最大熵原理(the principle of maximum entropy)起源于信息论和统计力学,是基于有限的已知信息对未知分布进行无偏推断的一种数学方法。这一方法在很多领域都有成功应用,但只是近几年才被应用到生态学研究中,并且还存在很多争论。我们...最大熵原理(the principle of maximum entropy)起源于信息论和统计力学,是基于有限的已知信息对未知分布进行无偏推断的一种数学方法。这一方法在很多领域都有成功应用,但只是近几年才被应用到生态学研究中,并且还存在很多争论。我们从基本概念和方法出发,用掷骰子的例子阐明了最大熵原理的概念,并提出运用最大熵原理解决问题需要遵从的步骤。最大熵原理在生态学中的应用主要包括以下方面:(1)用群落水平功能性状的平均值作为约束条件来预测群落物种相对多度的模型;(2)基于气候、海拔、植被等环境因子构建物种地理分布的生态位模型;(3)对物种多度分布、种-面积关系等宏生态学格局的推断;(4)对物种相互作用的推断;(5)对食物网度分布的研究等等。最后我们综合分析了最大熵原理在生态学应用中所存在的争议,包括相应模型的有效性、可靠性等方面,介绍了一些对最大熵原理预测能力及其局限性的检验结果,强调了生态学家应用最大熵原理需要注意的问题,比如先验分布的选择、约束条件的设置等等。在物种相互作用、宏生态学格局等方面对最大熵原理更广泛的讨论与应用可能会给生态学带来新的发展机会。展开更多
The identification of easily measured plant functional types (PFTs) that consistently predict grazing response would be a major advance.The responses to grazing of individual traits and PFTs were analyzed along a graz...The identification of easily measured plant functional types (PFTs) that consistently predict grazing response would be a major advance.The responses to grazing of individual traits and PFTs were analyzed along a grazing gradient in an alpine shrub meadow on the Qinghai-Tibet Plateau,China.Three response types were identified;grazing increaser (GI),grazing decreaser (GD),and neutral (NE) for both traits and PFTs.Seven traits were measured:plant height,economic group,cotyledon type,plant inclination,growth form,life cycle,and vegetative structure.The first five were significantly affected by grazing.Ordinal regressions for grazing response of the seven traits showed that the best single predictors of response were growth form (including the attributes "Scattered","Bunched" or "Closely Bunched"),and plant inclination ("Rosette","Prostrate",or "Erect"),followed by economic group ("Shrub","Grass","Sedge","Legume","Forb",or "Harmful") and plant height ("Tall","Medium",or "Small").Within the four optimal traits,the summed dominance ratio (SDR) of small plants,forbs,rosette and bunched plants,invariably increased,while that of tall plants,shrubs,grasses,and erect plants decreased,when grazing pressure was enhanced.Canonical correspondence analysis (CCA) identified eleven explanatory PFTs based on 195 defined PFTs,by combining the different attributes of the four optimal traits.Among explanatory PFTs,the most valuable in predicting the community response to grazing were Tall×Shrub×Erect×Scattered and Small×Forb×Rosette,as these have the closest connections with grazing disturbance and include fewer species.Species richness,diversity,and community evenness,did not differ among grazing treatments because turnover occurred in component species and their relative abundances along the grazing gradient.We have demonstrated that a minimum set of PFTs resulting from optimal individual traits can provide consistent prediction of community responses to grazing in this region.This approach provides a more accurate indicator of展开更多
To clarify the responses of plant functional traits to nitrogen(N) enrichment, we investigated the whole-plant traits(plant height and aboveground biomass), leaf morphological(specific leaf area(SLA) and leaf dry mass...To clarify the responses of plant functional traits to nitrogen(N) enrichment, we investigated the whole-plant traits(plant height and aboveground biomass), leaf morphological(specific leaf area(SLA) and leaf dry mass content(LDMC)) and chemical traits(leaf N concentration(LNC) and leaf phosphorus(P) concentration(LPC)) of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates(0 g N/(m2·yr), 6 g N/(m2·yr), 12 g N/(m2·yr) and 24 g N/(m2·yr)) in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.展开更多
文摘最大熵原理(the principle of maximum entropy)起源于信息论和统计力学,是基于有限的已知信息对未知分布进行无偏推断的一种数学方法。这一方法在很多领域都有成功应用,但只是近几年才被应用到生态学研究中,并且还存在很多争论。我们从基本概念和方法出发,用掷骰子的例子阐明了最大熵原理的概念,并提出运用最大熵原理解决问题需要遵从的步骤。最大熵原理在生态学中的应用主要包括以下方面:(1)用群落水平功能性状的平均值作为约束条件来预测群落物种相对多度的模型;(2)基于气候、海拔、植被等环境因子构建物种地理分布的生态位模型;(3)对物种多度分布、种-面积关系等宏生态学格局的推断;(4)对物种相互作用的推断;(5)对食物网度分布的研究等等。最后我们综合分析了最大熵原理在生态学应用中所存在的争议,包括相应模型的有效性、可靠性等方面,介绍了一些对最大熵原理预测能力及其局限性的检验结果,强调了生态学家应用最大熵原理需要注意的问题,比如先验分布的选择、约束条件的设置等等。在物种相互作用、宏生态学格局等方面对最大熵原理更广泛的讨论与应用可能会给生态学带来新的发展机会。
基金supported by National Natural Science Foundation of China (Grant Nos. 30671490, and 31070382)
文摘The identification of easily measured plant functional types (PFTs) that consistently predict grazing response would be a major advance.The responses to grazing of individual traits and PFTs were analyzed along a grazing gradient in an alpine shrub meadow on the Qinghai-Tibet Plateau,China.Three response types were identified;grazing increaser (GI),grazing decreaser (GD),and neutral (NE) for both traits and PFTs.Seven traits were measured:plant height,economic group,cotyledon type,plant inclination,growth form,life cycle,and vegetative structure.The first five were significantly affected by grazing.Ordinal regressions for grazing response of the seven traits showed that the best single predictors of response were growth form (including the attributes "Scattered","Bunched" or "Closely Bunched"),and plant inclination ("Rosette","Prostrate",or "Erect"),followed by economic group ("Shrub","Grass","Sedge","Legume","Forb",or "Harmful") and plant height ("Tall","Medium",or "Small").Within the four optimal traits,the summed dominance ratio (SDR) of small plants,forbs,rosette and bunched plants,invariably increased,while that of tall plants,shrubs,grasses,and erect plants decreased,when grazing pressure was enhanced.Canonical correspondence analysis (CCA) identified eleven explanatory PFTs based on 195 defined PFTs,by combining the different attributes of the four optimal traits.Among explanatory PFTs,the most valuable in predicting the community response to grazing were Tall×Shrub×Erect×Scattered and Small×Forb×Rosette,as these have the closest connections with grazing disturbance and include fewer species.Species richness,diversity,and community evenness,did not differ among grazing treatments because turnover occurred in component species and their relative abundances along the grazing gradient.We have demonstrated that a minimum set of PFTs resulting from optimal individual traits can provide consistent prediction of community responses to grazing in this region.This approach provides a more accurate indicator of
基金Under the auspices of Strategic Priority Research Program-Climate Change:Carbon Budget and Related Issues of Chinese Academy of Sciences(No.XDA05050508)Ministry of Land and Resources Program(No.201111023,GZH201100203)Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology,Ministry of Land and Resources(No.MRE201101)
文摘To clarify the responses of plant functional traits to nitrogen(N) enrichment, we investigated the whole-plant traits(plant height and aboveground biomass), leaf morphological(specific leaf area(SLA) and leaf dry mass content(LDMC)) and chemical traits(leaf N concentration(LNC) and leaf phosphorus(P) concentration(LPC)) of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates(0 g N/(m2·yr), 6 g N/(m2·yr), 12 g N/(m2·yr) and 24 g N/(m2·yr)) in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.
