jdp's blog

CAN FORESTS BUILD ARGILLIC HORIZONS?

Spoiler alert--the answer is: maybe, but I’m not sure.

Argillic horizons are subsoil layers that are enriched in silicate clays. I have long been interested in soil morphology as it relates to argillic horizons. First, it was with respect to soil erosion. As these horizons are by definition formed below the surface, their exposure at or near the ground surface indicates removal of overlying soil. To the extent soils have a characteristic depth, or range of depths, to the top of the argillic horizon, then variations in DTA (depth to argillic) can indicate erosion or deposition. I used this to study soil erosion in the North Carolina coastal plain and piedmont in the late 1980s and 1990s, and in the Ouachita Mountains of Arkansas in the 2000s and 2010s.

Multiple argillic horizons in a Kandiustult in Zambia (source: https://www.uidaho.edu/cals/soil-orders/ultisols).

CRISES & OPPORTUNITIES ON INFINITE EARTHS

Some incomplete thoughts and notes on Earth surface system (ESS) evolutionary pathways, focusing on how to think about the enormous variety and large number of possibilities.

 

ESS encompasses geomorphic and soil landscapes, hydrological systems, and ecosystems. There exists a huge variety of them on our planet. Assuming we could ever inventory or even estimate them all, we can define NESS  as the number of ESS. For each of these multiple possible evolutionary pathways exist. So we define

Ni(p) = number of possible evolutionary pathways for each of i = 1, 2, . . . , NESS.

Image credit: Turbosquid.com

At any given point in history there were multiple potential evolutionary possibilities, such that Nglobal(p) = number of total possible pathways = Σ Ni(p). However, only one history has occurred for each individual ESS, so that the number of actual past pathways now manifest = NESS.

STRUCTURAL REDUNDANCY IN BIOGEOMORPHOLOGY

In ecological systems, structural redundancy refers to the extent to which more than one species (or taxanomic group) can perform a given function or play a given role in the system. Microbial communities or ecosystems, for instance, tend to have high structural redundancy at the species level, as there usually exists multiple bacteria or other microbes that can, say, break down specific forms of organic matter, reduce iron, precipitate calcium, or what have you. Systems with a single keystone species have low redundancy, at least with respect to whatever the keystone organism does (if something else could perform the same function, then it would not be a keystone). Redundancy tends to be inversely correlated to the degree of biotic specialization, and directly related to ecosystem resilience. 

NEUSE NEWS: FLUVIAL-ESTUARINE TRANSITION ZONE

Just published in Earth Surface Processes and Landforms (vol. 47, p. 2044-2061): Geomorphology of the fluvial-estuarine transition zone, lower Neuse River, North Carolina. The abstract is below and the article is attached. 

 

 

STORE & POUR

Just published in Catena: Store and Pour: Evolution of Flow Systems in Landscapes (vol. 216, paper number 106357). The abstract is below, and the article is attached.

This continues my effort to figure out why certain "optimal" configurations appear recurrently in nature, despite the fact that most environmental entities have no intentionality, and that these must be emergent phenomena--accidental agency, if you will. This recognizes some similarities in the development of flow systems in terms of dual-porosity in soil and groundwater (preferential flow patterns and matrix), dendritic fluvial channel networks, and other hydrological (and related geomorphological and ecological) phenomena. It's really pretty simple, as reflected in the figure below (Fig. 4 from the published paper).

 

TALKING JUNCUS

Juncus romerianus or black needlerush is a graminoid plant that grows in coastal marshes from Virginia down the southeastern coast and around the Gulf of Mexico to Texas. It has high salinity tolerance and is often found in salt marshes, but can grow in near-about fresh water and everything in between. It has no direct, consumptive economic use that I know of (though in pre-industrial times it was used as a needle; hence the common name). However, anecdotal evidence from my neck of the woods suggests that it is highly resistant to erosion and perhaps a good candidate for “living shoreline” erosion control and wetland restoration. 

Juncus roemerianus near my house.

 

A quick-and-dirty literature search didn’t turn up anything on marsh fringe erosion or erosion resistance focused on needlerush, though there is plenty of field and experimental evidence of its efficacy in trapping sediment and promoting deposition. I have seen it eroded away where it becomes undermined, and the surface layer it is rooted in collapses. 

CHANNEL EVOLUTION & FLOW-CHANNEL FITNESS

In 2013 I developed and published something called the flow-channel fitness model (FCF; Phillips, 2013; attached). Fitness refers to the fit between channel size or conveyance capacity—yes, it’s a problematic concept, but a venerable one in hydrology and geomorphology. Underfit channels are “too large” for the range of flows they typically convey. They often occur where large channels and valleys were formed during previously wetter climates, or by megafloods or glaciers, with those big ‘ol channels now occupied by smaller streams that rarely overflow their banks and can’t do much to reshape the channel. Overfit channels are “too small.” They frequently can’t hold all the discharge that comes their way and flood frequently. Fit channels, at least as conventionally conceived for alluvial channels in humid climates, have a reasonably good match. They flood (on average and according to the conventional wisdom) every year or two but otherwise hold their water.

THE FIRST LAW

Everything is connected to everything else has been called the First Law—of ecology, of geography, and of environmental science. But why do environmental systems become so highly connected, and generally remain that way? Not quite satisfied to just say that's the way it is, and following Aristotle, who said that nature does nothing without purpose, I've been working on an answer to the why The First Law holds. I've produced a manuscript on this called Why Everything is Connected to Everything Else, abstract below, and attached to this post. I'm calling this a preprint, in hopes that it may eventually be published somewhere. But experience suggests that my odds of getting into a scientific journal are not great. Comments, criticisms, and corrections are welcome. 

Abstract

FROM WHENCE COMETH THE MUD?

Some recent kayak trips on the North River near Beaufort, NC (which, naturally enough, is north of North River, SC, but strangely enough well south of the other North River, NC, and even more strangely, south of the South River in the same county) revived some nagging questions about the source of sediment to coastal marshes. 

Freshly deposited mud on the North River marshes.

DEAD TREES AND LANDSCAPE FORMATION

Just published, in Ecosystems: Tree mortality may drive landscape formation: Comparative study from ten temperate forests. I am but one of 14(!) co-authors on this, but I've been involved in working out effects of trees on soils and landforms for 20 years. This study pulls together data from 10 protected forests and estimates the total volume of material affected by processes such as tree uprooting, and infilling of stump holes and decayed root channels, focusing on the differences between trees that die with their roots in the ground (eventually broken) vs. those that are uprooted. Uprooting-related soil volumes accounted annually for 0.01– 13.5 m3ha-1, reaching maximum values on sites with infrequent strong windstorms (European mountains). The redistribution of soils related to trees that died standing ranged annually between 0.17 and 20.7 m3ha-1 and were highest in the presence of non-stand-replacing fire (Yosemite National Park, USA). Comparing these results with long-term erosion rates indicates that tree effects may be a significant driver of landscape denudation.  The full abstract is given below.

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