Urbanization shifts long-term phenology and severity of phytoplankton blooms in an urban lake through different pathways.

Climate change can induce phytoplankton blooms (PBs) in eutrophic lakes worldwide, and these blooms severely threaten lake ecosystems and human health. However, it is unclear how urbanization and its interaction with climate impact PBs, which has implications for the management of lakes. Here, we used multi-source remote sensing data and integrated the Virtual-Baseline Floating macroAlgae Height (VB-FAH) index and OTSU threshold automatic segmentation algorithm to extract the area of PBs in Lake Dianchi, China, which has been subjected to frequent PBs and rapid urbanization in its vicinity. We further explored long-term (2000-2021) trends in the phenological and severity metrics of PBs and quantified the contributions from urbanization, climate change, and also nutrient levels to these trends. When comparing data from 2011-2021 to 2000-2010, we found significantly advanced initiation of PBs (28.6 days) and noticeably longer duration (51.9 days) but an insignificant trend in time of disappearance. The enhancement of algal nutrient use efficiency, likely induced by increased water temperature and reduced nutrient concentrations, presumably contributed to an earlier initiation and longer duration of PBs, while there was a negative correlation between spring wind speed and the initiation of PBs. Fortunately, we found that both the area of the PBs and the frequency of severe blooms (covering more than 19.8 km2 ) demonstrated downward trends, which could be attributed to increased wind speed and/or reduced nutrient levels. Moreover, the enhanced land surface temperature caused by urbanization altered the thermodynamic characteristics between the land and the lake, which, in turn, possibly caused an increase in local wind speed and water temperature, suggesting that urbanization can differently regulate the phenology and severity of PBs. Our findings have significant implications for the understanding of the impacts of urbanization on PB dynamics and for improving lake management practices to promote sustainable urban development under global change.

Total nitrogen and community turnover determine phosphorus use efficiency of phytoplankton along nutrient gradients in plateau lakes.

Numerous studies support that biodiversity predict most to ecosystem functioning, but whether other factors display a more significant direct impact on ecosystem functioning than biodiversity remains to be studied. We investigated 398 samples of the phytoplankton phosphorus resource use efficiency (RUEP = chlorophyll-a concentration/dissolved phosphate) across two seasons in nine plateau lakes in Yunnan Province, China. We identified the main contributors to phytoplankton RUEP and analyzed their potential influences on RUEP at different lake trophic states. The results showed that total nitrogen (TN) contributed the most to RUEP among the nine lakes, whereas community turnover (measured as community dissimilarity) explained the most to RUEP variation across the two seasons. Moreover, TN also influenced RUEP by affecting biodiversity. Species richness (SR), functional attribute diversity (FAD2), and dendrogram-based functional diversity (FDc) were positively correlated with RUEP in both seasons, while evenness was negatively correlated with RUEP at the end of the rainy season. We also found that the effects of biodiversity and turnover on RUEP depended on the lake trophic states. SR and FAD2 were positively correlated with RUEP in all three trophic states. Evenness showed a negative correlation with RUEP at the eutrophic and oligotrophic levels, but a positive correlation at the mesotrophic level. Turnover had a negative influence on RUEP at the eutrophic level, but a positive influence at the mesotrophic and oligotrophic levels. Overall, our results suggested that multiple factors and nutrient states need to be considered when the ecosystem functioning predictors and the biodiversity-ecosystem functioning relationships are investigated.

Impact of cropping system diversification on productivity and resource use efficiencies of smallholder farmers in south-central Bangladesh: a multi-criteria analysis.

Diversification of smallholder rice-based cropping systems has the potential to increase cropping system intensity and boost food security. However, impacts on resource use efficiencies (e.g., nutrients, energy, and labor) remain poorly understood, highlighting the need to quantify synergies and trade-offs among different sustainability indicators under on-farm conditions. In southern coastal Bangladesh, aman season rice is characterized by low inputs and low productivity. We evaluated the farm-level impacts of cropping system intensification (adding irrigated boro season rice) and diversification (adding chili, groundnut, mungbean, or lathyrus) on seven performance indicators (rice equivalent yield, energy efficiency, partial nitrogen productivity, partial potassium productivity, partial greenhouse gas footprint, benefit-cost ratio, and hired labor energy productivity) based on a comprehensive survey of 501 households. Indicators were combined into a multi-criteria performance index, and their scope for improvement was calculated by comparing an individual farmer's performance to top-performing farmers (highest 20%). Results indicate that the baseline system (single-crop aman season rice) was the least productive, while double cropped systems increased rice equivalent yield 72-217%. Despite gains in productivity, higher cropping intensity reduced resource use efficiencies due to higher inputs of fertilizer and energy, which also increased production costs, particularly for boro season rice. However, trade-offs were smaller for diversified systems including legumes, largely owing to lower N fertilizer inputs. Aman season rice had the highest multi-criteria performance index, followed by systems with mungbean and lathyrus, indicating the latter are promising options to boost food production and profitability without compromising sustainability. Large gaps between individual and top-performing farmers existed for each indicator, suggesting significant scope for improvement. By targeting indicators contributing most to the multi-criteria performance index (partial nitrogen productivity, energy efficiency, hired labor energy productivity), results suggest further sustainability gains can be achieved through future field research studies focused on optimizing management within diversified systems. Supplementary Information: The online version contains supplementary material available at 10.1007/s13593-022-00795-3.

Effect of Tractor Speed and Spray Application Volume on Severity of Scab and Fruit Weight at Different Heights in the Canopy of Tall Pecan Trees.

Scab (caused by Venturia effusa) is the most important yield-limiting disease of pecan in the southeastern USA. On susceptible cultivars, the disease is managed using fungicides, but spray coverage is an issue in tall trees. In four experiments, we used an air-blast sprayer to compare scab severity on fruit at 5.0 to 15.0 m height in trees receiving the same dose of fungicide at 468, 935, and 1,871 liter/ha at 2.4 and 3.2 km/h (in two additional experiments fungicides were applied at 4.0 km/h at 470 liter/ha, 4.0 km/h at 940 liter/ha and 4.0 km/h at 1,100 liter/ha). An air-blast sprayer was used for the applications, which included typical recommended active ingredients (a.i.). Nozzles were selected to provide similar proportions of spray to the upper and lower canopy. The treatments (or subsets thereof) were repeated in 2015 to 2017 on cv. Schley and in 2017, 2019, and 2020 on cv. Desirable. All treatments reduced scab compared with the control. Overall, there was no consistent difference among the treatments for severity of scab on foliage, immature fruit, or mature fruit at any height in the canopy up to 15.0 m (maximum height sampled). Fungicide applied at 2.4 or 3.2 km/h at 470 liter/ha was as effective at reducing disease as were the higher volumes (sometimes more so). The scab epidemic severity affected control efficacy. Estimated cost and water savings based on faster speed and lower volume were considerable. These preliminary observations indicate no single volume or speed was consistently superior to control scab; this suggests that, in most seasons, low volumes (higher concentration of a.i.) may be similarly efficacious as high volumes (lower concentration of a.i.) for controlling scab in tall pecan trees and offer greater resource use efficiency.

Structural and functional variations of phytoplankton communities in the face of multiple disturbances.

The global decline of freshwater biodiversity caused by climate change and human activities are supposed to disrupt ecosystem services related to water quality and alter the structure and function of aquatic communities across space and time, yet the effects of the combination of these factors on plankton community ecosystem has received relatively little attention. This study aimed to explore the impacts of disturbances (e.g. human activity, temperature, precipitation, and water level) on phytoplankton community structure (i.e. community evenness and community composition) and function (i.e. resource use efficiency) in four subtropical reservoirs over 7 years from 2010 to 2016. Our results showed that community turnover (measured as community dissimilarity) was positively related to disturbance frequency, but no significant correlation was found between phytoplankton biodiversity (i.e. evenness) and disturbance frequency. Phytoplankton resource use efficiency (RUE = phytoplankton biomass/ total phosphorus) was increased with a higher frequency of disturbance with an exception of cyanobacteria. The RUE of Cyanobacteria and diatoms showed significantly negative correlations with their community evenness, while the RUE of Chlorophyta exhibited a positive correlation with their community turnover. We suggest that multiple environmental disturbances may play crucial roles in shaping the structure and functioning of plankton communities in subtropical reservoirs, and mechanism of this process can provide key information for freshwater uses, management and conservation.

Below-ground determinants and ecological implications of shrub species' degree of isohydry in subtropical pine plantations.

The degree of plant iso/anisohydry is a popular framework for characterising species-specific drought responses. However, we know little about associations between below-ground and above-ground hydraulic traits as well as the broader ecological implications of this framework. For 24 understory shrub species in seasonally dry subtropical coniferous plantations, we investigated contributions of the degree of isohydry to species' resource economy strategies, abundance, and importance value, and quantified the hydraulic conductance (Kh ) of above-ground and below-ground organs, magnitude of deep water acquisition (WAdeep ), shallow absorptive root traits (diameter, specific root length, tissue density), and resource-use efficiencies (Amax , maximum photosynthesis rate; PNUE, photosynthetic nitrogen-use efficiency). The extreme isohydric understory species had lower wood density (a proxy for higher growth rates) because their higher WAdeep and whole-plant Kh allowed higher Amax and PNUE, and thus did not necessarily show lower abundance and importance values. Although species' Kh was coordinated with their water foraging capacity in shallow soil, the more acquisitive deep roots were more crucial than shallow roots in shaping species' extreme isohydric behaviour. Our results provide new insights into the mechanisms through which below-ground hydraulic traits, especially those of deep roots, determine species' degree of isohydry and economic strategies.

Cherry Tomato Production in Intelligent Greenhouses-Sensors and AI for Control of Climate, Irrigation, Crop Yield, and Quality.

Greenhouses and indoor farming systems play an important role in providing fresh and nutritious food for the growing global population. Farms are becoming larger and greenhouse growers need to make complex decisions to maximize production and minimize resource use while meeting market requirements. However, highly skilled labor is increasingly lacking in the greenhouse sector. Moreover, extreme events such as the COVID-19 pandemic, can make farms temporarily less accessible. This highlights the need for more autonomous and remote-control strategies for greenhouse production. This paper describes and analyzes the results of the second "Autonomous Greenhouse Challenge". In this challenge, an experiment was conducted in six high-tech greenhouse compartments during a period of six months of cherry tomato growing. The primary goal of the greenhouse operation was to maximize net profit, by controlling the greenhouse climate and crop with AI techniques. Five international teams with backgrounds in AI and horticulture were challenged in a competition to operate their own compartment remotely. They developed intelligent algorithms and use sensor data to determine climate setpoints and crop management strategy. All AI supported teams outperformed a human-operated greenhouse that served as reference. From the results obtained by the teams and from the analysis of the different climate-crop strategies, it was possible to detect challenges and opportunities for the future implementation of remote-control systems in greenhouse production.

Improvement and stabilization of rice production by delaying sowing date in irrigated rice system in central China.

BACKGROUND: Climate change has posed great challenges to rice production. Temperature and solar radiation show significant variations in central China. This study aims to analyze the responses of different rice genotypes to the variations of temperature and solar radiation in central China, and to find the way of identifying the optimal sowing date to improve and stabilize rice production. For this end, four rice genotypes (two Indica and two Japonica cultivars) were cultivated at two locations under irrigation conditions in 2 years with six sowing dates. RESULTS: We investigated variations of rice grain yield, resource use efficiency, average daily temperature and solar radiation during different phenological stages. Rice grain yield could increase by about 2-17% in central China. Compared with solar radiation, temperature was a more important factor affecting rice grain yield in central China. The grain yield showed great correlation with the means temperature during different phenological stages, especially during the first 20 days after heading (GT20). Besides our results demonstrated that the grain yield displayed slender variations when the GT20 was within 24.9-26.4 °C. However, GT20 was higher than 26.4 °C in most cases, which became more frequent due to climate changes. Analysis of climate change during the last 25 years revealed that the frequency of GT20 within 24.9-26.4 °C was increased by the delay of sowing date. CONCLUSION: We propose that delaying sowing date to achieve the optimal GT20 (24.9 °C-26.4 °C) can be an effective strategy to stabilize and improve rice grain yield and resource use efficiency in central China. © 2019 Society of Chemical Industry.

Remote Control of Greenhouse Vegetable Production with Artificial Intelligence-Greenhouse Climate, Irrigation, and Crop Production.

The global population is increasing rapidly, together with the demand for healthy fresh food. The greenhouse industry can play an important role, but encounters difficulties finding skilled staff to manage crop production. Artificial intelligence (AI) has reached breakthroughs in several areas, however, not yet in horticulture. An international competition on "autonomous greenhouses" aimed to combine horticultural expertise with AI to make breakthroughs in fresh food production with fewer resources. Five international teams, consisting of scientists, professionals, and students with different backgrounds in horticulture and AI, participated in a greenhouse growing experiment. Each team had a 96 m2 modern greenhouse compartment to grow a cucumber crop remotely during a 4-month-period. Each compartment was equipped with standard actuators (heating, ventilation, screening, lighting, fogging, CO2 supply, water and nutrient supply). Control setpoints were remotely determined by teams using their own AI algorithms. Actuators were operated by a process computer. Different sensors continuously collected measurements. Setpoints and measurements were exchanged via a digital interface. Achievements in AI-controlled compartments were compared with a manually operated reference. Detailed results on cucumber yield, resource use, and net profit obtained by teams are explained in this paper. We can conclude that in general AI performed well in controlling a greenhouse. One team outperformed the manually-grown reference.

Resource competition model predicts zonation and increasing nutrient use efficiency along a wetland salinity gradient.

A trade-off between competitive ability and stress tolerance has been hypothesized and empirically supported to explain the zonation of species across stress gradients for a number of systems. Since stress often reduces plant productivity, one might expect a pattern of decreasing productivity across the zones of the stress gradient. However, this pattern is often not observed in coastal wetlands that show patterns of zonation along a salinity gradient. To address the potentially complex relationship between stress, zonation, and productivity in coastal wetlands, we developed a model of plant biomass as a function of resource competition and salinity stress. Analysis of the model confirms the conventional wisdom that a trade-off between competitive ability and stress tolerance is a necessary condition for zonation. It also suggests that a negative relationship between salinity and production can be overcome if (1) the supply of the limiting resource increases with greater salinity stress or (2) nutrient use efficiency increases with increasing salinity. We fit the equilibrium solution of the dynamic model to data from Louisiana coastal wetlands to test its ability to explain patterns of production across the landscape gradient and derive predictions that could be tested with independent data. We found support for a number of the model predictions, including patterns of decreasing competitive ability and increasing nutrient use efficiency across a gradient from freshwater to saline wetlands. In addition to providing a quantitative framework to support the mechanistic hypotheses of zonation, these results suggest that this simple model is a useful platform to further build upon, simulate and test mechanistic hypotheses of more complex patterns and phenomena in coastal wetlands.

Growing fresh food on future space missions: Environmental conditions and crop management.

This paper deals with vegetable cultivation that could be faced in a space mission. This paper focusses on optimization, light, temperature and the harvesting process, while other factors concerning cultivation in space missions, i.e. gravity, radiation, were not addressed. It describes the work done in preparation of the deployment of a mobile test facility for vegetable production of fresh food at the Neumayer III Antarctic research station. A selection of vegetable crops was grown under varying light and temperature conditions to quantify crop yield response to climate factors that determine resource requirement of the production system. Crops were grown at 21 °C or 25 °C under light treatments varying from 200 to 600 µmol m-2  s-1 and simulated the dusk and dawn light spectrum. Fresh food biomass was harvested as spread harvesting (lettuce), before and after regrowth (herbs) and at the end of cultivation. Lettuce and red mustard responded well to increasing light intensities, by 35-90% with increasing light from 200 to 600 µmol m-2 s-1, while the other crops responded more variably. However, the quality of the leafy greens often deteriorated at higher light intensities. The fruit biomass of both determinate tomato and cucumber increased by 8-15% from 300 to 600 µmol m-2 s-1. With the increase in biomass, the number of tomato fruits also increased, while the number of cucumber fruits decreased, resulting in heavier individual fruits. Increasing the temperature had varied effects on production. While in some cases the production increased, regrowth of herbs often lagged behind in the 25 °C treatment. In terms of fresh food production, the most can be expected from lettuce, cucumber, radish, then tomato, although the 2 fruit vegetables require a considerable amount of crop management. Spread harvesting had a large influence on the amount of harvested biomass per unit area. In particular, yield of the 3 lettuce cultivars and spinach was ca. 400% than single harvesting. Increasing plant density and applying spread harvesting increased fresh food production. This information will be the basis for determining crop growth recipes and management to maximize the amount of fresh food available, in view of the constraints of space and energy requirement of such a production system.

Towards resilience through systems-based plant breeding. A review.

How the growing world population can feed itself is a crucial, multi-dimensional problem that goes beyond sustainable development. Crop production will be affected by many changes in its climatic, agronomic, economic, and societal contexts. Therefore, breeders are challenged to produce cultivars that strengthen both ecological and societal resilience by striving for six international sustainability targets: food security, safety and quality; food and seed sovereignty; social justice; agrobiodiversity; ecosystem services; and climate robustness. Against this background, we review the state of the art in plant breeding by distinguishing four paradigmatic orientations that currently co-exist: community-based breeding, ecosystem-based breeding, trait-based breeding, and corporate-based breeding, analyzing differences among these orientations. Our main findings are: (1) all four orientations have significant value but none alone will achieve all six sustainability targets; (2) therefore, an overarching approach is needed: "systems-based breeding," an orientation with the potential to synergize the strengths of the ways of thinking in the current paradigmatic orientations; (3) achieving that requires specific knowledge development and integration, a multitude of suitable breeding strategies and tools, and entrepreneurship, but also a change in attitude based on corporate responsibility, circular economy and true-cost accounting, and fair and green policies. We conclude that systems-based breeding can create strong interactions between all system components. While seeds are part of the common good and the basis of agrobiodiversity, a diversity in breeding approaches, based on different entrepreneurial approaches, can also be considered part of the required agrobiodiversity. To enable systems-based breeding to play a major role in creating sustainable agriculture, a shared sense of urgency is needed to realize the required changes in breeding approaches, institutions, regulations and protocols. Based on this concept of systems-based breeding, there are opportunities for breeders to play an active role in the development of an ecologically and societally resilient, sustainable agriculture.

Herbivores sculpt leaf traits differently in grasslands depending on life form and land-use histories.

Vertebrate and invertebrate herbivores alter plant communities directly by selectively consuming plant species; and indirectly by inducing morphological and physiological changes to plant traits that provide competitive or survivorship advantages to some life forms over others. Progressively excluding aboveground herbivore communities (ungulates, medium and small sized mammals, invertebrates) over five growing seasons, we explored how leaf morphology (specific leaf area or SLA) and nutrition (nitrogen, carbon, phosphorous, potassium, sodium, and calcium) of different plant life forms (forbs, legumes, grasses, sedges) correlated with their dominance. We experimented in two subalpine grassland types with different land-use histories: (1) heavily grazed, nutrient-rich, short-grass vegetation and (2) lightly grazed, lower nutrient tall-grass vegetation. We found differences in leaf traits between treatments where either all herbivores were excluded or all herbivores were present, showing the importance of considering the impacts of both vertebrates and invertebrates on the leaf traits of plant species. Life forms responses to the progressive exclusion of herbivores were captured by six possible combinations: (1) increased leaf size and resource use efficiency (leaf area/nutrients) where lower nutrient levels are invested in leaf construction, but a reduction in the number of leaves, for example, forbs in both vegetation types, (2) increased leaf size and resource use efficiency, for example, legumes in short grass, (3) increased leaf size but a reduction in the number of leaves, for example, legumes in the tall grass, (4) increased number of leaves produced and increased resource use efficiency, for example, grasses in the short grass, (5) increased resource use efficiency of leaves only, for example, grasses and sedges in the tall grass, and (6) no response in terms of leaf construction or dominance, for example, sedges in the short grass. Although we found multiple possible responses by life forms to progressive exclusion of herbivores, we also found some important generalities. Changes in leaf traits of legumes and grasses correlated with their increasing dominance in the short-grass vegetation and plants were more efficient at constructing photosynthetic tissue when herbivores are present with few exceptions. These results demonstrate that vertebrate and invertebrate herbivores are essential to maintain plant species richness and resource-use efficiency.

Belowground carbon flux links biogeochemical cycles and resource-use efficiency at the global scale.

Nutrient limitation is pervasive in the terrestrial biosphere, although the relationship between global carbon (C) nitrogen (N) and phosphorus (P) cycles remains uncertain. Using meta-analysis we show that gross primary production (GPP) partitioning belowground is inversely related to soil-available N : P, increasing with latitude from tropical to boreal forests. N-use efficiency is highest in boreal forests, and P-use efficiency in tropical forests. High C partitioning belowground in boreal forests reflects a 13-fold greater C cost of N acquisition compared to the tropics. By contrast, the C cost of P acquisition varies only 2-fold among biomes. This analysis suggests a new hypothesis that the primary limitation on productivity in forested ecosystems transitions from belowground resources at high latitudes to aboveground resources at low latitudes as C-intensive root- and mycorrhizal-mediated nutrient capture is progressively replaced by rapidly cycling, enzyme-derived nutrient fluxes when temperatures approach the thermal optimum for biogeochemical transformations.

Cyanobacteria dominance influences resource use efficiency and community turnover in phytoplankton and zooplankton communities.

Freshwater biodiversity loss potentially disrupts ecosystem services related to water quality and may negatively impact ecosystem functioning and temporal community turnover. We analysed a data set containing phytoplankton and zooplankton community data from 131 lakes through 9 years in an agricultural region to test predictions that plankton communities with low biodiversity are less efficient in their use of limiting resources and display greater community turnover (measured as community dissimilarity). Phytoplankton resource use efficiency (RUE = biomass per unit resource) was negatively related to phytoplankton evenness (measured as Pielou's evenness), whereas zooplankton RUE was positively related to phytoplankton evenness. Phytoplankton and zooplankton RUE were high and low, respectively, when Cyanobacteria, especially Microcystis sp., dominated. Phytoplankton communities displayed slower community turnover rates when dominated by few genera. Our findings, which counter findings of many terrestrial studies, suggest that Cyanobacteria dominance may play important roles in ecosystem functioning and community turnover in nutrient-enriched lakes.

Predictable shifts in diversity and ecosystem function in phytoplankton and zooplankton communities along thermocline stratification intensity continua.

Thermocline stratification is a global threat to water quality in drinking water reservoirs, though its underlying mechanisms are not clear. The impacts of thermocline stratification intensity on biodiversity-ecosystem relationships were assessed using phytoplankton and zooplankton indicators from four stages of stratification in Lake Qiandaohu. There were significant differences in biomass, species diversity, and resource use efficiency (RUEpp = phytoplankton biomass/total phosphorus) for phytoplankton between continuous stratification and mixing periods, but only in FDis and RaoQ diversity indices for zooplankton. Phytoplankton species diversity and RUE were higher in the formative and stable periods, while zooplankton species diversity and zooplankton biomass/phytoplankton biomass (RUEzp) were lower. When combining the data from the four periods, a negative linear pattern was found between phytoplankton Simpson's, functional dispersion (FDis), and Rao's Quadratic (RaoQ) diversity indices, and thermocline depth (TD). Only zooplankton FDis and RaoQ diversity indices were significantly positively related to TD. Phytoplankton RUE was significantly negatively related only to its Pielou's evenness (J) diversity, while zooplankton RUE was significantly negatively related to its J, FDis, and RaoQ diversity indices. The results of structural equation models (SEMs) showed that the R2 of RUE for phytoplankton was much higher than that for zooplankton. Thermocline stratification intensity exerted an indirect positive effect on phytoplankton RUE by affecting species diversity but had a negative effect on zooplankton RUE. These findings underscore the negative influence of thermocline stratification resulting in various biodiversity changes in freshwater ecosystems.

Experimental warming promotes phytoplankton species sorting towards cyanobacterial blooms and leads to potential changes in ecosystem functioning.

A positive feedback loop where climate warming enhances eutrophication and its manifestations (e.g., cyanobacterial blooms) has been recently highlighted, but its consequences for biodiversity and ecosystem functioning are not fully understood. We conducted a highly replicated indoor experiment with a species-rich subtropical freshwater phytoplankton community. The experiment tested the effects of three constant temperature scenarios (17, 20, and 23 °C) under high-nutrient supply conditions on community composition and proxies of ecosystem functioning, namely resource use efficiency (RUE) and CO2 fluxes. After 32 days, warming reduced species richness and promoted different community trajectories leading to a dominance by green algae in the intermediate temperature and by cyanobacteria in the highest temperature treatments. Warming promoted primary production, with a 10-fold increase in the mean biomass of green algae and cyanobacteria. The maximum RUE occurred under the warmest treatment. All treatments showed net CO2 influx, but the magnitude of influx decreased with warming. We experimentally demonstrated direct effects of warming on phytoplankton species sorting, with negative effects on diversity and direct positive effects on cyanobacteria, which could lead to potential changes in ecosystem functioning. Our results suggest potential positive feedback between the phytoplankton blooms and warming, via lower net CO2 sequestration in cyanobacteria-dominated, warmer systems, and add empirical evidence to the need for decreasing the likelihood of cyanobacterial dominance.

Effects of Aquatic Plant Coverage on Diversity and Resource Use Efficiency of Phytoplankton in Urban Wetlands: A Case Study in Jinan, China.

With the acceleration of urbanization, biodiversity and ecosystem functions of urban wetlands are facing serious challenges. The loss of aquatic plants in urban wetlands is becoming more frequent and intense due to human activities; nevertheless, the effects of aquatic plants on wetland ecosystems have received less attention. Therefore, we conducted field investigations across 10 urban wetlands in Jinan, Shandong Province, as a case in North China to examine the relationships between aquatic plant coverage and phytoplankton diversity, as well as resource use efficiency (RUE) in urban wetlands. Multivariate regression and partial least squares structural equation modeling (PLS-SEM) were used to analyze the water quality, phytoplankton diversity, and RUE. The results demonstrate that the increase in aquatic plant coverage significantly reduced the concentration of total nitrogen and suspended solids' concentrations and significantly increased the phytoplankton diversity (e.g., species richness and functional diversity). The aquatic plant coverage significantly affected the composition of phytoplankton functional groups; for example, functional groups that had adapted to still-water and low-light conditions became dominant. Furthermore, the increase in phytoplankton diversity improved phytoplankton RUE, highlighting the importance of aquatic plants in maintaining wetland ecosystem functions. This study may provide a scientific basis for the management strategy of aquatic plants in urban wetlands, emphasizing the key role of appropriate aquatic plant cover in maintaining the ecological stability and ecosystem service functions of wetlands.

Reproductive resilience of growth and nitrogen uptake underpins yield improvement in winter wheat with forced delay of sowing.

Winter wheat production is influenced by climate extremes worldwide. Heavy precipitation induced delay of sowing generates limited photothermal resources for wheat early growth. However, how wheat build resilience from stunted seedling growth has not been fully explored. Here, a twelve-year farmers' survey of wheat yield was recorded and four-year field experiments of wheat grown in normal and late-sowing were performed under zero nitrogen (N0) and optimum nitrogen (Opt.N) supply. Wheat growth and N uptake were measured at both vegetative and reproductive stages alongside photothermal resource-use efficiency. Farmers' survey showed 10.4 % yield losses due to delayed sowing compared to the normal. However, four-year field trials revealed that the combination of increasing seeding rates and Opt.N application recovered grain yield of sowing-delayed wheat and even increased by 13.2 % compared to plants in the normal seasons. Although delayed sowing substantially suppressed seedling growth and tillering before winter dormancy, the Opt.N application increased spring tillers by 2.4-fold which were productive at maturity. Further, plant growth and N uptake from jointing to anthesis of sowing-delayed wheat were accelerated by Opt.N, but not by N0 treatment. Delayed sowing significantly shortened the duration of lag phase of grain filling by 3.5 days and by 183 growing degree days compared with the normal, which initiated the linear and fast filling earlier. Increased leaf photosynthesis by 27.4 % during grain filling further supported the fast recovery of grain filling in the sowing-delayed wheat. Concomitantly, the physiological N-use efficiency increased by 46.7 % during grain filling and by 41.5 % at maturity by enhancing N availability and seeding rates, and photothermal resource-use efficiency increased by 1.3- to 1.7-fold for wheat with delayed vs. normal sowing. Overall, these findings highlight the integrated management of nutrient and cultivation to mitigate the impacts of climate extremes on crop productivity through building plant reproductive resilience.

Water-land-energy efficiency and nexus within global agricultural trade during 1995-2019.

Agricultural product demand driven by population and economic growth poses challenges to water, land, and energy utilization, and this increasing local demand is largely met through trade. However, the efficiency and nexus pattern of the water, land, and energy embodied in agricultural trade are not well understood. This study uses the multi-regional input-output framework to analyze agricultural water, land, and energy utilization efficiency of resource footprints per unit economic output as well as their transfer and nexus pattern in global agricultural trade for 1995-2019. The results show that many international agricultural trade paths are inefficient in the water, land, and energy resource use because the agricultural products in these paths are exported from relatively low- to high-efficiency economies/regions. However, these inefficient transfer paths show an increasing trend over the study period. Regarding the water-land-energy nexus, conflicts are prevalent in land-energy and water-energy couplings. Most trade paths are conducted to alleviate the pressure on a specific resource, inadvertently increasing the pressure on other resources. Although agricultural trade is important for meeting global food demands, it is not consistently beneficial to the local environment when considering agricultural resources use efficiency. This study is expected to improve our understanding of agricultural trade impacts to the agricultural resources and support the sustainable development of global agriculture.