Drought Periods Research Articles

The Association of Drought with Different Precipitation Grades in the Inner Mongolia Region of Northern China

Drought has become an important factor affecting the environment and socio-economic sustainable development in northern China due to climate change. This study utilized the Standardized Precipitation Index (SPI) as a drought metric to investigate the correlation between drought characteristics and different grades of precipitation and rain days. The analysis was based on a long-term time series of precipitation data obtained from 116 meteorological stations located in Inner Mongolia, spanning 1960 to 2019. To achieve the objectives of the current research, the daily precipitation was categorized into four grades based on the “24-h Precipitation Classification Standard”, and the frequency of rain days for each grade was determined. Subsequently, the SPI was calculated for 1 and 12 months, enabling the identification of drought events. The results revealed pronounced spatiotemporal regional variations and complexities in the dry–wet climatic patterns of Inner Mongolia, with significant decreases in precipitation emerging as the primary driver of drought occurrences. Approximately 6% of the entire study period experienced short-term drought, while long-term drought periods ranged from 23% to 38%. Regarding multi-year trends, precipitation exhibited a weak increasing trend, while rain days exhibited a weak decreasing trend. Drought exhibited an alleviating trend, with 92% of stations displaying coefficients > 0 for SPI_Month and over 62% of stations displaying coefficients > 0 for SPI_Year. At the monthly scale, drought was most correlated with light rainfall trends and least correlated with moderate rainfall trends. At the annual scale, drought was relatively highly correlated with moderate and heavy rainfall distributions but poorly correlated with light rainfall. The results suggested that achieving the precise monitoring and mitigation of drought disasters in Inner Mongolia in the future will require a combined analysis of indicators, including agricultural drought, hydrological drought, and socio-economic drought. Such an approach will enable a comprehensive analysis of drought characteristics under different underlying surface conditions in Inner Mongolia.

Small Farmers’ Agricultural Practices and Adaptation Strategies to Perceived Soil Changes in the Lagoon of Venice, Italy

Farmers have a pivotal responsibility in soil conservation: they can either preserve or deplete it through their choices. The responsibility of agriculture increases when practised in delicate ecosystems, such as lagoonal ones. The Venetian Lagoon islands, which are increasingly subjected to natural and anthropic subsidence, occasional flooding events (acqua alta), and eustatic sea level rise, are constantly exposed to erosive processes that challenge farmers to play with their adaptive capability. This research was carried out on the islands of Sant’Erasmo and Vignole, the most representative of island agriculture in the Venetian Lagoon: they almost exclusively rely on agriculture, which is non-existent in the other islands. This empirical research aimed to explore farmers’ agricultural practices, perceptions of soil changes, and how they adapt to them. It was fundamental for this study that the field research involved direct human contact with farmers (through semi-structured interviews) for data collection and using qualitative methods for data analysis, integrating scientific and non-scientific forms of knowledge and actors. The final purpose was to demonstrate the sustainability (valued on the potential depletion or regeneration capability) of agricultural practices and adaptation strategies on a theoretical basis. Despite their polycultural landscape (maintained by low-input farming systems), escaped from the predominant landscape oversimplification, Sant’Erasmo and Vignole are also subjected to unsustainable agricultural practices, including heavy mechanisation and synthetic inputs. Coupled with natural soil salinity that is exacerbated by increasing drought periods, these practices can contribute to soil degradation and increased salinity. The reported adaptation strategies, such as zeroed, reduced, or more conscious use of machines, were guided by the need to reduce the negative impact of soil changes on productivity. Our research revealed some of them as sustainable and others as unsustainable (such as increasing irrigation to contrast soil salinity). Participatory action research is needed to support farmers in designing effective sustainable agricultural practices and adaptation strategies.

Climate Response and Radial Growth Dynamics of Pedunculate Oak (Quercus robur L.) Plus Trees and Their Half-Sib Progeny in Periods of Severe Droughts in the Forest-Steppe Zone of Eastern Europe

The dendrochronological parameters of 97 pedunculate oak (Quercus robur L.) trees including 20 plus trees (142-year-old on average) and four half-sib families for four of them were analyzed considering also specifically years of the most severe droughts that were identified using average monthly air temperature and precipitation data. The tree-ring width (TRW) was mostly affected by air temperature that had the largest cross-dating indices (CDI), up to 78% maximum. However, the 32-year Brückner–Egeson–Lockyer cycle (a climatic cycle of approximately 30–40 years that correlates with sunspot activity) was more reflected in the TRW dynamics in plus trees than precipitation and air temperature. A high-frequency of abnormal TRW was clearly observed during drought periods and in the following 2–3 years. Tree radial-growth reduction due to drought stress varied significantly between families. The resistance to drought based on TRW was higher in the maternal plus oak trees than in progeny. Drought resulted in reduced growth during the subsequent year(s); hence, the minimum growth occurred after the actual climate event. Autumn–winter precipitation and weather conditions were of the greatest importance at the onset of active vegetation in April and May. The influence of air temperature on oak growth was the largest in March (r = 0.39, p < 0.05). The strongest positive correlation between precipitation and growth (with r up to 0.38) was observed in May 2023. Plus trees had a high adaptive potential due to the stability of radial growth during drought with high resistance (Rt = 1.29) and resilience (Rs = 1.09) indexes. The offspring of families 1 (Rt = 0.89, Rs = 0.89) and 2 (Rt = 1.04, Rs = 0.87) had similar resistance and resilience, but the recovery indices (Rc) for offspring in families 1, 2 and 3 exceeded the recovery values for plus trees. For offspring in families 3 and 4, the index values were lower. The revealed responses of wood growth of plus trees to climatic parameters estimated as resistance (Rt), resilience (Rs) and recovery (Rc) indexes and similar responses in their progeny can be used in breeding pedunculate oak for wood growth productivity and drought resistance.

Extreme Precipitation Events During the Wet Season of the South America Monsoon: A Historical Analysis over Three Major Brazilian Watersheds

Most of South America, particularly the region between the southern Amazon and southeastern Brazil, as well as a large part of the La Plata Basin, has its climate regulated by the South American Monsoon System. Extreme weather and climate events in these areas have significant socioeconomic impacts. The Madeira, São Francisco, and Paraná river basins, three major watersheds in Brazil, are especially vulnerable to wet and drought periods due to their importance as freshwater ecosystems and sources of water for consumption, energy generation, and agriculture. The scarcity of surface meteorological stations in these basins makes meteorological studies challenging, often using reanalysis and satellite data. This study aims to identify extreme weather (wet) and climate (wet and drought) events during the extended wet season (October to March) from 1980 to 2022 and evaluate the performance of two gridded datasets (CPC and ERA5) to determine which best captures the observed patterns in the Madeira, São Francisco, and Paraná river basins. Wet weather events were identified using the 95th percentile, and wet and drought periods were identified using the Standardized Precipitation Index (SPI) on a 6-month scale. In general, CPC data showed slightly superior performance compared to ERA5 in reproducing statistical measures. For extreme day precipitation, both datasets captured the time series pattern, but CPC better reproduced extreme values and trends. The results also indicate a decrease in wet periods and an increase in drought events. Both datasets performed well, showing they can be used in the absence of station data.

Hydraulic and structural traits of trees across light gradients in the Amazon secondary forest.

Amazonian species are generally unable to adapt to long drought periods, indicating a low capacity to adjust their hydraulic traits. Secondary forests account for 20% of forest cover in the Amazon, making natural regeneration species crucial under climate change scenarios. In this study, we compared the hydraulic traits of five species, including non-pioneers (Bertholletia excelsa Bonpl., Carapa guianensis Aubl., Hymenaea courbaril L.) and pioneers (Cedrela fissilis Vell., Tabebuia rosea (Bertol.) Bertero ex A.DC.), across light conditions (understory, intermediate, gap) in a 22-year-old secondary forest in Central Amazon, Brazil. Twenty-five saplings were planted and monitored in 3 plots × 5 blocks. Five years after the plantation, we assessed growth, wood density, leaf water potential at predawn and midday, xylem embolism resistance (P50), and hydraulic safety margins (HSM). Leaf water potential ranged from -2.9 to 0MPa. The non-pioneer species C. guianensis and H. courbaril exhibited the lowest P50 (-4.06MPa), indicating higher embolism resistance, whereas the pioneer T. rosea had the highest P50 (-1.25MPa), indicating lower resistance. HSM varied from -1.60 to 3.26MPa, with lower values in gap conditions during the dry period (-1.60MPa), especially affecting pioneer species. Wood density was influenced by both light and species type, with non-pioneers showing generally higher density, with H. courbaril reached 0.75gcm-3 in the understory while the pioneer T. rosea showed the lowest density (0.27gcm-3). These results highlight that light conditions affect hydraulic traits differently across species strategies, especially during early growth. Non-pioneer, slow-growing native species appear more resilient to light variation, making them suitable for future plantations aimed at climate adaptation in secondary forests.

Trunk climbing among ground-dwelling European amphibians – first observation from Poland

Most European amphibian species are considered land-dwelling, associated with moving along the ground and as poor climbers. However, more recent research indicates that non-arboreal amphibians use nesting boxes and tree hollows in Central and Western Europe. This study describes the first observation of tree climbing by the common toad Bufo bufo (Linnaeus, 1758) and common frog Rana temporaria Linnaeus, 1758 in Poland. While conducting a night survey of newt mortality in the ‘Traszki Ratajskie’ protected area in an urban park in the city of Poznań, Poland, we detected the unexpected use of trees by two species of amphibians. In June 2020, we observed cases of Bufo bufo and Rana temporaria foraging on and using arboreal ambush sites. The toads were found at an average height of 124 cm above the ground, and the frogs at 35 cm, on the tree trunks and branches of two willows (Salix cfr. alba L.) and a dead silver birch specimen (Betula pendula L.). The willows had an extensive multi-stem structure, and exhibited signs of maturity and ageing (hollow-bearing trees with open cavities and crevices). This is the first observation of arboreal behaviour in B. bufo and R. temporaria in Poland. The climbing behaviour and use of tree sites were likely linked to the search for a humid shelter provided by the interior of the ageing trees, as well as to the foraging behaviour that we observed. Trees exhibiting signs of maturity usually have complex structures, and seem particularly important for amphibians during periods of drought, as both a suitable shelter and an area from which to ambush prey. We recommend focusing greater attention on the protection of mature, ageing trees, especially Salix spp. within a terrestrial buffer zone of at least 250 metres from ponds, as these are poorly researched components within amphibian habitats. This type of resource may be essential for long-term amphibian conservation due to site fidelity and the limited number of shelters in human-altered landscapes. The recently adopted EU Nature Restoration Law presents an opportunity to develop good practices in this area, particularly urban tree planting and habitat management.

A full genome assembly reveals drought stress effects on gene expression and metabolite profiles in blackcurrant (Ribes nigrum L.)

Abstract Blackcurrant (Ribes nigrum L., family Grossulariaceae) is a perennial shrub that is widely cultivated for its edible berries. These are rich in antioxidants, vitamin C and anthocyanins, making them a valuable ingredient in the food and beverage industry. However, prolonged periods of drought during the fruiting season lead to drought stress, which has serious ecological and agricultural implications, inhibiting blackcurrant growth and reducing yields. To facilitate the analysis of underlying molecular processes, we present the first high-quality chromosome-scale and partially haplotype-resolved assembly of the blackcurrant genome (cv. Rosenthals Langtraubige), also the first in the family Grossulariaceae. We used this genomic reference to analyze the transcriptomic response of blackcurrant leaves and roots to drought stress, revealing differentially expressed genes with diverse functions, including those encoding the transcription factors bZIP, bHLH, MYB and WRKY, and tyrosine kinase-like kinases such as PERK and DUF26. Gene expression was correlated with the abundance of primary metabolites, revealing 14 with significant differences between stressed leaves and controls indicating a metabolic response to drought stress. Amino acids such as proline were more abundant under stress conditions, whereas organic acids were depleted. The genomic and transcriptomic data from this study can be used to develop more robust blackcurrant cultivars that thrive under drought stress conditions.

Subtle changes in topsoil microbial communities of drained forested peatlands after prolonged drought.

A major consequence of anthropogenic climate change is the intensification and extension of drought periods. Prolonged drought can alter conditions in drained peatlands and cause disturbances in microbial communities in the topsoil layer of the peat. Varying environmental conditions throughout the growing season, such as the availability of organic matter and nutrients, temperature and water table, further impact these communities and consequently affect carbon and nutrient cycles. The impact of drought and new forestry practices is largely unknown in drained peatland forests. We examined how microbial communities change over a growing season in different harvesting intensities (continuous cover forestry, clear-cut and uncut) in a drained peatland site using bacterial 16S and fungal ITS2 rRNA analysis. We found seasonal differences in bacterial and fungal diversity and species richness, and subtle changes in microbial communities at the phylum and genus levels when comparing various environmental factors. Diversity, species richness and relative abundance differed in spring compared to summer and autumn. However, significant differences in the microbial community structure were not detected. Understanding the responses of microbial communities to disturbances like drought and other environmental factors provides new insights into the consequences of climate change on drained forested peatlands.

Chlorophyll-Amended Organoclays for the Detoxification of Ochratoxin A

Climate change has been associated with outbreaks of mycotoxicosis following periods of drought, enhanced fungal growth, and increased exposure to mycotoxins. For detoxification, the inclusion of clay-based materials in food and drinking water has resulted in a very promising strategy to reduce mycotoxin exposure. In this strategy, mycotoxins are tightly sorbed to high-affinity clay particles in the gastrointestinal tract, thus decreasing bioavailability, uptake to blood, and potential toxicity. This study investigated the ability of chlorophyll and chlorophyllin-amended montmorillonite clays to decrease the toxicity of ochratoxin A (OTA). The sorption mechanisms of OTA binding to surfaces of sorbents, as well as binding parameters such as capacity, affinity, enthalpy, and free energy, were examined. Chlorophyll-amended organoclay (CMCH) demonstrated the highest binding (72%) and was better than the chlorophyllin-amended hydrophilic clay (59%), possibly due to the hydrophobicity of OTA (LogP 4.7). In silico studies using molecular dynamics simulations showed that CMCH improves OTA binding in comparison to parent clay in line with experiments. Simulations depicted that chlorophyll amendments on clay facilitated OTA molecules binding both directly, through enhancing OTA binding on the clay, or predominantly indirectly, through OTA molecules interacting with bound chlorophyll amendments. Simulations uncovered the key role of calcium ions in OTA binding, particularly in neutral conditions, and demonstrated that CMCH binding to OTA is enhanced under both neutral and acidic conditions. Furthermore, the protection of various sorbents against OTA-induced toxicity was carried out using two living organisms (Hydra vulgaris and Caenorhabditis elegans) which are susceptible to OTA toxicity. This study showed the significant detoxification of OTA (33% to 100%) by inclusion of sorbents. Organoclay (CMCH) at 0.5% offered complete protection. These findings suggest that the chlorophyll-amended organoclays described in this study could be included in food and feed as OTA binders and as potential filter materials for water and beverages to protect against OTA contaminants during outbreaks and emergencies.

Assessing climatic change impacts on mangrove structural dynamics on the northern coasts of the Persian Gulf

Abstract. Monitoring long-term trends in structural changes within mangrove ecosystems is essential for understanding their response to climate change and devising effective adaptation strategies in coastal regions. This study examines changes in mangrove patchiness within the Hara Biosphere Reserve (HBR) along the northern coasts of the Persian Gulf (PG) over a 31-year period (1986-2017), focusing on variations in rainfall patterns and drought occurrences. Employing a 35-year time series of monthly Standardized Precipitation Index (SPI) values alongside satellite imagery analysis, trends in both the number of patches (NP) and the Largest Patch Index (LPI) were assessed at the mangrove stand level. The analysis reveals a significant correlation between structural changes in mangroves and drought events. Pre-1998, characterized by wetter conditions, witnessed a decrease in both NP and LPI, indicating patch expansion and habitat extension. Conversely, post-1998, during drought periods, both indices increased, indicating habitat degradation due to heightened drought intensity. Pre-1998 structural changes in the HBR signify habitat expansion, with increased patch extent and core areas reflecting enhanced structural integrity. However, post-1998, a concerning trend of habitat degradation emerged, with increased NP and LPI attributed to intensified droughts. These findings highlight a transitional period marked by favourable conditions for mangrove growth followed by habitat degradation linked to increased drought intensity. This underscores the vulnerability of mangrove ecosystems to climate change impacts, particularly exacerbated droughts, necessitating urgent efforts for conservation and management to preserve biodiversity and ecosystem services in coastal regions.

Growth conditions but not the variety, affect the yield, seed oil and meal protein of camelina under Mediterranean conditions

European agriculture policies emphasize the importance of agricultural sustainability, focusing on increase of biodiversity through crop diversification. In Mediterranean dryland cropping systems, the introduction of crops in rotation with cereals is challenged by scarce precipitation and high evapotranspiration. In this scenario, camelina (Camelina sativa (L.) Crantz), a low-input annual oleaginous crop with a high morphological plasticity, short life cycle, and interesting oil and meal composition, could be an option to be included in rotation with winter cereals. The aim of this experiment was to study the agronomic performance, and seed oil and meal protein contents of camelina in two different climatic conditions, with a sowing delay in one of them. Several trials were conducted in Montargull (Mediterranean semihumid) and in Lleida (Mediterranean semiarid) in two seasons (2020–21 and 2021–22). In Montargull, two sowing dates (November, SD1 and January, SD2) were established. In each growing condition, three spring camelina varieties were sown (Calena, CO46 and GP204). Camelina was harvested between May and July, and yield and harvest index were measured. After cold pressing the seeds, seed oil and meal protein contents were analysed. Camelina yield and quality was not related to the variety, but to two climatic scenarios: 1) a favourable rainfall distribution without important drought periods (2020–21); 2) significant rainfalls in November and April, but with a drought period in between (2021–22). In the first situation, camelina production ranged from 1533 to 2187 kg ha−1, with high seed oil (40.4–41.4 %) and meal protein (41.0–44.8 %) contents. In the second situation, the yield decreased to 242–661 kg ha−1, seed oil content to 31.0–34.7 %, and meal protein content to 37.6–40.4 %. Despite these seasonal differences, SD1 in Montargull obtained higher average yields and protein content than in Lleida and in SD2. In contrast, in Lleida and in SD2 in Montargull camelina produced higher oil content. The implementation of camelina into Mediterranean dryland crop rotation systems is feasible. Considering the importance of moisture in these climatic conditions, the use of no-till practices is recommended in dryland fields to avoid excessive water loss, while the use of camelina in irrigated fields could be explored. However, more long-term agronomic and industrial research is still needed.

Forecast Of Rainfed Agricultural Production In The State Of Pernambuco, Brazil

This research assesses rainfed agricultural production in the state of Pernambuco, which has 137 of its 185 municipalities officially characterized as being part of the semi-arid climate regime. The study classified rainfall periods in Pernambuco between 1944 and 2022 and investigated rainfall instability and its impact on aggregate productivity, aggregate harvested area and production value per hectare of bean, cassava and maize crops. The Auto-Regressive Integrated Moving Average model with Exogenous Variable Inputs (ARIMAX) was used, considering rainfall as an exogenous variable. The results showed that rainfall has a direct effect on the variables investigated, especially the harvested area. It was proven that in periods classified as normal and rainy, productivity, harvested area and production value per hectare showed higher results than those observed in the dry periods of, as was the assumption of the research. The study also confirmed that the models developed were parsimonious and capable of predicting the variables investigated. The results showed that productivities, harvested areas and production values per hectare for beans, cassava and corn experienced greater instability during periods of drought. The research also shows that the aggregated production values per hectare for the three crops are very low. In dry years, they are even lower than the minimum wage. This result confirms that the rural areas of Pernambuco where these crops are mostly grown are very poor

Antimony Flux and Transport Dynamics in a Mining‐Impacted River Is Linked to Catchment Hydrodynamics and Climate Oscillations

ABSTRACTWe investigate how seasonal flow variations and a climatic regime that is dominated by the El Niño–Southern Oscillation (ENSO) influence Sb flux dynamics in an Australian river impacted by mining. Sampling (n = 496) spans a hydrologically complex 7‐year period of drought, bushfires and floods from 2016 to 2023, during which 17% of samples exceeded the Sb drinking water guideline concentration (3 μg L−1). Aqueous Sb (SbAq) concentration–discharge (C–Q) relationships are non‐continuous/non‐linear across the flow range, with chemodynamic behaviour at moderate flows reflecting hydrological connection to the primary Sb‐source area combined with variable dilution. In contrast chemostatic behaviour occurred at extreme low and high flows, reflecting hydrological disconnection from the source area and persistent dilution, respectively. SbAq was significantly positively correlated (p < 0.01, Spearman's ρ = 0.58) with a Q index representing the proportional contribution of sub‐catchment flow from the mineral‐field area, suggesting sufficient localised rainfall in the Sb mining‐impacted sub‐catchment contributes to downstream peaks in SbAq concentrations. Aqueous and particulate Sb (SbP) annual loads (La) during the study period spanned 24–5174 and 1.2–2820 kg, respectively and were strongly flow dependant with extreme interannual variability reflecting dry and wet years. We extrapolate daily load‐daily discharge (Ld–Qd) relationships for SbAq and SbP to estimate Ld over a 53‐year period (1970–2023) of continuous Q data (mean total Sb La = 1865 kg ± [SE] 247). Positive correlations between the annual Southern Oscillation Index and both Sb La (p < 0.05) and proportional SbP La over 53 years suggests ENSO fluctuations influence annual Sb transport dynamics. Upstream SbP load estimates correspond with downstream estimates of coastal floodplain sedimentary Sb mass, with approximately 10%–45% of the estimated SbP exported downstream since approximately 1880 accumulated on the Macleay coastal floodplain. Data suggest at current rates of export, complete flushing‐leaching of mine tailings‐derived Sb from the upper Macleay catchment may take in the order approximately 600–1000 years.

Unveiling the paleosalinity constraints on southern peri-Pannonian Lower Miocene lacustrine systems in Serbia and Bosnia and Herzegovina: Lopare (Dinaride Lake System) versus Toplica basin (Serbian Lake System)

Early Neogene saline lakes were widely developed across Central Paratethys, particularly across its „Dinaride-Anatolide“ landbridge (area of Dinarides, Balkans). The constraints on Lopare (western part of Jadar block; eastern Bosnia and Herzegovina) and Toplica (Jastrebac Mt., central Serbia) Neogene paleolakes provide a better understanding of deep-time climate evolution. The study focused on early Neogene paleolacustrine configuration, paleogeography, and the factors affecting a considerable paleosalinity increase. The study integrated available records on the predominantly Lower Miocene sedimentary sequence by analyzing and interpreting several paleosalinity markers (inorganic geochemical proxies, mineralogical data). The constraints on paleosalinity markers are afterward coupled with rather complex tectonic inferences. The two wellbores drilled in the Lopare and Toplica basins expose Neogene sections from which the critical paleosalinity markers are extracted (drillhole depths up to 350 and 1000 m, respectively). The mineral searlesite (NaBSi2O5(OH)2), and high B/Ga, markers of alkaline and arid paleoenvironmental lacustrine conditions, suggested intense evaporation (frequent drought periods). The evaporation was associated with paleoclimatic conditions during the Miocene Climatic Optimum. The Early Neogene arid climate and frequent evaporation episodes resulted in significant salinization of the Lower Miocene Lopare lacustrine sequence. The salinity in the Lopare sequence changed its character between brackish and saline, as evidenced by S/TOC and Ca/(Ca + Fe) ratios (TOC—Total Organic Carbon). At the same time, the salinity in the early Toplica basin was significantly lower and characterized by freshwater and brackish environments. The salinity variations between Toplica and Lopare were further exposed by Fe/(Ca + Mg), (Al + Fe)/(Ca + Mg), and C-value, yielding the change in the (paleo)water column. These markers further indicated the influence of warm climate conditions, consistent with the Miocene paleoclimatic record. Regarding paleogeography and Early Neogene tectonics, the results showed that before the Middle Miocene Badenian transgression, the Paratethyan Sea had no interference with the investigated intramontane lacustrine basins.

Climatic Influence on the Carotenoids Concentration in a Mediterranean Coastal Lagoon Through Remote Sensing

The Albufera of Valencia, a Mediterranean coastal lagoon, has experienced a shift to hypertrophic conditions over the past 40 years due to agricultural and urban-industrial pollution. From August 2023 to early 2024, the water of the lagoon turned reddish-brown. This change has been observed in the past, but never with this intensity or duration, which typically occurs during periods of drought. In this study, carotenoid concentrations were analyzed in relation to precipitation and temperature using field and remote sensing data from February 2016 to December 2023. In November 2023, samples showed unusually high concentrations of carotenoids. The study confirmed the effectiveness of a new algorithm for estimating carotenoids using Sentinel-2 imagery to complement chlorophyll-a data. Results showed that temperature and precipitation significantly influenced carotenoid/chlorophyll-a ratio, highlighting a climatic control of phytoplankton community structure. These results highlight the importance of long-term monitoring and conservation efforts to address climate change and human impacts. This research is a first step in using optical properties of lakes as an indicator of phytoplankton dynamics under environmental stress and warns of the potential for increased occurrence or persistence of such phenomena with future climate trends.

Water Use Efficiency Characteristics and Their Contributions to Yield in Diverse Sugarcane Genotypes with Varying Drought Resistance Levels Under Different Field Irrigation Conditions

Drought is the major abiotic constraint affecting sugarcane productivity and quality worldwide. This obstacle may be alleviated through sugarcane genotypes demonstrating good water use efficiency (WUE) performance. This study aims to investigate the WUE characteristics of various sugarcane genotypes under different soil water availability levels. Plant and ratoon field experiments were conducted using a split-plot randomized complete block design with three replications. The main plots were assigned three types of irrigation: (1) rainfed conditions (RF), (2) field capacity conditions (FC), and (3) half-available water (½ AW). The subplots consisted of six sugarcane genotypes with varying levels of drought resistance, i.e., KK3, UT13, Kps01-12, KKU99-03, KKU99-02, and UT12. Data on yield, stalk numbers, stalk diameter, height, and WUE were collected throughout the crop cycle for both plant and ratoon crops. For the plant crop, the net photosynthesis rate, transpiration rate, stomatal conductance, and leaf area index (LAI) were recorded during the crop period. In both plant and ratoon crops, the WUE in the RF treatment was lower than in the FC and ½ AW treatments during the drought stress period 4 months after planting (MAP). In the recovery phase, the WUE in the ½ AW treatment fell between the FC and RF treatments. The RF treatment exhibited the lowest WUE compared to the other two water regime treatments at the maturity stage. The drought-resistant genotypes KK3 and UT13 maintained high WUE values throughout both the drought and recovery periods and exhibited outstanding LAIs at 4 and 6 MAP. A significant relationship existed between WUE and LAI during these periods. Moreover, WUE was positively correlated with cane yields and yield components, such as stalk weight, shoot diameter, and height, during recovery and tiller number and height during ripening. Therefore, WUE and LAI are efficient parameters for supporting and maintaining growth and yield during water deficit and recovery phases under rainfed conditions.

The Current Phyto-Scape and Foodplants of Holley Shelter, KwaZulu-Natal (South Africa) and Its Potential for Past Foragers

AbstractCurrent phyto-scapes (plant populations in their geo-spatial context) are not exact replicas of past foraging potential, yet they provide valuable data about the carrying capacity or potential of a foraging-scape. Knowledge about contemporary micro-ecologies and ethno-historical plant use can inform on behavioral aspects, should such plants be found in archaeological deposits. It is in this context that we explore existing information (data and literature) to establish the current vegetation types and micro-ecologies around Holley Shelter, KwaZulu-Natal, South Africa, that contains Middle and Later Stone Age occupations. We present the first plant species inventory consisting of > 1500 taxa growing approximately a day’s foraging distance from the site, compiled from records provided by the South African National Biodiversity Institute and other sources. From this list, we generated separate checklists for foodplants (n = 450) and plants that have other uses (n = 337), to gain insight into the site’s current phyto-fitness potential. The resulting database is intended as a modern proxy for future work on the site’s archaeo-botany and palaeo-climatic reconstructions. The data is also applicable to other sites on the Savanna/Grassland Biomes of southern Africa with records of the same species. Here we use the foodplant checklist and what is known about the edible plant parts, their seasonality and the distribution of some species to speculate about land-use patterns. These hypotheses can be tested for the past with future archaeo-botanical work. We demonstrate that, compared to archaeological sites in the Eastern and Western Cape for which comparable data exist, Holley Shelter is rich in foodplants, and especially so in plant foods that are known to buffer against famine during the periodical droughts of inland South Africa.

Effects of multiple mammalian herbivores and climate on grassland-shrubland transitions in the Chihuahuan Desert.

The replacement of grasses by shrubs or bare ground (xerification) is a primary form of landscape change in drylands globally with consequences for ecosystem services. The potential for wild herbivores to trigger or reinforce shrubland states may be underappreciated, however, and comparative analyses across herbivore taxa are sparse. We sought to clarify the relative effects of domestic cattle, native rodents, native lagomorphs, and exotic African oryx (Oryx gazella) on a Chihuahuan Desert grassland undergoing shrub encroachment. We then asked whether drought periods, wet season precipitation, or interspecific grass-shrub competition modified herbivore effects to alter plant cover, species diversity, or community composition. We established a long-term experiment with hierarchical herbivore exclosure treatments and surveyed plant foliar cover over 25 years. Cover of honey mesquite (Prosopis glandulosa) proliferated, responding primarily to climate, and was unaffected by herbivore treatments. Surprisingly, cattle and African oryx exclusion had only marginal effects on perennial grass cover at their current densities. Native lagomorphs interacted with climate to limit perennial grass cover during wet periods. Native rodents strongly decreased plant diversity, decreased evenness, and altered community composition. Overall, we found no evidence of mammalian herbivores facilitating or inhibiting shrub encroachment, but native small mammals interacting with climate drove dynamics of herbaceous plant communities. Ongoing monitoring will determine whether increased perennial grass cover from exclusion of native lagomorphs and rodents slows the transition to a dense shrubland.

Precipitation and female experience are major determinants of the breeding performance of Canarian houbara bustards

Precipitation is one of the main triggers of reproduction in desert‐breeding birds. The unpredictability of rainfall patterns in arid environments has led species to adapt their breeding effort to episodes of abundant food after rainfall. The response is not the same for all individuals in a population, and may vary especially with the age and experience of each female. Here we investigate the effects of precipitation, temperature, body size and breeding experience, among other variables, on reproductive parameters of 20 females of Canarian houbara bustard (Chlamydotis undulata fuertaventurae), an endangered desert bird endemic of the eastern Canary Islands. Precipitation and breeding experience were the main determinants of female breeding performance. Higher rainfall determined an increase in nesting rate, and earlier autumn rains caused an advancement of nesting to October, allowing the breeding season to be extended to eight months. This favoured an extraordinary increase in productivity in more rainy breeding seasons, with 15 times more females nesting in the two most rainy winters than in dry years. In addition, females with more breeding experience showed a higher tendency to breed, higher nest attempt and fledging success, and longer breeding season, which allowed them to rear more chicks. A female even double brooded successfully in the same season, which, considering that chicks remain with the mother for up to six months, indicates a great capacity to optimise reproductive investment, by adapting to highly variable rainfall regimes. In recent decades, the eastern Canary Islands have undergone a process of aridification, and climate models predict a medium‐term increase in the frequency and duration of drought periods. Thus, Canarian houbaras are particularly vulnerable to climate change, so measures are urgently needed to reduce their mortality and improve the quality of their habitat, in order to favour their reproduction and prevent their extinction.

Evapotranspiration measurements in pasture, crops, and native Brazilian Cerrado based on UAV-borne multispectral sensor.

In Brazil, agriculture consumes most of the available freshwater, especially in the Cerrado biome, where the rain cycle is marked by long periods of drought. This study, conducted at the Brazilian Agricultural Research Corporation (Embrapa) Research Corporation unit in Santo Antônio de Goiás, Goiás, Brazil, estimated evapotranspiration (ET) in different crops and soil cover. Using multispectral unmanned aerial vehicle (UAV) images, Sentinel satellite data, weather station information, and towers employing the eddy covariance method, we applied the "Simple Algorithm for Evapotranspiration Retrieving" (SAFER) to calculate ET in common bean, pasture, and semideciduous seasonal forest areas. The results showed a good agreement between UAV and satellite data, with R2 = 0.84, also validated with flow towers by the eddy covariance method. UAV-based ET was observed to correspond well to tower (EC) during full vegetative development of beans but is underestimated at the beginning of planting and in the final periods of plant senescence, due to the influence of soil or straw cover. These findings contribute to a better understanding of water dynamics in the system and to enhancing sustainable agricultural practices. This method, adapted for multispectral aerial imaging, can be applied flexibly and on-demand, in different contexts and ground cover. The study highlights the importance of integrated agricultural practices for better management of water resources and preservation of the Cerrado in balance with cultivation areas.