies to determine more clearly the extent and underlying causes of elevation effects on pollination deficits are needed.

Burying straw deeply to establish interlayer is an effective strategy for saline soil improvement, and affects deep soil organic carbon (SOC) sequestration due to the landfill of exogenous carbon. However, the legacy effects of straw interlayer on deep SOC pools and its biotic regulatory mechanism remain unclear. Therefore, a field experiment was conducted with the buried interlayer at straw application rates of 0 Mg ha⁻¹ (CK), 6 Mg ha⁻¹ (SL6), 12 Mg ha⁻¹ (SL12) and 18 Mg ha⁻¹ (SL18). The straw interlayer was buried at 40 cm soil depth. Soil samples at the interlayer area (35–40 cm and 40–45 cm layers) and below the interlayer (45–55 cm, 55–65 cm and 65–75 cm layers) were collected to quantify changes in SOC fractions, as well as the mechanisms of soil microbial community and enzyme after a 6-year burying straw interlayer. Straw interlayer increased particulate organic carbon (POC), mineral-associated organic carbon (MAOC) and SOC contents, which were regulated by the straw application rate and soil depth. High amount of straw caused the positive effect of straw interlayer on SOC pools to extend deeper soil layer. Specifically, SL18 treatment with more straw inputs increased POC content by 33%-212%, MAOC content by 13%-28%, and SOC content by 22%-51% in relative to CK treatment, which was an effective practice to increase SOC sequestration in saline-alkali soil. Meanwhile, straw interlayer increased the POC/SOC, resulting in POC contribution to SOC greater than MAOC. Partial least squares path modeling showed that at the interlayer area, soil microbial community promoted the increases in POC and MAOC, contributing to SOC sequestration. Below the interlayer, soil enzymes promoted an increase in POC, contributing to SOC sequestration. These findings suggested that the regulation of SOC pool shifted from soil microorganisms to enzymes with soil depth, which will help us understand the regulatory mechanism of deep SOC pools after building straw interlayer in saline-alkali soil.

Soil salinization causes the degradation of soil structure, which seriously affects the global agricultural production. Currently, planting halophytes to improve saline soil has been widely used. However, most of the experiments were short-term, and the effect of long-term continuous cropping of halophytes on soil is still uncertain. This study aimed to investigate the multi-year effect of continuous cropping of euhalophyte Suaeda salsa on soil physicochemical properties. The space-for-time substitution approach was used to compare changes in soil physicochemical indicators under 3-year, 5-year, and 7-year continuous cropping periods of Suaeda salsa under drip irrigation, with bareland(0-year) serving as the control. In the 0–20 cm soil layer, the soil moisture content increased from 10.76% to 11.72–14.92%; in the 0–40 cm soil layer, the average bulk density decreased from 1.61 g cm⁻³ to 1.45–1.46 g cm⁻³ (P < 0.05), the average total porosity increased from 40.54% to 45.63–46.82% (P < 0.05), the average content of soil water-stable macroaggregates rose from 2.38% to 3.07–7.42%, and the average clay particle content declined from 20.88% to 16.63–18.63%; in the 0–60 cm soil layer, the average total salt content decreased from 48.11 g kg⁻¹ to 12.43–22.01 g kg⁻¹, and the average soil organic matter(SOM) content decreased from 8.73 g kg⁻¹ to 7.40–8.15 g kg⁻¹; in the 0–100 cm soil layer, the average pH value increased from 7.33 to 7.38–7.75, and the average content of Ca²⁺, Mg²⁺, Na⁺, K⁺, SO₄^2-, and Cl^- all decreased, whereas the average HCO₃^- content increased from 0.16 g kg⁻¹ to 0.25–0.29 g kg⁻¹. After 7 years of continuous cropping, the mean weight diameter (MWD) of 0–40 cm soil layer increased by 19.01%, the sodium adsorption ratio (SAR) of 0–40 cm soil layer decreased by 53.57% (P < 0.05), and the soil hydro-chemical type of 0–100 cm soil layer changed from Cl^--Na⁺·Ca²⁺ to Cl^-·SO₄^2--Na⁺·Ca²⁺. The salt accumulation in the aboveground part of Suaeda salsa accounted for only 1.85–4.36% of the annual desalination quantity in the 0–100 cm soil layer. The continuous cropping of Suaeda salsa improved the soil structure and promoted salt leaching, which was the main mechanism of soil salt reduction. The results showed continuous cropping of Suaeda salsa under drip irrigation in arid regions is an effective method to improve saline soil, providing a theoretical reference for long-term continuous cropping of halophytes to improve saline soil in arid regions.

Plant diversity’s effect on ecosystem functioning is well-established, but its effect on the spatial heterogeneity of soil carbon (C) stocks and microbial responses with increasing diversity is still unclear. Here we propose that increasing tree diversity (TD) would reduce the spatial heterogeneity of soil C stocks while increasing soil C storage, but with inconsistent effect on soil microbial distribution. We test these hypotheses in a subtropical forest comprising three plots each of a monoculture, 10-species, and 30-species plantations. Spatially explicit analysis along distance matrices was conducted on measured soil C fractions and microbial distribution using geostatistical modeling. We show that increasing TD, especially with 30 species reduced the sill value and spatial heterogeneity of soil organic C (SOC) (nugget ratio (NR): >75%) and dissolved organic C (DOC) (NR: 25–75%). Increasing TD reduced the standard deviation in SOC, total dissolved C (TDC), and dissolved inorganic C (DIC) values, while significantly (p<0.01) increasing their concentrations (SOC=16.8–19.2%, DOC=11.2–28.6%, DIC=21.7–34.0%, and TDC=13.1–28.0%) compared to the monoculture. The insignificant change in SOC after increasing TD from 10 to 30 species indicates the importance of litterfall quality and not quantity on SOC accumulation. Besides, the increase in soil pH and reduction in bulk density with increasing TD promoted soil microbial abundance, while inducing a strong spatial distribution (NR<25%) of most soil fungal groups, compared to the bacterial groups. Structural equation modeling indicated negative relationships between DOC and soil microbes in the 30 species mixture, while a positive relationship ensued in the monoculture. Thus, monocultures could accelerate SOC loss through higher DOC-microbes interaction. Therefore, diverse subtropical forests accumulate more SOC with less spatial heterogeneity and higher stability than monocultures. Promoting forest diversity would be valuable for enhancing C sequestration and ecosystem restoration, and measures of its C stocks can be scaled up to predict ecosystem processes with higher accuracy than in monocultures.

Contemporary approaches to agriculture must be reimaged to include ecological techniques that maximise ecosystem services, so that food can be produced sustainably whilst simultaneously meeting yield demands. Pest regulation services, harnessed through the conservation of natural enemies in the agri-environment are an economically important service degraded by conventional citrus production practices. For the first time, a sown wildflower strip composed of native forbs and tussock-forming grasses has been investigated for its influence on natural enemies and their pest regulation services in citrus orchards. A novel management strategy was applied, using the predicted generation times of Aonidiella aurantii Maskell (Hemiptera: Diaspididae), a key pest in citrus, to determine whether cutting the wildflower strips could force spill-over of natural enemies onto the adjacent crop, enhancing pest regulation services. Three treatments applied to orange orchard alleyways were compared: i) a control treatment, the standard orchard practice of regular cutting to 5 cm throughout the year, ii) a sown wildflower treatment managed with cutting once a year in February to a height of 10 cm (standard management wildflower treatment, SMWT), and iii) the same sown wildflower treatment but managed with two additional cuts in May and June (active management wildflower treatment, AMWT). Orange tree canopies were sampled for natural enemies, and pest regulation services were quantified using sentinel prey cards baited with Ephestia kuehniella eggs. Natural enemy richness was greatest in canopies with SMWT, supporting a greater relative abundance of primary parasitoids and lower relative abundances of antagonists (ants) compared to the control. This was associated with enhanced pest regulation services (depletion of sentinel prey from baited cards), especially during the early summer months, which coincides with a critical period to control A. aurantii and other key citrus pests. In contrast, AMWT did not enhance natural enemy richness, and pest regulation services were diminished. This study suggests that leaving wildflower strips uncut throughout the season, as in SMWT, may help to mitigate pest incidence through enhanced pest regulation services. Further studies are now required to determine how this would influence populations of target pests.

In the Alps, grasslands have been the basis for European mountain farming systems for centuries, but nowadays agro-pastoral abandonment is among the major threats to their conservation. Grazing and mowing interruption favours the spread of coarse plants, such as the tall grass Brachypodium rupestre, which negatively impacts grassland agroecosystem functions and ultimately leads to grassland degradation. Practices such as nutrient addition (i.e. fertilisation) and biomass removal (i.e. mowing) have been successfully applied in several mountain environments to reverse the degradation process and restore the original species composition. However, in the Alps, experiments combining both practices have been scarce so far. We hypothesised that the benefits of fertilisation and mowing on the species composition of a B. rupestre encroached grassland could be maximised by coupling fertilisation (120 kg ha⁻¹ N – 80 kg ha⁻¹ P₂O₅ – 80 kg ha⁻¹ K₂O) and mowing. Treatments were carried out yearly over ten years and data were collected throughout the entire period to study the changes in agronomic performances (i.e. pastoral value and abundance of meso-eutrophic grassland species cover), plant diversity (i.e. species richness and effective number of species), and botanical composition. Fertiliser addition effectively enhanced meso-eutrophic grassland species after five years but did not affect either B. rupestre cover or the sward pastoral value. Instead, it slightly reduced the dry grassland species cover, which is considered of conservation interest, and the plant diversity. Mowing successfully reduced B. rupestre presence after five years while maintaining the initial dry grassland species cover and overall species diversity as well. However, it did not improve either meso-eutrophic grassland species cover or the pastoral value. The combination of fertilisation and mowing showed the most promising results. It was able to decrease B. rupestre cover (- 80 %) in the short term while increasing meso-eutrophic grassland species cover (+ 300 %) and the pastoral value (+ 6.5), without negatively impacting dry grassland species cover and plant diversity. According to our long-term study, combining biomass removal by mowing and nutrient addition by fertilisation can be a suitable strategy to achieve agronomic performances and habitat conservation targets, and successfully restore degraded mountain grasslands in the Alps.

Due to increasing intensive agricultural activities, the importance of water quality for drinking is increasing over time. Especially, high concentrations of nitrate (NO₃^–) can cause severe health problems such as cyanosis in infants. This article reviewed the general plant biochemical responses to NO₃^– contamination and examined case studies currently used for NO₃^– removal and phytoremediation of most common tree species and confirmed whether conifer tree species have been conducted for nitrogen pollution research and compiled currently available 117 publications in forest tree species in phytoremediation study. It was explored how intensive agricultural activity can cause nitrate pollution and documented that 89% of the New Zealand’s plantation forests are Pinus radiata species, consisting of 1.63 million hectares and the N uptake potential by P. radiata ranged from 3 to 109 kg ha⁻¹ y⁻¹ based on literature review. Also, it was discussed that if it is necessary to pay attention to the role of Pinus radiata in farmlands and streams to develop novel ideas that can positively affect New Zealand’s environmental policy in the post-Paris Agreement era. I propose to consider choosing and exploiting Pinus radiata for several reasons: (1) to foster Pinus radiata research in nitrogen pollution research, finding new biological functions including the benefits of NO₃^– removal with conifer tree species; (2) to attract the attention to conduct the study of NO₃^– toxicity to plants and (3) to improve the attention of agroecosystem resilience based on fast-growing conifer trees’ regulating services. This article aims to re-evaluate our understanding of whether New Zealand’s Pinus radiata can deal with environmental stress conditions similar to more commonly studied fast-growing broad-leaved tree species.

Rice paddies contribute to ∼48% of greenhouse gas emissions from cropland, with ∼94% from methane (CH₄). Elevated atmospheric CO₂ concentrations (eCO₂) due to human activities, generally stimulate the rice growth, and in turn affect CH₄ emissions from rice paddies. However, the effects of eCO₂ on CH₄ emissions from rice paddies are still unclear under in situ straw incorporation, the popular agricultural practice. Therefore, we conducted a 3-yr field experiment to investigate the effects of eCO₂ on CH₄ emissions under in situ straw incorporation in the rice-wheat cropping system, using the open-top chamber technology. We found that eCO₂ reduced the CH₄ emissions from rice paddies by 10.9–23.8%, but increased rice plant biomass by 4.2–35.6%. The eCO₂ reduced the soil NH₄⁺ and NO₃^- concentrations, but did not affect the soil dissolved organic C. The eCO₂ did not affect the abundance of methanogens and CH₄ production potential, whereas it stimulated the abundance of methanotrophs and CH₄ oxidation potential by 102.5% and 15.1%, respectively. The eCO₂ also shifted the community composition of methanotrophs and reduced the relative abundance of type Ⅱ methanotrophs by 8.5%. The random forest analysis identified that soil CH₄ oxidation potential is the most important factor affecting CH₄ emissions. Our findings indicate that eCO₂ can reduce the CH₄ emissions from rice paddies under in situ straw incorporation mainly through increasing the soil CH₄ oxidation potential. Our study suggests the effects of eCO₂ on CH₄ emissions from global paddies may be overestimated and underline the need for smart agricultural management to reduce CH₄ emissions.

Rice is widely consumed as a staple food, being cultivated worldwide. However, in West Africa, production is not enough to satisfy demand. Rice often suffers intensive damage by herbivorous arthropods that affect quality and quantity of the grain. Birds and bats have been shown to suppress arthropod pests, potentially enhancing rice productivity and food security. However, the degree to which these taxa provide nature-based solutions for mitigating pest-induced rice losses is poorly known, especially in West Africa. Here, we used experimental exclosures to investigate whether birds and bats reduce plant damage and boost rice yield by suppressing arthropod abundance. In a rural area in northern Guinea-Bissau, we established 14 sets of paired control and experimental exclosures parcels, precluding access of birds and bats to rice plants. We then quantified how the absence of birds and bats influenced arthropod communities, plant damage, and rice yield over a full rice production cycle (six months). Arthropod numbers in exclosures (10.1 ± 9.1 ind./plot) were nearly double those in control plots (5.8 ± 3.0 ind./plot), a result mostly due to a lower spider abundance in the controls. The percentage of leaf and grain damage showed no difference between exclosure and control. Using Structural Equation Models, we uncovered that the exclusion of birds and bats boosted arthropod abundance but had only marginal effects on rice damage and no detectable effect on yield. The exclusion of flying vertebrates led to a marked increase in spider abundance, suggesting an effect of mesopredator release, which in turn likely helped maintaining pest abundance low and potentially contributing to the small overall effect on rice damage and yield. Enhancing the abundance of birds and bats is an interesting option to suppress agricultural pests, but our results highlight the need for a better understanding of ecological interactions in agricultural landscapes in West Africa. We stress the need for more research to inform evidence-based policies using nature-based solutions that foster the natural consumption of pests by vertebrates, as a means to improve food security.