Effects of grazing on grassland soil carbon: a global review

Soils of grasslands represent a large potential reservoir for storing CO₂, but this potential likely depends on how grasslands are managed for large mammal grazing. Previous studies found both strong positive and negative grazing effects on soil organic carbon (SOC) but explanations for this variation are poorly developed. Expanding on previous reviews, we performed a multifactorial meta‐analysis of grazer effects on SOC density on 47 independent experimental contrasts from 17 studies. We explicitly tested hypotheses that grazer effects would shift from negative to positive with decreasing precipitation, increasing fineness of soil texture, transition from dominant grass species with C₃ to C₄ photosynthesis, and decreasing grazing intensity, after controlling for study duration and sampling depth. The six variables of soil texture, precipitation, grass type, grazing intensity, study duration, and sampling depth explained 85% of a large variation (±150 g m^?2 yr^?1) in grazing effects, and the best model included significant interactions between precipitation and soil texture (P = 0.002), grass type, and grazing intensity (P = 0.012), and study duration and soil sampling depth (P = 0.020). Specifically, an increase in mean annual precipitation of 600 mm resulted in a 24% decrease in grazer effect size on finer textured soils, while on sandy soils the same increase in precipitation produced a 22% increase in grazer effect on SOC. Increasing grazing intensity increased SOC by 6–7% on C₄‐dominated and C₄–C₃ mixed grasslands, but decreased SOC by an average 18% in C₃‐dominated grasslands. We discovered these patterns despite a lack of studies in natural, wildlife‐dominated ecosystems, and tropical grasslands. Our results, which suggest a future focus on why C₃ vs. C₄‐dominated grasslands differ so strongly in their response of SOC to grazing, show that grazer effects on SOC are highly context‐specific and imply that grazers in different regions might be managed differently to help mitigate greenhouse gas emissions.     

Soil nitrous oxide emissions following crop residue addition: a meta‐analysis

Annual production of crop residues has reached nearly 4 billion metric tons globally. Retention of this large amount of residues on agricultural land can be beneficial to soil C sequestration. Such potential impacts, however, may be offset if residue retention substantially increases soil emissions of N₂O, a potent greenhouse gas and ozone depletion substance. Residue effects on soil N₂O emissions have gained considerable attention since early 1990s; yet, it is still a great challenge to predict the magnitude and direction of soil N₂O emissions following residue amendment. Here, we used a meta‐analysis to assess residue impacts on soil N₂O emissions in relation to soil and residue attributes, i.e., soil pH, soil texture, soil water content, residue C and N input, and residue C : N ratio. Residue effects were negatively associated with C : N ratios, but generally residue amendment could not reduce soil N₂O emissions, even for C : N ratios well above ca. 30, the threshold for net N immobilization. Residue effects were also comparable to, if not greater than, those of synthetic N fertilizers. In addition, residue effects on soil N₂O emissions were positively related to the amounts of residue C input as well as residue effects on soil CO₂ respiration. Furthermore, most significant and stimulatory effects occurred at 60–90% soil water‐filled pore space and soil pH 7.1–7.8. Stimulatory effects were also present for all soil textures except sand or clay content ≤10%. However, inhibitory effects were found for soils with >90% water‐filled pore space. Altogether, our meta‐analysis suggests that crop residues played roles beyond N supply for N₂O production. Perhaps, by stimulating microbial respiration, crop residues enhanced oxygen depletion and therefore promoted anaerobic conditions for denitrification and N₂O production. Our meta‐analysis highlights the necessity to connect the quantity and quality of crop residues with soil properties for predicting soil N₂O emissions.     

Detection of Architectural Distortion in Prior Mammograms via Analysis of Oriented Patterns

We demonstrate methods for the detection of architectural distortion in prior mammograms of interval-cancer cases based on analysis of the orientation of breast tissue patterns in mammograms. We hypothesize that architectural distortion modifies the normal orientation of breast tissue patterns in mammographic images before the formation of masses or tumors. In the initial steps of our methods, the oriented structures in a given mammogram are analyzed using Gabor filters and phase portraits to detect node-like sites of radiating or intersecting tissue patterns. Each detected site is then characterized using the node value, fractal dimension, and a measure of angular dispersion specifically designed to represent spiculating patterns associated with architectural distortion.Our methods were tested with a database of 106 prior mammograms of 56 interval-cancer cases and 52 mammograms of 13 normal cases using the features developed for the characterization of architectural distortion, pattern classification via quadratic discriminant analysis, and validation with the leave-one-patient out procedure. According to the results of free-response receiver operating characteristic analysis, our methods have demonstrated the capability to detect architectural distortion in prior mammograms, taken 15 months (on the average) before clinical diagnosis of breast cancer, with a sensitivity of 80% at about five false positives per patient.     

Field-based video observations of wild barnacle cyprid behaviour in response to textural and chemical settlement cues

Many marine invertebrate larvae respond behaviourally to environmental settlement cues, yet behaviours are often only inferred from settlement patterns or are limited to laboratory studies. The behaviour of wild cypris larvae of Semibalanus balanoides L. was filmed on settlement tiles in the field. Tiles were of five different textures with a nested treatment of crude conspecific adult extract (AE). The effects of texture and AE on eleven defined behaviours were analysed. Texture affected the gross and net exploratory distances, velocity, acceleration and time spent exploring. AE attracted more cyprids during the first minute of immersion and increased the time spent on surfaces. Relatively few arrivals that either travel far and fast, or exit the surface rapidly, may indicate a lower chance of settlement. An increase in time spent on a surface may increase the probability of being in contact with the surface when the sign stimulus to settle occurs.     

Texture formation in DNA films with alkali metal chlorides

The formation of textures in DNA films with LiCl, NaCl, KCl, RbCl, and CsCl salts has been studied. The films are prepared by evaporation of water solution with highly polymerized calf thymus DNA and excess salt of specific type. For DNA solution with 10 mM concentration of NaCl, KCl, and RbCl the films with dendritic textures have been obtained, whereas in case of CsCl the textures in the films appear only at 30 mM concentration of excess salt in the initial solution. In the solution with LiCl, the textures in DNA films have not been observed within the whole range of concentration of excess salt under consideration. The analysis of parameters of DNA films with different salts has showed that evaporation of solution leads to crystallization of salt ions on DNA macromolecule and formation of DNA‐salt complexes. Electrostatic energy of the system of crystalline ordered ions and charges of DNA chains has been estimated to study the stability of DNA‐salt complexes. The results obtained for different salts have been showed that the presence of DNA macromolecule enhances crystallization as compared with solution without DNA. The property of excess salt to form the crystalline structures has been found to decrease in the following order: KCl > NaCl > RbCl > CsCl > LiCl. The results of estimation are in good agreement with the experimentally observed dependence of texture formation on excess salt type. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 508–516, 2013.     

黄土丘陵区生物结皮对土壤可蚀性的影响

在采样分析生物结皮对土壤理化属性影响的基础上,采用EPIC模型估算与模拟降雨试验相结合的方法,研究了黄土丘陵区不同生物量、不同土壤质地和不同季节的生物结皮对土壤可蚀性(K值)的影响.结果表明： 生物结皮显著降低了土壤可蚀性,生物结皮层土壤可蚀性较下层土壤降低17%;土壤可蚀性随生物结皮生物量的增加呈降低趋势,藓结皮土壤可蚀性K值较藻结皮土壤降低21%;生物结皮土壤可蚀性在不同季节因其生物活性不同而存在差异,雨季中显著高于雨季前和雨季末;不同质地土壤上生物结皮对可蚀性的影响不同,可蚀性K值为砂壤>粉壤>砂土;模拟降雨条件下测定表明,生物结皮的发育使土壤可蚀性较对照（下层5~10 cm土壤）降低约90%.
     

Texture of Cooked Rice Prepared from Aged Rice and Its Improvement by Reducing Agents

The textures of cooked rice prepared from aged rice grains and their improvement by reducing agents were investigated. For aged rice that was stored for 5 months without air by the operation of a vacuum packing machine, the stickiness/hardness ratio of cooked rice was as low as that of aged rice stored in air. The results of electrophoresis showed that oxidation of proteins in the former was advanced to the same degree as in the latter. The stickiness/hardness ratios of the aged rice were increased by the addition of sodium sulfite, cysteine, and dithiothreitol to the cooking water. Sodium sulfite, cysteine, and dithiothreitol cleave disulfide bonds to sulfhydryl groups. Therefore, cleaving disulfide bonds to sulfhydryl groups improved the texture. The addition of them to the cooking water also increased the extractable solids at the time of heating. Hence cleaving disulfide bonds to sulfhydryl groups must increase extractable solids. Consequently, the gelatinized paste layer thickened and the thick paste layer softened the cooked rice.     

四倍体异育银鲫新品种长丰鲫肌肉品质和营养成分分析

研究对长丰鲫、彭泽鲫、异育银鲫D系以及红鲫的肌肉品质和营养成分进行了对比分析。结果显示:肌纤维密度方面, 单位面积肌纤维密度长丰鲫最高[(184.2624.11) fiber/mm2], 其次为彭泽鲫[(149.7212.51)fiber/mm2]、异育银鲫D系[(134.4515.96) fiber/mm2]和红鲫[(119.8522.86) fiber/mm2]。粗蛋白含量、总氨基酸和呈味氨基酸方面, 长丰鲫、彭泽鲫和异育银鲫D系无明显区别。高度不饱和脂肪酸中(n3), 长丰鲫含量最高(24.2%), 依次为彭泽鲫(14.4%), 异育银鲫(11.3%)和红鲫(8.3%)。在高度不饱和脂肪酸中, 二十二碳六烯酸(DHA)长丰鲫含量最高(10.3%), 依次为红鲫(4.9%)、彭泽鲫(4.5%)和银鲫(2.9%); 花生四烯酸(AA)长丰鲫含量最高(8.3%), 依次为彭泽鲫(5.1%)、银鲫(3.8%)和红鲫(0.6%)。结果表明, 长丰鲫新品种在所检测的肌肉品质和营养成分指标方面, 优于彭泽鲫、异育银鲫D系和红鲫。