Vegetation dynamics and its response to driving factors in typical karst regions,Guizhou Province,China

Analyzing the vegetation dynamics and its response to driving factors provides a vital reference for understanding regional ecological processes and ecosystem services.However,this issue has been poorly understood in karst areas.Taking Guizhou Province as a case study,based on the Normalized-Difference Vegetation Index of the Global Inventory Modeling and Mapping Studies and on meteorological data sets during 1982-2015,we evaluated vegetation dynamics and its response to climatic factors and human activities.We used several methods:the Mann-Kendall test,rescaled range analysis,partial correlation analysis,and residual analysis.The results are as follows:1)the mean annual Normalized-Difference Vegetation Index was 0.46 and exhibited a significant increasing trend with a variation rate of 0.01/10a during 1982-2015 in Guizhou Province.The vegetation cover showed was spatially heterogeneous:High vegetation cover was distributed mainly in the center and western margin of the study area,while the other parts of the study area mainly distributed with low vegetation cover,although the vegetation cover was higher in the nonkarst areas than in the karst areas;2)in general,the climate was getting warmer and drier in Guizhou Province during 1982-2015.Vegetation cover was positively correlated with temperature and negatively correlated with precipitation.Compared to precipitation,temperature was the dominant climatic factor impacting vegetation dynamics;3)'large-scale ecological restoration projects have obviously increased vegetation cover in Guizhou Province in recent years.The contribution of human activities to vegetation changes was 76%,while the contribution of climatic factors was 24%.In summary,compared to natural forces such as climatic factors and geographic parameters,human activities were the main factor driving the vegetation dynamics in Guizhou Province.

Effect of cross-flow direction of coolant on film cooling effectiveness with one inlet and double outlet hole injection

In order to study the effect of cross-flow directions of an internal coolant on film cooling performance,the discharge coefficients and film cooling effectiveness with one inlet and double outlet hole injections were simulated.The numerical results show that two different cross-flow directions of the coolant cause the same decrease in the discharge coefficients as that in the case of supplying coolant by a plenum.The different proportion of the mass flow out of the two outlets of the film hole results in different values of the film cooling effectiveness for three different cases of coolant supplies.The film cooling effectiveness is the highest for the case of supplying coolant by the plenum.At a lower blowing ratio of 1.0,the film cooling effectiveness with coolant injection from the right entrance of the passage is higher than that from the left entrance of the passage.At a higher blowing ratio of 2.0,the opposite result is found.