The drive to develop renewable energy is increasing the interest in energy forestry. Woody biomass from forest residues has the potential to make a significant contribution to greenhouse gas emission reduction through...The drive to develop renewable energy is increasing the interest in energy forestry. Woody biomass from forest residues has the potential to make a significant contribution to greenhouse gas emission reduction through fossil fuel substitution. However, there is a danger of operational practice running ahead of the understanding of the environmental impacts of such activities. Consequently, there is an urgent requirement for scientifically underpinned guidance on the best management practices to ensure soil and water protection, including sustaining forestry’s key role in carbon capture. This study addresses the main issues associated with stump harvesting practices and their impacts on soil carbon and nutrient capital and effects on the second rotation tree growth. It reports results from a clearfell site in the UK where experimental stump harvesting was carried out in 2005 before replanting with Sitka spruce Picea sitchensis (Bon.)Carr. Both stump harvested and conventional harvested areas (Control) were studied in 2009 and 2010, five years after harvesting, on the two distinct soil types at the site: podzolised brown earth and peaty gley soils. Results show impacts of stump harvesting on soil carbon and nitrogen stocks, residual water, base cations (K+, Ca2+ and Mg2+) concentrations and stocks and bulk density in both soil types. The organic peaty gley soil showed larger and deeper profile changes after stump harvesting compared with the podzolised brown mineral soil, where some of the negative changes in C, N and base cations in the top soil were compensated by increases at depth. Tree assessment showed positive effect of stump harvesting on K and Ca uptake by young seedlings, but N and P nutrient status was reduced on the peaty gley soils. The overall results support the current UK forestry guidance for stump harvesting which identifies that soil type is the most important site factor determining the sustainability of the practice.展开更多
以非生长季和生长季大盘山榧(Torreya dapanshanica X.F.Jin,Y.F.Lu et Zi L.Chen)幼龄树、中龄树为研究对象,分析大盘山榧不同器官、根际土壤中碳(C)、氮(N)、磷(P)含量,根际土壤酶活性及其化学计量比和养分限制特征。结果表明:总体上...以非生长季和生长季大盘山榧(Torreya dapanshanica X.F.Jin,Y.F.Lu et Zi L.Chen)幼龄树、中龄树为研究对象,分析大盘山榧不同器官、根际土壤中碳(C)、氮(N)、磷(P)含量,根际土壤酶活性及其化学计量比和养分限制特征。结果表明:总体上看,在非生长季和生长季,大盘山榧幼龄树叶片的C、N、P含量以及中龄树叶片的P含量显著(P<0.05)高于根和茎,幼龄树根的C/N比和中龄树根的N/P比显著高于茎和叶片;叶片的C、N含量,茎的P含量和C/P比以及根的N/P比在不同树龄间存在显著差异;大盘山榧中龄树根际土壤的含水量,C、N、P、硝态氮含量,N/P比以及亮氨酸氨基肽酶、酸性磷酸酶、β-1,4-N-乙酰氨基葡萄糖苷酶和β-1,4-葡萄糖苷酶活性显著或极显著(P<0.01)高于幼龄树。在非生长季,大盘山榧幼龄树和中龄树根际土壤微生物均受到P的限制,而在生长季基本受到C和P的共同限制。冗余分析结果表明:在非生长季和生长季,大盘山榧幼龄树植株各器官C、N、P含量及其化学计量比主要受根际土壤铵态氮含量的影响;在非生长季,中龄树各器官C、N、P含量及其化学计量比主要受根际土壤亮氨酸氨基肽酶活性和N/P比的影响;在生长季,中龄树各器官C、N、P含量及其化学计量比主要受根际土壤β-1,4-葡萄糖苷酶和β-1,4-N-乙酰氨基葡萄糖苷酶活性以及酶化学计量碳氮比的影响。综上,大盘山榧幼龄树应增施N肥,分次勤施有机肥和追施P肥;中龄树以追施P肥为主,配施N肥和补施有机肥,从而缓解大盘山榧的养分限制,促进大盘山榧的健康生长并实现可持续经营。展开更多
Nutrient resorption before abscission is an important nutrient conservation mechanism regulated by climatic conditions and soil nutrients. However, our current understanding of leaf nutrient resorption is primarily de...Nutrient resorption before abscission is an important nutrient conservation mechanism regulated by climatic conditions and soil nutrients. However, our current understanding of leaf nutrient resorption is primarily derived from site-specific studies or from the use of greenleaf nutrient concentrations to represent those in soils. It remains unknown how nutrient resorption responds to natural soil-nutrient concentrations at a global scale. The effects of plant functional groups, climatic conditions, and soil nutrients and their interactions on leaf nutrient resorption are also unknown. In this study, we established a global database derived from 85 published papers, including 547 reports of nitrogen and phosphorus resorption efficiency （NRE and PRE）, climatic factors （LAT, latitude; MAT, mean annual temperature; MAP, mean annual precipitation） and soil-nutrient data （STN, soil total nitrogen; STP, soil total phosphorus） across 111 research sites. The results demonstrated that mean NRE and PRE were 48.4 and 53.3%, respectively. NRE of trees was lower than those of shrubs. NRE and PRE of coniferous species were both higher than those of broad-leaved species. Evergreen species had higher PRE than did deciduous species. NRE was negatively related to STN, but PRE and STP were not related. Both NRE and PRE decreased with increasing MAT and MAP but increased with increasing LAT. Plant functional groups, climate and soil nutrients jointly explained 22 and 32% of the variations in NRE and PRE, respectively. It is important to note that climate （especially MAT） explained 12 and 29% of the variations in NRE and PRE, respectively, implying that continuing global warming will exert an increasingly profound influence on plant nutrient cycles.展开更多
Purpose: The purpose of this study was to examine the association between almond consumption, the most widely consumed tree nut in the US, and nutrient intake, nutrient adequacy, diet quality, and weight/adiposity in ...Purpose: The purpose of this study was to examine the association between almond consumption, the most widely consumed tree nut in the US, and nutrient intake, nutrient adequacy, diet quality, and weight/adiposity in adults. Methods: Data from adults (N=24,808), 19+ years, participating in the NHANES 2001-2010 were used. The NCI method was used to estimate the usual intake of almonds and selected nutrients. Almond consumers were defined as those consuming any amount of almonds/almond butter. Percentages of the consumers/non-consumers below the Estimated Average Requirement (EAR) or above the Adequate Intake (AI) for select nutrients were determined. To assess significant differences for the percentage of almond consumers vs. non-consumers with intakes less than the EAR or above the AI, a Z-statistic for differences in population proportions was used. Covariate-controlled linear regression was used to determine differences in diet quality, measured by the Healthy Eating Index-2010 (HEI-2010), between the consumer groups. Body mass indices and waist circumference were assessed. P was set at p < 0.01. Results: Almond consumers were more likely to be non-Hispanic white, older, of higher income, more physically active, and were less likely to be a current smoker than non-consumers. Usual intake of almonds among consumers was 29.5 ± 1.5 g/day. Usual intake of protein;dietary fiber;vitamins A, D, E, and C;thiamin;niacin;riboflavin;folate, calcium, copper, magnesium, iron, phosphorus, selenium, zinc, and potassium was higher in almond consumers. Almond consumers were less likely to be below the EAR for protein, vitamins A, D, E, B12, and C;riboflavin;calcium;copper;magnesium;iron;phosphorus;and zinc. They were also more likely to be above the AI for dietary fiber and potassium. Total HEI-2010 scores were approximately 15 points higher in almond consumers. Body mass indices and waist circumference measures were lower in almond consumers. Conclusions: Moderate consumption of almonds should be encouraged as part of a healthy diet.展开更多
文摘The drive to develop renewable energy is increasing the interest in energy forestry. Woody biomass from forest residues has the potential to make a significant contribution to greenhouse gas emission reduction through fossil fuel substitution. However, there is a danger of operational practice running ahead of the understanding of the environmental impacts of such activities. Consequently, there is an urgent requirement for scientifically underpinned guidance on the best management practices to ensure soil and water protection, including sustaining forestry’s key role in carbon capture. This study addresses the main issues associated with stump harvesting practices and their impacts on soil carbon and nutrient capital and effects on the second rotation tree growth. It reports results from a clearfell site in the UK where experimental stump harvesting was carried out in 2005 before replanting with Sitka spruce Picea sitchensis (Bon.)Carr. Both stump harvested and conventional harvested areas (Control) were studied in 2009 and 2010, five years after harvesting, on the two distinct soil types at the site: podzolised brown earth and peaty gley soils. Results show impacts of stump harvesting on soil carbon and nitrogen stocks, residual water, base cations (K+, Ca2+ and Mg2+) concentrations and stocks and bulk density in both soil types. The organic peaty gley soil showed larger and deeper profile changes after stump harvesting compared with the podzolised brown mineral soil, where some of the negative changes in C, N and base cations in the top soil were compensated by increases at depth. Tree assessment showed positive effect of stump harvesting on K and Ca uptake by young seedlings, but N and P nutrient status was reduced on the peaty gley soils. The overall results support the current UK forestry guidance for stump harvesting which identifies that soil type is the most important site factor determining the sustainability of the practice.
文摘以非生长季和生长季大盘山榧(Torreya dapanshanica X.F.Jin,Y.F.Lu et Zi L.Chen)幼龄树、中龄树为研究对象,分析大盘山榧不同器官、根际土壤中碳(C)、氮(N)、磷(P)含量,根际土壤酶活性及其化学计量比和养分限制特征。结果表明:总体上看,在非生长季和生长季,大盘山榧幼龄树叶片的C、N、P含量以及中龄树叶片的P含量显著(P<0.05)高于根和茎,幼龄树根的C/N比和中龄树根的N/P比显著高于茎和叶片;叶片的C、N含量,茎的P含量和C/P比以及根的N/P比在不同树龄间存在显著差异;大盘山榧中龄树根际土壤的含水量,C、N、P、硝态氮含量,N/P比以及亮氨酸氨基肽酶、酸性磷酸酶、β-1,4-N-乙酰氨基葡萄糖苷酶和β-1,4-葡萄糖苷酶活性显著或极显著(P<0.01)高于幼龄树。在非生长季,大盘山榧幼龄树和中龄树根际土壤微生物均受到P的限制,而在生长季基本受到C和P的共同限制。冗余分析结果表明:在非生长季和生长季,大盘山榧幼龄树植株各器官C、N、P含量及其化学计量比主要受根际土壤铵态氮含量的影响;在非生长季,中龄树各器官C、N、P含量及其化学计量比主要受根际土壤亮氨酸氨基肽酶活性和N/P比的影响;在生长季,中龄树各器官C、N、P含量及其化学计量比主要受根际土壤β-1,4-葡萄糖苷酶和β-1,4-N-乙酰氨基葡萄糖苷酶活性以及酶化学计量碳氮比的影响。综上,大盘山榧幼龄树应增施N肥,分次勤施有机肥和追施P肥;中龄树以追施P肥为主,配施N肥和补施有机肥,从而缓解大盘山榧的养分限制,促进大盘山榧的健康生长并实现可持续经营。
基金funded by the National Basic Research Program of China(973 Program)(2012CB416906)
文摘Nutrient resorption before abscission is an important nutrient conservation mechanism regulated by climatic conditions and soil nutrients. However, our current understanding of leaf nutrient resorption is primarily derived from site-specific studies or from the use of greenleaf nutrient concentrations to represent those in soils. It remains unknown how nutrient resorption responds to natural soil-nutrient concentrations at a global scale. The effects of plant functional groups, climatic conditions, and soil nutrients and their interactions on leaf nutrient resorption are also unknown. In this study, we established a global database derived from 85 published papers, including 547 reports of nitrogen and phosphorus resorption efficiency （NRE and PRE）, climatic factors （LAT, latitude; MAT, mean annual temperature; MAP, mean annual precipitation） and soil-nutrient data （STN, soil total nitrogen; STP, soil total phosphorus） across 111 research sites. The results demonstrated that mean NRE and PRE were 48.4 and 53.3%, respectively. NRE of trees was lower than those of shrubs. NRE and PRE of coniferous species were both higher than those of broad-leaved species. Evergreen species had higher PRE than did deciduous species. NRE was negatively related to STN, but PRE and STP were not related. Both NRE and PRE decreased with increasing MAT and MAP but increased with increasing LAT. Plant functional groups, climate and soil nutrients jointly explained 22 and 32% of the variations in NRE and PRE, respectively. It is important to note that climate （especially MAT） explained 12 and 29% of the variations in NRE and PRE, respectively, implying that continuing global warming will exert an increasingly profound influence on plant nutrient cycles.
文摘Purpose: The purpose of this study was to examine the association between almond consumption, the most widely consumed tree nut in the US, and nutrient intake, nutrient adequacy, diet quality, and weight/adiposity in adults. Methods: Data from adults (N=24,808), 19+ years, participating in the NHANES 2001-2010 were used. The NCI method was used to estimate the usual intake of almonds and selected nutrients. Almond consumers were defined as those consuming any amount of almonds/almond butter. Percentages of the consumers/non-consumers below the Estimated Average Requirement (EAR) or above the Adequate Intake (AI) for select nutrients were determined. To assess significant differences for the percentage of almond consumers vs. non-consumers with intakes less than the EAR or above the AI, a Z-statistic for differences in population proportions was used. Covariate-controlled linear regression was used to determine differences in diet quality, measured by the Healthy Eating Index-2010 (HEI-2010), between the consumer groups. Body mass indices and waist circumference were assessed. P was set at p < 0.01. Results: Almond consumers were more likely to be non-Hispanic white, older, of higher income, more physically active, and were less likely to be a current smoker than non-consumers. Usual intake of almonds among consumers was 29.5 ± 1.5 g/day. Usual intake of protein;dietary fiber;vitamins A, D, E, and C;thiamin;niacin;riboflavin;folate, calcium, copper, magnesium, iron, phosphorus, selenium, zinc, and potassium was higher in almond consumers. Almond consumers were less likely to be below the EAR for protein, vitamins A, D, E, B12, and C;riboflavin;calcium;copper;magnesium;iron;phosphorus;and zinc. They were also more likely to be above the AI for dietary fiber and potassium. Total HEI-2010 scores were approximately 15 points higher in almond consumers. Body mass indices and waist circumference measures were lower in almond consumers. Conclusions: Moderate consumption of almonds should be encouraged as part of a healthy diet.
