Biomedical subjects

Dehui Zeng

Publications and source records attributed to Dehui Zeng.

15 recordsLinked to original sources

PubMed2006

[Soil moisture characteristics at the boundary of forestland-grassland in hilly area of Loess Plateau].

In this paper, the spatial distribution pattern of soil moisture at the boundary of forestland-grassland in hilly area of Loess Plateau was studied in dry season of June and rainy season of August 2004. The results showed that the variance coefficient of soil moisture content was smaller, and the difference of moisture content between soil layers was less significant in forestland than in grassland in June while reversed in August. There was a weak or medium differentiation of moisture content in different soil layers at the boundary of forestland-grassland. The edge effect area at the boundary was from 2 m (0. 4 of tree height) outside forestland to 2 m inside forestland in June, and from 2 m outside forestland to 4 m (0. 8 of tree height) inside forestland in August. The forestland-grassland landscape could be divided into 3 parts, i.e., grassland area, forest edge area, and forestland area, and the vertical distribution of soil moisture in these three parts showed different traits. In June, soil moisture content increased with increasing soil depth, with a smaller increment in grassland than in forestland, but in August, it was reversed. The vertical distribution of soil moisture at forest edge area showed an in-between feature.

China↗

PubMed2006

[Rhizosphere effects of Pinus sylvestris var. mongolica on soil phosphorus transformation].

To understand the phosphorus (P) mobilization mechanism of Mongolian pine (Pinus sylvestris var. mongolica) on a P-deficient semi-arid sandy soil of northern China, this paper compared the P fractions and acid phosphomonoesterase (AP) activity in the bulk and rhizosphere soils under different age Mongolian pine plantations. The results showed that when compared with the bulk soil, the organic C, labile organic P, and organic C/P ratio increased significantly, microbial and AP activities improved, and organic P mineralization accelerated in the rhizosphere soil. Root activity of the Mongolian pine significantly increased the bioavailability of soil P, and accelerated the shift of organic P and Ca-P to Fe-P and Al-P. The rhizosphere effects on soil P in different forms enhanced with stand age, whereas in adverse on AP activity. The bulk and rhizosphere soil had the similar trend in the dynamics of its P fractions with stand age. Soil total P pool reduced gradually while labile P pool increased with stand age. It should be essential to protect forest floor to replenish soil P pool and guarantee a long-term soil P supply.

Ecosystem↗

PubMed2005

[Spatial heterogeneity of soil moisture after raining at forest-grassland landscape boundary in hilly area of Loess Plateau].

Soil moisture is a main factor limiting vegetation restoration in semi-arid region. In this paper, the spatial variability of different layers soil moisture after raining at the forest-grassland boundary in hilly area of Loess Plateau were studied by traditional and geostatistical analysis methods. The results showed that the moisture content in surface (0 - 10 cm) and subsurface soil layer (10 - 20 cm) of grassland was higher than that of forestland. The two layers soil moisture content at forest-grassland boundary showed a small variation but an obvious ecological distribution. By using moving split-window techniques, it was obtained that the width of edge influence in surface and subsurface layer was 8 and 6 m, respectively. Geostatistical analyses showed that the spatial distribution of two layers soil moisture had a pure nugget effect in grassland, linear model in forestland, and spherical model in forest-grassland boundary. The spatial heterogeneity of two layers soil moisture was higher at forest-grassland boundary than at forestland and grassland, which had a stronger spatial dependence and autorelation. Kriging maps expressed the spatial structural characters. The distribution of soil moisture in two layers showed a strip shape near forest edge, and a patch shape far from the edge.

China↗

PubMed2004

[Influence of shelterbelts structure on snow distribution pattern in shelternets in Northeast China].

The amount of snow that falls in farmland during winter in Northeast China is the important source of soil water in farmland, so the influence of shelterbelt structure on snow distribution pattern is the key problem in order to adjust structure of shelterbelts according to porosity in management practice. Based on snow depths in shelternets composed of shelterbelts with three levels of porosity, which were shelternet No. 1, shelternet No. 2, and shelternet No. 3, the snow distribution patterns in farmland were studied. The results showed that the structure of shelternet had great influence on snow distribution in farmland. With different levels of porosities, spatial pattern of snow distribution were obviously different in three shelternets. The more variant in porosity, the more obvious difference in snow distribution pattern, and the best uniformity of snow distribution appeared in shelternet with porosity of phi 2w = 0.579, phi 2s = 0.268, in which snow depth in farmland was relative even and the variability of snow depth was the least. Consequently, the relationship of porosity of shelterbelt with snow distribution pattern could be used to guide structure adjustment and optimization management of shelterbelts.

Agriculture↗

PubMed2004

[Effect of land use change on spatial distribution pattern of soil total nitrogen in Keerqin sandy land].

By using statistics and geostatistics, this paper studied the content and spatial pattern of soil total nitrogen (TN) in a glassland and an arable land of southeast Keerqin sandy land. The TN content in 0-10 cm soil layer of the arable land reclaimed from a glassland 8 years ago was not different from that of the virgin grassland, but the TN content in 10-20 cm soil layer was higher than that in the grassland (P < 0.05). The soil TN storage in the grassland was 262.36 g x hm(-2) higher than that in the arable land, and its spatial pattern was significantly different between arable land and grassland. The heterogeneity and spatial dependence of TN in each soil layer (0-10 cm and 10-20 cm) of the arable land were larger than those of the grassland, and the ranges and fractal dimensions of TN in each soil layer of the arable land were larger than those of the grassland. There existed a clear horizontal spatial structure heterogeneity and spatial distribution pattern in the arable land, while in the grassland, the horizontal spatial structure heterogeneity was very low, and the horizontal spatial distribution pattern was random and uniform. The TN content in the 0-10 cm and 10-20 cm soil layers of the arable land had no difference (P < 0.05), its spatial structure characters had some difference (P < 0.05), and its spatial distribution pattern was very similar (r = 0.683, P < 0.05). The TN content and its spatial structure characters between two soil layers of the grassland had remarkable difference (P < 0.05), but its spatial distribution pattern in the two layers was relatively similar (r = 0.395, P < 0.05). In conclusion, agricultural activity could not only influence soil TN content, but also influence its spatial structure characteristics and spatial distribution pattern. Therefore, our study might promote the further study on the effect of land use change on soil nitrogen distribution pattern and its cycling in ecosystems.

Crops, Agricultural↗

PubMed2004

[Applied ecology: retrospect and prospect].

Applied ecology is evolved into a principal part of modern ecology that rapidly develops. The major stimulus for the development of applied ecology roots in seeking the solutions for the problems of human populations, resources and environments. Through four decades, the science of applied ecology has been becoming a huge group of disciplines. The future for the applied ecology should concern more with human-influenced and managed ecosystems, and acknowledge humans as the components of ecosystems. Nowadays and in future, the top-priorities in applied ecology should include following fields: sustainable ecosystems and biosphere, ecosystem services and ecological design, ecological assessment of genetically modified organisms, ecology of biological invasions, epidemical ecology, ecological forecasting, ecological process and its control. The authors believe that the comprehensive and active research hotspots coupled some new traits would occur around these fields in foreseeable future.

Conservation of Natural Resources↗

PubMed2004

[Introduction of upland rice cultivars to eastern Keerqin sandy land and their biological characteristics].

Developing water-saving rice cultivation is one important strategy for food security in China. This paper reported the experimental results of introducing six upland rice cultivars to eastern Keerqin sandy land. The field experiment results showed that under the condition of 60% water-saving, the yield of cultivars XH 95-13 and XH 95-13-6 was 10.2% and 5.5% higher than the control, respectively, while other four cultivars decreased by 6.7%-18.6%. Economically, all the cultivars except JP 121 had a higher income than the control, and the profitability of cultivars XH 95-13 and XH 95-13-6 reached 24.0% and 19.3%, respectively. The water productivity of all the six cultivars was over 0.566 kg x m(-3), increased by 59.89%-116.38%. Pot experiment showed that 12.1%-16.3% of soil moisture in 0-15 cm layer was beneficial to the growth of upland rice. In eastern Keerqin sandy land, effective tillers occurred before July 18. In brief, upland rice production could be extensively applicable in eastern Keerqin sandy land to gradually alternate the traditional lowland rice cultivation with continuous flooding, and save much underground water.

Adaptation, Physiological↗

PubMed2003

[Eco-value level classification and ecosystem management strategy of broad-leaved Korean pine forest in Changbai Mountain].

To realize the sustainable management of forest ecosystems, we should explicitly clarify the types and differences of the ecosystem services provided by different ecosystems under different conditions, with rethinking about the value of forest ecosystems; then solid management strategies and measurements will be enacted and applied to achieve the objects. The broad-leaved Korean pine forest (BLKPF) in Changbai Mountain is a unique and important forest type in China, owing to its many important ecosystem services such as preventing soil erosion, regulating climates, nutrient cycling, providing wood and non-timber forest products, etc. This paper is a preliminary study on the management strategy of BLKPF on the basis of analyzing the characters of the ecosystems and the relative importance of services they provided in this region. Based on the latest research of ecosystem services of BLKPF in Changbai Mountain, an idea of eco-value level (EVL) was introduced, and accordingly, management strategies were summarized by adopting the advanced theories in ecosystem management science and by analyzing field survey data. EVL means the relative amount of the value of ecosystem services provided by certain ecosystem, which can indicate the difference between services in given objects. The EVL classification of BLKPF implies the relative amount of the eco-value of different ecosystems including virgin forest, secondary forest, forest with human disturbance, and man-made forest in the clear-cutting sites. Analytical Hierarchical Processing method was used to formulate the equation for EVL index. Eight factors, namely, slope, soil depth, stability of soil maternal material, coverage of above-ground canopy, species diversity, regeneration rate of the stand, life span of dominant tree species, and intensity of human disturbance were chosen to build the formula. These factors belonged to three aspects affecting ecosystem services including the physical environment, community, and disturbance regime, and their selection and scaling were based on the previous studies on the BLKPF. The equation of EVL index (EI) was expressed as: EI = 0.542A1 + 0.171A2 + 0.072A3 + 0.067B1 + 0.043B2 + 0.014B3 + 0.010B4 + 0.081C1. According to the range of EI, ecosystems were classified into three types: low EVL type with EI from 1.000 to 1.874, medium EVL type with EI 1.874-2.749, and high EVL type with EI 2.749-3.623. Typical plots were surveyed and scaled with EI, and the predominant characters of each EVL type were summarized. Most forests of high EVL type were those in sites at high risk of soil erosion and hard to recover after disrupted. Forests of medium EVL type were those with worse community structure and composition, and were disturbed by human activities in relative steep sites. Forest of low EVL type were those in plane site with serious disruption or some young man-made stands. Based on the analyses of the characters of these three types, different management strategies were put forward. For high EVL type forest, strictly protection is most important to maintain the forest in natural succession and its eco-services. For medium EVL type forest, the key points of management are restoring their health and vigor by regulating their composition and structure in a seminatural way. For low EVL type forest, some area could be used to extensive exploration for economic benefits, and the rests should be reconstructed towards the original stand in composition and structure, based on the 'shadow ecosystem' in a close-to-nature way to promote the capacity of providing more eco-services.

Ecosystem↗

PubMed2003

[A research review on "fertile islands" of soils under shrub canopy in arid and semi-arid regions].

Due to the inclemency of climate and soil conditions and the intense disturbance of human beings, the soil resources heterogeneity in arid and semi-arid grassland ecosystems worldwide was gradually increased during the last century. The interaction between soil heterogeneity and shrubs induced the autogenic development of "fertile islands" and the increasing spread of shrubs in the grassland ecosystems. The development of "fertile islands" around individual shrubs could change the vegetation composition and structure, as well as the distribution patterns of soil resources, and thus, reinforced the changes of the ecosystem function and structure from a relative stable grassland ecosystem to a quasi-stable shrubland ecosystem. The study of "fertile islands" phenomenon would help us to understand the causes, consequences and processes of desertification in arid and semi-arid areas. In this paper, the causes of "fertile islands", its study methods and significance and its relationship with shrub spreading as well as the responses of vegetation to it were summarized. The problems which might occur in the study of this phenomenon were also pointed out. Our aim was to offer some references to the study of land desertification processes and vegetation restoration in the arid and semi-arid regions.

Desert Climate↗

PubMed2002

[Natural regeneration of Pinus sylvestris var. mongolica plantation on sandy land].

By employing comparison analysis and field survey, the natural regeneration of Mongolian pine plantations on sandy soil was investigated. In plantation areas where regeneration can take place naturally, natural regeneration of Mongolian pine varied temporally and spatially. Natural regeneration wasn't temporally continuous; it had a close relationship with autumn precipitation in particular years. In spatial aspect, there were three regeneration types: regeneration in forest gaps, regeneration on edges of a forest, regeneration under young broadleaf forest. There was no significant difference between the growth of regeneration saplings and plantation trees.

Agriculture↗

PubMed2002

[Analysis of natural regeneration barriers of Pinus sylvestris var. mongolica plantation on sandy land].

By employing comparison analysis, and field experiment of watering and soil-covering before overwintering for seedlings, the barriers of natural regeneration for Mongolian pine plantations on sandy soil were identified. The experimental area was divided into 3 parts according to the state of natural regeneration. Crown closure, litter, understory coverage, and site condition were the factors which affect natural regeneration. Water deficit, but not low temperature during overwintering, is the key factor that limits survival for 1-2 years old seedlings in plantation area. The water deficit is due to higher air temperature, less accumulated snow, higher soil evaporation, higher plant transpiration in plantation area than in the area in which Mongolian pine is naturally distributed. Based on the above research, it is necessary to take effective artificial measures to promote its natural regeneration so as to guarantee its successful development. The following measures are recommended: 1) covering the 1-2 years old seedlings with soil before wintering, 2) irrigating seedlings before wintering, 3) suitable forest harvest, e.g., belt clear-cutting, or patch cutting, 4) planting the pine with broadleaf species, 5) protecting forest stands from livestock grazing, seed collecting and litter gathering.

Desert Climate↗

PubMed2002

[Sustainable management for farmland shelterbelts].

The spatio-temporal pattern of shelterbelt regeneration is an important issue which determintes whether shelterbelt network produces protective effects sustainably. This article developed a new method of imitating "normal forest" to manage shelterbelts. Based on an administrative village as an organized management unit, each shelterbelt in the organized management unit will be individually regenerated and regulated, until the number of the shelterbelts in each age-class from young to mature ones will be equal, and the shelterbelts in each age-class will be spatially distributed uniformly in the shelterbelt network of an organized management unit. Consequently, this method might temporally ensure sustainable and stable ecological services which are provided by the shelterbelts in an organized management unit.

Agriculture↗

PubMed2002

[Phase-directional management of protective plantations. II. Typical protective plantation: farmland shelterbelt].

This paper is the second part of the series reports on phase-directional management of protective plantations. Based on the fundamentals of phase-directional management for protective plantations in paper I, discussions on protective maturity, management phase, and regeneration patterns and methods for shelterbelt or windbreak were conducted. Firstly, the two points of protective maturity of Populus spp. i.e., initial protective maturity age (IPMA) and terminal protective maturity age (TPMA), were determined. According to the growth pattern of shelterbelt, the IPMA was 16 years and 24 years for local poplar and hybrid poplar shelterbelts, respectively, and TPMA was the natural age for both local and hybrid poplar shelterbelts, which was determined on the basis of change pattern of porosity. Secondly, the three management phases of shelterbelts were divided quantitatively based on the analyses of discrete degrees of diameter, IPMA and TPMA. Thirdly, the corresponding measures for phase-directional management in each phase were also developed. In pre-maturity phase, i.e., the period from establishment of shelterbelt to IPMA, the measures such as soil cultivation, irrigation, fertilization, weed clearing, intercropping and branch cutting etc. should be conducted. In maturity phase, i.e., the period from IPMA to TPMA in theory, but the period from IPMA to regeneration age in practice, the techniques of managing the shelterbelt porosity around 0.25 (the best porosity value for wind protection) should be developed. In this phase, the porosity model was constructed according to the distribution pattern of base area for the poplar shelterbelt. The classification of shelterbelt trees, i.e., 4-grade classification, was established by considering the contribution of trees to the shelterbelt structure, which can provide the standard for thinning and tending of shelterbelt. Additionally, the density controlling techniques were also discussed. In the period of regeneration, i.e., from the regeneration age to the establishment of next generation shelterbelt, the techniques of regeneration such as determination of regeneration age, arrangement of regeneration patterns should be paid great emphasis. The influences of regeneration patterns and methods on regeneration period were specially discussed, and the changes of three management phases were illustrated by different regeneration patterns in the end of this paper. These results were obtained from poplar shelterbelt, but the fundamentals could be applied in any other shelterbelts.

Agriculture↗

PubMed2002

[Introduction and selection of new poplar clones in shelterbelts/windbreaks in northern Liaoning].

Six new poplar clones were introduced in Qianshuanging township of Changtu county, Liaoning Province as experiment materials, and their indeces in growth, cold resistance, disease infection, and insect infection were evaluated and compared to the locally grown Fuzha II poplar. According to the comparison of the 4 indices, the study found that N-119 poplar showed all the scores obviously better than those of CK and other poplars, and was recommended for the area. The growth of Zhonglin 95 was higher, and its disease and pest infection was equal or near to the CK. So, the poplar Zhonglin 95 is also worthy to be recommended.

Agriculture↗

PubMed2002

[Ecological forecasting: a frontier in ecology].

An evolving science of ecological forecasting is beginning to emerge, and could have an increasingly important role in policy-making and management of natural resources and environment. The progress in computer science, quantitative analysis and ecological theory, together with the application of new high technology, will increase our ability to forecast ecosystem change. The authors introduced the connotation of ecological forecasting, relevant research advances, and some typical examples. Ecological forecasting is an important frontier in ecology, and also, would be an important direction for future ecological study.

Decision Making↗