Negative allometry of leaf xylem conduit diameter and double-wall thickness: implications for implosion safety.

Xylem conduits have lignified walls to resist crushing pressures. The thicker the double-wall (T) relative to its diameter (D), the greater the implosion safety. Having safer conduits may incur higher costs and reduced flow, while having less resistant xylem may lead to catastrophic collapse under drought. Although recent studies have shown that conduit implosion commonly occurs in leaves, little is known about how leaf xylem scales T vs D to trade off safety, flow efficiency, mechanical support, and cost. We measured T and D in > 7000 conduits of 122 species to investigate how T vs D scaling varies across clades, habitats, growth forms, leaf, and vein sizes. As conduits become wider, their double-cell walls become proportionally thinner, resulting in a negative allometry between T and D. That is, narrower conduits, which are usually subjected to more negative pressures, are proportionally safer than wider ones. Higher implosion safety (i.e. higher T/D ratios) was found in asterids, arid habitats, shrubs, small leaves, and minor veins. Despite the strong allometry, implosion safety does not clearly trade off with other measured leaf functions, suggesting that implosion safety at whole-leaf level cannot be easily predicted solely by individual conduits' anatomy.

Plant traits and associated data from a warming experiment, a seabird colony, and along elevation in Svalbard.

The Arctic is warming at a rate four times the global average, while also being exposed to other global environmental changes, resulting in widespread vegetation and ecosystem change. Integrating functional trait-based approaches with multi-level vegetation, ecosystem, and landscape data enables a holistic understanding of the drivers and consequences of these changes. In two High Arctic study systems near Longyearbyen, Svalbard, a 20-year ITEX warming experiment and elevational gradients with and without nutrient input from nesting seabirds, we collected data on vegetation composition and structure, plant functional traits, ecosystem fluxes, multispectral remote sensing, and microclimate. The dataset contains 1,962 plant records and 16,160 trait measurements from 34 vascular plant taxa, for 9 of which these are the first published trait data. By integrating these comprehensive data, we bridge knowledge gaps and expand trait data coverage, including on intraspecific trait variation. These data can offer insights into ecosystem functioning and provide baselines to assess climate and environmental change impacts. Such knowledge is crucial for effective conservation and management in these vulnerable regions.

Floristic characterization of an Atlantic Rainforest remnant in Southern Sergipe: Crasto forest / Caracterização florística de um remanescente de Mata Atlântica no sul de Sergipe: Mata do Crasto

The state of Sergipe has suffered extreme reduction of its Atlantic Forest area in the last decades. The objective of this study is to present an inventory of the Mata do Crasto flora, the largest Atlantic Forest Remnant in Sergipe (approximately 1,000 ha), located in the Municipality of Santa Luzia do Itanhy. An intensive survey was undertaken with monthly plant collections in the study area, for four years (1995 to 1999). Additionally, collections deposited in herbaria were consulted to complete the species list. A total of 324 species were found, belonging to 84 families and 193 genera. This study adds an additional 29 genera and 96 species to the Sergipe flora as new occurrences. The four most speciose families were the Fabaceae (33 species), Rubiaceae (24 species), Myrtaceae (23 species) and Melastomataceae (15 species), that accounted for ca. 30% of the total species. The taxonomic distinction of the area is very similar to three other lowland forests in Northeastern Brazil, although its species composition is quite distinct.

O estado de Sergipe sofreu extrema redução da área de Mata Atlântica nas últimas décadas. Este trabalho tem como objetivo inventariar a composição florística da Mata do Crasto, maior remanescente de Mata Atlântica de Sergipe (aproximadamente 1.000 ha), situada no Município de Santa Luzia do Itanhy. Um inventário intensivo foi realizado com coletas florísticas na área de estudo por quatro anos (1995 a 1999). Adicionalmente, exsicatas depositadas em herbários foram consultadas para complementar a lista de espécies. Um total de 324 espécies foram identificadas, pertencentes a 84 famílias e 193 gêneros. Este estudo adicionou 96 espécies è flora de Sergipe como novas ocorrências. As famílias com maior número de espécies são Fabaceae (33 espécies), Rubiaceae (24 espécies), Myrtaceae (23 espécies) e Melastomataceae (15 espécies), que juntas somam cerca de 30% do total de espécies. A distinção taxonômica do remanescente é surpreendentemente similar ao de outras florestas de terras baixas no Nordeste do Brasil embora suas espécies sejam bastante distintas.