Humid Subtropical Research Articles

Resilience and Resistance of Vegetation in Response to Droughts in a Subtropical Humid Region Dominated by Karst

The resilience and resistance of vegetation are important indicators of the vegetation’s response to droughts. Owing to the uniqueness of the environment in humid karst areas, results from studies on other climatic zones may not necessarily present the status of vegetation resilience and resistance in humid karst areas. Herein, We calculated vegetation resilience and resistance by autoregressive modeling using Enhanced Vegetation Index (EVI), Total Water Storage Anomaly (TWSA), temperature (TA), precipitation (PRE) data, An analysis of variance (ANOVA) was then conducted to compare the differences in resilience and resistance of different vegetation types in the study area, as well as the differences in resilience and resistance of vegetation in different sub-geomorphic zones. Finally, natural factors affecting vegetation resilience and resistance were quantified using partial least squares structural equation modeling (PLS-SEM). The results demonstrate the following points. First, vegetation resilience, total-water-storage anomaly resistance, and vegetation resistance against precipitation anomalies were lower in karst areas of the study area than in non-karst areas of the study area (except for vegetation resistance against temperature anomalies). Second, vegetation resilience was the lowest in some sub-geomorphic zones within karst areas, and it was still comparable to that in semiarid areas. Third, precipitation and temperature were important factors that affected the resilience and resistance of vegetation in karst areas, and the geochemical indicators (CaO, MgO, and SiO2) of soil parent material were major factors that affected the resistance and resilience of vegetation in non-karst areas. In summary, this study was undertaken to reveal the natural characteristics of vegetation resilience and resistance in humid karst regions. Our findings complement and expand the existing body of knowledge on vegetation resilience and resistance in other ecologically fragile zones limited by moisture.

Chasing cool: Unveiling the influence of green-blue features on outdoor thermal environment in Roorkee (India)

Urban environments in humid subtropical climates, like Roorkee, India, often experience high summer temperatures and uncomfortable outdoor thermal conditions. However, the impact of green-blue landscape configurations on cooling intensity (ΔTa) and outdoor thermal comfort (OTC) is insufficiently understood. This study, conducted in Roorkee during summer 2022, assessed the effect of green-blue landscape configurations on OTC using Physiological Equivalent Temperature (PET) and mean radiant temperature (Tmrt). PET values ranged from slight to extreme heat stress, with statistically significant differences in cooling intensity across varied landscape configurations. Tree shaded canal front locations registered lower Ta (1.6 °C) and Tmrt (9.3 °C). Similarly, shaded canal front locations registered 4.7 °C lower PET than sun-exposed locationsDifferent tree species showed significant variation in ΔTa, with the highest cooling effect (maximum average ΔTa of 3 °C) occurring during the morning hours. Notably Morus alba and Mangifera indica yielded the highest cooling effect, outperforming artificial and mixed shade. Eucalyptus alba, on the other hand, registered adverse comfort conditions. Denser tree canopies and attributes - canopy diameter, leaf area index, and height were strongly correlated to improved cooling performance.Additionally, increasing pervious surfaces and tree cover within 100 m of intervention areas enhanced cooling, with significant effects noted within a 25–50 m radius. This study highlights the role of green-blue infrastructure, particularly the combination of low sky-view factor (SVF), dense canopy trees, and proximity to water, in reducing heat stress. These findings offer crucial insights for climate-responsive open space design, particularly in Indian cities facing rampant urbanization and global warming.

Impact of altitudinal gradients on chemical profiling and pesticidal activities of Hedychium spicatum Sm

Hedychium spicatum Sm. is an endangered herb which grows preferably in humid tropics and subtropics known for its distinct camphoraceous flavour and medicinal properties. The essential oils of H. spicatum rhizomes from six different natural habitats at different altitudes in Uttarakhand, India were analyzed. Twenty compounds were identified, accounting for 87.4–98.5% of the essential oils, with 1,8-cineole (33.4–41.9%), α-terpinene (39.6%), camphor (31.4%), and linalool (29.9%), being the prevalent major constituents of all accessions. HS-ALM (H. spicatum rhizomes Almora essential oil), HS-DDN (H. spicatum rhizomes Dehradun essential oil), HS-PAU (H. spicatum rhizomes Pauri essential oil), HS-TEH (H. spicatum rhizomes Tehri essential oil), and HS-USN (H. spicatum rhizomes Udham Singh Nagar essential oil) were dominated by oxygenated monoterpenes with 43.1–74.0%, respectively. In contrast, in HS-PIT (H. spicatum rhizomes Pithoragarh essential oil), hydrogenated monoterpenes dominated 57.8% of the total oil constituents. All accessions were assessed for significant nematicidal potential against Meloidogyne incognita and insecticidal potential against Spodoptera litura. The proteins/enzymes used for validation using docking studies were acetylcholinesterase (PBD ID: IC2O) and carboxylesterase (PDB ID: 1CI8). The study produced significant outcomes, showing the binding energy estimation of tested oil components to active sites supported the structure-activity relationship with bioinformatics tools.

Unirrigated extensive green roofs in humid subtropics – Plant selection and substrate design for low maintenance and climate resilience

Low-maintenance extensive green roofs hold the potential for adapting to climate change, but there is a limited understanding of their effective design in humid subtropical regions. In this study, we aimed to investigate low-maintenance green roof ecosystems capable of thriving under heat stress. Plant growth performance was evaluated in the second year of an experimental green roof in southwest China. This green roof was unirrigated and involved two plant communities (forbs and grasses) cultivated in four substrate types. Metrics of growth performance, including plant survival, green coverage, visual appearance, leaf stomatal conductance, and substrate volumetric water content were used to analyze the impact of substrate on plant growth. ESP substrate, comprising 30 %v (percent of volume) expanded shale, 25 %v perlite, 25 %v vermiculite, and 20 %v compost, featured the highest porosity and optimal growth of forbs, achieving an average green coverage of 66.76 % and average visual appearance value of 3.56 throughout the monitoring period. The high total porosity of this substrate could be critical in facilitating root development and drainage. Moreover, during the summer’s heat and drought, while substrate water content is not a limiting factor for the survival of some established forbs, it remains crucial for the growth of grasses. Additionally, the same substrate impacts different plant communities variably. Four particularly well-performing forb species, namely Lycoris chinensis, Tradescantia pallida, Liriope muscari, and Salvia farinacea, demonstrated survival rates closed to 100 % and an average visual appearance value exceeding 3 was noted, and thus, they are recommended as plant candidates for unirrigated green roofs. The distinguished performance of these species is attributable to their adaptation to heat and drought through specific physiological traits. Our findings provide insights into vegetation selection and substrate optimization for the successful establishment of extensive green roofs that could be feasibly developed without irrigation in the humid subtropical regions.

Quantifying the potential of evidence-based planting-pattern for reducing the outdoor thermal stress from a bio-meteorological perspective in tropical conditions of Indian cities.

The impact of declined natural greenery and increased built surfaces exacerbates heat stress in urban areas causing limited usage of outdoor spaces. Greenery strategies such as trees are capable of mitigating outdoor thermal stress gain because of their phytological properties. While urban greenery guidelines have suggested the ad-hoc procedure of tree planting-schemes based on aesthetic-value, soil-water preservation etc., understanding of their morphological character help in regulating extreme thermal condition. Hence, this study aims to investigate the most efficient planting pattern based on canopies densities and trees clusters for reducing the outdoor thermal stress from bio-meteorological perspective.It initiates with the measurement of the site's morphological and meteorological attributes in existing commercial market of Bhopal City which has a humid sub-tropical climate (Aw, Koppen climate categorization). Furthermore, it leads to the development of 4-different iterated clusters incorporating moderate to high-density canopies and their overlaps pattern to estimate reduction potential in outdoors using field surveys and validated simulation model. The reduction potential in terms of magnitude and duration of thermal stress is quantified across 3-thermal variables i.e., air temperature, mean radiant temperature and universal thermal climate index. Results indicate highly-dense canopies are more effective in reducing greater magnitude of thermal stress along longer duration. Also overlapped planting pattern within the same canopy density does not make significant difference in stress reduction as compared to the changing the densities. This study will help planners and landscape architects to adopt evidence-based planting-pattern strategies for improving outdoor microclimate.

Energy saving potential of passive radiative cool coating in high-rise data center with neighboring infrastructure

To coordinate with the evolution of I&T, it is indicated to enhance the number of data center (DC) worldwide, which involves enormous cooling demand that may lead to energy wastage if the facility is not constructed energy-efficiently, impeding decarbonization. Passive radiative cooler (PRC) have exhibited their energy-saving capability in many studies. Being a windowless building, DC has extensive coverage area for PRC comparing to other buildings that require outdoor visual access. The power-saving potential of a dual-layer daytime radiative cooling paint (DDRCC) in a high-rise DC was investigated at multi-building scale using a self-created site model under Hong Kong's humid subtropical climate. Besides the roof, which has been the target PRC-employed surface in previous studies, this work deployed DDRCC on roof and vertical façade of the DC, attaining optimal saving of 652–821 kW and cooling power of 23.4–29.5 W/m2, demonstrating its practicability in high-rise building. DDRCC accomplished cooling power of 2.5–48.0 W/m2 in scenarios with various configuration of PRC-utilized envelope. Additionally, for the site studied, the cooling power of DDRCC enhanced with aspect ratio when the height of adjacent buildings was comparable to the DC. DDRCC was competent to achieve power-saving with walls of different thermal resistances.

Paspalum lepton - a valuable adjunct to the suite of grasses used in grazing systems in the subtropics or a potential weed

Native and exotic C4 grasses currently used in grazing systems in the subtropics have specific limitations with management, decline in feed quality as they mature and variable adaptation to soils and climates, providing opportunities to identify alternative species to complement or replace them. One option is Paspalum lepton (syn. P. nicorae), a sward- forming, rhizomatous grass native to subtropical South America with recognized forage value. An early maturing form of this species has become naturalized in Northern New South Wales since its introduction in the 1940s. More recent introductions with forage and amenity potential are being established vegetatively and by seed as it becomes available. This paper reviews published work on P. lepton and reports largely unpublished results and observations on its performance in research and development studies in subtropical Eastern Australia. The potential value of and threats posed by P. lepton in relation to its adaptation, productivity, competitiveness and role in limiting ingress of existing weedy species are discussed. APG 54281 and APG 54325 are palatable, productive and persistent lines of this grass that have proven to be adapted to livestock production systems in most of the humid lowland subtropics, and to a specific niche in the subtropical uplands of Southeast Queensland where there is a lack of adapted C4 grasses and C3 grasses are only marginally adapted.

Biochemical characteristics of some varieties of peach and nectarine grown in Sochi

Biochemical characteristics and features of the most promising varieties of stone fruit crops (peach, nectarine) submitted for research have been shown. Biochemical analyzes of peach and nectarine fruits grown in the humid subtropics of Russia were carried out in 2019-2020 at the Subtropical Scientific Center of the Russian Academy of Sciences in the Laboratory of Plant physiology and Biochemistry. The following varieties were used for biochemical analyzes: Rannyaya zarya, Larisa (control one), Osenniy rymyanets, Anton Chekhov, Big Top, Nectarine Sklor. The content of biologically valuable substances in stone fruits, which determine not only their taste characteristics, but also their nutritional and therapeutic and prophylactic effects, is a criterion for high commercial quality of products. That is why we are faced with the task of assessing the chemical composition of peaches and nectarines, which directly depends on weather and climate conditions, varietal characteristics, place of growth, etc. It is known that the pulp of peaches and nectarines contains a large amount of sugars, organic acids (mainly malic), vitamins, enzymes, macro- and microelements. In assessing the taste qualities of peaches and nectarines, the content of sugars, acids and vitamin C (or ascorbic acid), which acts as an antioxidant, is of great importance. Biochemical analysis of peach and nectarine fruits revealed the maximum sugar content - 10.16% in the Larisa variety (control one) of mid-late ripening period, the minimum in the Rannyaya Zarya variety of early ripening period, which is significantly lower by 1.3 times compared to the control one. High vitamin C content in the Larisa variety fruits was noted - up to 16.56 mg%, which is significantly higher than other studied varieties by 2.60-5.19 mg%. Promising varieties Larisa and Anton Chekhov were distinguished by a balanced taste of fruits and resistance to abiotic factors of the environment of the Black Sea coast of Russia.

Calibration and evaluation of various reference evapotranspiration estimation methods in a humid subtropical climate: A case study in Samsun Province, Türkiye

Reference evapotranspiration is crucial for estimating plant water needs and managing resources. Simplifying the Penman-Monteith model by reducing input parameters and local calibration can enhance efficiency and reliability. In this study, three empirical formulas—Hargreaves and Samani (HS, 1985), Priestley and Taylor (PT, 1972), and the World Meteorological Organization (WMO, 1966)—representing temperature-, solar radiation-, and mass-transfer-based approaches, respectively, were evaluated. To achieve this objective, meteorological data from five synoptic stations situated in the Samsun province in the Black Sea region of Türkiye, were utilized. Three methods, namely the traditional method, regression analysis, and genetic algorithm, were employed to estimate the local calibration coefficients of empirical equations based on the Penman-Monteith 56 equation. Finally, the outcomes were evaluated based on four criteria: root-mean-square error, coefficient of determination, mean bias error, and percentage error of estimate. The results of empirical formulas both before and after calibration were analyzed. Prior to calibration, HS and PT exhibited greater accuracy for the case study. This accuracy trend was also observed in the calibrated results. Additionally, among the three employed calibration methods, regression analysis and traditional methods demonstrated a higher level of accuracy.

Optimum Utilization of Different Nitrogen Fertilizer Sources for Improving Soil Properties and Agro-Physiological Indices of Maize Crop under Humid Subtropical Conditions of Pakistan

Optimum Utilization of Different Nitrogen Fertilizer Sources for Improving Soil Properties and Agro-Physiological Indices of Maize Crop under Humid Subtropical Conditions of Pakistan

Response of actinidia deliciosa plants to abiotic stress in the Russian subtropical zone

The article presents a general description of the culture of Actinidia deliciosa, grown in the humid subtropics of Russia. The work was carried out since 2017 at the site of the Adler experimental station of the branch of the Federal Research Center of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources and in the laboratory of plant physiology and biochemistry of the Subtropical Scientific Center of the Russian Academy of Sciences, Sochi. Physiological and biochemical indicators were determined that reflect the resistance of actinidia plants planted in 1988 to environmental stress factors to identify the most adapted varieties to the conditions of the humid subtropics of the Krasnodar Territory. The soil is alluvial meadow with low humus. The varieties studied were late ripening Hayward; Ellison, Abbott and Bruno – early; Monty – medium; Tomuri (pollinator of kiwi female varieties). The indicator organ is physiologically mature actinidia leaves, which were selected from May to September against the backdrop of a natural increase in air temperature. Water deficit was in 2022–2023 is 29.62–36.46%, the minimum is for the Ellison and Monty varieties (29.62–30.21), the maximum is Abbott (36.46%). The dry matter content is 25.47–35.53%, the water content of leaf blades is 46.09-62.66%. The Monti, Hayward and Tomuri varieties are the most resistant to the weather and climatic conditions of the Russian subtropical zone.

Climatic Stability of Organic Triplexes in Free and Loaded States under Humid Subtropical Marine Atmosphere Conditions

Climatic Stability of Organic Triplexes in Free and Loaded States under Humid Subtropical Marine Atmosphere Conditions

Risk assessment of the laboratory host range and a molecular characterisation determining the field host range of Lixus aemulus, for the biological control of Chromolaena odorata in South Africa

Chromolaena odorata (Asteraceae: Eupatorieae) is a sprawling shrub native to the Americas, and a destructive invader of much of the humid tropics and subtropics of the Old World. Opportunistic native-range exploration in 1995 identified a stem-boring weevil, Lixus aemulus, as a promising biological control candidate agent. Host-specificity testing was conducted on L. aemulus in South Africa using laboratory no-choice and paired-choice tests. Three invasive alien plants closely related to C. odorata may be utilized by L. aemulus but no indigenous, ornamental or crop species in South Africa was or is expected to be attacked by the weevil. A native-range field survey was conducted in Brazil to determine the exact identity of the host plant L. aemulus had been collected in 1995, and to identify additional host-plant species. Genetic assessments of the Lixus sp.(p.). adults collected on the three host plants (C. odorata, Chromolaena laevigata and Heterocondylus vitalbae) reveal these individuals are L. aemulus and the weevil can be classed as an oligophage in its native range. Over 5,500 adults were released in South Africa, but overall establishment has been poor. The most likely explanation appears to be a climate mismatch between the region of South Africa invaded by C. odorata and the collection locality in Rio Branco, Acre state, Brazil. Additionally, because the full extent of the native range of L. aemulus is unknown, it is uncertain whether individuals can be sourced from an area whose climate resembles that of South Africa. Furthermore, despite being oligophagous, L. aemulus may perform sub-optimally on the southern African C. odorata biotype.

Predictive modelling of multi-domain factors on window, door, and fan status in naturally ventilated school classrooms

Most studies regarding the investigation of occupant behaviour (OB) in school classrooms addressed the environmental influence on window operation solely and were conducted in oceanic climates. This study aimed to identify and quantify the influence of multi-domain factors (including thermal, indoor air quality, contextual and multi-behaviour domains) on window, door, and fan status in naturally ventilated school classrooms in a humid subtropical climate, in order to predict OB. Environmental variables, manual operation of windows, doors and fans, and occupancy rate were monitored and questionnaires were applied in a set of classrooms of three public school buildings in the state of São Paulo, Brazil, during four rounds at two-month intervals, resulting in a comprehensive year-long study. During part of the physical monitoring, restrictive occupancy measures due to the COVID-19 pandemic were observed. Generalized Linear Mixed Models were applied to assess the influence of the recorded parameters on the window, door, and fan status and to generate OB predictive models. Results showed that indoor environmental variables influenced window, door, and fan status in school classrooms, with few exceptions. Yet, the models including school routines, social norms and teachers’ behaviour as predictors led to the highest accuracy. This suggests that, while a more complex model with additional predictors can provide more accurate predictions of OB, it also becomes more context-dependent and less generalizable. The trade-off between model complexity and generalizability is an important consideration in this research study, and it highlights the nuanced relationship between multi-domain factors affecting occupant behaviour in school buildings.

Intra-annual variability of urban effects on streamwater quality: An examination of watersheds in the Atlanta, Georgia USA region

There has been considerable research on urban impacts on streamwater quality, but studies have mostly ignored intra-annual variations in water-quality variables and thus seasonally-varying impacts. Therefore, this study uses daily water-quality data over eight years for 38 streams in the Atlanta, Georgia USA region and watershed-level, urbanization variables to assess month-specific impacts of urbanization on water quality. The water-quality variables were mean specific conductance, mean temperature, mean dissolved oxygen, median pH, and median turbidity. The watershed-level variables were population density, housing density, proportion of watershed that is high-intensity developed land, imperviousness, proportion of watershed that is urban land use, an urban-intensity index, and change in developed land. Both differences in water quality between urban, suburban, and exurban streams and correlations between water quality and the watershed-level variables were examined. During all months, urban streams had significantly higher specific conductance than suburban and exurban streams, and the urban intensity of a watershed was significantly positively correlated with specific conductance. Differences and correlations were intensified during winter and spring. For temperature and dissolved oxygen, only during non-winter months did urban streams have significantly higher temperatures and significantly lower dissolved oxygen as well as significant positive correlations between urban intensity and temperature and significant negative correlations between urban intensity and dissolved oxygen. Urban streams had the highest pH during all months, but none of the differences were significant. Significant correlations between pH and urban intensity were restricted generally to winter and spring months. Turbidity was highest for exurban watersheds and thus was not significantly positively correlated with urban intensity. Seasonal and stream-group differences in the weathering of concrete, use of road salts, solar heating of streams, urban surface temperatures, baseflow, and land-disturbance activities explain the water-quality findings. Most of the findings should be applicable to urban areas in humid subtropical climates within the Piedmont physiographic region.

Effect of external shading on the temperature distribution performance of glass greenhouse in Wuhan region

The spatial temperature distribution within greenhouses plays a crucial role in agricultural management, particularly in large glass greenhouses that provide optimal growing conditions for crops. The current study investigated the effects of solar radiation and external shading on the spatial distribution of air temperature inside a large glass greenhouse. Experiments were conducted during summer in Wuhan, China, with cherry tomatoes grown under removable black plastic external shading (50 % transmittance). The use of external shading reduced greenhouse temperatures by 6.80 % on sunny days with air conditioning and 4.62 % on cloudy/rainy days without air conditioning. It also decreased the correlation between solar radiation and indoor temperatures by 60.71 % on sunny days and 7.20 % on rainy days. The greenhouse exhibited uneven temperature distribution in all directions, with much greater vertical temperature gradients (0.67 °C/m on sunny days, 0.33 °C/m on rainy days) compared to east-west and north-south directions. While external shading reduced overall temperature unevenness, on rainy days the north-south temperature difference was only 0.28 %, but the middle position was 2.24 % warmer than boundaries. The findings provide insights into regulating external shading techniques for large greenhouses in humid subtropical climates to optimize temperature management and crop production efficiency.

Correction: The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate

Correction: The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate

Association between heat and upper urinary tract stones morbidity and medical costs: A study in the subtropical humid climate zone

Urolithiasis is a heat-specific disease. Exploring heat-related urolithiasis susceptibility subtypes, economic burden, and modifying factors could assist governments in targeting interventions to reduce the heat-related health risks of urolithiasis morbidity. We collected data on 23,492 patients with upper urinary tract stones (main subtypes of urolithiasis) from 2013 to 2017 in Nanjing, China. We adopted generalized additive quasi-Poisson models to examine the associations between daily mean temperatures and morbidity of upper urinary tract stones, while generalized additive Gaussian models were used to explore the relationships between temperatures and log-transformed medical costs. We examined the modification effects of disease subtypes (kidney and ureteral calculus), sex, and age through stratified analyses and the modification effects of other meteorological factors by introducing interaction terms in the models. We found that short-term summer heat exposure has a statistically significant effect on ureteral calculus morbidity but not on kidney calculus morbidity. For ureter calculus, a 1 °C temperature increase was associated with a 4.36% (95% confidence interval [CI]: 1.94%, 6.83%) increase in daily hospitalization and a 5.44% (95% CI: 2.71%, 8.25%) increase in daily medical costs. The attributable fraction associated with heat (greater than the median value of daily mean temperature, 26.8 °C) was 7.85% (95% empirical confidence interval [eCI]: 3.64%, 11.44%) for hospitalization and 9.36% (95% eCI: 4.91%, 13.14%) for medical costs. The effects of heat on ureter calculus morbidity were significantly higher among the males and those with high sunshine duration than females and those with low sunshine duration. Short-term summer heat exposure was associated with increased morbidity and medical costs of ureteral calculus. Relevant government organizations should take effective intervention measures, including community health education, to reduce the health hazards and economic losses caused by heat.

Synergistic Landscape Design Strategies to Renew Thermal Environment: A Case Study of a Cfa-Climate Urban Community in Central Komatsu City, Japan

An effective community landscape design consistently impacts thermally comfortable outdoor conditions and climate adaptation. Therefore, constructing sustainable communities requires a resilience assessment of existing built environments for optimal design mechanisms, especially the renewal of thermally resilient communities in densely populated cities. However, the current community only involves green space design and lacks synergistic landscape design for renewing the central community. The main contribution of this study is that it reveals a three-level optimization method to validate the Synergistic Landscape Design Strategies (SLDS) (i.e., planting, green building envelope, water body, and urban trees) for renewing urban communities. A typical Japanese community in central Komatsu City was selected to illustrate the simulation-based design strategies. The microclimate model ENVI-met reproduces communities involving 38 case implementations to evaluate the physiologically equivalent temperature (PET) and microclimate condition as a measure of the thermal environments in humid subtropical climates. The simulation results indicated that the single-family buildings and real estate flats were adapted to the summer thermal mitigation strategy of water bodies and green roofs (W). In small-scale and large-scale models, the mean PET was lowered by 1.4–5.0 °C (0.9–2.3 °C), and the cooling effect reduced mean air temperature by 0.4–2.3 °C (0.5–0.8 °C) and improved humidification by 3.7–15.2% (3.7–5.3%). The successful SLDS provides precise alternatives for realizing Sustainable Development Goals (SDGs) in the renewal of urban communities.

Survival of Xanthomonas vasicola pv. vasculorum in Soil and in Corn Crop Residues under the Humid Subtropical Climate of Southern Brazil.

Bacterial leaf streak caused by Xanthomonas vasicola pv. vasculorum (Xvv) is an emerging disease in several corn-producing regions around the world. In Brazil, there is a lack of information on the survival of this bacterium in soil and crop residues. Thus, the objective of this study was to determine the survival of Xvv in soil and also in infected corn crop residues under the humid subtropical climate of southern Brazil. The survival of Xvv in soil was initially investigated in sandy and clayey soils maintained at 20, 25 and 30 °C under controlled conditions. The survival of the bacterium under field conditions was studied in artificially infested clayey soil. The survival of Xvv in corn crop residues was investigated in infected residues maintained on the soil surface or buried in the soil at 20 cm deep. Under controlled conditions, regardless of the type of soil, the bacterium survived longer at 20 °C than at higher temperatures. The bacterium survived for 40 days in clayey soil kept at 20 °C and four days in sandy soil maintained at 30 °C. Under field conditions, the survival of Xvv in the soil was only for 48 h and in infected corn crop residues for up to 15 days in the samples maintained on the soil surface. In samples of infected corn residues buried in the soil, the bacterium was only detected at the time the experiment was set up. In general, the results obtained in this study revealed that Xvv survives for a short period of time in soil and in infected corn crop residues under humid subtropical conditions. Therefore, soil and corn residues may not be highly important sources of primary inoculum for the development of bacterial leaf streak on corn crops under these conditions.