ABSTRACT
We estimated grassland NPP using CASA model in the Loess Plateau during 2000-2015 and further analyzed the spatiotemporal dynamics, stability and persistence of grassland NPP. The driving factors of grassland NPP were analyzed from four aspects, i.e., vegetation types, topographic factors, climate change, and human activities. The results showed that the average NPP was 202.93 g C·m-2·a-1. The grassland NPP showed an increasing trend with an average increase rate of 2.43 g C·m-2·a-1. The distribution of NPP in grassland had obvious spatial heterogeneity, which was generally high in the south and low in the north. 91.2% of the total grassland area showed an increasing trend, mainly distributed in most areas of Shaanxi Province, Longdong and Longzhong areas of Gansu Province, and most parts of Qinghai Province. The regions with a stable growth condition of grassland NPP mainly located in the south of Ordos, northern Shaanxi, and Gansu. The future change trend of grassland NPP would be consistent with that of the past in most areas. The grassland NPP would continue to increase in most areas of Shaanxi Province, Longzhong and Longdong areas in Gansu Province. The average NPP of slope grassland was 703.37 g C·m-2·a-1, while that of alpine and subalpine grassland was 57.28 g C·m-2·a-1. The grassland NPP was higher in high altitude area and relative low in plain and hilly area. The increased precipitation promoted the increase of grassland NPP during the study period. Human activities such as improvement of overgrazing and returning cropland to grassland also played an important role in the increase of grassland NPP in the Loess Plateau.
Subject(s)
Grassland , Models, Theoretical , China , Climate Change , Human ActivitiesABSTRACT
OBJECTIVE: To study the geographical variation of morphologic and germination characteristic of different Glycyrrhiza uralensis provenance seeds, approach the geographical variation mode and ecology mechanism, and laid theoretical foundation for districting and allocating of G. uralensis seeds. METHOD: Field investigation and laboratory analysis were applied. Seed shape and kilosseed weight were sampled randomly, germination rate germination force by general methods. RESULT: The morphologic characteristic of G. uralensis seeds showed roughly longitude variation tendency that the seeds increased gradually from west to east. While the germination characteristic showed roughly altitude variation tendency that the seeds germination rate and germination force increased with the increase of the altitude, and the average germination rate was the same with the seeds morphologic characteristic. The results of analysis correlated with the climatic factors show that the morphologic characteristic of G. uralensis was positive correlated with annual rain-fall of the habitat, and the germination rate was quickened by drought, high temperature and strong sunshine. CONCLUSION: The morphologic and germination characteristic and of G. uralensis seeds present distinguished geographical variation, and the formation of the variation was related to the ecological environment in which the seed provenance adapted.
