Evolution Of The Combined Forms Of Aluminum In Upland Soils Of Hunan Province And Their Pedogenetic And Taxonomic Implications

Due to different levels of soil development,various weathering stages and secondary minerals of different properties coexist,and a series of different active forms of aluminum are formed during the soil formation process.It is undoubtedly the current aluminum to clarify the meaning of form aluminum in soil genesis.An important research direction of morphology.This research is based on the research topic of Chinese soil system classification,through field survey sampling and indoor analysis and determination(the chemical combination of aluminum is extracted by six-step continuous extraction method,and the clay minerals are extracted by X-ray diffraction method)to explore the combination of aluminum in dryland soils in Hunan Province and The relationship between aluminosilicate clay minerals and soil occurrence and classification is expected to provide a theoretical basis for the utilization of dryland soil resources in Hunan Province.The main research conclusions are as follows:(1)The content of each chemical combination of aluminum in typical dryland soil in Hunan Province is:exchanged aluminum(Ex-Al)content is 0.26±0.19 g/kg,and adsorbed hydroxy aluminum(Hy-Al)content is 1.58±1.54 g/kg,the content of organic complex aluminum(Or-Al)is 4.82±3.64 g/kg,the content of iron oxide bound aluminum(DCB-Al)is 3.32±2.31 g/kg,the content of interlayer aluminum(In-Al)content is 6.59±2.84 g/kg,amorphous aluminosilicate and gibbsite(Nc-Al)content is23.48±10.25 g/kg;relative content of aluminosilicate clay mineral type They are:smectite(S)content of 5±21%,illite(It)content of 19±11%,kaolinite(Kao)content of 36±29%,chlorite(C)The content is 5±7%,the content of vermiculite(V)is 8±9%,the content of illite-smectite mixed layer mineral(I/S)is 11±27%,the content of illite-vermiculite mixed layer The content of minerals(I/V)is 17±11%.(2)In the tested soil profile,the content of Ex-Al,Hy-Al and Or-Al gradually decreased with the deepening of the soil,and the content of DCB-Al,In-Al and Nc-Al showed the same as the deepening of the soil.Increase first and then decrease.Affected by altitude,the content of 2:1 clay minerals(illite(It)and vermiculite(V))and illite-vermiculite mixed layer minerals(I/V)gradually increase with the elevation.The content of 1:1 clay mineral kaolinite(Kao)decreases with increasing altitude.The content of chlorite(C)is mainly present in the test soil at high altitude,and there is also a small amount in the soil at low altitude.Smectite(S)and illite-smectite mixed layer minerals(I/S)only appeared in the test soil at low altitude.(3)In the soils with different soil-forming parent materials,the Ex-Al content in the topsoil layer of the soil developed by weathered granite and the subsurface and parent material layers of the Quaternary red clay is higher than that in the same soil layers developed by other soil-forming parent materials.The contents of Hy-Al,In-Al and Nc-Al in the upper,lower and parent material layers where granite weathering is developed are higher than other parent materials.The content of Or-Al and DCB-Al in the upper surface layer,subsurface layer and parent material layer developed in limestone weathering is higher than other parent materials;there are illite-smectite mixed layer minerals(I/S)and illite in limestone weathering(It),chlorite(C),kaolinite(Kao)and illite-vermiculite mixed layer minerals(I/V),mainly I/S,with a relative content of 44%.There are Kao,illite-vermiculite mixed layer minerals(I/V),illite(It),vermiculite(V)and chlorite(C)in weathered granite,mainly kaolinite(Kao),The relative content accounts for 48%.There are smectite(S),illite-smectite mixed layer minerals(I/S),illite(It)and chlorite(C)in the weathered purple sand shale,mainly smectite(S)),the relative content accounts for 42%.There are kaolinite(Kao),illite-vermiculite mixed layer minerals(I/V),illite(It),illite-smectite mixed layered minerals(I/S)and vermiculite in the Quaternary red clay Stone(V),mainly Kao,with a relative content of 44%.(4)Among the 6 characteristic soil layers of humus surface layer>low activity iron-rich layer>polyiron reticulated layer>embryonic layer>cohesive layer>parent material layer,the content of Ex-Al and Or-Al in the humus surface layer is the highest,the embryonic layer The content of Hy-Al in the layer is much greater than that of other characteristic soil layers.The content of DCB-Al,In-Al and Nc-Al in the low-reactivity iron-rich layer is much higher than that in other characteristic soil layers;the difference in soil type also affects The content of Ex-Al,DCB-Al,In-Al,and Nc-Al gradually increase with the deepening of soil development.The distribution is:Ex-Al distribution is iron-rich soil>leaching Melt soil>embroid soil>new soil,DCB-Al distribution iron-rich soil>eluvial soil>embroid soil>new soil;In-Al distribution is iron-rich soil>eluvial soil>embroid soil>new soil,Nc The distribution of Al is iron-rich soil>newly formed soil>prototype soil>leached soil.The content of Hy-Al and Or-Al gradually decreases with the deepening of soil development,and the lowest value appears in the iron-rich soil.The distribution of Hy-Al is embryonic soil>newly formed soil>leached soil>iron-rich soil;Or-Al is distributed as embryonic soil>newly formed soil>eluvial soil>iron-rich soil;smectite(S)only appears in newly formed soil,illite-smectite mixed layer minerals(I/S)and green The content of debris(C)decreases with the increase of soil development.The content of illite(It),vermiculite(V),and illite-vermiculite mixed layer minerals(I/V)show the first trend with the deepening of soil development.Distribution that decreases after increasing.Kaolinite(Kao)is the main aluminosilicate clay mineral type in the soil,and its content increases with the depth of soil development,and is the largest in iron-rich soil.(6)The chemically bound form of aluminum in the tested soil is not only affected by the soil parent material and the degree of soil development,but also by other basic soil properties.For example,the content of Ex-Al is also affected by soil p H(r=-0.793^**),and the content of Hy-Al and Or-Al is also affected by soil organic matter,with r being 0.360^**and 0.442^**,respectively,DCB-Al The content of Nc-Al is also affected by free iron in soil(r=0.837^**),the content of In-Al is affected by ECEC(r=-0.569^**),and the content of Nc-Al is affected by clay particles(r=0.376^**);The main factors affecting the distribution of aluminosilicate clay minerals are altitude,soil parent material and soil type.