Altered Precipitation Patterns Research Articles

Species-specific flowering phenology responses to experimental warming and drought alter herbaceous plant species overlap in a temperate–boreal forest community

Warmer temperatures and altered precipitation patterns are expected to continue to occur as the climate changes. How these changes will impact the flowering phenology of herbaceous perennials in northern forests is poorly understood but could have consequences for forest functioning and species interactions. Here, we examine the flowering phenology responses of five herbaceous perennials to experimental warming and reduced summer rainfall over 3 years. This study is part of the B4WarmED experiment located at two sites in northern Minnesota, USA. Three levels of warming (ambient, +1.6 °C and +3.1 °C) were crossed with two rainfall manipulations (ambient and 27 % reduced growing season rainfall). We observed species-specific responses to the experimental treatments. Warming alone advanced flowering for four species. Most notably, the two autumn blooming species showed the strongest advance of flowering to warming. Reduced rainfall alone advanced flowering for one autumn blooming species and delayed flowering for the other, with no significant impact on the three early blooming species. Only one species, Solidago spp., showed an interactive response to warming and rainfall manipulation by advancing in +1.6 °C warming (regardless of rainfall manipulation) but not advancing in the warmest, driest treatment. Species-specific responses led to changes in temporal overlap between species. Most notably, the two autumn blooming species diverged significantly in their flowering timing. In ambient conditions, these two species flowered within the same week. In the warmest, driest treatment, flowering occurred over a month apart. Herbaceous species may differ in how they respond to future climate conditions. Changes to phenology may lead to fewer resources for insects or a mismatch between plants and pollinators.

Using a space‐for‐time substitution approach to predict the effects of climate change on nutrient cycling in tropical island stream ecosystems

AbstractClimate change is expected to alter precipitation patterns worldwide, which can have direct effects on streamflow dynamics. In many tropical regions, climate‐driven changes in rainfall are predicted to decrease streamflow and increase flash flooding, but the implications of these changes for stream ecosystem function are poorly understood. We used a rainfall gradient on Hawaii Island that mimics projected changes in rainfall and streamflow in order to estimate how climate change affects nutrient recycling. We measured per‐capita excretion (nitrogen, phosphorus) and egestion rates of three dominant taxa (shrimp, caddisfly, midge) in eight streams along the gradient for 3 years. We scaled these rates to the population and community levels and measured nitrogen and phosphorus demand of the ecosystem to estimate if the relative contribution of nutrients supplied by invertebrates changes along the gradient. Across all three taxa, population egestion and excretion rates declined by 10‐fold in drier streams. These declines were driven by lower population density, rather than differences in per‐capita rates. Under the current climate scenario, community excretion supplied up to 70% of the nitrogen demand, which was 10‐fold lower with projected changes in rainfall. Conversely, community excretion supplied up to 5% of the phosphorus demand, which did not vary across the rainfall gradient. This difference indicates that climate change may exacerbate nitrogen limitations in tropical island streams, and change the balance of nitrogen and phosphorus dynamics. Our study also demonstrates that space‐for‐time substitutions are a valuable tool to examine implications of climate change on ecosystem function in freshwater systems.

Seedlings from marginal and core populations of European beech (Fagus sylvatica L.) respond differently to imposed drought and shade

Key messageLocal adaptation largely segregates between traits affecting light responses and water relations, but population-level differences in stomatal conductance when growth is unconstrained converge among populations under water stress.Warming temperatures and altered precipitation patterns threaten plant populations worldwide. European beech (Fagus sylvatica) is a species that expresses both high phenotypic plasticity and local adaptation among populations. Beech seedlings’ susceptibility to prolonged drought may be dictated by their immediate light environment. We tested whether seedlings of four beech provenances, from contrasting edaphoclimatic environments, expressed differences in trait responses to imposed water stress under sun and shade treatments. Populations from the southern range margin were expected to display greater water-stress tolerance and core populations’ faster growth rates in the absence of abiotic limitations. Both high light and water stress induced differences in trait responses among provenances, but traits that failed to respond to our experimental treatments likewise did not segregate at the provenance level. Hence, those traits responding to light, e.g., increasing leaf flavonol index and leaf mass area, also tended to differ among provenances. Similarly, there was evidence of local adaptation among provenances in traits, like midday leaf water potential, responding to water stress. Exceptionally, there was a three way interaction water- × -light- × -provenance for stomatal conductance which converged among provenances under water stress. Leaf chlorophyll content also varied both with light and water in a provenance-specific manner. We found core provenances’ growth traits to outperform others under favourable conditions, whereas southern and high-elevation populations displayed traits adapted to tolerate high irradiance. Only stomatal conductance produced a complementary interactive response between light- × -water across provenances, whereas other traits responded less to combined water stress and high irradiance than to either treatment alone.

Driving and restraining forces for the implementation of the Agrophotovoltaics system technology – A system dynamics analysis

The innovative Agrophotovoltaics (APV) system technology combines agricultural biomass and solar power production on the same site and aims at reducing the conflict between food and power production. Unrelated to this benefit, this technology may impact the landscape negatively and could thus be subject to public opposition and/or restraining frameworks. The presented study offers a System Dynamics (SD) approach, through Causal Loop Diagrams (CLDs) models, based on the results of citizen workshops, literature research, and expert discussions on the technology. A comprehensive analysis of the driving and restraining forces for the implementation of APV-technology and expected or potential impacts reveals influential factors. Hence, this SD approach identifies bottlenecks and conflicting objectives in the technology implementation that need to be further addressed. A key finding is that successful APV-projects would require stakeholder involvement to achieve greater local acceptance. When it comes to production on agricultural land, APV-systems may drive the land use efficiency to up to 186 percent when the PV-panels serve for protection against heat stress. On the other hand, altered precipitation patterns and impacts on agricultural cultivation and, especially, the landscape caused by the technical system, may restrain the application of APV. Finally, system design factors and operator modes are amongst the criteria that may influence the local acceptance in society, farmers’ motivation for APV and economic factors for the market launch of APV.

Impact of high atmospheric CO2 concentrations on the seasonality of water-related processes, gas exchange, and carbohydrate metabolism in coffee trees under field conditions

Increasing atmospheric CO2 concentrations ([CO2]) are unequivocal, widespread, and responsible for increased mean global temperatures and altered precipitation patterns. In this context, among the topics that need to be better understood are the changes in the water-related processes and gas exchange properties of plants grown under these conditions. Notably, the effects of climate change on coffee (Coffea spp.) production are particularly concerning given the importance of this commodity. Especially, it has been reported that coffee trees exhibit better photosynthetic efficiency when grown at higher [CO2] levels. In order to elucidate the mechanisms involved with this response, the seasonality of water-related processes, gas exchange, and carbohydrate metabolism were investigated using C. arabica var. Red Catuai grown at ambient and high [CO2] under field conditions, at a free-air CO2 enrichment (FACE) facility for coffee, in Brazil. The trees were evaluated fortnightly, from November to February (hot and rainy—summer) and from June to September (cold and dry—winter). It was found that C. arabica trees grown under high [CO2] conditions exhibited increased photosynthetic rates (averaging 121% higher in summer and 45% higher in winter) in both seasons, without displaying any significant changes in the seasonal photosynthesis pattern. Additionally, there was a tendency for the coffee trees grown at high [CO2] to exhibit increased levels of soluble carbohydrates, organic acids, and amino acids in the leaves. Our findings suggest that coffee trees adapt to increased [CO2] through increased photosynthetic rates, enhanced stomatal conductance regulation, and augmented carbohydrate and organic acid synthesis. It is plausible that these features could help mitigate the effects caused by climate change.

Mitigating the global expansion of harmful cyanobacterial blooms: Moving targets in a human- and climatically-altered world

Cyanobacterial harmful algal blooms (CyanoHABs) are a major threat to human and environmental health. As global proliferation of CyanoHABs continues to increase in prevalence, intensity, and toxicity, it is important to identify and integrate the underlying causes and controls of blooms in order to develop effective short- and long-term mitigation strategies. Clearly, nutrient input reductions should receive high priority. Legacy effects of multi-decadal anthropogenic eutrophication have altered limnetic systems such that there has been a shift from exclusive phosphorus (P) limitation to nitrogen (N) limitation and N and P co-limitation. Additionally, climate change is driving CyanoHAB proliferation through increasing global temperatures and altered precipitation patterns, including more extreme rainfall events and protracted droughts. These scenarios have led to the “perfect storm scenario”; increases in pulsed nutrient loading events, followed by persistent low-flow, long water residence times, favoring bloom formation and proliferation. To meet the CyanoHAB mitigation challenge, we must: (1) Formulate watershed and airshed-specific N and P input reductions on a sliding scale to meet anthropogenic and climatic forcings. (2) Develop CyanoHAB management strategies that incorporate current and anticipated climatic changes and extremes. (3) Make nutrient management strategies compatible with other physical-chemical-biological mitigation approaches, such as altering freshwater flow and flushing, dredging, chemical applications, introduction of selective grazers, etc. (4) Target CyanoHAB toxin production and developing management approaches to reduce toxin production. (5) Develop broadly applicable long-term strategies that incorporate the above recommendations.

Drought risk to timber production – A risk versus return comparison of commercial conifer species in Scotland

Climate change will alter precipitation patterns across the world increasing drought risk to forests in some areas, especially where summer precipitation is reduced. Effective management of this risk requires quantified information on the probabilities and consequences of drought to support policy and strategic decisions on the choice of tree species that will provide drought resilience and ensure continued timber supply. Here we define a new approach to delivering this information to underpin management decisions on species choice for restocking. We derive location-specific risk versus return analyses, for twenty commercial timber species in Scotland, by quantifying the impact of drought risk under a high emission scenario on potential return, modelled as change in baseline volume of timber production (yield in m3 ha−1). We find that the current potential yield of Sitka spruce is likely to be sufficiently high to compensate for its relatively high drought susceptibility compared to alternative species, modelled over a new 50-year rotation. In regions projected to experience increased drought risk - particularly central and eastern areas of Scotland - the higher drought tolerance of some species means that they are likely to be viable alternatives to Sitka spruce, based on a threshold productivity which we set for the purposes of this analysis as ≥90% of predicted Sitka spruce yield. Since species diversification is a potential strategy to increase forest resilience against other risks, such as those from pest and diseases, our analysis provides a framework within which these regional decisions can be made. Risk management strategies should be introduced which include the risk from drought to commercial softwood plantations and thereby help protect timber volume production. The modelling approach outlined could be adapted to compare timber species in other regions where comparable data are available.

Dynamics of dissolved organic matter and disinfection byproduct precursors along a low elevation gradient in woody wetlands - an implication of hydrologic impacts of climate change on source water quality

Foliar litter is an important terrestrial source of dissolved organic matter (DOM) and disinfection byproducts (DBPs) in the source water supply. Climate changes could alter precipitation patterns and hydroperiods in woody wetlands, resulting in a hydrologic shift along the low elevation gradient and change the productions of DOC and DBP precursors and their exports to source water. Here, we conducted an 80-week field decomposition study using fresh-fallen leaves along an elevation gradient, representing well-drained, relatively moist, and inundated environments, in Congaree National Park, South Carolina. The dissolved organic carbon (DOC) yield and formation potential (FP) of trihalomethanes (THMs; a dominant category of studied DBPs) were 48.9–79.7 mg-DOC/g-litter and 2.23–6.57 mg/g-litter in the freshly fallen leaf litter, respectively. The level of leachable DOM and its DBP FP decreased with time, and during the first 16 weeks of decomposition, the decomposing litter served as an important source of leachable DOM and DBP precursors. Week 28 was a turning point for DOM optical properties, with fewer tyrosine/tryptophan/soluble microbial byproduct-like compounds and more aromatic, humified, and fulvic/humic acid-like compounds. Litterfall primarily occurred from September to January, while less precipitation occurred from October to January, indicating that large amounts of DOC and DBP precursors could be leached from litterfall in February. In the first 16 weeks of field exposure study, we observed higher residual mass and lower water-extractable DOC and DTN in more inundated environments, demonstrating that the shifts of DOM composition and DBP precursors if climate reduces rainfall in the southeastern US.

Lower soil carbon stocks in exotic vs. native grasslands are driven by carbonate losses.

Global change includes invasion by exotic (nonnative) plant species and altered precipitation patterns, and these factors may affect terrestrial carbon (C) storage. We measured soil C changes in experimental mixtures of all exotic or all native grassland plant species under two levels of summer drought stress (0 and+128mm). After 8 yr, soils were sampled in 10-cm increments to 100-cm depth to determine if soil C differed among treatments in deeper soils. Total soil C (organic+inorganic) content was significantly higher under native than exotic plantings, and differences increased with depth. Surprisingly, differences after 8 yr in C were due to carbonate and not organic C fractions, where carbonate was ~250g C/m2 lower to 1-m soil depth under exotic than native plantings. Our results indicate that soil carbonate is an active pool and can respond to differences in plant species traits over timescales of years. Significant losses of inorganic C might be avoided by conserving native grasslands in subhumid ecosystems.

Effect of repeated drying-rewetting cycles on soil extracellular enzyme activities and microbial community composition in arid and semi-arid ecosystems

Climate change is predicted to alter precipitation patterns, which may have profound consequences on soil microbial communities and functions in arid and semi-arid ecosystems. However, it is uncertain if the direction and magnitude of soil microbial function and community responses to repeated drying and rewetting (DRW) events differ in diverse arid and semi-arid ecosystems. We collected surface soils in forest, farmland, grassland, and desert ecosystems from the Chinese Ecosystem Research Network (CERN) with mean annual precipitation ranged from 164 to 600 mm. Soils were then exposed to 0, 2, 5, 7 and 14 DRW cycles with variable drought periods at 20 °C. Soil respiration was measured in the rewetting phases of each DRW cycle. We also measured microbial biomass carbon (C), dissolved organic C, inorganic nitrogen, activities of four C-acquisition extracellular enzymes (β-glucosidase, cellobiohydrolase, phenol oxidase, and peroxidase), and microbial community structure after the last DRW cycle. Results showed that repeated DRW cycles significantly affected most microbial parameters in our study. Specifically, repeated DRW cycles increased activities of β-glucosidase and cellobiohydrolase. Lower DRW frequencies with longer drought periods had higher soil respiration, microbial biomass C, and the relative abundance of fungi. The responses of soil enzyme activities to repeated DRW were similar in the four ecosystems. However, soil microbial biomass and community composition were generally more resistant to repeated DRW cycles in the forest soil, while they were more vulnerable to repeated DRW stress in the desert soil, suggesting that altered precipitation patterns may have a greater impact on soil microbial communities in more arid ecosystems.

Facing Water Stress in a Changing Climate: A Case Study of Drought Risk Analysis Under Future Climate Projections in the Xi River Basin, China

China, with its fragile environment and ecosystems, is vulnerable to climate change. Continuous changes in climatic conditions have altered precipitation patterns in most regions of China. Droughts become more frequent and severe in the Xi River basin in South China. It is expected that rapid urbanization and climate change will continue to aggravate water stress in this region. There is an urgent need to develop sustainable water management strategies in face of growing water demand and changing water availability. Projection of future climate change impacts on drought conditions has thus become imperative to support improved decision-making in sustainable water management. In this study, we assessed the risk of extreme droughts under future climate projections in the Xi River basin. The Variable Infiltration Capacity (VIC) model was applied to simulate the hydrological processes of the basin under a multitude of future climate scenarios from CMIP5. Based on the precipitation and runoff series obtained from the VIC model, a comprehensive analysis with respect to the major characteristics of meteorological and hydrological droughts had been carried out. This study is of practical and theoretical importance to both policymakers and scholars. First, this study may be a readily available reference work for policymakers when taking consideration of building drought mitigation plans into future water management practices. Second, the findings in this study may provide some valuable insights into the inherent connection between climatic and hydrological changes under a changing climate. Recognition of the connection and interrelation may contribute to the improvement of climatic and hydrological models in practices.

The Impacts of Climate-Induced Agricultural Drought on Four Cereal Crops: A Case Study in Bako Tibe District, Oromia National Regional State, Ethiopia

<p>Increasing temperature and altered precipitation patterns lead to the extreme weather events such as drought and flood, which severely affects the agricultural production. This study was aimed to assess the impact of climate change-induced agricultural drought on four cereal crops in Bako Tibe District. Time-series climate and crop yield data, recorded from 1989 to 2018, were acquired from NASA’s data portal and Bako Research Institute. The changes in temperature and precipitation were analyzed using Mann Kendall trend test. The agricultural drought index was analyzed using R-software. The correlation between the selected yield crops and drought indices were evaluated using Pearson correlation coefficient. The results show that trends of seasonal and annual maximum and minimum temperatures were significantly increased (P<0.05). However, seasonal and annual precipitations were insignificantly decreased (P>0.05). Moderate to severe agricultural drought intensities happened four times in the last three decades. These drought spells spatially covered about 36% of the total area of the district. Crop yields and drought indices were significantly correlated at p-values; 0.0034, 0.043, 0.003 and 0.001 for teff, wheat, barley and maize, respectively. The coefficient of determination (R2) values of crop yields were 28.3%, 30.9%, 28.5% and 34.6% for teff, wheat, barley and maize, correspondingly. The study clearly suggests that the increase in temperature and decrease in precipitation enhanced the frequency and intensity of drought events and these impacted the selected crop yields during the past three decades. The map-based results could be used as guides for governmental and non-governmental organizations concerning on drought impact mitigation activities in the district by encouraging farmers to adopt appropriate agricultural technologies, drought tolerant crop varieties and small scale irrigation.</p>

Ecosystem Capacity for Microbial Biodegradation of Munitions Compounds and Phenanthrene in Three Coastal Waterways in North Carolina, United States.

Munitions compounds (i.e., 2,4,6-trinitrotoluene (TNT), octahy-dro-1,3,5,7-tetranitro-1,3,5,7-tetrazocin (HMX), and hexadydro-1,3,5-trinitro-1,3,5-triazin (RDX), also called energetics) were originally believed to be recalcitrant to microbial biodegradation based on historical groundwater chemical attenuation data and laboratory culture work. More recently, it has been established that natural bacterial assemblages in coastal waters and sediment can rapidly metabolize these organic nitrogen sources and even incorporate their carbon and nitrogen into bacterial biomass. Here, we report on the capacity of natural microbial assemblages in three coastal North Carolina (United States) estuaries to metabolize energetics and phenanthrene (PHE), a proxy for terrestrial aromatic compounds. Microbial assemblages generally had the highest ecosystem capacity (mass of the compound mineralized per average estuarine residence time) for HMX (21–5463 kg) > RDX (1.4–5821 kg) ≫ PHE (0.29–660 kg) > TNT (0.25–451 kg). Increasing antecedent precipitation tended to decrease the ecosystem capacity to mineralize TNT in the Newport River Estuary, and PHE and TNT mineralization were often highest with increasing salinity. There was some evidence from the New River Estuary that increased N-demand (due to a phytoplankton bloom) is associated with increased energetic mineralization rates. Using this type of analysis to determine the ecosystem capacity to metabolize energetics can explain why these compounds are rarely detected in seawater and marine sediment, despite the known presence of unexploded ordnance or recent use in military training exercises. Overall, measuring the ecosystem capacity may help predict the effects of climate change (warming and altered precipitation patterns) and other perturbations on exotic compound fate and transport within ecosystems and provide critical information for managers and decision-makers to develop management strategies based on these changes.

Effects of soil warming and altered precipitation patterns on photosynthesis, biomass production and yield of barley

Effects of soil warming and altered precipitation patterns on photosynthesis, biomass production and yield of barley

Multi-temporal remote sensing data to monitor terrestrial ecosystem responses to climate variations in Ghana

Operational monitoring of vegetation and its response to climate change involves the use of vegetation indices (VIs) in relation to relevant climatic data. This study analyses the temporal variations of vegetation indices in response to climatic data (temperature and precipitation) to better understand the phenological changes in the Wa-West and Tolon districts of Ghana during 1999–2011. This study also examines the inter-annual variation of vegetation indices and lag effects of climate variables (temperature and precipitation) using simple regression and correlation approaches. Results indicate that the mean Normalized Difference Vegetation Index (NDVI) and Normalized Difference Soil Index (NDSI) were significantly correlated with the mean temperature, whereby the value of NDVI increases with a decrease in temperature and value of NDSI increases with an increase in temperature. On examining seasonal variations, our findings indicated that the months of August and September have the highest mean NDVI values. This study confirms that consistently rising temperature and altered precipitation patterns have exerted a strong influence on temporal distributions and productivities of the terrestrial ecosystems of the Tolon and Wa-West districts of Ghana. Furthermore, this research demonstrates how vegetation indices can be used as an indicator to monitor phenological changes in the terrestrial ecosystem.

Assessing climate change impacts on greenhouse gas emissions, N losses in drainage and crop production in a subsurface drained field

Future climate change-driven alterations in precipitation patterns, increases in temperature, and rises in atmospheric carbon dioxide concentration ([CO2]atm) are expected to alter agricultural productivity and environmental quality, while high latitude countries like Canada are likely to face more challenges from global climate change. However, potential climate change impact on GHG emissions from tile-drained fields is poorly documented. Accordingly, climate change impacts on GHG emissions, N losses to drainage and crop production in a subsurface-drained field in Southern Quebec, Canada were assessed using calibrated and validated RZWQM2 model. The RZWQM2 model was run for a historical period (1971–2000) and for a future period (2038 to 2070) using data generated from 11 different GCM-RCMs (global climate models coupled with regional climate models). Under the projected warmer and higher rainfall conditions mean drainage flow was predicted to increase by 17%, and the N losses through subsurface drains increase by 47%. Despite the negative effect of warming temperature on crop yield, soybean yield was predicted to increase by 31% due to increased photosynthesis rates and improved crop water use efficiency (WUE) under elevated [CO2]atm, while corn yield was reduced by 7% even with elevated [CO2]atm because of a shorter life cycle from seedling to maturity resulted from higher temperature. The N2O emissions would be enhanced by 21% due to greater denitrification and mineralization, while CO2 emissions would increase by 16% because of more crop biomass accumulation, higher crop residue decomposition, and greater soil microbial activities. Soil organic carbon storage was predicted to decrease 22% faster in the future, which would result in higher global warming potential in turn. This study demonstrates the potential of exacerbating GHG emissions and water quality problems and reduced corn yield under climate change impact in subsurface drained fields in southern Quebec.

Effects of changes in water status on soil microbes and their response mechanism: A review

Soil microbes play essential roles in maintaining terrestrial ecosystem services. Soil moisture is a primary determinant of soil microbial activities and ecosystem functions, which may fluctuate dramatically with the altered precipitation patterns and extreme drought caused by the ongoing global climate change. Due to the distinct soil microbial tolerance and life-strategy approaches to drought stress and different water status, fluctuation of soil moisture has a direct impact on microbial activities and community structure, thereby profoundly affecting microbial-mediated processes and ecosystem functions. Thus, it is of great significance to understand the dynamics and mechanisms that underlie the microbial responses to soil water status. In this review, we summarized recent progress in the study of responses of soil microbial activities (e.g. soil respiration and enzyme activities) and community structure to soil water status. We summarized underlying microbial physiological and ecological mechanisms, particularly 1) the cellular physiological accommodation such as osmolyte accumulation, exopolysaccharide production and transition into dormant states, and 2) the ecological strategies such as stress-resistant gene transfer and functional redundancy. Therefore, this investigation on the underlying relationship between soil microbial assembly and ecosystem functions under different water status could further demonstrate the microbially-mediated soil biogeochemical processes and provide a theoretical basis for future research and modelling of terrestrial ecosystem responses to climate change.

Partitioning of Water Between Differently Sized Shrubs and Potential Groundwater Recharge in a Semiarid Savanna in Namibia.

Introduction: Many semiarid regions around the world are presently experiencing significant changes in both climatic conditions and vegetation. This includes a disturbed coexistence between grasses and bushes also known as bush encroachment, and altered precipitation patterns with larger rain events. Fewer, more intense precipitation events might promote groundwater recharge, but depending on the structure of the vegetation also encourage further woody encroachment. Materials and Methods: In this study, we investigated how patterns and sources of water uptake of Acacia mellifera (blackthorn), an important encroaching woody plant in southern African savannas, are associated with the intensity of rain events and the size of individual shrubs. The study was conducted at a commercial cattle farm in the semiarid Kalahari in Namibia (MAP 250 mm/a). We used soil moisture dynamics in different depths and natural stable isotopes as markers of water sources. Xylem water of fifteen differently sized individuals during eight rain events was extracted using a Scholander pressure bomb. Results and Discussion: Results suggest the main rooting activity zone of A. mellifera in 50 and 75 cm soil depth but a reasonable water uptake from 10 and 25 cm. Any apparent uptake pattern seems to be driven by water availability, not time in the season. Bushes prefer the deeper soil layers after heavier rain events, indicating some evidence for the classical Walter’s two-layer hypothesis. However, rain events up to a threshold of 6 mm/day cause shallower depths of use and suggest several phases of intense competition with perennial grasses. The temporal uptake pattern does not depend on shrub size, suggesting a fast upwards water flow inside. δ2H and δ18O values in xylem water indicate that larger shrubs rely less on upper and very deep soil water than smaller shrubs. It supports the hypothesis that in environments where soil moisture is highly variable in the upper soil layers, the early investment in a deep tap-root to exploit deeper, more reliable water sources could reduce the probability of mortality during the establishment phase. Nevertheless, independent of size and time in the season, bushes do not compete with potential groundwater recharge. In a savanna encroached by A. mellifera, groundwater will most likely be affected indirectly.

State-of-the-art of tools and methods to assess vine water status

Rising global air temperatures will lead to an increased evapotranspiration and altered precipitation pattern. In many regions this may result in a negative water balance during the vegetative cycle, which can augment the risk of drought and will require mitigation strategies. These strategies, ultimately, will mean the installation of irrigation systems in some winegrowing regions where vines were cultivated historically under rain-fed conditions and growers do not have many years of experience with vine water management.This review aims to provide a state-of-the-art summary of the recent and most important literature on vine water assessment for monitoring and adapting vineyard management strategies to production goals in view of global warming. Plant, soil and atmospheric methods are reviewed, and their advantages and drawbacks are discussed. Recent advances in plant water status measurement reveal the limitation of traditional techniques such as water potential, particularly in the context of drought and high vapor pressure deficit and the discoveries regarding hydraulic and stomatal regulation. New technologies can integrate heterogeneous sources of information collected in the vineyard at different spatial and temporal resolutions. Such new approaches offer new synergies to overcome limitations inherent to plant water status measurement techniques obtained directly or indirectly from proxy measurements.

Multifaceted aspects of synchrony between freshwater prokaryotes and protists.

Community composition of freshwater prokaryotes and protists varies through time. Few studies contemporarily investigate temporal variation of these freshwater communities for more than 1year. We compared the temporal patterns of prokaryotes and protists in three distinct habitats for 4years (2014-2017) in Lake Tovel, a cold-water lake. This lake showed a marked temperature increase in 2017 linked to altered precipitation patterns. We investigated whether microbial communities reflected this change across habitats and whether changes occurred at the same time and to the same extent. Furthermore, we tested the concept of hydrological year emphasizing the ecological effect of water renewal on communities for its explanatory power of community changes. Microbe diversity was assessed by Illumina sequencing of the V3-V4 hypervariable region of the 16S rRNA gene and 18S rRNA gene, and we applied co-inertia analysis and asymmetric eigenvector maps modelling to infer synchrony and temporal patterns of prokaryotes and protists. When considering community composition, microbes were invariable in synchrony across habitats and indicated a temporal gradient linked to decreasing precipitation; however, when looking at temporal patterns, the extent of synchrony was reduced. Small-scale patterns were similar across habitats and microbes and linked to seasonally varying environmental variables, while large-scale patterns were different and partially linked to an ecosystem change as indicated by increasing water transparency and temperature and decreasing dissolved oxygen. Our advanced statistical approach outlined the multifaceted aspect of synchrony when linked to community composition and temporal patterns.