Net primary production and seasonal herbaceous dynamics following brush management

Abstract

Aboveground net primary production (ANPP), seasonal herbaceous dynamics, and herbage quality were evaluated in 1979 and 1980 in the northern Rolling Plains of Texas following the installation of brush management treatments in 1974. Treatments chosen for study were: untreated; aerial application of 2,4,5-T + picloram(1:1) at 0.6 kg/ha; and root plowed and seeded with Kleingrass. Environmental factors were related to the vegetational responses following brush management. Aboveground net primary production was estimated by summing peak standing crop measurements of current year's growth (live + recent dead tissue) by species functional groups. Averaged over the 2 years, ANPP on the seeded areas was 369 g/m('2) as compared to 201 and 202 g/m('2) on the untreated and sprayed areas, respectively. Herbage dynamics were similar on the untreated and sprayed areas, with standing crop measurements following the same trend during both years. Standing crop values were generally higher at each sampling date on the seeded area, with peak standing crop occurring approximately 1 month later than on untreated and sprayed areas. Herbage on untreated and sprayed rangeland was dominated by buffalograss. Crude protein (%) and digestible energy (kcal/g) were generally higher in the herbage from the untreated and sprayed plots than from the seeded area. Differences among treatments in species composition and amount of live material were the principle factors contributing to the quality differences. Brush management effected herbage productivity, growth dynamics, quality, and species diversity on the seeded area compared to the untreated area. However, the same parameters on the area sprayed with 2,4,5-T + picloram generally did not differ from those on the untreated site.