Historia de la vegetación del sitio Huapilacuy II durante el Holoceno Medio a partir del análisis polínico y de macrofósiles vegetales, Isla Grande de Chiloé, Chile

This study examines the new fossiliferous site Huapilacuy II of Mid-Holocene age (7,344±51-6,865±58 cal years BP.) located in the northwestern coast of the Isla Grande de Chiloé. This area was not affected by the successive Pleistocene glaciations, and therefore it presents a biogeographic relevance as a potential area of refugia and stability for the vegetation. The presence of plant macrofossils contained in a sedimentary sequence of ca. 300 cm thick, confers a special interest to the site, due to the scarce information available on this type of indicator in paleoenvironmental studies of southern Chile. Additionally, several pollen-based reconstructions from the southern Lake District of Chile (40-44˚ S), document the Holocene sequence of recolonization by the different temperate rainforests types that today occupy this region, although there are non-Holocene records for the Pacific coast of the region. The aim of this study is to reconstruct the local environmental conditions and paleoecology based on the stratigraphic context and the analysis of plant macrofossils at the site Huapilacuy II. In addition, based on the pollen analysis of the deposit, we provide new information to reconstruct the regional characteristics of the vegetation during the Middle-Holocene. In particular, the plant macrofossil record of marsh species contained in the sediments of the lower section of the studied sedimentary sequence, together with the pollen analysis of the same sequence, document a first phase of plant colonization at 7,344±51 cal yrs. BP, with predominance of Poaceae, ferns, and trees with regeneration capacity in open areas, such as Embothrium coccineum and Drimys winteri. The analysis of leaf macrofossils and palynomorphs recovered from several intercalated layers, from the middle section of the sedimentary sequence, show the local and regional development of dense and very humid forests dominated by Aextoxicon punctatum, associated with several species of Myrtaceae. The presence of soil moisture indicator species, such as Luma chequen, Myrceugenia sp. and Myrtaceae Blepharocalyx-type is consistent with the sedimentary environment and the local development of swamp or riverine forests. This hygrophile forest environment is also consistent with the assemblage of fossil mosses, dominated by species that grow today in dense closed-canopy forests, such as Weymouthia, Ptychomnium, Rigodium, Porothamnium and Eucamptodon. The regional correlation of the pollen spectra from Huapilacuy II and other records from the Lake District allows us to establish latitudinal and longitudinal differences of tree composition in the temperate-rainforests that expanded during the Early to Mid-Holocene. In particular, this study established for the northwestern coast of the Isla Grande de Chiloé the presence of the coastal association of the valdivian forest (As. Lapagerio-Aextoxiconetum), currently distributed along the Chilean coastline between 30˚- 43˚S. In contrast, the Valdivian associations recorded in other areas of the region exhibit the dominance of Eucryphia cordifolia, Caldcluvia paniculata, Weinmannia trichosperma and different species of Nothofagus. Despite the differences in tree composition, the fossil bryophyte species recorded in several of the sites compared are common with those reported for Huapilacuy II, thus showing the wide ecological range of Chilean bryophytes associated with closed-canopy temperate-rainforests.

Elemental and Molecular Composition of Humic Acids Isolated from Soils of Tallgrass Temperate Rainforests (Chernevaya taiga) by 1H-13C HECTCOR NMR Spectroscopy

The soils of Chernevaya taiga (tallgrass fir-aspen hemiboreal rainforest) have high fertility in comparison with oligotrophic analogs formed in boreal taiga. We have studied humic acids isolated from the soils of Chernevaya and oligotrophic taiga in the Novosibirsk, Tomsk, Kemerovo and the Altai regions of Russia and for the first time the structural and molecular composition of humic acids was determined using 13C CP/MAS and 1H-13C HETCOR NMR spectroscopy. According to data obtained in this study, up to 48% of aromatic compounds accumulate in the soils of Chernevaya taiga, which is higher than in the oligotrophic taiga and comparable with this rate of steppe Chernozems. In the course of active processes of transformation of organic matter, a significant number of aromatic fragments accumulates in the middle horizons of soil profiles. Using 13C CP/MAS spectroscopy, it was possible to identify the main structural fragments (aliphatic and aromatic) that formed in humic acids of the Chernevaya taiga. The HETCOR experiment made it possible to accurately determine the boundaries of chemical shifts of the main groups of structural fragments of humic acids. Our results demonstrate that the stabilization of organic compounds occurs in the soil of the Chernevaya taiga, which leads to the resistance of organic matter to biodegradation that is not typical for benchmark soils of boreal environments.

Canopy Gap Structure as an Indicator of Intact, Old-Growth Temperate Rainforests in the Valdivian Ecoregion

Forest degradation continues to increase globally, threatening biodiversity and the survival of species. In this context, identifying intact, old-growth forest stands is both urgent and vital to ensure their existence and multiple contributions to society. Despite the global ecological importance of the Valdivian temperate rainforests, they are threatened by forest degradation resulting from constant and intense human use in the region. Identification of remnant intact forests in this region is urgent to global forest protection efforts. In this paper, we analyzed whether forests-canopy alterations due to logging produce a distinctive canopy gap structure (e.g., a gap area and a fraction of canopy gaps in the forest) that can be used to remotely distinguish intact from altered forests. We tested this question by comparing the canopy gap structure of 12 old-growth temperate rainforests in south-central Chile (39–40° S), with different levels of canopy alterations due to logging. At each stand, we obtained aerial or satellite very high spatial-resolution images that were automatically segmented using the Mean-Shift segmentation algorithm. We validated the results obtained remotely with ground data on the canopy gap structure. We found that, in the variables, canopy gap fraction, gap area frequency distribution, and mean gap area could be measured remotely with a high level of accuracy. Intact forests have a distinct canopy gap structure in comparison to forests with canopy alterations due to logging. Our results provided a fast, low-cost, and reliable method to obtain canopy gap structure indicators for mapping and monitoring intact forests in the Valdivian ecoregion. The method provided valuable information for managers interested in maintaining and restoring old-growth forest structures in these southern-temperate rainforests.

Why is the rainforest lichen Methuselah’s Beard (Usnea longissima) so rare in British Columbia’s inland temperate rainforest?

Coastal (CTR) and inland temperate rainforests (ITR) in western North America share a rich oceanic lichen flora. The distinctive Methuselah’s beard lichen (Usnea longissima) is an exception to this pattern of shared distributions, with very few ITR locations. Does this absence reflect dispersal limitations or climatic intolerance? To answer this question, we transplanted U. longissima thalli from the CTR to three ITR locations, assessing growth rates against reciprocal CTR transplants. Canopy microclimate measurements provided concurrent data on growth conditions. Growth rate responses (length, mass and area) were evaluated after summer and full-year transplants. Notwithstanding extended drought conditions during the summer period, annual transplants at two of the three ITR locations supported growth rates comparable to those at the CTR source U. longissima population, with summer dewfall and autumn rains being major ITR hydration sources. Thalli transplanted to a third ITR site (summer measurements only) in a location transitional to the drier interior plateau lost both mass and length. Based on these findings we suggest that the absence of U. longissima from much of the ITR reflects the combined influence of dispersal limitations and requirements for stands with long site continuity and topographically induced summer wetting of thalli by dewfall.

Manganese Limitations and the Enhanced Soil Carbon Sequestration of Temperate Rainforests

Manganese (Mn) has been identified as a regulatory bottleneck in carbon (C) turnover because of its role as an enzymatic co-factor in the oxidative decomposition of C by Mn-peroxidase (MnP). We tested this limit on decay using forest soils from coastal British Columbia with contrasting Mn concentrations. Moderately weathered soils (Brunisols) had an average 3.6-fold increase in MnP activity within the upper soil profile in comparison to highly weathered Podzols. Ordination of the Agaricomycete fungal community, which are responsible for MnP production, confirmed significant differences in assemblages between soil types for saprotrophic fungi, particularly species within Agaricales, Trechisporales and Auriculariales. Ectomycorrhizal fungi of Pseudotsuga menziesii were equally aligned with soil type and select taxa more abundant on Brunisols may have supplemented MnP activity. A laboratory incubation with an Mn amendment produced significant interactions in MnP activity by soil type. Surprisingly, MnP activity of both Brunisol substrates declined substantially with an amendment (-56% and − 40% for forest floor and mineral soil, respectively), in contrast to Podzols (-30% and + 26%, respectively). This inhibitory response was linked to considerable uptake of the added Mn in Brunisols, and underscores how Mn2+ likely operates directly on fungi as a regulator of mnp transcription for MnP production. Our study highlights a new perspective concerning the abiotic drivers underpinning the expansive soil C stocks across perhumid temperate rainforests of the Pacific Northwest.

New palynological data from the East Tasman Plateau (ODP Site 1172) indicate rapid earliest Oligocene warming.

<p>Considered as one of the most significant climate reorganisations of the Cenozoic period, the Eocene-Oligocene (E/O) Transition (ca. 33.9-33.5 Ma) is characterised by global cooling coupled with glacial advance on Antarctica. Combined micropalaeontological (diatom and dinoflagellate) and sedimentological evidence hint of regional reorganisation of ocean currents around Antarctica, in association with the Eocene-Oligocene transition. The late Eocene to early Oligocene deepening of the Tasman Gateway resulted in the flow of warm surface waters from the Australo-Antarctic gulf into the southwestern Pacific Ocean.  However, the extent and effect of these changes in ocean circulation on regional terrestrial climate and vegetation across the E/O Transition is not readily known. Here, we present new well-dated, high resolution palynological (sporomorph) data from the East Tasman Plateau (ODP Site 1172) to reconstruct climate and vegetation dynamics from the late Eocene through to the early Oligocene. Results from our sporomorph data point to four vegetation communities occupying Tasmania under different precipitation and temperature regimes: (i) Paratropical rainforest along the coastlines and temperate rainforests at higher altitude of the hinterlands from 37.97-37.52 Ma; (ii) cool temperate forest expanding into areas previously occupied by the paratropical forests between 37.306-35.60 Ma; (iii) a complex mix of paratropical associations coexisting with frost-tolerant taxa, followed by a period of relative stability shown in the dominance of cold-temperate taxa from 35.50-33.36 Ma; (iv) a warm temperate forest present in the early Oligocene (33.25-33.06 Ma). Our sporomorph record showed a general cooling trend from the latest-middle Eocene to the late Eocene (37.97-35.60 Ma), fluctuations between warm and cold climates (35.50 – 34.19 Ma), a period of relative stable cooling across the E/O transition (33.94-33.5 Ma), and a rather unusual rapid warming right after the E/O transition (earliest Oligocene; 33.36 - 33.06 Ma). Our quantitative estimates of terrestrial temperature change and palaeoecological reconstructions show a close link with previously published dinoflagellate cyst data from this same study site, suggesting a possible vegetation and climate response to tectonic changes (most likely the tectonic opening and deepening of the Tasman Gateway ca. 35.5 Ma) and relative short-term regional reorganisation of ocean currents.</p><p><strong>Keywords: Antarctica, Eocene-Oligocene Transition, sporomorph, temperate rainforest, Tasman Gateway</strong></p>

Ecophysiological Performance of Proteaceae Species From Southern South America Growing on Substrates Derived From Young Volcanic Materials

Southern South American Proteaceae thrive on young volcanic substrates, which are extremely low in plant-available phosphorus (P). Most Proteaceae exhibit a nutrient-acquisition strategy based on the release of carboxylates from specialized roots, named cluster roots (CR). Some Proteaceae colonize young volcanic substrates which has been related to CR functioning. However, physiological functioning of other Proteaceae on recent volcanic substrates is unknown. We conducted an experiment with seedlings of five Proteaceae (Gevuina avellana, Embothrium coccineum, Lomatia hirsuta, L. ferruginea, and L. dentata) grown in three volcanic materials. Two of them are substrates with very low nutrient concentrations, collected from the most recent deposits of the volcanoes Choshuenco and Calbuco (Chile). The other volcanic material corresponds to a developed soil that exhibits a high nutrient availability. We assessed morphological responses (i.e., height, biomass, and CR formation), seed and leaf macronutrient and micronutrient concentrations and carboxylates exuded by roots. The results show that G. avellana was less affected by nutrient availability of the volcanic substrate, probably because it had a greater nutrient content in its seeds and produced large CR exuding carboxylates that supported their initial growth. Embothrium coccineum exhibited greater total plant height and leaf P concentration than Lomatia species. In general, in all species leaf macronutrient concentrations were reduced on nutrient-poor volcanic substrates, while leaf micronutrient concentrations were highly variable depending on species and volcanic material. We conclude that Proteaceae from temperate rainforests differ in their capacity to grow and acquire nutrients from young and nutrient-poor volcanic substrates. The greater seed nutrient content, low nutrient requirements (only for G. avellana) and ability to mobilize nutrients help explain why G. avellana and E. coccineum are better colonizers of recent volcanic substrates than Lomatia species.