Is Anthropogenic Pyrodiversity Invisible in Paleofire Records?

Abstract

Paleofire studies frequently discount the impact of human activities in past fire regimes. Globally, we know that a common pattern of anthropogenic burning regimes is to burn many small patches at high frequency, thereby generating landscape heterogeneity. Is this type of anthropogenic pyrodiversity necessarily obscured in paleofire records because of fundamental limitations of those records? We evaluate this with a cellular automata model designed to replicate different fire regimes with identical fire rotations but different fire frequencies and patchiness. Our results indicate that high frequency patch burning can be identified in tree-ring records at relatively modest sampling intensities. However, standard methods that filter out fires represented by few trees systematically biases the records against patch burning. In simulated fire regime shifts, fading records, sample size, and the contrast between the shifted fire regimes all interact to make statistical identification of regime shifts challenging without other information. Recent studies indicate that integration of information from history, archaeology, or anthropology and paleofire data generate the most reliable inferences of anthropogenic patch burning and fire regime changes associated with cultural changes.

Spatial variability of historical fires across a red pine–oak landscape, Pennsylvania,USA

“…These fire regime characteristics likely resulted in a spatially and temporally transient patchwork of varying standlevel vegetation age and structures. Interestingly, many of these fires would not have been included in any analyses if the fire record was filtered based on fire-scarring percentages (e.g., only included fire years recorded on ≥2, or 10% of the recorded trees), a common practice in treering based fire history research (Farris et al 2013, Roos et al 2019.…”

Simulation Modeling of Complex Climate, Wildfire, and Vegetation Dynamics to Address Wicked Problems in Land Management

“…elevation, western U.S. forests attributed to fire suppression and disrupted fire spread from lower elevations (Margolis and Balmat, 2009). This study and a related, growing body of research highlights the significant role of anthropogenic burning in some landscapes, even in environments with abundant natural ignitions (Guyette et al, 2002;Liebmann et al, 2016;Roos et al, 2019). In these places, contemporary ecological patterns and processes that are thought to be natural may in fact be highly influenced by past human land use legacies.…”

Native American fire management at an ancient wildland–urban interface in the Southwest United States

“…In these settings, fire may have been used to improve the productivity of wild plant harvesting areas ( 64 ), to process wild resources ( 65 ), to prepare trees for architectural use, perhaps to aid hunting ( 66 ), as well as for purposes associated with pilgrimage and ritual practices ( 67 – 69 ). Because these uses are located further from the archaeological record of occupation and intensive use, and potentially more diffuse in their distribution, these fire practices are more difficult to distinguish from natural fires, although this makes them no less ecologically significant ( 70 , 71 ). In summary, Hemish people manipulated both fire and fuels in woodland and forest contexts to satisfy the needs of particular activities in controlled and landscape contexts, but these varied geographically relative to features of the cultural landscape ( 72 ).…”

“…Within the agricultural landscapes of active and fallow fields, field houses, trails, and patches of intact vegetation, fires were probably very small (approximately 100 ha or less) and limited to particular fields or forest patches. At larger spatial scales, Hemish fire uses may be difficult to distinguish from nonhuman, frequent surface fires ( 70 , 82 ). Nevertheless, within 10 km of the intensively used agricultural landscape, patchy, frequent, low-severity, anthropogenic surface fires were detectable in the fire-scar network, as well in geomorphic ( 40 ) and sedimentary charcoal records ( 38 ).…”

“…The character of human impacts was scale-dependent relative to particular settlements and land-use activities but the emergent consequences of these impacts were felt at the landscape scale. The paleoecological signatures of these impacts were only recognizable by sampling at scales appropriate to the different land-use activities ( 83 ) and by explicitly negotiating the subtlety of human impacts on an already fire-rich landscape ( 70 – 72 ).…”