Treesearch

We evaluated net photosynthesis, respiration, leaf conductance, xylem pressure potential (XPP) and cold hardiness in red spruce (Picea rubens Sarg.) seedlings exposed to either a continuous thaw (CT) or a daytime thaw with freezing nights (FN) for 8 days during mid-winter. Physiological differences between CT and FN seedlings were evident for all measured parameters. However, the temporal expression of treatment differences varied among parameters. When compared to FN seedlings, CT seedlings had higher rates of respiration following 24 h of treatment, and a higher net photosynthetic rate,...

The atmospheric deposition of strong acid anions such as sulfate and nitrate shifts the ion exchange equilibrium in the rooting zone of sensitive forests. Red spruce and other northern coniferous forests are especially sensitive to deposition due to the shallow rooting of trees in a mor-type forest floor. Initially, the deposition of strong acid ions mobilizes essential cations such as calcium (Ca) from ion-exchange sites on soil organic matter. Hypothetically, this mobilization would result in a brief period of increased availability for root uptake. Evidence for this temporary period of...

Dendrochemistry, the interpretation of elemental analysis of dated tree rings, can provide a temporal record of environmental change. Using the dendrochemical record requires an understanding of tree biology. In this review, we pose four questions concerning assumptions that underlie recent dendrochemical research: 1) Does the chemical composition of the wood directly reflect that of the soil? 2) Can the analysis of individual rings pinpoint the specific year of environmental change? 3) Are differences in element concentration in the wood directly related to chemical differences in the...

Eastern white pine provenances from the extreme limits of the natural range of this species are changing from above- and below-average stability to average stability for height growth with increasing age. The regression method is useful for evaluating the stability of provenance to planting sites. The same general conclusions are reached for the performance at different planting sites from the regression method as from the relative difference method.

We tested 3 models of Kirtland's warbler (Dendroica kirtlandii) habitat suitability during a period when we believe there was a surplus of good quality breeding habitat. A jack pine canopy-cover model was superior to 2 jack pine stem-density models in predicting Kirtland's warbler habitat use and non-use. Estimated density of birds in high- and medium- class habitat was higher for the canopy-cover model (4.4 birds/100 ha in high class, 2.9 birds/100 ha in medium class) than for either stem-density model (2.2-2.5 birds/100 ha in high class, 1.2-1.7 birds/100 ha in medium class). Lower bird...

A geographic information system (GIS) approach was used to develop an Integrated Moisture Index (IMI), which was used to predict species composition for Ohio forests. Several landscape features (a slope-aspect shading index, cumulative flow of water downslope, curvature of the landscape, and the water-holding capacity of the soil) were derived from elevation and soils data to create the IMI. From IMI values for forest land harvested in the past 30 years, we estimated the percentage composition of two major forest types in the region as well as the prominence of many understory species and...

Physical and functional properties of foliage were measured at a variety of microsites in a broad-leaved Nothofagus fusca (Hook. f.) Orst. canopy. The light climate of the foliage at these sites was monitored for 39 days in the late sprlng and early summer with in situ sensors. Foliage nitrogen content (N), mean leaf angle, and gas exchange characteristics were all correlated with the amount of light reaching the microsites during foliage development.

Three major needs exist to better relate tree biology research to practical agroforesty (Larsen 1984). The first need is to identify the specific, desired product to be yielded from the forest. Valid and appropriate management techniques to yield one product may not be appropriate to yield a different product, even from the same species of trees. The second need is to synthesize the relevant scientific and technical knowledge. Frequently, the relevant knowledge to effectively yield a product needs to be integrated across a wide range of resources. The third need is to develop a comprehensiv...

Increasing recognition that anthropogenic CO2 and other greenhouse gas emissions may effect climate change has prompted research studies on global carbon (C) budgets and international agreements for action. At the United Nations Conference on Environment and Development in 1992, world leaders and citizens gathered and initiated the Framework Convention for Climate Change (FCCC), an agreement to address global climate change concerns.