scholarly journals Drought Increases Vulnerability of Pinus ponderosa Saplings to Fire-Induced Mortality

Fire ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 56
Author(s):  
Raquel Partelli-Feltrin ◽  
Daniel M. Johnson ◽  
Aaron M. Sparks ◽  
Henry D. Adams ◽  
Crystal A. Kolden ◽  
...  
Keyword(s):  
Pinus Ponderosa ◽  
Water Status ◽  
Western United States ◽  
Radiative Energy ◽  
Forest Composition ◽  
Fire Intensity ◽  
Surface Fires ◽  
Composition And Structure ◽  
In Fire ◽  
The Impact

The combination of drought and fire can cause drastic changes in forest composition and structure. Given the predictions of more frequent and severe droughts and forecasted increases in fire size and intensity in the western United States, we assessed the impact of drought and different fire intensities on Pinus ponderosa saplings. In a controlled combustion laboratory, we exposed saplings to surface fires at two different fire intensity levels (quantified via fire radiative energy; units: MJ m−2). The recovery (photosynthesis and bud development) and mortality of saplings were monitored during the first month, and at 200- and 370-days post-fire. All the saplings subjected to high intensity surface fires (1.4 MJ m−2), regardless of the pre-fire water status, died. Seventy percent of pre-fire well-watered saplings recovered after exposure to low intensity surface fire (0.7 MJ m−2). All of the pre-fire drought-stressed saplings died, even at the lower fire intensity. Regardless of the fire intensity and water status, photosynthesis was significantly reduced in all saplings exposed to fire. At 370 days post-fire, burned well-watered saplings that recovered had similar photosynthesis rates as unburned plants. In addition, all plants that recovered or attempted to recover produced new foliage within 35 days following the fire treatments. Our results demonstrate that the pre-fire water status of saplings is an important driver of Pinus ponderosa sapling recovery and mortality after fire.

Impacts of fire radiative flux on mature Pinus ponderosa growth and vulnerability to secondary mortality agents

2017 ◽  
Vol 26 (1) ◽  
pp. 95 ◽  
Author(s):  
Aaron M. Sparks ◽  
Alistair M. S. Smith ◽  
Alan F. Talhelm ◽  
Crystal A. Kolden ◽  
Kara M. Yedinak ◽  
...  
Keyword(s):  
Dose Response ◽  
Pinus Ponderosa ◽  
Radial Growth ◽  
Unit Area ◽  
Radiative Energy ◽  
Fire Intensity ◽  
Response Relationship ◽  
Fire Behaviour ◽  
Dose Response Relationship ◽  
Resin Duct

Recent studies have highlighted the potential of linking fire behaviour to plant ecophysiology as an improved route to characterising severity, but research to date has been limited to laboratory-scale investigations. Fine-scale fire behaviour during prescribed fires has been identified as a strong predictor of post-fire tree recovery and growth, but most studies report these metrics averaged over the entire fire. Previous research has found inconsistent effects of low-intensity fire on mature Pinus ponderosa growth. In this study, fire behaviour was quantified at the tree scale and compared with post-fire radial growth and axial resin duct defences. Results show a clear dose–response relationship between peak fire radiative power per unit area (W m–2) and post-fire Pinus ponderosa radial growth. Unlike in previous laboratory research on seedlings, there was no dose–response relationship observed between fire radiative energy per unit area (J m–2) and post-fire mature tree growth in the surviving trees. These results may suggest that post-fire impacts on growth of surviving seedlings and mature trees require other modes of heat transfer to impact plant canopies. This study demonstrates that increased resin duct defence is induced regardless of fire intensity, which may decrease Pinus ponderosa vulnerability to secondary mortality agents.

Fire effects on the spatial patterns of soil resources in a Nicaraguan wet tropical forest

2005 ◽  
Vol 21 (4) ◽  
pp. 435-444 ◽  
Author(s):  
Brent C. Blair
Keyword(s):  
Leaf Litter ◽  
Tropical Forests ◽  
Forest Fires ◽  
Soil Heterogeneity ◽  
Fire Effects ◽  
Fire Intensity ◽  
Vegetative Cover ◽  
Soil Resources ◽  
In Fire ◽  
The Impact

Anthropogenic wildfires are becoming increasingly frequent in wet tropical forests. This trend follows that of other anthropogenic disturbances, which are now acute and widespread. Fires pose a potentially serious threat to tropical forests. However, little is known about the impact of unintended forest fires on below-ground resources in these ecosystems. This study investigated the influence of fires on the distribution and variability of soil resources on two sets of 50×50-m burned and unburned plots in a Nicaraguan rain forest. Samples were collected at 5-m intervals throughout each plot as well as subsamples at 50-cm intervals. Geostatistical techniques as well as univariate statistics were used to quantify the spatial autocorrelation and variability of selected nutrients (N, P and K), carbon and standing leaf litter. Most variability in this forest was spatially dependent at a scale of 30 m or less. However the average range of autocorrelations varied greatly between properties and sites. Burning altered soil heterogeneity by decreasing the range over which soil properties were autocorrelated. Overall the average patch size (range) for nitrogen was reduced by 7%, phosphorus by 52%, potassium by 60% and carbon by 43%. While phosphorus and leaf litter increased in the burned plots compared to unburned plots, potassium was not different. Nitrogen and carbon did not display a consistent pattern between burning regimes and this may be explained by variation in fire intensity. Leaf litter measurements did not correlate with measured soil nutrients within plots. Observed changes in the burned forest were likely a result of both the intensity of burning and change in vegetative cover between the time of the fires and soil sampling.

scholarly journals Impulsive Fire Disturbance in a Savanna Model: Tree–Grass Coexistence States, Multiple Stable System States, and Resilience

2021 ◽  
Vol 83 (11) ◽  
Author(s):  
Alanna Hoyer-Leitzel ◽  
Sarah Iams
Keyword(s):  
Fire Frequency ◽  
Fire Disturbance ◽  
Fire Intensity ◽  
Ode Models ◽  
The Social ◽  
Impulsive Model ◽  
System States ◽  
Bifurcation Structures ◽  
In Fire ◽  
The Impact

AbstractSavanna ecosystems are shaped by the frequency and intensity of regular fires. We model savannas via an ordinary differential equation (ODE) encoding a one-sided inhibitory Lotka–Volterra interaction between trees and grass. By applying fire as a discrete disturbance, we create an impulsive dynamical system that allows us to identify the impact of variation in fire frequency and intensity. The model exhibits three different bistability regimes: between savanna and grassland; two savanna states; and savanna and woodland. The impulsive model reveals rich bifurcation structures in response to changes in fire intensity and frequency—structures that are largely invisible to analogous ODE models with continuous fire. In addition, by using the amount of grass as an example of a socially valued function of the system state, we examine the resilience of the social value to different disturbance regimes. We find that large transitions (“tipping”) in the valued quantity can be triggered by small changes in disturbance regime.

scholarly journals Investigating the Impact of Land Parcelization on Forest Composition and Structure in Southeastern Ohio Using Multi-Source Remotely Sensed Data

2019 ◽  
Vol 11 (19) ◽  
pp. 2195
Author(s):  
Xiaolin Zhu ◽  
Desheng Liu
Keyword(s):  
Aboveground Biomass ◽  
Forest Composition ◽  
Remotely Sensed Data ◽  
Forest Development ◽  
Composition And Structure ◽  
Forest Coverage ◽  
Parcel Size ◽  
Forest Attributes ◽  
Private Forestland ◽  
The Impact

Forestland parcelization (i.e., a process by which large parcels of forestland ownership are divided into many small parcels) presents an increasing challenge to sustainable forest development in the United States. In Southeastern Ohio, forests also experienced intensive forestland parcelization, where the majority of forest owners own parcels smaller than 10 acres currently. To better understand the impact of forestland parcelization on forest development, this study employed multi-source remotely sensed data and land ownership data in Hocking County, Ohio to examine the relationship between forestland parcel size and forest attributes, including forest composition and structure. Our results show that private forestland parcels are generally smaller than public forestland (the average parcel sizes are 21.5 vs. 275.0 acres). Compared with private lands, public lands have higher values in all forest attributes, including forest coverage, abundance of oak-dominant stands, canopy height and aboveground biomass. A further investigation focusing on private forestland reveals that smaller parcels tend to have smaller forest coverage, less greenness, lower height and aboveground biomass, indicating that forests in smaller parcels may experience more human disturbances than larger parcels. The results also show that logarithmic models can well quantify the non-linear relationship between forest attributes and parcel size in the study area. Our study suggests that forestland parcelization indeed has negative effects on forest development, so it is very important to take appropriate measures to protect forests in small ownership parcels.

scholarly journals Fuelwood Harvest and No Harvest Effects on Forest Composition, Structure, and Diversity of Arasbaran Forests—A Case Study

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1631
Author(s):  
Sajad Ghanbari ◽  
Christel C. Kern
Keyword(s):  
Species Diversity ◽  
Tree Height ◽  
Woody Species ◽  
Forest Composition ◽  
Stem Density ◽  
Regeneration Status ◽  
Composition And Structure ◽  
Composition Structure ◽  
The Impact

The impact of fuelwood harvesting on forest structure and composition is not clear, especially on the understudied and scarce Arasbaran forests in Iran. This research compared woody species density, species diversity, forest composition, and regeneration status in areas of continuous and ceased fuelwood harvesting in Arasbaran forests. We expected fuelwood harvesting to decrease stem density, species diversity, tree size (diameter at the breast height (DBH) and height), and shift composition away from preferred fuelwood species. We measured woody species size and frequency and identified species in three fuelwood harvest and three no harvest sites, with six sample plots (100 m × 50 m) per site. Results tended to show differences in composition, diversity, woody species height, and density. Carpinus orientalis, a preferred fuelwood species, tended to be more dominant in no harvest (importance values index (IVI) = 173.4) than harvest areas (IVI = 4.4). The diversity or richness of woody species tended to be higher in harvest (20 ± 1 species per ha) than in no harvest (14 ± 2 species per ha) areas, and other measures of diversity supported this trend as well. Harvest areas tended to also be characterized by shorter tree height and lower density of trees, a higher density of regeneration, and fewer small pole-sized trees than no harvest areas. Ongoing fuelwood harvests may further shift composition and structure away from no harvest area, compromising future fuelwood availability, but further detailed research is needed. Close to nature practices may be useful in sustaining fuelwood harvest areas and diversifying areas where fuelwood harvesting has ceased.

Seedbed variation from the interior through the edge of a large wildfire in Alberta

2005 ◽  
Vol 35 (7) ◽  
pp. 1640-1647 ◽  
Author(s):  
David F Greene ◽  
S Ellen Macdonald ◽  
Steve Cumming ◽  
Lynn Swift
Keyword(s):  
Populus Tremuloides ◽  
Life Histories ◽  
Fire Severity ◽  
Mineral Soil ◽  
Basal Area ◽  
White Spruce ◽  
Forest Composition ◽  
Fire Intensity ◽  
Soil Exposure ◽  
In Fire

Despite the importance of seedbeds in the life histories of many plant species, there has been little study of the seedbeds created by wildfire in fire-prone vegetation types such as the boreal forest. Both within the interior and at the edge of a very large (>100 000 ha) 2001 wildfire in the mixedwood boreal region of Alberta, we examined the postfire duff depth and the percent coverage of seedbed types. Minimizing the effect of site and forest composition, we looked only at Picea glauca (Moench) Voss – Populus tremuloides Michx. sites burned during a single day of high fire intensity. Good seedbeds (thin humus and exposed mineral soil, with or without ash) averaged 35% coverage within the interior of the fire but varied enormously among stands. There was a weak but significant positive correlation between prefire percent white spruce basal area and percent mineral soil exposure; that is, there is some tendency for conifer stands to create the seedbeds best suited for their own germinants. Fire severity played a clear role in mineral soil exposure, which was greatest in areas with 100% canopy mortality. Mineral soil exposure was far less at the edges of the fire, averaging only 5% even in areas where all trees had been killed; the burn edge was characterized by superficial flaming combustion with no evidence of substantial duff removal via smoldering combustion. In short, the areas where white spruce seed will be most common after the fire, the edges, are where the worst seedbeds in the burn will be found. Regeneration microsites at fire edges appear to be better suited to regeneration of broadleaf species, via suckering; the persistence of white spruce in fire-prone landscapes continues to be difficult to explain.

scholarly journals Processing Value of Small-Diameter Sawtimber at Conventional Stud Sawmills and Modern High-Speed, Small-Log Sawmills in the Western United States—A Comparison

2000 ◽  
Vol 15 (4) ◽  
pp. 208-212 ◽  
Author(s):  
Francis G. Wagner ◽  
Carl E. Fiedler ◽  
Charles E. Keegan
Keyword(s):  
United States ◽  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
High Speed ◽  
Fire Suppression ◽  
Small Diameter ◽  
Selective Logging ◽  
Western United States ◽  
Forest Composition ◽  
Delivery Costs

Abstract Past selective logging of early successional species [e.g., ponderosa pine (Pinus ponderosa)] and effective fire suppression have dramatically altered forest composition and health over millions of acres in the western United States. Implementation of ecological restoration treatments to address these conditions will produce large volumes of small-diameter sawtimber for processing. Since sawmills currently process a majority of sawtimber harvested in the West (more than 80% in some regions), this study concentrated on determining the value of small-diameter sawtimber delivered to sawmills. A conventional stud sawmill and a modern, high-speed, small-log sawmill were profiled. A simulator (MSUSP) was employed to describe these sawmills and to determine breakeven delivered-sawtimber values by dbh class for each sawmill. Data inputs included machinery type, mill layout, machine speeds, volume and grade recovery, product prices, and fixed and variable manufacturing costs. Results showed that sawtimber 9 in. dbh and under could not cover harvest and delivery costs and earn even a modest (10%) return on invested (ROI) capital at the conventional stud sawmill and that sawtimber 7.5 in. dbh and smaller had negative values. However with a 10% ROI capital, the value of all sizes of sawtimber at the modern, high-speed sawmill equaled or exceeded harvest and delivery costs. West. J. Appl. For. 15(4):208–212.

scholarly journals Forest plant and macrofungal differences in the Greater and Lesser Khingan Mountains in Northeast China: A regional-historical comparison and its implications

2021 ◽  
Author(s):  
Yuanyuan Wang ◽  
Hui Wen ◽  
Kai Wang ◽  
Jingxue Sun ◽  
Jinghua Yu ◽  
...  
Keyword(s):  
Northeast China ◽  
Dominant Species ◽  
Local Economy ◽  
Forest Composition ◽  
Historical Records ◽  
Historical Comparison ◽  
Composition And Structure ◽  
Total State ◽  
The 1960S ◽  
Forest Plants

AbstractForests in Northeast China in the Greater and Lesser Khingan Mountains (GKM and LKM) account for nearly 1/3 of the total state-owned forests in the country. Regional and historical comparisons of forest plants and macrofungi will favor biological conservation, forest management and economic development. A total of 1067 sampling plots were surveyed on forest composition and structure, with a macrofungi survey at Liangshui and Huzhong Nature Reserves in the center of two regions. Regional and historical differences of these parameters were analyzed with a redundancy ordination of their complex associations. There were 61–76 families, 189–196 genera, and 369–384 species, which was only 1/3 of the historical records. The same dominant species were larch and birch with Korean pine (a climax species) less as expected from past surveys in the LKM. Shrub and herb species were different in the two regions, as expected from historical records. There was 10–50% lower species diversity (except for herb evenness), but 1.8- to 4-time higher macrofungi diversity in the GKM. Compared with the LKM, both tree heights and macrofungi density were higher. Nevertheless, current heights averaging 10 m are half of historical records (> 20 m in the 1960s). Edible macrofungi were the highest proportion in both regions, about twice that of other fungal groups, having important roles in the local economy. A major factor explaining plant diversity variations in both regions was herb cover, followed by shrubs in the GKM and herb-dominant species in the LKM. Factors responsible for macrofungi variations were tree density and shrub height. Vaccinium vitis-idaea and Larix gmelinii in the GKM but tree size and diversity were important factors in the LKM. Our findings highlighted large spatial and historical differences between the GKM and LKM in plant-macrofungal composition, forest structure, and their complex associations, which will favor precise conservation and management of forest resources in two region in the future.

scholarly journals Twenty-first century droughts have not increasingly exacerbated fire season severity in the Brazilian Amazon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Libonati ◽  
J. M. C. Pereira ◽  
C. C. Da Camara ◽  
L. F. Peres ◽  
D. Oom ◽  
...  
Keyword(s):  
Forest Fires ◽  
Brazilian Amazon ◽  
First Century ◽  
Fire Season ◽  
Fire Intensity ◽  
Amazon Forest ◽  
Active Fire ◽  
Fire Activity ◽  
Twenty First Century ◽  
In Fire

AbstractBiomass burning in the Brazilian Amazon is modulated by climate factors, such as droughts, and by human factors, such as deforestation, and land management activities. The increase in forest fires during drought years has led to the hypothesis that fire activity decoupled from deforestation during the twenty-first century. However, assessment of the hypothesis relied on an incorrect active fire dataset, which led to an underestimation of the decreasing trend in fire activity and to an inflated rank for year 2015 in terms of active fire counts. The recent correction of that database warrants a reassessment of the relationships between deforestation and fire. Contrasting with earlier findings, we show that the exacerbating effect of drought on fire season severity did not increase from 2003 to 2015 and that the record-breaking dry conditions of 2015 had the least impact on fire season of all twenty-first century severe droughts. Overall, our results for the same period used in the study that originated the fire-deforestation decoupling hypothesis (2003–2015) show that decoupling was clearly weaker than initially proposed. Extension of the study period up to 2019, and novel analysis of trends in fire types and fire intensity strengthened this conclusion. Therefore, the role of deforestation as a driver of fire activity in the region should not be underestimated and must be taken into account when implementing measures to protect the Amazon forest.

scholarly journals Over half of western United States' most abundant tree species in decline

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hunter Stanke ◽  
Andrew O. Finley ◽  
Grant M. Domke ◽  
Aaron S. Weed ◽  
David W. MacFarlane
Keyword(s):  
United States ◽  
Tree Species ◽  
Tree Mortality ◽  
Temperate Forests ◽  
Size Structure ◽  
Forest Disturbance ◽  
Population Decline ◽  
Western United States ◽  
Scale Transformation ◽  
Forest Composition

AbstractChanging forest disturbance regimes and climate are driving accelerated tree mortality across temperate forests. However, it remains unknown if elevated mortality has induced decline of tree populations and the ecological, economic, and social benefits they provide. Here, we develop a standardized forest demographic index and use it to quantify trends in tree population dynamics over the last two decades in the western United States. The rate and pattern of change we observe across species and tree size-distributions is alarming and often undesirable. We observe significant population decline in a majority of species examined, show decline was particularly severe, albeit size-dependent, among subalpine tree species, and provide evidence of widespread shifts in the size-structure of montane forests. Our findings offer a stark warning of changing forest composition and structure across the western US, and suggest that sustained anthropogenic and natural stress will likely result in broad-scale transformation of temperate forests globally.

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