Litter removal impacts on soil biodiversity and eucalypt plantation development in the seasonal tropics

The little layer of tree plantations provides primary nutrients for uptake,buff ers changes in soil moisture,and provides habitat and substrate to soil epigeic fauna.However,this layer in eucalypt plantations is often removed to reduce fuel load during the fi re season in the Brazilian savanna(Cerrado).Therefore,it is necessary to quantify the eff ects of changes in litter dynamics on the function of these plantations,on key nutrient cycling processes and on epigeic fauna diversity and abundance.In two adjacent stands(one juvenile and one mature),the consequences of two years of litter removal were quantifi ed as monthly litterfall,leaf and fi ne wood litter decomposition,epigeic fauna abundance and diversity,soil biogeochemical variables,and tree diameter and basal area increments.Monthly litterfall rates in juvenile and mature stands did not change with litter removal over the study period.Annual litterfall ranged from 4.1 to 4.9 Mg ha^(−1)a^(−1)in litter removal plots and from 3.9 to 4.8 Mg ha^(−1)a^(−1)in control plots.Fine wood litter decomposition was slower in litter removal plots compared to controls,while leaf decomposition rates were similar in both.Two years of litter removal in the juvenile stand did not aff ect topsoil biogeochemical parameters but decreased available phosphorus at 20–40 cm depth relative to controls.In the mature stand,total cation exchange capacity(0–20 cm)was higher in controls(6.4 cmol c dm^(−3))relative to litter removal plots(6.3 cmol c dm^(−3)),while soil moisture(0–40 cm depth)was lower in litter removal(25.45 m 3 m^(−3))compared to control plots(26 m^(3)m^(−3))in the dry season.A non-metric multidimensional scaling ordination revealed an increased homogeneity in epigeic fauna where litter was removed.Litterfall,decomposition,diameter increment,four soil physical parameters and fourteen chemical parameters at 0–20 and 20–40 cm depth explained the diff erences in soil epigeic fauna composition between litter removal and control plots.Diameter increment decreased with litter removal only in the juvenile stand,which had reached its growth peak.The results indicate that removing excess litter to decrease fuel volume can alter soil biodiversity and edaphic conditions that negatively aff ect nutrient cycling and tree growth.

Modeling the Impacts of Nitrogen Dynamics on Regional Terrestrial Carbon and Water Cycles over China with Noah-MP-CN

As an important part of biogeochemical cycling,the nitrogen cycle modulates terrestrial ecosystem carbon storage,water consumption,and environmental quality.Modeling the complex interactions between nitrogen,carbon and water at a regional scale remains challenging.Using China as a testbed,this study presents the first application of the nitrogenaugmented community Noah land surface model with multi-parameterization options(Noah-MP-CN)at the regional scale.Noah-MP-CN parameterizes the constraints of nitrogen availability on photosynthesis based on the Fixation and Uptake of Nitrogen plant nitrogen model and the Soil and Water Assessment Tool soil nitrogen model.The impacts of nitrogen dynamics on the terrestrial carbon and water cycles are investigated by comparing the simulations with those from the original Noah-MP.The results show that incorporating nitrogen dynamics improves the carbon cycle simulations.NoahMP-CN outperforms Noah-MP in reproducing leaf area index(LAI)and gross primary productivity(GPP)for most of China,especially in the southern warm and humid regions,while the hydrological simulations only exhibit slight improvements in soil moisture and evapotranspiration.The impacts of fertilizer application over cropland on carbon fixation,water consumption and nitrogen leaching are investigated through a trade-off analysis.Compared to halved fertilizer use,the actual quantity of application increases GPP and water consumption by only 1.97%and 0.43%,respectively;however,the nitrogen leaching is increased by 5.35%.This indicates that the current level of fertilizer use is a potential concern for degrading the environment.

Spring and autumn phenology across the Tibetan Plateau inferred from normalized difference vegetation index and solar-induced chlorophyll fluorescence

Plant phenology is a key parameter for accurately modeling ecosystem dynamics.Limited by scarce ground observations and benefiting from the rapid growth of satellite-based Earth observations,satellite data have been widely used for broad-scale phenology studies.Commonly used reflectance vegetation indices represent the emergence and senescence of photosynthetic structures(leaves),but not necessarily that of photosynthetic activities.Leveraging data of the recently emerging solar-induced chlorophyll fluorescence(SIF)that is directly related to photosynthesis,and the traditional MODIS Normalized Difference Vegetation Index(NDVI),we investigated the similarities and differences on the start and end of the growing season(SOS and EOS,respectively)of the Tibetan Plateau.We found similar spatiotemporal patterns in SIF-based SOS(SOS_(SIF))and NDVI-based SOS(SOS_(NDV)I).These spatial patterns were mainly driven by temperature in the east and by precipitation in the west.Yet the two satellite products produced different spatial patterns in EOS,likely due to their different climate dependencies.Our work demonstrates the value of big Earth data for discovering broad-scale spatiotemporal patterns,especially on regions with scarce field data.This study provides insights into extending the definition of phenology and fosters a deeper understanding of ecosystem dynamics from big data.