Treesearch

Florida experiences sea breezes, lake breezes, and bay breezes almost every day during the year, and there are frequently complex interactions between many of these breezes. Given the often-rapid changes in temperature, humidity, and wind speed that accompany these breezes, most wildfires and prescribed fires in Florida are affected in some way by their interaction with these circulations. In this paper, we explore the interaction between sea breezes and wildland fires from both an observational and an idealized modeling perspective. The progression of the sea-breeze front and its interacti...

Tropical forests play a critical role in the Earth system; however, tropical landscapes have changed greatly in recent decades because of increasing demand for land to support agriculture and timber production, fuel wood, and other pressures of population and human economics. The observable results are a legacy of persistent deforestation, forest degradation, increased wildfires and loss of biodiversity, allied with losses of original forest lands and high CO2 emissions in the atmosphere. Besides these long-standing human pressures, tropical regions now have unprecedented vulnerability to...

Slow-growing conifers of the northern boreal forest may require several decades to reach reproductive maturity, making them vulnerable to increases in disturbance frequency. Here, we examine the relationship between stand age and seed productivity of black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) in Yukon Territory and Alaska. Black spruce trees were aged and surveyed for cone production and seed viability across 30 even-aged stands ranging from 12 to 197 years old. Logistic regression indicated that individual trees had a 50% probability of producing cones by age 30...

The aspen leaf miner, Phyllocnistis populiella Cham., has caused widespread and severe damage to aspen in the boreal forests of western North America for over a decade. We suppressed P. populiella on individual small aspen ramets using insecticide at two sites near Fairbanks, Alaska, annually for 7 years and compared plant performance with controls. Insecticide treatment successfully reduced leaf damage by P. populiella during most years and had little effect on herbivory by externally feeding invertebrates. By the end of the study, control ramets had suffered a reduction in height and...

The accumulation of discharge along a stream valley is frequently assumed to be the primary control on solute transport processes. Relationships of both increasing and decreasing transient storage, and decreased gross losses of stream water have been reported with increasing discharge; however, we have yet to validate these relationships with extensive field study. We conducted transient storage and mass recovery analyses of artificial tracer studies completed for 28 contiguous 100 m reaches along a stream valley, repeated under four base-flow conditions. We calculated net and gross gains...

Fire activity in the North American boreal region is projected to increase under a warming climate and trigger changes in vegetation composition. In black spruce forests of interior Alaska, fire severity impacts residual organic layer depth which is strongly linked to the relative dominance of deciduous versus coniferous trees in early succession. These alternate successional pathways may be reinforced by biogeochemical processes that affect the relative ability of deciduous versus coniferous trees to acquire limiting nutrients. To test this hypothesis, we examined changes in soil inorganic...

Horizontal gene transfer (HGT) of DNA from the plastid to the nuclear and mitochondrial genomes of higher plants is a common phenomenon; however, plastid genomes (plastomes) are highly conserved and have generally been regarded as impervious to HGT. We sequenced the 158 kb plastome and the 690 kb mitochondrial genome of common milkweed (Asclepias syriaca [Apocynaceae]) and found evidence of intracellular HGT for a 2.4-kb segment of mitochondrial DNA to the rps2–rpoC2 intergenic spacer of the plastome. The transferred region contains an rpl2 pseudogene and is flanked by plastid sequence in...

Floristic studies indicate the abundance of microalgae in northern boreal peatlands, but we know relatively little about their ecology or how they will respond to changes in environmental conditions expected in this region as climate changes. We examined changes in algal community structure at sites exposed to a long-term water-table manipulation, including drought (lowered water-table treatment), flooding (raised water-table treatment), and control (no manipulation) treatments in an Alaskan fen. Inprevious years, continuous algal colonization typically would have occurred only in the...

In long-lived N-fixing plants, environmental conditions affecting plant growth and N demand vary at multiple temporal and spatial scales, and symbiont assemblages on a given host and patterns of allocation to nodule activities have been shown to vary according to environmental factors, suggesting that hosts may alter partner choice and manipulate symbiont assemblages based on shifting plant needs. This study assessed economic trade-offs among N-fixing symbionts of thin-leaf alder (Alnus tenuifolia) by examining whether alder– Frankia associations change in response to the up-regulation (P...

Voluntary codes of conduct and best management practices are increasingly popular methods for addressing impacts of recreation and tourism in protected areas. In southeast Alaska, for example, a collaborative stakeholder process has been used for creating, implementing, and managing the voluntary Wilderness Best Management Practices (WBMP) for the Tracy Arm- Fords Terror Wilderness to address impacts associated with shore and marine based use in this area, especially from cruise ships. This article examines: (a) stakeholder motivations for collaborating in this WBMP process; (b) the extent...