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Titolo: INFLUENCE OF UNDERSTORY REMOVAL, THINNING AND P FERTILIZATION ON N2 FIXATION IN A MATURE MESQUITE (PROSOPISGLANDULOSA VAR GLANDULOSA) STAND
Autore: VILLAGRA GML; FELKER P;
 Indirizzi:
 TEXAS A&M UNIV KINGSVILLE,CAESAR KLEBERG WILDLIFE RES INST,CTR SEMIARID FOREST RESOURCES KINGSVILLE TX 78363
 Titolo Testata:
 Journal of arid environments
fascicolo: 4,
volume: 36,
anno: 1997,
pagine: 591  610
 SICI:
 01401963(1997)36:4<591:IOURTA>2.0.ZU;2P
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 SEMIARID SOUTH TEXAS; BIOMASS PRODUCTION; NATURALABUNDANCE; SONORAN DESERT; NITROGEN; GROWTH; SOIL; N15; ECOSYSTEMS; ACACIA;
 Keywords:
 PROSOPIS GLANDULOSA VAR GLANDULOSA; NATURAL STAND; MANAGEMENT TREATMENTS; N BALANCE; BIOMASS PRODUCTION; N2 FIXATION; N15 NATURAL ABUNDANCE METHOD; SEMIARID ECOSYSTEM; AGROFORESTRY;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Science Citation Index Expanded
 Science Citation Index Expanded
 Citazioni:
 43
 Recensione:
 Indirizzi per estratti:



 Citazione:
 G.M.L. Villagra e P. Felker, "INFLUENCE OF UNDERSTORY REMOVAL, THINNING AND P FERTILIZATION ON N2 FIXATION IN A MATURE MESQUITE (PROSOPISGLANDULOSA VAR GLANDULOSA) STAND", Journal of arid environments, 36(4), 1997, pp. 591610
Abstract
The natural abundance N15/N14 method was used to estimate the influence of silvicultural and P fertilization treatments on N accretion, N2 fixation and N partitioning among tissues in a mature mesquite Prosopis glandulosa var. glandulosa stand in Texas. The silvicultural treatments consisted of understory removal, herbicide treatment of brushy resprouts, thinning trees to single stems and 100 kg ha(1) P fertilization. The trees had a mean basal diameter of 17.8 cm with 8 to 35 cm range. The stand was slow growing with the increase in dry matter ranging from 0.465 Mg ha(1) year(1) to 0.701 Mg ha(1) year(1) for the 8 years after the treatments were applied. N accretion after 8 years ranged from 3.1 kg ha(1) year(1) to 4.4 kg ha(1) year(1). Due to the range in delta(15)N of the leaves, twigs, branches and trunk, we used the weighted (by biomass) average delta(15)N per tree in calculations of the percent N derived from N2 fixation (%Ndfa). There was considerable variability in delta(15)N Of the reference plants, i.e. from 3.3 to 5.9. In contrast there was low variability in the background delta(15)N of nearby soils (7.0 +/ 1.0). As the total aboveground biomass delta(15)N Of a grass grown outside the influence of mesquite (7.8 +/ 0.58) had the same delta(15)N as the soil (7.5 +/ 1.0), we used the grass outside the influence of mesquite and the weighted tree mean delta(15)N to calculate % of N derived from N2 fixation. The decrease in intraspecific competition by thinning multistemed trees to single stemmed trees was the only treatment that significantly (p = 0.0001) increased growth. Interspecific competition, i.e. understory removal, did not increase growth. There were no significant differences in total N production or N fixation among treatment means. The most striking result was the highly positive correlation between tree delta(15)N and total N per tree and biomass per tree (R2 = 0.90, F = 164.4, df. = 18,Mean square error (MSE) = 0.155, p 0.0001). This implies that the younger trees colonizing infertile soils relied more heavily on N2 fixation than larger trees which accumulated 1200 kg ha(1) more N under their canopies. The percentage N derived from N2 fixation ranged from 63 to 73% in the various treatments. Despite the high percentage of N derived from N2 fixation, the N2 fixation of the stand was very low, i.e. 1.98 to 2.80 kg N ha(1) year(1), due to the low growth of the stand. We believe that comparisons of the whole tree weighted delta(15)N to background soil delta(15)N provides a more reasonable approach toestimate % N2 fixation than comparisons of leaves of fixers and reference plants.
ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 05/12/20 alle ore 20:19:49