Variation in Bark Allocation and Rugosity Across Seven Co-occurring Southeastern US Tree Species

Bark is a complex multifunctional structure of woody plants that varies widely among species. Thick bark is a primary trait that can protect trees from heat generated in surface fires. Outer bark on species that allocate resources to thick bark also tends to be rugose, with bark being thickest at the ridges and thinnest in the furrows. Tree diameter or wood diameter is often used as a predictor for bark thickness but little attention has been made on other factors that might affect bark development and allocation. Here we test multiple mixed effect models to evaluate additional factors (height growth rate, measure height) that correlate with bark allocation and present a method to quantify bark rugosity. We focused on seven co-occurring native tree species in the Tallahatchie Experimental Forest in north Mississippi. Approximately ten saplings of Carya tomentosa, Nyssa sylvatica, Prunus serotina, Pinus echinata, Pinus taeda, Quercus marilandica, and Quercus falcata were destructively sampled for stem analyses. Outer bark thickness (OBT) ranged from 0.01 to 0.77 cm with the thickest maximum outer bark occurring on P. taeda (0.77 cm) and the thinnest maximum outer bark occurring on P. serotina (0.17 cm). Our outer bark allocation models suggest that some individuals with rapid height growth allocate less to outer bark in C. tomentosa, N. sylvatica, P. taeda, and P. serotina, but not for P. echinata or either oak species. All species except for C. tomentosa and N. sylvatica showed evidence for outer bark taper, allocating more outer bark at the base of the bole. Inner bark also was tapered in Carya and the oaks. Bark rugosity varied among species from 0.00 (very smooth) to 0.17 (very rugose) with P. Serotina and C. tomentosa having the smoothest bark. OBT was the best fixed effect for all species. Aside from providing data for several important yet understudied species, our rugosity measures offer promise for incorporating into fluid dynamics fire behavior models.

Establishment of Quercus marilandica Muenchh. and Juniperus virginiana L. in the Tallgrass Prairie of Oklahoma, USA Increases Litter Inputs and Soil Organic Carbon

The establishment of trees in grasslands alters ecosystem processes and services. Litter inputs shift from herbaceous to tree-derived, which affects the litter quantity and quality and may in turn alter soil carbon dynamics and ecosystem-level carbon sequestration. This study determined changes in the quantity of organic matter inputs following encroachment by two native tree species (Quercus marilandica Muenchh. and Juniperus virginiana L.) into a tallgrass prairie in northcentral Oklahoma, and related it to spatial heterogeneity in soil carbon by measuring variables near the stem, under the tree canopy, at the outer edge of the tree canopy, and beyond the tree canopy. Presence of trees increased aboveground litter inputs (dominated by foliage for J. virginiana and acorns for Q. marilandica) and increased the duff and litter layer. Regardless of leaf litter source, decomposition of foliage was slower under the tree canopy than beyond the tree canopy (7% slower) and this change was associated with cooler and potentially drier conditions. However, the foliage of trees decomposed more quickly than grass foliage when measured both beneath and beyond the tree canopy (25% faster). Coarse root biomass was greater under tree canopies than beyond, which increased total root biomass in the deeper soil layer (10–30 cm). The net effect was an approximately 15% increase in soil carbon stock under the trees as compared to areas beyond the tree canopy. Therefore, in addition to greater carbon storage in the aboveground biomass, tree encroachment increases carbon sequestration by increasing soil carbon.

Arthopyrenia salicis. [Descriptions of Fungi and Bacteria].

A description is provided for Arthopyrenia salicis. Some information on its dispersal and transmission and conservation status is given, along with details of its geographical distribution (Algeria, USA (Alabama, Louisiana, Minnesota, Nebraska and South Dakota), Armenia, Papua New Guinea, Turkey, Austria, Belgium, Bulgaria, Czech Republic, Finland, France, Germany, Greece, Hungary, Irish Republic, Italy, Luxembourg, Netherlands, Norway, Poland, Russia (Komi Republic, Krasnodar Krai, Nenets Autonomous Okrug, Republic of Adygea, Republic of Dagestan and Tver Oblast), Slovenia, Spain, Sweden, Switzerland, Ukraine and UK) and hosts (Salix elegans, Arthonia punctiformis, A. radiata, Lobaria sp., Naetrocymbe nitescens, N. punctiformis, Acer sp., Aesculus sp., Alnus glutinosa, Betula sp., Carpinus sp., Castanea sativa, Corylus avellana, Crataegus sp., Fagus sp., Fraxinus excelsior, Fraxinus sp., Ilex sp., Pistacia lentiscus, Populus tremula, Populus sp., Quercus marilandica, Q. robur, Quercus sp., Salix elaeagnos, Salix sp., Sorbus sp. and Trentepohlia sp.).

Ecotypic differentiation of mid-Atlantic Quercus species in response to ultramafic soils

Spatial heterogeneity of soil conditions combined with intraspecific variation confer site-specific edaphic tolerance, resulting in local adaptation and speciation. To understand the geoecological processes controlling community assembly of woodland tree species on serpentine and mafic soils, we investigated resource gradients and provenance (geographic area of propagule collection) as variables affecting typical representative upland oak (Quercus) species distribution. Accordingly, we conducted a year-long reciprocal transplant experiment in the greenhouse with serpentine and mafic soils, using seedlings of five oak species (Quercus marilandica, Q. stellata, Q. montana, Q. michauxii and Q. alba). All seedlings, regardless of provenance or soil depth, displayed more robust growth in the mafic soils. Soil depth was an important determinant, with all species exhibiting increased growth in the deeper-soil treatments. Fitness surrogates such as stem height, relative growth rate, and leaves per plant were greater when seedlings were grown in their home soil than when they were grown in the non-resident soil, suggesting an ecotypic effect. Mean stomatal conductance and stem growth were positively correlated with soil depth in all treatments. Taken together, the study showed provenance-specific growth responses of oak seedlings to soil type and depth, providing a better understanding of the mechanisms controlling species assembly in woodland communities.

Prescribed Burning Frequency Affects Post Oak and Blackjack Oak Regeneration

We studied post oak (Quercus stellata Wangenh.) and blackjack oak (Quercus marilandica Münchh.) regeneration in xeric upland oak forests burned from 0 to 5.3 times per decade for 19 years. Post oak and blackjack oak represented 76 and 11% of the site basal area. All reproduction was by sprouting; there were no true seedlings. Compared with post oak, blackjack oak had a substantially higher density of clumps and sprouts relative to its basal area, suggesting that basal area was not a good indicator of sprout production capacity across species. The number of sprouts per clump declined with time since last fire for both species, indicating that fire stimulated sprouting. Three growing seasons after fire, sprouts per clump was highest with the lowest fire frequency and declined with increasing fire. The decline was greatest for blackjack oak. This may have been due to reduced vigor of the root systems producing sprouts with increasing fire frequency. Results suggested that post oak and blackjack oak sprouting, growth rates, and response to fire are similar, but blackjack oak sprout mortality may be higher than that of post oak. This information is important for the maintenance of post oak-blackjack oak-dominated forests of the south-central United States.