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Responses of soil aggregate stability and nutrient stoichiometry to land use change are of great significance to the protection and restoration of fragile ecosystems. In order to explore the influence of the law of land use change on soil aggregate stability and C, N, and P nutrient stoichiometric characteristics in the karst ecosystem of Southwest China, a typical region of the Southwest China Karst was selected as the study area. A series of sample plots were established for the seven typical land use types, and the constitution; stability; and C, N, and P contents and stoichiometric ratios of soil aggregates were studied. The results showed that land use change significantly affected the soil aggregate stability. The soil aggregate stability of corn fields and abandoned land was relatively high, whereas that of grassland and bare land was relatively low. The soil aggregate stability generally decreased with the increase in soil layer. There were significant differences in the C, N, and P contents of soil aggregates between different land use types. The C and N contents of soil aggregates of open woodland and abandoned land were higher, the C and N contents of grassland were lower, and the P contents of soil aggregates of bare land and abandoned land were relatively higher. Land use change also significantly affected the stoichiometric ratio of soil aggregate C, N, and P. The C:N of soil aggregates of arbor forest land, open forest land, and abandoned land was relatively high, and that of grassland was the lowest. The C:P of soil aggregates of arbor woodland and open woodland was higher than that in shrub woodland and grassland. The soil aggregate N:P of arbor forest land, open forest land, and shrub forest land was higher and was significantly higher than that of bare land and abandoned land. There were significant or extremely significant correlations between the constitution and stability of soil aggregates and the stoichiometric characteristics of soil aggregate C, N, and P. Soil aggregate stability was positively correlated with the mass fraction of large soil aggregates. The mass fraction of large soil aggregates increased, and the stability of aggregates correspondingly increased, which was conducive to the maintenance and accumulation of soil C, N, and P nutrients. These results are of great significance for vegetation restoration, soil and water conservation, and land use regulation in karst ecosystems of Southwest China.

Three typical karst rocky desertification regions in South China Karst were selected as experiment sites. The succession of karst rocky desertification was divided into five typical degrees: nil, potential, slight, moderate, and severe. Based on the five typical degrees of rocky desertification, sample plots were set up and soil samples were collected to examine the physical and chemical properties. The pattern, dynamics, and change law of soil physical and chemical properties in the succession of karst rocky desertification were studied. The properties of bulk density, capillary porosity, total porosity, field moisture capacity, capillary moisture capacity, pH, organic matter content, hydrolyzed nitrogen content, available phosphorus content, total potassium content, and soil respiration were studied. Results showed that significant differences in soil physical and chemical properties were observed among different degrees of rocky desertification. These properties initially degenerated and then recovered with increased degree of rocky desertification. The soil quality of nil and severe degree of rocky desertification was better than all others. In the succession of soil physical and chemical properties, the key factors were organic matter content, nitrogen content, bulk density, and moisture capacity. Finally, the response mechanism of soil succession was concluded. The results of this study are useful for management of desertified karst ecosystems.

Background Tartary buckwheat are very popular as an important functional food material and its cultivation is very widespread in our whole world, but there obviously lack works in the researches of genetic breeding for agricultural and medicinal utilization. The aim of this study is to obtain good germplasm resources for agricultural and medicinal use of tartary buckwheat (Fagopyrum tataricum) by inducing the tetraploid plants. Results Four cultivars of F. tataricum, that is, Qianwei 2#, Jinku 2#, Chuanqiao 1#, and Liuqiao 1# were selected to experiment. The tips of seedlings with two true leaves were treated by 0.25% (w/v) colchicine solution for 48, 72, and 96 h, respectively. The chromosome number of treated plants was determined by metaphase chromosome counting of root tip cells and PMCs (pollen mother cells) meiosis observation. Tetraploid induction successfully occurred in all three treatments with an efficiency ranging from 12.13 to 54.55%. The chromosome number of the diploid plants was 2n = 2x = 16, and that of the induced tetraploid plants was 2n = 4x = 32. The typical morphological and physiological qualities were compared between the control diploid and corresponding induced tetraploid plants. Results showed that the induced tetraploid plants had obviously larger leaves, flowers, and seeds. Moreover, the content of seed protein and flavonoid were also increased in the tetraploid plants. The pollen diameter and capsule size of diploid plants were significantly smaller than those of tetraploid plants. Conclusion Fagopyrum tataricum can be effectively induced into tetraploids by colchicines. The tetraploid induction can produce valuable germplasm resources for breeding and is a practicable breeding way in F. tataricum.

Genetic diversity of 35 Fagopyrum populations belonging to thirteen taxa was studied using isozyme variation at 16 loci for nine enzyme systems ( ADH , α-AMY , EST , GDH , GOT , IDH , MDH , PGM , and POD ). The mean number of alleles per locus ( A p ) showed little variation, ranging from 1.38 to 1.71. The mean percentage of polymorphic ( P ) of the thirteen taxa was high, ranging from 68.75% to 93.75. The mean expected heterozygosity ( H e ) ranged from 0.21 to 0.37. Obvious grouping of populations according to taxonomic species was found in the cluster analysis, confirmed that the thirteen taxa studied were independent, with a clear boundary. Based on the dendrogram, the phylogenic relationship of Fagopyrum species are in agreement with the achene size were found, and it was inferred that southwestern China should be the original center of cultivated buckwheat.

104 samples from 27 accessions belonging to 12 species of genus Epimedium were studied on the basis of cytology observation, POD (i.e., peroxide) isozyme, high performance liquid chromatography (i.e., HPLC) fingerprint, and interspecific hybridization. The cytology observation showed karyotypes of twelve species studied; all are 2A symmetry type of Stebbins standard and similar to each other, and except for karyotype of E. leptorrhizum which is 2n = 2x = 8m (2SAT) + 4sm, the rest are 2n = 2x = 6m (2SAT) + 6sm. Chromosomes C-banding of barrenwort species varies, with 15 to 22 bands, consisting of centromeric bands, intercalary bands, terminal bands, and middle satellite bands. Results of POD isozyme showed that the zymographs vary greatly and sixteen bands were detected in the eleven species, and each species has its own characteristic bands different from the others. Studies on the HPLC fingerprint showed that the HPLC fingerprint of different species has characteristic peaks, divided into two regions (retention time < 10 min and retention time > 10 min). Results of interspecific hybridization showed that crosses of any combination among seven species studied are successful and the rates of grain set vary greatly. Based on these results, the system and phylogeny of this genus were inferred.