Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
INFLUENCE OF UNDERSTORY REMOVAL, THINNING AND P FERTILIZATION ON N-2 FIXATION IN A MATURE MESQUITE (PROSOPIS-GLANDULOSA 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:
0140-1963(1997)36:4<591:IOURTA>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
SEMIARID SOUTH TEXAS; BIOMASS PRODUCTION; NATURAL-ABUNDANCE; SONORAN DESERT; NITROGEN; GROWTH; SOIL; N-15; ECOSYSTEMS; ACACIA;
Keywords:
PROSOPIS GLANDULOSA VAR GLANDULOSA; NATURAL STAND; MANAGEMENT TREATMENTS; N BALANCE; BIOMASS PRODUCTION; N-2 FIXATION; N-15 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 N-2 FIXATION IN A MATURE MESQUITE (PROSOPIS-GLANDULOSA VAR GLANDULOSA) STAND", Journal of arid environments, 36(4), 1997, pp. 591-610

Abstract

The natural abundance N-15/N-14 method was used to estimate the influence of silvicultural and P fertilization treatments on N accretion, N-2 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 N-2 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 above-ground 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 N-2 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 (R-2 = 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 N-2 fixation than larger trees which accumulated 1200 kg ha(-1) more N under their canopies. The percentage N derived from N-2 fixation ranged from 63 to 73% in the various treatments. Despite the high percentage of N derived from N-2 fixation, the N-2 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 % N-2 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