| Nitrogen(N) and phosphorus(P) are the two most important limiting nutrients controlling the species composition,diversity,dynamicss,and functioning of terrestrial and aquatic ecosystems. The direct effects of fertilization on nutrient availability in ecosystems have been well studied, however little is known about the indirect effects of fertilization on herbivores or detritivores and subsequent changes imposed on community and ecosystem properties.To better understand animal community's responses to fertilization and the underlying ecological mechanisms,we studied the effects of different fertilizers(organic fertilizer,PK,NPK and N) and nitrogen application rate(0,172.5,345.0,690.0,and 1035.0 kg N·ha-l·y-1) on tea plants and animal communities in tea plantations in Wuyishan,Fujian,China from August 2004 to December 2005. The relationships between the fertilizer-induced changes on productivity and chemical quality of tea plants and the composition,diversity and abundance of animal communities in the tea plantations were analyzed.The results are as follows:1.Effects of fertilizer application on tea productivity and physiologyNPK and N application significantly increased productivity(i.e.,young shoot biomass) and yield of tea plants.The effects were greater with NPK than N application.The increase by PK or organic fertilizer application was insignificant.Applications of NPK,N,PK or organic fertilizer significantly increased tissue nitrogen,and total and individual amino acids,while they decreased the tissue C/N ratio.The effects were greater with NPK or N than PK or organic fertilizer.NPK,N or PK significantly increased caffeine concentration,but not organic fertilizer.Either NPK or PK significantly increased content of total sugars with NPK more so than PK,but not when N or organic fertilizer was applied.NPK or N significantly decreased tea polyphenol content and polyphenol/amino acid ratio,but not with PK or organic fertilizer.2.Effects of N application on tea productivity and physiologyTea plants showed a moderate response to the N applications.The relationship between productivity or yield and the application rate was mostly quadric patterns,with the highest productivity and yield achieved at N application of 732.60 and 769.26 kg·ha-1·y-1,respectively.The tissue N,caffeine,total and individual amino acid contents significantly correlated,either with a quadratic or linear relationship,to the application rate.Excessive N usually produced no further increase,if not a decrease.Response of total or individual amino acids to the application rate varied with time and largely depended on the tissue N concentration.Polyphenol content and polyphenol/amino acid ratio decreased significantly with increasing N application.Total sugars showed a significant,cubic correlation with the application.Moderate N application tended to increase,while a high level application reduced the sugar content. Amino acids and total sugars in young and mature shoots,as well as caffeine in young shoots and C in mature shoots,significantly and positively correlated to the tissue N concentration.C/N and polyphenol/amino acid ratios in young and mature shoots;and nitrate N in young shoots and polyphenols in mature shoots significantly and negatively correlated to tissue N.However, caffeine in mature shoots showed a significant,quadric relationship with tissue N.There was no correlation between C content or polyphenols and tissue N concentration.N,amino acids,caffeine and total sugar contents in young and mature shoots were significantly and negatively related to the C/N ratio.Tea polyphenols in mature shoots and polyphenol/amino acid ratio in young and mature shoots significantly and positively correlated with the C/N ratio,but C concentration in young and mature shoots and polyphenols in young shoots showed no correlation with the C/N ratio.The results indicated that tissue N and the C/N ratio could reflect the tea chemical quality to a certain extent,but not C or polyphenols in young shoots.Therefore,it would be necessary to consider tissue N,C/N ratio and polyphenols in studying N-induced changes relating to the plant quality(e.g.,chemical composition) and herbivores.The results suggested that the seasonal tea productivity reduction associated with excessive N application was the result of the decreased amino acid metabolism in spring shoots,total sugar metabolism in summer shoots and amino acid and caffeine metabolism in autumn shoots.3.Composition,structure and diversity of animal community in tea plantationIn total,149,725 animals belonging to 3 phylums,8 classes,31 orders,252 families and 1,188 species were collected from the tea plantation.Among them,450 were herbivores(i.e.,37.88%of all species),323 predators(27.19%),133 parasitoids(11.20%),230 detritivores(19.36%) and 52 omnivores(4.38%).Homoptera,Sarcoptiformes,Stylommatophora and Coleoptera were ecological dominance groups,and Stylommatophora,Orthoptera and Lepidoptera were resource dominance groups in the community.The greatest majority(i.e.,98.99%) of the total animal species were occasional and rare species,and 90.91%unimportant resource species.The relationships between species and abundance for all animals,herbivores,predators, parasitoids and detritivores fitted both logarithmic normal distribution and logarithmic series distribution.On the other hand,for omnivores the relationship fitted only a logarithmic series distribution.Diversity,abundance and evenness of animal community and trophic groups showed evidence of a seasonal dynamics.Their diversity indexes significantly and positively correlated to the species richness and evenness.The animal community stability was significantly and positively related to diversity and evenness.Animal species richness increased in a power function with increasing sampling area,while animal abundance(i.e.,number of individuals and total biomass) showed a linear increase. Separately,animal species richness,number of individuals and total biomass positively correlated with mean animal species richness,individual number and total biomass in adjacent plots.The species richness of the animal community,herbivores,predators,detritivores or omnivores showed a significant power function correlation with the number of the individuals.So did the species richness of Hemiptera,Homoptera,Coleoptera,Lepidoptera,Hymenoptera,Diptera and Araneida.On the other hand,the species richness of parasitoids or Orthoptera increased significantly as the number of the individuals increased.The results suggested that the size of sampling area and spatial pattern could affect animal diversity and abundance,and that species richness of animal community,as well as trophic and order groups positively correlated with the number of individuals.Based on the ecological and resource dominance indexes,it was found that Kaliella depressa (Moellendorff),Aonidiella citrine(Coquillet),Empoasca vitis Gothe,Toxoptera aurantii Boyer, Aleurocanthus spiniferus Quaintance,Carpophilus obsoletus Erichson,Dialeurodes citri Ashm, Pyralididae sp.1,Buzura suppressaria Guenee,Brddybaena similaris(Ferussac) and Xenocatantops brachycerus(Willenmse) were important animal pests in tea plantations;Anystis baccarum Linnaeus,Trachelas japonicus Boesenberg et Strand,Erigonidium graminicolum(Sun de Vall),Bdellidae sp.,Evarcha albaria(L.Koch),Ducetiajaponica Thunberg,Anotogaster sp., Sphedanolestes impressicollis St(?)l,Orius similis Zheng,Oxyopes sertatus L.Koch and Misumenops tricuspidatus(Fabricius) were important natural enemies;and,Oribatida sp.1 and Isotomidae sp.1 were dominant species of detritivores.However,there was no dominant species of parasitoids and omnivores.4.Animal species diversity,abundance and body size relationshipsThe empirical relationships among body size,species richness and number of individuals might give insight into the factors controlling species diversity and the relative abundances of species. Among total animals,trophic groups and the 8 most abundant taxonomic orders(i.e.,Hemiptera, Homoptera,Coleoptera,Lepidoptera,Hymenoptera,Orthoptera,Diptera and Araneida),species richness and numbers of individuals were related to body sizes as unimodal diversity patterns. However,the peak sizes,number of species and number of individuals differed among the groups. Species richness peaked with intermediate body sizes for all animals or individual groups.It was the same on the number of individuals for predators,parasitoids,omnivores and abundant taxonomic orders(except Homoptera).However,the number of individuals peaked with small body sizes for all animals,herbivores,detritivores and Homoptera.Body size of a species depended on the species' evolutionary history(taxonomic order),trophic role(contemporary trophic group) and interaction of the two factors.Species richness(Si) within a size class related to the number of individuals(Ii) as Si=1.511 Ii0.436.For the majority of the trophic groups(except herbivores) and taxonomic orders(except Homoptera),the correlations were of similar power functions.However,for herbivores or Homoptera the correlations belonged to more complicated power functions.Only a part of predators(i.e.,26%) was larger than their preys.Number of individuals or biomass) of most predators was less or smaller than their prey.Body mass,number of individuals or biomass of predators significantly and positively correlated to those of their preys.5.Effects of fertilizer application on animal communities and underlying ecological mechanismsApplication of organic fertilizer or PK increased,but that of NPK or N decreased species distribution evenness among orders for animal communities.Organic fertilizer,PK,NPK or N increased species abundance evenness for animal communities,and the effect of organic fertilizer or PK was greater than that of the others.Different fertilizers differed on their effect on species distribution evenness among orders,the species abundance evenness for each trophic group,as well as the species distribution evenness among families for the 8 most abundant orders.N and NPK significantly increased animal species richness.Organic fertilizer,N and PK significantly increased animal diversity.However,organic fertilizer and PK showed no effect on animal species richness,nor did NPK on animal diversity.Organic fertilizer significantly increased effective diversity of herbivores,while it decreased species richness of detritivores.N application significantly increased species richness of detritivores.However,no fertilizers showed any effect on other diversity indices for trophic groups.Organic fertilizer significantly decreased species richness of Hemiptera insects.N and NPK applications significantly increased effective diversity of Homoptera insects.However,all 4 fertilizers showed no effect on other diversity indices within orders.Applications of organic fertilizer and PK significantly decreased the number of individuals for all animals.NPK significantly increased total animal biomass.But,the effects of N and NPK on number of all animals and those of organic fertilizer,and PK and N on total animal biomass were not significant.Organic fertilizer significantly decreased numbers of herbivores,predators and omnivores,as well as detritivore biomass.NPK significantly increased herbivore biomass,and decreased numbers of predators and detritivores.PK significantly decreased number of predators and detritivores.However,all 4 fertilizers showed no effect on other abundance indices for trophic groups.The results showed that organic fertilizer or PK benefited the control of animal pests(esp. Homoptera pests);number of predators decreased as the numbers of herbivores and detritivores decreased;and,moderate N fertilization did not significantly increase the number of animal pests. Responses of individual animals to fertilization varied according to the application.Fertilizer application had different and significant effects on 10 of the 18 abundant animals(i.e.,8 most abundant herbivores,8 most abundant predators and 2 most abundant detritivores).Organic fertilizer and PK significantly increased animal community evenness.But,the effects of NPK and N were not significant.Organic fertilizer application significantly increased herbivore evenness.Organic fertilizer,PK and N significantly increased the evenness of Lepidoptera insects. However,the effects of different fertilizers on other trophic groups and orders were not significant. Organic fertilizer and PK increased animal community stability through increasing S/N,but not NPK or N. Fertilizer-induced changes in animal species richness in tea plantations depended on the integrated actions of plant productivity,and the contents of total sugars and polyphenols of tea plants.But the changes in number of animals depended on the integrated actions of plant productivity,and the contents of amino acids and total sugars of tea plants.Responses of species richness and abundance of trophic groups,as well as the abundance of 18 abundant animals,to fertilization varied with fertilizer-induced changes in plant productivity and chemical quality tea plants,through different mechanisms,which also often depended on the integrated actions of the productivity and chemicals of tea plants.This study demonstrated that short-term fertilizer application affected the entire food chain in the tea plantation ecosystem.6.Effects of N application on animal communities and underlying ecological mechanismsN application reduced species distribution evenness among orders for animal communities, predators and detritivores,while increasing it for herbivores.Different N application rates had different effects on species evenness distribution among families for the 8 most abundant orders. N slightly reduced species abundance evenness for the animal community.It had the greatest effect on species abundance evenness for detritivores.The effects for parasitoid and predators were greater than herbivores.Species richness of all animals and detritivores,as well as predator species richness and effective diversity,significantly correlated in quadratic functons with N application rate.Effective animal diversity showed a cubic relationship with the application rate.However,there was variation in trophic responses to N,species richness of herbivores and effective diversity of parasitoids increased as N increased,while effective diversity of herbivores decreased.But,the species richness of parasitoids and omnivores,as well as effective diversity of detritivores and omnivores,showed no responses to the N application.For the 8 most abundant orders,only N had a complicated and different effect on the species richness of Hemiptera,Lepidoptera and Araneida groups,as well as the effective diversity of Hemiptera and Coleoptera groups.Number of all animals and the abundance(i.e.,number of individuals,biomass) of herbivores, predators and detritivores were significantly and positively related to the rate of N application. Biomass of all animals and omnivores significantly correlated with N application rate in quadratic equations.But,parasitoid abundance(i.e.,number of individuals,biomass) and number of omnivores showed no responses to the application.For the 8 most abundant orders,N had a complicated and different effect on the abundance(i.e.,number of individuals,biomass) of Hemiptera and Homoptera insects,as well as biomass of Lepidoptera insect and number of Coleoptera,Orthoptera and Araneida arthropods.Responses of individual animals to the fertilization varied with N gradient.N had different and significant effects on 8 of the 18 abundant animals. Animal community evenness showed a cubic correlation with N application.Herbivore evenness increased as N increased;predator evenness showed a quadratic relationship with the N application,excessive N reduced the evenness;parasitoid evenness slightly increased with N increasing;and,evenness of detritivores and omnivores were not affected.Responses of the 8 most abundant orders to N fertilization varied with N gradient.It only affected the evenness of Hemiptera and Homoptera insects.Animal community stability index,S/N,decreased as N was increased,Sn/Sp(ratio of natural enemy species richness to animal pest species richness) and Sn/Sp'(ratio of natural enemy species richness to prey species richness) showed quadratic relationships,and Nn/Np(ratio of natural enemy number to animal pest number) and Nn/Np'(ratio of natural enemy number to prey number) showed cubic relationships with the rate of N application.This suggested that the effect of N on animal community stability was very complicated,and that N overuse could reduce it.N-induced changes in animal species richness in tea plantations depended on the integrated actions of plant productivity,the contents of tissue N,amino acids,caffeine,total sugars and polyphenols,and C/N ratio and polyphenol/amino acid ratio of tea plants.But the changes in effective animal diversity depended on the integrated actions of plant productivity,the contents of tissue N,caffeine and polyphenols,and C/N ratio of tea plants.N-induced changes in the number of all animals depended on the integrated actions of plant productivity,and amino acids and caffeine concentrations.But the changes in total animal biomass depended on the integrated actions of plant productivity,the contents of tissue N,amino acids,caffeine and polyphenols,and C/N ratio of tea plants.Responses of trophic group diversity(i.e.,species richness and effective diversity),as well as the abundance of trophic groups and 18 abundant animals,to N application varied with N-induced changes in plant productivity and chemical quality through different mechanisms,which also often depended on the integrated actions of the productivity and chemicals of tea plants.This study demonstrated that short-term N application affected the entire food chain in the tea plantation ecosystem.Better understanding of the interactions of varieties,nutrients,pests,yield and production costs involving the tea plantation will allow an improved integration of the pest and nutrient management to maximize benefits for the farmers and producers.A mathematic model for calculating tea production profit and N application was established as follows: Y=132,797+482.9079x-0.3177x2,where Y= profit in RMB·ha-1·y-1,and x= N in kg·ha-1·y-1.It suggests that the optimum rate of nitrogen application would be 760.01 kg·ha-1·y-1 for Wuyishan Rougui oolong tea plantations.
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