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During the DOE Atmospheric Radiation Measurement (ARM) Tracking Aerosol Convection Interactions Experiment (TRACER) IOP spanning June–September 2022, two fixed ARM sites and a mobile team concurrently sampled the airmass heterogeneity across sea- and bay-breeze fronts around the greater Houston metropolitan region. Here, we quantify the spatiotemporal variability between maritime (coastal/bay side of breeze fronts) and continental (inland side of breeze fronts) air masses over 15 IOP days characterized by strong sea-breeze forcing. We analyze environmental profile data from 177 radiosondes and use S- and C-band radar data to track and quantify the variability in attributes of more than 2300 shallow and transitioning cells across different air masses. The composite analysis of environmental profiles indicates that during the early afternoon, the sea-breeze maritime air mass exhibits lower convective available potential energy (CAPE) than the bay-breeze maritime air mass. As the sea breeze advances inland with time, CAPE within the maritime air mass exceeds that of the continental air mass to the north of the breeze fronts. In general, maritime cells have a larger mean composite reflectivity and cell widths than continental cells; however, the response varies between shallow and transitioning cells. Mean composite 20-dBZ echo-top heights, however, are similar across air masses for both shallow and transitioning cells. The continental and maritime inflow air mass for transitioning cells has significantly different mean values for mixed-layer entrainment CAPE, lifted condensation level, level of free condensation, boundary layer depth, and diluted equilibrium level. For shallow cells, only total precipitable water shows a significant difference. Significance Statement: The greater Houston metropolitan area is a natural laboratory for understanding the individual impacts of background meteorology and aerosols on convective clouds. Due to its proximity to the Gulf Coast and Galveston Bay, the Houston region experiences a diurnal precipitation cycle in the summer, driven by convection triggered from sea- and bay-breeze fronts. These fronts act as a boundary between air masses with distinct thermodynamic and environmental characteristics. Convergence along these fronts and interactions between storm outflow and the fronts facilitate convection initiation in different mesoscale air masses. This study quantifies the heterogeneity among these air masses while investigating their influence on cloud microphysics. We find that the effect of airmass heterogeneity is more pronounced for the bulk microphysical properties in shallow clouds. [ABSTRACT FROM AUTHOR]

The Pacific meridional mode (PMM) is one of the dominant coupled modes in the northeastern tropical Pacific (NETP), characterized by strip-like sea surface temperature (SST) anomalies spanning from Baja California to the central equatorial Pacific. While the majority of the El Niño events follow a positive PMM, only a few La Niña events are preceded by a negative PMM. Such an asymmetric activity of PMM before the onset of El Niño–Southern Oscillation (ENSO) was previously attributed to the inherent nonlinear response of the wind–evaporation–SST (WES) feedback to trade winds in the NETP. Through data analysis and coupled model experiments, we pointed out that PMM is in fact a highly symmetric phenomenon, and the asymmetry of PMM before the ENSO onset thus must be associated with ENSO. On the one hand, the nonlinear response of deep convection over the equator to symmetric ENSO forcing in the central equatorial Pacific permits a stronger Pacific–North America (PNA) pattern in El Niño years than in La Niña years. On the other hand, since the majority of La Niña events are preceded by a sharp decay of an El Niño, the warm equatorial SST anomalies associated with the preceding El Niño provide another source to trigger PNA before the La Niña onset. The two mechanisms modulate the trade winds and heat fluxes in NETP more heavily before the La Niña onset than the El Niño onset and equally contribute to PMM asymmetry before the ENSO onset. [ABSTRACT FROM AUTHOR]

The cultivation of sunflower (Helianthus annuus L.) as a cut flower stands out in floriculture due to its aesthetic beauty and commercial value. Understanding how cut sunflower genotypes adapt to different edaphoclimatic regions and management practices is essential to optimize flower quality and productivity. This study aimed to evaluate the effect of plant density and location on the development, growth, and quality of cut sunflower in tropical and subtropical environments. Plant densities of 10, 20, 30, 40, and 50 plants/m2 were evaluated in tropical climate and subtropical climate using a randomized block design in a factorial scheme. Results showed significant differences between locations for plant height, capitulum and stem diameter, final number of leaves, leaf area, leaf area index, phyllochron, and the developmental cycle. Plant density significantly influenced these variables except for plant height and developmental cycle. The interaction between location and plant density was significant only for capitulum diameter and final leaf number. The findings indicate that both planting density and location significantly influence the developmental cycle of cut sunflowers, with lower densities favoring more robust plants at harvest. A density of 30 plants/m2 is recommended for efficient space use without significantly compromising floral stem quality. All produced stems are marketable, suggesting that adjusting planting density can optimize production without compromising quality, adapting to specific regional conditions. [ABSTRACT FROM AUTHOR]

Remote sensing has demonstrated validity in determining the planting year of deciduous fruit trees; however, its effectiveness in ascertaining the planting year of evergreen fruit trees remains unverified. Furthermore, the sources of error associated with using remote sensing to determine the planting year of fruit trees remain unclear. This study investigates several cultivated sweet orange (Citrus sinensis) varieties, which are extensively cultivated throughout subtropical China. We analyzed Landsat time series data from 132 navel orange orchards in Gannan, covering the period from 1993 to 2021. For each orchard, Google Earth Engine was employed to extract three vegetation indices—Enhanced Vegetation Index (EVI), Normalized Difference Vegetation Index (NDVI), and Normalized Burn Ratio (NBR)—for each available date, thereby generating three distinct vegetation index time series. The planting year of navel orange trees was identified based on abrupt changes observed in these time series. The principal sources of error in determining the planting year were investigated using the Wilcoxon signed-rank test, Spearman's correlation analysis, and Kruskal-Wallis H test. Key findings include: (1) Following the planting of navel orange trees, EVI, NDVI, and NBR exhibited fluctuations and a gradual increase over time, peaking approximately 10 to 15 years later. (2) The vegetation index time series derived from Landsat imagery effectively determined the planting year of evergreen navel orange trees in orchards, even within highly fragmented landscapes. Among these indices, NDVI and NBR time series outperformed the EVI time series. Specifically, the average determination errors for EVI, NDVI, and NBR time series were 6.4, 1.8, and 2.8 years, respectively. (3) Major sources of error included the methods used to construct the time series, the selection of vegetation indices, and the orchard management practices. Overall, this study provides a viable method for determining the planting year of evergreen navel orange trees in fragmented landscapes and offers insights into factors contributing to uncertainty in planting year determination. [ABSTRACT FROM AUTHOR]

Febrile seizures are convulsions predominately occurring in young children. The effects of various exposomes, including influenza infection and external environmental factors, on febrile seizures have not been well-studied. In this study, we elucidated the relationships between ambient temperature, air pollutants, influenza infection, and febrile seizures using 22-year territory-wide hospitalization data in Hong Kong. The aggregated data were matched with the meteorological records and air pollutant concentrations. All-type and type-specific influenza-like illness positive (ILI+) rates were used as proxies for influenza activity. Distributed lag non-linear model in conjunction with the quasi-poisson generalized additive model was used to examine the associations of interest. According to the results, all-type influenza infections were significantly associated with an increased risk of hospital admissions for febrile seizures (cumulative adjusted relative risk [ARR] = 1.59 at 95th percentile vs. 0; 95% CI, 1.51–1.68). The effect of ILI + A/H3N2 on febrile seizure was more pronounced than other type-specific ILI + rates. A low mean ambient temperature was identified as a significant risk factor for febrile seizures (cumulative ARR = 1.50 at 5th percentile vs. median; 95% CI, 1.35–1.66), while the redox-weighted oxidant capacity and sulfur dioxide were not associated with febrile seizures. In conclusion, our study underscores that influenza infections and exposure to cold conditions were related to an increased risk of febrile seizures in children. Thus, we advocate for influenza vaccination before the onset of the cold season for children to mitigate the burden of febrile seizures. [ABSTRACT FROM AUTHOR]

The role of species interactions in setting species range limits is rarely empirically explored. Here, we quantify host and parasite densities in subtropical eastern Australia (26.65°–30.20°S) to examine whether parasitism might contribute to range limitation of Acropora corals at their cold-range boundary. 79% of Acropora corals had endolithic barnacles (family Pyrgomatidae), with higher parasite load in larger corals and up to 141 barnacles per coral. Parasite load increased poleward and closer to the mainland and was greater in cooler and high nutrient environments. Parasite burden was higher at sites with fewer Acropora corals, broadly consistent with the hypothesis that parasites can fragment host populations where host densities are low, and the parasite is a better disperser than the host. Whilst the mechanism is unclear, our findings suggest that at the high densities recorded here, coral-barnacles could influence range dynamics of Acropora corals at their poleward range limit. [ABSTRACT FROM AUTHOR]

Focusing on summer precipitation over the Tibetan Plateau (TP), this study mainly investigates the joint impacts of the North African subtropical high (NASH) and the western Pacific subtropical high (WPSH) by examining circulation and moisture anomalies. Results show that there are several boundary combination types of the two subtropical highs. The anomalous vertical motion with sufficient moisture transport under different boundary types plays a dominant role in TP precipitation anomaly. When the WPSH strengthens westward approaching the TP, it can transport water vapor northward from the northwest Pacific and north Indian Oceans to the south edge of the TP and induce ascending motion over the southeastern TP, contributing to more precipitation there. When the NASH enhances and extends eastward, it can transport water vapor eastward from the North Atlantic Ocean to the southwest eastern TP and give rise to ascending motion there, inducing positive precipitation anomaly over the southwest eastern TP. When the two subtropical highs simultaneously intensify and extend to the TP, water vapor can be transported to the TP widely from the North Atlantic Ocean, the north Indian Ocean, and the northwest Pacific Ocean with the strengthening of the westerly, resulting in the location of the ascending motion and rain belt shifting obviously northward. Further analyses indicate that the prewinter El Niño–Southern Oscillation (ENSO) and summer North Atlantic air–sea interaction are two indispensable possible modulation factors for the joint impact of the two subtropical highs on TP precipitation. Significance Statement: Under the thermal and topographic effects of the Tibetan Plateau (TP), the subtropical high belt breaks over the TP, forming the western Pacific subtropical high (WPSH) on its east and the North African subtropical high (NASH) on its west. As a permanent anticyclonic circulation over the northwest Pacific, the formation, impact, and prediction of WPSH have been fully revealed. However, few studies have been focused on the NASH. In this study, we examine the joint impacts of the two subtropical highs on TP summer precipitation based on various reanalysis datasets and phase 6 of Coupled Model Intercomparison Project (CMIP6) historical simulations. The results show distinct precipitation features with several boundary combination types of the two subtropical highs. Besides, controlling water vapor transport and vertical motion is an important way for the two subtropical highs to affect TP precipitation in summer. Further study shows that the effect of the two subtropical highs on TP summer precipitation is generally modulated by the prewinter El Niño–Southern Oscillation (ENSO) and summer North Atlantic air–sea interaction. The results from CMIP6 support the conclusions drawn from reanalysis. These findings could help deepen our understanding of the joint influencing factors on TP summer precipitation. [ABSTRACT FROM AUTHOR]

This study selected five typical near-natural landscape types and nearby the artificial hardened surface (as control) after taking mountain scenic spot Huaxi park in Guiyang city as the research object, to monitor the daytime changes of microclimate related indexes. The results showed that different landscape types had cooling and humidifying effects on microclimate in the region, shrubland had the most obvious effect on wind speed. Both vegetation types and water body could improve the microclimate effect. Light intensity, ultraviolet intensity and soil temperature could also reflect microclimate changes to a certain extent. For the construction of mountain scenic area, it was necessary to follow the collocation of different vegetation landscape types and the comprehensive consideration of the compound effect on vegetation types and water body, so as to create a more comfortable landscape microclimate environment. [ABSTRACT FROM AUTHOR]

In order to improve the phosphorus(P)deficiency in the soil of Eucalyptus plantations in subtropical China, we used biochar(BC)as a soil amendment to investigate the soil of Eucalyptus plantations(15 years old). Meanwhile, we added the different amounts [0(CK), 2%, 5%, 10% and 20%] of BC through the laboratory culture experiment to evaluate the effects of different amounts of BC on P components and transformation in soil and its relationship with soil physicochemical properties. The results were as follows: (1) Compared to CK, the nitrate nitrogen(NO3--N), total phosphorus(TP), microbial biomass phosphorus(MBP)and pH values were significantly increased at 20% BC addition, respectively(P<0. 05), the MBP and pH values were significantly increased at 2%, 5%, and 10% BC addition, respectively(P<0. 05), while no marked difference was found in other soil physicochemical properties. (2)Compared to CK, the labile P(LP)was significantly increased at 2% of BC addition(P<0. 05), the available P(AP)and LP were significantly increased at 5% and 10% of BC additions, respectively(P<0. 05). Moreover, the AP, LP and occluded P(OP)were significantly increased at 20% BC addition(P<0. 05), whereas the moderately available P(MP)had no significant change under the four BC additions. (3)The total activities of β-glucosidase(BG), β-N-acetylglucosaminidase(NAG), L-leucine aminopeptidase(LAP), and acid phosphatase(ACP)involved in C, N and P transformations increased significantly at 10% and 20% BC additions than those in CK(P<0. 05). (4)Correlation analysis showed that ln(BG)and ln(NAG+LAP)were positively correlated with ln(ACP), respectively(P<0. 05). In addition, redundancy analysis(RDA)indicated that pH, TN and TP appeared to be the primary drivers of variations in soil P components of Eucalyptus plantations. Furthermore, structural equation model(SEM)revealed that the pH, C : P and N : P of soil were the most critical factors driving P transformation. In conclusion, our findings suggest that different amounts of BC improve the enzyme activities related to C, N cyclings by affecting soil physicochemical properties and improving the P supply potential of soil in Eucalyptus plantations. Notably, 20% BC addition had the optimum effect. This study provides critical theoretical guidance for gaining knowledge on soil nutrient management in Eucalyptus plantations and facilitating the sustainable development of forests in subtropical China. [ABSTRACT FROM AUTHOR]

Organic phosphorus(Po)is an important part of soil phosphorus reservoir. In order to investigate the effects of soil aggregate Po distribution properties in Pinus massoniana plantations after close-to-nature transformation, the pure P. massoniana plantations(PP)and P. massoniana-broad-leaved mixed plantations(CP)after close-to-nature transformation were investigated in southern subtropical China. Soil samples collected from 1-10 cm were screened into >2 mm, 0. 25-2 mm and <0. 25 mm three-part aggregates using the dry-sieving method. The Po fraction, microbial biomass phosphorus(MBP)content and acid phosphatase(ACP)activity in the bulk soil and aggregates were measured to understand the distribution of the Po fraction and its drivers. The results were as follows: (1)Soil Po fractions changed in CP compared to PP, with highly recalcitrant organic phosphorus(HRO-P)and moderately labile organic phosphorus(MLO-P)significantly greater in the bulk soil and soil aggregates than in PP(P<0. 05), while labile organic phosphorus(LO-P)and moderately recalcitrant organic phosphorus(MRO-P)were not significantly different in CP and PP. In addition, there was no consistent pattern of change in Po fractions in the bulk soil and soil aggregates between PP and CP. (2)The size of the proportion of each form of Po in PP was HRO-P>MRO-P>MLO-P>LO-P, while CP was HRO-P>MLO-P>MRO-P>LO-P. (3)The MBP content and ACP activity in CP were significantly greater than that of PP in the bulk soil and soil aggregates, and there was a tendency for the ACP activity to increase with the decrease in the size of aggregates. (4)Redundancy analysis revealed that soil available phosphorus(AP), soil aggregate mean weight diameter(MWD), MBP and total nitrogen(TN)were the main drivers of soil Po fractions. In conclusion, the close-to-nature transformation is beneficial to the accumulation and transformation of soil phosphorus in P. massoniana plantation. This study provides a theoretical reference for the improvement of soil quality and productivity in P. massoniana plantations. [ABSTRACT FROM AUTHOR]

Phenological changes play a central role in regulating seasonal variation in the ecological processes, exerting significant impacts on hydrologic and nutrient cycles, and ultimately influencing ecosystem functioning such as carbon uptake. However, the potential impact mechanisms of phenological events on seasonal carbon dynamics in subtropical regions are under-investigated. These knowledge gaps hinder from accurately linking photosynthetic phenology and carbon sequestration capacity. Using chlorophyll fluorescence remote sensing and productivity data from 2000 to 2019, we found that an advancement in spring phenology increased spring gross (GPP) and net primary productivity (NPP) in subtropical vegetation of China by 2.1 gC m−2 yr−1 and 1.4 gC m−2 yr−1, respectively. A delay in autumn phenology increased the autumnal GPP and NPP by 0.4 gC m−2 yr−1 and 0.2 gC m−2 yr−1, respectively. Temporally, the contribution of the spring phenology to spring carbon uptake increased significantly during the study period, while this positive contribution showed a nonsignificant trend in summer. In comparison, the later autumn phenology could significantly contribute to the increase in autumnal carbon uptake; however, this contributing effect was weakened. Path analysis indicated that these phenomena have been caused by the increased leaf area and enhanced photosynthesis due to earlier spring and later autumn phenology, respectively. Our results demonstrate the diverse impacts of vegetation phenology on the seasonal carbon sequestration ability and it is imperative to consider such asymmetric effects when modeling ecosystem processes parameterized under future climate change. [ABSTRACT FROM AUTHOR]

Existing research on outdoor thermal comfort in urban areas focuses on meteorological factors such as temperature, relative humidity, wind speed, and radiation on sunny or cloudy days. However, climate conditions before, during, and after rainfall events can cause changes in meteorological factors in subtropical regions. Rainfall is an atmospheric condition with a large influence on thermal comfort, particularly in subtropical areas with abundant rain. Big data on temperature, relative humidity, wind speed, precipitation, and total cloud cover from the Taipei Weather Station under the Central Weather Administration from June to August each year from 2011 to 2020 were analyzed, dividing the data into categories based on precipitation. Using a k-means clustering algorithm, we quantified the relationships between meteorological factors and apparent temperature as well as physiological equivalent temperature in different rainfall scenarios. The results indicate that rainfall in the summers of subtropical oceanic climates indeed influence outdoor thermal comfort in urban areas: 37.7% of the rainfall weather patterns improved thermal comfort and 62.3% of the rainfall weather patterns reduced thermal comfort. RWP 46 represent the weather conditions that most significantly improve thermal comfort, at 1:00 PM, with a rainfall of 15 mm, there is a decrease in ΔAT by 14.4 ℃ and ΔPET by 22.1 ℃. With the hot, humid, and rainy climate conditions in Taiwan, apparent temperature is the most accurate index of thermal comfort. KEY POLICY HIGHLIGHTS Rainfall events may affect outdoor thermal comfort in subtropical cities. Different rainfall weather patterns have different impacts on urban outdoor thermal environments. 62.3% of rainfall weather patterns resulted in worsened thermal comfort, for low and concentrated rainfall resulting in a stuffier thermal environment. [ABSTRACT FROM AUTHOR]

IntroductionThe Dicranopteris dichotoma fern community plays vital roles in nutrient sequestration, succession regulation, and ecological threshold control. However, the mechanisms underlying the formation of the D. dichotoma–dominant community remain unclear.MethodsThis study established four different community types to investigate the effects of environmental factors on the formation of a D. dichotoma–dominant community.ResultsWe found that climate was the primary factor affecting the formation of patches dominated by D. dichotoma at the regional scale. Specifically, higher annual mean temperature and annual mean precipitation were associated with larger single-dominant-species patches of D. dichotoma. Understory light intensity was the major factor affecting the formation of the D. dichotoma community at the community scale. Light intensity ranging from 200 to 500 µmol·m⁻²·s⁻¹ was most conducive to the development of a large D. dichotoma community. Additionally, understory light intensity enhanced the importance value of D. dichotoma in the herb community by decreasing its biomass proportion of support modules and increasing its biomass proportion of photosynthetic and reproductive modules. Soil properties and D. dichotoma characteristics showed interactions with each other. Acidic red-yellow soil was most suitable for the formation of single-dominant-species patches of D. dichotoma, and the growth of D. dichotoma further decreased the soil pH. Soil total phosphorus content was identified as a limiting factor for formation of the D. dichotoma community.DiscussionIn summary, the formation of single-dominant-species patches of D. dichotoma is mainly influenced by a combination of climate, community, and soil.

The genus Lycianthes (Dunal) Hassl. (Solanaceae) has in the past been treated as a section of the large genus Solanum L. but is more closely related to Capsicum L. Outside of the Americas, where the highest species diversity occurs, the genus is found in tropical and subtropical habitats from India to Japan and the Philippines, including the islands of Indonesia, New Guinea and the Solomons. The 19 species from Australia, New Guinea and the Pacific were treated in 'PhytoKeys 209'. Here I treat the remaining 10 species occurring across Asia; including two native species, L. biflora (Lour.) Bitter and L. oliveriana (Lauterb. & K.Schum) Bitter, and one cultivated species, L. rantonnetii (Carrière) Bitter that were also included in the earlier work. The Asian species treated here occupy a wide range of forested and disturbed habitats and are diverse in habit, ranging from epiphytic vines to small or medium sized trees, shrubs or creeping herbs. Many of the species are weedy plants of highly disturbed habitats and are best characterised as "ochlospecies", with complex polymorphic variation. Lycianthes rantonnetii, a species native to southern South America, is recorded as cultivated in India and Pakistan, but may be more widespread than collections indicate. The history of taxonomic treatments of Lycianthes in Asia is discussed, along with details of morphology found in all species. All species are treated in full, with complete morphological descriptions, including synonymy, lecto- or neotypifications, discussions of ecology and vernacular names, distribution maps and preliminary conservation assessments (for all except the cultivated L. rantonnetii). Searchable lists of all specimens examined are presented as Suppl. materials 1, 2. [ABSTRACT FROM AUTHOR]

Rainfall over the southern African tropical boundary is highly variable, particularly around the onset of the summer rains. However, understanding of the causes of variability in onset timing is poor. A lack of observational data in the region is compounded by the complexity of climate dynamics and variability at the interface of the tropics and the midlatitudes. The key to onset over the region is the Congo air boundary (CAB), a distinguishing circulation feature present in September and declining in frequency until November. The CAB is crucial to early season rainfall; precipitation is broadly inhibited when the CAB is present, while its breakdown allows large-scale rainfall and onset over central southern Africa. This work identifies a remote midlatitude influence on the timing of CAB breakdown using the high-resolution reanalysis dataset ERA5. Propagating and (upstream) breaking low-wavenumber Rossby waves in the Southern Hemisphere westerly jet are shown to be related to >70% of breakdown events. Breakdown is forced by 1) the replacement of subsidence over eastern southern Africa with synoptically forced ascent and 2) wind field modification that leads to positive 850-hPa continental convergence anomalies and enhanced moisture advection from the Congo basin and Indian Ocean. Upper-level anticyclonic vorticity tendency induced by enhanced convection slows Rossby wave propagation aloft, contributing to wave breaking and the persistence of conditions favorable to convection. The identification of this midlatitude influence on CAB breakdown reveals new potential sources of predictability for onset and demonstrates the significant equatorward extent of midlatitude influences to the tropical edge. Significance Statement: This study aims to improve our understanding of the causes of variability in the start date of the summer rainy season in central southern Africa. The research reveals that certain upper-level waves in the Southern Hemisphere westerly jet are associated with patterns of weather that force a large-scale transition from dry pre-onset conditions to widespread rainfall in a time scale of 2–5 days, and that these waves account for a large proportion of such transitions. This finding is of interest to subseasonal weather forecasters and may help to improve the long-range forecasting of onset date. [ABSTRACT FROM AUTHOR]

Rates at which a community recovers after disturbance, or its resilience, can be accelerated by increased net primary productivity and recolonization dynamics such as recruitment. These mechanisms can vary across biogeographic gradients, such as latitude, suggesting that biogeography is likely important to predicting resilience. To test whether community resilience, informed by functional and compositional recovery, hinges on geographic location, we employed a standardized replicated experiment on marine invertebrate communities across four regions from the tropics to the subarctic zone. Communities assembled naturally on standardized substrate while experiencing distinct levels of biomass removal (no removal, low disturbance, and high disturbance), which opened space for new colonizers, thereby providing a pulse of limited resource to these communities. We then quantified functional (space occupancy and biomass) and compositional recovery from these repeated pulse disturbances across two community assembly timescales (early and late at 3 and 12 months, respectively). We documented latitudinal variation in resilience across 47° latitude, where speed of functional recovery was higher toward lower latitudes yet incomplete at late assembly in the tropics and subtropics. The degree of functional recovery did not coincide with compositional recovery, and regional differences in recruitment and growth likely contributed to functional recovery in these communities. While biogeographic variation in community resilience has been predicted, our results are among the first to examine functional and compositional recovery from disturbance in a single large‐scale standardized experiment. [ABSTRACT FROM AUTHOR]

Study region: A well-preserved subalpine peatland in the subtropics, the Dajiuhu peatland, in Shennongjia, Hubei Province, China. Study focus: Over a seven-year period, constant in-situ carbon flux monitoring was conducted using the eddy covariance method. The patterns of CO2 and H2O fluxes were analyzed, encompassing both daytime and nocturnal period observations, spanning both growing and non-growing seasons, and the interconnection between carbon and water within the Dajiuhu peatland. Furthermore, this investigation identified meteorological parameters shaping these flux dynamics. New hydrological insights for the region: The water source function was more resilient to the effects of extreme weather events and showed higher stability when compared to the carbon sink function. Daytime carbon-water coupling presented a pronounced negative correlation during the growing season, contrasting with a more complex trinomial relationship evident during the non-growing season; however, nocturnal periods did not reveal any apparent correlation. Relative humidity (RH), water table depth (WTD), and evapotranspiration (ET) emerged as key variables impacting jointly on both CO2 and H2O fluxes. Furthermore, net radiation (Rn) magnifies the hysteresis loops associated with net ecosystem exchanges of CO2 (NEE) during the growing season, with WTD being the prime determinant influencing seasonal fluctuations in hysteresis related to H2O fluxes. These findings exemplify the complexities inherent in the management of carbon and water resources within subalpine peatlands, underscored by their intricately intertwined and inseparable relationship.

The cultivation of sunflower (Helianthus annuus L.) as a cut flower stands out in floriculture due to its aesthetic beauty and commercial value. Understanding how cut sunflower genotypes adapt to different edaphoclimatic regions and management practices is essential to optimize flower quality and productivity. This study aimed to evaluate the effect of plant density and location on the development, growth, and quality of cut sunflower in tropical and subtropical environments. Plant densities of 10, 20, 30, 40, and 50 plants/m2 were evaluated in tropical climate and subtropical climate using a randomized block design in a factorial scheme. Results showed significant differences between locations for plant height, capitulum and stem diameter, final number of leaves, leaf area, leaf area index, phyllochron, and the developmental cycle. Plant density significantly influenced these variables except for plant height and developmental cycle. The interaction between location and plant density was significant only for capitulum diameter and final leaf number. The findings indicate that both planting density and location significantly influence the developmental cycle of cut sunflowers, with lower densities favoring more robust plants at harvest. A density of 30 plants/m2 is recommended for efficient space use without significantly compromising floral stem quality. All produced stems are marketable, suggesting that adjusting planting density can optimize production without compromising quality, adapting to specific regional conditions.

Humans' essential ability to combat heat stress through sweat-based evaporative cooling is modulated by ambient air temperature and humidity, making humid heat a critical factor for human health. In this study, we relate the occurrence of extreme humid heat in two focus regions to two related modes of intraseasonal climate variability: the Madden-Julian oscillation (MJO) and the boreal summer intraseasonal oscillation (BSISO). In the Persian Gulf and South Asia during the May-June and July-August seasons, wet-bulb temperatures of 288C are found to be almost twice as likely during certain oscillation phases than in others. Variations in moisture are found, to varying degrees, to be an important ingredient in anomalously high wet-bulb temperatures in all three areas studied, influenced by distinct local circulation anomalies. In the Persian Gulf, weakening of climatological winds associated with the intraseasonal oscillation's propagating center of convection allows for anomalous onshore advection of humid air. Anomalously high wet-bulb temperatures in the northwestern region of South Asia are closely aligned with positive specific humidity anomalies associated with the convectively active phase of the oscillation. On the southeastern coast of India, high wet-bulb temperatures are associated with convectively inactive phases of the intraseasonal oscillation, suggesting that they may be driven by increased surface insolation and reduced evaporative cooling during monsoon breaks. Our results aid in building a foundation for subseasonal predictions of extreme humid heat in regions where it is highly impactful.

This study investigates momentum transport in shallow cumulus clouds as simulated with the Dutch Atmospheric Large Eddy Simulation (DALES) for a 150 × 150 km2 domain east of Barbados during 9 days of EUREC4A. DALES is initialized and forced with the mesoscale weather model HARMONIE–AROME and subjectively reproduces observed cloud patterns. This study examines the evolution of momentum transport, which scales contribute to it, and how they modulate the trade winds. Daily-mean momentum flux profiles show downgradient zonal momentum transport in the subcloud layer, which turns countergradient in the cloud layer. The meridional momentum transport is nontrivial, with mostly downgradient transport throughout the trade wind layer except near the top of the surface layer and near cloud tops. Substantial spatial and temporal heterogeneity in momentum flux is observed with much stronger tendencies imposed in areas of organized convection. The study finds that while scales < 2 km dominate momentum flux at 200 m in unorganized fields, submesoscales O (2–2 0) km carry up to 50% of the zonal momentum flux in the cloud layer in organized fields. For the meridional momentum flux, this fraction is even larger near the surface and in the subcloud layer. The scale dependence of the momentum flux is not explained by changes in convective or boundary layer depth. Instead, the results suggest the importance of spatial heterogeneity, increasing horizontal length scales, and countergradient transport in the presence of organized convection. [ABSTRACT FROM AUTHOR]

Since the launch of the Google Earth Engine (GEE) cloud platform in 2010, it has been widely used, leading to a wealth of valuable information. However, the potential of GEE for forest resource management has not been fully exploited. To extract dominant woody plant species, GEE combined Sentinel-1 (S1) and Sentinel-2 (S2) data with the addition of the National Forest Resources Inventory (NFRI) and topographic data, resulting in a 10 m resolution multimodal geospatial dataset for subtropical forests in southeast China. Spectral and texture features, red-edge bands, and vegetation indices of S1 and S2 data were computed. A hierarchical model obtained information on forest distribution and area and the dominant woody plant species. The results suggest that combining data sources from the S1 winter and S2 yearly ranges enhances accuracy in forest distribution and area extraction compared to using either data source independently. Similarly, for dominant woody species recognition, using S1 winter and S2 data across all four seasons was accurate. Including terrain factors and removing spatial correlation from NFRI sample points further improved the recognition accuracy. The optimal forest extraction achieved an overall accuracy (OA) of 97.4% and a map-level image classification efficacy (MICE) of 96.7%. OA and MICE were 83.6% and 80.7% for dominant species extraction, respectively. The high accuracy and efficacy values indicate that the hierarchical recognition model based on multimodal remote sensing data performed extremely well for extracting information about dominant woody plant species. Visualizing the results using the GEE application allows for an intuitive display of forest and species distribution, offering significant convenience for forest resource monitoring. [ABSTRACT FROM AUTHOR]

Leaf respiration in the light (R light) is crucial for understanding the net CO2 exchange of individual plants and entire ecosystems. However, R light is poorly quantified and rarely discussed in the context of the leaf economic spectrum (LES), especially among woody species differing in plant functional types (PFTs) (e.g. evergreen vs. deciduous species). To address this gap in our knowledge, R light, respiration in the dark (R dark), light-saturated photosynthetic rates (A sat), leaf dry mass per unit area (LMA), leaf nitrogen (N) and phosphorus (P) concentrations, and maximum carboxylation (V cmax) and electron transport rates (J max) of 54 representative subtropical woody evergreen and deciduous species were measured. With the exception of LMA, the parameters quantified in this study were significantly higher in deciduous species than in evergreen species. The degree of light inhibition did not significantly differ between evergreen (52%) and deciduous (50%) species. R light was significantly correlated with LES traits such as A sat, R dark, LMA, N and P. The R light vs. R dark and N relationships shared common slopes between evergreen and deciduous species, but significantly differed in their y-intercepts, in which the rates of R light were slower or faster for any given R dark or N in deciduous species, respectively. A model for R light based on three traits (i.e. R dark, LMA and P) had an explanatory power of 84.9%. These results show that there is a link between R light and the LES, and highlight that PFTs is an important factor in affecting R light and the relationships of R light with R dark and N. Thus, this study provides information that can improve the next generation of terrestrial biosphere models (TBMs). [ABSTRACT FROM AUTHOR]

We present a list of grasshoppers of two families from Ghyalchok, Gorkha district with four new species records for Nepal. The checklist of species is given to provide basic information on the grasshopper diversity of that region. With detailed information of all species recorded and plates with photos from different angles of each species, the present work shall contribute towards a better understanding of grasshoppers of Nepal's Ghyalchok, Gorkha region. This study contributes to future revisionary works on grasshopper diversity and distribution in Nepal. We surveyed 13 different localities of Ghyalchok for three years from 2019–2022, following visual count, while the specimens were collected by using a sweep net or by handpicking where feasible. We recorded 29 species of grasshoppers, of which 26 species belong to Acrididae and 3 species to Pyrgomorphidae. Four grasshopper species, Phlaeoba antennata antennata Brunner von Wattenwyl, 1893; Bibracte burmana burmana Ramme, 1941; Caryanda cachara (Kirby, 1914) and Gonista bicolor (Haan, 1942) are recorded for the first time from Nepal.

A new species, Byssoloma orientale K. Miyaz. & Y. Ohmura, is described from East Asia. It is characterized by a minutely farinose light green thallus, apothecia with a well-developed byssoid margin that spreads laterally over the thallus surface, a pure black apothecial disc caused by the presence of an aeruginous pigment in the epithecium, (7–)9–12(–17)-septate cylindrical colourless ascospores, and oblong conidia. This species grows on living leaves as well as on tree bark. The molecular phylogenetic position of B. orientale within this genus was inferred based on mtSSU sequences, and the species was shown to be closely related to B. vanderystii , which has up to 7-septate ascospores and an absence of aeruginous pigment in the epithecium. [ABSTRACT FROM AUTHOR]

Clouds observed by the airborne High‐Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) were classified into twelve categories, based on their convective/stratiform nature. Dimensional and convective cloud properties were analyzed in three climatic regions: The subtropical easterlies off the coast of California, the Southern Ocean, and the tropics surrounding Central America. The convective properties of the stratocumulus clouds in the subtropical easterlies are closely related to the degree of boundary layer decoupling. In regions of strong boundary layer coupling, convectivity and updrafts in the clouds are weak and precipitation is light. In regions where the boundary layer is more decoupled, convective properties increase together with cloud top altitudes and cloud depth. Cloud properties of stratocumulus and cumulus clouds over the Southern Ocean show similarities to those observed in the subtropics, but overall they are less convective, indicating a strongly coupled boundary layer. Sea surface temperatures are much lower and the development of clouds is driven by transient synoptic conditions rather than zonal ocean temperature gradients. Clouds observed over the tropical oceans are much more convective in nature. As in the two other regions, they are mostly shallow, but clouds in regions with high sea surface temperatures have high convectivity and reflectivity values and stronger updrafts. Some of them grow to extreme depths (>14 km) and widths (>500 km). They have strong and large updraft regions and are heavily precipitating throughout their life cycle as they transition from the convective to the stratiform stage. Plain Language Summary: Clouds were observed in three climatic regions by a radar mounted under the wing of an aircraft. The clouds were organized in twelve different categories. These categories are based on the nature of the clouds, and whether they developed more vertically or horizontally. Cloud properties, such as their horizontal/vertical extent, the strength of the up and downward air motion within the cloud, or the nature of their precipitation, were calculated for the different cloud categories. Comparing these cloud properties for clouds observed in the different climatic regions shows that the cloud categories are related to the different developmental stages of the clouds. In mid‐latitude and subtropical regions, clouds develop more horizontally, and their nature is determined by conditions in the lowest layer of the atmosphere. The development of tropical clouds is related to the temperature of the underlying ocean, where warm ocean surface temperatures allow some clouds to grow into large storm systems. Key Points: Clouds observed with an airborne cloud radar in polar, subtropical, and tropical regions were classified based on their convective naturePolar and subtropical stratocumulus clouds are stratiform in coupled boundary layer conditions but more convective in decoupled conditionsTropical clouds exhibit highly convective characteristics, which are associated with their ability to develop into deep convective systems [ABSTRACT FROM AUTHOR]

Concerns about widespread human-induced declines in insect populations are mounting, yet little is known about how land-use change modifies both the trends and variability of insect communities, particularly in understudied regions. Here, we examine how the seasonal activity patterns of ants—key drivers of terrestrial ecosystem functioning—vary with anthropogenic land-cover change on a subtropical island landscape, and whether differences in temperature or species composition can explain observed patterns. Using trap captures sampled biweekly over 2 years from a biodiversity monitoring network covering Okinawa Island, Japan, we processed 1.2 million individuals and reconstructed activity patterns within and across habitat types. Forest communities exhibited greater temporal variability of activity than those in more developed areas. Using time-series decomposition to deconstruct this pattern, we found that sites with greater human development exhibited ant communities with diminished seasonality, reduced synchrony and higher stochasticity compared with sites with greater forest cover. Our results cannot be explained by variation in regional or site temperature patterns, or by differences in species richness or composition among sites. Our study raises the possibility that disruptions to natural seasonal patterns of functionally key insect communities may comprise an important and underappreciated consequence of global environmental change that must be better understood across Earth's biomes. [ABSTRACT FROM AUTHOR]

The relative impacts of the Tibetan Plateau–Himalaya (TPH) and the adjacent narrow mountains on the South Asian summer monsoon (SASM) are still unclear. We used a general circulation model to evaluate the relative effects of the TPH, the Hindu Kush Mountains (HKM), and the Iranian Plateau on the SASM from the perspective of the asymmetrical onset of the Bay of Bengal (BOB) summer monsoon (BOBSM) and the Indian summer monsoon (ISM). The results show that the abrupt onset of the BOBSM in May is affected by the TPH and HKM, which significantly strengthen precipitation over the BOB. By contrast, precipitation over the Indian subcontinent is suppressed by the TPH. In June, the TPH and the HKM contribute to strengthening and expanding precipitation over the Indian subcontinent and the ISM is significantly intensified. The strengthening of the SASM onset induced by the HKM is comparable with, or even larger than, that induced by the TPH. The effect of the Iranian Plateau on the SASM is much weaker and localized. The distinct role of the HKM is caused by the appearance of an anomalous low-level cyclone around the HKM and an anticyclone to the south, strengthening the India–Burma trough and the Somali jet. The topographic control of the HKM depends on the pre-existence of the TPH. We show that the sensible heat from the HKM accounts for 78.6% and 31.6% of the HKM-induced increase in precipitation during the onset of the BOBSM and ISM, respectively. Significance Statement: The South Asian summer monsoon shows a prominent asynchronous feature in that it starts earlier over the Bay of the Bengal (BOB) during May and appears over the Indian subcontinent in June. However, how the adjacent mountain ranges modulate this monsoon advance is still unclear. Our climate model experiments show that both the Hindu Kush Mountains (HKM) and the Tibet Plateau–Himalaya (TPH) contribute to the strengthening of the asymmetrical onset of the monsoon. During May, the monsoon over the BOB is significantly intensified while the precipitation over the Indian subcontinent is largely suppressed. The HKM–TPH strengthens the precipitation over the Indian subcontinent in June. The HKM-induced strengthening is comparable with, or even larger than, that induced by the TPH. [ABSTRACT FROM AUTHOR]

We aimed to understand the stand biomass and their allocation in Pinus taiwanensis forests at different altitudes（922, 1 170, and 1 405 m) along the Lushan Mountains. The results from our study will provide a basis for assessing and predicting the productivity and carbon sequestration potential of subtropical mountain coniferous forests, in the context of future climate change conditions. We sampled nine forest plots and used allometric equations to estimate the biomass of different organs of each individual. The one-way analysis of variance and least significant difference method were used to assess the differences in forest characteristics, stand biomass, biomass allocations, and root-to-shoot ratio among the three altitudes. All stand characteristics peaked in the forest plots at mid-elevation. The stand biomass of P. taiwanensis forests ranged from 47.22 to 131.55 t·hm-2 and showed a unimodal altitudinal pattern, with the value at 1 405 m being significantly lower than those at 922 and 1 170 m（P＜0.05). The contributions of the biomass of each organ to the stand biomass（trunk＞root＞branch＞leaf) did not differ among altitudes. The average root-to-shoot ratio of P. taiwanensis was 0.23, which increased with increasing altitude. The root-to-shoot ratio at 1 405 m was significantly higher than that at the mid-and low-elevation sites（P＜0.05). Both the stand biomass and biomass of each organ showed a unimodal altitudinal pattern, indicating that the optimal growing conditions at mid-elevations could favor biomass accumulation in Taiwan pine. Contrastingly, the increase in root-to-shoot ratio with increasing altitude implied that Taiwan pine tended to allocate more carbon to belowground structures at high elevations, to withstand unfavorable growing conditions. These altitudinal patterns in stand biomass, carbon allocation, and root-to-shoot ratio reflected the integrated adaptations of P. taiwanensis forests to environmental changes, such as that in temperature, soil moisture, and nutrient availability. [ABSTRACT FROM AUTHOR]

IntroductionLocal biodiversity is increasing in many temperate and subtropical waters due to climate change. It is often caused by shifting fish distributions, thus the biodiversity gradient, from lower to higher latitudes. However, these shifts in distributions do not occur uniformly across all species. Consequently, communities are not only shifting their spatial distributions, but species compositions are also changing. We investigated spatiotemporal differences in the compositions of fish species in the bays of the northeastern Gulf of Mexico and identified species that contribute to the temporal changes.MethodsWe used fish count data collected using gillnets in eight major bays, encompassing over 600 km of coastline, during spring and fall seasons from 1982 to 2019. The nonmetric multidimensional scaling (NMDS) on the Bray-Curtis dissimilarity index among species composition vectors was used to detect the differences in species composition, and the similarity percentages (SIMPER) were used to determine the contribution of species to the differences. ResultsThe result shows there was a gradual change in species composition in all bays over the years, and the composition was different among bays and seasons. The species contributing to the temporal changes included those that are expanding (e.g., Common snook, Centropomus undecimalis, and Smallscale fat snook, C. parallelus) as well as retracting (e.g., Southern flounder, Paralichthys lethostigma, and Spanish mackerel, Scomberomorus maculatus) their distributions toward the north. The species observed only in recent years in these bays tended to have a preference for warmer water (e.g., Gulf pipefish, Syngnathus scovelli, and Chain pipefish, S. louisiana). DiscussionThe results are consistent with the potential effects of climate change. However, the salinity of the bays in the study area generally exhibits an increasing trend from the northern to southern bays. The spatial salinity gradient has a substantial impact on species compositions, indicating that species distributions are influenced by multiple environmental conditions. This complexity makes our ability to accurately predict future species compositions under changing environmental conditions challenging.

Avocado (Persea americana Mill.) is a tropical fruit that has gained immense popularity worldwide due to its unique flavor, nutritional value, and numerous health benefits. The growth and maturation of avocados are influenced by various environmental and climatic factors. Temperature is one of the most critical factors, as it plays a significant role in various physiological processes of this fruit. This study aimed to investigate the effect of air temperature on avocado development and assess the harvest maturity period (determined by the dry matter content) of Fuerte, Zutano, and Hass, the most common avocado varieties, grown in Western Crete, Greece. Fruit samples collected from avocado orchards in five regions of Western Crete were subjected to dry matter analysis during the ripening period for the years 2017 to 2022. Maturation time is determined based on the EU regulation for dry matter concentration. The results of this study revealed that dry matter concentration can be affected by both very high summer temperatures and low temperatures during the ripening period. Specifically, high temperatures during the summer months can have a significant impact on avocado development and result in a reduced dry matter concentration. On the other hand, low temperatures during the maturation stage can slow down enzymatic activity and metabolic processes, resulting in delayed ripening and a prolonged time to reach optimal maturity. This delay in maturation and reduced dry matter concentration can significantly affect the harvest timing, as growers may need to wait for the avocados to develop the desired characteristics before they can be harvested. Our findings are the first data on avocado maturation (dry matter concentration) in relation to temperature and provide valuable insights into harvest maturity period of avocado cultivation in Crete and other regions with similar Mediterranean climatic conditions. [ABSTRACT FROM AUTHOR]

The positive phase of the Pacific meridional mode (PMM) is closely related to the onset of El Niño. Previous studies have indicated that positive sea surface temperature anomalies (SSTAs) in the central equatorial Pacific (CEP) during the spring and summer of positive PMM years primarily originate from the northeastern tropical Pacific (NETP) via positive wind–evaporation–SST feedback. We review the evolution of PMM and find weak evidence to support such a linkage. Coupled model experiments show that the positive PMM-regressed SSTAs in the NETP only account for ∼24% of those in the CEP from winter to spring, illustrating the principle that correlation does not necessarily mean causality. The strongest positive PMM SSTAs in the NETP and CEP increase El Niño intensity by 1.07°C, whereas that in the NETP alone increase El Niño intensity by 0.69°C. When the composite SSTAs in the NETP during positive PMM years are used, however, the El Niño intensity is increased merely by 0.17°C. The change in the subsurface temperature in the equatorial Pacific is curtailed for the NETP SSTAs to trigger El Niño, while the wind–evaporation–SST feedback plays a less important role. Our results indicate that the impact of PMM on El Niño might be overestimated by ∼55%. Moreover, a comprehensive understanding about the role of the tropical North Pacific on El Niño can be obtained only when the impact from the western North Pacific is considered. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the adjustment times of the atmospheric boundary layer (ABL) on the control of low-cloud coverage (LCC) climatology by large-scale atmospheric conditions in the subtropics. Using monthly data, we calculate back-trajectories and use machine learning statistical models with feature selection capabilities to determine the influence of local and upstream large-scale conditions on LCC for four physical cloud regimes: the stratocumulus (Sc) deck, the along-flow transition into the Sc deck ("Inflow"), the Sc-to-cumulus transition, and trade-cumulus clouds. All four regimes have unique local and upstream relationships with the large-scale meteorological variables within our parameter space, with upstream controls of LCC being the dominant processes in Sc deck and Sc-to-cumulus transition regimes. The time scales associated with these upstream controls across all regimes are consistent with known adjustment time scales of the ABL, determined in both modeling and observational studies. We find that low-level thermodynamic stratification (estimated inversion strength) is not the most important large-scale variable for LCC prediction in transition and trade-cumulus regimes despite its ubiquitous use as a proxy for LCC throughout the subtropics. Including upstream control provides significant improvements to the skill of statistical models predicting monthly LCC, increasing explained variance on the order of 15% in the Inflow, Sc deck, and transition regimes, but provides no improvement in the tradecumulus regime. [ABSTRACT FROM AUTHOR]

Incorporating native shrubs into restoration projects can improve biodiversity conservation and enhance the sustainability of ecosystem functions. Shrubs grow under different forest canopy structures, having varied microclimatic conditions according to forest type and composition. Currently, there is a lack of information on propagation from seed and planting material availability for the utilization of shrubs in forest restoration.In the present study, we evaluated the effects of temperature and light on germination of ten shrub species (Ardisia japonica, Callicarpa cathayana, Callicarpa giraldii var. subcanescens, Deutzia schneideriana, Fraxinus sieboldiana, Hydrangea chinensis, Maesa japonica, Rhododendron simsii, Spiraea japonica var. fortunei and Weigela japonica var. sinica) occurring in subtropical forests in China.No seeds of any species germinated in the coolest thermal regime (5/10 °C), while optimal temperature requirements varied from 10/20 °C to 25/35 °C. Seeds of small‐seeded species had higher germination percentages in the light treatments, while larger seeds were not photoblastic. There was no relationship between germination in the light and the seed shape index.Our results may assist in identification of seed traits and suitable shrub species for restoration in specific forest types, thus aiding native forest recovery of structure and composition. Successful recovery leads to enhanced biodiversity, reestablishment of microhabitats and ecological interactions in the forest understorey. [ABSTRACT FROM AUTHOR]

Extensive research has been performed into the effectiveness of nitrification inhibitors (NIs) in preventing N losses; however, tropical agriculture has been underrepresented in recent meta-analyses. Here, we apply a meta-analytic approach using data from 50 articles to identify the impact of NIs (DMPP, DCD, and DCD + NBPT) on crop yield, N2O emissions, soil NH4+ and NO3− concentrations, and NH3 volatilization in subtropical and tropical regions of Brazil. In addition, the survey includes information about location; climate zone; cultivated crops; soil pH; soil organic carbon; soil texture; experimental method; soil management; irrigation; fertilizer source, rate, and type; and NI type and rate. Overall, the data set showed that NIs increased crop yield and soil NH4+ concentrations by 3 and 60%, respectively, whereas N2O emissions and soil NO3− concentrations were reduced by 62 and 31%, respectively. Ammonia volatilization was not changed by NI application. However, the combination of a NI with a urease inhibitor decreased such losses by 39%. The effectiveness of the NIs was highest in irrigated fields, fine-textured soils, and mineral N sources. Moreover, NI performance in Brazil was found to be similar in tropical and subtropical climates, and was also comparable to values previously reported in meta-analyses, including those conducted in temperate climates. Therefore, NI application is indicated to be an efficient strategy to delay nitrification and mitigate N2O emissions in tropical agroecosystems. [ABSTRACT FROM AUTHOR]

The control of nitrogen (N) and phosphorus (P) loadings to receiving waters is often overcompensated for by catchment planners. The objectives of this study, which investigated nine catchments in the subtropics of China, were to (i) quantify the explicit relationships between the N and P loadings to receiving waters and the topographic, soil and landscape characteristics of catchments, (ii) identify key impact factors and (iii) identify the most influential N and P loading pathways via catchments. Our collective data indicated that elevation–relief ratio, soil elemental stoichiometry and landscape structure determined the N and P loadings of the studied agricultural catchments. The N export from catchments characterized by a woodland backdrop (Masson pine) mosaic with the intrusion of paddy fields in the subtropics was postulated to be driven by two simultaneous processes: discharge and retention. In addition, a soil C:P threshold ratio for the catchment N and P loadings was estimated to be in the range of 107–117. Our PLS-SEM path analyses suggested that to reduce the N export from agricultural catchments in the subtropics, mitigation practices in landscape ecosystems (e.g., landscape patterns, ditches and streams) need to be taken into consideration and predominantly deployed, despite traditional measures used for soils. Strategies to lower the catchment P export can be directly proposed at the source site. Our findings provide greater insights into the transport and retention of N and P nutrients through catchments and may optimally direct the focus of catchment planners, thus increasing the control efficacy of catchment N and P losses. [ABSTRACT FROM AUTHOR]

In sub-tropical and tropical regions, the diversity patterns of soft-sediment macrobenthic communities are still poorly understood, particularly when compared to temperate shelf environments. The present study investigates spatial patterns of variability in macrobenthic distribution along the eastern Red Sea margin, and the role of sediment composition and other explanatory variables in determining such patterns. This study has two main objectives: (i) to produce a baseline characterization of the Saudi Arabian Red Sea macrobenthic infauna, particularly along the central and southern regions, (ii) to assess the relative contribution of two major processes driving macrobenthic communities (i.e., dispersal-based and environmental filtering), based on changes on beta-diversity components (turnover and nestedness) across multiple scales (up to ~600km), using relevant modeling methodologies. Shallow soft-sediment macrobenthic communities in the Red Sea showed extremely high small-scale variability, highlighted by the percentage of rare species (44% of species present at a single sample) and the dominance of turnover (species replacement) over nestedness. Our results also suggest a strong influence of broad- over fine-scale variation in the species composition. However, sedimentary characteristics, particularly grain-size, played a critical role governing the distribution patterns of soft-sediment macrobenthic communities in the Red Sea. Our findings highlight the importance of regional factors in shaping the macrofaunal community composition whilst also highlighting the role of high species diversity at local scales. The current results suggest the need for conservation measures from regional levels (to maintain genetic diversity) to local levels (to preserve the high occurrence of rare species). To our knowledge, no other study investigated the distribution of Red Sea marine species over large spatial scales combining modeling methods and the partitioning of beta-diversity. The current approach applied to soft-sediment macroinvertebrates can be extended to other marine communities since conservation strategies can be more effective when mechanisms governing species distribution are considered.

Southwest cloud bands during spring (April and May) bring rains to central Caribbean islands at the end of the dry season. A cluster analysis of daily 500-hPa geopotential height fields for 1980–2021 identifies a low-west–high-east dipole pattern related to Pacific–North America response to El Niño–Southern Oscillation (ENSO) and springtime wet spells over the Dominican Republic and Puerto Rico. The regional dipole and local rain time series are ranked to identify the top 10 cases for analysis of meteorological conditions. Hovmöller plots of midlevel meridional wind and specific humidity during April 1983 and May 1986 wet spells reveal a standing Rossby wave train pattern that converges moisture onto the leading edge of a subtropical trough. Composite vertical sections during Caribbean Sea wet spells reveal lower easterly–upper westerly wind anomalies over South America associated with the equatorial Madden–Julian oscillation. Thunderstorm clusters within the southwesterly airflow induce multiday wet spells and flash floods. A second statistical method demonstrated how ENSO underpins Caribbean spring climate anomalies via tropical ocean–atmosphere Rossby wave coupling. Historical trends and long-range projections indicate that springtime tropical–midlatitude interactions may diminish due to an accelerating Hadley cell and retreating jet stream, leading to a delayed onset of the wet season across the Antilles Islands. [ABSTRACT FROM AUTHOR]

Light, temperature and rainfall affect the growth and yield of strawberry plants (Fragaria × ananassa Duch.). The objective of this review was to determine the impact of global warming on the yields of strawberry in a temperate (summer crop) and subtropical environment (winter crop) in southern Queensland, Australia. Information was collected on the changes in temperature over five decades in two locations in this area. The relationship between relative yield and temperature from published data was used to determine the impact of global warming on productivity in the two locations. Finally, the impact of elevated concentrations of CO2 and temperature on yield was examined from studies in the literature. The average daily mean temperature has increased by 2 °C over the season on the Sunshine Coast (winter crop) since 1967 (p < 0.001, R2 = 0.69). The impact of global warming has been less severe on the Granite Belt (summer crop), with a 1 °C increase in temperature (p < 0.001, R2 = 0.37). Information was collected from the literature on the yield in individual temperature regimes in an experiment and these data were compared with the maximum yield in the same experiment (relative yield). There was a negative linear relationship between relative yield and temperature in most of the published literature. The mean (± s.d. or standard deviation) estimate of the slope from the regression was −0.14 (± 0.14), the median was −0.11 and the range was from −0.51 to 0.11 (n = 14 studies). Increases in temperature were associated with a decrease in yield of 14% to 28% in the two areas in Queensland. The results of other research indicated that elevated concentrations of CO2 do not benefit productivity when combined with elevated temperatures. Further decreases in yield are expected in the next few decades in the absence of heat-tolerant cultivars or other mitigating strategies. [ABSTRACT FROM AUTHOR]

There is a knowledge gap in the effects of climate warming and nitrogen (N) deposition on root N absorption capacity, which limits our ability to predict how climate change alters the N cycling and its consequences for forest productivity especially in subtropical areas where soil N availability is already high. In order to explore the effects and mechanism of warming and the N deposition on root N absorption capacity of Chinese fir (Cunninghamia lanceolata), a subtropical arbuscular mycorrhizal conifer, the fine root 15NH4+ and 15NO3− uptake kinetics at a reference temperature of 20 °C were measured across different seasons in a factorial soil warming (ambient, +5 °C) × N addition (ambient, +40 kg N ha−1 yr−1) experiment. The results showed that (i) compared with the control, warming increased the maximal uptake rate of NH4+ (V max,20 °C-NH4+) in summer, while N addition enhanced it in spring and summer; compared with non-warming treatments, warming treatments increased the uptake rate of NO3− at a reference concentration of 100 μmol (V100,20 °C-NO3−) in spring. (ii) The analysis of covariance showed that V max,20 °C-NH4+ was positively correlated with root mycorrhizal colonization rate (MCR) and V100,20 °C-NO3− was positively correlated with specific root respiration rate (SRR), whereas no N uptake kinetic parameter was correlated with specific root length, root N and non-structural carbon concentrations. Thus, our results demonstrate that warming-increased root NH4+ uptake might be related to warming-increased MCR, whereas warming-increased root NO3− uptake might be related to warming-increased SRR. We conclude that root NH4+ and NO3− uptake capacity of subtropical Chinese fir can be elevated under warming and N deposition, which could improve plantation productivity and mitigate N leaching loss and soil acidification. [ABSTRACT FROM AUTHOR]

The subtropical North Pacific and North Atlantic are controlled by basin-scale anticyclones in boreal summer. Based on a novel metric regarding the strengths of the rotational and the divergent circulation of anticyclones, we investigated the possible future responses in the intensity of these two subtropical anticyclones to global warming. While the North Atlantic subtropical anticyclone (NASA) is projected to strengthen, the North Pacific subtropical anticyclone (NPSA) is projected to weaken, in terms of both the rotational and the divergent circulation. The distinct responses of the NPSA and NASA are corroborated by the models participating in the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP), under both intermediate and high emission scenarios. We further investigated the possible mechanism for their distinct responses by decomposing the effect of greenhouse gas forcing into the direct effect of increased CO2 concentration and the indirect effect through sea surface temperature (SST). The intensified NASA results from the CO2 direct forcing while the weakened NPSA is dominated by the SST warming. The CO2 direct forcing enhances the NASA by increasing land–ocean thermal contrast anchored by the largest subtropical continental area, the Eurasian–African continent. Both the uniform SST warming and the change in SST pattern act to weaken the NPSA by increasing the latent heating over the subtropical North Pacific basin, as suggested by atmospheric component model simulations. The distinct responses of the NPSA and the NASA may lead to zonal asymmetry of the subtropical climate change. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata) is the most important conifer tree species in plantations in subtropical China. Soil extracellular enzyme activities (EEAs) play key roles in mediating multiple forest ecosystem functions, such as organic matter decomposition, nutrient cycling, and plant productivity. In this study, the activities of five soil extracellular enzymes and their stoichiometric (EES) features were investigated at eight Chinese fir plantation locations. The results showed that the soil EEAs exhibited distinct biogeographic differences and were primarily affected by the spatial heterogeneity of soil nutrients. We found that the soil EES was strongly influenced by soil pH and mean annual temperature. Moreover, soil properties were found to be more important than climatic factors in influencing changes in soil microbial nutrient restrictions based on vector length (0.43 vs. −0.1). Random forest analysis indicated that changes in microbial nitrogen (N) and phosphorus (P) limitations were mainly affected by soil NO 3 −-N and dissolved organic carbon (DOC), whereas soil microbial C limitation was largely influenced by pH, DOC, and total C content. This study sheds light on how soil and climatic factors affect soil EES in subtropical Chinese fir plantation ecosystems and provides useful insights for the development of management strategies to improve the productivity of Chinese fir forests. [ABSTRACT FROM AUTHOR]

The capacity of no-tillage and fertilization to promote soil organic carbon (SOC) accumulation and the impacts of occasional tillage on that SOC are topics of current debates. We quantified (i) the SOC and total nitrogen accumulations resulting from the adoption of long-term (23 years) no-tillage relative to conventional tillage by plowing, (ii) the impact of occasional chiseling every three years on SOC and total nitrogen stocks and (iii) the improvement in SOC and total nitrogen stocks due to normal fertilization relative to reduced fertilization (suppression of P and K application) in a subtropical Ferralsol of a field experiment in southern Brazil. After 23 years under normal fertilization, no-tilled soil stored significantly more carbon and nitrogen than conventional tillage soil, either to 30 cm depth (85.5 vs 71.3 Mg C ha‐1; and 6.12 vs 5.13 Mg N ha−1; P < 0.10) or to 100 cm depth (185.0 vs 163.2 Mg C ha−1; and 11.99 vs 10.32 Mg N ha−1; P < 0.10), which means that no-tillage significantly accumulated 0.60 Mg C ha−1 year−1 and 0.04 Mg N ha−1 year−1 compared to conventional tillage to 30 cm depth, and 0.93 Mg C ha−1 year−1 and 0.07 Mg N ha−1 year−1 to 100 cm depth. Those results indicate the capacity of no-tillage to promote SOC and total nitrogen accumulation in this Ferralsol, despite its aboveground residue being not significantly higher than that in conventional tillage (9.22±0.46 vs 8.47±0.44 Mg DM ha−1 year−1, normal fertilization), and also indicate that it might be useful to assess SOC and total nitrogen to 100 cm depth. Occasional chiseling did not significantly change SOC and total nitrogen stocks to 100 cm depth compared to no-tilled soil (180.4 vs 185.0 Mg C ha−1, and 11.02 vs 11.99 Mg N ha−1; P > 0.10), but this result should not serve as pretext to chiseling, a practice to be cautiously used only when and where needed. Across tillage systems, normal fertilization promoted SOC accumulation compared to reduced fertilization at rates of 0.04–0.25 Mg C ha−1 year−1 in the 0–100 cm, rates that were lower compared to those obtained with no-tillage relative to conventional. Overall, no-tillage system was efficient to accumulate SOC and total nitrogen, and therefore should continue to be encouraged, as well as the application of fertilizer; while occasional chiseling seemed not to change those stocks relative to no-tillage in this Ferralsol. • C and N measured to 1 m depth in a Ferralsol under tillage and fertilization systems. • Over 23 years, no-tillage sequestered 0.93 Mg C ha−1 and 0.07 Mg N ha−1 annually. • Occasional chiseling did not significantly change C and N stocks compared to no-till • Fertilization sequestered 0.04–0.25 Mg C ha−1 year−1 compared to reduced fertilization. • It might be useful to assess C and N to 100 cm depth, not only to 30 cm. [ABSTRACT FROM AUTHOR]

The tropics have long been a focal point of interest in ecology and evolutionary biology - but where actually are the tropics? Classically, the tropics have been defined as all areas lying between 23.4° North and South as these zones receive direct overhead solar radiation at some point during the year. However, a suite of different environmental and climatic characteristics have also been employed to classify regions as tropical or not. The aims of this paper are to 1) briefly review some of the different criteria commonly used to define the tropics, 2) map the extent and distribution of tropical land areas according to these different criteria, and 3) asses the concordance between these criteria and a sample of recent “tropical” studies. More specifically, we review eight criteria that are frequently used (implicitly or explicitly) to define the tropics. We then map the location and extent of land areas that are “definitely tropical” (i.e., the core tropics) and areas that are “tropical by most definitions”. Finally, we examine how the different classifications apply to tropical research through an analysis of the study locations of >200 recent tropical biology articles. Depending on the definition, the extent of the terrestrial tropics ranges from 23 million to 66 million km2 – a nearly threefold difference. Likewise, the classification of many areas as being tropical vs. non-tropical depends on the specific criterion employed. Of the tropical studies reviewed here, only 44% were based on data collected from the core tropics, and 12% of tropical studies were based on data collected from sites outside of the geographic tropics but with tropical climates. Many different criteria are used to classify areas as tropical vs. non-tropical, leading to inconsistencies when estimating the extent of tropical areas and variation in the classification of ecosystems and species as being tropical vs. non-tropical.

The article presents experimental data on physiological and biochemical studies of stone fruit culture on the example of Persica vulgaris (Mill.) In the humid subtropics of Russia. The research has been carried out since 2011 in the Laboratory of plant physiology and biochemistry of the Subtropical Scientific Center of the Russian Academy of Sciences on peach varieties of different ripening periods grown in the humid subtropics of Russia. To identify any physiological changes in the body of peach plants during drought, especially in summer, comprehensive diagnostic studies of the water regime (leaf turgidity, determination of the thickness of the leaf blade, water deficiency) and pigment composition are carried out, characterizing the functional state of peach plants. Under unfavorable conditions, promising varieties have a higher ratio of chlorophylls to carotenoids, which confirms their more developed adaptive potential. Studies of this nature have been carried out in order to identify and select resistant peach plants among the studied varieties, which would correspond to the humid region of the Black Sea coast of the Krasnodar Territory. In the subtropical zone of our region, the issue of drought resistance has always been acute, since the impact of negative environmental factors (cool spring, accompanied by drizzling rains and a long summer shortage of air and soil moisture) on peach plants lead to a decrease in productivity and a deterioration in the quality of fruits, which makes their unsuitable and non-transportable. It has been found that among the tested plants, peach varieties Maycrest, Fayet, Larisa have been distinguished by high physiological indicators, such as: low water deficiency – 12,20–14,65%, leaf turgidity ­– 0,18 mm, saturation of leaf tissues within 70,12–79,21%, the content of carotenoids is 0,5–0,7 units, which is a confirming sign of their high resistance to the negative effects of weather conditions in the south of Russia.

Context: In subtropical latitudes, most goats are managed in semi-extensive management systems, eating only available vegetation. Underfeeding is common during the dry season and may reduce the endocrine and sexual activities of male goats. Aims: The aim of the study was to determine plasma testosterone concentrations, sexual behaviour and sperm production of male goats kept in a semi-extensive management system for 12 months, from March to February. Methods: Control males were placed indoors and were well nourished (n = 5). Experimental males were placed in a flock and grazed daily with females for 7 h, eating only natural vegetation (n = 5). Experimental males were fitted with an apron to prevent mating during the study. Plasma testosterone concentrations were determined every 2 weeks. Sexual behaviour and sperm production were determined in May and June (beginning of breeding season), August and October (middle of season), and November and December (end of season). Key results: Plasma testosterone concentrations were higher (P < 0.05) in control than experimental males in June and from August to December. The percentage of males refusing to ejaculate was lower (P < 0.05) in control than experimental males throughout the study. Total number of spermatozoa per ejaculate was higher (P < 0.05) in control than experimental males in May, June, November and December. Sperm progressive motility was higher (P < 0.05) in control than experimental males in May and June and from October to December. Conclusions: The results indicate that male goats in a semi-extensive management system have lower plasma testosterone concentrations, sexual behaviour, and sperm quantitative and qualitative production than those in a confined management system. Implications: Nutritional supplementation may improve the endocrine and sexual activity of male goats in semi-extensive management systems. During the dry season (early autumn-late spring) in subtropical semi-extensive management systems, food availability decreases markedly, leading to undernutrition of male goats. We demonstrate that this undernutrition reduces sexual behaviour and sperm production during the breeding season (early summer–late autumn). This study indicates that nutritional supplementation may improve the sexual activity of male goats kept under semi-extensive management. [ABSTRACT FROM AUTHOR]

A climatology of synoptic drylines on the subtropical southern African interior plateau (SAP) is developed using ERA5 reanalysis specific humidity and surface temperature gradients and an objective detection algorithm. Drylines are found to occur regularly during spring and summer (September–March), and almost daily during December of that period, but rarely in winter. A westward shift in peak dryline frequency takes place through the summer. Drylines peak first over the eastern parts of the SAP during November with a mean of 10 drylines and then over the central (mean of 12) and western SAP (mean of 20) in December. During midsummer, drylines over the eastern SAP are negatively correlated with drylines in the west. Between 1980 and 2020, a significant correlation exists between ENSO and dryline days over the eastern (r = 0.44; p value = 0.004) and central (r = 0.41; p value = 0.008) SAP with fewer drylines (up to 10) occurring during years with increased surface moisture and more drylines (up to 45) occurring during years with decreased surface moisture. Drylines forming over the eastern parts of the SAP were more likely to move westward than drylines over the central and western parts. Onset times across the SAP show that drylines have a tendency to form during either the late morning to early afternoon (1100 and 1400 LST) or during the early evening hours (1700 and 2000 LST), suggesting that the surface heat trough (Kalahari heat low) and westward moisture transport mechanisms, such as the Limpopo low-level jet and ridging highs, are responsible for the formation of most drylines across the SAP. Significance Statement: "Drylines" are used to describe boundaries separating regions of very dry air from those with much higher moisture content. The importance of these drylines is that they tend to act as a trigger for thunderstorms, which can produce severe weather. In this study, we build a long-term climatological description of drylines in subtropical southern Africa. We find that drylines are most frequent over eastern South Africa during the early summer, a time when storms with large hail and damaging winds are most likely to occur. Drylines are sensitive to moisture circulation patterns and respond differently during El Niño and La Niña years, with generally more drylines during El Niño over eastern South Africa and fewer during La Niña. [ABSTRACT FROM AUTHOR]

The oceanic biological carbon pump modulates atmospheric CO2 concentrations by transporting carbon from the sunlit surface to greater depths. The efficiency of the biological pump and its response to warming temperatures are of great importance to future projections of global change. Here, we investigate a time series of organic carbon fluxes from a monthly resolved sediment trap mooring in the Gulf of Aqaba (GOA), northern Red Sea, between 2014 and 2016. We evaluate the attenuation of sinking organic carbon in the context of the seasonally changing euphotic zone and provide the first estimates of biological pump efficiency in this region. The base of the euphotic zone changed seasonally as the system transitioned from oligotrophic and stratified conditions in summer to mesotrophic conditions during the winter mixing period. Carbon attenuation assessed using a power law fit yields an average coefficient of b = 0.80 ± 0.37, lower than expected based on the warm temperatures in the GOA. Estimates of export efficiency decreased from 40% in summer to 20% in winter, and show the opposite seasonal pattern as transfer efficiencies, which increased from 50% in summer to ∼95% in winter. Overall, the efficiency of the carbon pump was close to ∼20% in both seasons. These observations challenge the notion of a globally uniform positive correlation between increasing temperature and increasing carbon attenuation in the ocean and imply that warm subtropical ecosystems can support moderately enhanced carbon pump efficiencies, possibly also related to increased, dust‐driven, mineral ballasting in low latitude regions such as the GOA. Plain Language Summary: Phytoplankton growth in the upper sunlit ocean drives the oceans' biological carbon pump, a collection of processes that sequester atmospheric CO2 into the deeper ocean where it is stored for centuries to millennia. However, a large fraction of carbon does not reach greater depths but is respired by bacteria and other microorganisms as it sinks. Earlier field work found that, for water temperatures between 2 and 17°C, warmer water is associated with more carbon respiration. However, we observe that carbon respiration in the Gulf of Aqaba, a deep warm water body in the northern Red Sea, is much less intense than expected based on water temperature (≥20°C). Moreover, the local ecosystem exports a considerable fraction of carbon to intermediate depths (∼300–570 m). These results question the universal role of temperature in regulating carbon export in the ocean. They also suggest that ecosystems dominated by small phytoplankton can support considerable carbon export despite warm temperatures, especially when mineral dust is available to enhance the sinking of marine particles. Key Points: Particulate organic carbon fluxes in the Gulf of Aqaba (GOA) are studied from a moored array of sediment traps between 2014 and 2016We report GOA seasonal patterns of the power law coefficient b, export efficiency, and transfer efficiencyAttenuation is lower than expected based on temperature, challenging its universal control on carbon remineralization in the ocean [ABSTRACT FROM AUTHOR]