摘要
Forest degradation is a worldwide problem,although its causes vary due to geographical and climatic differences and man-made causes.In recent years,the Robinia pseudoacacia forest in the Yellow River Delta has suffered severe degradation.The causative mechanisms were investigated in the field over two years,and the results show that increased forest degradation was reflected by increased tree mortality,high leaf and soil sodium salt levels and groundwater depth.Average tree diameters decreased,and leaf chlorophyll and soil microbial contents decreased.Redundancy discriminate analysis(RDA)showed that degradation of the forest was correlated positively with soil salt content,but negatively with groundwater depth.Correlation analysis showed that 0.79%–0.95%soil salt content and above 1.20 m groundwater depth caused the death of R.pseudoacacia trees due to localized anthropogenic economic activities,such as rice farming,that disrupted the original water–salt balance.Measures are recommended to prevent further degradation and restore degraded forests.
基金
supported by Shandong Provincial“Bohai Granary”Science and Technology Demonstration Project(2019BHLC004)
the major projects of science and technology in Shandong province(2017CXGC0313)
Agricultural Variety Improvement Project of Shandong Province(2019LZGC009)
Shandong Province Natural Science Foundation(ZR2019MC065)
the Taishan Scholar Program(tsqn20161058)
the Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province。
