| Highland barley is a crop in the Qinghai-Tibet Plateau.Whether it is used as a ration crop for the population in the plateau,or as a source of feed for livestock such as cattle and sheep,or as a sacrificial product in religious activities,Highland barley is used in various fields.Existing studies have shown that under the background of climate change in the Qinghai-Tibet Plateau in recent decades,the habitat and yield of Highland barley have changed to a certain extent.In order to try to quantitatively evaluate the impact of climate change on Highland barley planting on the Qinghai-Tibet Plateau,this paper carried out the following work:First,based on medium-resolution remote sensing images and combined with object-oriented extraction method,we extracted the Highland barley planting area on the Qinghai-Tibet Plateau,which can help us understand the spatial distribution characteristics of Highland barley at the patch scale,and establish the relationship between Highland barley distribution and altitude;Then,we selected typical areas to analyze the impact of climate change on Highland barley planting space,time and yield,and quantitatively evaluate the contribution rate of climate factor change to Highland barley yield based on the EPIC model;Finally,the potential suitable areas for Highland barley planting under the current and future scenarios were estimated,and the changes in time and space of the potential suitable areas for Highland barley were analyzed.The above research aims to provide data reference for the development of characteristic agriculture on the Qinghai-Tibet Plateau,the security of grain reserves,the optimization of the spatial distribution pattern of Highland barley cultivation in the future,and the decision-making to deal with future climate change.Based on the above analysis,the following conclusions are drawn:(1)This paper proposed a fast and efficient interpretation method for Highland barley with multi-element fusion of partition classification.Based on agricultural divisions,the method limited the range of Highland barley spots by elevation,slope,precipitation and hydrological elements.We used image segmentation technology to partition the Highland barley interpretation samples,and used the Gaussian radial basis kernel function in the support vector machine model to solve the Highland barley.From the results,the total planting area of Highland barley was about 2.74×10~5ha.From the perspective of spatial distribution,Highland barley on the Qinghai-Tibet Plateau was mainly planted in the eastern and southern regions.The result improved the spatial distribution pattern of Highland barley from the administrative unit to the patch unit.(2)There was obvious spatial heterogeneity in the elevation of Highland barley planting in different districts.Generally,the main planting range of Highland barley was the area with an elevation of 2500-4500 m.From the perspective of sub-regions,due to the differences in terrain,temperature,moisture,light,distribution of cultivated land,and irrigation conditions in each sub-region,there were differences in the planting scale of Highland barley in different sub-regions at the same elevation.In the Qinghai-Tibet Plateau,where agricultural land resources were scarce,it was particularly important to rationally optimize land use.Therefore,this conclusion provides data support and reference for the research on the upper limit of crop planting under the background of climate change.(3)On the transect in the typical Highland barley planting area,there was little wheat planting in Menyuan County before 1980.With the warming of the climate,the wheat planting area in Menyuan County gradually expanded,replacing the originally planted Highland barley.The planting elevation of Highland barley was risen,forcing the lower limit of Highland barley to rise.Therefore,with the warming of the climate,the upper limit of wheat planting has been raised from 2600m to 2800m,an increase of 200m;this has increased the lower limit of barley cultivation from 2600m to2750m,an increase of 150m.(4)Judging from the highland barley yield simulated by the EPIC model,the average highland barley yield in Menyuan County from 1960 to 2020 was about 4103kg/ha,and the actual highland barley yield in 2020 was 3750 kg/ha,which was 353kg/ha higher than the actual value.Based on the control variable method,the EPIC model was used to simulate the contribution rate of various climatic factors to the yield of highland barley.When the monthly average precipitation increases by 10%,the yield of highland barley increases by about 0.206t/ha.When the average monthly average solar radiation value increases by 10%,the unit yield of highland barley increases by about 0.139t/ha.(5)During 1991-2000,the total highland barley yield of each station on the Qinghai-Tibet Plateau caused by climate change ranged from-0.38 to 0.75 t/ha,with an average value of 0.09 t/ha.During 2000-2010,the total highland barley yield of each site due to climate change was-0.45-0.94 t/ha,with an average of 0.15 t/ha,a slight increase compared to the previous period.During the period from 2011 to 2020,the total yield of highland barley caused by climate change was between 0.40 and1.69 t/ha,with an average value of 0.85 t/ha,which was significantly improved compared with the previous period.(6)Judging from the distribution of the potential suitable areas for Highland barley planting in the historical period,one third of the Qinghai-Tibet Plateau is not suitable for Highland barley planting,nearly half of the area is the low suitable area for Highland barley planting,and the medium and high suitable areas are less than20%.In the east,southeast and south of the plateau.According to the estimated results,the area of high suitable area for the potential planting of Highland barley will continue to expand over time.Compared with the area of 6%in the historical period,the proportion of the area will rise to 12%in the near future,and will further expand in the medium term in the future.to 14%?16%.The areas with reduced or basically unchanged suitability were concentrated in the northwest of the Qinghai-Tibet Plateau and the Qaidam Basin.Besides,the areas with significantly increased suitability were located in the southern,central and eastern parts of the plateau,which increased significantly.In the low suitable area for Highland barley planting,the area with relatively low suitability was transformed from the unsuitable area,and the area with relatively high suitability was transformed into the medium suitable area,so the total area remained basically unchanged;Part of the area is converted into a high suitability area,which increases the area of the high suitability area.(7)The average elevations of all types of potential suitable areas for Highland barley planting showed an upward trend,among which the average elevation of the unsuitable and low suitable areas were relatively slow,and the average elevations of the middle and high suitable areas were larger.Under the RCP 4.5 scenario,from the historical period to the near-term and mid-term future,the average elevation of the high-suitability area has risen from 3759 m to 3937 m and 4017 m,with an increase by 178 m and 258 m,respectively.In the RCP 8.5 scenario,the average elevations of the high suitability areas increased from 3759 m to 3959 m and 4090 m,respectively,and increased by 200 m and 331 m,respectively. |
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