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1.
North-east (NE) China covers considerable climatic gradients and all major forests types of NE Asia. in the present study, 10 major forest types across the forest region of NE China were sampled to Investigate forest distribution in relation to climate. Canonical correspondence analysis (CCA) revealed that growing season precipitation and energy availability were primary climatic factors for the overall forest pattern of NE China, accounting for 66% of the explanatory power of CCA. Conversely, annual precipitation and winter coldness had minor effects. Generalized additive models revealed that tree species responded to climatic gradients differently and showed three types of response curve: (i) monotonous decline; (ii) monotonous Increase; and (iii) a unimodai pattern. Furthermore, tree species showed remarkable differences in limiting climatic factors for their distribution. The power of climate in explaining species distribution declined significantly with decreasing species dominance, suggesting that the distribution of dominant species was primarily controlled by climate, whereas that of subordinate species was more affected by competition from other species.  相似文献   

2.
The radial growth of trees In mountainous areas is subject to environmental conditions associated with changes In elevation. To assess the sensitivity of tree-ring growth to climate variation over a wide range of elevations, we compared the chronological characteristics of Sabina przewalskii Kom. and their relationships with climatic variables at the upper and lower treellnes In the Dulan region of the northeastern Qlnghal-Tlbetan Plateau. It was found that the radial growth in this region was controlled primarily by precipitation in late spring and early summer (from May to June). In addition, a higher temperature from April to June could Intensify drought stress and lead to narrow tree rings. The significant similarity In climate-tree growth relationships at both the upper and lower treellnes Indicated that tree rings of S. przewalskU In this region are able to provide common regional climate information. However, the chronologies at the lower forest limits showed a higher standard deviation and more significant correlations with climatic factors, suggesting that the radial growth there was more significantly Influenced by climate variation. The first principal component of the four chronologies showed a common growth response to local climate. The second principal component showed a contrasting growth response between different sampling sites. The third principal component revealed different growth patterns In response to altitudinal variation. Further analysis Indicated that the precipitation In late spring and early summer controlled the growth of S. przewalskii on a regional scale and that other factors, such as mlcroenvlronment at the sampling sites, also affected the strength of the climatic response of tree growth.  相似文献   

3.
The climatic preferences of Pelias barani, a rare Pontic endemic viper, are analysed and a new locality record is reported. According to species distribution modeling, with the average test AUC was was 0.904 ± 0.068, bioclimatic variables such as Precipitation of driest month(45.5%), Temperature seasonality(18.9%), Precipitation seasonality(17.9%) and Maximum temperature of warmest period(14.7%) appear to have the most useful information on geographic distribution of Pelias barani. Distribution models of Pelias barani under current climatic conditions showed better adaptation to the northwest and northeast part of Turkey.  相似文献   

4.
We tested two questions:(i)whether the climatic conditions of the Azorean Islands in Portugal may have restricted the invasion of Harmonia axyridis across this archipelago and(ii)determine what population of this species could have a higher probability of invading the islands.We used MaxEnt to project the climate requirements of different H.axyridis populations from three regions of the world,and the potential global niche of the species in the Azorean islands.Then we assessed the suitability of the islands for each of the three H.axyridis populations and global potential niche through histograms analysis,Principal Component Analysis(PCA)of climate variables,and a variable-by-variable assessment of the suitability response curves compared with the climatic conditions of the Azores.Climatic conditions of the Azores are less suitable for the U.S.and native Asian populations of H.axyridis,and more suitable for European populations and the global potential niche.The PCA showed that the climatic conditions of the islands differed from the climatic requirements of H.axyridis.This difference is mainly explained by precipitation of the wettest month,isothermality,and the minimum temperature of the coldest month.We concluded that the climatic conditions of the Azores could have influenced the establishment and spread of H.axyridis on these islands from Europe.Our results showed that abiotic resistance represented by the climate of the potentially colonizable zones could hinder the establishment of invasive insects,but it could vary depending of the origin of the colonizing population.  相似文献   

5.
The objective of this study was to identify whether the miR-502-binding site single nucleotide polymorphism (SNP) in the 3'-untranslated region (3'-UTR) of set domain-containing protein 8 (SET8) and the tumor protein p53 (TP53) codon 72 polymorphism were associated with the risk for non-small cell lung cancer (NSCLC), either in- dependently or jointly, among Chinese people from south- ern Han. The genotypes of SET8 and TP53 codon 72 polymorphisms of peripheral blood DNA were detected using polymerase chain reaction-restriction fragment length polymorphism and direct DNA sequencing in a case-control study on 164 NSCLC cases and 199 controls. The SET8 TT (odds ratio, OR = 2.173, 95% confidence interval, CI = 1.0454.517) or TP53 GG (OR = 2.579, 95% CI = 1.366-4.870) genotype was associated with an increased risk of NSCLC by comparing with the SET8 CC or TP53 CC genotype, respectively. Similar results were obtained in SET8 recessive model (OR = 2.074, 95% CI = 1.019-4.221, P〈 0.05), and the dominant and recessive model of TP53 codon 72 were performed, respectively (OR = 1.809, 95% CI = 1.159-2.825, P〈 0.05; OR = 1.933, 95% CI = 1.096-3.409, P 〈 0.05). In addition, inter- action between the SET8 and TP53 polymorphisms increased the risk of NSCLC in a multiply manner, with the OR being 3.032 (95%CI = 1.580-5.816) for subjects carrying both SET8 TT and TP53 GG genotypes. Therefore, the miR-502-binding site SNP in the 3'-UTR of SET8 and the TP53 codon 72 polymorphism may he markers of genetic susceptibility to NSCLC in Chinese population, and there is a possible gene-gene interaction in the incidence of NSCLC.  相似文献   

6.
1 INTRODUCTION Bailong River valley is situated in the south of Gansu Province and northeast of Qinghai-Tibet Plateau at longitudes of 101°40'-105°20' E and latitudes of 32°21'-35°50' N.The mean annual precipitation is 448.9-911.6ram and the mean annual temperature 4.7℃-12.7℃.The drainage area has an elevation from 550m to 4920m.The complex habitats give rise to a variety of forest communities and varied patterns of ecosystems.  相似文献   

7.
The West Indian fruit fly, Anastrepha obliqua (Macquart), is one of the most important pests throughout the Americas. CLIMEX 3.0 and ArcGIS 9.3 were used to model the current and future potential geographical distribution of this pest. Under current climatic conditions, A. obliqua is predicted to be able to establish throughout much of the tropics and subtropics, including not only North and South America, where it has been reported, but also southern Asia, northeastern Australia and Sub-Saharan Africa. The main factors limiting the pest's range expansion may be cold stress. Climate change expands the potential distribution of A. obliqua poleward as cold stress boundaries recede, but the predicted distribution in northwestern Australia and northern parts of Sub-Saharan Africa will decrease because of heat stress. Considering the widely suitable range for A. obliqua globally and in China, enhanced quarantine and monitoring measures should be implemented in areas that are projected to be suitable for the establishment of the pest under current and future climatic conditions.  相似文献   

8.
Predictive potential distribution modeling is of increasing importance in modern herpetological studies and determination of environmental and conservation priorities. In this article we provided results of analysis and forecasts of the potential distribution of smallscaled rock agama Paralaudakia microlepis (Blanford, 1874) using the distribution models through Maxent (www.cs.princeton.edu/- schapire / maxent). We made an attempt for comparison of input of bioclimatic factors and characteristics of biotope distribution for three species of genus Paralaudalda. Constructed model identified dissemination of Paralaudakia microlepis enough performance (AUC = 0.972 with dispersion 0.003). According to the map constructed, the most suitable habitats of smallscaled rock agama Paralaudakia microlepis are located in southern and eastern Iran, the west of central Pakistan and southeastern Afghanistan.  相似文献   

9.
Leaves of 407 individuals of Reaumuria soongorica (Pall.) Maxim. collected from the major distribution areas were measured to investigate the distribution characteristics of the stable carbon isotope in this desert plant, as well as correlations between δ^13C values and environmental factors. Results showed that δ^13C values in R. soongorica ranged from -22.77‰ to -29.85‰ and that the mean δ^13C value (-26.52‰) was higher than a previously reported δ^13C value for a different desert ecosystem. This indicates that R. soongorica belongs to the C3 photosynthetic pathway and has higher water use efficiency than other species. The correlations between δ^13C values and environmental factors demonstrated that the foliar δ^13C values in R. soongorica increased significantly with decreasing mean annual precipitation and mean relative humidity, and decreased with decreasing duration of sunshine and evaporation. The spatial distribution trend of δ^13C values in R. soongorica was not obvious and there was no significant correlation between the δ^13C values and mean annual temperature. We conclude that different distribution trends in δ^13C values for R. soongorica were likely caused by stomatal limitation rather than by nutrient-related changes in photosynthetic efficiency and that precipitation played an important role in the wide distribution range of R. soongorica. This pattern of δ^13C values for R. soongorica reinforced that it is a super-xerophil in terms of its adaptive strategies to a desert environment.  相似文献   

10.
The genetic diversity of Stipa grandis P.Smirn and its relationship with the climatic variables were studied using the RAPD technique for 90 genes from five natural populations sampled in the Xilingol steppe, China. Sixteen oligonucleotides screened from 100 random primers were used to amplify 310 trackable RAPD loci, which were all polymorphic. By analyzing the RAPD data using POPGENE software, different geographic S. grandis populations were studied, which indicated a high level of genetic diversity, and the maximum variation was observed within the populations with a 28% variation observed among the populations. Using Pearson correlation analysis, significant (P < 0.05) or highly significant (P < 0.01) relationships were found between gene diversity indexes and temperature factors (≥10°C cumulative temperature in a year, annual mean temperature and mean temperature in January). Mantel's tests showed that there was no significant correlation between Nei's unbiased genetic distance and the geographic distance of S. grandis populations (r = 0.184, P = 0.261). However, there were significant or highly significant correlations between Nei's genetic distance and the several climatic divergences in pairwise S. grandis populations. All results indicated that natural selection resulting from variations in water and temperature was responsible for the adaptive eco-geographical differentiation indicated by the RAPD markers of different S. grandis populations, and that immigration and gene drift did not play an important role in affecting the differentiation of S. grandis populations.  相似文献   

11.
Evergreen sclerophyllous oaks (the E.S. oaks, Quercus section Heterobalanus) are the dominant species of the local ecosystem in the eastern Himalaya and the Hengduan Mountains, southwest China. In this study, we document the climatic envelope of the seven E.S. oak species and examine the relationships between climate and their distribution. This was done using a principal components analysis (PCA) and multiple regression analysis (MRA) of nine climatic indices. The main climatic envelope of the E.S. oaks were: mean temperature of the warmest month (MTW)=12.0-19.5 ℃, warmth index (WI) = 33.2-88.9 ℃ month, annual biotemperature (BT)=-6.9- -0.3 ℃, coldness index (CI)=-30.4- -10.1 ℃ month, mean temperature of the coldest month (MTC)=-3.7-3.0 ℃ and annual precipitation (AP)=701-897 mm at the lower limits; and MTW=8.3-16.1 ℃, WI=15.7-59.1 ℃ month, BT=3.6-8.9 ℃, CI=-55.4--19.3 ℃ month, MTC=8.3-16.1 ℃ and AP=610-811 mm at the upper limits. The climatic range of the E.S. oaks is wide and includes two climatic zones, the cool-temperature zone and the subpolar zone. The PCA and MRA results suggest that the thermal climate plays a major role and precipitation plays a secondary role in controlling the large-scale distribution of the E.S. oaks, except Quercus monimotricha. In thermal regimes, BT and/or MTW are most important for both lower and upper limits of the E.S. oaks. Furthermore, our results indicate that the upper distribution limits of the E.S. oaks are less determined by low temperatures and their duration (CI) than by other factors.  相似文献   

12.
The mechanical properties of the skull and the anti-shock characteristics of woodpecker's head were investigated by ex- periment and numerical simulation. We measured the micro-Young's modulus of the skull by nano-indentation method and calculated the macro-equivalent Young's modulus of the skull at different positions using homogenization theory. Based on the Computerized Tomography (CT) images of woodpecker head, we then built complete and symmetric finite element models of woodpecker's skull and its internal structure and performed modal analysis and stress spectrum analysis. The numerical results show that the application of pre-tension force to the hyoid bone can increase the natural frequency of woodpecker's head. The first natural frequency under the pre-tension force of 25 N reaches 57 Hz, which is increased by 21.3% from the non-pre-tension state and is more than twice the working frequency of woodpecker (20 Hz 25 Hz). On the application of impact force to the tip of beak for 0.6 ms, high magnitudes of stress component occur at around 100 Hz and 8,000 Hz, far away from both the working frequencies and the natural frequencies of woodpecker head. The large gaps among the natural, working and stress response frequencies enable the woodpecker to effectively protect its brain from the resonance injury.  相似文献   

13.
Spatial and temporal patterns of insect damage in relation to aflatoxin contamination in a corn field with plants of uniform genetic background are not well understood. After previous examination of spatial patterns of insect damage and aflatoxin in pre-harvest corn fields, we further examined both spatial and temporal patterns of cob- and kernel- feeding insect damage, and aflatoxin level with two samplings at pre-harvest in 2008 and 2009. The feeding damage by each of the ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs) and maize weevil population were assessed at each grid point with five ears. Sampling data showed a field edge effect in both insect damage and aflatoxin contamination in both years. Maize weevils tended toward an aggregated distribution more frequently than either corn earworm or stink bug damage in both years. The frequency of detecting aggregated distribution for aflatoxin level was less than any of the insect damage assessments. Stink bug damage and maize weevil number were more closely associated with aflatoxin level than was corn earworm damage. In addition, the indices of spatial-temporal association (χ) demonstrated that the number of maize weevils was associated between the first (4 weeks pre-harvest) and second (1 week pre-harvest) samplings in both years on all fields. In contrast, corn earworm damage between the first and second samplings from the field on the Belflower Farm, and aflatoxin level and corn earworm damage from the field on the Lang Farm were dissociated in 2009.  相似文献   

14.
中国栎属植物的数量分类研究   总被引:11,自引:1,他引:10  
在全面衡量中国栎属49种4变种性状特征的基础上,观测了25个定性性状和18个数量性状。通过聚类分析,可以将中国栎属分为5个特征明显的表征群,即5组:麻栎组(Section Aegilops)、槲栎组(Section Quercus)、高山栎组(Section Brachylepides)、巴东栎组(Section Engleriana)和橿子栎组(Section Echinolepides)。在主成分分析中,虽然性状的累积贡献率增长不明显,前3个主成分累积贡献率仅有50.4%,但结果仍然显示出和聚类分析同样的结果。说明栎属的分类性状仍存在主要方面,只不过在演化过程中由于性状变异的多样性,产生了多个不同的表征类群。分析结果对我们解决个别有疑问种的分类地位也有启示作用。因此,数量分类方法对解决栎属组间及种间的分类问题有重要的意义。  相似文献   

15.
16.
In this study, we propose to use the principal component analysis (PCA) and regression model to incorporate linkage disequilibrium (LD) in genomic association data analysis. To accommodate LD in genomic data and reduce multiple testing, we suggest performing PCA and extracting the PCA score to capture the variation of genomic data, after which regression analysis is used to assess the association of the disease with the principal component score. An empirical analysis result shows that both genotype-basod correlation matrix and haplotype-based LD matrix can produce similar results for PCA. Principal component score seems to be more powerful in detecting genetic association because the principal component score is quantitatively measured and may be able to capture the effect of multiple loci.  相似文献   

17.
Both the study and the relationship between sperm design and sperm function have been a target of several researchers. In our study we have evaluated the relationship between the morphometry of sperm head and midpiece as well as the relationship between morphometry of these two spermatic components and sperm motion characteristics in the boar. Analysis of regression (lineal and multiple) and principal components analysis were used for the study of these relationships. Semen samples from five Iberian boars were taken for analysis. Analysis of morphometry was assessed by CASMA system and motility by CASA system. Sperm midpiece showed a significant relationship (positive or negative, depending on the morphometric parameter evaluated) with sperm head. VSL, LIN, STR, BCF and VAP showed a significant relationship with several head and midpiece morphometric parameters. Finally, through the analysis of multiple lineal regression we obtained several statistical models that predict STR, LIN, VCL, ALH, BCF, PC1 and PC2 (the last two variables have been obtained from a principal components analysis) as a function of one, two or three morphometric parameters. Our results suggest a co-evolution of sperm head and midpiece and in addition that sperm motion characteristics of porcine spermatozoa are influenced by morphometry of head and midpiece.  相似文献   

18.
The spatial distribution of 49 macrofungal species in Swedish beech forests was related to the statistical variation in 31 edaphic variables. In order to reduce the multicollinearity problem, the variables were transformed into eight principal components, PCs, which are used in two-group discriminant analysis (on absence/presence patterns) and multiple regression analysis (on number of fruit-bodies). The results suggested that base saturation and organic matter content are of outstanding importance. However, significant relationships were also found with other variables, i.e. Cd or Zn in soil and litter, soil nitrogen mineralization rate, and Na or S in litter. One interesting interpretation of the results is that fungi do not only respond to the main variables of a gradient (soil pH, organic mater, base saturation) but also to other variables. Attempts were made to interpret the PCs to characterize fungal occurrence from the models they formed.  相似文献   

19.
Regression problems with a number of related response variables are typically analyzed by separate multiple regressions. This paper shows how these regressions can be visualized jointly in a biplot based on reduced-rank regression. Reduced-rank regression combines multiple regression and principal components analysis and can therefore be carried out with standard statistical packages. The proposed biplot highlights the major aspects of the regressions by displaying the least-squares approximation of fitted values, regression coefficients and associated t-ratios. The utility and interpretation of the reduced-rank regression biplot is demonstrated with an example using public health data that were previously analyzed by separate multiple regressions.  相似文献   

20.
Quercus is one of the most abundant and economically important genera of woody plants in the Northern Hemisphere. To infer phylogenetic relationships within Quercus subgenus Quercus, chloroplast DNA (cpDNA) restriction sites and nucleotide sequences of the internal transcribed spacers (ITS) and the 5.8S coding region of the nuclear ribosomal DNA repeat were obtained for 44 individuals, including 25 species, intraspecific samples, and three outgroups. Separate parsimony analyses of each data set showed that individual gene trees were congruent and often complementary in supporting clades that generally corresponded to previously recognized taxonomic groups. Only one instance of strongly supported gene tree incongruence was detected and this anomalous pattern was explained best by ancient introgression of cpDNA across sectional boundaries. Simultaneous parsimony analysis of the pruned data sets supported the recognition of the strictly Eurasian section Cerris and resolved a novel hypothesis for the major infrageneric groups (Cerris- (Lobatae- (Protobalanus + Quercus sensu stricto))). The biogeographic hypothesis that all major oak lineages evolved locally at middle latitudes within the general distribution of their fossil ancestors was fully supported. This set of relationships also suggested a New World origin for the widespread white oaks of the Northern Hemisphere (section Quercus s. s.). For both data sets, inter- and intraspecific sampling within section Protobalanus showed little correspondence to morphological species. Greater cladistic structure among the samples was obtained by cpDNA restriction sites and two well-delimited plastomes types comprising a total of 15 distinct haplotypes were resolved. Haplotypes of 2 of the peripheral species in this species complex occupy terminal portions of one of the plastome clades, suggesting a more recent origin relative to those of more widespread species. The phylogeography of the two divergent plastome types suggested a north-south pattern, consistent with a Late Tertiary disjunction in the ancestral distribution of section Protobalanus.  相似文献   

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