[Advances in Ecological Research] Litter Decomposition: A Guide to Carbon and Nutrient Turnover Volume 38 || Appendix II: Exercises

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  • Appendix II: Exercises

    In this section, we present a set of problems to solve, using real data.

    Appendix II contains a few simple exercises that can be solved with basic

    calculations as well as some more advanced problems for which some

    knowledge in statistics is necessary. The section consists of two parts, the

    first one presenting the problems and the data sets and the second giving

    the solutions. In those cases where some statistics has been used, we have

    included printouts from a statistical package with additional comments

    (in italics) helping to understand the results of tests performed.

    The number of problems oVered here is limited and an additional andincrea sing num ber is foun d on the web page http: //www.eko .uj.edu.pl /deco.

    Some of the exercises are clearly related to a specific chapter and some

    integrate information from several chapters. Please note that Chapter 9

    contains some general information about selected statistical methods. Com-

    ments on the exercises are welcome, as are suggestions and new data sets

    for additional exercises which you would like to appear on the web site.

    Should you have such comments or suggestions, please send them to

    r.laskowski@eko.uj.edu.pl.SECTION I: PRESENTATION OF TASKSExercise I: Foliar Litter Fall

    Presentation of the ProblemYou measure foliar litter fall in a mature Austrian pine forest. The canopy is

    not really closed and you have placed 15 litter traps with 0.25 m2 surface

    randomly over an area of ca 50 50 m. The litter traps are placed in the fieldon August 15. You decide to empty the traps three times in the first year, the

    first time after the litter fall peak in late October, the 2nd time in late May,

    and the 3rd time on August 15. As you will note, two litter traps were found

    disturbed, one in the 2nd and one in the 3rd sampling.ADVANCES IN ECOLOGICAL RESEARCH VOL. 38 0065-2504/06 $35.00

    # 2006 Elsevier Ltd. All rights reserved DOI: 10.1016/S0065-2504(05)38014-7

    http://www.eko.uj.edu.pl/deco

  • 338 APPENDIX IIAfter samplings, the foliar litter is sorted out from other litter, dried at

    85C, weighed, and approximately one month after the last sampling, youhave the following table, with foliar litter mass given as grams per trap.

    The task is to calculate the annual foliar litter fall and give the results as

    kg/ha.Table I.1 Amount of litter (g dry mass) recorded in particular traps, 1 through 15,on the three sampling occasions

    Littertrap No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

    Sampling 1 45 61 42 21 55 59 75 52 48 19 38 43 62 59 44Sampling 2 18 15 19 9 11 9 16 14 13 5 22 13 14 12Sampling 3 10 14 15 8 7 5 7 11 17 2 12 8 5 14Exercise II: Comparing Foliar Litter Fall of DiVerentTree Species

    Presentation of the ProblemThe stand describ ed in the Exercis e I was , in fact , one of the stands in a block

    experiment. You have four stands of Austrian pine and four stands of Sitka

    spruce, each stand measuring 50 50 m. All stands, which are paired, arelocated within a limited area that is less than 1000 1000 m. The climate isthe same and the soil conditions are similar throughout this area. You have

    measured foliar litter fall for one year, using 15 replicate litter traps in each

    stand as in the Exercis e I.

    The task is to determine whether there is any significant diVerence in litterfall between the two tree species.Table II.1 Litter fall measured at the eight stands used in the experiment. Theresults are given in kg dry matter per hectare with standard deviation in parentheses

    Stand pair 1 Stand pair 2 Stand pair 3 Stand pair 4

    Austrian pine 2843 (514) 3063 (634) 2438 (386) 2987 (624)Sitka spruce 2207 (563) 2577 (483) 1989 (351) 2416 (462)

  • APPENDIX II 339Exercise III: Foliar Litter Fall in a Climatic Transect afterClimate Change

    Presentation of the ProblemWe have seen (Chapter 2) that the foliar litter fall of mature Norway spruce

    stands is well related to the climate index actual evapotranspiration (AET)

    (R2 0.787) for a boreal to temperate area ranging from about 66300N toabout 55450N, corresponding to an AET interval from 370 to 626 mm. Theequation relating litter fall to AET is:

    Litter fall 12:1 AET 3650:4In a given forest stand with the AET value of 405 mm, the annual foliar

    litter fall today is 724 kg/ha1. A new climate prediction suggests thatthere will be a full climate change in approximately year 2050. This boreal

    system (in Fennoscandia) is energy limited (Berg and Meentemeyer, 2002)

    and we can estimate that a climate change will give an increase in AET of ca

    27%, corresponding to an increase in annual average temperature of ca 4Cand an increase in precipitation of ca 40%.

    The task is to estimate foliar litter fall at that stand in the year 2050 for

    a mature Norway spruce forest. We make the assumption that nutrient

    availability does not become limiting for tree growth in the new climate.Exercise IV: Calculating Litter Mass Loss

    Problem PresentationYou have prepared a set of litter bags, incubated them, made a sampling,

    and want to determine litter mass loss. When you prepared the litter bags,

    you dried them in the air at room temperature for 4 weeks. To make an exact

    determination of the moisture content, you took 20 samples of the airdriedlitter and dried them at 85C for 24 hours. That determination gave amoisture level of 6.04% and a standard error of 0.17. Thus, the litterbags

    were prepared with litter containing 6.04% water and the registered litter

    weight thus also includes that moisture.

    The litterbags were then incubated in the field, and you have made a first

    sampling of 20 bags, cleaned their contents, dried the leaves at 85C, andweighed them. Finally, when ready to calculate the mass loss, you have the

    following data listed (Table IV.1).

    The task to calculate litter mass loss for all samples as well as the average

    mass loss.

  • Table IV.1 Litter mass in litter bags before and after incubation (airdried mass)

    Original weight(grams per litter bag)

    The same litter after 1 yrincubation (grams per litterbag)

    0.613 0.27830.611 0.28020.611 0.17980.613 0.10980.614 0.27330.616 0.29440.613 0.19230.619 0.17170.615 0.24490.617 0.16500.612 0.18800.610 0.16120.618 0.25510.614 0.30310.617 0.20490.618 0.24430.619 0.25330.615 0.30370.613 0.14220.615 0.2605

    340 APPENDIX IIExercise V: Calculating Annual Litter Mass Lossduring Decomposition

    Presentation of the ProblemThe data used for this example originate from a study on decomposition of

    Scots pine needle litter. The litter bags were incubated for 5 years and

    collected a few times a year with 20 replicates (Table V.1).

    The task is to calculate annual mass loss rates for consecutive years of

    decomposition.Exercise VI: Describing Accumulated Litter Mass LossDynamics by Functions

    Problem PresentationA decomposition experiment has been made using two diVerent litter spe-cies, one being lodgepole pine needle litter and the other, grey alder leaf

    litter. The litterbags of the two litter species were incubated in parallel in the

  • Table V.1 Average accumulated mass loss and the remaining mass for consecutivesamplings for decomposing Scots pine needle litter

    Date(yy-mm-dd)

    Incubationtime (days)

    Accumulatedmass loss (%)

    Remainingmass (%)

    74-05-02 0 0 10074-09-02 123 10.4 89.674-11-03 185 17.8 82.275-04-11 344 24.4 75.675-05-13 376 27.3 72.775-09-04 490 35.7 64.375-10-29 545 43.2 56.876-04-28 734 44.4 55.676-08-25 846 51.2 48.876-11-10 923 55.8 44.277-06-01 1126 58.8 41.277-09-12 1229 63 3777-10-27 1274 63.8 36.278-05-22 1481 66.5 33.578-08-31 1582 70.8 29.278-10-16 1628 71.4 28.679-05-14 1838 75 2579-10-02 1979 77.1 22.9

    APPENDIX II 341same stand and samplings were made at the same time and with the same

    intervals, with 25 replicate bags in each sampling. Table VI.1 reports average

    accumulated mass loss for each time interval with accompanying standard

    errors (SE), and Table VI.2 gives initial chemical composition of both litters,

    which may be helpful in interpreting the results of the exercise.

    The task is to determine which function describes the accumulated

    mass loss best and to determine whether the decomposition patterns diVeramong the litter species studied. You should compare the three functions

    you find in the book, namely the onecompartment exponential, the twocompartment exponential and the asymptotic function.Exercise VII: Regulating Factors for LitterDecomposition Rates

    Problem PresentationThe data given in Table VII.1 present results of an experiment with litter

    decomposition rates in one Scots pine stand using needle litter with five

  • Table VI.1 Accumulated mass loss (%) with standard errors (SE) for the twospecies being compared

    Grey alder leaves Lodgepole pine (%)

    Incubation time (days) (%) (SE) (%) (SE)

    0 0 0 204 40.3 0.7 10.5 1.6286 42.1 1.2 15.6 3.0359 44.0 1.0 23.5 2.8567 48.3 1.0 30.3 4.3665 48.3 0.7 39.4 6.1728 48.4 0.8 45.4 5.5931 49.4 0.7 51.6 6.9

    1021 49.2 0.8 55.9 8.51077 50.1 0.9 58.7 10.11302 51.3 0.7 61.0 7.31393 53.1 1.2 65.9 12.11448 55.5 1.6 63.1 12.7

    Table VI.2 The initial chemical composition (mg/g) of nutrients in the twolitter species

    N P S K Ca Mg Mn

    Grey alder leaves 30.7 1.37 6.12 15.6 12.3 2.32 0.10Lodgepole

    pine needles3.9 0.34 0.62 0.56 6.35 0.95 1.79

    342 APPENDIX IIdiVerent nutrient levels. Ih needles originate from a very nutrientpoor Scotspine forest, N0 from a Scots pine forest on relatively rich soil although N

    is still limiting for the microorganisms. N1, N2, and N3 are denominations

    for litter originating from stands fertilized with 40, 80, and 120 kg N as

    ammonium nitrate per hectare and year. The litter bags were incubated in

    parallel with all five litter types in the same design in the same stand for 4

    years and sampled at the same dates. Besides litter mass loss, the litter was

    also analyzed for concentrations of N, P, and lignin.

    The task: to determine possible regulating factors for the decomposition

    rate of Scots pine needle litter, using needles from trees fertilized with

    diVerent concentrations of N.

  • Table VII.1

    Incubationtime (days)

    Accumulatedmass loss (%)

    N(mg g1)

    P(mg g1)

    lignin(mg g1)

    Ih litter

    0 0 4 0.21 267202 11.1 4.4 n.d. n.d.305 21.6 4.6 0.22 308350 26.5 5.3 0.24 323557 35 6 0.25 370658 47 7.2 0.29 419704 48.1 8.3 0.41 415930 52.6 8.6 0.52 4391091 59.9 9.7 0.59 4421286 n.d. n.d. n.d. n.d.1448 67.5 10.9 0.67 482

    N0 litter

    0 0 4.4 0.32 256202 13.8 4.9 0.33 327305 26.2 5.6 0.35 338350 32.7 5.8 0.37 364557 n.d. n.d. n.d. n.d.658 47.4 8.4 0.48 418704 51.2 8.2 0.45 438930 56.3 8.9 0.61 4371091 62 11.1 0.7 4561286 62.2 10.8 0.6 4671448 68.8 11.6 0.71 486

    N1 litter

    0 0 4.4 0.3 251202 14 4.9 0.31 310305 26.7 5.9 0.34 340350 31.3 5.9 0.32 367557 n.d. n.d. n.d. n.d.658 47.6 8.3 0.44 431704 49.3 8.7 0.43 437930 53.4 9.6 0.53 4561091 59.4 10.9 0.66 4631286 63.2 10.9 0.67 4661448 67.7 11.6 0.67 480

    N2 litter

    0 0 7 0.34 269202 15.5 7.2 0.39 344305 28.5 7.6 0.37 369

    (continued)

    APPENDIX II 343

  • 350 32.2 7.7 0.38557 n.d. n.d. n.d. n.d.658 50 11.3 0.57 442704 51.1 11.8 0.53 453930 53.6 11.9 0.58 453

    1091 60 12.8 0.68 4661286 64.8 13.8 0.68 4671448 70.4 13.4 0.69 490

    N3 litter

    0 0 8.1 0.42 268202 18.3 8.8 0.4 353305 30.3 9.1 0.39 388350 36.3 11.2 0.44 401557 n.d. n.d. n.d. n.d.658 50.7 13.8 0.63 452704 53 13.9 0.59 464930 58 14.4 0.68 469

    1091 60.4 14.3 0.72 4581286 64.9 15.2 0.71 4811448 67.6 14.9 0.72 480

    Table VII.1 (continued )

    Incubationtime (days)

    Accumulatedmass loss (%)

    N(mg g1)

    P(mg g1)

    lignin(mg g1)

    344 APPENDIX IIExercise VIII. Nitrogen DynamicsConcentrationsand Amounts

    Problem PresentationThe data set below originates from decomposing local Scots pine needle

    litter in a boreal Scots pine monoculture stand, covering approximately 3 ha.

    Bags were incubated on 20 spots, distributed randomly all over the stand. At

    each sampling, 20 replicate litter bags were collected. Litter mass loss was

    determined and nitrogen concentration was measured on combined samples

    from each sampling (Table VIII.1).

    The task in this exercise is to calculate and plot the changes in absolute

    amount and in concentrations of N with time for decomposing Scots pine

    needle litter using the following data set.

  • Table VIII.1 Litter mass loss and N concentration during decomposition of Scotspine needle litter

    Time (days) Litter mass loss (%) N concentration (mg g1)

    0 0 4.8204 15.6 5.1286 22.4 5.4358 29.9 5.4567 38.4 8.3665 45.6 9.2728 47.5 8.8931 54.1 9.81021 58.4 11.11077 62.5 11.51302 66.0 12.21393 67.4 12.5

    APPENDIX II 345Exercise IX: Increase Rate in Litter N Concentration

    Problem PresentationThe data set to be used in this exercise is that in Table VIII.1, which originates

    from decomposing local Scots pine needle litter in a boreal Scots pine mono-

    culture stand, covering approximately 3 ha. Bags were incubated on 20 spots,

    distributed randomly all over the stand. At each sampling, 20 replicate litter

    bags were collected. Litter mass loss was determined and nitrogen concentra-

    tion was measured on combined samples from each sampling.

    The task in this excercise is to calculate the increase rate in litter N

    concentration.Exercise X: DiVerences in Increase Rates for NitrogenConcentrations

    Problem PresentationTwo litter types have been incubated in the same stand during the same time

    period and using the same incubation and sampling design. The data origi-

    nate from decomposing green and brown local Scots pine needle litter

    incubated in a boreal Scots pine monoculture (Table X.1). Twenty replicate

    litter bags were taken of each litter type at each sampling.

    The task in this exercise is to calculate the increase rate in litter N

    concentration in the two litter types and to determine whether the slopes

    (NCIR) are significantly diVerent.

  • Table X.1 Accumulated mass loss and corresponding N concentration in decom-posing green and brown Scots pine needles

    Green needle litter Brown needle litter

    Mass loss (%) N (mg g1) Mass loss (%) N (mg g1)

    0 15.1 0 4.823.3 19.0 15.6 5.128.8 20.8 22.4 5.438.0 23.8 29.9 5.444.9 27.3 38.4 8.348.8 30.4 45.6 9.252.1 30.8 47.5 8.854.2 30.7 54.1 9.858.0 31.7 58.4 11.160.5 29.5 62.5 11.563.4 31.6 66.0 12.265.9 31.6 67.4 12.5

    346 APPENDIX IIExercise XI: Calculating the Sequestered Fraction of Litter N

    Problem PresentationDuring a 4year experiment, you have collected the following data(Table XI.1) for the decomposition of Scots pine needle litter. The experi-

    ment was performed in a Scots pine monoculture covering 3 hectares and

    there were 20 litter bag replicates in each sampling. For each sampling date,

    you have the accumulated litter mass loss and N concentration in the litter.

    The task is to calculate the fraction of the original amount of N that will

    be stored in the recalcitrant part of the litter.Table XI.1 Accumulated mass loss and N concentrations in decomposing Scotspine needle litter

    Days Accumulated mass loss (%) N conc (mg g1)

    0 0 4.8204 15.6 5.1286 22.4 5.4358 29.9 5.4567 38.5 8.3665 45.6 9.2728 47.5 8.8932 54.1 9.81024 58.4 11.11078 62.5 11.51304 66.0 12.21393 67.4 12.5

  • APPENDIX II 347Exercise XII: Nitrogen Stored in Litter at the Limit Value

    Problem PresentationTh...

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