Changes In Landscape Pattern And Carbon Storage Of Main Forest Types At Huoditang Forest Region In The Qinling Mountains

Analysis on the landscape pattern is one of important parts in structure and function research of ecosystem. Carbon storage is the foundation in research of carbon cycle and carbon balance in ecosystem. Based on the inventory data including maps and words of Huoditang forest region in the Qinling Mountains in 1958 and 1988 and some representative pattern indices, changes in landscape pattern, and human disturbance effects on the pattern at Huoditang forest region were analyzed by using GIS (Citystar 4.0). At the same time, changes in carbon storage and carbon density of main forest types in this area were calculated based on the biomanss regression equatios established by other scholars in our lab. The results are as follows: Forests in this area were cut from 1960s to 1970s. In 1988, the area of woodland was 91.32 % compared with the area in 1958. This showed that natural renewal capacity of the forests was strong after large-scale disturbance. This suggests a prospective future for the project of Natural Forest Protection. According to the principles of landscape classification produced based actual conditions, the secondary landscape types were classified into four levels. At first level, 10 landscapes types and 24 patches were classified; 11 landscape types and 35 patches at second level; 23 landscape types and 85 patches at third level; 38 landscape types and 110 patches at the fourth level. Analysis on the characteristics of patch, patch area, patch perimeter, and heterogeneity at the different levels showed that closed woodland was matrix of first landscape level with the highest area, longest perimeter, and lowest fragmentation. Natural secondary forest landscape type was main element of second landscape level with the highest area, longest perimeter, and lowest fragmentation. Natural secondary forest landscape and artificial plantation forest landscape types were produced by large-scale cutting between 1960s and 1970s. Fragmentation of artificial plantation forest landscape type was higher than secondary forest landscape type. Mixed forest landscape was the main type at third landscape level. Hard broadleaves mixed forest was main type at the fourth landscape level. The landscape spatial pattern changed with elevation. In the range of <1600 m elevations, the main forest landscape type was secondary broadleaves mixed forest that with the highest diversity and largest areas. In the range of 1600 m～1800 m elevations, secondary firm broadleaves forest was main landscape type. Owing to large areas of Quercus aliena var. acuteserrata, Pinus tabulaeformis, and P. armandii, the landscape characters in this elevation range showed exhibition of mixed forest between pine and oak. The growth suitable elevation of P. armandii lie in the range of 1800 m～2000 m. Mixed forest type that dominant species was P. armandii, and subdominant was Betula albo-sinensis was main type that effected the landscape characteristics in this elevation. The area of secondary hard broadleaves was the largest in the range of 2000 m～2200 m elevation. The areas of others were equal. So the secondary firm broadleaves was dominant landscape type in this elevation. Picea asperata mixed forest types was the dominant landscape above 2200 m elevations. Artificial landscape types were distributed along the road. Its spatial distribution pattern was affected by human will in some extent. The artificial P. tabulaeformis forest, artificial P. armandii and Larix principis-rupprechtii were distributed from low elevation to high elevation. Cutting was the main force that induced the changes of landscape pattern at Huoditang forest region. The changes of landscape pattern happened in the landscape types and the number of landscape types, namely disturbance made part landscape types disappeared in original landscape, and some new landscape types appeared in secondary landscape. The new appeared landscape types in secondary were artificial landscape type, mixed broadleaves forest type, and others. This showed that renewal species in this area become complex after cutting. The disappeared landscape types were willow type and poplar types that include Populus davidiana and P. purdomii. None changed landscape types were P. armandii mixed forest, Q. aliena var. acuteserrata mixed forest, B. albo-sinensis mixed forest, and P. asperata mixed forest. These forest types were zone of vegetation at Huoditang forest region which had strong renewal ability. The changes of these types in distribution of patches, patch areas, and heterogeneity. The patch number of P. armandii mixed forest landscape type increased from 3 to 14, area of it increased from 104.499 hm2 to 569.781 hm2, and its diversity and dominance increased distinctly. The patch numbers of B. albo-sinensis increased from 5 to 8, but the area of it reduced from 727.991 hm2 to 396.298 hm2, its dominance decreased. Use Markovian model analyzed the transfer probability among areas of different landscape types in 1958 and 1988. The results showed that the actual conditions were consistent with the model results. Age and elevation were two main factors that affected forest carbon storage and carbondensity in the research of mountain forest types. With the increasing of age, carbon density of forest increased, carbon storage increased at beginning and then followed. Forest carbon accumulation included three parts. In the phase of stabilization of carbon accumulation, B. albo-sinensis had the highest capacity of carbon accumulation. In the suitable growth elevation range of middle-aged B. albo-sinensis and middle-age P. armandii forest, the value of carbon accumulation of these types were the highest. After cutting, P. armandii plantation, P. tabulaeformis plantation, and L. principis-rupprechtii plantation were planted in part of mountain. Because the consistent of forests planted time, the main artificial forest types were all middle-aged. In this age, carbon density of artificial forest types was higher than secondary forest types. So, the function of carbon sink of forest ecosystem could be increased by planting trees in the place where no forests and desolation area in the Qinling Mountains. Most of CO2 were set free into the air induced by cutting. The carbon storage in secondary forest ecosystem were 67.54 %, and 32.37 % of them were stored in the artificial forest types. It was needed very long time to comeback to original situation. Because lack of carbon storage soil and fall, the function as carbon resource or carbon sink of forest ecosystem at Huoditang forest region was can't be explained reasonable. Carbon storage and carbon density spatial distribution were changed by cutting in 1958 and 1988. The areas of higher carbon storage forest in 1958 transformed into the areas of lower carbon storage in 1988. The area lower carbon storage in 1958 transformed into the area of higher carbon in 1988.