Mechanical Rejuvenation to Dampen Seasonal Variation in Chemical Composition of Browse

Reynolds, J. L.; Fulbright, Timothy E.; Beasom, Samuel L.

doi:10.2307/4002577

Cited by 14 publications

(7 citation statements)

References 7 publications

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“…Although both species coexist in nutrient-limited habitats throughout most of their range, blackbrush acacia seedlings are smaller and are more physically defended than guajillo seedlings. The lower height and mass of blackbrush acacia seedlings, relative to guajillo seedlings, is consis-tent with observations that sprouts of mature blackbrush acacia grow less rapidly than those of mature guajillo following removal of top growth (Bozzo et al 1992, Reynolds et al 1992. Anti-herbivore defense strategies of the 2 species were similar in that both species had high tannin concentrations when nutrients were limited.…”

Section: Blackbrush Acacia Guajillosupporting

confidence: 72%

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Nutrient Enrichment, Tannins, and Thorns: Effects on Browsing of Shrub Seedlings

Cash

Fulbright

2005

Journal of Wildlife Management

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Blackbrush acacia (Acacia rigidula) and guajillo (Acacia berlandieri) are major browse species in diets of white-tailed deer (Odocoileus virginianus) in southern Texas and northern Mexico. We conducted both field and greenhouse experiments to test the hypotheses that (1) fertilization reduces tannins and spinescence in blackbrush acacia and guajillo seedlings, (2) thorn removal increases utilization of shrub seedlings by deer, and (3) fertilization alters seedling nutrient content, chemical composition, and growth characteristics. Guajillo seedlings grown in a greenhouse with high soil fertility were lower (P < 0.05) in protein-precipitating tannin content relative to guajillo seedlings grown with low fertility. In the field, tannin content and spinescence of fertilized and unfertilized seedlings were similar (P > 0.05). Fertilization increased the levels of nitrogen and digestible protein in shrub seedlings of both species grown in the greenhouse (P < 0.05), but low rainfall during the field study may have precluded a similar response. Intensity of browsing was similar on fertilized and unfertilized seedlings. Seedlings with thorns removed were browsed more heavily than those with thorns (P < 0.05) in the field, where several species of herbivores were present. However, in feeding trials with tame deer, thorns did not affect browsing intensity. Thorns may be more important than tannins in defending seedlings against herbivory, and may be more important in defending against browsing by lagomorphs and small mammals than against browsing by whitetailed deer. Transplanted seedlings of both species should be protected from herbivores during early stages of establishment. JOURNAL OF WILDLIFE MANAGEMENT 69(2):782-793; 2005

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Section: Blackbrush Acacia Guajillosupporting

confidence: 72%

“…Although blackbrush acacia and guajillo occur sympatrically on calcareous, relatively infertile soils, guajillo appears to grow relatively rapidly following plant damage, but blackbrush acacia grows slowly (Bozzo et al 1992, Reynolds et al 1992. Both shrub species are spinescent-armed with sharp-pointed woody outgrowths.…”

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confidence: 99%

Nutrient Enrichment, Tannins, and Thorns: Effects on Browsing of Shrub Seedlings

Cash

Fulbright

2005

Journal of Wildlife Management

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“…Chemical changes in the regrowth vegetation are typically short‐lived responses. For example regrowth shoots of Acacia berlandieri increased in crude protein, in vitro organic matter digestibility, and P and K content for about 6–8 months after disturbance (Fulbright et al 1991, Reynolds et al 1992). Morphological changes in the regrowth architecture of plants, such as increased branching or spine production, following mechanical damage are more permanent changes.…”

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confidence: 99%

The architecture of shrubs after defoliation and the subsequent feeding behavior of browsers

Cooper¹,

Owens²,

Spalinger³

et al. 2003

Oikos

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We examined regrowth architecture of 4 species of savanna shrubs following 4 levels of defoliation. Defoliation had little effect on the regrowth architecture of honey mesquite (Prosopis glandulosa), which is rarely browsed by mammalian herbivores. The 3 acacia species (Acacia berlandieri, A. greggii, A. schaffneri) responded to defoliation by increasing leaf and spine density on the regrowth branches, but spine length and branching architecture remained unchanged. Only A. greggii, which is a preferred food plant of many browsers, exhibited an increase in the number and length of current annual growth branches in response to defoliation. The changes in plant architecture due to defoliation had little effect on the subsequent feeding behavior of captive white‐tailed deer (Odocoileus virginianus). Food intake rate of the deer was most strongly related to internode distance, a parameter not significantly altered by defoliation. This suggests that the architectural responses of these shrubs to defoliation may not provide increased defense against browsing by co‐evolved mammals.

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“…Juvenile stems reached peak tyramine concentrations in July and peak NMP concentrations in September. Diet quality of ungulates during this period (July to September) is typically poor because low rainfall reduces biomass of forbs (Bozzo et al 1992, Reynolds et al 1992, Windels 1999. Wild and domestic ungulates rely heavily on browse from guajillo and blackbrush during dry summer and winter periods (Barnes et a1.1991, Martinez et al 1997, and thus may be doubly stressed from low nutrient and high phenolic amine intake.…”

Section: Discussionmentioning

confidence: 99%

Effects of aeration on phenolic amine content of guajillo

Windels¹,

Hewitt²,

Forbes³

2003

REM

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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.

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Mechanical Rejuvenation to Dampen Seasonal Variation in Chemical Composition of Browse

Cited by 14 publications

References 7 publications

Nutrient Enrichment, Tannins, and Thorns: Effects on Browsing of Shrub Seedlings

Nutrient Enrichment, Tannins, and Thorns: Effects on Browsing of Shrub Seedlings

The architecture of shrubs after defoliation and the subsequent feeding behavior of browsers

Effects of aeration on phenolic amine content of guajillo

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