Discussion on geobiology, biogeology and geobiofacies

Here we first discuss the definition of and the difference between geobiology and biogeology following a brief introduction of recent geobiology research in China. Geobiology is defined as an interdisciplinary study of life sciences and earth sciences, and biogeology as an interdisciplinary study of biology and geology. Scope of the term geobiology covers that of the term biogeology. Branch interdisciplines of both are listed. We then propose the term geobiofacies, defined as the facies of a geologic body embodying the whole process of interaction between organisms and environments. Differences among geobiofacies, biofacies, and organic facies are discussed. Main parameters defining a geobiofacies include habitat type, biotic composition and productivity, paleo-oxygenation regimes, and early diagenesis phases. Each of them is discussed in detail, and a semi-quantitative assessment of the biogeofacies of source rocks is proposed based on these parameters. A two-fold terminology for geobiofacies is recommended, namely, the biological and environmental aspects of biota and the redox conditions during life-burial-diagenesis process

The universal applicability of logistic curve in simulating ecosystem carbon dynamic

As an S-shaped curve,the logistic curve has both high and low limit,which provides advantages in modelling the influences of environmental factors on biogeological processes.However,although the logistic curve and its transformations have drawn much attention in theoretical modelling,it is often used as a classification method to determine a true or false condition,and is less often applied in simulating the real data set.Starting from the basic theory of the logistic curve,with observed data sets,this paper explored the new application scenarios such as modelling the time series of environmental factors,modelling the influence of environmental factors on biogeological processes and modelling the theoretical curve in ecology area.By comparing the performance of traditional model and the logistic model,the results indicated that logistic modelling worked as well as traditional equations.Under certain conditions,such as modelling the influence of temperature on ecosystem respiration,the logistic model is more realistic than the widely applied Lloyd-Taylor formulation under extreme conditions.These cases confirmed that the logistic curve was capable of simulating nonlinear influences of multiple factors on biogeological processes such as carbon dynamic.

Origin area and migration route: Chloroplast DNA diversity in the arctic-alpine plant Koenigia islandica

The Hengduan Mountains(henceforth H-D Mountains) on the Tibet Plateau are a distribution and diversity center for many alpine genera. We examine patterns of genetic variation in an arctic-alpine plant to evaluate the possibility that the H-D Mountains constitute the area of origin of the species as well as to uncover postglacial migration routes. 220 individuals of the arctic-alpine plant Koenigia islandica were sampled from 26 populations distributed in western China and northern Finland. DNA haplotypes were identified using restriction site analysis of two chloroplast DNA intergene spacer regions, atpB-rbcL and trnL-trnF. We examined the geographical distribution of haplotype diversity in relation to latitude, and also compared various indices of diversity in putatively glaciated and unglaciated regions. Patterns of migration were inferred using nested clade analysis. A total of 25 haplotypes were detected. High haplotype diversity was found in the H-D Mountains. H3 and its radiated haplotypes were distributed in the Himalayas. Two haplotypes were fixed concurrently in the H-D Mountains and northern Finland. High genetic diversity of K. islandica and high species diversity of K. islandica are expected in the origin area. Our observations suggest that the H-D Mountains are not only the place of origin of K. islandica, but also the refugia for K. islandica on the Tibet Plateau. What is more, the migration route for the arctic-alpine plant K. islandica must have originated in the region defined by the H-D Mountains in western China extending northward to the Arctic circumpolar, and moved westward along the Himalayas, then northward across the Altay Mountains and the Central Siberian Plateau at different time periods.