Impacts of different land management histories on forest change

Abstract

Many western North American forest types have experienced considerable changes in ecosystem structure, composition, and function as a result of both fire exclusion and timber harvesting. These two influences co-occurred over a large portion of dry forests, making it difficult to know the strength of either one on its own or the potential for an interaction between the two. In this study, we used contemporary remeasurements of a systematic historical forest inventory to investigate forest change in the Sierra Nevada. The historical data opportunistically spanned a significant land management agency boundary, which protected part of the inventory area from timber harvesting. This allowed for a robust comparison of forest change between logged and unlogged areas. In addition, we assessed the effects of recent management activities aimed at forest restoration relative to the same areas historically, and to other areas without recent management. Based on analyses of 22,007 trees (historical, 9,573; contemporary, 12,434), live basal area and tree density significantly increased from 1911 to the early 2000s in both logged and unlogged areas. Both shrub cover and the proportion of live basal area occupied by pine species declined from 1911 to the early 2000s in both areas, but statistical significance was inconsistent. The most notable difference between logged and unlogged areas was in the density of large trees, which declined significantly in logged areas, but was unchanged in unlogged areas. Recent management activities had a varied impact on the forest structure and composition variables analyzed. In general, areas with no recent management activities experienced the greatest change from 1911 to the early 2000s. If approximating historical forest conditions is a land management goal the documented changes in forest structure and composition from 1911 to the early 2000s indicate that active restoration, including fire use and mechanical thinning, is needed in many areas.

Wildfire activity and land use drove 20th‐century changes in forest cover in the Colorado front range

“…, Collins et al. ). Historical mining activity also led to increases in soil disturbance, logging, and fire activity in many parts of the western United States in the late 1800s and early 1900s (Gruell , , Veblen and Lorenz , Hessburg and Agee , Dethier et al.…”

“…For example, moisture availability and changes in land use have been noted as important correlates with changes in dry forests of the northwest and southwest United States since the late 1800s (Merschel et al 2014, Johnston 2017, Rodman et al 2017. Extractive logging of large-diameter trees has altered stand structure in many coniferous forests in the western United States; in some cases, late 20th-century forest cover may still be responding to timber extraction in the 19th and early 20th centuries (Naficy et al 2010, Merschel et al 2014, Collins et al 2017. Historical mining activity also led to increases in soil disturbance, logging, and fire activity in many parts of the western United States in the late 1800s and early 1900s (Gruell 1983, 2001, Veblen and Lorenz 1991, Hessburg and Agee 2003, Dethier et al 2018.…”

The climate sensitivity of carbon, timber, and species richness covaries with forest age in boreal–temperate North America

“…Forest age class distributions, disturbance dynamics, and stand development pathways (i.e., trajectories of structural and compositional development) have been profoundly altered by land-use history and forest management over large portions of the boreal and temperate biomes (Bürgi, Östlund, & Mladenoff, 2017;Collins, Fry, Lydersen, Everett, & Stephens, 2017;Foster et al, 2003;Thom, Rammer, Garstenauer, & Seidl, 2018). For instance, the majority of forests in the US Northeast are still recovering from 19th century clearing and are younger and structurally more simple compared to pre-European settlement conditions (Foster, Motzkin, & Slater, 1998).…”

Risk of vector tick exposure initially increases, then declines through time in response to wildfire in California

“…, Collins et al. ), comparatively recent changes in forestry practices, including fire suppression and fuels management, have contributed to an increase in the number and severity of wildfires in the state. Further, in California, wildfire activity has increased in recent years and is expected to increase into the future due to climate change (Westerling and Bryant , Westerling et al.…”

“…In the western United States, wildfire is one of the most important and significant natural, as well as anthropogenic, disturbances and plays a central role in the ecology of Californian forests (Steel et al 2015). While California oak woodlands were burned regularly by Native Americans as part of early land management practices (Stephens et al 2007, Collins et al 2017, comparatively recent changes in forestry practices, including fire suppression and fuels management, have contributed to an increase in the number and severity of wildfires in the state. Further, in California, wildfire activity has increased in recent years and is expected to increase into the future due to climate change (Westerling and Bryant 2007, Westerling et al 2011, Westerling 2016.…”