Ecological dynamics

Ecological Dynamics of the Site:
Plant tables have not been developed for this site. Until such time as they can be updated, use the plant tables in the referenced literature that correlates to this concept (refer to Other Information within the Interpretations section, and to Legacy Site Information below in this narrative). With respect to the imperfect alignment of such correlations, be aware of these shortcomings in their applicability to conservation planning.

Early work by Kuchler (1964) identified the potential natural vegetation type for the Canadian Plateaus LRU as that of the grama/buffalograss short grass prairie. The Low Terraces ecological site is dominated by short grasses, but also contains a mix of shrubs, forbs, and succulents. As is typical of plant communities, pronounced annual variations in precipitation translate to considerable short-term fluctuations in annual production within a given plant community phase.

There are numerous variables which affect the range of characteristics for this ecological site. Variables such as elevation, latitude, and orographic effects create a climatic gradient which influence the distribution of C3 and C4 plants. Soil properties such as surface texture, depth to clay layer, parent material, and accumulated salts affect species diversity and composition. Natural disturbances such as drought and wildfire affect species density and cover.

The climate gradient across the CP LRU shows a greater distribution of C3 plants such as western wheatgrass and bottlebrush squirreltail where temperatures are cooler, and moisture is more abundant. Where surface texture trends toward clay loam, western wheatgrass, galleta, and vine mesquite grass increase. Where the plateau bedrock is Cretaceous shale and the site trends toward a surface texture of clay loam with an increase in salt in the profile, alkali sacaton and four-wing saltbush increase. Refer to Appendix C to see scientific names and plant codes alongside common names.

Fire is a disturbance regime that reduces succulents and shrubs while stimulating grasses and forbs. Not all fires are equal. According to Gebow (2001), fire effects in the same location will vary, especially with fire timing, both seasonally and within the scheme of year-to-year moisture variation. Precipitation during seasons before and after fire has a major effect on recovery of plants. Fire promotes rhizomatous plant species, such as western wheatgrass, that can take advantage of below-ground rhizomes from which tillering is rapidly initiated.

Correlation to Current Ecological Sites:
Bottomland- R070AY004NM: This site was written for drainageways, alluvial fans, and floodplains, none of which are affected by stream hydrology. The soil systems that are impacted by stream hydrology are significantly different, and yet ecologically important enough from these other types of bottomland soils to differentiate into a separate site.

Loamy Upland- R070AY001NM: This site is not specific to stream terraces and thus does not take into account the soil morphology or hydrology of these specific types of ecology. Thus, while the Loamy Upland ecological site has been applied to areas that currently correlate to Low Terraces, the former is a poor fit for these areas.

Most components of the Low Terraces ecological site are currently tied to the Bottomland ecological site (R070AY004NM). The bottomland site was established for all broad drainageways, floodplains, and alluvial fans. In addition, the Bottomland ecological sites are described as “not influenced by water from a stream”.

Historic Climax Plant Community:

Grasses dominate this site. Mid-grasses such as western wheatgrass, alkali sacaton, and sideoats grama are dominant with a variety of short grasses. Forbs and shrubs are only a minor portion of the plant community. This site occurs in elongated drainages that transport surface runoff from adjoining upland sites and swales. Because of the extra water received by this site, the grass is denser, stands higher and is one of the most productive sites in the resource area.

Grazing:
This site can be grazed any season of the year by all classes and kinds of livestock. Because of the forage produced by alkali sacaton, cattle and horses may best be suited. Continuous grazing during the growing season will cause the more desirable forage plants such as western wheatgrass, vine-mesquite, sideoats grama, Canada wildrye, and fourwing saltbush to decrease. Species most likely to invade this site are buffalograss, ring muhly, cholla cactus, plains pricklypear, and rubber rabbitbrush. Species most likely to increase are blue grama, galleta, alkali sacaton, and desert saltgrass. As the ecological condition deteriorates, it is accompanied by a loss of vegetative cover causing channeling of the water, and the productivity is greatly reduced. The plant community may be dominated either by blue grama/galleta or alkali sacaton/galleta as deterioration advances. Where alkali sacaton dominates the site, livestock should be concentrated into small pastures to fully utilize the forage. Livestock should be rotated in the summer or pasture should be rested in alternate years. A system of deferred grazing, which varies the time of grazing and rest in a pasture during successive years, is needed to maintain or improve the plant community. Spring deferment is beneficial to western wheatgrass and allows alkali sacaton sufficient time to green up.

Tables from Bottomland ecological site (R070AY004NM)
Annual production by plant type
Plant Type----------Low(Lb/Acre) ----------Representative Value(Lb/Acre) ----------High(Lb/Acre)
Grass/Grasslike----------880----------------------------------2200----------------------------------3520
Forb-------------------------80------------------------------------200------------------------------------320
Shrub/Vine----------------30-------------------------------------75------------------------------------120
Total------------------------990----------------------------------2475---------------------------------3960

Community 1.1 plant community composition
Common Name----------------Symbol----------Scientific Name----------Annual Production (Lb/Acre)
GRASS/GRASSLIKE
1 alkali sacaton-------------------SPAI----------Sporobolus airoides----------625–750
2 western wheatgrass----------PASM--------Pascopyrum smithii-----------500–625
3 vine mesquite------------------PAOB--------Panicum obtusum-------------500–625
4 blue grama---------------------BOGR2-------Bouteloua gracilis--------------375–500
5 James' galleta-----------------PLJA-----------Pleuraphis jamesii-------------250–375
6 sideoats grama---------------BOCU---------Bouteloua curtipendula-------250–375
7 silver bluestem---------------BOSA----------Bothriochloa saccharoide----25–125
8 cane bluestem---------------BOBA3---------Bothriochloa barbinodis------25–125
9 saltgrass-----------------------DISP------------Distichlis spicata----------------25–125
10 Canada wildrye------------ELCA4----------Elymus canadensis--------------25–125
11 Graminoid (grass or grass-like)-2GRAM-Graminoid (grass or grass-like)-25–125
FORB
12 globemallow----------------SPHAE----------Sphaeralcea---------------------25–125
13 Cuman ragweed------------AMPS----------Ambrosia psilostachya--------25–125
14 upright prairie coneflower-RACO3-------Ratibida columnifera----------25–125
15 Forb, perennial--------------2FP-------------Forb, perennial-----------------25–125
16 Forb, annual-----------------2FA-------------Forb, annual--------------------25–125
SHRUB/VINE
17 fourwing saltbush---------ATCA2----------Atriplex canescens-------------0–125
18 Apache plume-------------FAPA----------Fallugia paradoxa---------------0–125
19 Shrub, deciduous---------2SD------------Shrub, deciduous---------------25–125
--------------------------------------------------------------------------------------------------------------------
Components tied to the Loamy Upland ecological site (R070AY001NM).
Historic Climax Plant Community:

This site is a grassland characterized by mid and short-grasses. Blue grama is the dominant warm-season species. Western wheatgrass is the dominant cool-season species.

Grazing:
This site can be used by all classes of livestock during any season of the year. Because of the occasional severe winter storms, emergency feed may be necessary. Yearling calves grazing from May to October may be favored because of these winter storms. Approximately 90 percent of the total yield is from species that furnish forage for grazing. Continuous grazing during the growing season will cause the more desirable forage plants such as western wheatgrass, bottlebrush squirreltail, galleta, sideoats grama, and winterfat to decrease. Species most likely to increase are blue grama, ring muhly and buffalograss. As the ecological condition deteriorates, it is accompanied by a sharp increase of blue grama. Continuous heavy grazing will cause blue grama to form a low, dense turf, which is low in productivity. A system of deferred grazing, which varies the time of grazing and rest in the pastures during successive years in needed to maintain or improve the plant community. Grazing western wheatgrass during the months of May and June will cause a sharp decrease; therefore, rest during this period will allow western wheatgrass to grow and reproduce.
Tables from Loamy Upland ecological site (R070AY001NM):
Annual production by plant type
Plant Type-------Low(Lb/Acre) -------RV(Lb/Acre)-------High(Lb/Acre)
Grass/Grasslike -------610--------------860---------------------1100
Forb---------------------130--------------130---------------------140
Shrub/Vine------------130--------------130---------------------130
Total---------------------870--------------1120-------------------1370

Community 1.1 plant community composition
Common Name--------------Symbol-------Scientific Name-------Annual Production (Lb/Acre)
GRASS/GRASSLIKE
1-------blue grama--------------BOGR2-------Bouteloua gracilis---------312–357
2-------western wheatgrass-PASM--------Pascopyrum smithii-------178–223
3-------squirreltail----------------ELEL5--------Elymus elymoides---------89–133
4-------James' galleta-----------PLJA---------Pleuraphis jamesii----------43–89
5-------sideoats grama-----------BOCU-------Bouteloua curtipendula---43–89
6-------threeawn------------------ARIST---------Aristida-----------------------25–44
7-------ring muhly-----------------MUTO2------Muhlenbergia torreyi-----25–44
8-------buffalograss---------------BODA2------Bouteloua dactyloides-----25–44
9-------common wolfstail--------LYPH---------Lycurus phleoides-----------25–44
10-------sand dropseed-----------SPCR---------Sporobolus cryptandrus----25–44
FORB
12-------Forb, annual---------------2FA-------------Forb, annual------------------10–48
13-------Forb, perennial------------2FP-------------Forb, perennial---------------10–48
14-------Cuman ragweed----------AMPS---------Ambrosia psilostachya------10–25
15-------scurfpea--------------------CULLE---------Cullen-------------------------5–25
16-------prairie clover---------------DALEA---------Dalea---------------------------5–25
17-------dotted blazing star---------LIPU----------Liatris punctata--------------5–25
18-------locoweed--------------------OXYTR---------Oxytropis---------------------5–25
19-------upright prairie coneflower-RACO3------Ratibida columnifera-------5–25
20-------scarlet globemallow--------SPCO--------Sphaeralcea coccinea-------5–25
SHRUB/VINE
21-------winterfat---------------------KRLA2----------Krascheninnikovia lanata--29–48
22-------prairie sagewort-------------ARFR4-------Artemisia frigida-------------29–48
23-------Shrub, deciduous-------------2SD---------Shrub, deciduous-------------29–48
------------------------------------------------------------------------------------------------------------

From the San Miguel Soil Survey Manuscript (NM630), map unit Md-Manzano clay loam, 1 to 3 percent slopes
This unit is used for irrigated crops, mainly alfalfa, small grain, vegetables, and orchards. Among the other crops grown are corn, grain sorghum, and legumes. This unit is also used for livestock grazing and for wildlife habitat.
If this unit is used for irrigated crops, the main limitations are moderately slow permeability and moderate hazards of soil blowing and water erosion.
Furrow, border, corrugation, and sprinkler irrigation systems are suited to this unit. The method used generally is governed by the crop. Water should be applied in amounts sufficient to wet the root zone but in amounts small enough to minimize the leaching of plant nutrients. Soil blowing can be reduced by using all crop residue and practicing minimum tillage. Yield can be maintained or increased by applying fertilizer. Most crops, except for legumes, respond to nitrogen. Legumes respond to phosphate. Rotation grazing helps to maintain the quality and quantity of forage. Timely harvesting of crops improves their quality.
The potential plant community on the Manzano soil is mainly western wheatgrass, blue grama, alkali sacaton, and vine-mesquite. As the range deteriorates, the proportion of these forage plants decreases and the proportion of galleta, ring muhly, and broom snakeweed increases. Grazing management should be designed to increase the productivity and reproduction of western wheatgrass, blue grama, and buffalograss. Forage production is reduced in areas where gullies have formed. This unit is suited to such range improvement practices as mechanical treatment, earthen ponds, and seeding.
Adapted from the Rangeland Productivity table in the NM630 Manuscript
Manzano component of map unit Md (correlated here to the “Loamy” range site – not to be confused with R070AA001NM) -- The approximate species composition of the potential plant community is as follows:
Blue Grama-----------------------------------------------45
Western Wheatgrass-------------------------------------25
Galleta-----------------------------------------------------10
Buffalograss--------------------------------------------5
Mat muhly-------------------------------------------------5
Total production in pounds per acre for unfavorable, normal, and favorable years: 350, 800, and 1,450.