Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studi...Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density(SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period(viz. 0–10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0–10 year. During 0–30 year, the SOCD from 0–100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.展开更多
Alfalfa(Medicago sativa L.) is a legume forage that is widely cultivated owing to its high biomass yield and favorable nutrient values. However, alfalfa contains relatively high lignin, which limits its utilization.Do...Alfalfa(Medicago sativa L.) is a legume forage that is widely cultivated owing to its high biomass yield and favorable nutrient values. However, alfalfa contains relatively high lignin, which limits its utilization.Downregulation of two transcriptional factors, Transparent Testa8(TT8) and Homeobox12(HB12), has been proposed to reduce lignin content in alfalfa. Therefore, silencing of TT8(TT8i) and HB12(HB12i) in alfalfa was achieved by RNAi technology. The objective of this project was to determine effect of gene modification through silencing of TT8 and HB12 genes in alfalfa plants on lignin and phenolic content,bioenergic value, nutrient supply from rumen degradable and undegradable fractions, and in vitro ammonia production in response to the silencing of TT8 and HB12 genes in alfalfa. All gene silenced alfalfa plants(5 TT8i and 11 HB12i) were grown under greenhouse conditions with wild type as a control.Samples were analyzed for bioactive compounds, degradation fractions, truly digestible nutrients, energetic values and in vitro ammonia productions in ruminant systems. Furthermore, relationships between physiochemical, metabolic and fermentation characteristics and molecular spectral parameters were determined using vibrational molecular spectroscopy. Results showed that the HB12i had higher lignin, while TT8i had higher phenolics. Both silenced genotypes had higher rumen slowly degraded carbohydrate fractions and truly digestible neutral detergent fiber, but lower rumen degradable protein fractions. Moreover, the HB12i had lower truly digestible crude protein, energetic values and ammonia production compared with other silenced genotypes. In addition, in relation to the nutritive values of alfalfa, structural carbohydrate parameters were negatively correlated, whereas alpha/beta ratio in protein structure was positively correlated. Furthermore, good predictions were obtained for degradation of protein and carbohydrate fractions and energy values from molecular spectral parameters. In conclusion, silencing of the TT8 and HB12 genes decreased protein availability and increased fiber availability. Silencing of the HB12 gene also increased lignin and decreased energy and rumen ammonia production. Moreover, nutritional alterations were closely correlated with molecular spectral parameters. Therefore, gene modification through silencing the TT8 and HB12 genes in alfalfa influenced physiochemical, metabolic and fermentation characteristics.展开更多
Alfalfa(Medicago sativa L.)is acclaimed as“Queen of forages”because of its great yield and high feeding value.China is the second biggest country in acreage of alfalfa cultivation,but the cultivation regions of alfa...Alfalfa(Medicago sativa L.)is acclaimed as“Queen of forages”because of its great yield and high feeding value.China is the second biggest country in acreage of alfalfa cultivation,but the cultivation regions of alfalfa are distinguished by adverse climatic and edaphic conditions in northern China.Moreover,the lack of elite alfalfa varieties with great adaptation and poor field management are vital factors limiting development of alfalfa pasture in China.In addition,nutritional quality of alfalfa in China is also poor compared to that in countries of developed animal husbandry industrial.Here,we propose several priorities in terms of a comprehensive system of alfalfa breeding,field management,harvest and processing with Chinese characteristics,based on the theories and methodologies of breeding science,agronomy,plant physiology and agricultural machinery.Implementation of these priorities will greatly contribute to the sustainable development of the alfalfa pasture in China.展开更多
【目的】在豆科与禾本科牧草混播草地中不仅存在种内竞争也存在种间竞争,由于不同植物之间竞争力强弱不同,竞争的结果将出现一方逐渐消退,另一方逐渐占据优势的现象,因此研究豆科与禾本科牧草之间竞争与共存机制对于维持混播草地稳定高...【目的】在豆科与禾本科牧草混播草地中不仅存在种内竞争也存在种间竞争,由于不同植物之间竞争力强弱不同,竞争的结果将出现一方逐渐消退,另一方逐渐占据优势的现象,因此研究豆科与禾本科牧草之间竞争与共存机制对于维持混播草地稳定高产具有重要意义。【方法】在温室栽培条件下设置3个氮肥水平(0,75,150kg N·hm-2,记作N0,N75,N150)以及单播和混播两种种植模式(无芒雀麦单播,紫花苜蓿单播,无芒雀麦和紫花苜蓿1﹕1混播),采用相对生物量(RY)、相对密度(RD)、竞争率(CR)和相对产量总值(RYT)以及紫花苜蓿的固氮比例(%Ndfa)和转氮比例(%N Trans)等指标研究无芒雀麦和紫花苜蓿在1﹕1混播中的竞争关系与共存机制。【结果】施氮量从0增加到150 kg N·hm-2,单播中无芒雀麦的地上和地下生物量和分蘖数显著增加(P<0.05),而紫花苜蓿的地上和地下生物量和分枝数无显著变化(P>0.05)。在混播中无芒雀麦的地上和地下生物量和分蘖数也显著增加(P<0.05),在一定程度上抑制了紫花苜蓿的生物量和分枝数。另外,在混播中无芒雀麦以增加分蘖数的方式来扩张地上空间的能力要强于紫花苜蓿。无芒雀麦的单株生物量和分蘖数在混播模式下都极显著高于单播(P<0.01),而紫花苜蓿的单株生物量和分枝数在混播模式下极显著低于单播(P<0.01)。在混播中无芒雀麦的竞争率始终大于1.0,而紫花苜蓿的竞争率始终小于1.0,这说明无芒雀麦的竞争力要大于紫花苜蓿的竞争力,且在整个生育期中,无芒雀麦的竞争力逐渐减弱,而紫花苜蓿的竞争力逐渐增强。在N0处理下,第2次、第3次和第4次取样时,无芒雀麦和紫花苜蓿的相对产量总值(RYT)显著大于1.0(P<0.05),说明无芒雀麦和紫花苜蓿无明显的竞争效应,这主要归功于紫花苜蓿的生物固氮对无芒雀麦的贡献(地上部转移的氮素占无芒雀麦氮素含量的15.26%—29.92%)。在N75和N150处理下,其RYT值与1.0无显著差异(P>0.05)。另外,施入氮肥明显抑制了紫花苜蓿的生物固氮比例和对无芒雀麦的氮素转移的比例,导致混播中无芒雀麦和紫花苜蓿同时竞争土壤氮素和肥料氮。【结论】施入75和150 kg N·hm-2的氮肥增强了无芒雀麦的竞争力,而抑制了紫花苜蓿的生物固氮和对无芒雀麦氮素的转移,二者促进作用减弱,竞争效应增强。展开更多
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05000000)National Natural Science Foundation of China(No.41271518)Sci-technology Project of Shaanxi Province(No.2013kw19-01)
文摘Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density(SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period(viz. 0–10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0–10 year. During 0–30 year, the SOCD from 0–100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.
文摘Alfalfa(Medicago sativa L.) is a legume forage that is widely cultivated owing to its high biomass yield and favorable nutrient values. However, alfalfa contains relatively high lignin, which limits its utilization.Downregulation of two transcriptional factors, Transparent Testa8(TT8) and Homeobox12(HB12), has been proposed to reduce lignin content in alfalfa. Therefore, silencing of TT8(TT8i) and HB12(HB12i) in alfalfa was achieved by RNAi technology. The objective of this project was to determine effect of gene modification through silencing of TT8 and HB12 genes in alfalfa plants on lignin and phenolic content,bioenergic value, nutrient supply from rumen degradable and undegradable fractions, and in vitro ammonia production in response to the silencing of TT8 and HB12 genes in alfalfa. All gene silenced alfalfa plants(5 TT8i and 11 HB12i) were grown under greenhouse conditions with wild type as a control.Samples were analyzed for bioactive compounds, degradation fractions, truly digestible nutrients, energetic values and in vitro ammonia productions in ruminant systems. Furthermore, relationships between physiochemical, metabolic and fermentation characteristics and molecular spectral parameters were determined using vibrational molecular spectroscopy. Results showed that the HB12i had higher lignin, while TT8i had higher phenolics. Both silenced genotypes had higher rumen slowly degraded carbohydrate fractions and truly digestible neutral detergent fiber, but lower rumen degradable protein fractions. Moreover, the HB12i had lower truly digestible crude protein, energetic values and ammonia production compared with other silenced genotypes. In addition, in relation to the nutritive values of alfalfa, structural carbohydrate parameters were negatively correlated, whereas alpha/beta ratio in protein structure was positively correlated. Furthermore, good predictions were obtained for degradation of protein and carbohydrate fractions and energy values from molecular spectral parameters. In conclusion, silencing of the TT8 and HB12 genes decreased protein availability and increased fiber availability. Silencing of the HB12 gene also increased lignin and decreased energy and rumen ammonia production. Moreover, nutritional alterations were closely correlated with molecular spectral parameters. Therefore, gene modification through silencing the TT8 and HB12 genes in alfalfa influenced physiochemical, metabolic and fermentation characteristics.
基金supported by the National Natural Science Foundation of China (31830011,32070351).
文摘Alfalfa(Medicago sativa L.)is acclaimed as“Queen of forages”because of its great yield and high feeding value.China is the second biggest country in acreage of alfalfa cultivation,but the cultivation regions of alfalfa are distinguished by adverse climatic and edaphic conditions in northern China.Moreover,the lack of elite alfalfa varieties with great adaptation and poor field management are vital factors limiting development of alfalfa pasture in China.In addition,nutritional quality of alfalfa in China is also poor compared to that in countries of developed animal husbandry industrial.Here,we propose several priorities in terms of a comprehensive system of alfalfa breeding,field management,harvest and processing with Chinese characteristics,based on the theories and methodologies of breeding science,agronomy,plant physiology and agricultural machinery.Implementation of these priorities will greatly contribute to the sustainable development of the alfalfa pasture in China.
文摘【目的】在豆科与禾本科牧草混播草地中不仅存在种内竞争也存在种间竞争,由于不同植物之间竞争力强弱不同,竞争的结果将出现一方逐渐消退,另一方逐渐占据优势的现象,因此研究豆科与禾本科牧草之间竞争与共存机制对于维持混播草地稳定高产具有重要意义。【方法】在温室栽培条件下设置3个氮肥水平(0,75,150kg N·hm-2,记作N0,N75,N150)以及单播和混播两种种植模式(无芒雀麦单播,紫花苜蓿单播,无芒雀麦和紫花苜蓿1﹕1混播),采用相对生物量(RY)、相对密度(RD)、竞争率(CR)和相对产量总值(RYT)以及紫花苜蓿的固氮比例(%Ndfa)和转氮比例(%N Trans)等指标研究无芒雀麦和紫花苜蓿在1﹕1混播中的竞争关系与共存机制。【结果】施氮量从0增加到150 kg N·hm-2,单播中无芒雀麦的地上和地下生物量和分蘖数显著增加(P<0.05),而紫花苜蓿的地上和地下生物量和分枝数无显著变化(P>0.05)。在混播中无芒雀麦的地上和地下生物量和分蘖数也显著增加(P<0.05),在一定程度上抑制了紫花苜蓿的生物量和分枝数。另外,在混播中无芒雀麦以增加分蘖数的方式来扩张地上空间的能力要强于紫花苜蓿。无芒雀麦的单株生物量和分蘖数在混播模式下都极显著高于单播(P<0.01),而紫花苜蓿的单株生物量和分枝数在混播模式下极显著低于单播(P<0.01)。在混播中无芒雀麦的竞争率始终大于1.0,而紫花苜蓿的竞争率始终小于1.0,这说明无芒雀麦的竞争力要大于紫花苜蓿的竞争力,且在整个生育期中,无芒雀麦的竞争力逐渐减弱,而紫花苜蓿的竞争力逐渐增强。在N0处理下,第2次、第3次和第4次取样时,无芒雀麦和紫花苜蓿的相对产量总值(RYT)显著大于1.0(P<0.05),说明无芒雀麦和紫花苜蓿无明显的竞争效应,这主要归功于紫花苜蓿的生物固氮对无芒雀麦的贡献(地上部转移的氮素占无芒雀麦氮素含量的15.26%—29.92%)。在N75和N150处理下,其RYT值与1.0无显著差异(P>0.05)。另外,施入氮肥明显抑制了紫花苜蓿的生物固氮比例和对无芒雀麦的氮素转移的比例,导致混播中无芒雀麦和紫花苜蓿同时竞争土壤氮素和肥料氮。【结论】施入75和150 kg N·hm-2的氮肥增强了无芒雀麦的竞争力,而抑制了紫花苜蓿的生物固氮和对无芒雀麦氮素的转移,二者促进作用减弱,竞争效应增强。
