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A0945 Juglans microcarpa Riparian Scrub Alliance

The U.S. National
Vegetation Classification
Type Concept Sentence: This alliance is found primarily along intermittently to temporarily flooded low-elevation (below 1500 m) streambeds and stream margins in desert canyons and valleys. Stream gradients are gentle. The headwaters of these streams are often in montane areas, and even when the streambed is dry, it is usually subirrigated. Following monsoonal rains, the streambed can be shallowly inundated for several weeks at a time. These are riparian scrublands with Juglans microcarpa as a dominant.
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Common (Translated Scientific) Name: Little Walnut Riparian Scrub Alliance
Colloquial Name: Little Walnut Riparian Scrub
Hierarchy Level: Alliance
Type Concept: This alliance is found primarily along intermittently to temporarily flooded low-elevation (below 1500 m) streambeds and stream margins in desert canyons and valleys. Stream gradients are gentle. The headwaters of these streams are often in montane areas, and even when the streambed is dry, it is usually subirrigated. Following monsoonal rains, the streambed can be shallowly inundated for several weeks at a time. These are riparian scrublands with Juglans microcarpa as a dominant. Other woody species can include Celtis laevigata var. reticulata, Fallugia paradoxa, Brickellia laciniata, Salix gooddingii, Salix nigra, Platanus occidentalis, Ungnadia speciosa, and Quercus spp.
Diagnostic Characteristics: Juglans microcarpa; open, scrubby riparian vegetation.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: The old alliance A.945 has been split, with two associations (CEGL004593 and CEGL004594) moving to A0957 in M508. These two associations are likely to be closely related to other riparian vegetation of New Mexico, Arizona, and Mexico. There may also be undescribed associations representing this alliance. In addition, the group placement of this alliance needs review and more information is needed to fully document the range and floristics of this alliance.
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Physiognomy and Structure: This alliance consists of structurally variable broad-leaved deciduous shrublands. The woody vegetation varies in both height and density, and from shrubby growth to well-developed small trees. The canopy of the woody plants may be dense to somewhat open or consist of widely scattered individuals. Woody vines are common in some stands, and most have an herbaceous layer, usually dominated by graminoids.
Floristics: This alliance is composed of structurally and compositionally variable riparian shrublands, with Juglans microcarpa being the most abundant and characteristic woody species. Other woody shrubs and small trees that can be present can include Celtis laevigata var. reticulata, Fallugia paradoxa, Fraxinus velutina, Ostrya knowltonii, Chilopsis linearis, Brickellia laciniata, Salix gooddingii, Salix nigra, Platanus occidentalis, Ungnadia speciosa, and Quercus spp. The understory, particularly in the Texas examples, is composed primarily of perennial grasses typical of adjacent upland vegetation, such as Leptochloa dubia, Bothriochloa barbinodis (= var. barbinodis), Bouteloua curtipendula, Schizachyrium scoparium var. scoparium (= Schizachyrium scoparium ssp. neomexicanum), and Andropogon gerardii. Cladium mariscus ssp. jamaicense is the graminoid dominant in one association in Texas. Woody vines, such as Vitis arizonica can be important in stands in New Mexico.
Dynamics: Juglans microcarpa is shade-intolerant. Young individuals direct much of their energy into developing a large, deep taproot, which permits the walnut to survive the periods of extreme drought that are common.
Environmental Description: Little information is available about the environmental factors related to this alliance. It is found primarily along intermittently to temporarily flooded low-elevation (below 1500 m) streambeds and stream margins in desert canyons and valleys. Stream gradients were reported by Szaro (1989) to be 8 to 9 m per kilometer, fairly low gradients. The headwaters of these streams are in montane areas, and even when the streambed is dry, it is usually subirrigated. Following monsoonal rains, the streambed can be shallowly inundated for several weeks at a time. In western Texas and the Edwards Plateau, this alliance occurs on limestone cobbles or flat-bedded limestone streambeds. New Mexico sites are reported to be bouldery or gravelly
Geographic Range: This alliance has been reported from the Edwards Plateau region of Texas.
Nations: MX?, US
States/Provinces: TX
US Forest Service Ecoregions (1994/1995)
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Confidence Level: Low
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Grank: GNR
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Synonomy: ? Juglans microcarpa Community Type (Szaro 1989)
? Little Walnut Series (Dick-Peddie 1993)
Concept Author(s): J. Teague, in Faber-Langendoen et al. (2013)
Author of Description: J. Teague and M. Pyne
Acknowledgements:
Version Date: 19Dec2014
References:
  • Diamond, D. D. 1993. Classification of the plant communities of Texas (series level). Unpublished document. Texas Natural Heritage Program, Austin. 25 pp.
  • Dick-Peddie, W. A. 1993. New Mexico vegetation: Past, present, and future. University of New Mexico Press, Albuquerque. 244 pp.
  • Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
  • Szaro, R. C. 1989. Riparian forest and scrubland community types of Arizona and New Mexico. Desert Plants Special Issue 9(3-4):70-139.