Seasonal Growth Cycle Research Articles

Water Composition, Biomass, and Species Distribution of Vascular Plants in Lake Agmon-Hula (LAH) (1993–2023) and Nearby Surroundings: A Review

A significant change to the land cover in the Hula Valley was carried out during the 1950s: A swampy area densely covered by aquatic vegetation and the old shallow lake Hula were drained. The natural shallow lake and swamps land cover were converted into agricultural development land use in two stages: (1) Drainage that was accomplished in 1957; (2) Implementation of the renovated hydrological system structure, including the newly created shallow Lake Agmon-Hula (LAH), was completed in 2007. The long-term data record of the restored diversity of the submerged and emerged aquatic plant community, and its relation to water quality in the newly created shallow Lake Agmon-Hula LAH, was statistically evaluated. Internal interactions within the LAH ecosystem between aquatic plants and water quality, including nitrification, de-nitrification, sedimentation, photosynthetic intensity, and plant biomass and nutrient composition, were statistically evaluated. The plant community in LAH maintains a seasonal growth cycle of onset during late spring–summer and dieback accompanied by decomposed degradation during fall–early winter. The summer peak of aquatic plant biomass and consequent enhancement of photosynthetic intensity induces a pH increase during daytime and carbonate precipitation. Nevertheless, the ecosystem is aerobic and sulfate reduction and H2S concentration are negligible. The Hula reclamation project (HP) is aimed at the improvement of eco-tourism’s integration into management design. The vegetation research confirms habitat enrichment.

Effects of Seasonal Variations in Seagrass Density and Storms on Sediment Retention and Connectivity Between Subtidal Flats and Intertidal Marsh

AbstractBoth submerged aquatic vegetation and salt marsh are important coastal ecosystems known for their effectiveness in sediment trapping and carbon burial. However, their proximity can lead to competition for limited sediment resources, potentially compromising their capacity to facilitate sufficient sediment deposition to withstand sea‐level rise. Here we applied the Delft3D flow and sediment transport model in a shallow coastal bay to assess how seasonal variations in seagrass density and storms modulate sediment retention and connectivity between subtidal flats and intertidal marsh. Results show that submerged seagrass meadows acted as temporary storage for fine sediment and altered the timing of sediment transport to an adjacent marsh through seasonal growth cycles. When seagrass occupied subtidal flats, sediment flux to the marsh was controlled by seasonal seagrass density variations, with peak fluxes during winter senescence. In contrast, wave‐induced sediment resuspension on the flats was the major contributor for marsh sediment input in the simulation with no seagrass, with peak storm‐driven fluxes in summer/autumn. Overall, seagrass meadows significantly increased annual sediment accumulation on the vegetated subtidal flats by tenfold, while reducing annual marsh sediment flux and edge erosion by 20%. Seagrass meadows and marsh were both able to maintain a sediment deposition rate comparable to the rapid sea‐level rise at the study site despite the absence of terrestrial sediment sources. Our findings highlight the strong seasonal control subtidal aquatic vegetation has in the vertical and horizontal dynamics of tidal flat‐marsh systems and provide insights that can inform wetland restoration and management strategies in similar systems.

Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl.)

The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year. Vegetative growth dominates from spring to late summer when terminal buds bloom as panicles. Thus, its floral buds do not undergo winter dormancy until flowering, but a summer heat period of dormancy is required for floral bud differentiation, and that is why we used loquat to study the mechanism by which this summer rest period contributes to floral differentiation of Rosaceae species. As for the deciduous species, the bud transition to the generative stage is initiated by the floral integrator genes. There is evidence that combinations of environmental signals and internal cues (plant hormones) control the expression of TFL1, but the mechanism by which this gene regulates its expression in loquat needs to be clarified for a better understanding of its floral initiation and seasonal growth cycles. Under high temperatures (>25ºC) after floral bud inductive period, EjTFL1 expression decreases during meristem transition to the reproductive stage, and the promoters of flowering (EjAP1 and EjLFY) increase, indicating that the floral bud differentiation is affected by high temperatures. Monitoring the apical meristem of loquat in June-August of two consecutive years under ambient and thermal controlled conditions showed that under lower temperatures (<25ºC) during the same period, shoot apex did not stop growing and a higher EjTFL1 expression was recorded, preventing the bud to flower. Likewise, temperature directly affects ABA content in the meristem paralleling EjTFL1 expression, suggesting signaling cascades could converge to refine the expression of EjTFL1 under specific conditions (Tª<25ºC) during the floral transition stage.

Diverging Northern Hemisphere Trends in Meteorological Versus Ecological Indicators of Spring Onset in CMIP6

AbstractPlant phenology regulates the carbon cycle and land‐atmosphere coupling. Currently, climate models often disagree with observations on the seasonal cycle of vegetation growth, partially due to how spring onset is measured and simulated. Here we use both thermal and leaf area index (LAI) based indicators to characterize spring onset in CMIP6 models. Although the historical timing varies considerably across models, most agree that spring has advanced in recent decades and will continue to arrive earlier with future warming. Across the Northern Hemisphere for the periods 1950–2014, 1981–2014, and 2015–2099 in the historical and SSP5‐8.5 simulations, thermal‐based indicators estimate spring advances of −0.7 ± 0.2, −1.4 ± 0.4, and −2.4 ± 0.7 days/decade, while LAI‐based indicators estimate −0.4 ± 0.3, −0.1 ± 0.3, and −1±1.1 days/decade. Thereby, LAI‐based indicators exhibit weaker trends toward earlier onset, leading to uncertainties from different indices being as large or larger than model uncertainty. Reconciling these discrepancies is critical for understanding future changes in spring onset.

An Overview of Extreme Years in Quercus sp. Tree Ring Records from the Northern Moldavian Plateau

In this study, we made use of a regional oak tree-ring network from six stands that cover the northern Moldavian Plateau (eastern Europe) to analyze how different tree ring parameters (i.e., early wood tree-ring width, late wood tree-ring width, and total tree-ring width) of Quercus sp. are influenced by the occurrence of extreme climatic events (e.g., long-lasting drought events). In order to explore the influence of extreme hydroclimatic events on tree ring width, we have selected each of the six most extreme positive and negative years of tree growth and addressed the seasonal cycle of tree growth in comparison with the main climatic parameters, then evaluated both the current and lagged consequences of extreme hydroclimatic events on tree ring width and the capacity of trees to recover. Our results indicate that the variability of oak tree ring width from the Moldavian Plateau is mainly influenced by the availability of water resources, and that an important limiting growth factor for Quercus sp. is the occurrence of long-lasting drought events, e.g., at least two years in a row with severe drought conditions.

Soil Moisture Mapping Along Climatic Gradient by Dual-Polarization Sentinel-1 C-Band Data

Soil moisture plays an important role in agriculture, hydrology, plants’ seasonal growth cycle, and their sustainability under climate change. This letter presents a novel method for regional mapping of soil moisture with partial vegetation cover by using dual-polarized Sentinel-1 C-band SAR data. Model-based retrieval of soil moisture from radar backscatter under partial vegetation cover first necessitates the separation of the backscatter of the underlying soil from total radar backscatter and then the implementation of an inversion technique to estimate its soil moisture content from the backscattering coefficient of the underlying soil. The regional mapping of soil moisture was verified with in situ measurements along a climatic gradient (650–100 mm/year) in central Israel. A good agreement between the estimated soil moisture and the measured from ground samples was found, with an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula> of 0.793 with an RMSE of 0.047.

Spatio-temporal analysis of the environmental ranges and phenotypic traits of Zostera muelleri subpopulations in Central Queensland

Intraspecific variation in phenotypic traits of seagrasses enables populations to tolerate varying environmental conditions and facilitates population persistence and expansion. Significant variation in seagrass population morphometrics may reflect highly plastic responses to abiotic and biotic factors, allowing populations to acclimate to changing environmental conditions. Alternatively, morphological variation may arise from developmental canalisation or genetically determined fixed traits, which may inhibit future plasticity and adaptive flexibility to changing environmental conditions. Understanding the drivers behind intraspecific variation in phenotypic traits is important for seagrass restoration practitioners when identifying populations that may provide suitable donor propagules with high adaptability to new sites or propagules that may be more resilient to future environmental changes. This study aimed to investigate whether variation in morphological traits of four subpopulations of Zostera muelleri on the Curtis Coast of the Great Barrier Reef World Heritage Area, Queensland, correlated with meadow-specific environmental conditions and whether this varied between seasons. Morphometric analysis was conducted on Z. muelleri apical shoots, sampled during the spring growing/flowering season and autumn senescent season. Meadow-specific environmental conditions were assessed using historical data dating back to 2008 and environmental simulation models developed for predicting wave, and light conditions. Results indicated that Z. muelleri subpopulations exhibited distinct morphologies throughout their seasonal growth cycle that may correlate with meadow-specific differences in sediment composition, hydrodynamic stress, and light availability. However, further investigation is required to understand if expressed morphological traits are reflective of environmentally driven phenotypic plasticity or genetically predetermined fixed traits (local adaptation or developmental canalisation). Knowledge gained from further studies into the drivers behind the observed variations in morphological traits would increase the understanding of the importance of trait-based selection of propagules for seagrass restoration meadows’ resilience and persistence.

Growth of alpine grassland will start and stop earlier under climate warming

Alpine plants have evolved a tight seasonal cycle of growth and senescence to cope with a short growing season. The potential growing season length (GSL) is increasing because of climate warming, possibly prolonging plant growth above- and belowground. We tested whether growth dynamics in typical alpine grassland are altered when the natural GSL (2–3 months) is experimentally advanced and thus, prolonged by 2–4 months. Additional summer months did not extend the growing period, as canopy browning started 34–41 days after the start of the season, even when GSL was more than doubled. Less than 10% of roots were produced during the added months, suggesting that root growth was as conservative as leaf growth. Few species showed a weak second greening under prolonged GSL, but not the dominant sedge. A longer growing season under future climate may therefore not extend growth in this widespread alpine community, but will foster species that follow a less strict phenology.

Spatio-temporally varying Strickler coefficient: A calibration approach applied to a Danish river using in-situ water surface elevation and UAS altimetry

Hydraulic roughness (e.g., expressed in terms of Manning’s or Strickler’s coefficient) is an essential input to numerical hydrodynamic models. One way to estimate roughness parameters is by hydraulic inversion, using observed water surface elevation (WSE) collected from gauging stations, satellite platforms, or Unmanned Aerial System (UAS) altimeters. Specifically, UAS altimetry provides close to instantaneous observations of longitudinal profiles and seasonal variations of WSE for various river types, which are helpful for calibrating roughness parameters. However, it is computationally expensive to run high-resolution hydrodynamic models thousands to millions of times as required for the global optimization of distributed parameter sets (e.g., spatio-temporally varying river roughness).This study presents an efficient calibration approach for hydrodynamic models using a simplified steady-state hydraulic solver, UAS altimetry datasets, and in-situ observations. The calibration approach minimized the weighted sum of a misfit term, spatial smoothness penalty, and an a-priori sinusoidal temporal variation constraint. The approach was first demonstrated for several synthetic calibration experiments, and the results indicated that the global search algorithm accurately recovered the variations of Strickler coefficient (Ks) for short river reaches in temporal (due to the seasonal growth cycle of the aquatic vegetation) and spatial (e.g., due to spatially variable density of submerged vegetation) scales. Subsequently, the calibration approach was demonstrated for a real WSE dataset collected at a Danish test site (Vejle Å). In this river, friction is dominated by submerged vegetation growing in the stream and shows strong seasonal and longitudinal variations due to the plant growth cycle and variable vegetation density and species composition. Results indicated that spatio-temporal variation of Ks was required to fit in-situ observations and UAS altimetry accurately. This study illustrates how UAS altimetry and hydrodynamic modeling can be combined to achieve an improved understanding and better parameterization of small and medium-sized rivers, where river channel conveyance is controlled by vegetation growth and other spatio-temporally variable factors.

Revisiting Biological Nitrogen Fixation Dynamics in Soybeans.

Biological nitrogen (N) fixation is the most relevant process in soybeans (Glycine max L.) to satisfy plant N demand and sustain seed protein formation. Past studies describing N fixation for field-grown soybeans mainly focused on a single point time measurement (mainly toward the end of the season) and on the partial N budget (fixed-N minus seed N removal), overlooking the seasonal pattern of this process. Therefore, this study synthesized field datasets involving multiple temporal measurements during the crop growing season to characterize N fixation dynamics using both fixed-N (kg ha−1) and N derived from the atmosphere [Ndfa (%)] to define: (i) time to the maximum rate of N fixation (β2), (ii) time to the maximum Ndfa (α2), and (iii) the cumulative fixed-N. The main outcomes of this study are that (1) the maximum rate of N fixation was around the beginning of pod formation (R3 stage), (2) time to the maximum Ndfa (%) was after full pod formation (R4), and (3) cumulative fixation was positively associated with the seasonal vapor-pressure deficit (VPD) and growth cycle length but negatively associated with soil clay content, and (4) time to the maximum N fixation rate (β2) was positively impacted by season length and negatively impacted by high temperatures during vegetative growth (but positively for VPD, during the same period). Overall, variation in the timing of the maximum rate of N fixation occurred within a much narrower range of growth stages (R3) than the timing of the maximum Ndfa (%), which varied broadly from flowering (R1) to seed filing (R5–R6) depending on the evaluated studies. From a phenotyping standpoint, N fixation determinations after the R4 growth stage would most likely permit capturing both maximum fixed-N rate and maximum Ndfa (%). Further investigations that more closely screen the interplay between N fixation with soil-plant-environment factors should be pursued.

EVALUATION OF INTRODUCED GENOTYPES OF GENUS ACTINIDIA LIND L. AFTER THE VEGETATION PERIOD FOR THE PURPOSE OF USE IN GREENING RIGHT-BANK FOREST STEPPE OF UKRAINE

The article analyzes the results of phenological observations on the growth and development of parental plants of introduced varieties of Аctinidia (Actinidia Lindl.) And identifies the importance of agroclimatic and phenological observations for their cultivation in the Right Bank Forest-Steppe of Ukraine. The correspondence of the phases of growth and development of Аctinidia cultivars with the weather conditions of the Right-Bank Forest-Steppe of Ukraine has been studied. Climatic features and weather conditions (changes in the amount of heat, precipitation, moisture, wind strength, clouds, etc.) during the growing season of actinidia plants of the studied varieties significantly affect their vegetative and reproductive productivity. Peculiarities of seasonal development of Аctinidia cultivars are clarified and terms of passing of phenological phases of seasonal cycle of growth and development of uterine plants which are characterized by high vegetative productivity, which is a biological basis for root reproduction are considered. The most popular for landscaping and use in ornamental horticulture varieties of Аctinidia (Actinidia Lindl.) Are summarized and recommended for cultivation in soil and climatic conditions of the Right-Bank Forest-Steppe of Ukraine. Observation of the growing season and the accompanying weather conditions makes it possible to correctly apply agro-technological measures for growing Аctinidia plants in parks and landscapes. The decorative properties of the studied varieties are determined, the success of the introduction is assessed and practical recommendations for their use in the green construction of the Right-Bank Forest-Steppe of Ukraine are offered.

Seasonally related metabolic changes and energy allocation associated with growth and reproductive phases in the liver of male goldfish (Carassius auratus)

Reproduction and growth follow a seasonal pattern in many fish species involving changes in gonadal development, growth, and metabolism. Significant metabolic energy is needed during gametogenesis in both female and male to produce hundreds of eggs and billions of sperms. Seasonal variations are controlled by the hormones of brain-pituitary-peripheral axis and are accompanied by significant metabolic changes. There is evidence that GnRH and GnIH are among the key neurohormones that regulate the reciprocal control of growth and reproduction. The objective of this study was to investigate changes in metabolic profile and energy allocation patterns at different stages of reproduction, using goldfish as a model organism and LC-MS as analytical platform for metabolic analysis. Goldfish undergoes a clear seasonal cycle of growth and reproduction. In vivo experiments were conducted at three different time point of the annual cycle: regressed gonadal phase (peak growth phase), mid gametogenesis and late gametogenesis. Emphasis is placed on changes in liver metabolic pathways to energetically sustain the physiological processes related to growth and reproduction. Moreover, we tested the hypothesis that GnRH and GnIH may play a role in the regulation of metabolism by investigating acute effects of these peptides at different stages of reproductive cycle. SignificanceThe findings in this paper provide novel information on the seasonal changes in basal metabolism during different stages of reproductive cycle, and evidence for differential allocation of energy during reciprocal control of reproduction and growth in goldfish. Chemometrics combined with pathway-driven bioinformatics elucidated a shift in the metabolic profile, indicating distinct patterns of energy allocation in the reproductive and growth seasons. Furthermore, to our knowledge this is the first study to provide evidence for a possible regulatory role of GnRH and GnIH in liver metabolism and energy allocation patterns associated with growth and reproductive processes. Together our findings present a framework for better understanding of the hormonally induced changes in metabolism to energetically sustain growth and reproduction in fish and other oviparous species undergoing seasonal cycle.

On tropical Drosera rotundifolia L.

Two aspects on the morphology and biology of the Philippine population of D. rotundifolia were not answered by Coritico and Fleischmann (2016), namely its seed morphology and seasonal growth cycle - especially regarding hibernaculum formation, as it is known from its temperate congeners. These gaps can now be covered from observations made from cultivated plants and shall be reported here. Further aspects on the biology of Philippine D. rotundifolia (and other tropical populations of temperate Drosera) in cultivation and natural habitat are presented.

The seasonal profile of proliferation and apoptosis in the prostate gland of the wild ground squirrel (Spermophilus dauricus)

The seasonal cycle of growth and regression in the prostate gland of wild ground squirrel provide a unique research model to understand the morphological changes of prostate glands. Our previous studies showed that the local production of dihydrotestosterone could affect the morphology and function of the prostate gland in either an autocrine or paracrine manner. In the present study, we attempted to gain more insight into this process by investigating the expression of key factors implicated in cell proliferation, apoptosis, and the cell cycle, including mechanistic target of rapamycin (mTOR), cyclin-D2, p21, p27 and retinoblastoma 1 (pRB). Morphological and histological observations confirmed that the prostate increased significantly in both size and weight during the breeding season. Positive immunostaining for proliferating cell nuclear antigen (PCNA) was mainly localized to the prostate epithelial cells during the breeding season, which is significantly higher in the prostate gland during the breeding season (2470 ± 81/mm2) than that in the nonbreeding season (324 ± 54/mm2). However, there was no significant difference in the prostate gland when compared between the breeding and nonbreeding seasons, with regards to TUNEL staining. Moreover, cell cycle regulators were mainly localized to the epithelial cells, including mTOR, cyclin-D2, p21, p27 and pRB. the immunostaining of mTOR and cyclin D2 were stronger during the breeding season, whereas the immunostaining of p27 and pRB were stronger during the nonbreeding season. The mRNA expression levels of mTOR, cyclin D2, and PCNA, were higher during the breeding season while those of p27 and p21 were higher during the nonbreeding season. Collectively, this study profiled the distinct expression pattern of key cell cycle regulators throughout the breeding and nonbreeding seasons. Collectively, these factors may play important roles in regulating the seasonal growth and regression of the prostatic epithelium in the wild ground squirrel.

Біологічні властивості та інтродукція представників роду Allium L у Кременецькому ботанічному саду

Розширення асортименту квітниково-декоративних рослин для ландшафтного проектування сьогодні актуальне в усьому світі, зокрема і в Україні. Найбільш ефективні методи вирішення цього питання – інтродукція представників роду Allium L., вивчення їх еколого-біологічних особливостей, стійкості в культурі. Представники роду Allium L. здавна відомі своїми декоративними якостями та лікувальними властивостями. Колекція представників роду Allium Кременецького ботанічного саду нараховує 10 видів (Allium giganteum Regel, Allium schubertii Zucc., Allium karataviense Regel, Allium odorum L., Allium molly L., Allium nutans L., Allium scorodoprasum L., Allium sphaerocephalon L., Allium oreophilum C. A. Mey, Allium montanum F.W. Schmidt), гібрид (Allium azureum), 2 форми (Allium schoenoprasum cv ‘blooming’, Allium schoenoprasum cv ‘snowcap’) та 3 сорти (Allium ‘Hair’, Allium ‘Powder purf’, Allium ‘Miami’). Інтродуценти послужили об’єктами досліджень з огляду на декоративні ознаки та доцільність їх використання в озелененні. Згідно з аналізом фенологічних спостережень фаза бутонізації наступила у всіх 15 видів, найперше була зафіксована 22 квітня в A. ‘Powder purf’, 26 квітня – A. schoenoprasum cv ‘blooming’, A. schoenoprasum cv ‘snowcap’, A. karataviense, найпізніше 8 липня – A. odorum, A. nutans, A. montanum. Найперше зацвіла A. ‘Powder purf’, A. karataviense, A. schoenoprasum cv ‘snowcap’, A. giganteum – 13 травня, найпізніше зацвіли A. nutans, A. odorum – 5 серпня. Найдовша фаза цвітіння відзначена у видів: A. sphaerocephalon, Allium ‘Hair’ – 46 днів, найкоротша фаза цвітіння в A. molly (13 днів). Дані про особливості сезонного циклу росту і розвитку, строки цвітіння мають практичне значення для озеленення при створенні квітникових композицій.

Seasonal Zinc Storage and a Strategy for Its Use in Buds of Fruit Trees.

Bud dormancy allows deciduous perennial plants to rapidly grow following seasonal cold conditions. Although many studies have examined the hormonal regulation of bud growth, the role of nutrients remains unclear. Insufficient accumulation of the key micronutrient zinc (Zn) in dormant buds affects the vegetative and reproductive growth of perennial plants during the subsequent year, requiring the application of Zn fertilizers in orchard management to avoid growth defects in fruit trees. However, the mechanisms of seasonal Zn homeostasis in perennial plants remain poorly understood. Here, we provide new insights into Zn distribution and speciation within reproductive and vegetative buds of apple (Malus domestica) and four other deciduous fruit trees (peach [Amygdalus persica], grape [Vitis vinifera], pistachio [Pistacia vera], and blueberry [Vaccinium spp.]) using microscopic and spectroscopic characterization techniques comprising synchrotron-based x-ray fluorescence and x-ray absorption near-edge-structure analyses. By establishing a link between bud development and Zn distribution, we identified the following important steps of Zn storage and use in deciduous plants: Zn is preferentially deposited in the stem nodes subtending apical and axillary buds; Zn may then be sequestered as Zn-phytate prior to dormancy; in spring, Zn effectively releases for use during budbreak and subsequent meristematic growth. The mechanisms of Zn homeostasis during the seasonal cycles of plant growth and dormancy described here will contribute to improving orchard management, and to selection and breeding of deciduous perennial species.

Model simulation of seasonal growth of Fucus vesiculosus in its benthic community

AbstractNumerical models are a suitable tool to quantify impacts of predicted climate change on complex ecosystems but are rarely used to study effects on benthic macroalgal communities. Fucus vesiculosus L. is a habitat‐forming macroalga in the Baltic Sea and alarming shifts from the perennial Fucus community to annual filamentous algae are reported. We developed a box model able to simulate the seasonal growth of the Baltic Fucus–grazer–epiphyte system. This required the implementation of two state variables for Fucus biomass in units of carbon (C) and nitrogen (N). Model equations describe relevant physiological and ecological processes, such as storage of C and N assimilates by Fucus, shading effects of epiphytes or grazing by herbivores on both Fucus and epiphytes, but with species‐specific rates and preferences. Parametrizations of the model equations and required initial conditions were based on measured parameters and process rates in the near‐natural Kiel Outdoor Benthocosm (KOB) experiments during the Biological Impacts of Ocean Acidification project. To validate the model, we compared simulation results with observations in the KOB experiment that lasted from April 2013 until March 2014 under ambient and climate‐change scenarios, that is, increased atmospheric temperature and partial pressure of carbon dioxide. The model reproduced the magnitude and seasonal cycles of Fucus growth and other processes in the KOBs over 1 yr under different scenarios. Now having established the Fucus model, it will be possible to better highlight the actual threat of climate change to the Fucus community in the shallow nearshore waters of the Baltic Sea.

Decoupling seasonal and temporal dynamics of macroalgal canopy cover in seagrass beds

Many seagrass habitats are susceptible to undesirable macroalgal overgrowth in response to growing watershed development, but the mechanisms leading to overgrowth remain unresolved. Partitioning the influences of intermittent seasonal cycles and directional human stressors is one main challenge. We examined the dynamics of macroalgal canopies within Halodule uninervis beds across a 10-year period in a tropical lagoon and first hypothesized that seasonal and temporal variances were distinguishable. We found that cooler and dryer winter months were consistently associated with blue-green algal canopies, mainly Lyngbya sp. and Phormidium sp., with an inverse relationship between sea-surface temperatures and coverage. For example, given that winter temperatures during the coolest month of February ranged between ±1.0 °C of the mean over the past decade, the expected coverage of blue-green algae shifted by ±15%. In contrast, the warmer and wetter summer months were associated with red algae canopies, predominantly Acanthophora spicifera, which were positively related to rainfall. Last, a weaker seasonal trend existed between some green and brown algae and a tidal-height proxy to groundwater discharge where karst watersheds existed. We next hypothesized that removing the variances associated with seasonal growth cycles in the differing phyla would reveal temporal trends in total macroalgal persistence associated with watershed development that were otherwise masked. Following seasonal adjustments, we found that persistent macroalgal canopies existed in the central, urbanized lagoon over the past decade; however, when moving to the north or south of the urban center, significant increases in macroalgal canopies were revealed. Watershed size and development were the strongest predictors of seasonally-adjusted macroalgal canopies through time. No similar trends were found when using unadjusted macroalgal cover data. More importantly, predictions were used to determine thresholds in watershed development associated with the transition between seagrass-versus-macroalgal dominance. The results offered a novel approach for ecological studies that may be limited by financial and logistical constraints to partition seasonal versus temporal change, and better appreciate their differences. For our study lagoon, the results unmasked a growing human footprint into seagrass beds and identified predictive thresholds for management to consider.

Antarctic Seasonal Sea Ice Melts Faster Than It Grows

Winds are thought to play a significant role in driving the asymmetric seasonal cycle of Antarctic sea ice growth and melt.

Consistency Between NASS Surveyed Soil Moisture Conditions and SMAP Soil Moisture Observations

AbstractThe U.S. Department of Agriculture National Agricultural Statistics Survey (NASS) collects and publishes crop growth status and soil moisture conditions in major U.S. agricultural regions. The operationally produced weekly reports are based on survey information. The surveys are based on visual assessments and—in the case of soil moisture—report soil moisture levels in one of four categories (Very Short, Short, Adequate, and Surplus). In this study, we show that these reports have remarkable correspondence with the National Aeronautics and Space Administration Soil Moisture Active Passive (SMAP) Level‐4 Soil Moisture (L4SM) product. This consistency allows for combining the two different types of data to produce a value‐added assessment, which enables cropland soil moisture mapping and state‐level statistics. Moreover, it enables daily assessment rather than weekly. In this study classification thresholds are derived for L4SM by mapping cumulative distribution functions of L4SM surface and root zone SM to the categorical NASS SM conditions. The results show that, year over year, the SMAP cumulative SM distributions are consistent with the NASS SM conditions and, furthermore, that the temporal evolution of the SMAP‐derived thresholds is consistent with the seasonal crop growth cycles from year to year. The results signify that the SMAP SM retrievals are relatable to SM estimation conducted in agricultural crop land by land managers and farmers, which underlines the general applicability of the SMAP data.