Fourth Principal Component Research Articles

Characterizing the morphology of gully cross-sections based on PCA: A case of Yuanmou Dry-Hot Valley

A cross-section of a gully (GC) is important not only for computing the volume and rate of erosion of the gully but also for understanding the relationship of the gullying process, landforms, land use and erosional features. To effectively characterize the accurate morphology of GCs and to explain their statistical regularity, this study proposes 26 morphological parameters for describing the cross-sections of permanent gullies. We surveyed 456 GCs with a laser distance meter located at the mouth, middle and head of 152 gullies in the Yuanmou Dry-Hot Valley of China, mapped them with CASS software, and calculated the morphologic parameters. Based on principal component analysis (PCA), the morphological characteristics can be notably expressed by four principal components and fewer parameters with heavier load information. The first principal component (PC) reflected the dimensions of GCs, with the key parameters of width, depth, and area of the cross-section. Over 94% of the depth of the left side (dl), the top width (wt) and the area (s) were in the range of 0–12m, 3–27m, and 0–200m2, respectively. The second PC indicated the degree of the gully's asymmetry in terms of the parameter of asymmetry ratio of width. There are 201 GCs of right-deflection and 184 of left-deflection. The third PC expressed the degree of erosion in terms of erosiveness and shape. There are 77 V-shaped, 25 U-shaped, and 354 intermediate shaped gullies. The percentage of U-shaped cross-sections is noticeably higher at the gully head than at the gully mouth and middle. The fourth PC reflects the erosional pattern difference. The value of the width/depth ratio was distributed and varied greatly within the range of 0.92–10.69 with an average value of 3.33. These key parameters differed at different locations and sites. The shape of GCs differs at different stages of development. Weathering crusts, soil properties, and vegetation cover are important for controlling the morphology of GCs in the Yuanmou Dry-Hot Valley. This study will not only help to improve the content of gully morphology, but will also contribute to understanding the controlling factors and evolution mechanism of gullies.

Principal Component Analysis of Long-Lag,Wide-Pulse Gamma-Ray Burst Data

We have carried out a Principal Component Analysis (PCA) of the temporal and spectral variables of 24 long-lag, wide-pulse gamma-ray bursts (GRBs) presented by Norris et al. (2005). Taking all eight temporal and spectral parameters into account, our analysis shows that four principal components are enough to describe the variation of the temporal and spectral data of long-lag bursts. In addition, the first-two principal components are dominated by the temporal variables while the third and fourth principal components are dominated by the spectral parameters.

The environmental impact of crude oil formation water: A multivariate approach

Water bodies receiving effluents from gas flow stations were sampled for ten months (March to December). Fifteen physicochemical parameters were monitored at six locations. Results obtained were analyzed unsing principal component analysis and cluster analysis. Five principal componets accounting for 72.43% of total variance were isolated. The first principal component was a measure of sea water intrusion, the second componet was a measure of total solids, the third component was a measure of organic pollution while the fourth and fifth principal component depicted the impact of effluent discharges. Effluents from gas flow stations were not the major causes of pollution of water resources in the locations of study. Cluster analysis showed no significant variation in the physicochemical characteristics of water samples based on location. Physicochemical parameters exhibited a seasonal pattern as a result of dilution by rainfall, reduced rate of evaporation in rainy season and dissolution of gaseous products of gas flaring in rain. Metals had no significant effect on the quality of water sampled from the six locations during the period of monitoring.

Molecular imaging of paper cross sections by FT-IR spectroscopy and principal component analysis

The molecular imaging of paper cross sections containing the wet-strength additive poly(amidoamine)-epichlorohydrin (PAE) was effected by Fourier transform infrared (FT-IR) spectroscopic imaging. Thin cross sections of laboratory sheet samples were prepared and transferred onto CaF2 substrates. A laboratory sheet sample without PAE acted as a reference. Principal component analysis (PCA) was applied to identify and to reveal the distribution of PAE across the section. Differences in the loading plots of the fourth and fifth principal components for the sheets with and without PAE were found in the region of the amide I, amide II, and amine bands within a variance of 0.4-0.8%. The score images of the PCA reveal inhomogeneous distribution of PAE. Small areas of higher concentration of PAE occur across the cross section. The aim of this study was to demonstrate that FT-IR spectroscopic imaging provides spatially resolved quantitative information about the chemical composition of paper, which was successfully achieved.

A kultúra területi mérhetősége és a kistérségek közművelődési jellemzői

A kultúra gazdasági szerepének elemzése és területfejlesztéssel való viszonyának értelmezése egyre nagyobb jelentőséggel bír napjainkban. A tanulmány a kultúra és kultúraelemzés néhány regionális vonatkozásának bemutatását követően arra a kérdésre keresi a választ, hogy miként számszerűsíthető a kultúra, valamint miként ragadható meg annak térszerkezeti hatása. Ami mérhető – vagyis amire elérhető statisztikai adatok léteznek – az valóban a kultúra teljes spektrumát öleli-e fel, avagy csak néhány szegmensre koncentrálnak az „adatbányászok”, miközben számos értékes információ rejtve marad. A dolgozatban a kulturális gazdaság közművelődési alrendszerét előtérbe helyezve empirikus elemzést is közlünk a hazai kistérségekre vonatkozóan. A hazai kistérségek közművelődési helyzetét többváltozós statisztikai módszerekkel (faktorelemzés, nem hierarchikus klaszteranalízis) vizsgáljuk, továbbá korrelációelemzéssel kísérletet teszünk a kulturális fejlettség vagy lemaradás és a kistérségek komplex fejlettsége közötti összefüggések számszaki megragadására.

Water Quality Assessment for Wastewater Reclamation Using Principal Component Analysis

The water quality assessment for wastewater reclamation is usually related to many parameters. This would introduce difficulty in objectively and comprehensively evaluating the overall water quality, and affect the water reuse safety. To address this problem, a principal component analysis (PCA) method was employed in this study to identify the components that mainly affect water quality. By examining eleven indices, a large amount of water quality data of four typical wastewater reclamation treatment plants (WRTP) in northern China were collected. The PCA results indicated that four uncorrelated principal components (PC) could represent the majority of water quality information. The first PC was mainly involved with the COD index and the sensory properties of water, including chroma, turbidity, dissolved solids, and total hardness. The second PC included the indices of NH3-N, DBP (di-n-butyl phthalate), and DEHP (Di (2-ethylhexyl) phthalate), reflecting the water reuse safety on both human health and ecological environment. The total phosphorus (TP) and iron (Fe) were included in the third PC, while the fourth PC included dissolved oxygen (DO). Based on PCA analysis, a comprehensive score of water quality was also obtained for each WRTP during each representative month, and it was found that the wastewater reclamation process could greatly affect the quality of reclaimed water. These four identified principle components can help evaluate the overall water quality, and much attention should be given to their effective monitoring and control during the operation of WRTP or the selection of appropriate treatment process.

Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region

The boreal summer intraseasonal oscillation (BSISO) of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system. Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator. In order to facilitate detection, monitoring and prediction of the BSISO we suggest two real-time indices: BSISO1 and BSISO2, based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S–40°N, 40°–160°E, for the extended boreal summer (May–October) season over the 30-year period 1981–2010. BSISO1 is defined by the first two principal components (PCs) of the MV-EOF analysis, which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward MJO with quasi-oscillating periods of 30–60 days. BSISO2 is defined by the third and fourth PCs, which together mainly capture the northward/northwestward propagating variability with periods of 10–30 days during primarily the pre-monsoon and monsoon-onset season. The BSISO1 circulation cells are more Rossby wave like with a northwest to southeast slope, whereas the circulation associated with BSISO2 is more elongated and front-like with a southwest to northeast slope. BSISO2 is shown to modulate the timing of the onset of Indian and South China Sea monsoons. Together, the two BSISO indices are capable of describing a large fraction of the total intraseasonal variability in the ASM region, and better represent the northward and northwestward propagation than the real-time multivariate MJO (RMM) index of Wheeler and Hendon.

CHEMOMETRIC CHARACTERIZATION OF MODEL COMPOUNDS RETENTION IN SALTING-OUT THIN LAYER CHROMATOGRAPHY ON CELLULOSE

The current paper presents a second part of chemometric characterization of retention behavior of thirty-five simple model compounds in salting-out chromatography on cellulose. Twelve inorganic salts, dissolved in high concentrations (0.5–4 mol/l) in water, were used as mobile phases. The resulting retention dataset was subjected to Principal Component Analysis (PCA). First principal component (PC) (explaining majority of variance) is connected with compound contribution, independent of the salt used. The differences between the salts are modeled by the second PC. Third PC explains mainly differences in retention slopes, whereas the fourth PC models weak minor differences. The remaining PCs contain only noise.

Population structure of Hispanics in the United States: the multi-ethnic study of atherosclerosis.

Using ∼60,000 SNPs selected for minimal linkage disequilibrium, we perform population structure analysis of 1,374 unrelated Hispanic individuals from the Multi-Ethnic Study of Atherosclerosis (MESA), with self-identification corresponding to Central America (n = 93), Cuba (n = 50), the Dominican Republic (n = 203), Mexico (n = 708), Puerto Rico (n = 192), and South America (n = 111). By projection of principal components (PCs) of ancestry to samples from the HapMap phase III and the Human Genome Diversity Panel (HGDP), we show the first two PCs quantify the Caucasian, African, and Native American origins, while the third and fourth PCs bring out an axis that aligns with known South-to-North geographic location of HGDP Native American samples and further separates MESA Mexican versus Central/South American samples along the same axis. Using k-means clustering computed from the first four PCs, we define four subgroups of the MESA Hispanic cohort that show close agreement with self-identification, labeling the clusters as primarily Dominican/Cuban, Mexican, Central/South American, and Puerto Rican. To demonstrate our recommendations for genetic analysis in the MESA Hispanic cohort, we present pooled and stratified association analysis of triglycerides for selected SNPs in the LPL and TRIB1 gene regions, previously reported in GWAS of triglycerides in Caucasians but as yet unconfirmed in Hispanic populations. We report statistically significant evidence for genetic association in both genes, and we further demonstrate the importance of considering population substructure and genetic heterogeneity in genetic association studies performed in the United States Hispanic population.

Noninvasive estimation of chronological and photoinduced skin damage using Raman spectroscopy and principal component analysis

Skin aging can be attributed to endogenous and exogenous factors which modify the hydration and protein structure of the skin which can be measured using Raman spectroscopy. This study included 21 healthy adult volunteers, aged 32-81 years, Raman spectra were obtained from sun-protected and sun-exposed skin, also three millimeter punch biopsies of sun-exposed skin were collected and analyzed. The Raman spectra were analyzed using principal component analysis and the results were correlated with clinical and histological findings. The principal component analysis of the Raman spectra shows that the first principal component (PC1) obtained from the sun-protected skin is related to the age of the subject, which can be taken as a measure of chronological aging, the second (PC2) and fourth (PC4) principal components obtained from Raman spectra of sun-exposed skin are related to the amount of solar elastosis and collagen, respectively. In this work a relationship was found between histological properties of photoaged skin and noninvasive measurements based on Raman and principal components analysis (PCA). These relationships can be used to assess noninvasively the photoinduced damage and chronological characteristics of skin.

Spatial variability of daily rainfall over northeast India during summer monsoon season

The summer monsoon rainfall over northeast India shows characteristic spatial and temporal variability due to the interaction of basic monsoon flow with orography and the synoptic scale systems developing over Indian region. The aim of this study is to find out the main features of spatial variability of daily monsoon rainfall over northeast India and associated synoptic systems. The principal component analysis (PCA) is a good tool to filter out the main components from the noise and this is applied to daily monsoon rainfall (June-September) data of 50 almost uniformly distributed stations of northeast India over a period of 10 years (1991-2000). The association of synoptic systems with significant principal components (PC) has been confirmed by analyzing daily synoptic systems over northeast India and neighbourhood during the same period.
 Eight PCs explaining about 46% of the total variance of daily monsoon rainfall over northeast India are significant and can be attributed to different physical processes. The first PC associated with good monsoon condition over northeast India may be attributed to low over Sub Himalayan West Bengal (SHWB). Similarly, the second PC may be attributed to good monsoon condition due to low level cyclonic circulation (cycir) over East Madhya Pradesh and Chattisgarh (EMPC), third PC to good monsoon condition due to depression over Bihar, fourth PC to good monsoon condition due to low level cycir over Arunachal Pradesh, fifth and sixth PCs to weak monsoon condition due to low over west central Bay and cycir extending upto mid tropospheric level (MTL) over North Coastal Andhra Pradesh respectively, seventh and eighth PCs to rainfall activity due to cycir extending upto MTL over Bangladesh and northwest Bay respectively.
 According to rotation of these significant PCs in S-mode, northeast India consists of eight homogeneous regions with the rainfall over each region being dominantly associated with one significant PC.

Groundwater depletion and quality deterioration due to environmental impacts in Maheshwaram watershed of R.R. district, AP (India)

Maheshwaram watershed is situated in Ranga Reddy district of Andhra Pradesh at a distance of about 30 km south of Hyderabad, capital of Andhra Pradesh. The watershed has an area of 60 km2 and has hard rock aquifers with semi-arid climate. The study area has been expanding at a fast pace and now has the distinction of being one of the fastest growing urban centers facing the problem of groundwater depletion and quality deterioration due to the absence of perennial source of surface water and also due to over exploitation. Human activities involving industrial and agricultural development and the inadequate management of land and water resources have, directly or indirectly resulted in the degradation of environment viz. water and soil. In the present study chemical analysis of groundwater samples of the study area, collected during pre- and post-monsoon seasons of 2007–2008 has been carried out. The analyzed data are utilized to characterize the hydro chemical process dominant in the area. Various classification methods such as Piper, Back and Hanshaw, Wilcox, USA. Salinity Laboratory are employed to critically study the geochemical characteristics of groundwater of the study area. Finally, principal component analysis (PCA) is also employed to the chemical variables of groundwater to characterize the hydro chemical process that is dominant in the area. In the analysis four principal components emerged as significant contributors to the groundwater quality. The total contribution of these four components is about 85–87%. The contribution of the first component is about 49–50% and has significant positive loadings of Ca2+, Mg2+, Na+, and Cl− ions. The second, third, and fourth principal components have significant positive loadings of F−, NO3−, SO42+, and HCO3− ions.

Analysis of lip motion using principal component analyses

Objectives The aim of this study was to quantitatively determine lip movement characteristics during the phonation of Japanese vowels. Materials and methods Lip motions of 14 normal individuals during the phonation of five Japanese vowels, /a/, /i/, /u/, /e/, and /o/ were analyzed. Using our developed motion analyzing system, range images were produced across the whole sequence during lip motions, and virtual grids were fitted onto surfaces. Principal component analyses were applied with three-dimensional coordinates of intersections for virtual grids regarded as variables. Results and conclusion The fourth and fifth principal component scores were shown to be parameters that control mouth opening and the retraction of the corners of the mouth, respectively. Discriminate analyses show it is possible to distinguish motion during the phonation of /u/ from that of other vowels.

Environmental factors of road slope stability in mountain area using principal component analysis and hierarchy cluster

Nine environmental factors of 147 roadside soil samples were administered in Sichuan Basin of China and principal component analysis was conducted using the Pearson correlation matrix. The results show that the first four principal components whose eigenvalue is over 1.00 can be extracted. The first principal component which is consisted of rock type, soil type, weathering degree, and soil depth is the most important factor of all. The geographical position which is consisted of altitude, longitude, and latitude is included in the second and the third principal components. The fourth principal component shows that the terrain factor influences the rock slope stability. The hierarchy cluster shows that rock type and soil type play the maximum positive correlation, while the slope and the aspect present the maximum negative correlation.

Near Infrared Hyperspectral Imaging for the Evaluation of Endosperm Texture in Whole Yellow Maize (Zea maizeL.) Kernels

Near infrared hyperspectral images (HSI) were recorded for whole yellow maize kernels (commercial hybrids) defined as either hard, intermediate, or soft by experienced maize breeders. The images were acquired with a linescan (pushbroom) instrument using a HgCdTe detector. The final image size was 570 x 219 pixels in 239 wavelength bands from 1000 to 2498 nm in steps of approximately 6.5 nm. Multivariate image cleaning was used to remove background and optical errors, in which about two-thirds of all pixels were removed. The cleaned image was used to calculate a principal component analysis (PCA) model after multiplicative scatter correction (MSC) and mean-centering were applied. It was possible to find clusters representing vitreous and floury endosperm (different types of endosperm present in varying ratios in hard and soft kernels) as well as a third type of endosperm by interactively delineating polygon based clusters in the score plot of the second and fourth principal components and projecting the results on the image space. Chemical interpretation of the loading line plots shows the effect of starch density and the protein matrix. The vitreous and floury endosperm clusters were used to make a partial least-squares discriminant analysis (PLS-DA) model, using four components, with a coefficient of determination (R(2)) for the y data (kernel hardness category) for the training set of over 85%. This PLS-DA model could be used for prediction in a test set. We show how the prediction images can be interpreted, thus confirming the validity of the PCA classification. The technique presented here is very powerful for laboratory studies of small cereal samples in order to produce localized information.

Relationships among udder characteristics, milk yield and, non-yield traits in Frizarta dairy sheep

In the present study the relationships between five body structural and nine udder morphological traits with milk yield and non-yield traits, i.e. milk contents, somatic cell count and body weight in n = 171 Frizarta ewes were investigated. Positive correlations of moderate to high magnitude were observed among body measurements ranging from 0.25 (body length-chest width) to 0.61 (chest width-chest girth). High correlations were observed between udder width and udder circumference ( r = 0.69) as well as between udder circumference at base and middle ( r = 0.62). Udder height was found to be positively correlated with cistern depth ( r = 0.32), udder width ( r = 0.40) and udder circumference ( r = 0.42) as well as with teat measurements (0.19 and 0.25 with teat length and teat circumference, respectively). Cistern depth was positively and highly correlated with teat angle ( r = 0.64). The correlation between teat length and circumference was also high ( r = 0.57). Teat angle was found to be negatively correlated with teat measurements ( r = −0.39 and −0.23 for teat length and teat circumference, respectively). Principal components analysis revealed four components that jointly explained 67% of the variance of all the body and the udder morphological traits. The first principal component interpreted as the body dimensions was found to be associated with body weight of ewes. The second component interpreted as global and rear measurements of the udder was significant for milk yield traits. The third and fourth principal components were interpreted as the udder type and teat dimensions, respectively. Ewes’ body weight could be adequately predicted by chest girth, body length, chest width and withers height. Test day milk yields were found to be associated with udder circumference and udder width as well as with udder height and teat length. None of the udder measurements and/or teat characteristics was found to be correlated with milk content(s) and/or somatic cell count. New statistical techniques can be successfully implemented in investigation of relationships between various traits in dairy sheep.

Agrupamento em amostras de sementes de espécies florestais nativas do Estado do Rio Grande do Sul - Brasil

Este trabalho teve como objetivos agrupar por espécie as matrizes de porta-sementes mais similares, utilizando as variáveis observadas em análises de sementes de espécies florestais nativas no Centro de Pesquisas Florestais e Conservação do Solo, Santa Maria, Rio Grande do Sul, analisadas a partir de 1997 até março de 2001. Para a análise de agrupamento, foram utilizadas todas as espécies que possuíam quatro ou mais análises de amostras de sementes por lote coletado, pelo método de agrupamento aglomerativo hierárquico tendo a distância euclidiana média padronizada como medida de similaridade. O dendograma foi construído utilizando o método da ligação completa. Utilizou-se também a técnica de componentes principais para a redução do número de variáveis. O gênero Schinus sp. e as espécies nativas Cassia leptophylla Vogel, Peltophorum dubium (Spreng.) Taub., Cedrela fissilis Vell., Allophylus edulis (A. St.-Hil., Cambess. & A. Juss.) Radlk., Lafoensia pacari A. St.-Hil., Enterolobium contortisiliquum (Vell.) Morong. e Apuleia leiocarpa (Vogel) J. F. Macbr. foram as espécies em que, no terceiro e quarto componentes principais, conseguiram explicar aproximadamente 80% da variação existente no conjunto de dados com a umidade e a percentagem de germinação de plântulas anormais, sendo eliminadas na maioria das espécies e as percentagem de germinação de plântulas normais e de sementes mortas presentes em todos os grupos. A análise de agrupamento mostrou-se eficiente na separação dos grupos de todas as espécies testadas sendo que a procedência pouco influenciou na formação dos grupos.

Hydrogel-Based Piezoresistive pH Sensors: Investigations Using FT-IR Attenuated Total Reflection Spectroscopic Imaging

The strong swelling ability of the pH-responsive poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) hydrogel makes the development of a new type of sensor possible, which combines piezoresistive-responsive elements as mechanoelectrical transducers and the phase transition behavior of hydrogels as a chemomechanical transducer. The sensor consists of a pH-responsive PAA/PVA hydrogel and a standard pressure sensor chip. However, a time-dependent sensor output voltage mirrors only the physical swelling process of the hydrogel but not the corresponding chemical reactions. Therefore, an investigation of the swelling behavior of this hydrogel is essential for the optimization of sensor design. In this work, Fourier transform infrared (FT-IR) spectroscopic imaging was used to study the swelling of the hydrogel under in situ conditions. In particular, laterally and time-resolved FT-IR images were obtained in the attenuated total reflection mode and the entire data set of more than 80,000 FT-IR spectra was evaluated by principal component analysis (PCA). The first and third principal components (PCs) indicate the swelling process. Molecular changes within the carboxyl groups were observed in the second and fourth PC and identified as key processes for the swelling behavior. It was found that time-dependent molecular changes are similar to the electrical sensor output signal. The results of the FT-IR spectroscopic images render an improved chemical sensor possible and demonstrate that in situ FT-IR imaging is a powerful method for the characterization of molecular processes within chemical-sensitive materials.

Post-natal sexual development of testis and epididymis in the rabbit: Variability and relationships among macroscopic and microscopic markers

The present work was performed to examine the existence of some relationships between macroscopic and microscopic traits of testis and epididymis in rabbit. The variables studied were live weight (LW), testis length (TL), testis width (TWh), testis weight (TW), testis volume (TV), epididymis length (EL), epididymis width (EWh), epididymis weight (EW), epididymis volume (EV), percentage of seminiferous tubules with presence of lumen (STL), percentage of seminiferous tubules with presence of elongated spermatids (STES), percentage of seminiferous tubules with presence of spermatozoa (STS) and diameter of seminiferous tubules (STD). Measurements began after weaning and continued until males reached 33 weeks of age. Phenotypic correlations between testis and epidydimis traits and the principal component analysis were estimated as the residual correlation from an analysis of variance, including the effects of line, birth-season, age, and the double interactions line × age and birth-season × age. Four principal components (PCs) explained 79% of the total variation. The predominant variables defining the first PC were TL, TW and TV. Epididymis width and STS were located in the second PC. Epididymis weight and EV were important in the definition of the first and third PC. Tubular diameter seems important in the definition of the fourth PC. It has been not found correlation between traits related to either testis or epididymis size and variables related to active spermatogenesis. Therefore, TW and/or TV seemed not to be good markers of maturity.

Growth responses to climate in a multi-species tree-ring network in the Western Carpathian Tatra Mountains, Poland and Slovakia

We analyzed growth responses to climate of 24 tree-ring width and four maximum latewood density chronologies from the greater Tatra region in Poland and Slovakia. This network comprises 1183 ring-width and 153 density measurement series from four conifer species (Picea abies (L.) Karst., Larix decidua Mill., Abies alba (L.) Karst., and Pinus mugo (L.)) between 800 and 1550 m a.s.l. Individual spline detrending was used to retain annual to multi-decadal scale climate information in the data. Twentieth century temperature and precipitation data from 16 grid-boxes covering the 48-50 degrees N and 19-21 degrees E region were used for comparison. The network was analyzed to assess growth responses to climate as a function of species, elevation, parameter, frequency and site ecology. Twenty ring-width chronologies significantly correlated (P<0.05) with June-July temperatures, whereas the latewood density chronologies were correlated with the April-September temperatures. Climatic effects of the previous-year summer generally did not significantly influence ring formation, whereas site elevation and frequency of growth variations (i.e., inter-annual and decadal) were significant variables in explaining growth response to climate. Response to precipitation increased with decreasing elevation. Correlations between summer temperatures and annual growth rates were lower for Larix decidua than for Picea abies. Principal component analysis identified five dominant eigenvectors that express somewhat contrasting climatic signals. The first principal component contained highest loadings from 11 Picea abies ring-width chronologies and one Pinus mugo ring-width chronology and explained 42% of the network's variance. The mean of these 12 high-elevation chronologies was significantly correlated at 0.62 with June-July temperatures, whereas the mean of three latewood density chronologies, which loaded most strongly on the fourth principal component, significantly correlated at 0.69 with April-September temperatures (P<0.001 over the 1901-2002 period in both cases). These groupings allow for a robust estimation of June-July (1661-2004) and April-September (1709-2004) temperatures, respectively. Comparison with reconstructions from the Alps and Central Europe supports the general rule of the dominant influence of growing season temperature on high-elevation forest growth.