Seasonal Changes Research Articles

Preserving isohydricity: vertical environmental variability explains Amazon forest water use strategies.

Increases in hydrological extremes, including drought, are expected for Amazon forests. A fundamental challenge for predicting forest responses lies in identifying ecological strategies which underlie such responses. Characterization of species-specific hydraulic strategies for regulating water use, thought to be arrayed along an 'isohydric-anisohydric' spectrum, is a widely used approach. However, recent studies have questioned the usefulness of this classification scheme, because its metrics are strongly influenced by environments, hence can lead to divergent classifications even within the same species. Here, we propose an alternative approach positing that individual hydraulic regulation strategies emerge from the interaction of environments with traits. Specifically, we hypothesize that the vertical forest profile represents a key gradient in drought-related environments (atmospheric vapor pressure deficit, soil water availability) that drives divergent tree water use strategies for coordinated regulation of stomatal conductance (gs) and leaf water potentials (ΨL) with tree rooting depth, a proxy for water availability. Testing this hypothesis in a seasonal eastern Amazon forest in Brazil, we found that hydraulic strategies indeed depend on height-associated environments. Upper canopy trees, experiencing high VPD, but stable soil water access through deep rooting, exhibited isohydric strategies, defined by little seasonal change in the diurnal pattern of gs and steady seasonal minimum ΨL. By contrast, understory trees, exposed to less variable VPD but highly variable soil water availability, exhibited anisohydric strategies, with fluctuations in diurnal gs that increased in the dry season along with increasing variation in ΨL. Our finding that canopy height structures the coordination between drought-related environmental stressors and hydraulic traits provides a basis for preserving the applicability of the isohydric-to-anisohydric spectrum, which we show here may consistently emerge from environmental context. Our work highlights the importance of understanding how environmental heterogeneity structures forest responses to climate change, providing a mechanistic basis for improving models of tropical ecosystems.

Variation and Interaction of Distinct Subgenomes Contribute to Growth Diversity in Intergeneric Hybrid Fish.

Intergeneric hybridization greatly reshapes regulatory interactions among allelic and non-allelic genes. However, their effects on growth diversity remain poorly understood in animals. In this study, we conducted whole-genome sequencing and RNA sequencing (RNA-seq) analyses in diverse hybrid varieties resulting from the intergeneric hybridization of goldfish (Carassius auratus red var.) and common carp (Cyprinus carpio). These hybrid individuals were characterized by distinct mitochondrial genomes and copy number variations. Through a weighted gene correlation network analysis, we identified 3693 genes as candidate growth-regulated genes. Among them, the expression of 3672 genes in subgenome R (originating from goldfish) displayed negative correlations with growth rate, whereas 20 genes in subgenome C (originating from common carp) exhibited positive correlations. Notably, we observed intriguing patterns in the expression of slc2a12 in subgenome C, showing opposite correlations with body weight that changed with water temperatures, suggesting differential interactions between feeding activity and weight gain in response to seasonal changes for hybrid animals. In 40.31% of alleles, we observed dominant trans-regulatory effects in the regulatory interaction between distinct alleles from subgenomes R and C. Integrating analyses of allelic-specific expression and DNA methylation data revealed that the influence of DNA methylation on both subgenomes shapes the relative contribution of allelic expression to the growth rate. These findings provide novel insights into the interaction of distinct subgenomes that underlie heterosis in growth traits and contribute to a better understanding of multiple allele traits in animals.

Overlooked cooling effects of albedo in terrestrial ecosystems

Abstract Radiative forcing (RF) resulting from changes in surface albedo is increasingly recognized as a significant driver of global climate change but has not been adequately estimated, including by IPCC assessment reports, compared with other warming agents. Here, we first present the physical foundation for modeling albedo-induced radiative forcing (RF¬) and the consequent global warming impact (GWI∆α). We then highlight the shortcomings of available current databases and methodologies for calculating GWI∆α at multiple temporal scales. There is a clear lack of comprehensive in situ measurements of albedo due to sparse geographic coverage of ground-based stations, whereas estimates from satellites suffer from biases due to the limited frequency of image collection, and estimates from Earth System Models suffer from very coarse spatial resolution land cover maps and associated albedo values in pre-determined lookup tables. Field measurements of albedo show large differences by ecosystem type and large diurnal and seasonal changes. As indicated from our findings in southwest Michigan, GWI∆α is substantial, exceeding the RF∆α values of IPCC reports. Inclusion of GWIΔα to landowners and carbon credit markets for specific management practices are needed in future policies. We further identify four pressing research priorities: developing a comprehensive albedo database, pinpointing accurate reference sites within managed landscapes, refining algorithms for remote sensing of albedo by integrating geostationary and other orbital satellites, and integrating the GWI∆α component into future Earth System Models.

Days to re-entrainment following the spring and autumn changes in local clock time: beyond simple heuristics

Circadian disruption, a breakdown in the regularity of activity patterns across the 24-h day, can lead to a variety of maladies. Some individuals and organizations object to the twice-yearly, seasonal changes in local time because it contributes to circadian disruption. The number of days required to re-entrain the circadian system to the new local time following transitions to or from daylight saving time is not completely understood, but several simple rules of thumb (i.e., heuristics) have been offered to minimize the days to re-entrainment and, thus, circadian disruption (e.g., go for a morning walk). Recently, the authors developed a computational model for predicting circadian phase from calibrated light-dark exposure patterns, based largely on the pioneering work of Kronauer and colleagues. This model was used here to predict the days to re-entrainment of the circadian systems of “larks” and “owls” to a new local time if they were exposed to one of three specific light interventions. Simulations showed that the timing of a light intervention must account for chronotypes (e.g., timing of minimum core body temperature) and direction of shift (i.e., phase advance or delay) to achieve re-entrainment to the time change more quickly. Simple heuristics are not necessarily adequate for minimizing the days to re-entrainment.

The Effect of Climate on Strongly Disturbed Vegetation of Bait Sites in a Central European Lower Montane Zone, Hungary

Human landscape-transforming activities contribute to the global change in vegetation in different forms. Hunting is one of the most ancient human landscape-shaping activities. Feeders for hunting are particularly disruptive to vegetation. In the present study, we conducted a vegetation survey in these highly disturbed places. We investigated the vegetation dynamics over several years in the turkey oak–sessile oak zone, in two areas with different moisture and shade conditions (forest and clearing). Important background factors are the changes in precipitation and temperature. Our results confirm that weed infestation is detectable at bait sites over a long period. The seasonal changes in field weed vegetation, as well as the increase in the number and coverage of weed species at the end of summer, resulting from lifestyle characteristics, were generally detectable in all years and locations, especially in the case of open and more strongly degraded clearings. Meteorological factors played a role in the degree of weed infestation in each year. Degradation was more significant in drought years, while regeneration was also observed in wetter periods. At baits located in the clearing, we showed a positive correlation between the amount of summer precipitation and the total coverage of weed species, as well as between the average spring temperature and the coverage of certain weed species. With the drying of the climate, the disturbed areas are constantly losing their natural value, but wetter weather is not an automatic solution either. Considering that there are approx. 30,000 bait sites in the country, and they are used regularly and very intensively, they can serve as major infection hotspots for alien species in a network.

Anchovy and sardine condition and energy content in the North Aegean Sea (eastern Mediterranean) in relation to their contrasting reproductive strategies.

Forage species with high biomass, such as anchovies and sardines, play a key role in pelagic ecosystems and make up a significant proportion of the world's capture fisheries production. In recent years, condition indices have gained interest as significant indicators for assessing the effects of environmental and human pressures on these species and the quality of their habitats. In the present study, we examined, for the first time in the North Aegean Sea (eastern Mediterranean), the year-round variation in somatic and gonadal condition, energy density, and percentage of lipid content of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus). Energy density was measured with bomb calorimetry and percentage lipid content with the fatmeter, a portable electronic device. Finally, the monthly changes in gonadal and energetic condition were examined in relation to the annual cycle of temperature and mesozooplankton biomass, simulated by the implementation of a coupled hydrodynamic-biogeochemical model (POM-ERSEM). There was a strong relationship between fish energy density (kJ g-1) and percentage dry weight. Furthermore, the mean monthly energy density and fatmeter measurements were strongly correlated, especially in sardine. Overall, the monthly changes in energetic condition were indicative of the species' different strategies for energy acquisition and allocation to reproduction (capital vs. income breeding): sardine exhibited low energy density and percentage lipid content during the winter spawning period (November-March) and markedly higher energetic condition from spring to autumn (April-October). Anchovy spawning period, as inferred from gonadal condition, lasted from April to September, i.e., during the warm period of the year but its energy density and percentage lipid content did not exhibit any seasonal changes and were markedly lower than in sardine from April to October. Finally, the simulated mesozooplankton biomass was higher from January to July, which corresponded to the second half of the spawning season for sardine, but first half of the spawning season for anchovy.

A reliable method for quick comparisons of enchytraeid (Oligochaeta) densities in soil and their seasonal changes under cultivated and natural fields in central Greece

Although Enchytraeidae constitute an important component of soil fauna, their communities have not been adequately studied in cultivated soils. We studied the species composition and the seasonal fluctuations of the enchytraeid communities in a four-year alfalfa plantation and its boundary zone in the valley of Kopaida, Central Greece for a period of one year. The population densities were recovered at 15 cm depth. There were remarkable seasonal changes in the population densities that took their highest value in autumn and their lowest in summer in both soils. The composition of the plantation community consisted of two distinct species with opportunistic life strategy and developed higher density compared to the boundary zone. The boundary zone harbored four species which mainly had robust, long living developmental pattern. We concluded that the specific characteristics of the dominant plant species were the most decisive differentiating factor determining the enchytraeid communities, followed by the cultural practices. The results from the sucrose centrifugation method of extraction exhibited strong correlation with those of the cold wet extraction method without filtering. This indicates that sucrose centrifugation method can be safely used in quickly processing high number of samples and for the enchytraeid estimation in multidisciplinary research works.

The Influence of Technological Factors on the Structure and Chemical Composition of Tuberous Dahlia Roots Determined Using Vibrational Spectroscopy

This research investigated the structural and chemical modifications of Dahlia ‘Kennemerland’ across different technological conditions and throughout the vegetation period. Using FT-IR imaging, this study focused on the changes in the inulin, lignin, and suberin contents of tuberous roots. FT-IR maps were generated to visualize the distribution of these compounds across scanned areas, highlighting variations across cultivation methods and seasonal stages. The key compounds analyzed included inulin, lignin, and suberin, which were identified in different root zones. The results showed that inulin was distributed in all analyzed areas, predominantly in zone 1 (periderm), with a distribution that increased with forced cultivation, while lignin and suberin distributions varied with zone and season. Forced tuberous root lignin was detected in all four areas analyzed, in the fall accumulating mainly in area 4 and in suberin starting from summer until autumn. Based on the evaluation of the maps obtained by representing the area ratios of specific bands (inulin/lignin and inulin/suberin), we established where the inulin was present in the highest quantity and concluded that suberin was the constituent with the lowest concentration in tuberous Dahlia roots. These findings emphasize the influence of technological factors and seasonal changes on the biochemical makeup of tuberous Dahlia roots. This detailed biochemical mapping provides insights for optimizing Dahlia cultivation and storage for various industrial applications. This study concludes that FT-IR spectroscopy is an effective tool for monitoring and understanding the biochemical dynamics of Dahlia roots, aiding their agricultural and industrial utilization.

Physical performance changes in season are associated with GPS data in soccer players.

This study investigated the associations between preseason and in-season performance with external workload in professional soccer players. Twenty-one players completed hamstring strength, countermovement jump (CMJ), 20-m sprint, and Yo-Yo intermittent recovery tests before (preseason) and after 8 weeks (in-season). External workload (total distance, high-intensity running distance, number of sprints, and power plays) was quantified during this period, and used to divide the average above and below subgroups outcome by outcome for further analyses. Significance was accepted when P≤0.05. Hamstring strength declined from pre- to in-season [-6%; p=0.014; effect size (ES): -0.41], while Yo-Yo performance improved (46%; p=0.001; ES: 1.31). When divided by high-intensity running distance, only the below-average subgroup improved CMJ performance (5%; p=0.030). For minutes played, the above-average subgroup improved Yo-Yo performance (41%; p<0.001), but not the below-average subgroup. Furthermore, playing time correlated with improved Yo-Yo performance (p=0.040; r=0.534). Improved 20-m sprint performance associated with more sprints performed (p=0.045; r=-0.453). Physical capabilities changed over a competitive season and were related to, and differentiated by, external workload. Because hamstring strength decreased and CMJ only improved in players exposed to less high-intensity external load, practitioners should individualize approaches to counteract these conditions when high external workload is performed over the season.

A taste of youth: Seasonal changes in the diet of immature white sharks in eastern Australia

White sharks (Carcharodon carcharias) play a crucial ecological role, shaping ecosystems through direct predation and risk effects. On the east coast of Australia, immature white sharks are broadly distributed, inhabiting a wide range of habitats and ecosystems from temperate Tasmania to tropical North Queensland. Using stable isotopes and fatty acids of muscle and plasma, we examined the diet and habitat use of 136 immature white sharks (152–388 cm total length) captured on SMART drumlines on the East Australian coast. This facilitated the temporal assessment of white shark trophic ecology from a few weeks to approximately a year. Biochemistry of muscle samples showed that white sharks predominantly feed on low trophic level prey from coastal environments. A seasonal shift in diet was evident, with the increasing proportions of essential fatty acids in muscle tissues during spring and summer suggesting a greater consumption of high-nutrition preys during those months compared to autumn and winter. By combining stable isotope and fatty acid analysis, we gain a comprehensive understanding of immature white shark diet in eastern Australia. Our results confirm that white sharks are generalist predators that exhibit seasonal shifts in their diet. Their high use of coastal habitats reinforces the importance of these areas for foraging, which is crucial for growth and development during this critical life stage.

Exploring Performance of Using SCM Concrete: Investigating Impacts Shifting along Concrete Supply Chain and Construction

Concrete is one of the most used building materials globally, leading to a large amount of greenhouse gas (GHG) emissions. Using supplementary cementitious materials (SCM) as replacements for cement in concrete provides an effective way to reduce GHG emissions. However, quantifying the construction performance of using SCM concrete is hard because of complex interactions between concrete’s mechanical properties and construction characteristics, like local energy supply, surrounding temperature and construction plans, which leads to only the fragmental performance of using SCM concrete being explored in previous studies. There still lacks an effective way to quantify the comprehensive performance and provide decision support for contractors about how to use SCM concrete. To deal with the gap, this research proposes a Collection–Simulation–Calculation–Decision (CSCD) method to analyze the complex interactions between concrete and construction, and to quantify the performance of the supply chain–construction when using SCM. A case study is also conducted to demonstrate the effectiveness of the proposed method. The results show that the proposed method is effective in quantifying the performance of using SCM concrete in construction and providing decision support for construction decision makers. A scenario analysis is also conducted to demonstrate the effectiveness of the proposed method in different project characteristics, including the global warming potential (GWP) factors for different construction sites, seasonal temperature changes and different construction plans. The proposed method is an effective tool to quantify the construction performance of using SCM concrete considering complex interactions between concrete mechanical properties and construction characteristics. The results of the research can assist construction decision makers to make decisions about using SCM concrete by comprehensively understanding the impacts shifting along the concrete supply chain and construction.

Spatial and temporal heterogeneity of land surface phenology in Shanxi Province from 2001 to 2020

AbstractLand surface phenology encompasses variations in the life cycle events of plants induced by seasonal changes in environmental factors, primarily meteorological conditions. This study leverages Google Earth Engine to extract a comprehensive time series of two‐band Enhanced Vegetation Index (EVI 2) from Landsat images. Utilizing relatively sparse data spanning from 2001 to 2020, a Bayesian hierarchical model is applied at a 30 m resolution to capture the continuous temporal evolution of phenology. The fitting results of this study demonstrate excellent performance, with annual correlation coefficients consistently exceeding 0.89. The findings indicate that between 2001 and 2020, the Start of Season in Shanxi advanced by an average of 0.79 days per year, the End of Season was delayed by an average of 0.83 days per year, and the Length of Season (LOS) extended by an average of 0.80 days per year. Spatial disparities in phenological periods in Shanxi are evident, with an average LOS of 192 days on 35–36° N and only 122 days on 40–41° N. Below 1200 m, phenological periods exhibit significant changes influenced by human activities, while between 1200 m and 2600 m, LOS shows a weak trend of shortening. Above 2600 m, there is a noticeable reduction in LOS. With an increasing slope, LOS increases from an average of 175 days to 187 days (&gt;25°). This study, utilizing Shanxi as a case study, explores the spatiotemporal evolution characteristics of vegetation phenology, aiming to support fine land management and enhance agricultural productivity.

Impact of seasonal changes in urban green spaces with diverse vegetation structures on college students' physical and mental health

Based on the perceptions of college student participants in winter and summer, the effects of different vegetation structures within landscapes (single-layer woodland, tree-shrub-grass composite woodlands, tree-grass composite woodland, and single-layer grassland) and concrete squares without plants were investigated, and the skin conductivity level (SCL) and environmental perception recovery score (PRS) associated with landscape types were calculated. The results indicated that seasonal differences in landscape perception significantly affected college student participants' PRS but not their SCL scores, both in winter and summer. Viewing single-layer and tree-shrub-grass composite woodlands in summer, as well as single-layer woodland in winter, enhanced the environmental perception of the college student participants. The restorative effects of the four vegetation types in green spaces were ranked as follows: single-layer woodland, tree-shrub-grass composite woodlands, single-layer grassland, and tree-grass composite woodlands and concrete squares without plants. These findings underscore the importance of considering seasonal variations when choosing plant species for landscaping purposes, with evergreen single-layer woodland being a suitable choice for winter urban landscapes. This provides a scientific basis for assessing landscape perception and preferences in the future.

The Impact of Seasonal Changes on the Composition of Cow Milk in Jalalabad City, Afghanistan

The study investigated the impact of seasonal variations on the components of cow milk in Jalalabad City, Afghanistan. A total of 80 milk samples were collected from six different local points within the city from January to August 2023. The research spanned two distinct periods: winter (January-February-March) and summer (June-July-August). During the winter, cows were fed hay, while in the summer; they grazed on green grass in pastures. Analysis revealed significant differences in fat content and titratableacidity between the winter and summer periods, with both factors being significant at the p&lt;0.05 level according to paired t-test results. The study concluded that seasonal variations significantly affected the protein content, total solids, fat, and titratableacidity, with significance levels of p&lt;0.05 and p&lt;0.01, respectively.

The Relationship between Genetic Variability and Seasonal Changes in Vertical Jump Performance in Amateur Soccer Players

This study aimed to investigate the longitudinal evolution of vertical jump height in soccer players and its association with their genotypic profiles. The genotypes of 37 soccer players were characterized and the countermovement jump (CMJ) height, concentric mean power, force, and jump strategy were assessed at two time points: at the onset of the regular season (Pre) and at the conclusion of the first half (Mid). AMPD1 (rs17602729), ACE (rs4646994), ACTN3 (rs1815739), CKM (rs8111989), and MLCK (rs2849757 and rs2700352) polymorphisms were genotyped. No significant differences were found between Pre and Mid in concentric power (p = 0.068; d = 0.08) or force (p = 0.258; d = 0.04), while jump height displayed trivial increases (p = 0.046; d = 0.15). Individual analysis revealed that 38% of participants increased the vertical jump height and mean concentric power over the smallest worthwhile change (SWC), while 27% experienced an increased mean concentric force. The positive responders were characterized by a decreased frequency of the AA genotype and an increased frequency of the CA genotype for the c.37885C&gt;A polymorphism of MLCK (p = 0.035), as well as a decreased frequency of the TT genotype of ACTN3 (p = 0.042) and the CC genotype of AMPD1 (p = 0.022). Our findings suggest that genetic analysis could explain some variability in neuromuscular adaptations during the in-season.

Predicting the Future Distribution and Habitat Suitability of Ilex latifolia Thunb. in China under Climate Change Scenarios

Ilex latifolia Thunb., a plant of significant economic and medicinal value, is both edible and medicinal. Assessing the climate suitability for I. latifolia has profound implications for advancing medical progress and enhancing the quality of human life. This study comprehensively utilized data on the field distribution of I. Latifolia, as well as corresponding climatic, topographical, and soil data at these distribution points, with the aid of future climate data predicted by global climate models, and employed the MaxEnt model to predict and analyze the climate suitability areas of I. latifolia under three greenhouse gas emission scenarios (SSP126, SSP245, and SSP585). The research covers the spatiotemporal distribution characteristics, suitable growth range, and influencing factors from the present to the end of the 21st century (2041–2100). The predictive results of the MaxEnt model indicate that, under current climatic conditions, the main suitable growth areas for I. latifolia are concentrated in the southeastern part of China, especially in the provinces of Fujian and Zhejiang. However, facing the challenges of future climate change, it is expected that the moderately high suitable growth areas for I. latifolia will show a trend of gradual reduction. The primary climatic factors crucial for I. latifolia’s growth are annual precipitation (1469.05 to 4499.50 mm), the lowest temperature in the coldest month (−18.72 to 3.88 °C), seasonal precipitation changes (11.94 to 64.69 mm), and topographic slope (0.37 to 3.00 °), with annual precipitation being the most influential. The findings of this study provide a scientific basis for the introduction of I. latifolia and offer important reference information for the artificial cultivation, resource development, and achievement of sustainable industrial development of this species.

Landscape and paleoenvironmental change in stream valleys of the Central Great Plains, North America, during Marine Isotope Stage 3 (ca. 59–27 ka)

Recent studies of late Quaternary landscape evolution in stream valleys throughout the central Great Plains of North America have identified thick packages of MIS 3-age alluvium and colluvium beneath terraces, alluvial fans, and footslopes. Here, we review and build on these studies to highlight the geomorphic history of river systems in the Central Plains during MIS 3 and reconstruct the paleoclimatic conditions and vegetation communities that existed in the region at that time.A suite of 50 radiocarbon and optically stimulated luminescence ages indicate that late MIS 3 was a period of widespread landscape stability and soil development in the Central Plains. In general, river systems were actively aggrading during early MIS 3, but aggradation slowed after ca. 40 ka, allowing soils to develop until ca. 30–27 ka. In some river valleys, a second pulse of aggradation occurred shortly after that time followed by a period of landscape stability and pedogenesis during early MIS 2 (ca. 24–19 ka). Evidence for widespread landscape stability in stream valleys implies that high magnitude flooding was minimal. Atmospheric circulation patterns that favor these conditions include zonal airflow that inhibits incursions of moist, maritime air from the Gulf of Mexico.Paleoenvironmental conditions during late MIS 3 were reconstructed using the stable carbon, oxygen, and hydrogen isotopic composition of pedogenic phyllosilicates, carbonates, and organic matter. Estimated paleotemperatures ranged from 6 to 9 °C ± 3 °C and are approximately 4–7 °C lower than modern mean annual temperature. The estimated δ18O values of soil water from phyllosilicates range from −10.6‰ to −9.6‰. These estimates are lower (18O-depleted) by about 1.5–3‰ relative to modern meteoric δ18O values and we estimate that the δ18O of paleoprecipitation was likely 18O-depleted by up to 8.5‰ relative to modern values. Our estimated δ18O values for soil waters in the Central Plains during late MIS 3 can be explained by climatic conditions characterized by 1) cooler temperatures, 2) precipitation being sourced primarily from Pacific/Arctic air masses, 3) seasonal changes in precipitation patterns (i.e., predominantly winter precipitation), or 4) a combination of the above. δ13C values indicate the presence of a notable proportion of C4 vegetation in the Central Plains during late MIS 3. We suggest that C4 productivity was likely favored at that time by a low atmospheric CO2 environment that had sufficiently warm temperatures and effective precipitation during the growing season.

Effects of Seasonality on the Large and Medium-Sized Mammal Community in Mountain Dry Forests

Seasonality drives natural processes, impacting environmental factors like temperature and resource availability, leading to shifts in wildlife communities. The Andean dry forests exhibit a marked seasonality, with a dry and cold season (May–September) and a warm, wet season (October–April). In a year-long remote camera survey in Southern Bolivia, we identified 29 medium to large mammal species, 18 outside their known distribution ranges. While overall species richness remained stable, photographic records varied between seasons. Capture rates, reflecting species richness and abundance, were more influenced by season and habitat. Wet season rates were lower, but higher in all other habitats compared to the mountain bush and grasslands. Rates increased with altitude and distance to hiking trails, but decreased with increasing distance from main roads. Medium to large mammals were more active during the dry season, indicating adjustments in response to seasonal changes. Our results suggest a cumulative impact of various factors beyond mere seasonality, and call for adjustments in global species distributions. Moreover, emphasize the need for biodiversity monitoring in dry forest habitats, particularly regarding responses to environmental shifts and human-induced alterations.

Seasonal variations in drag coefficient of salt marsh vegetation

Understanding the seasonal variations of vegetation drag coefficients is crucial for improving wave attenuation predictions and adapting to climate impacts. This study explores the seasonal changes in drag coefficients within salt marsh vegetation, using data from a year-long series of field measurements at the Chongming Dongtan Wetland. It uncovers the complex seasonal variations of drag coefficients. Results demonstrate that incorporating a nonlinear equation for characteristic flow velocity and effective vegetation length significantly improves the precision of drag coefficient predictions, ensuring a closer match with field observations. Furthermore, it introduces a refined drag coefficient formula that incorporates adjustments for vegetation stiffness and relative submergence, offering a more accurate representation of the seasonal variability in drag forces exerted by salt marsh vegetation. This enhanced formula is crucial for accurately assessing vegetation's role in wave attenuation, providing critical insights for the design and implementation of coastal defense and wetland conservation initiatives.

Succession and seasonality of a Brazilian secondary tropical dry forest: Phenology and climate moderation

With large tracts of Tropical Dry Forests (TDF) in the Americas previously deforested, many places are currently undergoing secondary ecological succession. These processes vary in time and space, creating a landscape with forests of different ages or successional stages. These secondary forests need moreneed more understanding about how their ecosystem functionality is restored and recovering along the succession path. In particular, it is poorly understood how different successional stages moderate extremes of Essential Climatic Variables (ECV) such as temperature, relative humidity, soil moisture, and the fraction of Absorbed Photosynthetic Active Radiation (fAPAR). This paper, therefore, studies the linkages between high temporal resolution tower-based optical canopy phenology time series and seasonal changes in local ECV conditions between early (10–12 years) and late (50+ years) successional stage TDF in southeastern Brazil. We compare diurnal and seasonal patterns of understory ECVs between early/late plots and investigate the canopy’s Climate Moderating Capacity (CMC). Our data indicate at least 100 mm of precipitation within two weeks is necessary to initiate leaf flushing in this TDF. We also find that soil moisture and daytime air humidity strongly correlate (R2 > 0.75) with seasonal patterns in canopy vegetation greenness indices and fAPAR with a cross-correlation time lag peak of 12–15 days. Our results suggest that the late stage is more effective at cooling (−1.4 ± 0.6 °C vs −0.8 ± 0.6 °C) and reducing daytime evaporation (−0.41 ± 0.2 kPa vs −0.18 ± 0.12 °C) in the understory during the growing season than the early stage. Results suggest that the CMC varies with seasonal canopy leaf area dynamics and with heat and moisture scales, becoming significantly stronger when temperatures and vapour pressure deficits were highest, and correlated strongly with canopy fAPAR dynamics (R2 = 0.82). These findings demonstrate that TDFs can effectively regain microclimatic buffering capacity.