Modern pollen dynamics and surficial sedimentary processes at Lake Tyrrell, semi-arid northwestern Victoria, Australia

1997 ◽  
Vol 97 (3-4) ◽  
pp. 301-318 ◽  
Author(s):  
J.G. Luly
The Holocene ◽  
2012 ◽  
Vol 22 (12) ◽  
pp. 1385-1392 ◽  
Author(s):  
Yan Zhao ◽  
Hongyan Liu ◽  
Furong Li ◽  
Xiaozhong Huang ◽  
Jinghui Sun ◽  
...  

The Artemisia/Chenopodiaceae (A/C) ratio is assumed to be a useful index for reconstructing moisture changes in arid and semi-arid regions. Thorough modern pollen studies are still lacking to understand the reliability and limitation of A/C ratio as a moisture indicator, however. Here we review how well this ratio can be applied in arid and semi-arid China on the basis of new surface pollen data, previous data synthesis and other publications. Results indicate that variance in the A/C ratio can permit identification of modern vegetation types and that the A/C ratio generally has a positive relationship with annual precipitation. However, soil salinity, vegetation community composition, human activity and sample provenance (e.g. soil and lake sediments) will affect the values of the A/C ratio in different vegetation zones and therefore the A/C ratio is not comparable in different regions. We argue that the A/C ratio can only be used to reconstruct vegetation types and climate change in regions with precipitation <450–500 mm, and in steppe, steppe desert and desert areas. Careful studies should be undertaken to understand the modern pollen–vegetation–climate relationships in various regions before using the A/C ratio to interpret vegetation and climate.


2017 ◽  
Vol 13 (2) ◽  
pp. 362
Author(s):  
Bouchra Lemdeghri Alaoui ◽  
Abdennasser Baali

In northern Middle Atlas, the Dayet Iffère is located in an area affected by karst and tectonic. After its watershed genesis of middle altitude during the upper Pleistocene, two lacustrine formation were deposed. The detailed sedmentological study as well as the correlations between the different lacustrine formations defined in Dayet Afourgagh and Dayet Agoulmam, and the 14C dating allowed to reconstitute the major stages of the filling evolution of the lake basin and its sedimentary dynamic. The variations of sedimentation are interpreted as climatic fluctuations and evolution of vegetation since upper Soltanien. These results show a complex interaction between sedimentary processes and climatic phenomena that tend to a stability marked by heat, permanent humidity and a fairly dense vegetation cover at the end of the Soltanian, after probably a hot arid to semi-arid episode.


The Holocene ◽  
2017 ◽  
Vol 28 (5) ◽  
pp. 834-841 ◽  
Author(s):  
Nannan Li ◽  
Dorothy Sack ◽  
Guizai Gao ◽  
Lidan Liu ◽  
Dehui Li ◽  
...  

The Songnen grasslands were traditionally thought to be dominated by Artemisia and Chenopodiaceae plants as early as the late Pleistocene. However, increasing evidence has called that interpretation into question. To shed new light on the paleovegetation evolution of the arid and semi-arid steppe in North China, phytolith assemblages preserved in the region’s sand-paleosol sequence (section Daike) are used as a proxy for paleovegetation structure. Results show that both the sand and paleosol layers in the Songnen grassland sections contain well-preserved phytoliths attributed to different families of grass. This is the first direct evidence of the nature of the vegetation that existed during the sandy layer episodes. Moreover, the phytolith evidence represented in the samples indicates that plant successions happened within the subfamilies of Poaceae through the time. Referring to phytoliths in modern plants and topsoils, and using statistical analyses, we propose that phytolith assemblages in the section Daike originated from Poaceae-dominant communities rather than an Artemisia-Chenopodiaceae ecosystem. The phytoliths, and evidence from the historical and modern pollen-vegetation relationships, lead to rejection of the hypothesis of a past widespread Artemisia-Chenopodiaceae ecosystem in the Songnen grasslands. Using published radiocarbon and thermoluminescence data, it is proposed that the present Poaceae-dominated grasslands developed as early as the early Holocene. This study also highlights the usefulness of phytolith analysis in paleovegetation reconstruction in arid and semi-arid lands.


2020 ◽  
Author(s):  
Arindam Malakar ◽  
Michael Kaiser ◽  
Daniel D. Snow ◽  
Harkamal Walia ◽  
Chittaranjan Ray

Author(s):  
I.G.C. Kerr ◽  
J.M. Williams ◽  
W.D. Ross ◽  
J.M. Pollard

The European rabbit (Oryctolagus cuniculus) introduced into New Zealand in the 183Os, has consistently flourished in Central Otago, the upper Waitaki, and inland Marlborough, all areas of mediterranean climate. It has proved difficult to manage in these habitats. The 'rabbit problem' is largely confined to 105,000 ha of low producing land mostly in semi arid areas of Central Otago. No field scale modifications of the natural habitat have been successful in limiting rabbit numbers. The costs of control exceed the revenue from the land and continued public funding for control operations appears necessary. A system for classifying land according to the degree of rabbit proneness is described. Soil survey and land classification information for Central Otago is related to the distribution and density of rabbits. This intormation can be used as a basis for defining rabbit carrying capacity and consequent land use constraints and management needs. It is concluded that the natural rabbit carrying capacity of land can be defined by reference to soil survey information and cultural modification to the natural vegetation. Classification of land according to rabbit proneness is proposed as a means of identifying the need for, and allocation of, public funding tor rabbit management. Keywords: Rabbit habitat, rabbit proneness, use of rabbit prone land.


2007 ◽  
Vol 23 (5) ◽  
pp. 546-555 ◽  
Author(s):  
R. Burgos ◽  
L.J. Odens ◽  
R.J. Collier ◽  
L.H. Baumgard ◽  
M.J. VanBaale

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