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Patterns in Decomposition Rates Among Photosynthetic Organisms: the Importance of Detritus C :N :P Content

Patterns in Decomposition Rates Among Photosynthetic Organisms: the Importance of Detritus C :N :P Content

Oecologia (1993) 94:457M71 Oecologia Springer-Verlag 1993

Review article

Patterns in rates among photosynthetic : the importance of C :N :P content

S. Enriquez ~, C.M. Duarte ~, K. Sand-Jensen 2 t Centro de Estudios Avanzados de Blanes, (CSIC), Cami de Santa BArbara, 17300 Blanes, Girona, Spain 2 Freshwater Biological Laboratory, University of Copenhagen, 51 Helsingorsgade, 3400 Hillerod, Denmark

Received: 30 January 1993 / Accepted: 4 April 1993

Abstract. The strength and generality of the relationship chemical conditions under which the decomposition oc- between decomposition rates and detritus carbon, nitro- curs, and substrate quality (e.g. biochemical composition gen, and concentrations was assessed by of litter), which constrains its suitability for micro- comparing published reports of decomposition rates of bial growth. Photosynthetic organisms can directly in- detritus of photosynthetic organisms, from unicellular fluence decomposition rates through their biochemical algae to trees. The results obtained demonstrated the composition. For instance, may accumulate de- existence of a general positive, linear relationship be- fence chemicals in their tissues which, besides decreasing tween plant decomposition rates and and phos- their palatability to grazers (e.g. Coley et al. 1985), also phorus concentrations. Differences in the carbon, nitro- reduce their quality as a substrate for mi- gen, and phosphorus concentrations of plant detritus croorganisms (Swift et al. 1979). Similarly, reab- accounted for 89% of the variance in plant decom- sorption before abscission of plant tissues may, in addi- position rates of detritus originating from photosynthetic tion to improving the internal nutrient economy of the organisms ranging from unicellular microalgae to trees. plant (Chapin 1980), affect their suitability as substrate The results also demonstrate that moist plant material for microbial . decomposes substantially faster than dry material with Decomposer organisms tend to have very high nitro- similar nutrient concentrations. Consideration of , gen and phosphorus contents (Findlay 1934; Thayer instead of carbon, concentrations did not improve the 1974; Swift et al. 1979; Goldman et al. 1987; Vadstein relationships obtained. These results reflect the coupling and Olsen 1989) indicative of high requirements for these of phosphorus and nitrogen in the basic biochemical . For instance balanced bacterial growth re- processes of both plants and their microbial decom- quires substrates with carbon, nitrogen, and phosphorus posers, and stress the importance of this coupling for in an (atomic) ratio of 106:12:1 (Goldman et al. 1987), carbon and nutrient flow in . although have some capacity to vary these re- quirements (e.g. Tezuka 1990). These high nutrient con- Key words: Decomposition - Plant kingdom - Nutrients tents are only encountered in fast-growing phytoplank- ton cells (Goldman et al. 1979; Duarte 1992), and micro- bial decomposers are often supplied with plant detritus depleted in nitrogen and phosphorus relative to their Carbon fixed by photosynthetic organisms is made avail- requirements. Recent research has demonstrated that able to other components via or bacterial growth efficiency (i.e. the fraction of the carbon . The detrital path is a major determinant of used allocated to growth) decreases about 100-fold with the flow of carbon fixed by plants in ecosystems were increasing C/N and C/P ratios in their substrate (Gold- herbivores consume a modest fraction of primary man et al. 1987). Thus, detritus with high nitrogen and production, as is often the case (Swift et al. 1979). De- phosphorus content should decompose fast because of composition of plant detritus is largely conducted by the associated fast growth of the microbial populations, bacteria and fungi (e.g. Persson et al. 1980), and the rate whereas excess carbon in the should lead to of this process depends, therefore, on all factors influenc- nutrient-controlled carbon remineralization (cf. Gold- ing their activity. These may be separated, following man et al. 1987; Vadstein and Olsen 1989). Swift et al. (1979), into abiotic factors, the physico- These arguments provide an explanation for the in- crease in decomposition rate with increasing nutrient This work was funded through a grant of CICYT (MAR91~503) concentration, or decreasing carbon/nutrient ratios, to C.M.D. demonstrated six decades ago (Tenny and Waksman Correspondence to: S. Enriquez 1929), and confirmed since for different aquatic (e.g. 458

Valiela et al. 1984; Twilley et al. 1986; Harrison 1989; days) since the initiation of the experiments using the equation, Reddy and DeBusk 1991) and terrestrial (e.g. Gosz et al. wt = Wo e-kt 1973; Swift et al. 1979; Berg et al. 1982; Taylor et al. 1989; Upadhyay et al. 1989) systems. In addition to which is the model most often used in the literature (Olson 1963) reflecting direct nutrient effects, these relationships also and simpler than the double-exponential model (e.g. O'Connell 1987). Because these decomposition rates have logarithmic units, we appear to have an indirect component, derived from a also described decomposition rates as the half- of plant detritus tendency towards reduced carbon quality and increasing (Ta/2, days), which, although a function of exponential decom- amounts of secondary metabolites in plant litter as nu- position rates (T1/2 = k-1. In 2), provides a more intuitive des- trient availability decreases (Coley et al. 1985, Chapin et cription of detritus turnover times. Decomposition rates were often al. 1987). Hence, some ratios incorporating a descriptor reported in the studies, and were otherwise calculated from tab- of carbon quality (e.g. lignin/N ratios) have also been ulated data or digitized graphs of weight remaining with time shown to be related to decay rates of plant litter (e.g. elapsed. We included in the data set (Appendix) all studies encoun- tered during our search that included estimates of decomposition Melillo et al. 1982; Aber et al. 1990). However, lignin/N rates of plant litter (e.g. photosynthetic tissues, , rhizomes, ratios appear to outperform C/nutrient ratios as a predic- stems), and any of the descriptor of chemical composition tor of decay rates only when comparing plant litters of needed to test our hypotheses (i.e. C, N, P, and lignin concentra- similar lignin contents (Taylor et al. 1989). tions). Whether the widespread finding of strong relation- Additional detail in the general description of the data set was obtained by grouping the data according to detritus origin (phyto- ships between litter nutrient content and decomposition , macroalgae, seagrasses, freshwater angiosperms, am- rates reflects the existence of a general relationship, ap- phibious plants, sedges, mangroves, grasses, shrubs, conifers, and plicable to detritus originating from different photosyn- broad-leaved deciduous and evergreen trees). The relationships be- thetic , is not known as yet. The existence of tween decomposition rates and nutrient concentrations were des- such a general relationship is expected because all micro- cribed using least-squares regression analyses of log-transformed bial decomposers have high nitrogen and phosphorus, in data. Logarithmic transformation was found to be necessary to avoid heteroscedasticity in these analyses (Draper and Smith 1965). addition to carbon, needs in both aquatic (Goldman et Differences in the relationship between plant litter decomposition al. 1987; Vadstein and Olsen 1989) and terrestrial (Find- rate and nutrient content depending on detritus origin (as defined lay 1934; Thayer 1974; Swift et al. 1979) environments. above) were tested for using analysis of covariance (Draper and Conversely, these relationships might differ between dif- Smith 1966). The simultaneous influence of carbon (or lingin), ferent sorts of plant detritus if they were indirect, result- nitrogen, and phosphorus on litter decomposition rates was tested ing from covariation between carbon quality (e.g. con- for using multiple least squares regression analyses, instead of carbon/nutrient ratios, for the use of these ratios is conducive to tents of lignin, polyphenols, etc.) and nutrient content statistical artifacts (cf. Chayes 1971; Atchley and Anderson 1978). within plant types (e.g. Melillo et al. 1982; Abet et al. The (statistical) influence of nitrogen, phosphorus, carbon (or lig- 1990; Upadhyay et al. 1989). nin) contents on decomposition rates was partitioned into direct Here we examine the strength and generality of the and indirect effects using path analysis (e.g. Williams et al. 1990). relationship between decomposition rates and plant nu- Separate path analyses were used to test the effects of C, N, and P, trient concentrations by comparing published reports of on the one hand, and those oflignin, N, and P, on the other, because lignin contents were only reported in a small subset of the studies, decomposition rates and litter nutrient contents across a which did not include any study on or macroalgae. broad spectrum of plant detritus, from unicellular algae to trees. We first examine the variability in decom- position rates of litter from different sources, and then assess the power of differences in their nutrient concen- Results and discussion tration to statistically account for the observed variabil- ity. A subset of these data, for which lignin contents were The data set comprised 256 reports of decomposition available in addition to nitrogen and phosphorus con- rates of plant litters originating from different photosyn- tents, was used to compare the strength of the relation- thetic organisms, from land an aquatic environments ship between lignin and nutrient contents and litter de- (Appendix). These data were gathered under a broad composition rates. Because plant nutrient concentrations variety of conditions, from controlled laboratory experi- are often strongly intercorrelated (Garten 1976; Duarte ments to field studies, and included decomposition of 1992), we used path analysis (Williams et al. 1990) to plant litter originating from photosynthetic tissues, statistically resolve the direct contribution of carbon, roots, rhizomes, stems and branches, and mixtures of nitrogen, phosphorus, and, where available, lignin, to the these (Appendix). Unfortunately, detailed descriptions observed relationship between nutrient content and de- of the experimental conditions (e.g. , pH, tritus decomposition rate. tension) were only reported in a few studies and could not be included in the analysis. Decomposition rates ranged between 0.00019 day -1 for non-photosynthetic tissues of an Australian shrub Methods (Leucospermun parile), and 0.098 day- i for the cells of a cyanobacterium (Anabaena sp.) and the leaves of a We searched the literature for published reports of plant litter decomposition rates and chemical composition (carbon, lignin, submerged freshwater angiosperm (Vallisneria spiralis), nitrogen, and phosphorus concentrations) at initiation of decom- and differed significantly according to their origin (ANO- position. Decomposition rates (k, natural log units day-1) were VA, F=41.3, P< 0.0001; Fig. 1). Decomposition rates described from the changes in plant dry weight (W) with time (t, were faster for detritus derived from phytoplankton and 459

i Microalgae Freshwater plants ** I'---f] Amphibious plants I I t'--- b Macroalgae Seagrasses t I I I ' . O Grasses i 7--3---1 , Sedges I I F~ Mangroves m~ I I . Broad decid.tree leave: r-l----q Shrubs ,- f-y-- ] Conifers O Broad perennial P tree leaves P I [ 0.0001 0.001 0.01 0.1 0 500 1000 1500 2000

Decomposition rates (day -1) Half-life of detritus (days) Fig. 1. Box plots showing the distribution of detritus decomposition confidence limits, asterisks-represent observations extending be- rates and half- for detritus of different sources. Boxes encom- yond the 95% confidence limits, and circles represent observations pass the 25 and 75% quartiles of all the data for each plant type, beyond the 99% confidence limits the central line represents the median, bars extend to the 95%

Table 1. Regression equations between detritus decomposition rate (K, In units day x) and carbon (C), phosphorus (P), nitrogen (N), and lignin concentrations (as % DW) in the plant litter

Variable Intercept Slope N Slope P Slope C Slope n rz F P dependent lignin k -2.45 1.19+0.095 231 0.40 155 <0.001 k - 1.42 0.93 • 0.066 143 0.58 198 < 0.001 k 1.17 -2.1• 78 0.12 11.6 <0.001 k - 1.38 - 1.04• 0.20 54 0.32 25.8 <0.001 k - 1.89 0.80• 0.50• 141 0.64 123 <0.001 k -0.22 0.71 • 0.220 0.66+0.154 - 1.0• 50 0.85 92 < 0.001 k - 1.87 0.31 ~ 0.240 0.39• -0.22• 43 0.37 9.14 < 0.001 Submersed detritus: k -2.30 1.33• 136 0.50 134 <0.001 k - 1.22 1.01 • 80 0.66 153 <0.001 Terrestrial detritus: k -2.77 0.48• 98 0.14 17 <0.001 k - 2.20 0.46 • 0.09 66 0.26 24 < 0.001

All variables were tog-transformed prior to regression analyses. F-statistic (F), and the associated probability level (P) for the regres- Also shown are the SE of the regression coefficients, the number of sion analysis observations involved (n), the coefficient of determination (r2), the

amphibious and submerged freshwater plants (Fig. 1), P<0.005; Table 1). Regression analysis indicated that which had average half-lives between 17 and 58 days, and decomposition rates (k) increased linearly (Ho: were slowest for litter derived from shrubs and perennial- slope= 1, t-test, P> 0.05) with increasing litter nitrogen leaf trees, which had average half-lives ranging between and phosphorus concentrations (Table 1). This implies 2 and 3 years (Fig. 1). Litter nutrient concentrations also that half-lives (half life = k -1 In 2), and, therefore, de- differed significantly according to the detritus source tritus turnover times are inversely scaled to litter nutrient (ANOVA, F= 17.9 and 16.8 for N and P, respectively, concentration. Detritus lignin content was negatively P< 0.001), such that plants whose detritus decomposed correlated with its nitrogen and phosphorus contents fast also tended to produce detritus with high nitrogen (r = - 0.36 and - 0.57, respectively, P < 0.05), and was and phosphorus concentrations. significantly, negatively related to litter decomposition Decomposition rates were strongly positively cor- rates (Table 1), supporting the importance of carbon related with the initial nitrogen and phosphorus concen- quality on decomposition rates (e.g. Melillo et al. 1982; tration of the detritus (r=0.64 and 0.76, respectively, Aber et al. 1990; Upadhyay et al. 1989). P< 0.0001 ; Table 1, Fig. 2), and were weakly, negatively The relationships between decomposition rates and correlated to its carbon concentration (r=-0.37; nitrogen and phosphorus concentrations differed signifi- 460

0.1 , , -./t,

0.01 o ~/y'o_ wO~O e ~0 Fig. 2. The relationships between de- composition rate and the initial nitro- gen and phosphorus concentrations 0.001 o ~ o in the detritus. Solid lines represent the fitted regression lines (Table 1), eo o and open and solid circles represent detritus decomposing on land and 0.0001 I I I I I submersed, respectively 0.01 0.10 1 10 0.001 0.01 0.1 1 10

Nitrogen (% DW) Phosphorus (% DW)

i ' O.1 0.1 2 1

3 5

8 6 0.01 j t_ 0.01 -- 4 e~ e~ 0 0 9 9 6 0.0Ol 0.001 -- E E 0 0

O.O00l 0.0001 I I I 0.01 0.1 0 10 0.001 0.01 0.1 0 10

Nitrogen content (% DW) Phosphorus content (% DW) Fig. 3. Regression lines describing the relationships between decom- 2 - freshwater plants; 3 amphibious plants; 4 macroalgae; position rates and nitrogen and phosphorus concentrations for 5 - seagrasses; 6- grasses; 7- sedges; 8 - mangroves; 9 - broad detritus of different sources. Lines extend the range of nutrient con- deciduous tree leaves; 10 - shrubs; 11 - conifers; 12 - broad centrations for detritus source in the data set. 1 - microalgae; perennial tree leaves

cantly depending on detritus origin (ANCOVA, F= 11.2 decomposing on land were much weaker and scaled as and 5.0, P< 0.001, for nitrogen and phosphorus concen- the 1/2 power of nutrient concentration (Table 1). trations, respectively), which accounted for 32 % and 24 % The large variance in detritus decomposition rates of the unexplained variance in the relationship between unexplained by nitrogen or phosphorus concentration, decomposition rate and litter nitrogen and phosphorus as well as the lack of relationship within some sources of concentrations, respectively. Decomposition rate of am- detritus, may be partially attributable to the need to phibious plant litter increased fastest with increasing consider the effects of carbon, nitrogen and phosphorus nitrogen and phosphorus concentration (Fig. 3, Table 2), contents on plant decomposition in concert. This has and no relationship between litter nitrogen or phospho- been achieved in the past using the carbon/nitrogen and rus content and decomposition rate was observed within carbon/phosphorus ratios of the detritus, which reflect some litter sources (e.g. phytoplankton, freshwater the relative limitation of decomposers by carbon - and angiosperms; Fig. 3, Table 2). These differences were energy - versus nutrients (e.g. Twilley et al. 1986; Taylor partially attributable to the different where the et al. 1989; Reddy and DeBusk 1991; and others). We detritus decomposed, for litter decomposed faster, for a also found strong negative correlations between decom- given nutrient concentration, in than on land (AN- position rates and C/N and C/P ratios (Fig. 4), and COVA, F=12.4 and 4.9, P<0.001, for nitrogen and simultaneous consideration of detritus nitrogen, phos- phosphorus, respectively), consistent with the stimulato- phorus, and carbon concentrations accounted for most ry effect of moisture on decomposition rates (Swift et al. (89%, SE of regression estimates = 1.7-fold) of the vari- 1979). Moreover, decomposition rates of submerged ance in decomposition rates (Table 1), independently of plant detritus were strongly, linearly scaled to nutrient detritus origin (ANCOVA, F-test, P>0.05). A similar concentrations (Table 1), whereas those of plant material relationship based on lignin, nitrogen, and phosphorus 461

Table 2. Regression equations between detritus decomposition rate (K, in units d 1) and nitrogen (N), and phosphorus (P) concentrations (as % DW), for the different detritus sources in the data set

Plant type Intercept Slope N Intercept Slope P Range n r 2 F P

Phytoplankton N - 1.51 0.314- 0.274 (8.94-2.30) 15 0.02 1.24 0.286 P - 1.26 0.23 • 0.204 (1.70-0.26) 13 0.02 1.25 0.287 Macroalgae N - 1.46 - 1.30 • 0.662 (3.92-1.00) 8 0.29 3.85 0.098 P - 1.54 1.11 • 1.401 (0.36-O.19) 6 0.000 0.63 0.473 Seagrasses N -2.19 0.16• (4.36-0.53) 24 0.000 0.15 0.702 P - 1.64 0.41 • 0.068 (2.50-0.04) 7 0.85 35.33 0.002 Freshwater N - 1.55 0.40:t:0.516 (3.66-1.15) 17 0.000 0.59 0.454 angiosperms P - 1.29 0.134-0.230 (0.85-0.10) 14 0.000 0.35 0.580 Amphibious plants N - 2.35 1.98 4- 0.384 (3.25-0.59) 12 0.701 26.75 0.000 P - 0.42 2.22 • 0.343 (0.47-0.08) 9 0.836 41.75 0.000 Sedges N - 1.78 0.744- 0.188 (2.77-0.18) 50 0.505 50.92 0.000 P - 1.78 0.744- 0.188 (0.29-0.01) 24 0.388 15.56 0.001 Mangroves N -2.17 1.62:6 1.046 (1.24-0.36) 8 0.165 2.38 0.174 P -3.71 1.564-0.739 (0.13-0.06) 4 0.537 4.47 0.169 Grasses N -2.48 0.6012.62 (3.52-0.18) 9 0.341 5.14 0.058 P - 1.85 0.684-0.165 (0.58-0.02) 8 0.699 17.22 0.006 Shrubs N - 2.62 1.19 4- 0.464 (2.15-0.44) 18 0.247 6.57 0.040 P - 1.96 0.574- 0.208 (0.56-0.005) 14 0.329 7.38 0.019 Conifers N - 2.91 0.71 4- 0.227 (4.96-0.35) 25 0.271 9.93 0.040 P -2.02 0.764-0.265 (0.55-0.02) 15 0.340 8.22 0.013 Broad deciduous tree N - 2.70 0.08 ~: 0.209 (3.07-0.07) 43 0.000 0.15 0.704 leaves P - 2.31 0.25 4- 0.291 (0,28-0,02) 26 0.000 0.76 0.391 Broad perennial tree N -2.14 1.53i363 (0.70-0.13) 6 0.770 17.76 0.014 leaves P - 1.57 0.76 • 0.329 (0.06-0.004) 6 0.465 5.34 0.082

All variables were log-transformed prior to regression analyses. detritus, the number of observations involved (n), the coefficient of Also shown are the SE of the regression coefficients, the range of determination (r2), the F-statistic (F), and the associated probability nitrogen and phosphorus concentrations for the different sources of level (P) for the regression analysis

66 z \0 I 9 0.1 od ~t. o.~. $" 4it.. 9 9 00 o 9

0.01 "7

0.001 Fig. 4. The relationship between detritus decomposition rate and initial C/N and C/P atomic ratios. Solid lines represent the fitted re- 0.0001 I r I I gression lines 1 10 100 1000 10 100 1000 10000

C/N C/P concentrations, was much weaker (37% of the variance 1966). The statistical influence of litter nitrogen, phos- explained, SE of regression estimates = 2.2-fold), perhaps phorus, and carbon (or lignin) concentrations on de- because of the narrower range of detritus sources for composition rates is best depicted, therefore, as a mixture which estimates of lignin concentration were available. of direct (i.e. dependent on the concentration of a par- Nitrogen and phosphorus concentrations in the plant ticular element) and indirect effects, acting through the detritus were highly correlated (r= 0.83, P< 0.0001), as relationship to other nutrients (Fig. 5). We used path demonstrated for terrestrial (Garten 1976) and aquatic analysis (Williams et al. 1990) to elucidate these different (Duarte 1990, 1992) plants. The strong colinearity be- effects. This showed that indirect effects were indeed tween phosphorus and nitrogen concentrations implies important, and accounted for 52% and 44% of the effect that the coefficients of determination obtained in the of nitrogen and phosphorus, respectively, on litter de- multiple regression analysis (Table 1) may be inflated, composition rates (Fig. 5), whereas no significant direct and the regression coefficients biased (Draper and Smith effect could be attributed to differences in carbon concen- 462

~0 N, 0.41 P, 0.03 C)

86 0.87~ -0 17 Phosphorus " i' k (0.48 P, 0.34 N, 0.04y Decomposition rate \ ~ Ca~rbon ~ -0.37 (-0"18 c, -0.07 N, -0.12 p)

Fig. 5a, b. Path diagrams describing the structure of the relationship be- tween decompositionrates and a ni- Nitrogen trogen, phosphorus and carbon, or ~ / ~0.49(0.19 N, 0.26 P, 0.04 Lignin) b lignin concentrations. Numbers in 13/ /0.61 bold type show the Pearson correla- tion coefficientsamong the variables, and numbers in parentheses partition "0!36 " Phosnl~orusP-- (0.43 P, 0.120.61 N, 0.06 lignin~,,~"~ Decomposition. rate. the Pearson correlations between de- composition rates and nutrient con- \ \0. .... centration into direct and indirect (i.e. attributable to indirect relation- ~ /-0.43 (-0.11 Lignin, -0.07 N, -0.25 P) ships to other variables) effects Lignin (cf. Williams et al. 1990) tration. Similarly, path analysis on the smaller data set flow in ecosystems. Nutrient constraints on carbon flow for which lignin concentration was available also re- through detrital food webs may be, at least qualitatively, vealed no significant direct effect of lignin concentration similar to the demonstrated importance of plant nutrient on detritus decomposition rates (Fig. 5). status for herbivory (e.g. Mattson 1980). Microbial de- These results provide evidence of the importance of composers also play a major role in the digestion of the the nitrogen and phosphorus concentration in the plant plant material ingested by herbivores, so that the diges- litter in regulating decomposition rates, consistent with tion process in guts involves, in fact, decom- current knowledge of microbial nutrient requirements. position. Thus, there are close relationships between That detritus carbon concentrations were not particular- plant nutrient status and herbivory (Mattson 1980), and ly important in accounting for differences in decom- between plant nutrient concentration and the efficiency position rates is expected from the high C/N and C/P of conversion of ingested food (Mattson 1980). The par- ratios characteristic of plant detritus (Fig. 4), relative to allel between detritivory and herbivory extends beyond those of bacteria (Thayer 1974; Swift et al. 1979) and nutrient control of their rates. For instance, increasing saprophytic fungi (Findlay 1934; Swift et al. 1979). The temperature accelerates decomposition rates (Godshalk lack of strong relationships between detritus carbon or and Wetzel 1978; Swift et al. 1979; Best et al. 1990; lignin concentrations and decomposition rates does not Aizaki and Takamura 1991). Likewise, the digestive conflict with the important role of carbon quality in tracts of homeotherm herbivores provide, compared with regulating decomposition rates. Instead, it probably re- those of poikilotherms, a suitable "digestion reactor" flects the fact that carbon quality is a compound variable, with high enabling efficient microbial activ- involving a broad array of compounds besides lignin in ity (Swift et al. 1979). Thus, herbivory and detritivory the diverse set of detritus sources compared here. These are, to some extent, constrained by similar factors, results are, therefore, consistent with previous reports through similar causes. The recent awareness of the im- that differences in decomposition rates were best related portance of microbial as links between pri- to nutrient content when comparing litters from a broad mary produceres and herbivores in planktonic ecosys- range of plant sources, but to carbon quality when com- tems (i.e. the , Azam et al. 1983), may well paring litter derived from similar plants (Taylor et al. reflect the general structure of ecosystems, where primary 1989). The relationship between plant decomposition producers and herbivores are linked by such microbial rates and detritus carbon, nitrogen and phosphorus con- loop (whether internally, i.e. intestinal flora, or external- centration found here accounted for most (89%) of the ly, i.e. decomposers). differences in the decomposition rates of detritus derived The important role of nutrients in controlling plant from photosynthetic organisms ranging from unicellular decomposition rates has also the indirect effect of cou- microalgae to trees. These results highlight, therefore, the pling growth and decomposition rates, for fast-growing importance of the nutritional balance (C :N :P) of plant plants tend to have high nutrient concentrations (Chapin detritus in regulating decomposition rates. et al. 1987), and also decompose fast because of the The nutritional balance of plant detritus plays, adequacy of their litter as substrate for microbial growth. therefore, an important role in the control of material Exceptions to this rule are systems where climatic con- 463 ditions reduce decomposition rates, such as water-logged Birch PB, Gabrielson JO, Hamel KS (1983) Decomposition of , , and the sea floor, where plant decomposition Cladophora. I. Field studies in the Peel-Harvey estuarine sys- is reduced by low pH and/or anoxia (Godshalk and tem, Western Australia. Bot Mar 26:165-171 Bockheim JG, Jepsen EA, Heisey DM (1991) Nutrient dynamics in Wetzel 1978; Swift et al. 1979; Best et al. 1990), leading decomposing leaf of four tree species on a sandy in north- to an inordinate accumulation of . How- western Wisconsin. Can J For 21 : 803-812 ever, the general association of fast growth rates with fast Breteler RJ, Teal JM (1981) Trace element enrichments in decom- decomposition rates, resulting from the controlling role posing litter of Spartina alterniflora. Aquat Bot 11 : 111-120 of nutrients in both processes, acts to prevent the accu- Briggs SV, Maher MT, Tongway DJ (1985) Dry matter and nutrient mulation of carbon and associated nutrients as plant loss from decomposing Vallisneria spiralis L. Aquat Bot 22:387-392 detritus. Conversely, the association between slow plant Brock TCM (1984) Aspects of the decomposition of Nymphoides growth rates and slow litter decomposition rates ensures peltata (Gmel.) O. Kuntze (Menyantheceae). 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marsh litter on decay rates and feeding by detritivores. Bull Mar Wahbeh MI, Mahasneh AM (1985) Some aspects of decomposition Sci 35:261-269 of leaf litter of the seagrass Halophila stipulacea from the Gulf Vadstein O, Olsen Y (1989) Chemical composition and phosphate of Aqaba (Jordan). Aquat Bot 21:237-244 uptake kinetics of limnetic bacterial communities cultures in Walsh I, Dymond J, Collier R (1988) Rates of recycling of biogenic chemostats under phosphorus limitation. Limnol Oceanogr components of settling particles in the ocean derived from sedi- 34:939-946 ment trap experiments. Deep-Sea Res 35:43-58 Van der Valk AG, Attiwill PM (1984) Decomposition of leaf and Williams WA, Jones MB, Demment MW (1990) A concise table for root litter of Avicennia marina at Westernport bay, Victoria, path analysis statistics. Agron J 82:1022-1024 Australia. Aquat Bot 18: 205-221 Yavitt JB, Fahey TJ (1986) Litter decay and leaching from the Van der Valk AG, Rhymer JM, Murkin HR (1991) Flooding and in Pinus contorta (Lodgepole pine) ecosystems. the decomposition of litter of four emergent plant species in a J Ecol 74:525-545 prairie . Wetlands 11 : 1-16 Appendix. Nutrient content, decomposition rate, and plant and experimental characteristics for the plant decomposition experiments compiled in the data set used here

Plant type Species Fraction Conditions %N %P %C CN CP K(d-1) Author

Aquatic plants ." Phytoplankton Mixed natural Whole organism Water 8.55 0.0360 (Aizaki & Takamura 1991) Mixed natural community Whole organism Water 6.75 0.0560 (Aizaki & Takamura 1991) Mixed natural community Whole organism Water 8.26 0.0660 (Aizaki & Takamura 1991) Crysophyceae Whole organism Water 4.19 0.800 25.50 7.10 82.34 0.0360 (Aizaki & Takamura 1991) Crysophyceae Whole organism Water 4.19 0.800 25.50 7.10 82.34 0.0360 (Aizaki & Takamura 1991) Mixed natural community Whole organism Water 8.72 0.0470 (Aizaki & Takamura 1991) Mixed natural community Whole orgamsm Water 9.29 0.0680 (Aizaki & Takamura 1991) Mixed natural community Whole orgamsm Water 6.51 0.0270 (Aizaki & Takamura 1991) Mixed natural community Whole orgamsm Water 7.40 0.0980 (Aizaki & Takamura 1991) Anabaena sp. Whole organism Water 8.94 0.388 0.0980 (Aizaki & Takamura 1991) Microcystis sp. Whole orgamsm Water 4.34 0.602 0.0528 (Aizaki & Takamura 1991) Synechococcus sp. Whole organism Water 6.08 0.850 29.27 5.62 88.96 0.0956 (Biddanda 1988) Dunaliella sp. Whole orgamsm Water 4.52 0.983 45.40 11.73 119.29 0.0498 (Biddanda 1988) Cylindrotheca sp. Whole organism Water 4.19 0.800 25.50 7.10 82.34 0.0417 (Biddanda 1988) Seston Whole organism Water 2.40 0.260 15.10 7.30 146.00 0.0294 (Garber 1984) Skeletonema costatum Whole orgamsm Water 3.30 0.690 27.40 9.62 102.00 0.0449 (Garber 1984) Scenedesmus sp. Whole organasm Water 8.00 48.00 7.00 0.0233 (Golterman 1972) SkeIetonema costatum Whole orgamsm Water 5.92 1.700 31.30 6.17 52.17 0.0676 (Newell et al. 1981) Chaetoceros tricomutum Whole organism Water 2.30 18.08 9.19 0.0699 (Newell et al. 1981) Thalassiosira anpstii Whole organasm Water 3.59 0.340 22.60 7.34 171.90 0.0388 (Newell et al. 1981) Mixed natural community Whole orgamsm Water 11.10 0.0093 (Otsuki & Hanya 1972) Chlorella sp. Whole orgamsm Water 6.63 1.090 49.6 8.73 117.55 0.0540 (Twilley et al. 1986) Mixed natural community Whole orgamsm Water 5.95 1.097 45.00 8.83 106.00 0.0658 (Walsh et al. 1988) Macroalgae Macrocystis integrifolia Stipes Water 1.00 29.50 34.42 0.0295 (Albright et al. 1980) Maerocystis inteyrifolia Photosyn. tissue Water 2.10 30.00 16.67 0.0321 (Albright et al. 1980) Cladophora aft. albida Photosyn. tissue Water 2.50 0.190 40.00 18.67 543.86 0.0076 (Birch et al. 1983) Cladophora aft. albida Photosyn. tissue Water 3.92 0.335 43.50 12.95 330.51 0.0082 (Gabrielson et al. 1983) Cladophora aft. albida Photosyn. tissue Water 3.44 0.291 40.70 13.80 362.56 0.0038 (Gabrielson et al. 1983) Cladophora aft. albida Photosyn. tissue Water 3.21 0.313 43.40 15.77 361.67 0.0076 (Gabrielson et al. 1983) Cladophora aft. albida Photosyn. tissue Water 2.73 0.278 40.30 17.22 372.74 0.0035 (Gabrielson et al. 1983) Ulva sp. Photosyn. tissue Water 2.89 0.360 31.2 12.60 223.89 0.0230 (Twilley et al. 1986) Seagrasses Zostera marina Mixed litter Water 20.80 0.0010 (Godshalk & Wetzel 1978a) Zostera marina Mixed litter Water 20.80 0.0020 (Godshalk & Wetzel 1978b) Zostera marina Leaves Water 1.90 0.0035 (Harrison 1982) Zostera marina Leaves Water 4.00 0.0180 (Harrison 1982) Thalassia testudinum Leaves Water 2.80 0.0007 (Harrison 1989) Zostera marina Leaves Water 3.50 0.0070 (Harrison 1989) Thalassia testudinum Leaves Water 2.00 0.0170 (Harrison 1989) Thalassia testudinum Leaves Water 1.80 0.0085 (Harrison 1989) Thalassia testudinum Leaves Water 1.80 0.0080 (Harrison 1989) Posidonia australis Leaves Water 1.90 0.0013 (Harrison 1989) Heterozostera tasmanica Leaves Water 3.00 0.0040 (Harrison 1989) Zostera marina Leaves (average) Water 2.64 0.550 55.00 24.31 258.33 0.0124 (Hemminga & Nieuwenhuize 1991) Cymodocea nodosa Leaves (average) Water 2.76 0.500 37.00 15.64 191.17 0.0230 (Hemminga & Nieuwenhuize 1991) Thalassia testudinum Rhizomes Water 1.12 34.40 35.42 0.0007 (Kenworthy & Thayer 1984) Thalassia testudinum Roots Water 1.00 32.00 37.33 0.0183 (Kenworthy & Thayer 1984) Plant type Species Fraction Conditions %N %P %C CN CP K (d 1) Author

Zostera marina Roots Water 0.73 32.00 51.14 0.0048 (Kenworthy & Thayer 1984) Zostera marina Rhizomes Water 0.53 34.40 74.84 0.0035 (Kenworthy & Thayer 1984) Thalassia testudinum Leaves (average) Water 2.10 36.30 20.17 0.0048 (Newell et al. 1986) Thalassia testudinum Leaves (average) Water 1.80 33.90 21.97 0.0279 (Newell et al. 1986) Cymodocea nodosa Leaves Water 4.36 50.60 13.54 0.0039 (Peduzzi & Herndl 1991) Zostera marina Leaves Water 1.61 0.550 28.98 21.00 140.91 0.0136 (Pellikaan 1982) Zostera marina Leaves Water 2.41 2.500 33.80 16.36 34.93 0.0357 (Pellikaan 1984) Zostera marina Mixed litter Water 1.27 2.100 24.10 22.14 29.65 0.0357 (Pellikaan 1984) Posidonia oceanica Mixed litter (+wood) Water (20 m.) 1.40 0.078 31.20 26.00 1040 0.0087 (Romero et al. 1992) Posidonia oeeanica Mixed litter (+wood) Water (5 m.) 0.58 0.038 23.70 47.67 1633 0.0066 (Romero et al. 1992) Thalassia testudinum Leaves Water 1.86 28.18 17.68 0.0149 (Rublee & Roman 1982) Halophila stipulacea Leaves Water 0.0032 (Wahbeh & Mahasneh 1985) Freshwater Potamogeton perfoliatus Leaves Water 1.15 0.0446 (Bastardo 1979) angiosperms Potamogeton lucens Leaves Water 2.40 0.160 0.0517 (Bastardo 1979) Potamogeton lucens Leaves Water 1.20 0.100 0.0458 (Bastardo 1979) Elodea canadensis Leaves Water 1.26 0.200 0.0475 (Bastardo 1979) Elodea canadensis Leaves Water 3.66 0.820 0.0859 (Bastardo 1979) Ceratophyllum Leaves (average) Water 3.44 0.848 55.38 18.78 168.69 0.0247 (Best et al. 1990) Vallisneria spiralis Leaves Water 2.61 0.370 0.0987 (Briggs et al. 1985) Najasflexilis Leaves Water 1.80 31.2 20.22 0.0070 (Godshalk & Wetzel 1978a) Myriophyllum heterophyllum Leaves Water 2 24.7 14.41 0.0090 (Godshalk & Wetzel 1978a) Myriophyllum heterophyllum Leaves Water 2 24.7 14.41 0.0340 (Godshalk & Wetzel 1978a) Najasflexilis Leaves Water 1.80 31.2 20.22 0.0280 (Godshalk & Wetzel 1978a) Potamogeton nodosus Leaves (average) Water 2.40 0.430 41.60 20.22 249.2 0.0483 (Hill 1979) Potamogeton crispus Leaves Water 2.15 0.290 0.0648 (Rogers & Breen 1982) Potamogeton crispus Leaves Water 1.90 0.290 0.0640 (Rogers & Breen 1982) Justicia americana Leaves, petioles, stems Water 0.137 0.0138 (Twilley et al. 1985) Justicia americana Roots and Rhizomes Water 0.298 0.0398 (Twilley et al. 1985) Potamogeton Leaves Water 1.77 0.360 31.9 21.03 228.912 0.0310 (Twilley et al. 1986) Rappia Leaves Water 1.37 0.510 32.6 27.76 165.130 0.0280 (Twilley et al. 1986) Myriophyllum Leaves Water 2.79 0.560 30.4 12.71 140.238 0.0450 (Twilley et al. 1986) Amphibious Sagittaria lanc~folia Leaves Water 2.40 0.150 0.0058 (Bayley et al. 1985) Plants Sagittaria lancifolia Stems Water 1.40 0.130 0.0076 (Bayley et al. 1985) Nymphoides peltata Petioles Water 77 0.0420 (Brock /984) Nymphoides peltata Long Shoots Water 178 0.0440 (Brock 1984) Nymphoides peltata Leaves Water 3.248 0.465 50.04 22 0.0560 (Brock 1984) Nymphoides peltata Leaves Water 3.248 0.465 50.04 16 0.0910 (Brock 1984) Nymphoides peltata Petioles Water 48 0.0450 (Brock 1984) Nymphoides peltata Roots Water 179 0.0790 (Brock 1984) Nymphoides peltata Roots Water 137 0.0490 (Brock 1984) Nymphoides peltata Short Shoots Water 143 0.0350 (Brock 1984) Nymphoides peltata Long Shoots Water 151 0.0370 (Brock 1984) Nymphoides peltata Short Shoots Water 152 0.0550 (Brock 1984) Nuphar variegatum Leaves Water 2.4 39.3 19.14 0.0600 (Godshalk & Wetzel 1978a) Nuphar variegatum Leaves Water 2.4 39.3 19.10 0.0200 (Godshalk & Wetzel 1978a) Sparganium eurycarpum Mixed litter Water 1.41 38.67 32 0.0076 (Neeley & Davis 1985) Sparganium eurycarpum Mixed litter Water 0.59 0.079 38.43 76 570.00 0.0021 (Neeley & Davis 1985) Sparganium eurycarpum Mixed litter Water 0.59 0.130 38.43 76 570.00 0.0017 (Neeley & Davis 1985) Eichhornia crassipes Mixed litter (average) Water 2.53 0.270 88.91 41 710.00 0.0095 (Reddy & DeBusk 1991) 4~ Plant type Species Fraction Conditions %N %P %C CN CP K (d-l) Author

Nuphar luteum Leaves, petioles, stems Water 2.92 0.383 0.0988 (Twilley et al. 1985) Nuphar luteum Roots and rhizomes Water 1.67 0.245 0.0142 (Twilley et al. 1985) Terrestrial plants : Sedges Phragmitescommunis Mixed litter Water 1.04 0.001.8 (Andersen 1978) Phragmites communis Mixed litter Water 0.60 0.0014 (Andersen 1978) Panicum sp. Mixed litter Water 1.60 0.070 0.0071 (Bayley et al. 1985) Spartina alterniflora Roots Belowground 0.39 38.24 114.39 0.0067 (Benner et al. 1991) Spartina alternifolia (short form) Mixed litter Soil/Fertilized 2.54 41.90 19.25 0.0052 (Breteler & Teal 1981) Spartina alternifolia (tall form) Mixed litter Soil/Fertilized 1.20 41.70 40.54 0.0081 (Breteler & Teal 1981) Spartina alternifolia (short form) Mixed litter Soil/Control 0.77 43.10 65.30 0.0033 (Breteler & Teal 1981) Spartina alternifolia (tall form) Mixed litter Soil/Control 0.53 41.90 92.23 0.0063 (Breteler & Teal 1981) Typha domingensis Mixed litter Water 0.50 0.014 0.0010 (Davis 1991) Typha domingensis Mixed litter Water 0.35 0.012 0.00099 (Davis 1991) Cladiumjamaicense Mixed litter Water 0.40 0.020 0.0013 (Davis 1991) Cladium jamaicense Mixed litter Water 0.50 0.022 0.0007 (Davis 1991) Cladium jamaicense Mixed litter Water 0.30 0.006 0.0007 (Davis 1991) Typha domingensis Mixed litter Water 0.50 0.028 0.0021 (Davis 1991) Typha marsh Mixed litter Water 0.48 0.001 (Findley et al. 1990) Scirpus subterminalis Mixed litter Water 1.2 30.4 29.56 0.0090 (Godshalk & Wetzel 1978a) Scirpus acutus Mixed litter Water 1.5 43.6 33.91 0.0020 (Godshalk & Wetzel 1978a) Scirpus acutus Mixed litter Water 1.5 43.6 33.91 0.0050 (Godshalk & Wetzel 1978a) Scirpus subterminalis Mixed litter Water 1.2 30.4 29.56 0.0020 (Godshalk & Wetzel 1978a) Spartina alterniflora Mixed litter Water 1.33 0.0111 (Haines & Hanson 1979) Juncus roemerianus Mixed litter Water 0.79 0.0091 (Haines & Hanson 1979) Spartina anglica Mixed litter Water 1.12 0.0079 (Hemminga & Buth 1991) Spartina anglica Mixed litter Water 0.71 0.0022 (Hemminga & Buth 1991) Trigloehin maritima Leaves Water 2.54 0.0256 (Hemminga & Buth 1991) Spartina angliea Mixed litter Water 0.90 0.0033 (Hemminga & Buth 1991) Spartina angIica Mixed litter Water 1.29 0.0093 (Hemminga & Buth 1991) Triglochin maritima Mixed litter Water 2.09 0.0025 (Hemminga & Buth 1991) Spartina anglica Leaves Water 1.67 0.0061 (Hemminga & Buth 1991) Typha 9lauca Mixed litter Water 0.48 0.050 38.67 94 1800.00 0.0011 (Neeley & Davis 1985) Typha glauca Mixed litter Water 0.55 38.66 82 0.0016 (Neeley & Davis 1985) Typha glauca Mixed litter Water 0.48 0.025 38.67 94 1800.00 0.0011 (Neeley & Davis 1985) Typha glauca Leaves (senesced) Water 0.63 0.050 0.0104 (Nelson et al. 1990) Typha glauca Leaves (green) Water 2.77 0.290 0.0235 (Nelson et al. 1990) Juncus roemerianus Mixed litter Water 0.70 45.62 76.03 0.0017 (Newell et al. 1984) Phragmites eommunis Leaves Water 0.71 40.00 65.73 0.0045 (Tanaka 1991) Spartina Mixed litter Water 1.07 0.150 42.3 46.12 728.5 0.0098 (Twilley et al. 1986) Spartina alternifolia Mixed litter Water 0.71 0.0043 (Valiela et al. 1984) Spartina alternifolia Mixed litter Water 1.64 0.0071 (Valiela et al. 1984) Typha glauca Mixed litter Water 0.82 0.108 47.10 67.01 1131.86 0.0012 (Van der Valk et al. 1991) Scolochloafestucacea Mixed litter Water 0.77 0.053 43.10 65.30 2100.79 0.0016 (Van der Valk et al. 1991) Scirpus laeustris Mixed litter Water 0.40 0.034 45.40 132.42 3449.51 0.001 (Van der Valk et al. 1991) Phragmites australis Mixed litter Water 0.30 0.029 47.50 187.85 4305.56 0.0007 (Van der Valk et al. 1991) Scolochloafestucacea Mixed litter Water 0.87 0.060 43.35 58.13 1866.46 0.0022 (Van der Valk et al. 1991) Typha x g!auca Mixed litter Water 0.75 0.092 46.00 71.56 1291.67 0.0012 (Van der Valk et al. 1991) Phragmites australis Mixed litter Water 0.18 0.016 48.60 315 7846.88 0.0003 (Van der Valk et al. 1991) Plant type Species Fraction Conditions %N %P %C CN CP K (d-1) Author

Scirpus lacustris Mixed litter Water 0.63 0.051 45.35 83.98 2319.88 0.0015 (Van der Valk et al. 1991) Typhaxglauca Mixed litter Water 0.89 0.123 48.20 63.18 1012.33 0.0010 (Van der Valk et al. 1991) Seoloehloafestucaeea Mixed litter Water 0.97 0.067 43.60 52.44 1681.09 0.0023 (Van der Valk et al. 1991) Phragmites australis Mixed litter Water 0.41 0.041 46.40 132.03 2923.58 0.0008 (Van der Valk et al. 1991) Scirpus lacustris Mixed litter Water 0.86 0.067 45.30 61.45 1746.64 0.0011 (Van der Valk et al. 1991) Mangroves Kandelia candel, Mixed litter (+wood) Water 0.75 31.50 49 0.0018 (Lee 1989) Avicennia marina Rhizophora mangle Mixed litter (+wood) Water 0.40 43.35 126.44 0.0095 (Newell et al. 1984) Rhizophora spp. Mixed litter (+wood) Soil 0.37 37.19 117.27 0.0008 (Robertson & Daniel 1989) Rhizophora spp. Mixed litter (+wood) Soil 0.36 34.48 111.74 0.0002 (Robertson & Daniel 1989) Avicennia marina Mixed litter (+wood) Water/Bagged 0.74 0.065 0.0114 (Van der Valk & Attiwill 1984) Avicennia marina Mixed litter (+wood) Water/ 0.76 0.061 0.0189 (Van der Valk & Attiwill 1984) Unbagged Avicennia marina Roots Water 1.18 0.106 0.0038 (Van der Valk & Attiwill 1984) Avicennia marina Leaves Water 1.24 0.127 0.0071 (Van der Valk & Attiwill 1984) Grasses Molinia caerulea Mixed litter Soil 1.95 0,580 0.0153 (Aerts 1989) Elymus pycnanthus Mixed litter Water 0.90 0.0079 (Hemminga & Buth 1991) Erythrina sp. Mixed litter Soil 3.52 0.210 0.0095 (Palm & Sanchez 1990) Cajanus cajan Mixed litter Soil 3.48 0.180 0.0047 (Palm & Sanchez 1990) Inga edulis Mixed litter Soil 3.18 0.220 0.0025 (Palm & Sanchez 1990) Tallgrass prairie Mixed litter (average) Soil 0.18 0.015 0.0009 (Seastedt 1988) White pine Needles Soil 0.35 0.0012 (McClaugherty et al. 1985) Hemlock Needles Soil 0.66 0.00096 (McClaugherty et al. 1985) White spruce Needles Soil 0.52 0.060 0.0014 (Taylor et al. 1989) Douglas fir Needles Soil 0.61 0.110 0.0017 (Taylor et al. 1989) Pinus roxburghii Needles Soil 0.67 0.050 0.0021 (Upadhyay et al. 1989) Broad Red maple Leaves Soil 1.59 0.0020 (Aber et al. 1990) deciduous Red oak Leaves Soil 1.90 0.0011 (Abet et al. 1990) tree leaves Aspen Leaves Soil 2.14 0.0014 (Aber et al. 1990) Red oak Leaves Soil 1.94 0,0011 (Aber et al. 1990) maple Leaves Soil 2.05 0.0023 (Aber et al. 1990) Paper birch Leaves Soil 2.22 0.0017 (Abet et al. 1990) Red maple Leaves Soil 1.80 0.0019 (Aber et al. 1990) Red oak Leaves Soil 2.26 0.0009 (Abet et al. 1990) White oak Leaves Soil 1.67 0.0012 (Aber et al. 1990) Sugar maple Roots Soil 2.62 0.0006 (Aber et al. 1990) Alnus ineana Leaves Soil 3.07 0.137 0.0009 (Berg & Ekbohm 1991) Betulapubescens Leaves Soil 0.77 0.105 0,0009 (Berg & Ekbohm 1991) Betula pubescens Leaves Soil 1.74 0.180 0.0009 (Berg & Ekbohm 1991) Populus tremuloides Leaves Soil 0.84 0,120 0.0012 (Bockheim et al. 1991) Quercus ellipsoidalis Leaves Soil 1.40 0.120 0.0009 (Bockheim et al. 1991) Betula papyrifera Leaves Soil 0.92 0.110 0.0012 (Bockheim et al. 1991) Frangula alnus Leaves Soil 0.88 0.030 0.0054 (Escudero et al. 1991) Quercus pyrenaica Leaves Soil 0.6 0,042 0.0030 (Escudero et al. 1991) Betula pubeseens Leaves Soil 0.61 0,029 0.0033 (Escudero et al. 1991) Salix fragilis Leaves Water 1.20 0.100 0.0246 (Gessner et al. 1991) Alnus glutinosa Leaves Water 2.60 0,118 0.0252 (Gessner et al. 1991) Fagus sylvatica Leaves Soil 0.71 0.030 0.0007 (Gosz et al. 1973) Sugar maple Leaves Soil 0.57 0.020 0.0014 (Gosz et al. 1973) 4~ Plant type Species Fraction Conditions %N %P %C CN CP K (d 1) Author

Sugar maple Leaves Soil 0.62 0.020 0.0009 (Gosz et al. 1973) Yellow birch Leaves Soil 1.09 0.080 0.0017 (Gosz et al. 1973) Yellow birch Leaves Soil 0.85 0.060 0.0023 (Gosz et al. 1973) Fagus sylvatica Leaves Soil 0.82 0.090 0.0010 (Gosz et al. 1973) Fagus sylvatica Leaves Water 0.67 0.0035 (Iversen 1973) Fagus sylvatica Leaves (average) Soil 1.12 0.0021 (Joergensen & Meyer 1990) Fagus sylvatica Leaves Soil 1.12 0.0013 (Joergensen 1991) Aspen Leaves Soil 0.66 0.0016 (McClaugherty et al. 1985) White oak Leaves Soil 0.67 0.0015 (McClaugherty et al. 1985) Red maple Wood chips Soil 0.07 0.0008 (McClaugherty et al. 1985) Sugar maple Leaves Soil 0.66 0.0022 (McClaugherty et al. 1985) Alnus nepalensis Wood part Soil 2.56 0.072 0.0029 (Sharma & Ambasht 1987) Aspen Leaves Soil 0.64 0.120 0.0018 (Taylor et al. 1989) Balsam poplar Leaves Soil 0.58 0.130 0.0016 (Taylor et al. 1989) Cow-parsnip Mixed litter Soil 1.31 0.290 0.0036 (Taylor et al. 1989) Grass Mixed litter Soil 0.81 0.060 0.0022 (Taylor et al. 1989) Dogwood leaf litter Leaves Soil 0.78 0.080 0.0021 (Taylor et al. 1989) Shrubs Salicornia virginiea Mixed litter (+wood) Water 1.56 0.560 0.0413 (Haines & Hanson 1979) Halimione portulacoides Mixed litter (+wood) Water o 2.09 0.0090 (Hemminga & Buth 1991a) Lirnonium vulgare Mixed litter (+wood) Water 2.06 0.0025 (Hemminga & Buth 1991a) Limonium vulgare Leaves Water 2.15 0.0048 (Hemminga & Buth 1991a) Halimione portulaeoides Mixed litter (+wood) Water 1.70 0.0090 (Hemminga & Buth 1991a) Leucosperrnumparile Mixed litter (+wood) Soil 0.53 0.023 51.0666 112.41 5653.81 0.0002 (Mitchell et al. 1986) Acacia urophylla Mixed litter (+wood) Soil 0.71 0.010 0.0010 (O'Connell 1987) Trymalium spathulatum Leaves Soil 0.6 0.019 0.0031 (O'Connell 1987) Bossiaea laidlawaiana Leaves Soil 1.78 0.019 0.0016 (O'Connell 1987) Casuarina decussata Leaves Soil 0.44 0.005 0.0012 (O'Connell 1987) Acacia urophylla Leaves Soil 1.27 0.015 0.0015 (O'Connell 1987) B. laidlawaiana pods Pods Soil 0.61 0.006 0.0008 (O'Connell 1987) Ceanothus megacarpus Leaves Soil 0.63 0.028 0.0010 (Schlesinger 1985) Salvia melifera Leaves Soil 0.58 0.105 0.0011 (Schlesinger 1985) Salvia melifera Leaves Soil 0.65 0.133 0.0009 (Schlesinger 1985) Ceanothus megacarpus Leaves Soil 0.67 0.046 0.001 (Schlesinger 1985) Rose sp. Leaves Soil 1.15 0.190 0.0032 (Taylor et al. 1988) Mallotusphilippensis Leaves Soil 0.50 0.130 0.0110 (Upadhyay et al. 1989) Conifers Pinus contorta Needles Soil 0.45 0.0004 (Yavitt & Fahey 1986) White pine Roots Soil 1.83 0.0008 (Aber et al. 1990) Hemlock Needles Soil 1.50 0.001 (Aber et al. 1990) White pine Needles Soil 0.97 0.001 (Aber et al. 1990) Red pine Needles Soil 1.26 0.0009 (Aber et al. 1990) Scots pine Needles Soil 1.89 0.0008 (Berg et al. 1982) Scots pine Needles Soil 0.37 0.0007 (Berg et al. 1982) Scots pine Needles Soil 1.22 0.0009 (Berg et al. 1982) Pinus sylvestris Needles Soil 0.48 0.033 0.0008 (Berg & Ekbohm 1991) Pinus sylvestris Needles Soil 1.51 0.131 0.0010 (Berg & Ekbohm 1991) Lodgepole pine Needles Soil 0.48 0.033 0.0008 (Berg & Ekbohm 1991) Lodgepole pine Needles Soil 1.05 0.082 0.0008 (Berg & Ekbohm 1991) Brown spruce Needles Soil/ 0.42 0.041 0.0006 (Berg & Tamm 1991) Fertilizeed Plant type Species Fraction Conditions %N %P %C CN CP K (d- 1) Author

Brown spruce Needles Soil 0.43 0.041 0.0005 (Berg & Tamm 1991) Green spruce Needles Soil/ 0.85 0.132 0.0008 (Berg & Tamm 1991) Fertilizeed Green spruce Needles Soil 0.85 0.132 0.001 (Berg & Tamm 1991) Pinus banksiana Needles Soil 0.88 0.080 0.0005 (Bockheim et al. 1991) Pinus pinaster Needles Soil 0.4 0.017 0.0010 (Escudero et al. 1991) Pinus sylvestris Needles Soil 0.69 0.037 0.0020 (Escudero et al. 1991) Sitka spruce Branches Soil 4.96 0.550 0.0355 (Fahey et al. 1991) Quercus lanuginosa Leaves Soil 1.32 0.120 0.0049 (Upadhyay et al. 1989) Lyonia ovalifolia Leaves Soil 0.80 0.080 0.0073 (Upadhyay et al. 1989) Quereus glauca Leaves Soil 0.94 0.070 0.0073 (Upadhyay et al. 1989) Shorea robusta Leaves Soil 0.99 0.280 0.0076 (Upadhyay et al. 1989) Quercusfloribunda Leaves Soil 0.97 0.120 0.0051 (Upadhyay et al. 1989) Quercus leucotrichophora Leaves Soil 1.15 0.220 0.0052 (Upadhyay et al. 1989) Broad perennial Eucalyptus diversicolor Fruit Soil 0.21 0.027 0.0005 (O'Connell 1988) tree leaves Eucalyptus diversicolor Leaves Soil 0.41 0.010 0.0015 (O'Connell 1988) Eucalyptus diversicolor Twigs Soil 0.21 0.008 0.0003 (O'Connell 1988) Eucalyptus diversicolor Bark Soil 0.13 0.004 0.0006 (O'Connell 1988) Myrica esculenta Leaves Soil 0.58 0.057 0.0043 (Upadhyay et al. 1989) Rhododendron arboreum Leaves Soil 0.70 0.060 0.0048 (Upadhyay et al. 1989)

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