Topsoil Temperature Research Articles

Multifrequency Radiometric Method of the Temperature Profile Measurement in the Active Topsoil

In this theoretical paper, we propose a method for measuring the temperature profile in the active topsoil of the Arctic tundra using observations of the brightness temperature for two different polarizations of the radiation at frequencies of 1.4, 6.93, 7.3, and 10.7 GHz. A multifrequency physical model of microwave emission of bare soil, a dielectric model of the Arctic tundra soil, and temperature profiles, which were measured in the active topsoil at the Toolik field station on the Alaska North Slope, were used to calculate the observed values of the brightness temperature. Temperature profiles were retrieved from the observed values of the brightness temperature in the approximation of a piecewise-linear profile of topsoil temperature during 2010–2011. Correlation analysis of the temperature profiles measured at the Toolik station and retrieved from the radiometric data has shown that in winter the error of measurement of the soil temperature at depths of 0.6 and 16.0 cm in terms of the variance (correlation coefficient) does not exceed 2.3 (0.98) and 7.2 (0.62°C), respectively. In summer, the error of measurement of the soil temperature using the radiometric method is two times less than in winter.

Facilitation and edge effects influence vegetation regeneration in old‐fields at the tropical Andean forest line

AbstractQuestionsDo local plant–plant interactions and facilitation play an important role in vegetation dynamics after disturbance in the high tropical Andes? In particular, does the dominant shrub Baccharis prunifolia have an effect on microclimate and local vegetation structure within old‐fields at the upper forest line? Does distance from the border of the surrounding forests also influence community structure within fallow plots? Is there an interaction between facilitation and edge effects on vegetation regeneration?LocationGavidia Valley, Sierra Nevada de Mérida, Venezuela.MethodsPlant cover, species richness and community structure were compared in circular micro‐plots placed under the canopy of B. prunifolia shrubs and in open areas (12 micro‐plots in each case) both near and far from the forest border within two 10–12 yr successional plots at 3400 m a.s.l. (a total of 96 micro‐plots). Additionally, topsoil temperature was monitored for 1 mo in the four situations under study.ResultsAverage and maximum temperature and temperature amplitudes were lower under the canopy of B. prunifolia shrubs than in open areas; this effect being more marked far from the forest edge. Species richness, vegetation cover and the density of dominant forest trees were higher under the shrubs’ canopy than in the inter‐shrub spaces. The proximity to the edge of the surrounding forest also had a positive effect on species richness, with no significant interaction with the local sampling situation (under shrub vs outside).ConclusionsOur results suggest that both facilitation and edge effects influence the effectiveness of vegetation regeneration within old‐fields in the high tropical Andes. Consequently, these processes should be considered for interpreting vegetation dynamics in environmental change scenarios at the tropical mountain tree line and for the design of ecological restoration strategies in these high‐diversity ecotones, which have been subjected to large‐scale anthropogenic transformations in recent decades.

Optimum ridge–furrow ratio and suitable ridge-mulching material for Alfalfa production in rainwater harvesting in semi-arid regions of China

Alfalfa (Medicago sativa L.) is traditionally sown in field without ridge and furrow, in rain-fed semi-arid areas of Northwest China, and forage yields are normally low because of drought, water loss and soil erosion. A field study was conducted to determine (1) Monthly runoff efficiency and threshold rainfall for different ridge widths (30, 45 and 60cm), and mulched with different materials (common plastic film, bio-degradable mulching film and manually compacted soil); and (2) the effects of different ridge–furrow ratios (30:60, 45:60 and 60:60) and ridge-mulching materials on soil water storage, topsoil temperature, forage yields, and water use efficiency (WUE) of Alfalfa in ridge–furrow rainwater harvesting (RFRWH) system, during 2 consecutive years: 2012 and 2013. Average monthly runoff efficiency over these 2 years, was 16%, 18%, 19%, 65%, 71%, 77%, 70%, 72% and 79% for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60 (SR, BMR and CMR were ridges with manually compacted soil, mulched with bio-degradable mulch film and common plastic film, respectively, and subscripts 30, 45 and 60 refer to ridge widths (cm) all with 60cm furrow width), respectively. For the same treatments, threshold rainfall was 4.3, 4.3, 4.2, 3.0, 2.9, 2.8, 2.9, 2.9 and 2.8mm. The field experiment showed that ridge mulching materials and ridge widths had distinct effects on topsoil temperature at ridge tops, but not at furrow bottoms. Soil water storage in 140cm soil depth at furrow bottoms increased with increasing ridge width and in the order of CMR≈BMR>SR>FP. Average annual total forage yields for FP, SR, BMR and CMR were 6276, 5642, 7563 and 7817kgha−1, respectively, over 2 years. The total precipitation in both years was higher than average of rainfall, leading to significant decreases of forage yields for SR, and significant increases of forage yields for BMR and CMR. Compared with FP, average forage yields decreased by 3%, 10% and 17% for SR30, SR45 and SR60, and increased by 27%, 21%, 13%, 32%, 26% and 16% for BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60, respectively, over 2 years. WUE for SR, BMR and CMR was 1.69, 1.74 and 1.74 times greater than that for FP over 2 years, and increased with decreasing ridge width. Optimum furrow width was 35–36cm for CMR and BMR in the RFRWH system with 60cm width furrows for Alfalfa production in this region. Future study is needed to investigate optimum ridge–furrow ratio and suitable ridge-mulching material for achieving the best environmental and economic benefit under different climatic conditions, soil types and plant species, and using bio-degradable mulching materials.

The effects of plastic film mulching on maize growth and water use in dry and rainy years in Northeast China.

Plastic film mulching (PM) has been widely used to improve maize (Zea mays L.) yields and water use efficiency (WUE) in Northeast China, but the effects of PM in a changing climate characterized by highly variable precipitation are not well understood. Six site-year field experiments were conducted in the dry and rainy years to investigate the effects of PM on maize growth, grain yield, and WUE in Northeast China. Compared to crops grown without PM treatment (control, CK), PM significantly increased the grain yield by 15-26% in the dry years, but no significant yield increase was observed in the rainy years. Yield increase in the dry years was mainly due to a large increase in dry matter accumulation pre-silking compared to the CK, which resulted from a greater dry matter accumulation rate due to the higher topsoil temperature and water content. As a result, the WUE of the crops that underwent PM (3.27 kg m-3) treatment was also increased by around 16% compared to the CK, although the overall evapotranspiration was similar between the two treatments. In the rainy years, due to frequent precipitation and scant sunshine, the topsoil temperature and water content in the field that received PM treatment was improved only at some stages and failed to cause higher dry matter accumulation, except at the 8th leaf stage. Consequently, the grain yield and WUE were not improved by PM in the rainy years. In addition, we found that PM caused leaf senescence at the late growth stage in both dry and rainy years. Therefore, in practice, PM should be applied cautiously, especially when in-season precipitation is taken into account.

Organic Carbon Accumulation in Topsoil Following Afforestation with Willow: Emphasis on Leaf Litter Decomposition and Soil Organic Matter Quality

Short-rotation intensive cultures (SRICs) of willows can potentially sequester carbon (C) in soil. However, there is limited information regarding the factors governing soil organic C (Corg) accumulation following afforestation. The objectives of this study were to: (i) determine whether willow leads to Corg accumulation in the topsoil (0–10 cm) two to six years after establishment in five SRICs located along a large climatic/productivity gradient in southern Quebec, and (ii) assess the influence of leaf litter decomposition and soil organic matter (OM) quality on Corg accumulation in the topsoil. Topsoil Corg concentrations and pools under SRICs were, on average, 25% greater than reference fields, and alkyls concentrations were higher under SRICs. On an annualized basis, Corg accumulation rates in the topsoil varied between 0.4 and 4.5 Mg ha−1 yr−1. Estimated annual litterfall C fluxes were in the same order of magnitude, suggesting that SRICs can accumulate Corg in the topsoil during early years due to high growth rates. Leaf litter decomposition was also related to Corg accumulation rates in the topsoil. It was positively correlated to growing season length, degree-days, and growing season average air and topsoil temperature (r > 0.70), and negatively correlated to topsoil volumetric water content (r = −0.55). Leaf litter decomposition likely occurred more quickly than that of plants in reference fields, and as it progressed, OM became more decay resistant, more stable and accumulated as Corg in the topsoil.

Improved yield by harvesting water with ridges and subgrooves using buried and surface plastic mulchs in a semiarid area of China

This paper determines the responses of soil temperature, water status and crop yields to a new planting pattern involving ridges and subgrooves with plastic film mulching in a millet-field pea-spring wheat-potato cropping system. The study was conducted in a typical semiarid area, during the four annual growing seasons of 2005–2008 and five treatments were designed: (1) a flat plot with no mulching, which is the conventional tillage practice (CK); (2) alternating ridges and furrows with no mulching (M0C0); (3) alternating ridges and furrows with no mulching, and subgrooves mulched with plastic film (M0C); (4) alternating ridges and furrows, with only the ridges mulched with plastic film on the surface (MC0); and (5) alternating ridges and furrows, as well as subgrooves, with the ridges and subgrooves mulched with plastic film (MC). The subgrooves with plastic film mulching increased topsoil temperature, the average daily soil temperature of the 4-growing seasons was 16.7, 16.8, 16.9, 17.4 and 17.2°C for the CK, M0C0, MC0, M0C and MC, respectively. The soil temperature was significantly higher in the M0C and MC than in the CK, M0C0 and MC0 in May 2006, September in 2007 and May 2008. In average and wet years, the soil water content in the 20–40cm soil layer was 6.2–37.7% higher in the MC than in the CK. The ridges and subgrooves with plastic film mulching improved crop yields, and the average yield over the four years was higher in the MC than in the CK, M0C0, M0C and MC0 by 163%, 98%, 62% and 21%, respectively. Potato is a staple and economic crop in this region, and the ratio of large and moderate-sized potato tuber yield to total tuber yield was 21.7% higher in the treatments with subgrooves than in the treatments without subgrooves. In conclusion, the technique of ridges and subgrooves with plastic film mulching is an effective practice for improving crop yields in semiarid agroecosystems.

Methane uptake and emissions in a typical steppe grazing system during the grazing season

This study investigated the effects of livestock grazing on CH4 emissions by testing six grazing conditions at Guyuan State Key Monitoring and Research Station of Grassland Ecosystem (China) in 2011 and 2012. Under all grazing systems, steppe soils were measured to be CH4 sinks. The uptake of CH4 by grassland was primarily determined by topsoil (7 cm) temperature and soil (0–7 cm) moisture in grassland at short-term grazing and non-grazing. The cumulative uptake of CH4 during the grazing period for all conditions was 0.88–3.23 kg hm−2 CH4, and the highest level was observed in the continuously moderate grazing condition. Reducing grazing stocking in the short-term did not significantly change the uptake of CH4 when compared with continuously heavy grazing condition. Enteric CH4 emissions were not significantly affected by the grazing period or conditions. The uptake of CH4 by grassland soil offset 3.1–8.6% of the CH4 emissions from the grazing sheep and was most effective at the continuously moderate grazing condition. These findings imply that continuously moderate grazing is the best approach considered here for optimizing the soil as a sink for atmospheric CH4.

Method for Soil Moisture and Surface Temperature Estimation in the Tibetan Plateau Using Spaceborne Radiometer Observations

A method for soil moisture and surface temperature estimation in the Tibetan Plateau (TP) using spaceborne radiometer observations was presented. Based on the physical basis that the 36.5-GHz (Ka-band) vertical brightness temperature is highly sensitive to the topsoil temperature, a new surface temperature model was developed using all ground measurements available from three networks named CAMP/Tibet, Maqu, and Naqu, established in the TP, which can significantly improve the accuracy of surface temperature derived from the land parameter retrieval model (LPRM). Then, the new surface temperature model, which was calibrated with in situ data, was integrated into the soil moisture retrieval algorithm proposed in this letter using Advanced Microwave Scanning Radiometer (AMSR-E) observations. The algorithm combines the vegetation optical depth and roughness into an integrated factor to avoid making unreliable assumptions and using auxiliary data to get these two parameters. Finally, the algorithm was validated by ground measurements from the dense Naqu network and was compared with NASA AMSR-E and Soil Moisture and Ocean Salinity (SMOS) official algorithms. The results show that the proposed algorithm can provide much more accurate soil moisture retrievals than the other two satellite algorithms in the Naqu network region. The algorithm can be applied to the areas with spare vegetation but may not be very suitable for densely vegetated surfaces.

The optimum ridge–furrow ratio and suitable ridge-covering material in rainwater harvesting for oats production in semiarid regions of China

Drought, water loss and soil erosion are the main factors limiting agricultural production in semi-arid regions of China. A field study was conducted to determine (1) the runoff efficiencies of different ridge widths (30, 45 and 60cm) covered with different materials (common plastic film, biodegradable mulching film and manual compacted soil) and (2) the effects of different ridge–furrow ratios (30:60, 45:60 and 60:60) and ridge-covering materials on soil water storage, topsoil temperature, hay yield, grain yield and water use efficiency (WUE) of oats in ridge–furrow rainwater harvesting (RFRH) system at the Dingxi Agri-meteorological station, during 2 consecutive years of 2012 and 2013. Average runoff efficiency was 18%, 20%, 22%, 71%, 77%, 83%, 76%, 77% and 84% for SR30, SR45, SR60, BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60 (SR, BMR and CMR were ridges with compacted soil, covered with biodegradable mulch film and common plastic film, respectively, and subscript numbers 30, 45 and 60 stand for ridge widths (cm)) over 2 years, respectively. The field experiment using oats as an indicator crop showed that mulching materials and ridge widths had distinct effects on topsoil temperature on the top of the ridges, but not in the bottom of the furrows. The soil water storage in the 140cm depth of soil at the bottom of furrows increased with increasing ridge widths and in the order of CMR≈BMR>SR>FP (FP was the flat planting). The total precipitation was 414.4mm in 2012 and 448.8mm in 2013, which were higher than the average of rainfall (388.1mm), leading to a significant increase of hay and grain yield in CMR, and an equivalent of hay and grain yield in BMR compared with FP in most cases. In the SR system, the positive effects of rainwater harvesting could not compensate for the negative effects of planting area reduction resulting in decrease in hay and grain yield. Compared with FP, the average grain yield decreased by 19%, 27% and 34% for SR30, SR45 and SR60, and increased by 6%, 4%, 1%, 12%, 9% and 6% for BMR30, BMR45, BMR60, CMR30, CMR45 and CMR60 over 2 years, respectively. The WUE of SR, BMR and CMR was 1.31, 1.41 and 1.47 times greater than that in FP over 2 years, and increased with increasing ridge width. The optimum furrow width was 32–38cm for CMR and was 30–34cm for BMR. Future study is needed to investigate the impact of RFRH on crop production, WUE and economic benefit under different precipitations, soil types, slopes and plant species using biodegradable mulching materials.

Effects of a ridge-furrow micro-field rainwater-harvesting system on potato yield in a semi-arid region

To evaluate the effects of mulching and ridge and furrow widths on soil temperature and moisture, crop growth and yield, and water use efficiency (WUE), a series of field experiments were conducted in a potato field in Inner Mongolia, China. In 2009 and 2010, four treatments (flat plot without mulching (CK), plastic film mulched ridge (MR), MRF (plastic film mulched ridge and furrow (MRF), and non-mulched (NM0.5)) were conducted on the same widths of ridge (0.5m) and furrow (0.5m), and two additional non-mulching treatments (1.0m ridge and furrow width (NM1.0), and 1.5m ridge and furrow width (NM1.5)) were tested in 2011 and 2012. The results indicated that mulching practices increased topsoil temperature compared to non-mulching treatments at the emergence stage. Compared to CK, the soil water storage in furrows was increased by 10.2mm on average in 2009 for the MRF treatment, 8.1mm and 15.1mm in 2011, and 14.0mm and 21.2mm in 2012 for NM1.0 and NM1.5, respectively, and plant leaf area index and dry biomass values during the potato growth stage were also increased. The MR treatment produced greater effects on crop productivity than NM0.5, and increased total yield and marketable yield by 21.4% and 36.3% compared to CK in 2010. Of three non-mulching treatments (i.e., NM0.5, NM1.0, and NM1.5), the NM1.0 treatment produced the highest total yield and marketable yield; compared to CK, the WUE, total yield, and marketable yield were increased by 12.7%, 8.2%, and 52.0% in 2011, and 23.4%, 16.4%, and 81.0% in 2012, respectively.

Effects of harvest residue management on soil carbon and nitrogen processes in a Chinese fir plantation

Plantation management can affect ecosystem soil carbon (C) and nitrogen (N) cycles. However, how different harvest residue management strategies impact soil C and N processes over the long term is largely unclear. In this study, we examined effects of harvest residue management on soil C and N concentrations, labile soil C and N pools and soil CO2 efflux (Rs) at different stages after Chinese fir (Cunninghamia lanceolata) was replanted in subtropical China. The residue management treatments were slash and burning, whole-tree harvesting, stem-only harvesting and stem only harvesting with double residue retention. Our results showed that the harvest residue management treatments did not differ significantly in their effect on soil C and N, mineral N (NH4+-N plus NO3−-N), dissolved organic C or total dissolved N concentrations, except for soil N concentrations in surface soil (0–10cm) at year 3 and soil total dissolved N concentrations at year 12, which were significantly lower where the slash was burnt than in the double residue retention treatment. Similarly, Rs did not differ significantly among the four residue management strategies at year 15. Topsoil temperature and topsoil moisture were also unaffected by harvest residue management treatment. Soil temperature was found to be the most important factor controlling the temporal pattern of Rs, accounting for 65.8% of seasonal variation of Rs. There was no significant difference in temperature sensitivity of Rs (Q10) or annual Rs among the four treatments. These results indicated that harvest residue management may not significantly cause long-term effects on soil C cycling and N availability in subtropical Chinese fir plantations.

Ridge-furrow with full plastic film mulching improves water use efficiency and tuber yields of potato in a semiarid rainfed ecosystem

A planting pattern of alternate ridges and furrows with plastic film mulching has been viewed as a best management practice for crop production in the arid and semiarid regions, but there is a lack of insight into the underlying changes in soil–crop water relations on mulching areas and ridge-furrow shapes for potato (Solanum tuberosum L.) production. A field study with comparisons of three mulching areas and two ridge-furrow shapes was conducted for two years (2009 and 2010) to assess evapotranspiration, water use efficiency, and tuber yields in the semiarid Northwest China. The experiment included five mulching area and ridge-furrow shape combinations: (1) full mulching on double ridges and furrows (DRFFM), (2) full mulching on both ridges and furrows (RFFM), (3) half mulching only on ridges (RFHM), (4) no mulching on ridges and furrows (RFNM), and (5) traditional-flat planting and without mulching as the control (CK). The two full mulching treatments had the best effect on topsoil temperature–moisture, improved emergence rate by 9.3–14.4% and advanced emergence by 8.1–11.7 days (P<0.05). Full mulching treatments reduced evapotranspiration by about 24.0–45.0% during emergence, but increased it by up to 18.7% thereafter, primarily due to rapid increase of LAI under faster development, and also enhanced root/shoot ratio (P<0.05). Full mulching produced the highest tuber yields (57.4–78.2% higher than the CK) with higher cost of mulching material and labour than the half or no mulching treatments. The full mulching also resulted in the highest water use efficiency (increased by 56.8–70.3% than the CK). The beneficiary effects became smaller with the decrease of mulching areas. However, the difference between the two full mulching treatments was not significant (P>0.05) despite there was slightly higher WUE in DRFFM than RFFM. Our results revealed that the full mulching on ridge-furrow planting strategy was effective to increase potato productivity and water use efficiency in the semiarid area of Chinese Loess Plateau.

Impact of Overgrazing on Semiarid Ecosystem Soil Properties: A Case Study of the Eastern Hovsgol Lake Area, Mongolia

The present study investigates the impacts of overgrazing on soil properties in eastern Hovsgol, Mongolia. The results have shown that soil fertility decreases and soil chemical properties change as a result of overgrazing and pasture degradation. In overgrazed areas, SOM content was 30-50% lower (p=0.012), and exchangeable calcium 40-60% lower when compared to non-grazing areas. Nitrate nitrogen content was also lower in overgrazed valleys. Overgrazing was also found to affect physical soil water properties, increasing topsoil temperature and decreasing moisture content. Moreover, topsoil becomes denser and more compact as a result of animal pressure on the soil surface, increasing bulk and particle density. The results indicate that overgrazing can lead to significant decreases in soil organic content and fertility, highlighting the need to implement soil conservation and pasture management policies based on traditional nomadic husbandry.

Greenhouse gas emissions in double sequence pea-wheat rotation fields under different tillage conditions

为了研究耕作措施对双序列轮作农田土壤温室气体的排放及影响, 采用CO₂分析仪、静态箱 气相色谱法在陇中黄土高原半干旱区对传统耕作不覆盖、免耕不覆盖、免耕秸秆覆盖和传统耕作+秸秆还田4种耕作措施下豆麦双序列轮作农田土壤温室气体(CO₂、N₂O和CH₄)的排放及影响因素进行了连续测定和分析。结果表明: 测定期内4种耕作措施下农田土壤均表现为CO₂源、N₂O源和CH₄净吸收汇; 除传统耕作不覆盖措施, 其他3种耕作措施不同程度地减少了2种轮作序列土壤的N₂O排放通量, 并显著增加了土壤对CH4的吸收。CO₂和N₂O的排放通量分别与地表、地下5 cm处、地下10 cm处的土壤温度呈极显著和显著正相关关系, 相关系数分别为0.92^**和0.89^**、0.95^**和0.91^**、0.77^*和0.62^*; 而CH₄吸收通量与不同地层的温度之间无明显的相关关系; CO₂和CH₄的通量与0~5 cm、5~10 cm的土壤含水量均呈显著正相关关系, 相关系数分别为0.69^*和0.72^*、0.77^*和0.64^*, 而与10~30 cm土壤含水量无明显相关关系; N₂O排放通量与各层次的土壤含水量之间均呈不显著负相关关系。对2种轮作序列各处理下土壤中排放的3种温室气体的增温潜势计算综合得出: 4种耕作措施中, 免耕不覆盖处理可相对减少土壤温室气体的排放量, 进而降低温室效应。

The cultivation of oak seedlings inoculated with Tuber aestivum Vittad. in the boreal region of Finland

Despite recent findings, truffles are rarely found in Finland. In 2006, we began to explore the cultivation potential of Tuber aestivum/uncinatum in Finland. In 2006–2008, roughly 1,200 Quercus robur seedlings and 200 Q. pubescens seedlings were planted in 20 orchards. We aimed to challenge the Southern European (France) tree provenances of oak seedlings in a boreal climate. Additional winter coverings made up of fabric or plastic and twigs prevented the seedlings’ mortality even when the air temperature was below −30 °C during the second winter. The results showed that the top soil temperature at 15 cm depth has to be above −5 °C to guarantee the survival of seedlings. Q. pubescens was more sensitive to low soil temperatures than Q. robur. Morphological and PCR analysis of root samples collected over 2007–2010 confirmed the presence of T. aestivum in all orchards despite unfavorable temperatures during the winter time. The first T. aestivum sporocarps were found under Q. robur in October 2012 in the orchards established in 2006 on old agricultural land, showing truffle cultivation to be successful in the boreal climate.

Hierarchy of factors drivingN2Oemissions in non‐tilled soils under different crops

SummaryNitrous oxide (N2O) is emitted to the atmosphere as a by‐product of nitrification and denitrification by soil microbial processes. Differences in climate, soil and management regulate these processes, causingN2Oemissions to vary in space and time. This study aimed to identify and rank the soil properties that controlN2Oemissions in non‐tilled soils under different crops. Over a period of 2 years, gas samples were taken from closed chambers and soil properties were determined once per season.N2Oemission rates were highly variable (from −15 to 314 µgN2O‐N m−2 hour−1). A regression tree analysis allowed us to classify soilN2Oemissions into three groups, separated by topsoil temperature (primary factor) and water‐filled pore space (WFPS, secondary factor).N2Oemissions were small (mean 4.22 µgN2O‐N m−2 hour−1) with topsoil temperature less than 14°C (Group 1), large (mean 61.87 µgN2O‐N m−2 hour−1) with topsoil temperature between 14 and 23°C andWFPSmore than 58.5% (Group 2) and moderate (mean 21.4 µgN2O‐N m−2 hour−1) with topsoil temperature more than 23°C andWFPSless than 58.5% (Group 3). These emission groups allow for more efficient sampling ofN2Oemissions in the field: in winter, when topsoil temperatures are less than 14°C andN2Oemissions are expected to be small or even negligible, sampling frequency can be reduced; in autumn and spring, when topsoil temperatures are more than 14°C andWFPSis more than 60–70%, sampling frequency should be increased.

Impacts of planting systems on soil moisture, soil temperature and corn yield in rainfed area of Northeast China

The effects of different planting systems on soil conditions and crop growth are not well documented in cool high-latitude rainfed regions. Therefore, a field experiment was conducted from 2009 to 2011 to evaluate the impacts of planting systems on soil moisture, soil temperature and corn yield in the center of Northeast China. The experimental design was randomized complete block with three replications. Three planting systems (RP: ridge planting, FRP: flat planting with ridging at early jointing stage, and FP: flat planting without ridging) were tested in this study. Corn yield was significantly higher under FRP than under RP and FP by 302.2 and 552.3kgha−1, respectively, on average across the three experimental years (P<0.05). Significant differences in soil moisture were found in the early stage of the growing season. Soil water storages in 0–40cm depth under FRP and FP were higher than under RP during the period from sowing to seedling stages (VE to V1 stages). Meanwhile, significant differences in topsoil temperatures occurred among planting systems during early growth period. The FRP and FP significantly increased the daily minimum temperature in the soil layer of 5cm on average by 1.2 and 1.1°C compared to RP during the period from VE to V1 stage, despite the fact that the daily maximum temperatures were correspondingly 2.4 and 2.6°C lower, respectively. Compared to FP, RP and FRP could reduce waterlogging by draining extra rainwater through furrows during the later growth period. The above findings indicate that FRP can benefit corn cropping for higher yield through mitigating soil temperature and moisture limitations to corn growth in cool high-latitude rainfed areas.

Brightness Temperature and Soil Moisture Validation at Different Scales During the SMOS Validation Campaign in the Rur and Erft Catchments, Germany

The European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite was launched in November 2009 and delivers now brightness temperature and soil moisture products over terrestrial areas on a regular three-day basis. In 2010, several airborne campaigns were conducted to validate the SMOS products with microwave emission radiometers at L-band (1.4 GHz). In this paper, we present results from measurements performed in the Rur and Erft catchments in May and June 2010. The measurement sites were situated in the very west of Germany close to the borders to Belgium and The Netherlands. We developed an approach to validate spatial and temporal SMOS brightness temperature products. An area-wide brightness temperature reference was generated by using an area-wide modeling of top soil moisture and soil temperature with the WaSiM-ETH model and radiative transfer calculation based on the L-band Microwave Emission of the Biosphere model. Measurements of the airborne L-band sensors EMIRAD and HUT-2D on-board a Skyvan aircraft as well as ground-based mobile measurements performed with the truck mounted JULBARA L-band radiometer were analyzed for calibration of the simulated brightness temperature reference. Radiative transfer parameters were estimated by a data assimilation approach. By this versatile reference data set, it is possible to validate the spaceborne brightness temperature and soil moisture data obtained from SMOS. However, comparisons with SMOS observations for the campaign period indicate severe differences between simulated and observed SMOS data.

Spaceborne radar monitoring of soil freezing/thawing processes in the Arctic tundra

In this article, the possibility of measuring the average temperature in the active topsoil of the Arctic tundra from the temperature dependence of the radar backscattering coefficient is theoretically studied. The radar backscattering coefficient is simulated by the small perturbation method at a frequency of 1.26 GHz of radars placed onboard ALOS-2 and SMAP satellites. In simulation, the soil density, surface roughness, and temperature and moisture profiles measured in situ at the biosphere station Franklin Bluffs, Alaska (69°39′ N, 148°43′ W), from August 1, 2000 to July 1, 2001 were used. The soil permittivity was calculated for the generalized temperature-dependent refractive mixing dielectric model for organic rich soil whose sample was taken on the Alaska North Slope (68°38′N, 149°35′W). This model allows the complex dielectric constant of moist thawed and frozen soil to be calculated at temperatures in the range from –30°С to +25°С. It is demonstrated that the radar backscattering coefficient is correlated with the topsoil temperature with the error less than 5.7°С during the entire period of freezing and thawing.

The manipulation of organic residues affects tree growth and heterotrophic CO2 efflux in a tropical Eucalyptus plantation

Fast-growing plantations are increasingly being established on tropical soils, where fertility is largely supported by soil organic matter (SOM) and where different management options of harvest organic residues is thought to impact the long-term sustainability of these plantations. The objectives of this study were: (1) to quantify the effect of contrasting methods of organic residue management on tree growth and soil CO2 effluxes in the first 2years after planting and (2) to evaluate the impact of organic residue manipulations on the mineralization of soil organic matter over the length of the experiment. Three treatments were setup in 0.125ha plots and replicated in three blocks at the harvesting of a Congolese Eucalyptus stand, resulting in an aboveground organic residue mass ranging from 0 to 6.3kgm−2. The mineralization of SOM was deduced in each treatment by partitioning sources of soil CO2 effluxes using decomposition experiments and by upscaling specific root respiration. Soil CO2 effluxes were greatly affected by seasons and organic residue manipulation, although there were no significant changes in topsoil water content and topsoil temperature over most of the study period. Aboveground organic residue was the first contributor to soil CO2 efflux in the two treatments with a litter layer. Organic residue management did not significantly influence the mineralization of SOM in our study, probably due to the low quality of Eucalyptus litter, or to the hypothetical lack of dissolved organic carbon transfers from litter to soil. A strong relationship was found between cumulative heterotrophic CO2 efflux and tree growth, supporting the hypothesis that the early growth of Eucalyptus trees in a sandy tropical soil is largely dependent on the nutrients released by the decomposition of organic residues.