查看更多>>摘要：In order to improve the accuracy and reliability of identifying wood defects and to realize the maximum wood utilization of trees, we employed an experimental method to test the stress wave propagation velocity in standing Fraxinus mandshurica trees selected from the Harbin Forest Experimental Station in winter. Thirty standing trees in good conditions were taken as test specimens and stress wave propagation velocities were measured using a FAKOPP Microsecond Timer in trees in both fall and winter. The test data were processed with the aid of Excel and SPSS software. The results show that 1) the velocities in longitudinal and radial stress wave propagation in frozen F. mandshurica trees were much higher than those in the non-frozen trees; 2) there was a highly positive correlation between longitudinal stress wave propagation velocity in frozen and non-frozen states, with a correlation coefficient of 0.82, as well as a positive correlation between radial stress wave propagation velocity in frozen and non-frozen states with a correlation coefficient of 0.87; 3) in the frozen state, the longitudinal stress wave propagation velocity was significantly affected by the moisture content (MC) of standing tree, while it was not obvious in the non-frozen state and 4) the radial stress wave propagation velocity was not significantly affected by MC in either frozen or non-frozen state.
查看更多>>摘要：In May 12, 2008, a strong earthquake occurred in Wenchuan County in the northern Sichuan Province of China. It registered 8.0 on the Richter scale with an 11-degree quake intensity, killing a large number of people, and causing extensive damage to the local environment. Wolong National Nature Reserve is about 30 km away from the epicenter and is one of the most important giant panda (Ailuropoda melanoleuca) habitats in China. Based on the impacts of the Wenchuan 512 earthquake and those of other strong earthquakes in the world, this paper reviews and discusses effects of strong earthquakes on geomor- phology, soil chemical and physical properties, forests, bamboo growth, biodiversity, and giant panda habitat. This information may be useful for scientists when undertaking research projects on natural geography, ecological restoration, and habitat restoration in the Reserve and the disaster area.
查看更多>>摘要：Water shortage is a crucial problem in northern China, but in southern China, enormous floods frequently occur. The water problems seriously disturb human life and the sustainable development of the economy and society in the country. To solve the water problem, the government of China approved the South to North Water Transfer Project in 2002. The project will build the east, middle and west routes in which 44.8 billion m3 of water will be transported from the Yangtze River in the southern part to the northern region annually. The east and middle routes are 1154 and 1267 km long, and their respective constructions have been started since 2002 and 2003. The west route is reevaluated. However, the establishment of conservation buffer systems beside the routes to protect the water from severe non-point pollution from agricultural runoff was ignored. Except for pollution, change in the environment from the water exporting to importing area also alters the physical and chemical properties of the transferred water. The protection of the water quality along the routes is a critical issue that significantly influences the purpose of the project. The paper proposes the establishment of conservation buffer systems beside the routes for the protection of the water, and discusses the buffer construction based on some successful cases in western countries.
查看更多>>摘要：The images of post atmospheric correction reflectance (PAC), top of atmosphere reflectance (TOA), and digital number (DN) of a SPOT5 HRG remote sensing image of Nanjing, China were used to derive four vegetation indices (Vis), that is, normalized difference vegetation index (NDVI), trans-formed vegetation index (TVI), soil-adjusted vegetation index (SAVI), and modified soil-adjusted vegetation index (MSAVI). Based on these Vis and the vegetation fractional coverage (VFC) data obtained from field measurements, thirty-six VI-VFC relationship models were established. The results showed that cubic polynomial models based on NDVI and TVI from PAC were the best, followed by those based on SAVI and MSAVI from DN, with their accuracies being slightly higher than those of the former two models when VFC > 0.8. The accuracies of these four models were higher in medium densely vegetated areas (VFC = 0.4-0.8) than in sparsely vegetated areas (VFC = 0-0.4). All the models could be used elsewhere via the introduction of a calibration model. In VI-VFC modeling, using Vis derived from different radiometric correction levels of remote sensing images could help explore and show valuable information from remote sensing data and thus improve the accuracy of VFC estimation.
查看更多>>摘要：By using the forest gap model-FAREAST, we simulated the effects of future climate change on forest composition and forest biomass of typical forests in northeastern China. We selected three different climate change scenarios, developed from GCMs results, of the ECHAM5-0M and HadCM3 models: the current climate, a warmer climate and a state of changing precipitation with higher temperatures. The results are as follows: if the climate does not change, the composition and forest biomass of the northeastern forests will retain their dynamic balance. A warmer climate is detrimental to the major forest types in the northeast. The percentage of major conifers is expected to decrease, along with a proportional increase of some broad-leafed species. The southern treeline of the mixed broad-leafed tree species/ Korean pine forest in the temperate zone will tend to move northward. The warmer the climate, the more distinct the transition. If, furthermore, we were to take account of rainfall, the treeline in the northeast will tend to move northward. Rainfall seems to have little effect on the mixed broad-leafed tree species/Korean pine forests in the temperate zone.
查看更多>>摘要：Floristic composition of the evergreen broad-leaved forest in Jiulianshan Mountain was analyzed based on field investigations and community ecology. The community is rich in species diversity, with 144 sperma-tophyte families including 379 genera and 647 species, in which there are 6 gymnosperm families including 8 genera and 9 species, 21 monocotyledon families including 77 genera and 116 species, and 117 dicotyledon families including 294 genera and 522 species. Dominant families of the flora are Fagaceae, Lauraceae, Aquifoliaceae, Rosaceae, Ternstroemiaceae, Theaceae, Rubiaceae, Mor-aceae and Euphoarbiaceae, most of which are of tropical & subtropical distribution. As for family systematic distribution, the ratio of tropical & subtropical to temperate genera is 100:62.8 in 142 genera of 16 families. As for generic distribution in field investigation data, the tropical & subtropical areal type accounts for the majority of genera, in which there are 205 genera belonging to the tropical & subtropical areal type, 131 genera belonging to the temperate areal type, 35 genera belonging to the cosmopolitan areal type and 8 genera belonging to the endemic-to-China areal type. The ratio of the tropical & subtropical to temperate genera was 100:63.9. Floristic composition of the evergreen forest community in Jiulianshan and the typical species of the zonal flora will provide a scientific foundation for stand rehabilitation and stand establishment approximating a natural evergreen broad-leaved forest community. This study also indicates that the sample data based on community research are valid and convenient for floristic and environmental analysis of the evergreen broad-leaved forest community from the Jiulianshan Mountain.
查看更多>>摘要：Forestry division has been discussed rarely since 1995 in China. The growing interest in forestry provides an opportunity to improve the research tools and approaches that can help achieve a broader understanding of forestry division. Based on research in Yong'an, Fujian Province of China, a framework that may be useful in correlative forestry division study was proposed: 1) the factor-system for Yong'an forestry division was established; 2) the factors were extracted with spatial analysis; 3) the forestry division method of integrated modeling at county level based on GIS was processed. The method was taken through principal components analysis, building the comprehensive model, discriminate analysis, seeking the ideal number of divisions and eliminating the fine polygons. The outcome showed that the method based on GIS with comprehensive modeling could reflect the present situation of forestry development. The relative dominant subdivisions were distinguished reasonably, and a specific direction in forestry development is presented. According to the statistics of the subdivisions' state, the relative dominant subdivisions were clearly demonstrated.
查看更多>>摘要：The subalpine coniferous forests on the eastern Qinghai-Tibet Plateau provide a natural laboratory for studying the effect of climate warming on terrestrial ecosystems. Research on differences between tree species in their responses to experimental warming can provide insights into their regeneration behavior and community composition under a future warmer climate. We used open-top chamber (OTC) to determine the short-term effect of two levels of air temperature (ambient and warmed) and light (full light and ca. 10% of full-light regimes) on the early growth and physiology of Betula albo-sinensis and Abies faxoniana seedlings. The OTC manipulation increased mean air temperature and soil surface temperature by 0.51 and 0.34°C, respectively, in a 60-year-old plantation and 0.69 and 0.41 °C in forest openings, respectively. Warming generally increased plant growth, biomass accumulation, and advanced physiological pro cesses for seedlings of both species. In response to warming, both tree species allocated relatively more biomass to foliage and had significantly decreased root/ shoot ratios (R/S), which might provide the two species with an adaptive advantage when other environmental factors were not limiting. Warming may enhance photosynthesis in the two seedlings by increasing efficiency of PSII in terms of increases in Fv/Fm, photosynthetic pigment concentrations, and apparent quantum yield (Φ)However, the effects of warming on seedling growth and physiological performance varied by light conditions and species. For B. albo-sinensis seedlings, the effects of warming were pronounced only under full-light condi tions, while the growth and physiological responses of A. faxoniana seedlings to warming were found only under low-light conditions. Competitive and adaptive relation ships between the two species may be altered as a result of response differences to warming manipulation. The short-term beneficial impact of warming on the early growth and development of the two species suggests that global warming may lead to changes in regeneration dynamics and species composition in subalpine coniferous forest ecosystems.
查看更多>>摘要：With the aid of canonical correlation analysis, the relations among soil nutrients, soil microorganisms, and soil enzyme activities were studied in vegetation restoration areas of degraded and eroded soils in the Nverzhai watershed in northwestern Hunan. The main results were as follows: the key factors in soil nutrients, microorganisms, and enzyme activities were N and P elements, number of bacteria, carbon and nitrogen in soil microbial biomass and the activities of urease, polyphenol oxidase, phosphatase, and invertase. The activities of urease and polyphenol oxidase are related to the inversion of N and P elements that had important impact on the accumulation of carbon and nitrogen in soil microbial biomass. Moreover, the activities of urease, polyphenol oxidase, and phosphatase could promote carbon accumulation in microbial biomass; however, invertase activities inhibited the accumulation of microbial biomass nitrogen. On the other hand, urease activities were beneficial to the N element content in soils but unfavorable for P elements. There is a negative relation between polyphenol oxidase activity and N element content. For every canonical variable group, the tendencies of soil nutrients, microorganisms, and enzyme activities to accumulate in different soil layers in different vegetation restoration communities could offer some scientific basis for the diagnosis of the health of the soil and the site type division in the process of vegetation restoration.
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