基于MODIS数据的内蒙古野火时空变化特征

野火是陆地生态系统的重要干扰因子,影响生态系统的演替和更新。研究基于MCD45A1火烧迹地和MCD12Q1土地利用数据,提取2002—2014年内蒙古不同生态分区、土地利用类型的过火面积及火点分布,分析该区域野火的时空分布格局,同时结合降水数据,探讨野火年际变化对降水的响应特性。结果表明:1)2002—2014年内蒙古野火火点空间分布格局表现为由东北向西南逐渐减少,高密度火点主要分布在中蒙边境区域、森林-草原区以及平原典型农耕区。2)内蒙古野火过火面积2003年最大,2006年次之,2010年最小,分析表明过火面积的年际变动与火灾高发月降水异常有关。过火面积的季节变化表现为春秋多,冬夏少,尤其是3月、4月、5月和9月灾情严重。在7大生态分区中,90%的过火面积集中在兴安岭山地丘陵区、呼伦贝尔高平原丘陵区和锡林郭勒高平原区,过火面积占比分别为52%、28%和10%。3)野火干扰最严重的土地利用类型为草地,火点主要集中分布于草甸草原和典型草原,其次为农业用地和林地,对其他类型干扰程度最小。充分认识野火时空分布格局有利于深入了解其发生规律,为区域火灾预警监测提供科学依据。

MODIS-based spatio-temporal distribution of wildfire in Inner Mongolia

Wildfire is a key disturbance factor in terrestrial ecosystems that greatly influences not only ecosystem patterns and processes, but also maintaining of diversity, productivity and nutrient cycling throughout global ecosystems. Fire is the result of interaction between natural and anthropogenic factors. The determination of the spatial and temporal distribution characteristics of the fire regimes is critical for predicting the response of fire to climate change and designing strategic fire management plans. Inner Mongolia is an ideal area for studying the distribution patterns of wildfire because of its strategic location, high ecological value and severe wildfire hazards. Inner Mongolia endures severe wildfires, and the area burned by fire in the province is one of the highest among all the provinces in China. Here, we analyzed the spatial and temporal distribution patterns of burned areas and fire spots in Inner Mongolia using MCD45A1 burned areas (a monthly Level-3 gridded 500 meter fire burned area product) and MCD12Q1 (Land Cover Type Yearly L3 Global 500 m SIN Grid) land use data for the period 2002-2014. Through the integration of precipitation data, the impact of precipitation on the characteristics of annual variations in wildfire was investigated. The results showed that:1) the spatial distribution of fire spots gradually decreased from northeast to southwest and the high density areas were mainly distributed in the border region between China and Mongolia, the forest-grassland belt and typical arable zones. 2) The largest wildfire area in Inner Mongolia was in 2003, followed by 2006, and the smallest was in 2010. Analysis showed that the interannual change of burning area was closely linked to fire high-risk monthly precipitation anomaly. The happening of fire showed seasonal variations, which autumn and spring was high-incidence season, especially the months of March, April, May and September. The fire-burned areas in Xing''anling mountainous and hilly region, Hulunbuir plateau and hilly region, and Xilingol Plateau accounted for 90% of the total burned areas in the seven ecological zones of Inner Mongolia, with area ratios of 52%, 28% and 10%, respectively. 3) The fire-burned areas ranked from large to small was in the sequence of pasture land, agriculture land, woodland and other land use types in the study area. Fire spots were mainly distributed in meadow steppe and typical steppe zones. A large proportion of the fire enhanced recovery of old pastures overtaken by invasive species and secondary growth. This form of pasture management in Inner Mongolia was an important cause of wildfires in pasture lands. The practice of burning straw every spring and autumn also intensified the distribution of fire in typical arable lands, especially in the Nenjiangxian Plain, Hetao Plain and Songnen Plain. The fire-burned area in Xing''anling mountainous and hilly region and Hulunbuir plateau and hilly region had the same variation trend. The results were critically helpful in understanding the spatial and temporal patterns of wildfire and provided scientific basis for wildfire monitoring and alert system.