RESUMO
China, one of the most populous countries in the world, has suffered the highest number of natural disaster-related deaths from fire. On local scales, the main causes of urban fires are anthropogenic in nature. Yet, on regional to national scales, little is known about the indicators of large-scale co-varying urban fire activity in China. Here, we present the China Fire History Atlas (CFHA), which is based on 19 947 documentary records and represents fires in urban areas of China over the twentieth century (1901-1994). We found that temperature variability is a key indicator of urban fire activity in China, with warmer temperatures being correlated with more urban fires, and that this fire-temperature relationship is seasonally and regionally explicit. In the early twentieth century, however, the fire-temperature relationship was overruled by war-related fires in large urban areas. We further used the fire-temperature relationship and multiple emissions scenarios to project fire activity across China into the twenty-first century. Our projections show a distinct increase in future urban fire activity and fire-related economic loss. Our findings provide insights into fire-climate relationships in China for densely-populated areas and on policy-relevant time scales and they contribute spatial coverage to efforts to improve global fire models.
RESUMO
We sampled Pinus massoniana and Cunninghamia lanceolata in both plantation and natural forests in central and western Fujian Province, China. Using tree-ring width, tree-ring width index, and basal area increment, we reconstructed the annual growth of 109 conifer individuals from four sites for the 20-year period from 1993 to 2012. We then calculated resistance, recovery, and resilience indices of those trees in response to two consecutive extreme droughts (2003-2004 and 2011) and analyzed the differences in resistance and resilience between plantations and natural fore-sts. The results showed that there were temporal differences in moisture requirements between P. massoniana and C. lanceolata, which accounted for their inconsistent responses to drought in 2003-2004. For both species, drought induced a marked growth reduction, without any clear lag effect. The growth responses during and following the 2003-2004 drought were significantly stronger than that for the 2011 drought. Those results indicated that P. massoniana was more resilient to drought stress than C. lanceolata, and the natural forests were more sensitive than plantations, but with stronger capacity to recover. C. lanceolata plantations were more susceptible to frequent extreme drought events. To mitigate the vulnerability of plantation trees to more frequent droughts in the future, we suggested select trees from genetic provenances with strong drought resistance.
Assuntos
Cunninghamia , Pinus , China , Secas , Florestas , HumanosRESUMO
Pinus massoniana is a typical pioneer afforestation tree species widely distributed in southern China. It is crucial to study the ecological resilience of P. massoniana to disturbances under global warming, drying, and frequent pest infestation, which can shed lights on forest mana-gements. In this study, tree-ring samples collected from old-growth P. massoniana trees in Baisong Village, Xianyou County, Fujian Province, were used to develop the first standard chronology of P. massoniana ring width (1865-2014) in this region. The results showed that the low relative humidity from July to September and the extremely high temperature from May to September were the main limiting factors for tree growth. The extremely narrow years were identified in 1869, 1889, 1986, 1991 and 1993. These extremely narrow years were exacerbated after the persistently low values of the previously two years via the superposed epoch analysis (SEA). The insect infestations were more likely to happen in dry years. Insect outbreak exerted strongest effect on tree growth in 1889. The narrow tree-rings in 1986 and 1991 were affected by both insect infestation and drought. The other extremely narrow years were mainly affected by drought. The resistance of trees to insect infestation was weaker than that to drought event. The relative resilience of trees to insect infestation was higher than that to drought event, except for 1991. The relative resilience was the highest in 1889 and the lowest in 1991 under the influence of successive extreme events. Under the enhanced drying trend since 2000, more trees had died possibly due to the combined effects of insect infestation and drought.
