Carbon accumulation and distribution were studied at three sampling plots in a 13-year-old mixed planatation of and in Daqingshan, Guangxi, China. The results showed that carbon content varied with tissues and tree species, but the total carbon content of was higher than that of . The average tissue carbon contents of were: wood (58.6%) > root (56.3%) > branch (51.2%) > bark (49.8%) > leaf (46.8%), while those of were: bark (52.2%) > leaf (51.8%) > wood (50.2%) > root (47.5%) > branch (46.7%). The carbon contents of the soil (at a depth of 60cm) ranged from 1.45% to 1.84% with an average of 1.70%. Carbon contents were higher in the surface soil (0–20cm) than in the deep layer (below 20cm). The average carbon contents were the highest for trees (51.1%), followed by litter (48.3%), shrubs (44.1%), and herbs (33.0%). The biomass of the trees in the three plots ranged from 85.35 t hm to 101.35 t hm with an average of 93.83 t hm , in which 75.7%–82.6% was . The biomass of the understory was 2.10–3.95 t hm with an average of 2.72 t hm , while the standing stock of ground litter was 5.49–7.91 t hm with an average of 6.75 t hm . The carbon storage in the mixed plantation reached the maximum in the soil layer (69.02%), followed by vegetation (29.03%), and standing litter (1.82%). The carbon storage in the tree layer occupied 23.90% of the total ecosystem and 97.7% of the vegetation layer. accounted for 65.39% of the total carbon storage in the tree layer. Tissue carbon storage was directly related to the corresponding amount of biomass. Trunks had the highest carbon storage, accounting for 53.23% of the trees in and 55.57% in , respectively. Roots accounted for about 19.22% of the total tree carbon. The annual net productivity of the mixed plantation was 11.46 t hm a , and that of sequestered carbon was 5.96 t hm a , which was equivalent to fixing CO of 21.88 t hm a . The plantation was found to be an important sink of atmospheric CO .
The relationship between land features and their spectral characteristics is important for the interpretation of remote sensing images. In this study, the spectral characteristics of a submerged plant with varied coverage was measured with a ground sensor/radiometer, FieldSpec™ Pro JR Spectroradiometer in the laboratory and in the constructed wetland of “Mengqingyuan”, Shanghai, China. The results showed that the reflectance rate of rose with its increasing coverage, which was exhibited both at the visible band (500–650 nm) and the near infrared band (700–900 nm). Water quality influenced the reflectance rate with the primary differences between the laboratory and field experiments mainly occurring at the near-infrared band (700–900 nm). A regression analysis was carried out respectively between the coverage of and the reflectance rate at the wavelengths of Quick Bird 4 bands where the coverage responded to the strongest. These results of regression analyses showed a clear linear relationship, by which the coverage of could be quantitatively deduced from the reflectance rate measured in situ. The implications in terms of the ability of hyperspectral remote sensing to distinguish and monitor the distribution and dynamics of submerged vegetation on a large scale are discussed.
Over the last century urbanization on the landscape has increased and intensified. Urban development has a great impact on the environment at the local, regional and even global levels. As a driving force in global change, the need to understand the dynamics of urban pattern and its change in an accurate and efficient manner is ever more pressing. Based on aerial color infrared photography in 1985 and QuickBird satellite imagery in 2004 and according to the standard for plan and construction of city land use, the landscape of Guigang City was divided into 11 types. In the landscape classification maps, 31 buffer zones, each being 200 m wide, were divided. With the aid of GIS software ArcView 3.2 and landscape pattern analysis software FRAGSTATS 3.3, the landscape spatial patterns of each buffer zone were analyzed at the landscape level and class level. The landscape indices, such as patch size, patch fractal dimension, diversity index and evenness index, were calculated. The results indicated the following: The total area of the residential land and the communal land in 2004 covered 46.3% of the entire constructed area of Guigang City and the sum of the patch number of the two patch types occupied about 39.7% of the total patch number, while the percentages were respectively 48.2% and 45.4% in 1985. This showed that the mosaic landscape with the residential land and communal facilities land became increasingly unclear following urban development and landscape diversity. Based on the gradient analysis with the landscape-level index and the class-level index, there were two business and finance centers in the constructed area. One was located in the urban center with a range of 0.8 km; the other was from the 10 to the 16 zone. In each buffer zone, the mean patch size was larger and the landscape shape was more regular in 2004 than in 1985. Furthermore, the Shannon diversity index of each buffer zone rose in 2004 with patch richness and evenness increasing. The landscape index computed for the main landscape types (communal facilities land, industrial estate land, residential land and farmland) in the middle of the buffer zones clearly indicated the changes taking place in urbanization. The patch size and the patch number of industrial estate land and farmland also pointed to these changes, while communal facilities land and residential land assumed another similar tendency towards changes. In each gradient zone, industrial estate land had the most complex shape, the lowest area percentage of each zone and the biggest mean patch size, whereas communal facilities land and residential land were opposite to industrial estate land. Farmland had a steady percentage along the buffer zone and its continuous distribution had an important impact on the urban eco-environment. The question of how to relate the pattern of changing characteristics along the buffer zone to the urban ecological process and urban ecological planning remains to be studied further in the future.
用特殊设计的气体采集箱法对玉米生长期间潮土呼吸强度进行了测定。结果表明，施用150kgNhm^-2的裸地土壤CO2累积排放量是294g C m^-2，约为种植玉米土壤的一半。用根去除法测得的玉米对土壤呼吸的贡献率，苗期小于20％，拔节到收获期波动在30％-70％之间，全生长期平均为46％。玉米生长期间因土壤有机碳分解而释放出的CO2总量为2．94MgChm^-2，大约是0—40cm土层中土壤有机碳总储存量的8％，因此需要输入7．35Mghm^-2的碳含量40％的作物残留物才能平衡土壤中有机碳的损失，约为玉米收获时残留于土壤中根量的一倍，但与残留根量及玉米生长期间根系分泌到土壤的有机物量的总和相当，因此土壤中有机碳总体处于平衡状态。在玉米生长期间，施用氮肥可使土壤CO2排放量降低10％。土壤排放CO2主要受土壤温度的影响，温度效应Q10为1．90-2．88。