scholarly journals A new Hauterivian palynoflora from the Vale Cortiço site (central Portugal), and its palaeoecological implications for western Iberia

2019 ◽  
Vol 59 (2) ◽  
pp. 215-228
Author(s):  
Mário Miguel Mendes ◽  
France Polette ◽  
Pedro P. Cunha ◽  
Pedro Dinis ◽  
David J. Batten
Keyword(s):  
Ground Cover ◽  
Fossil Plants ◽  
Conifer Forest ◽  
Understorey Vegetation ◽  
Palynological Assemblage ◽  
Mixed Conifer Forest ◽  
Riverine Environment ◽  
Central Portugal ◽  
Angiosperm Pollen ◽  
Open Woodland

Abstract Palynofloral assemblages are an invaluable source of information about the interactions between fossil plants and their environments. Here we describe a new Early Cretaceous palynoflora from the Lusitanian Basin in the Estremadura region of central western Portugal. A palynological assemblage of 28 genera and 40 species was extracted from 14 samples collected in the Vale Cortiço clay pit complex near the small village of Ameal (Torres Vedras Municipality). The source is a dark grey mudstone layer belonging to the lower part of the Santa Susana Formation, which is considered to be of early Hauterivian age. The palynoflora is dominated by fern spores and gymnosperm pollen. Bryophyte and lycophyte palynomorphs are also present but subordinate. Angiosperm pollen and algal or dinoflagellate cysts were not recognised in the studied samples. The palynological assemblage represents mixed conifer forest with the ground cover and understorey vegetation dominated by ferns, with patchy occurrences of bryophytes and lycophytes. A riverine environment with surrounding vegetation of open woodland and ground cover primarily of ferns is strongly indicated for the region.

Tertiary vegetation, climate, and altitude of the Rio Grande depression, New Mexico–Colorado

Paleobiology ◽  
1976 ◽  
Vol 2 (3) ◽  
pp. 235-254 ◽  
Author(s):  
Daniel I. Axelrod ◽  
Harry P. Bailey
Keyword(s):  
Rio Grande ◽  
Late Eocene ◽  
Rio Grande Rift ◽  
Mean Annual Temperature ◽  
Late Oligocene ◽  
Fossil Plants ◽  
Conifer Forest ◽  
Mixed Conifer Forest ◽  
Subalpine Zone ◽  
Volcanic Pile

Late Eocene to middle Oligocene floras from the area of the present Rio Grande depression represent a time sequence from the upper part of mixed subtropical forest (Bernalillo flora), to an ecotone between broadleaved sclerophyll and mixed conifer forest (Red Rock Ranch flora), to subalpine conifer forest (Hillsboro and Hermosa floras). The implied difference in mean annual temperature of ~ 11°C suggests that altitude increased 2,000 m in 6–8 my. Construction of the Datil-Mogollon volcanic pile, averaging about 1,200 to 1,500 m thick, is thought to be largely responsible for the forest zonation, but regional doming accompanying volcanism may also be involved. The Oligocene subalpine conifer forests now occur in the piñon-juniper belt 900 and 1,200 m below the present subalpine zone, consistent with the subsidence that formed the Rio Grande rift beginning in the late Oligocene/early Miocene and continuing to the present. Later epeirogenic uplift of ~ 1200 m is implied by fossil plants in the Galisteo (~ 40 my bp), Creede (~ 27 my bp) and Tesuque (~ 14 my bp) Formations that border, or are in the rift.

Spatial variability in microclimate in a mixed-conifer forest before and after thinning and burning treatments

2010 ◽  
Vol 259 (5) ◽  
pp. 904-915 ◽  
Author(s):  
Siyan Ma ◽  
Amy Concilio ◽  
Brian Oakley ◽  
Malcolm North ◽  
Jiquan Chen
Keyword(s):  
Spatial Variability ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
Before And After

Development of the mixed conifer forest in northern New Mexico and its relationship to Holocene environmental change

2008 ◽  
Vol 69 (2) ◽  
pp. 263-275 ◽  
Author(s):  
R. Scott Anderson ◽  
Renata B. Jass ◽  
Jaime L. Toney ◽  
Craig D. Allen ◽  
Luz M. Cisneros-Dozal ◽  
...  
Keyword(s):  
New Mexico ◽  
Pinus Ponderosa ◽  
Late Glacial ◽  
Conifer Forest ◽  
Lake Levels ◽  
Mixed Conifer ◽  
The Holocene ◽  
Groundwater Levels ◽  
Mixed Conifer Forest ◽  
Jemez Mountains

Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one of the few records of late-glacial and postglacial development of the mixed conifer forest in southwestern North America. The Chihuahueños Bog record extends to over 15,000 cal yr BP. AnArtemisiasteppe, then an openPiceawoodland grew around a small pond until ca. 11,700 cal yr BP whenPinus ponderosabecame established. C/N ratios,δ13C andδ15N values indicate both terrestrial and aquatic organic matter was incorporated into the sediment. Higher percentages of aquatic algae and elevated C/N ratios indicate higher lake levels at the opening of the Holocene, but a wetland developed subsequently as climate warmed. From ca. 8500 to 6400 cal yr BP the pond desiccated in what must have been the driest period of the Holocene there. C/N ratios declined to their lowest Holocene levels, indicating intense decomposition in the sediment. Wetter conditions returned after 6400 cal yr BP, with conversion of the site to a sedge bog as groundwater levels rose. Higher charcoal influx rates after 6400 cal yr BP probably result from greater biomass production rates. Only minor shifts in the overstory species occurred during the Holocene, suggesting that mixed conifer forest dominated throughout the record.

scholarly journals Changes in Nitrogen-Fixing and Ammonia-Oxidizing Bacterial Communities in Soil of a Mixed Conifer Forest after Wildfire

2005 ◽  
Vol 71 (5) ◽  
pp. 2713-2722 ◽  
Author(s):  
Chris M. Yeager ◽  
Diana E. Northup ◽  
Christy C. Grow ◽  
Susan M. Barns ◽  
Cheryl R. Kuske
Keyword(s):  
Bacterial Communities ◽  
Fragment Length Polymorphism ◽  
Rflp Analysis ◽  
Ammonia Oxidizing Bacteria ◽  
Nitrogen Fixing ◽  
Conifer Forest ◽  
Mixed Conifer ◽  
Mixed Conifer Forest ◽  
In Fire ◽  
Sequence Types

ABSTRACT This study was undertaken to examine the effects of forest fire on two important groups of N-cycling bacteria in soil, the nitrogen-fixing and ammonia-oxidizing bacteria. Sequence and terminal restriction fragment length polymorphism (T-RFLP) analysis of nifH and amoA PCR amplicons was performed on DNA samples from unburned, moderately burned, and severely burned soils of a mixed conifer forest. PCR results indicated that the soil biomass and proportion of nitrogen-fixing and ammonia-oxidizing species was less in soil from the fire-impacted sites than from the unburned sites. The number of dominant nifH sequence types was greater in fire-impacted soils, and nifH sequences that were most closely related to those from the spore-forming taxa Clostridium and Paenibacillus were more abundant in the burned soils. In T-RFLP patterns of the ammonia-oxidizing community, terminal restriction fragments (TRFs) representing amoA cluster 1, 2, or 4 Nitrosospira spp. were dominant (80 to 90%) in unburned soils, while TRFs representing amoA cluster 3A Nitrosospira spp. dominated (65 to 95%) in fire-impacted soils. The dominance of amoA cluster 3A Nitrosospira spp. sequence types was positively correlated with soil pH (5.6 to 7.5) and NH3-N levels (0.002 to 0.976 ppm), both of which were higher in burned soils. The decreased microbial biomass and shift in nitrogen-fixing and ammonia-oxidizing communities were still evident in fire-impacted soils collected 14 months after the fire.

scholarly journals Morphological Responses Explain Tolerance of the Bamboo Yushania microphylla to Grazing

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Kesang Wangchuk ◽  
Andras Darabant ◽  
Prem Bahadur Rai
Keyword(s):  
Dry Matter ◽  
Belowground Biomass ◽  
Conifer Forest ◽  
Ungulate Herbivory ◽  
Mixed Conifer Forest ◽  
Allocation Patterns ◽  
Culm Density ◽  
Rhizome Biomass ◽  
The Cost ◽  
Lower Biomass

Mechanisms of tolerance of the bamboo Y. microphylla to ungulate herbivory were investigated by measuring above- and belowground morphogenetic traits and biomass allocation patterns of the bamboo Y. microphylla under grazed and ungrazed conditions in a Himalayan mixed conifer forest. Data were collected from 5 populations consisting of 10 ramets each in adjacent grazed and ungrazed plots. Compared with ungrazed ramets, the aboveground morphological modifications of grazed ramets were higher culm density, shorter and thinner culms, shorter internode, and shorter top leaf. The belowground morphological modifications for the grazed ramets were thinner rhizomes, lower rhizome biomass and dry matter, more nodes, and shorter internodes. Despite the lower biomass and dry matter, the root-to-shoot ratio was higher for grazed ramets. Results suggest that Y. microphylla subjected to herbivory shows aboveground overcompensation in terms of densification at the cost of belowground biomass, but at the same time maintains a higher proportion of belowground reserves, as compared to ungrazed conditions. These responses provide adequate evidence to conclude that Y. microphylla tolerates ungulate herbivory through above- and belowground morphological modifications.

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