Green water is vital to vegetation recovery in karst area. Considering the processes in green water cycle, this paper coupled the canopy interception process, soil moisture movement process and evaportranspiration process, and built a green water cycle processes model to simulate and analyze green water cycle of typical vegetation types in karst area. Under the rainfall simulation experiment calibration and soil moisture monitor calibration, the model was extended to regional scale, and was used to simulate the green water cycle in a karst area, Guizhou Province, China, during October 2005 to March 2006. The results show that: First, most of the rainfall during this period turns into green water through canopy interception and infiltration into soil, which totally occupies 87.4% of rainfall and is supplied for vegetation ecosystem water use. Second, there are many differences in green water cycle processes of different vegetation types in the study area. The percentages of green water of different vegetation types are 93.3%, 93.2%, 91.5%, 81.9% for shrubs, coniferous woodland, mix woodland, grassland respectively. It can be concluded that with the vegetation recovery from grassland to shrubs and woodland in the study area, there will be more and more rainfall turning into green water which is used by the vegetation ecosystem and benefits the vegetation recovery. Third, the changes of green water cycle between months in different vegetation types share the same characteristics. The green water storage is increasing in October, January, and March in all vegetation types, and is decreasing in November, December, and February. In this period, the amount of green water is much greater than that of blue water, and the green water storage is increasing overall. Drought is unlikely to occur during October to March and the green water storage is supplemented in this period before the "spring drought" and "summer drought" in this karst area.
Land development and consolidation plan is bound to affect ecological environmental conditions within the planned area. However, the specific evaluation method, index system and modeling algorithm should be standardized. By taking Lianshui County of Jiangsu Province as an example, Land Development and Arrangement Plan of Lianshui County (2000~2010) was analyzed, and the affection was compared by a evaluation model of scenarios. The result shows that the influence in 1997 was lower than in 2000 in Lianshui County. This can be explained as: during the three years, not only the occupation of cultivated land has been strictly controlled, but more cultivated lands have been transferred also. Environmental quality declined in 2010 because of without planning. The possible reason is that the construction of land fragmented farmland and unutilized land, which increases density of plaques. In comparison of future scenarios without planning and with planning in 2010, it is indicated that eco-environmental conditions could obviously increase by 0.6736 percentage point. This shows that proper land development and consolidation plan plays an important role in promoting a healthy eco-environment within the planned area.
Recently, a lot of orchards in the gully region of the Loess Plateau have been degenerated, which should be returned to cultivated land. But the ecological water effect of returning orchard to cultivated land is still unclear. Taking the Wangdonggou watershed as a case study, this paper chose three land use types such as peak period orchard, waste orchard and cultivated land converted from orchard, the ecological water effects of returning orchard to cultivated land have been studied based on the soil moisture data of 1986, 2002 and 2009. The results show that: (1) The mean soil moisture content and water storage of wasted orchard and cultivated land converted from orchard are significantly bigger than those of the peak period orchard in 2009. With the orchard disuse or return to cultivated land, the soil moisture content will increase significantly. (2) When the land use changes from peak period orchard in 2002 to cultivated land in 2009, the mean soil moisture content of 200-600 cm profile of cultivated land converted from orchard is 10.62%, which is significantly bigger than that of the peak period orchard (8.53%). (3) Dried soil layer affected by biota use is a common soil water phenomenon in the peak period orchard, wasted orchard, and cultivated land converted from orchard, which is an urgent ecological problem that need to be resolved.
The study on soil carbon sequestration at regional scale is of great significance, as the Kyoto Protocol and other accords of the United Nations Framework Convention on Climate Change have prescribed that carbon (C) sequestration in soil can be included in the measures to meet the Quantified Emission Limitation or Reduction Commitments in the first period (2008~2012). The methods on estimating the amount of C sequestration in soil at regional scale were reviewed, and the development of the methods was prospected. According to the estimation accuracy and principle, the approaches could be categorized into four methods: (1) Simple model, which scaled up the estimation of SOC sequestration from local plots to region simply or by statistical model, was used widely but with low accuracy. The method was recommended in the region without sufficient data. (2) Inventory method, which was used in soil database of different periods to estimate the change of soil carbon between the two periods, could be used to estimate the amount of carbon sequestered in soil in the past with higher precision, but it could not be used to predict the change of soil carbon in the future. (3) Empirical model including the Book-keeping Model and the Tier 1 and Tier 2 recommended in IPCC Report (2006 IPCC Guidelines for National Greenhouse Gas Inventories) could provide environmental interpretation in soil carbon sequestration with no mechanism explanation. (4) Mechanism model developed from soil organic matter mechanism model (e.g. CENTURY model) based on geographic information system (GIS) could estimate SOC sequestration with highest accuracy among these four methods, which could also provide mechanism explanation in the process of the change in SOC. In summary, each type of the four methods had its own limitation and applicability, so the methods should be chosen based on the site-specific conditions and the research purposes. Finally, based on the analysis of some gaps in the mechanism of soil carbon sequestration, scaling, scenario analysis and soil organic matter model, we proposed that the integrated model,based on GIS, coupling SOM mechanism model, land-use model, econometrical model and regional scale eco-hydrological model, would be developed for studying soil carbon sequestration at regional scale in the future.
The Qinling Mountain Range is considered as an important geo-ecological boundary between the warm temperate and the subtropical zones in eastern China, however, the specific line of the boundary has been controversial among the academic circles. Several studies based on vegetation ecology and flora geography have been done on discussing the division of this boundary, but in all of which Pteridophyta is not included. Pteridophyta is a transitional link between different flora groups in plant evolution, and thus is more sensitive to the environment that fosters it than other plant groups. It is conducive to and necessary for a better understanding of the division of the geo-ecological boundary in Qinling Mountain Range to research into the Range's Pteridophyta flora. In this paper, the composition and geographical elements of the flora of Pteridophyta were studied, and the division of the vertical Pteridophyta spectrum and the further division of the geo-ecological boundary in Qinling Mountain Range were also discussed, by applying the principles of classical florology and using quantitative ecology method as TWINSPAN and DCA into the analyses, based on comparison between the field investigation data and the relevant literatures. The results of our research have shown and revealed: 1) There are 311 species of Pteridophyta, belonging to 85 genera and 36 families in the Qinling Mountain Range; in which the dominant families are Dryopteridaceae, Athyriaceae, and Polypodiaceae, and the dominant genera Dryopteris and Polystichum; meanwhile, the main areal-types of family and genera are tropical elements, while the areal-types of species is dominated by the temperate elements. 2) The altitude of 1000 m a.s.l. at the southern piedmont of the Range should be an important ecological boundary, since the floristic composition of the Pteridophyta below this elevation showed more similar features to the subtropics, while above it the features of the composition and the vertical vegetation spectrum of the Pteridophyta are much closer to the temperate zones. 3) DCA ordination of FER (floristic element ratio) among 15 regions in northern and southern China and the both sides of Qinling Mountain Range strongly supported the hypothesis mentioned above. Based on these results, we tend to deem that the geo-ecological boundary between the subtropical and warm temperate zones lies around the altitude of 1000 m a.s.l. at the southern piedmont of the Range.
The impact of anthropogenic activities on carbon cycle is fulfilled through land use change. It is helpful to study the impacts of land use change on carbon cycle through linking carbon emissions to different land use types. By using data of energy consumption and land use of Jiangsu province from 2003 to 2007, this paper estimated carbon emission by energy consumption through carbon emission model, and analyzed the carbon emission and carbon footprint of different land use types through linking carbon emission to different land use types. The conclusions can be drawn as follows.(1) Total carbon emission from energy consumption of Jiangsu province increased from 8792.24×104 t (2003) to 16329.85×104 t (2007) with an annual rate of 86%, of which carbon emission from terminal fossil energy use accounted for 53.6%. Because carbon emission from fossil energy use was the main reason for the increase of total carbon emission, developing clean energy and improving energy efficiency are the key methods to decreasing total carbon emission. (2) Per unit area carbon emission of Jiangsu increased from 8.24 t/hm2 (2003) to 15.53 t/hm2 (2007) with an annual rate of 88.5%, of which per unit area carbon emission from residential and industrial areas was the highest (95.62 t/hm2), indicating that dwelling districts and industrial parks were the regions that contributed carbon emission mostly. So, improving energy structure and improving energy efficiency of the above regions was crucial in carbon emission reduction. (3) Carbon footprint of energy consumption was greater than the area of ecological productive land, and the ecological deficit was 1351.28×104 hm2 in Jiangsu in 2007. It is indicated that the carbon absorption of terrestrial ecosystems of Jiangsu Province cannot compensate the carbon emission of energy use. So strengthening environmental protection and enhancing carbon sequestration rate could effectively decrease the carbon emission intensity. (4) The descending order of carbon footprint of different land use types was: residential and industrial area, transportation area, unused land and special use area, agricultural land and water conservancy area. So, adjusting the land use pattern and introducing carbon footprint and carbon emission reduction into land use planning is one of the effective methods to reduce regional carbon footprint. (5) Per unit area carbon footprint of Jiangsu increased from 0.938 hm2/hm2 (2003) to 1.769 hm2/hm2 (2007), which indicates that the carbon footprint of land use had been expanded since 2003.
