The Effect Of Genotypic Diversity On Community Ecological Function

In recent years, human activities have affected the global environments continuously and seriously, which followed by rapid global extinction rate, and the ecosystem consequences have got wide attention. So the study of relationship between biodiversity and ecological function is attached great importance. But these studies were mostly focused on species diversity level. Results showed that the species diversity had a positive effect on the ecological function, such as increasing productivity, improve the system stability and so on. Genotypic diversity is a key component of biodiversity. In recent years, with the development of molecular genetic marker, the relationship between the genotypic diversity and ecological function gradually began to get the wide attention of people. Studies have shown that genotypic diversity can have ecological effects similar to the species diversity. For example, genotypic diversity can increase productivity, speed up the recovery ability after interference, enhance the capacity of resistance to interference, change the community structure and so on. But not all studies have consistent results, genotypic diversity and ecological function relationship is worthy of further discussion. Leymus chinensis is widely distributed in Eurasia and is one of the important building groups in the eastern Eurasia savanes meadow steppe and arid steppe. Because of its wide distribution, diversity habitat type and strong ecological adaptability, Leymus chinensis formed the populations of different genotypes eventually in the long evolution process to adapt to the environments.This study used Leymus chinensis of 12 different genotypes as the experimental material. Through the control of the number of genotypes within Leymus chinensis population, we’ve set Leymus chinensis population having five genotypic diversity levels, namely, one genotype level,2-,4-,8-and 12- genotypic diversity level. And basing on the measurement and analysis of Leymus chinensis biomass, soil nutrient content, insect diversity and weed diversity at each genotypic diversity level, we preliminary discussed the effects of genotypic diversity on community ecological function. At the same time, we measured the growth characteristic index of Leymus chinensis of 12 different genotypes and comparised the growth characteristic of Leymus chinensis of different genotypes. We mainly got the following results:(1)Leymus chinensis vegetative tiller height and weight of different genotypes had significant difference, at the same time Leymus chinensis vegetative tiller height and weight of different genotypes were in accordance with significant and different linear regression relationships. Reproductive tiller height, weight, spike length, spike weight and reproductive allocation of different genotypes were significant different. Population density, above-ground biomass and leaf area index of different genotypes also existed significant differences. But analysis of leaf nutrient content of different genotypes showed only total nitrogen content had significant differences, and organic carbon content did not exist significant differences. Although there was no significant difference between the overall phosphorus content, significant differences also existed between some two genotypes. At the same time, none all indicators of the genotype were optimal or better. SMA regression analysis showed that spike weight and tiller weight of Leymus chinensis of different genotypes conformed to significant allometric relationships, and allometric slopes of all genotypes were significantly different with 1 except for 4 genotype. That suggested that reproductive allocation of all genotypes were allometric process and depend on tiller size, plants allocated more biomass to the spikes except for 4 genotype. However, the different allometric slopes among the different genotypes also showed the different allometric allocation strategied among the different genotypes. These results above indicated that Leymus chinensis of different genotypes had formed the different strategies of growth and reproduction.(2)With the increase of genotypic diversity level, total biomass, under-ground biomass,0-10cm under-ground biomass,10-20cm under-ground biomass of Leymus chinensis significantly increased, but there was no significant difference between 20-30cm under-ground biomass. The above-ground biomass increased first but then reduced as genotypic diversity level increasing, but multi-genotype populations always had more above-ground biomass than one genotype populations. With the increase of the genotypic diversity level, the rate of the above-ground biomass and under-ground biomass had no significant differences. This suggested that the primary productivity of Leymus chinensis population was affected by genotypic diversity level, primary productivity of multi-genotype populations were higher than one genotype populations, but the rate of the above-ground biomass and under-ground biomass did not influenced by genotypic diversity.(3)Within a certain range,0-10cm soil organic carbon content increased with the increase of genotypic diversity level. As genotypic diversity level increased to a certain extent,0-10cm soil organic carbon content decreased. And except for 12-genotypic diversity level,0-10cm soil organic carbon content of the rest genotypic diversity level increased. It meant that the increase of genotypic diversity level can promote the increase of 0-10cm soil organic carbon content within a certain range, but when the genotypic diversity level increased to a certain degree, the increase effect on 0-10cm soil organic carbon content reduced. Both 20-30cm soil organic carbon and total nitrogen content was not significantly different between each genotypic diversity level, and the change in 20-30cm soil organic carbon and total nitrogen content also had no significant differences. It suggested that 20-30cm soil organic carbon and nitrogen content did not influenced by genotypic diversity. Genotypic diversity had no significantly effect on 10-20cm soil organic carbon content,0-10cm and 10-20cm soil total nitrogen content. Among genotypic diversity levels,0-10cm,10-20cm and 20-30cm soil total phosphorus content were not significantly different, variations of oil total phosphorus content were also not significantly different, which indicated the content of soil phosphorus did not influenced by genotypic diversity.(4)In may, with the increase of genotypic diversity level, insect Patrick richness index, Gleason richness index, Shannon-weinner information index and Simpsom index increased first and then decreased, but were always higher than that of one genotype level. And there was no significant difference between Pielou evenness index. It showed that the richness and evenness of insect influenced by genotypic diversity level, insect richness and evenness of multi-genotype population were higher than that of one genotype population. Simpsom index in June, Shannon-weinner information index in July and Simpsom index and Pielou evenness index in September, they decreased first and then increased with the increase of genotypic diversity level. It indicated that genotypic diversity reduced the richness and evenness of insect, and then increased the richness and evenness of insect. In August, with the increase of the genotypic diversity level, insect diversity index had no significant difference. Analysis of insect diversity index data in different periods showed that the effects of genotype diversity on insect diversity changed over time.(5)With the increase of genotypic diversity level, weed Patrick richness index, Gleason richness index, Shannon-weinner information index, Simpsom index and Pielou evenness index showed increasing trends, but the Shannon-weinner information index and Pielou evenness index did not differ significantly. With the increase of genotypic diversity level, weed richness and evenness increased. It indicated that genotypeic diversity affected the species coexistence, the increase of genotypic diversity level can contribute to species coexistence.Synthesize the above results, growth charateristics of Leymus chinensis of different genotypes were significantly different. The increase in Leymus chinensis genotypic diversity could improve primary productivity of populations, change composition of insect community and improve species coexistence. But genotypic diversity only had influence on the surface soil organic carbon content, which indicated that the effect of genotypic diversity on soil nutrient dynamic was not obvious. It may take longer time that genotypic diversity shows the influence on the dynamic of soil nutrients. The results will provide scientific theoretical guidance for the protection and rational utilization of Leymus chinensis grassland in the future.