Showing papers by "Jingyun Fang published in 1998"

Forest biomass of china: an estimate based on the biomass–volume relationship

Abstract: In this study, a method was developed to estimate the forest biomass of China based on the relationship between stand biomass and volume. Biomass-volume relationships were quantified for all the main forest types in China using 758 sets of data obtained from direct field measurements. These relationships were used to convert volume measurements into total biomass values (above- and belowground dry masses) based on 1984-1988 forest inventory data for China. The latter had been compiled from more than 250000 permanent and temporary field plots across the country. This data contained information on forest area and timber volume for each ape class and site class for all forest types at the provincial level. As a result, the total forest biomass of China was estimated as 9103 Tg (1 Tg 10(12) g), with 8592, 326, and 185 Tg from forests, special product plantations, and bamboo Forests, respectively. The area-weighted mean biomass density was 84 Mg/ha (1 Mg = 10(6) g). For comparison, two additional estimates, one based on the mean biomass density method and another based on the mean ratio of biomass to stem volume, were also derived. Compared to the biomass-volume relationship method, the mean biomass density method considerably overestimated the forest biomass of China (by 59.6%), while the mean ratio of biomass to stem volume method slightly underestimated it (by 12.1%). Despite the small forest biomass value due to a low forest cover, the area-weighted mean biomass density was comparable to those of other regions in the middle and high latitudes except in the United States. We believe that our study provided not only an appropriate estimate of forest biomass for China, but also an improved methodology for estimating forest biomass at the regional, national, and global level.

Factors affecting soil respiration in reference with temperature’s role in the global scale

Abstract: Soil respiration is CO2 evolution process from soil to atmosphere, mainly produced by soil micro-organism and plant roots. It is affected not only by biological factors (vegetation, micro-organism, etc.) and environmental factors (temperature, moisture, pH, etc.), but also more and more strongly by man-made factors. Based on literature survey, main factors affecting soil respiration were reviewed. The relationship of soil respiration to latitude and to mean annual temperature were analyzed by using the data measured from forest vegetation in the world. As a result, soil respiration rate decreased exponentially with an increase of latitude, and increased with increasing temperature. Following the relationship between soil respiration and temperature, Q10 value (law of Van Hoff) was obtained as 1.57 in the global scale.