Aliena Var Research Articles

Effects of insect infestation on Quercus aliena var. acuteserrata acorn dispersal in the Qinling Mountains, China

The nutritious acorns produced by oak trees (Quercus spp.) are attacked frequently by insects that feed on seed reserves. However, previous studies have partly considered the effects of insect infestations on animal seed dispersal and subsequent plant regeneration. In this study, we tested whether the effects of insect infestations on seed dispersal were frequency dependent (i.e., ratio of noninfested to infested acorns). We tracked the seed dispersal of plastic-tagged noninfested and insect-infested Q. aliena var. acuteserrata acorns with different frequencies in the Qinling Mountains in central China. Our results demonstrated that noninfested acorns were removed more rapidly, regardless of the infestation rates. Insect-infested acorns were also more likely to be eaten in situ, whereas noninfested acorns were more likely to be scatter-hoarded independent of infestation rates. Moreover, noninfested acorns were dispersed further and had higher survival rates than insect-infested acorns. Our findings suggest that the seed dispersal advantages of noninfested acorns compared with infested acorns was not frequency dependent, thereby indicating a consistently higher dispersal likelihood of noninfested acorns.

Description of a new species of <i>Saphonecrus</i> Dalla Torre & Kieffer from China (Hymenoptera: Cynipidae: Synergini)

A new inquiline species of Saphonecrus Dalla Torre & Kieffer, S. reticulatus sp. n., is described with its host gall. This species emerged from stem galls on Quercus aliena var. acutiserrata (Fagaceae). Diagnosis, distribution, and biology of the new species are included and themost important morphological characters are illustrated.

Does Animal-Mediated Seed Dispersal Facilitate the Formation of Pinus armandii-Quercus aliena var. acuteserrata Forests?

The Pinus armandii and Quercus aliena var. acuteserrata mixed forest is one of the major forest types in the Qinling Mountains, China. P. armandii is considered to be a pioneer species during succession and it is usually invaded by late successional Q. aliena var. acuteserrata. However, the mechanism that underlies its invasion remains unclear. In the present study, we tracked seed dispersal of P. armandii and Q. aliena var. acuteserrata using coded plastic tags in the western, middle and eastern Qinling Mountains to elucidate the invasion process in the mixed forests. Our results indicated that the seeds of both P. armandii and Q. aliena var. acuteserrata were removed rapidly in the Qinling Mountains, and there were no differences in the seed removal rates between the two species. There were significant differences in rodent seed-eating and caching strategies between the two tree species. For P. armandii, seeds were more likely to be eaten in situ than those of Q. aliena var. acuteserrata in all plots. By contrast, the acorns of Q. aliena var. acuteserrata were less frequently eaten in situ, but more likely to be removed and cached. Q. aliena var. acuteserrata acorns had significantly longer dispersal distances than P. armandii seeds in all plots. Although P. armandii seeds were less likely to be dispersed into the Q. aliena var. acuteserrata stands, over 30% of the released acorns were transported into the P. armandii stands where they established five seedlings. Based on the coupled recruitment patterns of P. armandii and Q. aliena var. acuteserrata, we suggest that the animal-mediated seed dispersal contributes to the formation of Pinus armandii-Quercus aliena var. acuteserrata forests.

Variation in soil respiration under the tree canopy in a temperate mixed forest, central China, under different soil water conditions

AbstractThe forest canopy cover can directly and indirectly affect soil conditions and hence soil carbon emission through soil respiration. Little is known, however, on the effects of canopy cover on soil respiration under the canopy of different tree species and soil water conditions. We have examined the variation in soil respiration at different soil water conditions (dry <10 %, wet >20 %, v/v) under different tree canopy covers in comparison with the canopy interspace in a temperate coniferous (Pinus armandii Franch) and broadleaved (Quercus aliena var. acuteserrata) mixed forest in central China. The results show that soil respiration measured under tree canopy cover varied with canopy size and soil water content. Soil respiration under small‐sized canopies of P. armandii (PS) was higher than that under large‐sized (PL) canopies, but the difference was only significant under the dry soil condition. However, soil respiration under large‐sized canopies of Q. aliena (QL) was significantly greater than that under small‐sized (QS) canopies under both dry and wet soil conditions. The difference in soil respiration between differently sized canopies of Q. aliena (33.5–35.8 %) was significantly greater than that between differently sized canopies of P. armandii (2.4–8.1 %). Differences in soil respiration between inter‐plant gaps and under QS canopies in both the dry and wet soil conditions were significant. Significant increases in soil respiration (9.7–32.2 %) during the transition from dry to wet conditions were found regardless of canopy size, but the increase of soil respiration was significantly lower under P. armandii canopies (9.7–17.7 %) than under Q. aliena canopies (25.9–31.5 %). Our findings that the canopy cover of different tree species influences soil respiration under different soil moisture conditions could provide useful information for parameterizing and/or calibrating carbon flux models, especially for spatially explicit carbon models.

Acorns containing deeper plumule survive better: how white oaks counter embryo excision by rodents

Several squirrel species excise the embryo of acorns of most white oak species to arrest germination for long-term storage. However, it is not clear how these acorns counter embryo excision and survive in the arms race of coevolution. In this study, we simulated the embryo excision behavior of squirrels by removing 4 mm of cotyledon from the apical end of white oak acorns differing in embryo depths to investigate the effects of embryo excision on acorn germination and seedling performance of white oak species. The embryo depth in the cotyledons was significantly different among white oak acorns, with Quercus mongolica containing the embryo most deeply in the acorns. We found that artificial embryo excision significantly decreased acorn germination rates of Quercus variabilis, Quercus acutissima, Quercus aliena, Quercus aliena var. acutiserrata, Quercus serrata. var. brevipetiolata but not Q. mongolica. Artificial embryo excision exerted significant negative impacts on seedling performance of all oak species except Quercus aliena. Our study demonstrates the role of embryo depth of acorns in countering embryo excision by squirrels and may explain the fact that squirrels do not perform embryo excision in acorns of Q. mongolica with deeper embryos. This apparent adaptation of acorns sheds light on the coevolutionary dynamics between oaks and their seed predators.

Biomass Carbon Storage of Three Forests at Different Altitudes in Baotianman Mountain, Central China

Basing on field data ofQuercus glandulifera var. brevipetiolataandQuercus variabilismixed forest (MF),Quercus aliena var. acutiserrataforest (QF1) andQuercus aliena var. acutiserrataforest (QF2) at different altitudes of Baotianman Mountain, we revealed biomass C storage of tree organs for each forest, and the distribution patterns of biomass C in different forests were also indicated. We found that total biomass C of forests decrease as altitude increase. The species mixed forest store more biomass C than others. However, biomass C storages at the scale 5m×5m vary dramatically for most of the plots. Biomass C storage in organs follows the law trunk>branch>root>leaf for all the three types of forests. It is interesting that biomass C of both above̶ and belowground are MF>QF1>QF2, whereas the ratios of aboveground/belowground biomass C are QF2 > QF1 > MF. Our results indicate that both altitude and forest type are key influence factors of forest biomass C in Baotianman Mountains.

Seed dispersal by small rodents favors oak over pine regeneration in the pine-oak forests of the Qinling mountains, China

Natural regeneration differences between oak and pine are common in the Qinling Mountains of central China. Thus, we examined whether this difference could be explained by seed dispersal. We investigated the seed dispersal of Quercus aliena var. acuteserrata Maxim. and Pinus tabulaeformis Carr. and the regeneration characteristics of both species were investigated in the pine-oak forest belt (oak stands, pine-oak stands, and pine stands) of Huoditang Forest in the Qinling Mountains in central China. We found that Q. aliena var. acuteserrata acorns were usually scatterhoarded, while seeds of P. tabulaeformis were generally consumed immediately. We found that 55% of the released acorns were transferred to the P. tabulaeformis stands. Moreover, Q. aliena var. acuteserrata regenerated successfully and was recruited in the three forest stands. However, the natural regeneration of P. tabulaeformis was very low in all stands because of high predation by small rodents. We propose, therefore, that the seed dispersal advantage of Q. aliena var. acuteserrata compared with P. tabulaeformis contributed greatly to the regeneration difference between these two species in the pine-oak forest belt of the Qinling Mountains in China.

Influence of Pericarp, Cotyledon and Inhibitory Substances on Sharp Tooth Oak (Quercus aliena var. acuteserrata) Germination

In order to explore the mechanism of delayed and uneven germination in sharp tooth oak (Quercus aliena var. acuteserrata) (STO), mechanical scarification techniques were used to study STO root and shoot germination and growth. The techniques used were: removing cup scar (RS), removing the pericarp (RP), and cutting off 1/2 (HC) and 2/3 (TC) cotyledons. Germination percentage and root and shoot length for Chinese cabbage (Beassica pekinensis) seeds (CCS) were also investigated for CCS cultivated in a Sanyo growth cabinet watered by distilled water and 80% methanol extracts from the acorn embryo, cotyledon and pericarp with concentrations of 1.0 g, 0.8 g, 0.6 g and 0.4 g dry acorn weight per ml methanol. The results showed that the majority of roots and shoots from acorns with RP and HC treatment emerged two weeks earlier, more simultaneously, and their total emergences were more than 46% and 28% higher, respectively. TC accelerated root and shoot emergence time and root length, but root and shoot germination rate and shoot height had no significant difference from the control. Positive consequences were not observed on all indices of RS treatment. The germination rates of CCS watered by 1.0 g·ml−1 methanol extracts from the embryo and cotyledon were significantly lower than those from the pericarp, and all concentrations resulted in decreased growth of root and shoot. Methanol extracts from pericarp significantly reduced root length of CCS, but presented little response in germination percentage and shoot length. The inhibitory effect was gradually increased with the increasing concentration of the methanol extract. We conclude that both the mechanical restriction of the pericarp and the presence of germination inhibitors in the embryo, cotyledon and pericarp are the causes for delayed and asynchronous germination of STO acorns.

秦岭山地锐齿栎次生林幼苗更新特征

PDF HTML阅读 XML下载 导出引用 引用提醒 秦岭山地锐齿栎次生林幼苗更新特征 DOI: 10.5846/stxb201103230361 作者: 作者单位: 西北农林科技大学生命科学学院,西北农林科技大学林学院,西北农林科技大学生命科学学院,西北农林科技大学生命科学学院,西北农林科技大学生命科学学院,西北农林科技大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业专项(20100400206,200804022B);国家自然科学基金(31070570);国家科技基础性工作专项重点项目(2007FY110800) Characteristics of seedlings regeneration in Quercus aliena var. acuteserrata secondary forests in Qinling Mountains Author: Affiliation: College of Life,Northwest Sci-Tech University of Agriculture and Forestry,College of forestry,Northwest Sci-Tech University of Agriculture and Forestry,College of Life,Northwest Sci-Tech University of Agriculture and Forestry,College of Life,Northwest Sci-Tech University of Agriculture and Forestry,College of Life,Northwest Sci-Tech University of Agriculture and Forestry,College of Life,Northwest Sci-Tech University of Agriculture and Forestry Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:分析了秦岭山地锐齿栎次生林群落乔木及木本幼苗物种特征值、更新生态位宽度及不同影响因子下(包括林分密度、坡向、海拔等)乔木的更新动态。结果表明,乔木层物种有25种,锐齿栎占有明显的优势,重要值为149.18%;其次为华山松(Pinus armandii)和千斤榆(Carpinus cordata)等。更新层共有木本植物41种,其中乔木种有28种,占所有木本植物总数量的68%,优势种有青蛙皮槭(Acer grosseri)、木姜子(Litsea pungens)等。林下有丰富的幼苗库,更新方式以实生为主;分析了10种更新优势乔木种群的生态位宽度,同种幼树种群生态位宽度均大于幼苗种群生态位宽度。幼苗种群生态位宽度从大到小依次为榛子(Corylus heterophylla)、锐齿栎、青蛙皮槭等。幼树种群生态位宽度从大到小依次为榛子、青蛙皮槭、锐齿栎等;林分密度对林下乔木幼苗和幼树数量影响不同。当林分密度从720增加到1460株/hm2时,幼苗密度逐渐增大。随后随着林分密度的增加,又呈现出减少的趋势。而幼树密度随着林分密度增加一直呈现出减少的趋势。坡向对锐齿栎次生林林下乔木幼苗和幼树的影响各异,阳坡(南偏西3°)均利于幼苗和幼树的更新。南偏西45°林分内,幼苗密度急剧减少。随着坡向转为阴坡,幼苗密度又逐渐增加。而幼树密度逐渐减少。当海拔从1083 m增加到1547 m时,幼树密度逐渐增加。随后,随着海拔增加到1882 m,幼树密度则逐渐减小。而幼苗密度随着海拔的增高一直呈现减小的趋势。 Abstract:Quercus aliena Blume var. acuteserrata Maxim. ex Wenz. is an important dominant species in temperate mid-elevation mountainous areas of China with significant functions in water resource conservation and ecological stabilization in forested ecosystems. Forty-two plots, including 210 subplots, were used to document the occurrence of trees, saplings, woody seedlings and habitat characteristics for this tree and associated woody species in a second growth forest in the Qinling Mountains in 2010. We analyzed the important values of trees, saplings and woody seedlings, regeneration niche breath, and tree regeneration dynamics under different conditions, including stand density, aspect, and altitude in Q. aliena var. acuteserrata secondary forests. The results show Q. aliena var. acuteserrata had an important value of 149.18% with none of the other 24 woody tree species in the tree layer approaching that level of importance. The subdominant species in the tree layer were Pinus armandii Franch. and Carpinus cordata Blume. 25 tree species of the 41 woody species in the regeneration layer. The woody plants in the regeneration layer were abundant with trees seedlings dominating. This appears to be beneficial to the optimization of the community structure and function. The dominant seedling species were Acer grosseri Pax, Litsea pungens Hemsl., and others. Seedlings of these two species were abundant in the regeneration layer with their height and age class lower than the dominant species. The height class of seedlings and saplings in the understory of Q. aliena var. acuteserrata secondary forest shows that woody plants regenerated vigorously. The biological chain of seedling to sapling was complete. Most regeneration was from seedlings rather than stump sprouts. We analyzed ten kinds of dominant regeneration tree populations. The regeneration niche breath of the sapling population was higher than that of seedling population for the same tree species which indicated the saplings has the broader use of community resources. The niche breath sequence from high to low seedling population was: Corylus heterophylla Fisch. ex Trautv. > Q. aliena var. acuteserrata > A. grosseri > other species. For saplings it was Corylus heterophylla > A. grosseri > Q. aliena var. acuteserrata > other species. Stand density had different effects on the density of saplings and seedlings. Sapling and seedling density increased with the stand density from 720 trees/ha to 1460 trees/ha, then decreased with the stand density increasing. The saplings density decreased continuously as the stand density increased. The direction of slope had various effects on the seedlings and saplings. A sunny SW facing slope of 3° was the most beneficial to seedlings and saplings. As the slope changed direction to create a shady slope, the seedlings density increased and the sapling density decreased. Sapling and seedling density changed with altitude. The saplings density increased as altitude increased from 1083 m to 1547 m, then decreasing with altitude up to 1882 m. The seedlings density increased from lower altitude to higher altitude. 参考文献 相似文献 引证文献

Study on Characteristics of <i>Quercus aliena var. acuteserrata</i> Community in Mt. Qinling

In Quercus aliena var. Acuteserrata community, phanerophytes (Ph) accounting for 58.7% was main Life form. Hemicryptophytes (H) with 28.1% was the second in Qinling Mountains. Mesophyll which accounted for 61.64% was major leaf physiognomy, and microphyll the second accounting for 27.40%. Simple leaf taking 84.93% was primary leaf-form. Herbaceous leaf accounted for 80.82% and was a major type of leaf property. The temperate elements, which were 43.17% of the genera, were in dominant position and were consisted of 98 genera; the tropical areal types including 58 genera accounted for 25.55%. These showed that Quercus aliena var. Acuteserrata community has the transitional character, that is, it is in the ecotone.

Belowground carbon pools and dynamics in China's warm temperate and sub-tropical deciduous forests

Abstract. We report the first estimates of pools and dynamics of microbes, roots, plant litter and soil organic carbon (SOC) in three dominant types of China's vast deciduous forest area: Betula platyphylla, Quercus liaotungensis, and Quercus aliena var. acuteserrata. Organic matter degradation rates overshadowed litter inputs as the main determinant of the soil carbon stocks. Across the three forests, rates of litter decomposition were also indicative for turnover rates of SOC. Litter and SOC decay was faster in the sub-tropical than in the warm-temperate forests. Among the latter, SOC turnover was highest in the forest producing the higher-quality litter. Microbial biomass was, as expected, correlated with SOC content. Microbial activity, in contrast, was highest at the sub-tropical forest, despite the lower SOC availability, lower fraction of labile SOC, and lower soil microbial biomass. These results may contribute to increased understanding of controls over belowground carbon cycling in deciduous forests.

Frequency-dependent selection by tree squirrels: adaptive escape of nondormant white oaks

Frequency-dependent selection is theoretically predicted to have an important impact on predator–prey dynamics, but little is understood about this process in nature. We investigated oak–squirrel interactions to test the hypothesis that tree squirrels predate/disperse white oak acorns based on the frequency of their germination phenotypes (dormancy, i.e., delayed germination vs. nondormancy, i.e., immediately germinating), which in turn influences dispersal and establishment of these oaks. In Central China, we manipulated the relative frequency of dormant and nondormant acorns available to Père David's Rock squirrel (Sciurotamias davidianus) with 2 white oaks (QAA, Quercus aliena var. acutesevata and QSB, Quercus serrata var. breviptiolata) that exhibit considerable variation in acorn germination between and within oak species throughout the fruiting season. We predicted that dispersal success (i.e., the probability of a viable acorn being hoarded) of each germination phenotype would vary with the phenotype frequency and hence show either positive or negative frequency-dependent selection. We found that acorn-embryo removal by squirrels may select for the dormant phenotype but is more likely to occur for early germinating acorns. We also found that both absolute and relative dispersal success of each germination phenotype increased with their frequency in the 2 white oaks, thus demonstrating positive frequency-dependent selection. Our results reveal that the frequency of germination phenotypes can account for as much as 40.5% and 21.4% of the observed dispersal success in QAA and QSB, respectively. We show that behavioral preferences of scatter-hoarding animals could result in frequency-dependent selection in nature, and such selection may help maintain variation in germination phenotypes in prey species.

Influences of leaf litter replacement on soil biochemical characteristics of main planted forests in Qinling Mountains of China

Long-term continuous growth of the same tree species in planted pure forest will lead to soil polarization and degradation. Mixed forestation or litter replacement between different needle- and broad-leaved forests are effective measures, except fertilization, to control soil polarization according to the mutual compensation principle of different tree species. Through a two-year leaf litter replacement experiment in 4 typical planted pure forests of Larix kaempferi, Pinus tabulaeformis, Catalpa fargesii and Quercus aliena var. acuteserrata in Qinling Mountains of China, influences of leaf litter replacement on soil biochemical characteristics and their interspecific relationships were studied and main conclusions were reached as follows. (1) Annual leaf litter decomposition rate of broadleaved forests was 33.70% higher than those of needle-leaved forests and increased by 8.35%–12.15% when needle-leaved litter was replaced with broad-leaved forests, whereas it decreased by 5.38%–9.49% when broad-leaved litter was replaced with needle-leaved forests. (2) Leaf litter replacement between needle- and broad-leaved forests popularly raised the contents of organic C, available N, P and K in soil, whose content increments in the needle-leaved forests (8.70%–35.84%) were obviously more than those in the broad-leaved forests (3.73%–10.44%), and in the former, the content increments after replacement with the litter of Catalpa fargesii (24.63%–35.84%) were more than those after replacement with the litter of Quercus aliena var. acuteserrata (8.70%–28.15%). Furthermore, the litter replacement was found to make the soil pH of needle-leaved forests developed from light-acid to neutral. (3) Litter replacement of the needle-leaved forests with the broad-leaved litter popularly raised enzyme activities, amounts of microorganisms and contents of micro-biomass C and N in soil, the increments of which after replacement with the litter of Catalpa fargesii were also more than those after replacement with the litter of Quercus aliena var. acuteserrata; while the litter replacement of broad-leaved forests with needle-leaved litter resulted differently depending upon the tree species. Among them, the soil enzyme activities and contents of micro-biomass C and N in the forest of Quercus aliena var. acuteserrata raised while they lowered in the forest of Catalpa fargesii.

Features of soil enzyme activities and the number of microorganisms in plantations and their relationships with soil nutrients in the Qinling Mountains, China

We studied the distribution of soil nutrients, the number of soil microorganisms, soil enzyme activities, and their relationships in pure and mixed plantations. Soil enzyme activities, the number of soil microorganisms, and soil nutrients were measured in plantations of Chinese pine (Pinustabulaeformis), larch (Larix kaempferi), sharp tooth oak (Quercus aliena var. acuteserrata), Manchurian catalpa (Catalpa fargesii), and mixed plantations in the Qinling Mountains, China. Compared with pure plantations, the conifer-broad-leaved broadleaf mixed plantations increased total N, available N, total P, available K, and organic matter in the forest soil; promoted the activities of invertase and urease by 16.7% and 53.8%; and increased the total amount of soil microorganisms by 95.9% and the number of bacteria by 104.5% (p<0.05). The correlations between soil enzymes, number of microorganisms, and soil nutrients were significant (p<0.05), and the correlations between the number of soil bacteria and basic nutrient prosperities (total N, available N, available K, and organic matter (OM)) were significant or highly significant. The correlations between the number of soil actinomycetes, and soil total N, available N, OM, and pH were also significant or highly significant. A suitable mixture of planted conifers and broad-leaved species improves the quality and amount of soil nutrients, increases the number of soil microorganisms and changes their redistribution. The change of soil enzymes and the number of soil microorganisms are indications of the change tendency of soil nutrients.

Forest biomass at Xiaolong Mountain in Gansu Province, China

In order to accurately estimate the size of the carbon pool and the capacity of the carbon sink in the forested areas of Xiaolong Mountain in Gansu Province, we have established regression equations of organ biomass of eight tree species. We measured and investigated the biomass of different forest stand types based on data from 1259 standard sample plots and 836 standard sample trees. The results show that stand biomass, expressed in t·hm−2 for eight types of forest stands on Xiaolong Mountain, are as follows: Quercus aliena var. acuteserrata 84.05, Pinus tabulaeformis 62.44, Quercus variabilis 81.77, Populus sp. and Betula sp. combined 77.44, Larix sp. 69.00, Pinus armandii 70.07, Picea sp. 96.49 and Abies sp. 98.72. We also looked at other broad-leaved mixed forests. Our study shows that the biomass of a single tree of each tree species is closely related to the diameter at breast height (DBH) and to tree height. The biomass of single trees as well as stand volumes is closely related to average DBH, average tree height and to stand density.

Comparing soil CO2 emission in pine plantation and oak shrub: dynamics and correlations

AbstractThe magnitude of soil CO2 emission varying significantly among different vegetation types for plants could alter the microclimatic environment of soil. In a Pinus tabulaeformis plantation and an adjacent Quercus aliena var. acuteserrata shrub, which are located in a dry‐hot valley region of Minjiang River in the Southwest of China, the daily soil CO2 emission dynamics was measured in August 2004 and in May, July, and October 2005. The results showed that the soil CO2 emission in the oak shrub was significantly higher than the pine plantation in each measurement period. Additionally, soil organic matter, microbial biomass carbon, and the leaf litter decomposition rate in the two vegetations differed significantly from each other. The variation of soil organic matter and microbial biomass carbon partially contributed to the evident difference in soil CO2 emission. Moreover, the correlations between soil CO2 emission, soil temperature, and soil water content were evaluated in this study. The soil temperature positively controlled soil CO2 emission in the pine plantation and the oak shrub, while the soil water content negatively influenced soil CO2 emission in the two vegetation types. However, the soil temperature and soil water content played varied roles in the different vegetation types. By the means of stepwise regression, the soil temperature more significantly influenced the dynamics of soil CO2 emission for the plantation than the soil water content; oppositely, the soil water content was the more significant controlling factor for the shrub. Based on the exponent model between the soil CO2 emission and soil temperature, the Q10 values were estimated, which was 1.7 in the pine plantation and 3.0 in the oak shrub. The former was lower than the global average level of 2.0, whereas the latter was higher than the global average level.

Three New 24-Noroleanane Triterpenoids fromQuercus aliena var.acuteserrata

Three new 24-noroleanane triterpenoids, i.e., 2α,19α-dihydroxy-3-oxo-24-norolean-12-en-28-oic acid (1) and 19α-hydroxy-3-oxo-24-norolean-12-en-28-oic acid (2), and 2α,3β,19α-trihydroxy-24-norolean-12-en-28-oic acid (3) were isolated from Quercus aliena var. acuteserrata, together with three known compounds, bartogenic acid (4), ilexgenin A (5), and aophitolic acid (6). Their structures were established by spectroscopic methods, especially 2D-NMR and MS analyses.

Study on reproduction ecology of endangered species Abies chensiensis

Qinling fir, Abies chensiensis, is endemic to China and has been listed in the China Plant Red Data Book as one of the second class conservation plants. It is found scattered only in the forested pockets of the Qinling, Bashan, and Shennongjia Mountains with altitude from 1 300 m to 2200 m in Shaanxi, Gansu, Henan, Sichuan, and Hubei Provinces. To conserve and effectively restore this species and explore its processes of reproduction, the production characteristics of cone and seed yields, seed bank dynamics, and seed germination rates of five Abies chensiensis populations (A, B, C, D, and E, respectively, in the Abies chensiensis-Pinus tabulaeformis-Sinarundinaria nitida-Carex lanceolata association, Abies chensiensis-Quercus aliena var. acutserrata-Litsea pungens-Carex lanceolata association, Abies chensiensis-Betula albo-sinensis-Sinarundinaria nitida-Duchesnea indica association, Abies chensiensis-Indigofera amblyantha-Carex lanceolata association and Abies chensiensis-Pinus tabulaeformis-Smilax stans-Carex lanceolata association) were studied in their natural habitats across 18 plots in the Qinling Mountain area. Experiments were carried out in laboratory and field conditions. The results showed that all the five populations had the potential to produce seeds, and higher yields occurred in the lower and middle altitude areas every three to five years. The majority of cones appeared on the upper and middle crown and the west, south, and east faces of the crown, and the majority of full seed appeared on the middle portion of the cone. The weight per 1000 seeds was 43.2 g, in which 44.8% had growing potential. The germination rate of seeds in the natural forest was 6.1% and the proportion of seeds lost or destroyed in different populations in the natural forest was 93.9%. The germination rate of seeds planted in the nursery was higher than that in the natural forest, and the germination rate in the lower or middle altitude populations was higher than that in the upper altitude populations. The course from seed to seedling was the critical period in the life cycle of A. chensiensis populations under natural conditions. Reproduction courses were influenced positively by an abundant coverage of tree layer, organic material in the soil, thick soil, and a dense population of parent trees, whereas they were influenced negatively by human disturbance and light. In situ conservation of A. chensiensis should be carried out in the future so as to promote expansion of the population. Thinning the shrub layer and grass layer will also help seeds to penetrate the soil, promoting seed germination. The artificial population should be expanded by collecting seeds in the harvest years. Fast-growing and high-yield plantations should be developed on cloudy slopes at lower or middle altitudes.

Biomass dynamics of Quercus aliena var. acutesrata community on Mountain Xiaolong in Gansu Province, China

The dynamics of tree layer biomass was studied by combining 35 sample plots of field census with biomass model estimation in a natural Quercus aliena var. acutesrata community on Mountain Xiaolong in Gansu Province, China. The tree layer biomass of Quercus aliena var. acutesrata community was 183 660 kg/ha, in which the slow growth group accounted for 64.89% of the total biomass. The fast-medium growth group accounted for 33.40% and the coniferous group accounted for 1.38%. The organs biomass was found to be in the following order: trunk > root > branch > leaf. The total biomass accumulated with the development of the community. The total biomass and the biomass of the organs were highest in the mature community and became stable as the community developed. The relative growth rate of organs was in the following order: trunk > branch > root > leaf. The biomass ratio of the slow growth group trees tended to increase and the fast-medium group trees tended to decrease as the community developed, which was reveresed in the decline development stage. The biomass of the coniferous group was very small throughout the development process.

EFFECTS OF GAP AND UNDERSTORY EVIRONMENTS ON THE REGENERATION OF QUERCUS ALIENA VAR. ACUTESERRATA AND FAGUS ENGLERIANA

Quercus aliena var. acuteserrata and Fagus engleriana are important species in the temperate and subtropical middle-elevation mountainous areas of China. In this study, we investigated the regeneration dynamics, diameter size class distributions, and the light response curve of these two species to better understand the effects of light availability on the regeneration of Q. aliena var. acuteserrata and F. engleriana. The results showed that both species had a high abundance of seedlings in the field, but the survival rate from seedling to sapling stage was nearly zero for Q. aliena var. acuteserrata and only 6%-8% for F. engleriana. In the mixed-forest that contained both species, the population of F. engleriana showed a stable pyramidal age structure, but the size structure of Q. aliena var. acuteserrata was dominated by a few cohorts of trees that were able to establish within a short time period. From the light saturation response curve of the two-year old cohort, Q. aliena var. acuteserrata seedlings in gaps had a higher maximum photosynthetic rate (4.61 #mu#mol·m~(-2)·s~(-1)) than F. engleriana (4.16 #mu#mol·m~(-2)·s~(-1)) and, for the seedlings under canopy, F. engleriana had higher maximum photosynthetic rate (3.89#mu#mol·m~(-2)·s~(-1)) than Q. aliena var. acuteserrata (3.68 #mu#mol·m~(-2)·s~(-1)). Moreover, seedlings of F. engleriana reached maximum photosynthetic rates with lower photosynthetic photon flux density than Q. aliena var. acuteserrata. The light induction curve indicated that both the response speed and the maximum photosynthetic rate of Q. aliena var. acuteserrata understorey seedlings were lower than that of F. engleriana, which demonstrated different competitive abilities and shade-tolerance characteristics of the two species. Resource allocation experiments showed that Q. aliena var. acuteserrata seedlings allocated more biomass to above-ground growth whereas F. engleriana seedlings allocated more biomass to under-ground growth. These results are consistent with the different light use strategies of the two species.