Effects of tree diversity on insect herbivory

Tree diversity has long been considered a key driver of insect herbivory in forest ecosystems.However,studies have given contradictory results:increased tree diversity can have positive,negative or neutral effects on insect herbivory.Since many issues can complicate the tree-herbivore interactions,the descriptor‘tree diversity’per se actually has only limited explanatory power for insect herbivory.Particularly,in addition to the direct bottom-up effects on insect herbivores,tree diversity may have stronger indirect top-down effects via natural enemies of insect herbivores.However,most research has addressed only direct bottom-up impacts.In fact,insect herbivory is the result of complex interactions(food webs)among all the species in a community.Although it is hard to integrate all functionally important species and dynamic information into food webs,the effects of tree diversity on insect herbivory are highly dependent on the dominant species at different trophic levels.It is important and practical to simultaneously consider the characteristics of main trees,herbivores,and natural enemies when attempting to predict the overall effects of forest tree diversity on insect herbivory.In order to ensure comparability between studies,it is necessary to classify them according to the descriptors of insect herbivory and tree diversity,and to compare results within each category.These measures might enhance our understanding of the mechanisms by which tree diversity drives insect herbivory and,in turn,help to develop sustainable pest management strategies for forests.

Application of integrated formation evaluation and three-dimensional modeling in shale gas prospect identification

Identifying the shale gas prospect is crucial for gas extraction from such reservoirs.Junggar Basin(in Northwest China)is widely considered to have high potential as a shale gas resource,and the Jurassic,the most significant gas source strata,is considered as prospective for shale gas exploration and development.This study evaluated the Lower Jurassic Badaowan Formation shale gas potential combined with geochemical,geological,and well logging data,and built a three-dimensional(3D)model to exhibit favorable shale gas prospects.In addition,methane sorption capacity was tested for verifying the prospects.The Badaowan shale had an average total organic carbon(TOC)content of 1.30 wt.%and vitrinite reflectance(Ro)ranging from 0.47%to 0.81%with dominated type III organic matter(OM).X-ray diffraction(XRD)analyses showed that mineral composition of Badaowan shale was fairly homogeneous and dominated by clay and brittle minerals.67 wells were used to identify prospective shale intervals and to delineate the area of prospects.Consequently,three Badaowan shale gas prospects in the Junggar Basin were identified:the northwestern margin prospect,eastern Central Depression prospect and Wulungu Depression prospect.The middle interval of the northwestern margin prospect was considered to be the most favorable exploration target benefitted by wide distribution and high lateral continuity.Generally,methane sorption capacity of the Badaowan shale was comparable to that of the typical gas shales with similar TOC content,showing a feasible gas potential.