Historical forest changes in the western United States

Abstract

Changes in factors such as temperature, precipitation, fire regimes, ozone, atmospheric CO2, and nitrogen deposition may have altered forest growth over the past century. Determining changes in forest growth over long intervals is complicated by constantly changing growing conditions due to tree maturation, stand self-thinning, disturbance, and other factors. Because a comprehensive review is lacking, results from publications examining forest growth trends in the western United States over the past 100 years were evaluated. Across the region, upper elevational forest ecotones have been expanding upward in many but not all locations, possibly due to warming and reduced snowpack. Across most of the region, both growth increases and decreases are localized and spatially dispersed. For the inland West, historical photography and long-term inventory data show clear densification and expansion of ponderosa pine (Pinus ponderosa) and mixed conifer forest across the region, mostly due to reduced fire incidence. However, a recent drought, probably linked to ocean cycles and exacerbated by warming, has caused a growth setback and mortality, especially in the Southwest. Forest densification due to altered fire regimes does not equate to enhanced growth per se. Aspen (Populus tremuloides) dieback has been noted due to recent drought and local conifer mortality caused by drought has also been documented in several locations. Regeneration after recent fires appears to be inadequate in many localities. Except for local increased growth at some high elevation and coastal sites and possible periodic drought effects in the Southwest, it is difficult to detect any growth trends with available data.

The Role of Wildfires in the Interplay of Forest Carbon Stocks and Wood Harvest in the Contiguous United States During the 20th Century

“…Federal and other forests seem to have burned significantly less in the beginning of the observed timeframe but their relative share in total forest area burned, compared to state and private forests, increased significantly in the last decades of the period (Figure 1c , Figure S5 in Supporting Information S1 ). This is probably due to more accurate reporting of burned area via remote sensing data (Chuvieco et al., 2019 ; Short, 2015 ) compared to early field observations, which did not report some fires in woodlands (Loehle, 2020 ).…”

Mathematical Simulation of Heat Transfer in the Structures of a Passenger Carriage Under the Influence of Forest Fires

“…Objects of JSC Russian Railways are sources of anthropogenic pressure on forested areas [4]. On the other hand, the rolling stock of the railway is exposed to the negative impact of forest fires in the event of forest fires near to the railway line [5], [6]. The main factor affecting a forest fire is the radiant heat flux from the forest fire front [7]- [9].…”