Geology topics

John J. Battles

Publications and source records attributed to John J. Battles.

12 recordsLinked to original sources

USGS2025

The structural and functional impacts of invasive Psidium cattleianum in forests on the Island of Hawai’i

During the past century, the proliferation of invasive species has contributed to loss of biodiversity and ecosystem degradation. In forests, invasive tree species can alter ecosystem function, but the underlying mechanisms of these changes are not fully understood. We use the ongoing invasion of P. cattleianum on the Island of Hawai’i to test the hypotheses that invasive structural changes drive changes to forest evapotranspiration (ET). The aim of our study is first to quantify the structural changes to native ‘ōhi‘a -dominated forest impacted by a gradient of P. cattleianum invasion. Our results suggest that invasive P. cattleianum causes significant changes to the vegetation density and structure of native forest on the Island of Hawai’i, including increased vegetation area index, decreased mean leaf height, and decreased structural heterogeneity. Second, we strove to understand the functional implications of structural changes through a biophysical modeling simulation, testing the sensitivity of ET to canopy structure under contrasting scenarios. Modeling the functional impact of structural change, we found that plots with P. cattleianum invasion importance value (IV inv ) above 0.35 have a higher likelihood to increase ET compared to plots with P. cattleianum invasion less than 0.35 IV inv . Modeled increases in ET due to invasion ranged from 19 and 123% relative to native transects. The large variation in ET increases is caused by structural variation because the modeling scenarios did not include potential species differences in leaf physiology. Diagnostic scenario modeling shows the effect size of increased leaf area on modeled ET is constrained by the structural arrangement, that is vertical distribution, of the increased vegetation. Thus, invasion structure that increases vegetation density in taller, more sunlit forest strata will lead to a greater increase in ET compared to invasion structure that increases vegetation density in the shaded forest understory. Overall, we conclude the vertical distribution of vegetation is an important factor shaping the impact of invasive P. cattleianum on the forest water balance.

Hawaii↗

USGS2023

Snag dynamics and surface fuel loads in the Sierra Nevada: Predicting the impact of the 2012–2016 drought

Forest die-backs linked to extreme droughts are expected to increase as the climate dries and warms. An example is the 2012-2016 hotter drought in California that induced widespread tree mortality in the Sierra Nevada, California. The sudden increase in snags (i.e., standing dead trees) raised immediate concerns about their impact on wildfire hazard and longer-term questions about their impact on ecosystem structure and function. We quantified the likely progression of snag fall and fuel succession following the recent extensive mortality event in the southern Sierra Nevada mixed conifer forest. Our results used data from a long-term demography study to project trends in surface fuel loads at three study sites in Yosemite and Sequoia Kings Canyon National Parks. In the short term (2017-2021), fine woody debris and litter + duff significantly increased across all three sites (>145% and >55%, respectively); coarse woody debris increased significantly at one site (48.6%); and total fuel loads increased significantly at two of the three sites (38% and 69%). Snag longevity increased with size, with the relationship varying by species. Yellow pine was a notable outlier: size played a small role in influencing its fall rates. Overall, species-specific snag fall rates in the southern Sierra Nevada were 20% to 40% slower than previously reported. By 2040, projected median cumulative inputs of biomass from future snag fall range from 49.4 Mg ha-1 to 136.1 Mg ha-1across our three sites, which exceeds the amounts currently present (47.17-89.97 Mg ha-1) and is well above estimates of historical coarse woody debris amounts in the Sierra Nevada (17.7 Mg ha -1). These results provide a robust empirical basis to refine the snag fall algorithm in vegetation simulation models. Options to manage the impact of extreme number of snags and their large surface combustible biomass include salvage operations and prescribed burning, with both methods having operational, financial, and legal limitations that need to be considered.

Forest Ecology and Management↗

USGS2022

Methods for robust estimates of tree biomass from pollen accumulation rates: Quantifying paleoecological reconstruction uncertainty

Pollen accumulation rates (PAR, grains cm –2 year –1 ) have been shown to be a reliable but methodologically complex bioproxy for quantitative reconstruction of past tree abundance. In a prior study, we found that the PARs of major tree taxa – Pseudotsuga , Pinus , Notholithocarpus , and the pollen group TC (Taxaceae and Cupressaceae families) – were robust and precise estimators of contemporary tree biomass. This paper expands our earlier work. Here, we more fully evaluate the errors associated with biomass reconstructions to identify weaknesses and recommend improvements in PAR-based reconstructions of forest biomass. We account for uncertainty in our biomass proxy in a formal, coherent fashion. The greatest error was introduced by the age models, underscoring the need for improved statistical approaches to age-depth modeling. Documenting the uncertainty in pollen vegetation models should be standard practice in paleoecology. We also share insights gained from the delineation of the relevant source area of pollen, advances in Bayesian 210 Pb modeling, the importance of site selection, and the use of independent data to corroborate biomass estimates. Lastly, we demonstrate our workflow with a new dataset of reconstructed tree biomass between 1850 and 2018 AD from lakes in the Klamath Mountains, California. Our biomass records followed a broad trend of low mean biomass in the ∼1850s followed by large contemporary increases, consistent with expectations of forest densification due to twentieth century fire suppression policies in the American West. More recent reconstructed tree biomass estimates also corresponded with silviculture treatments occurring within the relevant source area of pollen of our lake sites.

California↗

USGS2022

Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains

For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management are informed by historical baselines. This need is particularly acute in California, where 20th-century fire suppression, coupled with a warming climate, has caused forest densification and increasingly large wildfires that threaten forest ecosystem integrity and management of the forests as part of climate mitigation efforts. We examine climatic versus anthropogenic influence on forest conditions over 3 millennia in the western Klamath Mountains—the ancestral territories of the Karuk and Yurok Tribes—by combining paleoenvironmental data with Western and Indigenous knowledge. A fire regime consisting of tribal burning practices and lightning were associated with long-term stability of forest biomass. Before Euro-American colonization, the long-term median forest biomass was between 104 and 128 Mg/ha, compared to values over 250 Mg/ha today. Indigenous depopulation after AD 1800, coupled with 20th-century fire suppression, likely allowed biomass to increase, culminating in the current landscape: a closed Douglas fir–dominant forest unlike any seen in the preceding 3,000 y. These findings are consistent with precontact forest conditions being influenced by Indigenous land management and suggest large-scale interventions could be needed to return to historic forest biomass levels.

California↗

USGS2021

Nonlinear shifts in infectious rust disease due to climate change

Range shifts of infectious plant disease are expected under climate change. As plant diseases move, emergent abiotic-biotic interactions are predicted to modify their distributions, leading to unexpected changes in disease risk. Evidence of these complex range shifts due to climate change, however, remains largely speculative. Here, we combine a long-term study of the infectious tree disease, white pine blister rust, with a six-year field assessment of drought-disease interactions in the southern Sierra Nevada. We find that climate change between 1996 and 2016 moved the climate optimum of the disease into higher elevations. The nonlinear climate change-disease relationship contributed to an estimated 5.5 (4.4–6.6) percentage points (p.p.) decline in disease prevalence in arid regions and an estimated 6.8 (5.8–7.9) p.p. increase in colder regions. Though climate change likely expanded the suitable area for blister rust by 777.9 (1.0–1392.9) km 2 into previously inhospitable regions, the combination of host-pathogen and drought-disease interactions contributed to a substantial decrease (32.79%) in mean disease prevalence between surveys. Specifically, declining alternate host abundance suppressed infection probabilities at high elevations, even as climatic conditions became more suitable. Further, drought-disease interactions varied in strength and direction across an aridity gradient—likely decreasing infection risk at low elevations while simultaneously increasing infection risk at high elevations. These results highlight the critical role of aridity in modifying host-pathogen-drought interactions. Variation in aridity across topographic gradients can strongly mediate plant disease range shifts in response to climate change.

California↗

USGS2021

Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm −2 year −1 ) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen deposition processes be quantitatively linked to spatially-explicit measures of plant abundance. Our study addressed these methodological challenges. Modern PAR and vegetation data were obtained from seven lakes in the western Klamath Mountains, California. To determine how to best calibrate our PAR-biomass model, we first calculated the spatial area of vegetation where vegetation composition and patterning is recorded by changes in the pollen signal using two metrics. These metrics were an assemblage-level relevant source area of pollen (aRSAP) derived from extended R-value analysis ( sensu Sugita, 1993) and a taxon-specific relevant source area of pollen (tRSAP) derived from PAR regression ( sensu Jackson, 1990). To the best of our knowledge, aRSAP and tRSAP have not been directly compared. We found that the tRSAP estimated a smaller area for some taxa (e.g. a circular area with a 225 m radius for Pinus ) than the aRSAP (a circular area with a 625 m radius). We fit linear models to relate PAR values from modern lake sediments with empirical, distance-weighted estimates of aboveground live biomass (AGL dw ) for both the aRSAP and tRSAP distances. In both cases, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus , and TCT (Taxodiaceae, Cupressaceae, and Taxaceae families) – were statistically significant and reasonably precise estimators of contemporary AGL dw . However, predictions weighted by the distance defined by aRSAP tended to be more precise. The relative root-mean squared error for the aRSAP biomass estimates was 9% compared to 12% for tRSAP. Our results demonstrate that calibrated PAR-biomass relationships provide a robust method to infer changes in past plant biomass.

California, Oregon↗

USGS2020

Compounding effects of white pine blister rust, mountain pine beetle, and fire threaten four white pine species

Invasive pathogens and bark beetles have caused precipitous declines of various tree species around the globe. Here, we characterized long‐term patterns of mountain pine beetle ( Dendroctonus ponderosae ; MPB) attacks and white pine blister rust, an infectious tree disease caused by the pathogen, Cronartium ribicola . We focused on four dominant white pine host species in Sequoia and Kings Canyon National Parks (SEKI), including sugar pine ( Pinus lambertiana ), western white pine ( P. monticola ), whitebark pine ( P. albicaulis ), and foxtail pine ( P. balfouriana ). Between 2013 and 2017, we resurveyed 152 long‐term monitoring plots that were first surveyed and established between 1995 and 1999. Overall extent (plots with at least one infected tree) of white pine blister rust (blister rust) increased from 20% to 33%. However, the infection rate across all species decreased from 5.3% to 4.2%. Blister rust dynamics varied greatly by species, as infection rate decreased from 19.1% to 6.4% in sugar pine, but increased in western white pine from 3.0% to 8.7%. For the first time, blister rust was recorded in whitebark pine, but not foxtail pine plots. MPB attacks were highest in sugar pines and decreased in the higher elevation white pine species, whitebark and foxtail pine. Both blister rust and MPB were important factors associated with elevated mortality in sugar pines. We did not, however, find a relationship between previous fires and blister rust occurrence. In addition, multiple mortality agents, including blister rust, fire, and MPB, contributed to major declines in sugar pine and western white pine; recruitment rates were much lower than mortality rates for both species. Our results highlighted that sugar pine has been declining much faster in SEKI than previously documented. If blister rust and MPB trends persist, western white pine may follow similar patterns of decline in the future. Given current spread patterns, blister rust will likely continue to increase in higher elevations, threatening subalpine white pines in the southern Sierra Nevada. More frequent long‐term monitoring efforts could inform ongoing restoration and policy focused on threats to these highly valuable and diverse white pines.

California↗

USGS2020

Coming to terms with the new normal: Forest health in the Sierra Nevada

The vast conifer forests of California’s Sierra Nevada range inspire awe and create lasting memories. The size and longevity of these trees make them seem both otherworldly and everlasting. Indeed, their grandeur is such that visitors may not appreciate how these forests are connected to the larger landscape, and so there is little understanding that something as common as a drought could lead to the death of so many trees and trigger massive and irreversible changes in the nature of these forests (Box 1: Reflections on the California Drought). Although tree death is a natural and essential process, human activity is increasing the mortality rate to such an extent that it threatens the persistence of the "big tree" forests we have come to associate with the Sierra Nevada. Here, we briefly explain how forests change, with a focus on the role of tree mortality. We then describe the contemporary risks and outline a way toward restoring the resilience of Sierran forests.

California↗

USGS2018

Sierra Nevada summary report. California’s Fourth Climate Change Assessment

The Sierra Nevada region is critical to the environment and economy of California. Its places and peoples provide essential natural resources including fresh water, clean power, working lands, and famous wilderness. The region encompasses tremendous geographical, climatological, and ecological diversity that spans majestic mountains to deep desert basins. The climate consists of cool, wet winters and warm, dry summers with large differences due to latitude (e.g., the southern Sierra is snowier than northern Sierra) and topography (e.g., the Westside is wetter than the Eastside). Variability is another notable feature of the climate with the region experiencing some of the largest year-to-year climatic fluctuations in the United States. Herein we summarize our assessment of climate-change vulnerabilities and adaptation actions in the region.

Report↗

USGS2017

Centennial-scale reductions in nitrogen availability in temperate forests of the United States

Forests cover 30% of the terrestrial Earth surface and are a major component of the global carbon (C) cycle. Humans have doubled the amount of global reactive nitrogen (N), increasing deposition of N onto forests worldwide. However, other global changes—especially climate change and elevated atmospheric carbon dioxide concentrations—are increasing demand for N, the element limiting primary productivity in temperate forests, which could be reducing N availability. To determine the long-term, integrated effects of global changes on forest N cycling, we measured stable N isotopes in wood, a proxy for N supply relative to demand, on large spatial and temporal scales across the continental U.S.A. Here, we show that forest N availability has generally declined across much of the U.S. since at least 1850 C.E. with cool, wet forests demonstrating the greatest declines. Across sites, recent trajectories of N availability were independent of recent atmospheric N deposition rates, implying a minor role for modern N deposition on the trajectory of N status of North American forests. Our results demonstrate that current trends of global changes are likely to be consistent with forest oligotrophication into the foreseeable future, further constraining forest C fixation and potentially storage.

Scientific Reports↗

USGS2014

Beyond reducing fire hazard: fuel treatment impacts on overstory tree survival

Fuel treatment implementation in dry forest types throughout the western United States is likely to increase in pace and scale in response to increasing incidence of large wildfires. While it is clear that properly implemented fuel treatments are effective at reducing hazardous fire potential, there are ancillary ecological effects that can impact forest resilience either positively or negatively depending on the specific elements examined, as well as treatment type, timing, and intensity. In this study, we use overstory tree growth responses, measured seven years after the most common fuel treatments, to estimate forest health. Across the five species analyzed, observed mortality and future vulnerability were consistently low in the mechanical-only treatment. Fire-only was similar to the control for all species except Douglas-fir, while mechanical-plus-fire had high observed mortality and future vulnerability for white fir and sugar pine. Given that overstory trees largely dictate the function of forests and services they provide (e.g., wildlife habitat, carbon sequestration, soil stability) these results have implications for understanding longer-term impacts of common fuel treatments on forest resilience.

Ecological Applications↗

USGS2013

A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 11a: giant sequoias

For natural resource managers in the southern Sierra Nevada, giant sequoia requires very little introduction. It receives great attention as an icon of western forests and as a common namesake with the areas where it occurs. While it is a single component of a very complex system, its attention in this assessment and in general is well deserved. Giant sequoia is one of the few "destination species" that attracts a wide swath of the public by nature of it simply being present. It draws people, who otherwise may not travel, to a natural environment. The result is an expansion of the public’s sense of natural resource stewardship. Because park managers could not achieve their mission without public support, this fostering role of giant sequoia is critical for park natural resources and is important for natural resources in general. Despite its social relevance and physical size, we re-emphasize here that the giant sequoia resource is a relatively small component of the ecosystems of the southern Sierra Nevada. As is the case with all of the resources assessed in the NRCA, we focus on giant sequoia with the understanding that other resources will be considered simultaneously when evaluating management decisions that impact giant sequoia. While we attempt to explicitly address the interaction of giant sequoia with other resources and stressors, we also realize that ultimately managers will integrate much more information than is presented here when making decisions that influence giant sequoia. The autecology and management issues surrounding giant sequoia have been thoroughly reviewed elsewhere (Harvey et al. 1980, Aune 1994, Stephenson 1996). Stephenson (1996), in particular, should be reviewed when considering any management decisions that potentially impact giant sequoia. For those who may not be familiar with giant sequoia ecology, a summary of basic information is provided in a table below. In some parts of this assessment, we reproduce text from Stephenson’s review because it is still relatively current for addressing some of the stressors. Numerous recent studies reported since 1996 have confirmed and expanded the understanding of giant sequoia, especially in areas related to ecophysiology and the effectiveness of restoration treatments. These recent studies are integrated into this assessment. Additionally, much unpublished work has been done that is useful for establishing baselines and evaluating trends. This work is presented in detail in order to expand upon previous work and to inform the final assessments. Instead of providing an introductory description of giant sequoia distribution and the various landowners who manage groves, we refer readers to the more recent descriptions provided by Stephenson (1996) and Willard (2000). Some of the relevant points from these descriptions with respect to giant sequoia within SEKI and Giant Sequoia National Monument (GSNM) include: - Of the native giant sequoia grove area in SEKI and GSNM approximately 38% is within SEKI and 62% is within GSNM. - 35 of the groves that make up the entire population are all or partially managed by SEKI and 33 are managed by GSNM. - As we have done above, reviewers addressing giant sequoia widely recognize its transcendence beyond an ecologically important species to one with considerable added cultural value.

California↗