The Lenglongling Mountains(LLM)located in northeastern part of the Tibet Plateau,belong to a marginal area of the East Asian summer monsoon(EASM)and are sensitive to monsoon dynamics.Two tree-ring width chronologies developed from six sites of Picea crassifolia in the LLM were employed to study the regional drought variability.Correlation and temporal correlation analyses showed that relationships between the two chronologies and self-calibrated Palmer Drought Severity Index(sc_PDSI)were significant and stable across time,demonstrating the strength of sc_PDSI in modeling drought conditions in this region.Based on the relationships,the mean sc_PDSI was reconstructed for the period from 1786 to 2013.Dry conditions prevailed during 1817–1819,1829–1831,1928–1931 and 1999–2001.Relatively wet periods were identified for 1792–1795 and 1954–1956.Spatial correlations with other fourteen precipitation/drought reconstructed series in previous studies revealed that in arid regions of Northwest China,long-term variability of moisture conditions was synchronous before the 1950 s at a decadal scale(1791–1954).In northwestern margin of the EASM,most of all selected reconstructions had better consistency in low-frequency variation,especially during dry periods,indicating similar regional moisture variations and analogous modes of climate forcing on tree growth in the region.
On the basis of analyzing yearly data and spatial relationships between tourism spots, star hotels and travel agencies of Hainan Province, and comparing all the methods of measuring industrial spatial agglomeration, this paper chose Hefindahl index, Location Quotient, nearest neighbor index, spatial connection index and geographic concentration index to measure Hainan tourism agglomeration. By applying these methods, total tourism agglomeration, agglomeration of tourism factors and regional agglomeration differences were studied. The results showed that the overall agglomeration increases as time flows, and the eastern part is the most agglomerated, the west takes the second, with the middle ranking the least. The large-scale agglomeration regions are Sanya and Haikou. The influencing factors of Hainan tourism spatial agglomeration were concluded as tourism resource endowment, industrial attributes, geographic conditions, governmental policies and the overall economic development level, etc. In addition, the paper proposed tourism spatial agglomeration modes of Hainan Province at various spatial scales.
