Robert P. Gibbens

Vegetation Changes from 1935 to 1980 in Mesquite Dunelands and Former Grasslands of Southern New Mexico

On the Jornada Experimental Range in southern New Mexico, 2 belt transects, 30.5 cm in width and totnling 2,188 m in length, were established in 1935 on 2 areas where honey mesquite (Prosopis ghzndulosa Torr.) was spreading into black grama [Boutelouu eriopoda (Torr.) Torr.] grassland. Maps were made of the transects which portrayed the vegetation occurring in each of the 7,180 contiguous, O.OPm2 plots along the transect. The vegetation on the transects in 1980 was compared to that portrayed by the transect maps made in 1935. One transect had been read in 1950 and 1955. During the 45-year period mesquite attained complete dominance and many new mesquite dunes formed. Black grama had a relatively high frequency in 1935 but bad completely disappeared by 1980, both on an area grazed by livestock and on an area protected from grazing. Mesa dropseed [Sporobolus fZexuosus (Thurb.) Rydb.], fluffgrass [Erloneuronpu&hellum (H.B.K.) Tateokalbnd broom snakeweed [Xmthocephuhm sarottVae (Pursh) Shinners] increased in abundance, even during the drought period between 1950 and 1955. Only 25% of the perennial forb species encountered in 1935-55 were found in 1980. The spread of honey mesquite (Prosopis glandulosa Torr.) and other shrubs in the Southwest has been well documented, with heavy grazing, seed dispersal by domestic animals and periodic droughts being advanced as causes contributing to the increase in shrubs (Buffington and Herbel 1965; York and Dick-Peddie 1969). Mesquite has many features which enable it to exploit altered ecosystems. These include rapidly developing, deep taproots and long lateral roots, long-lived seeds, high germination rates over a wide range of temperature and moisture conditions, ability to withstand high negative water potentials, high water use efficiency, and the ability to regenerate from underground dormant buds following injury (Glendening and Paulsen 1955, Mooney et al. 1977). Mesquite has increased in abundance on a wide range of soil types but in southern New Mexico its greatest increase has been on sandy soils (Buffington and Herbel 1965). In arid areas mesquite typically grows as a low multi-stemmed shrub. These multistemmed plants entrap drifting sand, forming what has been called “coppice dunes” (Melton 1940). Vast areas of former desert grassland have been transformed into hummocky landscapes dominated by mesquite dunes. Dunes large enough to class as pedons have developed soils which are distinct from those of the interdunal areas (Giles 1966). Mesquite dunelands have an appearance of stability but considerable soil movement was found over a 45-year period (Gibbens et al. 1983). The transformation of desert grasslands into dynamic dunelands has resulted in the complete loss of Authors are respectively,. former graduate student, Department of Animal and Range Science, New Mexico State Univ., Las Cruces 88003, now Range Science Officer, Gaburone, Botswanna. Africa; range scientist and hydrologist. USDA, Agricultural Research Service, Las Cruces, N. Mex. 88004; and associate professor, Department of Experimental Statistics, New Mexico State Univ., Las Cruces. This report is published as journal article 905. AgriCUhd Experiment StatiOn, New Mexico State Univ., Las Cruces. 370 some former dominant plants and in major shifts in abundance of other herbaceous plants. Early researchers at the Jornada Experimental Range in southcentral New Mexico witnessed the encroachment of mesquite into desert grasslands. They established belt transects across mesquitegrassland ecotones and made detailed records of the existing vegetation. During the ensuing years mesquite continued to increase in abundance. A comparison of present with past vegetation on the transects provides much insight on the reactions of grassland species to an increase of mesquite. This information is of value both in an ecological sense and in managing mesquite-dominated lands as a grazing resource.

Changes in grass basal area and forb densities over a 64-year period on grassland types of the Jornada Experimental Range.

Between 1915 and 1932, permanent 1 X 1-m quadrats were established on grasslands of the Jornada Experimental Range in southern New Mexico. Quadrat records accumulated from 1915 to 1979 on grasslands dominated by black grama [Bouteloua eriopoda (Torr.) Torr.], poverty threeawn (A ristida divaricata Willd.), tobosa [Hilaria mutica (Buckl.) Benth.], and burrograss (Scleropogon brevifolius Phil.) were used to examine changes in perennial grass basal area and forb densities. Quadrats originally dominated by black grama had large reductions in basal area during droughts, and basal area increased slowly following droughts. By 1979, black grama no longer occurred on 77% of the quadrats. Quadrats originally dominated by poverty threeawn changed to a mesquite (Prosopis glandulosa Torr. var. glandulosa) type. Perennial grass basal area on quadrats dominated by tobosa and burrograss decreased during droughts, but recovery was relatively rapid. Antecedent precipitation was associated with only 10 to 38% of the variation in perennial grass basal area. Perennial forb densities were low and fluctuated among years in all types. Annual forbs and grasses displayed large fluctuations in densities among years. The necessity of basing management of Chihuahuan Desert ranges on the perennial grass component is borne out by the low densities of palatable perennial forbs, and the extreme fluctuation and unpredictability in densities of annual forbs and grasses.

Soil Movement in Mesquite Dunelands and Former Grasslands of Southern New Mexico from 1933 to 1980

Soil levels were marked on grid and transect stakes in mesquite duneland and grassland areas at 3 sites on the Jomada Experimental Range in 1933 and 1935. Soil levels on one set of transect stakes were remeasured in 1950 and 1955. Remeasurement of soil levels at both transect and grid stakes in 1980 revealed that extensive soil movement had occurred during the intervening years. On a 259-ha site containing large mesquite dunes in 1935, maximum deposition and deflation was 86.9 and 64.6 cm, respectively, in 1980. There was a net gain of 1.9 cm in soil depth over the entire area. On a 25Pha site only partially occupied by mesquite dunes in 1933, there was a net loss of 4.6 cm in soil depth and mesquite dunes had completely occupied the site by 1980. On a transect established across a mesquite duneland-grassland ecotone in 1935, there was a net loss in soil depth of 3.4 cm. Mesquite dunes had completely occupied the former grassland and dune intercept increased from 34.9 m in 1935 to 149.6 m in 1980. Gross erosion rates on wind deflated areas were equivalent to 69 tonnes ha“ yr-’ on the area of large mesquite dunes. On the area partially occupied by mesquite in 1935 the gross erosion rate was 52 tonnes ha-’ yr-‘. At the ecotone transect gross erosion rates were 45,101, and 40 tonnes ha-’ yr-’ for 1935-50, 1950-55, and 1955-80 periods, respectively. Honey mesquite (Prosopisglundulosu Torr.) is a plant native to the Southwest, which has spread widely during the historical period. Overgrazing, seed dispersal by domestic livestock and rodents, and periodic droughts have been advanced as causes contributing to the proliferation of mesquite (Buffington and Herbe1 1965). The spread of mesquite, primarily into former grassland areas, has caused profound changes in plant communities and in soils and microrelief. Since mesquite makes large demands on a limited soil water supply (Haas and Dodd 1972), herbaceous vegetation between mesquite plants is often reduced in abundance and cover. Baring of the soil surface permits wind erosion and the formation of “coppice dunes” (Melton 1940) as sand is entrapped by mesquite stems. Mesquite dunes now dominate vast areas which once had a relatively flat surface covered primarily by herbaceous vegetation. The formation of mesquite dunes involves the physics of soil movement by wind, a subject which has been the object of many studies (Bagnold 1941, Chepil and Woodruff 1963, Gillette 1978). An understanding of the processes, i.e., saltation, creep, and suspension, by which soil particles move under the impetus of wind and the influence of surface roughness factors has led to the development of a generalized soil loss equation for wind erosion (Woodruff and Siddoway 1965). This equation has been used in assessing potential wind erosion problems in the United States Authors are range scientist and hydrologist, USDA, Agricultural Research Service, Las Cruces, N. Me.%; former graduate student, Animal and Range Science Department, New Mexico State University, now range science officer, Gaborone, Botswanna, Africa; and associate professor, Department of Experimental Statistics, New Mexico State University, Las Cruces. respectively. Published as journal article 904, Agricultural Experiment Station, New Mexico State University, Las Cruces, NM. Manuscript received November 23, 1981. JOURNAL OF RANGE MANAGEMENT 36(Z). March 1983 (Kimberlin et al. 1977). The arid Southwest, where sandy soils predominate and vegetation cover is often minimal, has a high wind erosion potential. In the early 1930’s, scientists at the Jornada Experimental Range were concerned with the spread of mesquite and concomitant wind erosion. As part of their research program, large exclosures and transects were established in mesquite dunelands and on ecotones between grassland and mesquite dunelands. Soil levels were marked on a large number of grid and transect stakes. This farsighted action provided a unique opportunity to quantify soil movement. Soil levels at the original stakes were remeasured in 1980. Soil movement during the 45 to 47-year period shows that mesquite dunelands, while having an appearance of stability, are actually a dynamic, constantly shifting system.

Distribution and concentration of total phenolics, condensed tannins, and nordihydroguaiaretic acid (NDGA) in creosotebush (Larrea tridentata)

This paper focuses on the presence and distribution of secondary phenolic compounds found within creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov.]. Total phenolics, condensed tannins and nordihydroguaiaretic acid (NDGA) were measured in nine categories of tissue within creosotebush. Total phenolic and condensed tannin concentrations were determined using colorimetric methods while NDGA content was determined with high performance liquid chromatography (HPLC). Phenolics were present throughout the plant with the highest concentrations in leaves (36.2 mg/g), green stems (40.8 mg/g) and roots (mean for all root categories=28.6 mg/g). Condensed tannins were found in all tissues with highest concentrations in flowers (1.7 mg/g), seeds (1.1 mg/g), and roots less than 5 mm in diameter (1.1 mg/g). Flowers, leaves, green stems and small woody stems (<5 mm in diameter) all contained NDGA with highest concentrations in leaves (38.3 mg/g) and green stems (32.5 mg/g).This is the first report we are aware of giving secondary chemical characteristics of creosotebush roots. Data reported here will be used to support further research into the dynamics of shrub replacement and dominance of arid grasslands.

Multi-scale factors and long-term responses of Chihuahuan Desert grasses to drought

Factors with variation at broad (e.g., climate) and fine scales (e.g., soil texture) that influence local processes at the plant scale (e.g., competition) have often been used to infer controls on spatial patterns and temporal trends in vegetation. However, these factors can be insufficient to explain spatial and temporal variation in grass cover for arid and semiarid grasslands during an extreme drought that promotes woody plant encroachment. Transport of materials among patches may also be important to this variation. We used long-term cover data (1915–2001) combined with recently collected field data and spatial databases from a site in the northern Chihuahuan Desert to assess temporal trends in cover and the relative importance of factors at three scales (plant, patch, landscape unit) in explaining spatial variation in grass cover. We examined cover of five important grass species from two topographic positions before, during, and after the extreme drought of the 1950s. Our results show that dynamics before, during, and after the drought varied by species rather than by topographic position. Different factors were related to cover of each species in each time period. Factors at the landscape unit scale (rainfall, stocking rate) were related to grass cover in the pre- and post-drought periods whereas only the plant-scale factor of soil texture was significantly related to cover of two upland species during the drought. Patch-scale factors associated with the redistribution of water (microtopography) were important for different species in the pre- and post-drought period. Another patch-scale factor, distance from historic shrub populations, was important to the persistence of the dominant grass in uplands (Bouteloua eriopoda) through time. Our results suggest the importance of local processes during the drought, and transport processes before and after the drought with different relationships for different species. Disentangling the relative importance of factors at different spatial scales to spatial patterns and long-term trends in grass cover can provide new insights into the key processes driving these historic patterns, and can be used to improve forecasts of vegetation change in arid and semiarid areas.

Water properties of caliche.

Water absorption and retention by hard caliche nodules (rocks) collected from soils in southern New Mexico were determined. The rate of water uptake by the criiche rocks was rapid and water content at saturation was 13.0% by weighht (24.7% by volume). At a matrix potential of -0.7 MPa, the rocks retained 10.6% water by weight, an 18% loss from saturation. Water loss from saturated rocks to a dry atmosphere was slow, but most of the absorbed water was released. The rocks contained only 0.6% water by weight (1.1% by volume) after 34 days in a desiccator. Both iaboratory and field trials indicated that, although indurated caqche iayers will absorb iarge amounts of water, the water does not pass through the layers to the soil below. Caliche is commonly found in soils in the arid and semiarid southwestern United States. Although the chemical composition of caliche varies spatially, calcium carbonate (CaCOs) is always the major constituent. Deposits of caliche often limit the downward extension of plant roots and the volume of soil from which plants can extract water. Thus, an understanding of plant distributions on arid rangelands is often dependent upon a knowledge of how caliche deposits influence the availability of soil water. The dissolving and leaching of CaCOs by rainwater, followed by the evaporation and rapid removal of soil water by plants, leads to precipitation of CaCOsand the development of caliche deposits in soils (Gile et al. 1966, Shreve and Mallery 1932, Stuart and Dixon 1973, Stuart et al. 1961). Deposits of caliche often form along and below contacts between coarse-textured soil layers or between coarseand fine-textured interfaces (Stuart and Dixon 1973). These carbonate deposits may be in the form of indurated or “hard”caliche-which does not slake when an air-dried portion is placed in water-or in the form of nonindurated “soft” calichewhich does slake when an air-dried portion is placed in water (Gile 1961). Both types of caliche often exist together. Caliche deposits may be in the form of either nodules or layers. In either form, the material is usually parallel to the soil surface in either continuous or discontinuous layers. Depth of the deposits varies from near the surface to a depth of a meter or more. With maturity, whole deposits may become hardened and strongly indurated, especially if they contain high amounts of calcium or aluminum silicates (Stuart et al. 1961). Where soil horizons are so strongly impregnated with carbonate that their morphology is determined by the carbonate, a petrocalcic or Bkm horizon may be designated (USDA Soil Conserv. Serv. 1981). Since hardened deposits are not easily weathered, the layer, upon exposure, can form a caprock (Lattman 1977). The development of carbonate horizons is a useful indicator in determining soil age (Gile 1970). In calcareous soils, those with caliche layers and those with enough CaC03 to potentially form caliche, water penetrability and soil sorptivity decrease as the CaCOs content in the sand fraction increases. Precipitates in such soils can block pore spaces and increase the length of passages available for soil water movement. As a result, both the water storage-capacity and the rate of water Authors are former graduate student, Animal and Range Science Department, New Mexico State University, Las Cruces, now range research officer, Gaborone, Botswana, Africa; range scientist and hydrologist, U.S. Department of Agriculture, Agricultural Research Service, Las Cruces, N. Mex. 88003; and associate professor, Department of Experimental Statistics, New Mexico State University, Las Cruces, respectively. This article is published as journal article 960, Agricultural Experiment Station, New Mexico State Univ., Las Cruces. Manuscript received November 1, 1982. JOURNAL OF RANGE MANAGEMENT 36(6), November 1983 advancement (hydraulic conductivity) in the soil are decreased (Tayel 1975, Verplancke et al. 1976). Removal of CaCOs from a soil increased soil porosity and soil water retention at all suction levels tested by Stakman and Bishay (1976). Calcareous soils were also found to be more susceptible to compaction damage and clogging of micropores by cementation (Talha et al. 1978). Gile (1961) found that infiltration rates of carbonate horizons ranged from 0.13 to 14.99 cm per hour and that infiltration rates decreased exponentially as carbonate content increased. Caliche is highly insoluble in soil water except when the soil water contains abundant CO2 (Shreve and Mallery 1932). The insolubility of caliche in water has lead to the assumption that most caliche is highly impermeable to water (Lattman 1977). However, Shreve and Mallery (1932) found that “hard”caliche would absorb small amounts of water (3-6% by dry weight) whereas “soft” caliche absorbed up to 17% water. Shreve and Mallory (1932) also found that water transferred slowly through thin (l-cm thick) caliche layers. They concluded that caliche was a deterrent to the penetration of water from the surface to lower depths, and that, once water reached lower depths, caliche effectively retained it. Caliche often occurs within the rooting zone of plants on arid rangelands (Gile and Grossman 1979). Thus, water properties of caliche may influence the amount of soil water available to plants. The objective of this study was to determine the water absorption, retention, and transfer characteristics of indurated caliche. Materials and Methods Caliche samples were obtained from a mesquite (Prosopis glandulosa Torr.) duneland site on the Jornada Experimental Range (administered by the U.S. Department of Agriculture, Agricultural Research Service) in Dona Ana County, N. Mex. On-site examination was made by Soil Conservation Service personnel. Interdunal soils were identified as coarse-loamy, mixed, thermic Typic Haplargids of the Onite series and as coarse-loamy, mixed, thermic Typic Calciorthids of the Wink series. Dunes tall enough to qualify as pedons were classified as mixed Typic Torripsamments of the Pintura series. All of the soils contain petrocalcic layers, generally horizontally discontinuous and ranging from the surface to a meter or more in depth. These soils are in an arid area where mean annual rainfall is 230 mm. Mean annual temperature is 15OC. The average temperatures are maximum in June (36“C) and lowest in January (13.3OC). Hard caliche nodules (rocks) were gathered from the field site. A layer of caliche rocks is typically found just above the solidly indurated caliche layers. Four weight classes, with 5 rocks in each class, were chosen, based on oven-dry weight as follows: (1) 40-70 g; (2) 70-100 g; (3) 100-150 g; and (4) 150-300 g. Water Absorption To determine rate of water uptake and water content at saturation, we oven-dried (105OC) the caliche rocks to a constant weight (48 hr) and submerged them in distilled water. The rocks were removed from the water and excess water removed with towels, then immediately weighed and replaced in water. This procedure was performed after 1, 5, and 15 min; 1 hr; 5 hr; and 24 hr of submergence. Weight determinations at 36 hr showed that a constant weight had been reached at 24 hr. Water content (percentage of dry weight) was calculated for each rock at each time interval.

Persistence of Municipal Biosolids in a Chihuahuan Desert Rangeland 18 Years After Application

The experimental application of municipal biosolids to degraded arid and semiarid rangelands has been practiced for many years and is becoming more common in the western United States. Previous studies have examined the effects of applying biosolids to land areas that have been degraded by one or more different factors including overgrazing, fire suppression, and increased drought frequency, duration, or intensity. However, few of these studies have measured the persistence of biosolids in the soil. This study is an attempt to recover information from an abandoned reclamation effort in which municipal biosolids were spread on a degraded rangeland on the Jornada Experimental Range in southern New Mexico. The biosolids were applied in 1979 and were still present in substantial amounts when soil samples were taken in 1997. An estimated 32% of the applied biosolids persisted as fragments greater than 2 mm in diameter for almost 20 years. There were no apparent benefits of biosolid application at this site in terms of vegetation establishment within the first four years, and there was no correlation between vegetation patterns and the concentration of biosolids remaining in the soil in 1997. It is hypothesized that much of the applied sludge remains in the soil because of the recalcitrant nature of digested biosolids combined with the environmental conditions of soil in arid systems. Long-term results from biosolid addition experiments in arid and semiarid rangelands should be considered before the practice is widely used for reclamation of degraded rangeland sites.

Some effects of precipitation patterns on mesa dropseed phenology.

Phenology of mesa dropseed [Sporobolus flexuosus (Thurb.) Rydb.] was studied from 1979 to 1987 on the Jomadr Experimental Range in southern New Mexico. Growing season (March through November) precipitation ranged from 99 to 308 mm during the &year period. Foliage height and number of leaves were recorded weekly for individually marked cuhns on 20 piants. New cuims usually appeared during the first week in March and green leaf tissue often persisted until the end of November. Correlation analyses of accumulated weekly height increments and accumulated weekly precipitation showed that growth was highly dependent upon rainfall (r = 0.81 to 0.97). Leaf formation was also correlated with raidail (r = 0.79 to 0.98). Even in relatively wet years tbere were 1 or 2 periods of no growth. In drier years, no growth periods totaled as much as 87 days. Periods of rapid growth occurred only rfttr rainfall events > 13 mm. The first exsertion of seed heads occurred as early as the last week of July and as iate as tbe second week of October. The temporal plasticity of mesa dropseed phenology indicates that it is well adapted to the arid environment.

Herbicide treatment and vegetation response to treatment of mesquites in southern New Mexico.

Mesquite (Prosopk juliifrora) is a major unwanted plant in the Southwest This study evaluated the herbage responses obtained from various aerial applications of 2,4,5-T on mesquites in southem New Mexico. The dead plants on the various areas ranged from 7-64% of the mesquite. Yields of perennial grasses ranged from 3-1931 kg/ha on the untreated controls and 11-2696 kg/ha on the areas sprayed with 2,4,5-T. In dense stands of mesquite, about 30% of the mesquites must be kIIled before grass yields are significantly increased. There are an estimated 38 million ha of land infested with mesquite [Prosopis julifroru (Swartz) DC.] in the United States (Platt 1959). An estimated 4 million ha occur in New Mexico (Sampson and Schultz 1956). Although mesquite is an indigenous plant, it has invaded large areas and has become dominant on some of these in the last 100 years (Norris 1950, Wright 1960, Paulsen and Ares 1962, Buffington and Herbel 1965, York and DickPeddie 1969). The invasion and increase of mesquites have resulted in a decrease in cover and production of the perennial grass plants that once dominated these areas. As mesquites become established, an area devoid of herbaceous vegetation develops around the maturing mesquite plants. As the herbaceous cover is depleted wind erosion becomes more severe, particularly on sandy rangelands of the Southwest. Eventually, the “A” horizon and part of the “B” horizon is deposited around the mesquite or removed from the area entirely, resulting in a further decrease of the desirable perennial herbaceous plants and a build-up of sand dunes. Because of the competition for soil water by mesquite, few herbaceous plants become established on the eroded soils unless the mesquite is controlled. associations, the Upton-Simona association (shallower soils) and the Kermit-Maljamar-Berino association (Maker et al. 1970). The soils of the Jomada site are in the Simona-Harrisburg association (Bulloch and Neher 1980). These soils have a sandy surface that are quite susceptible to wind erosion. The surface relief is undulating or duned. The vegetation on the deeper sands in southeastern New Mexico is dominantly tall and mid-grasses, mesquite, sand shinnery oak [Quercus havurdi Rydb.)] and sand sagebrush [ArtemisiuJilifolia (Torr.)]. The more shallow soils support short and mid-grasses, mesquite, broom snakeweed [Xunthocephulum surothe (Pursh) Shinners] and some creosotebush [Lurreu tridentutu (DC.) Cov.]. The average annual precipitation varies from 258 mm at the Ochoa Weather Station in the southeast portion of the study area to 3 13 mm at Roswell. The study site on the Jornada Experimental Range is dominated by mesquite, broom snakeweed, and short and mid-grasses. The average precipitation is 225 mm.

Increase in number of dominant plants and dominance-classes on a grassland in the northern Chihuahuan Desert.

Between 1915 and 1932,194 permanent 1 X l-m quadrats were established on grasslands of the Jornada Experimental Range in southern New Mexico. Primaryand secondary-dominant species were determined from the first quadrat records and each quadrat was reevaluated in 1981 to determine current dominants. The first records showed that 13 species of perennial grasses occupied all primaryand secondarydominant positions on all quadrats. In 1981, there were 12 perennial grass species as primaryor secondary-dominants. Six shrub species occurred as primaryor secondary-dominants on 47% of the quadrat sites in 1981. Dominance-classes, i.e., single-species dominance or two-species dominant combinations, increased from 24 to 43. Thus, vegetation on this range has become more diverse and this diversity must be considered in grazing management.