Distribution of epiphytic macrolichens in relation to remnant trees in a multiple-age Douglas-fir forest

Alternatives to clear-cutting are being implemented to increase biodiversity of managed forests in the Pacific Northwest. Lichens are an integral component of old growth, but lichen biomass develops slowly in forests. We evaluated the long-term potential of live tree retention for lichen conservation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. We sampled lichen litterfall in a 2-ha stand that contained 200- to 600-year-old remnant trees scattered in a forest composed mostly of 100-year-old trees that established following fire. We used association, principal components, and regression analyses to relate lichen litterfall biomass to the proximity of remnant trees. Two epiphytic lichens were strongly associated with remnant trees: the foliose cyanolichen Lobaria oregana (Tuck.) Müll. Arg. and the fruticose green algal lichen Sphaerophorus globosus (Hudson) Vainio. Biomass of both species was highest near remnant trees, and biomass was slightly higher within groves of remnant trees than it was at the edges of these groves or near isolated trees. Lichens appear to have persisted on remnant trees through the last fire and are slowly recolonizing younger trees from this source of propagules. Retention of live trees, maintenance of hardwoods, and longer rotation periods have great potential to maintain old-growth-associated lichens in at least some managed forests

Appendix E. Crown shapes of 70 Pseudotsuga trees, grouped by stand.

Crown shapes of 70 Pseudotsuga trees, grouped by stand

Appendix B. Measurements and calculations used to derive a Cartesian coordinate system connecting all structures in mapped tree crowns and to error-check the resulting models in Microsoft Excel.

Measurements and calculations used to derive a Cartesian coordinate system connecting all structures in mapped tree crowns and to error-check the resulting models in Microsoft Excel

Data from: Pushing the limits to tree height: could foliar water storage compensate for hydraulic constraints in Sequoia sempervirens

1. The constraint on vertical water transport is considered an important factor limiting height growth and maximum attainable height of trees. Here we show evidence of foliar water storage as a mechanism that could partially compensate for this constraint in Sequoia sempervirens, the tallest species. 2. We measured hydraulic and morpho-anatomical characteristics of foliated shoots of tall S. sempervirens trees near the wet, northern and dry, southern limits of its geographic distribution in California, USA. 3. The ability to store water (hydraulic capacitance) and saturated water content (leaf succulence) of foliage both increased with height and light availability, maintaining tolerance of leaves to water stress (bulk leaf water potential at turgor loss) constant relative to height. 4. Transverse-sectional area of water-storing, transfusion tissue in leaves increased with height, while the area of xylem tissue decreased, indicating increasing allocation to water storage and decreasing reliance on water transport from roots. 5. Treetop leaves of S. sempervirens absorb moisture via leaf surfaces and have potential to store more than five times the daily transpirational demand. Thus, foliar water storage may be an important adaptation that helps maintain physiological function of treetop leaves and hydraulic status of the crown, allowing this species to partially compensate for hydraulic constraints and sustain turgor for both photosynthesis and height growth

The limits to tree height.

Trees grow tall where resources are abundant, stresses are minor, and competition for light places a premium on height growth 1,2 . The height to which trees can grow and the biophysical determinants of maximum height are poorly understood. Some models predict heights of up to 120 m in the absence of mechanical damage According to the cohesion-tension theory, water transport in plants occurs along a gradient of negative pressure (tension) in the dead, tube-like cells of the xylem, with transpiration, water adhesion to cell walls, and surface tension providing the forces necessary to lift water against gravity 7 . Height growth may slow if the xylem tension and therefore leaf water potential (W) predicted for great heights, &22 MPa (ref. 7), reduces sufficiently the positive pressure (turgor) necessary for expansion of living cells or increases the risk of xylem cavitation-cavitation is the formation of embolisms that reduce hydraulic conductivity and can cause branch dieback and plant death Reduced water potential due to soil drought causes a decline in the turgor of living plant cells that is necessary for cell growth and leaf expansion 11 . To determine if this also occurs as water potential declines with height, we estimated turgor at dry-season water potentials from pressure-volume measurements. Turgor (in MPa) declined linearly with height, h, as turgor ¼ 2ð0:0074^0:0004Þh þð1:30^0:07Þ, n ¼ 4 trees, ranging from 0.93 MPa at 50 m to 0.48 MPa at 110 m. At night when xylem pressure increased, the turgor gradient was less steep, turgor ¼ 2ð0:0044^0:0023Þh þð1:39^0:19Þ, and turgor was 0.3-0.4 MPa higher than at midday. Given the role of turgor in leaf expansion, its reduction with height may underlie the distinct vertical gradient in leaf structure in redwood

Appendix A. Equations used to estimate structural components of woody plants in the 1-ha plot.

Equations used to estimate structural components of woody plants in the 1-ha plot

Appendix C. Untransformed and transformed scatterplot matrices summarizing bivariate relationships among tree-level structural variables used in principal components analysis.

Untransformed and transformed scatterplot matrices summarizing bivariate relationships among tree-level structural variables used in principal components analysis

Appendix D. Pearson correlations (r) between tree-level variables and two independent dimensions of tree structure revealed by principal components analysis.

Pearson correlations (r) between tree-level variables and two independent dimensions of tree structure revealed by principal components analysis