Effects of Vegetation Succession on Soil Fertility Within Farming-Plantation Ecotone in Ziwuling Mountains of the Loess Plateau in China

To further understand the relationship between vegetation succession and soil fertility within farming-plantation ecotone in Ziwuling Mountains of the Loess Plateau, nine kinds of widely distributed communities at different succession stages were selected, and the effects of vegetation succession on soil fertility were studied through the methods of comparing two hierarchical clustering （similarity index： B） and other multivariate analysis. The results showed that： （i） the similarity in clustering pattern of nine communities which classified by plant species and soil nutrients respectively showed a trend of B ^-overall plant-soil0-10cn〉B^-overall plant-soil 10-20 cm 〉B^- overall plant-soil 20-40 cm, and for the top soil, it showed a trend of B^- grass-soil 0-10 cm 〉 B^-shrub-soil 0-10 cm 〉 Btree-soil0-10 cm; （ii） soil fertility increased during the succession process from abandoned land to forest community, and the soil fertility of forest community showed an increased order of coniferous forest →mixed forest →broadleaf forest; （iii） during the process of vegetation succession, the variation of topsoil fertility was higher than that of the subsurface soil （coefficient of variation： CV0-10 cm 〉CV 10-20 cm 〉 CV20-40 cm）, and when the succession developed into the stages of shrub and forest communities, the top soil fertility had been improved significantly; and （iv） for the subsurface soil of the communities at the advanced succession stages, the soil fertility also increased to some extent. Our results suggested that the method of comparing two hierarchical clustering reflected the similarity level of different cluster patterns, therefore, it was helpful to study the relationship between vegetation succession and soil fertility. There was a corresponding relationship between the change process of soil fertility from the top soil to subsurface soil and the process of vegetation succession from the early stages to the advanced stage. The differentiations of soil fertility in vertical space and horizontal space were both caused by vegetation succession, which was significant for both the shrub and forest communities. The improved level of forest soil fertility was related to forest vegetation types and the improved fertility level of broad-leaved forest-soil community was higher than that of the coniferous forest soil. In the practice on soil fertility ecological restoration of the loess plateau, it is important to carry out reasonably artificial forestation so as to enhance the restoration and improvement of soil fertility.

Aeolian Activities and Protective Effects of Artificial Plants in Re-vegetated Sandy Land of Qinghai Lake,China

Land desertification and aeolian activity are currently the greatest threats to alpine ecological environments and are also the primary challenges of desertification control and ecological restoration projects.Afforestation of sandy lands around the Qinghai Lake in China has effectively controlled the desertification of this watershed.However,certain issues remain which challenge its overall success,including lack of diverse biological species and poor theoretical understanding of aeolian processes,such as controlling wind-sand flow in relation to complex alpine ecological factors.Therefore,to help improving afforestation techniques,this research focused on Hippophae rhamnoides,Salix cheilophila,Pinus sylvestris,Populus simonii and Artemisia desertorum vegetation implanted in the mobile dunes on the eastern shore of Qinghai Lake.Aeolian transport characteristics and annual changes to community ecological factors from 2010–2016 were monitored in comparison with uncontrolled sand dunes.Based on simultaneous observations using gradient anemometers and sand samplers,it was found that the aeolian activities exhibited the following features:1)In re-vegetated lands,the logarithmic growth of wind speed was disrupted by the wind speed amplification in the middle and high layers and wind speed reduction in the low layers,while vegetation had significant wind-breaking(>37%)and sand-fixing(>85%)effects in 2016.2)Wind speeds in re-vegetated lands and mobile dunes showed a linear correlation,especially in lower layers of H.rhamnoides and S.cheilophila,while sand transport in re-vegetated land increased linearly or exponentially with increasing wind speed.3)The four artificial shrubs and forests had greater sand deposition with intensities of 280–860 t/(ha·yr),largely concentrated during winter and spring which accounted for 60%–85%of the annual cycle,while A.desertorum experienced significant root undercutting;and 4)Intensity of aeolian activity in re-vegetated lands,except for A.desertorum,was significantly negative with respect to plant growth structure,community cover,topsoil moisture,and regional precipitation.Overall,these five sand-binding species produced optimistic wind-sand protection effects for the alpine sandy lands,which relied on the plants’physical disturbance of wind-sand flow during the early stages of community development.In comparison,H.rhamnoides and S.cheilophila individually maintained stable wind-sand protection effects,while P.sylvestris and P.simonii were better in mixing with other shrubs and herbs to achieve a comprehensive ecological system for future control of aeolian activity.

Management of re‐established artificial grasslands via grazing or fencing: Effects on plant and soil properties

Background:Revegetation is widely used in degraded grassland restoration.However,the responses of grassland plant and soil properties to fencing(FC)and grazing(GZ)remain poorly understood,especially the vegetation–soil coupling coordination(C_(d))mechanism.This study explored single and interactive responses of vegetation and soil properties under FC and GZ after revegetation.Methods:A field experiment with FC and GZ treatments was conducted in Loess Plateau reconstructed grassland,with degraded grassland as the control(CK).Plant and soil properties and C_(d) were analyzed using the analytic hierarchy process(AHP)and principal component analysis(PCA).Results:The order of soil comprehensive evaluation(SCE)was GZ>FC>CK,while that of vegetation comprehensive evaluation(VCE)was FC>GZ>CK.The C_(d) of CK was 0.39(mild imbalance),while the values of FC and GZ were 0.57 and 0.54,respectively(little coordination).The VCE/SCE of FC was 1.48(soil lag type),and the values of GZ and CK were 0.69 and 0.35,respectively(vegetation lag and vegetation loss type,respectively).Conclusions:Both GZ and FC improved C_(d) and facilitated recovery.However,degraded grasslands should be restored via moderate grazing for sustainable ecological and economic development.

The influence of soil on vegetation structure and plant diversity in different tropical savannic and forest habitats

Aims Soil plays an important role in the formation and heterogene-ity of habitats and thus can cause changes in vegetation struc-ture and plant diversity.The differentiation between Cerrado/savanna and forest is well known,but the relationship between soil and habitats from savannic or forest formations still needs to be better understood,particularly in tropical ecotonal areas.We studied the association between attributes of plant com-munities,namely structure and diversity,and physicochemical characteristics of soils in the Caatinga domain at the transition to Cerrado in Brazil.Methods Chemical and physical analyses of soils were performed in samples of 38 plots from savannic formations and 30 plots from forest forma-tions.Vegetation was characterized floristically and structurally in all plots,five habitats being assessed in each plant formation.Soil features and vegetation parameters were highly distinct among the different habitats.Important Findingsin general,forest habitats were more nutrient rich than savannic formation.Furthermore,soil variables showed effects both on vegetation structure and on its species diversity,more pronouncedly in the savannic formations.Habitats were structurally distinct,and diversity differed between savannic and forest communities;however,a higher differentiation occurred when the savannic formation habitats were compared among them.Although plant diversity did not differ among forest formation habitats,soil attributes showed a close relationship with edaphic factors and can contribute for similar vegetation.The soil-vegetation relationship in highly diverse ecotonal landscapes is important from the conservation biology point of view and aid in the execution of proactive plans for the maintenance of biodiversity.Thus,we noticed that diversity and soil behaves distinctly between savannic and forest communities.