The Dynamics of Forest Litter and Its Responses to Global Warming
2002; Elsevier BV; Linguagem: Inglês
ISSN
1000-0933
Autores Tópico(s)Environmental Changes in China
ResumoIn this article we reviewed the latest development in the studies on the forest the litter dynamics. Study on the litter dynamics advances with the improvement of research methods. Litter decomposition rate is controlled by both the intrinsic factors such as the chemical and physical properties of litter and by the extrinsic factors i.e. environmental conditions including biotic factors such as the species, abundance and activity of the heterotrophic microbiomes and soil fauna, and abiotic factors such as climate, soil and atmospheric compositions. As the control factors of litter decomposition, the chemical properties of litter (also called litter substrate quality) include concentrations of nitrogen, phosphorus, lignin and cellulose; and the ratios of C/N, lignin/N, C/P etc. Among them C/N and lignin/N are the best predication indexes of litter decomposition rates, because they reflect the ratio of carbohydrate and lignin to protein in litter, which is the essential property of litter. However on the different stages of litter decomposition the predication indexes should be altered with the change of litter substrate quality. With respect to the abiotic factors, rising temperature increases the litter decomposition rate. Rainfall affects the leaching of chemical substances in litter. Nutrient status of soils affects the litter quality, hence influences the litter decomposition rate. Temperature, rainfall and other abiotic factors also indirectly influence litter decomposition through their effects on the biotic factors. With regard to the biotic factors, the activities of microbiomes and soil fauna are more important on the later stage to decompose recalcitrant component in litter. We also discussed the likely changes of forest litter dynamics due to global warming. Global warming might lead to the moving of forest zone and the changes of the factors that control litter decomposition, thus it affect the dynamics of forest litter and the function of nutrient cycling in forest ecosystems. Global warming may increase the biomass of forest ecosystems and increase the litter production. The incretion of the litter production in the tropical and subtropical forests is lower than that in temperate and boreal forests because of the different contents of climate warming in those forests. The litter standing depends on the rates of litter production and litter decomposition. If the incretion of the litter production rate is more than that of litter decomposition rate,litter becomes the source of atmosphere CO 2. While in the late one, it becomes the sink. The effects of global warming on litter decomposition rate can be divided into direct effects and indirect ones. With respect to the direct effects, it is not clear whether the litter substrate quality will change with the climate warming. The effects of abiotic factors on litter decomposition are not consistent under climate warming. On one hand rising temperature reinforces soil N mineralization and promotes the availability of soil nutrients, thus is in favor of litter decomposition. On the other hand, it causes evaporation strengthening on soil surface and the decrease of soil humidity, which is unfavorable of litter decomposition. The effects of the biotic factors change are more prominent than the other two. Rising temperature enhances the activities of microbiomes and promotes litter decomposition rate. In dry areas the function of bacterial will intensify on litter decomposition. Indirect effects of global warming affect the control factors of litter decomposition rate through the migration of climate and forest zones and phenological change. Global warming might induce changes of forest distribution. The areas of tropical forests and subfrigid forests might increase and that of temperate forests and boreal coniferous forests might decrease, which might change the structure and species of the original forest communities and the kinds of litter. More decomposable litter from tropical forests and subfrigid forests falling down the forest floor will increase t
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