Effect of six years of nitrogen additions on soil chemistry in a subtropical Pleioblastus amarus forest, Southwest China

Soil chemistry influences plant health and carbon storage in forest ecosystems. Increasing nitrogen(N) deposition has potential effect on soil chemistry. We studied N deposition effects on soil chemistry in subtropical Pleioblastus amarus bamboo forest ecosystems. An experiment with four N treatment levels(0, 50, 150,and300 kg N ha-1a-1,applied monthly, expressed as CK,LN,MN, HN,respectively) in three replicates. After6 years of N additions, soil base cations, acid-forming cations, exchangeable acidity(EA), organic carbon fractions and nitrogen components were measured in all four seasons. The mean soil pH values in CK,LN,MN and HN were 4.71, 4.62, 4.71, and 4.40, respectively, with a significant difference between CK and HN. Nitrogen additions significantly increased soil exchangeable Al3+,EA, and Al/Ca,and exchangeable Al3+ in HN increased by 70%compared to CK. Soil base cations(Ca2+, Mg2+, K+, and Na+) did not respond to N additions. Nitrogen treatments significantly increased soil NO3--N but had little effect on soil total nitrogen, particulate organic nitrogen, or NH4~+-N. Nitrogen additions did not affect soil total organic carbon, extractable dissolved organic carbon,incorporated organic carbon, or particulate organic carbon.This study suggests that increasing N deposition could increase soil NO3--N, reduce soil pH, and increase mobilization of Al3+. These changes induced by N deposition can impede root grow and function, further may influence soil carbon storage and nutrient cycles in the future.

The Chemistry of Serpentine Soils Developed Over A Podiform Chromite Deposit,Western Sierra Nevada,USA

The Chinese Camp mining district in the western Sierra Nevada of California,USA,contains a serpentinized,ultramafic dunite intrusion with podiform chromite deposits.Serpentine soils have developed over this intrusion,creating a unique ecosystem of endemic vegetation and soils characterized by low Ca/Mg ratios and high Ni and Cr contents.The vegetation and red coloration make it easy to visually distinguish between soils developed over intruded,serpentinized bedrock and unmineralized,adjacent andesite bedrock(Fig.1).The purpose of our study was to compare soil chemistry and vegetative parameters among 3 study-design levels:1)undisturbed serpentine soil,2)undisturbed background soil(non-serpentine,developed over andesite),and 3)serpentine soil disturbed by mining activities.Within each of these l e v*e ls,3 random locations were chosen where weestablished 3,30-m transects(spaced 120-degrees apart).One soil sample was collected at a random location along each transect(0-15 cm depth after removing litter/O horizon).This scheme resulted in the collection of 9replicate soil samples per study-design level.Samples were analyzed for total metal content by ICP-AES/MS(inductively coupled plasma atomic emission spectroscopy/mass spectroscopy),p H,electrical conductivity,and total C/N/S.The vegetative parameter of%canopy cover was measured with a line-point intercept survey along each transect,using 0.6m intervals.Above-ground net primary productivity(ANPP)was estimated by harvesting all aboveground living plant material within a 0.5 m quadrant at 3 random locations along each transect,drying,and weighting the material.Significant differences among design levels were observed for ANPP,canopy cover,total P,total N,and Ca/Mg,where the median values for these parameters decreased in the order undisturbed background>undisturbed serpentine>mining-disturbed serpentine.The highest concentrations of Cr and Ni were found in undisturbed serpentine(medians of 1960 ppm and 2529ppm,respectively)followed by mining-disturbed serpentine(medians of 420 and 2120,respectively)then undisturbed non-serpentine(medians 47.0 and 32.2 ppm,respectively).Soil p H varied significantly among the design levels with a median 5.74 in undisturbed background,median 6.25 in undisturbed serpentine,and median of 7.17 in mining-disturbed serpentine.These data document the distinct differences in soil chemistry and vegetation parameters between undisturbed serpentine soil and adjacent,undisturbed background soil.Efforts toward mining reclamation must recognize these differences and include the correct baseline conditions in the reclamation plan.

Effects of mulch and planting methods on Medicago ruthenica seed yield and soil physical-chemical properties

Medicago ruthenica (L.) Trautv., a wild grass species, is commonly grown as a forage crop in arid and semi-arid areas of China. Herein, we explored mulch patterns and planting methods for optimizing M. ruthenica seed production in the loess plateau of the Gansu Province, China from 2017 to 2019. The experiments comprised of six treatments including (1) flat ground without mulch (F0, control);(2) flat ground with a transparent white 0.008 mm thick plastic film mulch (FP);(3) flat ground with 4500 kg/hm2 straw mulch (FS);(4) furrow with 10 cm ridges (R0);(5) furrow with plastic film mulch (RP);and (6) furrow with straw mulch (RS). Results showed that the harvested seed yield of M. ruthenica was the highest under RP treatment, followed by FP and FS treatments. Soil moisture content from mid-May to mid-August in 2017 was the highest under RP and FP treatments, followed by RS and FS treatments. In 2018, soil moisture content was the highest under RS and FS treatments. In 2017 and 2018, soil temperature was the highest under FP and RP treatments, followed by F0 and R0 treatments. Total and available nitrogen, phosphorus, and potassium contents were the highest under RS and FS treatments, followed by RP and FP treatments. Comprehensive analysis result showed that surface mulch improved soil microenvironment and increased seed yield of M. ruthenica. Straw mulch also effectively recycled excess crop straw, thereby encouraging the sustainable development of agriculture in this area. In conclusion, FS treatment was considered the best mode for M. ruthenica seed production in this area.

Nutrient changes in potting mix and Eucalyptus nitens leaf tissue under macadamia biochar amendments

The effect of macadamia nut shell biochar on nitrogen,potassium,phosphorus,magnesium,calcium and sodium concentrations in potting mix used to grow Eucalyptus nitens seedlings was investigated in a glasshouse experiment.The treatments combined two fertiliser rates（50 and 100% rate of the commercial mix commonly used in forestry nurseries） with eight biochar rates(0,2,5,10,20,50,80 and 100 t ha;) arranged in a randomised complete block with three replicates of four sample plants.Nutrients were quantified in the potting mix and seedling leaves at four destructive harvests 135,177,219 and269 days after planting.Biochar significantly increased nitrate-N,Colwell P,Colwell K and exchangeable Na andreduced ammonium-N,Mg and Ca concentrations in the potting mix.Seedling leaf concentrations of P,K and Na were increased by biochar application,while N remained dependent on fertiliser rate only.Mg and Ca leaf concentrations decreased in response to increasing biochar rates.Elevated nitrate-N and decreased ammonium-N concentrations suggest that biochar might have increased nitrification in the potting mix.We presumed that biochar mediated processes that reduced uptake of P and K when high doses of biochar were combined with full fertilisation.Changes in potting mix K,Na,Mg and Ca were consistent with selective adsorption of ions to biochar surfaces.

Soil biotic and abiotic conditions negate invasive species performance in native habitat

Background:Most studies on plant invasion consider the enemy release hypothesis when analyzing native habitats.However,the lower performance of invasive species in the native habitats can be the result of unfavorable soil conditions in the native habitats.While soil biotic and abiotic factors have a potential to restrict the growth of invasive species in their native habitats,our understanding of belowground environment of invasive species in their native habitats is very limited.In this study,we analyzed soil characteristics associated with an exotic invasive plant,Old World Climbing Fern(Lygodium microphyllum),in its native habitat in Australia and the recipient habitat in South Florida.Rhizosphere soil samples from both habitats were analyzed for soil physical,chemical and biological characteristics.Results:Soil characteristics in the recipient habitats were significantly different compared to those in the native habitats.Soil samples from the native habitat had low soil pH,and high concentrations of elements such as aluminum and zinc which are phytotoxic in acidic soil environments.Additionally,mycorrhizal fungi spores were more diverse in the recipient habitat in Florida compared to the native habitat in Australia.Conclusion:Overall,our results indicate that growth of an invasive plant in its native habitats could be restricted by the toxic effects associated with strong soil acidity.Results from this study indicate that invasive plants not only escape from their natural herbivores but also from toxic soil environment in their native habitats.

Bedrock geology interacts with altitude in affecting leaf growth and foliar nutrient status of mountain vascular plants

Aims Altitude is often used as a proxy for ascertaining how warming affects plant growth and leaf level properties.However,we have a poor understanding of how the effects of altitude-related warming varies across geology.therefore,this study examined the independ-ent and interactive effects of altitude and geology and species on plant growth and foliar nutrient status.Methods We determined leaf growth rates and concentrations of major nutrients(nitrogen,N and phosphorus,P)in leaves of five spe-cies across two altitudinal gradients(1200-2200 m)in the Dolomites(south-eastern Alps,Italy).the two transects were located on carbonate bedrock and silicate bedrock,respec-tively.We also determined concentrations of inorganic and organic N and P forms in soils,andδ15N signature in leaves and soils.Important Findings Foliar N concentrations were unrelated to bedrock geology.the negative foliarδ^(15)N signature suggested that organic N was the primary source of N supply across the gradients.Foliar P concentrations were strongly affected by bedrock geology and their altitudinal patterns depended on the concentrations of organic and inorganic P forms in the soil.Phosphates and organic P appeared to be the main sources of P supply.Leaf growth rates increased with higher altitude on silicate bedrock and decreased with higher altitude on carbonate bedrock and presented a significant positive correlation with foliar N:P.In conclusion,bedrock geology inter-acted with altitude in controlling the foliar nutrient status mainly owing to availability of soil P and its effect on foliar nutrient stoichiometry.

No-till systems on the Chequen Farm in Chile:A success story in bringing practice and science together

No-till cropping systems provide an opportunity to protect the soil from erosion,while contemporaneously maintaining high yields and contributing to global food security.The historical aspects and the remarkable development of no-till systems on the Chequen Farm in Chile are reviewed.The adoption of no-till over the last 40 years has been a major turning point in reducing the devastating effects of soil erosion and a model for the evolution of sustainable crop production in highly erodible terrain in other parts of the world.The process of adoption of no-till systems in severely eroded foothills of Chile is described,as well as the environmental benefits and the sustainability of the system.The practical aspects of these developments are supported by scientific literature where appropriate,illustrating the value and coincident knowledge gained when combining analogue observations and information with scientific principles.