Changes in species biomass in the Coastal Prairie of Texas when light and nutrients are altered

Abstract

1992. Changes in species biomass in thc Coastal Prairic of Texas when light and nutrients are altered. Can. J. Bot. 70: 1777-1783. A 2 X 2 factorial experiment using light and nutrients as factors was carried out over 2 % years in a remnant, native Coastal Prairie of Texas. Light level, nutrient level, and date of sampling all had significant influences on total biomass, but changes were subtle, suggesting additional limiting factors. More obvious were changes in biomass of individual species, especially the dominant C, grass species. Schizachyriutn scopnrilirn (Michx.) Nash (little bluestem), Pnspal~irrr plicnt~ilum Michx. (brownseed paspalum), and Sorghastrurtr lzutans (L.) Nash (Indian grass), three C, grasses, maintained their biomass at low nutrient levels throughout the study. Sorghastrurn trrirans responded to higher nutrient levels with increased biomass, whereas the biomass of S. scopariurn and P. plicatrilurn decreased. Results suggest that remnant grassland communities dominated by P. plicaturn and S. scopariur~r are relatively stable conlnlunities maintained by yearly mowing, which removes biomass and nutrients. With the accunlulation of litter, surface light levels would decrease, soil nutrients would increase, and S. nutans biomass would increase at the expense of P. plicatulurn and S. scopariurn. VAN AUKEN, 0. W., BUSH, J. K., et DIAMOND, D. D. 1992. Changes in species biomass in the Coastal Prairie of Tcxas when light and nutrients are altered. Can. J. Bot. 70 : 1777-1783. Les auteurs ont conduit une expkrience factorielle 2 x 2 impliquant les facteurs lumikre et nutriment; cette expCrience a d u d deux ans et demi dans un vestige de la prairie c6tikre aborigttne du Texas.L'intensitC lumineuse, la teneur en nutriments et la date d'Cchantillonage montrent toutes des influences significatives sur la biomasse totale, mais il y a des modifications subtiles qui suggkrent l'existence d'autres facteurs limitants. Ce qui est le plus remarquable, ce sont les changements de biomasse d'espttces individuelles, surtout les espkces herbacCes dominantes en C,. Trois herbacees en C, ont maintenu une biomasse constante aux niveaux infkrieurs en nutriments : ce sont Sclliznchyririm scoparium (Michx.) Nash, Pnspalrirn plicatulrttn Michx. et Sorghnsrrritn nutans (L.) Nash. Le S. trutans reagit 5 des teneurs plus ClevCes en nutriments par une augmentation de biomasse, alors que les biomasses du S. scoparium et du P. plicatrilurn diminuent. Les rksultats suggkrent que les communautCes d'herbacies vestigiales dominCes par les P. plicntrilri~~z et S. scopnrirtm sont des communautCs relativement stables, maintenues par une tonte annuelle, qui Climine la biomasse et les nutriments. Avec une accumulation de litikre, les niveaux de lumikre en surface diminueraient, les nutriments augmenteraient dans le sol et la biomasse du S. nutans augmenterait aux dCpens de celles des P. plicatulrttn et S. scopnrium.

Restoration of Former Grassland in South-Central Texas

“…Present in the San Antonio grasslands in the past were Schizachyrium scoparium, Paspalum plicatulum and Sorghastrum nutans communities over Alifisol soils (Diamond and Smeins 1985). Two of these species (Schizachyrium scoparium and Sorghastrum nutans, but no Paspalum plicatulum or Andropogon gerardii) were found in the restored area of our study but at low cover compared to mature tallgrass prairie (Collins et al 1975;Sims 1988;Van Auken et al 1992a, 1992bDiggs et al 1999). These species were not present in the woodland understory adjacent to the restored area of the Park.…”

“…2). However, some C 4 grasses established and further development and spread of these grasses is expected as succession continues (Sims 1988;Van Auken et al 1992a, 1992b Van Auken and Bush 2013). In the future, a variety of additional C 4 grasses should establish and those present will increase in cover, with a plateau of the C 4 grasses occurring between 10 and 20 years after the establishment on the restoration site.…”

Soil Depth and Changes in Dry Mass and Competitive Intensity of Two C<sub>4</sub> Grasses

“…When S. scoparium was examined in common garden competition experiments, it was one of the strongest competitors [51], however, in field experiments it was one of the most suppressed species [51,61]. In unfertilized plots, belowground competition limited S. scoparium; while in fertilized field plots, both above-and belowground competition limited S. scoparium [51].…”

“…Schizachyrium scoparium can reduce soil nitrate at shallow soil depths and in the middle of the growing season, thus deeper rooted and earlier growing species are more likely to be co-dominants [22]. Apparently S. scoparium is restricted to low productivity habitats or deeper soils [61][62][63].…”

Competition between Schizachyrium scoparium and Buchloe dactyloides: The role of soil nutrients

“…In common garden competition experiments, S. scoparium was one of the strongest competitors (see Wilson and Tilman, 2002), however in field experiments, S. scoparium was one of the most suppressed species (Van Auken et al, 1992a;see Wilson and Tilman, 2002). Competition experiments showed that in unfertilized plots belowground competition limited S. scoparium; while in fertilized field plots, both above-and belowground competition limited S. scoparium (see Wilson and Tilman, 2002).…”