Functional assembly of tropical montane tree islands in the Atlantic forest is shaped by stress-tolerance, bamboo-invasion and facilitation

Aims: Amidst the Campos the Altitude (Highland Grasslands) in the Brazilian Atlantic Forest, woody communities grow either clustered in tree islands or interspersed within the herbaceous matrix. The functional ecology, diversity and biotic processes shaping these communities are largely unstudied. We characterised the functional assembly and diversity of these tropical montane woody communities and investigated how those communities fit within the Grime’s CSR (C – competitor, S – stress-tolerant, R – ruderal) scheme, what trade-offs they exhibit and how traits and functional diversity vary in response to bamboo invasion. Methods: We sampled five leaf traits and wood density along transects covering the woody communities both inside tree islands and outside (i.e. woody plants in the grasslands community) to characterise the functional ecology of the community. We used Kruskal-Wallis test, t-test and variation partitioning to determine effects of inside vs outside the tree island and bamboo invasion on traits, woody species diversity and functional diversity. Results: We found a general SC/S strategy with drought-related functional trade-offs. Woody plants in tree islands had more acquisitive traits, whereas woody plants within the grasslands had more conservative traits. Trait variation was mostly taxonomically driven, and species composition varied between inside and outside tree islands. Leaf thickness, wood density and foliar water uptake were unrelated to CSR-strategies, suggesting independent trait dimensions and multiple drought-coping strategies within the predominant S-strategy. Bamboo-invaded islands showed lower Simpson diversity, lower functional dispersion, lower foliar water uptake and greater leaf thickness than non-invaded tree islands. Conclusions: The observed functional assembly in response to bamboo and facilitation have implications for future forest expansion and response of the communities to climate change. Further studies on eco-physiological and establishment traits and the mechanisms behind biotic interactions are needed to better understand the response of these communities to future environmental changes.

Diversity and Structure of Soil Fungal Communities across Experimental Everglades Tree Islands

Fungi play prominent roles in ecosystem services (e.g., nutrient cycling, decomposition) and thus have increasingly garnered attention in restoration ecology. However, it is unclear how most management decisions impact fungal communities, making it difficult to protect fungal diversity and utilize fungi to improve restoration success. To understand the effects of restoration decisions and environmental variation on fungal communities, we sequenced soil fungal microbiomes from 96 sites across eight experimental Everglades tree islands approximately 15 years after restoration occurred. We found that early restoration decisions can have enduring consequences for fungal communities. Factors experimentally manipulated in 2003–2007 (e.g., type of island core) had significant legacy effects on fungal community composition. Our results also emphasized the role of water regime in fungal diversity, composition, and function. As the relative water level decreased, so did fungal diversity, with an approximately 25% decline in the driest sites. Further, as the water level decreased, the abundance of the plant pathogen–saprotroph guild increased, suggesting that low water may increase plant-pathogen interactions. Our results indicate that early restoration decisions can have long-term consequences for fungal community composition and function and suggest that a drier future in the Everglades could reduce fungal diversity on imperiled tree islands.

Community Structure and Functional Role of Limber Pine (Pinus flexilis) in Treeline Communities in Rocky Mountain National Park

Research Highlights: Limber pine (Pinus flexilis) is abundant in some alpine treeline ecotone (ATE) communities east of the Continental Divide in Rocky Mountain National Park (RMNP) and the Colorado Front Range. Limber pine may be able to colonize the ATE under changing climate aided by directed seed dispersal by Clark’s nutcrackers (Nucifraga columbiana). Cronartium ribicola, white pine blister rust, is a growing threat to limber pine and may affect its functional role within the ATE. Background and Objectives: The ATE is sensitive, worldwide, to increasing temperature. However, the predicted advance of treeline under a changing climate may be modified by tree species composition and interactions. We aimed to (1) examine the conifer species composition and relative abundances in treeline communities with limber pine; (2) assess which functional roles limber pine assumes in these communities—tree island initiator, tree island component, and/or solitary tree; and (3) determine whether limber pine’s occurrence as a tree island initiator can be predicted by its relative abundance as a solitary tree. Materials and Methods: We selected four study sites in RMNP above subalpine forest limber pine stands. We sampled the nearest tree island to each of forty random points in each study site as well as solitary tree plots. Results: Across study sites, limber pine comprised, on average, 76% of solitary trees and was significantly more abundant as a solitary tree than Engelmann spruce (Picea engelmannii) or subalpine fir (Abies lasiocarpa). Limber pine was a frequent component of multi-tree islands in three study sites, the major component in one study site, and dominated single-tree islands at two study sites. At three of four study sites, no species had significantly greater odds of being a tree island initiator. Limber pine was found less often as a tree island initiator than predicted from its relative abundance as a solitary tree, given the likely role of solitary trees in tree island formation.

Preservation of Culture in Connection with the Largest Environmental Restoration Project Ever

The vast-scale projects currently being undertaken within the Everglades, collectively referred to as Everglades Restoration, represent an enormous challenge in terms of Tribal consultation. In broad terms, few people relate the Everglades to a cultural environment, and most research undertaken to date has been biologically driven. Despite the intensity of research, basic questions regarding the building blocks of the Everglades ecosystem—tree islands—remain largely unanswered. Archaeological research demonstrates that as long as the Everglades have existed people have lived within this environment. Discussion regarding restoration therefore must include a cultural voice. The enormity of the task is made clear by referencing the wall-sized Comprehensive Everglades Restoration Plan map that adorns the wall of the THPO. Each component of the overall project is given an individual designation and assigned a project management team. The challenge, as with many interrelated projects occurring at any given time, is ensuring a Tribal voice is heard.