Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was develo...Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal area.For any tree size,this maximum increased as site productivity increased.However,the size at which this maximum occurred decreased as productivity increased.Much research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive ones.Taller trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth rates.It was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive site.The model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.展开更多
The source and significance of two nutrients, nitrogen and phosphorous, were investigated by a modified dilution method performed on seawater samples from the Jiaozhou Bay, in autumn 2004. This modified dilution metho...The source and significance of two nutrients, nitrogen and phosphorous, were investigated by a modified dilution method performed on seawater samples from the Jiaozhou Bay, in autumn 2004. This modified dilution method accounted for the phytoplankton growth rate, microzooplankton grazing mortality rate, the internal and external nutrient pools, as well as nutrient supplied through remineralization by microzooplankton. The results indicated that the phytoplankton net growth rate increased in turn from inside the bay, to outside the bay, to in the Xiaogang Harbor. The phytoplankton maximum growth rates and microzooplankton grazing mortality rates were 1.14 and 0.92 d^-1 outside the bay, 0.42 and 0.32 d^ -1 inside the bay and 0.98 and 0.62 d^-1 in the harbor respectively. Outside the bay, the remineralized nitrogen （Kt = 24.49） had heavy influence on the growth of the phytoplankton. Inside the bay, the remineralized phosphorus（Kt = 3.49） strongly affected the phytoplankton growth. In the harbor, the remineralized phosphorus （Kt = 3.73） was in larger demand by phytoplankton growth. The results demonstrated that the dif- ferent nutrients pools supplied for phytoplankton growth were greatly in accordance with the phytoplankton community structure, microzooplankton grazing mortality rates and environmental conditions. It is revealed that nutrient remineralization is much more important for the phytoplankton growth in the Jiaozhou Bay than previously believed.展开更多
【背景】玉米(Zeamays)间作花生(Arachishypogaea)(玉米||花生)地上、地下种间作用明显,间作产量优势突出,在缓解我国油粮争地矛盾中起到重要作用,但花生处于种间竞争劣势,成为限制间作优势进一步提高的瓶颈。【目的】探明提高玉米||花...【背景】玉米(Zeamays)间作花生(Arachishypogaea)(玉米||花生)地上、地下种间作用明显,间作产量优势突出,在缓解我国油粮争地矛盾中起到重要作用,但花生处于种间竞争劣势,成为限制间作优势进一步提高的瓶颈。【目的】探明提高玉米||花生体系中花生种间竞争的调控措施及其机理,为玉米||花生高产栽培提供理论依据和技术支撑。【方法】2021—2022年在河南科技大学试验农场,以玉米‘郑单958’和花生‘花育16’为供试材料,设种植方式、花生播种方式和施磷量3因素完全随机区组试验,即种植方式设花生单作和玉米||花生,花生播种方式设花生单粒播种和双粒播种,施磷量设0(P0)和180 kg P2O5·hm-2(P180);以花生双粒播种的玉米||花生体系为对照,研究花生单粒播种对间作花生相对玉米的种间竞争力、净光合速率、最大生长速率、干物质积累和分配及间作产量优势的影响。【结果】与花生双粒播种的强势株和弱势株相比,单粒播种显著提高了间作花生相对玉米的侵占力和拥挤系数,相对侵占力分别提高29.72%—80.85%和38.91%—87.07%,相对拥挤系数分别提高76.59%—172.02%和244.43%—308.70%。单粒播种间作花生的净光合速率显著高于双粒播种,最大生长速率明显高于双粒播种的强势株和弱势株,其生育后期的干物质显著提高、干物质向荚果的分配比例增加,提高了茎、叶干物质对荚果的贡献率。单粒播种间作花生的产量和间作优势高于双粒播种,其中产量高出18.84%—33.32%,差异显著。与不施磷相比,施磷显著提高间作花生净光合速率,增加最大生长速率、促进干物质积累,增加产量。【结论】花生单粒播种能提高间作花生产量和间作优势,关键在于单粒播种较双粒播种能增强间作花生种间竞争能力,显著提高净光合速率,促进干物质积累及其向荚果分配。施磷对单粒播种间作花生的生长发育具有促进作用。展开更多
已有研究表明食源性致病菌因菌株多样性,表现出致病力、耐药及生长等表型的显著差异,具有典型的菌株异质性。为研究温度影响的单增李斯特菌(Listeria monocytogenes)的生长差异,为精准风险评估提供支撑,该研究选取40株不同分离来源(临...已有研究表明食源性致病菌因菌株多样性,表现出致病力、耐药及生长等表型的显著差异,具有典型的菌株异质性。为研究温度影响的单增李斯特菌(Listeria monocytogenes)的生长差异,为精准风险评估提供支撑,该研究选取40株不同分离来源(临床和食品来源各20株)、不同血清型菌株,开展其在37、25、10℃的基于最大比生长速率(μ_(max))的生长差异研究。结果表明,在37、25、10℃时,菌株间μ_(max)的变异系数(coefficient of variation,CV)分别为10.528%、8.566%和12.303%;临床分离菌株的μ_(max)的CV小于食品分离菌株,表现出较小的温度生长异质性;25℃条件下,具有较强致病力的1/2b和4b血清型菌株μ_(max)值显著大于弱致病力的1/2a型菌株;4b血清型菌株在10℃下表现出最小的生长异质性。综上,较强致病力的菌株表现出显著的生长优势,显示了对环境较强的生长适应性,菌株间具有显著的生长差异,通过异质性研究有助于降低对风险评估不确定因素的影响,为科学精准开展风险评估和防控研究提供数据支撑。展开更多
文摘Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal area.For any tree size,this maximum increased as site productivity increased.However,the size at which this maximum occurred decreased as productivity increased.Much research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive ones.Taller trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth rates.It was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive site.The model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.
基金This study was supported by the Funds of the Chinese Academy of Sciences for Key Topics in Innovation Engineering under contract No.KZCX2-YW-213the National Natural Science Foundation of China under contract Nos 40306025 and 40676089.
文摘The source and significance of two nutrients, nitrogen and phosphorous, were investigated by a modified dilution method performed on seawater samples from the Jiaozhou Bay, in autumn 2004. This modified dilution method accounted for the phytoplankton growth rate, microzooplankton grazing mortality rate, the internal and external nutrient pools, as well as nutrient supplied through remineralization by microzooplankton. The results indicated that the phytoplankton net growth rate increased in turn from inside the bay, to outside the bay, to in the Xiaogang Harbor. The phytoplankton maximum growth rates and microzooplankton grazing mortality rates were 1.14 and 0.92 d^-1 outside the bay, 0.42 and 0.32 d^ -1 inside the bay and 0.98 and 0.62 d^-1 in the harbor respectively. Outside the bay, the remineralized nitrogen （Kt = 24.49） had heavy influence on the growth of the phytoplankton. Inside the bay, the remineralized phosphorus（Kt = 3.49） strongly affected the phytoplankton growth. In the harbor, the remineralized phosphorus （Kt = 3.73） was in larger demand by phytoplankton growth. The results demonstrated that the dif- ferent nutrients pools supplied for phytoplankton growth were greatly in accordance with the phytoplankton community structure, microzooplankton grazing mortality rates and environmental conditions. It is revealed that nutrient remineralization is much more important for the phytoplankton growth in the Jiaozhou Bay than previously believed.
文摘【背景】玉米(Zeamays)间作花生(Arachishypogaea)(玉米||花生)地上、地下种间作用明显,间作产量优势突出,在缓解我国油粮争地矛盾中起到重要作用,但花生处于种间竞争劣势,成为限制间作优势进一步提高的瓶颈。【目的】探明提高玉米||花生体系中花生种间竞争的调控措施及其机理,为玉米||花生高产栽培提供理论依据和技术支撑。【方法】2021—2022年在河南科技大学试验农场,以玉米‘郑单958’和花生‘花育16’为供试材料,设种植方式、花生播种方式和施磷量3因素完全随机区组试验,即种植方式设花生单作和玉米||花生,花生播种方式设花生单粒播种和双粒播种,施磷量设0(P0)和180 kg P2O5·hm-2(P180);以花生双粒播种的玉米||花生体系为对照,研究花生单粒播种对间作花生相对玉米的种间竞争力、净光合速率、最大生长速率、干物质积累和分配及间作产量优势的影响。【结果】与花生双粒播种的强势株和弱势株相比,单粒播种显著提高了间作花生相对玉米的侵占力和拥挤系数,相对侵占力分别提高29.72%—80.85%和38.91%—87.07%,相对拥挤系数分别提高76.59%—172.02%和244.43%—308.70%。单粒播种间作花生的净光合速率显著高于双粒播种,最大生长速率明显高于双粒播种的强势株和弱势株,其生育后期的干物质显著提高、干物质向荚果的分配比例增加,提高了茎、叶干物质对荚果的贡献率。单粒播种间作花生的产量和间作优势高于双粒播种,其中产量高出18.84%—33.32%,差异显著。与不施磷相比,施磷显著提高间作花生净光合速率,增加最大生长速率、促进干物质积累,增加产量。【结论】花生单粒播种能提高间作花生产量和间作优势,关键在于单粒播种较双粒播种能增强间作花生种间竞争能力,显著提高净光合速率,促进干物质积累及其向荚果分配。施磷对单粒播种间作花生的生长发育具有促进作用。
文摘已有研究表明食源性致病菌因菌株多样性,表现出致病力、耐药及生长等表型的显著差异,具有典型的菌株异质性。为研究温度影响的单增李斯特菌(Listeria monocytogenes)的生长差异,为精准风险评估提供支撑,该研究选取40株不同分离来源(临床和食品来源各20株)、不同血清型菌株,开展其在37、25、10℃的基于最大比生长速率(μ_(max))的生长差异研究。结果表明,在37、25、10℃时,菌株间μ_(max)的变异系数(coefficient of variation,CV)分别为10.528%、8.566%和12.303%;临床分离菌株的μ_(max)的CV小于食品分离菌株,表现出较小的温度生长异质性;25℃条件下,具有较强致病力的1/2b和4b血清型菌株μ_(max)值显著大于弱致病力的1/2a型菌株;4b血清型菌株在10℃下表现出最小的生长异质性。综上,较强致病力的菌株表现出显著的生长优势,显示了对环境较强的生长适应性,菌株间具有显著的生长差异,通过异质性研究有助于降低对风险评估不确定因素的影响,为科学精准开展风险评估和防控研究提供数据支撑。
