Biomedical subjects

Zhengquan Wang

Publications and source records attributed to Zhengquan Wang.

10 recordsLinked to original sources

PubMed2006

[Distribution patterns of Fraxinus mandshurica root biomass, specific root length and root length density].

Employing soil core method, an investigation in Maoershan Experiment Station was made on the root biomass, specific root length (SRL), and root length density (RLD) of Fraxinus mandshurica plantation (17 yr) within a growth season in stand level. The results showed that the total root biomass was 1,637 g x m(-2), in which, living biomass accounted for 85%, and necrotic biomass was 15%. In the living biomass, coarse roots (5 approximately 30 mm in diameter) had the highest percentage (69.95 %), followed by fine roots (< 1 mm in diameter) (13.53 %), medium roots (2 approximately 5 mm in diameter) (7.21%), and small roots (1 approximately 2 mm in diameter) (9.31%). Among the four diameter classes, fine roots had a higher SRL (32.20 m x g(-1)), while coarse roots had a lower one (0.08 m x g(-1)). The total RLD in living biomass was 6,602.54 m x m(-2) in stand level, among which, fine root accounted for 92.43%, and the others was less than 8%. Fine root biomass and RLD had a positive correlation with soil available nitrogen, while no significant correlation was found between SRL and soil available nitrogen.

Biomass↗

PubMed2006

[Application of minirhizotron in fine root studies].

Due to the production, death, and decomposition of fine root, its turnover plays an important role in carbon allocation and nutrient cycling in terrestrial ecosystems. Some methods such as sequential root coring, compartmental flow model, and ingrowth core have been widely used in collecting root biomass data and estimating fine root turnover, but failed in monitoring the dynamics of fine root due to its simultaneous production and death. Minirhizotron is a nondestructive in situ method for studying the dynamics of fine root, which allows the simultaneous measurement of fine root growth and mortality. This paper reviewed the application of minirhizotron in fine root studies, with the focus on minirhizotron tube installation, image collection, data extraction, and calculation parameters. In a case study, the total fine root length, fine root length density per unit volume, fine root length density per unit area, fine root biomass density, and fine root production and mortality of Fraxinus mandshurica and Larix gmelini were calculated, and the results showed that minirhizotron method was feasible in studying the processes of fine root development, eclipse, death, and decomposition. The factors affecting fine root measurement and its precision mainly included the quality and quantity of tube installation, sampling interval and quantity, and analysis technique of images, etc. Soil texture, tube material, and disturbance of light on root were also the factors affecting the precision of the method. How to improve the measurement precision of minirhizotron would be the critical problem in future study.

Fraxinus↗

PubMed2006

[Root decomposition and nutrient release of Fraxinus manshurica and Larix gmelinli plantations].

A two-year buried bag experiment with different sizes of Fraxinus mandshurica and Larix gmelinii roots showed that the coarse (5 to approximately 10 mm), medium (2 to approximately 5 mm) and fine ( <2 mm) roots of F. mandshurica had an annual decomposition coefficient of 0.3649, 0.4381 and 0.2720, while those of L. gmelinii had the coefficient of 0.1967, 0.1955 and 0.2464, respectively. During root decomposition, large amounts of carbon and nutrients released. After buried into soil for 150 days, more than 90% of soluble sugar in all sizes of the two species roots was released, and about 40%, 71% and 95% of potassium was released from the coarse and medium, and fine roots of F. mandshurica, and all sizes of L. gmelinii roots, respectively. In the second year of the experiment, about 50% of nitrogen and 40% of phosphorus were released from the coarse and medium roots of the two species, and 60% of nitrogen and phosphorus were released from their fine roots. In the study of forest ecosystem's carbon and nutrient cycles, root decomposition shouldn't be ignored.

Carbon↗

PubMed2004

[Effect of phosphorus stress on chlorophyll biosynthesis, photosynthesis and biomass partitioning pattern of Fraxinus mandchurica seedlings].

Phosphorus is essential to forest trees for their growth and development, because of its important role in many metabolic processes of trees. But, most part of phosphorus in soils of Northeastern China is immobile and unavailable, and thus, many forest trees often suffer from phosphorus stress which affects the biomass accumulation of forest trees. The aim of this study is to understand how the chlorophyll biosynthesis, photosynthesis and biomass partitioning of Fraxinus mandchurica seedlings response to phosphorus stress. Sand culture experiment showed that when the seedlings were under phosphorus stress, their 5-aminolevulinic acid (ALA) biosynthesis rate and porphobilinogen (PBG) synthase activity were reduced, but no significant changes in chlorophyll a and b, total chlorophyll and carotenoid contents were found. The nitrogen content in leaves and roots and the phosphorus content in all parts of seedlings were reduced under phosphorus stress, and the reduction of N content in leaves induced the decrease of maximum quantum efficiency of PS II (Fv/Fm) efficiency of PS II photochemistry (phi(PS II)), electron transport rate (E(TR)), and maximum photosynthesis rate (Amax). The effect of phosphorus stress on chlorophyll biosynthesis didn't affect photosynthesis. Under phosphorus stress, the total biomass decreased, but more biomass was partitioned into roots.

Biomass↗

PubMed2004

[Significance of senescence study on tree roots and its advances].

Root system is one of the important components of trees, and has some important physiological functions such as nutrient and water absorption, transport and storage, anchoring, and supporting. After tree root systems formed, roots often suffer from nutrient- and water-deficient stress, and thus, their absorption of nutrients and water appears more important. Soil nutrient and water have a great spatiotemporal heterogeneity. As the heterogeneity occurs, trees regulate carbon partitioning to roots, resulting in the senescence or death of some roots of the whole root system. In forestry, the senescence of tree roots is closely related to tree productivity, because there is a close relationship between the senescence of tree roots and the absorption of soil nutrient and water. At ecosystem and global scale, the senescence of tree roots influences the cycling of carbon and nutrients, because roots exhaust a great deal of carbon fixed by source leaves through photosynthesis, and there are great amounts of nutrients in tree roots. The senescence of tree roots is influenced by many environmental factors, biotic (e.g., fungi, bacteria, viruses, small edaphic animals) and abiotic (e.g., water, temperature, soil nutrients, heavy metals). These factors affect the senescence of tree roots by different mechanisms. Although we have much knowledge on the senescence of tree roots and some hypotheses have been proposed, some problems still remain to be resolved, and further experiments are needed to test these hypotheses. Interdisciplinary studies integrating cytology, biochemistry, soil science, and genetics are the prerequisite for rapid advances in understanding the essence of tree root senescence.

Biological Transport↗

PubMed2004

[A preliminary study on wood-inhabiting fungi on charred wood in Daxinganling forest areas].

Study on wood-inhabiting fungi is one of the active fields of mycology during past 30 years in China, and the study mostly focused on natural forest without fire disturbing. Forest fire changes forest ecology dramatically, and the fungi on charred wood are different from those in nature forests without fires. In this paper, we focused on the wood-inhabiting fungi growing on charred wood in Daxinganling forest areas. Seventeen species were reported: Antrodia sp., Antrodia rantha, Ceriporiopsis mucida, Diplomitoporus lindbladii, Gloeophyllum carbonarium, Gloeophyllum sepiarium, Gloeoporus taricola, Laurilia sulcata, Oligoporus sericeomollis, Phellinus igniarius, Postia caesia, Postia leucomallella, Postia tephroleuca, Schizopora flavipora, Skeletocutis ochroalba, Skeletocutis vulgaris, and Trichaptum fuscoviolaceum. Among them, eight species caused brown rot, and nine species caused white rot. Based on our field studies, eight species were pioneer fungi in charred wood, four species were common one, and three species were rare or threatened in the studied area. Setting up nature reserve should be the best way to protect the rare or threatened species of wood-inhabiting fungi.

China↗

PubMed2004

[Effect of different nitrogen supply on Fraxinus mandshurica seedling's biomass, N partitioning and their seasonal variation].

Nitrogen is one of the most important limiting nutrients for tree growth in temperature forest ecosystems. In this paper, the effects of nitrogen treatments on nitrogen partition and biomass allocation in roots and leaves of one-year-old Fraxinus mandshurica seedlings were studied during a five-month period. The plants were sand-cultured in pots supplied with various concentrations of N (1, 4, 8, 16 mmol x L(-1)). The results suggested that N supply could significantly increase the N concentration in roots and leaves. In the initial (June) and middle growth stage (July and August), the N concentration in leaves was over 9.40, 9.55 and 4.21 mg x g(-1) respectively, which was higher than that in roots, but in the latter growth stage (September), it was lower than that in roots. From June to September, the N content of whole plant increased markedly, and was 4 times more in September than in June. The N content in Ash seedlings varied with N supply. It increased by 5.5 times in 16 mmol x L(-1) N treatment, in comparing with 1 mmol x L(-1) N treatment in September. The N allocation also varied in leaf, stem, and root. The proportion of N allocation in leaf was the highest in June (43% in average), and the lowest in September (9% in average). The proportion of N allocation to root increased with plant growth, which was the highest in September (81% in average). Regardless N treatments and tree growth stages, the proportion of N allocation to root was the highest, followed by to leaf, and the lowest was to stem. These results provided the theoretical foundation for the further studies of nitrogen absorption and carbon allocation mechanism in root system of Manchurian ash.

Biomass↗

PubMed2004

[Effects of nitrogen stress on nutrient uptake by Fraxinus mandshurica seedlings and their biomass distribution].

Under environmental stresses, trees often change their morphological and physiological components to acquire the most limited resources. In northeastern forest region of China, the decomposition and mineralization of litters occur slowly due to low temperature, which often results in forest trees suffering from nutritional stress. With pot culture in greenhouse, this paper studied the effects of nitrogen stress on the physiological and morphological components of Fraxinus mandshurica seedlings. The results showed that under N stress, the net uptake rate of nitrogen and phosphate by the seedlings decreased, while their nitrogen and phosphate use efficiency were higher than those of the seedlings supplied with 8 mmol x L(-1) or 16 mmol x L(-1) of nitrogen during the early growth stage. When suffering from N stress, the leaf mass ratio of the seedlings reduced, with specific leaf area and root mass ratio increased. The relative growth rate increased with the increasing N concentrations supplied to the seedlings during the whole growth period. Under N stress, the net assimilation rate decreased, which resulted in the decrease of total biomass, and the root/shoot ratio was significantly higher than that of the seedlings supplied with 8 mmol x L(-1) or 16 mmol x L(-1) of nitrogen during the early growth stage. There was no significant difference during the late growth stage.

Biomass↗

PubMed2003

[Quantification comparison of spatial pattern of soil seed bank of Fraxinus mandshurica in two stands].

The spatial pattern of soil seed bank of Fraxinus mandshurica were examined by geostatistics in two stands with different densities, tree species composition and ground plants, in the Northeast of China. A sampling grid of 559 points, at each point a sample was located, was established according to regular grid design at three spatial scales (cell size were 0.5 m x 0.5 m, 1 m x 1 m, and 2 m x 2 m) in each plot. Spatial pattern were quantified by using semivariance analysis, fractal dimension and Kriging maps. The object of this paper is to quantify the spatial pattern of seed bank, to compare its variations between two stands, and to explore what sort of mechanism would control its variations. The results indicated seed distribution showed appreciable heterogeneity within stand and clearly difference between the two stands. In plot 1 (mixed stand), seed bank, with a mean of 158.1 +/- 96.7 seeds.m-2, higher sill (C0 + C = 0.549) and 4.25 m scales, has a stronger spatial pattern. There were a high autocorrelated variation (89.4%) and lowly random variation (10.6%) at this scale. However, at scale from 5 m to 31.3 m, its autocorrelated variation ranged 51.4%-69.8% and random variation ranged 30.2%-47.6%, also has distinctly mosaic patterns. Fractal dimension (D) analysis showed that the D values was relatively lower(1.728-1.865), their coefficient of variation only about 26.7%-68.35%, indicated that there was a high self-similarity of patch shapes of seed bank. In plot 2 (pure stand), with a mean of 57.4 +/- 44.7 seed.m-2, and lower sill (C0 + C = 0.125), spatial patterns were not so strong as plot 1, which has a smaller scale (2.59 m). Its spatially autocorrelated variation was 56.8% and randomly variation was 43.2%. Over the scale there were no clearly autocorrelated spatial patterns. Fractal dimension analysis showed higher D value (1.906-1.960), and their coefficient of variation varying wildly (69.51%-134.14%), implying highly random variation and more complex patch shapes. The differences of spatial pattern of seed bank between the two stands were likely to be due to spatial heterogeneity at the level of stands.

Seeds↗

PubMed2002

[Spatial heterogeneity and forest regeneration].

The research on spatial heterogeneity is meaningful for forest regeneration dynamics, which is a critical part in the forest ecosystem dynamics. Traditionally, forestry scientists are mainly concentrated their attention to the studies on the process of regeneration. However forests are spatiotemporal heterogeneous. In regeneration, there exists an ecological dynamic process at temporal scale, but also a heterogeneous pattern at spatial scale. Almost of the factors influencing forest regeneration, including both botic and abotic environment, both natural and human disturbances, and both characteristics of tree species and response of tree species to different disturbance agents, are spatially heterogeneous. Discussion on spatial heterogeneity and its effect on regeneration is indispensable for the understanding of the pattern, process and mechanism of forest regeneration. Main research contents and viewpoints of spatial heterogeneity in forest regeneration were summarised on the basis of available literature, and sources of spatial heterogeneity in the process of regeneration were analysed. The response of species to spatial heterogeneity, small-scale spatial heterogeneity and regeneration dynamics, spatial heterogeneity of lights in stand and regeneration pattern, and correlative relationships between the scales of soil heterogeneity and regeneration heterogeneity were reviewed.

Trees↗