Rainfall induced changes in soil moisture: A comparative study of conventional and strip tillage

Reduced throughfall decreases autotrophic respiration, but not heterotrophic respiration in a dry temperate broadleaved evergreen forest

Changes in agricultural water demands and soil moisture in China over the last half-century and their effects on agricultural production

Influence of changes in rainfall and soil moisture on trends in flooding

The aim of this research was to determine how changes in soil moisture and temperature influence ecosystem C fluxes in the context of changing grazing regimes in subalpine grasslands in the Pyrenees. We (i) measured CO2 fluxes in the field in cattle- and sheep-grazed areas, and (ii) compared responses of CO2 and CH4 fluxes from soil turf samples from cattle- and sheep-grazed areas to changes in soil temperature and moisture. The cattle-grazed area showed greater ecosystem respiration and gross ecosystem photosynthesis than the sheep-grazed areas. With respect to the temperature and moisture treatments, the two areas responded in a similar way: Soil moisture was the strongest driver of soil respiration rates; although temperature also increased CO2 effluxes from the soils, the effects were transient. The greatest effluxes of CO2 were found in soils incubated at elevated temperature and 80% soil moisture content. Methane fluxes were only influenced by the moisture treatment, with the greatest methane oxidation rates found at 40% soil moisture content. We conclude that regional changes in moisture availability resulting from climate change are likely to be the most important driver of soil respiration and methane fluxes in these grazed subalpine ecosystems.

The temperature, moisture, and salt content of soil in alpine regions are sensitive to changes in climatic factors and are important indicators of ecosystem functions. In this study, we collected soil moisture, temperature and electrical conductivity data at different depths at a sampling site on Bird Island in Qinghai Lake during winter using a continuous soil temperature, moisture and salt content monitoring system and analyzed their variations and influential factors. The variation in soil moisture showed an obvious ‘V-shaped’ pattern from 00:00 to 23:00 and an upward trend with soil layer depth. From 00:00 to 23:00, the overall soil temperature data fitted a ‘unimodal’ curve and showed a clear and continuous upward trend with soil layer depth at a rate of 0.684 (p < 0.001). Soil electrical conductivity data also exhibited a distinct ‘V-shaped’ pattern from 00:00 to 23:00 and a continuous increase with increasing soil depth. The correlation between soil temperature, moisture, and conductivity and the spatial distribution of five climate factors indicated that climate factors accounted for 53.6% of the changes in soil temperature, moisture, and salinity. Climate factors showed a significant positive correlation with soil temperature, moisture, and conductivity (p < 0.001), and air temperature was the most important factor influencing soil temperature and soil moisture changes, whereas wind direction was the most important factor influencing soil conductivity. (Wind direction and wind speed affect soil evapotranspiration, and then affect soil moisture and solute transport process). The results of this preliminary study reveal the characteristics associated with soil temperature, moisture, and salinity changes in winter within the wetlands of Bird Island on Qinghai Lake in the context of climate change, and they can be used as valuable reference data in further studies investigating associated changes in ecosystem functions.

We studied the influence of the statistical properties of soil moisture changes on the Interferometric Synthetic Aperture Radar (InSAR) coherence and closure phase to determine whether the InSAR coherence and closure phase can be used to estimate soil moisture changes. We generated semi-synthetic multi-looked interferograms by pairing n real single-looked pixels of an observed SAR image with n synthetic single-looked pixels. The synthetic SAR data are generated from the real SAR data by applying soil moisture changes with a pre-defined mean and standard deviation of changes. Our results show that the diversity of soil moisture changes within the multi-look window gives rise to decorrelation, a multi-looked phase artifact, and a non-zero phase triplet. The decorrelation and closure phase increase by enlarging the diversity of soil moisture changes. We also showed that non-soil moisture changes can lead to larger decorrelations and closure phases. Furthermore, the diversity of phase changes, decorrelation, and closure phases are correlated with land cover type. We concluded that the closure phase and coherence are independent of the magnitude of soil moisture changes and are inappropriate tools to estimate soil moisture changes. Coherence, however, can be used as a proxy for soil moisture changes if the diversity and magnitude of soil moisture changes within a multi-looked pixel are strongly correlated.

As the mulching practice in pineapple culture in Hawaii has developed over the last 50 years, a number of functions have been assigned to the action of the mulch. This study gives primary consideration to the effect of soil moisture and soil temperature changes upon pineapple growth. Soil moisture changes were determined from field samplings and lysimeter studies at Wahiawa, Oahu. Changes in the soil moisture budget with the mulch were so slight that the variability of field sampling precluded assessment without excessive replication. Coefficients of variability for samples taken at the plant butt were 3 to 5% of a moisture constant (e.g., 15‐bar point) for a soil series or within a single field. Moisture use, measured by semicontained hydraulic lysimeters, was reduced by the mulch when the soil was very wet but changed little when the soil moisture ranged from field capacity (0.15‐bar) to the 15‐bar point. The mulch raised the average soil temperature about 1.6C during the winter. The measured one‐third increase in the plant growth was nearly identical with the increase calculated from the growth‐response of pineapple to temperature.

Hydro-climatic changes and their impacts on vegetation in Xinjiang, Central Asia

Contributions of changes in soil moisture to the projected climate change in the tropics at the end of the twenty first century are quantified using the simulations from five different global climate models, which contributed to the GLACE–CMIP5 experiment. “GLACE” refers to the Global Land Atmosphere Coupling Experiment and “CMIP5” to the fifth phase of the Coupled Model Intercomparison Project. This is done by relating the overall projected changes in climate to those changes in climate that are related to the projected changes in soil moisture. The study focusses on two particular aspects of the interactions of the soil moisture with climate, the soil moisture–temperature coupling and the soil moisture–precipitation coupling. The simulations show distinct future changes in soil moisture content in the tropics, with a general tendency of increases in the central parts of the tropics and decreases in the subtropics. These changes are associated with corresponding changes in precipitation, with an overall tendency of an approximate 5 % change in soil moisture in response to a precipitation change of 1 mm/day. All five individual models are characterized by the same qualitative behaviour, despite differences in the strength and in the robustness of the coupling between soil moisture and precipitation. The changes in soil moisture content are found to give important contributions to the overall climate change in the tropics. This is in particularly the case for latent and sensible heat flux, for which about 80 % of the overall changes are related to soil moisture changes. Similarly, about 80 % of the overall near-surface temperature changes (with the mean temperature changes in the tropics removed) are associated with soil moisture changes. For precipitation, on the other hand, about 30–40 % of the overall change can be attributed to soil moisture changes. The robustness of the contributions of the soil moisture changes to the overall climate change varies between the different meteorological variables, with a high degree of robustness for the surface energy fluxes, a fair degree for near-surface temperature and a low degree for precipitation. Similar to the coupling between soil moisture and precipitation, the five individual models are characterized by the same qualitative behaviour, albeit differences in the strength and the robustness of the contributions of the soil moisture change. This suggests that despite the regional differences in the projected climate changes between the individual models, the basic physical mechanisms governing the soil moisture–temperature coupling and the soil moisture–precipitation coupling work similarly in these models. The experiment confirms the conceptual models of the soil moisture–temperature coupling and the soil moisture–precipitation coupling described Seneviratne et al. (Earth-Sci Rev 99:125–161, 2010). For the soil moisture–temperature coupling, decreases (increases) in soil moisture lead to increasing (decreasing) sensible heat fluxes and near-surface temperatures. The soil moisture–precipitation coupling is part of a positive feedback loop, where increases (decreases) in precipitation cause increases (decreases) in soil moisture content, which, in turn, lead to increasing (decreasing) latent heat fluxes and precipitation.

天山北坡积雪消融对不同冻融阶段土壤温湿度的影响

[1] The nature of the climate–carbon cycle feedback depends critically on the response of soil carbon to climate, including changes in moisture. However, soil moisture–carbon feedback responses have not been investigated thoroughly. Uncertainty in the response of soil carbon to soil moisture changes could arise from uncertainty in the relationship between soil moisture and heterotrophic respiration. We used twelve soil moisture–respiration functions (SMRFs) with a soil carbon model (RothC) and data from a coupled climate–carbon cycle general circulation model to investigate the impact of direct heterotrophic respiration dependence on soil moisture on the climate–carbon cycle feedback. Global changes in soil moisture acted to oppose temperature-driven decreases in soil carbon and hence tended to increase soil carbon storage. We found considerable uncertainty in soil carbon changes due to the response of soil respiration to soil moisture. The use of different SMRFs resulted in both large losses and small gains in future global soil carbon stocks, whether considering all climate forcings or only moisture changes. Regionally, the greatest range in soil carbon changes across SMRFs was found where the largest soil carbon changes occurred. Further research is needed to constrain the soil moisture–respiration relationship and thus reduce uncertainty in climate–carbon cycle feedbacks. There may also be considerable uncertainty in the regional responses of soil carbon to soil moisture changes since climate model predictions of regional soil moisture changes are less coherent than temperature changes.

To explore soil nutrients and moisture changes in different karst mountain agroforestry, in the plateau mountains of Southern China Karst, we used secondary tree and irrigation forest (C) as a reference for our study and selected four mixed agroforestry species (walnut + maize + potato (HYM), walnut + maize (HTY), poplar + ryegrass (YSH), and maize + ryegrass (YMH)) for comparison. First, soil moisture change characteristics were monitored in situ in the field. Second, for soil samples, soil bulk density, porosity, and permeability were analyzed, soil nutrient (K, Na, Ca, and Mg) characteristics were tested and analyzed. Then, we explored the relationship between agroforestry and soil moisture, soil moisture and soil nutrients, soil moisture and precipitation, and agroforestry and soil nutrients. It is shown (1) during the monitored period, variation trends in soil nutrients in four types of agroforestry was small, but it increased/decreased significantly compared with the secondary forest, which the variation range was more than 5%; (2) the changes of soil water content were significantly affected by precipitation, soil porosity and permeability, the moisture content changes of HYM, HTY, YSH, and YMH agroforestry were significantly correlated with precipitation, soil porosity, and permeability; (3) under the same precipitation conditions, different types had different lags on soil water regulation, with the average HYM 0.8 h, HTY 0.6 h, YSH 0.3 h, and YMH 0.4 h, each type soil responded at 2–3 h after rain, and the soil moisture content returned to the normal level; and (4) the variation of soil moisture content fluctuated seasonally, and the most obvious was HYM and HTY agroforestry, their Cv value between winter and summer exceeded 21%. The results provide basic theoretical support for further exploring the relationship among agroforestry, soil, moisture, and nutrients and enrich the content of the development of agroforestry in karst areas. They are of importance to promote ecological restoration and agroforestry development in karst areas.

<p>Peatlands comprise 19% of the permafrost area in the subarctic zone, they store 277 Pg of organic carbon. Peatlands in that area are represented by palsa mire. The palsa mire consists of frozen peat mounds (palsa), thermokarst depression and the wet bog without permafrost.</p><p>Climate change and thawing of permafrost leads to a change in soil moisture, both drying and wetting. This can lead to a change in the carbon balance of the ecosystem and increase or decrease the emission of greenhouse gases (CO<sub>2</sub> and CH<sub>4</sub>).</p><p>The aim of the work was to study the effect of changes in soil moisture on the biological activity of palsa mire peat soils in the north of Western Siberia (65°18'52"N, 72°52'32"E). The studies were conducted in 2018-2021 in the northern taiga in the discontinuous permafrost zone.</p><p>The two palsas (Cryic Histosol) and the surrounding bog (Fibric Histosol) were examined. Palsa soils were characterized by high variability of the studied parameters; active layer thickness was 0.66±0.07 m, soil moisture - 30.98±2.49%, soil temperature - 8.31±0.45°C. The soils of the bog were characterized by the absence of permafrost, a higher soil temperature - 13.58±0.26°C and soil moisture - 74.59±0.26%. Despite the difference in the studied parameters of these ecosystems, no significant differences in biological activity were found (185.97±30.51 mgCO<sub>2</sub>/m<sup>2</sup>/h).</p><p>Based on field measurements, 3 plots were identified with the same type of vegetation and soil temperature, but significantly differ in soil moisture. Depending on soil moisture, the plots were named “Dry” (25.73±1.89%), “Wet” (38.44±0.70%) and “Moist” (53.09±1.06%). Biological activity did not vary significantly between the studied sites but had a multidirectional dynamic in different years. This shows the complexity of palsa, their multifactorial nature and an ambiguous response to changes in moisture.</p><p>An added experiment was set up to change soil moisture - transplantation. Measured of CO<sub>2</sub> emissions from undisturbed peat soil of a large volume transferred from dry palsa to a wetting bog. And vice versa. The biological activity of the soils did not differ considerable both during wetting and draining. In different years, there was a vary dynamics in CO<sub>2</sub> emissions.</p><p>According to the results of the study, with climate change, thawing of permafrost and palsa degradation, there will be no significant CO<sub>2 </sub>flux. This may be due to the multifactorial nature of ecosystems, a wide optimum of soil moisture for peat soils. The influence of additional factors is also significant: the size of the methanotrophic barrier, the transport of CO<sub>2</sub> with solutions over the surface of the palsa permafrost.</p>

Soil moisture distribution emerges as a key link between hydrologic and ecologic processes in semiarid grassland and shrubland, as it influences evapotranspiration, respiration, and assimilation. In support, we present three years of data (2002–2004) collected from a semiarid grassland and shrubland within the Sevilleta National Wildlife Refuge of central New Mexico; the two sites are separated by about 5 km. Instrumentation includes an eddy covariance tower and typical micrometeorological devices at both locations. Additionally, the grassland site features six soil moisture profiles and the shrubland site features four soil moisture profiles, with the maximum depth at 52.5 cm. At both sites, most rain falls during the warm season, but large storms do occur at other times of the year, e.g., spring of 2004. Soil moisture pulses at 2.5 cm follow almost all rain events, whereas only four pulses in the 3‐year record are observed at 52.5 cm in the grassland and two in the shrubland; these deeper pulses follow large precipitation events or a series of smaller events. The daily times series of evapotranspiration (ET) is similar between the grassland and shrubland, supporting the results of Kurc and Small (2004). ET variations largely reflect changes in the soil moisture at 2.5 cm. In contrast, though the daily time series of net ecosystem exchange (NEE) at both sites covary, the magnitudes of peaks in net negative ecosystem exchange (NEE−) and net positive ecosystem exchange (NEE+) are over twice the magnitude at grassland than at the shrubland. Furthermore, pulses associated with NEE− peaks last much longer than ET pulses, of the order of 1–2 months, without any particular adherence to the climatologically defined rainy season. These NEE− pulses reflect changes in deeper soil moisture, i.e., 52.5 cm at the grassland and 37.5 cm at the shrubland. Finally, evidence of soil moisture driven respiration is found throughout the NEE time series, with spikes of NEE+ following most rain events; however, longer periods of NEE+ also occur during relatively dry periods. Modeled assimilation suggests that the relationship between assimilation and soil moisture is strongest at depths at least 30 cm below the surface.

Imaging of hill-slope soil moisture wetting patterns in a semi-arid oak savanna catchment using time-lapse electromagnetic induction