An examination of rockshelter palynology: Carpenter’s Gap 1, northwestern Australia

Carpenter’s Gap 1 is a large rockshelter located within the Kimberley region of northwestern Australia. The site provides valuable archives of late Quaternary palaeoecological information within an area known for a lack of deposits preserving long-term continuous botanical records. Previous studies of the macrobotanic, phytolith and wood charcoal records from Carpenter’s Gap 1 are in general agreement about changes in broad vegetation patterns over time but differ in the time scales used, in the representation of some species, and in the interpretation of changes – particularly on the degree to which the variations in the record represent cultural activities. An examination of palynology (the transport, deposition and preservation of pollen within the rockshelter environment) provides more detail to the vegetation patterns identified in these previous studies. In addition, because the pollen most likely reflects the vegetation of the site’s surrounds over time rather than plants introduced into the shelter by people, interpretation can be more confidently linked to environmental change, and by inference climatic conditions. The pollen data reveal pre-glacial mixed wooded vegetation. From the beginning of the Holocene, tree loss occurred in a transition from monsoonal forest to thicket and eucalypt forest to woodland. Vegetation transition around the mid Holocene suggests a shift in climate, becoming drier and more variable towards and into the late Holocene. The role of fire in the establishment of vegetation communities remains under investigation.

LANDFIRE Remap Prototype Mapping Effort: Developing a New Framework for Mapping Vegetation Classification, Change, and Structure

LANDFIRE (LF) National (2001) was the original product suite of the LANDFIRE program, which included Existing Vegetation Cover (EVC), Height (EVH), and Type (EVT). Subsequent refinements after feedback from data users resulted in updated products, referred to as LF 2001, that now served as LANDFIRE’s baseline datasets and are the basis for all subsequent LANDFIRE updates. These updates account for disturbances and vegetation transition changes that may not represent current vegetation conditions. Therefore, in 2016 LANDFIRE initiated the Remap prototype to determine how to undertake a national-scale remap of the LANDFIRE primary vegetation datasets. EVC, EVH, and EVT were produced (circa 2015) via modeling for ecologically variable prototyping areas in the Pacific Northwest (NW) and Grand Canyon (GC). An error analysis within the GC suggested an overall accuracy of 52% (N = 800) for EVT, and a goodness of fit of 51% (N = 38) for percent cover (continuous EVC) and 53% (N = 38) for height (continuous EVH). The prototyping effort included a new 81-class map using the National Vegetation Classification (NVC) within the NW. This paper presents a narrative of the innovative methodologies in image processing and mapping used to create the new LANDFIRE vegetation products.

Effects of large herbivores on tundra vegetation in a changing climate, and implications for rewilding

In contrast to that of the Pleistocene epoch, between approximately 2.6 million and 10 000 years before present, the extant community of large herbivores in Arctic tundra is species-poor predominantly due to human extinctions. We here discuss how this species-poor herbivore guild influences tundra ecosystems, especially in relation to the rapidly changing climate. We show that present herbivore assemblages have large effects on tundra ecosystem composition and function and suggest that the effect on thermophilic species expected to invade the tundra in a warmer climate is especially strong, and that herbivores slow ecosystem responses to climate change. We focus on the ability of herbivores to drive transitions between different vegetation states. One such transition is between tundra and forest. A second vegetation transition discussed is between grasslands and moss- and shrub-dominated tundra. Contemporary studies show that herbivores can drive such state shifts and that a more diverse herbivore assemblage would have even higher potential to do so. We conclude that even though many large herbivores, and especially the megaherbivores, are extinct, there is a potential to reintroduce large herbivores in many arctic locations, and that doing so would potentially reduce some of the unwanted effects of a warmer climate. This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change’.

Keystone mutualists can facilitate transition between alternative ecosystem states in the soil

Symbioses between plants and microbial organisms can fundamentally alter the structure of ecosystems, from their species diversity to rates of nutrient cycling. Yet, many aspects of how differences in the prevalence of microbial symbioses arise are unclear. This is a key knowledge gap, as if co-variation in plant and microbial distributions are primarily determined by extrinsic abiotic factors then symbioses should exert little independent control over ecosystems. To examine the potential for alternative symbiotic communities to arise under similar conditions we examined biogeochemical cycling and microbial community structure in a coastal landscape where historical patterns of vegetation transition are known, allowing us to eliminate abiotic determinism. We found that alternative states in microbial community structure and ecosystem processes emerged under different plant species. Greenhouse studies further demonstrated that plant selection of symbiotic microbes is central to emergence of these alternative states and occurs independent of soil abiotic conditions. Moreover, we provide evidence that transition between states may be highly dependent on the presence of a small set of ruderal symbionts that are rare in mature systems but may act as keystone mutualists. Because differences between these alternative states can be directly linked to plant-microbe symbioses, independent of initial conditions, our results suggesting that biotic feedbacks between keystone symbiotic microbes and plants play a foundational role in the diversity and function of soils.