Haishan Dang

Dendroecological study of a subalpine fir (Abies fargesii) forest in the Qinling Mountains, China

Dendroecological techniques were used to investigate the stand dynamics and the disturbance history of the subalpine fir forest in the Qinling Mountains of Shaanxi Province, China. The results indicated that 68% of the fir trees experienced 1–2 release events for a total of 10–29 (an average of 15.8) years, and 1–2 suppression events for a total of 10–27 (an average of 13.4) years before they reached canopy. Large number of Abies fargesii and Betula albo-sinensis recruitment coincided temporally with larger increases in the ring-width index from the 1830s to 1880s, suggesting occurrence of a major stand-wide disturbance during this time period. Few seedlings and saplings were found in the forest, and there was a dramatic decline in recruitment after 1890, probably because of the intensive cover of understory umbrella bamboo (Fargesiaspathacea). Radial growth analyses indicated frequent canopy opening resulting from small-scale disturbances in the forest. Thus, the subalpine fir forest experienced frequent small-scale disturbances and infrequent large-scale disturbances in its developmental history, and these disturbances coupled with the understory umbrella bamboo might have influenced tree growth and species recruitment.

Climate-growth relationships of subalpine fir (Abies fargesii) across the altitudinal range in the Shennongjia Mountains, central China

Dendroecological techniques were employed to explore the growth response of subalpine fir (Abies fargesii) to climatic conditions across its altitudinal range in both the north and south aspects in the Shennongjia Mountains, central China. Correlation function analyses indicated that temperatures in current summer were significantly negatively correlated with fir radial growth at the lower limits, while temperatures in previous autumn and in current spring showed significantly positive correlations with fir radial growth at the mid- and high-elevations in both aspects. Radial growth of the subalpine fir was significantly and positively influenced by precipitation in previous autumn and in current spring at the lower elevations and by precipitation in current spring at the mid-elevations, while precipitation had no significant effects on its radial growth at the upper elevations. Moving correlation functions showed that temperatures in early spring of the current year (i.e., February-April) had a relatively stable effect on tree growth over time at the mid- and upper-elevations in both aspects. Thus, the growth of the subalpine fir responded differently to climatic conditions along the altitudinal gradient, showing that the importance of temperatures for the fir radial growth increased while the importance of precipitation decreased with increasing altitude in both aspects in the Shennongjia Mountains, central China.

Rare earth elements tracing the soil erosion processes on slope surface under natural rainfall

A field experiment using rare earth elements (REEs) as tracers was conducted to investigate soil erosion processes on slope surfaces during rainfall events. A plot of 10m×2m×0.16m with a gradient of 20° (36.4%) was established and the plot was divided into two layers and four segments. Various REE tracers were applied to the different layers and segments to determine sediment dynamics under natural rainfall. Results indicated that sheet erosion accounted for more than 90% of total erosion when the rainfall amount and density was not large enough to generate concentrated flows. Sediment source changed in different sections on the slope surface, and the primary sediment source area tended to move upslope as erosion progressed. In rill erosion, sediment discharge mainly originated from the toe-slope and moved upwards as erosion intensified. The results obtained from this study suggest that multi-REE tracer technique is valuable in understanding the erosion processes and determining sediment sources.

Karyomorphology of Epimedium (Berberidaceae) and its phylo- genetic implications

Abstract The karyomorphology of 21 species and one variety of Epimedium was investigated in this study, among which 14 species and one variety were reported for the first time. The interphase nucleus and mitotic pro-phase chromosomes were found to be of the complex chromocenter type, and the interstitial type, respectively. The chromosome numbers of all species studied were 2n = 2x = 12. The investigated Epimedium species had a uniform karyotype with 2n = 6m + 6sm, except for three species, E. platyplatum, E. pubescens and E. stellulatum, which had a pair of chromosomes with subterminal centromeres. A secondary constriction was commonly found on the proximal side of the short arm of the chromosome pair I in these species, except for E. pseudowushanense and E. elachyphyllum in which the constriction was on chromosome pair II. The karyotype symmetry of all the investigated species was relatively primitive 2A. Pericentric inversion was observed in E. leptorrhizum, and unequal translocation occured in E. franchetii, E. sutchuenense, E. dolichostemon and E. koreanum. These chromosomal variations probably result in speciation of Epimedium to some extent. The infrageneric and intergeneric relationships of Epimedium in Berberidaceae were discussed.

A taxonomic revision of unifoliolate Chinese Epimedium L. (Berberidaceae)

SummaryFive Chinese species of Epimedium (Berberidaceae), E. simplicifolium T. S. Ying, E. baojingensis Q. L. Chen & B. M. Yang, E. zhushanense K. F. Wu & S. X. Qian, E. glandulosopilosum H. R. Liang and E. elachyphyllum Stearn are the only species of the genus previously described with unifoliolate leaves. Here, the authors review these five species based on extensive examination of specimens in herbaria and careful observation in the field and garden. E. simplicifolium is treated as a synonym of E. acuminatum Franch., and with the exception of E. elachyphyllum, the taxa are found to have predominantly trifoliolate and only occasionally unifoliolate leaves. Neotypes for E. zhushanense and E. glandulosopilosum are designated. In addition, we describe some characters of E. baojingensis, E. zhushanense, E. glandulosopilosum and E. elachyphyllum.

Observation on meiotic behavior in three Mahonia species, with special reference to the intergeneric relationship of Mahonia and Berberis

Abstract Cytological characters in meiosis of three Mahonia species-Mahonia fortunei, M. bealei and M. polydonta were investigated using the method of wall degradation and hypotonic treatment for chromosomal preparations. Chromosome numbers of the three species were all 2n = 2x = 28; those of M. fortunei and M. polydonta represent the first report. The three species at metaphase I possessed the same configuration of 14II, however, the secondary association was also observed. During anaphase I, 1.5% of the cells of M. fortunei had lagging chromosomes and chromosome bridges. During anaphase II, lagging chromosomes, chromosome bridges and asynchronism in second division were observed, with abnormality rate in M. fortunei being about 9.5%. The rate of fertile pollen grains of the three species amounted to more than 90%, which was consistent with the cell abnormality rate at anaphase II. The results indicate that, overall, meiotic process of the three species is normal, which is in line with the high pollen fertility rate and high seed yield of the three species. Our results support the view that Mahonia and Berberis represent a sister group in phylogenetic evolution, and that they should be treated as two distinct genera.

Five new synonyms in Epimedium (Berberidaceae) from China

Abstract Five new synonyms in Chinese Epimedium are designated in the present paper. Epimedium chlorandrum is treated as a synonym of Epimedium acuminatum; Epimedium rhizomatosum as a synonym of Epimedium membranaceum; Epimedium brachyrrhizum as a synonym of Epimedium leptorrhizum; Epimedium dewuense as a synonym of Epimedium dolichostemon; and Epimedium sagittatum var. oblongifoliolatum as a synonym of Epimedium borealiguizhouense.

Growth performance and range shift of the subalpine fir (Abies fargesii) in the Qinling Mountains, China.

Trees in the subalpine environment, a particularly vulnerable area being the first to reflect climate changes, are most likely to show strong effects of climate variability. The aim of this study was to identify growth responses of subalpine fir (Abies fargesii) to climate variability, and investigate range shifts along an altitudinal gradient in the subalpine region of the Qinling Mountains, China. Standard correlation functional analysis showed different growth responses of fir trees to climatic variables between north and south aspects. In the north aspect, radial growth was significantly positively correlated with temperatures in early spring (February–April) and summer (July) of the current year, while radial growth was significantly positively correlated with temperatures in November and December of the previous year and early spring (February–April) of the current year in the south aspect. Analysis of age structure distribution displayed a decrease in number of mature fir trees and an increase in number of saplings along the altitudinal gradient on both aspects. Fir saplings/seedlings only occur in the treeline environment, and this fir population was significantly younger than that at lower elevations. Thus, fir trees show different radial growth patterns in response to climatic variability between north and south aspects, and age-class distributions along the altitudinal gradient imply an upward shift in range in the subalpine region during the past century in the Qinling Mountains of China.

Variations in carbon source-sink relationships in subalpine fir across elevational gradients

Cold-adapted trees display acclimation in both carbon source and carbon sink capacity to low-temperature stress at their upper elevational range limits. Hence a balanced carbon source-sink capacity might be required for their persistence and survival at the elevational tree limits. The present study examined the spatial dynamics of carbon source-sink relationship in subalpine fir (Abies fargesii) trees along elevational gradients in the northern slope of the temperate region and in the southern slope of the subtropics in terms of climate in the Qinling Mountain range, north-central China. The results showed that non-structural carbohydrate (NSC) concentrations in both the source and sink tissues increased with the increase in elevation. The ratio of carbon source-sink displayed a consistent decreasing trend with the increase in elevation and during growing season, showing that it was lowest at a ratio of 2.93 in the northern slope and at a ratio of 2.61 in the southern slope at the upper distribution elevations in the late growing season. Such variations of carbon source-sink ratio might be attributable to the balance between carbon source and sink activities, which changed seasonally across the elevational distribution range. We concluded that a ratio of carbon source-sink of at least 2.6 might be essential for subalpine fir trees to persist at their upper range limits. Therefore, a sufficient source-sink ratio and a balanced source-sink relationship might be required for subalpine fir trees to survive and develop at their upper elevational distribution limits.