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Winter soil CO_2 efflux in two contrasting forest ecosystems on the eastern Tibetan Plateau, China

Journal of Forestry Research 2015年第3期26卷 679-686页

作者： zhenfeng xu Feifei Zhou Huajun Yin Qing Liu Institute of Forest & Ecology Sichuan Agricultural University Chengdu Institute of Biology Chinese Academy of Sciences

Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems （a Picea asperata plantation and a natural forest）. Mean winter soil CO2 effluxes were 1.08 μmol m-2 s-1 in the plantation and 1.16 μmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing sea- son was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration toannual soil efflux were 15.4 % tor the plantation and 16.5R for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforesta- tion （natural coniferous forests were deforested and refor- ested with P. asperata plantation） may reduce soil respiration by reducing soil carbon substrate availability and input.

关键词： Winter soil CO2 efflux Eastern TibetanPlateau Natural coniferous forest Picea asperataplantation

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Ab initio MO study of reaction mechanism for carbonyl migration of Co complex

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Chinese Science Bulletin 2000年第13期45卷 1176-1178页

作者： LEI Ming FENG Wenlin xu zhenfeng Department of Applied Chemistry Beijing University of Chemical TechnologyBeijing 100029China Department of Chemistry Beijing Normal UniversityBeijing 100875China

Ab initio method under the effective core potential (ECP) approximation is employed to study the reaction mechanism of carbonyl migration of the cycle of olefin hydroformylation catalyzed by a carbonyl cobalt HCo(CO)3 at Hartree-Fock (HF) level. The structures of the reactant, transition state and product for the reaction are determined. The energy of each stationary point is corrected at MP2/LAN2DZ//LANL2DZ+ZPE (zero-point energy) level. The calculated activation barrier is 28.89 kJ/mol.

关键词： carbonyl cobalt hydroformylation ab initio method effective core potential.

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Variations in root chemistry of three common forest species,southwestern China

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Journal of Forestry Research 2019年第3期30卷 827-834页

作者： Qun Liu Wanqin Yang Fuzhong Wu Bo Tan Li Zhang zhenfeng xu Long-term Research Station of Alpine Forest Ecosystems Institute of Forest and Ecology Sichuan Agricultural University

Root chemistry varies with tree species and root diameter but little information is available about Tibetan forest species. The root chemistry of three root diameter classes (fine: 0–2 mm, medium: 2–5 mm, coarse: 5–10 mm) of three subalpine species (Abies faxoniana Rehd. and Wild, Picea asperata Mast., and Betula albosinensis Burkill) were investigated. Carbon concentrations, and carbon/nitrogen and carbon/phosphorus ratios increased but nitrogen, phosphorus and nitrogen/phosphorus ratios decreased with increasing root diameter. The roots of the conifers had higher carbon levels, and higher carbon/nitrogen and carbon/phosphorus ratios than birch roots. The opposite was found with nitrogen and phosphorus levels and nitrogen/phosphorus ratios. Lignin concentrations decreased but cellulose concentrations increased with greater root diameters. The results indicate that diameter-associated variations in root chemistry may regulate their contribution to detrital pools which has important implications for below-ground carbon and nutrient cycles in these subalpine forests.

关键词： Root diameter Lignin Cellulose Stoichiometry Subalpine forest

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Effects of litter quality and climate change along an elevational gradient on litter decomposition of subalpine forests, Eastern Tibetan Plateau, China

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Journal of Forestry Research 2016年第3期27卷 505-511页

作者： zhenfeng xu Jianxiao Zhu Fuzhong Wu Yang Liu Bo Tan Wanqin Yang Key Laboratory of Ecological Forestry Engineering of Sichuan Province Institute of Ecology & Forest Sichuan Agricultural University Chengdu 611130 China Long-term Research Station of Alpine Forest Ecosystems and Monitoring Station for Eco-environments in the Rainy Zone of SW China Chengdu China Department of Ecology College of Environmental SciencesKey Laboratory for Earth Surface of Ministry of EducationPeking University Beijing 10087 China

Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold *** global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter *** the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter *** mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.

关键词： Alpine forest Elevational gradient Freeze-thaw Global warming Mass losses

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Soil fauna accelerated litter C and N release by improving litter quality across an elevational gradient

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Ecological Processes 2023年第1期12卷 632-644页

作者： Li Zhang Jingru Liu Rui Yin zhenfeng xu Chengming You Han Li Lixia Wang Sining Liu Hongwei xu Lin xu Yang Liu Yong Wang Bo Tan Forestry Ecological Engineering in Upper Reaches of Yangtze River Key Laboratory of Sichuan Province College of ForestrySichuan Agricultural UniversityChengdu 611130China College of Natural Resources and Environment Northwest A&F UniversityYangling 712100ShaanxiChina

Background Soil fauna is an important driver of carbon(C)and nitrogen(N)release from decomposing litter in forest ***,its role in C and N cycling concerning climate and litter traits remains less *** a 4-year field experiment,we evaluated the effects of soil fauna on litter C and N release across an elevation gradient(453,945,3023,and 3582 m)and litter traits(coniferous ***)in southwestern *** Our results showed that N was retained by–0.4%to 31.5%,but C was immediately released during the early stage(156–516 days)of decomposition for most litter *** fauna significantly increased the peak N content and N retention across litter species,but reduced the C/N ratio for certain species(i.e.,Juniperus saltuaria,Betula albosinensis,Quercus acutissima,and Pinus massoniana litter),leading to more C and N being released from decomposing litter across the elevation *** of soil fauna to C and N release were 3.87–9.90%and 1.10–8.71%,respectively,across litter species after 4 years of *** environment and initial litter quality factors caused by elevation directly affected litter C and N *** in soil fauna resulting from elevation and fauna exclusion factors had a direct or indirect impact on C and N release during litter *** Our findings suggest that soil fauna promote C and N release from decomposing litter in different magnitudes,mainly controlled by environmental conditions(i.e.,temperature and moisture),litter quality(i.e.,lignin and cellulose content,and lignin/cellulose),and its diversity across the elevation gradient.

关键词： Carbon remaining Nitrogen remaining Nitrogen retention Soil fauna Elevational gradient

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Nitrogen addition promotes foliar litterfall and element return in a subtropical forest,southwestern China

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Journal of Forestry Research 2023年第4期34卷 939-948页

作者： Yue Zhang Shichen Xiong Chengming You Sining Liu Lixia Wang Li Zhang Han Li Bo Tan Yang Liu zhenfeng xu Forestry Ecological Engineering in the Upper Reaches of the Yangtze River Key Laboratory of Sichuan Province&National Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River&Institute of Ecology and Forestry Sichuan Agricultural UniversityChengdu 611130People’s Republic of China

Nitrogen deposition has a considerable impact on biogeochemical cycling in terrestrial ***,how litter production and element return respond to N addition remains poorly understood in nitrogen-rich subtropical *** this study,a 4-year nitrogen addition experiment explored its eff ects on foliar litter production and carbon,nitrogen and phosphorus in a subtropical Michelia wilsonii forest.A clear seasonal pattern in foliar litterfall was observed,regardless of nitrogen treatments,with a peak in spring and a smaller one in *** litter increased with increasing nitrogen but did not aff ect litter carbon concentrations and often decreased nitrogen and phosphorous *** eff ect of nitrogen addition was dependent on time(month/year).Carbon,nitrogen and phosphorous return showed similar bimodal seasonal *** addition increased carbon and nitrogen return but did not aff ect *** results suggest that the addition of nitrogen stimulates carbon and nutrient return via litterfall.

关键词： Nitrogen addition Litterfall Seasonal patterns Element return Subtropical forest

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Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe-C-Cr Weld Surfacing Layer

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Journal of Materials Science & Technology 2003年第4期19卷 351-354页

作者： Daqian SUN, Wenquan WANG, Zhaozhi xuAN, Yue xu and zhenfeng ZHOUSchool of Materials Science and Engineering, Jilin University, Changchun 130025, China Sch. of Mat. Sci. and Eng. Jilin Univ. Changchun 130025 China

Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).

关键词： Weld surfacing layer Alloying elements Erosion resistance

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Do root modules still exist after they die?

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Forest Ecosystems 2021年第2期8卷 303-310页

作者： Jihong Li Chengming You Li Zhang Han Li Bo Tan Yang Liu Lixia Wang Sining Liu zhenfeng xu Forestry Ecological Engineering in the Upper Reaches of the Yangtze River Key Laboratory of Sichuan Province&National Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River&Rainy Area of West China Plantation Ecosystem Permanent Scientific Research Base Institute of Ecology&ForestrySichuan Agricultural UniversityChengdu 611130China

Background:The terminal branch orders of plant root systems are increasingly known as an ephemeral *** concept is crucial to recognize belowground ***,it is unknown if root modules still exist after they die?Methods:The decomposition patterns of the first five root orders were observed for 3 years using a branch-order classification,a litter-bag method and sequential sampling in a common subalpine tree species(Picea asperata)of southwestern ***:Two root modules were observed during the 3-year *** the first five branch orders,the first three order roots exhibited temporal patterns of mass loss,nutrients and stoichiometry distinct from their woody mother roots throughout the experimental *** study,for the first time,reported the decomposition pattern of each individual root order and found a similar decomposition dynamic among ephemeral root branches in a forest tree ***:Results from this study suggest that root modules may also exist after death,while more data are needed for *** findings may further advance our understanding of architecture-associated functional heterogeneity in the fine-root system and also improve our ability to predict belowground processes.

关键词： Root branch order Fine roots Picea asperata Nitrogen Phosphorus Stoichiometry Root decomposition

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Soil C, N and P stocks and stoichiometry under different vegetation on the surface of the Leshan Giant Buddha

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Soil Ecology Letters 2022年第1期4卷 57-68页

作者： Fujia Wu Wanqin Yang Bo Sun Tianyu Yang xuli Chen zhenfeng xu Huixing Song College of Landscape Architecture Sichuan Agricultural UniversityChengdu 611130China College of Life Science Taizhou UniversityTaizhou 318000China Northwest Research Institute Co. Ltdof China Railway Engineering CorporationLanzhou 730000China Grottoes Research Center Management Committee of Leshan Grand Buddha Scenic SpotLeshan 614003China Provincial Key Laboratory of Ecological Forestry Engineering Institute of Ecology and ForestrySichuan Agricultural UniversityChengdu 611130China

The accumulation of soil organic matter and nutrients is an important pathway in effectivelyunderstanding the mechanisms of plant settlement and rock weathering, while the characteristics ofsoil organic carbon (C), nitrogen (N) and phosphorus (P) under different vegetation remain *** this study, the stocks and stoichiometry of soil organic C, N and P were determined in differentpositions and types of vegetation on the surface of the Leshan Giant Buddha. We found that the totalstocks of soil organic C, N and P were 1689.77, 134.6 and 29.48 kg, respectively, for the *** stocks of soil organic C, N and P under vascular plants were higher than those under othervegetation, with highest values observed under herb. Higher stocks per unit area (m2) of soil organicC, N and P were found on the left and right arms, shoulders, and two platforms. These results providea full primary picture in understanding soil organic C, N and P accumulation and distribution on thesurface of the Buddha, which could supply the fundamental data on weathering management of theBuddha and other similar open-air stone carvings.

关键词： Rock weathering Soil organic matter Plant settlement Open-air stone carving

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Nitrogen addition mediates the response of foliar stoichiometry to phosphorus addition: a meta-analysis

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Ecological Processes 2021年第1期10卷 804-816页

作者： Chengming You Changhui Peng zhenfeng xu Yang Liu Li Zhang Rui Yin Lin Liu Han Li Lixia Wang Sining Liu Bo Tan Paul Kardol Forestry Ecological Engineering in the Upper Reaches of the Yangtze River Key Laboratory of Sichuan Province and National Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River and Rainy Area of West China Plantation Ecosystem Permanent Scientifc Research Base Institute of Ecology and ForestrySichuan Agricultural University211 Huimin RoadWenjiang DistrictChengdu 611130SichuanPeople’s Republic of China. Department of Biological Science Institute of Environment SciencesUniversity of Quebec at MontrealCase Postale 8888Succursale Centre-VilleMontrealQC H3C 3P8Canada. Laboratory for Ecological Forecasting and Global Change College of ForestryNorthwest A&F UniversityNo.3 Taicheng RoadYangling 712100People’s Republic of China. Department of Community Ecology Helmholtz-Centre for Environmental Research-UFZTheodor-Lieser-Strasse 406110 HalleSaaleGermany. College of Animal Science and Technology Sichuan Agricultural UniversityChengdu 611130People’s Republic of China. Department of Forest Ecology and Management Swedish University of Agricultural Science90183 UmeåSweden.

Background:Changes in foliar nitrogen(N)and phosphorus(P)stoichiometry play important roles in predicting the efects of global change on ecosystem structure and ***,there is substantial debate on the efects of P addition on foliar N and P stoichiometry,particularly under diferent levels of N ***,we conducted a global meta-analysis to investigate how N addition alters the efects of P addition on foliar N and P stoichiometry across different rates and durations of P addition and plant growth types based on more than 1150 ***:We found that P addition without N addition increased foliar N concentrations,whereas P addition with N addition had no *** positive efects of P addition on foliar P concentrations were greater without N addition than with N ***,the efects of P addition on foliar N,P and N:P ratios varied with the rate and duration of P *** particular,short-term or low-dose P addition with and without N addition increased foliar N concentration,and the positive efects of short-term or low-dose P addition on foliar P concentrations were greater without N addition than with N *** responses of foliar N and P stoichiometry of evergreen plants to P addition were greater without N addition than with N ***,regardless of N addition,soil P availability was more efective than P resorption efciency in predicting the changes in foliar N and P stoichiometry in response to P ***:Our results highlight that increasing N deposition might alter the response of foliar N and P stoichiometry to P addition and demonstrate the important efect of the experimental environment on the *** results advance our understanding of the response of plant nutrient use efciency to P addition with increasing N deposition.

关键词： Ecological stoichiometry Plant nutrient regime Nutrient resorption efciency Soil N and P availability Global change Global synthesis

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