Increasing Soil Moisture Content Research Articles

An approach for delineating homogeneous within-field zones using proximal sensing and multivariate geostatistics

At the landscape scale, the soil moisture distribution derives from the combination of hydrologic, pedologic, and geomorphic processes. This study uses multicollocated factorial cokriging to determine the spatial scale(s) at which soil properties and terrain attributes affect the soil moisture distribution and can be used to identify homogeneous zones in the field. Georeferenced sensing (e.g. geoelectric sensing and LiDAR) acquires real-time, non-invasive and high resolution data over large spatial extents that can be used in combination with spatial, temporal and scale-dependent information of primary interest. This study uses high resolution geoelectric and LiDAR data as auxiliary measures to supplement data obtained by the analysis of 127 soil cores taken from a 40hectare Central Kentucky (USA) karst landscape. Shallow and deep apparent electrical conductivities (EC) were measured using a Veris 3100 in tandem with soil moisture on three separate dates with increasing soil moisture contents ranging from plant wilting point up to field capacity. Terrain features were produced from 2010 LiDAR returns collected at ≤1m nominal pulse spacing. Exploratory statistics were used to identify 12 field characteristics that would be useful in determining the spatial distribution of soil moisture, including terrain features (slope and elevation), soil physical and chemical properties and geoelectric measurements (EC for each date). A linear model of coregionalization (LMC) was fitted to the matrix of direct and cross experimental variograms for the 12 characteristics. The LMC consisted of 3 basic components: nugget, spherical (short-range scale=40m) and exponential (long-range scale=250m) where each component explained 17%, 22% and 60% of the total measured variation, respectively. Results suggest that soil texture and organic matter affect the soil moisture variability. Mapping the long-range regionalized factor allows us to delineate the field into homogeneous zones. This study shows the potential for using proximal sensing and multivariate geostatistics to develop soil moisture management strategies under water stressed conditions.

Influence of tillage intensity and nitrogen placement on nitrogen uptake and yield in strip-tilled white cabbage (Brassica oleracea convar. capitata var. alba)

Field grown vegetables with wide row spacing would likely benefit from the conservation tillage practice, strip-tillage, with regards to minimizing soil erosion or increasing soil moisture contents, but there are only few studies for strip-tilled vegetables at present. For this reason, a 2-year field experiment was performed in South West Germany to investigate the effect of strip-tillage under broadcast and placed nitrogen application on nitrogen availability and yield of white cabbage (Brassica oleracea convar. capitata var. alba). The treatments were fall strip-tillage (ST), intensive strip-tillage with tillage both in fall and spring (STi; all of them with broadcast nitrogen fertilization) and intensive strip-tillage with band-placed nitrogen (STi_pN). In 2013, a fifth treatment was added, which was ST additional sowing of Phacelia (Phacelia tannacetifolia) as a cover crop (ST_Phac). A conventional tillage treatment (MP; moldboard plowing) was used as the control. No significant differences in soil mineral nitrogen (SMN) were detected in spring (20±5kgNha−1) and at harvest time (5±0.9kgNha−1) between the MP and all strip-tillage treatments from 0–90cm soil depth, except for significantly lower SMN contents in ST_Phac in spring 2013 (5kgNha−1). During the growing period, the SMN contents in strip-tillage treatments tended to be higher than in the MP control. Results of nitrogen content in plants, N-uptake, and nitrogen use efficiency (NUE) showed higher values under ST compared to the more intensive strip-tillage treatments (STi and STi_pN). The cabbage yield ranged between 65tha−1 (MP) and 74tha−1 (ST) in 2012 and 50tha−1 (STi_pN) and 58tha−1 (MP) in 2013. The fall strip-tillage treatment (ST) seems to be as effective as the conventional moldboard plowing for white cabbage in terms of N availability and yield. These results could be used to apply or improve strip-till systems with respect to other similar vegetables, which are (i) exposed to high erosion risk because of the wide row spaces and (ii) which are dependent on high N demand for adequate growth.

Nitrogen mineralization and gaseous nitrogen losses from waterlogged and drained organic soils in a black alder (<i>Alnus glutinosa</i> (L.) Gaertn.) forest

Abstract. Black alder (Alnus glutinosa (L.) Gaertn.) forests on peat soils have been reported to be hotspots for high nitrous oxide (N2O) losses. High emissions may be attributed to alternating water tables of peatlands and to the incorporation of high amounts of easily decomposable nitrogen (N) into the ecosystem by symbiotic dinitrogen (N2)-fixation of alder trees. Our study addressed the question to what extent drainage enhances the emissions of N2O from black alder forests and how N turnover processes and physical factors influence the production of N2O and total denitrification. The study was conducted in a drained black alder forest with variable groundwater tables at a southern German fen peatland. Fluxes of N2O were measured using the closed chamber method at two drained sites (D-1 and D-2) and one undrained site (U). Inorganic N contents and net N mineralization rates (NNM) were determined. Additionally a laboratory incubation experiment was carried out to investigate greenhouse gas and N2 fluxes at different temperature and soil moisture conditions. Significantly different inorganic N contents and NNM rates were observed, which however did not result in significantly different N2O fluxes in the field but did in the laboratory experiment. N2O fluxes measured were low for all sites, with total annual emissions of 0.51 ± 0.07 (U), 0.97 ± 0.13 (D-1) and 0.93 ± 0.08 kg N2O–N ha−1 yr−1 (D-2). Only 37% of the spatiotemporal variation in field N2O fluxes could be explained by peat temperature and groundwater level, demonstrating the complex interlinking of the controlling factors for N2O emissions. However, temperature was one of the key variables of N2O fluxes in the incubation experiment conducted. Increasing soil moisture content was found to enhance total denitrification losses during the incubation experiment, whereas N2O fluxes remained constant. At the undrained site, permanently high groundwater level was found to prevent net nitrification, resulting in a limitation of available nitrate (NO3−) and negligible gaseous N losses. N2O flux rates that were up to four times higher were measured in the incubation experiment. They reveal the potential of high N2O losses under changing soil physical conditions at the drained alder sites. The high net nitrification rates observed and high NO3− contents bear the risk of considerable NO3− leaching at the drained sites.

Influence of soil moisture content on surface albedo and soil thermal parameters at a tropical station

Half hourly data of soil moisture content, soil temperature, solar irradiance, and reflectance are measured during April 2010 to March 2011 at a tropical station, viz., Astronomical Observatory, Thiruvananthapuram, Kerala, India (76°59’E longitude and 8°29’N latitude). The monthly, seasonal and seasonal mean diurnal variation of soil moisture content is analyzed in detail and is correlated with the rainfall measured at the same site during the period of study. The large variability in the soil moisture content is attributed to the rainfall during all the seasons and also to the evaporation/movement of water to deeper layers. The relationship of surface albedo on soil moisture content on different time scales are studied and the influence of solar elevation angle and cloud cover are also investigated. Surface albedo is found to fall exponentially with increase in soil moisture content. Soil thermal diffusivity and soil thermal conductivity are also estimated from the subsoil temperature profile. Log normal dependence of thermal diffusivity and power law dependence of thermal conductivity on soil moisture content are confirmed.

Effect of soil moisture status and a nitrification inhibitor, dicyandiamide, on ammonia oxidizer and denitrifier growth and nitrous oxide emissions in a grassland soil

Nitrous oxide (N2O) is a potent greenhouse gas and is produced in the soil by nitrification and denitrification processes. These processes are catalysed by a number of key enzymes from microbial communities in the soil. In grazed pasture soils, most of the N2O is emitted from nitrogen (N) returned in animal excreta deposited during outdoor grazing, particularly in the urine. The nitrification inhibitor, dicyandiamide (DCD), has been used to mitigate N2O emissions from grazed pasture soils. However, how the nitrifying and denitrifying communities and N2O emissions are affected by the urine and DCD applications under contrasting soil moisture conditions in grazed pasture soils is poorly understood. Here we report a laboratory incubation study to determine the impact of soil moisture status in combination with animal urine and DCD applications on the abundance of ammonia oxidizer (AO) and denitrifier functional genes, and N2O emissions from a grazed pasture soil. The soil used was a Horotiu silt loam (Typic Udivitrand) developed from volcanic ash. The treatments included three soil moisture contents: 60%, 100% and 130% field capacity (FC), each with Control, Urine and Urine + DCD treatments. The incubation temperature was 12 °C to simulate New Zealand autumn/winter soil temperatures (when DCD is used). Results showed that soil moisture significantly increased N2O emissions from the urine treated soil, with total N2O emissions at 100% and 130% FC being 9 and 400 times that at 60% FC, respectively. Soil moisture content also significantly affected the growth of ammonia oxidiser and denitrifier communities, with the functional genes increasing with increased soil moisture content. The application of urine significantly increased the abundance of AOB amoA, nirK and nosZ (clades I and II) genes, but decreased the abundance of AOA amoA and narG genes at 130% FC. DCD was highly effective in inhibiting the growth of AOB communities, and reducing N2O emissions at 100% and 130% FC. The abundance of nirK gene was also reduced by DCD at 130% FC, but this was, most likely, a reflection of changes in AOB populations, bearing the majority of the nirK gene detected in this study. DCD did not affect the other denitrifier genes studied. Total N2O emissions were significantly related to the abundance of AOB (R2 = 0.94, p < 0.001) and nirK genes (R2 = 0.57, p < 0.05), but not to the other genes studied. These results suggest that soil moisture has a major influence on ammonia oxidizing and denitrifying microbial communities in urine treated soils and that this affects the N2O emissions. Ammonia oxidizers are able to grow under very wet soil conditions, probably in part due to the growth of AOB communities that also carry the nirK gene.

Soil–geosynthetic inclined plane shear behavior: influence of soil moisture content and geosynthetic type

This paper deals with the inclined plane shear on three different geosynthetics (a geocomposite (GC), a non-woven geotextile (GTX), and an extruded geogrid (GGR)) with a residual soil from granite. Soil and geosynthetic properties, test equipment, and procedures are described. The influence of soil moisture content and geosynthetic type on soil–geosynthetic interaction behavior is discussed by analyzing the results of the inclined plane shear tests. The main conclusions that can be outlined from the present study are the following: (1) the influence of soil moisture content was relevant for the soil–GTX and soil–GC interfaces. Indeed, the resistance of those interfaces decreased with the increase of soil moisture content. No significant differences were observed between the behavior of those geosynthetics; (2) the influence of soil moisture content on the behavior of the soil–GGR interface was less evident. A slight decrease on the interface friction angle was only observed for the highest soil moisture content; (3) the dry soil–GGR interface resistance was lower than that observed for the other two geosynthetics due to the relevance of soil–soil friction at the GGR apertures, to the high percentage of fines of the soil used in the research (D50 = 1·00 mm), and to the smoother solid lateral surface of the extruded GGR when compared with the surface of the GTX or GC.

Effects of Soil Moisture Content on Groundwater Electrical Resistivity Values in Irrigation Paddy Scheme, Tanjong Karang, Malaysia

Electrical Resistivity Tomography (ERT) analyses have been conducted in Irrigation Paddy Scheme, Tanjong Karang, Malaysia as part of investigation on groundwater potential aquifer to provide an alternative water resource for paddy irrigation. Based on recent studies on groundwater resistivity in paddy field, irrigation system mentioned as soil moisture content was observed to affect the value of electrical resistivity and subsurface geological profile resulted from ERT analysis. The objective of this study was to proof any correlation between soil moisture content and electrical resistivity values and to determine at what level of soil moisture content which will be the best condition to conduct ERT survey. ERT analysis was conducted by using ABEM Terrameter SAS 4000 of Wenner-Schlumberger array with 5.0 meter and 10.0 meter for minimum and maximum electrode spacing. Visually, based on subsurface geological profile resulted from ERT analysis soil moisture content affected (changed) electrical resistivity values. With all different treatments of soil moisture ranged from 16.96% to 27.50%, electrical resistivity values decreased in certain points and in certain depth along with the increase of soil moisture content. This was proofed by ANOVA and Duncan’s multiple range tests showing that Pr > F value was less than 0.0001. Further on Chi-square test showed that at soil moisture level of 22.54%, it was the best condition which gave more correct counts of electrical resistivity values compared to well lithology. This was assumed to be the best condition to conduct ERT survey.

Biodiversity of Soil Arthropods in Nigerian Institute for oil Palm Research (NIFOR), Nigeria

A survey of soil arthropod fauna inhabiting Nigeria Institute for Oil Palm Research (NIFOR) was carried out from July-September 2012, with a view to determine the diversity and distribution of soil arthropods of the area. Two study stations were identified at the area, namely; Station one (Plantation site) and Station two (Control site). One thousand eight hundred and seventy-seven (1877) individual soil arthropods were recorded from both stations. These individuals were represented in 4 classes, 11 orders and 21 families which were collected and extracted using the pitfall trap method and the Berlese Tullgren Extractor Funnel. Data collected from the study stations were subjected to appropriate statistical analyses which included Simpson’s index (Ds), the Shannon Wiener index (H’), the Shannon Diversity T-test and Evenness (E) to determine the diversity of the soil arthropod fauna. Station one (Plantation site), was the most diverse station (Ds=2.99) and (H’=1.84) while station two (Control site) having (Ds= 2.94) and (H’= 1.69) is the least diverse station which may be as a result of anthropogenic activities. The Order Hymenoptera and Family Formicidae (50.5%) and (38.7%) respectively were the dominant and abundant group in both stations with the Order Crustacea and Family Armadillidae (22.2%) and (1.63%) respectively were the least dominant and abundant in both stations. The soil arthropod fauna correlated positively with the soil organic carbon (r=0.16), soil moisture content (r= 0.26) and soil pH (r=0.60) while the soil temperature correlated negatively (r= -0.89) in both stations. This implies that soil arthropods increase with increasing soil moisture content and decreasing soil temperature. © JASEM

Runoff characteristics and nutrient loss mechanism from plain farmland under simulated rainfall conditions

In recent years, nonpoint source (NPS) pollution has become the main contributor to water quality problems. Research on nitrogen (N) and phosphorus (P) losses from farmland and the factors that influence these losses is very meaningful both for increasing the crop yield and for improving environmental water quality. To explore the mechanism by which N and P are lost from farmland in the North China Plain (NCP), 16 simulated rainfalls were conducted in 14 experimental fields (each of which had different conditions) in the NCP from July to August in 2010. The results showed that the rainfall intensity, the antecedent soil moisture content, and the vegetation cover status were the main factors that affected the surface runoff in the NCP. The runoff volume increased with the increasing rainfall intensity and the increasing soil moisture content, and decreased with the increasing vegetation cover. These factors also significantly affected the losses of P and N. The losses of P and N were positively correlated with the rainfall intensity and the antecedent soil moisture content, and negatively correlated with the vegetation cover. A longer and more intense rainfall resulted in a higher loss of N and P. Dissolved nitrogen was the predominant form of N loss. For phosphorous, the predominant loss form was greatly influenced by the rainfall intensity, the vegetation cover, and the antecedent soil moisture content. Most of phosphorus existed as dissolved phosphorus in Baizhuang (BZ) and as particulate phosphorus in Tangcheng (TC) and Fentai (FT). The minimum requirements for runoff occurrence in experimental regions were a rainfall depth of 5.1mm, a rainfall intensity of 50mm/h, and an antecedent soil moisture of approximately 29.6%.

Spatial explicit soil moisture analysis: pattern and its stability at small catchment scale in the loess hilly region of China

AbstractSoil moisture is essential for plant growth and terrestrial ecosystems, especially in arid and semi‐arid regions. This study aims to quantify the variation of soil moisture content and its spatial pattern as well as the influencing factors. The experiment is conducted in a small catchment named Yangjuangou in the loess hilly region of China. Soil moisture to a depth of 1 m has been obtained by in situ sampling at 149 sites with different vegetation types before and after the rainy season. Elevation, slope position, slope aspect, slope gradient and vegetation properties are investigated synchronously. With the rainy season coming, soil moisture content increases and then reaches the highest value after the rainy season. Fluctuation range and standard deviation of soil moisture decrease after a 4‐month rainy season. Standard deviation of soil moisture increases with depth before the rainy season; after the rainy season, it decreases within the 0‐ to 40‐cm soil depth but then increases with depths below 40 cm. The stability of the soil moisture pattern at the small catchment scale increases with depth. The geographical position determines the framework of soil moisture pattern. Soil moisture content with different land‐use types is significantly increased after the rainy season, but the variances of land‐use types are significantly different. Landform and land‐use types can explain most of the soil moisture spatial variations. Soil moisture at all sample sites increases after the rainy season, but the spatial patterns of soil moisture are not significantly changed and display temporal stability despite the influence of the rainy season. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Maximising adaptive potential in translocated populations of clonal saltmarsh plants: a case study on Wilsonia backhousei, Convolvulaceae

We investigated the implications of clonality for translocation of Wilsonia backhousei, a threatened, outbreeding, saltmarsh plant with tidally-dispersed fruit. Eight microsatellite loci were used to characterise samples from three estuaries in New South Wales, Australia, and to determine the size and distribution of genetically distinct individuals (genets). Within-population diversity was compared to the presence or absence of seed production using the t test. Ordinal logistic regression was used to investigate the relative influence on seed yield of soil characteristics (soil moisture, salinity, pH) and the number of clonal lineages within a 5 and 10 m radius. Principal coordinate analysis, analysis of molecular variance and Bayesian analysis were used to investigate the extent of gene flow within and among the three estuaries. We found individual genets could cover extensive areas (up to 225 m2) and apparently large populations could consist of only a few individuals. Populations that failed to produce seed had significantly less genetic diversity than populations that produced seed (P = 0.001). Seed yield showed a significant positive response to both increasing soil moisture content (P = 0.003) and increasing genetic diversity in a 5 m radius (P = 0.003). Gene flow was found to occur chiefly within estuaries though occasional longer-distance gene transfer was evident. To maximise adaptive potential in translocated populations of W. backhousei, we recommend sourcing propagules from multiple populations and planting representatives of the different populations in close proximity to facilitate sexual reproduction. These findings are likely to be applicable to other outbreeding clonal saltmarsh plants with tidally-dispersed fruit or seed.

Una nueva herramienta para evaluar la susceptibilidad de los suelos a los procesos de sufosión o piping : el pinhole test

Piping has been observed in natural and anthropogenic landscapes, in different lithologies and climates, and under different types of land uses and vegetation covers. Despite its importance, no standard widely-applied methodology exists to assess susceptibility of soils to piping. The pinhole test, originally developed by Sherard et al. in 1976 is an empirical test based on the qualitative evaluation of the dispersibility (colloidal erodibility) of compacted fined-grained soils. This study aims at evaluating the pinhole test for assessing the susceptibility of soils to piping and establishes recommendations to use the pinhole test, and assesses the effects of hydraulic head, water quality and soil moisture content on the hydrological and erosion responses. Topsoil Ap horizon samples with different moisture contents were taken in Central Belgium. Four hydraulic heads (50, 180, 380 and 1020 mm) and two water qualities (tap and distilled water) were used in the laboratory. The results show: (i) a linear increase in pipe flow discharge (Qw) and sediment discharge (Qs) with increasing hydraulic head, (ii) a negative trend (not significant) for Qw and Qs with increasing soil moisture content, and (iii) significantly higher Qw and Qs for distilled water than for tap water. This study indicates that the pinhole test is suitable for assessing the susceptibility of soil horizons to piping in a quantitative way (Qw, Qs, the time to flow out and the hole size after the test). We recommend the use of: (i) two different and contrasting hydraulic heads (i.e. 180 and 1020 mm), (ii) distilled water, and (iii) different soil moisture contents.

Uso de un polímero hidrófilo en chile Anaheim (Capsicum annuum L.) bajo condiciones de invernadero

In order to improve the efficiency of water use in vegetable production, during autumn-winter 2011-2012 the use of a polyacrylamide-based hydrophilic polymer (PAM) was evaluated in Anaheim pepper cv. Cardon in full production using drip irrigation undergre-enhouse conditions. The experimental design was a randomized complete block with five replicates. The experimental unit was 4 m long, 1.5 m wide (6 m2) with 20 total plants and five used for measurements. The parameters evaluated were: fruits per plant, fruit weight, commercial yield, size (length and diameter), volume of water applied, water use efficiency (WUE) and chlorophyll content. The incorporation of the hydrophilic polymer had no positive effect on production, fruit quality or WUE; however, there was an effect on the volume of applied water and chlorophyll content. With the polymer a yield of 1.5 kg m-2 with 24.9 fruits m-2, fruit weight 59.2 g, 16.2 cm length, 3.9 cm diametr, and WUE of 5.0 kg m-3 were obtained; whereas in the control without polymer the yield was 1.7 kg m-2, with 26.7 fruits m-2, fruit weight 62.1g, 16.3 cm length, 4.0 cm diameter and WUE of 4.9 kg m-3. With the incorporation of the polymer a 1.5% increase in soil moisture content was obtained, which represented a 12% reduction in the volume of water applied and a SPAD reading of 58.4 versus 57.7 of the control, thus the use of a hydrophilic polymer may be an important practice for producers who need to irrigate less frequently and reduce watering time.

Carbon and water fluxes in an arid-zone Acacia savanna woodland: An analyses of seasonal patterns and responses to rainfall events

The study of landscape gas exchange in arid and semi-arid regions is less common than those of more mesic environments, despite their large geographical extent, their importance to regional climate, their socioeconomic values and the carbon and water balances of such regions. In this study we used eddy covariance measurements to examine net ecosystem exchange and water fluxes of a landscape dominated by a N-fixing tree (Acacia aneura; Mulga) as a function of soil moisture content, vapour pressure deficit, leaf area index and pulses of rain. Seasonal budgets of carbon and water, ecosystem-scale water-use-efficiency (the ratio of net ecosystem exchange to evapotranspiration) and inherent water-use-efficiency (ecosystem water-use-efficiency×vapour pressure deficit) were also examined. Across the 12 month study, the landscape was a net sink for carbon, despite prolonged periods of zero rain.Changes in both net ecosystem exchange and evapotranspiration were tightly coupled to changes in the moisture content of the upper (10cm) soil profile, but not the deeper profile and both responded rapidly to changes in soil moisture content. As vapour pressure deficit increased over the course of several consecutive days in the wet season there was no significant response of ecosystem water-use-efficiency. In contrast, in the dry season, as vapour pressure deficit increased ecosystem water-use-efficiency declined curvilinearly. However, in both wet and dry seasons, ecosystem water-use-efficiency declined with increasing soil moisture content. Daily inherent water-use-efficiency increased gradually following each rainfall event. As daily mean vapour pressure deficit increased between rain events, inherent water-use-efficiency increased in both the wet and dry seasons but with a steeper slope in the wet season. However, inherent water-use-efficiency decreased with increasing soil moisture in both seasons, and the slope of a semi-log plot of inherent water-use-efficiency versus soil moisture content decreased faster in the dry season than in the wet season. Similarly, the marginal carbon cost of water was smaller (0.3) in the wet than dry season (0.6). Variations in ecosystem leaf area index were correlated with the under storey component, which was highest in the wet season and lowest in the dry season. We therefore conclude that changes in under storey leaf area index were significant drivers of seasonal changes in canopy gas exchange. Mulga, despite maintaining leaf area index through the dry season in a semi-arid environment, supports little dry season evapotranspiration and relies, to a very large extent, on soil moisture in the upper soil profile rather than deeper stores of water.

Global warming accelerates the upfreezing of permafrost in arid middle Tianshan Mountains

Upfreezing is an important geomorphic process in the periglacial environment. It is a product of cold climate and thus an important part of the cryospheric processes. Based on the long-term positioning observations in the source area of the Urumqi River, this article represents an in-depth discussion of the characteristics of sorted circles and upfreezing mechanisms in the Tianshan Mountains. In the source area of the Urumqi River, the intensity of upfreezing is the highest within the top 25 cm near the surface, while targets with a diameter of 3 cm are least affected by upfreezing. There is no distinct difference between the centre with fine grains and the margin with coarse debris within the same sorted circle in terms of the intensity of upfreezing. The correlation analysis demonstrates that temperature plays an important role in upfreezing and the development of sorted circles. A long-time positioning observation of sorted circles reveals that periglacial landforms are sensitive to regional climate change and respond quickly to the temperature increase of the recent two decades. Enhanced upfreezing was found to be due to increased soil moisture content.

N2O consumption by low-nitrogen soil and its regulation by water and oxygen

Soils can be a source and sink for atmospheric nitrous oxide (N2O). Consumption of N2O has been reported for anoxic soils and sediments rich in organic matter and depleted in nitrates (NO3−), and also for some dry, oxic soils. However, the mechanisms and controls of N2O consumption in dry soil are not clear.Here, we report on a field study in China (Taihang mountain region, Shijiazhuang), in which N2O uptake by a sandy loam soil was measured for the greater part of the season (from April to October in 2011), and on four incubation experiments, in which we tried to reveal the roles of water content and oxygen (O2) concentrations on N2O consumption. Flux measurements in the field were made bi-weekly on unfertilized cropped land with static flux chambers (5 replicates) for 6 months. The results show that N2O–N fluxes ranged from −26.0 to −726.6 μg m−2 h−1. Consumption of N2O was largest when the soil was dry (5–20% soil water filled pore space). In the incubation experiments, N2O consumption and N2 production were measured in (an)aerobic soil with soil moisture content ranging from 1% to 50% (wt/wt) and with N2O addition, using a thermostatic, robotized incubation system. Under anaerobic conditions, N2O was rapidly consumed at water content of >10% (wt/wt). However, a significant consumption also occurred at 1% soil moisture. Under aerobic conditions, N2O consumption increased with increasing soil moisture content, but significant consumption was still measured at 2% moisture. Sterilization of oxic soil completely blocked N2O consumption, suggesting that the consumption had a biological nature. In conclusion, the steady N2O consumption measured in the field was confirmed by the laboratory experiments, but the relationship with soil moisture content was reversed. Further studies are required to understand this apparent anomaly.

Estoque e capacidade de retenção hídrica da serrapilheira acumulada na restauração florestal de áreas perturbadas na Mata Atlântica

A serrapilheira, em restauracao florestal espontânea, pode influir no balanco hidrico e em seus processos ecologicos. Neste estudo, foi avaliado o estoque de serrapilheira acumulada e sua retencao hidrica ex situ, pelo metodo de Blow, em locais similares em quatro niveis de restauracao florestal espontânea, desenvolvidos a partir da especie espontânea Clidemia urceolata DC., nos seguintes ambientes: pastagem abandonada (S1); capoeira (S2); capoeirao (S3), e fragmento florestal (S4). O amostrador (0,25 × 0,25 × 0,05 m) foi disposto aleatoriamente em 12 amostras por tratamento, durante o periodo de estiagem. O maior estoque de serrapilheira acumulada foi observado em S4 (5,15 Mg.ha-1) e a maior retencao hidrica, em S2 (343,87%) e S3 (339,94%), evidenciando que biomassa e diversidade de especies condicionam a producao, porem nao afetam as respostas hidricas da serrapilheira, cujas maiores retencoes estao vinculadas a presenca de material deciduo da especie facilitadora nas fases pouco evoluidas e as menores retencoes, nas fases mais evoluidas (30 anos de restauracao), aumentando a umidade do solo.

Analysis of Land-Atmosphere Interactions Over the North Region of Mt. Qomolangma (Mt. Everest)

To better understand the basic characteristics of the land surface energy budget, nearly 7 years of continuous measurements at the Qomolangma Station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences (QOMS/CAS) (28.21°N, 86.56°E, 4276 m a.s.l.) have been analyzed systematically. Seasonal and annual variations of micrometeorological measurements and land surface energy balance were analyzed. The general nature of the diurnal variation of the surface winds on the north of Mt. Everest is represented by a maximum in the afternoon and a constant wind speed in the early morning, which is controlled not only by the significant glacier wind but also by the local mountain-valley circulation and upper-level wind. Surface albedo decreases with increasing soil moisture content, showing the typical exponential relation between surface albedo and soil moisture. The data set disclosed that the high soil moisture in summer is coordinated with low albedo. The ratio between sensible heat and net radiation (H/Rn) can be as high as 0.49 when the soil is dry. The ratio (H/Rn) decreases to 0.14 with the increasing of soil moisture. On the contrary, the ratio between latent heat flux and net radiation (LE/Rn) is increased when soil moisture is rising. The highest ratio (LE/ Rn) can be as high as 0.5 when soil moisture changes between 15% and 20%. After defining the effects of different soil moisture level on partitioning of surface available energy into sensible and latent heat fluxes, we can qualify how much the sensible heating is decreasing and the latent heating is increasing in this region under current plateau environment changes of warming and moistening.

Response of deep soil moisture to land use and afforestation in the semi-arid Loess Plateau, China

Soil moisture is an effective water source for plant growth in the semi-arid Loess Plateau of China. Characterizing the response of deep soil moisture to land use and afforestation is important for the sustainability of vegetation restoration in this region. In this paper, the dynamics of soil moisture were quantified to evaluate the effect of land use on soil moisture at a depth of 2 m. Specifically, the gravimetric soil moisture content was measured in the soil layer between 0 and 8 m for five land use types in the Longtan catchment of the western Loess Plateau. The land use types included traditional farmland, native grassland, and lands converted from traditional farmland (pasture grassland, shrubland and forestland). Results indicate that the deep soil moisture content decreased more than 35% after land use conversion, and a soil moisture deficit appeared in all types of land with introduced vegetation. The introduced vegetation decreased the soil moisture content to levels lower than the reference value representing no human impact in the entire 0-8 m soil profile. No significant differences appeared between different land use types and introduced vegetation covers, especially in deeper soil layers, regardless of which plant species were introduced. High planting density was found to be the main reason for the severe deficit of soil moisture. Landscape management activities such as tillage activities, micro-topography reconstruction, and fallowed farmland affected soil moisture in both shallow and deep soil layers. Tillage and micro-topography reconstruction can be used as effective countermeasures to reduce the soil moisture deficit due to their ability to increase soil moisture content. For sustainable vegetation restoration in a vulnerable semi-arid region, the plant density should be optimized with local soil moisture conditions and appropriate landscape management practices. (C) 2012 Elsevier B.V. All rights reserved.

INFLUENCE OF SOIL MOISTURE CONTENT ON SOIL SOLARIZATION EFFICIENCY

The experiments of this study were carried out to investigate how soil temperature is influenced by different soil moisture content regimes during soil solarization. The ten plots were brought to five volumetric moisture regimes (M1-M5). The moistened soils were mulched with 100-μm-thick black and transparent polyethylene covers. Maximum and minimum soil temperatures for depths of 10, 20 and 30 cm were recorded from 1 June to 30 July, 2010at Faculty of Agriculture, Omar Al-Mukhtar University, El-Beida, Libya. For black and transparent covers, the results showed that the maximum soil temperatures decreased with increasing soil moisture content. Moreover, soil solarization efficiency decreased with increasing moisture content. The higher temperatures under the M4 (0.39 and 0.37 m3/m3 at start solarization) irrigation regime resulted in faster eradication of the pathogenic fungus.