Treesearch

Social complexity and sustainability emerge from successful problem solving, rather than directly from environmental conditions. Social complexity develops from problem solving at all scales from local to national and international. Complexity in problem solving is an economic function, and can both support and hinder sustainability. Sustainability outcomes may take decades or centuries to develop. Historical studies reveal three outcomes to longterm change in problem-solving institutions: collapse, resiliency through simplification, or continuity based on growing complexity and increasing...

The species–time relationship (STR) describes how the species richness of a community increases with the time span over which the community is observed. This pattern has numerous implications for both theory and conservation in much the same way as the species–area relationship (SAR). However, the STR has received much less attention and to date only a handful of papers have been published on the pattern. Here we gather together 984 community time-series, representing 15 study areas and nine taxonomic groups, and evaluate their STRs in order to assess the generality of the STR, its...

We counted birds monthly from October through April of 1999-2000 and 2000-2001 on regularly grazed and rested (since 1973) semiarid grassland of central New Mexico. Horned larks (Eremophila alpestris) and chestnut-collared longspurs (Calcarius ornatus) accounted for 66% and 10% of all birds detected, respectively. We examined variation in counts of these species relative to grazing history, site, and vegetation characteristics. We used an information-theoretic approach to evaluate a set of 11 candidate models to determine which best described the variation in abundance of horned larks and...

Tracking seasonal movements of songbirds is a key step in understanding the annual cycle of migrants. To be er understand autumn migration of wood warblers, I analyzed stable-hydrogen isotope ratios of feathers collected from three species captured during stopover at the Bosque del Apache National Wildlife Refuge, New Mexico. To assess the form and strength of the relationship between timing of migration and breeding origins, I regressed stable-hydrogen isotope ratios of feathers against date of capture. These analyses indicated that Orange-crowned Warblers (Vermivora celata) and Common...

Spatial and temporal landscape patterns have long been recognized to influence biological processes, but these processes often operate at scales that are difficult to study by conventional means. Inferences from genetic markers can overcome some of these limitations. We used a landscape genetics approach to test hypotheses concerning landscape processes influencing the demography of Lahontan cutthroat trout in a complex stream network in the Great Basin desert of the western US. Predictions were tested with population- and individual-based analyses of microsatellite DNA variation, reflectin...

We studied 282 nesting attempts on 107 territories of Northern Goshawks (Accipiter gentilis) on the Kaibab Plateau in northern Arizona from 1991–1996. Mark-recapture methods were used to estimate recruitment, turnover of adults on territories, fi delity to territories by adults, and apparent annual survival of breeding adults. Territories were regularly spaced at a mean nearest-neighbor distance of 3.9 km. Annual proportion of pairs breeding and recapture rates were high in 1991–1993, sharply declined in 1994, and partially recovered in 1995–1996. Average annual turnover of breeding...

We proposed the hydraulic limitation hypothesis (HLH) as a mechanism to explain universal patterns in tree height, and tree and stand biomass growth: height growth slows down as trees grow taller, maximum height is lower for trees of the same species on resource-poor sites and annual wood production declines after canopy closure for even-aged forests. Our review of 51 studies that measured one or more of the components necessary for testing the hypothesis showed that taller trees differ physiologically from shorter, younger trees. Stomatal conductance to water vapour (gs), photosynthesis...

Two blends of manufactured wood strands with different lengths were tested for effectiveness in controlling erosion. Wood strand blends were tested on two soils, two slopes, and at three coverage amounts. Laboratory rainfall simulations were conducted to evaluate runoff and sediment loss. Wood strands were effective in delaying runoff, reducing runoff volume, and reducing sediment loss. There was no statistically significant difference between the two wood strand blends with respect to runoff or sediment loss. In comparison to bare soil with no cover, sediment loss was reduced by at least...

We examined the influence of topography and stand structure on fire effects within the perimeter of the ~34 000 ha Jasper fire of 2000 in ponderosa pine (Pinus ponderosa Laws.) forests of the South Dakota Black Hills, USA. We used a remotely sensed and field-verified map of post-fire burn severity (accuracy 69%, kappa statistic 0.54), the Digital Elevation Model, and vegetation databases maintained by the Black Hills National Forest to empirically test relationships at 500 randomly located points in each of three severity classes. Burn severity was defined as the relative degree of...

The release of carbon as CO2 from belowground processes accounts for about 70% of total ecosystem respiration. Insights about factors controlling soil CO2 efflux are constrained by the challenge of apportioning sources of CO2 between autotrophic tree roots (and mycorrhizal fungi) and heterotrophic microorganisms. In some temperate conifer forests, the reduction in soil CO2 efflux after girdling (phloem removal) has been used to separate these sources. Girdling stops the flow of carbohydrates to the belowground portion of the ecosystem, which should slow respiration by roots and mycorrhizae...