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Denitrification and the challenge of scaling microsite knowledge to the globe

mLife 2023年第3期2卷 229-238页

作者： G.Philip Robertson W.K.Kellogg Biological Station Michigan State UniversityHickory CornersMichiganUSA Department of Plant Soiland Microbial SciencesMichigan State UniversityEast LansingMichiganUSA Great Lakes Bioenergy Research Center Michigan State UniversityEast LansingMichiganUSA

Our knowledge of microbial processes—who is responsible for what,the rates at which they occur,and the substrates consumed and products produced—is imperfect for many if not most taxa,but even less is known about how microsite processes scale to the ecosystem and thence the globe.In both natural and managed environments,scaling links fundamental knowledge to application and also allows for global assessments of the importance of microbial processes.But rarely is scaling straightforward:More often than not,process rates in situ are distributed in a highly skewed fashion,under the influence of multiple interacting controls,and thus often difficult to sample,quantify,and predict.To date,quantitative models of many important processes fail to capture daily,seasonal,and annual fluxes with the precision needed to effect meaningful management outcomes.Nitrogen cycle processes are a case in point,and denitrification is a prime example.Statistical models based on machine learning can improve predictability and identify the best environmental predictors but are—by themselves—insufficient for revealing process-level knowledge gaps or predicting outcomes under novel environmental conditions.Hybrid models that incorporate well-calibrated process models as predictors for machine learning algorithms can provide both improved understanding and more reliable forecasts under environmental conditions not yet experienced.Incorporating trait-based models into such efforts promises to improve predictions and understanding still further,but much more development is needed.

关键词： ecosystems microsites N_(2) N_(2)O modeling

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Seed rain and soil seed bank compensatory roles on Nassella tenuis(Phil.)Barkworth seedling recruitment in ungrazed and grazed sites

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Journal of Arid Land 2022年第5期14卷 550-560页

作者： Cintia Vanesa LEDER Dianela Alejandra CALVO Guadalupe PETER Universidad Nacional de Río Negro Sede AtlánticaCentro de Estudios Ambientales desde la NorPatagonia(Center of Environmental Studies from North Patagonia(CEANPa)National University of Río Negro)Viedma 8504Argentina Universidad Nacional de Río Negro Sede AtlánticaCentro de Estudios Ambientales desde la NorPatagonia-National Council of Scientific and Technical Research(CONICET)(Center of Environmental Studies from North Patagonia(CEANPa)National University of Río Negro)Viedma 8504Argentina

In semi-arid lands,vegetation is distributed in shrub patches immersed in a less vegetated interpatch matrix.Grazing affects perennial grass seed bank through a decrease in seed rain and an increase in seed predation and soil compaction.Nevertheless,some species with anchorage mechanisms in their seeds might overcome this,such as Nassella tenuis(Phil.)Barkworth.This is an important species in grazing paddocks because it has an intermediate palatability and its relatively tolerant to grazing.These characteristics allow N.tenuis to increase its abundance in grazed sites.Our objective was to assess how grazing affects the key palatable species from seeds to seedlings:i.e.,seed rain,soil seed bank,and seedling recruitment in different microsites along a windward-leeward transect across shrub canopy.We hypothesized that:(1)the negative effects of grazing on N.tenuis fructification are reflected in its seed rain,soil seed bank,and seedling recruitment,especially in interpatches;(2)Nassella tenuis seed rain reduction,soil compaction by cattle in grazed sites,and removal of seeds by wind decrease its soil seed bank,especially in microsites exposed to the predominant wind;and(3)the decrease in N.tenuis soil seed bank and cover increase in annual species in grazed sites have negative effects on its seedling recruitment,especially in microsites exposed to predominant wind.We placed seed traps,collected soil samples,and monitored seedling recruitment in different locations around shrub canopy to address our hypotheses.Also,we established a manipulative experiment in which we sow N.tenuis seeds and followed its recruitment in different microsites.We compared the seed rain,soil seed bank,natural seedling recruitment,and sown seeds recruitment of N.tenuis between grazed and ungrazed sites.We analyzed differences between microsites along a windward-leeward transect across shrubs patches.Seed rain and soil seed bank had the same density in patches and interpatches both in ungrazed and grazed sites.But seed rain was higher,and soi

关键词： seed rain soil seed bank seedling recruitment microsites grazing

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Effects of biological soil crusts and drought on emergence and survival of a Patagonian perennial grass in the Monte of Argentina

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Journal of Arid Land 2014年第6期6卷 735-741页

作者： Flavia Alejra FUNK Alejro LOYDI Guadalupe PETER Center for Renewable Natural Resources of the Semi-arid Zone National Scientific and Technical Research Council (CONICET)Bahía Blanca 8000Argentina Río Negro National University Viedma 8500Argentina

Biological soil crusts are widely distributed in arid and semiarid regions. They have an important eco- logical role, especially by modifying physical and chemical properties of soils. Biological crusts may also modify seed germination and seedling establishment. The effects vary widely according to the type of crust and the vas- cular plant species. The objective of this study was to determine the effect of moss-dominated biological soil crusts on the emergence, biomass and survival of Poa ligularis Nees ex Steud. under different irrigation regimes. We col- lected seeds of P. ligularis and biological soil crusts composed of two species of mosses： Syntrichia princeps （De Not.） Mitt and Ceratodon purpureus （Hedw.） Brid. from an area in the Monte of Argentina. The result showed that seedling emergence of P. ligularis was higher in treatments with bare soil than in soil covered by crusts, and also in those with watering to field capacity. Mean emergence time was higher in treatments with bare soil and watering to field capacity. Seedling biomass also showed significant differences between treatments. These results suggest that biological soil crusts dominated by mosses do not promote P. ligularis emergence, although they would not affect its survival.

关键词： drought field capacity recruitment microsites mosses semiarid region Poa ligularis

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Influence of experimental soil disturbances on the diversity of plants in agricultural grasslands

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Journal of Plant Ecology 2014年第6期7卷 509-517页

作者： Jörg Müller Johannes Heinze Jasmin Joshi Steffen Boch Valentin H.Klaus Markus Fischer Daniel Prati Institute of Biochemistry and BiologyUniversity of PotsdamMaulbeerallee 114469 PotsdamGermany Freie Universität Berlin Institut für BiologieBerlin-Brandenburg Institute of Advanced Biodiversity ResearchAltensteinstrasse 614195 BerlinGermany Institute of Plant Sciences University of BernAltenbergrain 213013 BernSwitzerland Institute of Landscape Ecology University of MünsterHeisenbergstr.248149 MünsterGermany Biodiversity and Climate Research Centre BIK-F Senckenberg Gesellschaft für Naturforschung603257 FrankfurtGermany

Aims and Methods Disturbance is supposed to play an important role for biodiversity and ecosystem stability as described by the intermediate disturbance hypoth-esis(IDH),which predicts highest species richness at intermediate levels of disturbances.In this study,we tested the effects of artificial soil distur-bances on diversity of annual and perennial vascular plants and bryo-phytes in a field experiment in 86 agricultural grasslands differing in land use in two regions of Germany.On each grassland,we implemented four treatments:three treatments differing in application time of soil dis-turbances and one control.One year after experimental disturbance,we recorded vegetation and measured biomass productivity and bare ground.We analysed the disturbance response taking effects of region and land-use-accompanied disturbance regimes into account.Important Findings Region and land-use type strongly determined plant species rich-ness.Experimental disturbances had small positive effects on the species richness of annuals,but none on perennials or bryophytes.Bare ground was positively related to species richness of bryophytes.However,exceeding the creation of 12%bare ground further distur-bance had a detrimental effect on bryophyte species richness,which corresponds to the IDH.As biomass productivity was unaffected by disturbance our results indicate that the disturbance effect on spe-cies richness of annuals was not due to decreased overall produc-tivity,but rather due to short-term lowered inter-and intraspecific competition at the newly created microsites.Generally,our results highlight the importance of soil disturbances for species richness of annual plants and bryophytes in agricultural grasslands.However,most grasslands were disturbed naturally or by land-use practices and our additional experimental soil dis-turbances only had a small short-term effect.Overall,total plant diversity in grasslands seemed to be more limited by the availabil-ity of propagules rather than by suitable microsites for germination.Thus,na

关键词： annuals bryophytes colonization intermediate disturbance hypothesis microsites

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