Changes of Soil Erosion and Possible Impacts from Ecosystem Recovery in the Three-River Headwaters Region, Qinghai, China from 2000 to 2015

Soil erosion poses a great threat to the sustainability of the ecological environment and the harmonious development of human well-being.The revised universal soil loss equation(RUSLE)was used to quantify soil erosion in the Three-River Headwaters region(TRH),Qinghai,China from 2000 to 2015.The possible effects of an ecosystem restoration project on soil erosion were explored against the background of climatic changes in the study area.The model was validated with on-ground observations and showed a satisfactory performance,with a multiple correlation coefficient of 0.62 from the linear regression between the estimations and observations.The soil erosion modulus in 2010–2015 increased 6.2%,but decreased 1.2%compared with those in the periods of 2000–2005 and 2005–2010,respectively.Based on the method of overlay analysis,the interannual change of the estimated soil erosion was dominated by climate(about 64%),specifically by precipitation,rather than by vegetation coverage(about 34%).Despite some uncertainties in the model and data,this study quantified the relative contribution of ecological restoration under global climatic change;meanwhile the complexity,labor-intensiveness and long-range character of ecological restoration projects have to be recognized.On-ground observations over the long-term,further parameterization,and data inputs with higher quality are necessary and essential for decreasing the uncertainties in the estimations.

Impact of Land-Use Change on Soil Microbial Community Composition and Organic Carbon Content in the Dry Tropics

Restoration of forests poses a major challenge globally, particularly in the tropics, as the forests in these regions are more vulnerable to land-use change. We studied land-use change from natural forest(NF) to degraded forest(DF), and subsequently to either Jatropha curcas plantation(JP) or agroecosystem(AG), in the dry tropics of Uttar Pradesh, India, with respect to its impacts on soil microbial community composition as indicated by phospholipid fatty acid(PLFA) biomarkers and soil organic carbon(SOC) content. The trend of bacterial PLFAs across all land-use types was in the order: NF > JP > DF> AG. In NF, there was dominance of gram-negative bacterial(G^-) PLFAs over the corresponding gram-positive bacterial(G^+) PLFAs. The levels of G^- PLFAs in AG and JP differed significantly from those in DF, whereas those of G^+ PLFAs were relatively similar in these three land-use types. Fungal PLFAs,however, followed a different trend: NF > JP > DF = AG. Total PLFAs, fungal/bacterial(F/B) PLFA ratio, and SOC content followed trends similar to that of bacterial PLFAs. Across all land-use types, there were strong positive relationships between SOC content and G-, bacterial, fungal, and total microbial PLFAs and F/B PLFA ratio. Compared with bacterial PLFAs, fungal PLFAs appeared to be more responsive to land-use change. The F/B PLFA ratio, fungal PLFAs, and bacterial PLFAs explained 91%, 94%,and 73% of the variability in SOC content, respectively. The higher F/B PLFA ratio in JP favored more soil C storage, leading to faster ecosystem recovery compared to either AG or DF. The F/B PLFA ratio could be used as an early indicator of ecosystem recovery in response to disturbance, particularly in relation to land-use change.

Enduring legacy of coal mining on the fungal community in a High Arctic soil after five decades

Mineral extraction is known to affect soil fungi in polar environments,but it is unknown how long these effects persist.Here,by amplifying the internal transcribed spacer regions of rRNA genes in soil fungi,we compared soil fungal community in intact natural tundra with that in a nearby former coal mining area,abandoned 52 years previously,on Svalbard in the High Arctic.Compared with those in intact tundra,soils in the former mining area were more acidic and had lower plant coverage.Despite of similar diversity in the two areas,the fungal community was dominated by Basidiomycota in the intact tundra,but by Ascomycota in the former mining area.Ectomycorrhizal genera formed a major part of the tundra community,but were notably less abundant in the mining area.The principal variation among samples was soil pH.Surprisingly,network connectivity analysis indicated that the fungal community in the former mining area had greater network connectivity than that in the tundra area.Overall,the ecosystem in the former mining area has made only limited recovery towards the natural tundra state even after more than five decades.It is unclear whether the recovery of the fungal community is limited more by the low primary productivity,slow migration of fungi and plants,or slow changes in soil parameters.Our findings emphasize the susceptibility of polar ecosystems to disturbance,given their particularly slow recovery back towards the natural state.