Effect Of Biotic And Abiotic Factors On Biomass Allocation Pattern For Different Plant Types

Resource metabolism and allocation are the basic traits of all organisms.The metabolic and allocation rules are the central scientific issues,and many biologists and ecologists pay much attention to them.Plant resource metabolism and allocation play an important role in the ecosystem because the allocation of plant photosynthetic product between different plant organ parts not only affects species fitness and product,but also it affects the resource circulation and other functions in the whole ecosystem.Plant resource allocation pattern is often influenced by both biotic and abiotic factors in order to adapt to the local environment.However,it is still not clear how the biomass allocation patterns of desert plants such as shrubs and ephemerals are regulated by the interactive stress of environmental factors such as water and temperature.Moreover,how these biotic and abiotic factors regulate plant biomass allocation pattern and whether there is a general regulation law is still unknown.Therefore,we focus on this program based on the data from desert plants and global forests.First,we study the biomass allocation pattern and the intrinsic mechanism for two different types of desert plants.Second,we develop a general theoretical framework to discuss the effect of biotic and abiotic factors on plant biomass allocation pattern based on the desert plant data we surveyed in the field and global forest data.In addition,based on the theory from optimal control and kin selection,we study how plants achieve the optimal allocation strategy between plant vegetative organ and reproductive organ under the interactions among neighborhoods.According to the analysis,we achieve the following conclusions:1.The scaling relationship between above-and belowground biomass is allometric for both desert ephemerals and shrubs(i.e.the scaling exponent is not 1)which is much different from that of forests.Moreover,the numerical values of the scaling exponents exhibit species-and environmental-specific patterns.For ephemeral species,the numerical values of the scaling exponents of above-vs.belowground biomass sorted for rainfall are significantly different between species in arid zones and in semiarid zones.In contrast,the scaling exponents for desert shrubs are numerically insensitive to differences in rainfall in arid zones and semiarid zones.For ephemeral species,the scaling exponents are insensitive to differences in temperature in temperate zones and warm temperate zones.For desert shrub species,however,the numerical values of the scaling exponents differ significantly with respect to the differences in temperature in temperate zones and warm temperate zones.The regression relationships for root-shoot ratio vs.total biomass and root-shoot ratio vs.aboveground biomass are statistically much weaker in comparison with these of root-shoot ratio vs.belowground biomass for both ephemeral plants and desert shrubs.The main reason is that ephemerals allocate more biomass to aboveground to finish the life history during the rainy season,while desert shrubs need to allocate more to belowground to reduce the damage from low temperature and to achieve available water from underground.2.The numerical values of the empirically determined scaling exponents for biotic interactions are in statistical agreement with those predicted by theoretical models for the worldwide forest datasets and different forest growth types.Pairwise correlation analysis shows that the leaf biomass fraction for all forest communities is inversely proportional to plant height and have a positive correlation with plant density,but is little affected by mean annual precipitation and temperature(MAP and MAT).However,the shoot biomass fractions are insensitive to differences in plant density and plant height as well as MAP and MAT.Moreover,multiple regression analyses and structural equation models also show similar results.The same results are observed for each of the three forest datasets.The temperature has a relatively strong effect on plant leaf biomass fraction for desert plants in comparison with other biotic and abiotic factors.With the pooled data from both forest and desert plants,the analysis shows that biotic factors have a bigger effect on plant leaf biomass fraction than abiotic factors,and all biotic and abiotic factors have much weak effect on shoot biomass fraction.3.The data show that either MAP or MAT,or both have a statistically discernable effect on the numerical values of normalization constants for the scaling relationships of leaf vs.total biomass and leaf biomass fraction vs.height.Both the Relative Variation Coefficient of leaf biomass and shoot biomass fraction are significantly proportional to that of climate across all of the plant families in forest data sets although the climate has a weak effect on leaf and shoot biomass fraction for total forest data.According to Monte Carlo simulations,our statistical analyses show that the overlap in the numerical values of biomass fractions across ten families is significantly higher than that for climatic factors.The results indicate that plants with different types have different biomass allocation pattern under the influence of the local environment rather than under the global climate gradients.4.The effects of both positive and negative kin selection on plant transition process from vegetative growth to reproductive growth provide another mechanism to explain plant optimal life history strategies,and the theoretical analyses lay the foundation for improving crop yield in population level.According to the research,we observed the mechanisms that regulate plant biomass allocation pattern for different plant types under different environmental conditions,and we developed a general theoretical framework about plant resource allocation pattern under the regulation of both biotic and abiotic factors.This will provide a foundation for further discussing the generality of isometric theory and optimal allocation theory.In addition,it will have great significance in improving agricultural yield and the management of desert and forest ecosystems.