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ROBERT M. BODDEY CLAUDIA P. JANTALIA PAULO C. CONCEIÇÃO JOSILEIA A. ZANATTA CIMÉLIO BAYER JOÃO MIELNICZUK JEFERSON DIECKOW HENRIQUE P. DOS SANTOS JOSÉ E. DENARDIN CELSO AITA SANDRO J. GIACOMINI BRUNO J.R. ALVES SEGUNDO URQUIAGA 《Global Change Biology》2010,16(2):784-795
Conservation agriculture can provide a low‐cost competitive option to mitigate global warming with reduction or elimination of soil tillage and increase soil organic carbon (SOC). Most studies have evaluated the impact of zero till (ZT) only on surface soil layers (down to 30 cm), and few studies have been performed on the potential for C accumulation in deeper layers (0–100 cm) of tropical and subtropical soils. In order to determine whether the change from conventional tillage (CT) to ZT has induced a net gain in SOC, three long‐term experiments (15–26 years) on free‐draining Ferralsols in the subtropical region of South Brazil were sampled and the SOC stocks to 30 and 100 cm calculated on an equivalent soil mass basis. In rotations containing intercropped or cover‐crop legumes, there were significant accumulations of SOC in ZT soils varying from 5 to 8 Mg ha?1 in comparison with CT management, equivalent to annual soil C accumulation rates of between 0.04 and 0.88 Mg ha?1. However, the potential for soil C accumulation was considerably increased (varying from 0.48 to 1.53 Mg ha?1 yr?1) when considering the soil profile down to 100 cm depth. On average the estimate of soil C accumulation to 100 cm depth was 59% greater than that for soil C accumulated to 30 cm. These findings suggest that increasing sampling depth from 30 cm (as presently recommended by the IPCC) to 100 cm, may increase substantially the estimates of potential CO2 mitigation induced by the change from CT to ZT on the free‐draining Ferralsols of the tropics and subtropics. It was evident that that legumes which contributed a net input of biologically fixed N played an important role in promoting soil C accumulation in these soils under ZT, perhaps due to a slow‐release of N from decaying surface residues/roots which favored maize root growth. 相似文献
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SEGUNDO RIOS MANUEL B. CRESPO DIEGO RIVERA 《Botanical journal of the Linnean Society. Linnean Society of London》2001,136(2):247-254
Orophilous taxa of Sideritis sect. Sideritis (Lamiaceae) are rare, although highly diversified in south-eastern Spain. Most of them belong to subsections Hyssopifolia and Fruticulosa and show very reduced distribution areas in the summits of the highest Betic mountains. The inaccessibility of their habitats has meant that many of them have been described only within the last twenty years. In this context, a new species Sideritis tugiensis is described in subsection Hyssopifolia , from the Oromediterranean summits of Sierra de Segura (south-eastern Spain). It is a woody, cushion-shaped plant, resembling both S. carbonellis Socorro (subsect. Hyssopifolia) and S. glacialis Boiss., s.l. (subsect. Fruticulosa) , though important morphological divergences warrant recognition at species rank. Data on morphology, ecology and chorology of the new species are reported, and affinities and differences with regard to close taxa from other subsections are presented. Evolutionary trends in the whole aggregate are briefly discussed. 相似文献
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MANUEL B. CRESPO SEGUNDO RÍOS JOSÉ L. VIVERO JOSEFA PRADOS ESTEBAN HERNÁNDEZ-BERMEJO M. DOLORES LLEDÓ 《Botanical journal of the Linnean Society. Linnean Society of London》2005,149(1):121-128
Vella castrilensis sp. nov. is described from the high mountains of Granada and Jaén provinces (south-eastern Iberian Peninsula), where it grows on calcareous soils. It is a hexaploid (2 n = 68) spineless dwarf shrub, woody at the base, with oblong-lanceolate, entire to shallowly dentate leaves and fruit with an acute tongue-shaped stylar segment and strongly reticulate-nerved valves. The characteristic unique combination of vegetative, karyological and reproductive features of V. castrilensis is not present in any described taxon of the genus, and warrants recognition at the species rank. Affinities and differences with other related taxa are discussed. Phylogenetic, biogeographical, bioclimatic, ecological data and conservation proposals are also reported. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 121–128. 相似文献
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