摘要:

SummaryThe dry‐weight losses of samples of oak and ash litter, enclosed in nylon hairnets and placed on two sites with contrasting humus forms, a mull and a moder, have been followed for a period of 14 months. Sub‐samples of the same oak litter disappear at similar rates on the two sites. Sub‐samples of the same ash litter disappear at different rates on the two sites, but always more quickly than oak litter. On the mull site the loss of whole ash leaflets as well as fragments of leaflets is considerable whereas oak leaves on both sites and ash leaflets on the moder site disappear mainly as small fragments. For both oak and ash litter the results from the mull site are more variable than those from the moder site, suggesting that there are differences in the heterotrophic activity on the two

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02196.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryDifferent trends have been demonstrated in the changes in composition taking place in sub‐samples of the same ash litter placed in nylon hair‐nets on neighbouring sites with mull and moder‐type humus forms. Similar trends have been shown to occur for oak litter and ash litter placed on the same moder site. The percentage nitrogen content of ash litter on the mull site remains virtually constant during the first 7 months of decomposition whereas on the moder site the content increases steadily for both ash litter and oak litter. The nitrogen content of oak litter is increased by considerable addition from outside. Possible sources of this additional nitrogen are considered. Extraction with hot water of litter at different stages of decomposition shows that the initially large water‐soluble fraction, which is poor in nitrogen, is leached out more quickly from ash than from oak

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02197.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryThe polyphenols of fresh green and dried leaves, litter, and superficial humus from mull and mor sites were examined by paper chromatography and paper electrophoresis. The greatest diversity and quantity of phenolic substances obtained in the extract of the fresh beech leaves from the mor site. There was a change in quantity of simple polyphenols grading from a maximum in fresh growing green leaves, falling through senescent leaves to dead leaves to fresh fallen leaves, to a minimum in decayed leaves and humus or stored dry leaves. Tannin stripping and especially hydrolysis and reduction of the decayed leaves and superficial humus released polyphenolic substances. The role of polyphenols in mull and mor formation is discussed.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02198.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryThe two pure polyphenols, D‐ andepi‐catechin, known to be present in the fresh green leaves of a number of tree species, have been shown to be capable of reducing ferric iron, in the form of hydrated ferric oxide, to an organic ferrous complex and solubilizing it in much the same way as do Bloomfield's leaf extracts. These polyphenols can remove iron, even when held firmly as in Triassic sand, and transport it as ferrous iron at low pH. Model soils, consisting of alumina and diatomaceous earth impregnated with ferric chloride, were treated with catechin solutions and fresh green‐leaf extracts. Both produced dark coloured bands in which substantial amounts of ferric iron had been converted to ferrous iron. Extracts of green beech leaves from a mor site were more effective than those from a mull site (June leaf collection). Extracts of humus and litter were singularly low in reducing and iron‐complex‐forming substances, corresponding to their low free polyphenol status.The illuvial horizon of a podzol formed on Barton sand has yielded organic matter on extraction with acetyl acetone. This contained much material of polyphenol origin associated with iron.The role of polyphenol activity towards iron is discussed in relation to podzolic and ot

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02199.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryIn a red latosol loam under bare fallow at Kawanda, Uganda, nitrate accumulates to as much as 70 p.p.m, nitrate nitrogen during short periods of dry weather. Nitrate accumulation appears to be a microbiological process involving nitrifying bacteria similar toNitrosomonasandNitrobacter.Nitrate accumulation in an isolated topsoil, 3 in. deep, ceased when the moisture content fell below 10 per cent. Accumulation continued on plots which were in contact with the subsoil and which remained at 10 per cent. moisture.It was concluded that under the conditions of these experiments, transport of ions to the surface by capillary transport or diffusion does occur, but is not responsible for the major nitrate accumulation, which seems to depend on progressive drying of the topsoil during which nitrate, as formed, becomes protected by the dry conditions from microbial reduction, assimilation, and leaching. Any process which prevents the progressive drying, e.g. shading, mulching, and watering, can be expected to favour nitrate removal and so to prevent nitrate accumulation.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02200.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02201.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryBands of acacia trees rhythmically disposed occur in the Sudan in a form resembling grass patterns. They have been found only on the red sand belt of Western Sudan, and aerial and ground observations and measurements seem to indicate that they all lie on gentle slopes very roughly on the contour, that they are as much as zoo m. wide with similar or wider spaces between them usually occupied by ground patchily covered by grass.Though sometimes tree bands may have a man‐made origin, the cause is generally natural and is probably the same as that producing grass pattern

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02202.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryAnalytical data are given for deep‐water sediments from Esthwaite Water in the English Lake District representing different depths below the mud surface and sediments of ages back to and including the late‐glacial, of which the pollen status is known. Nitrogen content and loss on ignition increase steadily in muds laid down during the time of post‐glacial forest development, showing also a small previous rise which represents the temporary late‐glacial climatic amelioration (Allerad). Nitrogen remains approximately constant in muds representing the stage of post‐glacial alder‐oak‐birch forest. Deforestation, as shown by increases in grass pollen in the muds, is associated with falls in the values for nitrogen and loss‐on‐ignition. These decreases occur in two stages, believed to represent two stages of human settlement and land use.Analyses for elements such as sodium, potassium, magnesium, calcium, and iron, show signs of increasing solubility in the muds representing the time of forest development. Thereafter the amount of calcium diminishes progressively in later muds, while the Ca/Fe ratio falls, changes which could be correlated with the leaching effects of a rainfall of 170‐zoo cm. per annum on the soils in the lake basin. Similar data are recorded for a core from Rydal Water.The results are interpreted as records of the regional changes in soils from the lake drainage systems during the

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02203.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryThe chemical composition of the soils and of the colloidal separates of twelve red earths from three widely differing locations in Italy has been determined. The red earths of southern Italy are characterized by low organic matter, little if any CaCO3, and appreciable quantities of soluble salts. Those of northern Italy have opposite characteristics. The SiO2/R2O3ratios of the colloids range from 1.60 to 2.09 and bear no relationship to location or climatic factors.It is concluded that similar pedogenetic processes have occurred throughout the Italian peninsula and are independent of geographical position or climatic conditions. In particular the SiO2/R2O3ratio of the colloids of the southern soils is not unusually low as has been suggested by other workers.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02204.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SummaryBy their chemical composition, the colloids from various types of soils in Israel may be grouped into three classes. According to their mineralogical composition the colloids represent various associations, two of which are conspicuous.(a) Colloids with SiO2/R2O3ratio of 2.0–2.6. They are devoid of calcium carbonate, relatively poor in potassium and phosphorus, and content of organic matter is generally moderate. In the combination of clay minerals found, kaolin is predominant; in addition there are present illite, hematite, quartz, and, in some instances, montmorillonite. These colloids are characteristic of soils belonging to the Mediterranean red earths including terra rossas, brown Mediterranean soils, and brown‐red sandy soils‐leached soils of the humid and sub‐humid regions, formed from hard limestone, dolomite, hard chalk, and kurkar.(b) Colloids with SiO2/R2O3ratio of 3.6–5.2. Rich in calcium carbonate, potassium, and phosphorus, relatively poor in organic matter. In the association of clay minerals, montmorillonite is predominant; in addition there are also present illite, kaolin, and quartz. In some instances attapulgite was identified in appreciable quantities. The colloids also contain considerable quantities of calcite. The soils for which these colloids are characteristic were formed from soft chalk, marl, aeolian desert dust, and are found principally in the semi‐arid and arid regions of Israel. They include rendzinas of the mountains and valleys, loess, aeolian sandy soils, and hamadas.(c) Colloids with SiO2/R2O3ratio of 3.4–3.8. Most of them contain calcium carbonate, their potassium content is moderate, and they are relatively poor in phosphorus and organic matter. By their mineralogical composition these colloids resemble the combination in which montmorillonite is the principal clay mineral. They are characteristic of alluvial soils formed from alluvium of the Mediterranean red earths and rendzinas. The soils were developed under subhumid and semi‐arid clim

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1960.tb02205.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY