Font Size: a A A

The Characters Of "Fertile Island" And Carbon Sequestration Of Shrub Reaumuria Soongorica In The Desert

Posted on:2015-02-08Degree:MasterType:Thesis
Country:ChinaCandidate:H Y ChenFull Text:PDF
GTID:2250330431952699Subject:Grassland
Abstract/Summary:PDF Full Text Request
In the arid desert, the shrub "fertile island" which was very important to maintain the desert ecosystem health and stablility, was considered as the hub linking the desert vegetation and ecological environment. In addition, the desert as an important part of terrestrial ecosystem, played an important role in regulating in global carbon balance. The research on carbon exchange characteristics of shrub "fertile island", was beneficial to evaluate accurately the desert ecosystem carbon flux and understand the carbon sequestration value of desert ecosystem. Five different size shrub groups were randomly selected.in the dominant shrub Reaumuria soongorica of desert in Alxa. Based on a large number of field survey and lab analysis, the effects of shrub Reaumuria soongorica on its surrounding vegetation and soil resources nutrition, water, microorganism was studied and the ecological characteristics associated with the development of shrub "fertile island"was also discussed in this paper. Meanwhile, the seasonal dynamics of net ecosystem exchange rate (NEE) and ecosystem respiration rate (ER) of different size shrub groups and interspace grassland were measured, and the relationship between the ecosystem CO2exchange rate and its surrounding environment factors was analyzed to discover the process and potential of carbon sequestration of the desert ecosystem. The main conclusions are as follows:(1) The habitat under the shrub canopy inhibited the growth of other herbs. With the spreading of shrub canopy, the inhabitation effect was gradually strengthened, which resulted in the significant reduction of the herb coverage and density. One year later after removing the shrub, the herb community under the shrub became similar with the interspace grassland.(2) The nebkha under the shrub was rich in nutrition, with significant higher soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN) and available phosphorus (AP) than the shrub surrounding soil. Owing to the special protective effects of the nebkha on the soil under the shrub, the soil water content was significant higher than the nebkha and outside soil. The shrub size and soil depth played a significant role in the spatial distribution of shrub surrounding soil SOC, TN, AN and total phosphorus (TP), and the spatial changes of AP were influenced by the interaction of shrub size, soil depth and sampling location while pH was influenced together by shrub size and sampling location. Furthermore, the soil microbial biomass carbon (MBC) surrounding the shrub was relatively lower (55.23-123.77mg/kg), the soil MBC and microbial quotient (qMB) were higher significantly beneath the shrub canopies than outside the canopies, which was the inverse of soil microbial metabolic quotient (qCO2). With the development of shrub, these data gave direct evidence that the soil microbial biomass and activity beneath the shrub canopy remained relatively stable with small changes. Therefore, the formation of nebkhas had played an important role in maintaining the stability and health of soil microenvironment beneath the shrub canopy.(3) In the desert, the shrubs and interspace grassland were the net carbon sinks (-0.012~-1.566C m-2d-1) in the summer (August) and fall (November), while they were the net carbon sources (positive values) in the spring (May) and winter (February). During summer, the net carbon sequestration capability (=-NEE) of the middle size shrub group (III) was the strongest (1.566g C m-2s-1), which was more than five times as much as that of the largest shrub group (V). In August, diurnal NEE fluctuations of shrubs and interspace grassland showed relatively high single-peak curves and asymmetric patterns, with maximum occurring at12:00, presenting that Ⅲ>Ⅲ>Ⅰ>Ⅳ>Ⅴ> interspace grassland. After removing the herb plants from the measuring quadrats of shrub, the net carbon sequestration capability of individual shrub displayed a marked difference compared with the original shrub community, presenting that interspace grassland>Ⅴ>Ⅲ>Ⅲ> Ⅲ> Ⅰ, which indicated the herbs influence significantly the carbon sequestration ability of shrub ecosystems.(4) The NEE seasonal changes of shrub and interspace herb communities were mainly affected by soil temperature. The environmental factors influencing the seasonal changes of ER and GEP in the desert ecosystem were different, the ER changes of middle shrub groups (Ⅱ,Ⅲ,Ⅳ) were controlled by soil temperature and moisture, while the large shrub group, small shrub group and interspace grassland were only influenced by soil temperature. The GEP seasonal changes of all shrub communities were closely related with soil moisture while they in the interspace grassland were affected together by soil moisture and photosynthetically active radiation (PAR).
Keywords/Search Tags:desert steppe, "fertile island", spatial heterogeneity, NEE, carbonsequestration potential
PDF Full Text Request
Related items