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41.
Anna Laine Terhi Riutta Sari Juutinen Minna Vliranta Eeva-Stiina Tuittila 《Ecological modelling》2009,220(20):2646-2655
Chamber method is commonly used to measure the CO2 exchange from plant communities. Due to low time resolution, actual measurements reflect only momentary CO2 exchange rates. Therefore, a common way to derive seasonal or annual estimates is to establish models describing the response of CO2 exchange to environmental variables, and then to reconstruct the CO2 exchange over the desired time period. There are several alternative ways to obtain the CO2 balance for the entire mire: models can be parameterized by individual sample plots, plant communities or the entire site. Similarly, the CO2 balance can be reconstructed by plots, plant communities or the entire site. We tested how the choice of the modelling and reconstruction approach influences the CO2 exchange estimates for the entire mire and for individual sample plots and plant communities. We measured the CO2 exchange in a spatially heterogeneous sedge-dominated northern aapa mire for two growing seasons. We observed high spatial variation in CO2 balance between the plant communities. We noticed that when the CO2 balances of individual sample plots or plant communities are of interest, using a model appropriate for the entire site may result in biased estimates. In worst case the different modelling approaches may turn the CO2 balance of an individual sample plot from positive to negative. Further, while using the whole ecosystem approach in modelling, the superior ability of chamber method in acknowledging spatial variation is lost. While the modelled growing season CO2 balance of the mire ranged from 232 to 625 g CO2 m−2 depending on the chosen modelling and reconstruction approach, the average estimates still remained within the uncertainty range of one another. Acknowledgement of the spatial variation in plant community level makes the areal estimate more robust to varying weather conditions. Further, the reliability of estimates is improved by explicit formulation of the choices behind the modelling and reconstruction units reflecting the study objectives. 相似文献
42.
Kivimäenpää M Jönsson AM Stjernquist I Selldén G Sutinen S 《Environmental pollution (Barking, Essex : 1987)》2004,127(3):441-453
Light (LM) and transmission electron (TEM) microscopy were used to study previously specified ozone symptoms in the foliage of Norway spruce. The three youngest green needle generations from twenty mature trees in two stands on sites of different soil fertility at Asa, southern Sweden, were sampled in 1999. The critical dose of ozone, expressed as AOT40, was 6,362 ppb.h. LM showed ozone-specific symptoms: decreased chloroplast size with electron dense stroma advancing gradually from the outer to the inner cell layers, being most severe in the needle side facing the sky. The symptoms were expressed as ozone syndrome indices at the needle generation, tree and stand levels. The index had higher values at the low fertility site. TEM was used to confirm the LM results. The study shows that LM can be used for diagnosis of the impact of ozone on conifers in the field. 相似文献
43.
Soil fungistasis and its relations to soil microbial composition and diversity: a case study of a series of soils with different fungistasis 总被引:1,自引:0,他引:1
Fungistasis is one of the important approaches to control soil-borne plant pathogens.Some hypotheses about the mechanisms for soil fungistasis had been established,which mainly focused on the soil bacterial community composition,structure,diversity as well as function.In this study,the bacterial community composition and diversity of a series of soils treated by autoclaving,which coming from the same original soil sample and showing gradient fungistasis to the target soil-borne pathogen fungi Fusarium gr... 相似文献
44.
Li Weian Cui Guangyao Zheng Minna 《Environmental science and pollution research international》2022,29(4):5162-5171
Environmental Science and Pollution Research - Green finance is one of the most important ways to help companies achieve green transformation and development. We construct a quasi-natural... 相似文献