1. Jushan Liu Institute of Grassland Science Ecological functions of litter in ecosystem 2013.4.23

2. Instruction Litter dynamics Effects of litter on environment Effects of litter on plant community DIRT project

3. Plant litter: the dead plant material of small size lying loose on the ground Introduction

4. Litter may affect environment and plant community structure and dynamics, linked to climatic conditions and environmental management Substrate for the detritus food web, nutrient reservoir, and contributor to mineral-nutrient cycling and energy flow Alter microenvironment and plant community

5. Introduction Production and decomposition have been widely studied, carbon balance and cycling of nutrients Effects on particular populations, but only recently on community structure and dynamics. Few attempts have been made to understand the mechanisms underlying the effects of litter on plant populations and communities

6. Litter accumulation is a complex process and change in time and space, and affect the physical and chemical environment Balance among liter production, litter deposition from outside system, litter destruction by physical and biotic agents, and removal of litter Litter dynamics

7. Litter production Productivity of the plant community Climate, rainfall and the length of growing season Soil fertility, soil water retention, and species composition is important Herbivores may increase or decrease the production of litter, though consumption usually reduces the standing biomass

8. (Xiong and Nilsson 1914-2002)

9. Litter disappearance Litter accumulated may be reduced by physical and chemical degradation, heterotrophic consumption and decomposition Decomposition rates vary among ecosystems, regulated mainly by temperature and water regimes and soil fertility is secondarily important Litter dynamics

10. Litter decomposition Microenvironment surrounding the litter affects decomposition rate Decomposition is faster when trampling by cattle or snow packing Litter exposed to air is decomposed mostly by fungi Litter dynamics

12. Litter decomposition Chemical composition of litter is another important variable, lignin, nitrogen, cellulose and second compounds Short-lived organs have less lignin and secondary chemicals Adverse growth condition and herbivory may also increase the concentration of tannin and phenolic Litter dynamics

13. Effects on environment Chemical environment During life and senescence of organs, organic and inorganic substances are accumulated, released by leaching, or attacked by decomposers and their products released into the soil Chemical properties of the leachates depend on the nature of the substances and on the biochemical transformations

14. Effects on environment Chemical environment Mineral nutrients: retranslocated to other organs, consumed by herbivores or pathogens, or lost by plants with litter Environmental conditions and physicochemical characters of litter regulate the rate of nutrient release from the organic matter

15. Effects on environment Chemical environment Litter indirect effects on nutrient availability through changes in environmental variables that regulate mineralization Litter accumulation can create patchy distribution of nutrient and produce high concentrations of toxic minerals, heavy metals or salt

16. Effects on environment Physical environment Litter intercepts incident light and the rain, and changes surface structure, affecting transfer of heat and water between soil and the atmosphere Direct effects on germination and establishment and indirect effects on resource availability and other biotic components

17. Effects on environment Physical environment Light environment Light interception by litter is important and may exert an important effect on the plant community Changes in the light spectrum may have important ecological significance, since light quality affects germination, seedling development and tillering

18. Effects on environment Physical environment Light environment Litter may prevent the germination of plants and establishment is negatively affected by litter Higher mortality of seedlings under a thick layer of litter and establishment of species with very large seeds may be hindered by litter

19. Effects on environment Physical environment Light environment Sprouting of perennial herbs may also be negatively affected as a result of light deprivation Grass shoots growing under dense litter must spend energy to reach the light, and tillers lessen their capacity to fix carbon and reduce plant productivity

20. Effects on environment Physical environment Soil temperature Litter modifies soil temperature by intercepting solar radiation, and by insulating the soil from air temperature Temperature of soil surface under litter is lower than air temperature, and burning or hand litter removal can increase soil temperature

21. Effects on environment Physical environment Soil temperature Changes in soil temperature produced by litter may directly affect plant growth, but may also enhance the rate of mineralization, and therefore nutrient availability Early sprouting may be a result of increased soil temperature and in bare areas higher temperature early in the spring promotes early emergence

22. Effects on environment Physical environment Water dynamics Litter affects exchange of water between soil and atmosphere and increases water availability Litter accumulation can increases infiltration, reduce evaporation from the soil and decreases run-off, indirectly by reducing the soil temperature

23. Effects on environment Physical environment Water dynamics Changes in water availability mediated by litter may have obvious effects on different plant population, increase establishment of grass seedlings and seedling survivorship. Litter removal can decrease productivity where water may be the main limiting factor

24. Effects on plant community Germination and establishment Sensitive to litter, and there exist both positive and negative responses Improving water conditions in dry habitats, protecting seeds from or by reducing competition Shading or obstructing plants, reducing temperature, attracting predators, and probably fostering pathogens

25. Effects on plant community Community productivity Production is enhanced, unchanged or inhibited, attributable to different substrate conditions, species compositions, and litter amounts, as well as litter types and qualities Substrate is one of most important factors, affect the rates of both litter production and litter disappearance and thus community responses

26. Effects on plant community Species richness Positive and negative effects have been found Moderate input of litter may reduce dominance and increase diversity Thick mat of tree litter may reduce diversity of ground vegetation and quadratic relationship with the highest numbers of species at low to intermediate accumulations of litter

27. Effects on plant community Community dynamics Litter-induced changes in soil nutrients, light, and soil temperature and moisture initiate community successions in different systems Associated with a change of interspecific relations induced by litter Litter alters species interactions in a deciduous forest (Sydes and Grime 1981)

28. Effects on plant community Community dynamics Litter changed the relative importance of different species categories (Monk and Gabrielson 1985) Succession of oldfield communities was indirectly controlled by changing interspecific interactions because of litter (Facelli and Pickett 1994) Berendse (1994) developed a model suggesting that species replacements were triggered by the decomposability of litter

29. Effects on plant community Community dynamics Litter accumulation may affect seasonal changes of a community Litter addition suppresses and removal increases density and richness (Carson and Peterson 1990) Litter layer may prevent seeds from reaching the soil and germinating in early spring Redistribution of litter have different outcomes for a specific vegetation

30. Conclusions Litter is an important factor affecting community organization and dynamics far beyond a transitory bank of nutrients. Litter can alter the physical and chemical environment, and therefore the demography of various populations. The response of different populations, with effect of the changes in the performance of other populations, may play an important role in shaping community structure

31. (Sayer 2006)

32. (Richard and Cotrufo 1998)

33. Detritus Input and Removal Treatments is an international network of fieldbased organic matter manipulations (Nadelhoffer et al 2004)  How rates and sources of plant litter inputs control the accumulation and dynamics of organic matter and nutrients in soils?  To determine contributions of live roots, above- ground litter, and belowground detritus to SOM and nutrient dynamics DIRT project

34. Francis D. Hole (1914-2002) DIRT project

36.  Live root respiration, aboveground litter and root detritus constitute one-third of C inputs  Doubling or excluding litter proportionally increased or decreased respiration  C and N stocks respectively increased or decreased in response to doubling or excluding aboveground litter inputs to root-intact soil  Aboveground inputs strongly influence SOM, root inputs on SOM quality DIRT project

39.  To determine how nitrogen and carbon inputs interact in controlling nutrient cycling and stock  How does different quantity and quality of litter input influence ecosystem structure and functions? The function of litter on grassland under the background of nitrogen deposition