Decreasing Soil Moisture Research Articles

Modelling the regional sensitivity of snowmelt, soil moisture, and streamflow generation to climate over the Canadian Prairies using a basin classification approach

Abstract. This study evaluated the effects of climate perturbations on snowmelt, soil moisture, and streamflow generation in small Canadian Prairies basins using a modelling approach based on classification of basin biophysical characteristics. Seven basin classes that encompass the entirety of the Prairies Ecozone in Canada were determined by cluster analysis of these characteristics. Individual semi-distributed virtual basin (VB) models representing these classes were parameterized in the Cold Regions Hydrological Model (CRHM) platform, which includes modules for snowmelt and sublimation, soil freezing and thawing, actual evapotranspiration (ET), soil moisture dynamics, groundwater recharge, and depressional storage dynamics including fill and spill runoff generation and variable connected areas. Precipitation (P) and temperature (T) perturbation scenarios covering the range of climate model predictions for the 21st century were used to evaluate climate sensitivity of hydrological processes in individual land cover and basin types across the Prairies Ecozone. Results indicated that snow accumulation in wetlands had a greater sensitivity to P and T than that in croplands and grasslands in all basin types. Wetland soil moisture was also more sensitive to T than the cropland and grassland soil moisture. Jointly influenced by land cover distribution and local climate, basin-average snow accumulation was more sensitive to T in the drier and grassland-characterized basins than in the wetter basins dominated by cropland, whilst basin-average soil moisture was most sensitive to T and P perturbations in basins typified by pothole depressions and broad river valleys. Annual streamflow had the greatest sensitivities to T and P in the dry and poorly connected Interior Grasslands (See Fig. 1) basins but the smallest in the wet and well-connected Southern Manitoba basins. The ability of P to compensate for warming-induced reductions in snow accumulation and streamflow was much higher in the wetter and cropland-dominated basins than in the drier and grassland-characterized basins, whilst decreases in cropland soil moisture induced by the maximum expected warming of 6 ∘C could be fully offset by a P increase of 11 % in all basins. These results can be used to (1) identify locations which had the largest hydrological sensitivities to changing climate and (2) diagnose underlying processes responsible for hydrological responses to expected climate change. Variations of hydrological sensitivity in land cover and basin types suggest that different water management and adaptation methods are needed to address enhanced water stress due to expected climate change in different regions of the Prairies Ecozone.

Screening of cacao clones for drought tolerance by assessing predawn leaf water potential, growth, and leaf gas exchange

Drought in cacao-producing regions worldwide is causing a decrease in yield and, in severe cases, leading to plant death. This primarily affects small farmers who lack sufficient financial resources or water availability to irrigate their plantations. This study aimed to test 83 cacao clonal genotypes for drought tolerance by evaluating their physiological and morphological features. These genotypes, referred to as drought-tolerant cacao (DTC) genotypes, were selected through mass selection from regions of Bahia, Brazil, severely affected by prolonged droughts. Seedlings of the DTC clonal genotypes and two control clones (CCN 51- drought-intolerant and CEPEC 2002 – drought-tolerant) were obtained from rooted cuttings of plagiotropic branches and evaluated under greenhouse conditions. Three experiments (EXP 1, 2, and 3) were conducted using a randomized block design, with three replications each and two plants per replication of each clonal genotype to test for drought tolerance. Data analyses were conducted using univariate and multivariate statistical analysis. DTC and control clones were subjected to varying soil moisture contents [70, 60, 50, 40, and 30 % of field capacity (FC)] and their controls (maintained close to 100 % of FC) for approximately 40 to 60 days. The results revealed significant statistical differences in growth variables before the plants were subjected to drought. They were categorized based on vigor into three, four, and three groups for EXP 1, 2, and 3, respectively during cluster analysis. DTC and control clones subjected to drought (70, 60, 50, 40, and 30 % of FC) exhibited significant statistical differences in physiological traits compared to the traits of their respective controls (100 % of FC). However, plant growth remained largely unchanged under drought stress (30 or 40 % of FC). DTC clonal genotypes 15, 17, 23, 41, 61, 66, 90, 91, 92, and 93 were more efficient in maintaining net photosynthesis (A) with decreases in soil moisture, showing greater changes only at 40 % of FC. DTC clonal genotypes 14, 32, 41, 61, 69, 70, 88, 89, 92, 95, and 108 maintained stomatal conductance (gs) values similar to those of their controls. Twenty-three DTC clonal genotypes maintained values of A, gs, E, Ci, A/gs, and A/E close to their respective controls, suggesting that these genotypes present features for drought tolerance.

Non-native earthworms increase the abundance and diet quality of a common woodland salamander in its northern range.

The online version contains supplementary material available at 10.1007/s10530-023-03168-3.

Land inclination controls CO2 and N2O fluxes, but not CH4 uptake, in a temperate upland forest soil

Abstract. Inclination and spatial variability in soil and litter properties influence soil greenhouse gas (GHG) fluxes and thus ongoing climate change, but their relationship in forest ecosystems is poorly understood. To elucidate this, we explored the effect of inclination, distance from a stream, soil moisture, soil temperature, and other soil and litter properties on soil–atmosphere fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) with automated static chambers in a temperate upland forest in eastern Austria. We hypothesised that soil CO2 emissions and CH4 uptake are higher in sloped locations with lower soil moisture content, whereas soil N2O emissions are higher in flat, wetter locations. During the measurement period, soil CO2 emissions were significantly higher on flat locations (p<0.05), and increased with increasing soil temperature (p<0.001) and decreasing soil moisture (p<0.001). The soil acted as a CH4 sink, and CH4 uptake was not significantly related to inclination. However, CH4 uptake was significantly higher at locations furthest away from the stream as compared to at the stream (p<0.001) and positively related to litter weight and soil C content (p<0.01). N2O fluxes were significantly higher on flat locations and further away from the stream (p<0.05) and increased with increasing soil moisture (p<0.001), soil temperature (p<0.001), and litter depth (p<0.05). Overall, this study underlines the importance of inclination and the resulting soil and litter properties in predicting GHG fluxes from forest soils and therefore their potential source-sink balance.

The structure of beta-diversity explains why the relevance of phytoindication increases under the influence of park reconstruction

Urbanization causes the highest local extinction rates and often leads to the loss of the vast majority of native species. Plant communities are sensitive to urban expansion and are therefore indicators of human land use. A city park, part of which has undergone reconstruction, was studied. The study found that the changes in ecological conditions caused by the reconstruction of a city park can be detected using phytoindication. The informativeness of phytoindication scales was shown to increase under conditions of anthropogenic load. The phytoindication scales are a reliable source of information for assessing the state of the vegetation cover of park plantations. The ecological regimes were assessed based on descriptions of the vegetation cover using Didukh's phytoindication scales. The phytoindication approach allows one to identify changes in ecological regimes that occur as a result of park reconstruction and to separate them from ecological regimes of natural origin. The study showed that the reconstruction of the park significantly affects the conditions of the park and the diversity of vegetation. The ratio of useful phytoindicative information compared to information noise in the structure of beta-diversity of the park's plantations increases significantly as a result of the park's reconstruction. The reconstruction of the park has led to changes in the spatial organization of the vegetation cover. The results obtained indicate a decrease in soil moisture as a result of the park's reconstruction. The park’s reconstruction leads to a significant change in the light regime of the park’s plantings, which leads to changes in the park’s vegetation and soils. Reducing the density of plantations as a result of their pruning during the reconstruction process also decreases the amount of fallen leaves that form leaf litter. A significant increase in the variability of the moisture regime under the influence of the park reconstruction was found. The phytoindication revealed a decrease in the acidity of the soil solution as a result of the reconstruction. The changes in soil acidity are accompanied by an increase in phytoindication estimates of carbonate content in the soil. The observed increase in carbonate content estimates may be an artifact when representatives of another ecological group also have related ecological properties that can be misinterpreted as indicators of certain regimes. The phytoindication also revealed trends in the variability of microclimatic conditions in the park as a result of reconstruction. The reconstruction of the park leads not only to a change in the modal levels of ecological regimes, but also to the formation of specific patterns of their spatial distribution. The heterogenization of the ecological space under the influence of reconstruction has been established. This heterogenization is evident in the fact that areas with homogeneous vegetation cover are decreasing. The accuracy of the description of the spatial process was found to have decreased after the park reconstruction procedures. Smooth spatial structures of the park’s vegetation cover without reconstruction are changing into rough spatial structures of the park after reconstruction. The park’s reconstruction obviously disrupts the course of long-term processes that structure the vegetation cover, which leads to temporal and spatial desynchronization of the dynamics of ecological processes. The spatial variation of variables that indicate soil processes can best be described. In contrast, the phytoindication scales that indicate climatic factors are much less spatially structured. The best variogram model to describe the spatial process is also changing under the influence of reconstruction. The significant consequences of the park reconstruction are time variability and spatial heterogeneity of ecological processes.

PENGARUH DURASI IRIGASI TETES TERHADAP REDUKSI LENGAS TANAH PADA LAHAN POLYBAG

Soil moisture is an important factor needed by plants for growth, and therefore the amount of soil moisture that can be stored depends on the type of soil or the composition of the soil-forming materials. Compost is one of the nutrients that is often used in the manufacture of planting media on land in the form of polybags, and the amount of compost composition on the soil is thought to greatly affect the ability to store water in the media, both the size and duration of storage. This study aims to examine the effect of using compost on storage of irrigation water in the form of soil moisture and how long it can be stored. in three-storey drip irrigation. The main data analyzed is soil moisture data (w) and the results of the analysis and discussion and conclusions are drawn descriptively. The results of the analysis show that the initial soil moisture content in the range of 19% -25%, can be given additional soil moisture by irrigation of about 12%. The average daily decrease in soil moisture that occurs in soil variation 1 (70%: 30% ) is 3% -4.4% and in soil variation 2 (50%: 50%), the average moisture reduction is around 3% -6%, soil moisture reduction in variation 2 is greater than soil variation 1 for all floors.

The Results of Experimental Studies of the Physical and Mechanical Properties of an Elastic-Plastic Material for Tribological Properties during Separation

The obtained results of experimental studies on the influence of the physical and mechanical properties of an elastoplastic material (clods of soil and potato tubers) on the factors of its destruction when interacting with an absolutely solid body (separating working body) established that an increase in the density of a soil clod leads to an increase in the effort expended on dynamic destruction, regardless of the size fraction. Within one fractional group, the increase in force from the minimum value necessary for the destruction of the soil clod in the density range from 1300 to 1700 kg/m3 is on average 56–67 N. However, there is a tendency to increase the effort to destroy the soil clod with an increase in the size fraction, including identical density, by 7–8 N, which is 4–5% of the initial value of the destruction force of a given density. The greatest destruction of soil clods is provided at a moisture content of 22–24%, which should be explained by the formation of the physical ripeness of the leached chernozem. In addition, a decrease in soil moisture leads to a more intense adhesion of soil particles to each other and, consequently, to an increase in the force on the soil clod to destroy it.

How temperature and aridity drive lignin decomposition along a latitudinal transect in western Siberia

AbstractClimate change drives a northward shift of biomes in high‐latitude regions. This might have consequences on the decomposition of plant litter entering the soil, including its lignin component, which is one of the most abundant components of vascular plants. In order to elucidate the combined effect of climate and soil characteristics on the decomposition pattern of lignin, we investigated lignin contents and its degree of oxidative decomposition within soil profiles along a climosequence in western Siberia. Soil samples were collected from organic topsoil to mineral subsoil at six sites along a 1500‐km latitudinal transect, stretching from tundra, through taiga and forest steppe to typical steppe. The stage of lignin degradation, as mirrored by decreasing organic carbon‐normalized lignin contents and increasing oxidative alteration of the remnant lignin (acid‐to‐aldehyde ratios of vanillyl‐ and syringyl‐units [(Ac/Al)V and (Ac/Al)S]) within soil horizons, increased from tundra to forest steppe and then decreased to the steppe. Principal component analysis, involving also climatic conditions such as mean annual temperature and aridity index, showed that the different states of lignin degradation between horizons related well to the activity of phenoloxidases and peroxidases, enzymes involved in lignin depolymerization that are produced primarily by fungi and less importantly by bacteria. The low microbial lignin decomposition in the tundra was likely due to low temperature and high soil moisture, which do not favour the fungi. Increasing temperature and decreasing soil moisture, facilitating a higher abundance of fungi, led to increased fungal lignin decomposition towards the forest‐steppe biome, while drought and high pH might be responsible for the reduced lignin decomposition in the steppe. We infer that a shift of biomes to the north, driven by climate change, might promote lignin decomposition in the northern parts, whereas in the south a further retardation might be likely.

Simulation of Hydrological Processes in the Jing River Basin Based on the WEP Model

Inappropriate vegetation reconstruction in the Loess Plateau region has led to a significant increase in regional evapotranspiration and water consumption, further aggravating the shortage of soil water resources in the Loess Plateau region. The Jing River basin is a typical area for vegetation reconstruction in the Loess Plateau region. A thorough understanding of changes in hydrological processes in the Jing River basin is of significant scientific importance for efficient utilization of soil water resources and sustainable vegetation restoration in the region. In this study, the physically based Water and Energy Transfer Processes (WEP) distributed hydrological model was used to simulate key hydrological processes in the Jing River Basin during different periods before and after the implementation of cropland conversion to forest and grassland from 1980 to 2019. The results showed that after the implementation of cropland conversion to forest and grassland from 2000 to 2019, the average runoff volume in the Jing River Basin decreased by 20.91%. The most significant decrease in average runoff occurred in the central and northern parts of the basin, with a maximum reduction of 48.6%. The decrease in runoff in flood season is more obvious. The peak discharge decreased by 24.91%, and the most significant decrease occurred in the northern and central parts of the basin, ranging from 10.3% to 50.2%. The spatial distribution pattern of average soil moisture in the 0–0.8 m soil layer showed more moisture in the south and less in the north, with the minimum value occurring in certain areas in the eastern part of the basin. Overall, the implementation of cropland conversion to forest and grassland led to a certain degree of decrease in soil moisture in the basin. After the implementation of cropland conversion to forest and grassland, reference evapotranspiration fluctuated only in specific areas of the basin with no significant overall change.

Changes in Mediterranean flood processes and seasonality

Abstract. Floods are a major natural hazard in the Mediterranean region, causing deaths and extensive damages. Recent studies have shown that intense rainfall events are becoming more extreme in this region but, paradoxically, without leading to an increase in the severity of floods. Consequently, it is important to understand how flood events are changing to explain this absence of trends in flood magnitude despite increased rainfall extremes. A database of 98 stations in southern France with an average record of 50 years of daily river discharge data between 1959 and 2021 was considered, together with a high-resolution reanalysis product providing precipitation and simulated soil moisture and a classification of weather patterns associated with rainfall events over France. Flood events, corresponding to an average occurrence of 1 event per year (5317 events in total), were extracted and classified into excess-rainfall, short-rainfall, and long-rainfall event types. Several flood event characteristics have been also analyzed: flood event durations, base flow contribution to floods, runoff coefficient, total and maximum event rainfall, and antecedent soil moisture. The evolution through time of these flood event characteristics and seasonality was analyzed. Results indicated that, in most basins, floods tend to occur earlier during the year, the mean flood date being, on average, advanced by 1 month between 1959–1990 and 1991–2021. This seasonal shift could be attributed to the increased frequency of southern-circulation weather types during spring and summer. An increase in total and extreme-event precipitation has been observed, associated with a decrease of antecedent soil moisture before rainfall events. The majority of flood events are associated with excess rainfall on saturated soils, but their relative proportion is decreasing over time, notably in spring, with a concurrent increased frequency of short rain floods. For most basins there is a positive correlation between antecedent soil moisture and flood event runoff coefficients that is remaining stable over time, with dryer soils producing less runoff and a lower contribution of base flow to floods. In a context of increasing aridity, this relationship is the likely cause of the absence of trends in flood magnitudes observed in this region and the change of event types. These changes in flood characteristics are quite homogeneous over the domain studied, suggesting that they are rather linked to the evolution of the regional climate than to catchment characteristics. Consequently, this study shows that even in the absence of trends, flood properties may change over time, and these changes need to be accounted for when analyzing the long-term evolution of flood hazards.

Wildfires in the Larch Range within Permafrost, Siberia

Throughout the larch range, warming leads to frequent fires and an increase in burned areas. We test the hypothesis that fires are an essential natural factor that reset larch regeneration and support the existence of larch forests. The study area included Larix sibirica and L. gmelinii ranges within the permafrost zone. We used satellite-derived and field data, dendrochronology, and climate variables analysis. We found that warming led to an increase in fire frequency and intensity, mean, and extreme (>10,000 ha) burned areas. The burned area is increasing in the northward direction, while fire frequency is decreasing. The fire rate exponentially increases with decreasing soil moisture and increasing air temperature and air drought. We found a contrasting effect of wildfire on regeneration within continuous permafrost and within the southern lowland boundary of the larch range. In the first case, burnt areas regenerated via abounded larch seedlings (up to 500,000+ per ha), whereas the south burns regenerated mostly via broadleaf species or turned into grass communities. After the fire, vegetation GPP was restored to pre-fire levels within 3–15 years, which may indicate that larch forests continue to serve as carbon stock. At the southern edge of the larch range, an amplified fire rate led to the transformation of larch forests into grass and shrub communities. We suggested that the thawing of continuous permafrost would lead to shrinking larch-dominance in the south. Data obtained indicated that recurrent fires are a prerequisite for larch forests’ successful regeneration and resilience within continuous permafrost. It is therefore not necessary to suppress all fires within the zone of larch dominance. Instead, we must focus fire suppression on areas of high natural, social, and economic importance, permitting fires to burn in vast, larch-dominant permafrost landscapes.

Effects of Spring Drought and Nitrogen Addition on Productivity and Community Composition of Degraded Grasslands.

To explore whether there were differences among the patterns of response of grasslands with different levels of degradation to extreme drought events and nitrogen addition, three grasslands along a degradation gradient (extremely, moderately, and lightly degraded) were selected in the Bashang area of northern China using the human disturbance index (HDI). A field experiment with simulated extreme spring drought, nitrogen addition, and their interaction was conducted during the growing seasons of 2020 and 2021. The soil moisture, aboveground biomass, and composition of the plant community were measured. The primary results were as follows. (1) Drought treatment caused soil drought stress, with moderately degraded grassland being the most affected, which resulted in an 80% decrease in soil moisture and a 78% decrease in aboveground biomass. The addition of nitrogen did not mitigate the impact of drought. Moreover, the aboveground net primary production (ANPP) in 2021 was less sensitive to spring drought than in 2020. (2) The community composition changed after 2 years of drought treatment, particularly for the moderately degraded grasslands with annual forbs, such as Salsola collina, increasing significantly in biomass proportion, which led to a trend of exacerbated degradation (higher HDI). This degradation trend decreased under the addition of nitrogen. (3) The variation in drought sensitivities of the ANPP was primarily determined by the proportion of plants based on the classification of degradation indicators in the community, with higher proportions of intermediate degradation indicator species exhibiting more sensitivity to spring drought. These findings can help to provide scientific evidence for the governance and restoration of regional degraded grassland under frequent extreme weather conditions.

Effects of hotter, drier conditions on gaseous losses from nitrogen fertilisers

Global warming is expected to cause hotter, drier summers and more extreme weather events including heat waves and droughts. A little understood aspect of this is its effects on the efficacy of fertilisers and related nutrient losses into the environment. We explored the effects of high soil temperature (>25 °C) and low soil moisture (<40% water filled pore space; WFPS) on emissions of ammonia (NH3) and nitrous oxide (N2O) following application of urea to soil and the efficacy of urease inhibitors (UI) in slowing N losses. We incubated soil columns at three temperatures (15, 25, 35 °C) and three soil moisture contents (20, 40, 60% WFPS) with urea applied on the soil surface with and without UIs, and measured NH3 and N2O emissions using chambers placed over the columns. Four fertiliser treatments were applied in triplicate in a randomised complete block design: (1) urea; (2) urea with a single UI (N-(n-butyl) thiophosphoric triamide (NBPT); (3) urea with two UI (NBPT and N-(n-propyl) thiophosphoric triamide; NPPT); and (4) a zero N control. Inclusion of UI with urea, relative to urea alone, delayed and reduced peak NH3 emissions. However, the efficacy of UI was reduced with increasing temperature and decreasing soil moisture. Cumulative NH3 emission did not differ between the two UI treatments for a given set of conditions and was reduced by 22–87% compared with urea alone. Maximum cumulative NH3 emission occurred at 35 °C and 20% WFPS, accounting for 31% of the applied N for the urea treatment and 25%, on average for the UI treatments. Urease inhibitors did not influence N2O emissions; however, there were interactive impacts of temperature and moisture, with higher cumulative emissions at 40% WFPS and 15 and 25 °C accounting for 1.85–2.62% of the applied N, whereas at 35 °C there was greater N2O emission at 60% WFPS. Our results suggest that inclusion of UI with urea effectively reduces NH3 losses at temperatures reaching 35 °C, although overall effectiveness decreases with increasing temperature, particularly under low soil moisture conditions.

Projection of Future Fire Emissions Over the Contiguous US Using Explainable Artificial Intelligence and CMIP6 Models

AbstractIncreasing temperature and water cycle changes due to warming climate may increase the frequency and intensity of wildfires. Fire emission projections are useful for informing strategies for adaptation and mitigation of fire impacts on societies and ecosystems. Here, we construct a neural network (NN) model explained by the Shapley Additive explanation to predict fire PM2.5 emissions change and understand their drivers over the contiguous US (CONUS) in the mid‐21st century under a high greenhouse gas emissions scenario (SSP5‐8.5). Using future meteorology and leaf area index (LAI) simulated by eight global climate models from the Coupled Model Intercomparison Project Phase 6, future population density, and present‐day land use and land cover (LULC) as input to the NN model, the total fire PM2.5 emissions over CONUS are projected to increase by 4%–75% (model spread). Among different regions, fire emissions in the western US are projected to increase more significantly in June‐July‐August than in other seasons and regions, with the median ratios of future to present‐day fire emissions ranging from 1.67 to 2.86. The increases in fire emissions are mainly driven by increasing normalized temperature (23%–29%) and decreasing soil moisture (2%–10%) in the future. When future LULC change is considered, the projected fire emissions further increase by 58%–83% over the western US compared to projections without LULC change because of future increases in vegetation fraction. The results highlight the important role of warmer temperature, decreasing soil moisture, and LULC change in increasing fire emissions in the future.

Increasing amounts of midwestern Tibetan Plateau vortices and their response to soil moisture distribution coupled with different synoptic systems

AbstractTibetan Plateau Vortices (TPVs) are important synoptic systems that affect precipitation over the Tibetan Plateau (TP) and downstream weather. By using daily reanalysis data provided by ECMWF and the objective identification methods, the study identified the basic spatiotemporal changes of TPVs, clustered the TPVs by different dynamic circulation types and explored the dynamic circulation background of the classified TPVs in the midwestern TP and their relationship with thermal factors, such as sensible heat and soil moisture. The results show that TPVs in the midwestern TP exhibited an increasing trend from May to August, resulting from the coupling of dynamics with thermal forcing. The related synoptic circulations were divided into four types according to the dynamic circulations: the shortwave trough, the longwave trough, the shear line and the plateau anticyclone type. Among the TPVs, the percentage of TPVs in the shortwave and longwave trough type was relatively large, accounting for 48.7% and 31.5%, respectively, both of which were dominated by the coupling of increased sensible heat and decreased soil moisture. The shear line type was less affected by thermal factors, and mainly driven by dynamic factors, whereas the soil moisture gradient was responsible for the plateau anticyclone type. The simulation experiment also proved this conclusion.

Assessing hydrological sensitivity to future climate change over the Canadian southern boreal forest

This study develops a physically based hydrological process model using the Cold Region Hydrological Modelling (CRHM) platform to simulate the water budget storages and fluxes over the Canadian southern boreal forest (SBF). Evaluation of the CRHM-based model in a well-gauged SBF basin, White Gull Creek (WGC), Saskatchewan, Canada, indicated quite good performance in reproducing historical observations of streamflow, snow water equivalent (SWE), evapotranspiration (ET) and soil moisture without parameter calibration from streamflow. The entire SBF was then evenly divided into 2243 virtual basins, each of which was structured and parameterized with the same land cover, soil and hydrological parameters as the WGC basin, but with local latitude and topography in order to examine the sensitivity of governing hydrological processes to future climate variability and perturbation. Hydrological sensitivity in the virtual basins was assessed by examining the differences between hydrological simulations driven by 4-km gridded convection-permitting Weather Research and Forecasting (WRF) outputs in the current period (ctrl, 2001–2013) and a Pseudo Global Warming period (pgw, 2087–2099). The WRF simulation in the pgw period was forced by a perturbation of the same boundary conditions from ERA reanalysis data as for the ctrl period, and the perturbation was based on the ensemble-mean of projected changes from the CMIP5 RCP 8.5 emission scenario. Results showed that temperature would increase by 4.5℃ to 7℃ over the SBF but increases in annual precipitation of 15–24% would more than compensate for the effects of warming on runoff generation and result in greater streamflow volumes. Annual streamflow volumes would increase by 64 mm (35%) and 95 mm (16%) in the west and east, and by 48 mm (17%) in the central SBF. Annual snowfall and maximum SWE would decrease by 89–109 mm (∼29%) in the east, 3–8 mm (∼6%) in the west, and 31–50 mm (∼20%) in the central SBF. Annual mean soil moisture storage would decrease by 54–56 mm (27%) in the west and central, and by only 37 mm (14%) in the east SBF. Decreases in soil moisture would be caused by reduced soil freezing and enhanced thawing under future warming which would increase soil water loss from ET, subsurface runoff and percolation into groundwater storage. The larger sensitivity of streamflow and snow processes in the east SBF is partly due to the wetter climate and the larger increase in annual precipitation, the later also buffered the sensitivity of soil moisture to warming. These results show that the SBF would switch to a higher water yield region, dominated by rainfall-runoff fed streamflow over a longer snow-free season, and provide first-order guidance for sustainable water management of the SBF in the future.

Contrasting Drought Propagation Into the Terrestrial Water Cycle Between Dry and Wet Regions

AbstractDrought's intensity and duration have increased in many regions over the last decades. However, the propagation of drought‐induced water deficits through the terrestrial water cycle is not fully understood at a global scale. Here we study responses of monthly evaporation (ET) and runoff to soil moisture droughts occurring between 2001 and 2015 using independent gridded datasets based on machine learning‐assisted upscaling of satellite and in‐situ observations. We find that runoff and ET show generally contrasting drought responses across climate regimes. In wet regions, runoff is strongly reduced while ET is decoupled from soil moisture decreases and enhanced by sunny and warm weather typically accompanying soil moisture droughts. In drier regions, ET is reduced during droughts due to vegetation water stress, while runoff is largely unchanged as precipitation deficits are typically low in these regions and ET decreases are buffering runoff reductions. While these water flux drought responses are controlled by the large‐scale climate regimes, they are additionally modulated by local vegetation characteristics. Land surface models capture the observed water cycle responses to drought in the case of runoff, but not for ET where the ET deficit (surplus) is overestimated (underestimated), related to a misrepresentation of the general soil moisture‐evaporation interplay. In summary, our study illustrates how the joint analysis of machine learning‐enhanced Earth observations can advance the understanding of global eco‐hydrological processes, as well as the validation of land surface models.

РЫХЛЕНИЕ ПОЧВЫ ПЕРЕД РАБОТОЙ СВЕКЛОУБОРОЧНЫХ КОМБАЙНОВ

Sugar beet is an important industrial crop, which, in addition to sugar, contains vitamins, organic acids, microelements, fiber, fructose, etc. Processed products such as pulp and molasses are widely used in animal husbandry. An analysis of long-term observations showed that in dry years, with a decrease in soil moisture by 3-8%, its hardness increases to 47%. At the same time, the shift output of combines decreases, and the average specific fuel consumption per hectare increases and there is an increased wear of the digging working bodies. We studied the effect of loosening the soil before the operation of beet harvesters on the force of extracting root crops, increasing the productivity of combines and reducing specific fuel consumption. In a search experiment to identify the ability of a needle disk to loosen the soil layer and possibly reduce its ability to hold root crops, a prototype soil cultivator was developed. In order to identify the most efficient operation of the ripper, the number of teeth (needles) was changed: 8 - 10 - 12 and the depth of the teeth from 5 to 15 cm in increments of 5 cm. extraction force. During the search experiment, indicators characterizing the physical and mechanical properties of the soil were taken. An analysis of the working bodies of soil rippers was carried out and a model sample of a needle disc ripper was developed. The conducted field tests have shown a decrease in the force of retaining root crops by the soil after the passage of the developed cultivator, which in turn can help reduce the resistance to the work of diggers and, as a result, increase the efficiency of beet harvesters.

Functional response and resistance to drought in seedlings of six shrub species with contrasting leaf traits from the Mediterranean Basin and California.

Extreme drought events during post-fire regeneration are becoming increasingly frequent in Mediterranean-type ecosystems. Understanding how plants with different traits and origins respond to such conditions during early life stages is therefore critical for assessing the effect of climate change. Here, seedlings of three Cistus (semi-deciduous malacophylls from the Mediterranean Basin) and three Ceanothus (evergreen sclerophylls from California) species, two post-fire seeder genera with contrasting leaf traits, were subjected to complete water deprivation for three months in a common garden experiment. The leaf and plant structure, as well as plant tissue water relations were characterized before the drought, and the functional response (water availability, gas exchange, and fluorescence) were monitored during the drought. Both genera exhibited contrasting leaf structure and tissue water relations traits, with higher leaf area, specific leaf area, as well as higher osmotic potential at maximum turgor and turgor loss point in Cistus than Ceanothus. During drought, Ceanothus showed a more conservative use of water than Cistus, with a water potential less sensitive to decreasing soil moisture and a strong decline in photosynthesis and stomatal conductance in response to water deficit, but also a level of fluorescence more responsive to drought than Cistus. However, we could not find a different degree of drought resistance between the genera. This was particularly clear between Cistus ladanifer and Ceanothus pauciflorus, the two most functionally contrasting species, but at the same time the two most drought resistant. Our findings demonstrate that species with different leaf traits and functional responses to water stress may not differ in their degree of drought resistance, at least during the seedling stage. This underlines the need to take general categorizations by genus or functional traits with caution and deepen our knowledge about Mediterranean-type species ecophysiology, especially during early life stages, for anticipating their vulnerability to climate change.

Climate change perception, adaptation strategies, and constraints amongst urban farmers in Anambra Metropolis, Nigeria

ABSTRACT Urban agriculture has been recognized as a climate change and risk reduction strategy. However, it is still unclear how urban farmers perceive climate change and what constraints they encounter in adapting to its impacts. This study aims to understand urban farmers’ perceptions and climate change adaptation constraints in Nigeria. Data were obtained through household surveys using a structured questionnaire. Descriptive and component factor analyses were used in data analysis. The result shows that most urban farmers perceived climate change through its effects on increased weed infestation, drying up of streams/rivers, decrease in soil moisture, etc. Adaptation strategies range from soil and water adaptation options to various adjustments in the farming system. The principal adaptation constraints faced by urban farmers are somewhat diverse in nature and fall within broader institutional, information, and financial constraints. The study reveals that the socioeconomic conditions of urban farmers in developing countries pose a threat to urban agriculture's potential to mitigate climate change. Therefore, there is a need to support urban farmers in developing countries by providing credit facilities and integrating agricultural lands into urban land-use policies.