ecology

THE GEOMORPHOLOGICAL NICHE OF TREES

In a 2009 article I introduced the concept of a geomorphological niche, defined as the resources available to drive or support a particular geomorphic process (the concept has not caught on). The niche is defined in terms of a landscape evolution space (LES), given by

where H is height above a base level, rho is the density of the geological parent material, g is the gravity constant, and A is surface area. The k’s are factors representing the inputs of solar energy and precipitation, and Pgrepresents the geomorphically significant proportion of biological productivity (see this for the  background and justification).

BREAKAGE VS. UPROOTING & HILLSLOPE GEOMORPHOLOGY

Just published in Geomorphology:

Samonil, P., Danek, P., Adam, D., Phillips, J.D. 2017. Breakage or uprooting: how tree death affects hillslope processes in old-growth temperate forestsGeomorphology 299: 276-284. 

The abstract is below:

Posted 14 November 2017

 

SELF-LIMITING ECOSYSTEM ENGINEERING IN NON-KARST REGOLITH

This is a follow-up to my previous post on emergent ecosystem engineering in epikarst, so I won't repeat much of the background or analytical details. There I argued that interactions among rock weathering, moisture flux, biological effects (particularly roots and their symbionts) and soil operate such that if weathering is moisture-limited, and biota are limited by water availability and below-ground space, the system is dynamically unstable. Positive feedbacks dominate so as to reinforce or accelerate dissolution, joint/fracture widening, root growth, and soil accumulation. The net effect is to develop the epikarst as increasingly hospitable habitat. This continues, according to the analysis, until weathering becomes reaction-limited and subsurface space and moisture are no longer significant limiting factors for plant growth. Under the latter circumstances the system is dynamically stable, implying resilience to relatively small changes or disturbances and slower change.

EMERGENT ECOSYSTEM ENGINEERING IN EPIKARST

Epikarst is defined as the uppermost zone of dissolution in karst, including whatever soil cover exists. The purpose of this analysis is to explore some of the interactions among geological controls, weathering, biota, moisture flux and soil accumulation in the regolith or critical zone of karst systems.

Epikarst exposed by gullying, Bowman's Bend, Kentucky

Figure 1 shows the interactions among geological controls (joints, fractures, bedding planes), weathering, subsurface biological activity, moisture flux, and soil accumulation the earlier stages of soil development in epikarst. The system is dominated by positive feedbacks because in early stages of epikarst development there is limited space for biological activity (e.g., roots), and moisture fluxes are limited by the size of joints, fractures, and incipient conduits. The other positive feedbacks reflect well established relationships among chemical weathering, enlargement of joints, etc., water availability, and organisms. I assume some external (to the system shown) limitations on biological activity and moisture flux.

Negotiating Life: Resilience in an Era of the China Dream

Ecological practices of daily life have taken on new urgency and approaches as consumer citizens increasingly voice awareness of environmental sustainability in China. This lecture will focus on "everyday ecologies"--personal engagement with social and material worlds to negotiate well-being. 

Professor Nancy Chen is Chair of the Anthropology Department and an affiliate of East Asian Studies and Feminist Studies at UC/Santa Cruz. Her research interests include Chinese biotechnology, food and medicine, and alternative healing practices. She is author or editor of six books, including China Urban

Sponsored by the Department of Anthropology and the UK Confucius Institute. 

 

Date: 
Friday, September 15, 2017 - 3:30pm
Location: 
White Hall Classroom Building Rm 106

BIOGEOMORPHIC NICHE CONSTRUCTION BY UPROOTING

Tree uprooting in forests has all sorts of ecological, pedological, and geomorphological impacts. Those are not just related to disturbance--because of the time it takes uprooted trees to decompose, and the distinctive pit-mound topography created, those impacts may last decades to centuries (and sometimes even longer).  One discussion I've often had with colleagues who study this sort of thing has to do with ecosystem engineering and niche construction. Obviously uprooting is a major biogeomorphic process. Obviously it has important impacts on habitat. But do these impacts favor either the engineer species (i.e., the tipped over tree) or some species? Or are they more or less neutral, in the sense of modifying habitat but not necessarily in such a way as to systematically favor any given species?

Uprooted Norway spruce.

STAGES OF BIOGEOMORPHIC EFFECTS

The biogeomorphic impacts of organisms may differ at different stages in the development of landforms, ecosystems, or the individual organisms. I was thinking about this recently here along the shoreline bluffs of the Neuse River estuary, North Carolina, where I have been both looking at some soil profiles and enjoying the coastline.

There are at least five distinctly different biogeomorphic roles trees play along this shoreline--many more if you wanted to get more specific within these categories. The specifics are probably of only limited applicability elsewhere, but the general principle--multiple effects, which vary at different stages of both landform and vegetation development--is widely valid.

Trees and other vegetation grow thick and fast in this moist subtropical climate.

Stage 1A Surface Bioprotection

Trees (including canopy, roots, and litter) protect the ground surface from erosion and add organic matter to soil.

BIOGEOMORPHOLOGICAL SELECTION

Biogeomorphology considers the impacts of organisms on surface processes and landforms (e.g., biological weathering, effects of burrowing animals), and vice-versa (e.g., the role of landforms as habitat, effects of erosion on biota). We are particularly concerned these days, however, with reciprocal interactions, such as sediment trapping by vegetation, and the feedback effects of this deposition on plants and their habitat. We are also learning a lot about biogeomorphic ecosystem engineering (BEE), whereby biota modify the abiotic environment in ways that influence habitat or resources (positively or negatively) for themselves or other species, and biogeomorphic niche construction, where BEE effects influence selection pressures and biological evolution.

MORE FOREST BIOGEOMORPHOLOGY & GEOECOLOGY

Imagine exploring and mapping a newly discovered cave opening. At this point, there is only one set of questions--how long, deep, tall, wide, etc. is the passage, and where does it go? But as you begin to map it, more often than not, other passages and fissures will be discovered (and many of them will lead to others, and so on). This opens up a whole new set of questions. Some of the passages can be mapped, assuming someone can get the time and resources. Others can't be no matter how skilled the spelunker; they are too small. But even these can possibly be explored later, perhaps with remote control or AI tiny robots or probes; or with imaging techniques that can see through rock.

This is a pretty good metaphor, I think, for research in general. The more you learn, the more you discover you don't know, and more potential pathways for research appear--some possible now, some awaiting new techniques.

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