Old world bluestems (Bothriochloa spp.) have been successfully introduced as grasses for livestock forage in the semiarid Texas High Plains. Questions remain, however, on effects of these grasses on soil resources. We...Old world bluestems (Bothriochloa spp.) have been successfully introduced as grasses for livestock forage in the semiarid Texas High Plains. Questions remain, however, on effects of these grasses on soil resources. We tested the hypothesis that differences in grass species produce differences in soil properties important to crop growth and useful in selecting the optimum species for the Southern High Plains of Texas. Three old world bluestem (Bothriochloa) species [C.E. Hubbard ‘Caucasian’, B. caucasica (Trin.);‘WW Spar’, B. ischaemum (L.) Keng.var ischaemum (Hack.);and S.T. Blake ‘WW-B Dahl’, B. bladhii (Retz)] were grown in a randomized complete block design, with three replications, for nine years on a clay loam soil near Lubbock, Texas. Soil samples were collected in the ninth year to determine soil texture, wet aggregate stability, bulk density (BD), soil organic carbon (SOC), particulate organic carbon (POC), and soil strength as measured by the cone pentrometer. The grass species differed in their above-ground biomass and below- ground root production. In the ninth year of production, Bothriochloa caucasica and B. bladhii produced about twice the above-ground biomass with about 25% fewer roots than B. ischaemum. Soils where B. caucasica was grown had the highest BD (1.36 Mg m–3) and B. ischaemum had the lowest (1.31 Mg m–3). The soil in which B. ischaemum was growing had a lower BD, greatest root biomass, organic matter content, and aggregate stability suggesting superior soil quality for agricultural production. The species B. bladhii, however, often exhibited soil properties that were similar to both other species tested. Since Bothriochloa bladhii had superior or similar soil properties for plant growth among the species tested and has been shown to be higher in forage quality, animal performance, and carrying capacity than the other species, it appears to be the best choice among these three species to optimize both animal performance and desirable soil properties.展开更多
Biomass has been identified as alternative renewable energy resource to replace 30%transportation fossil fuel through biofuels by 2.025.Big bluestem is a warm season native perennial grass warrants attention and studi...Biomass has been identified as alternative renewable energy resource to replace 30%transportation fossil fuel through biofuels by 2.025.Big bluestem is a warm season native perennial grass warrants attention and studies revealed its potential as energy feedstock.Extrusion pretreatments employed on big bluestem showed a significant improvement on sugar recovery.The current study was undertaken to understand and optimize pretreatment conditions such as barrel temperature(45-225℃),screw speed(20-200 r/min),moisture content(10%-50%w.b.),and particle size(2-10 mm)for maximum sugar recovery from big bluestem;and to propose a model to predict the glucose,xylose,and combined sugar recovery.Statistical analyses confirmed that all the independent variables included in this study had a strong influence on sugar recovery.A quadratic polynomial model was proposed to predict the glucose,xylose,and combined sugar recoveries from big bluestem,which had high F and R2 values with low p values.The optimum pretreatment conditions such as barrel temperature 180℃,screw speed 150 r/min,moisture content 20%w.b.,and particle size 8 mm resulted in maximum glucose,xylose,and combined sugar recoveries of 71.3%,78.5%,and 56.9%,respectively.Surface area of the optimum pretreated big bluestem increased 68.5%than that of control sample,which is the main cause for increase in sugar recovery.展开更多
The presence of grassland biomes and species cannot be predicted by examining bottom up causes such as precipitation and temperature. Top down causes including herbivory and fire seem to be major controlling aspects w...The presence of grassland biomes and species cannot be predicted by examining bottom up causes such as precipitation and temperature. Top down causes including herbivory and fire seem to be major controlling aspects with other factors secondary. We examined soil depth and competitive ability of two North American C4 grasses in a greenhouse experiment. Changes in dry mass were determined and competitive intensity was calculated for both species. Species were grown separately or together in pots 30, 90, or 180 cm deep. When grown in monoculture, Schizachyrium scoparium total and belowground dry mass increased from the 30 to 90 cm depth, with no further significant increase from 90 to 180 cm. Aboveground dry mass did not increase significantly with depth. Total dry mass of Buchloe dactyloides increased significantly with depth when grown in monoculture. Aboveground dry mass increased from 30 to 90 cm depth but not from 90 to 180 cm. Belowground dry mass of B. dactyloides did not increase significantly with depth. In 180 cm pots, 53% of S. scoparium root dry mass was in the top 30 cm;74% of B. dactyloides root dry mass was in the top 30 cm. Roots of B. dactyloides were not found deeper than 90 cm. Aboveground dry mass of S. scoparium was not different in mixture or monoculture at any depth. Buchloe dactyloides aboveground dry mass in mixture was significantly lower than monoculture at the 30 cm depth, but not at 90 or 180 cm. The greatest competitive intensity was in the shallow soil pots. Soil depth could partially explain mosaics found in C4 grasslands where both species were found together with S. scoparium on deeper soils and B. dactyloides on shallower soils.展开更多
植物生长及养分利用特征可揭示半干旱区植物对多变水肥环境条件的适应策略。在白羊草分蘖期设置2个供水条件(正常供水和干旱胁迫21天后复水)和2个磷添加水平(复水当日1 kg干土添加0,0.2 g P2O5),2周后测定其根冠生物量、根系形态以及氮...植物生长及养分利用特征可揭示半干旱区植物对多变水肥环境条件的适应策略。在白羊草分蘖期设置2个供水条件(正常供水和干旱胁迫21天后复水)和2个磷添加水平(复水当日1 kg干土添加0,0.2 g P2O5),2周后测定其根冠生物量、根系形态以及氮磷含量。结果表明,旱后复水条件下,磷添加后白羊草根冠生物量、总生物量和根冠比无显著变化,总根长和根表面积显著增加27.1%和24.1%,比根长和比根面积分别显著增加18.3%和15.9%,根系平均直径显著降低1.3%;白羊草地上部、根系和整株磷含量分别显著增加61.1%,35.8%和49.6%,磷累积量分别显著增加68.6%,52.0%和61.3%,氮磷比显著降低。除地上部氮累积量外,各水分和磷处理下白羊草地上部、根系和整株氮磷累积量与总根长和根表面积呈显著正相关关系。本研究表明,根长和根表面积增加是白羊草响应水肥环境条件改善的主要策略。展开更多
Aims a key idea in plant community ecology is that the identity of the limiting resource shifts from soil nutrients in low productivity sites to light in high productivity sites.This idea,and its implications for plan...Aims a key idea in plant community ecology is that the identity of the limiting resource shifts from soil nutrients in low productivity sites to light in high productivity sites.This idea,and its implications for plant community structure,has been tested many times in artificial productivity gradients(fertilization studies),but whether it applies to natural productivity gradients is unclear.Methods To test whether seedling light limitation would increase across a natural productivity gradient,I conducted a cross-site field experi-ment in southwest michigan,USA.A each of six old fields natu-rally varying in productivity,I exposed transplanted seedlings of big bluestem(Andropogon gerardii)to a light addition(tie-back)treat-ment that increased light availability and measured their biomass after one and two growing seasons.Important Findingsseedlings responded positively to the tie-back treatment,but positive responses did not increase across the natural productivity gradient.These results suggest that although light does limit seedling establishment,the strength of light limitation does not depend on variation in productivity in natural systems.Instead,light limitation interacted with a variety of site differences to determine establishment.although the general principle that light limitation increases with productivity is well established,these results indicate that it may not always occur in natural systems.展开更多
文摘Old world bluestems (Bothriochloa spp.) have been successfully introduced as grasses for livestock forage in the semiarid Texas High Plains. Questions remain, however, on effects of these grasses on soil resources. We tested the hypothesis that differences in grass species produce differences in soil properties important to crop growth and useful in selecting the optimum species for the Southern High Plains of Texas. Three old world bluestem (Bothriochloa) species [C.E. Hubbard ‘Caucasian’, B. caucasica (Trin.);‘WW Spar’, B. ischaemum (L.) Keng.var ischaemum (Hack.);and S.T. Blake ‘WW-B Dahl’, B. bladhii (Retz)] were grown in a randomized complete block design, with three replications, for nine years on a clay loam soil near Lubbock, Texas. Soil samples were collected in the ninth year to determine soil texture, wet aggregate stability, bulk density (BD), soil organic carbon (SOC), particulate organic carbon (POC), and soil strength as measured by the cone pentrometer. The grass species differed in their above-ground biomass and below- ground root production. In the ninth year of production, Bothriochloa caucasica and B. bladhii produced about twice the above-ground biomass with about 25% fewer roots than B. ischaemum. Soils where B. caucasica was grown had the highest BD (1.36 Mg m–3) and B. ischaemum had the lowest (1.31 Mg m–3). The soil in which B. ischaemum was growing had a lower BD, greatest root biomass, organic matter content, and aggregate stability suggesting superior soil quality for agricultural production. The species B. bladhii, however, often exhibited soil properties that were similar to both other species tested. Since Bothriochloa bladhii had superior or similar soil properties for plant growth among the species tested and has been shown to be higher in forage quality, animal performance, and carrying capacity than the other species, it appears to be the best choice among these three species to optimize both animal performance and desirable soil properties.
基金supported by funding from the Agricultural Experiment Station and North Central Sun Grant Center at South Dakota State University through a grant provided by the US Department of Transportation,Office of the Secretary,Grant No.DTOS59-07-G-00054.
文摘Biomass has been identified as alternative renewable energy resource to replace 30%transportation fossil fuel through biofuels by 2.025.Big bluestem is a warm season native perennial grass warrants attention and studies revealed its potential as energy feedstock.Extrusion pretreatments employed on big bluestem showed a significant improvement on sugar recovery.The current study was undertaken to understand and optimize pretreatment conditions such as barrel temperature(45-225℃),screw speed(20-200 r/min),moisture content(10%-50%w.b.),and particle size(2-10 mm)for maximum sugar recovery from big bluestem;and to propose a model to predict the glucose,xylose,and combined sugar recovery.Statistical analyses confirmed that all the independent variables included in this study had a strong influence on sugar recovery.A quadratic polynomial model was proposed to predict the glucose,xylose,and combined sugar recoveries from big bluestem,which had high F and R2 values with low p values.The optimum pretreatment conditions such as barrel temperature 180℃,screw speed 150 r/min,moisture content 20%w.b.,and particle size 8 mm resulted in maximum glucose,xylose,and combined sugar recoveries of 71.3%,78.5%,and 56.9%,respectively.Surface area of the optimum pretreated big bluestem increased 68.5%than that of control sample,which is the main cause for increase in sugar recovery.
文摘The presence of grassland biomes and species cannot be predicted by examining bottom up causes such as precipitation and temperature. Top down causes including herbivory and fire seem to be major controlling aspects with other factors secondary. We examined soil depth and competitive ability of two North American C4 grasses in a greenhouse experiment. Changes in dry mass were determined and competitive intensity was calculated for both species. Species were grown separately or together in pots 30, 90, or 180 cm deep. When grown in monoculture, Schizachyrium scoparium total and belowground dry mass increased from the 30 to 90 cm depth, with no further significant increase from 90 to 180 cm. Aboveground dry mass did not increase significantly with depth. Total dry mass of Buchloe dactyloides increased significantly with depth when grown in monoculture. Aboveground dry mass increased from 30 to 90 cm depth but not from 90 to 180 cm. Belowground dry mass of B. dactyloides did not increase significantly with depth. In 180 cm pots, 53% of S. scoparium root dry mass was in the top 30 cm;74% of B. dactyloides root dry mass was in the top 30 cm. Roots of B. dactyloides were not found deeper than 90 cm. Aboveground dry mass of S. scoparium was not different in mixture or monoculture at any depth. Buchloe dactyloides aboveground dry mass in mixture was significantly lower than monoculture at the 30 cm depth, but not at 90 or 180 cm. The greatest competitive intensity was in the shallow soil pots. Soil depth could partially explain mosaics found in C4 grasslands where both species were found together with S. scoparium on deeper soils and B. dactyloides on shallower soils.
文摘植物生长及养分利用特征可揭示半干旱区植物对多变水肥环境条件的适应策略。在白羊草分蘖期设置2个供水条件(正常供水和干旱胁迫21天后复水)和2个磷添加水平(复水当日1 kg干土添加0,0.2 g P2O5),2周后测定其根冠生物量、根系形态以及氮磷含量。结果表明,旱后复水条件下,磷添加后白羊草根冠生物量、总生物量和根冠比无显著变化,总根长和根表面积显著增加27.1%和24.1%,比根长和比根面积分别显著增加18.3%和15.9%,根系平均直径显著降低1.3%;白羊草地上部、根系和整株磷含量分别显著增加61.1%,35.8%和49.6%,磷累积量分别显著增加68.6%,52.0%和61.3%,氮磷比显著降低。除地上部氮累积量外,各水分和磷处理下白羊草地上部、根系和整株氮磷累积量与总根长和根表面积呈显著正相关关系。本研究表明,根长和根表面积增加是白羊草响应水肥环境条件改善的主要策略。
基金National Science Foundation[0909942]Lauff and Porter awards from the Kellogg Biological Station+2 种基金an A.L.Rogers Endowed Research Scholarship from Michigan State Universitythe NSF Long-Term Ecological Research Program at KBSMSU AgBioResearch.This is KBS contribution 1705.
文摘Aims a key idea in plant community ecology is that the identity of the limiting resource shifts from soil nutrients in low productivity sites to light in high productivity sites.This idea,and its implications for plant community structure,has been tested many times in artificial productivity gradients(fertilization studies),but whether it applies to natural productivity gradients is unclear.Methods To test whether seedling light limitation would increase across a natural productivity gradient,I conducted a cross-site field experi-ment in southwest michigan,USA.A each of six old fields natu-rally varying in productivity,I exposed transplanted seedlings of big bluestem(Andropogon gerardii)to a light addition(tie-back)treat-ment that increased light availability and measured their biomass after one and two growing seasons.Important Findingsseedlings responded positively to the tie-back treatment,but positive responses did not increase across the natural productivity gradient.These results suggest that although light does limit seedling establishment,the strength of light limitation does not depend on variation in productivity in natural systems.Instead,light limitation interacted with a variety of site differences to determine establishment.although the general principle that light limitation increases with productivity is well established,these results indicate that it may not always occur in natural systems.
