The transfer mechanisms, calculating methods and ecological significance of nitrogen transfer between legumes and non-legumes are briefly reviewed. There are three pathways of nitrogen transfer from legumes to neighboring non-legumes: (1) the nitrogen pass in soluble form from the donor legume root into the soil solution, move by diffusion or/and mass flow to the receiver root and be taken up by the latter; (2) nitrogen pass into the soil solution as before, be taken up and transported by mycorrhizal hyphae attached to the receiver roots; (3) if mycorrhizal hyphae form connections (bridges) between the two root systems, the nitrogen could pass into the fungus within the donor root and be transported into the receiver root without ever being in the soil solution. The mechanisms of nitrogen transfer between N2-fixing plants and non-N2-fixing plants are reviewed in terms of indirect and direct pathways. The indirect N-transfer process is related to the release of nitrogen from legumes (donor plants), the possible interaction of this nitrogen with soil, the decomposition and mineralization of legumes and turnover of nitrogen, the nitrogen absorbing and competing abilities of the legume and the non-legume (receiver plant). The direct nitrogen transfer process is generally considered to be related to the nitrogen gradient and physiological imbalance between legumes and non-legumes, and when the donor legume lies in stressful stage (i.e. removal of shoots or attacked by insects), the nitrogen transfer can be improved significantly. The methods of determining nitrogen transfer (indirect15N-isotope dilution method and direct15N determination method) are evaluated, and their advantages and shortcomings are shown in this review.
Based on the biological hypothesis of tree growth, the generalized Korf growth equation, was derived theoretically. From a standpoint of applications, the equation can be used in two ways associated with the power exponent ofp, and two types of growth equations: the Korf-A (p>1) and the Korf-B (O<p<1) were developed and between them, there is the Gompertz equation (p=1) to separate each other. All of the three types of equations are independent. It was concluded that the Korf-A equation could be used to describe the growth of trees, of which inflection point is between 0 andA/e, while the Korf-B equation with the inflection point betweenA/e andA could be applied to describe the biological population growth. It was found that the Korf-A equation had a better property in describing the growth process of a tree or a stand and its applications to predicting height growth and stand self-thinning showed general good fitness.
The spatial patterns of seedlings originating from natural regeneration are often heterogeneous since they are strongly influenced by microsite gradient. We supposed that the patterns of Manchurian ash (Fraxinus mandshurica Rupr.) seedlings, which were originated from natural seed rain, were also spatial heterogeneous in spite of relative homogeneous of planted forest. The tree seedling establishment and growth were monitored in the Forest-experimental-station of Northeast Forestry University during growing season from early May to late September in 1999. The emergence of seedlings began in middle May; but the peak was about in late May. Seedlings were counted in 635 grid cells in late June, there were about 16–30 individuals/m2, but almost all of them died off in late September. The scale and extent of seedling heterogeneity were assessed by semivariogram and fractal dimension. The study showed that over 70% of seedling pattern was spatially autocorrelated, and that the variation caused by random factors was in less than 30%. The spatial dependent scales, both isotropy and anisotropy, were 1.95–2.92 m and 1.83–6.40 m respectively in the research stands. Our hypothesis was supported although there was difference when samples were chose at both different spatial scale and different density stands.
Competition is the common ecological phenomenon that exists in a stand after canopy closure. The effect of competition on DBH, height, crown diameter and crown area of individual amur linden trees was examined. We used two plots data, from amur linden (Tilia amurensis) plantation, 14 years old, in Liaoning province, to analyze the correlations among DBH, total height, crown diameer and crown area, and used the size-ratio of competiting tree DBHs to subject tree DBH to calculate distance-dependent competition index. The results show that DBH has the largest variation comparing with standard deviations and coeficeints. DBH and crown factors have higher correlations. Competition index is an important factor in tree growth. The best fitting models are exponent, for Cl vs height and Cl vs crown factors, and power, for Cl vs DBH. The more closed correlation model is Cl vs DBH (R2=0.7028), which performed 16.32%–18.86% better than other models. These reflect that DBH is an important indicator to display stand competition for amur linden.
Data were collected from Three-north Region, Middle and upper reaches region of Yangtze River and Coastal region. By analysis of factors influencing soil erosion, the longitude, latitude, annual precipitation, and the slope degree were selected as regional independent variables and canopy density and stock litter were selected as independent variables, and integral diffusing models were established for evaluation of the benefit of soil and water conservation of forest. By solving the parameters of models using the package of STATISTICA, the Power function between independent variables and dependent variables was set up. The soil conservation amount of forest and economic values were estimated using the contrast method for the ecological forestry engineering of the above three areas.
Allelopathic effect of larch (Larix gmelini) leaching on ash (Fraxinus mandshurica) growth was studied with sand culture test. It was understood that the ash growth was stimulated by the larch leaching. The chemical compositions of the larch and ash leaching were identified and determined by chemical and instrumental analysis. The results showed that in the larch and ash leaching there were fatty acids (including monocarboxylic, dicarboxylic and tricarboxylic acids), phenolic acids, tannin, aromatic alcohols, polylol, aminoacids and carbohydrate, etc. On the basis of the analytical results of chemical composition, with reference to the results of model compound test, it is considered that the citric acid in the larch leaching was the main simulative allelochemical to the ash growth, and trihydroxybenzeneacetic acid was the subordinate stimulative allelochemical.
Soil samples were collected from the surface soil of three kinds of plantations mixed plantation of Dahurian larch and Manchurian ash, pure ash plantation and pure larch plantation, at Maoershan Forest experiment center in Heilongjiang Province. The result of measuring and analysis showed that the number of the bacteria was the most and their effective scope and active strength were the most remarkable comparing with various kinds of soil microorganisms. Actinomyces were the second most and the fungi were the least in number. Numbers of the soil microorganisms in mixed plantation had a more number than that in the pure ash plantation. The number and species of microorganisms were different among different soil layers. For the same kind of soil, the number and species of the microorganisms in the surface layer were the most, and declined with the increase of the soil depth. The seasonal change of the number of the soil microorganisms in pure or mixed plantations was also remarkable. The number of the microorganisms increases obviously with the increase of the atmospheric temperature. The total number of microorganisms in Jan. was 30.0%–40.2% of the number in Sep. Both the vertical distribution and seasonal change being concerned, the number of the soil microorganisms in mixed plantation was on a higher level than that in pure plantation.
Taishan Mountain has diverse habitats and abundant groups of soil animals. Five habitats,Platycladus orientalis forest,Pinus densiflora forest,Robinia pseudoacacia forest,Pinus tablaerormis forest and Grassland, were selected and the diversity of soil animals in different habitats in Mt. Taishan were investigated and studied in 1997–1999. Totally 52 groups of soil animals were found, belonging separately to 7 Phyla, 11 Classes, 25 Orders and 28 suborders or families. There exists remarkable difference in groups, quantity and diversity of soil animals among the five habitats. Grassland habitat was the highest andPinus densiflora forest was the lowest in groups, quantities, Density-group index (DG) and Diversity index of comparing many communities (DIC) of soil animals. Shannon-Wiener’s diversity index (H′) for soil animals of different habitats was in order ofPlatycladus orientalis forest>Pinus densiflora forest>Pinus tablaerormis forest>Grassland>Robinia pseudoacacia forest, Pielou’s equality index (J′) wasPlatycladus orientalis forest>Pinus densiflora forest>Grassland>Pinus tablaerormis forest>Robinia pseudoacacia forest, and Simposn’s dominant index (C) was Grassland>Robinia pseudoacacia forest>Pinus tablaerormis forest>Pinus densiflora forest>Platycladus orientalis forest. The H index and J index of macro-soil animal all were larger than that of mid-small soil animal. Clustering analysis for five soil animal communities and ordination analysis for community structure by multidimensional scaling (MDS) were made and completely identical results were obtained. Soil animal communities of five habitats were divided into 3 groups.
Ips subelongatus Motschulsky were raised indoors and in the field using fresh baits for study of biological and ecological characteristics during 1992–1994. The life cycle of the pest in Lishu County, Jilin Province was described. The study results indicated that temperature was a main factor affecting the development ofIps subelongatus. The initial temperature for development of egg, larva, pupa and adult was 6.1, 8.0, 10.3 and 9.8°C, respectively. To complete one-generation needs, respectively, 48 d at temperature of 18°C, 39 d at 20°C and 33 d at 22°C. The pest has different number of generations in different area as a result of temperature change. In Jilin Province, it generally has three generations, except that some individuals have 2 generations. The nature enemies for this pest areThanasinus substriatus, Tomimicobia seitneri Ruschk,Coeliodes sp. etc.
Investigation and observation were made on bionomics and occurrence regulation ofPhigalia djakonovi Moltrecht, which is a major pest of white birch, in Daxing’an Mountain forest area of Inner Mongolia during 1997 to 1999. The pest has one generation per year and overwinters as pupae in the soil in this area. Development, bionomics and outbreak of the pest are closely related with the food and environment conditions.
Observations on life cycle, habits and characteristics ofBiston betularia (L.), which is a major pest infecting birch, were made in Daxing’an Mountain forest area, Heilongjiang Province during 1997–1998. In this area, the pest has one generation per year and overwinters as eggs in cracks of the lower part of stem. Adults emerge from mid-July to late August, and the damage of larvae occurs mainly in May and June. Life cycle table ofBiston betularia was given and control suggestions were made in this paper.
The use of resting sites of sables (Martes zibellina) was studied by radio-tracking techniques in Daxing’an Mountains in 1994–1996. The results showed that the males used 191 different resting sites, while females used 159 sites averagely in a year. The number of used resting sites varied among seasons, and the reuse index calculated for each individual in each season varied from 0.07 to 0.94. The reuse index was highest for males in autumn-winter. In spring the number of resting sites of females was significantly less than that of males. In summer, both sexes used more resting sites. In winter, the reuse index was negative related to snow depth. The average distance between consecutively used resting sites differed significantly between males (716 m, SD=479,n=1 081) and females (455 m, SD=298,t=8.59,P<0.001). For males the average distance was the shortest in February–March and the longest in August–September, whereas the shortest distance was recorded in April–May for females. In spring and autumn-winter, most individuals used resting sites that randomly distribute in their home ranges. The standardized Morisita coefficient of resting site dispersion in the home range varied from 0.06 to 0.50. In summer, the standardized Morisita coefficient of resting site dispersion in the home range varied from 0.38 to 0.51. Furthermore, in summer, 72% of all resting sites used by sables were located near the edges of their home ranges.
Molecular genetic maps were commonly constructed by analyzing the segregation of restriction fragment length polymorphisms (RFLPs). Here we described methodology-marker sequences in a new mapping based on recent documents. With the methods they were unique sequences detected by the polymerase chain reaction (PCR). Each of the methods had its limitations and the current trend was to integrate the maps produced by the different methods. Market sequences contained mainly expressed sequence tags (ESTs), polymorphic sequence-tagged sites (STSs), randomly amplified polymorphic DNA (RAPDs), cleaved amplified polymorphic sequences (CAPS), amplified fragment length polymorphism (AFLPs), genome sequence sampling (GSS) and sequence-tagged connectors (STCs) in this paper.
In the recent 20 years, it is a trend that forest will be distributed to villagers to manage in the world. Also in China, “forestry three determinations” has been carried out since 1980, and many new forestry devolutions have been put forward to and come into being. To face the fact of overusing up natural forest to result in the deterioration of ecology environment, the strategy of natural forest protection project (NFPP) is raised after the heavy flood in 1998. Now, it is paid close attention to systematically study to carry out the strategies of NFPP in collective forest area, especially in the community of minority nationalities. Based on the case of forest resource management in Datu Miao Village, the experience of its forest management in the past is analyzed and the strategies of NFPP in collective forest area are put forward.
Through more than one month of investigation on runoff forestry in Luliang mountainous areas of Shanxi Province, the runoff forestry techniques were regarded as having a popularized value in arid and semi-arid areas. The development of runoff forestry in Shanxi Province was summarized and the sustainable development tactics was put forward.
Brazil has a variety of native vegetation. This paper gives introduction about caatinga in the northeastern dry part, cerrado in central part, patanal in southwest, Amazon rain forest in north and northwest, grassland in south, Atlantic rain forest in eastern coast and mangrove and marsh in coast lines. Where there has the greatest biological diversity in the world, about 10% of all the Earth’s species are found. It’s the luckiest country in the world for abundant natural resources. Unfortunately, Brazilian ecosystems were and are threatened by massive deforestation, burning and pollution, due to the uncontrolled expansion of agriculture, timber exploitation, land speculation, colonization, and mining.
In this paper, the theoretical expressions of the specific heat and thermal conductivity of wood are first derived from the micro-structure of wood by applying some basic principles in statistical thermodynamics and physical mechanics. Tested by a great many experiments, the average error of theoretical values is about 5%, much less than that of all kinds of exiting empiric equations in the world.
Dioscorea nippnica Mak is an important traditional Chinese medicinal material with significant economic value. Seeds ofDioscorea nippnica Mak were collected from three forest areas. Germination experiment was carried out with three mediums. Experimental results showed that the species had lower percentage of germination on all mediums. The limiting factors for germination were analyzed.