Search Results (5)

The “divergence problem” in recent decades is a tendency for trees in high latitudes to lose climate sensitivity. Growth divergence has been reported for certain tree species in alpine or northern latitude locations but has yet to be found in species with southern distributions. This retrospective study used tree ring data collected from longleaf pine trees (Pinus palustris Mill.) in natural stands and a young plantation to test whether divergence exists in this important southeastern tree species. Our results demonstrate that a growth divergence in basal area increment (BAI) occurred among individual longleaf pines within stands. The BAI of each tree followed Taylor’s law but with differing exponents, which varied from 0.75 to 6.4. Divergence of BAI among trees increased with time, and it might be related to the local drought, as the highest BAI divergence occurred when the SPEI (standardized precipitation-evapotranspiration index) was approximately 0 (−0.3–0.3). Hourly dendrometer measurements confirmed growth divergence among individuals. Collectively, our study provides new information about the growth characteristics of longleaf pine, which may partially explain how this species persists and thrives in southeastern environments. Our current management strategy on longleaf pine forests, such as prescribed burning and genetics improvement efforts, needs to be adapted. Full article

Pine straw, the uppermost forest floor layer of undecayed, reddish-brown pine needles, is raked, baled, and sold as a landscaping mulch throughout the southeastern United States. Loblolly (Pinus taeda, L.), longleaf (P. palustris, Mill.), and slash (P. elliottii Engelm. var. elliottii) pine are the three southern pine species commonly raked for pine straw. The value of pine straw as a forest product is large. Private landowner pine straw revenues have steadily increased throughout the southeastern United States over the past two decades and now total more than USD 200 million. Information is limited on the short- or long-term effects of pine straw removal on foliage production or stand growth in southern pine stands. Results from most published studies suggest that annual pine straw raking without fertilization on non-old-field sites reduces straw yields compared to no raking. Old-field sites often do not benefit from fertilization with increased pine straw or wood volume yields. Though fertilization may be beneficial for pine straw production on some sites, understory vegetation presence and disease prevalence may increase following fertilization. This review addresses pine straw removal effects on pine straw production and stand growth parameters based on recent studies and provides fertilization recommendations to maintain or improve pine straw production and stand growth and yield. Full article

Cluster planting of shortleaf pine, along with various site preparation and release treatments, were tested to restore mixed shortleaf pine (Pinus echinata Mill.)–hardwood stands in areas where the shortleaf pine has diminished in recent years. Shortleaf pine–hardwood mixtures were once a common forest type throughout the Cumberland Mountains and Plateau physiographic regions of the southeastern United States. Knowledge of how to restore shortleaf pine–hardwood mixtures is limited throughout shortleaf pine’s large native range. The objectives of this study were to compare planted shortleaf pine and natural hardwood regeneration survival, growth, and composition following various site preparation and early release treatments. Cluster planting and partial timber harvesting were used to reintroduce shortleaf pine and create two-aged stands in the Cumberland Mountains of Tennessee, USA. Results indicated that shortleaf pine survival, basal diameter, and height growth did not differ following four growing seasons among treatments. Natural regeneration stem densities and heights within shortleaf pine clusters did not differ significantly by treatment. Natural regeneration stem densities differed by species group and height class across the site, while the treatment × species interaction term was also significant. At this early stage of stand development, the brown-and-burn treatment appears poised for greater shortleaf pine growth rates than the other treatments. The herbicide treatment had the fewest regenerating hardwoods per hectare and the most desirable hardwood species composition. Full article

IaaS (Infrastructure as a Service) is a well-known computing service, which provides infrastructures over the cloud without owning real hardware resources. This is attractive as resources can be scaled up and down instantly according to the user’s computing demands. Customers of such services would like to adjust the utilization policy promptly by considering the charge of the service, but an instantaneous response is not possible as it takes several hours or even a couple of days for cloud service providers to inform the billing information. In this article, we present an instant cost estimation model for estimating the cost of public cloud resources. Specifically, our model estimates the cost of IaaS by monitoring the usage of resources on behalf of virtual machine instances. As this is performed by generating a user-side metering daemon, it is very precise and thus similar to the resource usage evaluated by the cloud service provider. To validate our model, we run PC laboratory services for 50 students in two classes by making use of a public cloud during a semester. Experimental results show that the accuracy of our model is over 99.3% in comparison with the actual charge of the public cloud. Full article

A recent wildland fire history and climate database was compiled for South Dakota, USA (SD). Wildfires are generally a warm season phenomenon across central and western SD while eastern SD exhibits a spring peak in annual wildfire activity. It is hypothesized that regional climate and land use are the two primary drivers of the spatiotemporal wildfire distribution across the state. To assess the relative impacts of climate to wildfire activity, Spearman’s rank order correlation coefficients were calculated for monthly values of temperature, precipitation, and the Palmer Drought Modified Index (PMDI) as compared to both monthly area burned and numbers of fire starts data for each of the nine climate divisions in South Dakota. Results show statewide variations in significant correlations but positive temperature anomalies, negative precipitation anomalies, and negative values of the PMDI were most frequently associated with months showing substantial area burned and large numbers of wildfire starts. Time-lagged significant correlations were also seen implying month(s)-ahead predictive capabilities. Positive PMDI values were most significantly correlated to warm season wildfire activity suggesting that the influence of drought on wildfires within SD may be limited to the summer months. Full article