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Aboveground resilience to species loss but belowground resistance to nitrogen addition in a montane plant community

Journal of Plant ecology 2018年第3期11卷 351-363页

作者： Quentin D.Read Jeremiah A.Henning Aimée t.Classen Nathan J.Sanders Department of ecology and evolutionary Biology University of Tennessee569 Dabney HallKnoxvilleTN 37996USA Rocky Mountain Biological Laboratory PO Box 615Crested ButteCO 81224USA Center for Macroecology Evolutionand ClimateNatural History Museum of DenmarkUniversity of CopenhagenUniversitetsparken 152100 CopenhagenDenmark Rubenstein School of environment and Natural Resources University of VermontBurlingtonVT 05405USA

aims Decades of empirical work have demonstrated how dominant plant species and nitrogen fertilization can influence the structure and function of plant communities.More recent studies have examined the interplay between these factors,but few such studies use an explicit trait-based framework.In this study,we use an explicit trait-based approach to identify potential mechanisms for community-level responses and to test ecological niche theory.Methods We experimentally manipulated plant communities(control,−dom-inant species,−random biomass)and nitrogen(N)inputs(control,+organic N,+inorganic N)in a fully factorial design.We predicted that traits related to plants’ability to take up different forms of soil N would differ between dominant and subordinate species,resulting in interactive effects of dominant species loss and N fertilization on plant community structure and function.the study took place in a montane meadow in the Rocky Mountains,Colorado,USA.Important Findings After four years,the plant community in removal plots converged toward a species composition whose leaf and root functional traits resembled those of the previously removed dominant species.ecosystem productivity generally increased with N addition:soil carbon efflux was~50%greater when either form of N was added,while inorganic N addition increased aboveground biomass pro-duction by~60%relative to controls.the increase in production was mediated by increased average height,leaf mass:area ratio and leaf dry matter content in plant communities to which we added inorganic N.Contrary to our predictions,there were no interactive effects of N fertilization and dominant species loss on plant com-munity structure or ecosystem function.the plant community com-position in this study exhibited resistance to soil N addition and,given the functional convergence we observed,was resilient to spe-cies loss.together,our results indicate that the ability of species to compensate functionally for species loss confers resilience and maintains diversity in montane m

关键词： dominant species fertilization functional trait removal experiment resilience

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Variation in the methods leads to variation in the interpretation of biodiversity-ecosystem multifunctionality relationships

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Journal of Plant ecology 2020年第4期13卷 431-441页

作者： Xin Jing Case M.Prager Aimée t.Classen Fernando t.Maestre Jin-Sheng He Nathan J.Sanders Rubenstein School of environment and Natural Resources University of VermontBurlingtonVT 05405USA Gund Institute for environment University of VermontBurlingtonVT 05405USA Center for Macroecology Evolutionand ClimateNatural History Museum of DenmarkCopenhagenDenmark Departamento de Biología GeologíaFísica y Química InorgánicaEscuela Superior de Ciencias Experimentales y TecnologíaUniversidad Rey Juan CarlosMóstoles 28933Spain Departamento de ecología and Instituto Multidisciplinar para el estudio del Medio“Ramon Margalef” Universidad de AlicanteAlicanteSpain Department of ecology College of Urban and Environmental SciencesPeking UniversityBeijingChina environmental Program Rubenstein School of Environment and Natural ResourcesUniversity of VermontBurlingtonVT 05405USA Present address:Department of earth and environmental Sciences KU LeuvenCelestijnenlaan 200E3001 LeuvenBelgium

生物多样性常常和生态系统多功能性(生态系统同时提供多个生态系统功能的能力)正相关。然而,生物多样性与生态系统多功能性的关系是否依赖于生态系统功能的数目有诸多争议。其中,生物多样性对生态系统多功能性的影响或许不随生态系统功... 详细信息

生物多样性常常和生态系统多功能性(生态系统同时提供多个生态系统功能的能力)正相关。然而,生物多样性与生态系统多功能性的关系是否依赖于生态系统功能的数目有诸多争议。其中,生物多样性对生态系统多功能性的影响或许不随生态系统功能数目的变化而变化,或者随生态系统功能数目的增多而增强。我们期望通过研究不同生态系统多功能性指数的统计原理来解决这些争议。我们使用了模型模拟和一系列来自不同空间尺度(从局域到全球)和不同生物群系(温带和高寒草地、森林和干旱地)的经验数据。我们回顾了量化生态系统多功能性的三种方法,包括平均值法、加和法和阈值法。我们发现随着生态系统功能数目的增加,生物多样性与生态系统多功能性的关系要么不变,要么增强。这些结果可由平均和加和的多功能性指数的统计原理来解释。具体来讲,当利用生态系统功能的平均值计算多功能性指数时,由于多样性对多功能性的效应等于多样性对单个生态系统功能效应的平均值,所以不会随生态系统功能数目的变化而变化。同样的道理,当利用单个生态系统的加和值计算多功能性指数时,多样性的效应会随着生态系统功能数目的增加而增强。我们提出了一个改进的多功能性指数,将平均或加和多功能性指数转化为标准化的多功能性指数,以便于对不同研究的结果进行比较。此外,我们提出了基于变量数值范围的标准化方法来解决阈值法的数学假象问题(多样性效应随生态系统功能数目的增加而增强)。我们的研究结果表明,量化多功能性指数的方法不同,结果也不同。因此,有必要加深对不同方法数理基础的理解。而标准化的多功能性指数为比较不同研究中的生物多样性与生态系统多功能性的关系提供了有效的方法。

关键词：平均值法生物多样性生态系统多功能性多阈值法植物物种丰富度空间尺度

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Investigating drivers of microbial activity and respiration in a forested bog

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Pedosphere 2020年第1期30卷 135-145页

作者： Kenna e.ReWCAStLe Jessica A.M.MOORe Jeremiah A.HeNNING Melanie A.MAYeS Courtney M.PAtteRSON Gangsheng WANG Daniel B.MetCALFe Aimée t.Classen Rubenstein School of environment and Natural Resources University of VermontBurlington VT 05405(USA) ecology&evolutionary Biology University of TennesseeKnoxville TN 37996(USA) the Gund Institute for environment University of VermontBurlington VT 05405(USA) Department of Biology University of South AlabamaMobile AL 36688(USA) Climate Change Science Institute and environmental Sciences Division Oak Ridge National LaboratoryOak Ridge TN 37830(USA) Institute for environmental Genomics&Department of Microbiology and Plant Biology University of OklahomaNorman OK 73019(USA) the Department of Physical Geography and ecosystem Science Lund UniversityLund 22362(Sweden)

Northern peatlands store nearly one-third of terrestrial carbon(C)stocks while covering only 3%of the global landmass;nevertheless,the drivers of C cycling in these often-waterlogged ecosystems are different from those that control C dynamics in upland forested soils.to explore how multiple abiotic and biotic characteristics of bogs interact to shape microbial activity in a northern,forested bog,we added a labile C tracer(13C-labeled starch)to in situ peat mesocosms and correlated heterotrophic respiration with natural variation in several microbial predictor variables,such as enzyme activity and microbial biomass,as well as with a suite of abiotic variables and proximity to vascular plants aboveground.We found that peat moisture content was positively correlated with respiration and microbial activity,even when moisture levels exceeded total saturation,suggesting that access to organic matter substrates in drier environments may be limiting for microbial activity.Proximity to black spruce trees decreased total and labile heterotrophic respiration.this negative relationship may reflect the influence of tree evapotranspiration and peat shading effects;i.e.,microbial activity may decline as peat dries and cools near trees.Here,we isolated the response of heterotrophic respiration to explore the variation in,and interactions among,multiple abiotic and biotic drivers that influence microbial activity.this approach allowed us to reveal the relative influence of individual drivers on C respiration in these globally important C sinks.

关键词： carbon cycling enzyme activity heterotrophic respiration labile carbon respiration ombrotrophic bog peat moisture plant proximity soil carbon sink

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Responses of an old-field plant community to interacting factors of elevated[CO_(2)],warming,and soil moisture

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Journal of Plant ecology 2009年第1期2卷 1-11页

作者： e.Cayenne engel Jake F.Weltzin Richard J.Norby aimee t.classen Department of ecology and evolutionary Biology University of Tennessee569 Dabney HallKnoxvilleTN 37996-1610USA environmental Sciences Division Oak Ridge National LaboratoryOne Bethel Valley RoadBuilding 1062Oak RidgeTN 37831-6422USA Present address:USA National Phenology Network National Coordinating Office1955 East 6th StreetTucsonAZ 85721USA

aims the direct effects of atmospheric and climatic change factors—atmospheric[CO_(2)],air temperature and changes in precipitation—can shape plant community composition and alter ecosystem function.It is essential to understand how these factors interact to make better predictions about how ecosystems may respond to change.We investigated the direct and interactive effects of[CO_(2)],warming and altered soil moisture in open-top chambers(OtCs)enclosing a constructed old-field community to test how these factors shape plant communities.Materials and methods the experimental facility in Oak Ridge,tN,USA,made use of 4-m diameter OtCs and rain shelters to manipulate[CO_(2)](ambient,ambient+300 ppm),air temperature(ambient,ambient+3.5C)and soil moisture(wet,dry).the plant communities within the chambers comprised seven common old-field species,including grasses,forbs and legumes.We tracked foliar cover for each species and calculated community richness,evenness and diversity from 2003 to 2005.Important findings this work resulted in three main findings:(1)warming had speciesspecific effects on foliar cover that varied through time and were altered by soil moisture treatments;(2)[CO_(2)]had little effect on individual species or the community;(3)diversity,evenness and richness were influenced most by soil moisture,primarily reflecting the response of one dominant species.We conclude that individualistic species responses to atmospheric and climatic change can alter community composition and that plant populations and communities should be considered as part of analyses of terrestrial ecosystem response to climate change.However,prediction of plant community responses may be difficult given interactions between factors and changes in response through time.

关键词： climate change foliar cover multi-factor interactions diversity richness

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Hulless barley and β-glucanase affect ileal digesta soluble β-glucan molecular weight and digestive tract characteristics of coccidiosis-vaccinated broilers

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Animal Nutrition 2021年第3期7卷 595-608页

作者： Namalika D.Karunaratne Rex W.Newkirk Nancy P.Ames Andrew G.Van Kessel Michael R.Bedford Henry L.classen Department of Animal and Poultry Science University of SaskatchewanSaskatoonS7N 5A8SaskatchewanCanada Agriculture and Agri-food Canada WinnipegR3T 2E1ManitobaCanada AB Vista MarlboroughWiltshireSN84ANUnited Kingdom

exogenousβ-glucanase(BGase)in barley-based feed has been shown to reduce digesta viscosity in chickens,and thereby improve performance.Less well studied is the potential for BGase to convert barleyβ-glucan into low molecular weight carbohydrates,which might influence digestive tract function and enteric disease.Coccidiosis-vaccinated broiler chickens were fed graded levels of hulless barley(HB)and BGase to determine their effects onβ-glucan depolymerization and digestive tract characteristics.Broilers were fed highβ-glucan HB(0%,30%and 60%replacing wheat)and BGase(0%,0.01%and 0.1%)in a 3×3 factorial arrangement.A total of 5,346 broilers were raised in litter floor pens and vaccinated for coccidiosis on d 5.each treatment was assigned to 1 pen in each of 9 rooms.the significance level was set at P≤0.05.At both 11 and 33 d of broiler ages,peak molecular weight ofβ-glucan in ileal digesta decreased with increasing BGase for 30%and 60%HB.the maximum molecular weight for the smallest 10%β-glucan molecules(MW-10%)decreased with BGase at both ages for 30%and 60%HB;for birds fed 0%HB,only 0.1%BGase decreased MW-10%.the 0.1%BGase increased caecal short chain fatty acids(SCFA)compared to the 0.01%BGase at d 11 only for the 60%HB.Ileal pH increased with increasing HB and BGase at d 11 and 33.Caecal pH was lower for 0.1%BGase than 0%BGase for 60%HB at d 11.Relative mRNA expression of interleukin 6(IL-6)and IL-8 in the ileum increased with 0.1%BGase at d 11 and 33,respectively,whereas expression of ileal mucin 2(MUC2)decreased with 0.1%BGase at d 33.In the caeca,interactions between HB and BGase were significant for monocarboxylate transporter 1(MCt1)and mucin 5AC(MUC5AC)on d 11,but no treatment effects were found at d 33.In conclusion,BGase depolymerized high molecular weightβ-glucan in HB in a dose-dependent manner.Hulless barley and BGase did not increase SCFA concentrations(except for 60%HB with 0.1%BGase at d 11)and caused minor effects on digestive tract histomorphological measurements and relative mRNA gene expression.

关键词： Prebiotic Non-starch polysaccharide Fermentation Short-chain fatty acid Feed enzyme

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Diet medication and beta-glucanase affect ileal digesta soluble betaglucan molecular weight,carbohydrate fermentation,and performance of coccidiosis vaccinated broiler chickens given wheatbased diets

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Animal Nutrition 2023年第4期15卷 288-296页

作者： Namalika D.Karunaratne Henry L.classen Andrew Gvan Kessel Michael R.Bedford Nancy P.Ames Rex W.Newkirk Department of Animal and Poultry Science University of SaskatchewanSaskatoonSK S7N5A8Canada AB Vista MarlboroughWiltshireSN84ANUnited Kingdom Agriculture and Agri-Food Canada WinnipegR3T 2E1ManitobaCanada

exogenous enzymes as alternatives to feed antibiotics in poultry has become an emerging research area with the emergence of antibiotic resistance.the objective was to evaluate the effects of diet medication(antibiotics)andβ-glucanase(BGase)on digesta solubleβ-glucan depolymerization,carbohydrate fermentation,and performance of coccidiosis-vaccinated broiler chickens fed wheat-based diets.A total of 1,782 broilers were raised on litter floor pens,and each treatment was assigned to 1 pen in each of the9 rooms.the 3 dietary treatments were based on wheat as the sole grain(control,control+medication and control+0.1%BGase),and the birds were fed the respective treatments ad libitum from 0 to 33 d.treatments were arranged in a randomized complete block design and analyzed as a one-way ANOVA.Beta-glucanase reduced the peak molecular weight,weight average molecular weight(Mw)and maximum molecular weight for the smallest 10%β-glucan molecules(MW-10%)in ileal digesta at d 11and 33,whereas diet medication reduced Mw and MW-10%at d 33 compared to the control(Peta-glucanase and medication reduced the ileal viscosity at d 11 compared to the control(P=0.010).Ileal propionic acid concentration at d 11 and caecal total SCFA,acetic,and butyric acid concentrations at d 33 were lower in the BGase-supplemented diet than in the control(Pthe BGase-added diet had higher duodenal p H compared to the control at d 33(P=0.026).the effect of medication on carbohydrate fermentation was minimal.Diet medication increased weight gain after d 11,whereas BGase increased the gain for the total trial period compared to the control(Peed intake was not affected by the dietary treatment.Medication and BGase improved feed efficiency after d 11 compared to the control(Pthe response to diet medication was larger than BGase,considering weight gain and feed efficiency after d 11(Pet medication and BGase depolymerized high molecular weight ileal solubleβ-glucan and increased overall bird performance.Die

关键词： Beta-glucan Prebiotic Non-starch polysaccharide Soluble fiber Feed antibiotic

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光照时间对肉鸡生长及腿病的影响

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国外畜牧学（猪与禽） 1990年第5期10卷 44-46页

作者：倪苗娟 H.L.classen 加拿大萨斯卡切温大学动物和家禽科学及兽医病理系

先是短光照然后逐渐或突然增加光照时间,可促进肉鸡生长,改善健康,减少腿病和死亡,从而产生巨大经济效益。引言在饲养肉鸡时补充光照能最大限度地提高饲料采食t和饲料利用率。

关键词：肉鸡鸡光照时间生长腿病

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