Effects of Aeration on Phenolic Amine Content of Guajillo

Abstract

Aeration is a common range management technique used in southern Texas and northern Mexico to reduce shrub cover and increase biomass of more palatable forages. Guajillo (Acacia berlandieri Benth.) is an important forage plant for deer and domestic livestock throughout its range in northeastern Mexico and southern Texas. It responds to top removal, such as by aeration, by producing large numbers of juvenile sprouts which can have higher total leaf nitrogen content up to 6 months after treatment. However, the concentration of phenolic amines, potentially toxic secondary plant chemicals, may also increase. We compared concentrations of tyramine and N-methyl-phenethylamine (NMP), 2 prominent phenolic amines that can negatively affect reproduction in herbivores, between juvenile (regrowth) and mature stems of guajillo in areas that had been aerated and also between mature stems in aerated and control sites. Aeration increased NMP but not tyramine concentrations in mature stems. Juvenile stems had higher total nitrogen concentration than mature stems but also had higher amine concentrations until about 1 year after aeration. A greater percent of total nitrogen was incorporated into amines in juvenile stems (2.5-6.0%) than mature stems (1.8-4.2%). Amine concentrations peaked in summer and early autumn, a period when herbivores may rely heavily on browse because forbs are scarce. Our results suggest that while aeration may result in higher nitrogen concentrations in guajillo, increases in amines may limit benefits to herbivores.

Above-ground biomass and carbon and nitrogen content of woody species in a subtropical thornscrub parkland

“…The former has implications for primary production, whereas the latter has implications for decomposition and herbivory. For example Windels et al (2003) showed stems of Acacia berlandieri, a species not included in this study, contained 1.8-6.0% of N in stems as amine-based defensive compounds.…”

Effects of Plant Secondary Compounds on Nutritional Carrying Capacity Estimates of a Browsing Ungulate

“…Because juvenile-phase root sprouts and seedlings of Acacia spp. are often higher in total nitrogen and secondary metabolites such as tannins and phenolic amines (Bryant et al 1991;Windels et al 2003), juvenile blackbrush and guajillo stems were counted separately each season within one 2 X 5 m plot at each sample point to determine density. Biomass of juvenile sprouts was estimated by clipping 5-15 samples of five sprouts each of guajillo and blackbrush, which were dried and weighed as above.…”

“…Estimates of nitrogen in phenolic amines present in Acacia spp. leaf tissues were derived from a concurrent study of tyramine and n-methyl-B-phenethylamine (NMP) content of guajillo for the same pastures (see Windels et al 2003).…”

“…and blackbrush (Acacia rigidula Benth. ), grow in the region, seasonally may comprise up to 60% of white-tailed deer diets (Barnes et al 1991;Ramirez et al 1997), and contain high concentrations of tannins (Seigler et al 1986) and nitrogen containing phenolic amines (Clement et al 1997(Clement et al , 1998Windels et al 2003).…”

Diet Mixing and Supplementation Present an Opportunity to Increase the Use of Encroaching Woody Plants by Goats

“…Even though the effects of diet mixing [18][19][20][21][22] and nutrient supplementation [16,23] on the intake of PSM-rich plants have previously been shown elsewhere, very little evidence (if at all) is based on arid/semiarid African savannas. Most of what is known so far on diet mixing is based on studies in North American and Mediterranean ecosystems [18][19][20][21][22] that are predominantly endowed with nitrogen-based PSMs [18,24]. Given that African savanna woody plants are predominantly defended by carbon-based PSMs [25][26][27], such as condensed tannins, the detoxification limitation theory may not adequately explain how PSMs mediate plant-herbivore interactions in African savanna ecosystems.…”