金沙江干热河谷典型区生态安全问题探析

金沙江干热河谷典型区的生态安全问题与西部大开发中金沙江流域及长江中下游地区工农业可持续发展息息相关。初步调查研究了金沙江干热河谷典型区元谋段生态安全现状,指出区域内自然环境条件恶劣、植被退化与破坏严重、不良耕作与过渡放牧、生态安全意识薄弱、生产力低下和经济落后等是威胁区域内生态安全的主要因素,进而提出建立金沙江干热河谷区生态安全体系的基本措施。     

Soil nutrient stoichiometries and enzymatic activities along an elevational gradient in the dry-hot valley region of southwestern China

Changes in vegetation type and climate associated with elevation can strongly affect the soil properties, but their effects on soil nutrient stoichiometry and enzymatic activities have rarely been studied. The contents of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) and activities of six soil enzymes involved in C, N and P cycles were measured along an elevational gradient in the dry-hot valley region of China. C:P, N:P ratios first increased and then decreased with elevation, with the highest values of 89.57 and 4.07, respectively. AN:AP and AN:AK ratios increased linearly with elevation. Absolute enzymatic activities (i.e. per unit of oven-dried soil) tended to increase slightly with elevation, and specific enzymatic activities (i.e. per unit of SOC), except for phosphatase, first significantly decreased and then increased with elevation. A redundancy analysis showed that variations of soil nutrient content and stoichiometry were explained 76.1% by absolute and specific enzymatic activities. The elevational gradient was associated with a shift in nutrient limitation for ecosystem functions and processes, and the specific enzymatic activities responded more clearly than the absolute enzymatic activities to the elevational gradient in this dry-hot valley region.     

金沙江干涸峡谷中6种固氮绿篱品种剪枝中氮的矿化研究

A litterbag experiment of 12 weeks was conducted to study nitrogen mineralization process of prunings of six nitrogen-fixing hedgerow species in a dry valley of the Jinsha River. Prunings were incorporated into soil or used as mulch. The results indicated that pruning N of the six hedgerow species was mineralized fast in the first week and then decreased slowly in the rest of the study period. When prunings were incorporated into soil, the amount of nitrogen mineralized by the end of the first week accounted for 69.9%, 58.2%, 54.5%, 43.0%, 29.6% and 20.6% of the total N in prunings of Desmodium rensonii, Tephrosia candida, Leucaena leucocephala, Albizia yunnanensis, Acacia dealbata, and Acacia mearnsii, respectively. When prunings of L. leucocephala were used as mulch materials, the amount of nitrogen mineralized in the first week was 16.2% less than that of prunings incorporated into soil. The mineralization pattern of pruning N could be simulated by an exponent model N_t% = N₀₁% (1 -exp(-k₁t)) + N₀₂% (1-exp (-k₂t)) where N_t% is cumulative mineralized N in time t, N₀₁% and N₀₂% are readily and less readily mineralizable N in prunings, respectively, and k₁ and k₂ are rate constants. A half-life period of pruning nitrogen mineralization could also be determined by this model. The nitrogen content in the pruning residues decreased quickly in the first week but fluctuated thereafter. The initial C/N ratio was negatively related to the mineralization rate of prunings.     

SSR-based population structure,molecular diversity and identity cards of Ziziphus species from Pakistan and China

Genetic Resources and Crop Evolution - Research work on the genetic diversity within Pakistani and Chinese Ziziphus species is limited, and to date, no single report on the application of DNA...     

Genetic diversity and population structure in medicinal plant Melissa officinalis L. (Lamiaceae)

Genetic Resources and Crop Evolution - Melissa officinalis is an important medicinal plant and is extensively used by locals. This species is growing in different regions of Iran and forms several...     

Genetic structure,clonality and diversity in commercial pomegranate (Punica granatum L.) cultivars

Genetic Resources and Crop Evolution - The pomegranate fruit is one of the most important horticultural products due to the presence of polyphenols, anti-oxidant and anti-fungal compounds. In the...     

Comparative analysis of the soil cover diversity in floodplain areas of the Partizanskaya River valley (Sikhote-Alin Mountains)

The regularities of the soil cover formation and pattern in the Partizanskaya River valley (Sikhote-Alin Mountains) were revealed. The diversity of the soil cover was shown to depend on the landscape hydrological zone of the river basin, the structure of the floodplain, and the difference in flooding of the floodplain sections. The comparative assessment of the soil cover diversity using the Shannon index showed that, in the zone of accumulative landscapes, the soil cover diversity of the floodplain sections that were formed under the meandering of the river was higher than the diversity of the soil cover in the sections formed upon branching (furcation) of the channel. The maximum values of the Shannon index and the maximum supply with water characterize the floodplain in the mouth zone of the valley with the most stable conditions of soil formation. The determination of the diversity index for the soil cover and water supply of the floodplain sections is expedient in planning the economic activities in the valley.     

Genetic diversity and population structure of cultivated Dendrobium nobile Lindl. in southwest of China based on genotyping-by-sequencing

Genetic Resources and Crop Evolution - Dendrobium nobile Lindl. is one of the most important Orchid plants worldwide. The genotype-by-sequencing (GBS) method has now been widely used to access...     

Genetic diversity of the African hexaploid species Solanum scabrum Mill. and Solanum nigrum L. (Solanaceae)

Two hexaploid species of Solanum sect. Solanum are present in Africa: Solanum scabrum and S. nigrum. Solanum scabrum is a widely cultivated species and is used as a leafy vegetable, as a source of medicine and as a source of ink dye. In previous studies a wide range of morphological diversity has been reported in this species and in some studies subspecies have been proposed. Subspecies are also recognized in S. nigrum. However, it has not been established whether or not the morphological differences are reflected at the genomic level. The present study applies AFLPs to study the genetic diversity in S. scabrum and its relationship to geographical provenance, morphological differences and the possible existence of subspecies within S. scabrum and S. nigrum. The data obtained were analyzed with cluster analysis (using UPGMA and NJ). The results indicate that the genetic variation within S. scabrum was higher within accessions than between accessions. Accessions did not cluster according to their geographical provenance, indicating that accessions from different geographical areas were not significantly different genetically. The clustering reflected neither morphological differences nor domestication status (cultivated or wild). The morphological differences exhibited by S. scabrum could be due to selection by farmers for different plant types. The AFLP derived clustering pattern did not segregate the subspecies recognized in S. scabrum and S. nigrum into separate subclusters.     

近50年金沙江干热河谷区泥沙变化及影响因素分析——以云南省元谋县为例

 以金沙江干热河谷典型区域元谋县为例,通过对该区龙川江小黄瓜园水文站20世纪50年代以来输沙量的变化分析,结果表明,河流输沙量有增加的趋势,特别是80年代末至2000年,年均输沙量由400万t(1971—1980年)增加至750万t(1991—2000年)。为研究输沙量变化的原因,为当地生态环境建设提供理论指导,采用统计分析等方法对输沙量增加的影响因素进行分析,结果表明:50年来局地气候变化,特别是降雨量及降雨强度的增加使地表侵蚀加速,进入河道泥沙增多。同时,由于受牲畜数量快速增加、人口的迅速膨胀、生产方式的落后及农作物市场价格等因素影响,土地覆被及结构变化明显,即覆被盖度减小,坡耕地增加,灌草地等蓄水保土作用好的地类面积迅速减少,进而导致生态极为脆弱的元谋干热河谷区土壤侵蚀加剧,河道泥沙含量增加。此外,元谋县强烈的冲沟侵蚀也是龙川江输沙量增加的重要原因之一。     

AFLP fingerprinting of Anchusa (Boraginaceae) in the Corso-Sardinian system: Genetic diversity, population differentiation and conservation priorities in an insular endemic group threatened with extinction

Although several plants endemic to Corsica and Sardinia are included in various redlists, no attempts have been made to analyse their genetic diversity with molecular techniques. Genus Anchusa occurs with seven taxa in either mountain or coastal habitats of the two islands, but the very restricted range and low population size pose these endemisms in a very precarious conservation status. Highly variable markers (AFLP) were therefore used to analyse the patterns and levels of genetic diversity in a sample of 11 populations from the entire range of the group.Results indicate the separation between a mountain genic pool including Anchusa formosa, Anchusa capellii and Anchusa montelinasana, and four groups of coastal accessions. In spite of small size, mountain taxa show low interpopulation differentiation (F_st = 0.02) and relatively high intrapopulation genetic variation (0.365), while coastal accessions showed on average a stronger differentiation (mean F_st = 0.20) and a lower diversity (0.281), possibly due to higher rates of inbreeding. The particularly low levels of variation found in A. sardoa, A. littorea and A. crispa ssp. maritima from the Coghinas bay are likely due to a historical decrease of populations and to bottleneck events caused by loss of habitat and natural stochastic factors on sand dune ecosystems. While habitat maintenance and regulation of grazing by domestic herbivores should be sufficient to ensure the persistence of the mountain endemics, additional actions of in situ and ex situ conservation are needed for the critically endangered coastal species A. sardoa and A. littorea. A. crispa showed a relatively high variation, especially on Corsica. No correlation between population size and genetic variation was found in the latter species, highlighting the importance of the small patches for its conservation. Also, the genetic separation between subspecies crispa and maritima stresses the need of keeping them distinct in redlists and conservation actions on Sardinia.     

Artificial soil-like bodies of a river valley and their evolution in an urban environment (Based on the example of the Moscow River valley)

Technogenic soil-like bodies and raw soils on technogenic sediments in the valley of the Moscow River in the city territory were investigated. Soil destruction and the accumulation of techogenic sediments, as well as their remediation, result in the formation of soil-like bodies called replantozems. Spontaneous overgrowth and the formation of raw soils that gradually evolve into mature urban soils result in soils called urbanozems. It is shown that the best foundation for replantozems in river valleys is in situ alluvium with relatively favorable physical and physical-chemical properties.     

Genetic diversity in <Emphasis Type="Italic">Eremostachys superba</Emphasis> Royle ex Benth. (Lamiaceae), an endangered Himalayan species,as assessed by RAPD

Eremostachys superba Royle ex Benth. (Lamiaceae) has undergone a severe decline in population size since its discovery in the North-western Himalayas in late 19th century. One hundred and seventy-two plants from six populations in the Indian states of Uttar Pradesh and Jammu & Kashmir, located between 0.45 km and 455.72 km apart from each other were evaluated for RAPD polymorphism. Sixteen random primers generated 92 bands overall, 77 of which were polymorphic. Shannon’s index of genetic diversity within populations (H _o) ranged between 0.305 and 0.421; the average within-population diversity (H _pop) was 0.389; and the total species diversity (H _sp) was 0.478. The population from Mohand (representing the type locality) had the fewest plants, at 18, and was genetically the most depauperate. Among the other populations, ranging in size between 52 and 1,022 individuals, no relation between population size and genetic diversity was evident. It is suggested that these six populations represent relics of a larger, extended population, in which the presence of perennating rootstocks has helped preserve historic patterns of genetic diversity. AMOVA revealed that 83.01% of the variation exists within populations, which was consistent with earlier studies on the reproductive biology of E. superba, which indicated this species is predominantly allogamous. FST distances between all populations were significant, indicating geographic differentiation despite some of them being closely separated. Habitat restoration and protection from indiscriminate harvesting are proposed as primary strategies for conserving E. superba. Rejuvenation of the Mohand population through intrapopulation crossing between plants bearing diverse molecular phenotypes is also suggested.     

Genetic diversity of thiamin and folate in primitive cultivated and wild potato (Solanum) species

Biofortification of staple crops like potato via breeding is an attractive strategy to reduce human micronutrient deficiencies. A prerequisite is metabolic phenotyping of genetically diverse material which can potentially be used as parents in breeding programs. Thus, the natural genetic diversity of thiamin and folate contents was investigated in indigenous cultivated potatoes (Solanum tuberosum group Andigenum) and wild potato species (Solanum section Petota). Significant differences were found among clones and species. For about 50% of the clones there were variations in thiamin and folate contents between years. Genotypes which contained over 2-fold the thiamin and 4-fold the folate content compared to the modern variety Russet Burbank were identified and should be useful material to integrate in breeding programs which aim to enhance the nutritional value of potato. Primitive cultivars and wild species with widely different amounts of thiamin and folate will also be valuable tools to explore their respective metabolic regulation.     

Genetic diversity,population structure and differentiation of rice species from Niger and their potential for rice genetic resources conservation and enhancement

Rice genetic resources conservation and evaluation is crucial to ensure germplasm sources for further crop breeding. We conducted a wide collection of Oryza species in Niger and characterize its diversity with microsatellites (or simple sequence repeats, SSR). The aims of this research were to get a better understanding of the extent of genetic diversity, its structure and partition within rice eco-geographical zones of Niger. There were 264 accessions found in farmers’ and other fields: 173 O. sativa (Asia’s rice), 65 O. glaberrima (Africa’s rice), 25 O. barthii, and 1 O. longistaminata (weedy perennial rice), which were genotyped with 18 SSR. A total of 178 alleles were detected, with a mean of 9.89 alleles per locus. The polymorphism information content was 0.65 and heterozygosity was estimated as 0.14. Two main well-differentiate genotypic groups, which correspond to Asian and African rice species, were identified. The SSR set divided the Asia’s rice group (solely indica) into irrigated and floating rice, with rainfed lowland rice in between. The African rice species group was composed of O. glaberrima, O. longistaminata and O. barthii accessions, but without any clear genetic differentiation among them likely due admixtures within the samples of O. barthii. Five accessions that could be natural interspecific hybrids were too admixed for assigning them to any of the two well-differentiated groups. The partitioning of the overall diversity showed that maximum variation was within genotypic groups and subgroups or cropping ecologies, rather than between eco-geographical zones. The eco-geographical distribution of the diversity suggests germplasm exchange in Niger. Next-steps for conserving rice and crop wild relatives in Niger could be taken using the findings of this research.     

Genetic diversity and population structure of vegetable soybean (Glycine max (L.) Merr.) in China as revealed by SSR markers

Vegetable soybean is a kind of value-added specialty soybean serving as vegetable or snacks. Understanding the genetic structure of vegetable soybean is a key point for further utilization in breeding programs. In the present study, the genetic structure and diversity of 100 vegetable soybean accessions planted in China was analyzed using 53 simple sequence repeat (SSR) markers. A total of 296 alleles were detected with an average of 5.6 alleles per SSR locus. The polymorphism information content (PIC) values of SSR markers ranged from 0.074 to 0.831, with an average of 0.573. Nei’s genetic distance between accessions ranged from 0 to 0.9434 with an average of 0.6286. These vegetable soybean germplasms could be divided into 8 subgroups based on STRUCTURE analysis, or 11 subgroups based on unweighted pair group method with arithmetic average (UPGMA) cluster. Further comparison showed that the UPGMA subgroups and STRUCTURE subgroups were in fact highly consistent. Germplasms in each classified groups showed great consistency with their origins, seed coat colors or pedigrees. Genetic relationships among germplasm panels that initially came from different geographical regions were also analyzed. Germplasm panels from China Mainland, Taiwan Island and Japan were highly similar to each other with the similarities of over 98 %. Molecular data and cluster analysis also showed that germplasms from China Mainland are more diverse than those from other areas. These results gave us a deep insight into the genetic structure of vegetable soybeans in China and will help us to improve the breeding strategies.     

Patch connectivity and genetic diversity conservation in the federally endangered and narrowly endemic plant species Astragalus albens (Fabaceae)

To evaluate the sufficiency of US federal critical habitat designations and a proposed conservation plan in promoting the long-term persistence of the endangered plant Astragalus albens, patterns of genetic diversity and landscape connectivity were examined. A. albens harbors substantial genetic variation and shows no evidence of historic bottlenecks, suggesting little risk of extinction due to genetic homogeneity (A = 2.40; P = 0.50) or inbreeding (f = −0.08) within occurrences. Low genetic differentiation among occurrences (θ_p = 0.01) indicates relatively high gene flow or little genetic drift. The 91 patches of A. albens were connected into a single network at a distance of 2100 m; 94% of patches were <1000 m from at least one other patch. Managing ecological conditions that maintain large population sizes and connectivity among populations throughout the species’ ecological and geographic ranges will most likely conserve existing diversity. Both reserve networks partially accomplish these goals by including most extant occurrences and >89% of the aerial extent of the species, including the largest populations, and capturing all detected alleles. However, both conservation networks fail to conserve occurrences from one portion of the species’ range, possibly speeding loss of unique local adaptations. In addition, connectivity of the whole network is reduced with the 65 patches designated as critical habitat being connected at a distance of 6200 m and the proposed reserve sites being connected at a distance of 9500 m. Although total network connectivity would be reduced, connectivity at scales most relevant to gene flow (e.g., <1000 m) remains sufficiently in tact to provide a relatively promising outlook for species persistence.     

金沙江干热河谷坡改梯及生物地埂对土壤可蚀性的影响

以金沙江干热河谷试验区不同土壤类型、修建年限及生物地埂类型的梯田为研究对象,系统分析梯田和地埂土壤基本物理性质、团聚体分布特征及其抗冲、抗蚀性指标,研究了坡改梯和生物地埂对土壤可蚀性的影响。结果表明:(1)与坡耕地相比,新修梯田土壤物理性质和抗冲性及抗蚀性无显著变化,甚至有所退化,可能与土壤结构破坏、原表土搬离和坡改梯初期土壤侵蚀加剧等有关,随修建时间延长,老梯田土壤容重和孔隙度分别显著减小和增大,粒径0.25 mm水稳性大团聚体、水稳性团聚体几何平均直径(GMD)和有机质含量较坡耕地分别呈显著或极显著增加;(2)新修红壤和黄红壤梯田生物地埂土壤容重、孔隙度和抗蚀性与裸土地埂基本无显著差异,而红壤老梯田生物埂土壤紧实度和粒径2mm水稳性大团聚体显著增加,抗冲性和抗蚀性整体上较裸土地埂显著改善,说明生物地埂的长期利用可以有效增强土壤抗冲和抗蚀能力,加强地埂稳定性,有利于梯田水土保持效应的持续性;(3)地埂长期生物利用的老梯田水土保持功能最强。