The Study On Characteristic Of Soil Seed Bank And Its Impact For Spontaneous Vegetation Recovery In Mountainous Region Of Northern Hebei

Chain is one of the countries that their mountain ecosystem are under serious degradation,which has promoted the practice and research of vegetation restoration and reconstruction of degraded mountain earlier in the world.Due to longer recovery times of degraded mountain and bigger expenditure, researchers are eager to seek the key mechanism and solute technical matters as soon as possible. Spontaneous recovery of vegetation is one of the effective approach,which can prevent biological invasion and guarantees ecological system security and promotes ecosystem progressive succession radically,and it is the widely supposed by international communities as major development tendency too. The soil seed bank is the animate seeds consist in surface soil.Its existence would offer the propagulum for succession of phytocoenosium and recovery of damaged ecosystem,thus, proceeding vegetation spontaneous recovery with the help of soil seed bank is the effective approach of nearly natural vegetation restoration.In this study the characteristic of soil seed bank and condition of overground vegetation under different soil edaphic conditions and site types by field survey and indoor culture are compared and analysised, with main conclusions being achieved as follows:1.Biotype of species of soil seed bank was based on the principle of the perennial herbs,dicotyledons were in the majority, in which the composite family and the grass family occupyed larger proportion,and shrubs and woody plants appeared by chance in mountainous region of Northern Hebei.Average reserves of seed bank was between1992 and 3446 grain/m~2, similarity coefficients between soil seed bank and overground vegetation are all lower,between 0.16 and 0.38.2.Number of species,seed density,indexes of diversity and sorensen similarity index with overground vegetation were higher in well water condition compared with other different water conditions in BR、UR and NR,whereas,seed density under drought condition was almost the same with well water conditions.3.Number of species and indexes of diversity were the higher in sand burial 0.5cm conditions compared with other different sand burial conditions in BR、UR and NR. Seed density were significantly reduced with sand buried depth increased in BR and NR,whereas that in UR was not reduced obviously.The date of sorensen similarity index between seed bank and overground vegetation had shown that the value under 0.5cm depth sand burial is equal to 2cm in BR, less than 2cm in UR, and more than 2cm in NR.4.The number of species of seed bank under protected measure was 7,and and seed density achieved 1992.87 grain/m~2, anb sorensen similarity index with overground vegetation was 0.27.5.The number of species and seed density of seed bank were higest at lower foot slope in the natural secondary forest of Pinus tabulaeformis and artificial larch forest in different slopes, and sorensen similarity index with overground vegetation were the highest at middle of slope, 0.33 and 0.21 respectively.6.Seed density of 2cm thickness of soil were greater than 4、6、8 and 10cm, and number of species and indexes of diversity of 4cm were relative to that of 6, 8 and 10cm, and sorensen similarity indexs with overground vegetation of these five kinds of thickness of soil were mainly equal.7.Quantity of species in experimental filed of forestation increased six species than grassland before forestation,seed density increased from 843.75 to 3645.83 grain/m~2, and sorensen similarity indexs with overground vegetation was from 0.12 to 0.23. Evergreen trees and various shrubs began to appear in the aboveground vegetation and soil structure under woodland was compacter than previous sandy soil, and water retention capacity increased and content of organic matter and N, P, K were all enhanced markedly.8.More than 70% of the seeds concentrated in 0~5cm soil layer,the layer was more depth,the seed density of seed bank was reduced observably,the number of species decreased with it.