Carbohydrate Reserve, Phenology, and Growth Cycles of Nine Colorado Range Species

Abstract

Nine Colorado range species were studied for two consecutive years to relate the carbohydrate reserve status with phenological stage of development and current annual growth, including leaf, twig, or seedstalk length, or plant height. The species were fourwing saltbush (A triplex canescens), antelope bitterbrush (Purshia tridentata), little rabbitbrush (Chrysothamnus vicidiflorus), fringed sagewort (A rtemisia frigida), scarlet globemallow (Sphaeralcea coccinea), blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), James' cryptantha (Cryptantha jamesii), and pricklypear cactus (Opuntia polyacantha and rhodantha in a mixed stand). Seasonal total nonstructural carbohydrate (TNC) reserve cycles were related to phenological stages of development. Growth of all species appeared to be stimulated by late-summer or fall precipitation. Growth was found to be related inversely to carbohydrate reserve storage. Fourwing saltbush and antelope bitterbrush had typical V-shaped annual carbohydrate reserve cycles, and little rabbitbrush had a somewhat flat or extended V-shaped cycle. Fringed sagewort, scarlet globemallow, and western wheatgrass had flat or extended V-shaped cycles and maintained low reserves for more of the growing season than any of the species with typical reserve cycles. Blue grama was the only species that exhibited a narrow V-shaped cycle. The shape of the seasonal TNC cycle appeared to be a good screening tool for assessing the relative effects of defoliation on different plant species. Plants that replenished reserves rapidly after spring drawdown and regrowth periods, and minimized the part of the growing season with low reserve status, were least affected by defoliation and recovered rapidly from severe defoliation.

Rhizosphere interactions, carbon allocation, and nitrogen acquisition of two perennial North American grasses in response to defoliation and elevated atmospheric CO2

“…Plant production responses in our study were consistent with multiple field and laboratory studies indicating that B. gracilis is highly grazing resistant, while P. smithii can exhibit some negative responses (Menke and Trlica 1981;Polley and Detling 1988;Eneboe et al 2002;Milchunas et al 2008). Also consistent with previous field studies, we found elevated CO 2 influenced both species through water relations (reduced water stress; LeCain et al 2003), enhanced production of the C 3 grass (Read and Morgan 1996;Morgan et al 2004b), and reduced shoot [N] for the C 3 grass (Read and Morgan 1996;King et al 2004).…”

“…Both species increased allocation of N and 15 N to regrowing shoots during the first 8 days after defoliation. However, the large allocation to shoot regrowth in P. smithii occurred at the expense of roots, while the smaller amount of N allocated to shoot regrowth in B. gracilis was not associated with a concomitant decline in root N. Over the course of a growing season, B. gracilis maintains more consistent levels of root and crown carbohydrate reserves compared to other co-occuring grasses and forb species, while P. smithii can show substantially depleted root and crown carbohydrate reserves during periods of aboveground growth (Menke and Trlica 1981). This pattern reflects the relatively high and consistent allocation of photosynthate to roots and crowns by B. gracilis, and the substantially higher root:shoot ratios found in shortgrass steppe dominated by B. gracilis, as compared with other grassland ecosystems .…”

“…Previous studies emphasized the importance of root carbohydrate remobilization and allocation aboveground to support leaf regrowth (e.g., Detling et al 1979;Menke and Trlica 1981;Detling and Painter 1983), but have given less attention to rhizosphere processes and their effects on N acquisition for regrowth. Root exudates comprise 15-17% of total C fixed by B. gracilis and P. smithii under hydroponic conditions (Biondini et al 1988) and at least 17% in native shortgrass steppe (Milchunas and Lauenroth 1992), but the effect of grazing on rhizodeposition has not been evaluated.…”

Photosynthetic parameters and carbon reserves of a resurrection plant Reaumuria soongorica during dehydration and rehydration

“…The continued oversupply and accumulation of carbon suggest that storage carbohydrates have an important ecological role. The following hypotheses have been proposed to account for the functional significance of storage: (1) support of vegetative regrowth following dormancy (Menke and Trlica 1981), (2) support of sexual or vegetative reproduction during the absence or shortage of photosynthesis (Tissue and Nobel 1990), (3) recovery from herbivory (Dankwerts 1993) and (4) survival during dormant periods and under shading (Wyka 1999).…”

Facteurs de pression sur les parcs agroforestiers à <i>Vitellaria paradoxa</i> et à <i>Neocarya macrophylla</i> dans le Sud-ouest du Niger (Afrique de l’Ouest)

“…En effet, elle laisse sur place soit des sols fortement dénudés, soit à une nouvelle végétation indésirable, à une prolifération des espèces buissonnantes et non fourragères et à une augmentation des espèces annuelles éphémères aux dépens de la régénération naturelle (Boujghagh et Chajia, 2001). Les effets directs du broutage sur la production et la survie des ligneux ont été profondément étudiés par plusieurs chercheurs en simulant le broutage des herbivores en coupant des feuilles, rameaux et petites branches (Willard et McKell, 1978 ;Menke et Trlica, 1981 ;Tothill et Mott, 1985 ;Roy, 1991). Il ressort de ces études que l'impact d'une exploitation des ligneux dépend de la quantité d'eau et d'éléments nutritifs extraite du système, de la saison, de la fréquence de prélèvement et de la capacité de la plante à supporter le stress.…”