Photosynthetic Metabolism,Respiratory Metabolism And Allometric Law Of Herbaceous Plants Under Different Density Gradient

According the metabolic theory of ecology (MTE), the relationship of metabolic rate and plant body size has a different allometric exponent for plant individuals which have different body size. The exponent is 1 when plant body size is little, but to the large individual that is 3/4. Furthermore, according the metabolic theory of ecology, metabolic rate increase exponently with temperature. As a consequence, we should correct the metabolic rate by the use of temperature. Based the metabolic theory of ecology, we can deduce some isometric relationship between different biomass. It is well-know that in high density population, compete for the limited resource will resulted a part of plant individuals to die, we called this process self-thinning. According the metabolic theory, we can deduce the allometric exponent between population density and body size is -4/3. Although that conclusion has been prove but there are still some controversy. Especially for plants which growth under different density, whether its metabolic rate and biomass-partitioning rule followed the deduction of MTE is unknown. Because of the competitive stress caused by neighborhood plant. In order to solve that reason, we use 10 species herbaceous plant as research object, set three density gradient and measure correlative index. Our results showed that:1) In low density gradient, the allometric exponent between photosynthetic rate and body size is 0.974, and between respiratory rate and body size is 1.004. There is no significant differences between the two exponents and 1. The results accord with theoretical predictions.2) In medium and high density gradient, the allometric exponent between metabolic rate and body size is diminished gradually along with density increased. Furthermore, that allometric exponent between 1 and 3/4.3) The allometric scaling relationship between above-biomass and population density complied with the -4/3 self-thinning rules, the relationship between individual biomass and population density is similar.4) The relationship between stem biomass and population density complied with -3/2 self-thinning rule, and the root biomass comply with the law of constant final yield.5) In low density gradient, the scaling exponent between leaf biomass and stem biomass is 0.945, the similar exponent between leaf and root is 1.001. In addition, the exponent between stem and root is 1.057.6) In medium density gradient, the similar exponents are 0.700,0.781 and 1.203 respectively. In high density gradient, the exponents are 0.659,0.623 and 1.499 respectively. In a word, we concluded that all allometric scaling relationship conform to the MTE theoretical predictions in low intensity of competition, but in high intensity of competition is not conformed. As a consequence, not only the MTE but also all the inference come from MTE need further improvement and development. And it should be integrate the physiological mechanism of competition in order to make the MTE expanded to plant community level. Our research by means of the different density gradient study of different species, collected the first-hand experimental data, obtained a series of results above-mentioned, lay the foundation for the further development of the metabolic theory.