Biophysical influences on the spatial distribution of fire in the desert grassland region of the southwestern USA

Context

Fire is an important driver of ecological processes in semiarid systems and serves a vital role in shrub-grass interactions. In desert grasslands of the southwestern US, the loss of fire has been implicated as a primary cause of shrub encroachment. Where fires can currently be re-introduced given past state changes and recent restoration actions, however, is unknown and controversial.

Objectives

Our objective was to evaluate the interactive effects of climate, urban development, and topo-edaphic properties on fire distribution in the desert grassland region of the southwestern United States.

Methods

We characterized the spatial distribution of fire in the Chihuahuan Desert and Madrean Archipelago ecoregions and investigated the influence of soil properties and ecological site groups compared to other commonly used biophysical variables using multi-model inference.

Results

Soil-landscape properties significantly influenced the spatial distribution of fire ignitions. Fine-textured bottomland ecological site classes experienced more fires than expected in contrast to upland sites with coarse soil textures and high fragment content that experienced fewer fire ignitions than expected. Influences of mean annual precipitation, distance to road/rail, soil available water holding capacity (AWHC) and topographic variables varied between ecoregions and political jurisdictions and by fire season. AWHC explained more variability of fire ignitions in the Madrean Archipelago compared to the Chihuahuan Desert.

Conclusions

Understanding the spatiotemporal distribution of recent fires in desert grasslands is needed to manage fire and predict responses to climate change. The use of landscape units such as ecological sites presents an opportunity to improve predictions at management scales.

     

Urbanization's impact on sustained yield management as perceived by forestry professionals in central New York

The urbanizing forested landscape in the United States is creating challenges for resource managers and land-use planners. Logistic regression models developed to assess urbanization's effect on forestland for the mid-Atlantic and southern states found that population density was the best predictor of reduced commercial harvest opportunity. We applied similar methodologies in central New York to assess urbanization's impact on sustained yield management. We surveyed professional foresters in a five-county area and asked them to rate the potential for sustained yield management by township. We utilized those expert opinions to develop a logistic regression model that predicted the probability of sustained yield management in central New York while exploring the factors that influence sustained yield management. We found that road density was the primary variable influencing the likelihood of sustained yield management in central New York. Population density, which is highly correlated with road density, also proved to be a strong determinant of sustained yield management. The results suggest that the potential for sustained yield management approaches 10% at a road density of 3 mi/mi², 50% at 2.5 mi/mi², and 90% at 2 mi/mi². The corresponding figures for population density were 150 people per square mile (ppsm), 75 ppsm and 25 ppsm, respectively. In addition, we determined that the probability of sustained yield management approaches 100% for a property that is approximately 30 acres and drops to 50% for a parcel that is between 15 and 20 acres. This study provides resource managers and land-use planners a guide in which to effectively gauge the cumulative effect of urbanization on the forest resource in central New York. Unlike other regions of the United States, central New York's growth pattern is characterized by stagnant population growth (declining in some places) combined with continued urbanization and low-density sprawl. Because growth patterns vary regionally, different indicators may be needed to accurately assess the urbanizing forested landscape across the United States.     

Grand Challenges for Resilience-Based Management of Rangelands

The social and ecological contexts for rangeland management are changing rapidly, prompting a reevaluation of science, management, and their relationship. We argue that progression from steady-state management to ecosystem management has served the rangeland profession well, but that further development toward resilience-based management is required to ensure that ecosystem services are sustained in an era of rapid change. Resilience-based management embraces the inevitability of change and emphasizes that management should seek to guide change to benefit society. The objectives of this forum are to: 1) justify the need for adopting resilience-based management, 2) identify the challenges that will be encountered in its development and implementation, and 3) highlight approaches to overcoming these challenges. Five grand challenges confronting the adoption of resilience-based management, based upon the insights of 56 rangeland researchers who have contributed to this special issue, were identified as: 1) development of knowledge systems to support resilience-based management, 2) improvement of ecological models supporting science and management, 3) protocols to assess and manage tradeoffs among ecosystem services, 4) use of social-ecological system models to integrate diverse knowledge sources, and 5) reorganization of institutions to support resilience-based management. Resolving the challenges presented here will require the creation of stronger partnerships between ecosystem managers, science organizations, management agencies, and policymakers at local, regional, and national scales. A realistic near-term goal for achieving such partnerships is to initiate and support collaborative landscape projects. The creation of multiscaled social learning institutions linked to evolving knowledge systems may be the best approach to guide adaptation and transformation in rangelands in the coming century.     

Effects of day length on flowering and yield production of Salicornia and Sarcocornia species

Salicornia is a new vegetable crop that can be irrigated with highly saline water, even at salt concentrations equivalent to full-strength seawater. During leafy vegetable cultivation, the onset of the reproductive phase is an undesired phenomenon that reduces yield and quality and prevents year-round cultivation. Knowledge about the regulation of floral induction in the members of the tribe Salicornieae, however, is lacking. To establish year-round cultivation, we studied the flower induction of five Salicornia and two Sarcocornia varieties. Plants were grown under two day lengths, 13.5 h and 18 h, and harvested by a repetitive harvest regime. A 13.5-h day length prevented flower induction in the Israeli Salicornia varieties, but a longer day length was required to prevent flower induction in two species originating from more northern latitudes. The onset of the reproductive phase under suboptimal short day length conditions severely reduced vegetative growth and yields in Salicornia. In Sarcocornia, the repetitive harvest regime prevented flowering, making it a promising candidate for year-round cultivation. Irrigating the plants with full-strength seawater (electrical conductivity 48 dS m⁻¹) vs. water with moderate salinity (electrical conductivity 10 dS m⁻¹) did not change the general flowering pattern of the studied Salicornieae members.     

Evidence for macromolecular protein rings in the absence of bulk water

We have examined the architecture of a protein complex in the absence of bulk water. By determining collision cross sections of assemblies of the trp RNA binding protein, TRAP, we established that the 11-membered ring topology of the complex can be maintained within a mass spectrometer. We also found that the binding of tryptophan enhances the stability of the ring structure and that addition of a specific RNA molecule increases the size of the complex and prevents structural collapse. These results provide definitive evidence that protein quaternary structure can be maintained in the absence of bulk water and highlight the potential of ion mobility separation for defining shapes of heterogeneous macromolecular assemblies.     

Evaluating habitat associations of a fish assemblage at multiple spatial scales in a minimally disturbed stream using low‐cost remote sensing

相似文献   

Extremely long-lived nuclear pore proteins in the rat brain

To combat the functional decline of the proteome, cells use the process of protein turnover to replace potentially impaired polypeptides with new functional copies. We found that extremely long-lived proteins (ELLPs) did not turn over in postmitotic cells of the rat central nervous system. These ELLPs were associated with chromatin and the nuclear pore complex, the central transport channels that mediate all molecular trafficking in and out of the nucleus. The longevity of these proteins would be expected to expose them to potentially harmful metabolites, putting them at risk of accumulating damage over extended periods of time. Thus, it is possible that failure to maintain proper levels and functional integrity of ELLPs in nonproliferative cells might contribute to age-related deterioration in cell and tissue function.     

Role of the Arabidopsis glucose sensor HXK1 in nutrient,light, and hormonal signaling

Glucose modulates many vital processes in photosynthetic plants. Analyses of Arabidopsis glucose insensitive2 (gin2) mutants define the physiological functions of a specific hexokinase (HXK1) in the plant glucose-signaling network. HXK1 coordinates intrinsic signals with extrinsic light intensity. HXK1 mutants lacking catalytic activity still support various signaling functions in gene expression, cell proliferation, root and inflorescence growth, and leaf expansion and senescence, thus demonstrating the uncoupling of glucose signaling from glucose metabolism. The gin2 mutants are also insensitive to auxin and hypersensitive to cytokinin. Plants use HXK as a glucose sensor to interrelate nutrient, light, and hormone signaling networks for controlling growth and development in response to the changing environment.     

An updated geographic distribution of Myxobolus cerebralis (Hofer, 1903) (Bivalvulida: Myxobolidae) and the first diagnosed case of whirling disease in wild-caught trout in the south-eastern United States

Myxobolus cerebralis (Bivalvulida: Myxobolidae), the aetiological agent of salmonid whirling disease, was detected in 2 river basins of North Carolina during 2015, which initiated the largest spatial–temporal monitoring project for the disease ever conducted within the south-eastern United States (focused mainly in eastern Tennessee and western North Carolina). A total of 2072 rainbow trout Oncorhynchus mykiss, 1,004 brown trout Salmo trutta and 468 brook trout Salvelinus fontinalis were screened from 113 localities within 7 river basins during June 2017 through October 2019. Infections were detected by pepsin–trypsin digest, microscopy and the species-specific nested polymerase chain reaction (PCR) in 19 localities across 6 river basins. Myxospore morphology was indistinguishable from the published literature. In 2019, five rainbow trout that symptomatic for whirling disease (sloping neurocranium and lordosis) were captured and processed for histopathology. Myxospores were detected in the calvarial cartilage of two deformed trout with associated erosion of the cartilage consistent with reported whirling disease lesions. This is the first report of M. cerebralis in Tennessee and the first histologically confirmed cases of whirling disease in southern Appalachian (south-eastern United States) rivers and streams and expands the distribution of M. cerebralis throughout western North Carolina and eastern Tennessee.