Climate predicts wildland fire extent across China

Wildland fire extent varies seasonally and interannually in response to climatic and landscape-level drivers, yet predicting wildfires remains a challenge. Existing linear models that characterize climate and wildland fire relationships fail to account for non-stationary and non-linear associations, thus limiting prediction accuracy. To account for non-stationary and non-linear effects, we use time-series climate and wildfire extent data from across China with unit root methods, thus providing an approach for improved wildfire prediction. Results from this approach suggest that wildland area burned is sensitive to vapor pressure deficit (VPD) and maximum temperature changes over short and long-term scenarios. Moreover, repeated fires constrain system variability resulting in non-stationarity responses. We conclude that an autoregressive distributed lag (ARDL) approach to dynamic simulation models better elucidates interactions between climate and wildfire compared to more commonly used linear models. We suggest that this approach will provide insights into a better understanding of complex ecological relationships and represents a significant step toward the development of guidance for regional planners hoping to address climate-driven increases in wildfire incidence and impacts.

Homeowner perceptions and responses to buffelgrass invasion risk in the Tucson, Arizona Wildland-Urban Interface

In this study, we aimed to analyze homeowners' level of awareness and perceived risk about buffelgrass invasion in the Tucson, Arizona Wildland-Urban Interface (WUI), as well as the factors influencing their participation in buffelgrass control and fire risk mitigation efforts. Data for the study were generated through the administration of an online survey among 117 members of Home Owner Associations (HOAs) in the Tucson WUI. The results showed that the overwhelming majority of respondents were aware of buffelgrass, but their knowledge about buffelgrass control mechanisms appeared to be limited. Respondents also more frequently expressed concern about the risks posed by buffelgrass invasion to general targets, such as the Sonoran Desert ecosystem, native plants and wildlife than risks to their private property and neighborhoods. The results also showed that the level of involvement in HOAs, and leadership in HOAs had significant positive effects on homeowners' participation in buffelgrass control efforts. Homeowners' duration of residence also had a significant negative effect on participation in buffelgrass control efforts, suggesting that newcomers may be more involved than long-term residents. Similarly, the number of months respondents spent in Tucson per year had a negative effect on the number of hours spent on buffelgrass control efforts. Respondents' perceived risk about buffelgrass invasion also had a positive effect on the hours spent on buffelgrass control as well as their level of involvement in fire risk mitigation efforts. These results highlight the importance of local institutions and community heterogeneity in social responses to threats in WUI communities. Policies aimed at building the resilience of WUI communities need to account for their complexity as coupled social-ecological systems.

Seasonal weather and climate prediction over area burned in grasslands of northeast China

Grassland fire dynamics are subject to myriad climatic, biological, and anthropogenic drivers, thresholds, and feedbacks and therefore do not conform to assumptions of statistical stationarity. The presence of non-stationarity in time series data leads to ambiguous results that can misinform regional-level fire management strategies. This study employs non-stationarity in time series data among multiple variables and multiple intensities using dynamic simulations of autoregressive distributed lag models to elucidate key drivers of climate and ecological change on burned grasslands in Xilingol, China. We used unit root methods to select appropriate estimation methods for further analysis. Using the model estimations, we developed scenarios emulating the effects of instantaneous changes (i.e., shocks) of some significant variables on climate and ecological change. Changes in mean monthly wind speed and maximum temperature produce complex responses on area burned, directly, and through feedback relationships. Our framework addresses interactions among multiple drivers to explain fire and ecosystem responses in grasslands, and how these may be understood and prioritized in different empirical contexts needed to formulate effective fire management policies.

Watershed Vulnerability to Invasive N2-Fixing Autumn Olive and Consequences for Stream Nitrogen Concentrations

Autumn olive ( Thunb.) is an invasive and exotic N-fixing plant species found throughout the United States. Proliferation and spread of autumn olive have displaced native plants and raised concerns about the effects of N fixation and cycling on water quality in invaded areas. This study investigated the relationship between autumn olive cover and stream N concentrations. Twelve forested watersheds were selected and classified into edge, mid-distance, and interior-of-the-forest watersheds based on autumn olive density and distance from the permanent edge of invasion point along a major road corridor. For the 2012 vegetation survey, autumn olive cover in edge, mid, and interior watersheds ranged from 37 to 61%, 18 to 37%, and 4 to 10%, respectively. From 2006 to 2012, mean stream water NO-N concentration in the edge watersheds was significantly higher (1.39 mg L, < 0.0001) than mid (0.37 mg L) and interior (0.27 mg L) watersheds. A linear relationship was found between NO-N concentration and autumn olive cover ( = 0.72, = 0.0001). Mean stream water NH-N, specific conductivity, and pH were significantly less in the interior watersheds than in the edge watersheds. Additionally, peak specific conductivity and NO-N from edge watersheds coincided with peak stage for these watersheds, demonstrating that N flushing events were driven by surface and shallow subsurface flow pathways proximal to the stream. Results from this study demonstrate how encroachment of autumn olive can influence water quality and transform biogeochemical cycles in natural systems, which points to the need for effective management of autumn olive in the edge watersheds and riparian zones that are vulnerable to invasion and increased N export.

Data on ecological associations and stand structure of chilgoza pine (Pinus gerardiana Wall. ex D. Don) in Afghanistan

Reported here are original data related to the article “Indigenous knowledge and stand characteristics of a threatened tree species in a highly insecure area: Chilgoza pine in Afghanistan” (Shalizi et al., 2018) [1]. A dendrochronological summary of all known chilgoza pine tree growth increment cores collected in Afghanistan is presented in this data in brief article. Chilgoza pine trees and regeneration density profiles are reported for four provinces of eastern Afghanistan. In addition, images depicting chilgoza pine forest structure, stand conditions, and utilization impacts are presented.

Sediment Dynamics Within Buffer Zone and Sinkhole Splay Areas Under Extreme Soil Disturbance Conditions

Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees (Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year(-1) translating to a sediment loss rate of 46.1 metric ton year(-1) from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year(-1)) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management.

Reforestation strategies amid social instability: lessons from Afghanistan

Foreign and domestic government agencies and other international organizations pursue reforestation programs in rural upper watershed areas of Afghanistan over the past decade to alleviate poverty, combat the insurgency and rehabilitate a depleted forest resource base. Popular programs incorporate cash-for-work to conduct hillside terracing, check dam construction and tree-planting for nut production, fuel wood, timber, dune stabilization, and erosion abatement. Programmatic approaches have varied as a function of accessibility, security and local objectives. Uncertain land tenure and use rights, weak local environmental management capacity, and a focus on agricultural production to meet immediate needs limit interest, nationally and locally. Unreliable security, a lack of high quality tree planting stock, limited technical knowledge and coordination among government agencies, and poor security hamper program expansion. Reforestation success would be most likely where these issues are least acute. The Afghan government should focus on supporting community based natural resource management, developing and disseminating improved conservation tree nursery strategies, and promoting watershed management schemes that incorporate forestry, range management and agronomic production. Reforestation practitioners could benefit from the human and material resources now present as part of the international war effort. Successes and failures encountered in Afghanistan should be considered in order to address similar problems in insecure regions elsewhere when reforestation may help reverse environmental degradation and contribute to broader social stabilization efforts.

Field characterization of external grease abatement devices

This study characterized some of the physical and chemical features of large outside field grease abatement devices (GADs). 24-hour measurements of several food service establishments' (FSEs') influent GAD flowrates indicated highly intermittent conditions with hydraulic retention times (HRTs) that exceeded the common recommendation (30 minutes) by two to five times. Investigation into the chemical characteristics of GADs indicated highly variable influent and effluent fat, oil, and grease (FOG) concentrations. Low pH and dissolved oxygen values were measured throughout the GAD, indicating the likely occurrence of anaerobic microbial processes. Detailed spatial and temporal observations of the accumulation of FOG and food solids were also discussed. Though the FOG layer remained relatively constant for all GAD configurations investigated, results indicated that commonly-used GAD configurations with a straight submerged inlet tee or no-inlet tee configuration may result in the transport of food solids into the second compartment. The present research showed increased accumulation of food solids in the first compartment with a retro-fit flow distributive inlet. This retro-fit displays promise for potentially improving the separation characteristics of existing GADs.

Composition of Oak Stands in the Illinois Ozark Hills 2 Decades following Light Harvesting and No Cutting

Light harvesting and no cutting are two common management regimes in oak-dominated forests in the Ozark Hills of southern Illinois. We compared changes in overstory stand composition between 1980 and 2000 among forest inventory plots that were lightly harvested after initial sampling and plots that were uncut during the same time period. Total white oak (Quercus alba L.) basal area increased for both management regimes. Black oak (Quercus velutina Lam.) overstory density decreased, and sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrh.) density increased for both management regimes. Although overall density of oak was maintained by both management regimes, species and diameter class-specific response varied. Additional silvicultural activities may be necessary to sustain oak in both lightly harvested and uncut plots, with light harvesting providing opportunities to at least partially offset costs.

Soil and groundwater nitrogen response to invasion by an exotic nitrogen-fixing shrub

Autumn-olive (Elaeagnus umbellata Thunb.) is an invasive, exotic shrub that has become naturalized in the eastern United States and can fix nitrogen (N) via a symbiotic relationship with the actinomycete Frankia. Fixed N could potentially influence nutrient cycling rates and N leaching into soil water and groundwater. In situ net N mineralization, net nitrification, and net ammonification rates, as well as soil water and groundwater nitrate N (NO(3)-N) and ammonium N (NH(4)-N) concentrations, were measured under autumn-olive-dominated and herbaceous open field areas in southern Illinois. Soil net N mineralization and net nitrification rates were higher under autumn-olive compared with open field (p < 0.05) and could be driven, in part, by the relatively low C/N ratio (11.41 +/- 0.29) of autumn-olive foliage and subsequent litter. Autumn-olive stands also had greater soil water NO(3)-N (p = 0.003), but soil water NH(4)-N concentrations were similar between autumn-olive and open field. Groundwater NO(3)-N and NH(4)-N concentrations were similar beneath both types of vegetation. Groundwater NO(3)-N concentrations did not reflect patterns in soil N mineralization and soil water NO(3)-N most likely due to a weak hydrologic connection between soil water and groundwater. The increased N levels in soil and soil water indicate that abandoned agroecosystems invaded by autumn-olive may be net sources of N to adjacent terrestrial and aquatic systems rather than net sinks.

Oak Ecosystem Management Considerations for Central Hardwoods Stands Arising from Silvicultural Clearcutting

Silvicultural clearcutting was widely used during the late 20th century to regenerate stands on upland sites and achieve timber production objectives within the central hardwood region. As these even-aged stands develop, silvicultural guidelines are needed to address newer management objectives emphasizing oak ecosystem maintenance. The US Forest Service Common Stand Exam procedure (Common Stand Exam Users Guide, 2003, Ver. 1.5.1, US Forest Service, Washington, DC, 87 p.) was modified to assess stand stocking, composition, oak (Quercus) competitive status, and other emerging management concerns. A total of 74 randomly selected upland stands that had been silviculturally clearcut between 1980 and 1990 were sampled across the Shawnee National Forest in southern Illinois. Maples (Acer spp.) and yellow-poplar (Liriodendron tulipifera L.) predominated across all landscape positions 15–26 years after stand initiation. Oak (Quercus spp.) trees per acre was related to landscape position and averaged less than 50 trees/ac on the more productive lower slope positions and north aspects. However, when yellow-poplar was present, oaks were in a competitively inferior canopy position regardless of slope position or aspect. Our results show that for sustaining oak ecosystems in this region, management interventions favoring oaks should focus on the most productive sites, where crop tree release would reduce yellow-poplar interference with a sparse oak resource, as well as on less productive sites, where thinning to reduce stocking may be needed to maintain stand health.

Growth and photosynthetic responses of four Virginia Piedmont tree species to shade

To determine the effects of shade on biomass, carbon allocation patterns and photosynthetic response, seedlings of loblolly pine (Pinus taeda L.), white pine (Pinus strobus L.), red maple (Acer rubrum L.), and yellow-poplar (Liriodendron tulipifera L.) were grown without shade or in shade treatments providing a 79 or 89% reduction of full sunlight for two growing seasons. The shade treatments resulted in less total biomass for all species, with loblolly pine showing the greatest shade-induced growth reduction. Yellow-poplar was the only species to show increased stem height growth in the 89% shade treatment. The shade treatments increased specific leaf area of all species. Quantum efficiency, dark respiration and light compensation point were generally not affected by the shade treatments. Quantum efficiency, dark respiration, maximum photosynthesis and light compensation point did not change consistently between the first and second growing seasons. We conclude that differences in shade tolerance among these species are not the result of changes in the photosynthetic mechanism in response to shade.