Zhang Yiping

Managing carbon sinks in rubber (Hevea brasilensis) plantation by changing rotation length in SW China.

Extension of the rotation length in forest management has been highlighted in Article 3.4 of the Kyoto Protocol to help the countries in their commitments for reduction in greenhouse gas emissions. CO2FIX Model Ver.3.2 was used to examine the dynamics of carbon stocks (C stocks) in a rubber plantation in South Western China with the changing rotation lengths. To estimate the efficiency of increasing the rotation length as an Article 3.4 activity, study predicted that the rubber production and C stocks of the ecosystem increased with the increasing rotation (25, 30, 35, 40 and 45 years). While comparing the pace of growth both in economical (rubber production) and ecological (C stocks) terms in each rotation, 40 years rotation length showed maximum production and C stocks. After elongation of 40 year rotation to four consecutive cycles, it was concluded that the total C stocks of the ecosystem were 186.65 Mg ha-1. The longer rotation lengths showed comparatively increased C stocks in below ground C stock after consecutive four rotations. The pace of C input (Mg C ha-1yr-1) and rubber production indicated that 40years rotation is best suited for rubber plantation. The study has developed carbon mitigation based on four rotation scenarios. The possible stimulated increase in C stocks of the entire ecosystem after consecutive long rotations indicated that the emphasis must be paid on deciding the rotation of rubber plantation in SW China for reporting under article 3.4 of the Kyoto Protocol.

A preliminary study on the heat storage fluxes of a tropical seasonal rain forest in Xishuangbanna

In order to discuss the values and daily variation characteristics of heat storage fluxes in a tropical seasonal rain forest in Xishuangbanna, the sensible and latent heat storage flux within air column, canopy heat storage flux, energy storage by photosynthesis and ground heat storage above the soil heat flux plate, as well as the ratios of these heat storage fluxes to the net radiation in the cool-dry, hot-dry and rainy season were compared and analyzed based on the observation data of carbon fluxes, meteorological factors and biomass within this tropical seasonal rain forest from January 2003 to December 2004. The findings showed that heat storage terms ranged significantly in the daytime and weakly in the nighttime, and the absolute values of sensible and latent heat storage fluxes were obviously greater than other heat storage terms in all seasons. In addition, the absolute values of total heat storage fluxes reached the peak in the hot-dry season, then were higher in the rainy season, and reached the minimum in the cool-dry season. The ratios of heat storage fluxes to net radiation generally decreased with time in the daytime, moreover, the sensible and latent heat storage dominated a considerable fraction of net radiation, while other heat storage contents occupied a smaller fraction of the net radiation and the peak value was not above 3.5%. In the daytime, the ratios of the total heat storage to net radiation were greater and differences in these ratios were distinct among seasons before 12:00, and then they became lower and differences were small among sea-sons after 12:00. The energy closure was improved when the storage terms were considered in the energy balance, which indicated that heat storage terms should not been neglected. The energy closure of tropical seasonal rain forest was not very well due to effects of many factors. The results would help us to further understand energy transfer and mass exchange between tropical forest and atmosphere. Moreover, they would supply a research basis for studying energy closure at other places.

Comparison of spatial-temporal distribution characteristics of water temperatures between Lancang River and Mekong River

Water temperature (WT) is one of the important indicators of water body physical properties. Understanding the characteristics of spatial-temporal variation on WT in the river continuum will help to develop the rational river-water-resource utilization plan, to avoid the possible ecology crisis, and to take full advantages of the natural resources in the involved region. As the biggest international river continuum in Asia, the Lancang-Mekong river subregion (known as Greater Mekong Subregion, GMS) has become a famous economic, political, and ecological natural territory. This study examined the spatial-temporal distribution characteristics of the Lancang River water temperature, using the observational data of WT values from 11 hydrological stations in 1960s. Furthermore, the WT differences between Yunjinghong hydrological station (one representative station in China) and Chiang Saen hydrological station (one representative station in Thailand) were analyzed. Results indicated that: 1) Water temperature was higher in the lower part of the river continuum than the upper part. Latitude variation is the main influencing factor. This effect is more obvious in dry season than in rainy season, more obvious in winter than in summer, and more obvious of the average minimum WT than the average maximum WT; 2) WT difference between the upper and the lower parts of the river continuum was decreasing due to little increase of WT in the upper part (Yunjinghong hydrological station) and obvious decrease of the WT in the lower part (Chiang Saen hydrological station) during the research period. Therefore, the parameters of WT are affected by the latitude, and the Lancang-Mekong river continuum lies in the north-south direction, so the tropical aquatic creatures, such as the tropical aquatic fishes, cannot survive in the upper part of this river continuum in winter season, while in summer season, the tropical aquatic creatures properly swim to the upper stream. The water temperature in the lower Mekong River is mainly influenced by the regional water temperature and regional climate change.

Factors acting on the distribution region of Carlemanniaceae: Rainfall, temperature and the plants' biological characteristics

The family Carlemanniaceae in East Asia and tropical Asia, comprising two genera, Carlemannia and Silvianthus, are mainly distributed along the southern foot of the Himalaya Mountains and the western and southern interface of the Yunnan Plateau. The main reproductive process for Carlemannia tetragona was verified as self-pollination by the pollination experiments in this work. Germination rates for seeds of both C. tetragona and Silvianthus bracteatus could reach 100% when the seeds were collected after two months, while the rates decreased to 25% when collection took place in the previous year. It was found that the seed had no dormancy stages, and their seed banks were of the Transient Soil type. In field observations, the dehiscence status for fruits showed that their seeds could not be ejected effectively by capsules for dispersal. After analyzing the temperature and rainfall data from the years 1971 to 2000, it was shown that annual rainfall, the lowest mean monthly temperature in a year, and the extreme lowest temperature in a month had a great effect on the distribution range of Carlemanniaceae, while the mean annual temperature had a lesser effect. The narrow distribution range of Carlemanniaceae was affected by multiple factors, such as the short pollen dispersal distance and the Transient Soil Seed Bank. The population sizes of Carlemanniaceae were also easily affected by the level of rainfall, not by any single variable.