Height and mowing of pasture at the end of winter modulate the tillering of Marandu palisadegrass in spring

In pastures subjected to stockpiling, the tiller population goes through an intense process of self-thinning, hindering the recruitment of new tillers in the subsequent season. We evaluated different pasture management strategies in late winter in an attempt to modify tiller recruitment during spring. Urochloa brizantha cv. Marandu was maintained at 4 different levels (heights) of stockpiled pasture at the end of winter: short (15.1 cm), medium (23.2 cm), tall (31.4 cm) and tall/mown (31.3 cm, mown to 8 cm). In October (early spring), the short and tall/mown pastures had a tiller appearance rate (TAR) and a population stability index (PSI) superior (P<0.05) to that of the tall pasture. During the remainder of the growing season, these characteristics (TAR and PSI) were similar for all pastures. Tiller survival rate (TSR) was also highest (P<0.05) in short pasture in early spring. TAR values were highest in early spring and these tillers persisted throughout the growing season. When stockpiling Marandu palisadegrass pasture during spring it is important to have it short at the end of winter to ensure early and intense tillering in spring. If pasture is tall at the end of winter mowing at this time before spelling is advantageous.

Higher-order bud production increases tillering capacity in the perennial caespitose grass Scribner’s Panicum (Dichanthelium oligosanthes)

The persistence and dynamics of perennial grass populations strongly depend on tiller recruitment from the bud bank. Because of the structural organization of grasses as populations of phytomers, bud production and tillering are constrained by morphology. An infrequent trait observed in only a few caespitose grasses is the branching of buds to produce higher-order buds prior to tiller development. We studied bud bank dynamics in Dichanthelium oligosanthes (Schult.) Gould a C3 perennial caespitose grass widely distributed in the eastern Great Plains. A hierarchy of bud development occurred in D. oligosanthes, with primary buds branching to produce secondary, tertiary, and quaternary buds. This higher-order bud production increased the overwintering propagule supply for spring recruitment by 4.5 times, and more than half of successful tiller recruits originated as higher-order buds. The temporal patterns of higher-order bud production and development suggest that growing season length may be an important factor determining the extent of higher-order bud production and subsequent year tiller natality in D. oligosanthes. Higher-order bud production likely has important consequences for the population dynamics of grasses. It may increase bud bank densities and tillering capacity, buffer population dynamics, and increase intraclonal tiller densities and resource consolidation in caespitose grasses.

Aerial and detritus production of the cordgrass Spartina densiflora in a southwestern Atlantic salt marsh

We used a nondestructive method to estimate aerial and detritus productivity of the cordgrass Spartina densiflora Brongn. and evaluated the relative contribution of newly emerged and preexisting tillers to net aerial biomass and detritus production, the relative contribution of tiller detachment and leaf shedding to detritus production, and the incidence of crab ( Neohelice ( Chasmagnathus ) granulata (Dana, 1851)), herbivory in relation to tiller age and its implications for tiller survival. Estimates of aerial and detritus productivity varied between 706.72 (SD = 153.38) and 786.15 (SD = 162.75) g·m–2·year–1 and between 1054.23 (SD = 224.49) and 1223.17 (SD = 246.84) g·m–2·year–1, respectively. These estimates of aerial production are far below the higher productivity estimates known for species of the genus Spartina but within the range of values obtained with nondestructive methods (i.e., 300–1500 g·m–2·year–1). Detachment of standing-dead tillers and leaf shedding contributed virtually in equal quantities to detritus production (i.e., 52% and 48% of the total detritus biomass, respectively). On the other hand, net aerial biomass production was highly dependent on tiller recruitment, with 67% of total biomass production contributed by the growth of tillers that emerged during the course of the study. However, crabs seem to graze on tillers irrespective of their age. Such nonselective crab grazing on tillers of different age together with the long tiller survival after crab grazing (often more than a year) suggests that crabs do not ostensibly affect S. densiflora production.