Some effects of precipitation, soil moisture, and neighbor plant removal on growth of Lehmann lovegrass (Eragrostis lehmanniana) and mesa dropseed (Sporobolus flexuosus) in southern New Mexic

The phenological responses of mesa dropseed (Sporobolus flexuosus) and Lehmann lovegrass (Eragrostis lehmanniana) to precipitation, soil moisture and neighbor plant removal were investigated every two weeks during the summer growing seasons of 1993 and 1994. The two trials were conducted at three locations north of Las Cruces, NM. Plant responses measured were changes in plant basal area, plant height, tiller length, total number of leaves per tiller, number of green leaves per tiller, number of brown leaves per tiller, number of missing leaves per tiller, and upper most leaf length. Neighbor plant removal treatment levels were control (no removal), 4 plants/m$sp2$, 2 plants/m$sp2$, and 1 plant/m$sp2.$ Seedling growth and development trials were conducted in the greenhouse to monitor the growth of seedlings of both species at 20, 40, 60, and 80 days of age.;Plant growth was more directly associated with soil moisture rather than precipitation received during short intervals during the summer. Increase in plant height and tiller length of both species was moderately associated with current and previous date surface soil moisture and the association of plant height and tiller length growth of Lehmann lovegrass (R$sp2$ = 0.22-0.59) was stronger than that for mesa dropseed (R$sp2$ = 0.15-0.31). Growth of total number of leaves per tiller and number of green leaves per tiller was generally associated with current and previous subsoil moisture. Growth of plant basal area, and first top leaf length was not strongly correlated with either soil moisture or precipitation. Plant growth during the dry summer 1994 very low compared to that of 1993. Plant responses to neighbor plant removal started during August. Mesa dropseed growth increased with decreasing plant density; whereas Lehmann lovegrass either did not respond or showed negative responses.;The general growth of Lehmann lovegrass seedlings was faster and the growing period was shorter than that for mesa dropseed. Lehmann lovegrass reached reproductive stage within the period between 40 to 60 days of age; whereas mesa dropseed reached tiller elongation stage at 80 days of age. Lehmann lovegrass fresh root volume, dry weight, and root to shoot ratio decreased dramatically after 60 days of age.