Zonal aspects of the influence of forest cover change on runoff in northern river basins of Central Siberia

Background:Assessment of the reasons for the ambiguous influence of forests on the structure of the water balance is the subject of heated debate among forest hydrologists.Influencing the components of total evaporation,forest vegetation makes a significant contribution to the process of runoff formation,but this process has specific features in different geographical zones.The issues of the influence of forest vegetation on river runoff in the zonal aspect have not been sufficiently studied.Results:Based on the analysis of the dependence of river runoff on forest cover,using the example of nine catchments located in the forest-tundra,northern and middle taiga of Northern Eurasia,it is shown that the share of forest cover in the total catchment area(percentage of forest cover,FCP)has different effects on runoff formation.Numerical experiments with the developed empirical models have shown that an increase in forest cover in the catchment area in northern latitudes contributes to an increase in runoff,while in the southern direction(in the middle taiga)extensive woody cover of catchments“works”to reduce runoff.The effectiveness of geographical zonality in regards to the influence of forests on runoff is more pronounced in the forest-tundra zone than in the zones of northern and middle taiga.Conclusion:The study of this problem allowed us to analyze various aspects of the hydrological role of forests,and to show that forest ecosystems,depending on environmental conditions and the spatial distribution of forest cover,can transform water regimes in different ways.Despite the fact that the process of river runoff formation is controlled by many factors,such as temperature conditions,precipitation regime,geomorphology and the presence of permafrost,the models obtained allow us to reveal general trends in the dependence of the annual river runoff on the percentage of forest cover,at the level of catchments.The results obtained are consistent with the concept of geographic determinism,which explains the contradictions that exist in assessing the hydrological role of forests in various geographical and climatic conditions.The results of the study may serve as the basis for regulation of the forest cover of northern Eurasian river basins in order to obtain the desired hydrological effect depending on environmental and economic conditions.

Quantitative Analysis of Land Degradation in Mongolia from the Perspective of Geographical Zone

Natural and anthropogenic disturbances accelerate land degradation(LD)in arid,semi-arid,and dry sub-humid areas,leading to reduced land quality and productivity,loss of biodiversity,degradation of ecosystem services,and a decline in the quality of life of local people.To address this issue,the United Nations Convention to Combat Desertification(UNCCD)has set a target for LD neutrality(LDN).However,quantifying and comparing the status of LD at global or regional scales remains challenging due to the lack of coherent quantitative methods and tools.In this study,we focused on Mongolia,a region with significant LD problems,to examine patterns of LD and changes from 2015 to 2020,accounting for regional differences.Trends.Earth was used,as recommended by the UNCCD.The main findings are as follows:(1)Overall,the degraded land area in Mongolia accounted for 12.11%of the total land area,predominantly located in the southwest desert and desert steppe,gradually spreading to the northeast steppe.(2)The areas showing improvement in the land productivity index and degradation were 17.62%and 11.79%,respectively,with the most severely degraded areas concentrated in the southern desert and desert steppe regions.(3)The areas of improvement and degradation in the land cover index were 1.80%and 0.16%,respectively,with degraded areas scattered across regions of steppe,high mountains,and mountain taiga.(4)The areas of improvement and degradation in the land organic carbon index were 1.54%and 0.22%,respectively,with degradation primarily observed in adjacent areas of mountain taiga,steppe,and desert steppe.(5)The improved area(2.999×10^(5)km^(2))of LDN are more than the degraded area(1.895×10^(5)km^(2)),indicating a positive trend toward LDN in Mongolia.

The spatial variation of soil bacterial community assembly processes affects the accuracy of source tracking in ten major Chinese cities

Urban soils harbor billions of bacterial cells and millions of species.However,the distribution patterns and assembly processes of bacterial communities remain largely uncharacterized in urban soils.It is also unknown if we can use the bacteria to track soil sources to certain cities and districts.Here,Illumina MiSeq sequencing was used to survey soil bacterial communities from 529 random plots spanning 61 districts and 10 major cities in China.Over a 3,000 km range,community similarity declined with increasing geographic distance(Mantel r=0.62),and community composition was clustered by city(R^(2)=0.50).Within cities(<100 km),the aforementioned biogeographic patterns were weakened.Process analysis showed that homogenizing dispersal and dispersal limitation dominated soil bacterial assembly at small and large spatial scales,respectively.Accordingly,the probabilities of accurately tracking random soil sources to certain cities and districts were 90.0% and 66.7%,respectively.When the tested samples originated from cities that were more than 1,265 km apart,the soil sources could be identified with nearly 100% accuracy.Overall,this study demonstrates the strong distance-decay relationship and the clear geographic zoning of urban soil bacterial communities among cities.The varied importance of different community assembly processes at multiple spatial scales strongly affects the accuracy of microbial source tracking.