森林立地学会誌 森林立地43(1),2001,9〜15
jpn.J.For.Environment
43(1),9-15 2001
中国北西部の乾燥地における土壌塩類濃度の分布
斉藤昌宏・谷本丈夫・張 立 運・李 振 武
中国北西部の乾燥地、タクラマカン砂漠および河西回廊において土壌の粒径組成および塩類集積を調査した。扇状地，ペヂメント上部およびワヂで粒径10mm以上の大きな礫を含む場合が多く、ペヂメント下部では粒径0.2mm前後の成分を多く含む。電気伝導度（EC）およびNaCl含有量の測定からペヂメント中部・下部においては軽い塩類集積を起こしていることが認められた。タマリクス円錐の上層外縁は塩類濃度が高く，内部はほとんど塩類をほとんど含んでいなかった。Populus puruinosa および P. euphratica の若い萌芽林では、両土壌断面とも表層ではECが20mS/cmを超え，NaCl含有量は1.5%以上となったが，下層に移るに従って値は下がった。P. puruinosa林下の土壌断面中部ではECが0.2mmS/cmであるのに対し，P. euphratica林下の土壌では2〜5mS/cmと10倍以上の差があり，両樹種の耐塩性の違いを反映していた。河岸に成立した両種の混交林に設けたトランセクトの調査結果も，両樹種の耐塩性の違いを示唆していた。調査地域に出現した8地形について土壌の塩類集積度をECおよびNaCl含有量によって評価した。砂丘地の表層土はほとんど塩類を含まず，ペヂメント上部・下部はNaCl以外の塩類により軽い塩類集積が起きている例が認められた。氾濫原ではNaClによる塩類集積とそれ以外の塩による塩類集積が区分され，塩類集積地では主にNaClによる塩集積が起きていた。
Masahiro Saito, Takeo Tanimoto,Li-yun Zhang and Zheng-wu Li:Distribution of the soil salinity in northwest china
Soil size
composition and salt accumulation were investigated in the Taklimakan Desert
and the Hexi Corridor, arid area in the northwest of China. The soil was
including large gravels over 10 mm in the size, in the upper parts of alluvial
fan, pediment and wadi, and the soil in the lower pediment mainly consisted of
the sand about 0.2 mm in the size. On the electric conductivity (EC) and NaCl
content, salt accumulation have been occurred lightly on some soil samples from
the middle to low part of the pediment. The upper-edge of the Tamarix cone has high saline
concentration, it decreases as going down, and on the center and bottom of it
the salinity is very little. Though in surface soils under the young coppice
forests of Populus puruinosa and P. euphratica, EC and NaCl content were shown over 20 mS/cm and
over 1.5%, these values dropped as it to the lower layer. EC value was 0.2
mS/cm in the midle of soil profile under the
P. pruinosa forest, while it was 2-5 mS/cm in same layer under the P. euphratica
forest. This difference of the soil salinity seems to reflect the difference of
salt tolerance between the two Populous species.
The results of survey on the mixed forest of these poplars on a flood plain,
also supported difference of the salt torelance between both species. The
degree of salt accumulation on the soil was evaluated on 8 land-forms by EC and
NaCl content. In most of samples from sand-dune and pediment, the salt
accumulation had not been caused, however, in few ones were shown lightly salt
accumulation by the salt except for NaCl. In the flood plain, there were two
types of salt accumulation, by NaCl or other kinds of salt, while in the salt
accumulation area the accumulated salt was mainly NaCl.