Shifting sand: Why we’re running out of aggregate

2019 ◽  
Vol 10 (3) ◽  
pp. 69-71
Author(s):  
Stephen Cousins
Keyword(s):  
2021 ◽  
Author(s):  
Julissa Rojas-Sandoval ◽  
Pedro Acevedo-Rodríguez

Abstract C. procera is a fleshy evergreen shrub about 1.8-5.5 m tall, with a diameter at breast height of 15-20 cm (von Maydell, 1986). The flowers are pale green to white, with purple tips. A fibre obtained from the bark is used to make lines, bow-strings and twine; it can also be spun with cotton, or used to stuff mattresses and pillows. The fibre is strengthened by soaking in water for 1-2 days, but extensive soaking may reduce durability. The wood is of small dimensions and is too light for most uses. C. procera produces a distinctive white latex, which contains cardiotoxins and hydrocarbons with many medicinal and pesticidal properties. C. procera has been widely planted for fibre production and has become naturalized on the American and Australian continents. It is often abundant on degraded areas and is an indicator of overgrazing. C. procera is a widespread pioneer in semi-desert grassland and bushland (e.g. in Africa), and it also colonizes shifting sand-dunes such as in Rajasthan, India. However, due to its properties as a pioneer, there is a risk that this species may become a weed. More research is needed on C. procera to maximize production and marketing of its many potential products.


2014 ◽  
Vol 478 ◽  
pp. 1-11 ◽  
Author(s):  
Haotian Yang ◽  
Xinrong Li ◽  
Zengru Wang ◽  
Rongliang Jia ◽  
Lichao Liu ◽  
...  

2016 ◽  
Vol 75 (21) ◽  
Author(s):  
Jian Guo Zhang ◽  
Xin Wen Xu ◽  
Ying Zhao ◽  
Jia Qiang Lei ◽  
Sheng Yu Li ◽  
...  

Nature ◽  
1963 ◽  
Vol 200 (4913) ◽  
pp. 1275-1275 ◽  
Author(s):  
A. H. STRIDE
Keyword(s):  

2019 ◽  
Vol 30 (1) ◽  
pp. 90-105 ◽  
Author(s):  
Richard Fairchild ◽  
David Gwilliam ◽  
Oliver Marnet

1974 ◽  
Vol 52 (5) ◽  
pp. 1057-1073 ◽  
Author(s):  
A. G. van der Valk

Shifting sand, which either buries the seeds or seedlings of dune forbs or carries them away, is responsible for the absence of forbs on the front of the foredune and in other zones accumulating sand regularly. Experimental work with the seedlings of six dune forbs showed that they can withstand burial by no more than 5 cm of sand and that their seeds can survive burial under only 1 to 16 cm, depending on the species. At least 20 to 30 cm of sand normally accumulates each winter in a zone subject to regular sand deposition. Salt spray plays a secondary role in preventing the establishment of forbs on the front of the foredune. It is responsible for the elimination of species which may occasionally escape burial during the winter months and which happen to be susceptible to salt spray injury. Measurements of soil moisture, soil nutrients, and soil temperatures indicate that these factors differ only slightly on the front, top, and back of the foredune. These three factors, then, appear to have little influence on the distribution of the forbs.


1985 ◽  
Vol 42 (7) ◽  
pp. 1296-1302 ◽  
Author(s):  
Daniel A. Soluk

Abundance and biomass of benthic macroinvertebrates from shifting sand areas in the bed of the Sand River in central Alberta, Canada, were examined for 1 yr. Macroinvertebrate density ranged from 12 000 to 78 000 individuals/m2, but total biomass was low (50–490 mg/m2 dry mass) due to the small size of most organisms. The interstitial larvae of two chironomid species (Robackia demeijerei and Rheosmittia sp.) contributed a mean of 80.6% biomass and 92.8% of total number of macroinvertebrates. Total annual secondary production of these two species (752.0 ± 144.5 mg∙m−2∙yr−1) was used as an estimate of total secondary production of benthic macroinvertebrates in shifting sand areas. Both R. demeijerei and Rheosmittia sp. exhibited larval growth and development rates much slower than those reported for comparably sized species in other habitats. Food or frequent disturbance may limit the growth of these species. Although unit area biomass and production were low relative to other lotie habitats, shifting sand areas make significant contributions to the river ecosystem because they occupy a large proportion of the river bed.


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