An Analysis of Atlantic White Cedar (Chamaecyparis thyoides (L.) B.S.P.) Tree Rings as Indicators of Ghost Forest Development in a Globally Threatened Ecosystem

Atlantic White Cedar (AWC) swamps are a globally threatened type of wetland ecosystem and are a new form of ghost forest in the mid-Atlantic region of the US. Hydrogeomorphic regimes foster peat formation, resulting in unique biodiversity and carbon sequestration services. Our sites include regimes that are exposed to sea-level rise and storm-driven seawater intrusion, yet other sites are protected by higher elevations. In this study, we evaluated climatic variables to discern differences in tree ring formation as an indicator of growth among nine stands including micro-tidal, oligohaline sites as well as other protected areas which served as a control. Standard dendrochronological techniques were used, and series were divided into two sub-chronologies, 1895 to 1971 (early) and 1972 to 2018 (recent). AWC growth in response to precipitation parameters, e.g., Palmer Drought Severity Index (PDSI), were largely non-significant but were somewhat reversed among sub-chronologies. Early correlations were primarily negatively correlated with PDSI, while recent correlations were mostly positive, which suggests that even though inundation may reduce photosynthate availability for growth, precipitation has begun to increase growth by alleviating osmotic and toxic stresses associated with seawater. Analysis of climatic variables and tree growth at the reference site found that other anthropogenic stressors associated with ditching exert a greater influence. Hurricane impacts on tree growth exhibited no lasting negative effects; however, an AWC ghost forest report from New Jersey connected mortality to a hurricane. Hydrogeomorphic regimes may delay rather than eliminate risks associated with sea-level rise and storm-driven seawater.

Diversidad de especies leñosas en remanente de mesófilo alterado con producción agroforestal

En el año 2017 se evaluó la diversidad de especies leñosas en la comunidad de Xaltepuxtla, Puebla en un remanente de bosque mesófilo de montaña alterado, sistema ornamental y sistema silvopastoril con la finalidad de conocer la diversidad arbórea y proponer especies de alto valor ecológico para su restauración. Se emplearon índices ecológicos y un diseño de muestreo sistemático con distancias predeterminadas en arreglo a manera de cuadricula. Se muestrearon 22 sitios utilizando cuadrantes con punto central para vegetación arbórea con sitios de 100 m2 y cuadros empotrados para vegetación arbustiva y herbácea. Se obtuvo la riqueza, abundancia y diversidad de las especies leñosas con estimadores de Jacknife 1, índice de abundancia relativa (IAR) y índice de Shannon-Wiener. Se registraron 19 especies en 15 familias y 18 géneros. Las especies de mayor abundancia relativa por sitio fueron: Chamaecyparis lawsoniana (IAR= 0.96), Rhododendron simssi (IAR= 0.46) y Chamaecyparis. thyoides. (IAR= 0.25). Los sitios con mayor diversidad fueron: el 22 con un índice de 2.54 y el 20 y 21 con índices de 2.53 respectivamente. La mayor diversidad por condición fue en el RBMM con un índice de 2.92. Con la prueba de Kruskal Wallis no se obtuvieron diferencias significativas entre los estimadores ecológicos, por lo que las tres condiciones se encuentran sujetas al mismo nivel de alteración. Se logró conocer la riqueza, abundancia y diversidad de las especies leñosas en la zona de estudio.

The potential to strengthen temperature reconstructions in ecoregions with limited tree line using a multispecies approach

Tree-ring reconstructions of temperature often target trees at altitudinal or latitudinal tree line where annual growth is broadly expected to be limited by and respond to temperature variability. Based on this principal, regions with sparse tree line would seem to be restricted in their potential to reconstruct past temperatures. In the northeastern United States, there are only two published temperature reconstructions. Previous work in the region reconstructing moisture availability, however, has shown that using a greater diversity of species can improve reconstruction model skill. Here, we use a network of 228 tree-ring records composed of 29 species to test the hypothesis that an increase in species diversity among the pool of predictors improves reconstructions of past temperatures. Chamaecyparis thyoides alone explained 31% of the variability in observed cool-season minimum temperatures, but a multispecies model increased the explained variance to 44%. Liriodendron tulipifera, a species not previously used for temperature reconstructions, explained a similar amount of variance as Chamaecyparis thyoides (12.9% and 20.8%, respectively). Increasing the species diversity of tree proxies has the potential for improving reconstruction of paleotemperatures in regions lacking latitudinal or elevational tree lines provided that long-lived hardwood records can be located.

Measuring species diversity to determine land-use effects on reptile and amphibian assemblages

Populations of herpetofauna are declining globally primarily due to land-use practices (e.g., silviculture or conversion to agriculture) and declines require monitoring of all herpetofauna communities. Therefore, forest management plans for Bull Neck Swamp, a pocosin wetland in North Carolina, USA, initiated an inventory of the herpetofauna community. Our objectives were to: (1) derive diversity measures for four designated habitat preserves (i.e., Atlantic whitecedar [Chamaecyparis thyoides], Pond pine [Pinus serotina], Non-riverine Swamp, and Shoreline/Islands) and a Forest manageable area, (2) determine if there were benefits to habitat preserves for the herpetofauna community, and (3) provide recommendations for future monitoring. We employed 11 different sampling techniques across the four habitat preserves and Forest manageable area. Species richness estimates and similarity indices were derived using EstimateS 8.0. For post hoc comparisons, we derived species distributions with the Nestedness Temperature Calculator Program. Observed species richness ranged from 7 to 32 species (S = 13 to 44) and abundances ranged from 99 to 873 individuals. Similarity indices suggested species compositions were similar among habitats. Further, nestedness temperature (T = 12.6°C) indicated an even species distribution among assemblages. Comparable similarity indices among habitats, an even species distribution, and habitat continuity suggested management practices would have little impact on the herpetofauna community. Nevertheless, future management practices should be carefully considered and planned to mitigate effects to individual species. We recommend studies employ species richness, relative abundance, species composition, and distribution as conservation tools when inventorying or monitoring herpetofauna communities.