内蒙古典型草原区退耕方式对植物群落特征与土壤特性的影响

退耕后不恰当的植被建设会严重影响植物群落演替及土壤性质.本文以内蒙古太仆寺旗境内典型草原为研究区,以天然草地为对照,研究退耕后自然恢复与人工种草2种退耕方式对植物群落特征及土壤性状的影响,揭示不同退耕方式的生态恢复效应.通过样方法调查不同退耕方式草地的盖度、生物量和多样性特征,并对土壤密度、机械组成及养分含量等进行了室内测定分析.结果表明:1)植物群落多样性、盖度、地上及地下生物量均表现为人工种草＜自然恢复＜天然草地,且相比于人工种草,自然恢复草地的物种组成与天然草地更为相似;2)不同退耕方式影响下土壤性质的差异主要集中在表层0～10 cm;3)在表层0～ 10 cm,土壤密度及砂粒含量表现为人工种草＞自然恢复＞天然草地,而土壤黏粒、有机质(SOM)及全氮(TN)含量则表现为人工种草＜自然恢复＜天然草地.以上结果说明,在内蒙太仆寺旗退耕后采用自然恢复方式比人工种草更有助于改善土壤理化性质、建立稳定的植被系统.经过12年的恢复,退耕草地(人工种草与自然恢复草地)仍未恢复到天然草地的水平.

Changes in soil properties and plant community characteristics among different vegetation restoration models in the semiarid steppe zone of Inner Mongolia in China

Background]" Grain for Green Program" (GGP),i.e.,reconversion of cropland into forest or grassland,initiated by Chinese government has a profound impact on mitigating environmental degradation.After cropland is re-converted into grassland,land use and vegetation can be altered radically within a short period,and soil physical,chemical,and microbial properties can be improved.In general,natural recovery and artificial forestation/grass planting are two main ways to restoration after re-conversion from cropland to grassland.However,there has not yet formed a unified conclusion on which way is more favorable to improve the vegetation community and soil environment.The objectives of this study were hence to discover the differences in characteristics of vegetation community and soil properties between natural recovery (N-CG) and artificial grass planting (P-CG) in the semiarid steppe region of north China,and then to assess a more suitable restoration ways in the study area.Methods] Three sites were selected,representing two restoration ways (natural recovery and artificial forestation) and natural grassland (NG),respectively.Vegetation cover,biomass and species diversity were investigated by quadrat method in the field.Soil samplings were collected with different depths to investigate soil properties including organic matter (SOM),total nitrogen (TN) and phosphorus (TP),bulk density (BD) and particle size distribution.Particle size composition was determined by the hydrometer method and SOM was measured by the K2Cr2O7-H2SO4 oxidation method.Additionally,TN was measured using a Nitrogen/Carbon Analyzer and TP was measured by molybdenum blue colorimetry,after H2 SO4-HC1O4 digestion.Results] 1) Species diversity,plant coverage,aboveground and belowground biomass were significantly (P ＜ 0.01) lower in P-CG among the three typed sites,and the differences between N-CG and NG were not significant.Meanwhile,species composition in N-CG was similar with NG,compared with P-CG.2) Surface soil (0-10 cm) properties were deeply affected by different restoration ways.P-CG tended to have higher bulk density and sand content,but lower SOM,TN,silt and clay content than N-CG at the soil depths of 0-10 cm,although the differences were not significant.Moreover,NG had the lowest bulk density and sand content,and the highest SOM,TN,TP,silt and clay content.Conclusions] Soil properties and plant community characters did not return to natural grassland status as before cultivation after 12 years of re-conversion in our study area.N-CG might be a more suitable restoration way to facilitate vegetation community and improve soil physicochemical properties in the study area compared with P-CG.Extra efforts are needed to persistently investigate the changes of vegetation and soil properties in a long time within different restoration ways and to make reliable policy decisions while choosing suitable ways for re-conversion from cropland to grassland in the semiarid steppe region of north China.