Seed rain across fire-created edges in a Neotropical rainforest

Human-induced wildfires are increasing in frequency in tropical forests, and their deleterious consequences for biodiversity include decreases in seed rain, which may be affected directly by fire or indirectly by the creation of edges between forest and non-forest environments. Understanding seed rain is key to assess the potential for natural regeneration in plant communities. We assessed the impact of fire and fire-created edges on seed rain species richness, abundance, size, weight, and dispersal syndromes in Atlantic Forest remnants in Bahia, Brazil. We assessed seed rain at monthly intervals for an entire year along seven 300 m-long transects placed perpendicular to the edge. We installed seed traps at the edge and at 20, 40, 60, 80, 100, and 150 m into the burnt area and into the forest from forest edge. We recorded a total of 9,050 seeds belonging to 250 morphospecies. We did not observe edge influence; however, we detected a lower abundance and proportion of animal-dispersed seeds in the burnt than in the unburnt areas. The seed abundance in the burnt areas was lower and seeds were smaller and lighter than those in the unburnt area. Seed rain in the burnt area was not greater near to the forest than far from it. The abundance and richness of seed rain was positively correlated with tree density. Our findings highlight the lack of seed rain in burnt areas and differences in community composition between the burnt and unburnt areas. Collectively, these results indicate negative consequences on natural regeneration, which can lead to permanent secondarization and challenges for early regeneration of burnt areas, which will initially have impoverished forests due to low seed richness.

Phylogenetic Relationships of Tovomita (Clusiaceae): Carpel Number and Geographic Distribution Speak Louder than Venation Pattern

Abstract—Tovomita is a Neotropical clade of Clusiaceae that includes 52 species widely distributed throughout the Amazon, Atlantic, Antilles, and Chocoan/southern Mesoamerican rainforests. Species-level relationships within Tovomita remain largely unexplored, thus hindering our understanding of their biogeography and the evolution of key morphological characters in the genus. Here, we inferred a plastid genome phylogeny containing 18 Tovomita species using maximum likelihood and Bayesian inference approaches. Our results indicate that current infrageneric classification of Tovomita, which relies largely on leaf venation, does not reflect phylogenetic relationships. Instead, we identify carpel number as a more reliable morphological trait for infrageneric classification: clades within Tovomita tend to include species that possess either four or five (or more) carpels. Moreover, groups of species within Tovomita tend to exhibit a high degree of geographic endemicity corresponding to their clade affiliation: species within these clades are restricted to either Amazon or Atlantic forests. The well supported clade of Atlantic forest inhabitants we identify is sister to a clade of mostly Amazonian species that also includes Amazon and Atlantic forest disjunct species, which are more closely related to Amazonian than to other Atlantic forest species. These findings represent a first important step in elucidating morphological evolution and biogeography in this widespread genus of neotropical rainforest trees and shrubs.

Comparative mycorrhizal fungal production and respiration of a neotropical rainforest versus a California mixed forest

<p>Mycorrhizae are a symbiosis between fungi and plants. We have learned about the complexity of mechanisms of interaction and interactions between the mycorrhizae and the local environment from over a century of laboratory observations experiments. Point observations and laboratory studies identify processes, but cannot delineate activity. Our goal is to use an in situ system to study mycorrhizal roots and fungi during hot moments, daily shifts, and seasonal change.</p><p>We integrated continuous in situ observation-sensor measurements using our Soil Ecosystem Observatories. As turnover rate estimates are related to sample frequency, individual scans using manual minirhizotrons (Bartz and Rhizosystems) and Rhizosystems Automated Minirhizotrons (32,000-3.01mm x 2.26mm 307,200 pixel images). Automated scans were collected up to 4x daily. Manual scans across multiple tubes in campaigns provided spatial variation. Images were organized into mosaics using RootView software, and roots and hyphae identified and length, width and biovolume determined using RootDetector <http://www.rhizosystems.com/>. Individual roots and hyphae were tracked using RootFly <https://cecas.clemson.edu/~stb/rootfly/>. Lifespans were determined using Mark-Recapture modeling and turnover calculated. With each minirhizotron tube, sensors were placed at 3 or 4 depths for temperature, moisture, CO<sub>2</sub> and O<sub>2</sub> at 5minute intervals.</p><p>Mycorrhizal fungi (MF) explore soil for nutrients and requiring C. Most C to the hyphae is respired (with a <sup>14</sup>C signal of autotrophic respiration), with the remaining divided into decomposing (heterotrophic respiration) and sequestered C pools.</p><p>Our first site is a mature neotropical rainforest, the La Selva Biological Station, Costa Rica. Trees predominantly form arbuscular mycorrhizae (AM). AMF fungi comprise 50% of total fungal mass (PLFA). Aboveground NPP-C was 750g/m<sup>2</sup>. Root standing crop C was 120g/m<sup>2</sup>, average lifespan 60days, =6 generations/y, = root NPP of 720g/m<sup>2</sup>/y. The AMF hyphal standing crop C was 12.5g/m<sup>2</sup>, average lifespan of 25 days, =14.7 generations/y, = AMF NPP of 183g/m<sup>2</sup>/y. With an NPP of 1,650g/m<sup>2</sup>/y, then AMF comprises 11% of NPP.</p><p>Soil respiration provides CO<sub>2</sub>, converting in water to HCO<sub>3</sub><sup>-</sup>, altering soil pH (Henry's Law). AMF respiration thereby increases P availability. If 10% of the AM fungal hyphae are live, then the hyphal respiration is 438g/m<sup>2</sup>/y of C, =38% of total soil respiration and 16% of site respiration.</p><p>Our second site is a mature California mixed forest, USA. Ectomycorrhizal (EM) trees predominate. Annual NPP-C was 200g/m<sup>2</sup>, and root NPP was 200g/m<sup>2</sup>. EMF NPP was 162.6g/m<sup>2</sup>, or 27% of the NPP. N, water, and temperature limit NPP. The seasonal signal was very high in this ecosystem. Peak standing crop of extramatrical EM hyphae was 19gC/m<sup>2</sup> in April. Total soil respiration in April was 0.26g/h, and extramatrical hyphae 0.029g/h, or 11% of the total soil respiration. Since P is less limiting, but N and water are, hyphae likely play a greater role in enzymatic activity and exploratory surface area.</p><p>In summary, different mycorrhizal fungi play different roles depending on ecosystem limiting factors. With global change, our challenge is to determine how an ecosystem will change and the extent and rapidity of mycorrhizal fungal change.</p>