Effect of vegetation changes on soil erosion on the loess plateau

Vegetation is one of the key factors affecting soil erosion on the Loess Plateau. The effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from long-term field runoff plots established on the eastern slope of the Ziwuling secondary forest region, China and a field survey. The results showed that before the secondary vegetation restoration period （before about 1866-1872）, soil erosion in the Ziwuling region of the Loess Plateau was similar to the current erosion conditions in neighboring regions, where the soil erosion rate now is 8 000 to 10 000 t km^-2 year^-1. After the secondary vegetation restoration, soil erosion was very low; influences of rainfall and slope gradient on soil erosion were small; the vegetation effect on soil erosion was predominant; shallow gully and gully erosion ceased; and sediment deposition occurred in shallow gully and gully channels. In modern times when human activities destroyed secondary forests, soil erosion increased markedly, and erosion rates in the deforested lands reached 10 000 to 24000 t km^-2 year^-1, which was 797 to 1682 times greater than those in the forested land prior to deforestation. Rainfall intensity and landform greatly affected the soil erosion process after deforestation. These results showed that accelerated erosion caused by vegetation destruction played a key role in soil degradation and eco-environmental deterioration in deforested regions.     

A simulation study on effect of surface film-forming material on water evaporation

A greenhouse experiment was conducted to investigate the effect of surface film-forming material (SFFM), a mixture of 16~18-octadecanols by emulsification, on water evaporation. Air-dried soil with distilled water was incubated firstly for 7 days to reestablish soil biological activity and then for another 7 days after treated with SFFM at rates of 0, 1, 2, 4, 6 and 8 g m^-2, respectively. Everyday during the 7-day incubation after addition of SFFM, water losses due to evaporation were measured by an electronic balance. The rate of water evaporation with the addition of SFFM was reduced significantly compared with the control treatment and the effectiveness of SFFM on water evaporation reduced with time. According to the equation expressions of the effect of SFFM on water evaporation, the half-life of effectiveness of SFFM on water evaporation was introduced and calculated to analyze quantitative relationship between the effectiveness of SFFM on water evaporation and the addition rate of SFFM. The calculated half-life increased with the addition rate of SFFM and the confidence of the calculated values of the half-life was high, suggesting that the half-life of effectiveness of SFFM on water evaporation could be described quantitatively and may be helpful for ameliorating application method of SFFM and screening surface-film forming materials in order to improve nitrogen fertilizer use efficiency in flooded rice fields.     

Cultivation‐Induced Effects on the Soil Organomineral Matrix and Their Bearing on Crust Development on Two Soil Formations from Tanzania

Abstract

Land degradation as a result of land‐use practices is a major environmental concern to sustainable agricultural production in Tanzania. The effect of clearing and long‐term cultivation on physical, chemical, and biological characteristics is described in two representative soil formations from eastern Tanzania: Mkindo (Eutric Fluvisol) in the Mvomero district and Mafiga (Ferric Lixisol) in the Morogoro district. The results have shown that in the Mkindo site, 10 years of continuous rice cultivation has led to severe changes in most characteristics of the soil. Significant effects of cultivation coincide with those considered to favor clay dispersion and crusting phenomena, including changes in soil reaction, clay content, and mineralogy as well as generalized desaturation of the exchange complex, increasing sodicity, and severe losses of soil organic matter (SOM). In contrast, at the Mafiga site, 30 years of a less disturbing cultivation system, including periodic fallows, have also modified some soil characteristics but to a lower extent than at Mkindo. Decreased soil colloidal properties at the Mkindo site and lower stability against biological degradation, reflected by carbon (C)–release curves, than the Mafiga site could be causally connected to clay illuviation processes leading to accumulation of calcium (Ca) and magnesium (Mg) but mainly caused by changes in SOM characteristics such as losses of humic (HA) and fulvic acid (FA) and accumulation of humin.     

Study on the Topographic Effect on Soil Erosion Using RUSLE Model for Small Size Watershed

1 IntroductionSoil erosion has been recognized to be a serious environ-mental and soil degradation problem:it can reduce soil pro-ductivity,and it can also increase sedi ment load in receivingwater.The purpose of this researchis to evaluate an availa-bili…     

Humble View on Soil Water Resources

Soil water is one of renewable water resources.Some properties of soil water concerning with its availability to plant are briefly described.An equation for estimating the amount of soil water resource is presented.Based on the evaporation demand of atmosphere,the evaluation coefficient for soil water resource is suggested.     

Broadcast application versus band application of polyolefin‐coated fertilizer on green peppers grown on andisol

Green pepper (Capsicum annuum L.) field experiments were conducted in Northeastern‐Japan in order to evaluate the effects of band and broadcast applications of a polyolefin‐coated fertilizer (POCF) on yield of green pepper grown on Andisol in comparison with conventional, rapidly available fertilizers (RAF). POCF broadcast treatment produced the best yield while POCF band treatment and RAF treatment gave similar results. At the POCF treatments similar or better nutrient uptake was observed than in the RAF treatment resulting similar or better fresh and dry matter productions and consequently similar or higher fruit yield. Thus, by using POCF, labor and energy costs and environmental loading can be reduced without any yield decrease. Among the relatively cold field conditions roots could not reach the POCF band quickly, that caused slower early plant development and eventually lower yield than in comparison with the broadcast application. The very low pH of the soil solutions, having taken from the POCF band throughout the growing period, provided a further possible explanation for the inferiority of band application method. According to these results for green peppers grown on Andisol in Northeastern Japan the broadcast application of POCF is a more effective fertilization method than the band application.     

Study on “Blind—Ear”——Copper Deficiency Symptom in Wheat on Subtropic Hill Soils

The “blind-ear” as a Cu deficiency symptom in wheat on upland soils in the hilly area of Zhejiang Province was discussed in this paper.Through 3 years of field experiments,it was elucidated that “blind-ear” in wheat plant appeared due to the low level of available Cu in the soils,and the critical value 3 mg/kg for total Cu in the plant at grain filling stage and 1 mg/kg for available Cu(0.1 M HCl)in the soils.A basal dressing of 30 kg/ha of Cu sulfate to the soils could completely eliminate Cu deficiency symptoms,obtain normal grain yield and have residual effect for at least 3 years.     

Preliminary investigations on the effects of no‐till corn production methods on specific soil mesofauna populations

Abstract

Moldboard plowing, chisel plowing and no‐till methods were used to produce field corn (Zea mays) in an old grass sod. Grain yields were similar ranging between 13,100 and 14,186 kg/ha. The greatest spread in soil temperatures was only 2.1 C with the plowed soil always being warmest. Mean soil organic matter levels of the surface soil ranged between 1.9 percent on the moldboard plowed plots and 3.3 on the no‐till plots. Ten species of soil Collembola were identified. Collembola and Acarina populations were concentrated in the surface 5 cm of soil and were present in greatest numbers in the No‐Till soil.     

Adsorption of Phosphate on Variable Charge Soils

The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing.     

Influence of Loss‐on‐Ignition Temperature and Heating Time on Ash Content of Compost and Manure

Abstract

Loss‐on‐ignition (LOI) is a simple method for determining ash content, and by reciprocation, organic matter content of compost and manure. However, reported ignition temperatures and heating times for LOI measurements vary widely, and this brings into question the accuracy of one specific combination of ignition temperature and heating time over another. This study examined the effect of 42 temperature‐heating time combinations (six ignition temperatures from 400 to 650°C in 50°C increments by seven heating times of 1, 2, 8, 12, 16, 20, and 24‐h) on the ash content of a finished compost and a fresh manure. The experiment included the 550°C for 2‐h method recommended in Test Methods for Evaluation of Compost and Composting. The magnitude of the decrease in ash content due to increase in temperature was not consistent across all heating times. For example, after a 1‐h heating time for compost, ash content was 75.7% at 400°C and 67.5% at 650°C, compared to 69.6% at 400°C and 66.8% at 650°C after 24‐h. Irrespective of heating time, an ignition temperature of 400°C overestimated ash content for both compost and manure compared to the TMECC method. The TMECC method with its moderate temperature and short heating time requirement could reduce energy costs without affecting ash content results.     

Dicyandiamide sorption-desorption behavoir on soils and peat humus

The sorption-desorption behavior of dicyandiamide (DCD) is an important chemical process that affects DCD fate and mobility in soils. Therefore, this study quantified DCD sorption-desorption on a phaeozem (Mollisol), a burozem (Alfisol), a soil with organic matter-removed and peat humus using the batch-equilibration procedure, and identified soil properties that influenced DCD sorption. The sorption on peat humus was higher than that on the phaeozem and the burozem, with much lower sorption observed on the soil with organic matter-removed, indicating that soil organic matter was the main carrier of DCD sorption. Due to its amphipathic property the DCD molecule sorption on the phaeozem and the burozem decreased as pH increased from about 2 to 5, but a further increase in pH led to a rise in DCD sorption.The DCD desorption hysteretic effect for peat humus was greater than that for the phaeozem and the burozem using 0.01 mol L^-1 CaCl2 as the background electrolyte, suggesting that the hydrophobic domains of organic matter may play an important role in DCD sorption.     

Salinity effects on nitrogen metabolism in plants – focusing on the activities of nitrogen metabolizing enzymes: A review

Nitrogen (N) metabolism is of great economic importance because it provides proteins and nucleic acids which in turn control many cellular activities in plants. Salinity affects different steps of N metabolism including N uptake, NO₃^? reduction, and NH₄⁺ assimilation, leading to a severe decline in crop yield. Major mechanisms of salinity effects on N metabolism are salinity-induced reductions in water availability and absorption, disruption of root membrane integrity, an inhibition of NO₃^? uptake by Cl^?, low NO₃^? loading into root xylem, alteration in the activities of N assimilating enzymes, decrease in transpiration, and reduction in relative growth rate which results in a lower N demand. However, the effects of salinity on N metabolism are multifaceted and may vary depending on many plant and soil factors. The present review deals with salinity effects on N metabolism in plants, emphasizing on the activities of N metabolizing enzymes in a saline environment.     

Effects of permafrost thawing on vegetation and soil carbon pool losses on the Qinghai–Tibet Plateau,China

Bearing a total organic carbon (TOC) content of 9.3–10.7 kg C/m², alpine grassland soils of the Qinghai–Tibet plateau's permafrost region bear a greater organic carbon pool than do grassland soils in other regions of China or than tropical savannah soils. The easily released light fraction organic carbon (LFOC) accounts for 34–54% of the TOC and is particularly enriched in the topsoil (0–0.10 m). The LFOC in the organic carbon pool of alpine cold meadow and alpine cold steppe soils decreased at exponential and quadratic rates, respectively, as the vegetative cover decreased. When the vegetative cover of alpine cold meadows decreased from > 80 dm²/m² to 60 dm²/m², the topsoil TOC and LFOC dropped by 20.4% and 38.4%, respectively. Similarly, when the vegetative cover of alpine cold meadow decreased from 50 dm²/m² to 30 dm²/m² and < 15 dm²/m², the topsoil LFOC content dropped by 60% and 86.7%, respectively. Under climatic warming, the degradation of permafrost and vegetation have resulted in serious soil organic carbon (SOC) loss from the carbon pool. Land cover changes that occurred between 1986 and 2000 are estimated to have resulted in a 1.8 Gg C (120 Mg C/yr) loss in SOC, and a concomitant 65% decrease in the LFOC, in the 0–0.30 m soil layer in the Qinghai–Tibet plateau's permafrost regions. Since the region's ecosystems are quite sensitive to global climate changes, if global warming persists, alpine cold grassland ecosystems are expected to further degrade. Hence, the influence of global climatic change on soil carbon emissions from alpine grasslands should receive more attention.     

Discussion on the Landscape Pattern Change of Watershed

1 IntroductionLandscape Patternis fundamental to many relationshipsthat we seek to understand.It is i mportant to be familiarwith the metrics that are used and more i mportantly,to un-derstand the factors whichinfluence the interpretation of anylandscape …     

Quantifying the influence of thermal process parameters on in vitro β-carotene bioaccessibility: a case study on carrots

This study describes a detailed and systematic investigation on the effect of thermal processing in terms of temperature and time (kinetic study) on β-carotene in vitro bioaccessibility in carrots. β-Carotene in vitro bioaccessibility increased with increasing processing temperature and time until steady-state conditions were reached after prolonged heating. The bioaccessibility values in steady-state conditions were temperature dependent. The experimental bioaccessibility data could adequately be modeled with a fractional conversion model. For the first time, modeling of processing-induced bioaccessibility changes is reported in literature. The results of the present kinetic study were used to estimate the impact of industrially relevant thermal processes on β-carotene bioaccessibility in carrots by simulation. It was shown that, to achieve a high β-carotene bioaccessibility, processing of carrots is essential (i.e., on the one hand, intense thermal processing or, on the other hand, mild thermal processing combined with intense mechanical processing).     

Effect of fused magnesium phosphate on paddy grown on “akiochi” soil with particular reference to phosphorus and silicon

In order to increase the p:tady prodution of our country, a better fertilizer practice is needed Particularly in the low productive areas known as “akiochi” fields which are now said to occupy about one fifth of the whole paddy areas in Japan.     

A comment on “a note on estimating the mean level of photosynthesis from radiation measurements” by Chris Koen

Koen (1987) derived several approximate formulae for the calculation of mean photosynthesis from radiation measurements. We present a critical review of his equations and suggest that most of his equations provide logically inconsistent estimates. We claim also that his exact algebraic equation is based on a misconception of the real estimation problems.     

Heavy metal accumulation in plants on Mn Mine tailings

The profile distribution of β-gulcosidase activity in twelve typical paddy soil profiles with high productivity in the Taihu Lake region of China were investigated. Activities of β-gulcosidase in the plow layers were in the range of 52.68- 137.02μg PNP g^-1 soil h^-1 with a mean of 89.22μg PNP g^-1 soil h^-1. However, most plow layers ranged from 70 to 110 μg PNP g^-1 soil h^-1. The profile distribution of β-gulcosidase activity in the 12 soil profiles decreased rapidly with soil depth, with activity at the 60 cm depth only about 10% of that in the surface layers （0-15 cm or 0-20 cm）. In these soil profiles, β-gulcosidase activity was significantly positively correlated with soll organic carbon and arylsulphatase activity. Meanwhile, a significantly negative correlation was shown between β-gulcosidase activity and soil pH.     

Which impact for beta-damascenone on red wines aroma?

beta-Damascenone, a C-13 norisoprenoid compound, is usually presented as an impact odorant in red wines. Its direct contribution to their aroma was investigated. Both free beta-damascenone and beta-damascenone precursors were isolated from various French red wines and then analyzed by gas chromatography-mass spectrometry, revealing concentrations in the vicinity of 1 and 2 microg/L for free compounds and both forms, respectively. Gas chromatography-olfactometry analyses were also performed on dilutions of both red wine extracts and pure beta-damascenone. The very low detection threshold in olfactometry for this compound explains why it is found at the highest dilution factor in aroma extract dilution analysis methods. Moreover, determination of beta-damascenone's odor thresholds confirmed the huge importance of the matrix: beta-Damascenone is characterized by a very low perception threshold in hydroalcoholic solution as compared to red wine, where it is over 1000-fold higher. In hydroalcoholic solution, beta-damascenone enhanced fruity notes of ethyl cinnamate and caproate and masked the herbaceous aroma of IBMP. Globally, these results suggested that beta-damascenone has more an indirect than a direct impact on red wine aroma.     

The impact of vegetation and soil on runoff regulation in headwater streams on the east Qinghai–Tibet Plateau,China

Vegetation type is one of many factors that affect watershed hydrology and is an especially important influence on surface hydrological processes. Canopy and ground cover vegetation provide a natural cushion against the impact energy of rainfall in headwater portions of a stream basin, increasing water filtration into the soil and reducing surface runoff, but effects of different vegetation types are not fully understood. We sought to evaluate the capacity of different vegetation communities to regulate surface runoff in an alpine landscape. We collected water samples for stable hydrogen and oxygen isotopic analyses from precipitation, throughfall, soils, streams, and rivers and compared their isotopic signatures. Results indicated that different vegetation types had different capacities for water conservation. Forested vegetation types were best able to regulate surface runoff. Land use changes have dramatically affected water conservation in the study area in the past several decades; if forested land cover existed at the levels present in 1986 or 1974, the ability of the watershed to intercept surface runoff would increase by about 7% and 3%, respectively, over its capacity in 2000.