Factors controlling decomposition rates of fine root litter in temperate forests and grasslands

Background and aims

Fine root decomposition contributes significantly to element cycling in terrestrial ecosystems. However, studies on root decomposition rates and on the factors that potentially influence them are fewer than those on leaf litter decomposition. To study the effects of region and land use intensity on fine root decomposition, we established a large scale study in three German regions with different climate regimes and soil properties. Methods In 150 forest and 150 grassland sites we deployed litterbags (100 μm mesh size) with standardized litter consisting of fine roots from European beech in forests and from a lowland mesophilous hay meadow in grasslands. In the central study region, we compared decomposition rates of this standardized litter with root litter collected on-site to separate the effect of litter quality from environmental factors.

Results

Standardized herbaceous roots in grassland soils decomposed on average significantly faster (24?±?6 % mass loss after 12 months, mean ± SD) than beech roots in forest soils (12?±?4 %; p?Conclusions Grasslands, which have higher fine root biomass and root turnover compared to forests, also have higher rates of root decomposition. Our results further show that at the regional scale fine root decomposition is influenced by environmental variables such as soil moisture, soil temperature and soil nutrient content. Additional variation is explained by root litter quality.     

Mixtures with grass litter may hasten shrub litter decomposition after shrub encroachment into mountain grasslands

Aims

Shrub encroachment in mesic grasslands alters the identity and quality of litters entering the system. As litter from shrubs and grasses can differ in their quality, this can lead to differences in litter decomposition by the direct effect of quality, but also to litter interaction during decomposition. The objective of this study was to examine the occurrence of non-additive effects of litter mixtures on the decomposition rates of legume shrub litter (poor in P) or conifer shrub litter (poor in N) and grass litter.

Methods

In addition to single litter type litterbags for the three species, we mixed litters of each pair of possible combinations to determine the influence of each species on mass loss. Litterbags were placed in the field and collected after 1, 6, 8, 12 and 24 months. In each collection, litter of each species remaining in mixed bags was separated, dry weighed and analyzed for C, N and P.

Results

With respect to shrub litter decomposing alone, mass loss of shrub litter when mixed with grass showed a 9–10 % increase in decomposition rate for conifer and a 3 % increase for legume litter. These litter mixture effects varied with time and they were detected after a decomposition period of 1 year in legume litter and of 2 years in conifer litter.

Conclusions

Grass litter hastened conifer and legume litter decomposition in leaf litter mixtures, at least during the first stages of the process. The potential consequences of this result to alter litter accumulation patterns and thus carbon sequestration rates after shrub encroachment into grasslands will depend on whether the observed trends are maintained in the advanced decomposition stages.     

Interactions between leaf litter and soil organic matter on carbon and nitrogen mineralization in six forest litter-soil systems

Background and aims

Leaf litter decomposes on the surface of soil in natural systems and element transfers between litter and soil are commonly found. However, how litter and soil organic matter (SOM) interact to influence decomposition rate and nitrogen (N) release remains unclear.

Methods

Leaf litter and mineral soil of top 0–5 cm from six forests were incubated separately, or together with litter on soil surface at 25 °C for 346 days. Litter N remaining and soil respiration rate were repeatedly measured during incubation. Litter carbon (C) and mass losses and mineral N concentrations in litter and soil were measured at the end of incubation.

Results

Net N transfer from soil to litter was found in all litters when incubated with soil. Litter incubated with soil lost more C than litter incubated alone after 346 days. For litters with initial C: N ratios lower than 52, net N_min after 346 days was 100 % higher when incubated with soil than when incubated alone. Litter net N_min rate was negatively related to initial C: N ratio when incubated with soil but not when incubated alone. Soil respiration rate and net N_min rate did not differ between soil incubated with litter and soil incubated alone.

Conclusions

We conclude that soils may enhance litter decomposition rate by net N transfer from soil to litter. Our results together with studies on litter mixture decomposition suggest that net N transfer between decomposing organic matter with different N status may be common and may significantly influence decomposition and N release. The low net N_min rate during litter decomposition along with the small size of litter N pool compared to soil N pool suggest that SOM rather than decomposing litter is the major contributor to plant mineral N supply.     

The effects of leaf litter evenness on decomposition depend on which plant functional group is dominant

Background and aims

Climbing plants are increasing in dominance in the subtropical forests of South China and other areas around the world, altering patterns of plant dominance and evenness in community. We investigated how changes in species’ identity and patterns of leaf litter evenness affected decomposition of litter mixtures.

Methods

We used litter-bag method to study the influence of different relative abundance mixtures (75 % : 25 %; 50 % : 50 %; 25 % : 75 %) of plant litter from two functional groups (climbing plants and trees) on decomposition rates in a subtropical forest in Guangdong, China.

Results

We found negative non-additive effects of mixing litter overall and species composition affected decomposition rates the most. In addition, when climbing plants were dominant, even mixtures decomposed slower significantly than uneven mixtures. Evenness did not affect decomposition rates, however, when trees were dominant. The magnitude of antagonistic effects increased with increasing dominance of climbing plants but decreased with time, suggesting a strong negative feedback between litter proportion of climbing plant and decomposition rates at the initial stage.

Conclusion

The evenness in leaf litter composition affects rates of decomposition, but these effects depend on which plant functional group is dominant. Thus, we should pay more attention to shifts in identity of dominant species and patterns of community evenness.     

Combination of nitrogen deposition and ultraviolet-B radiation decreased litter decomposition in subtropical China

Aims

The interactive effects of enhanced nitrogen (N) deposition and ultraviolet-B (UV-B) radiation on litter decomposition are still unknown. The aims are to test whether the interactive effects of the two environmental factors on litter decomposition and nutrient loss are stronger than that of each factor alone.

Methods

Experiment included five treatments: elevated UV-B radiation (UV-B, 10 % enhancement), low N addition (N1, 30 kg N ha^?1 year^?1), high N addition (N2, 60 kg N ha^?1 year^?1), the two combined treatments of the two factors (UV-B+N1 and UV-B+N2), and an unmanipulated control.

Results

The annual decomposition rates under combination of UV-B and N addition significantly decreased compared with that under UV-B and N additions for Pinus massoniana, and did also compared with that under UV-B but did not significantly differ with N additions for Cyclobalanopsis glauca. Negative effects of N additions alone on lignin degradation and P loss were partly offset but negative effect on N loss was further amplified when was combined with UV-B.

Conclusions

The combination of N deposition and UV-B radiation on litter decomposition and nutrient loss was significantly different from that of each factor alone without a general response pattern of decomposition, and was regulated by litter chemistry.     

Boreal peat properties link to plant functional traits of ecosystem engineers

Aims

Warming has the potential to alter plant litter mass loss and nutrient release during decomposition. However, a great deal of uncertainty remains concerning how other factors such as litter species or substrate quality might modify the effects of increased temperature on decomposition. Meanwhile, the temperature sensitivity of plant litter decay in tropical and subtropical forest ecosystems remains poorly resolved.

Methods

This study was designed to assess the effects of experimental warming on litter decomposition and nutrient release of two contrasting tree species (Schima superba and Machilus breviflora) by translocating model forest ecosystems from the high-elevation sites to the lower-elevation sites in subtropical China. Translocating model mountain evergreen broad-leaved forest (MEBF) to the altitude of 300 m and 30 m increased the average monthly soil temperature at 5 cm depth by 0.88 and 1.84 °C, respectively during the experimental period. Translocating model coniferous and broad-leaved mixed forest (CBMF) to the altitude of 30 m increased the average monthly soil temperature at 5 cm depth by 0.85 °C.

Results

We found that experimental warming accelerated litter decomposition in both model forest types, and the promoting efficiency was greater when the temperature increased. The litter with high quality (Schima superba) had stronger response to warming than low quality litter (Machilus breviflora). Warming accelerated Na, K, Mg, P, N and Ca release from Schima superba litter, but only simulated Ca release from Machilus breviflora litter. Overall, litter decomposition was controlled by the order: soil temperature > litter quality > soil moisture > litter incubation forest type under experimental warming in the subtropical China.

Conclusion

We conclude that leaf litter decomposition was facilitated by experimental warming in subtropical China. Litter species might modify the effects of increased temperature on litter decomposition; however, forest type has no effect on litter decomposition.

     

Slow decomposition and limited nitrogen release by lower order roots in eight Chinese temperate and subtropical trees

Background and aims

Roots of the lowest branch orders have the highest mortality rate, and may contribute predominately to plant carbon (C) and nutrient transfer into the soil. Yet patterns and controlling factors of the decomposition of these roots are poorly understood.

Methods

We conducted a two-year field litterbag study on different root orders and leaf litter in four temperate and four subtropical tree species.

Results

Five species showed slower decay rates in lower- (order 1–2) than higher-order (order 3–5) roots, and all species showed slower decay rates in lower-order roots than leaf litter. These patterns were strongly related to higher acid-insoluble fraction in lower- than higher-order roots, and in roots than in leaf litter, but were unrelated to initial N concentration. Litter N was predominantly in recalcitrant forms and limited amount of N was released during the study period;only 12 % of root N and 26 % of leaf litter N was released in 2 years.

Conclusions

We conclude that the slow decomposition of lower-order roots may be a common phenomenon and is mainly driven by their high acid-insoluble fraction. Moreover, litter N, especially root N, is retained during decomposition and may not be available for immediate plant uptake.     

Further evidence for slow decomposition of very fine roots using two methods: litterbags and intact cores

Background and aims

Root decomposition studies have rarely considered the heterogeneity within a fine-root system. Here, we investigated fine root (< 0.5 and 0.5–2 mm in diameter) decomposition and accompanying nutrient dynamics of two temperate tree species—Betula costata Trautv and Pinus koraiensis Sieb. et Zucc.

Methods

Both litterbag and intact-core techniques were used to examine decomposition dynamic and nutrient release of the two size class roots over a 498-day period. Moreover, we examined differences between the two approaches.

Results

The very fine roots (< 0.5 mm) with an initially lower C:N ratio, decomposed more slowly than 0.5–2 mm roots of both tree species. The differences in mass loss between size classes were smaller when using the intact-core technique compared with litterbag technique. In contrast to root biomass loss, net N release was much higher in the fine roots (< 0.5 mm). All fine roots initially released N (0–75 days), but immobilized N to varying extent in the following days (75–498 days) during decomposition.

Conclusions

Our results suggest that the slow decomposition rate of very fine roots (< 0.5 mm) may be determined by their high concentration of acid-unhydrolyzable structural components. Additionally, the heterogeneity within a bulk fine-root system could lead to differences in their contribution to soil in terms of carbon and nitrogen dynamics.     

Convergence and divergence of nutrient stoichiometry during forest litter decomposition

Background and aims

General theory of forest floor dynamics indicates convergence of properties during detrital decomposition. This study examined the hypothesis that nutrient stoichiometry, i.e. the relative amounts of nutrients, converges during litter decomposition.

Methods

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.) foliar litters that decomposed in their respective forests were analyzed for N, P, Ca, Mg, K, S, Mn, Fe, Zn, and Cu. A novel approach quantified the stoichiometric difference as the angle between nutrient vectors. The approach was also used to synthesize data from 11 previously published studies representing a broad array of litter types and locations.

Results

The stoichiometries of the Douglas-fir and red alder litters converged during the first 2 years of decomposition, but diverged in the subsequent 4 years. This temporal trajectory was explained by two competing sets of processes: stoichiometric convergence occurs when different litters decompose in the same environment, and divergence occurs when the same litter decomposes in different environments. Manganese, Fe, and Ca were important contributors to stoichiometric differences.

Conclusions

Stoichiometric convergence processes often dominate over divergence processes. Consideration of multi-nutrient stoichiometries may enhance the understanding of the functions of litter, including rates of decomposition and relative rates at which nutrients are released.     

Root decomposition of <Emphasis Type="Italic">Artemisia halodendron</Emphasis> and its effect on soil nitrogen and soil organic carbon in the Horqin Sandy Land,northeastern China

Root decomposition is a critical feedback from the plant to the soil, especially in sandy land where strong winds remove aboveground litter. As a pioneer shrub in semi-mobile dunes of the Horqin sandy land, Artemisia halodendron has multiple effects on nutrient capture and the microenvironment. However, its root decomposition has not been studied in terms of its influence on soil organic carbon (SOC) and nitrogen (N). In this study, we buried fine (≤2 mm) and coarse roots in litterbags at a depth of 15 cm below semi-mobile dunes. We measured the masses remaining and the C and N contents at intervals during 434 days of decomposition. The soils below the litterbags were then divided into layers and sampled to measure the SOC and N contents. After rapid initial decomposition, both coarse and fine roots decomposed slowly. After 53 days, 36.2 % of coarse roots and 39.8 % of fine roots had decomposed. In contrast, only 18.4 % of coarse roots and 30.5 % of fine roots decomposed in the following 381 days. Fine roots decomposed significantly faster, and their decomposition rate after the initial rapid decay was strongly related to climate (R ² = 0.716, P < 0.05). Root decomposition increased SOC and N contents below the litterbags, with larger effects for fine roots. The SOC content was more variable between soil layers than the N content. Thus, decomposition of A. halodendron roots cannot be ignored when studying SOC and N feedbacks from plants to the soil, particularly for fine roots.     

The effects of the moss layer on the decomposition of intercepted vascular plant litter across a post-fire boreal forest chronosequence

Aims

Feather mosses form a thick ground layer in boreal forests that can intercept incoming litter fall. This interception may influence the decomposition of incoming litter but this has been little explored. We investigated how the moss layer influences decomposition of intercepted litter along a 362-year fire driven forest chronosequence in northern Sweden across which soil fertility declines.

Methods

We placed leaf litter from three plant species into plots in which mosses and dwarf shrubs were either experimentally removed or left intact, at each of ten stands across the chronosequence. After one year we measured litter mass loss, and litter nitrogen and phosphorous.

Results

Litter decomposed consistently faster, and had higher nitrogen and phosphorus, in the presence of mosses and at greater depth in the moss layer. Despite an increase in moss depth across the chronosequence we did not find consistent increases in effects of moss removal on litter decomposition or on litter N or P.

Conclusions

Our findings identify a clear role of the moss layer in boreal forests in promoting the decomposition of intercepted leaf litter, and highlight that this role is relatively consistent across chronosequence stages that vary greatly in productivity and moss depth.     

Soil nutrient patchiness and plant genotypes interact on the production potential and decomposition of root and shoot litter: evidence from short-term laboratory experiments with Triticum aestivum

Aims

The purpose of this study was to test the hypotheses that soil nutrient patchiness can differentially benefit the decomposition of root and shoot litters and that this facilitation depends on plant genotypes.

Methods

We grew 15 cultivars (i.e. genotypes) of winter wheat (Triticum aestivum L.) under uniform and patchy soil nutrients, and contrasted their biomass and the subsequent mass, carbon (C) and nitrogen (N) dynamics of their root and shoot litters.

Results

Under equal amounts of nutrients, patchy distribution increased root biomass and had no effects on shoot biomass and C:N ratios of roots and shoots. Roots and shoots decomposed more rapidly in patchy nutrients than in uniform nutrients, and reductions in root and shoot C:N ratios with decomposition were greater in patchy nutrients than uniform nutrients. Soil nutrient patchiness facilitated shoot decomposition more than root decomposition. The changes in C:N ratios with decomposition were correlated with initial C:N ratios of litter, regardless of roots or shoots. Litter potential yield, quality and decomposition were also affected by T. aestivum cultivars and their interactions with nutrient patchiness.

Conclusions

Soil nutrient patchiness can enhance C and N cycling and this effect depends strongly on genotypes of T. aestivum. Soil nutrient heterogeneity in plant communities also can enhance diversity in litter decomposition and associated biochemical and biological dynamics in the soil.     

Plant species effect on the decomposition and chemical changes of leaf litter in grassland and pine and oak forest soils

Aims

The aim of this study was to examine the effect of plant species differing in functional and phylogenetic traits on the decomposition processes of leaf litter in a grassland of Japanese pampas grass (Miscanthus sinensis) and adjacent forests of Japanese red pine (Pinus densiflora) and Japanese oak (Quercus crispula), representing sequential stages of secondary succession.

Methods

The litterbag experiments were carried out for 3 years in a temperate region of central Japan.

Results

The decomposition constant (Olson’s k) was 0.49, 0.39, and 0.56/year for grass, pine, and oak, respectively. Nitrogen mass decreased in grass leaf litter during decomposition, whereas the absolute amount of nitrogen increased in leaf litter of pine and oak during the first year. Holocellulose in grass leaf litter decomposed selectively over acid-unhydrolyzable residues more markedly than in leaf litter of pine and oak. ¹³C nuclear magnetic resonance analysis also revealed a decrease in the relative area of O-alkyl-C in grass.

Conclusions

The different decomposition among the three litter species implied that the secondary succession from grassland to pine forest and from pine to oak forests could decrease and increase, respectively, the rate of accumulation and turnover of organic materials and N in soils.     

Short-term effects of litter from 21 woody species on plant growth and root development

Background and aims

Plant litter has an important role in terrestrial ecosystems (Lambers et al. 2008). Our aim was to assess the short-term effect of litter from 21 woody species (deciduous and evergreens) on plant growth and root development.

Methods

We conducted a short-term experiment (10 weeks) under controlled conditions adding litter from 21 woody species to pots with Dactylis glomerata (target species). We determined plant biomass and root development and related these variables to decomposition rate and litter quality.

Results

Litter from two species enhanced plant growth whereas litter of five species inhibited it. Considering all species in the data set, plant growth was associated to litter with high decomposition rate and high litter quality: high Ca and N concentration and low polyphenols concentration. However, excluding from the analyses the two species that increased growth, litter inhibition effect on plant growth was related to the litter-polyphenols concentration. Plants growing with nutrient-richer litter had a lower proportion of fine roots which could be related to a litter mediated increase in soil nutrient.

Conclusions

Enhanced plant growth or, on the contrary, plant growth inhibition could be the result of a positive or, in turn, negative balance between nutrient and polyphenols concentration in litter.     

Minor contribution of leaf litter to N nutrition of beech (Fagus sylvatica) seedlings in a mountainous beech forest of Southern Germany

Aims

Our aims were to characterize the fate of leaf-litter-derived nitrogen in the plant-soil-microbe system of a temperate beech forest of Southern Germany and to identify its importance for N nutrition of beech seedlings.

Methods

¹⁵N-labelled leaf litter was traced in situ into abiotic and biotic N pools in mineral soil as well as into beech seedlings and mycorrhizal root tips over three growing seasons.

Results

There was a rapid transfer of ¹⁵N into the mineral soil already 21 days after tracer application with soil microbial biomass initially representing the dominant litter-N sink. However, ¹⁵N recovery in non-extractable soil N pools strongly increased over time and subsequently became the dominant ¹⁵N sink. Recovery in plant biomass accounted for only 0.025 % of ¹⁵N excess after 876 days. After three growing seasons, ¹⁵N excess recovery was characterized by the following sequence: non-extractable soil N?>>?extractable soil N including microbial biomass?>>?plant biomass?>?ectomycorrhizal root tips.

Conclusions

After quick vertical dislocation and cycling through microbial N pools, there was a rapid stabilization of leaf-litter-derived N in non-extractable N pools of the mineral soil. Very low ¹⁵N recovery in beech seedlings suggests a high importance of other N sources such as root litter for N nutrition of beech understorey.     

Effects of freeze damage on litter production, quality and decomposition in a loblolly pine forest in central China

Background and aims

Freeze events can strongly influence many ecosystem processes. However, the effects of freeze events on litter production, litter quality, and decomposition are rarely documented.

Methods

In this study, litter fall was measured monthly for 2 years. Two litter decomposition experiments were also performed using freeze-damaged litter and non-damaged litter in a loblolly pine forest.

Results

The freeze event in November 2009 caused a pronounced pulse of needle litter fall. The freeze-damaged needle litter was shown to have higher N concentration and lower C/N ratio compared with the normal falling needle litter. This finding indicates that freeze damage significantly increased needle quality because of incomplete nutrient resorption. The decomposition of freeze-damaged needle litter was faster than that of normal falling yellow needle litter and slower than that of hand-picked green needle litter. The decomposition rate constant (k) was negatively correlated with the C/N ratio in the needle litter. Our results also showed that the different climatic conditions influence patterns of litter decomposition.

Conclusions

This study suggests that freeze events significantly alter litter quantity and quality, thus affecting litter decomposition rates in a loblolly pine forest in central China.     

Mass loss and nutrient dynamics during litter decomposition under three mixing treatments in a typical steppe in Inner Mongolia

Background and aims

Mixing effects during litter decomposition could occur between two or more different litter species because of the potential nutrient transfer. However, evidence of mixing effects is variable and the underlying mechanisms remain unclear. Using a three-year decomposition experiment, we aim to examine for the effects of litter mixing and position on decomposition rates and nitrogen (N) and phosphorus (P) dynamics.

Methods

We studied litter decomposition of Stipa krylovii (Sk) and Astragalus galactites (Ag), two dominant species with contrasting litter quality, in a typical steppe of northern China in both single decomposition and three mixing treatments. The three mixing treatments included thorough mixing (Sk-Ag), Ag over Sk (Ag/Sk), and Sk over Ag (Sk/Ag).

Results

Both the Sk-Ag and the Sk/Ag mixture had negative mixing effects on the mass loss of the litter mixture, while the Ag/Sk mixture had a neutral mixing effect. The percent mass loss was higher when the litter species was placed at the top (25.0 and 51.9 % of mass remaining for Ag and Sk, respectively) than at the bottom (38.3 and 61.8 % of mass remaining for Ag and Sk, respectively). The Sk/Ag mixture had negative effects on the release of N while all three mixing treatments had positive effects on the release of P.

Conclusions

Our results indicate that: (1) mixing treatments can induce different mixing effects; (2) environmental factors likely play an important role in controlling the mixing effect; and (3) litter-mixtures have different non-additive effects on N and P, which may further increase the heterogeneity of N and P availability as the two litter species may fall differentially in terms of space and time.     

Contribution of 15N-labelled leaf litter to N turnover, nitrous oxide emissions and N sequestration in a beech forest during eleven years

Aims

Decomposition of leaf litterfall plays a major role for nitrogen (N) dynamics in soils. However, little is known as to which extent beech leaf litter contributes to N turnover and nitrous oxide (N₂O) emissions within one decade after litterfall.

Methods

In 1997, we exchanged recently fallen leaf litter by ¹⁵N-labelled litter in a beech stand (Fagus sylvatica) at the Solling, Germany. Measurements were conducted 2–3 and 10–11 years after litter exchange.

Results

Two years after litter exchange, 92 % of added ¹⁵N was recovered in the surface 10 cm of the soil. The labelled N was primarily found in the upper part of the F layer of the moder type humus. Eleven years after litter exchange, 73 % of the added ¹⁵N was lost and the remaining 27 % was mainly recovered in the lower part of the F layer indicating N sequestration. The remaining leaf litter N was subject to measurable N mineralisation (2–3 % of litter N) and N₂O production (0.02 %). Between 0.3 % (eleventh year) and 0.6 % (second year) of total annual N₂O emissions were attributed to beech leaf litter of a single year.

Conclusions

Most of the annual N₂O emissions (1.33–1.54 kg N ha^?1 yr^?1) were probably derived from older soil N pools.     

The measurement of woody root decomposition using two methodologies in a Sitka spruce forest ecosystem

Background and aims

The decomposition of roots is an important process in the loss of carbon (C) and the mineralization of nitrogen (N) in forest ecosystems. The early stage decomposition rate of Sitka spruce (Picea sitchensis (Bong.) Carr.) roots was determined using trenched plots and decomposition bags.

Methods

Stumps of known age were trenched and quadrants (50?cm by 50?cm) excavated from randomly selected stumps every 6?months over 4?years, while the mass loss from buried roots in decomposition bags, divided among four diameter categories (ranging from fine roots <2?mm to large roots >50?mm), was monitored for 27?months. The C and N concentrations of excavated samples at different time points were analysed.

Results

The change in total root necromass per quadrant showed a higher decomposition rate-constant (k) of 0.24?±?0.068?year^?1 than the k-value of roots in decomposition bags (0.07?±?0.005?year^?1). The C concentration (47.24?±?0.609?%) did not significantly change with decomposition. There was a significant increase in the C:N ratio of roots in all diameter categories (fine: 48.92?%, small: 38.53?%, medium 11.71?%, large: 76.25?%) after 4?years of decomposition, driven by N loss. Root diameter accounted for 78?% of the variation in the N concentration of roots as decomposition progressed.

Conclusion

Though the trenched plot approach offered an alternative to the more common decomposition bag method for estimating root decomposition, high spatial variation and sampling difficulties may lead to an overestimation of the mass loss from trenched roots, thus, the decomposition bag method gives a more reliable decomposition rate-constant.     

Nutrient input from hemiparasitic litter favors plant species with a fast-growth strategy

Aims

Hemiparasitic plants often produce nutrient-rich litter with high decomposition rates, and thus can enhance nutrient availability. When plant species have differential affinities for this nutrient source, hemiparasitic litter might influence species composition in addition to the parasitic suppression of host species. We expected that species adapted to fertile habitats derive a higher proportion of nutrients from the hemiparasitic litter compared to other species.

Methods

¹⁵N-labeled litter of Rhinanthus angustifolius and Pedicularis sylvatica was added to experimental field plots and adjacent litter bags. We examined N release from the litter, N uptake by the vegetation 2, 4 and 12 months after litter addition and differences in the proportion of N taken up from the litter (N_L) between co-occurring species.

Results

The percentage of N in shoots of co-occurring plant species that is derived from the added hemiparasitic litter (N_L) strongly differed between the species (0.1–6.2 %). After exclusion of species with an alternative N source (legumes as well as ectomycorrhizal and ericoid mycorrhizal species), N_L was positively related (p?<?0.001) with specific leaf area (SLA) and at Pedicularis sites with leaf N concentration (LNC) and leaf phosphorus concentration (LPC) (p?<?0.05), i.e. leaf traits associated with a fast-growth strategy and adaptation to high-nutrient environments.

Conclusions

Our results suggest that nutrient release from hemiparasitic litter favors plant species with a fast-growth strategy adapted to high-nutrient environments compared to species with a slow-growth strategy. Whether continued hemiparasitic litter inputs are able to change species composition in the long term requires further research.