Terrell T. Baker

Fine Root Productivity and Dynamics on a Forested Floodplain in South Carolina

The highly dynamic, fine root component of forested wetland ecoi&g fine root dynamics is a challenging endeavor in any system, but the dilficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (53 mm) biomass, production, and turnover were estimated for three soils exhibiting different drainage patterns within a mixedoak community on the Coosawhatchie River floodplain, Jasper County, South Carolina. Within a 45cm-deep vertical profile, 74% of total fine root biomass was restricted to the upper 15 cm of the soil surface. Fine root biomass decreased as the soil became less well drained (e.g., tine root biomass in well-drained soil > intermediately drained soil > poorly drained soil). Fine root productivity was measured for 1 yr using minirhiitrons and in situ screens. Both methods suggested higher fine root production in better drained soils but showed frequent fluctuations in fine root growth and mortality, suggesting the need for frequent sampling at short intervals (e.g., monthly) to accurately assess fine root growth and turnover. Fine root production, estimated with in situ screens, was 1.5, l-g, and 0.9 Mg ha-’ yr-’ in the well-drained, intermediately drained, and poorly drained soils, respectively. Results from minirhizotrons indicated (hat fine roots in well-drained soils grew to greater depths while fine roots in poorly drained soils were restricted to surface soils. Minimizotrons also revealed that the distribution of fine roots among morphological dasses changed between well-drained and poorly drained soils. P WETLAND ECOSYSTEMS has been the focus of numerous studies. Most commonly, productivity is estimated using aboveground parameters such as litterfall and stemwood production (B&son et al., 1980; Conner and Day, 1992; Conner et al., 1993; Conner, 1994; Megonigal et al., 1997). Many investigators have acknowledged, however, that failure to include belowground data will seriously underestimate forest ecosystem productivity (Vogt et al., 1986a; Day and Megonigal, 1993). It has been suggested that fine root production accounts for up to 75% of total net primary production (NPP) in some forests (Nadelhoffer and Raich, 1992). Similar to aboveground foliage, large amounts of fine roots die annually and can contribute a quantity of litter similar in magnitude to foliar litter (McClaugherty et al., 1984). Fine root dynamics, therefore, represent a significant source of energy and nutrient flow through forested systems, particularly for those TerreU T. Baker III, College of Agriculture and Home Economics, New Mexico State Univ., Box 30003, MSC 3AE, Las Cruces, NM 88003-8003; William H. Conner, Baruch Forest Science Institute, P.O. Box 596, Georgetown, SC 29442; B. Graeme Lockaby, School of Forestry, Auburn Univ., 108 M.W. Smith Hall, Auburn, AL 36849. 5418; John A. Stanturf, USDA-Forest Service, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 38776; Marianne K. Burke, USDA-Forest Service, Southern Research Station Center for Forested Wetlands Research, 2730 Savannah Hwy., Charleston, SC 29414. Received 11 Mar. 1999. *Corresponding author (ttbaker@

Hydrologic, Riparian, and Agroecosystem Functions of Traditional Acequia Irrigation Systems

ABSTRACT Traditional cultures in arid landscapes of the southwestern United States and northern Mexico developed irrigation systems to irrigate floodplain valleys along streams and rivers. Many of these traditional irrigation systems, referred to as acequias, continue to be used today. Population growth in the region is creating pressures to convert agricultural land and irrigation water to urban and other uses. Unique hydrologic features of the acequia systems suggest that, beyond providing crop irrigation, they may provide additional valuable hydrologic, riparian, and agroecosystem functions worth maintaining. We investigated in detail the seepage and the groundwater response to seepage from a traditional acequia irrigation ditch along the Rio Grande in north-central New Mexico. We found that 16% of ditch flow seeps into the ditch bed and banks. Groundwater levels near the ditch and midway between the ditch and the river rise 1 m or more within three to four weeks following the start of the irrigation season. The elevated groundwater table produced by ditch and field seepage is sustained until late summer when groundwater levels again drop. The seepage that provides this annual groundwater recharge also sustains riparian vegetation along the main ditch and side ditches. In light of our hydrologic analysis, we considered seepage-supported riparian areas and their ecological functions including aquatic habitat, terrestrial habitat, and water quality effects. Acequia hydrology plays an important role in contributing to an ecologically healthy, agriculturally productive, and community-sustaining floodplain agroecosystem.

Riparian vegetation response to different intensities and seasons of grazing

Sustainable management of riparian ecosystems depends on our understanding of these complex systems. Thus far, the scientific literature has not adequately addressed the effects of livestock grazing on riparian areas in the American southwest. Most available information is observational, anecdotal, based on unreplicated experiments, or compares heavily grazed areas to areas from which livestock have been completely excluded. This study, in the Black Range of western New Mexico, compared effects of different seasons of use (cool season, warm season, and dormant season) and grazing intensities (light, moderate, and none) of cattle on young narrowleaf cottonwood (Populus angustifolia James) populations, and herbaceous vegetation in 2 adjacent southwestern riparian areas. Cottonwoods in lightly grazed and moderately grazed plots received significantly greater use than cottonwoods in ungrazed plots which experienced negligible grazing pressure. Increased grazing pressure did not have significant impacts on cottonwood populations. Effects of season of use were significant on both herbaceous species richness and diversity. We conclude that no single riparian area management approach is best in all situations, but the grazing treatments used in this study appear to have been successful at maintaining riparian communities.

One-Seed Juniper Sapling Use by Goats in Relation to Stocking Density and Mixed Grazing With Sheep

Abstract Suppression of one-seed juniper (Juniper monosperma [Englem.] Sarg.) reinvasion with goats requires achieving levels of defoliation of newly established saplings that eventually kill or suppress plant growth. We tested the effects of stocking density and mixed grazing with sheep on the level of use of one-seed juniper saplings by goats. In summer and spring, groups of 10 does (goats alone, GA) or 5 does and 4 ewes (mixed grazing, MG), grazed 20 × 30 m cells infested with saplings (500–533 · ha−1; mean: 0.8 m tall), either continuously for 6 d (low stocking density, LD) or with daily rotation through 10 × 10 m cells during the 6-d period (high stocking density, HD) in a block design. Feeding activity; juniper in feces; utilization of herbaceous vegetation; frequency of saplings with light, moderate, and heavy foliage and bark use; and branch utilization were determined. Goats in HD spent more time feeding on saplings, less time feeding on herbaceous forages, and tended to consume more juniper than goats in LD. Utilization of herbaceous vegetation ranged from 52% to 73% and was higher for MG than GA and for LD than HD. The MG–HD treatment resulted in the highest frequency of short saplings (< 0.5 m) with heavy defoliation in summer and spring, and lowest frequency of saplings with light debarking in spring. Heavy defoliation was more frequent in short saplings, whereas heavy debarking was more frequent in tall (> 1 m) saplings. Sapling mortality was not affected by treatments (P > 0.05) and averaged 5% across treatments. Branch debarking was greater in spring (P  =  0.02) and explained approximately 80% of branch mortality and 62% and 52% of the reduction in sapling live crown height and volume. Branch utilization (percent length) was not affected by grazing treatments (range: 45–48%), but was influenced by the length and diameter of branches. This study suggests that high stocking density and mixed grazing stimulate feeding behaviors that increase utilization of juniper saplings by goats. Susceptibility of saplings to defoliation and debarking varies with sapling size, branch structure, and season. Targeted grazing in spring appears to have a greater impact on sapling suppression and branch mortality due to higher debarking frequency.

New Mexico Blue Grama Rangeland Response to Dairy Manure Application

Abstract New Mexico supports over 290 000 dairy cattle. These cattle produce large quantities of manure. It has been suggested excess dairy manure could be applied to rangelands as an organic fertilizer to increase soil fertility and herbaceous production. Manure was applied June 2000 to a rangeland in New Mexico dominated by blue grama (Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths) according to phosphorus (P) content: a recommended (light) rate (54 kg P·ha−1) to enhance blue grama growth and a gross overapplication (heavy) rate (493 kg P·ha−1) to determine their effects on vegetation. The actual application rate of manure on a dry weight basis was 0, 11 739, and 107 174 kg·ha−1. Four replications of control, light, and heavy rates were established. Herbaceous standing crop (kg·ha−1) was similar 1 growing season after manure application, and greater 2 and 3 growing seasons after application on the light treatment compared with the control. Initially the heavy treatment suppressed herbaceous standing crop; thereafter, standing crop responded in a linear fashion to rainfall. Three growing seasons after manure application, basal cover was similar between light and control treatments, whereas the heavy treatment continued to be characterized principally by manure/litter cover. Heavy disposal-oriented treatments are not suitable for blue grama rangelands because of persistent declines in herbaceous cover and changes in soil salinity. A light manure application rate that is based on P content can increase forb and in particular grass standing crop on arid blue grama rangelands. Successful rangeland manure applications will depend on proper management to insure objectives are met while minimizing any hazards to the environment.

Streambank morphology and cattle grazing in two montane riparian areas in western New Mexico

Streambank morphology plays an important role in the ecosystem functions of stream and riparian areas. Large gaps remain in our understanding of the effects of livestock grazing on southwestern stream channels. The purpose of this study was primarily to evaluate the effects of different grazing intensities and different seasons of use on streambank morphology in two montane riparian areas in western New Mexico. We did not find significant larger-scale changes to streambanks over the duration of the study. In contrast, we found many smaller-scale changes that had taken place following cattle grazing. Because the smaller-scale changes we observed were not associated with other indicators of streambank alteration such as bank collapse, widening of the active channel, plant community change, or other larger-scale changes, we conclude that the smaller-scale changes we observed were part of the normal geomorphological adjustments made by streambanks and did not ultimately contribute to lasting streambank morphological change. We also stress that care needs to be given to the selection of appropriate response variables when examining streambank change. Livestock can potentially have large impacts on streambanks, and understanding the effects of grazing on streambank morphology is important in order to make good management decisions.

Mammals in Mechanically Thinned and Non-Thinned Mixed-Coniferous Forest in the Sacramento Mountains, New Mexico

Abstract Mechanical thinning is an important silviculture technique for timber production and reducing woody fuels in coniferous forest, but little is known about its effect on wildlife in mixed-coniferous forests in the American Southwest. During 2005–2006 we examined diversity, abundance and survival of terrestrial mammals in thinned and non-thinned mixed-coniferous forest in the Sacramento Mountains, Lincoln National Forest, in southern New Mexico. The three thinning treatments included two non-commercial thins with different slash treatments (i.e., lop-pile, lop-scatter) and a commercial harvest using selective logging. There were two non-thinned treatments that differed in age of stand (i.e., 20–30 years and 60–100 years post harvest). In general, thinned treatments had higher richness and abundance of mammals in comparison with the older non-thinned stand, but did not differ in richness and abundance from the younger non-thinned stand. Abundance of the North American deermouse (Peromyscus maniculatus) and red squirrel (Tamiasciurus hudsonicus) did not differ among treatments. However, survival of P. maniculatus varied more in the non-thinned stands. Abundances of the gray-footed chipmunk (Tamias canipes) and long-tailed vole (Microtus longicaudus) were significantly lower in the older non-thinned stand than in all thinned treatments. Most large mammals were documented in thinned treatments. These results suggest that thinning older stands of mixed-coniferous forest that are overly dense compared with historical conditions benefit the mammal community through increases in diversity and abundance. In comparing the three mechanical-thinning treatments evaluated, none provided a clear cost or advantage to mammals. However, additional controlled experiments are needed to further corroborate these results.

Elk Distributions Relative to Spring Normalized Difference Vegetation Index Values

Rocky Mountain elk (Cervus elaphus) that winter near San Antonio Mountain in northern New Mexico provide important recreational and economic benefits while creating management challenges related to temporospatial variation in their spring movements. Our objective was to examine spring distributions of elk in relation to vegetative emergence as it progresses across the landscape as measured by remote sensing. Spring distributions of elk were closely associated with greater photosynthetic activity of spring vegetation in 2 of 3 years as determined using NDVI values derived from AVHRR datasets. Observed elk locations were up to 271% greater than expected in the category representing the most photosynthetic activity. This association was not observed when analyses at a finer geographic scale were conducted. Managers facing challenges involving human-wildlife interactions and land-use issues should consider environmental conditions that may influence variation in elk association with greener portions of the landscape.

Rapid Assessment Methodology for Proactive Rangeland Management

April 2007 There is an increasing need for rangeland monitoring methodologies that provide rapid assessment of grazing conditions, with reasonable cost and labor requirements. Controversies and problems regarding livestock grazing management decisions on public lands have been on the rise during the past 15 years. Agencies managing public rangelands, primarily the Forest Service and Bureau of Land Management, are under increased pressure to be more proactive in their management decisions and to base these decisions on reliable quantitative data. These pressures have come from an affl uent rapidly growing human population that demands high-quality recreation, aesthetic appearance, and abundant wildlife populations from public rangelands. Drought, enforcement of the National Environmental Policy Act, and the desire by ranchers to better manage their rangelands have further increased the need for quick, practical, low-cost, and rapid assessment methods for grazing management decisions. In the late spring of 2002, rangelands throughout New Mexico were in the third year of severe drought (Fig. 1). In July, ranchers and agency personnel were facing important decisions regarding forage availability, carrying capacity, and length of grazing season on Forest Service lands near Santa Rapid Assessment Methodology for Proactive Rangeland Management

The effects of thinning trees and scattering slash on runoff and sediment yield within dense piñon-juniper woodlands in New Mexico, United States

This study evaluated the hydrologic effects of thinning piñon-juniper (P-J) (Pinus edulis var. Engl. and Juniperus spp.) woodlands in conjunction with oil and gas (O&G) development in dense woodlands. Utilizing rainfall simulation we compared the effects on the thinned areas to pipelines, undisturbed sites, and existing nearby roads with specific interest in (1) runoff and runoff per unit of precipitation (runoff/ppt), (2) infiltration, and (3) suspended sediment and sediment yield. Trees were removed with a combination of chainsaw cutting and mastication in 2004. Randomly selected within each of the eight research blocks and five treatments, rainfall simulation plots were randomly placed within intercanopy and canopy areas. Thinned intercanopy plots with basal areas of 1.2 m2 ha−1 (5 ft2 ac−1) had significantly less runoff and lower runoff/ppt levels when compared to the basal area 2.3 m2 ha−1 (10 ft2 ac−1) and control intercanopy plots. Roads exhibited significantly greater runoff than every other treatment in the analysis. Suspended sediment was hypothesized to trend similar to runoff; however, the results of this analysis revealed that only roads differed statistically from other treatments. Sediment yield was similar to the results for suspended sediment with the exception of the intercanopy plots. Both thinning treatments (363.1 and 234. 7 kg ha−1 [324.2 and 209.6 lb ac−1]) were significantly less than the control mean (719.7 kg ha−1 [642.7 lb ac−1]). When comparing whole treatments (combining basal area 5 [BA5] and basal area 10 [BA10] plots), there is convincing evidence that mean runoff/ppt was different among all treatments, except between the control and pipeline. Analysis of suspended sediment indicated that all treatments were significantly different from the roads, but not between all other treatments. There was, however, convincing evidence (p = 0.0033) that sediment yield of the treatment was less than the control. These whole treatment comparisons demonstrate the success of the treatments in reducing runoff/ppt and sediment yield within P-J woodlands and the potential for management to improve the hydrological function along O&G disturbances within the San Juan Basin.