Dry Soil Conditions Research Articles

Spatial simulation of soil‐water content in dry and wet conditions in a hectometer‐scale degraded alpine meadow

AbstractSoil‐water content (SWC) is a key factor in restoring degraded vegetation in alpine meadow ecosystems, but it has rarely been spatially simulated on a hectometer scale. We simulated SWC for typical dry and wet days in an alpine meadow using multivariate linear regression and autoregressive state‐space equations based on SWC and other soil, terrain, and vegetation parameters to evaluate the efficiency of these two methods in dry and wet soil‐moisture conditions. SWC measured on a typical dry day (SWC‐D) and a wet day (SWC‐W) increased and decreased with depth, respectively, and SWC‐D was similar to SWC‐W at a depth of 50 cm. Both SWC‐D and SWC‐W were significantly correlated with soil bulk density (BD), capillary porosity, silt content (Silt), gravel and stone content (GSC), pH, and organic carbon density (OCD), and both SWC‐D and SWC‐W were significantly auto‐correlated and cross‐correlated with BD, Silt, GSC, pH, and OCD at more than one lag distance. Multivariate linear regression using three variables in both dry and wet conditions had the highest accuracy, and the accuracy was generally higher for dry conditions than it was for wet conditions. The bivariate state‐space model was the most accurate for both dry and wet soil conditions, but the expression variables were totally different, with pH and OCD for dry day and BD and Silt for wet day. The conditions of soil moisture should thus be considered when choosing variables with which to simulate SWC, instead of only considering the relationships between SWC and other variables.

Dye Tracer Visualization of Infiltration Patterns in Soils on Relict Charcoal Hearths

Anthropogenically modified soils are often characterized by a high heterogeneity of substrates and show unique patterns of water infiltration. Such effects are not limited to intensively used or disturbed agricultural and technogenic soils, but can also occur as legacies of former land use in forested areas. The remains of historic charcoal hearths represent a widespread legacy of historic land use. Soils at relict charcoal hearths (RCHs) are most prominently altered by the deposition of a layer of charcoal-rich substrate on top of the natural soil surface. The presence of such a technogenic layer can considerably influence infiltration and soil wetness patterns on the sites. This study describes the spatial patterns of infiltration and soil wetness at charcoal hearth sites compared with undisturbed sandy forest soils for a historic charcoal production area north of Cottbus, Germany. We characterized six plots on RCH and reference soils under pine, oak and mixed forest by visualizing preferential flow patterns of infiltrating water in dye tracer experiments. Additionally, we characterized bulk density, soil organic matter contents and water repellency, using water drop penetration time (wdpt) tests, of the RCH and reference soil horizons. The results reflect that the persistence of water repellency of both the technogenic substrates and the natural topsoils is extremely high under dry conditions, but is drastically reduced after wet antecedent conditions. The dye tracer experiments reflect increased preferential flow on the RCHs for dry soil conditions, for which infiltration is limited to very few flow paths in the technogenic substrate layer. Differences between RCH and reference soils are less clear for higher antecedent soil wetness, for which the results indicate more uniform wetting of the technogenic substrates. We conclude that the structural properties of the additional technogenic substrate layer of RCHs have characteristic effects on water infiltration, causing a high temporal variation of preferential flow in relation to antecedent soil moisture conditions. These effects can result in high heterogeneity of soil moisture for dry conditions, and generally in a high temporal variation of soil wetness in RCHs soils.

Hysteresis analysis of nitrate dynamics in the Neuse River, NC

Anthropogenic activities have caused N saturation in many terrestrial ecosystems. The transfer of nutrients and sediments to freshwater environments has resulted in water quality impairments including eutrophication, increased turbidity, ecosystem acidification, and loss of biodiversity. Storm events account for the transport of a large proportion of nutrients and sediments found in watersheds on an annual basis. To implement effective water-quality management strategies, the importance of surface and subsurface flow paths during storm events and low flow conditions need to be quantified. The increased availability of optical in-situ sensors makes high-frequency monitoring of catchment fluxes practical. In this study, we present a high-resolution nitrate monitoring record over a 10-year period in the Neuse River Basin near Clayton, North Carolina. The relationship between discharge and nitrate concentration for 365 storm events are categorized into hysteresis classes that indicate different transport mechanisms into the river. Storm events over the entire period of this study are divided between clockwise, counter-clockwise, and complex hysteresis patterns, indicating multiple nitrate flow paths during different seasons and years. Logistic regression of a suite of environmental variables demonstrates that antecedent soil moisture is a significant factor in determining the storm hysteresis class, with the odds of counter-clockwise hysteresis increasing by 10.3% for every 1 percentage point increase in the soil moisture. There is also an overlying seasonal effect, which indicates that dry soil conditions and frequent small storms during summer leads to greater nitrate transport on the rising limb, in contrast to slower, groundwater-driven inputs during the rest of the year.

ESTIMATION OF VERTICAL DUST EMISSION FLUX AT A SITE IN THE MONGOLIAN GOBI DURING A DUST STORM PERIOD

A meteorological and dust monitoring tower with 20 m height set up at a Nomgon site in Umnugobi Aimag in the Mongolian Gobi in 2010. The Nomgon monitoring tower equipped with wind speed sensors at 2, 4, 10 and 20 m height above the ground level (AGL), a wind direction sensor at 10 m height, a sonic anemometer to measure turbulent momentum flux at 8 m height and a soil moisture sensor at 5 cm depth. We had a purpose to measure dust concentration of PM10 at two levels using Dust-Trak instruments during an intensive observation period (IOP) of a dust event in spring. A dust storm was expected in the Mongolian Gobi from 30 April to 1 May 2016 and two Dust-Traks were set at 0.9 and 2.95 m heights in the tower during this IOP for measuring PM10. Wind data at 2 and 10 m height, three wind components at 8 m height by a sonic anemometer, soil moisture (volumetric water content) data in 5 cm depth and dust concentrations of PM10 at two levels are used in this study. These data from the sensors and instruments in the tower were used for estimation friction velocity and vertical dust flux at the Nomgon site. In association with a surface cyclone, its frontal system and a trough aloft, the expected dust storm occurred in the Mongolian Gobi during the IOP period. Dust concentrations of PM10 increased during the dust storm period due to raised wind speed in the dry conditions of air and soil. The present study aimed to estimate friction velocity (u*) and vertical dust flux (F) around Nomgon site in the Mongolian Gobi desert during the dust storm period. The estimation results were presented in this paper.

Orphan Legumes Growing in Dry Environments: Marama Bean as a Case Study.

Plants have developed morphological, physiological, biochemical, cellular, and molecular mechanisms to survive in drought-stricken environments with little or no water caused by below-average precipitation. In this mini-review, we highlight the characteristics that allows marama bean [Tylosema esculentum (Burchell) Schreiber], an example of an orphan legume native to arid regions of southwestern Southern Africa, to flourish under an inhospitable climate and dry soil conditions where no other agricultural crop competes in this agro-ecological zone. Orphan legumes are often better suited to withstand such harsh growth environments due to development of survival strategies using a combination of different traits and responses. Recent findings on questions on marama bean speciation, hybridization, population dynamics, and the evolutionary history of the bean and mechanisms by which the bean is able to extract and conserve water and nutrients from its environment as well as aspects of morphological and physiological adaptation will be reviewed. The importance of the soil microbiome and the genetic diversity in this species, and their interplay, as a reservoir for improvement will also be considered. In particular, the application of the newly established marama bean genome sequence will facilitate both the identification of important genes involved in the interaction with the soil microbiome and the identification of the diversity within the wild germplasm for genes involved drought tolerance. Since predicted future changes in climatic conditions, with less water availability for plant growth, will severely affect agricultural productivity, an understanding of the mechanisms of unique adaptations in marama bean to such conditions may also provide insights as to how to improve the performance of the major crops.

Catchment‐Scale Shifts in the Magnitude and Partitioning of Carbon Export in Response to Changing Hydrologic Connectivity in a Northern Hardwood Forest

AbstractThe capacity of forest soils to store organic carbon is influenced by changing hydrologic connectivity. We hypothesized that hydrologic connectivity, the water‐mediated transfer of matter and energy between different landscape positions, controls the partitioning between aquatic and atmospheric soil carbon fates. Results from a 5‐year study of a northern hardwood forested catchment indicated that hydrologic connectivity affected both the magnitude and fate of carbon export. Atmospheric carbon export was the major export pathway from the catchment; its rate was regulated by topographic position (i.e., uplands, ecotones, and wetlands) but enhanced or supressed through changes in soil moisture and hydrologic connectivity. Wetter soil conditions reduced CO2 flux from the ecotones and wetlands where microbial respiration was oxygen‐limited, whereas drier soil conditions that decreased hydrologic connectivity increased CO2 flux by relieving the oxygen limitation. In contrast, aquatic carbon export was a minor export pathway from the catchment and was driven by hydrologic connectivity, with less carbon export during relatively low discharge years. Past trends suggest a shift to a warmer climate and changes in the timing, duration, and intensity of hydrologic connectivity that are leading to an increase in annual atmospheric carbon export but a decrease in annual aquatic carbon export, despite the intensification of autumn storms. The increase in atmospheric carbon export creates a positive feedback for climate warming that will further disrupt hydrologic connectivity and aquatic carbon export, with consequences for downstream streams and lakes.

Tree Water Use Patterns as Influenced by Phenology in a Dry Forest of Southern Ecuador.

Tropical dry forests are composed of tree species with different drought coping strategies and encompass heterogeneous site conditions. Actual water use will be controlled by soil moisture availability. In a premontane dry forest of southern Ecuador, tree water use patterns of four tree species of different phenologies were studied along an elevational gradient, in which soil moisture availability increases with altitude. Main interest was the influence of variation in soil moisture, vapor pressure deficit, species (representing phenology), elevation, and tree diameter on water use. Special emphasis was put on the stem succulent, deciduous Ceiba trichistandra, as high water use rates and drought coping involving stem succulence was to be expected. Tree water use rates increased linearly with diameter across species at high soil water content. However, when soil moisture declined, sap flux densities of the species responded differently. The stem succulent, deciduous Ceiba and other deciduous tree species reduced sap flux sensitively, whereas sap flux densities of the evergreen (broad leaved) Capparis scabrida were increasing. This was also reflected in diurnal hysteresis loops of sap flux vs. vapor pressure deficit (VPD) of the air. Under dry soil conditions, Ceiba and other deciduous tree species had much smaller areas in the hysteresis loop, whereas the area of Capparis was largely enhanced compared to wet conditions. The evergreen Capparis potentially had access to deeper soil water resources as water use patterns suggest that top soil drought was tolerated. The deciduous species followed a drought avoidance strategy by being leafless in the dry season. The stem succulent deciduous Ceiba flushed leaves at the end of the dry season before the rainy season began and also re-flushed early in the dry season after a rain event; however, water use rates at this occasion remained low. Ceiba was also ready for fast and strong response in water use when conditions were most favorable during the wet season. The study thus indicates a strong influence of species’ drought coping strategy on water use patterns in tropical dry forests.

Variation and driving factors of nitrous oxide emissions from irrigated paddy field in the arid and semiarid region

Agricultural pollution source as Nitrous oxide (N2O) emission from irrigated paddy field as affected by overuse of chemical fertilizer application and flooding irrigation is the primary anthropogenic source of nitrogen (N) losses in the Ningxia irrigation district. The emissions variation and driving factors of N2O emission in the large irrigation districts needs much more investigation. A static chamber-gas chromatograph method was conducted to quantify N losses from a paddy field in Lingwu Farm during 2009–2010. Three nitrogen (N) treatments were conducted, including the conventional N application rate of 300 kg ha−1 (N300), the reducing N application rate of 240 kg ha−1 (N240) and control plot (N0). The N2O emissions due to combined effects of the fertilizer application and flood irrigation after winter dry follow was 2.86–3.27 kg ha−1 in N300. The flood irrigation at the beginning of the rice transplanting promotes N2O emissions due to nitrification–denitrification of a richer N source provided by the N fertilizer accumulation of soil NH4+ and NO3-. During the rice growth stage when the paddy field was submerged, N2O emission was very low while intermittent irrigation before tillering and the maturation stages, frequent alteration of dry and wet soil condition enhance N2O emission. The reducing N fertilizer application improved the recovery rate in rice and resulted in a less N2O emission from irrigated paddy field in the arid and semiarid region while keeping the rice yield.

Quantifying Water Productivity Using Seed Priming and Micro Irrigation in Wheat

Field studies were conducted during the four Rabi seasons (2011-12 to 2014-15) to investigate the impact of seed priming and micro irrigation on crop establishment, growth, productivity, and water productivity in wheat under different moisture regimes. Results indicated that sprouted seed (5830 kg ha-1) and primed seed (5766 kg ha-1) produced significantly higher grain yield in comparison to un-primed seeds (5416 kg ha-1). The germination was quick in the primed and sprouted seeds relative to non-primed seeds resulting in a better crop establishment and higher yield under optimum, sub-optimum and dry soil conditions. Irrigation method treatments viz., check basin, drip, sprinkler and drip + rainport showed that the grain yield was highest in the drip + rainport. Water productivity was highest in drip method of irrigation (1.61 kg m-3 ) followed by drip + rainport method (1.60 kg m-3 ) with a maximum mean productivity of 5539 kg ha-1 . Around 600 m3 ha-1 has been saved using seed priming thus reducing the cultivation cost by 382/ha. Among the micro irrigation techniques, water saved was highest in drip followed by sprinkler and drip + rainport. The study suggests for adoption of drip and seed priming to take advantage of yield enhancement as well as cost reduction through reduced utilisation of water.

Potensi Tumbuhan Xanthostemon novoguineensis Valeton (Myrtaceae) dalam Fitoteknologi

This article is essential in a further analysis that related with potential feasibility function of Xanthostemon novoguineensis in phytotechnology from one of an endemic plant in Papua, particularly in the remediation of polluted environment and the phytostructure of open green space area. This review aims to analyse the potential of this plant based on literature review and compare each research results  towards some species from Myrtaceae family. X. novoguineensis may be cultivated on an open green space area in Papua due to complying suitable requirements. Those requirements are namely ecology function as a source of insect diets, social-cultural functions in represent culture, the the relationship among Papuan Ethnic and their nature, and aesthetic functions due to its beautiful flower. In addition, the plant has a potential in phytoremediation of polluted environment due to its adaptation ability in a dry soil condition. As the comparison, the phytostructure of open green space area context, X. chrysanthus has been cultivated on a public and private open green space area in Malaysia and Singapore. It has an important role as ecology function due to provide the source of food to many birds species undirectly. Owing to make the city landscape greater, the flower of X. chrysanthus, which has conspicuously and magnificently yellow colour, is a suitable plant to be cultivated. Furthermore, in the remediation assessment of polluted environment, X. chrysanthus has the abilities in adaptation on the dry environment. The range levels acid (pH) of soil are 2-2.5. Interestingly, X. melanoxylon, which is an endemic species from Solomon Island, is growth naturally in an ultrafamic soils, consist of a high concentration of chromium, nickel, and magnesium. It also has a low degree of plants biodiversity. Therefore, according to X. chrysanthus and X. melanoxylon, X. novoguneensis has a tremendous potential as a candidate in Phytostructure and Phytoremediation. However, the further investigation is required to reveal the potential and the conservation challenge of this plant in Papua. Key words: phytoremediation, phytostructure, open green space area, X. chrysanthus, Potential.

Degradation of atrazine in soil by dielectric barrier discharge plasma – Potential singlet oxygen mediation

Dielectric barrier discharge (DBD) was used for the first time to remediate atrazine-polluted soil in a plane-to-grid plasma reactor operating with air at atmospheric pressure. It was established that atrazine degradation efficiency is an increasing function of applied voltage and discharge frequency. The degradation efficiency of atrazine in dry soil reached as high as 86.9% and 98.1% after 60 min of plasma treatment, starting from initial pollutant concentrations of 100 and 10 mg/kg, respectively. Low soil moisture content (5–10%) was found to enhance atrazine degradation in the DBD reactor in comparison to dry soil conditions. Atrazine mineralization after 60 min of treatment was 65.5% as confirmed by total organic carbon (TOC) analysis. The degradation profile of atrazine under DBD treatment was assessed using Fourier transform infrared spectroscopy (FTIR) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). Several degradation pathways of atrazine were identified in addition to those previously reported with OH, H2O2, or O3 as the main oxidizing agents. The detected degradants included des-ethyl atrazine, hydroxy atrazine and de-ethylated oligomers of atrazine with the isopropyl group being largely preserved. An atrazine degradation mechanism under DBD conditions is proposed that is consistent with the intermediates identified and supports the dominant involvement of singlet oxygen in initiating the degradation under DBD conditions.

Evaluation of Several Sampling Procedures for Spatial Analysis of Natural Turfgrass Sports Field Properties

Abstract Spatial analysis of sports field properties are valuable for the development of a site-specific management program. Our objective was to evaluate six sampling grid sizes (2.4 m × 4.8 m, 4.8 m × 4.8 m, 4.8 m × 9.6 m, 9.6 m × 9.6 m, 9.6 m × 19.2 m, and 19.2 m × 19.2 m) for the spatial analysis of volumetric water content (VWC), penetration resistance, and normalized difference vegetative index (NDVI) on two football fields (sandy loam and sand capped soils) near field capacity and under drier soil conditions. Descriptive statistics and geostatistical methods (spatial maps and kriging variances) were employed to compare results of the sampling grid sizes. Spatial variations of measured properties between soil moisture conditions were minimal for each sampling grid size; however, the magnitude of VWC and penetration resistance was strongly influenced. Small-scale variability of VWC decreased on maps created from the 9.6 m × 9.6 m sampling grid and greater, but large scale variability was evident with most sampling grids. Small-scale variability of penetration resistance was more noticeable on the native soil field, while comparable maps were observed for all sampling grids between 2.4 m × 4.8 m and 9.6 m × 9.6 m when the field was near field capacity. On the sand capped field, the 19.2 m × 19.2 m sampling grid produced the only incomparable map of penetration resistance, regardless of soil moisture condition. NDVI results were influenced by paint present on each field. It is recommended that sports field managers begin with a 4.8 m × 9.6 m sampling grid to conduct a baseline standard of field properties when soil is near field capacity. Subsequent sampling should be conducted under similar soil moisture conditions with the baseline used for comparison over time. The sampling grid can be adjusted depending on the variability of the field property and desired accuracy.

Cover Crop Mixtures Grown for Annual Forage in a Semi‐Arid Environment

Core IdeasCover crop species combinations can affect productivity and weed invasion.Mixtures with equal species proportions did not yield more forage or have less weeds.Spring‐planted cover crops suppressed weeds regardless of mixture or monoculture.Hot dry weather can reduce productivity of late‐summer planted cover crop mixtures.Use of cover crop mixtures in the dry short‐season environment of the northern Great Plains requires knowledge of how species combinations affect productivity and weed invasion. We hypothesized that mixtures would be more productive and suppress weeds better than monocultures. Fifteen combinations of proso millet (Panicum milaceumL), triticale (Triticosecale rimpauiWittm.), red clover (Trifolium pratenseL.), and radish (Raphanus sativusL.) were sown in spring (July harvest) and late‐summer (October harvest) for 3 yr at Mandan, ND. Treatments included four monocultures, four mixtures dominated by one species, six mixtures dominated by pairs of species, and one equal mixture. On average, spring‐planted mixtures yielded 30 to 60% more forage (2400 kg dry matter ha−, 3 yr avg) than the average of spring‐planted monocultures (1720 kg ha−, 3‐yr avg.) when planted in spring. Mixtures, however, did not yield more forage than the most productive monoculture (triticale; 3165 kg ha−, 3 yr avg.). The late‐summer planted cover crops produced little forage (94–155 kg ha−) because of dry soil conditions and erratic rainfall. Mixtures with equal proportions of species did not yield more forage or have fewer weeds than other mixtures. Species mixtures affected nutritive value. Grass‐dominated mixtures had lower crude protein and greater fiber concentrations than radish‐dominated mixtures. Cover crop mixtures can yield more than monocultures when planted in spring in this short‐season environment; however, use of cover crop mixtures in late‐summer does not mitigate risk of poor establishment and low productivity because of hot dry weather.

Rooting plasticity in wild and cultivated Andean Chenopodium species under soil water deficit

Rooting plasticity is critical for plants exploiting patchy soil-water resources, but empirical evidence remains controversial due to complex root/soil interactions in natural and agricultural environments. We compared cultivated and wild Chenopodium populations from distinct agroecological background to assess their rooting plasticity when exposed to contrasting wet-dry soil profiles in a controlled environment. Four treatments of increasing dryness were applied during 6 weeks in plants of Chenopodium hircinum, Chenopodium pallidicaule and two ecotypes (wet- and dry-habitat) of Chenopodium quinoa grown in rhizotrons. Root system architecture and growth were sequentially mapped. At the end of the experiment, plant and root morphological traits and dry biomass were measured. Contrary to the other two species, C. quinoa showed accelerated taproot growth in dry soil conditions. The dry-habitat C. quinoa ecotype showed consistently higher plant traits related to longer, coarser, and more numerous root segments which give it a faster taproot growth and sustained root branching at depth in dry soil. High rooting plasticity confers the advantage of fast root elongation and deep soil exploration under soil water deficit. Variation in intrinsic root traits and plastic responses among Chenopodium populations controls their root foraging capacity facing patchy soil-water resources.

Impacts of the Atlantic Multidecadal Variability on North American Summer Climate and Heat Waves

The impacts of the Atlantic multidecadal variability (AMV) on summertime North American climate are investigated using three coupled global climate models (CGCMs) in which North Atlantic sea surface temperatures (SSTs) are restored to observed AMV anomalies. Large ensemble simulations are performed to estimate how AMV can modulate the occurrence of extreme weather such as heat waves. It is shown that, in response to an AMV warming, all models simulate a precipitation deficit and a warming over northern Mexico and the southern United States that lead to an increased number of heat wave days by about 30% compared to an AMV cooling. The physical mechanisms associated with these impacts are discussed. The positive tropical Atlantic SST anomalies associated with the warm AMV drive a Matsuno–Gill-like atmospheric response that favors subsidence over northern Mexico and the southern United States. This leads to a warming of the whole tropospheric column, and to a decrease in relative humidity, cloud cover, and precipitation. Soil moisture response to AMV also plays a role in the modulation of heat wave occurrence. An AMV warming favors dry soil conditions over northern Mexico and the southern United States by driving a year-round precipitation deficit through atmospheric teleconnections coming both directly from the North Atlantic SST forcing and indirectly from the Pacific. The indirect AMV teleconnections highlight the importance of using CGCMs to fully assess the AMV impacts on North America. Given the potential predictability of the AMV, the teleconnections discussed here suggest a source of predictability for the North American climate variability and in particular for the occurrence of heat waves at multiyear time scales.

Effects of soil moisture on dust emission from 2011 to 2015 observed over the Horqin Sandy Land area, China

Abstract Using the observational data of dust concentrations and meteorological parameters from 2011 to 2015, the effects of soil moisture and air humidity on dust emission were studied at long (monthly) and short (several days or hours) time scales over the Horqin Sandy Land area, Inner Mongolia of China. The results show that the monthly mean dust concentrations and dust fluxes within the near-surface layer had no obvious relationship with the monthly mean soil moisture content but had a slightly negative correlation with monthly mean air relative humidity from 2011 to 2015. The daily mean soil moisture exhibited a significantly negative correlation with the daily mean dust concentrations and dust fluxes, as soil moisture changed obviously. However, such negative correlation between soil moisture and dust emission disappeared on dust blowing days. Additionally, the effect of soil moisture on an important parameter for dust emission, the threshold friction velocity (u∗t), was investigated during several saltation-bombardment and/or aggregation-disintegration dust emission (SADE) events. Under dry soil conditions, the values of u∗t were not influenced by soil moisture content; however, when the soil moisture content was high, the values of u∗t increased with increasing soil moisture content.

Comparing topsoil charcoal, ash, and stone cover effects on the postfire hydrologic and erosive response under laboratory conditions

AbstractWildfires typically transform vegetation and litter into a heterogeneous layer of ash and charred material covering the soil surface that can substantially modify the postfire hydrological and erosive response. To further elucidate the influence of postfire covering layers on sheet and concentrated flow erosion, we carried out laboratory rainfall and inflow simulations on 5 distinct soil surface conditions: bare soil, with a protective cover of char, ash, stones, and a combination thereof simulating field conditions. Each of 3 replicate simulations per treatment involved 4 runs, the first 2 simulating just rain (at 56 mm hr−1) under dry and wet soil conditions and the next 2 simulating rain together with inflow at high and extreme rates (0.76 and 1.4 L min−1). Overall runoff over the 4 runs together was lower for all 4 types of protective cover than for bare soil, but ash and char were clearly less effective than stones and, in particular, field conditions with runoff reductions of 25%, 23%, 40%, and 70%, respectively. Stones and field conditions were similarly effective in reducing overall erosion rates (with 47% and 77%, respectively), whereas ash and char even slightly increased overall erosion rates compared to bare soil. Ash and char were effective in reduction erosion but only during the first 2 runs under simulated rainfall. The greater effectiveness of the field conditions suggested synergistic effects between its 3 components, probably due to the stones enhancing infiltration and increasing flow resistance, thereby hampering detachment of ash and char and/or enhancing their deposition.

Water restriction in viviparous lizards causes transgenerational effects on behavioral anxiety and immediate effects on exploration behavior

Behavioral plasticity induced by maternal effects is crucial in adjusting offspring phenotype to match the environment. In particular, changes in water availability during development may initiate a range of behavioral responses, such as natal dispersal, but the contribution of maternal effects from water stress in explaining behavioral variation has been overlooked so far. In this study, we examined behavioral plasticity of juvenile common lizards (Zootoca vivipara) in response to changes in pre-natal and post-natal hydric conditions. We exposed pregnant mothers either to a moderate water restriction or to ad libitum access to water. We used neutral arena tests to measure repeatedly activity and space use behaviors of their offspring, either in dry or wet soil conditions, at two distinct life stages (juveniles and yearlings) in order to quantify behavioral flexibility, age differences, and personalities (consistent inter-individual differences). Juveniles and yearlings had greater exploration scores in dry than wet conditions regardless of the pre-natal conditions. Pre-natal water restriction and dry post-natal conditions enhanced thigmotaxis (i.e., a behavior related to anxiety) in juveniles. Maternal environment did not influence behavioral flexibility nor the behavior of yearlings. Behaviors were barely repeatable in juveniles and inconsistent through early life. Assuming that dry conditions may initiate flight responses, these results suggest complex relationships between the developmental timing of water stress, exploration and anxiety behaviors, and dispersal syndromes. Water restriction should initiate a range of behaviors related to a flight response. However, there is little evidence that changes in water availability across development influence offspring behavior in wild animals. Experiments with lizards demonstrate that maternal water restriction increased the anxiety of their juveniles, whereas their exploration was higher in dry environments. Thus, water availability may be a critical determinant of space use behavior and dispersal syndromes.

Effects of soil water decline on diurnal and seasonal variations in sap flux density for differently aged Japanese cypress (Chamaecyparis obtusa) trees

The effects of soil drought on transpiration are often neglected when predicting transpiration for forests in humid regions under the influence of the Asian monsoon. These effects have indeed been neglected for Japanese cypress, Chamaecyparis obtusa, a major plantation species in Japan and the surrounding area, probably because previous studies have reported no clear effects of soil drought on transpiration for Japanese cypress forests. However, a few studies have reported an apparent reduction in transpiration with soil drought for young Japanese cypress forests. It remains unclear whether such a reduction in transpiration is limited to young Japanese cypress forests or if it is not uncommon for mature Japanese cypress forests, which occupy a large area in Japan. To clarify this point, we conducted sap flux measurements in a year with soil drought on three differently aged Japanese cypress stands including mature (43 years old) and relatively young (23 and 26 years old) trees. In a diurnal time scale, a cross correlation analysis of sap flux density (Fd) and vapor pressure deficit (VPD) showed that the time lags between Fd and VPD were 1-3 h in dry soil conditions. These were larger than those of wet soil conditions (<1 h) for all sample trees. Fd at a given VPD in dry soil conditions was smaller than that in wet soil conditions for all sample trees; a 28%–63% reduction in the rate of change in Fd was observed under dry soil conditions. Because our results were obtained when the non-exceedance probability of recorded monthly precipitation was 9%–18%, the results suggest the need to consider the effects of soil drought more extensively. Those effects should be considered for not only relatively young but also mature Japanese cypress when predicting diurnal and seasonal patterns of transpiration in years with soil drought, and when predicting inter-annual patterns of transpiration for Japanese cypress despite humid temperate climate.

Interannual variations in needle and sapwood traits of Pinus edulis branches under an experimental drought.

In the southwestern USA, recent large‐scale die‐offs of conifers raise the question of their resilience and mortality under droughts. To date, little is known about the interannual structural response to droughts. We hypothesized that piñon pines (Pinus edulis) respond to drought by reducing the drop of leaf water potential in branches from year to year through needle morphological adjustments. We tested our hypothesis using a 7‐year experiment in central New Mexico with three watering treatments (irrigated, normal, and rain exclusion). We analyzed how variation in “evaporative structure” (needle length, stomatal diameter, stomatal density, stomatal conductance) responded to watering treatment and interannual climate variability. We further analyzed annual functional adjustments by comparing yearly addition of needle area (LA) with yearly addition of sapwood area (SA) and distance to tip (d), defining the yearly ratios SA:LA and SA:LA/d. Needle length (l) increased with increasing winter and monsoon water supply, and showed more interannual variability when the soil was drier. Stomatal density increased with dryness, while stomatal diameter was reduced. As a result, anatomical maximal stomatal conductance was relatively invariant across treatments. SA:LA and SA:LA/d showed significant differences across treatments and contrary to our expectation were lower with reduced water input. Within average precipitation ranges, the response of these ratios to soil moisture was similar across treatments. However, when extreme soil drought was combined with high VPD, needle length, SA:LA and SA:LA/d became highly nonlinear, emphasizing the existence of a response threshold of combined high VPD and dry soil conditions. In new branch tissues, the response of annual functional ratios to water stress was immediate (same year) and does not attempt to reduce the drop of water potential. We suggest that unfavorable evaporative structural response to drought is compensated by dynamic stomatal control to maximize photosynthesis rates.