| Loess Plateau is the biggest loess sedimentary area around the world, and it is one of the most important carbon pools. However, this area is facing a series of ecological issues like water loess and soil erosion, soil degradation and so on, therefore, the key measure for ecological environment construction in this area is vegetation restoration. Since the management for plantation could convert landuse process and increase the forest coverage rate at the same time, under this condition, the artifical forest plays a pivotal role in loess plateau ecological environment restoration.Robinia pseudoacacia, which has strong adaptability, easy propagation, fast growth, tolerant of drought and impoverishment, is one of the main afforestation tree species and has quite important influence in vegatation restoration and carbon storage in Loess plateau, but the studies about the effect of carbon storage on loess plateau brought by different stand age of black locust after afforestation are not too much.This study was on the basis of the project-Ecological Environment Monitoring Afforestation in Shaanxi Province supported by yen loans. After set3,10,26and35years old black locust as object, we surveyed and analyzed the cabon storage in the layer of tree, bush, herb, litter and soil respectively in forest land, and obtained the general dynamic variation trend of carbon storage in main layers of whole ecosystem of black locust plantation, then evaluated the ecological environment benefit synthetically, the conclusions are listed as follows:1. Followed with the rising of the tree age, the organic carbon density(OCD) in tree layer of forest land ascended apparently, besides, the SOCD in trunk account for38.07%,59.25%,40.69%,55.06%in tree layer of3,10,26and35years old Robinia pseudoacacia plantation respectively, which is the most primary source of organic carbon in tree layer.2. In the forest ecosystem of Robinia pseudoacacia, the value of biomass in bush layer and herb layer were all less than barren land, and with the increasing of the age, the OCD in those two layers showed a downward trend. By contrast, the biomass in litter layer expressed a opposite trend, which ascended followed with the adding of the forest age, however, within3years of afforestation, the OCD was lower than barren land. 3. In26years of afforestation, planting black locust in Robinia pseudoacacia could not improve SOCD, besides, the SOCD of forest land was less than barren land and minished with the increasing of the forest age when omit the content of organic carbon kept in tree roots, however this downward trend slowed down at the middle age of Robinia pseudoacacia, while at the35years old of afforestation, the SOCD in forest land was higher than barren land obviously.4. The result of this study showed that the afforestation of black locust in loess plateau have significant influence on changing the distribution of SOCD, which decreased following the deep of soil layer. The general shifty trend was the SOCD in the range of0～30cm were clearly higher than other soil levels(P<0.05), while the SOCD in the range of30～60cm has no obvious difference. Specifically, the SOCD in top lever(0～10cm) of forest land was distinctly higher than other levers’, which more than barren land and increased with the augmenting of the tree age, compared with top soil, the SOCD at the range of10～30cm had a opposite variational trend within the age of26at least, however this declined tendency retarded increasingly, at the range of26～35years of afforestation, the SOCD in this extent began to rise gradually but still under the value of barren land.5. In the whole forest ecosystem, the OCD in different layer has evident change, and the tree layer and soil layer were the two main sources of organic carbon storage. With the growth of the tree age, the tree layer showed its ability of carbon storage by degrees, the study showed that after10years later of afforestation, the ability of carbon storage would greater than soil layer and improved with the increasing of the tree age.6. The resrarch demonstrated the total OCD in forest ecosystem was elevated obviously with the increasing of the tree age. Comparing with the total OCD in barren land, the OCD in3a,10a,26a and35a black locust plantation increaed by2.04%,59.96%,77.38%,207.87%separately, which reflected that planting Robinia pseudoacacia in Loess plateau could achieve remarkable ecological benefits, and it would express its significant ability of carbon storage step by step after afforestation. |
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