石笋P/Ca重建宜昌地区9 000年以来的陆地生产力

陆地生产力在全球变化，尤其是全球碳循环研究领域中，具有重要的地位。本文通过分析湖北清江和尚洞HS4石笋中P和Ca的地球化学组成，考察P/Ca对陆地生物生产力的响应。结果发现，最近50年沉积的石笋P/Ca比值与Thornthwaite Memorial生产力模型计算的区域陆地生产力具有显著的相关性，可以作为陆地古生产力的指标。以石笋P/Ca 重建的宜昌地区陆地古生产力在过去9 000年呈现波动变化的特征:8.9～6.5ka BP，陆地生产力较低；6.5～5.0ka BP，陆地生产力显著升高，并在6.4～5.6ka BP期间达到9.0ka来的最高值；5.0～4.0ka BP，处于低生产力期；4.0～1.5ka BP，生产力逐渐回升；1.5ka BP以来，生产力再次处于低值期。陆地生产力的波动明显受到全球和区域气候的制约。 

Reconstruction of terrestrial productivity of Yichang region in the past 9000 years from stalagmite P/Ca ratio

Terrestrial productivity plays an important role in the field of global change research,especially in global carbon recycling research.In this paper,geochemical composition of P and Ca in stalagmite HS4 from Heshang Cave,Qingjiang,Hubei Province is analyzed to investigate the response of stalagmite P/Ca ratio to the terrestrial productivity.The results prove that the P/Ca recorded in the spleothem in recent 50 years is significantly correlated with the local terrestrial productivity calculated by Thornthwaite Memorial Productivity Model,which implying stalagmite P/Ca may be the index for local terrestrial paleo-productivity.Based on P/Ca in the stalagmite HS4,regional paleo-productivity in Yichang are reconstructed.It is found that terrestrial productivity fluctuated during the past 9 000 years,which was low in 8.9ka~6.5ka BP,increased significantly during 6.5ka~5.0ka BP,and reached the top in 6.4ka~5.6kaBP,then fell to a low lever in 5.0ka~4.0ka BP;and increased gradually in 4.0ka~1.5ka BP,and after 1.5kaBP,lowered again.The fluctuation of terrestrial productivity is obviously constrained by global and regional climate.