Grass-livestock balance based grassland ecological carrying capability and sustainable strategy in the Yellow River Source National Park, Tibet Plateau, China

The Yellow River Source National Park(YRSP)is one of the most sensitive and fragile ecological regions in the world.The historical intensive grazing and climate change have resulted in ecological degradation that threatens the wildlife and livestock.Exploring the sustainable strategy is urgent for policy makers to meet the demands for wild ungulates and livestock.In our study,the grassland ecological carrying capability(GECC)was assessed based on the updated grass-livestock balance that considered the grass competition from wild ungulates.The balances between grass and livestock,and GECC and grassland pressure index(GPI)in the YRSP were measured through overlay analysis and geostatistic analysis.The results showed that:(1)the ratio of livestock to wild ungulates in the research area was approximately 4.56:1,in which the proportion of livestock was 81.75%and the actual number of livestock was 33.84×104 standard sheep units;(2)Under the scenario of minimum grazing utilisation rate,the theoretical grazing capacity and GECC were 37.83×104 standard sheep units and−0.13,respectively.Under the maximum grazing utilisation rate,the theoretical grazing capacity and GECC were 41.93×104 standard sheep units and−0.21,respectively.Since GECC in both scenarios were both less than 0,the grassland was considered to be in surplus and the livestock was not overloaded.However,GPI in the two scenarios were 0.87 and 0.79,respectively,both of which exceeded the warning line of 0.70.Based on GECC,we recommend that the sustainable strategy in YRSP is either to increase the supplementary feeding about 6.40×104 standard sheep units or reduce the grazing livestock by about 3.50×10^(4) standard sheep units.

Characterizing the capability of mesoscale eddies to carry drifters in the northwest Pacific

Mesoscale eddies are common oceanic phenomena.Although many related studies have been conducted,the ability for mesoscale eddies to carry real particles remains poorly addressed.We considered the drifters as real particles to characterize the capability of mesoscale eddies to carry particles.Firstly,mesoscale eddies in the northwest Pacific(99°E-180°E,0°-66°N)were identified using sea level anomaly(SLA)data from 1993 to 2015.Secondly,three important parameters(the carrying days,the number of circles the drifter revolving around the eddy center,and the carrying distances)were calculated by colocalizing eddy data with drifters.Finally,statistical analysis and composite analysis were conducted,reflecting the capability of mesoscale eddies to carry particles.The mechanisms on the carrying capability of eddies were also discussed.Results show that(1)the motion of carried drifters reflects the upper limit of rotational speed of eddies that the drifters revolve around the eddy center by≤90°for one day in most cases;(2)the drifters tend to be carried for a longer time when their minimal distances to the eddy center measured with normalized distance are small;(3)there are two types of eddies(cyclonic and anticyclonic eddies)in different subregions of northwest Pacific,and each has a different carrying capability(on average,similar in the tropical ocean and Subtropical Countercurrent,cyclonic eddies tend to have stronger carrying capability in Southern Kuroshio Extension,and anticyclonic eddies tend to have stronger carrying capability in Northern Kuroshio Extension and Subarctic Gyre);(4)on average,the carried drifters tend to travel for a longer time around the normalized eddy radii ranging from 0.41 to 0.76;(5)the carrying days are related to the Rossby number of the eddy(in general when the Rossby number is smaller,the carrying days are longer).

A thick SOI UVLD LIGBT on partial membrane

A thick SOI LIGBT structure with a combination of uniform and variation in lateral doping profiles （UVLD） on partial membrane （UVLD PM LIGBT） is proposed. The silicon substrate under the drift region is selectively etched to remove the charge beneath the buried oxide so that the potential lines can release below the membrane, resulting in an enhanced breakdown voltage. Moreover, the thick SOI LIGBT with the advantage of a large current flowing and a thermal diffusing area achieves a strong current carrying capability and a low junction temperature. The current carrying capability （VAnode = 6 V, VGate = 15 V） increases by 16% and the maximal junction temperature （1 mW/μm） decreases by 30 K in comparison with that of a conventional thin SO1 structure.