Complete plastome sequence of Wrightia laevis Hook. f. a dyestuff species.

Wrightia laevis Hook. f. is a great tree of Apocynaceae. It is mainly distributed in Southeast provinces of China and Southeast Asian countries. It is a plant that combines dyestuff and economic value. There is no study on the genome of W. laevisso far. Here we report and characterize the complete plastid genome sequence of W. laevis in order to provide genomic resources useful for promoting its conservation. The complete chloroplast genome of W. laevis is 155,274 bp in length with a typical quadripartite structure, consisting of a large single-copy region (LSC, 85,463 bp), a single-copy region (SSC, 18,181 bp) and a pair of inverted repeats (IRs, 25,815 bp). There are 133 genes annotated, including 88 unique protein-coding genes, 8 unique ribosomal RNA genes, and 37 transfer RNA genes. The overall G/C content in the plastome of W. laevis is 38.05%. The complete plastome sequence of W. laevis will provide a useful resource for the conservation genetics of this species as well as for phylogenetic studies in Apocynaceae.

Complete plastome sequence of Caesalpinia sappan Linnaeus, a dyestuff and medicinal species.

Caesalpinia sappan Linnaeus is a great tree of Fabaceae. It is mainly distributed in the Southern provinces of China and Southeast Asian countries. It can be used to extract dyes. The heartwood has dyestuff and medicinal value. There is no study on the genome of C. sappan so far. Here, we report and characterize the complete plastid genome sequence of C. sappan in an order to provide genomic resources useful for promoting its conservation. The complete chloroplast genome of C. sappan is 160,176 bp in length with a typical quadripartite structure, consisting of a large single-copy region (LSC, 89,710 bp), a single-copy region (SSC, 18,357 bp), and a pair of inverted repeats (IRs, 26,054 bp). There are 129 genes annotated, including 84 unique protein-coding genes, eight unique ribosomal RNA genes, and 37 transfer RNA genes. The overall G/C content in the plastome of C. sappan is 36.0%. The complete plastome sequence of C. sappan will provide a useful resource for the conservation genetics of this species as well as for phylogenetic studies in Apocynaceae.

A simplified 137Cs transport model for estimating erosion rates in undisturbed soil.

(137)Cs is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of atmospheric testing of thermo-nuclear weapons primarily during the period of 1950s-1970s with the maximum rate of (137)Cs fallout from atmosphere in 1963. (137)Cs fallout is strongly and rapidly adsorbed by fine particles in the surface horizons of the soil, when it falls down on the ground mostly with precipitation. Its subsequent redistribution is associated with movements of the soil or sediment particles. The (137)Cs nuclide tracing technique has been used for assessment of soil losses for both undisturbed and cultivated soils. For undisturbed soils, a simple profile-shape model was developed in 1990 to describe the (137)Cs depth distribution in profile, where the maximum (137)Cs occurs in the surface horizon and it exponentially decreases with depth. The model implied that the total (137)Cs fallout amount deposited on the earth surface in 1963 and the (137)Cs profile shape has not changed with time. The model has been widely used for assessment of soil losses on undisturbed land. However, temporal variations of (137)Cs depth distribution in undisturbed soils after its deposition on the ground due to downward transport processes are not considered in the previous simple profile-shape model. Thus, the soil losses are overestimated by the model. On the base of the erosion assessment model developed by Walling, D.E., He, Q. [1999. Improved models for estimating soil erosion rates from cesium-137 measurements. Journal of Environmental Quality 28, 611-622], we discuss the (137)Cs transport process in the eroded soil profile and make some simplification to the model, develop a method to estimate the soil erosion rate more expediently. To compare the soil erosion rates calculated by the simple profile-shape model and the simple transport model, the soil losses related to different (137)Cs loss proportions of the reference inventory at the Kaixian site of the Three Gorge Region, China are estimated by the two models. The over-estimation of the soil loss by using the previous simple profile-shape model obviously increases with the time period from the sampling year to the year of 1963 and (137)Cs loss proportion of the reference inventory. As to 20-80% of (137)Cs loss proportions of the reference inventory at the Kaixian site in 2004, the annual soil loss depths estimated by the new simplified transport process model are only 57.90-56.24% of the values estimated by the previous model.