Soil Water Regime Research Articles

Accumulated Carbon Fractions in Tropical Sandy Soils and Their Effects on Fertility and Grain Yield in an Integrated Crop–Livestock System

Food production in sandy soils has evolved significantly, most notably through the advent of integrated crop–livestock systems (ICLSs). ICLSs increase soil cover, which maintains soil moisture and sequesters carbon (C). Here we investigate the influence of ICLSs on soil physical, chemical, and biochemical properties, and grain yield (GY) in tropical sandy soils in short-time. We compared seven ICLSs in two consecutive crops seasons (with soybean or maize as cash crops) in southeastern Brazil. These were (1) corn + Urochloa brizantha cv. BRS Paiaguás—soybean (ICL-Paiaguás); (2) corn + U. brizantha cv. BRS Piatã—soybean; (3) corn + U. ruziziensis—soybean; (4) corn–soybean under conventional tillage (CT) as a negative control; (5) corn–soybean under no-tillage (NT) as a positive control; (6) Paiaguás grass—continuous grazing (Perennial Paiaguás); (7) and Piatã grass—continuous grazing (Perennial Piatã). Soybean and corn GY data, soil physical and chemical attributes, and soil enzymatic activity were subjected to descriptive statistics and multivariate analysis. CT and NT shared high loadings of H + Al, Al, and soil temperature and low loadings of soil pH, SOM physical and chemical fractions, cationic exchange capacity, and arylsulfatase activity. ICL-Paiaguás and Perennial Piatã had a similarly high loading of total N, humin, total organic carbon, and mineral-associated carbon stocks. The fulvic acid fraction was the most sensitive to C accumulation in the sandy soil under ICLSs. Soil water and thermal regimes were limiting in both CT and NT. The study not only confirms the capacity of conservation mechanisms to enhance soil-based ecosystem functions, but it also highlights the potential of ICLSs to aid sustainable food production even in the context of tropical sandy soils, which frequently receive limited attention in intensive agricultural practices.

Drip Irrigation Soil-Adapted Sector Design and Optimal Location of Moisture Sensors: A Case Study in a Vineyard Plot

To optimise sector design in drip irrigation systems, a two-stage procedure is presented and applied in a commercial vineyard plot. Soil apparent electrical conductivity (ECa) mapping and soil purposive sampling are the two stages on which the proposal is based. Briefly, ECa data to wet bulb depth provided by the VERIS 3100 soil sensor were mapped before planting using block ordinary kriging. Looking for simplicity and practicality, only two ECa classes were delineated from the ECa map (k-means algorithm) to delimit two potential soil classes within the plot with possible different properties in terms of potential soil water content and/or soil water regime. Contrasting the difference between ECa classes (through discriminant analysis of soil properties at different systematic sampling locations), irrigation sectors were then designed in size and shape to match the previous soil zoning. Taking advantage of the points used for soil sampling, two of these locations were finally selected as candidates to install moisture sensors according to the purposive soil sampling theory. As these two spatial points are expectedly the most representative of each soil class, moisture information in these areas can be taken as a basis for better decision-making for vineyard irrigation management.

Hydrological Coupling and Decoupling of Hydric Hemiboreal Forest Sites Inferred from Soil Water Models and Tree-Ring Chronology

The soil water regime often controls whether an ecosystem is a source of greenhouse gases such as CO2 or CH4 or is, instead, a carbon sink. The soil water regime of wetland forests is complicated by ecosystem feedback and landscape scale interactions. An in-depth understanding of these processes is needed to optimize the management of such ecosystems to balance timber production, carbon sequestration and biodiversity preservation. To investigate the soil water regime of non-riparian wetland forests, we set up a physically based Hydrus-1D soil water model for two hydric black alder Alnus glutinosa sites in a lowland hemiboreal setting informed by field observations of the soil water. Further, to gain ecohydrological insights, we explored the correlations between modeled long-term soil water parameters and local dendrochronology. We found that, at the clay soil site, the simulated root water uptake had a significant correlation (up to 0.55) with the residual tree-ring chronology. However, in the sandy soil site, the meteorological conditions—air temperature and precipitation—were better predictors for tree radial growth (correlation up to 0.42). In addition, we observed a trend towards dryer conditions during the modeling period, which might enhance the growing conditions for the considered forest stands due to a reduction in soil waterlogging.

Soil Water Regime, Air Temperature, and Precipitation as the Main Drivers of the Future Greenhouse Gas Emissions from West Siberian Peatlands

This modeling study intended to solve a part of the global scientific problem related to increased concentrations of carbon dioxide in the atmosphere via emissions from terrestrial ecosystems that, along with anthropogenic emissions, make notable contributions to the processes of climate change on the planet. The main stream of CO2 from natural terrestrial ecosystems is related to the activation of biological processes, such as the production/destruction of plant biomass. In this study, the Wetland-DNDC computer simulation model with a focus on nitrogen and carbon biogeochemical cycles was used to study the effect of hydrothermal conditions on greenhouse gas fluxes in West Siberian peatlands. The study was implemented on the site of the world’s largest pristine wetland/peatland system, the Great Vasyugan Mire (GVM). The study was carried out based on data from permanent measurements at meteo stations and our own in situ measurements of hydrological and thermal parameters on sites, which allowed for testing different scenarios of changes in environmental conditions (temperature, precipitation, groundwater level) together with a change in GHG fluxes. The study revealed the air temperature and the level of groundwater as the main drivers controlling CO2 fluxes. The study of different scenarios of change in annual air temperature revealed the threshold of change in the wetland/peatland ecosystem from carbon sink to carbon source to the atmosphere to happen with an increase in the average annual air temperature by 3 °C with reference to the average annual air temperature values in 2019. Also, we found that the wetland/peatland ecosystem turned to act as an active carbon sink with about 7 cm increase in annual groundwater level, compared with its base level of −21 cm.

Responses of soil CO2 efflux and microbial activity to water deficit under conventional and adaptation technology

Frequent periods of low rainfall accompanying climate change are expected to affect many aspects of agricultural production and greenhouse gas emissions. In this work, we conducted field experiments on soil CO2 efflux and soil microbial activity using two precipitation treatments and two crop management technologies. While the control treatment was exposed to natural precipitation, the reduced water availability was induced during the early stages of crop growth using rain-exclusion shelters within the water deficit treatment. We aimed to test the difference in the response to water deficit between two management technologies: conventional tillage (CT - ploughed without cover crops) and adaptation technology (AT - no-till with species rich cover crops). After a month of simulated water deficit, the soil CO2 efflux under a regime of adaptation technology was essentially the same as that under the conventional technology, and the decrease in soil CO2 efflux ranged between 22 % and 55 %. The water deficit had a technology-specific effect on microbes. While no effect on the microbial carbon under CT was observed, the water deficit decreased Cmic under AT. In contrast, the opposite pattern was observed for DHA. When a normal soil water regime was restored, CO2 efflux recovered rapidly while recovery of microbial biomass and dehydrogenase activity was more variable. Generally, the soil microbial biomass and activity recovered better under AT. The results show that while the reduction in Rs during water deficit and its recovery after the restoration of the ambient precipitation regime were not affected by the technology, the response of microbial biomass and activity to water deficit depended on the technology with better recovery under AT.

Root growth and physiological responses in wheat to topsoil and subsoil compaction with or without artificial vertical macropores

The process of soil compaction can cause various stresses on roots, ultimately limiting their growth and development within the soil. Understanding this phenomenon in real-world conditions can be challenging since the growth of roots is influenced by the soil environment. To investigate this issue, four experiments were conducted to examine the impact of topsoil (two in pots: with clay loam and sandy loam soils under two soil water regimes) and subsoil (in rhizobox: one with clay loam soil and the other with sandy loam soil, containing artificial vertical macropores) compaction on the relationship between edaphic factors and the physiological response of wheat roots. The topsoil compaction reduced root length, volume, and weight by 30–50% and the root diameter by ∼15% compared to the non-compact soil. The effect was reduced in the soil with higher clay content (clay loam), especially under the limited soil water condition. Plant physiological responses were adversely affected by compaction with a reduction in plant height. The transpiration rate was highly impacted (21–47% reduction) with the build-up of intercellular CO2 content in leaves (13–31%), especially with limited water applications. Root growth was severely restricted (>60%) in the compact subsoil layer, although the surface area and volume of roots increased in the overlying non-compact layer. Naturally occurring or artificial vertical macropores acted as escape channels, facilitating the roots to pass through the compact subsoil and grow abundantly in the loose soil below. However, plants in field conditions encounter a mix of loose and compact soil zones. By studying how roots respond to this soil heterogeneity, we can develop strategies to reduce the negative effects of soil compaction.

Characteristics of Humic Acids in Drained Floodplain Soils in Temperate Climates: A Spectroscopic Study

This study aims to assess the characteristics of humic acids (HAs) in floodplain soils. HAs were isolated from the Fluvisols located out of the embankment in the riparian forest (unflooded riparian forest) and within the embankment (inter-embankment), in the area periodically flooded. HAs from these soils were examined for quantity, structure, and humification degree using extraction methods as well as elemental analysis, UV-Vis, FTIR, EPR, and 1HNMR spectroscopies. In the soils after drainage, a significant decrease in HAs has been observed compared to the periodically flooded areas. Obtained results showed that organic matter from periodically flooded soils is more humified and contains HAs with a more aromatic, lignin-like structure compared to the humus matter from unflooded Fluvisols. Humic acids from periodically flooded soil contained a lower amount of C and H compared to those isolated from unflooded soils located out of the embankment, which resulted in a less aliphatic or more aromatic character of their molecules. A higher H/C ratio of HAs from the Fluvisols after drainage exhibits more condensed aromatic ring or substituted ring structures in the molecules. Soils with organic matter with a higher humification index contained HAs with lower radical concentration values in comparison to soils with less humified organic matter. Results obtained show that in flooded areas with periodically reductive conditions, humic acids do not lose as many -OCH3 groups as in better oxidized soils and therefore exhibit a lignin-like aromatic structure. It has been proven that the formation and dynamics of HA transformation may vary due to the water regime in soils.

The role of hydropedology when aiming for the United Nations Sustainable Development Goals

AbstractSoil physics defines soil water, air, and temperature regimes that are crucial for agricultural production, the quality of water resources, and waste management. Positioning such activities in the context of the United Nations Sustainable Development Goals (SDGs) will provide a valuable link to the international policy arena and should also include consideration of other SDGs dealing with climate change, biodiversity preservation, and soil health, thereby covering aspects of SDG 2 (zero hunger), SDG3 (good health and wellbeing), SDG6 (clean water and sanitation), SDG13 (climate action), and SDG15 (life on land). Combined expertise of soil physicists and pedologists in hydropedology offers a basic soil package, to be completed by soil chemists and biologists, to interdisciplinary teams studying ecosystem services in line with SDGs. Soils not being isotropic and homogeneous, pedology offers descriptions of soil heterogeneity, requiring innovative measuring methods. Digital mapping significantly improves the quality of traditional soil maps by being more quantitative at lower cost. Socioeconomic conditions are important elements of sustainable development as is recognized by the soil security concept, distinguishing soil connectivity with users and soil codification, linking soil with the policy arena. The latter has been successfully achieved in South Africa. Innovative, “applied” interdisciplinary research is needed to develop operational methods, assessing ecosystem services that are relatively of low cost, simple, and transparent, allowing acceptance by critical stakeholders. Modern proximal sensing techniques offer a promising perspective. An exploratory case study of a Dutch: “Living Lab” is referred to as an example of such an “applied” interdisciplinary approach.

INFLUENCE OF SHORT-TERM CROP ROTATIONS WITH DIFFERENT PROPORTIONS OF SUNFLOWER ON SOIL WATER REGIME

The article analyses the features of water consumption of sunflowers in short-term crop rotations. Presents the results of the 2020‒2021 research carried out in the experimental field of Kharkiv National Agrarian University named after V. V. Dokuchaev, located in the area of the Left Bank Forest-Steppe of Ukraine. The soil cover of the experimental field is represented by typical chernozem heavy loam on loess-like loam. Soil moisture was determined by gravimetric technique. Sunflower water consumption was calculated using the water balance method. The sunflower yield was recorded manually. The purpose of our research was to determine how short-term crop rotations with different sunflower saturation affect the formation of the soil water regime and the yield of the crop itself. The experimental design included five-field crop rotations with sunflower saturation of 0, 20, 40, and 60 %. The control in the experiment was a five-field crop rotation without sunflowers. It was determined that the yield of sunflower seeds depended on the variants and ranged from 3,21 to 3,57 t/ha. The increase in the share of sunflower in crop rotation was accompanied by a decrease in its yield, in particular, due to the deterioration of moisture supply. Soil moisture consumption was the highest in crop rotation with sunflower saturation of 60 % (2969 m3/ha). Against the background of reducing the share of sunflower to 40 and 20%, moisture consumption was 2713 and 2824 m3/ha. The water consumption coefficient was high due to an increase in the share of sunflowers in short-term crop rotations. It was determined that in crop rotation with sunflower saturation of 40 % the coefficient of water consumption was the lowest. At the same time, this variant has the highest yield of sunflower seeds (3,57 t/ha). Increasing the saturation of short-term crop rotations with sunflowers up to 60 % should occur under conditions of the high culture of agriculture. Therefore, ways of efficient use of soil moisture to increase the yield of sunflowers in short-term crop rotations are being developed.

Interactive effects of soil compaction, biochar application, and soil water regime on the growth, yield, and water use efficiency of upland rice

Interactive effects of soil compaction, biochar application, and soil water regime on the growth, yield, and water use efficiency of upland rice

Reaction of soybean plants to seed inoculation and different irrigation regimes of light chestnut soils of the Lower Volga region

The purpose of the research is to find out the reaction of soybean plants to seed inoculation under different irrigation regimes (humidity not lower than 80% MWC (minimum water capacity) in the layers 0,4 and 0,6 m, differentiated by stages of growth and development water regime at the level of 70-8070% MWC in the layers 0,4 and 0,6 m) in the Lower Volga region conditions. The object of the study is soybean crops of the Volgogradka 2 variety selected by the All-Russian Scientific Research Institute of Irrigated Agriculture (VNIIOZ). The experiment was conducted in 2021 and 2022 on the experimental field of VNIIOZ. Geostim Fit G produced by Biotechagro (Timashevsk, Krasnodar Territory) was used asan inoculant at a concentration of 5-10 l/ha. For foliar feeding biopreparations, natural mineral bilator and fungicide Kolosal Pro were used. Based on the data obtained, it was found that the maximum increase in productivity (132%) was obtained by seed inoculation before sowing in the variant with a soil moisture level of 80% MWC. With differentiated water treatment, the productivity was 129% compared to the untreated control. Of the agents used during the growing season to control pathogens, preference should be given to biopreparations. The volume of the harvested grain was maximum (3.87 t/ha) in the control variant with soil moisture of 80% MWC and the use of seed inoculation. The second result in terms of productivity showed the variant with the use of natural mineral bilator (3.38 t/ha), the minimum yield (2.86 t/ha) was recorded in the case of using the chemical agent Kolosal Pro. The calculation of economic efficiency showed the profitability of soybean crops treatment with biological preparations. The scientific novelty of the study is that in the course of its implementation for the first time for the conditions of the Lower Volga region the efficiency of soybean cultivation was determined taking into account the influence of several factors at once: soil water regime, seed pre-sowing treatment with inoculants, treatment of plants during vegetation to control pathogens.

Nitrogen uptake preference and allocation in Populus cathayana in response to drought stress

The preference for different nitrogen (N) forms may enhance plant survival and fitness. However, little information is known about how soil water availability, N addition, and their interaction dynamically impact plant N uptake preference and allocation. Here, we conducted a pot experiment using Populus cathayana cuttings, consisting of soil water regime (well watering control/mild drought/intensive drought: 80/60/40 % of field capacity) combined with N addition (N0 as control/N4/N8: 0/4/8 g N m−2 yr−1) treatments based on 15N isotope tracer technology. Two tracer solution (15NH4NO3/NH415NO3, both at 10.2 atom%) were used in N4/N8 treatments. Root, stem and leaf were collected at 6 h, 1, 3, 7, 14, and 31 days after labeling. Results showed that N addition significantly increased plant biomass and N accumulation, and decreased N allocation to leaf. Drought significantly decreased plant biomass, N accumulation, and N uptake (indicated by δ15N), and intensive drought reduced more than mild drought did. Nitrogen allocation to leaf was increased by drought. NO3- uptake by P. cathayana (indicated by δ15N in NH415NO3 treatment) was correlated significantly positively with total root length (TRL), total root surface area (TRA), specific root length (SRL), specific root area (SRA), root vitality, and root nitrate reductase (NR) activity. Intensive drought significantly reduced TRL, TRA, SRL, SRA, root vitality, and root NR activity under N4 and N8 treatments, which resulted δ15N in NH415NO3 treatment reduction and lower than in 15NH4NO3 treatment, so P. cathayana exhibited ammonium preference under intensive drought treatment. Our study provides an essential insight into how plants adapt and prefer different N forms under drought stress in nature.

Soil Water Movement and Groundwater Recharge Under Different Land Uses in a Flood-Irrigated Area.

The water shortage in agriculture area in China requires to reduce the consumption of excessive water in flood irrigation. Therefore, the dynamics of soil water regime is needed to investigate and water-saving irrigation is necessary to alleviate water shortage. This study investigated the impact of flood irrigation on soil water movement and recharge to groundwater in the Yellow River irrigation area of Yinchuan Plain, China. Combining comprehensive field observation, stable isotopic techniques and water balance simulation, we described the soil water mechanism in vadose zone covered with bare soil in 2019 and planted with maize in 2020. The soil layers affected by precipitation infiltration and evaporation were mainly 0-50 cm, while the soil influenced by irrigation was the entire profile in the mode of piston flow. The maize root took up the soil water up to the depth of 100 cm during the tasseling period. The infiltration and capillary rise in 2020 were similar with those in 2019. However, the total deep percolation was 156.5 mm in 2020 which was about 50% of that in 2019 because of the maize root water uptake. The leakage of ditch water was the major recharge resource of groundwater for the fast water table rise. Precise irrigation is required to minimize deep percolation and leakage of ditch water and reduce excessive unproductive evapotranspiration. Therefore, understanding the soil water movement and groundwater recharge is critical for agricultural water management to improve irrigation efficiency and water use efficiency in arid regions.

Prewinter soil water regime affects the post-winter cracking position on gully sidewall and slumping soil dynamics in Northeast China

Gully erosion is one of the most destructive land degradation processes. Soil slumping along cracks on a gully sidewall is a crucial process of gully development, yet the factors controlling the dynamics and amount of slumped soil remain unclear. It was hypothesized that soil slumping along the cracks in summer might be affected by the prewinter soil water regime, as it determines the depth of freezing-induced fissures within the soil profile, which affects the depth and dynamics of the cracks on the gully sidewall. To test this hypothesis, the soil water regime was manipulated by infiltrating 250 mm of water into the plots placed with one edge 10, 30 and 50 cm away from a gully sidewall before winter. This plot layout eventually resulted in four treatments with different amounts of infiltrated water. The isolines of near-saturation soil water contents appeared closer to the ground and the sidewall under the higher infiltration treatments before and after winter. Soil freezing started from the topsoil on 14 Nov. 2017 and penetrated the 1-m soil profile within 24 days. Soil thawing started from both the topsoil and subsoils (1 m depth) on 13 Apr. 2018 and ended on 24 Apr. 2018. The cracks that appeared on the sidewalls in Apr. had similar lengths and widths at the depths with a near-saturation soil water content (between 25 and 45 g kg−1). The cracks appeared at deeper position on gully sidewall under lower infiltration treatments. The soil mass slumped from the sidewall was greater in Apr. and less from Jul. to Aug. under higher infiltration treatments. The annual total of slumped soil mass was the lowest in the low infiltration treatment, where the near-saturation isolines were the deepest. These findings suggested that the prewinter soil water regime along the slope controlled the depth of freezing within the soil profile. The freezing depth determined the depth and time of soil cracking and slumping on the gully sidewalls the following year. Our study implies that gully development through soil slumping depends on pre-winter slope hydrology, which should be considered in modeling and controlling gully development.

New approach to soil management focusing on soil health and air quality: one earth one life (critical review).

Soil plays a key role in ecosphere and air quality regulation. Obsolete environmental technologies lead to soil quality loss, air, water, and land systems pollution. Pedosphere and plants are intertwined with the air quality. Ionized O2 is capable to intensify atmosphere turbulence, providing particulate matter (PM2.5) coalescence and dry deposition. Addressing environmental quality, a Biogeosystem Technique (BGT*) heuristic transcendental (nonstandard and not direct imitation of nature) methodology has been developed. A BGT* main focus is an enrichment of Earth's biogeochemical cycles through land use and air cleaning. An intra-soil processing, which provides the soil multilevel architecture, is one of the BGT* ingredients. A next BGT* implementation is intra-soil pulse continuously discrete watering for optimal soil water regime and freshwater saving up to 10-20 times. The BGT* comprises intra-soil dispersed environmentally safe recycling of the PM sediments, heavy metals (HMs) and other pollutants, controlling biofilm-mediated microbial community interactions in the soil. This provides abundant biogeochemical cycle formation and better functioning of the humic substances, biological preparation, and microbial biofilms as a soil-biological starter, ensuring priority plants and trees nutrition, growth and resistance to phytopathogens. A higher underground and aboveground soil biological product increases a reversible C biological sequestration from the atmosphere. An additional light O2 ions photosynthetic production ensures a PM2.5 and PM0.1 coalescence and strengthens an intra-soil transformation of PM sediments into nutrients and improves atmosphere quality. The BGT* provides PM and HMs intra-soil passivation, increases soil biological productivity, stabilizes a climate system of the earth and promotes a green circular economy.

Different Cerrado Ecotypes Show Contrasting Soil Microbial Properties, Functioning Rates, and Sensitivity to Changing Water Regimes

Soil moisture is among the most important factors regulating soil biodiversity and functioning. Models forecast changes in the precipitation regime in many areas of the planet, but how these changes will influence soil functioning, and how biotic drivers modulate such effects, is far from being understood. We evaluated the responses of C and N fluxes, and soil microbial properties to different soil water regimes in soils from the main three ecotypes of the world's largest and most diverse tropical savanna. Further, we explored the direct and indirect effects of changes in the ecotype and soil water regimes on these key soil processes. Soils from the woodland savanna showed a better nutritional status than the other ecotypes, as well as higher potential N cycling rates, N2O emissions, and soil bacterial abundance but lower bacterial richness, whereas potential CO2 emissions and CH4 uptake peaked in the intermediate savanna. The ecotype also modulated the effects of changes in the soil water regime on nutrient cycling, greenhouse gas fluxes, and soil bacterial properties, with more intense responses in the intermediate savanna. Further, we highlight the existence of multiple contrasting direct and indirect (via soil microbes and abiotic properties) effects of an intensification of the precipitation regime on soil C- and N-related processes. Our results confirm that ecotype is a fundamental driver of soil properties and functioning in the Cerrado and that it can determine the responses of key soil processes to changes in the soil water regime.

Efficacy of Herbicides, Their Effects on Rice Yield Under Saturated Soil Condition

This study was carried out in containers which were placed outdoor to evaluate the efficacy of different herbicides with different mixtures on weed growth suppression in rice and their effects on rice grain yield under saturated soil water regime in two consecutive seasons (cropping season and off season) at the Universiti Putra Malaysia Farm, Serdang, Selangor, Malaysia during 2016 to 2017. Eight combinations of different herbicides, viz. T1, T2, T3, T4, T5, T6, T7 and T8 along with weed free and non-weeded treatments were used in the study following a RCBD. Weed composition in the experimental containers and their summed dominant ratio (SDR) at 60 days after planting were recorded from non-treated containers. Naturally grown eleven weed species mainly under the families of Poaceae, Cyperaceae and Pontederiaceae were found in the experimental containers. Based on the SDR values the dominant weed species were Monochoria vaginalis, Echinochloa crus-galli, and Fimbristylis miliacea in both the seasons. Results revealed that four herbicide treatments viz. Pretilachor fb Bentazon/MCPA (T1), Pretilachor+Pyribenzoxim fb Bentazon/MCPA (T2). Bispyribac-sodium fb Bentazon/MCPA (T2), Fenoxaprop+Ethoxysulfuron (T3), fb Bentazon/MCPA (T7) were superior in their effectiveness for weed control in both seasons and gave better rice grain yield with high economic return. Bangladesh J. Bot. 52(1): 37-44, 2023 (March)

Агромелиоративная характеристика черноземов южных в связи с орошением

Abstract. Sustainable highly productive agriculture in the arid steppe zone of Western Siberia is possible only on the basis of optimizing the water regime of soils. The relevance of irrigation is increasing due to the degradation of the soil cover, the geopolitical and resource potential of the territories and the fundamental change in the development strategy of Russia. Light soils prevailing in the Central and Northern Kulund, widely used for crop production, are characterized by a weak water-retaining capacity and require additional in-depth study of the features of reclamation properties. The purpose of the research is to solve scientifically and practically relevant problems of agrohydrophysics of southern light loamy chernozems in connection with the development of soil-saving irrigation technology based on knowledge about the processes of movement, moisture retention in the profile and the limits of its availability to plants. Methods. Field and laboratory methods of soil research were used: morphological study, determination of physical and water properties of the soil according to generally accepted methods. Results. Ameliorative properties of the southern light loamy chernozems of the Northern Kulunda have peculiarities in the granulometric composition, where sandy fractions of 1–0.25 and 0.25–0.05 mm in size predominate and make up to 46–77 % of all particles, providing a weak water-retaining capacity, soluble salts. Good drainage of the soil profile is provided by the underlying layers of sandy loam, loam, sand, up to 3–8 m thick. The reduced porosity of soil-forming and underlying rocks (up to 35.4–40.1 %), along with a high density of composition, ensures non-sagging irrigation of these soils. Weak structure along with favorable microaggregation create favorable water-physical properties. A significant part of the pores (11.9–37.3 %) along the profile in the state of the lowest moisture capacity (HB) is free from water. Water permeability and filtration are increased (from the surface at 1, 2, 3 hours, respectively, 38.6–95.5 mm; 34.0–51.4 and 31.1–49.9 mm). Moisture reserves at wilting moisture (WM) in layers 0–50 cm, 0–100, 0–200 cm are 45 mm and 90.82 mm, respectively. HB on arable land in the 0–50 cm layer is 114.7 mm (15.5 %), in the 0–100 cm layer it reaches 218.7 mm (14.2 %). Under natural conditions, the moisture content of these soils does not reach the HB value even in spring. The range of active moisture (AWM) is narrow, which must be taken into account, together with the characteristics of its movement, when calculating irrigation regimes for a particular soil. The scientific novelty. A complete description of the physical and hydrological properties that are in dire need of optimization of the water regime of southern light loamy chernozems is presented, which is necessary for further in-depth study of the behavior of moisture in their profile, the limits of its availability to plants and the development of modern soil protection technology for selective and local irrigation.

Earlywood Anatomy Highlights the Prevalent Role of Winter Conditions on Radial Growth of Oak at Its Distribution Boundary in NW Iberia

We compared climate-growth relationships (1956-2013) of two natural pedunculate oak (Quercus robur L.) stands with different water-holding capacities growing at the species distribution limit of the Mediterranean Region in NW Iberia. For this, tree-ring chronologies of earlywood vessel size (separating the first row from the other vessels) and latewood width were obtained. Earlywood traits were coupled to conditions during dormancy, whereby an elevated winter temperature appears to induce a high consumption of carbohydrates, resulting in smaller vessels. This effect was reinforced by waterlogging at the wettest site, whose correlation to winter precipitation was strongly negative. Soil water regimes caused differences between vessel rows, since all earlywood vessels were controlled by winter conditions at the wettest site, but only the first row at the driest one; radial increment was related to water availability during the previous rather than the current season. This confirms our initial hypothesis that oak trees near their southern distribution boundary adopt a conservative strategy, prioritizing reserve storage under limiting conditions during the growing period. We believe that wood formation is highly dependent on the balance between the previous accumulation of carbohydrates and their consumption to maintain both respiration during dormancy and early spring growth.

Effect of changes in forest water balance and inferred root reinforcement on landslide occurrence and sediment generation following Pinus radiata harvest on Tertiary terrain, eastern North Island, New Zealand

Background: The frequent occurrence of storm-initiated landslides following harvesting of Pinus radiata D.Don in steep, Tertiary terrain, East Coast region, North Island, New Zealand, is of increasing concern. This paper documents the influence of tree removal and of replacement plantings on the canopy water balance and soil moisture regime when slopes are at their most vulnerable to landslide occurrence. Methods: At a previously established study site, rainfall, throughfall, and soil moisture data were collected before a mature stand of P. radiata was harvested. After harvesting, part of the study site was replanted with P. radiata at 1000 stems ha-1 and part with 500 stems ha-1. Relationships between hydrological changes and landslide occurrence are discussed in relation to planting density, site factors, root system development, silvicultural regimes, and alternative land use options for mitigating erosion in highly erodible hill country. Results: Following harvesting, soil moisture levels remained higher for longer than under a mature forest until rainfall interception and evapotranspiration returned to pre-harvest levels. This coincided with canopy closure, irrespective of planting density. After thinning, interception and evapotranspiration decreased, then regained the equivalent of a closed canopy 2 years later. Landslide occurrence was highest on slopes >25° and with a NE aspect. Sediment generation rates were highest in 2─4-year-old plantings, then decreased markedly with increasing tree age. Conclusions: Irrespective of planting density, P. radiata had little influence on the soil-water regime until canopy interception, evapotranspiration rates, soil-drying and recharge cycles returned to pre-harvest levels, coinciding with canopy closure. During this period, pore-water pressures at times of heavy or prolonged rainfall likely result in soil saturation and an increase in landslides. The progressive loss of root strength of the harvested trees had a secondary influence. The duration of the post-harvest period of heightened slope vulnerability to landslide initiation is a function of the combined influences of site factors on rates of tree growth and survival, and of the planting density regime on the canopy water balance and soil water content until the development of an effective live soil-root reinforcement system. For areas identified as high risk, the targeting of high-value timber species with longer rotation length, including consideration of coppicing species, would minimise the risk of slope failure at harvest. Very high-risk areas unsuited to rotational harvesting will ultimately require transitioning to a permanent indigenous forest cover.