Long-Term Effects of Root Plowing on Vegetation in the Eastern South Texas Plains

Abstract

The long-term effects of root plowing ln plant communities in south Texas are not clearly understood. Our objective was to compare plant species composition and diversity on root-plowed rangelands and untreated rangelands. Two rangeland sites that were root plowed during 1973-74 and 2 sites of native, untreated brush were selected on the Santa Gertrudis Division of the King Ranch, Kleberg and Jim Wells counties, Texas. Woody plant canopy cover was estimated with the line intercept method, and density was estimated with 20-x l-m plots during 1990. Herbaceous canopy cover was estimated with 20 x 50-cm quadrats. Percent grass, litter, and bare ground coverage were similar on root-plowed and untreated rangelands. Woody plant species and diversity averaged 19 f 2 species/ treatment (Z f SE) and 2.56 f 0.15 on untreated areas compared to 7 f 1 species/treatment and 1.18 f 0.01 on root-plowed areas. Forb canopy coverage on root-plowed sites was about twice that of untreated sites. Huisache (Acucia smalfZIlsey) canopy cover and density were both more than 'I-fold greater on root-plowed sites than on untreated sites. Browse species preferred by white-tailed deer (OdocoiZeus virginianus Raf.), such as colima [Zanttroxylumfirgora (L.) Sarg.] and guajillo (Acucia berlandieri Benth.), were absent on root-plowed sites.

Plant and soil surface responses to a combination of shrub removal and grazing in a shrub-encroached woodland

“…We also predicted that grazing and ploughing would reduce plant diversity and composition by maintaining the dominance by shrubs, consistent with results worldwide (e.g., Bisigato and Bertiller, 1997;Ruthven III et al, 1993). Third, we anticipated shrub species-dependent treatment effects, specifically increases in the densities of grazing-and ploughing-tolerant species such as E. sturtii and Eremophila gilesii but reductions in grazing-and ploughing-sensitive species such as Acacia aneura and D. viscosa under the active pastoral treatment.…”

“…Stock removal through exclosure produces conflicting results (Trodd and Dougill, 1998;Angassa and Oba, 2007) and in most cases, shrubs continue to maintain their dominance even after complete grazing removal (West et al, 1984;Eccard et al, 2000;Valone et al, 2002;Guo, 2004;Mengitsu et al, 2005;Angassa and Oba, 2007). Mechanical removal of shrubs generally produces only short-term changes in plant community structure (Morton and Melgoza, 1991;Robson, 1995;Allegretti et al, 1997), often stimulates shrub regrowth, and leads to the eventual persistence and dominance by woody shrubs (e.g., Ruthven III et al, 1993). Post-treatment management of stocking rates is rarely considered by land managers, and many failures are thought to be due to the suppression of grass growth due to overgrazing (Cox et al, 1984).…”

Population Ecology of Hybrid Mesquite (Prosopis Species) in Western Australia: How Does it Differ from Native Range Invasions and What are the Implications for Impacts and Management?

“…Second, we found a sizeable mesquite sapling bank (seedlings and juveniles) in the Pilbara, which has not been reported within its native range where seedlings are typically absent under mature trees, and seedlings that do emerge eventually die (Bush and van Auken 1987; Ruthven et al 1993). This has important consequences for the long-term successional trajectories of mesquite in the Pilbara as compared with nativerange populations.…”

Above-ground biomass and carbon and nitrogen content of woody species in a subtropical thornscrub parkland

“…If this reversal in N concentrations held true for a large portion of stems within a canopy, such an allocation pattern could have physiological significance for individual plants. However, effects of G. angustifolium on ecosystem C and N dynamics would vary in relation to its abundance which ranges from uncommon at our La Copita site, to 13 plants ha À1 (Ruthven et al, 1993), and 41000 plants ha À1 on other sites in southern Texas (Fulbright and Beasom, 1987).…”