Background: Soil organic carbon(SOC) is a large reservoir of terrestrial carbon(C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help...Background: Soil organic carbon(SOC) is a large reservoir of terrestrial carbon(C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help better predict the trend of changes in SOC dynamics under climate change. Information on how physical fractions and chemical structures of SOC are related to climate and vegetation types is essential for spatial model ing of SOC processes and responses to global change factors.Method: Soil samples were col ected from multiple representative forest sites of three contrasting climatic zones(i.e. cool temperate, warm temperate, and subtropical) in eastern China. Measurements were made on SOC contents and physical fractions of the 0–20 cm soil layer, and the chemical composition of SOC of the 0–5 cm soil layer, along with measurements and compilation of the basic site and forest stand variables. The long-term effects of temperature, litter inputs, soil characteristics and vegetation type on the SOC contents and factions were examined by means of "space for time substitution" approach and statistical analysis.Result: Mean annual temperature(MAT) varied from 2.1 °C at the cool temperate sites to 20.8 °C at the subtropical sites. Total SOC of the 0–20 cm soil layer decreased with increasing MAT, ranging from 89.2 g·kg^(-1) in cool temperate forests to 57.7 g·kg^(-1) in subtropical forests, at an average rate of 1.87% reduction in SOC with a 1 °C increase in MAT.With increasing MAT, the proportions of aromatic C and phenolic C displayed a tendency of decreases, whereas the proportion of alkyl C and A/O-A value(the ratio of alkyl C to the sum of O-alkyl C and acetal C) displayed a tendency of increases. Overall, there were no significant changes with MAT and forest type in either the physical fractions or the chemical composition. Based on the relationship between the SOC content and MAT, we estimate that SOC in the top 20 soil layer of forests potentially contribute 6.58–26.3 Pg C globally to the atmosphere if global MAT increases by 1 °C–4 °C by the end of the twenty-first century, with nearly half of which(cf. 2.87–11.5 Pg C) occurring in the 0–5 cm mineral soils.Conclusion: Forest topsoil SOC content decreased and became chemical y more recalcitrant with increasing MAT,without apparent changes in the physical fractions of SOC.展开更多
Low carbohydrate diet(LCD)and nutrition is a very popular topic in the nutritional scientific literature.Main reason is that it is an old established therapy in intractable epilepsy and there are plenty of positive pr...Low carbohydrate diet(LCD)and nutrition is a very popular topic in the nutritional scientific literature.Main reason is that it is an old established therapy in intractable epilepsy and there are plenty of positive preclinical and sporadic clinical results in other disorders,including certain cancers.The problem is that a)the metabolic background of this therapy is not elucidated enough,b)animal studies and human experiences are sometimes divergent,c)there are negative human results and d)the clinical studies are not comparable because of the wide variety of study design and conclusion regarding the indication,the composition of diet and duration of treatment can not be drawn.This publication reviews the current situation and gives some hints to the solution.展开更多
KEY POINTS Because so much of the running in soccer is at less than maximal sprinting speed, creatine supplementation likely provides no benefit to match performance.Overwhelming evidence proves that a diet rich in ca...KEY POINTS Because so much of the running in soccer is at less than maximal sprinting speed, creatine supplementation likely provides no benefit to match performance.Overwhelming evidence proves that a diet rich in carbohydrates can fill muscles with glycogen, and glycogen is critical to optimal performance in soccer. Soccer players’ diets, especially in the days before hard training or competition, should include 8-10 grams of carbohydrate per kilogram of body weight (3.5-4.5 g/lb). Cereals, fruits, vegetables, breads, and pastas are good sources ofcarbohydrates. Refueling of muscle with carbohydrates should begin as soon as possible following a match or a strenuous training session. Inadequate replacement of fluids lost in sweat can lead to poor soccer performance and heat illness. Players should aim to drink enough during training sessions and matches so that their body weights after play are within about 1 kg (2.2 lb) of their starting weights. For a light workout or an easy match, especially when the weather is cool, water can be an adequate fluid replacement, if enough is ingested. But when play is strenuous and the weather is hot, carbohydrate-electrolyte sports drinks do a better job of maintaining body fluids.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.31470623)the National Basic Research Program of China(Grant No.2011CB403205)
文摘Background: Soil organic carbon(SOC) is a large reservoir of terrestrial carbon(C); it consists of different fractions of varying complexity and stability. Partitioning SOC into different pools of decomposability help better predict the trend of changes in SOC dynamics under climate change. Information on how physical fractions and chemical structures of SOC are related to climate and vegetation types is essential for spatial model ing of SOC processes and responses to global change factors.Method: Soil samples were col ected from multiple representative forest sites of three contrasting climatic zones(i.e. cool temperate, warm temperate, and subtropical) in eastern China. Measurements were made on SOC contents and physical fractions of the 0–20 cm soil layer, and the chemical composition of SOC of the 0–5 cm soil layer, along with measurements and compilation of the basic site and forest stand variables. The long-term effects of temperature, litter inputs, soil characteristics and vegetation type on the SOC contents and factions were examined by means of "space for time substitution" approach and statistical analysis.Result: Mean annual temperature(MAT) varied from 2.1 °C at the cool temperate sites to 20.8 °C at the subtropical sites. Total SOC of the 0–20 cm soil layer decreased with increasing MAT, ranging from 89.2 g·kg^(-1) in cool temperate forests to 57.7 g·kg^(-1) in subtropical forests, at an average rate of 1.87% reduction in SOC with a 1 °C increase in MAT.With increasing MAT, the proportions of aromatic C and phenolic C displayed a tendency of decreases, whereas the proportion of alkyl C and A/O-A value(the ratio of alkyl C to the sum of O-alkyl C and acetal C) displayed a tendency of increases. Overall, there were no significant changes with MAT and forest type in either the physical fractions or the chemical composition. Based on the relationship between the SOC content and MAT, we estimate that SOC in the top 20 soil layer of forests potentially contribute 6.58–26.3 Pg C globally to the atmosphere if global MAT increases by 1 °C–4 °C by the end of the twenty-first century, with nearly half of which(cf. 2.87–11.5 Pg C) occurring in the 0–5 cm mineral soils.Conclusion: Forest topsoil SOC content decreased and became chemical y more recalcitrant with increasing MAT,without apparent changes in the physical fractions of SOC.
文摘Low carbohydrate diet(LCD)and nutrition is a very popular topic in the nutritional scientific literature.Main reason is that it is an old established therapy in intractable epilepsy and there are plenty of positive preclinical and sporadic clinical results in other disorders,including certain cancers.The problem is that a)the metabolic background of this therapy is not elucidated enough,b)animal studies and human experiences are sometimes divergent,c)there are negative human results and d)the clinical studies are not comparable because of the wide variety of study design and conclusion regarding the indication,the composition of diet and duration of treatment can not be drawn.This publication reviews the current situation and gives some hints to the solution.
文摘KEY POINTS Because so much of the running in soccer is at less than maximal sprinting speed, creatine supplementation likely provides no benefit to match performance.Overwhelming evidence proves that a diet rich in carbohydrates can fill muscles with glycogen, and glycogen is critical to optimal performance in soccer. Soccer players’ diets, especially in the days before hard training or competition, should include 8-10 grams of carbohydrate per kilogram of body weight (3.5-4.5 g/lb). Cereals, fruits, vegetables, breads, and pastas are good sources ofcarbohydrates. Refueling of muscle with carbohydrates should begin as soon as possible following a match or a strenuous training session. Inadequate replacement of fluids lost in sweat can lead to poor soccer performance and heat illness. Players should aim to drink enough during training sessions and matches so that their body weights after play are within about 1 kg (2.2 lb) of their starting weights. For a light workout or an easy match, especially when the weather is cool, water can be an adequate fluid replacement, if enough is ingested. But when play is strenuous and the weather is hot, carbohydrate-electrolyte sports drinks do a better job of maintaining body fluids.
